An open acoustic device

Abstract

The present specification discloses an open acoustic device, which mainly comprises a fixing structure, a first microphone array, a signal processor and a loudspeaker. The fixing structure is used to fix the acoustic device near the user's ear and not to block the user's ear canal, so as to improve the user's comfort. The first microphone array is used to pick up environmental noise. The signal processor can estimate the noise signal at the user's ear canal based on the environmental noise and the primary path transfer function between the first microphone array and the user's ear canal, and generate a noise reduction signal based on the noise signal. The loudspeaker can output a noise reduction sound wave for eliminating the noise signal at the user's ear canal according to the noise reduction signal. The open acoustic device not only can not block the user's ear, is suitable for long-term wearing, and improves the user's comfort, but also can well eliminate the noise at the user's ear canal, has a good noise reduction effect, and improves the user's auditory experience.

Description

[0001] Priority information

[0002] This application claims priority to Chinese application 202111399590.6, filed on November 19, 2021, the contents of which are incorporated herein by reference. Technical Field

[0003] This specification relates to the field of acoustics, and in particular to an open acoustic device. Background Technology

[0004] Acoustic devices allow users to listen to audio content and make voice calls while maintaining the privacy of their interactions and avoiding disturbing those around them. Acoustic devices are generally divided into two main categories: in-ear and open-ear. In-ear acoustic devices have a structure inside the user's ear canal, which can cause blockage and discomfort during prolonged wear. Open-ear acoustic devices solve this problem by not blocking the ear, making them suitable for long-term wear. However, in open-ear acoustic devices, the microphone used to collect ambient noise and the speaker that emits noise-canceling waves are located near the user's ear (e.g., the area in front of the auricle), some distance from the ear canal. Directly treating the ambient noise picked up by the microphone as noise within the ear canal for noise reduction often results in ineffective noise cancellation and a degraded listening experience.

[0005] Therefore, it is desirable to provide an open-back acoustic device that can provide good noise reduction capabilities while opening the user's ears, thereby improving the user's auditory experience. Summary of the Invention

[0006] This specification provides an open acoustic device, comprising: a fixing structure configured to fix the acoustic device near a user's ear without obstructing the user's ear canal; a first microphone array configured to pick up ambient noise; a signal processor configured to: determine a primary path transfer function between the first microphone array and the user's ear canal based on the ambient noise; estimate a noise signal at the user's ear canal based on the ambient noise and the primary path transfer function; and generate a noise-reducing signal based on the noise signal at the user's ear canal; and a speaker configured to output a noise-reducing wave according to the noise-reducing signal, the noise-reducing wave being used to eliminate the noise signal at the user's ear canal.

[0007] The open acoustic device provided in this specification has the following advantages over the prior art: (1) The first microphone array can pick up ambient noise, and the signal processor can estimate the noise signal in the user's ear canal based on the picked-up ambient noise and the primary path transfer function between the first microphone array and the user's ear canal and generate a corresponding noise reduction signal. The speaker can output a noise reduction wave to eliminate the noise in the user's ear canal based on the noise reduction signal; (2) The second microphone array can pick up ambient noise and noise reduction wave, and the signal processor can update the noise reduction signal based on the signal picked up by the second microphone array to improve the noise reduction effect of the noise reduction signal; (3) The fixed structure can fix the open acoustic device in a position that does not block the user's ear canal, making it less likely to cause discomfort to the user and suitable for long-term wear. Attached Figure Description

[0008] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein:

[0009] Figure 1 This is an exemplary frame structure diagram of an open acoustic device according to some embodiments of this specification;

[0010] Figure 2 This is a noise reduction schematic diagram of an open acoustic device according to some embodiments of this specification;

[0011] Figure 3 These are exemplary structural diagrams of signal processors shown according to some embodiments of this specification;

[0012] Figure 4 This is an exemplary flowchart illustrating a noise reduction process according to some embodiments of this specification;

[0013] Figure 5 This is a schematic diagram illustrating the transmission of ambient noise in an exemplary open acoustic device according to some embodiments of this specification.

[0014] Figure 6 This is an exemplary flowchart illustrating the determination of the primary path transfer function between the first microphone array and the user's ear canal, according to some embodiments of this specification;

[0015] Figure 7 This is a schematic diagram illustrating the determination of the primary path transfer function from the first microphone array to the ear canal, according to some embodiments of this specification;

[0016] Figure 8 This is an exemplary flowchart illustrating the operation of a second microphone array according to some embodiments of this specification;

[0017] Figure 9 This is another exemplary flowchart illustrating the operation of a second microphone array according to some embodiments of this specification;

[0018] Figure 10 This is an exemplary flowchart illustrating the estimation of the noise-reduced signal according to some embodiments of this specification;

[0019] Figure 11 This is an exemplary flowchart illustrating the determination of the overall secondary path transfer function according to some embodiments of this specification;

[0020] Figure 12 This is an exemplary flowchart illustrating the determination of the first-level path transfer function according to some embodiments of this specification;

[0021] Figure 13A This is a schematic diagram of the distribution of a microphone array according to some embodiments of this specification;

[0022] Figure 13B This is a schematic diagram of the distribution of another microphone array according to some embodiments of this specification;

[0023] Figure 13C This is a schematic diagram of the distribution of another microphone array according to some embodiments of this specification;

[0024] Figure 13D This is a schematic diagram of the distribution of another microphone array according to some embodiments of this specification;

[0025] Figure 14A This is a schematic diagram of the microphone array arrangement when a user wears an open acoustic device, according to some embodiments of this specification;

[0026] Figure 14B This is a schematic diagram of another microphone array arrangement when a user wears an open acoustic device, according to some embodiments of this specification. Detailed Implementation

[0027] To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0028] Open-back acoustic devices can include acoustic devices such as open-back headphones. Open-back acoustic devices use a fixed structure (e.g., ear hooks, headbands, eyeglass temples) to secure the speaker to the user's ear without obstructing the ear canal. However, when using open-back acoustic devices, ambient noise can still be heard, resulting in a poorer auditory experience. For example, in noisy environments (e.g., streets, scenic spots), when playing music using open-back acoustic devices, ambient noise enters the ear canal directly, causing significant audibility and interfering with the music listening experience. Similarly, when making calls while wearing open-back acoustic devices, the microphone picks up not only the user's own voice but also ambient noise, leading to a poor call experience.

[0029] To address the aforementioned issues, this specification describes an open-back acoustic device in its embodiments. In some embodiments, the acoustic device may include a mounting structure, a first microphone array, a signal processor, and a speaker. The mounting structure is configured to fix the acoustic device near a user's ear without obstructing the user's ear canal. The first microphone array is configured to pick up ambient noise. In some embodiments, the signal processor may be configured to determine a primary path transfer function between the first microphone array and the user's ear canal based on the ambient noise. The primary path transfer function refers to the phase frequency response of ambient noise at the first microphone array transmitted to the user's ear canal. Further, the signal processor may estimate the noise signal at the user's ear canal based on the ambient noise and the primary path transfer function, and generate a noise-reduced signal based on the noise signal at the user's ear canal. In some embodiments, the speaker may be configured to output a noise-reduced wave based on the noise-reduced signal, the noise-reduced wave being used to eliminate the noise signal at the user's ear canal. In the open acoustic device provided in the embodiments of this specification, the first microphone array may include multiple microphones. The signal processor can determine the direction of the noise source by picking up ambient noise through the multiple microphones. The signal processor determines the primary path transfer function based on the parameter information of the ambient noise (e.g., frequency), the direction of the noise source, and the position information of the microphones in the first microphone array relative to the user's ear canal. The signal processor can estimate the noise signal at the user's ear canal based on the parameter information of the ambient noise (phase information, frequency information, amplitude information, etc.) and the primary path transfer function. Further, the signal processor generates a noise reduction signal based on the estimated noise signal at the user's ear canal, and the loudspeaker generates a noise reduction wave based on the noise reduction signal to cancel the noise at the user's ear canal. The open acoustic device provided in the embodiments of this specification can perform noise reduction for noise in different frequency ranges, presenting a specific noise reduction effect. For example, in the frequency range of 150Hz-2000Hz, it has a noise reduction depth of 5dB-25dB, thereby significantly improving the noise reduction effect of the open acoustic device in this frequency range.

