Open wearable acoustic device and active noise reduction method

Abstract

This application provides an open-type wearable acoustic device and an active noise cancellation method. The acoustic device includes a first sound sensor module, a speaker, and a noise cancellation circuit. The first sound signal acquired by the first sound sensor module includes an ambient noise signal from the surrounding environment and a leakage signal from the speaker. The noise cancellation circuit generates a quasi-ambient noise signal by first reducing the leakage signal component in the first sound signal, and then generates a first noise-cancelling signal based on the quasi-ambient noise signal. The speaker then converts the first noise-cancelling signal into a first noise-cancelling frequency, which cancels out at least a portion of the ambient noise at and around the eardrum, thereby achieving noise reduction. Because the noise cancellation circuit reduces the leakage signal component in the first sound signal during feedforward noise cancellation, it reduces the impact of the leakage signal on feedforward noise cancellation, thus improving the noise reduction effect of active noise cancellation.

Description

Technical Field

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

[0002] Nowadays, wearable devices with acoustic output capabilities (such as headphones) are increasingly used by users. In particular, a listening method where the acoustic device does not form a closed space with the human body (i.e., an open-ear listening method, for example, not requiring the acoustic device to be inserted into the ear canal or cover the ears, or having sound-permeable holes on the surface of the acoustic device to create an open space between the eardrum and the acoustic device) is increasingly being used in wearable acoustic devices due to its comfort and safety features. These types of wearable acoustic devices are called open-back wearable devices.

[0003] When the aforementioned open-back wearable acoustic devices are worn on a user's head, they do not create a closed space between the device and the user's eardrum. Therefore, compared to closed-back acoustic devices (such as in-ear headphones), more sound from external noise sources enters the ear. This results in users hearing more ambient noise while wearing open-back acoustic devices, thus reducing their auditory experience. Therefore, there is a need for an active noise cancellation design based on open-back wearable acoustic devices. Summary of the Invention

[0004] This specification provides an open-type wearable acoustic device and an active noise cancellation method that can improve the effectiveness of active noise cancellation.

[0005] In a first aspect, this specification provides an open-type wearable acoustic device, comprising: a support, a speaker, a first sound sensor module, and a noise reduction circuit, wherein the speaker is physically connected to the support, and an open space is formed between the speaker and the user's eardrum when the acoustic device is worn on the user's head; the first sound sensor module is physically connected to the support and configured to acquire a first sound and generate a first sound signal, the first sound signal including: an ambient noise signal from ambient noise and a leakage signal from the speaker; the noise reduction circuit is configured to: acquire the first sound signal from the first sound sensor module, generate a quasi-ambient noise signal by reducing the leakage signal component in the first sound signal, generate a first noise cancellation signal based on the quasi-ambient noise signal, and send the first noise cancellation signal to the speaker, so that the speaker converts the first noise cancellation signal into a first noise cancellation frequency to reduce the volume of ambient noise at the eardrum.

[0006] In some embodiments, the first sound sensor module is located away from the eardrum relative to the speaker, and the phase of the ambient noise reaching the first sound sensor module leads the phase of the ambient noise reaching the output end of the speaker.

[0007] In some embodiments, in order to generate the quasi-ambient noise signal, the noise reduction circuit: acquires an input signal corresponding to the loudspeaker; provides a first gain to the input signal to obtain a first gain signal, wherein the first gain is a transfer function between the loudspeaker and the first sound sensor module; and acquires the first sound signal from the first sound sensor module and subtracts the first gain signal from the first sound signal to obtain the quasi-ambient noise signal.

[0008] In some embodiments, the noise reduction circuit is further configured to: send a test audio signal to the speaker to cause the speaker to emit a corresponding test audio, the test audio being acquired by the first sound sensor module; acquire the acquired audio signal acquired by the first sound sensor module; and determine the transfer function based on the test audio signal and the acquired audio signal.

[0009] In some embodiments, the noise reduction circuit includes a feedforward filter, wherein, in order to generate the first noise-cancelled signal, the noise reduction circuit: inputs the quasi-ambient noise signal into the feedforward filter, and filters the quasi-ambient noise signal through the feedforward filter to obtain the first noise-cancelled signal, wherein the feedforward filter is configured to adjust at least one of the gain or phase of the quasi-ambient noise signal such that the obtained first noise-cancelled signal can cancel out at least a portion of the ambient noise at the eardrum.

[0010] In some embodiments, the distance between the first sound sensor module and the acoustic null position of the speaker is within a non-zero preset range.

[0011] In some embodiments, the acoustic device further includes a second sound sensor module physically connected to the support member, configured to acquire a second sound and generate a second sound signal; and the noise reduction circuit is further configured to: acquire the second sound signal from the second sound sensor module, generate a second noise cancellation signal based on the second sound signal, and send the second noise cancellation signal to the speaker so that the speaker converts the second noise cancellation signal into a second noise cancellation frequency to further reduce the volume of ambient noise at the eardrum.

[0012] In some embodiments, the second sound sensor module is positioned close to the eardrum relative to the speaker, and the phase of the ambient noise reaching the second sound sensor module lags behind the phase of the ambient noise reaching the output end of the speaker.

[0013] In some embodiments, in order to send the first noise cancellation signal and the second noise cancellation signal to the speaker, the noise reduction circuit: synthesizes the first noise cancellation signal and the second noise cancellation signal to obtain a synthesized noise cancellation signal; and sends the synthesized noise cancellation signal to the speaker.

[0014] In some embodiments, the noise reduction circuit includes a feedback filter, wherein, in order to generate the second noise-canceling signal, the noise reduction circuit: inputs the second sound signal into the feedback filter; and filters the second sound signal through the feedback filter to obtain the second noise-canceling signal, wherein the feedback filter is configured to adjust at least one of the gain or phase of the second sound signal such that the obtained second sound signal can cancel out at least a portion of the ambient noise at the eardrum.

[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 noise reduction; 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 running, the at least one processor reads the at least one instruction set and executes according to the instructions of the at least one instruction set: acquiring the first sound signal from the first sound sensor, generating a quasi-ambient noise signal by reducing the leakage signal component in the first sound signal, generating a first noise cancellation signal based on the quasi-ambient noise signal, and sending the first noise cancellation signal to the speaker, so that the speaker converts the first noise cancellation signal into a first noise cancellation frequency to reduce the volume of ambient noise at the eardrum.

[0016] In some embodiments, the acoustic device is one of headphones, a muffler, a hearing aid, or acoustic glasses.

[0017] Secondly, this specification also provides an active noise cancellation method applied to an open-type wearable acoustic device as described in the first aspect. The method includes, via a noise cancellation circuit: acquiring a first sound signal from a first sound sensor module; generating a quasi-ambient noise signal by reducing the leakage signal component in the first sound signal; generating a first noise cancellation signal based on the quasi-ambient noise signal; and sending the first noise cancellation signal to the speaker, causing the speaker to convert the first noise cancellation signal into a first noise cancellation frequency to reduce the volume of ambient noise at the eardrum.

[0018] In some embodiments, the phase of the ambient noise measured by the first sound sensor module leads the phase of the ambient noise reaching the output end of the speaker.

[0019] In some embodiments, generating a quasi-ambient noise signal by reducing the leakage signal component in the first sound signal includes: acquiring an input signal corresponding to the loudspeaker; providing a first gain to the input signal to obtain a first gain signal, wherein the first gain is a transfer function between the loudspeaker and the first sound sensor module; and acquiring the first sound signal from the first sound sensor module and subtracting the first gain signal from the first sound signal to obtain the quasi-ambient noise signal.

[0020] In some embodiments, the method further includes, through the noise reduction circuit: sending a test audio signal to the speaker to cause the speaker to emit a corresponding test audio, the test audio being acquired by the first sound sensor module; acquiring the acquired audio signal acquired by the first sound sensor module; and determining the transfer function based on the test audio signal and the acquired audio signal.

[0021] In some embodiments, the noise reduction circuit includes a feedforward filter; and the generation of a first noise-cancelled signal based on the quasi-ambient noise signal includes: inputting the quasi-ambient noise signal into the feedforward filter, and filtering the quasi-ambient noise signal through the feedforward filter to obtain the first noise-cancelled signal, wherein the feedforward filter is configured to adjust at least one of the gain or phase of the quasi-ambient noise signal such that the obtained first noise-cancelled signal can cancel out at least a portion of the ambient noise at the eardrum.

[0022] In some embodiments, the acoustic device further includes a second sound sensor module physically connected to the support member, configured to acquire a second sound and generate a second sound signal; and the method further includes, through the noise reduction circuit: acquiring the second sound signal from the second sound sensor module, generating a second noise cancellation signal based on the second sound signal, and sending the second noise cancellation signal to the speaker, so that the speaker converts the second noise cancellation signal into a second noise cancellation frequency to further reduce the volume of ambient noise at the eardrum.

[0023] In some embodiments, the phase of the ambient noise measured by the second sound sensor module lags behind the phase of the ambient noise reaching the output end of the speaker.

[0024] In some embodiments, the noise reduction circuit includes a feedback filter; and the generation of a second noise-canceling signal based on the second sound signal includes: inputting the second sound signal into the feedback filter, and filtering the second sound signal through the feedback filter to obtain the second noise-canceling signal, wherein the feedback filter is configured to adjust at least one of the gain or phase of the second sound signal such that the obtained second noise-canceling signal can cancel out at least a portion of the ambient noise at the eardrum.

[0025] As can be seen from the above technical solutions, the open-type wearable acoustic device and active noise cancellation method provided in this specification include a first sound sensor module, a speaker, and a noise cancellation circuit. The first sound signal collected by the first sound sensor module includes an ambient noise signal from the surrounding environment and a leakage signal from the speaker. The noise cancellation circuit generates a quasi-ambient noise signal by first reducing the leakage signal component in the first sound signal, and then generates a first noise-cancelling signal based on the quasi-ambient noise signal. The speaker then converts the first noise-cancelling signal into a first noise-cancelling frequency, which cancels out at least part of the ambient noise at and around the eardrum, thereby achieving noise reduction. Because the noise cancellation circuit reduces the leakage signal component in the first sound signal during the feedforward noise cancellation process, it reduces the impact of the leakage signal on the feedforward noise cancellation, thus improving the noise reduction effect of active noise cancellation.

[0026] Other features of the open-type wearable acoustic devices and active noise cancellation methods provided in this specification will be partially listed in the following description. The inventive aspects of the open-type wearable acoustic devices and active noise cancellation methods provided in this specification can be fully explained by practice or by using the methods, devices, and combinations described in the detailed examples below. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1A A schematic diagram of a wearing scenario for an acoustic device provided according to an embodiment of this specification is shown;

[0029] Figure 1B A schematic diagram of an acoustic device that is worn in the ear is shown;

[0030] Figure 1C A schematic diagram of an acoustic device that is worn with an ear loop is shown;

[0031] Figure 1D A schematic diagram of an acoustic device that uses an ear-clipping wearing method is shown;

[0032] Figure 2 A schematic diagram of the hardware structure of an acoustic device provided according to an embodiment of this specification is shown;

[0033] Figure 3 A schematic diagram showing leakage signals collected by sound sensors at different locations in an acoustic device is shown.

[0034] Figure 4 A flowchart of an active noise reduction method provided according to an embodiment of this specification is shown;

[0035] Figure 5 A schematic diagram illustrating the active noise reduction principle of an acoustic device according to an embodiment of this specification is shown.

[0036] Figure 6 A schematic diagram illustrating the noise reduction effect of an active noise reduction method provided according to an embodiment of this specification is shown.

[0037] Figure 7 A flowchart of another active noise reduction method provided according to an embodiment of this specification is shown;

[0038] Figure 8A A schematic diagram is shown of the frequency response curves for feedforward noise reduction of ambient noise at the eardrum using different feedforward filter gains when the first user is wearing acoustic devices.

[0039] Figure 8B A schematic diagram is shown of the frequency response curves of feedforward noise reduction of a second sound signal using different feedforward filter gains when the first user is wearing an acoustic device.

[0040] Figure 9A A schematic diagram is shown of the frequency response curves for feedforward noise reduction of ambient noise at the eardrum using different feedforward filter gains when a second user is wearing acoustic devices.

[0041] Figure 9B A schematic diagram is shown of the frequency response curves for feedforward noise reduction of a second sound signal using different feedforward filter gains when a second user is wearing an acoustic device.

[0042] Figure 10 A schematic diagram showing the distribution of each sound sensor in the case where the first sound sensor module includes two sound sensors is shown.

[0043] Figure 11 A schematic diagram showing the distribution of the sound sensors in the case where the first sound sensor module includes three sound sensors is shown.

[0044] Figure 12 A flowchart of yet another active noise reduction method provided according to an embodiment of this specification is shown;

[0045] Figure 13 A schematic diagram illustrating the active noise cancellation principle of another acoustic device provided according to an embodiment of this specification is shown;

[0046] Figure 14 A schematic diagram of a set of frequency response curves provided according to embodiments of this specification is shown;

[0047] Figure 15 A schematic diagram of yet another set of frequency response curves provided according to embodiments of this specification is shown; and

[0048] Figure 16 A flowchart of yet another active noise reduction method provided according to an embodiment of this specification is shown. Detailed Implementation

[0049] The following description provides specific application scenarios and requirements for this specification, intended to enable those skilled in the art to make and use the contents of this specification. Various partial modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of this specification. Therefore, this specification is not limited to the embodiments shown, but rather to the widest scope consistent with the claims.

[0050] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not restrictive. For example, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” used herein may also include the plural forms. When used in this specification, the terms “comprising,” “including,” and / or “containing” mean that the associated integers, steps, operations, elements, and / or components are present, 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.

[0051] Considering the following description, these and other features of this specification, as well as the operation and function of the related components of the structure, and the economy of assembly and manufacture of the parts, can be significantly improved. All of these form part of this specification with reference to the accompanying drawings. However, it should be clearly understood that the drawings are for illustrative and descriptive purposes only and are not intended to limit the scope of this specification. It should also be understood that the drawings are not drawn to scale.

[0052] The flowcharts used in this specification illustrate operations implemented according to some embodiments of this specification. It should be clearly understood that the operations in the flowcharts may not be implemented in a sequential order. Instead, the operations may be implemented in reverse order or simultaneously. Furthermore, one or more additional operations may be added to the flowcharts. One or more operations may be removed from the flowcharts.

[0053] For ease of description, the terms used in this manual will be explained first:

[0054] Closed-back acoustic devices: Some acoustic devices, when worn, create a closed space between the device and the user's eardrum; these devices can be called closed-back acoustic devices. For example, acoustic devices can use in-ear designs (such as earbuds), closed-back designs, or other similar designs to create a closed space between the device and the user's eardrum. When a user wears a closed-back acoustic device, this closed space physically isolates external noise, reducing interference from external noise. However, users often experience discomfort when wearing closed-back acoustic devices for extended periods.

[0055] Open-back acoustic devices: Some acoustic devices, when worn, create an open space between the device and the user's eardrum. These devices can be called open-back acoustic devices. For example, the device may not be inserted into or cover the ear canal, or its surface may have sound-permeable holes, creating an open space between it and the eardrum. Open-back acoustic devices improve user comfort and make the sound heard more transparent and natural.

[0056] Noise: In this application, any sound that is unwelcome to the user, unwanted by the user, or that interferes with the user's hearing can be called noise.

[0057] Passive noise cancellation refers to noise reduction techniques that employ passive methods. These passive methods include, but are not limited to, eliminating (or partially eliminating) noise sources, blocking noise propagation, or preventing the user's ears from hearing noise, or any combination thereof. For example, creating a closed space inside the ear to achieve noise reduction is a passive noise cancellation technique. Passive noise cancellation can also be called passive noise reduction technology. Passive noise cancellation does not eliminate noise, but rather suppresses it through physical means.

