Open-type wearable acoustic device and active noise reduction method

Abstract

The present application provides an open-type wearable acoustic device and an active noise reduction method, the acoustic device including a first sound sensor module, a speaker, and a noise reduction circuit, where the first sound sensor module includes N sound sensors. The noise reduction circuit determines N weights corresponding to the N sound sensors according to a target direction from which the environmental noise arrives, so that the phase of the integrated environmental noise signal measured by the first sound sensor module based on the N weights leads the phase of the environmental noise arriving at the sound output end of the speaker. The noise reduction circuit generates a first noise cancellation signal according to the N individual environmental noise signals collected by the N sound sensors and the N weights. The speaker converts the first noise cancellation signal into a first noise cancellation audio, thereby realizing the purpose of noise reduction. No matter which direction the environmental noise comes from, the method can ensure that the first sound sensor module has a phase lead with respect to the speaker, and improves the causality of the feedforward noise reduction system, so as to improve the active noise reduction effect.

Description

[Technical field]

[0001] The present specification relates to the field of audio technology, and in particular to an open-type wearable acoustic device and an active noise reduction method. [Background technology]

[0002] At present, wearable devices (e.g., earphones) with an audio output function are being used by an increasing number of users. In particular, listening methods in which the audio device does not form a sealed space with the human body (i.e., open-ear listening methods, for example, an audio device is used without being inserted into the ear canal or covering the ear, or a method in which a sound hole is provided on the surface of the audio device and an open space is formed between the eardrum and the audio device) are being increasingly applied to wearable audio devices due to features such as comfort and safety. Such wearable audio devices are called open-type wearable devices.

[0003] When the above-mentioned open-type wearable acoustic device is worn on the user's head, no sealed space is formed between the user's eardrum and the open-type wearable acoustic device, so compared to a closed-type acoustic device (such as an in-ear earphone), more sound from noise sources outside the ear enters the ear, and the user can hear more environmental noise when wearing the open-type acoustic device, resulting in a poor hearing experience for the user. Therefore, there is a need to provide an active noise reduction design based on an open-type wearable acoustic device. Summary of the Invention [Problem to be solved by the invention]

[0004] The present specification provides an open-type wearable acoustic device and an active noise reduction method that can improve the active noise reduction effect. [Means for solving the problem]

[0005] According to a first aspect, the present specification provides an open-type wearable acoustic device, the open-type wearable acoustic device including a support member, a speaker, a first sound sensor module, and a noise reduction circuit, wherein the speaker is physically connected to the support member, and an open space is formed between the speaker and the eardrum of the user when the acoustic device is worn on the user's head, the first sound sensor module includes N sound sensors, each of which is physically connected to the support member and distributed on a side away from the eardrum compared to the speaker, the N sound sensors having different directions with respect to a target point of the speaker, the N being an integer of 2 or more, and a noise reduction circuit. The sound reduction circuit is configured to determine a target direction from which environmental noise arrives, determine N weights corresponding to the N sound sensors based on the target direction, so that the phase of a total environmental noise signal measured by the first sound sensor module based on the N weights leads the phase of the environmental noise arriving at the sound output end of the speaker, generate a first noise cancellation signal based on the N individual environmental noise signals collected by the N sound sensors and the N weights, and transmit the first noise cancellation signal to the speaker, so that the speaker converts the first noise cancellation signal into a first noise cancellation audio to reduce the volume of the environmental noise at the eardrum.

[0006] In some embodiments, the total ambient noise signal is a signal obtained by performing a weighted sum of the N individual ambient noise signals based on the N weights.

[0007] In some embodiments, for an i-th audio sensor among the N audio sensors, an included angle between a direction of the i-th audio sensor relative to the target point and the target direction is defined as θ i and the corresponding weight is the θ i and i is a positive integer equal to or smaller than N.

[0008] In some embodiments, the noise reduction circuit includes N feedforward filters in one-to-one correspondence with the N sound sensors, where an i-th feedforward filter is connected to an i-th sound sensor and the speaker and configured to filter an individual environmental noise signal collected by the i-th sound sensor, where i is any positive integer less than or equal to N.

[0009] In some embodiments, to generate the first noise-canceled signal, the noise reduction circuit adjusts filter parameters of an i-th feedforward filter based on the weight corresponding to the i-th sound sensor for an i-th sound sensor among the N sound sensors, filters the individual environmental noise signal collected by the i-th sound sensor with the adjusted i-th feedforward filter, and generates an i-th individual noise-canceled signal, where i is any positive integer less than or equal to N, and superimposes the N individual noise-canceled signals generated by the N feedforward filters to obtain the first noise-canceled signal.

[0010] In some embodiments, the target direction is the direction of arrival of full-frequency band ambient noise, where in order to determine the target direction, the noise reduction circuit obtains the target direction by acquiring the N individual ambient noise signals collected by the N sound sensors and performing full-frequency band direction of arrival DOA analysis on the N individual ambient noise signals.

[0011] In some embodiments, the environmental noise includes M subband noises corresponding to M subbands, and the target direction includes M directions of arrival corresponding to the M subbands, where M is an integer greater than 1, and in order to determine the target direction, the noise reduction circuit acquires the N individual environmental noise signals collected by the N sound sensors, and for a j-th subband among the M subbands, extracts a subband noise signal corresponding to the j-th subband from each of the N individual environmental noise signals, obtains N subband noise signals corresponding to the j-th subband, and obtains the direction of arrival corresponding to the j-th subband by performing DOA analysis on the N subband noise signals, where j is any positive integer less than or equal to M.

[0012] In some embodiments, the first noise cancellation signal includes M subband noise cancellation signals corresponding to the M subbands, where to generate the first noise cancellation signal, the noise reduction circuit determines, for a jth subband among the M subbands, N subband weights corresponding to the N voice sensors based on an arrival direction corresponding to the jth subband, so that the phase of the overall subband noise signal measured by the first voice sensor module based on the N subband weights leads the phase of the environmental noise corresponding to the jth subband arriving at the audio output end of the speaker, generates N individual subband noise cancellation signals corresponding to the jth subband based on the N subband noise signals corresponding to the jth subband collected by the N voice sensors and the N subband weights, and superimposes the N individual subband noise cancellation signals to obtain the subband noise cancellation signal corresponding to the jth subband, where j is any positive integer less than or equal to M.

[0013] In some embodiments, N=2 and the N sound sensors are at acoustic null points of the speaker and in opposite directions to the target point.

[0014] In some embodiments, N=3, and the N sound sensors are distributed in a triangular shape at the acoustic zero points of the speaker.

[0015] In some embodiments, at least some of the N sound sensors are omnidirectional microphones or directional microphones.

[0016] In some embodiments, the noise reduction circuit includes at least one storage medium and at least one processor, where the storage medium stores at least one instruction set for performing noise reduction, and the processor is communicatively connected to the speaker, the first sound sensor module, and the at least one storage medium, where when the acoustic device is operated, the at least one processor reads the at least one instruction set and, according to an instruction of the at least one instruction set, determines a target direction from which the environmental noise arrives, and determines N weights corresponding to the N sound sensors based on the target direction, so that a phase of a total environmental noise signal measured by the first sound sensor module based on the N weights leads a phase of the environmental noise arriving at the sound output end of the speaker, generates a first noise cancellation signal based on the N individual environmental noise signals collected by the N sound sensors and the N weights, and transmits the first noise cancellation signal to the speaker, whereby the speaker converts the first noise cancellation signal into a first noise cancellation audio to reduce the volume of the environmental noise at the eardrum.

[0017] In some embodiments, the audio device is one of an earphone, a silencer, a hearing aid, and audio glasses.

[0018] According to a second aspect, the present specification further provides an active noise reduction method applied to the open-type wearable acoustic device described in the first aspect, the method being executed by the noise reduction circuit and including the steps of determining a target direction from which environmental noise arrives, determining N weights corresponding to the N sound sensors based on the target direction, such that the phase of a total environmental noise signal measured by the first sound sensor module based on the N weights leads the phase of the environmental noise arriving at the sound output end of the speaker, generating a first noise cancellation signal based on the N individual environmental noise signals collected by the N sound sensors and the N weights, and transmitting the first noise cancellation signal to the speaker, whereby the speaker converts the first noise cancellation signal into a first noise cancellation audio to reduce the volume of the environmental noise at the eardrum.

[0019] In some embodiments, the total ambient noise signal is a signal obtained by performing a weighted sum of the N individual ambient noise signals based on the N weights.

[0020] In some embodiments, for an i-th audio sensor among the N audio sensors, the included angle between the direction to the target point and the target direction is θ i and the corresponding weight is the θ i and i is a positive integer equal to or smaller than N.

[0021] In some embodiments, the noise reduction circuit includes N feedforward filters in one-to-one correspondence with the N sound sensors, where the i-th feedforward filter is connected to the i-th sound sensor and the speaker and configured to filter the individual environmental noise signal collected by the i-th sound sensor, where i is any positive integer not greater than N, and the step of generating the first noise cancellation signal includes a step of adjusting a filter parameter of the i-th feedforward filter based on the weight corresponding to the i-th sound sensor for the i-th sound sensor among the N sound sensors, filtering the individual environmental noise signal collected by the i-th sound sensor with the adjusted i-th feedforward filter, and generating the i-th individual noise cancellation signal, where i is any positive integer not greater than N, and a step of superimposing the N individual noise cancellation signals generated by the N feedforward filters to obtain the first noise cancellation signal.

[0022] In some embodiments, the target direction is the direction of arrival of full-frequency band ambient noise, and the aforementioned step of determining the target direction from which the ambient noise is arriving includes a step of obtaining the N individual ambient noise signals collected by the N sound sensors, and obtaining the target direction by performing full-frequency band direction of arrival DOA analysis on the N individual ambient noise signals.

[0023] In some embodiments, the environmental noise includes M subband noises corresponding to M subbands, and the target direction includes M arrival directions corresponding to the M subbands, where M is an integer greater than 1, and the aforementioned step of determining the target direction from which the environmental noise arrives includes a step of acquiring N individual environmental noise signals collected by the N sound sensors, and for a j-th subband among the M subbands, extracting a subband noise signal corresponding to the j-th subband from each of the N individual environmental noise signals to obtain N subband noise signals corresponding to the j-th subband, and performing DOA analysis on the N subband noise signals to obtain the arrival direction corresponding to the j-th subband, where j is any positive integer less than or equal to M.

[0024] In some embodiments, the first noise cancellation signal includes M subband noise cancellation signals corresponding to the M subbands, and the aforementioned step of generating the first noise cancellation signal includes a step of determining N subband weights corresponding to the N voice sensors based on an arrival direction corresponding to the jth subband for a jth subband among the M subbands, so that the phase of the total subband noise signal measured by the first voice sensor module based on the N subband weights leads the phase of the environmental noise corresponding to the jth subband arriving at the audio output end of the speaker; a step of generating N individual subband noise cancellation signals corresponding to the jth subband based on the N subband noise signals corresponding to the jth subband collected by the N voice sensors and the N subband weights; and a step of superimposing the N individual subband noise cancellation signals to obtain a subband noise cancellation signal corresponding to the jth subband, where j is any positive integer less than or equal to M.

[0025] As can be seen from the above technical solutions, in the open-type wearable acoustic device and active noise reduction method according to the present specification, the acoustic device includes a first sound sensor module, a speaker, and a noise reduction circuit. Here, the first sound sensor module includes N sound sensors. The noise reduction circuit determines N weights corresponding to the N sound sensors according to the target direction from which the environmental noise arrives, so that the phase of the total environmental noise signal measured by the first sound sensor module based on the N weights leads the phase of the environmental noise arriving at the audio output end of the speaker. The noise reduction circuit generates a first noise cancellation signal according to the N individual environmental noise signals collected by the N sound sensors and the N weights. The speaker converts the first noise cancellation signal into a first noise cancellation audio, thereby achieving the purpose of noise reduction. No matter what direction the environmental noise comes from, the method can ensure that the first sound sensor module has a phase lead with respect to the speaker, and improves the causality of the feedforward noise reduction system, so as to improve the active noise reduction effect.

[0026] Other features of the open-type wearable acoustic device and active noise reduction method according to the present specification are partially recited in the following description. The inventive aspects of the open-type wearable acoustic device and active noise reduction method according to the present specification can be fully understood by practice or use of the methods, apparatus and combinations described in the following detailed examples.

[0027] In order to more clearly describe the technical solutions in the embodiments of this specification, the following briefly introduces the drawings necessary for describing the embodiments. It is obvious that the drawings described below are only some embodiments of this specification, and those skilled in the art can obtain other drawings based on these drawings without creative efforts. [Brief description of the drawings]

[0028] [Figure 1A] 1 is a schematic diagram showing a wearing scene of an audio device provided according to an embodiment of the present specification. [Figure 1B]1 is a schematic diagram showing an audio device that employs an in-ear wearing method. [Figure 1C] 1 is a schematic diagram showing an audio device that employs an ear hook type mounting method. [Figure 1D] 1 is a schematic diagram showing an audio device that employs a clip-on type mounting method. [Diagram 2] 1 is a schematic diagram showing a hardware structure of an audio device provided in accordance with an embodiment of the present disclosure; [Diagram 3] 1 is a schematic diagram showing leakage signals collected by sound sensors at different positions in an acoustic device; [Figure 4] 4 is a flow chart illustrating an active noise reduction method provided in accordance with an embodiment of the present disclosure. [Diagram 5] 1 is a schematic diagram illustrating the principle of active noise reduction in an acoustic device provided according to an embodiment of the present specification; [Figure 6] 2 is a schematic diagram illustrating the noise reduction effect of the active noise reduction method provided in accordance with an embodiment of the present specification. [Figure 7] 4 is a flow chart illustrating another active noise reduction method provided in accordance with embodiments of the present disclosure. [Figure 8A] 11 is a schematic diagram illustrating frequency response curves for feedforward noise reduction of environmental noise near the eardrum using different feedforward filter gains when a first user is wearing the audio device. [Figure 8B] 4 is a schematic diagram illustrating frequency response curves for feedforward noise reduction of a second audio signal using different feedforward filter gains when a first user is wearing an audio device; [Figure 9A] 11 is a schematic diagram illustrating frequency response curves for feedforward noise reduction of environmental noise near the eardrum using different feedforward filter gains when a second user is wearing the audio device. [Figure 9B] 5 is a schematic diagram illustrating frequency response curves for feedforward noise reduction of a second audio signal using different feedforward filter gains when a second user is wearing the audio device. [Figure 10]FIG. 11 is a schematic diagram showing the distribution of the voice sensors when the first voice sensor module includes two voice sensors. [Figure 11] FIG. 11 is a schematic diagram showing the distribution of the voice sensors when the first voice sensor module includes three voice sensors. [Figure 12] 4 is a flow chart illustrating another active noise reduction method provided in accordance with embodiments of the present disclosure. [Figure 13] 2 is a schematic diagram illustrating an active noise reduction principle of another acoustic device provided in accordance with an embodiment of the present specification. [Figure 14] 2 is a schematic diagram illustrating a set of frequency response curves provided in accordance with embodiments of the present disclosure. [Figure 15] FIG. 4 is a schematic diagram illustrating another set of frequency response curves provided in accordance with embodiments of the present disclosure. [Figure 16] 4 is a flow chart illustrating another active noise reduction method provided in accordance with embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Specific application scenarios and requirements of the present specification are described below, but are intended to enable those skilled in the art to make and use the contents of the present specification. Various modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of the present specification. Therefore, the present specification is not intended to be limited to the embodiments shown, but is accorded the broadest scope consistent with the claims.

[0030] The terms used herein are for the purpose of describing particular example embodiments and are not intended to be limiting. For example, the singular forms "a", "one" and "the" as used herein may include the plural unless the context clearly dictates otherwise. The terms "comprise", "include", and / or "contain" as used herein indicate the presence of associated integers, steps, operations, elements and / or components, but do not exclude the presence of one or more other features, integers, steps, operations, elements, components and / or groups, or that other features, integers, steps, operations, elements, components and / or groups may be added to the system / method.

[0031] Consideration of the following description clearly allows for improved operation and function of these and other features of the present specification, and associated components, and economies of assembly and manufacture of parts. Reference is made to the accompanying drawings, all of which form a part of this specification. However, it should be clearly understood that the accompanying drawings are for illustration and explanation purposes only, and are not intended to limit the scope of this specification. It should also be understood that the drawings are not drawn to scale. Flowcharts used herein illustrate the operation of a system implementation based on some of the embodiments of this specification. It should be clearly understood that the operations of the flowcharts do not necessarily have to be performed in order. Rather, the operations may be performed in reverse order or simultaneously. Also, one or more other operations may be added to the flowcharts. One or more operations may be deleted from the flowcharts.