[0030] Figure 1 This is an exemplary frame structure diagram of an open acoustic device 100 shown according to some embodiments of this specification. Figure 1 As shown, the open-back acoustic device 100 may include a fixing structure 120, a first microphone array 130, a signal processor 140, and a speaker 150. In some embodiments, the open-back acoustic device 100 can be fixed near a user's ear by the fixing structure 120 without blocking the user's ear canal. The first microphone array 130 can pick up ambient noise. The signal processor 140 can be coupled (e.g., electrically connected) to the first microphone array 130 and the speaker 150. The signal processor 140 can receive signals from the first microphone array 130 and can also send signals to the speaker 150. For example, the signal processor 140 can receive and process the electrical signal converted from ambient noise transmitted by the first microphone array 130 to obtain parameter information of the ambient noise (e.g., amplitude information, phase information, etc.). In some embodiments, the first microphone array 130 may include multiple microphones, and the signal processor 140 can determine the location of the noise source based on the ambient noise picked up by the multiple microphones. In some embodiments, the signal processor 140 can determine the primary path transfer function between the first microphone array 130 and the user's ear canal based on the parameter information of the ambient noise (e.g., frequency), the location of the noise source, and the location information of the first microphone array 130 and the user's ear canal. The signal processor 140 can also estimate the noise signal at the user's ear canal based on the ambient noise and the primary path transfer function. The parameter information of the noise-reduced signal corresponds to the parameter information of the ambient noise; for example, the amplitude of the noise-reduced signal is approximately equal to the amplitude of the ambient noise, and the phase of the noise-reduced signal is approximately opposite to the phase of the ambient noise. The signal processor 140 can transmit the generated noise-reduced signal to the speaker 150, and the speaker 150 can output a noise-reduced wave according to the noise-reduced signal. This noise-reduced wave can cancel out the ambient noise at the user's ear canal location, thereby achieving active noise reduction of the open acoustic device 100 and improving the user's auditory experience during use of the open acoustic device 100.

[0031] The first microphone array 130 can be configured to pick up ambient noise. In some embodiments, ambient noise refers to a combination of various external sounds in the user's environment. In some embodiments, ambient noise may include one or more of traffic noise, industrial noise, construction noise, social noise, etc. In some embodiments, traffic noise may include, but is not limited to, the noise of motor vehicles driving and horn honking. Industrial noise may include, but is not limited to, the noise of factory machinery operating. Construction noise may include, but is not limited to, the noise of machinery digging, drilling, and mixing. Social environmental noise may include, but is not limited to, noise from mass gatherings, entertainment and publicity, crowd noise, and noise from household appliances. In some embodiments, the first microphone array 130 may be positioned near the user's ear canal to pick up ambient noise transmitted to the user's ear canal. The first microphone array 130 can convert the picked-up ambient noise signal into an electrical signal and transmit it to the signal processor 140 for signal processing. In some embodiments, ambient noise may also include the user's voice. For example, when the open-back headset 100 is not in a call state, the sound of the user speaking can be considered as ambient noise. The first microphone array 130 can pick up the user's own voice and other ambient noise, and convert the sound signal generated by the user's speech and other ambient noise into electrical signals, which are then transmitted to the signal processor 140 for signal processing. In some embodiments, the first microphone array 130 can be distributed at the user's left or right ear. In some embodiments, the first microphone array 130 can also be located at both the user's left and right ears. For example, the first microphone array 130 may include a first sub-microphone array and a second sub-microphone array, wherein the first sub-microphone array is located at the user's left ear and the second sub-microphone array is located at the user's right ear, and the first and second sub-microphone arrays can be in working state simultaneously or one of them can be in working state.

[0032] In some embodiments, ambient noise may include the sound of a user speaking. For example, the first microphone array 130 may pick up ambient noise based on the call status of the open acoustic device 100. When the open acoustic device 100 is not in a call state, the sound of the user speaking may be considered ambient noise, and the first microphone array 130 may pick up the user speaking sound along with other ambient noise. When the open acoustic device 100 is in a call state, the sound of the user speaking may not be considered ambient noise, and the first microphone array 130 may pick up ambient noise other than the user speaking sound. For example, the first microphone array 130 may pick up noise emitted from a noise source at a certain distance (e.g., 0.5 meters, 1 meter) from the first microphone array 130.

[0033] In some embodiments, the first microphone array 130 includes two or more microphones. The first microphone array 130 may include air conduction microphones and / or bone conduction microphones. In some embodiments, the first microphone array 130 may include two or more air conduction microphones. For example, when a user listens to music using the open acoustic device 100, the air conduction microphones can simultaneously acquire ambient noise and the user's voice, converting it as ambient noise into an electrical signal and transmitting it to the signal processor 140 for processing. In some embodiments, the first microphone array 130 may also include two or more bone conduction microphones. In some embodiments, the bone conduction microphones may directly contact the user's scalp, and the vibration signals generated by the facial bones or muscles when the user speaks can be directly transmitted to the bone conduction microphones, which then convert the vibration signals into electrical signals and transmit them to the signal processor 140 for signal processing. In some embodiments, the bone conduction microphones may not directly contact the human body; the vibration signals generated by the facial bones or muscles when the user speaks can first be transmitted to the housing structure, and then from the housing structure to the bone conduction microphone, which further converts the human body vibration signals into electrical signals containing speech information. For example, when a user is on a call, the signal processor 140 can process the sound signal collected by the air conduction microphone as ambient noise and retain the sound signal collected by the bone conduction microphone as a speech signal, thereby ensuring the call quality when the user is on a call.

[0034] In some embodiments, based on the working principle of the microphone, the first microphone array 130 may include dynamic microphones, ribbon microphones, condenser microphones, electret microphones, electromagnetic microphones, carbon microphones, etc., or any combination thereof. In some embodiments, the array arrangement of the first microphone array 130 may be a linear array (e.g., straight line, curved line), a planar array (e.g., regular and / or irregular shapes such as cross, circle, ring, polygon, mesh, etc.), or a three-dimensional array (e.g., cylindrical, spherical, hemispherical, polyhedral, etc.). For details regarding the arrangement of the first microphone array 130, please refer to this specification. Figures 13A-13D as well as Figure 14A , Figure 14B And related content.

[0035] The signal processor 140 is configured to determine a primary path transfer function (PFS) between the first microphone array 130 and the user's ear canal based on ambient noise, estimate a noise signal at the user's ear canal based on the ambient noise and the PFS, and generate a noise-reduced signal based on the noise signal at the user's ear canal. The PFS refers to the path transfer function from the first microphone array 130 to the user's ear canal. In some embodiments, the signal processor 140 may estimate the noise source direction based on the ambient noise and determine the PFS based on parameter information of the ambient noise (e.g., frequency), the noise source direction, and the position information of the first microphone array 130 and the user's ear canal. In some embodiments, the signal processor 140 may estimate the noise signal at the user's ear canal based on parameter information of the ambient noise (phase information, frequency information, amplitude information, etc.) and the PFS, and further, the signal processor 140 may generate a noise-reduced signal based on the estimated noise signal at the user's ear canal.