[0058] Active noise cancellation refers to a technique that actively reduces noise by generating a noise-canceling signal (e.g., a signal with the opposite phase to the noise to be suppressed). Specifically, acoustic devices employing active noise cancellation can collect noise signals using sound sensors, generate a noise-canceling signal through a noise reduction circuit, and play this signal through a speaker. The noise-canceling signal cancels out the noise signal, thus eliminating it. Active noise cancellation technology can also be called active noise reduction technology. Active noise cancellation technology can be categorized into feedforward noise cancellation, feedback noise cancellation, and hybrid noise cancellation.

[0059] Feedforward noise reduction: A sound sensor is placed outside the acoustic device to collect ambient noise and generate an ambient noise signal. This signal is then filtered by a feedforward filter to generate a noise-cancelled signal, which is played through a speaker. This noise-cancelled signal cancels out (or partially cancels out) the ambient noise at the eardrum, thus reducing the volume of ambient noise heard by the user. The feedforward filter primarily compensates for the difference between the ambient noise at the eardrum and the ambient 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.

[0060] Feedback noise reduction: A sound sensor is placed inside the acoustic device to collect ambient noise in the area near the eardrum. This ambient noise is then filtered by a feedback filter to generate a noise-canceling signal, which is played through a speaker. In this way, the noise-canceling signal cancels out (or partially cancels out) the ambient noise at the eardrum, thereby reducing the volume of 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.

[0061] Hybrid noise reduction: Hybrid noise reduction refers to the combined use of feedforward noise reduction and feedback noise reduction techniques. Generally speaking, compared to feedforward noise reduction or feedback noise reduction alone, hybrid noise reduction can further improve the noise reduction effect.

[0062] This application provides an open-type wearable acoustic device (hereinafter referred to as "acoustic device") and its active noise reduction method, which can reduce the volume of ambient noise heard by the user and reduce the interference of ambient noise on the user in the scenario where the user wears the acoustic device.

[0063] Figure 1AA schematic diagram of a wearing scenario for an acoustic device according to an embodiment of this specification is shown. In scenario 001, the acoustic device 100 is worn on the user's ear 200. The ear 200 may include an auricle 201 and an eardrum 202. The acoustic device 100 may be worn on the auricle 201, and there is no closed space between the acoustic device 100 and the eardrum 202, forming an open space. Scenario 001 may also include a noise source 300, and the number of noise sources 300 may be one or more. The noise source 300 is configured to emit ambient noise (e.g., unwelcome, unwanted, or interfering sounds). The acoustic device 100 is configured to suppress or eliminate ambient noise heard by the human ear. Specifically, the acoustic device 100 employs active noise cancellation, suppressing or eliminating ambient noise by generating and outputting a noise cancellation signal (a signal opposite in phase to the ambient noise).

[0064] In some embodiments, the acoustic device 100 may be headphones, a muffler, a hearing aid, acoustic glasses, or any combination thereof. For ease of understanding, Figure 1A The acoustic device 100 is illustrated using headphones as an example. When the acoustic device 100 is acoustic glasses, a sound output device can be provided in the area of ​​the temples of the acoustic glasses near the ears, configured to output sound to the user's ears. It should be noted that the acoustic device 100 can be worn on the user's ears 200 in any manner, and this application does not limit this. For example, the wearing method of the acoustic device 100 may include headband, in-ear, neckband, ear-hook, or clip-on, or any combination thereof.

[0065] In some embodiments, scenario 001 may further include: a network and a target device ( Figure 1A (Not shown in the image). The target device can be an electronic device with audio output functionality. The acoustic device 100 and the target device can be connected via network communication, and they can transmit data or signals to each other through the network. For example, the target device can send the target audio (e.g., music, voice, etc.) to be played to the acoustic device 100 via the network, so that the acoustic device 100 can output the target audio to the user.

[0066] In some embodiments, the target device may be equipped with an audio acquisition device to acquire target audio. In some embodiments, the target device may receive the target audio from other devices. In some embodiments, the target device may include a mobile device, tablet computer, laptop computer, built-in device of a motor vehicle, or similar content, or any combination thereof. In some embodiments, the mobile device may include a smart home device, smart mobile device, virtual reality device, augmented reality device, or similar device, or any combination thereof. In some embodiments, the smart home device may include a smart TV, desktop computer, smart speaker, etc., or any combination thereof. In some embodiments, the smart mobile device may include a smartphone, personal digital assistant, gaming device, navigation device, etc., or any combination thereof. In some embodiments, the virtual reality device or augmented reality device may include a virtual reality headset, virtual reality glasses, virtual reality patch, augmented reality headset, augmented reality glasses, augmented reality patch, or similar content, or any combination thereof. For example, the virtual reality device or the augmented reality device may include Google Glass, head-mounted display, VR, etc. In some embodiments, the built-in device in the motor vehicle may include an in-vehicle computer, in-vehicle TV, etc.

[0067] In some embodiments, the network can be any type of wireless network. For example, the network may include a telecommunications network, intranet, internet, local area network (LAN), wide area network (WAN), wireless local area network (WLAN), metropolitan area network (MAN), public switched telephone network (PSTN), Bluetooth network, ZigBee network, near field communication (NFC) network, or similar network. In some embodiments, the network may be a Bluetooth network, in which case the acoustic device 100 and the target device can communicate based on the Bluetooth protocol.

[0068] See also Figure 1A The acoustic device 100 may include: a support 101, a speaker 102, a noise reduction circuit 105, and at least one sound sensor module. The speaker 102 and the at least one sound sensor module can both be physically connected to the support 101.

[0069] The support member 101 can be used to assist in fixing the acoustic device 100 to the user's ear. For example, the support member 101 can be the housing of the acoustic device 100 or other additional structures. It should be noted that this application does not limit the specific shape of the support member 101. It should be understood that the specific shape of the support member 101 is related to the wearing method supported by the acoustic device 100.

[0070] Figure 1BA schematic diagram of an acoustic device worn in the ear is shown. In this case, the support member 101 can be designed to fit the auricle 201, with one or more support points on the support member 101 that fit with preset points on the auricle 201. Figure 1C A schematic diagram of an acoustic device worn on the ear is shown. In this case, the support 101 can be a suspension structure, allowing the acoustic device 100 to be suspended on the auricle 201. Figure 1D A schematic diagram of an acoustic device using a clip-on wearing method is shown. In this case, the support 101 can adopt a clamping structure so that the support 101 can be clamped onto the auricle 201.

[0071] See also Figure 1A The speaker 102 can be positioned on the side of the acoustic device 100 near the ear canal opening. When the acoustic device 100 is worn on the 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 the user's head, the speaker 102 can be close to the user's ear canal opening without blocking it, 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-enclosed housing, for example, the housing is provided with sound-permeable holes, so that an open space is formed between the speaker 102 and the eardrum 202.

[0072] The loudspeaker 102 can be configured to generate audio based on an audio signal (or convert an audio signal into audio). Here, the audio signal is an electrical signal carrying sound information; audio refers to the sound signal played through the loudspeaker. When sound is emitted from an initial sound source (such as an ambient noise source, a person's throat, etc.), it is converted into an electrical signal carrying that sound information, i.e., the audio signal, by a sensor (such as a microphone), which collects the sound. The loudspeaker 102 can also be called an electroacoustic transducer; during operation, it can receive the audio signal carrying sound information and then convert it back into a sound signal for playback. In some embodiments, the acoustic device 100 may include multiple loudspeakers 102. In this case, the multiple loudspeakers 102 can be arranged in an array, such as a linear array, a planar array, a spherical array, or other arrays.

[0073] In some embodiments, the at least one sound sensor module described above may include a first sound sensor module 103. For example... Figure 1AAs shown, the first sound sensor module 103 is located away from the eardrum 202 relative to the speaker 102. That is, the first sound sensor 103 can be positioned on the outer side of the acoustic device 100 (the side of the acoustic device 100 away from the eardrum 202 is considered the outer side when the acoustic device 100 is worn on the user's head). 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, these multiple sound sensors can be arranged in an array, such as a linear array, planar array, spherical array, or other arrays. In some embodiments, the sound sensor is a device for collecting sound and converting it into an electrical signal, such as a microphone.

[0074] In some embodiments, the at least one sound sensor module described above may include a second sound sensor module 104. The second sound sensor module 104 is positioned close to (or near) the eardrum 202 relative to the speaker 102. That is, the second sound sensor module 104 is disposed on the inner side of the acoustic device 100 (when the acoustic device 100 is worn on the user's head, the side of the acoustic device 100 closest to the eardrum 202 is considered the inner side). In some embodiments, the second sound sensor module 104 may include one or more sound sensors. When the second sound sensor module 104 includes multiple sound sensors, the multiple sound sensors may be arranged in an array, such as a linear array, a planar array, a spherical array, or other arrays.

[0075] In some embodiments, the at least one sound sensor module may simultaneously include a first sound sensor module 103 and a second sound sensor module 104.

[0076] The first sound sensor module 103 is configured to acquire a first sound and generate a first sound signal corresponding to the first sound. The first sound can be an analog sound signal or an electrical signal. It should be understood that, since a noise source 300 exists in the environment where the acoustic device 100 is located, the first sound sensor module 103 can acquire the ambient noise emitted by the noise source 300. Additionally, since an open space is formed between the speaker 102 and the eardrum 202, the first sound sensor module 103 can also acquire the sound emitted by the speaker 102. For ease of description, the sound acquired by the first sound sensor module 103 from the speaker 102 is referred to as leakage sound in this application. Therefore, the first sound acquired by the first sound sensor module 103 includes both ambient noise and leakage sound. Accordingly, the first sound signal generated by the first sound sensor module 103 includes: the ambient noise signal from the noise source 300 and the leakage signal from the speaker 102.

[0077] The first sound sensor module 103 is farther from the eardrum 202 relative to the speaker 102, meaning it is closer to the noise source 300. Therefore, the ambient noise arrives at the first sound sensor module 103 earlier than it arrives at the output end of the speaker 102. In other words, the phase of the ambient noise arriving at the first sound sensor module 103 leads the phase of its arrival at the output end of the speaker 102. Therefore, the first sound signal acquired by the first sound sensor module 103 can be used for feedforward noise reduction.

[0078] The second sound sensor module 104 is configured to acquire a second sound and generate a second sound signal corresponding to the second sound. The second sound can be an analog sound signal or an electrical signal. For open acoustic devices, the second sound sensor module 104 can acquire both the ambient noise emitted by the noise source 300 and the sound emitted by the speaker 102. Therefore, the second sound acquired by the second sound sensor module 104 includes components of both ambient noise and the sound emitted by the speaker 102. In an active noise cancellation scenario, the ambient noise emitted by the noise source 300 is conducted along the air to the open space. A portion of the ambient noise within the open space is canceled or attenuated by the sound from the speaker 102 during the active noise cancellation process. Therefore, the second sound acquired by the second sound sensor module 104 can also be referred to as residual noise, i.e., the ambient noise remaining within the open space.

[0079] The second sound sensor module 104 is positioned closer to the eardrum 202 relative to the speaker 102, meaning it is farther from the noise source 300. Therefore, the ambient noise arrives at the second sound sensor module 104 later than it arrives at the output end of the speaker 102. In other words, the phase of the ambient noise arriving at the second sound sensor module 104 lags behind the phase of its arrival at the output end of the speaker 102. Therefore, the second sound signal acquired by the second sound sensor module 104 can be used for feedback noise reduction.

[0080] See also Figure 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 ambient noise audible to the human ear. The active noise reduction described above can be any one of feedforward noise reduction, feedback noise reduction, or hybrid noise reduction.

[0081] In some embodiments, the noise reduction circuit 105 can be configured to perform feedforward noise reduction. In this case, the noise reduction circuit 105 can acquire a first sound signal from the first sound sensor module 103 and perform active noise reduction based on the first sound signal.

[0082] In some embodiments, the noise reduction circuit 105 performing active noise reduction based on the first sound signal may include: the noise reduction circuit 105 generating a first noise cancellation signal based on the first sound signal. The noise reduction circuit 105 sends the first noise cancellation signal to the speaker 102, causing the speaker 102 to convert the first noise cancellation signal into a first noise cancellation frequency. The phase of the first noise cancellation signal may be set to be opposite or approximately opposite to the phase of the ambient noise in the space at the eardrum 202, or to have a preset phase difference, so that the phase of the first noise cancellation frequency is opposite or approximately opposite to the phase of the ambient noise at and near the eardrum 202, thereby reducing the volume of the ambient noise at the eardrum 202. In some embodiments, the noise reduction circuit 105 may include a feedforward filter connected to the first sound sensor module 103 and the speaker 102. After acquiring the first sound signal from the first sound sensor 103, the noise reduction circuit 105 can input the first sound signal into the feedforward filter, filter the first sound signal through the feedforward filter to obtain the first noise cancellation signal, and output the first noise cancellation signal to the speaker 102. The feedforward filter is configured to adjust at least one of the gain or phase of the first sound signal, such that the resulting first noise-cancelled signal can cancel out at least a portion of the ambient noise at the eardrum 202.

[0083] In some embodiments, the noise reduction circuit 105 may also be configured to perform feedback noise reduction. In this case, the noise reduction circuit 105 can acquire a second sound signal from the second sound sensor module 104 and perform active noise reduction based on the second sound signal.

[0084] In some embodiments, the process of active noise reduction by the noise reduction circuit 105 based on the second sound signal may include: the noise reduction circuit 105 generating a second noise cancellation signal based on the second sound signal. The noise reduction circuit 105 sends the second noise cancellation signal to the speaker 102, so that the speaker 102 converts the second noise cancellation signal into a second noise cancellation frequency. The second noise cancellation signal may be set to be opposite, approximately opposite, or have a preset phase difference with the ambient noise at the eardrum 202, so that the phase of the second noise cancellation frequency is opposite or approximately opposite to the phase of the ambient noise at the eardrum 202 and the surrounding space, thereby reducing the volume of the ambient noise at the eardrum 202. In some embodiments, the noise reduction circuit 105 may include a feedback filter connected to the second sound sensor module 103 and the speaker 102. After acquiring the second sound signal from the second sound sensor 103, the noise reduction circuit 105 can input the second sound signal into the feedback filter, filter the second sound signal through the feedback filter to obtain the second noise cancellation signal, and output the second noise cancellation signal to the speaker 102. The feedback filter is configured to adjust at least one of the gain or phase of the second sound signal, such that the resulting second noise-cancelled signal can cancel out at least a portion of the ambient noise at the eardrum 202.

[0085] In some embodiments, the noise reduction circuit 105 may also be configured to perform hybrid noise reduction. In this case, the noise reduction circuit 105 may acquire a first sound signal from the first sound sensor module 103, acquire a second sound signal from the second sound sensor module 104, and perform active noise reduction based on the first and second sound signals.