[0032] For the sake of convenience, we will first explain the terms used in this specification.

[0033] Closed-type acoustic devices: When some acoustic devices are worn, a sealed space is formed between the acoustic device and the user's eardrum, and this type of acoustic device may be called a closed-type acoustic device. For example, the acoustic device may form a sealed space between the user's eardrum by an inner-type design (e.g., canal-type earphones), a sealed ear cup design, or other similar designs. When a user wears a closed-type acoustic device, the sealed space can physically block external noise and reduce interference with the user caused by external noise. However, a user may feel uncomfortable wearing a closed-type acoustic device for a long period of time.

[0034] Open-type acoustic devices: When some acoustic devices are worn, an open space is formed between the acoustic device and the user's eardrum, and this type of acoustic device may be called an open-type acoustic device. For example, the acoustic device is not inserted into the ear canal or does not cover the ear canal, or a sound hole is installed on the surface of the acoustic device, so that an open space can be formed between the acoustic device and the eardrum. Open-type acoustic devices can improve the comfort of the user when worn and make the sound that the user hears more natural and clear.

[0035] Noise: In this application, any sound that is not liked by the user, that is not desired by the user, or that interferes with the user's hearing is referred to as noise.

[0036] Passive noise reduction: refers to technology that reduces noise in a passive manner. Passive methods include, but are not limited to, eliminating (or partially eliminating) the noise source, blocking noise transmission, or preventing the user's ear from hearing the noise, or any combination thereof. For example, a technology that achieves noise reduction by forming a sealed space in the ear is considered a passive noise reduction technology. Passive noise reduction does not eliminate noise, but physically suppresses it.

[0037] Active noise reduction: refers to a technology that actively reduces noise by generating a noise cancellation signal (e.g., a signal that is in the opposite phase to the noise to be suppressed). An audio device that employs active noise reduction technology can eliminate noise by collecting a noise signal with an audio sensor, generating a noise cancellation signal for canceling the noise signal with a noise reduction circuit, playing the noise cancellation signal with a speaker, and canceling the noise cancellation signal with the noise signal. Active noise reduction technology may also be called active noise reduction technology. Active noise reduction technology can be classified into feedforward noise reduction, feedback noise reduction, and hybrid noise reduction.

[0038] Feedforward noise reduction: A sound sensor is placed outside the audio device, and the sound sensor collects the environmental noise to generate an environmental noise signal, and the feedforward filter filters the environmental noise signal to generate a noise cancellation signal, and the noise cancellation signal is played back by the speaker. In this way, the noise cancellation signal cancels (or partially cancels) the environmental noise at the eardrum, thereby reducing the volume of the environmental noise heard by the user. The feedforward filter is mainly used to compensate for the difference between the environmental noise at the eardrum and the environmental noise collected by the sound sensor. In the feedforward noise reduction system, an open-loop noise reduction control system is formed between the speaker and the sound sensor.

[0039] Feedback noise reduction: A sound sensor is placed inside the audio device, the sound sensor collects the environmental noise near the eardrum, the feedback filter filters the environmental noise to generate a noise cancellation signal, and the speaker plays the noise cancellation signal. In this way, the noise cancellation signal cancels (or partially cancels) the environmental noise at the eardrum, thereby reducing the volume of the environmental noise heard by the user. In the feedback noise reduction system, a closed-loop noise reduction control system is formed between the speaker and the sound sensor.

[0040] Hybrid noise reduction: Hybrid noise reduction is a technology that combines feedforward noise reduction and feedback noise reduction. In general, compared with feedforward noise reduction alone or feedback noise reduction alone, hybrid noise reduction can further improve the noise reduction effect.

[0041] The present application provides an open-type wearable acoustic device (hereinafter referred to as an acoustic device) and an active noise reduction method thereof, which can reduce the volume of environmental noise heard by the user in a scenario where the user wears the acoustic device, and reduce the interference of environmental noise with the user.

[0042] FIG. 1A shows a schematic diagram of wearing scenarios of an acoustic device provided according to an embodiment of the present specification. In scenario 001, an acoustic device 100 is worn at a user's ear 200. Here, the ear 200 may include an auricle 201 and an eardrum 202. The acoustic device 100 is worn at the auricle 201, and an open space is formed between the acoustic device 100 and the eardrum 202 without sealing. In scenario 001, a noise source 300 may be further included, and the number of the noise sources 300 may be one or more. The noise source 300 is configured to emit environmental noise (e.g., a sound that is not liked by the user, a sound that is not desired by the user, or a sound that interferes with the user's hearing). The acoustic device 100 is configured to suppress or eliminate the environmental noise heard by the ear. Specifically, the acoustic device 100 employs a method of active noise reduction to generate and output a noise cancellation signal (a signal in phase opposite to the environmental noise) to suppress or eliminate the environmental noise.

[0043] In some embodiments, the acoustic device 100 may be an earphone, a silencer, a hearing aid, acoustic glasses, or the like, or any combination thereof. For ease of understanding, FIG. 1A shows the acoustic device 100 as an earphone as an example. If the acoustic device 100 is acoustic glasses, an audio output device may be installed at a temple of the glasses close to the ear, and configured to output audio to the user's ear. The acoustic device 100 may be attached to the user's ear 200 in any manner, and the present application is not limited thereto. For example, the method of wearing the acoustic device 100 may include a headband type, an in-ear type, a neckband type, an ear hook type, or the like, or any combination thereof.

[0044] In some embodiments, scenario 001 may also include a network and a target device (not shown in FIG. 1A ), where the target device may be an electronic device with an audio output function. Audio device 100 and the target device are communicatively connected via a network, and data or signals can be transmitted between them via the network. For example, the target device transmits target audio (e.g., music, voice, etc.) to be played to audio device 100 via the network, and audio device 100 outputs the target audio to a user.

[0045] In some embodiments, the target device may have an audio collecting device installed thereon and may obtain target audio through the audio collecting device. In some embodiments, the target device may receive target audio from another device. In some embodiments, the target device may include a mobile device, a tablet, a laptop, an in-car device, or the like, or any combination thereof. In some embodiments, the mobile device may include a smart home device, a smart mobile device, a virtual reality device, an augmented reality device, or the like, or any combination thereof. In some embodiments, the smart home device may include a smart television, a desktop computer, a smart speaker, or the like, or any combination thereof. In some embodiments, the smart mobile device may include a smartphone, a personal digital assistant, a gaming device, a navigation device, or the like, or any combination thereof. In some embodiments, the virtual reality device or the augmented reality device may include a virtual reality helmet, virtual reality glasses, a virtual reality patch, an augmented reality helmet, augmented reality glasses, an augmented reality patch, or the like, or any combination thereof. For example, the virtual reality device or the augmented reality device may include Google Glass, a head mounted display, VR, or the like. In some embodiments, the onboard devices within the vehicle may include an onboard computer, an onboard television, and the like.

[0046] In some embodiments, the network may be any type of wireless network. For example, the network may include a telecommunications network, an intranet, the Internet, a local area network (LAN), a wide area network (WAN), a wireless local area network (WLAN), a metropolitan area network (MAN), a wide area network (WAN), a public switched telephone network (PSTN), a Bluetooth network, a ZigBee network, a near field communication (NFC) network, or a similar network. In some embodiments, the network may be a Bluetooth network, in which case the audio device 100 and the target device can communicate based on a Bluetooth protocol.

[0047] 1A, the audio device 100 may include a support member 101, a speaker 102, a noise reduction circuit 105, and at least one audio sensor module, where the speaker 102 and the at least one audio sensor module may both be physically connected to the support member 101.

[0048] The support member 101 may be used to assist in fixing the acoustic device 100 to the user's ear. For example, the support member 101 may be a housing of the acoustic device 100 or other additional structure. Note that the specific form of the support member 101 is not intended to be limited in this application. It should be understood that the specific form of the support member 101 is related to the wearing method of the acoustic device 100.

[0049] FIG. 1B shows a schematic diagram of an acoustic device that adopts an in-ear type wearing method. In this case, the support member 101 is designed to fit the auricle 201, and one or more support points on the support member 101 fit to a predetermined point on the auricle 201. FIG. 1C shows a schematic diagram of an acoustic device that adopts an ear hook type wearing method. In this case, the support member 101 may be a hanging structure, so that the acoustic device 100 can be suspended from the auricle 201. FIG. 1D shows a schematic diagram of an acoustic device that adopts a clip-on type wearing method. In this case, the support member 101 adopts a clip structure, so that the support member 101 can be clipped to the auricle 201.

[0050] 1A , the speaker 102 is disposed on the side of the acoustic device 100 that is closer to the entrance of the ear canal. When the acoustic device 100 is worn on the user's head, an open space is formed between the speaker 102 and the eardrum 202 of the user. In some embodiments, when the acoustic device 100 is worn on the user's head, the speaker 102 can be disposed close to the entrance of the ear canal without blocking the entrance of the ear canal, thereby forming an open space between the speaker 102 and the eardrum 202. In some embodiments, the housing of the acoustic device 100 can adopt a non-sealed housing, for example, a sound vent is provided on the housing, thereby forming an open space between the speaker 102 and the eardrum 202.

[0051] The speaker 102 is configured to generate audio based on an audio signal (or convert an audio signal into audio). An audio signal here is an electrical signal carrying audio information, and audio refers to an audio signal reproduced by a speaker. Sound is emitted from an initial sound source (e.g., an environmental noise source, a person's throat, etc.) and is converted into an electrical signal carrying the audio information, i.e., the audio signal, by a sound sensor (e.g., a microphone) that collects the sound. The speaker 102 may also be referred to as an electro-acoustic transducer, and during operation, the speaker 102 may receive the audio signal carrying the audio information, convert it into an audio signal, and reproduce it. In some embodiments, the audio device 100 may include multiple speakers 102. In this case, the multiple speakers 102 may be arranged in an array, such as a linear array, a planar array, a spherical array, or other arrays.

[0052] In some embodiments, the at least one sound sensor module may include a first sound sensor module 103. As shown in FIG. 1A, the first sound sensor module 103 is farther from the eardrum 202 than the speaker 102. That is, the first sound sensor module 103 may be disposed on the outside of the acoustic device 100 (when the acoustic device 100 is worn on the user's head, the side of the acoustic device 100 farther from the eardrum 202 is the outside). In some embodiments, the first sound sensor module 103 may include one or more sound sensors. When the first sound sensor module 103 includes multiple sound sensors, the multiple sound sensors may be arranged in the manner of an array, for example, a linear array, a planar array, a spherical array, or other arrays. In some embodiments, the sound sensor is a device for collecting sound and converting the sound into an electrical signal, for example, a microphone.

[0053] In some embodiments, the at least one sound sensor module may include a second sound sensor module 104. The second sound sensor module 104 is closer to the eardrum 202 than the speaker 102. That is, the second sound sensor module 104 is disposed inside the acoustic device 100 (when the acoustic device 100 is worn on the user's head, the side of the acoustic device 100 closer to the eardrum 202 is the inside). In some embodiments, the second sound sensor module 104 may include one or more sound sensors. When the second sound sensor module 104 includes multiple sound sensors, the multiple sound sensors may be arranged in an array, such as a linear array, a planar array, a spherical array, or other arrays.

[0054] In some embodiments, the at least one audio sensor module may include both the first audio sensor module 103 and the second audio sensor module 104 .

[0055] The first sound sensor module 103 is configured to collect a first sound and generate a first sound signal corresponding to the first sound. Here, the first sound may be an analog signal of sound, and the first sound signal may be an electrical signal. It should be understood that since a noise source 300 exists in the environment in which the acoustic device 100 is placed, the first sound sensor module 103 can collect environmental noise emitted from the noise source 300. In addition, since an open space is formed between the speaker 102 and the eardrum 202, the first sound sensor module 103 can also collect sounds emitted from the speaker 102. For ease of explanation, in this application, the sound from the speaker 102 collected by the first sound sensor module 103 will be referred to as "leakage sound". Therefore, the first sound collected by the first sound sensor module 103 includes environmental noise and leakage sound. In response, the first audio signal generated by the first audio sensor module 103 includes the ambient noise signal from the noise source 300 and the leakage signal from the speaker 102 .

[0056] The first sound sensor module 103 is farther from the eardrum 202 than the speaker 102, that is, the first sound sensor module 103 is closer to the noise source 300 than the speaker 102. Therefore, the time when the environmental noise arrives at the first sound sensor module 103 is earlier than the time when the environmental noise arrives at the audio output end of the speaker 102. In other words, the phase when the environmental noise arrives at the first sound sensor module 103 leads the phase when the environmental noise arrives at the audio output end of the speaker 102. Therefore, the first sound signal collected by the first sound sensor module 103 can be used for feedforward noise reduction.

[0057] The second sound sensor module 104 is configured to collect a second sound and generate a second sound signal corresponding to the second sound. Here, the second sound may be an analog signal of sound, and the second sound signal may be an electrical signal. In terms of an open-type acoustic device, the second sound sensor module 104 can collect the environmental noise emitted from the noise source 300 and also collect the sound emitted from the speaker 102. Therefore, the second sound collected by the second sound sensor module 104 includes a component of the environmental noise and a component of the sound emitted from the speaker 102. In an active noise reduction scenario, the environmental noise emitted from the noise source 300 is transmitted to the open space through the air, and during the active noise reduction process, some of the environmental noise in the open space is offset or attenuated by the sound of the speaker 102, and therefore the second sound collected by the second sound sensor module 104 may also be called residual noise, i.e., the environmental noise remaining in the open space.

[0058] The second sound sensor module 104 is closer to the eardrum 202 than the speaker 102, that is, the second sound sensor module 104 is farther away from the noise source 300 than the speaker 102. Therefore, the time when the environmental noise arrives at the second sound sensor module 104 is later than the time when the environmental noise arrives at the audio output end of the speaker 102. In other words, the phase when the environmental noise arrives at the second sound sensor module 104 is delayed from the phase when the environmental noise arrives at the audio output end of the speaker 102. Therefore, the second sound signal collected by the second sound sensor module 104 can be used for feedback noise reduction.

[0059] 1A, the noise reduction circuit 105 is connected to the first sound sensor module 103, the second sound sensor module 104, and the speaker 102, and is configured to perform active noise reduction to reduce the volume of the environmental noise heard by the ears, where the active noise reduction may be either feed-forward noise reduction, feedback noise reduction, or hybrid noise reduction.

[0060] In some embodiments, the noise reduction circuit 105 may be configured to perform feed-forward noise reduction, in which case the noise reduction circuit 105 may obtain a first audio signal from the first audio sensor module 103 and perform active noise reduction based on the first audio signal.

[0061] In some embodiments, the noise reduction circuit 105 performing active noise reduction based on the first audio signal may include the noise reduction circuit 105 generating a first noise cancellation signal based on the first audio signal. The noise reduction circuit 105 transmits the first noise cancellation signal to the speaker 102, which converts the first noise cancellation signal into a first noise cancellation audio. The phase of the first noise cancellation signal can be set to be inverse or approximately inverse to the phase of the environmental noise in the space at the eardrum 202, or to have a preset phase difference, such that the phase of the first noise cancellation audio is inverse or approximately inverse to the phase of the environmental noise in the eardrum 202 and the space nearby, thereby reducing the volume of the environmental noise near the eardrum 202. In some embodiments, the noise reduction circuit 105 includes a feed-forward filter, which is connected to the first audio sensor module 103 and the speaker 102. After obtaining a first audio signal from the first audio sensor module 103, the noise reduction circuit 105 can input the first audio signal to a feedforward filter, filter the first audio signal through the feedforward filter to obtain a first noise cancellation signal, and output the first noise cancellation signal to the speaker 102. Here, the feedforward filter is configured to adjust at least one of a gain or a phase of the first audio signal so that the obtained first noise cancellation signal can cancel out at least a part of the environmental noise at the eardrum 202.

[0062] In some embodiments, the noise reduction circuit 105 may be configured to perform feedback noise reduction, in which case the noise reduction circuit 105 may obtain a second audio signal from the second audio sensor module 104 and perform active noise reduction based on the second audio signal.

[0063] In some embodiments, the process of the noise reduction circuit 105 performing active noise reduction based on the second audio signal may include the noise reduction circuit 105 generating a second noise cancellation signal based on the second audio signal. The noise reduction circuit 105 transmits the second noise cancellation signal to the speaker 102, which converts the second noise cancellation signal into a second noise cancellation audio. The second noise cancellation signal can be set to be inverse, approximately inverse, or have a preset phase difference with the phase of the environmental noise at the eardrum 202, such that the phase of the second noise cancellation audio is inverse or approximately inverse with the phase of the environmental noise at and near the eardrum 202, thereby reducing the volume of the environmental noise at the eardrum 202. In some embodiments, the noise reduction circuit 105 includes a feedback filter, which is connected to the second audio sensor module 104 and the speaker 102. After obtaining a second audio signal from the second audio sensor module 104, the noise reduction circuit 105 can input the second audio signal to a feedback filter, filter the second audio signal through the feedback filter to obtain a second noise cancellation signal, and output the second noise cancellation signal to the speaker 102. Here, the feedback filter is arranged to adjust at least one of a gain or a phase of the second audio signal so that the obtained second noise cancellation signal can cancel at least a part of the environmental noise at the eardrum 202.