[0036] In some embodiments, the open acoustic device 100 further includes a second microphone array. The signal processor 140 can estimate the noise at the ear canal based on the ambient noise picked up by the second microphone array and the noise-reduced wave. Further, the signal processor 140 can update the noise-reduced signal based on the sound signal at the ear canal. In some embodiments, the signal processor 140 can also acquire the noise-reduced wave picked up by the second microphone array based on the sound signal picked up by the second microphone array. The signal processor 140 can determine a first-level path transfer function (the first-level path being the propagation path of the sound signal from the speaker 150 to the second microphone array) based on the noise-reduced wave output by the speaker 150 and the noise-reduced wave picked up by the second microphone array. The signal processor 140 can determine a second-level path transfer function (the second-level path being the propagation path of the sound signal from the second microphone array to the ear canal) based on the first-level path transfer function using a trained machine learning model or a pre-defined model. The signal processor 140 can determine an overall secondary path transfer function (the overall secondary path being the propagation path of the sound signal from the speaker 150 to the ear canal) based on the first-level and second-level path transfer functions. The signal processor 140 can estimate the noise-reduced wave in the user's ear canal based on the noise signal in the user's ear canal, and update the noise-reduced signal based on the noise-reduced wave in the user's ear canal and the overall secondary transfer function.

[0037] In some embodiments, the signal processor 140 may include hardware modules and software modules. As an example only, the hardware module may include a Digital Signal Processor (DSP) chip or an Advanced Reduced Instruction Set Machine (ARM), and the software module may include an algorithm module. Further details about the signal processor 140 can be found in the following sections. Figure 3 And its corresponding description.

[0038] The speaker 150 can be configured to output a noise-canceling wave based on a noise-canceling signal. This noise-canceling wave can be used to reduce or eliminate ambient noise transmitted to the user's ear canal (e.g., tympanic membrane, basilar membrane). By way of example only, the signal processor 140 controls the speaker 150 to output a noise-canceling wave with an amplitude approximately equal to and phase approximately opposite to the noise signal at the user's ear canal to cancel the noise signal at the user's ear canal. In some embodiments, when the user wears the open-back acoustic device 100, the speaker 150 may be located near the user's ear. In some embodiments, depending on the speaker's operating principle, the speaker 150 may include one or more of the following: an electrodynamic speaker (e.g., a moving-coil speaker), a magnetic speaker, an ionic speaker, an electrostatic speaker (or a capacitive speaker), a piezoelectric speaker, etc. In some embodiments, depending on the propagation mode of the sound output by the speaker, the speaker 150 may include an air-conduction speaker and / or a bone-conduction speaker. In some embodiments, the number of speakers 150 may be one or more. When there is only one speaker 150, it can be used to output noise-canceling waves to eliminate ambient noise and to deliver sound information (e.g., device media audio, far-end audio of a call) to the user. For example, when there is only one speaker 150 and it is an air-conduction speaker, it can be used to output noise-canceling waves to eliminate ambient noise. In this case, the noise-canceling wave can be a sound wave signal (i.e., vibration of air), which can be transmitted through the air to the target spatial location (e.g., the user's ear canal) and cancels out ambient noise. Simultaneously, the air-conduction speaker can also be used to deliver sound information to the user. As another example, when there is only one speaker 150 and it is a bone-conduction speaker, it can be used to output noise-canceling waves to eliminate ambient noise. In this case, the noise-canceling wave can be a vibration signal (e.g., vibration of the speaker housing), which can be transmitted through bone or tissue to the user's basilar membrane and cancels out ambient noise at the user's basilar membrane. Simultaneously, the bone-conduction speaker can also be used to deliver sound information to the user. When there are multiple speakers 150, some of them can be used to output noise-reducing waves to eliminate ambient noise, while others can be used to deliver the sound information that the user needs to hear (e.g., device media audio, far-end audio of a call). For example, when there are multiple speakers 150 and they include bone conduction speakers and air conduction speakers, the air conduction speakers can be used to output sound waves to reduce or eliminate ambient noise, while the bone conduction speakers can be used to deliver the sound information that the user needs to hear. Compared to air conduction speakers, bone conduction speakers can transmit mechanical vibrations directly to the user's auditory nerve through the user's body (e.g., bones, skin tissue, etc.), with less interference to the air conduction microphone that picks up ambient noise in this process.

[0039] It should be noted that the speaker 150 can be a standalone functional device or part of a single device capable of performing multiple functions. As an example only, the speaker 150 can be integrated with and / or formed as a single unit of the signal processor 140. In some embodiments, when there are multiple speakers 150, the arrangement of the multiple speakers 150 can include linear arrays (e.g., straight lines, curved lines), planar arrays (e.g., cross-shaped, mesh-shaped, circular, annular, polygonal, etc., regular and / or irregular shapes), three-dimensional arrays (e.g., cylindrical, spherical, hemispherical, polyhedral, etc.), or any combination thereof, which are not limited herein. In some embodiments, the speaker 150 can be positioned at the user's left ear and / or right ear. For example, the speaker 150 can include a first sub-speaker and a second sub-speaker. The first sub-speaker can be located at the user's left ear, and the second sub-speaker can be located at the user's right ear. The first sub-speaker and the second sub-speaker can be in working condition simultaneously, or one of them can be in working condition. In some embodiments, the speaker 150 can be a speaker with a directional sound field, its main lobe pointing towards the user's ear canal.

[0040] In some embodiments, to ensure consistent signal pickup, all microphones in the first microphone array 130 are located in positions that are not affected or minimally affected by the loudspeaker 150 in the open acoustic device 100. In some embodiments, the loudspeaker 150 may form at least one set of acoustic dipoles. For example, the front and back surfaces of the diaphragm of the loudspeaker 150 can be considered as two sound sources, which can output a set of sound signals with approximately opposite phases and approximately the same amplitude. These two sound sources can constitute an acoustic dipole or similar acoustic dipole, and the sound radiated outward has obvious directivity. Ideally, the sound radiated by the loudspeaker is larger in the straight line direction connecting the two point sound sources, and the sound radiated in other directions is significantly reduced. The sound radiated by the loudspeaker 150 is minimal in the region of the perpendicular bisector (or near the perpendicular bisector) of the line connecting the two point sound sources. Therefore, all microphones in the first microphone array 130 can be placed in the region of minimum sound pressure level of the loudspeaker 150, that is, the region of the perpendicular bisector (or near the perpendicular bisector) of the line connecting the two point sound sources.

[0041] In some embodiments, the open acoustic device 100 may include a second microphone array 160. In some embodiments, the second microphone array 160 may have two or more microphones, including bone conduction microphones and air conduction microphones. In some embodiments, the second microphone array 160 is at least partially distinct from the first microphone array 130. For example, the number, type, location, arrangement, etc., of the microphones in the second microphone array 160 may differ from those in the first microphone array 130. For example, in some embodiments, the microphones in the first microphone array 130 may be arranged linearly, while the microphones in the second microphone array 160 may be arranged circularly. As another example, the microphones in the second microphone array 160 may only include air conduction microphones, while the first microphone array 130 may include both air conduction and bone conduction microphones. In some embodiments, the microphones in the second microphone array 160 may be any one or more microphones included in the first microphone array 130, or they may be independent of the microphones in the first microphone array 130. The second microphone array 160 is configured to pick up ambient noise and noise-canceling waves. The ambient noise and noise-reduced signal picked up by the second microphone array 160 can be transmitted to the signal processor 140. In some embodiments, the signal processor 140 can update the noise-reduced signal based on the sound signal picked up by the second microphone array 160. In some embodiments, the signal processor 140 can determine the global secondary transfer function between the speaker 150 and the user's ear canal based on the sound signal picked up by the second microphone array 160, and estimate the noise-reduced signal based on the noise signal at the user's ear canal and the global secondary transfer function. For details on updating the noise-reduced signal based on the sound signal picked up by the second microphone array 160, please refer to this specification. Figures 8-12 And its related descriptions.