[0086] In some embodiments, the process of active noise reduction by the noise reduction circuit 105 based on a first sound signal and a second sound signal may include: the noise reduction circuit 105 generating a first noise-canceling signal based on the first sound signal and generating a second noise-canceling signal based on the second sound signal. The noise reduction circuit 105 sends the first noise-canceling signal and the second noise-canceling signal to the speaker 102, so that the speaker 102 converts the first noise-canceling signal and the second noise-canceling signal into noise-canceling frequencies to reduce the volume of ambient noise at the eardrum 202 and the surrounding space. In some embodiments, the noise reduction circuit 105 may include a feedforward filter and a feedback filter. The feedforward filter is connected to the first sound sensor module 103 and the speaker 102. The feedback filter is connected to the second sound sensor module 104 and the speaker 102. The noise reduction circuit 105 can input the first sound signal into the feedforward filter, filter the first sound signal through the feedforward filter to obtain the first noise-canceling signal, and input the second sound signal into the feedback filter, filter the second sound signal through the feedback filter to obtain the second noise-canceling signal. Then, the noise reduction circuit 105 sends the first noise-canceling signal and the second noise-canceling 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, such that the audio generated by the first noise-canceling signal after conversion by the speaker 102 can cancel out at least a portion of the ambient noise at and near the eardrum 202 (i.e., the phase of the audio is opposite or approximately opposite to the phase of at least a portion of the ambient noise at and near the eardrum 202). The feedback filter is configured to adjust at least one of the gain or phase of the second audio signal, such that the audio generated by the first noise-canceling signal after conversion by the speaker 102 can cancel out at least a portion of the ambient noise at the eardrum 202 (i.e., the phase of the audio is opposite or approximately opposite to the phase of at least a portion of the ambient noise at and near the eardrum 202). In some embodiments, the noise reduction circuit 105 can send the first noise-canceling signal and the second noise-canceling signal to the speaker 102 respectively. In some embodiments, the noise reduction circuit 105 can first synthesize the first noise-canceling signal and the second noise-canceling signal to obtain a synthesized noise-canceling signal, and then send the synthesized noise-canceling signal to the speaker 102.

[0087] In some embodiments, the noise reduction circuit 105 can be configured to perform the active noise reduction method described herein. In this case, the noise reduction circuit 105 may store data or instructions for performing the active noise reduction method described herein, and may execute or be used to execute said data or instructions. In some embodiments, the noise reduction circuit 105 may include a hardware device with data processing capabilities and the necessary programs required to drive the hardware device. The active noise reduction method described above will be described in detail later.

[0088] Figure 2A schematic diagram of the hardware structure of an acoustic device according to an embodiment of this specification is shown. Figure 2 As shown, 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 sound sensor module 103, and the second sound sensor module 104. It should be noted that, for illustrative purposes only, the noise reduction circuit 105 in this application includes at least one storage medium 106 and at least one processor 107. Those skilled in the art will understand that the noise reduction circuit 105 may also include other hardware circuit structures, which are not limited in this application, as long as they satisfy the functions mentioned in this application without departing from the spirit of this application.

[0089] In some embodiments, the acoustic device 100 may further include a communication port 108. The communication port 108 is used for data communication between the acoustic device 100 and the outside world, for example, the communication port 108 may be used for data communication between the acoustic device 100 and other devices.

[0090] In some embodiments, the acoustic device 100 may further include an internal communication bus 109. The internal communication bus 109 may connect different system components. For example, the speaker 102, the first sound sensor module 103, the second sound 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.

[0091] Storage medium 106 may include a data storage device. The data storage device may be a non-transitory storage medium or a temporary storage medium. For example, the data storage device may include one or more of a disk 1061, a read-only storage medium (ROM) 1062, or a random access storage medium (RAM) 1063. Storage medium 106 also includes at least one instruction set stored in the data storage device. The instruction set includes instructions, which are computer program code. The computer program code may include programs, routines, objects, components, data structures, procedures, modules, etc., that execute the active noise reduction method provided in this specification.

[0092] At least one processor 107 is used to execute the at least one instruction set described above. When the acoustic device 100 is running, the at least one processor 107 reads the at least one instruction set and, according to the instructions of the at least one instruction set, executes the active noise cancellation method provided in this specification. The processor 107 can execute all or some of the steps included in the communication method. The processor 107 can be in the form of one or more processors. In some embodiments, the processor 107 may include one or more hardware processors, such as a microcontroller, microprocessor, reduced instruction set computer (RISC), application-specific integrated circuit (ASIC), application-specific instruction set processor (ASIP), central processing unit (CPU), graphics processing unit (GPU), physical processing unit (PPU), microcontroller unit, digital signal processor (DSP), field-programmable gate array (FPGA), advanced RISC machine (ARM), programmable logic device (PLD), any circuit or processor capable of performing one or more functions, etc., or any combination thereof. This is merely for illustrative purposes. Figure 2 The acoustic device 100 shown illustrates a case comprising only one processor 107. However, it should be noted that the acoustic device 100 may also include multiple processors; therefore, the operational and / or method steps disclosed herein may be executed by a single processor as described herein, or they may be executed jointly by multiple processors. For example, if processor 107 of the acoustic device 100 in this specification executes steps A and B, it should be understood that steps A and B may also be executed jointly or separately by two different processors 120 (e.g., a first processor executes step A, a second processor executes step B, or the first and second processors jointly execute steps A and B).

[0093] As will be known to those skilled in the art, Figure 2 This is just one design scheme for the noise reduction circuit 105. The noise reduction circuit 105 can also be designed in other hardware forms without departing from the spirit of the invention disclosed in this application. The specific design scheme of the noise reduction circuit 105 is not limited in this application.

[0094] As previously stated, in an open acoustic device, the first sound signal collected and generated by the first sound sensor module 103 is not a simple ambient noise signal, but a mixed sound signal including both ambient noise and leakage signals. Therefore, if the noise reduction circuit 105 performs feedforward noise reduction directly based on the first sound signal, the leakage signal will affect the feedforward noise reduction process, resulting in poor feedforward noise reduction performance.

[0095] In some embodiments, to reduce the impact of leakage signals on the feedforward noise reduction effect, the acoustic device 100 can employ physical isolation by placing the first sound sensor module 103 at the acoustic null position of the speaker 102. For example, the speaker 102 can be designed as a dipole horn, with the first sound sensor module 103 located at the acoustic null position of the dipole horn. In this way, the first acoustic sensor module 103 cannot collect leakage signals from the speaker 102, or only collects a very small amount of leakage signal.

[0096] Figure 3 This diagram illustrates leakage signals collected by sound sensors at different locations within an acoustic device. FF1 and FF2 represent sound sensors located at the acoustic null point of speaker 102, and FF3 represents a sound sensor located near speaker 102. During testing, after applying an excitation signal to speaker 102, the leakage signal collected by FF1 is obtained as shown below. Figure 3 Curve 301 is shown, and the leakage signal collected by FF2 is obtained as follows. Figure 3 Curve 302 shown is used to obtain the leakage signal acquired by FF3, as shown in the figure. Figure 3 Curve 303 is shown. Figure 3 It can be seen that when the ambient frequency is low (e.g., below 1500Hz), the leakage signals collected by FF1 and FF2 are reduced by more than 20dB compared with the leakage signal collected by FF3, which can achieve a certain noise reduction effect.

[0097] In some embodiments, the distance between the first acoustic sensor module 103 and the acoustic null position of the speaker 102 can be within a non-zero preset range. That is, the first acoustic sensor module 103 can be positioned closer to the acoustic null position of the speaker 102, rather than being strictly located at the acoustic null position of the speaker 102. This reduces the requirements for the structural design and assembly process of the acoustic device 100.

[0098] This application provides an active noise reduction method P100, which can reduce the impact of leakage signal on feedforward noise reduction by reducing the component of leakage signal in the first audio signal, thereby improving the noise reduction effect. The above-mentioned active noise reduction method P100 can be applied to scenarios where "the first audio sensor module 103 is not located at the acoustic null position of the speaker 102" or "the first audio sensor module 103 is located at the acoustic null position of the speaker 102". In the scenario where "the first audio sensor module 103 is located at the acoustic null position of the speaker 102", there is still a problem of speaker signal leakage to the first audio sensor module in some frequency bands (e.g., Figure 3When the frequency is above 5000Hz, the leakage signals collected by FF1 and FF2 are basically equivalent to the leakage signal collected by FF3. Therefore, the active noise reduction method P100 provided in this application can be used for active noise reduction in the specific frequency band where leakage exists, so as to improve the noise reduction effect. The active noise reduction method P100 can be applied independently to the acoustic device 100 provided in this application, or it can be combined with other active noise reduction methods described in other parts of this document.

[0099] Figure 4 A flowchart of an active noise reduction method according to an embodiment of this specification is shown. This active noise reduction method P100 can be performed by a noise reduction circuit 105 in an acoustic device 100. For example, when the noise reduction circuit 105 employs... Figure 2 In the structure shown, the processor 107 in the noise reduction circuit 105 can read the instruction set stored in its local storage medium, and then execute the active noise reduction method P100 described in this specification according to the instructions of the instruction set. Figure 4 As shown, the active noise reduction method P100 may include:

[0100] S11: Obtain a first sound signal from the first sound sensor module, the first sound signal including an ambient noise signal from the ambient noise and a leakage signal from the speaker.

[0101] As previously described, the first sound sensor module 103 acquires a first sound and converts it into a first sound signal. The first sound is actually a mixture of ambient noise from the noise source 300 and leakage sound from the speaker 102. Therefore, the first sound signal simultaneously includes both the ambient noise signal corresponding to the ambient noise and the leakage signal corresponding to the leakage 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.

[0102] S12: A quasi-ambient noise signal is generated by reducing the leakage signal component in the first sound signal.

[0103] Specifically, the noise reduction circuit 105 can measure the leakage signal component contained in the first sound signal in some way, and then subtract the leakage signal component from the first sound signal to obtain a quasi-ambient noise signal. It should be noted that the measured leakage signal component may deviate from the actual leakage signal. Therefore, subtracting the measured leakage signal component from the first sound signal does not strictly equal the actual ambient noise signal, but rather approximates it. Therefore, in this application, the reduction result is referred to as the quasi-ambient noise signal. The quasi-ambient noise signal can be understood as a compensation signal obtained by compensating for leakage in the first sound signal.

[0104] Figure 5 A schematic diagram illustrating the active noise cancellation principle of an acoustic device according to an embodiment of this specification is shown. Figure 5 As shown, the assumption is:

[0105] The transfer function between the sound emitted by the noise source 300 and the audio signal measured by the first sound sensor module 103 is denoted as h1;

[0106] The transfer function between the sound emitted by the noise source 300 and the audio signal measured by the second sound sensor module 104 is denoted as h2;

[0107] The transfer function between the sound emitted by the speaker 102 and the audio signal measured by the first sound sensor module 103 is denoted as h3;

[0108] The transfer function between the sound emitted by the speaker 102 and the audio signal measured by the second sound sensor module 104 is denoted as h4;

[0109] The transfer function between the input and output of the feedforward filter is denoted as h5;

[0110] The transfer function between the input and output of the feedback filter is denoted as h6;

[0111] The acoustic transfer function between the sound emitted by the speaker 102 and the eardrum 202 is denoted as h7; and

[0112] The acoustic transfer function between the sound emitted by noise source 300 and the eardrum 202 is denoted as h8.

[0113] The ambient noise emitted by noise source 300 is denoted as S0; the first sound signal collected by the first sound sensor module 103 is denoted as S1; the second sound signal collected by the second sound sensor module 104 is denoted as S2; the noise reduction signal emitted by 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 the human ear, that is, the ambient noise remaining at the eardrum 202 after noise reduction processing.

[0114] Depend on Figure 5 The acoustic transmission process shown above has the following relationship between S0, S1, S2, S3, and S4:

[0115] S4=S3*h7+S0*h8 Formula (0)

[0116] S3=S1*h5 formula (1-1)

[0117] S3 = S2 * h6 (Formula 1-2)

[0118] S3 = S1*h5 + S2*h6 (Formula 1-3)

[0119] S1=S0*h1+S3*h3 Formula (2)

[0120] S2=S3*h4+S0*h2 formula (3)

[0121] Among them, the above formula (1-1) corresponds to the feedforward noise reduction mode, the above formula (1-2) corresponds to the feedback noise reduction mode, and the above formula (1-3) corresponds to the hybrid noise reduction mode.

[0122] The design principles of the feedforward filter h5 will be analyzed below, taking the feedforward noise reduction mode as an example.

[0123] In feedforward noise reduction mode, substituting equation (2) into equation (1-1) yields:

[0124]

[0125] Substituting formula (4) into formula (0), we get:

[0126]

[0127] In the ideal case (where the sound emitted by the speaker 102 does not leak to the first sound sensor module 103), h3 = 0. Substituting this into formula (5), we get:

[0128] S4=S0*(h8+h1*h5*h7) Formula (6)

[0129] The noise reduction goal of active noise cancellation technology is usually to minimize S4. Based on formula (6), it can be seen that, in an ideal case, h5 needs to compensate for h1, h7, and h8. In this case, the first sound sensor module can be called an ideal feedforward sound sensor module, and the feedforward filter can be called an ideal feedforward filter.

[0130] In non-ideal conditions, especially when the first sound sensor module 103 in an open acoustic device is not located at the acoustic null 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 internal model control, where h3′≈h3. In this application, considering that the transfer function h3′ is measured and may have a certain error compared to the true transfer function h3, the transfer function h3′ can also be called the measured transfer function. During the feedforward noise reduction process, the noise reduction circuit 105 can use h3′ to compensate for the first sound signal to obtain a quasi-ambient noise signal. Furthermore, the noise reduction circuit 105 can filter the quasi-ambient noise signal using an ideal feedforward filter to obtain the first noise-canceling signal.

[0131] In some embodiments, h3′ can be measured as follows: The noise reduction circuit 105 sends a test audio signal to the speaker 102, causing the speaker 102 to emit a corresponding test audio signal, which is then collected by the first sound sensor module 103. The noise reduction circuit 105 acquires the acquired audio signal from the first sound sensor module 103 and determines the transfer function h3′ based on the test audio signal and the acquired audio signal. For example, assuming the test audio signal is Y1 and the acquired audio signal is Y2, then h3′ = Y2 / Y1. Therefore, the noise reduction circuit 105 can measure h3′ by controlling the speaker 102 to send a test audio signal. This method of measuring h3′ is simple and does not affect the noise reduction performance of the noise reduction circuit 105.

[0132] In some embodiments, considering that h3 is generally related to the wearing posture of the acoustic device 100, the corresponding h3 may be different when the same acoustic device 100 is worn by different users, and the corresponding h3 may also be different when the same acoustic device is worn multiple times by the same user. Therefore, the noise reduction circuit 105 can perform the above measurement process when it detects that the acoustic device 100 is powered on or when it detects that the acoustic device 100 is being worn by a user, thereby improving the accuracy of h3′.

[0133] In some embodiments, after measuring h3′, the noise reduction circuit 105 can generate a quasi-ambient noise signal in the following manner: the noise reduction circuit 105 acquires the input signal (i.e., S3) corresponding to the speaker 102, and provides a first gain to the input signal (S3) to obtain a first gain signal, wherein the first gain is h3′. Thus, the first gain signal is S3*h3′. Furthermore, the noise reduction circuit 105 acquires a first sound signal (i.e., S1=S0*h1+S3*h3) from the first sound sensor module 103, and subtracts the first gain signal from the first sound signal to obtain the quasi-ambient noise signal. The quasi-ambient noise signal can be expressed as: S1′=S0*h1+S3*h3-S3*h3′.

[0134] S13: Generate a first noise-cancelled signal based on the quasi-ambient noise signal.

[0135] In some embodiments, see continue to see Figure 5 The noise reduction circuit 105 can input the quasi-ambient noise signal S1′ into the feedforward filter (h5), and filter the quasi-ambient noise signal (S1′) through the feedforward filter to obtain a first noise-cancelled signal. The feedforward filter is configured to adjust at least one of the gain or phase of the quasi-ambient noise signal (S1′), such that the obtained first noise-cancelled signal can cancel out at least a portion of the ambient noise at and / or in the space surrounding the eardrum 202. It should be understood that the above-mentioned feedforward filter can be an ideal feedforward filter, that is, the ideal amplitude and phase response of the above-mentioned feedforward filter can be designed based on formula (6).

[0136] S14: Send the first noise cancellation signal to the speaker so that the speaker converts the first noise cancellation signal into a first noise cancellation frequency to reduce the volume of the ambient noise at the eardrum.