[0064] In some embodiments, the noise reduction circuit 105 may be configured to perform hybrid noise reduction, where the noise reduction circuit 105 may receive a first audio signal from the first audio sensor module 103 and a second audio signal from the second audio sensor module 104, and perform active noise reduction based on the first audio signal and the second audio signal.

[0065] In some embodiments, the process of the noise reduction circuit 105 performing active noise reduction based on the first audio signal and the second audio signal may include the noise reduction circuit 105 generating a first noise cancellation signal based on the first audio signal and generating a second noise cancellation signal based on the second audio signal. The noise reduction circuit 105 transmits the first noise cancellation signal and the second noise cancellation signal to the speaker 102, which converts the first noise cancellation signal and the second noise cancellation signal into noise cancellation audio to reduce the volume of the environmental noise in the eardrum 202 and the space nearby. In some embodiments, the noise reduction circuit 105 includes a feed-forward filter and a feedback filter, where the feed-forward filter is connected to the first audio sensor module 103 and the speaker 102. The feedback filter is connected to the second audio sensor module 104 and the speaker 102. The noise reduction circuit 105 inputs a first audio signal to a feedforward filter, filters the first audio signal through the feedforward filter to obtain a first noise-canceled signal, and inputs a second audio signal to a feedback filter, filters the second audio signal through the feedback filter to obtain a second noise-canceled signal. The noise reduction circuit 105 further transmits the first noise-canceled signal and the second noise-canceled signal to the speaker 102, where the feedforward filter is configured to adjust at least one of the gain or phase of the first audio signal so that audio generated by converting the obtained first noise-canceled signal by the speaker 102 can cancel out environmental noise at the eardrum 202 and at least a part of the space nearby the eardrum (i.e., the phase of the audio is inverse or approximately inverse to the phase of environmental noise at the eardrum 202 and at least a part of the space nearby the eardrum).The feedback filter is configured to adjust at least one of the gain or phase of the second audio signal such that the audio produced by converting the resulting first noise cancellation signal by the speaker 102 can cancel out at least a portion of the ambient noise at the eardrum 202 (i.e., the phase of the audio is inverse or approximately inverse to the phase of at least a portion of the ambient noise at the eardrum 202 and the space nearby). In some embodiments, the noise reduction circuit 105 can transmit the first noise cancellation signal and the second noise cancellation signal separately to the speaker 102. In some embodiments, the noise reduction circuit 105 can combine the first noise cancellation signal and the second noise cancellation signal to obtain a combined noise cancellation signal and transmit the combined noise cancellation signal to the speaker 102.

[0066] In some embodiments, the noise reduction circuitry 105 may be configured to perform the active noise reduction method described herein. In this case, the noise reduction circuitry 105 may store data or instructions for performing the active noise reduction method described herein and may execute or be used to execute said data or instructions. In some embodiments, the noise reduction circuitry 105 may include a hardware device capable of processing data information and a program necessary to operate the hardware device. The active noise reduction method is described in detail in a later section.

[0067] FIG. 2 shows a schematic diagram of a hardware structure of an audio device provided according to an embodiment of the present specification. As shown in FIG. 2, in some embodiments, the noise reduction circuit 105 may include at least one storage medium 106 and at least one processor 107. The at least one processor 107 is communicatively connected with the speaker 102, the first sound sensor module 103, and the second sound sensor module 104. It should be noted that, for the sake of illustration only, the noise reduction circuit 105 of the present application includes at least one storage medium 106 and at least one processor 107. As one of ordinary skill in the art can understand, the noise reduction circuit 105 may include other hardware circuit structures, which are not limited herein and can achieve the functions described in the present application without departing from the spirit of the present application.

[0068] In some embodiments, the audio device 100 may further include a communication port 108. The communication port 108 is used for data communication between the audio device 100 and the outside world. For example, the communication port 108 can be used for data communication between the audio device 100 and other devices.

[0069] In some embodiments, the audio device 100 may further include an internal communication bus 109. The internal communication bus 109 may be connected to different system components. For example, the speaker 102, the first audio sensor module 103, the second audio sensor module 104, the processor 107, the storage medium 106, and the communication port 108 may all be connected via the internal communication bus 109.

[0070] The storage medium 106 may include a data storage device. The data storage device may be a non-transitory storage medium or a transitory storage medium. For example, the data storage device may include one or more of a magnetic disk 1061, a read-only memory (ROM) 1062, or a random access memory (RAM) 1063. The storage medium 106 further includes at least one set of instructions stored in the data storage device. The set of instructions includes instructions, the instructions being computer program code, and the computer program code may include programs, routines, objects, components, data structures, processes, modules, etc., that perform the active noise reduction methods provided herein.

[0071] At least one processor 107 is used to execute the at least one instruction set described above. When the audio device 100 operates, the at least one processor 107 reads the at least one instruction set and executes the active noise reduction method provided herein according to the instructions of the at least one instruction set. The processor 107 can execute all or some of the steps included in the communication method. The processor 107 may be in the form of one or more processors, and in some embodiments, the processor 107 may include one or more hardware processors, such as a microcontroller, a microprocessor, a reduced instruction set computer (RISC), a special-purpose integrated circuit (ASIC), an application-specific instruction set processor (ASIP), a central processing unit (CPU), a graphics processing unit (GPU), a physical processing unit (PPU), a microcontroller unit, a digital signal processor (DSP), a field programmable gate array (FPGA), an advanced RISC machine (ARM), a programmable logic device (PLD), any circuit or processor capable of performing one or more functions, or any combination thereof. For purposes of illustration only, the acoustic device 100 shown in FIG. 2 is illustrated as including only one processor 107. However, it should be noted that, as used herein, the acoustic device 100 may further include multiple processors, and thus, the operations and / or method steps disclosed herein may be performed by one processor or jointly by multiple processors, as described herein. For example, as used herein, when the processor 107 of the acoustic device 100 performs steps A and B, it should be understood that steps A and B may be performed jointly or separately by two different processors 120 (e.g., a first processor performs step A and a second processor performs step B, or the first and second processors perform steps A and B jointly).

[0072] Those skilled in the art can understand that Fig. 2 is merely a design example of the noise reduction circuit 105. The noise reduction circuit 105 may be designed in other hardware forms without departing from the spirit of the invention disclosed in this application. The specific design of the noise reduction circuit 105 is not limited in this application.

[0073] As mentioned above, in an open-type acoustic device, the first audio signal collected and generated by the first audio sensor module 103 is not just an environmental noise signal, but a mixed audio signal including the environmental noise signal and the leakage signal. Therefore, when the noise reduction circuit 105 directly performs feedforward noise reduction based on the first audio signal, the leakage signal may affect the process of feedforward noise reduction and reduce the effect of feedforward noise reduction.

[0074] In some embodiments, in order to reduce the influence of the leakage signal on the feed-forward noise reduction effect, the audio device 100 can adopt a physical isolation method and place the first sound sensor module 103 at the acoustic zero point of the speaker 102. For example, the speaker 102 may adopt a dipole speaker design, and the first sound sensor module 103 is placed at the acoustic zero point of the dipole speaker, so that the first sound sensor module 103 cannot collect the leakage signal from the speaker 102 or can only collect a very small leakage signal.

[0075] FIG. 3 shows a schematic diagram of leakage signals collected by sound sensors at different positions in an audio device. Here, FF1 and FF2 represent sound sensors arranged at the acoustic zero point position of the speaker 102, and FF3 represents a sound sensor arranged near the speaker 102. After applying an excitation signal to the speaker 102 during testing, the leakage signal collected by FF1 is obtained to obtain the curve 301 shown in FIG. 3, the leakage signal collected by FF2 is obtained to obtain the curve 302 shown in FIG. 3, and the leakage signal collected by FF3 is obtained to obtain the curve 303 shown in FIG. 3. As can be seen from FIG. 3, when the environmental frequency is low (e.g., less than 1500 Hz), the leakage signals collected by FF1 and FF2 are lower than the leakage signal collected by FF3 by more than 20 dB, and a certain noise reduction effect is obtained.

[0076] In some embodiments, the distance between the first sound sensor module 103 and the sound zero point position of the speaker 102 may be within a preset range that is not zero. That is, the first sound sensor module 103 may be installed near the sound zero point position of the speaker 102, rather than being positioned exactly at the sound zero point position of the speaker 102. In this way, the requirements for the structural design and assembly technology of the audio device 100 may be reduced.

[0077] The present application provides an active noise reduction method P100 that can improve the noise reduction effect by reducing the leakage signal component contained in the first audio signal, thereby reducing the influence of the leakage signal on the feedforward noise reduction. The above active noise reduction method P100 can be applied to both the scenario in which the "first audio sensor module 103 is not installed at the acoustic zero point position of the speaker 102" and the scenario in which the "first audio sensor module 103 is installed at the acoustic zero point position of the speaker 102". In the scenario in which the "first audio sensor module 103 is installed at the acoustic zero point position of the speaker 102", there is still a problem that the speaker signal leaks to the first audio sensor module in some frequency bands (for example, in FIG. 3, when the frequency is greater than 5000 Hz, the leakage signal collected by FF1 and FF2 is almost equivalent to the leakage signal collected by FF3), so that the active noise reduction method P100 provided by the present application can be used to perform noise reduction for a specific frequency band in which the above leakage exists, thereby improving the noise reduction effect. The active noise reduction method P100 may be applied alone to the acoustic device 100 provided by the present application, or may be used in combination with other active noise reduction methods described elsewhere in this specification.

[0078] FIG. 4 shows a flowchart of an active noise reduction method provided according to an embodiment of the present specification. The active noise reduction method P100 may be performed by a noise reduction circuit 105 in an acoustic device 100. For example, if the noise reduction circuit 105 adopts the structure shown in FIG. 2, the processor 107 in the noise reduction circuit 105 can read an instruction set stored in its local storage medium, and perform the active noise reduction method P100 described herein according to the instructions of the instruction set. As shown in FIG. 4, the active noise reduction method P100 may include the following steps:

[0079] S11: Obtain a first audio signal from a first audio sensor module, where the first audio signal includes an environmental noise signal from an environmental noise and a leakage signal from a speaker.

[0080] As described above, the first sound sensor module 103 collects a first sound and converts the first sound into a first sound signal. The first sound is actually a mixture of the environmental noise from the noise source 300 and the leakage sound from the speaker 102, and therefore the first sound signal contains both an environmental noise signal corresponding to the environmental noise and a leakage signal corresponding to the leakage sound. The noise reduction circuit 105 is connected to the first sound sensor module 103 and can obtain the first sound signal from the first sound sensor module 103.

[0081] S12: A pseudo ambient noise signal is generated by reducing the leakage signal component in the first audio signal.

[0082] Specifically, the noise reduction circuit 105 can measure the leakage signal component contained in the first audio signal in a specific manner, and then subtract the leakage signal component from the first audio signal to generate a pseudo ambient noise signal. It should be noted that the measured leakage signal component may have some deviation from the actual leakage signal, so the result of subtracting the measured leakage signal component from the first audio signal is not exactly the same as the actual ambient noise signal, but is approximately the same. Therefore, in this application, the result of this reduction is called a "pseudo ambient noise signal". The pseudo ambient noise signal can be understood as a compensation signal obtained by performing leakage compensation on the first audio signal.

[0083] 5 shows a schematic diagram of the principle of active noise reduction of an acoustic device provided according to an embodiment of the present specification. As shown in FIG. 5, assume that: Let the transfer function between the sound emitted by the noise source 300 and the audio signal measured by the first sound sensor module 103 be denoted as h1; Let the transfer function between the sound emitted by the noise source 300 and the audio signal measured by the second sound sensor module 104 be denoted as h2; The transfer function between the sound emitted from the speaker 102 and the audio signal measured by the first audio sensor module 103 is denoted as h3; The transfer function between the sound emitted from the speaker 102 and the audio signal measured by the second sound sensor module 104 is denoted as h4, and the transfer function between the input and output of the feedforward filter is denoted as h5; Let the transfer function between the input and output of the feedback filter be denoted as h6, The acoustic transfer function from the sound emitted from the speaker 102 to the eardrum 202 is denoted as h7. The acoustic transfer function from the sound emitted from the noise source 300 to the eardrum 202 is denoted as h8.

[0084] The ambient noise emitted from the noise source 300 is denoted as S0, the first audio signal collected by the first audio sensor module 103 is denoted as S1, the second audio signal collected by the second audio sensor module 104 is denoted as S2, the noise reduction signal emitted from the speaker 102 is denoted as S3, and the ambient noise at the eardrum 202 is denoted as S4. It should be noted that in this application, S4 refers to the ambient noise actually heard by a human ear, i.e., the ambient noise remaining at the eardrum 202 after noise reduction processing.

[0085] Based on the acoustic transfer process shown in FIG. 5, the following relationships exist among S0, S1, S2, S3 and S4.

[0086]

number

[0087] Here, the above formula (1-1) corresponds to the feedforward noise reduction mode, formula (1-2) corresponds to the feedback noise reduction mode, and formula (1-3) corresponds to the hybrid noise reduction mode.

[0088] Next, the feedforward noise reduction mode is taken as an example to analyze the design principle of the feedforward filter h5.

[0089] In the feedforward noise reduction mode, by substituting the above equation (2) into equation (1-1), the following equation is obtained:

[0090]

number

[0091] Substituting equation (4) into equation (0), we get:

[0092]

number

[0093] In an ideal case (when the sound emitted from the speaker 102 does not leak to the first sound sensor module 103), h3=0, and when substituted into equation (5), the following equation is obtained:

[0094]

number

[0095] Usually, the noise reduction goal of active noise reduction technology is to minimize S4. As can be seen from equation (6), under ideal conditions, h5 needs to compensate for h1, h7 and h8. In this case, the first sound sensor module may be called an ideal feedforward sound sensor module, and the feedforward filter may be called an ideal feedforward filter.

[0096] However, in non-ideal cases, especially when the first sound sensor module 103 in an open-type acoustic device is not located at the acoustic zero point of the speaker 102, h3≠0, so the noise reduction circuit 105 can measure the transfer function h3' between the speaker 102 and the first sound sensor module 103 through an internal model control method, where h3'≒h3. In this application, the transfer function h3' is obtained by measurement and may have some error from the actual transfer function h3, so this transfer function h3' is also called the actual transfer function. In the process of feedforward noise reduction, the noise reduction circuit 105 can use h3' to correct the first sound signal to obtain a pseudo ambient noise signal. Furthermore, the noise reduction circuit 105 can use an ideal feedforward filter to filter the pseudo ambient noise signal to obtain a first noise cancellation signal.

[0097] In some embodiments, h3' can be measured in the following manner: the noise reduction circuit 105 transmits a test audio signal to the speaker 102, so that the speaker 102 emits a corresponding test audio, and the test audio is collected by the first sound sensor module 103. The noise reduction circuit 105 obtains the audio signal collected by the first sound sensor module 103, and determines a transfer function h3' according to the test audio signal and the collected audio signal. For example, assuming that the test audio signal is Y1 and the collected audio signal is Y2, h3'=Y2 / Y1. Thus, the noise reduction circuit 105 can measure h3' by controlling the speaker 102 to transmit the test audio signal. The method of measuring the transfer function h3' in this manner is simple and does not affect the noise reduction performance of the noise reduction circuit 105.

[0098] In some embodiments, h3 is generally related to the wearing position and orientation of the acoustic device 100, and when the same acoustic device 100 is worn by a different user, the corresponding h3 may be different. Also, when the same acoustic device is worn by the same user multiple times, the corresponding h3 may be different. Therefore, the noise reduction circuit 105 can improve the accuracy of h3' by performing the above measurement process when it detects that the acoustic device 100 is turned on or the user wears the acoustic device 100.

[0099] In some embodiments, after the noise reduction circuit 105 measures h3', it can generate a pseudo ambient noise signal in the following manner: The noise reduction circuit 105 obtains an input signal (i.e., S3) corresponding to the speaker 102, and provides a first gain to the input signal (S3) to obtain a first gain signal, where the first gain is h3'. In this way, the first gain signal is S3*h3'. Furthermore, the noise reduction circuit 105 obtains a first audio signal (i.e., S1=S0*h1+S3*h3) from the first audio sensor module 103, and subtracts the first gain signal from the first audio signal to obtain a pseudo ambient noise signal. Here, the pseudo ambient noise signal can be expressed as h3'=S0*h1+S3*h3-S3*h3'.