[0042] In some embodiments, the open-back acoustic device 100 may include a fixing structure 120. The fixing structure 120 may be configured to secure the open-back acoustic device 100 near a user's ear without obstructing the user's ear canal. In some embodiments, the fixing structure 120 may be physically connected to the housing structure of the open-back acoustic device 100 (e.g., snap-fit, threaded connection, etc.). In some embodiments, the housing structure of the open-back acoustic device 100 may be part of the fixing structure 120. In some embodiments, the fixing structure 120 may include ear hooks, back hooks, elastic bands, temples, etc., to better secure the open-back acoustic device 100 near the user's ear and prevent it from falling off during use. For example, the fixing structure 120 may be an ear hook, which may be configured to be worn around the ear area. In some embodiments, the ear hook may be a continuous hook and may be elastically stretched to be worn on the user's ear, while also applying pressure to the user's auricle, so that the open-back acoustic device 100 is securely fixed to a specific location on the user's ear or head. In some embodiments, the ear hook may be a discontinuous band. For example, the ear hook may include a rigid portion and a flexible portion. The rigid portion can be made of a rigid material (e.g., plastic or metal) and can be fixed to the housing structure of the open acoustic device 100 by a physical connection (e.g., snap-fit, threaded connection, etc.). The flexible portion can be made of an elastic material (e.g., fabric, composite material, and / or neoprene). For example, the fixing structure 120 can be a neck strap configured to be worn around the neck / shoulder area. As another example, the fixing structure 120 can be an eyeglass temple, which, as part of the eyeglasses, is mounted on the user's ear.

[0043] In some embodiments, the open-back acoustic device 100 may include a housing structure. The housing structure may be configured to carry other components of the open-back acoustic device 100 (e.g., a first microphone array 130, a signal processor 140, a speaker 150, a second microphone array 160, etc.). In some embodiments, the housing structure may be a hollow, closed or semi-closed structure, with other components of the open-back acoustic device 100 located within or on the housing structure. In some embodiments, the housing structure may be a regular or irregular three-dimensional structure, such as a cuboid, cylinder, or frustum. When a user wears the open-back acoustic device 100, the housing structure may be located near the user's ear. For example, the housing structure may be located on the periphery of the user's auricle (e.g., the front or back). Alternatively, the housing structure may be located on the user's ear but not block or cover the user's ear canal. In some embodiments, the open-back acoustic device 100 may be a bone conduction headset, with at least one side of the housing structure in contact with the user's skin. An acoustic driver (e.g., a vibrating speaker) in the bone conduction headset converts audio signals into mechanical vibrations, which are transmitted to the user's auditory nerve through the housing structure and the user's bones. In some embodiments, the open-back acoustic device 100 may be an air-conducting headphone, with at least one side of the housing structure that may or may not contact the user's skin. The sidewall of the housing structure includes at least one sound-conducting hole, through which a speaker in the air-conducting headphone converts audio signals into air-conducting sound, which is radiated toward the user's ear.

[0044] In some embodiments, the open acoustic device 100 may further include one or more sensors. The one or more sensors may be electrically connected to other components of the open acoustic device 100 (e.g., signal processor 140). The one or more sensors may be used to acquire physical position and / or motion information of the open acoustic device 100. By way of example only, the one or more sensors may include an inertial measurement unit (IMU), a global positioning system (GPS), radar, etc. Motion information may include motion trajectory, motion direction, motion speed, motion acceleration, motion angular velocity, motion-related time information (e.g., motion start time, motion end time), etc., or any combination thereof. Taking an IMU as an example, the IMU may include a microelectromechanical system (MEMS). The microelectromechanical system may include a multi-axis accelerometer, a gyroscope, a magnetometer, etc., or any combination thereof. The IMU may be used to detect the physical position and / or motion information of the open acoustic device 100 to enable control of the acoustic device 100 based on the physical position and / or motion information.

[0045] In some embodiments, the open acoustic device 100 may include a transceiver. The transceiver may be electrically connected to other components of the open acoustic device 100 (e.g., signal processor 140). In some embodiments, the transceiver may include Bluetooth, an antenna, etc. The open acoustic device 100 can communicate with other external devices (e.g., mobile phones, tablets, smartwatches) via the transceiver. For example, the open acoustic device 100 can wirelessly communicate with other devices via Bluetooth.

[0046] In some embodiments, the open-back acoustic device 100 may further include an interactive module for adjusting the sound pressure level of the noise-canceling wave. In some embodiments, the interactive module may include a button, a voice assistant, a gesture sensor, etc. The user can adjust the noise-canceling mode of the open-back acoustic device 100 by controlling the interactive module. Specifically, the user can adjust (e.g., amplify or reduce) the amplitude information of the noise-canceling signal by controlling the interactive module to change the sound pressure level of the noise-canceling wave emitted by the speaker 150, thereby achieving different noise-canceling effects. As an example only, the noise-canceling mode may include a strong noise-canceling mode, a medium noise-canceling mode, a weak noise-canceling mode, etc. For example, when the user wears the open-back acoustic device 100 indoors where the ambient noise is low, the user can use the interactive module to turn off the noise-canceling mode of the open-back acoustic device 100 or adjust it to a weak noise-canceling mode. For example, when a user wears the open-back acoustic device 100 while walking in public places such as on the street, the user needs to maintain a certain level of awareness of the surrounding environment while listening to audio signals (e.g., music, voice information) to cope with emergencies. In this case, the user can select a medium noise reduction mode through an interactive module (e.g., a button or voice assistant) to preserve ambient noise (such as alarm sounds, impact sounds, car horns, etc.). As another example, when a user is taking public transportation such as a subway or airplane, the user can select a strong noise reduction mode through the interactive module to further reduce ambient noise. In some embodiments, the signal processor 140 can also send prompts to the open-back acoustic device 100 or a terminal device (e.g., a mobile phone, smartwatch, etc.) communicatively connected to the open-back acoustic device 100 based on the ambient noise intensity range to remind the user to adjust the noise reduction mode.

[0047] Figure 2 This is a noise reduction principle diagram of an open acoustic device 100 according to some embodiments of this specification. Figure 2As shown, x(n) is the primary noise signal (ambient noise signal) received by the first microphone array 130, P(z) is the primary path of the primary noise signal from the first microphone array 130 to the ear canal, d(n) is the primary noise signal propagating to the second microphone array 160, W(z) is the active noise reduction adaptive filter, y(n) is the output signal of the adaptive filter, S(z) is the overall secondary path of the secondary sound source (noise reduction wave) propagating from the speaker 150 to the ear canal, y'(n) is the sound of the noise reduction wave reaching the ear canal after passing through the overall secondary path, and e(n) is the sound at the user's ear canal. The goal of noise reduction in the open acoustic device 100 is to minimize the sound e(n) at the ear canal, for example, e(n) = 0. For details regarding the signal x(n) captured by the first microphone array 130, please refer to the following sections. Figure 5 The relevant descriptions will not be repeated here. In some embodiments, the signal processor 140 of the open acoustic device 100 can estimate the noise signal at the user's ear canal based on the primary path P(z) between the first microphone array 130 and the user's ear canal and the primary noise signal x(n) received by the first microphone array 130, so as to generate a corresponding noise reduction signal, and the speaker 150 generates a noise reduction wave based on the noise reduction signal. However, since there is a certain distance between the speaker 150 and the user's ear canal, the noise reduction wave received at the user's ear canal will be different from the noise reduction wave emitted by the speaker 150, resulting in a reduction in noise reduction effect. In some embodiments, the open acoustic device 100 can determine the overall secondary path S(z) between the speaker 150 and the ear canal based on the noise reduction wave picked up by the second microphone array 160 and the ambient noise, so as to determine the noise reduction signal based on the overall secondary path S(z), thereby improving the noise reduction capability of the noise reduction wave emitted by the speaker 150 received at the user's ear canal for the noise at the user's ear canal, so that the sound e(n) at the user's ear canal is reduced to a minimum.