[0137] As mentioned above, the noise reduction circuit 105 is communicatively connected to the speaker 102. After generating the first noise reduction signal, the noise reduction circuit 105 can send the first noise reduction signal to the speaker 102. In this way, the speaker 102 plays the first noise reduction frequency corresponding to the first noise reduction signal, so that the first noise reduction frequency cancels or partially cancels the environmental noise at the eardrum 202, thereby achieving the purpose of noise reduction.

[0138] Figure 6 A schematic diagram illustrating the noise reduction effect of an active noise reduction method provided according to an embodiment of this specification is shown. Figure 6 As shown, curves 601 and 602 correspond to the noise reduction results for two test scenarios, respectively. The test process corresponding to curve 601 is as follows: the noise reduction circuit 105 acquires... Figure 3The first sound signal acquired by FF1 (located at the acoustic null point of speaker 102) contains little or no leakage signal from speaker 102. The noise reduction circuit 105 uses an ideal feedforward filter to perform feedforward noise reduction based on the first sound signal, resulting in the noise reduction result shown in curve 601. The test process corresponding to curve 602 is as follows: the noise reduction circuit 105 acquires... Figure 3 The first sound signal acquired by FF3 (not located at the acoustic null position of speaker 102, or located outside the acoustic null position of speaker 102) contains leakage signals from speaker 102. The noise reduction circuit 105 employs... Figure 4 The active noise reduction method shown first reduces the leakage signal component in the first audio signal to obtain a quasi-ambient noise signal, and then uses an ideal feedforward filter to perform feedforward noise reduction based on the quasi-ambient noise signal. Figure 6 It can be seen that the noise reduction results of curves 601 and 602 are basically the same. Therefore, it can be seen that the noise reduction circuit 105 can effectively improve the noise reduction effect of open acoustic devices by first reducing the leakage signal component in the first sound signal to obtain the quasi-ambient noise signal, and then generating the first noise reduction signal based on the quasi-ambient noise signal.

[0139] The above Figure 4In the active noise reduction method P100 shown, after acquiring the first sound signal from the first sound sensor module, the noise reduction circuit 105 first reduces the leakage signal component from the first sound signal to generate a quasi-ambient noise signal, and then performs feedforward noise reduction based on the quasi-ambient noise signal to generate a first noise-canceling signal. In some embodiments, the noise reduction circuit 105 can interchange the above-mentioned reduction step and feedforward noise reduction step. Specifically, after acquiring the first sound signal (S1) from the first sound sensor module, the noise reduction circuit 105 first performs feedforward noise reduction (h5) on the first sound signal to generate an intermediate noise-canceling signal (S1*h5). Since the first sound signal includes both ambient noise signal and leakage signal, when the noise reduction circuit 105 performs feedforward noise reduction on the first sound signal, it will simultaneously perform feedforward noise reduction on both the ambient noise signal and the leakage signal. Thus, the intermediate noise-canceling signal (S1*h5) obtained contains both the feedforward noise reduction result of the ambient noise signal and the feedforward noise reduction result of the leakage signal. The feedforward noise reduction result of the leakage signal can be estimated as follows: The input signal (S3) corresponding to the 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 considered an estimate of the leakage signal. The first gain signal (S3*h3′) is filtered based on the feedforward noise reduction parameter (h5) to obtain the filtered result of the leakage signal (S3*h3′*h5). Further, the noise reduction circuit 105 subtracts the feedforward noise reduction result of the leakage signal (S3*h3′*h5) from the intermediate noise-reduced signal (S1*h5) to obtain the first noise-reduced 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. Its measurement method can be found in the description above and will not be repeated here.

[0140] In summary, the active noise reduction method P100 provided in this specification, when the first audio signal simultaneously includes both ambient noise and leakage signals, allows the noise reduction circuit 105 to generate a quasi-ambient noise signal by first reducing the leakage signal component in the first audio signal, then generating a first noise-cancelling signal based on the quasi-ambient noise signal, and finally converting the first noise-cancelling signal into a first noise-cancelling frequency through a loudspeaker, thereby achieving noise reduction. Because the noise reduction circuit 105 reduces the leakage signal component in the first audio signal during the feedforward noise reduction process, it lowers the impact of the leakage signal on feedforward noise reduction, thus improving the noise reduction effect of active noise reduction.

[0141] Typically, the noise reduction circuit 105 should be designed / adjusted with the goal of minimizing the ambient noise (S4) at the eardrum 202. In a closed acoustic device, the second sound signal (S2) collected by the second sound sensor module 104 is equal to or approximately equal to the ambient noise (S4) at the eardrum 202. Therefore, minimizing the second sound signal (S2) can be used as the noise reduction goal in a closed acoustic device. However, in an open acoustic device, since an open space is formed between the speaker 102 and the eardrum 202, the second sound signal (S2) measured by the second sound sensor module 104 is no longer equal to or approximately equal to the ambient noise (S4) at the eardrum 202.

[0142] During the research process of this application, it was found that the reasons why S2 and S4 are no longer equal or approximately equal are as follows: (Combined with...) Figure 5 The acoustic transmission process shown, the second sound signal (S2) measured by the second sound sensor module 104 can be expressed as formula (3), and the environmental noise (S4) at the eardrum 202 can be expressed as formula (0), as follows:

[0143] S2=S3*h4+S0*h2 formula (3)

[0144] S4=S3*h7+S0*h8 Formula (0)

[0145] As can be seen from the above formulas (3) and (0), S2 and S4 can both be regarded as mixed signals of two kinds of sound signals. The first kind of sound signal comes from the noise cancellation signal (S3) emitted by the speaker 102, and the second kind of sound signal comes from the ambient noise signal (S0) emitted by the noise source 300. Regarding the second kind of sound signal, considering that under normal circumstances, in the frequency band to be denoised, the transfer function (h2) between the sound emitted by the noise source 300 and the audio signal measured by the second sound sensing module 104 is equal to or approximately equal to the transfer function (h8) between the sound emitted by the noise source 300 and the eardrum 202, that is, h2 h8, the components of the second kind of sound signal in S2 and S4 are equivalent. The difference between S2 and S4 mainly comes from the difference between the noise cancellation signal component (S3*h4) in S2 and the noise cancellation signal component (S3*h7) in S4.

[0146] In a closed acoustic device, the transfer function (h4) between the sound emitted by the speaker 102 and the audio signal measured by the second sound sensor module 104 is equal to or approximately equal to the transfer function (h7) between the sound emitted by the speaker 102 and the eardrum 202, i.e., h4 ≠ h7. Therefore, S2 obtained based on formula (3) and S4 obtained based on formula (0) are also equal to or approximately equal. However, in an open acoustic device, the transfer function (h4) between the sound emitted by the speaker 102 and the audio signal measured by the second sound sensor module 104 is no longer equal to or approximately equal to the transfer function (h7) between the sound emitted by the speaker 102 and the eardrum 202. Therefore, S2 obtained based on formula (3) and S4 obtained based on formula (0) are no longer equal to or approximately equal.

[0147] It is understandable that, since S2 and S4 are no longer equal or approximately equal in open acoustic devices, if "minimizing S2" is still taken as the noise reduction target, the noise reduction effect will be poor.

[0148] To address the aforementioned technical problems, the inventors of this application proposed the following technical concept during the research process: By specially designing the structure of the acoustic device 100 and the positions of each component, although S4 and S2 are not equal, S4 can be estimated based on S2 (or in other words, S4 and S2 have the same trend of change). Thus, S4 can be estimated based on S2, and active noise reduction can be performed with minimizing S4 as the noise reduction target. Alternatively, the noise reduction parameters required to minimize S4 can be derived based on the noise reduction parameters required to minimize S2, thereby improving the active noise reduction effect.

[0149] Based on the foregoing analysis, the difference between S4 and S2 mainly stems from the difference between the noise-canceling signal components (S3*h4) in S2 and (S3*h7) in S4. To estimate S4 based on S2, it is generally considered that h4 and h7 need to be known separately. However, during the inventors' research, it was discovered that both h7 and h4 are quantities strongly correlated with the pose of the acoustic device 100. That is, h4 and h7 differ depending on the user wearing the acoustic device, and even when the same user wears the acoustic device multiple times, h4 and h7 remain different. Furthermore, since there is no acoustic sensor at the user's eardrum 202 in practical applications, measuring h7 is difficult, which poses a significant challenge to estimating S4. Further research by the inventors revealed that although h4 and h7 are both strongly correlated with the pose of the acoustic device 100, the positions of the second sound sensor module 104 and the speaker 102 can be designed to ensure that h4 and h7 satisfy a first preset relationship, and this first preset relationship is independent of the pose of the acoustic device 100. Specifically, the first preset relationship being independent of the pose of the acoustic device 100 means that h4 and h7 satisfy the first preset relationship regardless of the posture in which the acoustic device 100 is worn by the user. For example, when the acoustic device 100 is worn by different users, h4 and h7 still satisfy the first preset relationship. Similarly, when the acoustic device 100 is worn multiple times by the same user, h4 and h7 still satisfy the first preset relationship.

[0150] This application does not limit the specific form of the first preset relationship. During the design phase of the acoustic device 100, the first preset relationship between h4 and h7 can be obtained by testing a large number of users and repeatedly wearing the acoustic device. In some embodiments, the first preset relationship can be: h7 / h4 = h9. It should be noted that this application does not limit the value of h9. It should be understood that when the first preset relationship is satisfied between h4 and h7, the following relationship may be satisfied between S2 and S4: the component of the noise-canceling signal in S4 (S3*h7) and the component of the noise-canceling signal in S2 (S3*h4) have the following relationship: (S3*h7) / (S3*h4) = h9; or, the component of the noise-canceling signal in S2 (S3*h4) is x dB lower in intensity than the component of the noise-canceling signal in S4 (S3*h7), where x can be 1, 2, or any other arbitrary value.

[0151] It should be noted that this 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 preset relationship, and the first preset relationship is independent of the position of the acoustic device 100. In some embodiments, the speaker 102 can be located near the ear canal opening, and the sound-emitting surface (i.e., the surface where the sound-emitting end is located) faces the ear canal opening. For example, due to the shape and mass distribution of the acoustic device 100, no matter what position the acoustic device 100 is worn in, a certain position of the acoustic device 100 is close to the ear canal opening, so the speaker 102 can be located at this position. The second sound sensor module 104 can be located on the sound-emitting surface of the speaker 102. In addition, when designing the specific position of the second sound sensor module 104 on the sound-emitting surface, the following principles can be considered: (1) the sound-collecting end of the second sound sensor module 104 is far away from the user's skin, and (2) the sound-collecting end of the second sound sensor module 104 is as close as possible to the ear canal opening. It should be understood that the positions of the speaker 102 and the second sound sensor module 104 determined by the above method ensure that h4 and h7 are not easily affected by the wearing posture. That is, regardless of the posture in which the acoustic device 100 is worn, h4 and h7 satisfy the same first preset relationship. In addition, the positions of the speaker 102 and the second sound sensor module 104 determined by the above method also ensure that the second sound signal S2 collected by the second sound sensor module 104 is closer to the environmental noise S4 at the eardrum 202, and the second sound signal S2 is not easily affected by skin reflection. Thus, the S4 estimated based on the first preset relationship and the second sound signal S2 is more accurate.

[0152] When a first preset relationship is satisfied between h4 and h7, and this preset relationship is independent of the position of the acoustic device 100, this application provides an active noise cancellation method P200. Regardless of the position in which the acoustic device 100 is worn by the user, the noise cancellation parameters can be adjusted based on the second sound signal (S2) and the first preset relationship, thereby improving the active noise cancellation effect. The active noise cancellation method P200 can be applied independently to the acoustic device 100 provided in this application, or it can be combined with other active noise cancellation methods described in other parts of this document.

[0153] Figure 7 A flowchart of another active noise reduction method P200 provided according to an embodiment of this specification is shown. This active noise reduction method P200 can be executed by a noise reduction circuit 105 in the acoustic device 100. For example, a processor 107 in the noise reduction circuit 105 can read an instruction set stored in its local storage medium and then execute the active noise reduction method P200 described herein according to the instructions of the instruction set. Figure 7 As shown, the active noise reduction method P200 may include:

[0154] S21: Obtain the second sound signal from the second sound sensor module.

[0155] S22: Based on the second sound signal and the first preset relationship, adjust the noise reduction parameters of the noise reduction circuit.

[0156] In some embodiments, the noise reduction circuit 105 can determine the ambient noise (S4) at the eardrum 202 based on the second sound signal (S2) and the first preset relationship. Then, the noise reduction circuit 105 adjusts the noise reduction parameters with the goal of minimizing the ambient noise (S4) at the eardrum 202.

[0157] In some embodiments, the noise reduction circuit 105 can estimate S4 in the following manner:

[0158] (1) The first transfer function h4′ between the sound emitted by the loudspeaker 102 and the audio signal measured by the second sound sensor module 104 is measured.

[0159] In some embodiments, h4′ can be measured as follows: the noise reduction circuit 105 sends a test audio signal to the speaker 102, causing the speaker 102 to emit a corresponding test audio, which is collected by the second sound sensor module 104. The noise reduction circuit 105 acquires the collected audio signal from the second sound sensor module 104 and determines the first transfer function h4′ based on the test audio signal and the collected audio signal. For example, assuming the test audio signal is Y1 and the collected audio signal is Y2, then h4′ = Y2 / Y1. It can be seen that the noise reduction circuit 105 can measure h4′ by controlling the speaker 102 to send a 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, considering that h4 is usually related to the wearing posture of the acoustic device 100, the corresponding h4 may be different when the same acoustic device 100 is worn by different users, and the corresponding h4 may also be different when the same acoustic device is worn multiple times by the same user. Therefore, the noise reduction circuit 105 can perform the above measurement process when it detects that the acoustic device 100 is powered on or when it detects that the acoustic device 100 is being worn by a user, thereby improving the accuracy of h4′.

[0160] (2) Based on the first transfer function, the first preset relationship and the second sound signal, determine the ambient noise at the eardrum.

[0161] Specifically, the second transfer function h7′ between the sound emitted by the speaker 102 and the eardrum 202 can be determined based on the first transfer function h4′ and the first preset relationship.

[0162] For example, assuming the first preset relationship is: h7 / h4=h9, then based on the first transfer function h4' and the above first preset relationship, the second transfer function h7′=h4′*h9 can be obtained.

[0163] Furthermore, S4 can be determined based on the first transfer function h4′, the second transfer function h7′, and S2, as follows:

[0164] First, based on formula (3), we can obtain:

[0165] S0*h2=S2-S3*h4 Formula (12)

[0166] Based on the preceding analysis, the environmental noise component (S0*h2) in S2 is approximately equal to the environmental noise component (S0*h8) in S4, that is:

[0167] S0*h8≈S0*h2=S2-S3*h4 formula (13)

[0168] Substituting formula (13) into formula (0), we get:

[0169] S4≈S3*h7+(S2-S3*h4) Formula (14)

[0170] In formula (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 sound signal collected by the second sound sensor module 104. Therefore, the noise reduction circuit 105 can estimate S4 based on the first transfer function h4′, the second transfer function h7′, the second sound signal S2, and the input signal S3 of the speaker 102.

[0171] The above-mentioned active noise reduction process first determines the ambient noise at the eardrum 202 (S4) based on the second sound signal (S2) and the first preset relationship, and then takes minimizing the ambient noise at the eardrum 202 (S4) as the noise reduction target, which improves the accuracy of the noise reduction target and thus improves the effect of active noise reduction.