[0100] S13: Generate a first noise-canceled signal based on the pseudo-ambient noise signal.

[0101] In some embodiments, still referring to FIG. 5, the noise reduction circuit 105 inputs the simulated ambient noise signal S1' to a feedforward filter (h5), and filters the simulated ambient noise signal S1' to obtain a first noise-canceled signal. Here, the feedforward filter is configured to adjust at least one of the gain or phase of the simulated ambient noise signal S1' so that the obtained first noise-canceled signal can cancel out at least a part of the ambient noise of the eardrum 202 and / or the space around it. It should be understood that the feedforward filter may be an ideal feedforward filter, i.e., the ideal amplitude and phase response of the ideal feedforward filter may be designed based on Equation (6).

[0102] S14: Send the first noise cancellation signal to a speaker, such that the speaker converts the first noise cancellation signal into a first noise cancellation audio to reduce the volume of the environmental noise at the eardrum.

[0103] As mentioned above, the noise reduction circuit 105 is communicatively connected with the speaker 102. After generating the first noise cancellation signal, the noise reduction circuit 105 can transmit the first noise cancellation signal to the speaker 102. In this manner, the speaker 102 plays a first noise cancellation audio corresponding to the first noise cancellation signal, so that the first noise cancellation audio cancels or partially cancels the environmental noise at the eardrum 202, thereby achieving the purpose of noise reduction.

[0104] FIG. 6 shows a schematic diagram of the noise reduction effect of the active noise reduction method provided according to the embodiment of the present specification. As shown in FIG. 6, the curves 601 and 602 respectively correspond to the noise reduction results of two test scenarios. Here, the test process corresponding to the curve 601 is as follows: The noise reduction circuit 105 acquires a first audio signal collected by the FF1 (located at the acoustic zero point position of the speaker 102) shown in FIG. 3, and the first audio signal does not contain or contains little leakage signal from the speaker 102). The noise reduction circuit 105 uses an ideal feedforward filter to perform feedforward noise reduction based on the first audio signal, and obtains the noise reduction result shown in the curve 601. The test process corresponding to the curve 602 is as follows: The noise reduction circuit 105 acquires a first audio signal collected by the FF3 (located not at the acoustic zero point of the speaker 102 or located at a position other than the zero point) shown in FIG. 3, and the first audio signal contains leakage signal from the speaker 102. The noise reduction circuit 105 uses the active noise reduction method shown in Fig. 4, firstly reduces the leakage signal component in the first audio signal to obtain a pseudo-ambient noise signal, and then uses an ideal feedforward filter to perform feedforward noise reduction based on the pseudo-ambient noise signal. As can be seen from Fig. 6, the two noise reduction results of curve 601 and curve 602 are almost consistent. This shows that the noise reduction circuit 105 can effectively improve the noise reduction effect of the open-type acoustic device by reducing the leakage signal component in the first audio signal to obtain a pseudo-ambient noise signal, and then generate a first noise cancellation signal based on the pseudo-ambient noise signal.

[0105] In the active noise reduction method P100 shown in FIG. 4, after the noise reduction circuit 105 obtains the first audio signal from the first audio sensor module, it first reduces the leakage signal component from the first audio signal to generate a pseudo-ambient noise signal, and then performs feedforward noise reduction based on the pseudo-ambient noise signal to generate a first noise-canceled signal. In some embodiments, the noise reduction circuit 105 can perform the reduction step and the feedforward noise reduction step inversely. Specifically, after the noise reduction circuit 105 obtains the first audio signal from the first audio sensor module (S1), it first applies feedforward noise reduction (h5) to the first audio signal to generate an intermediate noise-canceled signal (S1*h5). Since the first audio signal includes the ambient noise signal and the leakage signal, when the noise reduction circuit 105 applies feedforward noise reduction to the first audio signal, feedforward noise reduction is performed on both the ambient noise signal and the leakage signal. As a result, the obtained intermediate noise-canceled signal (S1*h5) contains both the feedforward noise reduction result of the environmental noise signal and the feedforward noise reduction result of the leakage signal. Here, the feedforward noise reduction result of the leakage signal can be estimated in the following manner. An input signal (S3) corresponding to a speaker is obtained, and a first gain (h3') is applied to the input signal to obtain a first gain signal (S3*h3'), and it should be understood that the first gain signal S3*h3' can be regarded as an estimate of the leakage signal. The first gain signal (S3*h3') is filtered based on the feedforward noise reduction parameter (h5) to obtain a filtering result of the leakage signal S3*h3'*h5. Furthermore, the noise reduction circuit 105 subtracts the feedforward noise reduction result of the leakage signal (S3*h3'*h5) from the intermediate noise-canceled signal (S1*h5) to obtain a first noise-canceled signal (S1*h5-S3*h3'*h5). It should be noted that in the above method, h3' is the transfer function between the speaker and the first sound sensor module, and the measurement method thereof can be referred to the relevant content description above, so it will not be described in detail here.

[0106] To sum up, in the active noise reduction method P100 provided herein, when the first audio signal contains both the ambient noise signal and the leakage signal, the noise reduction circuit 105 first reduces the component of the leakage signal in the first audio signal to generate a pseudo-ambient noise signal, then generates a first noise cancellation signal based on the pseudo-ambient noise signal, and then converts the first noise cancellation signal into a first noise cancellation audio through a speaker, thereby achieving the purpose of noise reduction. Since the noise reduction circuit 105 reduces the component of the leakage signal in the first audio signal during the feedforward noise reduction process and reduces the impact of the leakage signal on the feedforward noise reduction, the noise reduction effect of the active noise reduction can be improved.

[0107] Typically, the noise reduction circuit 105 should design / adjust the noise reduction parameters of the noise reduction circuit 105 with the goal of "minimizing the environmental noise (S4) at the eardrum 202". In a closed acoustic device, the second audio signal (S2) collected by the second audio sensor module 104 is equal to or approximately equal to the environmental noise (S4) at the eardrum 202. Therefore, in a closed acoustic device, the goal of noise reduction can be "minimizing the second audio signal (S2)". However, in an open acoustic device, an open space is formed between the speaker 102 and the eardrum 202, so the second audio signal (S2) measured by the second audio sensor module 104 and the environmental noise (S4) at the eardrum 202 are no longer equal to or approximately equal to each other.

[0108] In the study of this application, the reason why S2 and S4 are not equal or approximately equal is as follows: Referring to the acoustic transmission process shown in Figure 5, the second sound signal (S2) measured by the second sound sensor module 104 may be expressed by Equation (3), and the environmental noise (S4) at the eardrum 202 may be expressed by Equation (0), as follows:

[0109]

number

[0110] From the above formula (3) and formula (0), it can be seen that both S2 and S4 can be regarded as a mixture signal of two audio signals. Here, the first audio signal is the noise cancellation signal (S3) emitted from the speaker 102, and the second audio signal is the environmental noise signal (S0) emitted from the noise source 300. For the second audio signal, in the noise reduction target frequency band, the transfer function (h2) between the sound emitted from the noise source 300 and the audio signal measured by the second audio sensor module 104 is usually equal or approximately equal to the transfer function (h8) between the sound emitted from the noise source 300 and the eardrum 202, i.e., h2≒h8, so that the components of the second audio signal in S2 and S4 are approximately equal, and the difference between S2 and S4 is caused by the difference between the component of the noise cancellation signal in S2 (S3*h4) and the component of the noise cancellation signal in S4 (S3*h7).

[0111] In a closed acoustic device, the transfer function (h4) between the sound emitted from the speaker 102 and the audio signal measured by the second sound sensor module 104 and the transfer function (h7) between the sound emitted from the speaker 102 and the eardrum 202 are equal or approximately equal, i.e., h4 ≈ h7, and therefore, S2 obtained based on the formula (3) and S4 obtained based on the formula (0) are equal or approximately equal. However, in an open acoustic device, the transfer function (h4) between the sound emitted from the speaker 102 and the audio signal measured by the second sound sensor module 104 and the transfer function (h7) between the sound emitted from the speaker 102 and the eardrum 202 are not equal or approximately equal, and therefore, S2 obtained based on the formula (3) and S4 obtained based on the formula (0) are no longer equal or approximately equal. It will be understood that in open-type sound equipment, S2 and S4 are no longer equal or nearly equal, so if the goal of noise reduction is still to "minimize S2," the noise reduction effect will be worsened.

[0112] In order to solve the above technical problems, the inventor of the present invention proposed the following technical idea during research: By specially designing the structure of the acoustic device 100 and the position of each component, S4 and S2 are not equal, but S4 can be estimated based on S2 (i.e., S4 and S2 have the same variation tendency). This makes it possible to estimate S4 based on S2 and perform active noise reduction with the minimization of S4 as the noise reduction goal, and further, derive the noise reduction parameters required for "minimizing S4 as the noise reduction goal" based on the noise reduction parameters required for "minimizing S2 as the noise reduction goal", thereby improving the effect of active noise reduction.

[0113] Based on the above analysis, the difference between S4 and S2 is due to the difference between the noise-canceled signal component (S3*h4) in S2 and the noise-canceled signal component (S3*h7) in S4. To realize the estimation of S4 based on S2, it is usually necessary to grasp both h4 and h7 individually. However, as discovered in the inventor's research, both h7 and h4 are quantities that are strongly dependent on the posture of the acoustic device 100, that is, when different users wear the acoustic device, h4 is different and h7 is also different, and even when the same user wears the acoustic device multiple times, h4 is different and h7 is also different. Moreover, in actual usage scenes, since there is no sound sensor on the eardrum 202, it is difficult to measure h7, which makes it difficult to estimate S4. As a result of further research, the inventors have found that although both h4 and h7 are strongly dependent on the wearing posture of the acoustic device 100, by designing the positions of the second sound sensor module 104 and the speaker 102, h4 and h7 satisfy a first predetermined relationship, and this predetermined relationship does not depend on the wearing posture of the acoustic device 100. Here, the fact that the first predetermined relationship does not depend on the wearing posture of the acoustic device 100 means that h4 and h7 always satisfy the predetermined relationship regardless of the posture in which the acoustic device 100 is worn by the user. For example, when the acoustic device 100 is worn by different users, h4 and h7 always satisfy the predetermined relationship. Also, for example, when the same user wears the acoustic device 100 multiple times, h4 and h7 always satisfy the predetermined relationship.

[0114] The specific form of the first predetermined relationship is not limited in the present application. In the design stage of the audio device 100, the first predetermined relationship between h4 and h7 can be derived by testing a large number of users and the process of wearing the audio device multiple times. In some embodiments, the first predetermined relationship may be h7 / h4=h9. It should be explained that the value of h9 is not limited in the present application. It should be understood that if h4 and h7 satisfy the first predetermined relationship, the following relationship may be established between S2 and S4, and the component of the noise cancellation signal at S4 (S3*h7) and the component of the noise cancellation signal at S2 (S3*h4) have the relationship ((S3*h7)) / ((S3*h4))=h9, or the intensity of the component of the noise cancellation signal at S2 (S3*h4) is x dB lower than the component of the noise cancellation signal at S4 (S3*h7), where the value of x may be 1, 2, or any other value. It should be noted that the present application does not limit the specific positions of the second sound sensor module 104 and the speaker 102, and it is sufficient that the positions of the two satisfy the first predetermined relationship between h4 and h7, and that the first predetermined relationship does not depend on the wearing posture of the acoustic device 100. In some embodiments, the speaker 102 may be disposed near the entrance of the ear canal, and the sound output surface (i.e., the surface on which the sound output end is located) faces the entrance of the ear canal. For example, depending on the shape and mass distribution of the acoustic device 100, a certain position of the acoustic device 100 is close to the entrance of the ear canal, regardless of the posture in which the acoustic device 100 is worn, so the speaker 102 can be disposed at that position. The second sound sensor module 104 can be disposed on the sound output surface of the speaker 102. Furthermore, when designing the specific position of the second sound sensor module 104 on the sound output surface, the following principles can be taken into consideration: (1) the sound collecting end of the second sound sensor module 104 is away from the user's skin, and (2) the sound collecting end of the second sound sensor module 104 is as close to the entrance of the ear canal as possible. It should be understood that if the positions of the speaker 102 and the second sound sensor module 104 are determined in the above manner, h4 and h7 are less susceptible to the influence of the wearing posture, that is, no matter in what posture the acoustic device 100 is worn, h4 and h7 always satisfy the same first predetermined relationship.In addition, by determining the positions of the speaker 102 and the second audio sensor module 104 in the above manner, the second audio signal S2 collected by the second audio sensor module 104 is close to the environmental noise S4 at the eardrum 202, and the second audio signal S2 is less affected by skin reflection, thus making the S4 estimated based on the first predetermined relationship and the second audio signal S2 more accurate.

[0115] In the case where h4 and h7 satisfy a first predetermined relationship and the first predetermined relationship does not depend on the wearing posture of the acoustic device 100, the present application provides an active noise reduction method P200, which can adjust noise reduction parameters based on the second sound signal (S2) and the first predetermined relationship no matter in what posture the acoustic device 100 is worn by the user, thereby improving the effect of active noise reduction. The active noise reduction method P200 can be applied independently to the acoustic device 100 provided by the present application, or can be applied in combination with other active noise reduction methods described elsewhere in this specification.

[0116] 7 shows a flowchart of another active noise reduction method P200 provided according to an embodiment of the present specification. The active noise reduction method P200 can be executed by the noise reduction circuit 105 in the acoustic device 100. For example, the processor 107 in the noise reduction circuit 105 can read an instruction set stored in its local storage medium, and execute the active noise reduction method P200 described herein according to the instructions of the instruction set. As shown in FIG. 7, the active noise reduction method P200 includes the following steps: S21: Obtaining a second audio signal from a second audio sensor module; S22. Adjusting a noise reduction parameter of the noise reduction circuit based on the second audio signal and the first predetermined relationship. In some embodiments, the noise reduction circuit 105 can determine the environmental noise (S4) at the eardrum 202 based on the second audio signal (S2) and the first predetermined relationship. Further, the noise reduction circuit 105 adjusts the noise reduction parameters with the goal of minimizing the environmental noise (S4) at the eardrum 202.

[0117] In some embodiments, the noise reduction circuit 105 can estimate S4 in the following manner: (1) A first transfer function h4' between the sound emitted from the speaker 102 and the audio signal measured by the second sound sensor module 104 is measured.

[0118] In some embodiments, the following method can be used to measure h4': the noise reduction circuit 105 transmits a test audio signal to the speaker 102, so that the speaker 102 emits a corresponding test audio, and the test audio is collected by the second sound sensor module 104. The noise reduction circuit 105 obtains the collected audio signal collected by the second sound sensor module 104, and determines a first transfer function h4' according to the test audio signal and the collected audio signal. For example, if the test audio signal is Y1 and the collected audio signal is Y2, then h4'=Y2 / Y1. It has been found that the noise reduction circuit 105 can measure h4' by controlling the speaker 102 to transmit the test audio signal. Such a method of measuring h4' is simple and does not affect the noise reduction performance of the noise reduction circuit 105. In some embodiments, it is considered that h4 is usually related to the wearing posture of the acoustic device 100, and when the same acoustic device 100 is worn by a different user, the corresponding h4 may be different, and when the same acoustic device is worn by the same user multiple times, the corresponding h4 may be different. Therefore, the noise reduction circuit 105 can improve the accuracy of h4' by performing the above measurement process when detecting that the acoustic device 100 is turned on or worn by a user.

[0119] (2) determining an environmental noise at the eardrum based on the first transfer function, the first predetermined relationship, and the second audio signal;

[0120] Specifically, a second transfer function h7' between the sound emitted from the speaker 102 and the eardrum 202 can be determined based on the first transfer function h4' and the first predetermined relationship.

[0121] For example, assuming that the first predetermined relationship is h7 / h4=h9, a second transfer function h7'=h4'*h9 can be obtained based on the first transfer function h4' and the first predetermined relationship.

[0122] Furthermore, S4 can be determined based on the first transfer function h4', the second transfer function h7' and S2, specifically as follows: First, based on equation (3), we can derive the following:

[0123]

number

[0124] Based on the above analysis, the ambient noise component S0*h2 in S2 and the ambient noise component S0*h8 in S4 are approximately equal, i.e.

[0125]

number

[0126] Substituting equation (13) into equation (0), we obtain the following equation:

[0127]

number

[0128] In equation (14), S3 is the input signal of the speaker 102, h4 can be replaced by the first transfer function h4', h7 can be replaced by the second transfer function h7', and S2 is the second audio signal collected by the second audio sensor module 104. As can be seen from the above, the noise reduction circuit 105 can estimate S4 based on the first transfer function h4', the second transfer function h7', the second audio signal S2, and the input signal S3 of the speaker 102.