[0048] It should be noted that the above regarding Figure 1 and Figure 2The description provided is for illustrative purposes only and is not intended to limit the scope of this specification. Various changes and modifications can be made by those skilled in the art based on the guidance of this specification. However, these changes and modifications will not depart from the scope of this specification. For example, one or more elements (e.g., fixing structures, etc.) in the open acoustic device 100 may be omitted. In some embodiments, an element may be replaced by another element that performs a similar function. For example, in some embodiments, the open acoustic device 100 may not include a fixing structure, and the housing structure of the open acoustic device 100 may be a housing structure with a shape adapted to the human ear, such as annular, elliptical, polygonal (regular or irregular), U-shaped, V-shaped, or semi-circular, so that the housing structure can be attached near the user's ear. In some embodiments, an element may be divided into multiple sub-elements, or multiple elements may be combined into a single element.

[0049] Figure 3 This is an exemplary structural schematic diagram of a signal processor 140 according to some embodiments of this specification. Figure 3 As shown, the signal processor 140 may include an analog-to-digital conversion unit 210, a noise estimation unit 220, an amplitude and phase compensation unit 230, and a digital-to-analog conversion unit 240.

[0050] In some embodiments, the analog-to-digital converter (ADC) unit 210 can be configured to convert signals input from the first microphone array 130 or the second microphone array 160 into digital signals. For example, the first microphone array 130 can pick up ambient noise and convert the picked-up ambient noise into an electrical signal, which is then transmitted to the signal processor 140. Upon receiving the electrical signal of the ambient noise transmitted by the first microphone array 130, the ADC unit 210 can convert the electrical signal into a digital signal. In some embodiments, the ADC unit 210 can be electrically connected to the first microphone array 130 and further electrically connected to other components of the signal processor 140 (e.g., the noise estimation unit 220). Furthermore, the ADC unit 210 can transmit the converted digital signal of the ambient noise to the noise estimation unit 220.

[0051] In some embodiments, the noise estimation unit 220 can be configured to estimate ambient noise based on a received digital signal of ambient noise. For example, the noise estimation unit 220 can estimate relevant parameters of the ambient noise at a target spatial location (e.g., the user's ear canal) based on the received digital signal of ambient noise. As an example only, the parameters may include the noise source direction, amplitude, phase, etc., or any combination thereof, at the target spatial location (e.g., the user's ear canal). In some embodiments, the noise estimation unit 220 can estimate the noise source direction based on the digital signal of ambient noise received by the first microphone array 130, and determine a primary path transfer function based on the ambient noise (e.g., frequency), the noise source direction, and the position information of the first microphone array 130 and the user's ear canal. Then, it estimates the noise signal at the user's ear canal based on the ambient noise and the primary path transfer function. In some embodiments, the noise estimation unit 220 can estimate the noise at the user's ear canal based on the ambient noise picked up by the second microphone array 160 and the noise-reduced signal, and update the noise-reduced signal based on the sound signal at the user's ear canal. In some embodiments, the noise estimation unit 220 may determine the overall secondary path transfer function between the speaker 150 and the user's ear canal based on the sound signal picked up by the second microphone array 160, and update the noise reduction signal according to the noise signal at the user's ear canal and the overall secondary path transfer function. In some embodiments, the noise estimation unit 220 may also be configured to estimate the sound field at a target spatial location (e.g., at the user's ear canal) using the first microphone array 130. In some embodiments, the noise estimation unit 220 may be electrically connected to other components of the signal processor 140 (e.g., the amplitude-phase compensation unit 230). Further, the noise estimation unit 220 may transmit the estimated ambient noise-related parameters and the sound field at the target spatial location to the amplitude-phase compensation unit 230.

[0052] In some embodiments, the amplitude-phase compensation unit 230 can be configured to compensate for estimated environmental noise-related parameters based on the sound field at the target spatial location. For example, the amplitude-phase compensation unit 230 can compensate for the amplitude and phase of the environmental noise based on the sound field at the user's ear canal, and the signal processor 140 generates a digital noise-reduced signal based on the environmental noise compensated by the amplitude-phase compensation unit 230. In some embodiments, the amplitude-phase compensation unit 230 can adjust the amplitude of the environmental noise and perform inverse compensation for the phase of the environmental noise, and the signal processor 140 generates a digital noise-reduced signal based on the environmental noise compensated by the amplitude-phase compensation unit 230. The amplitude of the digital noise-reduced signal can be approximately equal to the amplitude of the digital signal corresponding to the environmental noise, and the phase of the digital noise-reduced signal can be approximately opposite to the phase of the digital signal corresponding to the environmental noise. In some embodiments, the amplitude-phase compensation unit 230 can be electrically connected to other components of the signal processor 140 (e.g., the digital-to-analog converter unit 240). Furthermore, the amplitude-phase compensation unit 230 can transmit the digital noise-reduced signal to the digital-to-analog converter unit 240.

[0053] In some embodiments, the digital-to-analog converter 240 may be configured to convert a digital noise-reduced signal into an analog signal to obtain a noise-reduced signal (e.g., an electrical signal). By way of example only, the digital-to-analog converter 240 may include pulse width modulation (PMW). In some embodiments, the digital-to-analog converter 240 may be electrically connected to other components of the open acoustic device 100 (e.g., a loudspeaker 150). Furthermore, the digital-to-analog converter 240 may transmit the noise-reduced signal to the loudspeaker 150.

[0054] In some embodiments, the signal processor 140 may include a signal amplification unit 250. The signal amplification unit 250 may be configured to amplify the input signal. For example, the signal amplification unit 250 may amplify the signal input from the first microphone array 130. By way of example only, when the open acoustic device 100 is in a call state, the signal amplification unit 250 may be used to amplify the user's speech input from the first microphone array 130. In some embodiments, the signal amplification unit 250 may be electrically connected to other components of the open acoustic device 100 or the signal processor 140 (e.g., the first microphone array 130, the noise estimation unit 220, the amplitude and phase compensation unit 230).

[0055] It should be noted that the above regarding Figure 3The description provided is for illustrative purposes only and is not intended to limit the scope of this specification. Various changes and modifications can be made by those skilled in the art based on the guidance of this specification. In some embodiments, one or more components in the signal processor 140 (e.g., signal amplification unit 250) may be omitted. In some embodiments, a component of the signal processor 140 may be divided into multiple sub-components, or multiple components may be combined into a single component. For example, the noise estimation unit 220 and the amplitude-phase compensation unit 230 may be integrated into a single component to implement the functions of the noise estimation unit 220 and the amplitude-phase compensation unit 230. These changes and modifications do not depart from the scope of this specification.

[0056] Figure 4 This is an exemplary flowchart illustrating a noise reduction process according to some embodiments of this specification. Figure 4 As shown, process 400 may include the following steps:

[0057] Step 410: Pick up ambient noise.

[0058] In some embodiments, this step may be performed by the first microphone array 130.

[0059] According to the above Figure 1-2 According to the relevant description, environmental noise can refer to a combination of various external sounds in the user's environment (e.g., traffic noise, industrial noise, construction noise, social noise). In some embodiments, the first microphone array 130 can be located near the user's ear canal. When environmental noise is transmitted to the first microphone array 130, each microphone in the first microphone array 130 can convert the environmental noise signal it picks up into an electrical signal and transmit it to the signal processor 140 for signal processing.

[0060] Step 420: Determine the primary path transfer function between the first microphone array 130 and the user's ear canal based on ambient noise.

[0061] In some embodiments, this step may be performed by the signal processor 140.