[0172] The above embodiments determine S4 based on the following assumption: the transfer function (h2) between the sound emitted by the noise source 300 and the audio signal measured by the second sound sensing module 104 is approximately equal to the transfer function (h8) between the sound emitted by the noise source 300 and the eardrum 202, i.e., h2≈h8. The inventors considered that in practical applications, h2 and h8 are usually not strictly equal, which leads to a certain error in the S4 determined in the above embodiments. Therefore, to further improve the accuracy of S4, h2 and h8 can also be considered in the process of determining S4. However, h2 and h8 are also quantities related to the pose of the acoustic device 100. h2 and h8 are different when different users wear the acoustic device, and even when the same user wears the acoustic device multiple times, h2 and h8 are different. Therefore, measuring h2 and h8 separately is quite difficult. Further research by the inventors revealed that, in designing the positions of the second sound sensor module 104 and the speaker 102, in addition to ensuring a first preset relationship between h4 and h7, a second preset relationship can also be ensured between h2 and h8, and this second preset relationship is independent of the position of the acoustic device 100. Specifically, the second preset relationship being independent of the position of the acoustic device 100 means that regardless of the posture in which the acoustic device 100 is worn by the user, h2 and h8 always satisfy the second preset relationship. For example, when the acoustic device 100 is worn by different users, h2 and h8 always satisfy the second preset relationship. Similarly, when the acoustic device 100 is worn multiple times by the same user, h2 and h8 always satisfy the second preset relationship.

[0173] This application does not limit the specific form of the second preset relationship. During the design phase of the acoustic device 100, the relationship between h2 / h1 and h8 / h1 can be obtained by testing a large number of users and repeatedly wearing the acoustic device. Based on this relationship, the second preset relationship between h2 and h8 can be obtained. In some embodiments, the above-mentioned second preset relationship can be: h8 / h2 = h10. It should be noted that this application does not limit the value of h10. It should be understood that when the second preset relationship is satisfied between h2 and h8, the following relationship may be satisfied between S2 and S4: the component of the environmental noise signal (S0*h8) in S4 and the component of the environmental noise signal (S0*h2) in S2 have the following relationship: (S0*h8) / (S0*h2) = h10; or, the component of the environmental noise signal (S0*h2) in S2 is y dB lower than the component of the environmental noise signal (S0*h8) in S4, where the value of y can be 1, 2 or other arbitrary values.

[0174] In some embodiments, where a first preset relationship is satisfied between h4 and h7, and a second preset relationship is satisfied between h2 and h8, and both the first and second preset relationships are independent of the pose of the acoustic device 100, S4 can be estimated based on the first preset relationship, the second preset relationship, and S2. The specific method is as follows:

[0175] (1) The first transfer function h4′ between the sound emitted by the speaker 102 and the audio signal measured by the second sound sensor module 104 is measured. The measurement process of the first transfer function h4′ can be found in the previous description, and will not be repeated here.

[0176] (2) Based on the first transfer function, the first preset relationship, the second preset relationship and the second sound signal, determine the environmental noise at the eardrum.

[0177] Specifically, based on the first transfer function h4′ and the first preset relationship, the second transfer function h7′ between the sound emitted by the speaker 102 and the eardrum 202 can be determined. The process of determining the second transfer function h7′ can be found in the previous descriptions and will not be repeated here.

[0178] Furthermore, based on the second preset relationship, the first transfer function h4′, the second transfer function h7′, and S2, S4 can be determined as follows:

[0179] First, based on formula (3), we can obtain:

[0180] S0*h2=S2-S3*h4 Formula (12)

[0181] Based on the second presupposed relationship, we can obtain:

[0182] S0*h8=S0*h2*h10=(S2-S3*h4)*h10 Formula (15)

[0183] Substituting formula (15) into formula (0), we get:

[0184] S4=S3*h7+(S2-S3*h4)*h10 Formula (16)

[0185] In formula (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 sound signal collected by the second sound sensor module 104, and h10 can be obtained based on the second preset relationship. Therefore, S4 can be determined based on the first transfer function h4′, the second transfer function h7′, the second preset relationship, the second sound signal S2, and the input signal S3 of the speaker 102.

[0186] After estimating S4, the noise reduction parameters of the noise reduction circuit 105 can be adjusted with minimizing S4 as the noise reduction objective. In some embodiments, the noise reduction circuit 105 may include a feedforward filter, in which case the aforementioned noise reduction parameters may include the filtering parameters of the feedforward filter. In some embodiments, the noise reduction circuit 105 may include a feedback filter, in which case the aforementioned noise reduction parameters may include the filtering parameters of the feedback filter. In some embodiments, the noise reduction circuit 105 may include both a feedforward filter and a feedback filter, in which case the aforementioned noise reduction parameters may include at least one of the filtering parameters of the feedforward filter or the filtering parameters of the feedback filter.

[0187] In some embodiments, the filtering parameters of the feedforward or feedback filter described above may include at least one of: filter gain, filter phase, or quality factor. The quality factor can be expressed as the ratio of the filter's center frequency F (in Hz) to its -3dB bandwidth B (in Hz), i.e., quality factor Q = F / B, describing the filter's ability to separate adjacent frequency components in a signal. A higher quality factor indicates a higher resolution of adjacent frequency components by the filter.

[0188] In some embodiments, the noise reduction parameters of the noise reduction circuit 105 may include the filter gain of the feedforward filter. For ease of description, the filter gain of the feedforward filter required to minimize the second sound signal (S2) as the noise reduction target is referred to as the first filter gain, and the filter gain of the feedforward filter required to minimize the ambient noise at the eardrum 202 (S4) as the noise reduction target is referred to as the second filter gain. Then, when h4 and h7 satisfy a first preset relationship, there will be a certain relationship between the signal strengths of S2 and S4; for example, the signal strength of S2 is x dB lower than the signal strength of S4. In this case, the first filter gain and the second filter gain also satisfy this relationship.

[0189] For example, Figure 8A A schematic diagram is shown of the frequency response curves for feedforward noise reduction of ambient noise at the eardrum using different feedforward filter gains when the first user is wearing the acoustic device. Figure 8BA schematic diagram is shown of the frequency response curves for feedforward noise reduction of a second sound signal using different feedforward filter gains when the first user is wearing the acoustic device. It is assumed that, under the condition that a first preset relationship is satisfied between h4 and h7, the intensity of the second sound signal (S2) is 2 dB lower than the ambient noise (S4) at the eardrum 202.

[0190] See Figure 8A and Figure 8B When the acoustic device 100 is worn by the first user, the feedforward filter in the noise reduction circuit 105 performs active noise reduction using different filter gains (increasing sequentially from 0dB to 4dB). The frequency response curves obtained by feedforward noise reduction based on the ambient noise (S4) at the eardrum 202 under different filter gains are shown below. Figure 8A As shown. The frequency response curves obtained by feedforward noise reduction based on the second audio signal (S2) under different filter gains are as follows. Figure 8B As shown. By Figure 8A It can be seen that if minimizing the ambient noise (S4) at eardrum 202 is taken as the noise reduction objective, then the second filter gain required by the feedforward filter is 4dB. Figure 8B It can be seen that if minimizing the second sound signal (S2) is taken as the noise reduction target, the first filter gain required by the feedforward filter is 2dB.

[0191] Figure 9A A schematic diagram is shown of the frequency response curves for feedforward noise reduction of ambient noise at the eardrum using different feedforward filter gains when a second user is wearing the acoustic device. Figure 9B A schematic diagram is shown showing the frequency response curves of feedforward noise reduction of the second sound signal using different feedforward filter gains when user B is wearing an acoustic device. It is assumed that, under the condition that a first preset relationship is satisfied between h4 and h7, the intensity of the second sound signal (S2) is 2 dB lower than the ambient noise (S4) at eardrum 202.

[0192] See Figure 9A and Figure 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 sequentially from 0dB to 4dB). The frequency response curves obtained by feedforward noise reduction based on the ambient noise (S4) at the eardrum 202 under different filter gains are shown below. Figure 9A As shown. The frequency response curves obtained by feedforward noise reduction based on the second audio signal (S2) under different filter gains are as follows. Figure 9B As shown. By Figure 9A It can be seen that if minimizing the ambient noise (S4) at eardrum 202 is taken as the noise reduction objective, then the second filter gain required by the feedforward filter is 3dB. Figure 8BIt can be seen that if minimizing the second sound signal (S2) is taken as the noise reduction target, the first filter gain required by the feedforward filter is 1dB.

[0193] Depend on Figures 8A to 9B It can be seen that the relationship between the first filter gain and the second filter gain is the same as the relationship between the intensity of the second sound signal (S2) and the intensity of the ambient noise (S4) emitted from the eardrum 202. That is, if the intensity of the second sound signal (S2) is xdB lower than the intensity of the ambient noise (S4) at the eardrum 202, then the first filter gain is xdB lower than the second filter gain.

[0194] Therefore, the noise reduction circuit 105 can also adjust the filter gain of the feedforward filter in the following manner: First, taking minimizing the second sound signal (S2) as the noise reduction target, a first filter gain of the feedforward filter is determined. Then, based on the first filter gain and the first preset relationship, the noise reduction circuit 105 determines the second filter gain and adjusts the current filter gain of the feedforward filter to the second filter gain. For example, suppose the first preset relationship makes the intensity of the second sound signal (S2) 2dB lower than the intensity of the ambient noise (S4) at the eardrum 202. The noise reduction circuit 105 first takes minimizing the second sound signal (S2) as the noise reduction target and determines the first filter gain to be 2dB. Then, the noise reduction circuit 105 can increase the first filter gain by 2dB to obtain a second filter gain of 4dB. Therefore, the current filter gain of the feedforward filter is adjusted to 4dB.

[0195] In some embodiments, the acoustic device 100 may provide a user with multiple operating modes. Each operating mode corresponds to a default noise reduction parameter for the noise reduction circuit 105, and the default noise reduction parameters differ for different operating modes. In some embodiments, the acoustic device 100 may be equipped with an interactive control, allowing the user to switch between different operating modes. In some embodiments, the acoustic device 100 may provide an interactive interface, which may be displayed on the screen of the acoustic device 100 or on a target device communicatively connected to the acoustic device 100. The user can select different operating modes through the interactive interface. In some embodiments, the multiple operating modes correspond to different environment types. The user can interactively indicate the current environment type to the acoustic device 100, and the noise reduction circuit 105 can switch to the corresponding operating mode based on the current environment type. In some embodiments, the multiple operating modes may correspond to different user types. The user can interactively indicate their user type to the acoustic device 100, and the noise reduction circuit 105 can switch to the corresponding operating mode based on the user type.

[0196] Thus, in S22, the noise reduction circuit 105 can acquire the target operating mode indicated by the user among multiple operating modes, and then adjust the default noise reduction parameters corresponding to the target operating mode based on the second sound signal (S2) and the first preset relationship. It should be understood that the acoustic device 100, by providing multiple operating modes, can meet the noise reduction needs of different users or in different environments.

[0197] S23: Perform active noise reduction based on the adjusted noise reduction parameters.

[0198] In some embodiments, the noise reduction circuit 105 may also acquire a first sound signal from the first sound sensor module and filter at least one of the first sound signal or the second sound signal based on adjusted noise reduction parameters to generate a noise-canceling signal. Furthermore, the noise reduction circuit 105 sends the noise-canceling signal to the speaker, causing the speaker to convert the noise-canceling signal into a noise-canceling frequency to reduce the volume of ambient noise at the eardrum.

[0199] In some embodiments, when the acoustic device 100 operates in feedforward noise reduction mode, the noise reduction circuit 105 can filter the first sound signal based on adjusted noise reduction parameters to generate a noise-canceling signal. For example, the noise reduction circuit 105 can input the first sound signal into a feedforward filter, filter the first sound signal through the feedforward filter, and obtain a noise-canceling signal. In some embodiments, when the first sound signal simultaneously includes an ambient noise signal and a leakage signal, the noise reduction circuit 105 can first generate a quasi-ambient noise signal by reducing the leakage signal component in the first sound signal, and then filter the quasi-ambient noise signal based on the adjusted noise reduction parameters to obtain a noise-canceling signal. On the one hand, since the accuracy of the noise reduction target is ensured when adjusting the noise reduction parameters, active noise reduction based on the adjusted noise reduction parameters can improve the effect of active noise reduction. On the other hand, by reducing the leakage signal component in the first sound signal, the influence of the leakage signal on the feedforward noise reduction process is reduced, which can further improve the effect of active noise reduction.

[0200] In some embodiments, when the acoustic device 100 operates in feedback noise reduction mode, the noise reduction circuit 105 can filter the second audio signal based on adjusted noise reduction parameters to generate a noise-canceling signal. For example, the noise reduction circuit 105 can input the second audio signal into a feedback filter, and filter the second audio signal through the feedback filter to obtain a noise-canceling signal.

[0201] In some embodiments, when the acoustic device 100 operates in a hybrid noise reduction mode, the noise reduction circuit 105 can filter the first sound signal based on adjusted noise reduction parameters to obtain a first noise-reduced signal. For example, the noise reduction circuit 105 inputs the first sound signal into a feedforward filter and filters the first sound signal through the feedforward filter to obtain the first noise-reduced signal. The noise reduction circuit 105 can also filter the second sound signal based on adjusted noise reduction parameters to obtain a second noise-reduced signal. For example, the noise reduction circuit 105 inputs the second sound signal into a feedback filter and filters the second sound signal through the feedback filter to obtain the second noise-reduced signal. Further, the noise reduction circuit 105 synthesizes the first noise-reduced signal and the second noise-reduced signal to obtain a noise-reduced signal. In some embodiments, when the first sound signal simultaneously includes an ambient noise signal and a leakage signal, the noise reduction circuit 105 can first generate a quasi-ambient noise signal by reducing the leakage signal component in the first sound signal, and then filter the quasi-ambient noise signal based on the adjusted noise reduction parameters to obtain the first noise-reduced signal. On the one hand, because the accuracy of the noise reduction target is ensured when adjusting the noise reduction parameters, active noise reduction based on the adjusted parameters can improve the effectiveness of active noise reduction. On the other hand, by reducing the leakage signal component in the first audio signal, the impact of the leakage signal on the feedforward noise reduction process is reduced, which can further improve the effectiveness of active noise reduction.

[0202] In summary, in the active noise reduction method P200 provided in this specification, since the acoustic transfer function (h4) between the sound emitted by the speaker 102 and the audio signal measured by the second sound sensor module 104 and the acoustic transfer function (h7) between the sound emitted by the speaker 102 and the eardrum 202 satisfy a first preset relationship, and this first preset relationship is independent of the pose of the acoustic device 100, the noise reduction circuit 105 can adjust the noise reduction parameters based on the second sound signal (S2) and the first preset relationship, and 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 preset relationship, the adjusted noise reduction parameters meet the most fundamental noise reduction target, thereby improving the noise reduction effect of active noise reduction.

[0203] As previously mentioned, in some embodiments, the first sound sensor module 103 may include a sound sensor. In this case, since ambient noise may come from any direction, the ambient noise may reach the speaker 102 or eardrum 202 before reaching the sound sensor. For example, suppose the sound sensor is located on the first side of the acoustic device 100 (e.g., the side facing the user), and the noise source 300 is located on the second side of the acoustic device 100 (e.g., the side facing the user's rear). Since the sound sensor is farther from the noise source 300, the ambient noise emitted by the noise source 300 will reach the speaker 102 or eardrum 202 first before being collected by the sound sensor. Thus, the causality of the feedforward noise reduction performed by the noise reduction circuit 105 deteriorates, resulting in a worse noise reduction effect, especially in certain frequency bands (e.g., mid-to-high frequency bands), and may even lead to an increase in the noise perceived by the human ear.

[0204] Therefore, in some embodiments, the first sound sensor module 103 may include multiple sound sensors. For ease of description, the number of sound sensors included in the first sound sensor module 103 is denoted as N, where N is an integer greater than or equal to 2. The N sound sensors are physically connected to the support 101 and are distributed on the side of the speaker 102 furthest from the eardrum. Without considering leakage from the speaker 102, each sound sensor is configured to collect ambient noise from the noise source 300 and generate an ambient noise signal. For distinction, in the following text, the ambient noise signal collected by each sound sensor is referred to as an individual ambient noise signal, and the ambient noise signal collected by the first sound sensor module 103 is referred to as a composite ambient noise signal.