[0129] In the above-mentioned active noise reduction process, first, the environmental noise (S4) at the eardrum 202 is determined based on the second audio signal (S2) and the first predetermined relationship, and then the noise reduction goal is to minimize the environmental noise (S4) at the eardrum 202. By improving the accuracy of the noise reduction goal, the effect of active noise reduction can be improved.

[0130] In the above embodiment, the transfer function (h2) between the sound emitted from the noise source 300 and the audio signal measured by the second sound sensor module 104 and the transfer function (h8) between the sound emitted from the noise source 300 and the eardrum 202 are approximately equal, that is, h2 ≈ h8. The inventors have noticed that in actual application scenarios, h2 and h8 are usually not strictly equal, and therefore S4 determined in the above embodiment has some error. Therefore, in order to further improve the accuracy of S4, h2 and h8 may also be considered in the process of calculating S4. However, h2 and h8 are also values ​​that depend on the wearing posture of the acoustic device 100, and when different users wear the acoustic device, h2 and h8 are different, and when the same user wears the acoustic device multiple times, h2 and h8 are different. For this reason, it is difficult to measure h2 and h8 individually. Further research by the inventor has revealed that when designing the positions of the second sound sensor module 104 and the speaker 102, in addition to making h4 and h7 satisfy the first predetermined relationship, h2 and h8 may also satisfy a second predetermined relationship, and the second predetermined relationship is also independent of the wearing posture of the acoustic device 100. Here, the fact that the second predetermined relationship is independent of the wearing posture of the acoustic device 100 means that h2 and h8 always satisfy the second predetermined relationship regardless of the posture in which the acoustic device 100 is worn by the user. For example, when the acoustic device 100 is worn by different users, h2 and h8 always satisfy the second predetermined relationship. Also, for example, when the acoustic device 100 is worn by the same user multiple times, h2 and h8 always satisfy the second predetermined relationship.

[0131] The present application does not limit the specific form of the second predetermined relationship. In the design stage of the audio device 100, the relationship between h2 / h1 and h2 / h1 can be obtained by testing a large number of users and the process of wearing the audio device multiple times, and the second predetermined relationship between h2 and h8 can be derived based on the relationship. In some embodiments, the second predetermined relationship may be h8 / h2=h10. It should be noted that the present application does not particularly limit the value of h10. It should be understood that when h2 and h8 satisfy a second predetermined relationship, the following relationship may be established between S2 and S4: the relationship between the component of the ambient noise signal at S4 (S0*h8) and the component of the ambient noise signal at S2 (S0*h2) is ((S0*h8)) / ((S0*h2))=h10; or the intensity of the component of the ambient noise signal at S2 (S0*h2) is ydB lower than the component of the ambient noise signal at S4 (S0*h8), where the value of y may be 1, 2, or any other numerical value.

[0132] In some embodiments, when h4 and h7 satisfy a first predetermined relationship, h2 and h8 satisfy a second predetermined relationship, and both the first predetermined relationship and the second predetermined relationship do not depend on the posture of the acoustic device 100, S4 can be estimated based on the first predetermined relationship, the second predetermined relationship, and S2. A specific method is as follows.

[0133] (1) Measure a first transfer function h4' between the sound emitted from the speaker 102 and the audio signal measured by the second audio sensor module 104, where the measurement process of the first transfer function h4' can be referred to the description of the related content above, and will not be described in detail here.

[0134] (2) determining an environmental noise at the eardrum based on the first transfer function, the first predetermined relationship, the second predetermined relationship, and the second audio signal;

[0135] Specifically, based on the first transfer function h4' and the first predetermined relationship, a second transfer function h7' between the sound emitted from the speaker 102 and the eardrum 202 can be determined. Here, the process of determining the second transfer function h7' can be referred to the above related content, and therefore will not be described in detail here.

[0136] Furthermore, S4 can be determined based on the second predetermined relationship, the first transfer function h4', the second transfer function h4' and S2, specifically as follows:

[0137] First, based on equation (3), the following equation is obtained:

[0138]

number

[0139] Based on the second predetermined relationship, the following formula is obtained:

[0140]

number

[0141] Substituting equation (15) into equation (0), we obtain the following equation:

[0142]

number

[0143] In equation (16), S3 is the input signal of the speaker 102, h4 can be replaced by the first transfer function h4', h7 can be replaced by the second transfer function h7', S2 is the second audio signal collected by the second audio sensor module 104, and h10 is obtained based on the second predetermined relationship. Therefore, S4 can be determined based on the first transfer function h4', the second transfer function h7', the second predetermined relationship, the second audio signal S2, and the input signal S3 of the speaker 102.

[0144] After estimating S4, the noise reduction parameters of the noise reduction circuit 105 can be adjusted to minimize S4 as a noise reduction goal. In some embodiments, the noise reduction circuit 105 may include a feedforward filter, in which case the noise reduction parameters may include filter parameters of the feedforward filter. In some embodiments, the noise reduction circuit 105 may include a feedback filter, in which case the noise reduction parameters may include filter parameters of the feedback filter. In some embodiments, the noise reduction circuit 105 may include a feedforward filter and a feedback filter, in which case the noise reduction parameters may include at least one of the filter parameters of the feedforward filter or the filter parameters of the feedback filter.

[0145] In some embodiments, the filter parameters of the feedforward filter or the feedback filter may include at least one of a filter gain, a filter phase, or a quality factor, where the quality factor can be expressed as the ratio of the filter's center frequency F (unit: Hz) to the -3 dB bandwidth B (unit: Hz), i.e., quality factor Q=F / B, which describes the filter's ability to separate adjacent frequency components. A higher quality factor means a higher resolution of the filter to adjacent frequency components.

[0146] In some embodiments, the noise reduction parameters of the noise reduction circuit 105 may include a filter gain of a feedforward filter. In this case, for ease of explanation, the filter gain of the feedforward filter required when "minimizing the second audio signal (S2) is the target of noise reduction" is called the first filter gain, and the filter gain of the feedforward filter required when "minimizing the environmental noise (S4) at the eardrum 202 is the target of noise reduction" is called the second filter gain. If the following is satisfied, there is a specific relationship between the signal strengths of S2 and S4, for example, the signal strength of S2 is x dB lower than the signal strength of S4. In this case, the first filter gain and the second filter gain also satisfy such a relationship.

[0147] For example, Fig. 8A shows a schematic diagram of a frequency response curve for feedforward noise reduction of the environmental noise at the eardrum using different feedforward filter gains when a first user wears an acoustic device. Fig. 8B shows a schematic diagram of a frequency response curve for feedforward noise reduction of the second audio signal using different feedforward filter gains when a first user wears an acoustic device. Here, assume that the intensity of the second audio signal (S2) is 2 dB lower than the intensity of the environmental noise (S4) at the eardrum 202 when h4 and h7 satisfy a first predetermined relationship.

[0148] 8A and 8B, when the audio device 100 is worn by a first user, the feedforward filter of the noise reduction circuit 105 performs active noise reduction using different filter gains (increasing from 0 dB to 4 dB in sequence). The frequency response curves of the feedforward noise reduction based on the environmental noise (S4) at the eardrum 202 with different filter gains are shown in FIG. 8A. The frequency response curves of the feedforward noise reduction based on the second audio signal (S2) with different filter gains are shown in FIG. 8B. As can be seen from FIG. 8A, when the noise reduction goal is to minimize the environmental noise (S4) at the eardrum 202, the second filter gain required for the feedforward filter is 4 dB. As can be seen from FIG. 8B, when the noise reduction goal is to minimize the second audio signal (S2), the first filter gain required for the feedforward filter is 2 dB.

[0149] 9A shows a schematic diagram of a frequency response curve for feedforward noise reduction of the environmental noise at the eardrum using different feedforward filter gains when a second user wears an acoustic device. FIG. 9B shows a schematic diagram of a frequency response curve for feedforward noise reduction of the second audio signal using different feedforward filter gains when a user B wears an acoustic device. Here, it is assumed that when h4 and h7 satisfy a first predetermined relationship, the intensity of the second audio signal (S2) is 2 dB lower than the intensity of the environmental noise (S4) at the eardrum 202.

[0150] 9A and 9B, when the acoustic device 100 is worn by a second user, the feedforward filter in the noise reduction circuit 105 performs active noise reduction using different filter gains (increasing from 0 dB to 4 dB in sequence). The frequency response curves of the feedforward noise reduction based on the environmental noise (S4) at the eardrum 202 with different filter gains are shown in FIG. 9A. The frequency response curves of the feedforward noise reduction based on the second audio signal (S2) with different filter gains are shown in FIG. 9B. As can be seen from FIG. 9A, when the noise reduction goal is to minimize the environmental noise (S4) at the eardrum 202, the second filter gain required for the feedforward filter is 3 dB. As can be seen from FIG. 9B, when the noise reduction goal is to minimize the second audio signal (S2), the first filter gain required for the feedforward filter is 1 dB.

[0151] 8A to 9B, the "relationship between the first filter gain and the second filter gain" is the same as the "relationship between the intensity of the second audio signal (S2) and the intensity of the environmental noise (S4) at the eardrum 202." In other words, when the intensity of the second audio signal (S2) is x dB lower than the intensity of the environmental noise (S4) at the eardrum 202, the first filter gain is x dB lower than the second filter gain.

[0152] Therefore, the noise reduction circuit 105 can further adjust the filter gain of the feedforward filter in the following manner: first, the noise reduction target is to minimize the second audio signal (S2), and a first filter gain of the feedforward filter is determined. Then, the noise reduction circuit 105 determines the second filter gain based on the first filter gain and the first predetermined relationship, and adjusts the current filter gain of the feedforward filter to the second filter gain. For example, assume that the intensity of the second audio signal (S2) is 2 dB lower than the intensity of the environmental noise (S4) at the eardrum 202 according to the first predetermined relationship. The noise reduction circuit 105 first sets the noise reduction target to minimize the second audio signal (S2), and determines the first filter gain as 2 dB. Then, the noise reduction circuit 105 can add 2 dB to the first filter gain to obtain the second filter gain as 4 dB. Thus, the current filter gain of the feedforward filter is adjusted to 4 dB.

[0153] In some embodiments, the audio device 100 can provide a user with multiple operation modes, and in each operation mode, the noise reduction circuit 105 has default noise reduction parameters, and different operation modes correspond to different default noise reduction parameters. In some embodiments, the audio device 100 can be provided with an interactive control, and the user can operate the interactive control to switch to different operation modes. In some embodiments, the audio device 100 can provide an interactive interface, and the interface can be displayed on a screen of the audio device 100 or on a target device that is communicatively connected to the audio device 100. The user can select different operation modes through the interactive interface. In some embodiments, the above-mentioned multiple operation modes correspond to different environment types. The user can indicate the current environment type to the audio device 100 in an interactive manner, and the noise reduction circuit 105 can switch to the corresponding operation mode based on the current environment type. In some embodiments, the above-mentioned multiple operation modes correspond to different user types. The user can indicate the user type to the audio device 100 in an interactive manner, and the noise reduction circuit 105 can switch to the corresponding operation mode based on the user type to which the user belongs.

[0154] In this way, in S22, the noise reduction circuit 105 can obtain a target operation mode designated by the user among the multiple operation modes, and adjust default noise reduction parameters corresponding to the target operation mode based on the second audio signal (S2) and the first predetermined relationship. It should be understood that the acoustic device 100 can meet the noise reduction needs of different users or different environments by providing multiple operation modes.

[0155] S23: Perform active noise reduction based on the adjusted noise reduction parameters.

[0156] In some embodiments, the noise reduction circuit 105 can further obtain a first audio signal from a first audio sensor module, and filter at least one of the first audio signal or the second audio signal based on the adjusted noise reduction parameters to generate a noise cancellation signal. Furthermore, the noise reduction circuit 105 can transmit the noise cancellation signal to a speaker, which converts the noise cancellation signal into a noise cancellation audio to reduce the volume of the environmental noise at the eardrum.

[0157] In some embodiments, when the audio device 100 operates in the feed-forward noise reduction mode, the noise reduction circuit 105 can filter the first audio signal based on the adjusted noise reduction parameters to generate a noise-canceled signal. For example, the noise reduction circuit 105 can input the first audio signal into a feed-forward filter and filter the first audio signal by the feed-forward filter to obtain a noise-canceled signal. In some embodiments, when the first audio signal includes both an environmental noise signal and a leakage signal, the noise reduction circuit 105 can first reduce the component of the leakage signal in the first audio signal to generate a pseudo-environmental noise signal, and then filter the pseudo-environmental noise signal based on the adjusted noise reduction parameters to obtain a noise-canceled signal. On the one hand, the accuracy of the target of noise reduction is guaranteed when adjusting the noise reduction parameters, so that the effect of active noise reduction can be improved by performing active noise reduction based on the adjusted noise reduction parameters. On the other hand, by reducing the component of the leakage signal in the first audio signal, the influence of the leakage signal in the feed-forward noise reduction process can be reduced, and the effect of active noise reduction can be further improved.

[0158] In some embodiments, when the audio device 100 operates in a feedback noise reduction mode, the noise reduction circuit 105 may filter the second audio signal based on the adjusted noise reduction parameters to generate a noise-canceled signal. For example, the noise reduction circuit 105 may input the second audio signal to a feedback filter and filter the second audio signal by the feedback filter to obtain the noise-canceled signal.

[0159] In some embodiments, when the audio device 100 operates in the hybrid noise reduction mode, the noise reduction circuit 105 may filter the first audio signal based on the adjusted noise reduction parameters to obtain a first noise-cancelled signal. For example, the noise reduction circuit 105 may input the first audio signal to a feed-forward filter and filter the first audio signal by the feed-forward filter to obtain a first noise-cancelled signal. The noise reduction circuit 105 may further filter the second audio signal based on the adjusted noise reduction parameters to obtain a second noise-cancelled signal. For example, the noise reduction circuit 105 may input the second audio signal to a feedback filter and filter the second audio signal by the feedback filter to obtain a second noise-cancelled signal. Furthermore, the noise reduction circuit 105 may combine the first noise-cancelled signal and the second noise-cancelled signal to obtain a noise-cancelled signal. In some embodiments, when the first audio signal includes both the ambient noise signal and the leakage signal, the noise reduction circuit 105 can first reduce the component of the leakage signal in the first audio signal to generate a pseudo ambient noise signal, and then filter the pseudo ambient noise signal based on the adjusted noise reduction parameters to obtain a first noise-canceled signal. On the one hand, when adjusting the noise reduction parameters, the accuracy of the target of noise reduction is guaranteed, so that the effect of active noise reduction can be improved by performing active noise reduction based on the adjusted noise reduction parameters. On the other hand, reducing the component of the leakage signal in the first audio signal can reduce the influence of the leakage signal in the feed-forward noise reduction process, and further improve the effect of active noise reduction.

[0160] In summary, in the active noise reduction method P200 provided herein, the acoustic transfer function (h4) between the sound emitted from the speaker 102 and the audio signal collected by the second sound sensor module 104 and the acoustic transfer function (h7) between the sound emitted from the speaker 102 and the eardrum 202 satisfy a first predetermined relationship, and the first predetermined relationship does not depend on the wearing position of the acoustic device 100, so that the noise reduction circuit 105 can adjust the noise reduction parameters based on the second sound signal (S2) and the first predetermined relationship, and perform active noise reduction based on the adjusted noise reduction parameters. Since the noise reduction circuit 105 adjusts the noise reduction parameters based on the second sound signal (S2) and the first predetermined relationship, the adjusted noise reduction parameters are most consistent with the essential noise reduction goal, thereby improving the effect of active noise reduction.

[0161] As mentioned above, in some embodiments, the first sound sensor module 103 may include one sound sensor. In this case, since the environmental noise may arrive from any direction, a situation may occur in which the environmental noise has already reached the speaker 102 or the eardrum 202 before reaching the sound sensor. For example, assume that the sound sensor is installed on a first side (e.g., toward the front of the user) of the acoustic device 100, but the noise source 300 is located on a second side (e.g., toward the rear of the user) of the acoustic device 100, and since the sound sensor is far away from the noise source 300, the environmental noise emitted from the noise source 300 first reaches the speaker 102 or the eardrum 202 and is then collected by the sound sensor. In this way, the causality in the feedforward noise reduction of the noise reduction circuit 105 is deteriorated, which may result in a poor effect of the feedforward noise reduction, especially in those frequency bands (e.g., mid-high frequency bands), and may even result in an increase in the noise heard by the user.