[0062] The first microphone array 130 can convert ambient noise of different directions and types into electrical signals and transmit them to the signal processor 140. The signal processor 140 can analyze the electrical signals corresponding to the ambient noise to calculate the primary path transfer function from the first microphone array 130 to the user's ear canal. The primary path transfer function can include the phase frequency response of the ambient noise transmitted from the first microphone array 130 to the user's ear canal. The signal processor 140 can determine the noise at the user's ear canal based on the ambient noise received by the first microphone array 130 and the primary path transfer function. For an example of the primary path transfer function, please refer to [link to example]. Figure 5The description. Figure 5 This is a schematic diagram illustrating the transmission of ambient noise in an exemplary open acoustic device according to some embodiments of this specification. Figure 5 As shown, in some embodiments, the first microphone array 130 may have two or more microphones. When a user wears an open-back acoustic device, the open-back acoustic device 100 may be located near the user's ear (e.g., the facial area in front of the user's auricle, the user's auricle, or the area behind the user's auricle, etc.). Correspondingly, at this time, two or more microphones in the first microphone array 130 may be located near the user's ear (e.g., the facial area in front of the user's auricle, the user's auricle, or the area behind the user's auricle, etc.). The first microphone array 130 can pick up ambient noise from all directions. Figure 5 In the diagram, 1, 2, and 3 represent three microphones in the first microphone array 130. The black circle represents the ear canal, and the solid arrows represent ambient noise signals coming from different directions. The dashed arrows represent the primary path transfer function from the first microphone array 130 to the ear canal. Figure 5 As can be seen from this, even two environmental noise signals from different directions ( Figure 5 As shown, signals 1 and 2 are identical when they reach microphone 3, but they differ when they reach the ear canal; for example, signals 1 and 2 are out of phase at the ear canal. By determining the primary path transfer function between the first microphone array 130 and the user's ear canal, the ambient noise picked up by the first microphone array 130 can be converted into noise at the user's ear canal opening, thereby achieving more accurate noise reduction at the user's ear canal opening. For details on determining the primary path transfer function, please refer to the following sections. Figure 6 , Figure 7 And its related descriptions.

[0063] Step 430: Estimate the noise signal at the user's ear canal based on the ambient noise and the primary path transfer function.

[0064] In some embodiments, this step may be performed by the signal processor 140.

[0065] The noise signal at the user's ear canal refers to the sound field of ambient noise at the user's ear canal. In some embodiments, the sound field at the ear canal can refer to the distribution and variation of sound waves at or near the ear canal opening (e.g., variation with time, variation with location). Physical quantities describing the sound field can include sound pressure, sound frequency, sound amplitude, sound phase, sound source vibration velocity, or medium (e.g., air) density, etc. In some embodiments, the physical quantities of the sound field can be functions of position and time. Since the open-type acoustic output device is located near the user's ear canal and does not block the ear canal, the propagation path of external ambient noise can be considered as first being collected by the microphones in the first microphone array 130 and then transmitted to the user's ear canal. In order to accurately determine the noise signal at the user's ear canal, in some embodiments, the noise signal at the user's ear canal can be estimated by the ambient noise picked up by the first microphone array 130 and the primary path transfer function. Specifically, the signal processor 140 can estimate the noise signal at the ear canal opening based on the relevant parameters of the ambient noise picked up by the first microphone array 130 (e.g., amplitude, phase, etc.) and the primary path transfer function transmitted to the ear canal via the first microphone array 130.

[0066] Step 440: Generate a noise reduction signal based on the noise signal at the user's ear canal.

[0067] In some embodiments, this step may be performed by the signal processor 140.

[0068] In some embodiments, the signal processor 140 can generate a noise-reducing signal based on the noise signal at the ear canal obtained in step 430. To ensure the noise reduction effect of the open acoustic device, in some embodiments, the phase of the noise-reducing signal can be opposite or approximately opposite to the phase of the noise signal at the user's ear canal, and the amplitude of the noise-reducing signal can be equal or approximately equal to the amplitude of the noise at the ear canal opening, thereby causing the noise-reduced wave output by the speaker based on the noise-reducing signal to cancel out the ambient noise at the user's ear canal. In some embodiments, the user can also manually adjust the parameter information of the noise-reducing signal (e.g., phase, amplitude, etc.) according to the usage scenario. As an example only, in some embodiments, the absolute value of the phase difference between the phase of the noise-reducing signal and the phase of the noise signal at the ear canal can be within a preset phase range. In some embodiments, the preset phase range can be in the range of 90-180 degrees. The absolute value of the phase difference between the phase of the noise-reducing signal and the phase of the noise signal at the ear canal can be adjusted within this range according to the user's needs. For example, when the user does not want to be disturbed by the sound of the surrounding environment, the absolute value of the phase difference can be a larger value, such as 180 degrees, that is, the phase of the noise-reducing signal is opposite to the phase of the noise at the ear canal opening. For example, when a user wants to remain sensitive to their surroundings, such as when crossing a road or cycling, the absolute value of the phase difference can be relatively small, such as 90 degrees. It's important to note that the closer the absolute value of the phase difference is to 90 degrees, the more ambient sound the user wants to receive. When the absolute value of the phase difference is closer to 90 degrees, the cancellation and superposition effects between the noise reduction signal and the noise signal at the user's ear canal are relatively weak, allowing the user to receive more ambient sound without increasing the volume of the noise signal heard in the ear canal. Conversely, the closer the absolute value of the phase difference is to 180 degrees, the less ambient sound the user wants to receive. In some embodiments, when the phase of the noise reduction signal and the phase of the noise at the ear canal opening meet certain conditions (e.g., opposite phases), the difference between the amplitude of the noise at the ear canal opening and the amplitude of the noise reduction signal can be within a preset amplitude range. For example, when a user does not want to be disturbed by ambient sound, this amplitude difference can be relatively small, such as 0 dB, meaning the amplitude of the noise reduction signal is equal to the amplitude of the noise at the ear canal opening. For example, when a user wants to remain sensitive to their surroundings, this amplitude difference can be a larger value, such as approximately equal to the amplitude of the noise at the ear canal opening. It should be noted that the more ambient sound a user wants to receive, the closer this amplitude difference can be to the amplitude of the noise at the ear canal; the less ambient sound a user wants to receive, the closer this amplitude difference can be to 0 dB.

[0069] Step 450: Output the noise-reduced wave based on the noise reduction signal.

[0070] In some embodiments, this step may be performed by the speaker 150.

[0071] In some embodiments, the loudspeaker 150 can convert a noise-reducing signal (e.g., an electrical signal) into a noise-reducing wave based on a vibrating component in the loudspeaker 150. This noise-reducing wave can cancel out ambient noise at the user's ear canal. For example, when the ambient noise is a first ambient noise, the ambient noise is the sound field of the first ambient noise at the user's ear canal. As another example, when there are multiple ambient noises, the ambient noise includes a first ambient noise and a second ambient noise, and the ambient noise refers to the sound field of the first and second ambient noises at the user's ear canal. In some embodiments, the loudspeaker 150 can output a target signal corresponding to the sound field at the user's ear canal based on the noise-reducing signal. In some embodiments, when the noise at the ear canal is multiple ambient noises, the loudspeaker 150 can output noise-reducing waves corresponding to the multiple ambient noises based on the noise-reducing signal. For example, if the multiple ambient noises include a first ambient noise and a second ambient noise, the loudspeaker 150 can output a first noise-reducing wave with approximately opposite phase and approximately equal amplitude to the first ambient noise to cancel out the first ambient noise, and a second noise-reducing wave with approximately opposite phase and approximately equal amplitude to the second ambient noise to cancel out the second ambient noise. In some embodiments, when the speaker 150 is an air-conduction speaker, the location where the noise-canceling wave cancels out the ambient noise can be near the ear canal. Since the distance between the location near the ear canal and the user's ear canal is small, noise near the ear canal opening can be approximated as noise at the user's ear canal location. Therefore, the noise-canceling wave cancels out the noise near the ear canal, which can be approximated as the elimination of ambient noise transmitted to the user's ear canal, thus achieving active noise cancellation of the open-back acoustic device 100. In some embodiments, when the speaker 150 is a bone-conduction speaker, the location where the noise-canceling wave cancels out the ambient noise can be the basilar membrane. The noise-canceling wave cancels out the ambient noise at the user's basilar membrane, thereby achieving active noise cancellation of the open-back acoustic device 100.

