Open-type wearable acoustic device and active noise reduction method therefor

Abstract

The present application provides an open-type wearable acoustic device and an active noise reduction method, the acoustic device includes a first sound sensor module, a speaker, and a noise reduction circuit. The noise reduction circuit can obtain a first sound signal from the first sound sensor module, select a target noise reduction mode from a plurality of noise reduction modes based on the first sound signal, and execute the target noise reduction mode. The method can self-adaptively adjust the noise reduction mode based on the noise conditions of the external environment where the acoustic device is located, and make the active noise reduction process of the acoustic device more suitable for the noise conditions of the current environment, thereby improving the noise reduction effect of the acoustic device.

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 thereof. [Background technology]

[0002] Nowadays, wearable devices with audio output capabilities (e.g., earphones) 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, audio devices inserted into the ear canal or used without covering the ear, or audio devices with sound holes on the surface, creating an open space between the eardrum and the audio device) are increasingly being applied to wearable audio devices due to their comfort and safety. Such wearable audio devices are called open-type wearable devices.

[0003] When worn on a user's head, the above-mentioned open-type wearable acoustic devices do not form a sealed space between the user's eardrum and the device. Therefore, compared to closed-type acoustic devices (e.g., in-ear earphones), more sound from noise sources outside the ear enters the ear. This allows the user to hear more ambient noise when wearing the open-type acoustic device, resulting in a poor hearing experience. For this reason, there is a need to provide an active noise reduction design based on open-type wearable acoustic devices. 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 user's eardrum when the acoustic device is worn on a user's head, the first sound sensor module is physically connected to the support member and configured to collect a first sound and generate a first sound signal, the first sound signal including an environmental noise signal from environmental noise, and the noise reduction circuit is configured to acquire the first sound signal from the first sound sensor module, self-adaptively select a target noise reduction mode from a plurality of noise reduction modes based on the first sound signal, and perform the target noise reduction mode.

[0006] In some embodiments, the acoustic device further includes a second sound sensor module physically connected to the support member and configured to collect a second sound and generate a second sound signal, and to perform the target noise reduction mode, the noise reduction circuit obtains the second sound signal from the second sound sensor module and performs the target noise reduction mode on at least one of the first sound signal or the second sound signal.

[0007] In some embodiments, the first sound sensor module is farther from the eardrum than the speaker, and the phase in which the environmental noise reaches the first sound sensor module is earlier than the phase in which the environmental noise reaches the audio output end of the speaker; and the second sound sensor module is closer to the eardrum than the speaker, and the phase in which the environmental noise reaches the second sound sensor module is later than the phase in which the environmental noise reaches the audio output end of the speaker.

[0008] In some embodiments, the plurality of noise reduction modes include an anti-crackle noise reduction mode, wherein in the anti-crackle noise reduction mode, the noise reduction circuit generates a noise cancellation signal based on at least one of the first audio signal or the second audio signal, an amplitude of the noise cancellation signal is within an allowable amplitude range of the speaker, and transmits the noise cancellation signal to the speaker, whereby the speaker converts the noise cancellation signal into noise-canceling audio to reduce the volume of the ambient noise at the eardrum; and to self-adaptively select a target noise reduction mode, the noise reduction circuit determines that an intensity of the first audio signal is greater than or equal to a first intensity threshold and selects the anti-crackle noise reduction mode from the plurality of noise reduction modes.

[0009] In some embodiments, to generate the noise-canceled signal, the noise reduction circuit filters at least one of the first audio signal or the second audio signal to obtain a candidate noise-canceled signal, corrects the amplitude of the candidate noise-canceled signal based on the amplitude range so that the corrected amplitude is within the amplitude range, and defines the corrected signal as the noise-canceled signal.

[0010] In some embodiments, to generate the noise-canceled signal, the noise reduction circuit adjusts a filter gain corresponding to the noise reduction circuit based on the first audio signal to bring the amplitude of the filtered output signal within the amplitude range, and filters at least one of the first audio signal or the second audio signal based on the adjusted filter gain to obtain the noise-canceled signal.

[0011] In some embodiments, in the adjusted filter gains, 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, where frequencies within the first preset frequency band are lower than a preset frequency and frequencies within the second preset frequency band are equal to or greater than the preset frequency.

[0012] In some embodiments, the plurality of noise reduction modes includes a narrowband noise reduction mode, wherein in the narrowband noise reduction mode, the noise reduction circuit determines a target frequency band based on the first audio signal, and an energy concentration within the target frequency band exceeds a predetermined threshold, and performs active noise reduction within the target frequency band based on at least one of the first audio signal or the second audio signal, and to self-adaptively select a target noise reduction mode, the noise reduction circuit determines that the intensity of the first audio signal is greater than a second intensity threshold, determines that the type of the first audio signal is a narrowband type, and selects the narrowband noise reduction mode from the plurality of noise reduction modes.

[0013] In some embodiments, the plurality of noise reduction modes includes a negative noise reduction mode, wherein in the negative noise reduction mode, the noise reduction circuit turns off an active noise reduction function, and to self-adaptively select a target noise reduction mode, the noise reduction circuit determines that the intensity of the first audio signal is below a second intensity threshold and selects the negative noise reduction mode from the plurality of noise reduction modes.

[0014] In some embodiments, the first audio signal further includes a leakage signal from the speaker, and in this case, to self-adaptively select the target noise reduction mode, the noise reduction circuit generates a pseudo-ambient noise signal by reducing a component of the leakage signal in the first audio signal, and self-adaptively selects the target noise reduction mode from the plurality of noise reduction modes based on the pseudo-ambient noise signal.

[0015] In some embodiments, the noise reduction circuit includes at least one storage medium and at least one processor, wherein 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, wherein when the acoustic device is operating, the at least one processor reads the at least one instruction set, acquires the first sound signal from the first sound sensor module according to instructions in the at least one instruction set, self-adaptively selects a target noise reduction mode from a plurality of noise reduction modes based on the first sound signal, and executes the target noise reduction mode.

[0016] In some embodiments, the acoustic device is one of an earphone, a silencer, a hearing aid, or acoustic glasses.

[0017] 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 acquiring the first audio signal from the first audio sensor module, self-adaptively selecting a target noise reduction mode from a plurality of noise reduction modes based on the first audio signal, and executing the target noise reduction mode.

[0018] In some embodiments, the acoustic device further includes a second sound sensor module physically connected to the support member and configured to collect a second sound and generate a second sound signal, and the step of performing the target noise reduction mode described above includes obtaining the second sound signal from the second sound sensor module and performing the target noise reduction mode on at least one of the first sound signal or the second sound signal.

[0019] In some embodiments, the phase of the environmental noise measured by the first sound sensor module is ahead of the phase at which the environmental noise arrives at the sound output end of the speaker, and the phase of the environmental noise measured by the second sound sensor module is behind the phase at which the environmental noise arrives at the sound output end of the speaker.

[0020] In some embodiments, the plurality of noise reduction modes includes an anti-crackle noise reduction mode, and the step of self-adaptively selecting a target noise reduction mode from the plurality of noise reduction modes based on the first audio signal includes selecting the anti-crackle noise reduction mode from the plurality of noise reduction modes when it is determined that the intensity of the first audio signal is equal to or greater than a first intensity threshold, and the step of performing the anti-crackle noise reduction mode on at least one of the first audio signal or the second audio signal includes generating a noise cancellation signal based on at least one of the first audio signal or the second audio signal, wherein the amplitude of the noise cancellation signal is within an acceptable amplitude range of the speaker, and transmitting the noise cancellation signal to the speaker, thereby causing the speaker to convert the noise cancellation signal into noise-canceled audio to reduce the volume of the ambient noise at the eardrum.

[0021] In some embodiments, the step of generating the noise-canceled signal described above includes filtering at least one of the first audio signal or the second audio signal to obtain a candidate noise-canceled signal, correcting the amplitude of the candidate noise-canceled signal based on the amplitude range so that the corrected amplitude is within the amplitude range, and designating the corrected signal as the noise-canceled signal.

[0022] In some embodiments, the step of generating the noise-canceled signal described above includes a step of adjusting a filter gain corresponding to the noise reduction circuit based on the first audio signal so that the amplitude of the filtered output signal falls within the amplitude range, and a step of filtering at least one of the first audio signal or the second audio signal based on the adjusted filter gain to obtain the noise-canceled signal.

[0023] In some embodiments, in the adjusted filter gains, 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, where frequencies within the first preset frequency band are lower than a preset frequency and frequencies within the second preset frequency band are equal to or greater than the preset frequency.

[0024] In some embodiments, the plurality of noise reduction modes includes a narrowband noise reduction mode, and the step of self-adaptively selecting a target noise reduction mode from the plurality of noise reduction modes based on the first audio signal includes the steps of determining that the intensity of the first audio signal is greater than a second intensity threshold, determining that the type of the first audio signal is a narrowband type, and selecting the narrowband noise reduction mode from the plurality of noise reduction modes, and the step of performing the narrowband noise reduction mode on at least one of the first audio signal or the second audio signal includes the steps of determining a target frequency band based on the first audio signal, wherein the energy concentration within the target frequency band exceeds a predetermined threshold, and performing active noise reduction within the target frequency band based on at least one of the first audio signal or the second audio signal.

[0025] In some embodiments, the plurality of noise reduction modes includes a negative noise reduction mode, and the step of self-adaptively selecting a target noise reduction mode from the plurality of noise reduction modes based on the first audio signal as described above includes selecting the negative noise reduction mode from the plurality of noise reduction modes when it is determined that the intensity of the first audio signal is equal to or less than a second intensity threshold, and the step of executing the negative noise reduction mode includes turning off an active noise reduction function.

[0026] In some embodiments, the first audio signal further includes a leakage signal from the speaker, and the aforementioned step of self-adaptively selecting a target noise reduction mode from a plurality of noise reduction modes based on the first audio signal includes a step of generating a pseudo-ambient noise signal by reducing a component of the leakage signal in the first audio signal, and a step of self-adaptively selecting the target noise reduction mode from the plurality of noise reduction modes based on the pseudo-ambient noise signal.