[0162] Therefore, in some embodiments, the first sound sensor module 103 may include multiple sound sensors. For simplicity of explanation, the number of sound sensors included in the first sound sensor module 103 is set to N, where N is an integer equal to or greater than 2. The N sound sensors are each physically connected to the support member 102 and distributed on the side of the speaker 102 away from the eardrum. When leakage from the speaker 102 is not taken into consideration, each sound sensor is configured to collect environmental noise from the noise source 300 and generate an environmental noise signal. For the sake of distinction, hereinafter, the environmental noise signal collected by each sound sensor is referred to as an individual environmental noise signal, and the environmental noise signal collected by the first sound sensor module 103 is referred to as a total environmental noise signal.

[0163] The N audio sensors are disposed in different directions relative to a target point of the speaker 102. In some embodiments, the target point may be a center point or an audio output point of the speaker 102. Since the N audio sensors are disposed in different directions relative to the target point, when the environmental noise comes from different directions, at least one of the N audio sensors can collect the environmental noise before the speaker 102.

[0164] In some embodiments, N=2. FIG. 10 shows a schematic distribution diagram of each sound sensor when the first sound sensor module includes two sound sensors. As shown in FIG. 10, when N=2, the first sound sensor module 103 may include a sound sensor 1031 and a sound sensor 1032. Here, the two sound sensors may be located on two sides of the acoustic device 100 facing in opposite directions, or the two sound sensors have opposite directions with respect to the target point. For example, when the acoustic device 100 is worn on the user's head, the sound sensor 1031 is located on a first side of the acoustic device 100 facing the front of the user, and the sound sensor 1032 is located on a second side of the acoustic device 100 facing the rear of the user. In this way, when the environmental noise is generated from a noise source in front of the user, the phase at which the environmental noise arrives at the sound sensor 1031 (or the phase of the individual environmental noise signal measured by the sound sensor 1031) leads the phase at which the environmental noise arrives at the audio output end of the speaker 102. When the environmental noise is generated from a noise source behind the user, the phase in which the environmental noise arrives at the sound sensor 1032 (or the phase of the individual environmental noise signal measured by the sound sensor 1032) leads the phase in which the environmental noise arrives at the sound output end of the speaker 102. In some embodiments, the two sound sensors may be located at the acoustic zero point of the speaker 102. In this way, the signals collected by the two sound sensors do not include leakage signals from the speaker 102, thereby improving the active noise reduction effect.

[0165] In some embodiments, N=3. FIG. 11 shows a schematic distribution diagram of each sound sensor when the first sound sensor module includes three sound sensors. As shown in FIG. 11, when N=3, the first sound sensor module 103 may include a sound sensor 1031, a sound sensor 1032, and a sound sensor 1033. Here, the three sound sensors may be distributed on three sides of the acoustic device 100 facing different directions. For example, when the acoustic device 100 is worn on the user's head, the sound sensor 1031 is located on a first side of the acoustic device 100 facing the front of the user, the sound sensor 1032 is located on a second side of the acoustic device 100 facing the rear of the user, and the sound sensor 1033 is located on a third side of the acoustic device 100 facing the ground. In this way, when the environmental noise is generated from a noise source in front of the user, the phase in which the environmental noise arrives at the voice sensor 1031 (or the phase of the individual environmental noise signal measured by the voice sensor 1031) is ahead of the phase in which the environmental noise arrives at the audio output end of the speaker 102. When the environmental noise is generated from a noise source behind the user, the phase in which the environmental noise arrives at the voice sensor 1032 (or the phase of the individual environmental noise signal measured by the voice sensor 1032) is ahead of the phase in which the environmental noise arrives at the audio output end of the speaker 102. When the environmental noise is generated from a noise source below the acoustic device, the phase in which the environmental noise arrives at the voice sensor 1033 (or the phase of the individual environmental noise signal measured by the voice sensor 1033) is ahead of the phase in which the environmental noise arrives at the audio output end of the speaker 102. In some embodiments, the three voice sensors can be distributed at the acoustic zero points of the speaker 102 in a triangular shape. In this way, the signals collected by the three voice sensors do not include leakage signals from the speaker 102, thereby improving the active noise reduction effect.

[0166] It should be noted that the above Fig. 10 and Fig. 11 are only two possible arrangement methods. In actual design, N sound sensors can also adopt other distribution methods, which are not illustrated in this specification. In addition, the value of N is not particularly limited in this application, for example, the value of N can also be 4, 5, or any other integer.

[0167] In some embodiments, the N audio sensors may be arranged in an array, such as a linear array, a planar array, a spherical array, or other arrays, which is advantageous for reducing the signal processing complexity in the noise reduction circuit 105 and improving the active noise reduction performance.

[0168] At least some of the N sound sensors may be omnidirectional microphones. An omnidirectional microphone has high sensitivity to environmental noise from all directions and can collect environmental noise from any direction. At least some of the N sound sensors may also be directional microphones. A directional microphone can only collect environmental noise from a specific direction. For example, as shown in FIG. 10, the directionality of the sound sensor 1031 may be in front of the user and is configured to collect environmental noise coming from the front of the user, and the directionality of the sound sensor 1032 may be behind the user and is configured to collect environmental noise coming from the rear of the user. The directional microphones include, but are not limited to, cardioid directional microphones, supercardioid directional microphones, or other directional microphones. Here, the directional microphones may have the same or different directivities for different frequencies.

[0169] When the first sound sensor module 103 includes N sound sensors, the present application provides an active noise reduction method P300, in which the noise reduction circuit 105 can assign weights to the N sound sensors when performing active noise reduction, so that the first sound sensor module 103 has phase advantage in any direction. This method can enhance the causality of feedforward noise reduction and further improve the active noise reduction effect. The active noise reduction method P300 can be applied independently to the acoustic device 100 provided in the present application, and can also be combined with other active noise reduction methods described in other parts of this specification.

[0170] 12 shows a flowchart of another active noise reduction method P300 provided according to an embodiment of the present specification. The active noise reduction method P300 can be executed by the noise reduction circuit 105 in the acoustic device 100. For example, when the noise reduction circuit 105 adopts the structure shown in FIG. 2, the processor 107 in the noise reduction circuit 105 can read an instruction set recorded in its local storage medium, and execute the active noise reduction method P300 described in the present specification according to the instructions of the instruction set. As shown in FIG. 12, the active noise reduction method P300 may include:

[0171] S31: Determine the target direction from which the environmental noise comes.

[0172] Here, the target direction refers to the direction from which the environmental noise comes, i.e., the direction of the noise source 300. In some embodiments, the direction of a ray from a target point on the speaker 102 to the noise source 300 can be referred to as the target direction.

[0173] In some embodiments, the noise reduction circuit 105 can obtain N individual ambient noise signals collected by N sound sensors, and estimate a target direction from which ambient noise arrives based on the N individual ambient noise signals. In some embodiments, the noise reduction circuit 105 can obtain a target direction by performing a Direction Of Arrival (DOA) analysis of the N individual ambient noise signals over a full frequency band. In this case, the target direction represents the direction of arrival of ambient noise over a full frequency band (i.e., the entire ambient noise).

[0174] It should be noted that the present application does not have any particular limitations on the DOA algorithm, and may adopt, for example, one or more of the following algorithms: Estimating Signal Parameter via Rotational Invariance Techniques (ESPRIT) algorithm, Multiple Signal Classification (MUSIC) algorithm, etc.

[0175] S32: Based on the target direction, determine N weights corresponding to N sound sensors in a first sound sensor module, so that the phase of the total environmental noise signal of the first sound sensor module measured based on the N weights leads the phase of the environmental noise arriving at the sound output end of the speaker.

[0176] In some embodiments, the total environmental noise signal is a weighted sum of N individual environmental noise signals collected by N sound sensors based on N weights.

[0177] An example will be described with reference to FIG. 10. The first sound sensor module 103 includes a sound sensor 1031 and a sound sensor 1032. Here, the individual environmental noise signal collected by the sound sensor 1031 is:

[0178]

number

[0179] and the individual environmental noise signal collected by the sound sensor 1032 is

[0180]

number

[0181] It is.

[0182] Suppose the weight of the voice sensor 1031 is α1 , the weight of the sound sensor 1032 is α 2 Then, the total environmental noise signal measured based on the above two weights of the first sound sensor module 103 can be expressed as:

[0183]

number

[0184] The phase of the integrated ambient noise signal can be expressed as:

[0185]

number

[0186] As can be seen from the above, the noise reduction circuit 105 can set weights for each of the N audio sensors based on the target direction, so that the phase of the integrated noise signal is ahead of the phase at which the ambient noise arrives at the output of the speaker 102.

[0187] In some embodiments, the weight corresponding to the i-th sound sensor is related to the degree of leading of the phase of the individual environmental noise signal collected by the i-th sound sensor. For example, the more the phase of the individual environmental noise signal collected by the i-th sound sensor leads the phase of the environmental noise arriving at the sound output end of the speaker 102, the larger the weight corresponding to the i-th sound sensor will be, and conversely, the smaller the weight corresponding to the i-th sound sensor will be, where i is any positive integer equal to or smaller than N.

[0188] In some embodiments, the angle between the direction of the i-th audio sensor relative to a target point on the speaker 102 and the target direction is defined as θ i Then, the weight corresponding to the i-th audio sensor is θ i In other words, θ i The smaller θ is (indicating that the deviation between the direction of the sound sensor and the target direction with respect to the target point is small), the larger the weight is, and iThe larger i is (indicating a larger deviation between the direction of the audio sensor relative to the target point and the target direction), the smaller the weight is, where i is any positive integer less than or equal to N.

[0189] Explained with reference to Fig. 10. Assuming that the environmental noise comes from the front of the user, the weight of the voice sensor 1031 is greater than the weight of the voice sensor 1032, and thus, when performing active noise reduction, the voice sensor 1031 mainly plays a major role, and the phase lead is guaranteed. Assuming that the environmental noise comes from the rear of the user, the weight of the voice sensor 1032 is greater than the weight of the voice sensor 1031, and thus, when performing active noise reduction, the voice sensor 1032 mainly plays a major role, and the phase lead is guaranteed.

[0190] S33: Generate a first noise-reduced signal based on the N individual environmental noise signals collected by the N sound sensors and the N weights.

[0191] In some embodiments, the noise reduction circuit 105 may include N feedforward filters, which correspond one-to-one to the N sound sensors, where the i-th feedforward filter is connected to the i-th sound sensor and the speaker 102 and configured to filter the individual environmental noise signal collected by the i-th sound sensor, where i is any positive integer less than or equal to N. That is, the N feedforward filters in the noise reduction circuit 105 are connected in parallel.

[0192] Since the N feedforward filters are connected in parallel, there is no increase in the filter order or delay during the active noise reduction process. In addition, the N parallel-connected feedforward filters can further increase the filter complexity, for example, the N feedforward filters are responsible for noise reduction in different frequency bands, thereby enhancing the feedforward noise reduction ability.

[0193] Fig. 13 shows a schematic diagram of the active noise reduction principle of another audio device provided according to an embodiment of the present specification. As shown in Fig. 13, assume that the first sound sensor module 103 includes a sound sensor 1031 and a sound sensor 1032, and the noise reduction circuit includes a feedforward filter h51 and a feedforward filter h52. Here, the feedforward filter h51 is connected to the sound sensor 1031 and the speaker 102, and the feedforward filter h52 is connected to the sound sensor 1032 and the speaker 102.

[0194] Continuing to refer to Figure 13, assume that: The transfer function between the sound emitted by the noise source 300 and the audio signal measured by the sound sensor 1031 is denoted as h11, The transfer function between the sound emitted by the noise source 300 and the audio signal measured by the sound sensor 1032 is denoted as h12, The acoustic transfer function between the sound emitted from the speaker 102 and the eardrum 202 is denoted as h7. The acoustic transfer function from the sound emitted from the noise source 300 to the eardrum 202 is denoted as h8.

[0195] The noise signal emitted by the noise source 300 is denoted as S0, the individual environmental noise signal collected by the sound sensor 1031 is denoted as S11, the individual environmental noise signal collected by the sound sensor 1032 is denoted as S12, the noise cancellation signal emitted by the speaker 102 is denoted as S3, and the noise signal received by the eardrum 202 is denoted as S4.

[0196] In the acoustic transmission process shown in FIG. 13, the following relationships exist among S0, S11, S12, S3, and S4:

[0197]

number

[0198] Substituting equations (8) and (9) into equation (7), we get:

[0199]

number

[0200] Substituting equation (10) into equation (0), we get:

[0201]

number

[0202] From equation (11), it can be seen that the feedforward noise reduction effect is determined by h51 and h52.

[0203] In some embodiments, when performing active noise reduction, the noise reduction circuit 105 adjusts the filter parameters of the feedforward filter h51 based on the weight of the sound sensor 1031, and filters the individual environmental noise signal S11 collected by the sound sensor 1031 through the adjusted feedforward filter h51 to generate an individual noise cancellation signal. The noise reduction circuit 105 further adjusts the filter parameters of the feedforward filter h52 based on the weight of the sound sensor 1032, and filters the individual environmental noise signal S12 collected by the sound sensor 1032 through the adjusted feedforward filter h52 to generate an individual noise cancellation signal. Furthermore, the noise reduction circuit 105 combines the two individual noise cancellation signals generated by the two feedforward filters to obtain a first noise cancellation signal.

[0204] In some embodiments, adjusting the filter parameters of the feedforward filter h51 or the feedforward filter h52, as described above, may include adjusting a filter gain of the feedforward filter h51 or the feedforward filter h52. For example, the weight of the sound sensor 1031 may be multiplied by the current filter gain of the feedforward filter h51 to obtain the adjusted filter gain of the feedforward filter h51. The weight of the sound sensor 1032 may be multiplied by the current filter gain of the feedforward filter h52 to obtain the adjusted filter gain of the feedforward filter h52.

[0205] It should be understood that the noise reduction circuit 105 adjusts the filter parameters of the N feedforward filters based on the N weights, so that during the active noise reduction process, the voice sensors with higher weights (voice sensors with larger phase lead) and their corresponding feedforward filters have a larger contribution to the overall noise reduction, and the voice sensors with lower weights (voice sensors with smaller phase lead) and their corresponding feedforward filters have a smaller contribution to the overall noise reduction, thereby improving the effect of the active noise reduction.

[0206] In some embodiments, the N voice sensors may be N directional microphones with different directivities. Continuing to refer to FIG. 13, assume that the directivity of the voice sensor 1031 is in front of the user, and the directivity of the voice sensor 1032 is behind the user. When environmental noise comes from in front of the user, due to the directivities of the two voice sensors, h11 becomes much larger than h12 (i.e., h11 >> h12). As can be seen from the above formula (11), in the process of active noise reduction, mainly the voice sensor 1031 is acting, so the first voice sensor module 103 has phase precedence, thereby improving the effect of active noise reduction. When environmental noise comes from behind the user, due to the directivities of the two voice sensors, h11 becomes much smaller than h12 (i.e., h11 << h12). As can be seen from the above formula (11), in the process of active noise reduction, mainly the voice sensor 1032 is acting, so the first voice sensor module 103 has phase precedence and can improve the effect of active noise reduction.

[0207] As can be seen from the above, when the N voice sensors have different directivities, due to the different directivities of the N voice sensors, the optimal voice sensor is automatically selected in the process of active noise reduction, and the phase precedence in each direction of the first voice sensor module can be realized without adjusting the filter parameters of the feedforward filter.

[0208] S34: Transmit the first noise cancellation signal to the speaker, so that the speaker converts the first noise cancellation signal into a first noise cancellation audio, thereby reducing the volume of the environmental noise on the eardrum.

[0209] It should be understood that the above S31 to S34 describe estimating the direction of arrival for the environmental noise of the entire frequency band, and performing active noise reduction of the entire frequency band based on the estimated target direction. In some embodiments, the noise reduction circuit 105 can also perform estimation by dividing into subbands when estimating the target direction. For example, the entire frequency band is divided into M subbands, and the environmental noise includes M subband noises corresponding to the M subbands. The noise reduction circuit 105 can estimate the direction of arrival of M subband noises for each subband. In this case, the target direction in S31 includes M directions of arrival corresponding to the M subbands. It should be understood that the present application does not particularly limit the method of dividing the M subbands. In some embodiments, the M subbands may include a low frequency band (e.g., 0 to 150 Hz), a mid frequency band (e.g., 150 to 500 Hz), and a high frequency band (e.g., 500 to 2000 Hz).

[0210] In some embodiments, the noise reduction circuit 105 can obtain N individual ambient noise signals collected by N sound sensors, and then estimate the arrival direction of the jth subband in the following manner: extract subband noise signals corresponding to the jth subband from the N individual ambient noise signals, respectively, obtain N subband noise signals corresponding to the jth subband, and perform DOA analysis on the N subband noise signals to obtain the arrival direction corresponding to the jth subband, where j is any positive integer equal to or less than M.