[0072] In some embodiments, the signal processor 140 can also update the noise reduction signal based on manual input from the user. For example, when a user plays music while wearing the open-back acoustic device 100 in a noisy environment, their auditory experience may be unsatisfactory. The user can manually adjust the parameters of the noise reduction signal (e.g., frequency, phase, and amplitude information) based on their own auditory experience. As another example, when using the open-back acoustic device 100, the hearing ability of special users (e.g., hearing-impaired users or elderly users) differs from that of ordinary users. The noise reduction signal generated by the open-back acoustic device 100 itself may not meet the needs of the special users, resulting in a poor auditory experience. In this case, some adjustment factors for the noise reduction signal parameters can be preset. The special users can adjust the noise reduction signal based on their own auditory experience and the preset adjustment factors, thereby updating the noise reduction signal to improve their auditory experience. In some embodiments, the user can manually adjust the noise reduction signal using buttons on the open-back acoustic device 100. In other embodiments, the user can adjust the noise reduction signal through a terminal device. Specifically, the open acoustic device 100 or an external device (e.g., a mobile phone, tablet, or computer) that is communicatively connected to the open acoustic device 100 can display the parameter information of the suggested noise reduction signal to the user, and the user can fine-tune the parameter information according to their own auditory experience.

[0073] It should be noted that the above description of process 400 is for illustrative purposes only and does not limit the scope of this specification. Those skilled in the art can make various modifications and changes to process 400 under the guidance of this specification. For example, steps in process 400 can be added, omitted, or combined. As another example, environmental noise can be processed (e.g., filtered). However, these modifications and changes are still within the scope of this specification.

[0074] Figure 6 This is an exemplary flowchart illustrating the determination of the primary path transfer function between the first microphone array 130 and the user's ear canal, according to some embodiments of this specification. In some embodiments, step 420 can be performed by... Figure 6 The process is implemented as shown. Figure 6 As shown, process 600 may include the following steps.

[0075] Step 610: Estimate the direction of the noise source based on the ambient noise.

[0076] In some embodiments, this step may be performed by the signal processor 140.

[0077] The first microphone array 130 can convert the environmental noise picked up from different directions and of different types into electrical signals and transmit them to the signal processor 140. The signal processor 140 can analyze the electrical signals corresponding to the environmental noise and predict the direction of the noise source through a noise localization algorithm.

[0078] In some embodiments, noise localization algorithms may include one or more of beamforming algorithms, super-resolution spatial spectrum estimation algorithms, and time difference of arrival algorithms (also known as time delay estimation algorithms). Beamforming algorithms are sound source localization methods based on controllable beamforming with maximum output power. As examples only, beamforming algorithms may include Steering Response Power-Phase Transform (SPR-PHAT) algorithms, delay-and-sum beamforming, differential microphone algorithms, Generalized Sidelobe Canceller (GSC) algorithms, and Minimum Variance Distortionless Response (MVDR) algorithms. Super-resolution spatial spectrum estimation algorithms may include autoregressive AR models, minimum variance spectrum estimation (MV), and eigenvalue decomposition methods (e.g., Multiple Signal Classification (MUSIC) algorithms). These methods can calculate the correlation matrix of the spatial spectrum by acquiring the environmental noise picked up by the microphone array and effectively estimate the direction of the environmental noise source. The Time Difference of Arrival (TDOA) algorithm can first estimate the time difference of arrival of sound and obtain the acoustic delay (TDOA) between microphones in the microphone array. Then, by using the obtained TDOA and combining it with the known spatial location of the microphone array, the direction of the environmental noise source can be further located.

[0079] For example, a time delay estimation algorithm can determine the location of a noise source by calculating the time difference between the arrival of an ambient noise signal at different microphones in a microphone array, and then using geometric relationships. Another example is the SPR-PHAT algorithm, which can approximate the direction of the noise source by performing beamforming in the direction of each noise source, with the direction of strongest beam energy being the noise source's direction. Yet another example is the MUSIC algorithm, which can separate the direction of the ambient noise by performing eigenvalue decomposition on the covariance matrix of the ambient noise signal picked up by the microphone array to obtain a subspace of the ambient noise signal. Furthermore, in some embodiments, the signal processor 140 can divide the picked-up ambient noise into multiple frequency bands according to a specific bandwidth (e.g., each 500Hz band), with each band corresponding to a different frequency range, and determine the ambient noise corresponding to at least one frequency band. For example, the signal processor 140 can perform signal analysis on the divided frequency bands of the ambient noise to obtain parameter information of the ambient noise corresponding to each frequency band. Finally, the signal processor 140 can determine the ambient noise corresponding to each frequency band using a noise localization algorithm.

[0080] To more clearly illustrate the principle of noise source localization, the following uses a beamforming algorithm as an example to explain how noise source localization is achieved. Taking a linear microphone array as an example, the noise source can be a far-field sound source, where the incident sound waves from the noise source onto the microphone array are considered parallel. In a parallel sound field, when the incident angle of the noise source's incident sound wave is perpendicular to the microphone plane in the microphone array (e.g., the first microphone array 130 or the second microphone array 160), the incident sound wave can simultaneously reach each microphone in the microphone array (e.g., the first microphone array 130 or the second microphone array 160). In some embodiments, when the incident angle of the noise source's incident sound wave in the parallel sound field is not perpendicular to the microphone plane in the microphone array (e.g., the first microphone array 130 or the second microphone array 160), there will be a delay in the incident sound wave reaching each microphone in the microphone array (e.g., the first microphone array 130 or the second microphone array 160), and this delay can be determined by the incident angle. In some embodiments, different incident angles result in different superimposed noise waveform intensities. For example, the noise signal strength is weak when the incident angle is 0°, and strongest when the incident angle is 45°. The superposition intensity of the noise waveforms differs with different incident angles, giving the microphone array polarity, thus allowing the generation of a polarity diagram for the microphone array. In some embodiments, the microphone array (e.g., the first microphone array 130 or the second microphone array 160) can be a directional array. The directivity of this directional array can be achieved using time-domain algorithms or frequency-domain phase delay algorithms, such as delay and superposition. In some embodiments, different directions of pointing can be achieved by controlling different delays. In some embodiments, the controllable pointing of the directional array is equivalent to a spatial filter. First, the noise localization area is divided into grids. Then, the time-domain delay of each microphone is applied to each grid point. Finally, the time-domain delays of each microphone are superimposed to calculate the sound pressure level of each grid, thereby obtaining the relative sound pressure level of each grid and ultimately achieving the localization of the noise source.

[0081] Step 620: Determine the primary path transfer function based on the ambient noise, the direction of the noise source, and the position information of the first microphone array 130 and the user's ear canal.

[0082] In some embodiments, this step may be performed by the signal processor 140.