[0027] As can be seen from the above technical solutions, in the open-type wearable acoustic device and active noise reduction method according to this specification, the acoustic device includes a first sound sensor module, a speaker, and a noise reduction circuit. The noise reduction circuit is capable of receiving a first sound signal from the first sound sensor module, selecting a target noise reduction mode from a plurality of noise reduction modes based on the first sound signal, and then executing the target noise reduction mode. The method self-adaptively adjusts the noise reduction mode based on the noise conditions in the external environment where the acoustic device is located, thereby making the active noise reduction process of the acoustic device more suited to the noise conditions in the current environment, thereby improving the noise reduction effect of the acoustic device.

[0028] Other features of the open-type wearable acoustic device and active noise reduction method according to this specification are partially listed in the description that follows. The inventive aspects of the open-type wearable acoustic device and active noise reduction method according to this specification can be fully understood by practice or use of the methods, apparatus and combinations described in the detailed examples that follow.

[0029] 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 should be apparent 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 any creative efforts. [Brief explanation of the drawings]

[0030] [Figure 1A] 1 is a schematic diagram illustrating a wearing scene of an audio device provided in accordance with an embodiment of the present disclosure; [Figure 1B] 1 is a schematic diagram showing an audio device that employs an in-ear wearing method. [Figure 1C] Schematic diagram showing an audio device that employs an ear hook type wearing method. [Figure 1D] Schematic diagram showing an audio device that employs a clip-on type mounting method. [Figure 2] 1 is a schematic diagram illustrating a hardware structure of an audio device provided in accordance with an embodiment of the present disclosure; [Figure 3] 1 is a schematic diagram illustrating leakage signals collected by sound sensors at different positions in an acoustic device. [Figure 4] 1 is a flowchart illustrating an active noise reduction method provided in accordance with an embodiment of the present disclosure. [Figure 5] 1 is a schematic diagram illustrating the principle of active noise reduction in an acoustic device provided in accordance with an embodiment of the present disclosure; [Figure 6] 2 is a schematic diagram illustrating the noise reduction effect of an active noise reduction method provided in accordance with an embodiment of the present specification; [Figure 7] 4 is a flowchart illustrating another active noise reduction method provided in accordance with an embodiment of the present disclosure. [Figure 8A] 10 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 acoustic device. [Figure 8B]5A and 5B are schematic diagrams illustrating frequency response curves for feedforward noise reduction of a second audio signal using different feedforward filter gains when a first user is wearing audio equipment. [Figure 9A] 10 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 acoustic 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. 10 is a schematic diagram showing the distribution of the audio sensors when the first audio sensor module includes two audio sensors. [Figure 11] FIG. 10 is a schematic diagram showing the distribution of the audio sensors when the first audio sensor module includes three audio sensors. [Figure 12] 4 is a flowchart illustrating another active noise reduction method provided in accordance with an embodiment of the present disclosure. [Figure 13] 1 is a schematic diagram illustrating the active noise reduction principle of another acoustic device provided in accordance with an embodiment of the present disclosure; [Figure 14] 1 is a schematic diagram illustrating a set of frequency response curves provided in accordance with an embodiment of the present disclosure. [Figure 15] FIG. 10 is a schematic diagram illustrating another set of frequency response curves provided in accordance with examples herein. [Figure 16] 4 is a flowchart illustrating another active noise reduction method provided in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0031] Specific applications and requirements of the present specification are described below in order to enable those skilled in the art to make and use the teachings 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 may 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 to be accorded the broadest scope consistent with the claims.

[0032] The terms used herein are for the purpose of describing particular exemplary embodiments and are not intended to be limiting. For example, the singular forms "a," "an," 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.

[0033] These and other features of the present specification, and the operation and function of associated components, and economies of assembly and manufacture of parts, can be clearly improved upon in light of the following description. Reference is made to the accompanying drawings, all of which form a part of this specification. However, it should be expressly understood that the accompanying drawings are for illustration and explanation purposes only and are not intended to limit the scope of the present specification. It should also be understood that the drawings are not drawn to scale. Flowcharts used herein illustrate the operations of a system implementation based on some of the embodiments of the present specification. It should be expressly understood that the operations in the flowcharts do not necessarily have to be performed sequentially. Rather, operations may be performed in reverse order or simultaneously. Also, one or more other operations may be added to the flowcharts, and one or more operations may be deleted from the flowcharts.

[0034] For the sake of convenience, the terms used in this specification will first be explained.

[0035] Closed-type acoustic devices: When some acoustic devices are worn, a sealed space is formed between the acoustic device and the user's eardrum; this type of acoustic device can be called a closed-type acoustic device. For example, the acoustic device can form a sealed space between the user's eardrum through an inner-type design (e.g., canal-type earphones), a closed-type earcup design, or other similar designs. When a user wears a closed-type acoustic device, the sealed space physically blocks external noise and reduces interference with the user caused by external noise. However, users may find closed-type acoustic devices uncomfortable when worn for long periods of time.

[0036] Open-type acoustic devices: When some acoustic devices are worn, an open space is formed between the acoustic device and the user's eardrum; this type of acoustic device can 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 has sound holes on the surface of the acoustic device, thereby creating an open space between the acoustic device and the eardrum. Open-type acoustic devices can improve the user's comfort when worn and make the sound the user hears more natural and clear.

[0037] 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.

[0038] Passive noise reduction: Refers to technology that reduces noise passively. Passive methods include, but are not limited to, eliminating (or partially eliminating) the noise source, blocking noise propagation, or preventing the user's ear from hearing the noise, or any combination thereof. For example, technology that achieves noise reduction by creating a sealed space within the ear is considered a passive noise reduction technology. Passive noise reduction physically suppresses noise rather than eliminating it.

[0039] Active noise reduction: This refers to a technology that actively reduces noise by generating a noise cancellation signal (e.g., a signal that is out of phase with the noise being suppressed). An audio device that employs active noise reduction technology collects a noise signal using an audio sensor, generates a noise cancellation signal to cancel the noise signal using a noise reduction circuit, and plays the noise cancellation signal through a speaker to cancel the noise signal, thereby eliminating noise. 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.

[0040] Feedforward noise reduction: A sound sensor is placed outside the audio device, collects environmental noise using the sound sensor to generate an environmental noise signal, filters the environmental noise signal using a feedforward filter to generate a noise cancellation signal, and plays the noise cancellation signal through a 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 a feedforward noise reduction system, an open-loop noise reduction control system is formed between the speaker and the sound sensor.

[0041] Feedback noise reduction: A sound sensor is placed inside an audio device, and the sound sensor collects the ambient noise near the eardrum. The feedback filter filters the ambient noise to generate a noise-canceling signal, which is then played back by a speaker. In this way, the noise-canceling signal cancels (or partially cancels) the ambient noise at the eardrum, thereby reducing the volume of the ambient noise heard by the user. In a feedback noise reduction system, a closed-loop noise reduction control system is formed between the speaker and the sound sensor.

[0042] Hybrid noise reduction: Hybrid noise reduction is a technology that combines feedforward noise reduction and feedback noise reduction. Generally, hybrid noise reduction can further improve the noise reduction effect compared with feedforward noise reduction alone or feedback noise reduction alone.

[0043] This 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.

[0044] FIG. 1A shows a schematic diagram of wearing scenarios of an acoustic device provided according to an embodiment of the present disclosure. 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 a seal. In scenario 001, a noise source 300 may be further included, and the number of 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 preferred by the user, a sound that is unwanted 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 an active noise reduction method to generate and output a noise cancellation signal (a signal that is in phase opposite to the environmental noise) to suppress or eliminate the environmental noise.

[0045] In some embodiments, the acoustic device 100 may be an earphone, a silencer, a hearing aid, acoustic glasses, or any combination thereof. For ease of understanding, FIG. 1A illustrates the acoustic device 100 as an earphone. If the acoustic device 100 is acoustic glasses, an audio output device may be installed at the temples of the glasses near the ears, configured to output audio to the user's ears. Note that the acoustic device 100 may be worn around the user's ears 200 in any manner, and the present application is not limited thereto. For example, the acoustic device 100 may be worn in a headband-type, in-ear-type, neckband-type, earhook-type, or any combination thereof.

[0046] In some embodiments, scenario 001 may also include a network and a target device (not shown in FIG. 1A ). Here, the target device may be an electronic device with audio output capabilities. 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 the user.

[0047] In some embodiments, the target device may have an audio collecting device installed thereon and may acquire 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 TV, 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.

[0048] 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 audio device 100 and the target device can communicate based on the Bluetooth protocol.

[0049] 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.

[0050] 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 the present 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.

[0051] FIG. 1B shows a schematic diagram of an acoustic device employing an in-ear wearing method. In this case, a support member 101 is designed to fit onto an auricle 201, with one or more support points on the support member 101 fitting to predetermined points on the auricle 201. FIG. 1C shows a schematic diagram of an acoustic device employing an ear hook wearing method. In this case, the support member 101 may have a hanging structure, allowing the acoustic device 100 to be suspended from the auricle 201. FIG. 1D shows a schematic diagram of an acoustic device employing a clip-on wearing method. In this case, the support member 101 has a clip structure, allowing the support member 101 to be clipped onto the auricle 201.

[0052] 1A , the speaker 102 is disposed on a side of the acoustic device 100 that is closer to the entrance of the ear canal. When the acoustic device 100 is worn on a user's head, an open space is formed between the speaker 102 and the user's eardrum 202. In some embodiments, when the acoustic device 100 is worn on a 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 be a non-sealed housing, for example, with a sound vent provided on the housing, thereby forming an open space between the speaker 102 and the eardrum 202.

[0053] The speaker 102 is configured to generate audio based on an audio signal (or convert an audio signal into audio). An audio signal here refers to an electrical signal that conveys sound information, and audio refers to a sound signal reproduced by a speaker. Sound originates from an initial sound source (e.g., an ambient noise source, a person's throat, etc.) and is converted into an electrical signal conveying the sound information, i.e., the audio signal, by a sound-collecting sound sensor (e.g., a microphone). The speaker 102 may also be referred to as an electro-acoustic transducer, which, during operation, can receive the audio signal conveying sound information, convert it into a sound signal, and reproduce it. In some embodiments, the acoustic 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 array.