[0205] The N sound sensors are oriented differently relative to the target point on the speaker 102. In some embodiments, the target point can be the center point or the sound output point of the speaker 102. Since the N sound sensors are oriented differently relative to the target point, when ambient noise comes from different directions, at least one of the N sound sensors can detect the ambient noise before the speaker 102.

[0206] In some embodiments, N = 2. Figure 10 A schematic diagram showing the distribution of sound sensors in a first sound sensor module comprising two sound sensors is shown. Figure 10As shown, when N=2, the first sound sensor module 103 may include a sound sensor 1031 and a sound sensor 1032. These two sound sensors may be located on two opposite sides of the acoustic device 100, or in other words, their directions relative to the target point are opposite. For example, when the acoustic device 100 is worn on a user's head, sound sensor 1031 is located on the first side of the acoustic device 100 facing the user, and sound sensor 1032 is located on the second side of the acoustic device 100 facing the user's rear. Thus, when ambient noise is emitted from a noise source in front of the user, the phase of the ambient noise reaching sound sensor 1031 (or the phase of the individual ambient noise signal measured by sound sensor 1031) leads the phase of the ambient noise reaching the output end of speaker 102. When ambient noise originates from a noise source behind the user, the phase of the ambient noise reaching the sound sensor 1032 (or the phase of the individual ambient noise signal measured by the sound sensor 1032) leads the phase of the ambient noise reaching the output end of the speaker 102. In some embodiments, the two sound sensors can be located at the acoustic null point of the speaker 102. In this way, the signals collected by the two sound sensors do not contain leakage signals from the speaker 102, thereby improving the active noise cancellation effect.

[0207] In some embodiments, N = 3. Figure 11 A schematic diagram showing the distribution of the sound sensors in a first sound sensor module comprising three sound sensors is provided. Figure 11As shown, when N=3, the first sound sensor module 103 may include: sound sensor 1031, sound sensor 1032, and sound sensor 1033. These three sound sensors can be distributed on three sides of the acoustic device 100 facing different directions. For example, when the acoustic device 100 is worn on the user's head, sound sensor 1031 is located on the first side of the acoustic device 100 facing the user's front, sound sensor 1032 is located on the second side of the acoustic device 100 facing the user's rear, and sound sensor 1033 is located on the third side of the acoustic device 100 facing the ground. Thus, when ambient noise is emitted from a noise source in front of the user, the phase of the ambient noise reaching sound sensor 1031 (or the phase of the individual ambient noise signal measured by sound sensor 1031) leads the phase of the ambient noise reaching the output end of speaker 102. When ambient noise originates from a noise source behind the user, the phase of the ambient noise reaching the sound sensor 1032 (or the phase of the individual ambient noise signal measured by the sound sensor 1032) leads the phase of the ambient noise reaching the output end of the speaker 102. When ambient noise originates from a noise source below the acoustic device, the phase of the ambient noise reaching the sound sensor 1033 (or the phase of the individual ambient noise signal measured by the sound sensor 1033) leads the phase of the ambient noise reaching the output end of the speaker 102. In some embodiments, the three sound sensors can be distributed in a triangular pattern at the acoustic null position of the speaker 102. In this way, the signals collected by the three sound sensors do not contain leakage signals from the speaker 102, thereby improving the active noise cancellation effect.

[0208] It should be noted that the above Figure 10 and Figure 11 These are just two possible distribution methods. In actual design, the N sound sensors can also be distributed in other ways, which will not be illustrated in this paper. In addition, this application does not impose specific limitations on the value of N. For example, N can also be equal to 4, 5 or any other integer.

[0209] In some embodiments, the N sound sensors can be arranged in an array, such as a linear array, a planar array, a spherical array, or other arrays. Arranging them in an array also helps reduce the complexity of signal processing within the noise reduction circuit 105, thereby improving active noise reduction performance.

[0210] At least some of the N sound sensors can be omnidirectional microphones. Omnidirectional microphones have high sensitivity to ambient noise from all directions and can collect ambient noise from any direction. At least some of the N sound sensors can also be directional microphones. Directional microphones can only collect ambient noise from a specified direction. For example, ... Figure 10As shown, the sound sensor 1031 is directional in front of the user and is configured to collect ambient noise from in front of the user, while the sound sensor 1032 is directional behind the user and is configured to collect ambient noise from behind the user. The directional microphones mentioned above can include, but are not limited to, cardioid microphones, near-cardioid microphones, or other directional microphones. The directional characteristics of these microphones for different frequencies can be the same or different.

[0211] In the case where the first sound sensor module 103 includes N sound sensors, this application provides an active noise reduction method P300. When performing active noise reduction, the noise reduction circuit 105 can assign weights to the N sound sensors, ensuring that the first sound sensor module 103 has phase leadership in any direction. This scheme improves the causality of feedforward noise reduction, thereby enhancing the active noise reduction effect. The active noise reduction method P300 can be applied independently to the acoustic device 100 provided in this application, or it can be combined with other active noise reduction methods described in other parts of this document.

[0212] Figure 12 A flowchart of another active noise reduction method P300 provided according to an embodiment of this specification is shown. This active noise reduction method P300 can be performed by a noise reduction circuit 105 in the acoustic device 100. For example, when the noise reduction circuit 105 employs... Figure 2 In the structure shown, the processor 107 in the noise reduction circuit 105 can read the instruction set stored in its local storage medium, and then execute the active noise reduction method P300 described in this specification according to the instructions of the instruction set. Figure 12 As shown, the active noise reduction method P300 may include:

[0213] S31: Determine the target direction from which the environmental noise originates.

[0214] The target direction refers to the direction from which the environmental noise originates, i.e., the direction of the noise source 300. In some embodiments, the direction of the ray pointing from the target point on the speaker 102 to the noise source 300 can be referred to as the target direction.

[0215] In some embodiments, the noise reduction circuit 105 can acquire N individual environmental noise signals collected by N sound sensors, and estimate the target direction from which the environmental noise originates based on the N individual environmental noise signals. In some embodiments, the noise reduction circuit 105 can obtain the target direction by performing full-band Direction of Arrival (DOA) analysis on the N individual environmental noise signals. In this case, the target direction represents the direction of arrival of the full-band environmental noise (i.e., the overall environmental noise).

[0216] It should be noted that this application does not specifically limit the DOA algorithm. For example, one or more of the following algorithms can be used: Estimating Signal Parameter via Rotational Invariance Techniques (ESPRIT), Multiple Signal Classification (MUSIC), etc.

[0217] 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 comprehensive environmental noise signal measured by the first sound sensor module based on the N weights leads the phase of the environmental noise reaching the output end of the speaker.

[0218] In some embodiments, the comprehensive environmental noise signal is a signal obtained by weighted summation of N individual environmental noise signals collected by N sound sensors based on the N weights.

[0219] Combination Figure 10 For example, the first sound sensor module 103 includes a sound sensor 1031 and a sound sensor 1032. The individual environmental noise signal collected by the sound sensor 1031 is as follows: The individual environmental noise signal collected by the sound sensor 1032 is as follows:

[0220] Assuming the weight of sound sensor 1031 is α1 and the weight of sound sensor 1032 is α2, the comprehensive environmental noise signal measured by the first sound sensor module 103 based on the above two weights can be expressed as:

[0221]

[0222] The phase of the above-mentioned integrated environmental noise signal can be expressed as:

[0223]

[0224] Therefore, the noise reduction circuit 105 can set weights for each of the N sound sensors based on the target direction, so that the phase of the above-mentioned combined noise signal leads the phase of the ambient noise when it reaches the output end of the speaker 102.

[0225] In some embodiments, the weight corresponding to the i-th sound sensor is related to the phase lead of the individual environmental noise signal collected by the i-th sound sensor. For example, the more the phase of the individual environmental noise signal collected by the i-th sound sensor leads the phase of the environmental noise reaching the output end of the speaker 102, the larger the weight corresponding to the i-th sound sensor; conversely, the smaller the phase of the i-th sound sensor, the smaller the weight corresponding to the i-th sound sensor. Here, i is any positive integer less than or equal to N.

[0226] In some embodiments, it is assumed that the angle between the direction of the i-th sound sensor relative to the target point on the speaker 102 and the target direction is θ. i Then the weight corresponding to the i-th sound sensor is related to θ. i Negative correlation. That is to say, θ i The smaller the value (indicating a smaller deviation between the direction of the sound sensor relative to the target point and the target direction), the larger the weight, θ. i The larger the value (indicating a greater deviation between the direction of the sound sensor relative to the target point and the target direction), the smaller the weight. Here, i is any positive integer less than or equal to N.

[0227] Combination Figure 10 To illustrate, assuming the ambient noise comes from in front of the user, the weight of sound sensor 1031 is greater than that of sound sensor 1032. Therefore, during active noise cancellation, sound sensor 1031 primarily plays a major role, ensuring phase leadership. Conversely, assuming the ambient noise comes from behind the user, the weight of sound sensor 1032 is greater than that of sound sensor 1031. Again, during active noise cancellation, sound sensor 1032 primarily plays a major role, also ensuring phase leadership.

[0228] S33: Based on the N individual environmental noise signals collected by the N sound sensors and the N weights, generate a first noise reduction signal.

[0229] In some embodiments, the noise reduction circuit 105 may include N feedforward filters, each corresponding to one of the N sound sensors. The i-th feedforward filter is connected to the i-th sound sensor and the speaker 102, and is configured to filter the individual environmental noise signal collected by the i-th sound sensor. 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.

[0230] Since the N feedforward filters are connected in parallel, the filter order and delay will not increase during active noise reduction. Furthermore, the parallel connection of these N feedforward filters also increases filtering complexity; for example, N feedforward filters can handle noise reduction for different frequency bands, thereby enhancing the feedforward noise reduction capability.

[0231] Figure 13 A schematic diagram illustrating the active noise cancellation principle of another acoustic device provided according to an embodiment of this specification is shown. Figure 13 As shown, 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. The feedforward filter h51 connects the sound sensor 1031 and the speaker 102, and the feedforward filter h52 connects the sound sensor 1032 and the speaker 102.

[0232] See also Figure 13 Assumption:

[0233] The transfer function between the sound emitted by noise source 300 and the audio signal measured by sound sensor 1031 is denoted as h11;

[0234] The transfer function between the sound emitted by noise source 300 and the audio signal measured by sound sensor 1032 is denoted as h12;

[0235] The acoustic transfer function between the sound emitted by the speaker 102 and the eardrum 202 is denoted as h7; and

[0236] The acoustic transfer function between the sound emitted by noise source 300 and the eardrum 202 is denoted as h8.

[0237] The noise signal emitted by noise source 300 is denoted as S0; the individual environmental noise signal collected by sound sensor 1031 is denoted as S11; the individual environmental noise signal collected by sound sensor 1032 is denoted as S12; the noise cancellation signal emitted by speaker 102 is denoted as S3; and the noise signal received by eardrum 202 is denoted as S4.

[0238] Depend on Figure 13 The acoustic transmission process shown above has the following relationships between S0, S11, S12, S3, and S4:

[0239] S4=S0*h8+S3*h7 Formula (0)

[0240] S3=S11*h51+S12*h52 Formula (7)

[0241] S11=S0*h11 formula (8)

[0242] S12=S0*h12 formula (9)

[0243] Substituting formulas (8) and (9) into formula (7), we get:

[0244] S3=S0*h11*h51+S0*h12*h52 Formula (10)

[0245] Substituting formula (10) into formula (0) yields:

[0246] S4=S0*h8+S0*(h11*h51+h12*h52)*h7 Formula (11)

[0247] As can be seen from formula (11), the feedforward noise reduction effect is determined by h51 and h52.

[0248] In some embodiments, when the noise reduction circuit 105 performs active noise reduction, it can adjust the filtering parameters of the feedforward filter h51 based on the weights of the sound sensor 1031, and use the adjusted feedforward filter h51 to filter the individual environmental noise signal S11 collected by the sound sensor 1031 to generate an individual noise-reduced signal. Furthermore, the noise reduction circuit 105 can also adjust the filtering parameters of the feedforward filter h52 based on the weights of the sound sensor 1032, and use the adjusted feedforward filter h52 to filter the individual environmental noise signal S12 collected by the sound sensor 1032 to generate an individual noise-reduced signal. Further, the noise reduction circuit 105 combines the two individual noise-reduced signals generated by the two feedforward filters to obtain a first noise-reduced signal.

[0249] In some embodiments, adjusting the filtering parameters of feedforward filter h51 or feedforward filter h52 may include adjusting the filtering gain of feedforward filter h51 or feedforward filter h52. For example, the weight of sound sensor 1031 can be multiplied by the current filtering gain of feedforward filter h51 to obtain the adjusted filtering gain of feedforward filter h51. Similarly, the weight of sound sensor 1032 can be multiplied by the current filtering gain of feedforward filter h52 to obtain the adjusted filtering gain of feedforward filter h52.

[0250] It should be understood that the noise reduction circuit 105 adjusts the filtering parameters of N feedforward filters based on N weights, so that during active noise reduction, the sound sensor with higher weight (the sound sensor with higher phase lead) and its corresponding feedforward filter contribute more to the overall noise reduction, while the sound sensor with lower weight (the sound sensor with lower phase lead) and its corresponding feedforward filter contribute less to the overall noise reduction, thereby improving the active noise reduction effect.

[0251] In some embodiments, the aforementioned N sound sensors may be N directional microphones with different directivities. Continuing to refer to Figure 13 , assume that the directivity of the sound sensor 1031 is the front of the user, and the directivity of the sound sensor 1032 is the rear of the user. When the ambient noise comes from the front of the user, the directivities of the two aforementioned sound sensors make h11 much larger than h12 (i.e., h11>>h12). It can be seen from the aforementioned formula (11) that the sound sensor 1031 mainly functions in the active noise reduction process, therefore, the first sound sensor module 103 has phase lead performance, which can improve the active noise reduction effect. When the ambient noise comes from the rear of the user, the directivities of the two aforementioned sound sensors make h11 much smaller than h12 (i.e., h11<<h12). It can be seen from the aforementioned formula (11) that the sound sensor 1032 mainly functions in the active noise reduction process, therefore, the first sound sensor module 103 has phase lead performance, which can improve the active noise reduction effect.

[0252] It can thus be seen that, in the case where the N sound sensors have different directivities, the different directivities of the N sound sensors enable the active noise reduction process to automatically select the optimal sound sensor, without the need to adjust the filtering parameters of the feedforward filter, so as to realize the phase lead performance of the first sound sensor module in all directions.

[0253] S34: Sending the first noise reduction signal to a speaker, so that the speaker converts the first noise reduction signal into a first noise reduction audio to reduce the volume of the ambient noise at the eardrum.

[0254] It should be understood that the above descriptions from S31 to S34 relate to estimating the incoming wave direction of full-band ambient noise, and performing full-band active noise reduction based on the estimated target direction. In some embodiments, when the noise reduction circuit 105 estimates the target direction, it may also perform estimation by sub-bands. For example, the full frequency band is divided into M sub-bands, and the ambient noise includes M sub-band noises corresponding to the M sub-bands. The noise reduction circuit 105 may separately estimate the incoming wave directions of the M sub-band noises for each sub-band. In this case, the target directions obtained in S31 include M incoming wave directions corresponding to the M sub-bands. It should be noted that the present application does not limit the division manner of the M sub-bands. In some embodiments, the aforementioned M sub-bands may include: a low frequency band (for example, 0 to 150 Hz), a middle frequency band (for example, 150 to 500 Hz), and a high frequency band (for example, 500 to 2000 Hz).