[0211] After obtaining M directions of arrival corresponding to M subbands, the noise reduction circuit 105 can perform active noise reduction for each subband individually. Specifically, for the jth subband, the noise reduction circuit 105 determines weights of N subbands corresponding to N voice sensors based on the directions of arrival corresponding to the jth subband, so that the phase of the composite subband noise signal measured by the first voice sensor module 103 based on the weights of the N subbands is ahead of the phase at which the environmental noise of the jth subband arrives at the audio output end of the speaker 102. Here, the composite subband noise signal is a signal obtained by weighted addition of the subband noise signals corresponding to the jth subband collected by the N voice sensors based on the weights of the N subbands. Furthermore, the noise reduction circuit 105 generates N individual subband noise reduction signals corresponding to the jth subband based on the subband noise signals corresponding to the jth subband collected by the N voice sensors and the weights of the N subbands. The noise reduction circuit sums the N individual subband noise-reduced signals to obtain a subband noise-reduced signal corresponding to the jth subband, where j is any positive integer equal to or less than M. The noise reduction circuit 105 performs the above process for each of the M subbands to obtain M subband noise-reduced signals corresponding to the M subbands. Furthermore, the noise reduction circuit 105 transmits the M subband noise-reduced signals to the speaker 102, so that the speaker 102 converts the M subband noise-reduced signals into noise-reduced audio to reduce the volume of the environmental noise at the eardrum 202.

[0212] It should be understood that the process of performing active noise reduction for each subband is similar to the process of performing active noise reduction for the entire frequency band described above, and will not be described in detail here. It should be described that each feedforward filter may include M filter units corresponding to M subbands, and when performing active noise reduction for the jth subband, the filter parameter corresponding to the jth filter unit in the feedforward filter can be adjusted according to the weight, for example, the filter gain corresponding to the jth filter unit.

[0213] FIG. 14 shows a schematic diagram of a set of frequency response curves provided according to an embodiment of the present specification. As shown in FIG. 14, curve 141 shows the frequency response when the acoustic device 100 uses a single sound sensor FF1 and a feedforward filter, curve 142 shows the frequency response when the acoustic device 100 uses a single sound sensor FF2 and a feedforward filter, and curve 143 shows the frequency response when the acoustic device 100 uses both the sound sensor FF1 and the sound sensor FF2 and uses two feedforward filters connected in parallel. According to the curves 141 and 142, it can be seen that the single sound sensor FF1 and the single sound sensor FF2 each have a noise reduction effect in a different frequency band. According to the curve 143, it can be seen that the combination of the sound sensor FF1 and the sound sensor FF2 can provide a noise reduction effect in a wider frequency band and can provide deeper noise reduction.

[0214] As described above, in an open-type acoustic device, the environmental noise signal collected by the sound sensor includes a leakage signal (i.e., a leakage signal from the speaker 102). The acoustic device 100 can reduce the leakage signal to some extent by installing multiple sound sensors in the first sound sensor module 103. FIG. 15 shows a schematic diagram of another set of frequency response curves provided in accordance with an embodiment of the present specification. As shown in FIG. 15, curve 153 shows the frequency response when the acoustic device 100 uses both sound sensor FF1 and sound sensor FF2 in combination with two feedforward filters connected in parallel to perform noise reduction. Here, curve 151 shows the frequency response of FF1 and its corresponding feedforward filter, and curve 152 shows the frequency response of FF2 and its corresponding feedforward filter. As can be seen from FIG. 15, when two sound sensors are used, the feedforward filter gain required for each sound sensor is obviously smaller than the feedforward filter gain required when using a single sound sensor to achieve the same filter effect. Reducing the feedforward filter gain reduces the leakage signal, thereby avoiding system instability due to leakage and increased noise issues experienced by some users wearing audio equipment.

[0215] To sum up, in the active noise reduction method P300 provided herein, when the first sound sensor module 103 includes N sound sensors, the noise reduction circuit 105 determines N weights corresponding to the N sound sensors according to the target direction of the environmental noise when performing active noise reduction, so that the phase of the composite environmental noise signal measured by the first sound sensor module 103 based on the N weights leads the phase of the environmental noise arriving at the sound output end of the speaker. Then, the noise reduction circuit 105 generates a first noise reduction signal based on the N individual environmental noise signals collected by the N sound sensors and the N weights, and sends the first noise reduction signal to the speaker 102. As can be seen from the above, by introducing N sound sensors and assigning weights to the N sound sensors, the method can ensure that the first sound sensor module 103 has a phase lead with respect to the sound output end of the speaker 102 no matter which direction the environmental noise comes from, thereby improving the causality of the feedforward noise reduction, and further improving the active noise reduction effect, especially the noise reduction performance at high frequencies. In addition, using multiple sound sensors can reduce the gain compared to using a single sound sensor, which reduces leakage of some frequency bands (e.g., high frequency bands) in an open environment, thereby avoiding the system instability problem caused by the leakage of the above frequency bands and the problem of increased noise caused when some users wear audio equipment. Furthermore, this method estimates the direction of arrival with subbands as granularity and performs active noise reduction for each subband, which helps to improve the noise reduction depth for each subband and further enhances the effect of active noise reduction.

[0216] Usually, after activating the active noise reduction function, the audio device 100 performs active noise reduction in the entire frequency band range based on pre-designed noise reduction parameters. However, in actual use, the external environment in which the audio device 100 is placed is diverse, and the above pre-designed noise reduction parameters may not be suitable for performing active noise reduction against noise in various external environments. For example, in some special external environments, the noise reduction effect of the audio device may be poor, or the speaker 102 may generate distortion.

[0217] To address this, the noise reduction circuit 105 can provide multiple noise reduction modes. In this way, during the active noise reduction process, the noise reduction circuit 105 can self-adaptively select a target noise reduction mode from multiple noise reduction modes based on the noise conditions of the external environment, and execute the target noise reduction mode. Here, self-adaptively selecting a target noise reduction mode means switching the noise reduction mode independently, flexibly, intelligently, or adaptively according to the noise conditions of the external environment. It should be understood that the above noise reduction mode switching process is automatically performed by the noise reduction circuit 105, and does not require manual operation by the user.

[0218] In some embodiments, the plurality of noise reduction modes includes at least one of a passive noise reduction mode, an anti-crackle noise reduction mode, a narrowband noise reduction mode, or a normal noise reduction mode.

[0219] In the passive noise reduction mode, the active noise reduction function of the audio device 100 is turned off.

[0220] In the normal noise reduction mode, the active noise reduction function of the audio device 100 is turned on, and the noise reduction circuit 105 performs active noise reduction in the entire frequency band range based on at least one of the first audio signal or the second audio signal using pre-designed noise reduction parameters.

[0221] In the narrowband noise reduction mode, the active noise reduction function of the acoustic device 100 is turned on. The active noise reduction process includes the noise reduction circuit 105 determining a target frequency band based on a first audio signal, and the energy concentration in the target frequency band exceeds a preset threshold. Here, the energy concentration in the target frequency band refers to the energy concentration of the noise signal in the target frequency band. In some embodiments, the bandwidth of the target frequency band is narrower than the preset bandwidth, so the target frequency band can be called a narrowband. Furthermore, the noise reduction circuit 105 can perform active noise reduction in the target frequency band (narrowband) based on at least one of the first audio signal or the second audio signal.

[0222] In some embodiments, after the noise reduction circuit 105 determines the target frequency band, the noise reduction circuit 105 can adjust the noise reduction parameters of the noise reduction circuit 105 based on the target frequency band. The adjusted noise reduction parameters can specify that active noise reduction is performed mainly on the target frequency band (e.g., the noise reduction depth of the target frequency band is deeper than other frequency bands), or the adjusted noise reduction parameters can specify that active noise reduction is performed only on the target frequency band and not on other bands. In some embodiments, the "adjusting the noise reduction parameters of the noise reduction circuit 105" may include converting a full-frequency band filter in the noise reduction circuit 105 into a narrow-band filter. In the above embodiment, the noise reduction parameters can be adjusted based on the target frequency band to increase the noise reduction depth in the target frequency band and improve the noise reduction effect in the target frequency band.

[0223] In the anti-crackle noise reduction mode, the active noise reduction function of the audio device 100 is turned on. The active noise reduction process includes the noise reduction circuit 105 generating a noise reduction signal based on at least one of the first audio signal or the second audio signal, and making the amplitude of the noise reduction signal fall within the amplitude range supported by the speaker 102. Furthermore, the noise reduction circuit 105 transmits the noise reduction signal to the speaker 102, so that the speaker 102 converts the noise reduction signal into noise-reduced audio to reduce the volume of the environmental noise at the eardrum 202. Here, the above amplitude range refers to the range of signal width supported when the speaker 102 can normally reproduce sound without broken sound. The above-mentioned crackle refers to a phenomenon in which sound is significantly distorted due to the vibration of the speaker's diaphragm exceeding its linear range. If the amplitude of the signal input to the speaker 102 exceeds the new width range, the speaker 102 generates crackle. If the amplitude of the signal input to the speaker 102 is within the new width range, the speaker 102 does not generate crackle. It should be understood that when generating the noise reduction signal, the noise reduction circuit 105 ensures that the amplitude of the noise reduction signal is within the amplitude range supported by the speaker 102, so as to avoid distortion of the speaker 102.

[0224] In some embodiments, the noise reduction circuit 105 can generate the noise reduction signal in the following manner to make the amplitude of the noise reduction signal fall within the amplitude range supported by the speaker 102, and the noise reduction circuit 105 filters at least one of the first audio signal or the second audio signal to obtain the candidate noise reduction signal. The above filtering process has been described in the relevant part above, and will not be described in detail here. Furthermore, the noise reduction circuit 105 modifies the amplitude of the candidate noise reduction signal based on the amplitude range, makes the modified amplitude fall within a predetermined range, and uses the modified signal as the noise reduction signal. In some embodiments, a dynamic range control (DRC) device may be installed at the output end of the noise reduction circuit 105 (i.e., the connection part between the noise reduction circuit 105 and the speaker 102). The dynamic range control device is configured to adjust the amplitude of the input signal and make the amplitude of the output signal fall within a predetermined range. In this case, after obtaining the candidate noise reduction signal, the noise reduction circuit 105 inputs the candidate noise reduction signal to a dynamic range controller, and modifies the amplitude of the noise reduction signal by the dynamic range controller to obtain the noise reduction signal.

[0225] In this way, the noise reduction circuit 105 does not need to change the existing noise reduction parameters, but only adds an amplitude correction stage as post-processing (eg, adds a dynamic range controller) to avoid distortion of the speaker 102.

[0226] In some embodiments, the noise reduction circuit 105 can generate a noise reduction signal in the following manner to make the amplitude of the noise reduction signal fall within an amplitude range supported by the speaker 102, and the noise reduction circuit 105 adjusts a filter gain corresponding to the noise reduction circuit 105 based on the first audio signal, so that the amplitude of the output signal obtained after filtering falls within the new range. Furthermore, the noise reduction circuit 105 filters at least one of the first audio signal or the second audio signal based on the adjusted noise reduction parameters to obtain the noise reduction signal.

[0227] In this method, the noise reduction circuit 105 can place the amplitude of the noise reduction signal within the new range simply by adjusting the filter gain, and there is no need to change the circuit structure of the noise reduction circuit 105.

[0228] In some embodiments, in the adjusted filter gain, a first filter gain corresponding to a first preset frequency band is smaller than a second filter gain corresponding to a second preset frequency band. In some embodiments, a frequency of the first preset frequency band is lower than a frequency of the second preset frequency band. In some embodiments, a frequency of the first preset frequency band is lower than a preset frequency, where the preset frequency may be 500 Hz, 200 Hz, 150 Hz, or other frequency value. In some embodiments, the first preset frequency band may be a low frequency band (e.g., a frequency band with a frequency lower than 150 Hz). Since the filter gain corresponding to the first preset frequency band is small, the corresponding amplitude of the filtered noise reduction signal in the first preset frequency band can be reduced, thereby preventing distortion of the speaker 102 in the first preset frequency band.

[0229] In some embodiments, when the noise reduction circuit 105 adjusts the filter gain, the filter gain corresponding to the first preset frequency band can be reduced based on the default filter gain, and the filter gain corresponding to the second preset frequency band can be maintained unchanged. In this way, it is possible to prevent distortion of the speaker 102 without impairing the noise reduction effect corresponding to the second preset frequency band.

[0230] When the acoustic device 100 provides multiple noise reduction modes, the present application provides an active noise reduction method P400, which can adaptively switch to the most suitable noise reduction mode for the current environment based on the noise conditions of the current environment, so that the acoustic device 100 can always achieve excellent noise reduction effect in different environments. The active noise reduction method P400 can be applied independently to the acoustic device 100 provided by the present application, or can be used in combination with other active noise reduction methods described elsewhere in this specification.

[0231] 16 shows a flowchart of another active noise reduction method P400 provided according to an embodiment of the present specification. The active noise reduction method P400 may be executed by the noise reduction circuit 105 of the acoustic device 100. For example, the processor 107 in the noise reduction circuit 105 may read an instruction set stored in its local storage medium, and execute the active noise reduction method P400 described herein according to the instructions of the instruction set. As shown in FIG. 16, the active noise reduction method P400 may include: S41: A first audio signal is acquired from a first audio sensor module.

[0232] S42: Self-adaptively select a target noise reduction mode from a plurality of noise reduction modes of an acoustic device based on the first audio signal.

[0233] In some embodiments, the noise reduction circuit 105 can self-adaptively select a target noise reduction mode from a plurality of noise reduction modes based on at least one of the strength or bandwidth type of the first audio signal. Here, the bandwidth type of the first audio signal can be classified into two types: narrowband type and non-narrowband type. The narrowband type indicates that the bandwidth occupied by the first audio signal is smaller than a preset bandwidth. Compared with the non-narrowband type, the signal energy of the narrowband type is concentrated in a narrow frequency band.

[0234] In some embodiments, the process in which the noise reduction circuit 105 self-adaptively selects the target noise reduction mode may include at least one of the following S42-1, S42-2, S42-3.

[0235] S42-1: Determine that the strength of the first audio signal is equal to or less than a second strength threshold, and select a passive noise reduction mode from the plurality of noise reduction modes.

[0236] Here, the second intensity threshold may correspond to the upper limit of noise intensity in a quiet environment. For example, the second intensity threshold may be 40 dB. That is, when the noise intensity of the external environment is small (e.g., less than 40 dB), the noise reduction circuit 105 selects the passive noise reduction mode and turns off the active noise reduction function. In this way, the power consumption of the audio device 100 can be reduced.

[0237] S42-2: Determine that the strength of the first audio signal is greater than or equal to a first strength threshold, and select an anti-crackle noise reduction mode from the plurality of noise reduction modes.

[0238] Here, the first intensity threshold is greater than the second intensity threshold. For example, the first intensity threshold may be 90 dB. When the noise intensity of the external environment is large (for example, 90 dB or more), the noise reduction circuit 105 can select the distortion-preventing noise reduction mode. In this way, distortion of the speaker 102 can be avoided.

[0239] S42-3: Determine that the intensity of the first audio signal exceeds a second intensity threshold and the bandwidth type of the first audio signal is a narrowband type, and select a narrowband noise reduction mode from the plurality of noise reduction modes.

[0240] Here, "the intensity of the first audio signal exceeds the second intensity threshold" is a condition for turning on the active noise reduction function, and if the bandwidth type of the first audio signal is a narrowband type, the noise reduction circuit 105 selects the narrowband noise reduction mode. In this way, active noise reduction can be performed only for the target frequency band in which the energy of the first audio signal is concentrated, and there is no need to perform active noise reduction over the entire frequency band, which helps to increase the depth of noise reduction in the target frequency band and improve the effect of active noise reduction.

[0241] In some embodiments, the judgment logic of the self-adaptive selection of the target noise reduction mode by the noise reduction circuit 105 is as follows: first, the noise reduction circuit 105 judges whether the intensity of the first audio signal is less than the second intensity threshold, and if so, selects the passive noise reduction mode. If not, turns on the active noise reduction function. Then, the noise reduction circuit 105 judges whether the following two conditions are met, respectively: condition 1: the intensity of the first audio signal is equal to or greater than the first intensity threshold; condition 2: the bandwidth type of the first audio signal is a narrowband type. The judgment result at this time is divided into the following four cases: if only condition 1 is met, the anti-crackle noise reduction mode is selected; if only condition 2 is met, the narrowband noise reduction mode is selected; if both condition 1 and condition 2 are met, both the anti-crackle noise reduction mode and the narrowband noise reduction mode can be selected; if neither condition 1 nor condition 2 is met, the normal noise reduction mode is selected.