[0054] 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 a 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 form of an array, such as a linear array, a planar array, a spherical array, or other arrays. In some embodiments, the sound sensor is a device, such as a microphone, for collecting sound and converting the sound into an electrical signal.

[0055] 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 (or 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 a 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 array.

[0056] 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 .

[0057] 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 sound signal, or the first sound signal may be an electrical signal. It should be understood that because 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, because an open space is formed between the speaker 102 and the eardrum 202, the first sound sensor module 103 can also collect sound 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 .

[0058] 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 located 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.

[0059] 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 sound signal, or the second sound signal may be an electrical signal. In an open-type acoustic device, the second sound sensor module 104 can collect the ambient noise emitted from the noise source 300 and the sound emitted from the speaker 102. Therefore, the second sound collected by the second sound sensor module 104 includes components of the ambient noise and the sound emitted from the speaker 102. In an active noise reduction scenario, the ambient noise emitted from the noise source 300 propagates through the air into the open space. During the active noise reduction process, some of the ambient noise in the open space is canceled or attenuated by the sound from the speaker 102. Therefore, the second sound collected by the second sound sensor module 104 may also be referred to as residual noise, i.e., the ambient noise remaining in the open space.

[0060] 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 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 lags behind 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.

[0061] 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 ear, where the active noise reduction may be either feed-forward noise reduction, feedback noise reduction, or hybrid noise reduction.

[0062] 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.

[0063] 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 then 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 ambient noise in the space at the eardrum 202, or to have a predetermined phase difference, such that the phase of the first noise cancellation audio is inverse or approximately inverse to the phase of the ambient noise in the space at and near the eardrum 202, thereby reducing the volume of the ambient noise near the eardrum 202. In some embodiments, the noise reduction circuit 105 includes a feedforward filter connected to the first audio sensor module 103 and the speaker 102. After acquiring 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-canceling signal, and output the first noise-canceling signal to the speaker 102. Here, the feedforward filter is configured to adjust at least one of the gain or phase of the first audio signal so that the obtained first noise-canceling signal can cancel out 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 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.

[0065] In some embodiments, the process in which the noise reduction circuit 105 performs 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 then converts the second noise cancellation signal into second noise cancellation audio. The second noise cancellation signal can be set to be inverse, approximately inverse, or have a preset phase difference with respect to 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 to 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 connected to the second audio sensor module 104 and the speaker 102. After acquiring the 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-canceling signal, and output the second noise-canceling signal to the speaker 102. Here, the feedback filter is configured to adjust at least one of the gain or phase of the second audio signal so that the obtained second noise-canceling signal can cancel out at least a part of the environmental noise at the eardrum 202.

[0066] In some embodiments, the noise reduction circuit 105 may be configured to perform hybrid noise reduction, in which case 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.

[0067] In some embodiments, the process by which the noise reduction circuit 105 performs 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 then converts the first noise cancellation signal and the second noise cancellation signal into noise-canceling audio to reduce the volume of ambient 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 receives a first audio signal through a feedforward filter, filters the first audio signal through the feedforward filter to obtain a first noise-canceled signal, and receives a second audio signal through a feedback filter, filters the second audio signal through the feedback filter to obtain a second noise-canceled signal. The noise reduction circuit 105 also transmits the first noise-canceled signal and the second noise-canceled signal to the speaker 102. The feedforward filter is configured to adjust at least one of the gain or phase of the first audio signal so that audio produced by the speaker 102 converting the obtained first noise-canceled signal can cancel out ambient noise at the eardrum 202 and at least a portion of the space therearound (i.e., the phase of the audio is opposite or approximately opposite to the phase of ambient noise at the eardrum 202 and at least a portion of the space therearound).The feedback filter is configured to adjust at least one of the gain or phase of the second audio signal so that the audio produced by converting the resulting first noise-canceling signal by the speaker 102 cancels out at least some of the ambient noise at the eardrum 202 (i.e., the phase of the audio is opposite or approximately opposite to the phase of at least some 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-canceling signal and the second noise-canceling signal separately to the speaker 102. In some embodiments, the noise reduction circuit 105 can combine the first noise-canceling signal and the second noise-canceling signal to obtain a combined noise-canceling signal and transmit the combined noise-canceling signal to the speaker 102.

[0068] In some embodiments, the noise reduction circuitry 105 may be configured to perform the active noise reduction methods described herein. In this case, the noise reduction circuitry 105 may store data or instructions for performing the active noise reduction methods described herein, and may execute or be used to execute the data or instructions. In some embodiments, the noise reduction circuitry 105 may include a hardware device capable of processing data information and the necessary programs to operate the hardware device. The active noise reduction methods are described in more detail below.

[0069] 2 is a schematic diagram of a hardware structure of an audio device provided according to embodiments of the present disclosure. 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 to the speaker 102, the first audio sensor module 103, and the second audio sensor module 104. For illustrative purposes only, the noise reduction circuit 105 of the present disclosure includes at least one storage medium 106 and at least one processor 107. As will be appreciated by one of ordinary skill in the art, the noise reduction circuit 105 may include other hardware circuit structures, which are not limited herein and can achieve the functions described herein without departing from the spirit of the present disclosure.

[0070] 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.

[0071] 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.

[0072] 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 instruction set stored on the data storage device. The instruction set includes instructions, which may be 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.

[0073] The at least one processor 107 is used to execute the at least one instruction set described above. When the acoustic device 100 operates, the at least one processor 107 reads the at least one instruction set and performs the active noise reduction method provided herein according to the instructions of the at least one instruction set. The processor 107 may perform 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 explanation 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 a single processor or jointly by multiple processors, as described herein. For example, while the processor 107 of the acoustic device 100 may perform steps A and B herein, 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 jointly perform steps A and B).

[0074] Those skilled in the art will understand that Figure 2 is merely an example of the design 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.

[0075] As described above, in an open-type acoustic device, the first audio signal collected and generated by the first audio sensor module 103 is not simply an ambient noise signal, but a mixed audio signal including the ambient noise signal and a 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 feedforward noise reduction process and reduce the effectiveness of the feedforward noise reduction.

[0076] In some embodiments, to reduce the influence of leakage signals on the feedforward noise reduction effect, the acoustic device 100 may employ a physical isolation method, in which the first sound sensor module 103 is located at the acoustic null point of the speaker 102. For example, the speaker 102 may employ a dipole speaker design, and the first sound sensor module 103 is located at the acoustic null point of the dipole speaker. This prevents the first sound sensor module 103 from collecting any or only a small amount of leakage signals from the speaker 102.

[0077] FIG. 3 shows a schematic diagram of leakage signals collected by sound sensors at different positions within an acoustic device. Here, FF1 and FF2 represent sound sensors positioned at the acoustic null point of the speaker 102, and FF3 represents a sound sensor positioned near the speaker 102. After an excitation signal is applied to the speaker 102 during testing, the leakage signals collected by FF1 are obtained to obtain curve 301 shown in FIG. 3, the leakage signals collected by FF2 are obtained to obtain curve 302 shown in FIG. 3, and the leakage signals collected by FF3 are obtained to obtain curve 303 shown in FIG. 3. As can be seen from FIG. 3, when the environmental frequency is low (e.g., below 1500 Hz), the leakage signals collected by FF1 and FF2 are reduced by more than 20 dB compared to the leakage signal collected by FF3, achieving a certain noise reduction effect.

[0078] In some embodiments, the distance between the first sound sensor module 103 and the acoustic 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 acoustic zero point position of the speaker 102, rather than being positioned exactly at the acoustic zero point position of the speaker 102. In this way, the requirements for the structural design and assembly technology of the acoustic device 100 may be reduced.

[0079] The present application provides an active noise reduction method P100 that can improve noise reduction effectiveness by reducing the leakage signal component contained in the first audio signal, thereby reducing the influence of the leakage signal on feedforward noise reduction. The active noise reduction method P100 can be applied to both a scenario in which the first audio sensor module 103 is not installed at the acoustic zero point of the speaker 102 and a scenario in which the first audio sensor module 103 is installed at the acoustic zero point of the speaker 102. In the scenario in which the first audio sensor module 103 is installed at the acoustic zero point of the speaker 102, there is still a problem of speaker signals leaking into the first audio sensor module in some frequency bands (e.g., in FIG. 3 , when the frequency is above 5000 Hz, the leakage signals collected by FF1 and FF2 are approximately equal to the leakage signal collected by FF3). Therefore, the active noise reduction method P100 provided by the present application can be used to perform noise reduction in specific frequency bands where such leakage exists, thereby improving noise reduction effectiveness. The active noise reduction method P100 can be applied alone to the acoustic device 100 provided in this application, or can be used in combination with other active noise reduction methods described elsewhere in this specification.

[0080] 4 shows a flowchart of an active noise reduction method provided in accordance with an embodiment of the present specification. The active noise reduction method P100 can be performed by the noise reduction circuit 105 in the 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:

[0081] S11: Obtain a first audio signal from a first audio sensor module, where the first audio signal includes an ambient noise signal from the ambient noise and a leakage signal from a speaker.

[0082] 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 ambient noise from the noise source 300 and the leaked sound from the speaker 102. Therefore, the first sound signal contains both an ambient noise signal corresponding to the ambient noise and a leaked sound corresponding to the leaked sound. The noise reduction circuit 105 is connected to the first sound sensor module 103 and can acquire the first sound signal from the first sound sensor module 103.

[0083] S12: A pseudo ambient noise signal is generated by reducing the leakage signal component in the first audio signal.

[0084] Specifically, the noise reduction circuit 105 measures the leakage signal component contained in the first audio signal using a specific method, and then subtracts 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 deviate slightly 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 referred to as a "pseudo ambient noise signal." The pseudo ambient noise signal can be understood as a compensated signal obtained by performing leakage compensation on the first audio signal.

[0085] 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, assuming: Let h1 be the transfer function between the sound emitted from the noise source 300 and the audio signal measured by the first sound sensor module 103; The transfer function between the sound emitted by the noise source 300 and the audio signal measured by the second audio sensor module 104 is 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 audio 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.

[0086] 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-reduced 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.

[0087] Based on the acoustic transfer process shown in FIG. 5, the following relationships exist among the above S0, S1, S2, S3 and S4:

[0088]

number

[0089] 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.