[0255] In some embodiments, the noise reduction circuit 105 can acquire N individual environmental noise signals collected by N sound sensors, and then estimate the direction of arrival (DOA) of the j-th sub-band using the following method: Extract sub-band noise signals corresponding to the j-th sub-band from the N individual environmental noise signals to obtain N sub-band noise signals corresponding to the j-th sub-band; and perform DOA analysis on the N sub-band noise signals to obtain the DOA corresponding to the j-th sub-band. Here, j is any positive integer less than or equal to M.

[0256] After obtaining the M incoming wave directions corresponding to the M sub-frequency bands, the noise reduction circuit 105 can perform active noise reduction based on each sub-frequency band. Specifically, for the j-th sub-frequency band, the noise reduction circuit 105 determines N sub-frequency band weights corresponding to the N sound sensors based on the incoming wave direction corresponding to the j-th sub-frequency band, so that the phase of the comprehensive sub-frequency band noise signal measured by the first sound sensor module 103 based on the above N sub-frequency band weights leads the phase of the environmental noise of the j-th sub-frequency band reaching the output end of the speaker 102. The comprehensive sub-frequency band noise signal is obtained by weighted summation of the sub-frequency band noise signals corresponding to the j-th sub-frequency band collected by the N sound sensors based on the N sub-frequency band weights. Further, the noise reduction circuit 105 generates N individual sub-frequency band noise reduction signals corresponding to the j-th sub-frequency band based on the sub-frequency band noise signals collected by the N sound sensors corresponding to the j-th sub-frequency band and the N sub-frequency band weights. The noise reduction circuit superimposes the N individual sub-band noise reduction signals to obtain a sub-band noise reduction signal corresponding to the j-th sub-band. Here, 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 sub-bands to obtain M sub-band noise reduction signals corresponding to the M sub-bands. Further, the noise reduction circuit 105 sends the M sub-band noise reduction signals to the speaker 102, causing the speaker 102 to convert the M sub-band noise reduction signals into noise-reducing frequencies to reduce the volume of ambient noise at the eardrum 202.

[0257] It should be understood that the process of active noise reduction for each sub-band is similar to the active noise reduction process for the entire frequency band described above, and will not be repeated here. It should be noted that each feedforward filter may include M filter units corresponding to the M sub-bands. When performing active noise reduction for the j-th sub-band, the filter parameters corresponding to the j-th filter unit in the feedforward filter can be adjusted based on weights; for example, the filter gain corresponding to the j-th filter unit can be adjusted.

[0258] Figure 14 A schematic diagram of a set of frequency response curves provided according to embodiments of this specification is shown. For example... Figure 14As shown, curve 141 illustrates the frequency response of acoustic device 100 using a single sound sensor FF1 in conjunction with a feedforward filter; curve 142 illustrates the frequency response of acoustic device 100 using a single sound sensor FF2 in conjunction with a feedforward filter; and curve 143 illustrates the frequency response of acoustic device 100 using both sound sensors FF1 and FF2 in conjunction with two parallel feedforward filters. As can be seen from curves 141 and 142, individual sound sensors FF1 and FF2 achieve noise reduction effects in different frequency bands. As can be seen from curve 143, combining sound sensors FF1 and FF2 achieves noise reduction effects over a wider frequency band and reaches a deeper noise reduction depth.

[0259] As mentioned earlier, in open acoustic devices, there will be leakage signals (i.e., leakage signals from the loudspeaker 102) in the ambient noise signals collected by the sound sensors. The acoustic device 100 can reduce the above-mentioned leakage to a certain extent by setting multiple sound sensors in the first sound sensor 103. Figure 15 A schematic diagram of yet another set of frequency response curves provided according to an embodiment of this specification is shown. For example... Figure 15 As shown, curve 153 illustrates the frequency response of the acoustic device 100 when it simultaneously employs sound sensors FF1 and FF2, along with two parallel feedforward filters for noise reduction. Curve 151 illustrates the frequency response of FF1 and its corresponding feedforward filter, and curve 152 illustrates the frequency response of FF2 and its corresponding feedforward filter. Figure 15 It is evident that when using two sound sensors, the feedforward filter gain required for each sensor is significantly less than that required to achieve the same filtering effect using a single sound sensor. This reduction in feedforward filter gain decreases leakage, thereby avoiding system divergence problems caused by leakage, as well as noise amplification issues experienced by some users wearing acoustic devices.

[0260] In summary, in the active noise reduction method P300 provided in this specification, when the first sound sensor module 103 includes N sound sensors, the noise reduction circuit 105, during active noise reduction, can determine N weights corresponding to the N sound sensors based on the target direction from which the environmental noise originates. This ensures that the phase of the comprehensive environmental noise signal measured by the first sound sensor module 103 based on the N weights leads the phase of the environmental noise reaching the output end of the speaker. Then, the noise reduction circuit 105 generates a first noise cancellation signal based on the N individual environmental noise signals collected by the N sound sensors and the N weights, and sends the first noise cancellation signal to the speaker 102. Therefore, this scheme, by introducing N sound sensors and assigning weights to them, ensures that the first sound sensor module 103 has a phase lead relative to the output end of the speaker 102 regardless of the direction from which the environmental noise originates. This improves the causality of feedforward noise reduction, thereby enhancing the active noise reduction effect, especially improving high-frequency noise reduction performance. Furthermore, using multiple sound sensors, compared to a single sound sensor, can reduce gain, thereby reducing leakage in certain frequency bands (such as high frequencies) in open environments. This avoids system divergence problems caused by leakage in these frequency bands, as well as noise enhancement issues experienced by some users wearing acoustic devices. Moreover, this solution estimates the direction of arrival at the sub-frequency band level and performs active noise reduction for each sub-frequency band separately, which helps to improve the noise reduction depth of each sub-frequency band, thus further enhancing the effectiveness of active noise reduction.

[0261] Typically, after activating active noise cancellation, the acoustic device 100 performs active noise cancellation across the entire frequency band based on pre-designed noise cancellation parameters. However, in practical applications, due to the diverse external environments in which the acoustic device 100 operates, the aforementioned pre-designed noise cancellation parameters are usually not applicable to active noise cancellation in various external environments. For example, in some special external environments, the noise cancellation effect of the acoustic device may be poor, or there may be distortion in the speaker 102.

[0262] To this end, the noise reduction circuit 105 can provide multiple noise reduction modes. Thus, during active noise reduction, the noise reduction circuit 105 can adaptively select a target noise reduction mode from among the multiple noise reduction modes based on the noise conditions of the external environment, and execute the target noise reduction mode. Adaptively selecting the target noise reduction mode means that the noise reduction mode can be switched autonomously, flexibly, intelligently, and / or adaptively according to the noise conditions of the external environment. It should be understood that the above-mentioned process of switching noise reduction modes is automatically executed by the noise reduction circuit 105, without manual intervention from the user.

[0263] In some embodiments, the above-mentioned multiple noise reduction modes may include at least one of: passive noise reduction mode, anti-clipping noise reduction mode, narrowband noise reduction mode, or normal noise reduction mode.

[0264] In the passive noise reduction mode, the active noise reduction function of the acoustic device 100 is turned off.

[0265] In normal noise reduction mode, the active noise reduction function of the acoustic device 100 is activated, and the noise reduction circuit 105 uses pre-designed noise reduction parameters to perform active noise reduction in the full frequency band based on at least one of the first sound signal or the second sound signal.

[0266] In narrowband noise reduction mode, the active noise reduction function of the acoustic device 100 is activated. The active noise reduction process includes: the noise reduction circuit 105 determining a target frequency band based on a first sound signal, wherein the energy concentration within the target frequency band exceeds a preset threshold. Here, the energy concentration within the target frequency band refers to the degree of concentration of noise signal energy within the target frequency band. In some embodiments, the bandwidth corresponding to the target frequency band is less than a preset bandwidth; therefore, the target frequency band can be referred to as a narrowband. Further, the noise reduction circuit 105 can perform active noise reduction within the target frequency band (narrowband) based on at least one of the first sound signal or a second sound signal.

[0267] In some embodiments, after determining the target frequency band, the noise reduction circuit 105 can adjust its noise reduction parameters based on the target frequency band. The adjusted noise reduction parameters can specify that active noise reduction should be performed primarily on the target frequency band (e.g., the noise reduction depth of the target frequency band is greater than the noise reduction depth of other frequency bands), or the adjusted noise reduction parameters can specify that active noise reduction should only be performed on the target frequency band without active noise reduction on other frequency bands. In some embodiments, the above-mentioned "adjusting the noise reduction parameters of the noise reduction circuit 105" may include: converting the full-band filter in the noise reduction circuit 105 into a narrow-band filter. The above embodiments, by adjusting the noise reduction parameters based on the target frequency band, can increase the noise reduction depth within the target frequency band and improve the noise reduction effect within the target frequency band.

[0268] In the anti-distortion noise reduction mode, the active noise reduction function of the acoustic device 100 is activated. The active noise reduction process includes: the noise reduction circuit 105 generating a noise cancellation signal based on at least one of a first sound signal or a second sound signal, and ensuring that the amplitude of the noise cancellation signal is within the amplitude range supported by the speaker 102. Further, the noise reduction circuit 105 sends the noise cancellation signal to the speaker 102, causing the speaker 102 to convert the noise cancellation signal into a noise cancellation frequency to reduce the volume of ambient noise at the eardrum 202. The aforementioned amplitude range refers to the range of signal amplitudes that the speaker 102 can support while producing sound normally without distortion. Distortion refers to the phenomenon where the vibration of the speaker diaphragm exceeds its linear range, resulting in severe sound distortion. When the amplitude of the signal input to the speaker 102 exceeds the aforementioned amplitude range, it will cause the speaker 102 to distort. When the amplitude of the signal input to the speaker 102 is within the aforementioned amplitude range, it will not cause the speaker 102 to distort. It should be understood that since the noise reduction circuit 105 ensures that the amplitude of the noise reduction signal is within the amplitude range supported by the speaker 102 when generating the noise reduction signal, the speaker 102 can avoid distortion.

[0269] In some embodiments, the noise reduction circuit 105 can generate a noise-canceling signal such that the amplitude of the noise-canceling signal is within the amplitude range supported by the speaker 102: the noise reduction circuit 105 filters at least one of a first sound signal or a second sound signal to obtain a candidate noise-canceling signal. The filtering process described above has been described in the relevant sections above and will not be repeated here. Further, the noise reduction circuit 105 corrects the amplitude of the candidate noise-canceling signal based on the amplitude range, so that the corrected amplitude is within the amplitude range, and uses the corrected signal as the noise-canceling signal. In some embodiments, a dynamic range controller (DRC) can be provided at the output terminal of the noise reduction circuit 105 (i.e., at the interface between the noise reduction circuit 105 and the speaker 102). The DRC is configured to adjust the amplitude of the input signal so that the amplitude of the output signal is within the amplitude range. In this case, after obtaining the candidate noise-canceling signal, the noise reduction circuit 105 inputs the candidate noise-canceling signal to the DRC, and the DRC corrects the amplitude of the candidate noise-canceling signal to obtain the noise-canceling signal.

[0270] In this method, the noise reduction circuit 105 does not need to adjust the original noise reduction parameters, but only needs to add a post-amplitude correction stage (such as adding a dynamic range controller) to avoid the speaker 102 from distorting.

[0271] In some embodiments, the noise reduction circuit 105 may generate a noise-canceling signal in such a way that the amplitude of the noise-canceling signal is within the amplitude range supported by the speaker 102: the noise reduction circuit 105 adjusts the filter gain corresponding to the first audio signal so that the amplitude of the filtered output signal is within the amplitude range. Further, 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-canceling signal.

[0272] In this method, the noise reduction circuit 105 only needs to adjust the filter gain to make the amplitude of the noise reduction signal within the amplitude range, without needing to change the circuit structure of the noise reduction circuit 105.

[0273] In some embodiments, in the adjusted filter gain, the first filter gain corresponding to the first preset frequency band is less than the second filter gain corresponding to the second preset frequency band. In some embodiments, the frequency in the first preset frequency band is lower than the frequency in the second preset frequency band. In some embodiments, the frequency in the first preset frequency band is lower than a preset frequency, wherein the preset frequency can be 500Hz, 200Hz, 150Hz, or other frequency values. In some embodiments, the first preset frequency band can be a low-frequency band (e.g., a frequency band with a frequency less than 150Hz). Since the first preset frequency band corresponds to a smaller filter gain, the amplitude of the filtered noise-canceling signal corresponding to the first preset frequency band is smaller, thereby preventing the speaker 102 from distorting in the first preset frequency band.

[0274] In some embodiments, when adjusting the filter gain, the noise reduction circuit 105 can reduce the first filter gain corresponding to the first preset frequency band while keeping the second filter gain corresponding to the second preset frequency band unchanged, based on the default filter gain. This prevents the speaker 102 from distorting without reducing the noise reduction effect corresponding to the second preset frequency band.

[0275] In the case of acoustic device 100 providing multiple noise reduction modes, this application provides an active noise reduction method P400, which can adaptively switch the noise reduction mode suitable for the current environment based on the noise conditions of the current environment, so that acoustic device 100 can have a good noise reduction effect in different environments. The active noise reduction method P400 can be applied independently to the acoustic device 100 provided in this application, or it can be combined with other active noise reduction methods described in other parts of this document.

[0276] Figure 16A flowchart of another active noise reduction method P400 provided according to an embodiment of this specification is shown. This active noise reduction method P400 can be executed by a noise reduction circuit 105 in the acoustic device 100. For example, a processor 107 in the noise reduction circuit 105 can read an instruction set stored in its local storage medium and then execute the active noise reduction method P400 described herein according to the instructions of the instruction set. Figure 16 As shown, the active noise reduction method P400 may include:

[0277] S41: Obtain the first sound signal from the first sound sensor module.

[0278] S42: Based on the first sound signal, adaptively select the target noise reduction mode among multiple noise reduction modes of the acoustic device.

[0279] In some embodiments, the noise reduction circuit 105 can adaptively select a target noise reduction mode from multiple noise reduction modes based on at least one of the intensity or bandwidth type of the first audio signal. The bandwidth type of the first audio signal can be divided into two types: narrowband and non-narrowband. Narrowband indicates that the bandwidth occupied by the first audio signal is less than a preset bandwidth. Compared to the non-narrowband type, the signal energy of the narrowband type is concentrated within a narrower frequency band.

[0280] In some embodiments, the process by which the noise reduction circuit 105 adaptively selects the target noise reduction mode may include at least one of the following S42-1, S42-2, and S42-3.

[0281] S42-1: Determine that the intensity of the first sound signal is less than or equal to the second intensity threshold, and select the negative noise reduction mode from the plurality of noise reduction modes.

[0282] The second intensity threshold can correspond to the upper limit of noise intensity in a relatively quiet environment. For example, the second intensity threshold can be 40dB. That is, when the noise intensity in the external environment is low (e.g., less than 40dB), the noise reduction circuit 105 selects the passive noise reduction mode and turns off the active noise reduction function. This can reduce the power consumption of the acoustic device 100.

[0283] S42-2: Determine that the intensity of the first sound signal is greater than or equal to the first intensity threshold, and select the anti-distortion noise reduction mode from the plurality of noise reduction modes.

[0284] The first intensity threshold is greater than the second intensity threshold. For example, the first intensity threshold can be 90dB. When the noise in the external environment is high (e.g., greater than or equal to 90dB), the noise reduction circuit 105 can select an anti-distortion noise reduction mode. This can prevent the speaker 102 from distorting.

[0285] S42-3: Determine that the intensity of the first sound signal is greater than the second intensity threshold, and that the bandwidth type of the first sound signal is narrowband, and select the narrowband noise reduction mode from the plurality of noise reduction modes.