[0242] In some embodiments, when the first audio signal includes both the ambient noise signal and the leakage signal, the noise reduction circuit 105 can first reduce the leakage signal component in the first audio signal to generate a pseudo ambient noise signal, and then self-adaptively select a target noise reduction mode from a plurality of noise reduction modes based on the pseudo ambient noise signal. Here, the above method for reducing the leakage signal component in the first audio signal has been described above, and will not be described in detail here.

[0243] By reducing the leakage signal component in the first audio signal, the noise reduction circuit 105 makes the obtained pseudo-ambient noise signal closer to the actual ambient noise, and thus self-adaptively selects a target noise reduction mode based on the pseudo-ambient noise signal, so that the selected target noise reduction mode is more suitable for the current environment, thereby improving the noise reduction effect.

[0244] S43: The target noise reduction mode is executed.

[0245] In some embodiments, the acoustic device 100 operates in a feedforward feedback noise reduction mode and the noise reduction circuitry 105 performs a target noise reduction mode based on the first audio signal. In some embodiments, the acoustic device 100 operates in a feedback noise reduction mode and the noise reduction circuitry 105 performs a target noise reduction mode based on the second audio signal. In some embodiments, the acoustic device 100 operates in a hybrid noise reduction mode and the noise reduction circuitry 105 performs a target noise reduction mode based on the first audio signal and the second audio signal.

[0246] In summary, the active noise reduction method P400 provided herein can self-adaptively adjust the noise reduction mode based on the noise conditions of the external environment in which the acoustic device 100 is placed, so that the active noise reduction process of the acoustic device 100 is more suitable for the noise conditions of the current environment, which helps to improve the overall performance of the acoustic device 100. For example, when the noise of the current environment is low, the acoustic device 100 can turn off the active noise reduction function to reduce power consumption. When the noise of the current environment is high, the acoustic device 100 can select the anti-crackle noise reduction mode to prevent the speaker 102 from crackling. When the noise of the current environment is of narrowband type, the acoustic device 100 can select the narrowband noise reduction mode to increase the depth of noise reduction and improve the noise reduction effect.

[0247] When the acoustic device 100 provides multiple noise reduction modes, the present application further provides another active noise reduction method, which may be performed by the noise reduction circuit 105. In this active noise reduction method, the noise reduction circuit 105 can obtain a user's instruction, select a target noise reduction mode from the multiple noise reduction modes based on the user's instruction, and then perform the target noise reduction mode. For example, the acoustic device 100 is provided with an interactive control, through which the user can switch between different noise reduction modes. Also, for example, the acoustic device 100 can provide an interactive interface, which may be displayed on a screen of the acoustic device 100 or displayed on a target device communicatively connected to the acoustic device 100, and the user can select different noise reduction modes through the interactive interface. In some embodiments, the user's instruction can indicate a specific noise reduction mode, and thus the noise reduction circuit 105 can determine the noise reduction mode specified in the instruction as the target noise reduction mode. In some embodiments, the user's instruction may specifically indicate the noise conditions of the environment where the user is located, and the noise reduction circuit 105 may select a target noise reduction mode from a plurality of noise reduction modes based on the environmental noise conditions specified in the instruction. In this way, the user may independently select an appropriate active noise reduction mode according to his / her preference and / or the current environmental noise conditions, thereby meeting the individual needs of different users.

[0248] Another aspect of the present specification provides a non-transitory storage medium having at least one executable instruction stored thereon for performing active noise reduction. The executable instruction, when executed by a processor, directs the processor to perform the steps of the active noise reduction method described herein. In some possible embodiments, each aspect of the present specification may be further realized in the form of a program product including a program code. When the program product runs on the acoustic device 100, the program code is used to cause the acoustic device 100 to perform the steps of the active noise reduction method described herein. The program product for implementing the method may be a portable compact disc read-only memory (CD-ROM), including the program code and operable on the acoustic device 100. However, the program product of the present specification is not limited thereto, and in the present specification, a readable storage medium may be any tangible medium that includes or stores a program, and the program may be used by or in combination with an instruction execution system. The program product may use any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. The readable storage medium may be, for example, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. The readable storage medium may further include, for example, an electrical connection having one or more conductors, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical memory device, a magnetic memory device, or any suitable combination thereof. The computer-readable storage medium may include a data signal propagated in baseband or as part of a carrier wave, in which the readable program code is embedded. Such a propagated data signal may take various forms, such as, but is not limited to, an electromagnetic signal, an optical signal, or any suitable combination thereof.The readable storage medium may also be any readable medium other than a readable storage medium, which may transmit, propagate or transmit a program for use by or in combination with an instruction execution system, device or apparatus. The program code contained in the readable storage medium may be transmitted by any suitable medium, including, but not limited to, wireless, wired, optical cable, RF, or the like, or any suitable combination of the above. The program code for performing the operations herein may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, C++, or the like, general procedural programming languages ​​such as the "C" language, or similar programming languages. The program code may be executed entirely by the acoustic device 100, partially by the acoustic device 100, as separate software packets, partially by the acoustic device 100 and partially by a remote computing device, or entirely by a remote computing device.

[0249] The above describes certain embodiments of the present specification. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims may be performed in a different order than in the examples and still achieve desirable results. Also, the processes depicted in the figures do not necessarily require a particular order or sequential order to achieve desirable results. In some embodiments, multitasking and parallel processing may also be possible or advantageous.

[0250] As described above, upon reading this detailed disclosure, those skilled in the art will understand that the detailed disclosure above may be presented by way of example only and may not be limiting. Although not expressly stated herein, the present specification should cover various reasonable changes, modifications, and alterations to the embodiments, as would be understood by those skilled in the art. These changes, modifications, and alterations are intended to be presented by this specification and are within the spirit and scope of the exemplary embodiments of the present specification.

[0251] It should be noted that certain terms in this specification are used to describe embodiments of this specification. For example, "one embodiment," "embodiment," and / or "some embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of this specification. Therefore, it should be emphasized and understood that two or more references to "an embodiment" or "one embodiment" or "alternative embodiments" in various parts of this specification do not necessarily refer to the same embodiment. It should be noted that certain features, structures, or characteristics may be suitably combined in one or more embodiments of this specification.

[0252] It should be understood that in the above description of the embodiments of the present specification, in order to facilitate the understanding of one feature, the present specification combines various features into a single embodiment, drawing, or description thereof for the purpose of simplifying the specification. However, it is not necessary to combine these features, and a person skilled in the art can fully understand a single embodiment by focusing on some of the devices when reading the specification. In other words, the embodiments in the present specification can be understood as a combination of multiple sub-embodiments. The content of each sub-embodiment can be established even when it has less than all the features of the single embodiment disclosed above.

[0253] Each patent, patent application, patent application publication, and other materials, such as articles, books, specifications, publications, documents, articles, etc., cited herein may be incorporated herein by reference. All content for all purposes, now or hereafter, is associated with this document, except for any claim history related thereto, any identical claim history that is inconsistent or inconsistent with this document, or any identical claim history that has a limiting effect on the broadest scope of the claims. For example, in the event of any inconsistency or discrepancy between the explanation, definition, and / or use of a term associated with any of the included materials and the explanation, definition, and / or use of the term associated with this document, the term in this document shall control.

[0254] Finally, it should be understood that the embodiments of the application disclosed herein are explanations of the principles of the embodiments of the present specification. Other modified embodiments are also within the scope of the present specification. Therefore, the embodiments disclosed herein are merely examples and are not limiting. Those skilled in the art can realize the application of the present specification using alternative configurations based on the embodiments of the present specification. Therefore, the embodiments of the present specification are not limited to the embodiments exactly described in the application.

Claims

1. An open-type wearable acoustic device, A support member; a speaker physically connected to the support member, the speaker forming an open space between the speaker and the eardrum of the user when the acoustic device is worn on the user's head; A first sound sensor module including N sound sensors, each of which is physically connected to the support member and is distributed on a side farther from the eardrum than the speaker, the N sound sensors having different directions relative to a target point of the speaker, and N being an integer equal to or greater than 2; 1. A noise reduction circuit, comprising: determining a target direction from which the environmental noise is coming, Determine N weights corresponding to the N sound sensors according to the target direction, so that the phase of the integrated environmental noise signal measured by the first sound sensor module according to the N weights leads the phase of the environmental noise arriving at the sound output end of the speaker; Generate a first noise-canceling signal based on the N distinct environmental noise signals collected by the N sound sensors and the N weights; and a noise reduction circuit configured to transmit the first noise cancellation signal to the speaker, whereby the speaker converts the first noise cancellation signal into a first noise cancellation audio to reduce a volume of environmental noise at the eardrum.

2. 2. The acoustic device according to claim 1, wherein the total environmental noise signal is a signal obtained by performing weighted addition on the N individual environmental noise signals based on the N weights.

3. For the i-th sound sensor among the N sound sensors, the included angle between the direction of the i-th sound sensor with respect to the target point and the target direction is defined as θ ｉ and the corresponding weight is the θ ｉ 2. The acoustic device according to claim 1, wherein i is an arbitrary positive integer equal to or smaller than N, and i has a negative correlation with N.

4. The noise reduction circuit includes N feedforward filters that correspond one-to-one to the N sound sensors; 2. The acoustic device of claim 1, wherein the i-th feedforward filter is connected to the i-th sound sensor and the speaker and configured to filter the individual environmental noise signal collected by the i-th sound sensor, where i is any positive integer less than or equal to N.

5. To generate the first noise cancellation signal, the noise reduction circuitry comprises: For an i-th sound sensor among the N sound sensors, adjust a filter parameter of an i-th feedforward filter based on the weight corresponding to the i-th sound sensor, and filter the individual environmental noise signal collected by the i-th sound sensor using the adjusted i-th feedforward filter to generate an i-th individual noise cancellation signal, where i is any positive integer equal to or less than N; 5. The acoustic device according to claim 4, wherein the first noise cancellation signal is obtained by superimposing the N individual noise cancellation signals generated by the N feedforward filters.

6. the target direction is the direction from which the environmental noise of the entire frequency band comes, To determine the target direction, the noise reduction circuitry Obtaining the N individual environmental noise signals collected by the N sound sensors; 2. The acoustic device according to claim 1, wherein the target direction is obtained by performing a direction-of-arrival DOA analysis of the N individual ambient noise signals over a full frequency band.

7. The environmental noise includes M subband noises corresponding to M subbands, the target directions include M directions of arrival corresponding to the M subbands; M is an integer greater than 1; To determine the target direction, the noise reduction circuitry Obtaining the N individual environmental noise signals collected by the N sound sensors; For the j-th subband of the M subbands, Extracting subband noise signals corresponding to the j-th subband from the N individual environmental noise signals, respectively, to obtain N subband noise signals corresponding to the j-th subband; Obtain a direction of arrival corresponding to the jth subband by performing a DOA analysis on the N subband noise signals; 2. The acoustic device according to claim 1, wherein the j is an arbitrary positive integer equal to or smaller than M.

8. the first noise-canceled signal includes M subband noise-canceled signals corresponding to the M subbands; To generate the first noise-canceled signal, the noise reduction circuitry calculates, for a jth subband of the M subbands, Determine N subband weights corresponding to the N sound sensors according to the direction of arrival corresponding to the jth subband, so that the phase of the total subband noise signal measured by the first sound sensor module based on the N subband weights leads the phase of the environmental noise corresponding to the jth subband arriving at the sound output end of the speaker; Generate N individual subband noise-canceled signals corresponding to the jth subband based on the N subband noise signals collected by the N sound sensors and the N subband weights, corresponding to the jth subband; superimposing the N individual subband noise-canceled signals to obtain a subband noise-canceled signal corresponding to the jth subband; 8. The acoustic device according to claim 7, wherein the j is an arbitrary positive integer equal to or smaller than M.

9. 2. The acoustic device according to claim 1, wherein N=2, and the N sound sensors are located at acoustic zero point positions of the speaker and in opposite directions to the target point.

10. 2. The acoustic device according to claim 1, wherein N=3, and the N sound sensors are distributed in a triangular shape at acoustic zero point positions of the speaker.

11. 2. The acoustic device according to claim 1, wherein at least a part of the N sound sensors is an omnidirectional microphone or a directional microphone.

12. The noise reduction circuit includes: at least one storage medium having stored thereon at least one instruction set for performing noise reduction; at least one processor in communication with the speaker, the first audio sensor module, and the at least one storage medium; When the audio device is activated, the at least one processor reads the at least one instruction set and performs the following steps according to the instructions of the at least one instruction set: determining a target direction from which the environmental noise is coming, Determine N weights corresponding to the N sound sensors according to the target direction, so that the phase of the integrated environmental noise signal measured by the first sound sensor module according to the N weights leads the phase of the environmental noise arriving at the sound output end of the speaker; Generate a first noise-canceling signal based on the N distinct environmental noise signals collected by the N sound sensors and the N weights; 2. The acoustic device of claim 1, further comprising: transmitting the first noise canceling signal to the speaker, whereby the speaker converts the first noise canceling signal into a first noise canceling audio to reduce a volume of the environmental noise at the eardrum.

13. 2. The audio device according to claim 1, wherein the audio device is one of an earphone, a silencer, a hearing aid, and audio glasses.

14. An active noise reduction method, applied to an open-type wearable acoustic device according to claim 1, comprising: The method is performed by the noise reduction circuit, determining a target direction from which the environmental noise is coming; According to the target direction, determine N weights corresponding to the N sound sensors, so that the phase of the integrated environmental noise signal measured by the first sound sensor module according to the N weights leads the phase of the environmental noise arriving at the sound output end of the speaker; generating a first noise-canceling signal based on the N distinct environmental noise signals collected by the N sound sensors and the N weights; and transmitting the first noise canceling signal to the speaker, whereby the speaker converts the first noise canceling signal into a first noise canceling audio to reduce a volume of the environmental noise at the eardrum.

15. The method according to claim 14, wherein the total ambient noise signal is a signal obtained by performing weighted addition on the N individual ambient noise signals based on the N weights.

16. For the i-th sound sensor among the N sound sensors, the included angle between the direction to the target point and the target direction is θ ｉ and the corresponding weight is the θ ｉ 15. The method of claim 14, wherein i is a positive integer less than or equal to N, and i is a negative correlation with N.

17. The noise reduction circuit includes N feedforward filters that correspond one-to-one to the N sound sensors; an i-th feedforward filter coupled to the i-th sound sensor and the speaker and configured to filter the individual environmental noise signal collected by the i-th sound sensor; The i is an arbitrary positive integer equal to or smaller than N, The step of generating the first noise-canceling signal as described above includes: A step of adjusting a filter parameter of an i-th feedforward filter based on the weight corresponding to the i-th sound sensor for an i-th sound sensor among the N sound sensors, and filtering the individual environmental noise signal collected by the i-th sound sensor with the adjusted i-th feedforward filter to generate an i-th individual noise cancellation signal, where i is any positive integer equal to or less than N; and overlapping the N individual noise-canceled signals generated by the N feedforward filters to obtain the first noise-canceled signal.

18. the target direction is the direction from which the environmental noise of the entire frequency band comes, The step of determining the target direction from which the environmental noise arrives as described above includes: acquiring the N distinct environmental noise signals collected by the N sound sensors; and obtaining the target direction by performing a full frequency band direction of arrival DOA analysis on the N distinct ambient noise signals.

19. The environmental noise includes M subband noises corresponding to M subbands, the target directions include M directions of arrival corresponding to the M subbands; M is an integer greater than 1; The step of determining the target direction from which the environmental noise arrives as described above includes: acquiring N distinct environmental noise signals collected by the N sound sensors; For the j-th subband of the M subbands, Extracting subband noise signals corresponding to the j-th subband from the N individual environmental noise signals, respectively, to obtain N subband noise signals corresponding to the j-th subband; and performing DOA analysis on the N subband noise signals to obtain a direction of arrival corresponding to the jth subband; 15. The method of claim 14, wherein j is any positive integer less than or equal to M.

20. the first noise-canceled signal includes M subband noise-canceled signals corresponding to the M subbands; The generating of the first noise-canceled signal as described above includes, for a j-th subband of the M subbands: According to the arrival direction corresponding to the j-th subband, determine N subband weights corresponding to the N sound sensors, so that the phase of the total subband noise signal measured by the first sound sensor module based on the N subband weights leads the phase of the environmental noise corresponding to the j-th subband arriving at the sound output end of the speaker; generating N individual subband noise-canceled signals corresponding to the jth subband based on the N subband noise signals collected by the N sound sensors and the N subband weights; and overlapping the N individual subband noise-canceled signals to obtain a subband noise-canceled signal corresponding to the jth subband; 20. The method of claim 19, wherein j is any positive integer less than or equal to M.

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