[0090] Next, the feedforward noise reduction mode is taken as an example to analyze the design principle of the feedforward filter h5.

[0091] In the feedforward noise reduction mode, the above equation (2) is substituted into equation (1-1) to obtain the following equation:

[0092]

number

[0093] Substituting equation (4) into equation (0), we get:

[0094]

number

[0095] In an ideal case (when the sound emitted from the speaker 102 does not leak into the first sound sensor module 103), h3=0, and when substituted into equation (5), the following equation is obtained:

[0096]

number

[0097] Typically, 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.

[0098] However, in non-ideal cases, particularly 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. Therefore, 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, since the transfer function h3' is obtained by measurement and may have some error from the actual transfer function h3, this transfer function h3' is also referred to as the measured transfer function. During the feedforward noise reduction process, the noise reduction circuit 105 uses h3' to correct the first sound signal and obtain a pseudo-ambient noise signal. Furthermore, the noise reduction circuit 105 uses an ideal feedforward filter to filter the pseudo-ambient noise signal and obtain a first noise-canceled signal.

[0099] 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, causing the speaker 102 to emit a corresponding test audio, which is then 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' based on 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. This method of measuring the transfer function h3' is simple and does not affect the noise reduction performance of the noise reduction circuit 105.

[0100] In some embodiments, h3 is typically related to the wearing position and orientation of the acoustic device 100, and the corresponding h3 may be different when the same acoustic device 100 is worn by different users. Also, the corresponding h3 may be different when the same acoustic device is worn by the same user multiple times. 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 powered on or that the user has worn the acoustic device 100.

[0101] In some embodiments, after the noise reduction circuit 105 measures h3', it can generate a simulated 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 applies 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 simulated ambient noise signal. Here, the simulated ambient noise signal can be expressed as S1'=S0*h1+S3*h3-S3*h3'.

[0102] S13: Generate a first noise-canceling signal based on the pseudo ambient noise signal.

[0103] 5 , in some embodiments, 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′ through the feedforward filter 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 ambient noise of at least a portion 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-phase response of the ideal feedforward filter may be designed based on Equation (6).

[0104] S14: Send the first noise-canceling signal to a speaker, so that the speaker converts the first noise-canceling signal into a first noise-canceling audio to reduce the volume of the ambient noise at the eardrum.

[0105] 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 the first noise cancellation audio corresponding to the first noise cancellation signal, so that the first noise cancellation audio cancels or partially cancels out the environmental noise at the eardrum 202, thereby achieving the purpose of noise reduction.

[0106] FIG. 6 is a schematic diagram of the noise reduction effect of the active noise reduction method provided according to the embodiments of the present disclosure. As shown in FIG. 6, curves 601 and 602 respectively correspond to the noise reduction results of two test scenarios. Here, the test process corresponding to curve 601 is as follows: The noise reduction circuit 105 acquires a first audio signal collected by FF1 (located at the acoustic zero point of the speaker 102) shown in FIG. 3, where the first audio signal contains no or 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, thereby obtaining the noise reduction result shown in curve 601. The test process corresponding to curve 602 is as follows: The noise reduction circuit 105 acquires a first audio signal collected by FF3 (located at a position other than the acoustic zero point of the speaker 102) shown in FIG. 3, where the first audio signal contains leakage signal from the speaker 102. The noise reduction circuit 105 uses the active noise reduction method shown in Figure 4, first reducing the leakage signal component in the first audio signal to obtain a pseudo-ambient noise signal, and then using an ideal feedforward filter to perform feedforward noise reduction based on the pseudo-ambient noise signal. As can be seen from Figure 6, the two noise reduction results of curve 601 and curve 602 are almost identical. This shows that the noise reduction circuit 105 can effectively improve the noise reduction effect of open-type acoustic equipment by reducing the leakage signal component in the first audio signal to obtain a pseudo-ambient noise signal, and then generating a first noise cancellation signal based on the pseudo-ambient noise signal.

[0107] In the active noise reduction method P100 shown in FIG. 4, the noise reduction circuit 105 acquires a first audio signal from a first audio sensor module, 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 reverse the reduction and feedforward noise reduction steps. Specifically, after acquiring a first audio signal (S1) from the first audio sensor module, the noise reduction circuit 105 first applies feedforward noise reduction (h5) to the first audio signal to generate an intermediate noise-canceled signal (S1*h5). Because the first audio signal includes both 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 ambient 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 acquired, and a first gain (h3') is applied to the input signal to obtain a first gain signal (S3*h3'). 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 filtered 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 the 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 above related content description, so it will not be described in detail here.

[0108] In summary, in the active noise reduction method P100 provided in this specification, when the first audio signal contains both an ambient noise signal and a leakage signal, the noise reduction circuit 105 first reduces the leakage signal component in the first audio signal to generate a pseudo-ambient noise signal, then generates a first noise-canceling signal based on the pseudo-ambient noise signal, and then converts the first noise-canceling signal into a first noise-canceling audio through a speaker, thereby achieving the purpose of noise reduction. Because the noise reduction circuit 105 reduces the leakage signal component in the first audio signal during feedforward noise reduction and reduces the impact of the leakage signal on feedforward noise reduction, the noise reduction effect of active noise reduction can be improved.

[0109] Typically, the noise reduction circuit 105 should design / adjust its noise reduction parameters with the goal of noise reduction: "minimizing the environmental noise (S4) at the eardrum 202." In a closed-type acoustic device, the second sound signal (S2) collected by the second sound sensor module 104 is equal to or nearly equal to the environmental noise (S4) at the eardrum 202. Therefore, in a closed-type acoustic device, the goal of noise reduction can be "minimizing the second sound signal (S2)." However, in an open-type acoustic device, an open space is formed between the speaker 102 and the eardrum 202, so the second sound signal (S2) measured by the second sound sensor module 104 and the environmental noise (S4) at the eardrum 202 are no longer equal to or nearly equal to each other.

[0110] 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 audio signal (S2) measured by the second audio 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:

[0111]

number

[0112] From the above equations (3) and (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 ambient noise signal (S0) emitted from the noise source 300. For the second audio signal, typically, 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 equal to 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. Therefore, the components of the second audio signal in S2 and S4 are approximately equal, and the difference between S2 and S4 is due to 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).

[0113] In a closed-type 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 equation (3) and S4 obtained based on equation (0) are equal or approximately equal. However, in an open-type 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 equation (3) and S4 obtained based on equation (0) are no longer equal or approximately equal. Therefore, 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," it will be understood that the noise reduction effect will be worse.

[0114] To solve the above technical problems, the inventor of the present invention proposed the following technical concept during research: By specially designing the structure of the acoustic device 100 and the position of each component, S4 can be estimated based on S2, even though S4 and S2 are not equal (i.e., S4 and S2 have the same fluctuation tendency). This makes it possible to estimate S4 based on S2 and perform active noise reduction with the goal of minimizing S4. Furthermore, the effectiveness of active noise reduction can be improved by deriving the noise reduction parameters required for "minimizing S4" based on the noise reduction parameters required for "minimizing S2" as the noise reduction goal.

[0115] 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. Estimating S4 based on S2 typically requires grasping both h4 and h7 individually. However, as discovered in the inventor's research, both h7 and h4 are quantities that strongly depend on the posture of the acoustic device 100. That is, when different users wear the acoustic device, h4 and h7 are different for each user. Even when the same user wears the acoustic device multiple times, h4 and h7 are different for each user. Furthermore, in actual usage scenarios, there is no sound sensor on the eardrum 202, making it difficult to measure h7 and estimate S4. As a result of further research, the inventors 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 is independent of the wearing posture of the acoustic device 100. Here, the fact that the first predetermined relationship is independent of 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 user wears the acoustic device 100. For example, when the acoustic device 100 is worn by different users, h4 and h7 always satisfy the predetermined relationship. Furthermore, for example, when the same user wears the acoustic device 100 multiple times, h4 and h7 always satisfy the predetermined relationship.

[0116] The present application does not limit the specific form of the first predetermined relationship. During the design phase of the acoustic device 100, the first predetermined relationship between h4 and h7 can be derived by testing a large number of users and multiple wearing processes of the acoustic device. In some embodiments, the first predetermined relationship may be h7 / h4=h9. It should be noted 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: the noise-canceling signal component (S3*h7) at S4 and the noise-canceling signal component (S3*h4) at S2 have the relationship (S3*h7) / (S3*h4)=h9; or the intensity of the noise-canceling signal component (S3*h4) at S2 is x dB lower than the noise-canceling signal component (S3*h7) at S4, where 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, as long as their positions allow h4 and h7 to satisfy the first predetermined relationship, and the first predetermined relationship does not depend on the wearing posture of the acoustic device 100. In some embodiments, the speaker 102 may be located near the entrance of the ear canal, with the sound output surface (i.e., the surface on which the sound output end is located) facing 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 wearing posture of the acoustic device 100, and therefore the speaker 102 can be located at that position. The second sound sensor module 104 can be located 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 should be away from the user's skin, and (2) the sound collecting end of the second sound sensor module 104 should be 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 will be less affected by the wearing posture, that is, no matter what posture the acoustic device 100 is worn in, h4 and h7 will always satisfy the same first predetermined relationship.In addition, by determining the positions of the speaker 102 and the second sound sensor module 104 using the above method, the second sound signal S2 collected by the second sound sensor module 104 is close to the environmental noise S4 at the eardrum 202, and the second sound signal S2 is less affected by skin reflection, so that the S4 estimated based on the first predetermined relationship and the second sound signal S2 is more accurate.

[0117] When h4 and h7 satisfy a first predetermined relationship and the first predetermined relationship is independent of the wearing posture of the acoustic device 100, the present application provides an active noise reduction method P200 that can adjust noise reduction parameters based on the second audio signal (S2) and the first predetermined relationship, regardless of the posture in which 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.

[0118] 7 shows a flowchart of another active noise reduction method P200 provided in accordance with an embodiment of the present disclosure. This active noise reduction method P200 can be performed 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 perform 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: 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 ambient noise (S4) at the eardrum 202 based on the second audio signal (S2) and the first predetermined relationship. Furthermore, the noise reduction circuit 105 adjusts noise reduction parameters with the goal of minimizing the ambient noise (S4) at the eardrum 202.