[0286] The condition for enabling active noise cancellation is that "the intensity of the first sound signal is greater than the second intensity threshold". Furthermore, if the bandwidth of the first sound signal is narrowband, the noise cancellation circuit 105 selects the narrowband noise cancellation mode. This allows for active noise cancellation only on the target frequency band where the energy of the first sound signal is concentrated, rather than across the entire frequency band, thus increasing the noise cancellation depth within the target frequency band and improving the active noise cancellation effect.

[0287] In some embodiments, the noise reduction circuit 105 adaptively selects the target noise reduction mode based on the following logic: The noise reduction circuit 105 first determines whether the intensity of the first sound signal is less than a second intensity threshold. If so, it selects the passive noise reduction mode. If not, it activates 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 sound signal is greater than or equal to the first intensity threshold; Condition 2: The bandwidth type of the first sound signal is narrowband. The determination result includes the following four cases: If only Condition 1 is met, the anti-distortion noise reduction mode is selected; if only Condition 2 is met, the narrowband noise reduction mode is selected; if both Condition 1 and Condition 2 are met, both the anti-distortion noise reduction mode and the narrowband noise reduction mode can be selected simultaneously; if neither Condition 1 nor Condition 2 is met, the normal noise reduction mode is selected.

[0288] 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 quasi-ambient noise signal, and then, based on the quasi-ambient noise signal, adaptively select a target noise reduction mode from multiple noise reduction modes. The method for reducing the leakage signal component in the first audio signal has been described above and will not be repeated here.

[0289] The noise reduction circuit 105 reduces the leakage signal component in the first sound signal, making the obtained quasi-environmental noise signal closer to the actual environmental noise. Therefore, it adaptively selects the target noise reduction mode based on the quasi-environmental noise signal, making the selected target noise reduction mode more suitable for the current environment, thereby improving the noise reduction effect.

[0290] S43: Execute the target noise reduction mode.

[0291] In some embodiments, the acoustic device 100 operates in a feedforward noise reduction mode, and the noise reduction circuit 105 performs a target noise reduction mode based on the first sound signal. In some embodiments, the acoustic device 100 operates in a feedback noise reduction mode, and the noise reduction circuit 105 performs a target noise reduction mode based on a second sound signal. In some embodiments, the acoustic device 100 operates in a hybrid noise reduction mode, and the noise reduction circuit 105 performs a target noise reduction mode based on both the first and second sound signals.

[0292] In summary, the active noise cancellation method P400 provided in this specification can adaptively adjust the noise cancellation mode based on the noise conditions of the external environment in which the acoustic device 100 is located. This makes the active noise cancellation process of the acoustic device 100 more consistent with the noise conditions of the current environment, thus helping to improve the overall performance of the acoustic device 100. For example, when the noise level in the current environment is low, the acoustic device 100 can turn off the active noise cancellation function to reduce power consumption; when the noise level in the current environment is high, the acoustic device 100 can select an anti-distortion noise cancellation mode to prevent the speaker 102 from distorting; when the noise level in the current environment is narrowband, the acoustic device 100 can select a narrowband noise cancellation mode to increase the noise cancellation depth and improve the noise cancellation effect.

[0293] In the case that the acoustic device 100 provides multiple noise reduction modes, this application also provides another active noise reduction method, which can be executed by the noise reduction circuit 105. In this active noise reduction method, the noise reduction circuit 105 can obtain user instructions and select a target noise reduction mode from multiple noise reduction modes according to the user instructions, and then execute the target noise reduction mode. For example, the acoustic device 100 can be provided with an interactive control, through which the user can switch between different noise reduction modes. Alternatively, the acoustic device 100 can provide an interactive interface, which can be displayed on the screen of the acoustic device 100 or on a target device communicatively connected to the acoustic device 100, through which the user can select different noise reduction modes. In some embodiments, the user instructions can specify a particular noise reduction mode, so the noise reduction circuit 105 can determine the noise reduction mode indicated by the instructions as the target noise reduction mode. In some embodiments, the user instructions can specifically indicate the ambient noise level of the user, and the noise reduction circuit 105 can select the target noise reduction mode from multiple noise reduction modes based on the ambient noise level indicated by the instructions. In this way, users can choose the appropriate active noise cancellation mode according to their own preferences and / or the current ambient noise level, thereby meeting the personalized needs of different users.

[0294] This specification, in another aspect, provides a non-transitory storage medium storing at least one set of executable instructions for performing active noise cancellation. When the executable instructions are executed by a processor, they instruct the processor to implement the steps of the active noise cancellation method described in this specification. In some possible embodiments, various aspects of this specification can also be implemented as a program product comprising program code. When the program product is run on an acoustic device 100, the program code causes the acoustic device 100 to perform the steps of the active noise cancellation method described in this specification. The program product for implementing the above method may employ a portable compact disc read-only memory (CD-ROM) containing program code and may run on the acoustic device 100. However, the program product of this specification is not limited thereto. In this specification, a readable storage medium may be any tangible medium containing or storing a program that may be used by or in conjunction with an instruction execution system. The program product may employ any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A 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. More specific examples of readable storage media include: electrical connections having one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. The computer-readable storage medium may include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable storage medium may also be any readable medium other than a readable storage medium that can send, propagate, or transmit programs for use by or in connection with an instruction execution system, apparatus, or device. Program code contained on a readable storage medium may be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, RF, etc., or any suitable combination thereof. Program code for performing the operations described herein can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the acoustic device 100, partially on the acoustic device 100, as a standalone software package, partially on the acoustic device 100 and partially on a remote computing device, or entirely on a remote computing device.

[0295] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0296] In summary, after reading this detailed disclosure, those skilled in the art will understand that the foregoing detailed disclosure is presented by way of example only and is not restrictive. Although not explicitly stated herein, those skilled in the art will understand that this specification requires various reasonable changes, improvements, and modifications to the embodiments. These changes, improvements, and modifications are intended to be made by this specification and are within the spirit and scope of the exemplary embodiments described herein.

[0297] Furthermore, certain terms in this specification have been used to describe embodiments of this specification. For example, "an embodiment," "an embodiment," and / or "some embodiments" mean that a particular feature, structure, or characteristic described in connection with that embodiment may be included in at least one embodiment of this specification. Therefore, it is to be emphasized and understood that two or more references to "an embodiment" or "an embodiment" or "alternative embodiment" in various parts of this specification do not necessarily refer to the same embodiment. Moreover, specific features, structures, or characteristics may be suitably combined in one or more embodiments of this specification.

[0298] It should be understood that in the foregoing description of the embodiments in this specification, various features are combined in a single embodiment, drawing, or description for the purpose of simplifying the description and aiding in the understanding of a feature. However, this does not mean that the combination of these features is necessary, and those skilled in the art may readily identify some of the devices as separate embodiments when reading this specification. That is, the embodiments in this specification can also be understood as an integration of multiple secondary embodiments. It is also valid when each secondary embodiment contains fewer than all the features of a single foregoing disclosed embodiment.

[0299] Each patent, patent application, publication of the patent application, and other materials such as articles, books, specifications, publications, documents, articles, etc., cited herein may be incorporated by reference. All contents used for all purposes, except for any history of prosecution documents relating to it, that may be inconsistent with or conflict with this document, or any such history of prosecution documents that may have a limiting effect on the widest extent of the claims, are now or hereafter associated with this document. For example, in the event of any inconsistency or conflict between the description, definition, and / or use of terms associated with any of the included materials and the terms, description, definition, and / or used in connection with this document, the terms used herein shall prevail.

[0300] Finally, it should be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments described in this specification. Other modified embodiments are also within the scope of this specification. Therefore, the embodiments disclosed in this specification are merely examples and not limitations. Those skilled in the art can implement the applications described in this specification using alternative configurations based on the embodiments in this specification. Therefore, the embodiments in this specification are not limited to the embodiments precisely described in the applications.

Claims

1. An open wearable acoustic device, characterized by, include: Support components; A loudspeaker, physically connected to the support, forms an open space between the loudspeaker and the user's eardrum when the acoustic device is worn on the user's head; A first sound sensor module, physically connected to the support member, is configured to acquire a first sound and generate a first sound signal, the first sound signal including: an ambient noise signal from the ambient noise and a leakage signal from the speaker; A second sound sensor module, physically connected to the support member, is configured to acquire a second sound and generate a second sound signal. The transfer function from the speaker to the second sound sensor module and the transfer function from the speaker to the eardrum satisfy a first preset relationship, independent of the acoustic device's pose. The noise reduction circuit, which is communicatively connected to the first sound sensor module, the second sound sensor module, and the speaker, is configured as follows: The first sound signal is acquired from the first sound sensor module, and a quasi-ambient noise signal is generated by reducing the leakage signal component in the first sound signal. A first noise reduction signal is generated based on the quasi-ambient noise signal. The second sound signal is acquired from the second sound sensor module; the noise reduction parameters of the noise reduction circuit are adjusted based on the second sound signal and the first preset relationship; a second noise-canceling signal is obtained based on the adjusted noise reduction parameters; and Send the first noise cancellation signal and the second noise cancellation signal to the speaker so that the speaker converts the first noise cancellation signal and the second noise cancellation signal into a first noise cancellation frequency and a second noise cancellation frequency to reduce the volume of ambient noise at the eardrum.

2. The acoustic device of claim 1, wherein, The first sound sensor module is located away from the eardrum relative to the speaker.

3. The acoustic device of claim 1, wherein, To generate the quasi-ambient noise signal, the noise reduction circuit: Obtain the input signal corresponding to the speaker; A first gain is provided to the input signal to obtain a first gain signal, wherein the first gain is a transfer function between the speaker and the first sound sensor module; and The first sound signal is obtained from the first sound sensor module, and the first gain signal is subtracted from the first sound signal to obtain the quasi-ambient noise signal.

4. The acoustic device of claim 3, wherein, The noise reduction circuit is also configured to: A test audio signal is sent to the speaker to make the speaker emit a corresponding test audio, which is then collected by the first sound sensor module. Acquire the audio signal collected by the first sound sensor module; as well as The transfer function is determined based on the test audio signal and the acquired audio signal.

5. The acoustic device of claim 1, wherein, The noise reduction circuit includes a feedforward filter, wherein, in order to generate the first denoised signal, the noise reduction circuit: The quasi-ambient noise signal is input into the feedforward filter, and The first denoised signal is obtained by filtering the quasi-ambient noise signal using the feedforward filter. The feedforward filter is configured to adjust at least one of the gain or phase of the quasi-ambient noise signal, such that the resulting first noise-cancelled signal can cancel out at least a portion of the ambient noise at the eardrum.

6. The acoustic device of claim 1, wherein, The distance between the first sound sensor module and the acoustic null point of the speaker is within a non-zero preset range.

7. The acoustic device of claim 1, wherein, The second sound sensor module is positioned close to the eardrum relative to the speaker.

8. The acoustic device of claim 1, wherein, In order to send the first noise cancellation signal and the second noise cancellation signal to the speaker, the noise reduction circuit: The first denoised signal and the second denoised signal are combined to obtain a combined denoised signal; as well as The synthesized noise cancellation signal is sent to the speaker.

9. The acoustic device of claim 1, wherein, The noise reduction circuit includes a feedback filter, wherein, in order to generate the second noise-canceling signal, the noise reduction circuit: The second audio signal is input into the feedback filter; and The second audio signal is filtered by the feedback filter to obtain the second noise-reduced signal. The feedback filter is configured to adjust at least one of the gain or phase of the second sound signal, such that the resulting second noise-cancelled signal can cancel out at least a portion of the ambient noise at the eardrum.

10. The acoustic device of claim 1, wherein, The noise reduction circuit includes: At least one storage medium storing at least one instruction set for noise reduction; and At least one processor is communicatively connected to the speaker, the first sound sensor module, the second sound sensor module, and the at least one storage medium. When the acoustic device is running, the at least one processor reads the at least one instruction set and executes it according to the instructions of the at least one instruction set: The first sound signal is acquired from the first sound sensor module, and a quasi-ambient noise signal is generated by reducing the leakage signal component in the first sound signal. A first noise reduction signal is generated based on the quasi-ambient noise signal. The second sound signal is acquired from the second sound sensor module; the ambient noise at the eardrum is determined based on the second sound signal and the first preset relationship; the noise reduction parameters are adjusted with the goal of reducing or minimizing the estimated ambient noise at the eardrum; and a second noise reduction signal is obtained based on the noise reduction parameters; and Send the first noise cancellation signal and the second noise cancellation signal to the speaker so that the speaker converts the first noise cancellation signal and the second noise cancellation signal into a first noise cancellation frequency and a second noise cancellation frequency to reduce the volume of ambient noise at the eardrum.

11. The acoustic device of claim 1, wherein, The acoustic device is one of the following: headphones, muffler, hearing aid, or acoustic glasses.

12. The acoustic device of claim 1, wherein, The acoustic device has a specific location defined by its shape and mass distribution, which is close to the ear canal opening when the acoustic device is worn in different postures, and the speaker is located at the specific location.

13. The acoustic device of claim 1, wherein, The transfer function from the ambient noise source to the second sound sensor module and the transfer function from the ambient noise source to the eardrum satisfy a second preset relationship, which is independent of the pose of the acoustic device.

14. An active noise reduction method, characterized by, Applied to the open-type wearable acoustic device of claim 1, the method includes using the noise reduction circuit: The first sound signal is acquired from the first sound sensor module; a quasi-ambient noise signal is generated by reducing the leakage signal component in the first sound signal; and a first noise reduction signal is generated based on the quasi-ambient noise signal. The second sound signal is acquired from the second sound sensor module. Based on the second sound signal and the first preset relationship, the environmental noise at the eardrum is determined. The noise reduction parameters of the noise reduction circuit are adjusted with the goal of reducing or minimizing the estimated environmental noise at the eardrum. A second noise reduction signal is obtained based on the noise reduction parameters. as well as Send the first noise cancellation signal and the second noise cancellation signal to the speaker so that the speaker converts the first noise cancellation signal and the second noise cancellation signal into a first noise cancellation frequency and a second noise cancellation frequency to reduce the volume of ambient noise at the eardrum.

15. The method of claim 14, wherein, The first sound sensor module is located away from the eardrum relative to the speaker.

16. The method according to claim 14, characterized in that, The step of generating a quasi-ambient noise signal by reducing the leakage signal component in the first sound signal includes: Obtain the input signal corresponding to the speaker; A first gain is provided to the input signal to obtain a first gain signal, wherein the first gain is a transfer function between the speaker and the first sound sensor module; and The first sound signal is obtained from the first sound sensor module, and the first gain signal is subtracted from the first sound signal to obtain the quasi-ambient noise signal.

17. The method according to claim 16, characterized in that, It also includes the noise reduction circuit: A test audio signal is sent to the speaker to make the speaker emit a corresponding test audio, which is then collected by the first sound sensor module. Acquire the audio signal collected by the first sound sensor module; as well as The transfer function is determined based on the test audio signal and the acquired audio signal.

18. The method according to claim 14, characterized in that, The noise reduction circuit includes a feedforward filter; and The generation of the first noise-cancelled signal based on the quasi-ambient noise signal includes: The quasi-ambient noise signal is input into the feedforward filter, and The first denoised signal is obtained by filtering the quasi-ambient noise signal using the feedforward filter. The feedforward filter is configured to adjust at least one of the gain or phase of the quasi-ambient noise signal, such that the resulting first noise-cancelled signal can cancel out at least a portion of the ambient noise at the eardrum.

19. The method according to claim 14, characterized in that, The second sound sensor module is positioned close to the eardrum relative to the speaker.

20. The method according to claim 14, characterized in that, The noise reduction circuit includes a feedback filter; and The generation of the second noise-reduced signal includes: The second audio signal is input into the feedback filter, and The second audio signal is filtered by the feedback filter to obtain the second noise-reduced signal. The feedback filter is configured to adjust at least one of the gain or phase of the second sound signal, such that the resulting second noise-cancelled signal can cancel out at least a portion of the ambient noise at the eardrum.

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