[0119] 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.

[0120] In some embodiments, h4' can be measured using the following method: the noise reduction circuit 105 transmits a test audio signal to the speaker 102, causing the speaker 102 to emit a corresponding test audio, which is then collected by the second audio sensor module 104. The noise reduction circuit 105 obtains the collected audio signal collected by the second audio sensor module 104 and determines a first transfer function h4' based on 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. This 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 generally related to the wearing posture of the acoustic device 100, and that when the same acoustic device 100 is worn by different users, 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.

[0121] (2) determining an ambient noise at the eardrum based on the first transfer function, the first predetermined relationship, and the second audio signal;

[0122] 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.

[0123] 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.

[0124] 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:

[0125]

number

[0126] Based on the above analysis, the environmental noise component S0*h2 in S2 and the environmental noise component S0*h8 in S4 are approximately equal, i.e.,

[0127]

number

[0128] Substituting equation (13) into equation (0), we obtain the following equation:

[0129]

number

[0130] 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.

[0131] In the above-mentioned active noise reduction process, the ambient noise (S4) at the eardrum 202 is first determined based on the second audio signal (S2) and the first predetermined relationship, and then the noise reduction goal is to minimize the ambient noise (S4) at the eardrum 202. By improving the accuracy of the noise reduction goal, the effect of active noise reduction can be improved.

[0132] In the above embodiment, S4 is determined based on the following assumption: 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 is approximately equal to the transfer function (h8) between the sound emitted from the noise source 300 and the eardrum 202, i.e., h2≈h8. The inventors realized that in actual application scenarios, h2 and h8 are usually not strictly equal, which can lead to some error in S4 determined in the above embodiment. Therefore, to further improve the accuracy of S4, h2 and h8 can be taken into account in the process of calculating S4. However, h2 and h8 are also values ​​that depend on the wearing posture of the acoustic device 100. Different users will have different h2 and h8 when wearing the acoustic device, and the same user will also have different h2 and h8 when wearing the acoustic device multiple times. For this reason, measuring h2 and h8 separately can be difficult. Further research by the inventors has revealed that when designing the positions of the second sound sensor module 104 and the speaker 102, in addition to ensuring that h4 and h7 satisfy the first predetermined relationship, h2 and h8 may also satisfy a second predetermined relationship, and that 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.

[0133] The present application does not limit the specific form of the second predetermined relationship. During the design stage of the acoustic device 100, the relationship between h2 / h1 and h2 / h1 can be obtained by testing a large number of users and multiple wearing processes of the acoustic device, and the second predetermined relationship between h2 and h8 can be derived based on this 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 (S0*h8) at S4 and the component of the ambient noise signal (S0*h2) at S2 is (S0*h8) / (S0*h2)=h10; or the intensity of the component of the ambient noise signal (S0*h2) at S2 is ydB lower than the component of the ambient noise signal (S0*h8) at S4, where the value of y may be 1, 2, or any other numerical value.

[0134] 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 are independent of the posture of the acoustic device 100, S4 can be estimated based on the first predetermined relationship, the second predetermined relationship, and S2. The specific method is as follows.

[0135] (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.

[0136] (2) determining the ambient noise at the eardrum based on the first transfer function, the first predetermined relationship, the second predetermined relationship, and the second audio signal;

[0137] 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.

[0138] 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:

[0139] First, based on equation (3), the following equation is obtained:

[0140]

number

[0141] Based on the second predetermined relationship, the following equation is obtained:

[0142]

number

[0143] Substituting equation (15) into equation (0), we obtain the following equation:

[0144]

number

[0145] 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.

[0146] 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.

[0147] 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 its −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 for adjacent frequency components.

[0148] In some embodiments, the noise reduction parameters of the noise reduction circuit 105 may include the filter gain of the feedforward filter. In this case, for simplicity of explanation, the filter gain of the feedforward filter required when "minimizing the second audio signal (S2) is the noise reduction goal" is referred to as 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 noise reduction goal" is referred to as the second filter gain. If this condition is met, there is a specific relationship between the signal strengths of S2 and S4, for example, the signal strength of S2 is lower than the signal strength of S4 by x dB. In this case, the first filter gain and the second filter gain also satisfy this relationship.

[0149] For example, Figure 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 is wearing an acoustic device. Figure 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 is wearing an acoustic device. Here, assume 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] 8A and 8B, when the acoustic 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). Frequency response curves of the feedforward noise reduction based on the environmental noise (S4) at the eardrum 202 at different filter gains are shown in FIG. 8A. Frequency response curves of the feedforward noise reduction based on the second audio signal (S2) at 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.

[0151] 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 is wearing the 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 is wearing the 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.

[0152] 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). Frequency response curves of feedforward noise reduction based on the environmental noise (S4) at the eardrum 202 at different filter gains are shown in FIG. 9A. Frequency response curves of feedforward noise reduction based on the second audio signal (S2) at 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.

[0153] 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.

[0154] Therefore, the noise reduction circuit 105 can further adjust the filter gain of the feedforward filter in the following manner: first, the noise reduction goal 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. First, the noise reduction circuit 105 sets the noise reduction goal 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 a second filter gain of 4 dB. Therefore, the current filter gain of the feedforward filter is adjusted to 4 dB.

[0155] In some embodiments, the audio device 100 may provide a user with multiple operating modes, each with default noise reduction parameters for the noise reduction circuit 105, with different default noise reduction parameters corresponding to different operating modes. In some embodiments, the audio device 100 may be equipped with an interactive control, allowing the user to switch between different operating modes by manipulating the interactive control. In some embodiments, the audio device 100 may provide an interactive interface, which may be displayed on a screen of the audio device 100 or on a target device communicatively connected to the audio device 100. The user may select a different operating mode through the interactive interface. In some embodiments, each of the multiple operating modes corresponds to a different environment type. The user may interactively indicate the current environment type to the audio device 100, and the noise reduction circuit 105 may switch to a corresponding operating mode based on the current environment type. In some embodiments, each of the multiple operating modes corresponds to a different user type. The user may interactively indicate the user type to the audio device 100, and the noise reduction circuit 105 may switch to a corresponding operating mode based on the user type to which the user belongs.

[0156] In this way, at S22, the noise reduction circuit 105 can obtain a target operating mode designated by the user among the plurality of operating modes, and adjust default noise reduction parameters corresponding to the target operating mode based on the second audio signal (S2) and the first predetermined relationship. It should be understood that by providing a plurality of operating modes, the acoustic device 100 can meet the noise reduction needs of different users or different environments.

[0157] S23: Perform active noise reduction based on the adjusted noise reduction parameters.

[0158] In some embodiments, the noise reduction circuit 105 may 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-canceling signal. Further, the noise reduction circuit 105 may transmit the noise-canceling signal to a speaker, so that the speaker converts the noise-canceling signal into noise-canceling audio to reduce the volume of the ambient noise at the eardrum.

[0159] In some embodiments, when the acoustic device 100 operates in the feedforward 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 to a feedforward filter and filter the first audio signal through the feedforward filter to obtain a noise-canceled signal. In some embodiments, when the first audio signal includes both an ambient noise signal and a 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 filter the pseudo-ambient noise signal based on the adjusted noise reduction parameters to obtain a noise-canceled signal. On the one hand, adjusting the noise reduction parameters ensures the accuracy of the noise reduction target, so performing active noise reduction based on the adjusted noise reduction parameters can improve the effectiveness of the active noise reduction. On the other hand, reducing the leakage signal component in the first audio signal can reduce the influence of the leakage signal in the feedforward noise reduction process, thereby further improving the effectiveness of the active noise reduction.

[0160] In some embodiments, when the acoustic device 100 is operating 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 the 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 through the feedback filter to obtain the noise-canceled signal.

[0161] In some embodiments, when the acoustic 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 the first noise-cancelled signal. For example, the noise reduction circuit 105 may input the first audio signal to a feedforward filter and filter the first audio signal through the feedforward filter to obtain the 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 the 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 through the feedback filter to obtain the second noise-cancelled signal. The noise reduction circuit 105 may further combine the first noise-cancelled signal and the second noise-cancelled signal to obtain the noise-cancelled signal. In some embodiments, when the first audio signal includes both an ambient noise signal and a leakage signal, the noise reduction circuit 105 first reduces the leakage signal component in the first audio signal to generate a pseudo-ambient noise signal, and then filters the pseudo-ambient noise signal based on the adjusted noise reduction parameters to obtain a first noise-canceled signal. On the one hand, adjusting the noise reduction parameters ensures the accuracy of the noise reduction target, so that performing active noise reduction based on the adjusted noise reduction parameters can improve the effect of the active noise reduction. On the other hand, reducing the leakage signal component in the first audio signal can reduce the influence of the leakage signal in the feedforward noise reduction process, thereby further improving the effect of the active noise reduction.

[0162] 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 is independent of the wearing position of the acoustic device 100. Therefore, the noise reduction circuit 105 adjusts noise reduction parameters based on the second sound signal (S2) and the first predetermined relationship, and can perform active noise reduction based on the adjusted noise reduction parameters. Because 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 most closely match the essential noise reduction target, thereby improving the effect of active noise reduction.

[0163] As described above, in some embodiments, the first sound sensor module 103 may include one sound sensor. In this case, because environmental noise can arrive from any direction, a situation may arise in which the environmental noise has already reached the speaker 102 or the eardrum 202 before reaching the sound sensor. For example, suppose the sound sensor is installed on a first side (e.g., the side facing the user) of the acoustic device 100, but the noise source 300 is located on a second side (e.g., the side facing the user) of the acoustic device 100. Because the sound sensor is far 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 of the feedforward noise reduction of the noise reduction circuit 105 is deteriorated, which may result in a poorer effect of the feedforward noise reduction, particularly in those frequency bands (e.g., mid- to high-frequency bands), and may even result in an increase in the noise heard by the user.

[0164] For this reason, 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 defined as N, where N is an integer greater than or equal to 2. The N sound sensors are each physically connected to the support member 102 and distributed on a 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 distinction, hereinafter, the environmental noise signal collected by each sound sensor will be referred to as an individual environmental noise signal, and the environmental noise signal collected by the first sound sensor module 103 will be referred to as a total environmental noise signal.

[0165] The N audio sensors are arranged in different directions relative to a target point of the speaker 102. In some embodiments, the target point may be the center point or the audio output point of the speaker 102. Because the N audio sensors are arranged in different directions relative to the target point, when environmental noise comes from different directions, at least one of the N audio sensors can collect the environmental noise before the speaker 102.

[0166] In some embodiments, N=2. FIG. 10 shows a schematic diagram of the distribution of two sound sensors in the first sound sensor module. 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 opposite sides of the acoustic device 100, or the two sound sensors may have opposite directions relative 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 ambient noise is emitted from a noise source in front of the user, the phase at which the ambient noise arrives at the sound sensor 1031 (or the phase of the individual ambient noise signal measured by the sound sensor 1031) leads the phase at which the ambient noise arrives at the audio output terminal of the speaker 102. When the ambient noise is emitted from a noise source behind the user, the phase in which the ambient noise arrives at the audio sensor 1032 (or the phase of the individual ambient noise signal measured by the audio sensor 1032) leads the phase in which the ambient noise arrives at the audio output end of the speaker 102. In some embodiments, the two audio sensors may be located at the acoustic null point of the speaker 102. In this way, the signals collected by the two audio sensors do not include leakage signals from the speaker 102, thereby improving the active noise reduction effect.

[0167] In some embodiments, N=3. FIG. 11 shows a schematic diagram of the distribution of the sound sensors 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 sound sensor 1031, sound sensor 1032, and 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 a user's head, sound sensor 1031 is located on a first side of the acoustic device 100 facing the front of the user, sound sensor 1032 is located on a second side of the acoustic device 100 facing the rear of the user, and sound sensor 1033 is located on a third side of the acoustic device 100 facing the ground. In this way, when the ambient noise is emitted from a noise source in front of the user, the phase in which the ambient noise arrives at the audio sensor 1031 (or the phase of the individual ambient noise signal measured by the audio sensor 1031) leads the phase in which the ambient noise arrives at the audio output terminal of the speaker 102. When the ambient noise is emitted from a noise source behind the user, the phase in which the ambient noise arrives at the audio sensor 1032 (or the phase of the individual ambient noise signal measured by the audio sensor 1032) leads the phase in which the ambient noise arrives at the audio output terminal of the speaker 102. When the ambient noise is emitted from a noise source below the acoustic device, the phase in which the ambient noise arrives at the audio sensor 1033 (or the phase of the individual ambient noise signal measured by the audio sensor 1033) leads the phase in which the ambient noise arrives at the audio output terminal of the speaker 102. In some embodiments, the three audio sensors can be distributed in a triangular shape at the acoustic zero points of the speaker 102. In this way, the signals collected by the three audio sensors do not include leakage signals from the speaker 102, thereby improving the active noise reduction effect.

[0168] 10 and 11 are only two possible arrangement methods. In actual design, the N audio sensors may also adopt other distribution methods, which will not be illustrated in this specification. In addition, the value of N is not particularly limited in this application. For example, the value of N may be 4, 5, or any other integer.

[0169] 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 array, which is advantageous for reducing the complexity of signal processing in the noise reduction circuit 105 and improving the active noise reduction performance.

[0170] At least some of the N audio sensors may be omnidirectional microphones. Omnidirectional microphones are highly sensitive to environmental noise from all directions and can collect environmental noise from any direction. At least some of the N audio sensors may also be directional microphones. A directional microphone can collect environmental noise only from a specific direction. For example, as shown in FIG. 10 , audio sensor 1031 may have a directionality in front of the user and be configured to collect environmental noise from the front of the user, while audio sensor 1032 may have a directionality behind the user and be configured to collect environmental noise from the rear of the user. The directional microphones may 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.

[0171] 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, or can be combined with other active noise reduction methods described elsewhere in this specification.

[0172] 12 shows a flowchart of another active noise reduction method P300 provided in accordance with an embodiment of the present specification. This active noise reduction method P300 can be performed by the noise reduction circuit 105 in the 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 recorded in its local storage medium and perform the active noise reduction method P300 described herein according to the instructions of the instruction set. As shown in FIG. 12, the active noise reduction method P300 may include:

[0173] S31: Determine the target direction from which the environmental noise comes.

[0174] Here, the target direction refers to the direction from which the ambient noise is coming, 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 towards the noise source 300 can be referred to as the target direction.

[0175] In some embodiments, the noise reduction circuit 105 can acquire N individual ambient noise signals collected by N sound sensors and estimate a target direction from which the ambient noise is arriving based on the N individual ambient noise signals. In some embodiments, the noise reduction circuit 105 can obtain the target direction by performing a Direction of Arrival (DOA) analysis of the N individual ambient noise signals across the entire frequency band. In this case, the target direction represents the direction of arrival of the ambient noise across the entire frequency band (i.e., the entire ambient noise).

[0176] It should be noted that the present application does not particularly limit the DOA algorithm, and one or more of the following may be adopted, for example, the Estimating Signal Parameter via Rotational Invariance Techniques (ESPRIT) algorithm, the Multiple Signal Classification (MUSIC) algorithm, etc.

[0177] S32: Based on the target direction, determine N weights corresponding to the N sound sensors in the first sound sensor module, so that the phase of the total ambient noise signal of the first sound sensor module measured based on the N weights is ahead of the phase at which the ambient noise arrives at the sound output end of the speaker.

[0178] In some embodiments, the total environmental noise signal is a signal obtained by weighting N individual environmental noise signals collected by N sound sensors based on N weights.

[0179] 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

[0180]

number

[0181] and the individual environmental noise signals collected by the sound sensor 1032 are

[0182]

number

[0183] is.

[0184] Assuming that the weight of the sound sensor 1031 is α1 and the weight of the sound sensor 1032 is α2, the total environmental noise signal measured based on the above two weights of the first sound sensor module 103 can be expressed as follows:

[0185]

number

[0186] The phase of the integrated ambient noise signal can be expressed as follows:

[0187]

number

[0188] 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 above-mentioned total noise signal is ahead of the phase at which the ambient noise arrives at the output end of the speaker 102.

[0189] In some embodiments, the weight corresponding to the i-th audio sensor is related to the degree of phase lead of the individual environmental noise signal collected by the i-th audio sensor. For example, the more the phase of the individual environmental noise signal collected by the i-th audio sensor leads the phase of the environmental noise arriving at the audio output end of the speaker 102, the larger the weight corresponding to the i-th audio sensor will be, and conversely, the smaller the weight corresponding to the i-th audio sensor will be, where i is any positive integer less than or equal to N.

[0190] 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 Assuming that 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 relative to the target point is small), the larger the weight is, and θ 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. Here, i is any positive integer equal to or less than N.

[0191] This will be 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 will be greater than the weight of the voice sensor 1032, and thus, when performing active noise reduction, the voice sensor 1031 will play a major role and ensure phase lead. Assuming that the environmental noise comes from the back of the user, the weight of the voice sensor 1032 will be greater than the weight of the voice sensor 1031, and thus, when performing active noise reduction, the voice sensor 1032 will play a major role and ensure phase lead.

[0192] S33: A first noise-reduced signal is generated based on the N individual environmental noise signals collected by the N sound sensors and the N weights.

[0193] 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.

[0194] 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, by allowing the N feedforward filters to reduce noise in different frequency bands, thereby enhancing the feedforward noise reduction capability.

[0195] 13 shows a schematic diagram of the active noise reduction principle of another acoustic device provided according to an embodiment of the present specification. As shown in FIG. 13, it is assumed 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.

[0196] Continuing with reference to Figure 13, assume that: The transfer function between the sound emitted from 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.

[0197] 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.

[0198] In the acoustic transmission process shown in FIG. 13, the following relationships exist among S0, S11, S12, S3, and S4:

[0199]

number

[0200] Substituting equations (8) and (9) into equation (7), we get:

[0201]

number

[0202] Substituting equation (10) into equation (0), we get:

[0203]

number

[0204] From equation (11), it can be seen that the feedforward noise reduction effect is determined by h51 and h52.

[0205] In some embodiments, when performing active noise reduction, the noise reduction circuit 105 can adjust filter parameters of the feedforward filter h51 based on the weight of the sound sensor 1031, and generate an individual noise-canceled signal by filtering the individual environmental noise signal S11 collected by the sound sensor 1031 through the adjusted feedforward filter h51. The noise reduction circuit 105 can further adjust filter parameters of the feedforward filter h52 based on the weight of the sound sensor 1032, and generate an individual noise-canceled signal by filtering the individual environmental noise signal S12 collected by the sound sensor 1032 through the adjusted feedforward filter h52. The noise reduction circuit 105 further combines the two individual noise-canceled signals generated by the two feedforward filters to obtain a first noise-canceled signal.

[0206] In some embodiments, adjusting the filter parameters of feedforward filter h51 or feedforward filter h52, as described above, may include adjusting the filter gain of feedforward filter h51 or feedforward filter h52. For example, the weight of audio sensor 1031 may be multiplied by the current filter gain of feedforward filter h51 to obtain the adjusted filter gain of feedforward filter h51. The weight of audio sensor 1032 may be multiplied by the current filter gain of feedforward filter h52 to obtain the adjusted filter gain of feedforward filter h52.

[0207] 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 audio sensors with higher weights (audio sensors with larger phase leads) and their corresponding feedforward filters have a larger contribution to the overall noise reduction, and the audio sensors with lower weights (audio sensors with smaller phase leads) and their corresponding feedforward filters have a smaller contribution to the overall noise reduction, thereby improving the effect of the active noise reduction.

[0208] 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.

[0209] 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.

[0210] S34: Transmit the first noise cancellation signal to the speaker, so that the speaker converts the first noise cancellation signal into the first noise cancellation audio, thereby reducing the volume of the environmental noise on the eardrum.

[0211] It should be understood that the above steps S31 to S34 describe estimating the direction of arrival for environmental noise in the entire frequency band and performing active noise reduction for the entire frequency band based on the estimated target direction. In some embodiments, the noise reduction circuit 105 can also estimate the target direction by dividing the entire frequency band into subbands. 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 noted 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).

[0212] 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 j-th subband by the following method: extracting subband noise signals corresponding to the j-th subband from the N individual ambient 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 the arrival direction corresponding to the j-th subband, where j is any positive integer equal to or less than M.

[0213] After obtaining the M arrival directions corresponding to the M subbands, the noise reduction circuit 105 can perform active noise reduction individually for each subband. Specifically, for the jth subband, the noise reduction circuit 105 determines weights for N subbands corresponding to N sound sensors based on the arrival direction corresponding to the jth subband, so that the phase of the composite subband noise signal measured by the first sound sensor module 103 based on the weights of the N subbands leads the phase of the environmental noise of the jth subband arriving at the audio output terminal 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 sound sensors based on the weights of the N subbands. Furthermore, the noise reduction circuit 105 generates N individual subband noise-reduced signals corresponding to the jth subband based on the subband noise signals corresponding to the jth subband collected by the N sound sensors and the weights of the N subbands. The noise reduction circuit 105 adds 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 less than or equal to 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 ambient noise at the eardrum 202.

[0214] 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 therefore will not be described in detail here. It should be noted 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 based on the weight, for example, the filter gain corresponding to the jth filter unit.

[0215] FIG. 14 is a schematic diagram of a set of frequency response curves provided in accordance with embodiments of the present disclosure. 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. Curve 143 shows the frequency response when the acoustic device 100 uses both sound sensors FF1 and FF2 and two feedforward filters connected in parallel. Curves 141 and 142 indicate that the single sound sensor FF1 and the single sound sensor FF2 each provide noise reduction effects in different frequency bands. Curve 143 indicates that the combined use of sound sensors FF1 and FF2 provides noise reduction effects over a wider frequency band, enabling deeper noise reduction.

[0216] 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 disclosure. 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 clearly smaller than the feedforward filter gain required to achieve the same filter effect using a single sound sensor. 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.

[0217] In summary, 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, when performing active noise reduction, determines N weights corresponding to the N sound sensors based on the target direction of the environmental noise, 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 audio output end of the speaker. The noise reduction circuit 105 then generates a first noise-reduced signal based on the N individual environmental noise signals collected by the N sound sensors and the N weights, and transmits the first noise-reduced 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, this method ensures that the first sound sensor module 103 has a phase lead with respect to the audio output end of the speaker 102, regardless of the direction from which the environmental noise comes, thereby improving the causality of the feedforward noise reduction and further improving the active noise reduction effect, especially high-frequency noise reduction performance. In addition, using multiple audio sensors can reduce gain compared to using a single audio sensor, thereby reducing leakage of some frequency bands (e.g., high frequency bands) in open environments, thereby avoiding system instability problems caused by leakage of the above frequency bands and increased noise problems that occur when some users wear audio equipment. Furthermore, this method helps improve the noise reduction depth of each subband by estimating the direction of arrival at a granularity of subbands and performing active noise reduction for each subband, thereby further enhancing the effectiveness of active noise reduction.

[0218] Typically, after activating the active noise reduction function, the acoustic device 100 performs active noise reduction across the entire frequency range based on pre-designed noise reduction parameters. However, in actual use, the acoustic device 100 is placed in a variety of external environments, and the 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 acoustic device may have poor noise reduction effect, or the speaker 102 may produce distorted sound.

[0219] 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 the 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 independently, flexibly, intelligently, or adaptively switching the noise reduction mode 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. 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.

[0220] In the passive noise reduction mode, the active noise reduction function of the acoustic device 100 is turned off.

[0221] In the normal noise reduction mode, the active noise reduction function of the acoustic device 100 is turned on, and the noise reduction circuit 105 performs active noise reduction over the entire frequency range based on at least one of the first audio signal or the second audio signal using pre-designed noise reduction parameters.

[0222] 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, where the energy concentration within the target frequency band exceeds a preset threshold. Here, the energy concentration within the target frequency band refers to the energy concentration of the noise signal within 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 may be referred to as a narrowband. Furthermore, the noise reduction circuit 105 can perform active noise reduction within the target frequency band (narrowband) based on at least one of the first audio signal or the second audio signal.

[0223] In some embodiments, after determining 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 primarily on the target frequency band (e.g., the noise reduction depth of the target frequency band is deeper than that of 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 frequency bands. In some embodiments, "adjusting the noise reduction parameters of the noise reduction circuit 105" can include converting a full-frequency band filter in the noise reduction circuit 105 to a narrow-band filter. In the above embodiments, adjusting the noise reduction parameters based on the target frequency band can increase the noise reduction depth in the target frequency band and improve the noise reduction effect in the target frequency band.

[0224] In the anti-crackle noise reduction mode, the active noise reduction function of the acoustic device 100 is enabled. 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 and the second audio signal, and ensuring that the amplitude of the noise reduction signal falls within an amplitude range supported by the speaker 102. The noise reduction circuit 105 then transmits the noise reduction signal to the speaker 102, which then converts the noise reduction signal into noise-reduced audio to reduce the volume of the ambient noise at the eardrum 202. Here, the above amplitude range refers to the signal width range supported by the speaker 102 when the speaker 102 can normally reproduce sound without generating broken sound. The broken sound refers to a phenomenon in which the vibration of the speaker's diaphragm exceeds its linear range, resulting in significant sound distortion. If the amplitude of the signal input to the speaker 102 exceeds the new width range, the speaker 102 generates broken sound. If the amplitude of the signal input to the speaker 102 falls within the new width range, the speaker 102 does not generate broken sound. 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, thereby avoiding distortion of the speaker 102.

[0225] In some embodiments, the noise reduction circuit 105 can generate the noise reduction signal in the following manner to ensure that the amplitude of the noise reduction signal falls within the amplitude range supported by the speaker 102. 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 filtering process has been described above in the relevant section 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, ensures that the modified amplitude falls 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 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 to ensure that the amplitude of the output signal falls 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, which then modifies the amplitude of the noise reduction signal to obtain the noise reduction signal.

[0226] In this way, the noise reduction circuit 105 does not need to change the existing noise reduction parameters, and can avoid distortion of the speaker 102 simply by adding an amplitude correction stage as post-processing (for example, adding a dynamic range controller).

[0227] 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 an amplitude range supported by the speaker 102: 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; and 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.

[0228] In this method, the noise reduction circuit 105 can keep the amplitude of the noise reduction signal within the new width range simply by adjusting the filter gain, and there is no need to change the circuit structure of the noise reduction circuit 105.

[0229] In some embodiments, in the adjusted filter gains, 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, the frequency of the first preset frequency band is lower than the frequency of the second preset frequency band. In some embodiments, the 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). Because the filter gain corresponding to the first preset frequency band is small, the corresponding amplitude of the filtered noise-reduced signal in the first preset frequency band can be reduced, thereby preventing distortion of the speaker 102 in the first preset frequency band.

[0230] In some embodiments, when the noise reduction circuit 105 adjusts the filter gain, it may reduce the filter gain corresponding to the first preset frequency band based on the default filter gain, while keeping the filter gain corresponding to the second preset frequency band unchanged. In this way, distortion of the speaker 102 can be prevented without impairing the noise reduction effect corresponding to the second preset frequency band.

[0231] When the acoustic device 100 provides multiple noise reduction modes, the present application provides an active noise reduction method P400 that can adaptively switch to the noise reduction mode that is most suitable for the current environment based on the noise conditions of the current environment, thereby allowing the acoustic device 100 to always provide excellent noise reduction effects 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.

[0232] 16 shows a flowchart of another active noise reduction method P400 provided in accordance with an embodiment of the present specification. This active noise reduction method P400 may be performed 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 perform 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: Acquire a first audio signal from a first audio sensor module.

[0233] S42: Self-adaptively select a target noise reduction mode from a plurality of noise reduction modes of the acoustic device based on the first audio signal. 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 intensity 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 predetermined bandwidth. Compared with the non-narrowband type, the signal energy of the narrowband type is concentrated within a narrow frequency band.

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

[0235] S42-1: Determine that the intensity of the first audio signal is equal to or less than a second intensity 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 in the external environment is low (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 acoustic device 100 can be reduced.

[0237] S42-2: Determine that the intensity of the first audio signal is equal to or greater than a first intensity 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 high (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 exceeding the second intensity threshold" is the 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 on the target frequency band where the energy of the first audio signal is concentrated, eliminating the need to perform active noise reduction across the entire frequency band. This increases the depth of noise reduction in the target frequency band and helps improve the effect of active noise reduction.

[0241] In some embodiments, the noise reduction circuit 105 self-adaptively selects the target noise reduction mode through the following decision logic: First, the noise reduction circuit 105 determines whether the intensity of the first audio signal is less than a second intensity threshold. If so, it selects the passive noise reduction mode. If not, it turns on the active noise reduction function. Then, the noise reduction circuit 105 determines whether the following two conditions are met: Condition 1: The intensity of the first audio signal is greater than or equal to the first intensity threshold; Condition 2: The bandwidth type of the first audio signal is a narrowband type. The decision result is divided into the following four cases: If only Condition 1 is met, it selects the anti-crackle noise reduction mode; if only Condition 2 is met, it selects the narrowband noise reduction mode; if both Conditions 1 and 2 are met, it can select both the anti-crackle noise reduction mode and the narrowband noise reduction mode; and if neither Condition 1 nor Condition 2 is met, it selects the normal noise reduction mode.

[0242] In some embodiments, when the first audio signal includes both an ambient noise signal and a 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 and improves 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 located, thereby making the active noise reduction process of the acoustic device 100 more suitable for the noise conditions of the current environment and helping to improve the overall performance of the acoustic device 100. For example, if the noise level of the current environment is low, the acoustic device 100 can turn off the active noise reduction function to reduce power consumption. If the noise level of the current environment is high, the acoustic device 100 can select an anti-crackle noise reduction mode to prevent the speaker 102 from crackling. If the noise level of the current environment is narrowband, the acoustic device 100 can select a 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 that may be performed by the noise reduction circuit 105. In this active noise reduction method, the noise reduction circuit 105 can obtain a user instruction, select a target noise reduction mode from the multiple noise reduction modes based on the user instruction, and then execute 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. For example, the acoustic device 100 can provide an interactive interface, which may be displayed on a screen of the acoustic device 100 or on a target device connected in communication with the acoustic device 100, through which the user can select a different noise reduction mode. In some embodiments, the user instruction can indicate a specific noise reduction mode, and 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 can independently select an appropriate active noise reduction mode according to their own preferences and / or the current environmental noise conditions, thereby meeting the individual needs of different users.

[0248] Another aspect of the present disclosure provides a non-transitory storage medium having stored thereon at least one executable instruction for performing active noise reduction. When executed by a processor, the executable instruction instructs the processor to perform the steps of the active noise reduction method described herein. In some possible embodiments, each aspect of the present disclosure may be realized in the form of a program product including program code. When the program product runs on an 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. A program product for implementing the method may be a portable compact disc read-only memory (CD-ROM) that includes the program code and is operable on the acoustic device 100. However, the program product of the present disclosure is not limited thereto. In this disclosure, a readable storage medium may be any tangible medium that contains 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 computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. Further examples of the computer-readable storage medium include 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, carrying the computer-readable program code. Such a propagated data signal may take various forms, such as, but 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 can transmit, propagate, or transmit a program for use by or in connection with an instruction execution system, device, or apparatus. The program code contained in the readable storage medium may be transmitted over any suitable medium, including, but not limited to, wireless, wired, optical, RF, 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 and C++, general procedural programming languages ​​such as "C," 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 foregoing describes specific examples of the present specification. Other examples 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, 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 such, those skilled in the art will appreciate upon reading this detailed disclosure that the foregoing detailed disclosure may be presented by way of example only and not by way of limitation. Although not expressly stated herein, this specification should cover various reasonable changes, improvements, and modifications to the examples, as would be understood by those skilled in the art. These changes, improvements, and modifications are intended to be presented by this specification and are within the spirit and scope of the illustrative examples herein.

[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," "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 this specification, in order to facilitate understanding of a single feature, this specification combines various features into a single embodiment, drawing, or description thereof for the purpose of simplifying the specification. However, this combination of features is not essential, and those skilled in the art can easily understand some of the features as a single embodiment when reading this specification. In other words, the embodiments in this specification may be understood as a combination of multiple sub-embodiments. The content of each sub-embodiment may be valid even if it contains fewer than all of the features of the single embodiment disclosed above.

[0253] Each patent, patent application, patent application publication, and other material, e.g., article, book, specification, publication, document, article, etc., cited herein may be incorporated 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 with or contradicts 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 contradiction between the description, definition, and / or use of a term associated with any included material and the description, definition, and / or use of the related term in this document, the term in this document shall control.

[0254] Finally, it should be understood that the embodiments of the application disclosed herein are illustrative 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 implement 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 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 physically connected to the support member and configured to collect a first sound and generate a first sound signal, the first sound signal including an ambient noise signal from ambient noise; 1. A noise reduction circuit, comprising: acquiring the first audio signal from the first audio sensor module; a noise reduction circuit that self-adaptively selects a target noise reduction mode from a plurality of noise reduction modes based on the first audio signal, the plurality of noise reduction modes including an anti-crackle noise reduction mode; In the distortion-preventing noise reduction mode, the noise reduction circuit executes a first noise reduction mode or a second noise reduction mode; In the first noise reduction mode, the noise reduction circuit adjusts a first filter gain corresponding to a first predetermined frequency band so that the first filter gain is lower than a second filter gain corresponding to a second predetermined frequency band, so that the frequency of the first predetermined frequency band is lower than a predetermined frequency and the frequency of the second predetermined frequency band is higher than a predetermined frequency, thereby making the amplitude of the noise cancellation signal generated by the noise reduction circuit within an amplitude range allowed by the speaker.

2. The acoustic device comprises: a second sound sensor module physically connected to the support member and configured to collect a second sound and generate a second sound signal; To implement the target noise reduction mode, the noise reduction circuitry acquiring the second audio signal from the second audio sensor module; 2. The acoustic device according to claim 1, wherein the target noise reduction mode is executed based on at least one of the first audio signal and the second audio signal.

3. the first sound sensor module is located farther from the eardrum than the speaker; The acoustic device according to claim 2 , wherein the second sound sensor module is closer to the eardrum than the speaker.

4. In the distortion prevention noise reduction mode, the noise reduction circuit generating the noise cancellation signal based on at least one of the first audio signal or the second audio signal, wherein the amplitude of the noise cancellation signal is within the allowed amplitude range of the speaker; transmitting the noise canceling signal to the speaker, whereby the speaker converts the noise canceling signal into noise canceling audio to reduce the volume of the ambient noise at the eardrum; To self-adaptively select a target noise reduction mode, the noise reduction circuit comprises:

3. The acoustic device according to claim 2, further comprising: determining that the intensity of the first audio signal is greater than a first intensity threshold; and selecting the anti-crackle noise reduction mode from the plurality of noise reduction modes.

5. In the second noise reduction mode, the noise reduction circuit: filtering at least one of the first speech signal or the second speech signal to obtain a candidate noise-canceled signal; 2. The acoustic device according to claim 1, wherein the amplitude of the candidate noise-canceling signal is corrected based on the amplitude range, the corrected amplitude is set within the amplitude range, and the signal obtained by the correction is used as the noise-canceling signal.

6. the plurality of noise reduction modes includes a narrowband noise reduction mode; In the narrowband noise reduction mode, the noise reduction circuitry: determining a target frequency band based on the first audio signal, and determining whether an energy concentration in the target frequency band exceeds a predetermined threshold; performing active noise reduction within the target frequency band based on at least one of the first audio signal or the second audio signal; To self-adaptively select a target noise reduction mode, the noise reduction circuit comprises:

3. The acoustic device according to claim 2, further comprising: determining that the intensity of the first audio signal is greater than a second intensity threshold; determining that the type of the first audio signal is a narrowband type; and selecting the narrowband noise reduction mode from the plurality of noise reduction modes.

7. the plurality of noise reduction modes includes a passive noise reduction mode; In the passive noise reduction mode, the noise reduction circuitry turns off the active noise reduction function; To self-adaptively select a target noise reduction mode, the noise reduction circuit comprises:

3. The acoustic device according to claim 2, further comprising: determining that the intensity of the first audio signal is less than a second intensity threshold; and selecting the passive noise reduction mode from the plurality of noise reduction modes.

8. the first audio signal further includes a leakage signal from the speaker; To self-adaptively select the target noise reduction mode, the noise reduction circuit generating a pseudo ambient noise signal by reducing the leakage signal component in the first audio signal; 2. The acoustic device according to claim 1, wherein the target noise reduction mode is self-adaptively selected from the plurality of noise reduction modes based on the pseudo ambient noise signal.

9. A method for active noise reduction applied to an acoustic device according to claim 1, the method being performed by the noise reduction circuit; acquiring the first audio signal from the first audio sensor module; self-adaptively selecting a target noise reduction mode from a plurality of noise reduction modes based on the first audio signal, wherein the plurality of noise reduction modes includes an anti-crackle noise reduction mode; In the distortion prevention noise reduction mode, the first noise reduction mode or the second noise reduction mode is executed; Execution of the first noise reduction mode includes: adjusting a first filter gain corresponding to a first preset frequency band so that the first filter gain is lower than a second filter gain corresponding to a second preset frequency band, such that the frequency of the first preset frequency band is lower than a preset frequency and the frequency of the second preset frequency band is higher than a preset frequency, so that the amplitude of the noise cancellation signal generated by the noise reduction circuit is within an allowable amplitude range of the speaker; A method characterized by:

10. The acoustic device comprises: a second sound sensor module physically connected to the support member and configured to collect a second sound and generate a second sound signal; The method comprises: acquiring the second audio signal from the second audio sensor module; 10. The method of claim 9, further comprising: performing the target noise reduction mode based on at least one of the first audio signal or the second audio signal.

11. The step of self-adaptively selecting a target noise reduction mode from a plurality of noise reduction modes based on the first audio signal, as described above, comprises: selecting the anti-crackle noise reduction mode from the plurality of noise reduction modes when it is determined that the intensity of the first audio signal is greater than a first intensity threshold; The step of executing the distortion prevention noise reduction mode on at least one of the first audio signal and the second audio signal includes: generating the noise cancellation signal based on at least one of the first audio signal or the second audio signal, wherein the amplitude of the noise cancellation signal is within the allowed amplitude range of the speaker; and transmitting the noise canceling signal to the speaker, whereby the speaker converts the noise canceling signal into noise canceling audio to reduce the volume of the ambient noise at the eardrum.

12. Execution of the second noise reduction mode includes: filtering at least one of the first speech signal or the second speech signal to obtain a candidate noise-canceled signal; 12. The method of claim 11, further comprising: correcting the amplitude of the candidate noise-canceled signal based on the amplitude range so that the corrected amplitude is within the amplitude range, and the corrected signal is the noise-canceled signal.

13. the plurality of noise reduction modes includes a narrowband noise reduction mode; The step of self-adaptively selecting a target noise reduction mode from a plurality of noise reduction modes based on the first audio signal as described above includes: determining that the intensity of the first audio signal is greater than a second intensity threshold, determining that the type of the first audio signal is a narrowband type, and selecting the narrowband noise reduction mode from the plurality of noise reduction modes; The step of executing the narrowband noise reduction mode on at least one of the first audio signal and the second audio signal includes: determining a target frequency band based on the first audio signal, wherein an energy concentration in the target frequency band exceeds a predetermined threshold; and performing active noise reduction within the target frequency band based on at least one of the first audio signal or the second audio signal.

14. the plurality of noise reduction modes includes a passive noise reduction mode; The step of self-adaptively selecting a target noise reduction mode from a plurality of noise reduction modes based on the first audio signal as described above includes: selecting the passive noise reduction mode from the plurality of noise reduction modes when it is determined that the strength of the first audio signal is less than a second strength threshold; The method of claim 10, wherein implementing the passive noise reduction mode includes turning off active noise reduction functionality.

15. the first audio signal further includes a leakage signal from the speaker; The step of self-adaptively selecting a target noise reduction mode from a plurality of noise reduction modes based on the first audio signal as described above includes: generating a pseudo ambient noise signal by reducing the leakage signal component in the first audio signal; and self-adaptively selecting the target noise reduction mode from the plurality of noise reduction modes based on the simulated ambient noise signal.

Images