[0083] In some embodiments, the positional information of the first microphone array 130 relative to the user's ear canal refers to the distance between any microphone in the first microphone array 130 and the user's ear canal. For example, the first microphone array 130 may include a first microphone and a second microphone, and the positional information of the first microphone array 130 relative to the user's ear canal may refer to the distance between the first microphone and the user's ear canal. The first microphone may be the microphone closest to the user's ear canal, or a microphone located at another position. In some embodiments, determining the primary path transfer function based on ambient noise, the direction of the noise source, and the positional information of the first microphone array 130 relative to the user's ear canal may include determining the primary path transfer function based on the frequency of the ambient noise, the direction of the noise source, and the distance between the first microphone array and the user's ear canal. For details on determining the primary path transfer function, please refer to [link to relevant documentation]. Figure 7 And its related descriptions. Figure 7 This is a schematic diagram illustrating the determination of the primary path transfer function from the first microphone array 130 to the ear canal opening, according to some embodiments of this specification. Figure 7 As shown, the first microphone array 130 may include microphones 710, 720, and 730, wherein microphones 710, 720, and 730 are located near the user's ear canal. The distance between the first microphone array 130 and the ear canal opening can be considered as the distance d between microphone 710 and the user's ear canal opening. The angle θ between the direction X of the ambient noise transmission and the line connecting microphone 710 and the ear canal is θ. The frequency ω and amplitude A of the ambient noise sound signal picked up by microphone 710 in the first microphone array 130 are then expressed as P(z) = Aexp(-i*2πdcosθ / ω). Here, the primary path transfer function can be calculated based on information such as the direction of the ambient noise source using microphone 710 in the first microphone array 130. It should be noted that the calculation of the primary path transfer function is not limited to microphone 710 and its picked-up noise signal in the first microphone array 130, but can also include microphone 720 or microphone 730 and their picked-up noise signals.

[0084] In some embodiments, the parameter information (e.g., phase information, amplitude information, etc.) of the noise-canceling wave output by the speaker based on the noise-canceling signal changes after it reaches the user's ear canal, causing the noise-canceling wave to not completely cancel out the noise at the user's ear canal opening. To improve the noise reduction effect of the open acoustic device, in some embodiments, the open acoustic device may further include a second microphone array. The second microphone array can pick up ambient noise and the noise-canceling wave, and the signal processor can estimate the noise at a first spatial location based on the ambient noise and the noise-canceling wave picked up by the second microphone array. The signal processor further updates the noise-canceling signal based on the sound signal at the first spatial location. The first spatial location can be equivalently considered as a location in or near the user's ear canal. In some embodiments, the first spatial location is closer to the user's ear canal than any microphone in the second microphone array.

[0085] Figure 8 This is an exemplary flowchart illustrating the operation of a second microphone array 160 according to some embodiments of this specification. Figure 8 As shown, process 800 may include the following steps:

[0086] Step 810: Estimate the noise at the first spatial location based on the ambient noise and the noise-reduced wave picked up by the second microphone array 160.

[0087] In some embodiments, this step may be performed by the signal processor 140.

[0088] In some embodiments, the first spatial position refers to a spatial position at a specific distance from the user's ear canal, which is closer to the user's ear canal than any microphone in the second microphone array 160. This specific distance can be a fixed distance, such as 0.5cm, 1cm, 2cm, 3cm, etc. In some embodiments, the first spatial position is related to the distribution position and number of microphones in the second microphone array 160 relative to the user's ear. The first spatial position can be adjusted by adjusting the distribution position and / or number of microphones in the second microphone array 160 relative to the user's ear. For example, increasing the number of microphones in the second microphone array 160 can make the first spatial position closer to the user's ear canal.

[0089] The signal processor 140 can estimate the noise at a first spatial location based on the ambient noise and the reduced noise wave picked up by the second microphone array 160. The ambient noise picked up by the second microphone array 160 can be from different spatial noise sources of different directions and types, and therefore the parameter information (e.g., phase information, amplitude information) corresponding to each spatial noise source is different. In some embodiments, the signal processor 140 can perform signal separation and extraction of the noise at the first spatial location according to the statistical distribution and structural characteristics of different types of noise in different dimensions (e.g., spatial domain, time domain, frequency domain, etc.), thereby estimating different types of noise (e.g., different frequencies, different phases, etc.) and estimating the parameter information (e.g., amplitude information, phase information, etc.) corresponding to each type of noise. In some embodiments, the signal processor 140 can also determine the overall parameter information of the noise at the first spatial location based on the parameter information corresponding to different types of noise at the first spatial location. In some embodiments, estimating the noise at the first spatial location based on the picked-up ambient noise can also include identifying one or more spatial noise sources related to the picked-up ambient noise and estimating the noise at the first spatial location based on the spatial noise sources. For example, the captured environmental noise is divided into multiple sub-bands, each corresponding to a different frequency range. Within at least one sub-band, the corresponding spatial noise source is identified. It is important to note that the spatial noise source estimated through these sub-bands is a virtual noise source corresponding to a real external noise source.

[0090] The open-back acoustic device 100 does not obstruct the user's ear canal and cannot acquire ambient noise by placing a microphone in the ear canal. Therefore, the open-back acoustic device 100 can reconstruct the sound source in the ear canal using the second microphone array 160 to form a virtual sensor at a first spatial location. This virtual sensor can represent or simulate the audio data collected by a microphone if placed at the first spatial location. The audio data obtained through the virtual sensor can be approximated or equivalent to the audio data collected by a physical sensor if placed at the first spatial location. The first spatial location is the spatial region constructed by the second microphone array 160 to simulate the user's ear canal location. To more accurately estimate the ambient noise transmitted in the user's ear canal, in some embodiments, the first spatial location is closer to the user's ear canal than any microphone in the second microphone array 160. In some embodiments, the first spatial location is related to the distribution position and number of microphones in the second microphone array 160 relative to the user's ear. The first spatial location can be adjusted by adjusting the distribution position or number of microphones in the second microphone array 160 relative to the user's ear. For example, increasing the number of microphones in the second microphone array 160 can make the first spatial location closer to the user's ear canal. For example, the first spatial position can be made closer to the user's ear canal by reducing the spacing between the microphones in the second microphone array 160. Alternatively, the first spatial position can be made closer to the user's ear canal by changing the arrangement of the microphones in the second microphone array 160.

[0091] The signal processor 140 can estimate the noise parameters of the first spatial location based on the environmental noise and noise-reduced wave parameter information (e.g., frequency information, amplitude information, phase information, etc.) picked up by the second microphone array 160, thereby estimating the noise at the first spatial location. For example, in some embodiments, there is a spatial noise source in front of and behind the user's body. The signal processor 140 can estimate the frequency, phase, or amplitude information of the front spatial noise source when it reaches the first spatial location based on the frequency, phase, or amplitude information of the rear spatial noise source. The signal processor 140 can estimate the frequency, phase, or amplitude information of the rear spatial noise source when it reaches the first spatial location based on the frequency, phase, or amplitude information of the rear spatial noise source. The signal processor 140 estimates the noise information at the first spatial location based on the frequency, phase, or amplitude information of the front and rear spatial noise sources, thereby estimating the noise at the first spatial location. In some embodiments, parameter information of the sound signal can be extracted from the frequency response curve of the sound signal picked up by the second microphone array 160 using feature extraction methods. In some embodiments, the methods for extracting parameter information of the sound signal may include, but are not limited to, Principal Components Analysis (PCA), Independent Component Analysis (ICA), Linear Discriminant Analysis (LDA), and Singular Value Decomposition (SVD).

[0092] In some embodiments, one or more spatial noise sources related to the picked-up environmental noise can be determined using noise localization methods (e.g., beamforming algorithms, super-resolution spatial spectrum estimation algorithms, time difference of arrival algorithms, etc.). For details on noise source localization using noise localization algorithms, please refer to [link to relevant documentation]. Figure 6 The relevant descriptions in the document will not be repeated here.

[0093] Step 820: Update the noise reduction signal based on the sound signal at the first spatial location.

[0094] In some embodiments, this step may be performed by the signal processor 140.

[0095] In some embodiments, the signal processor 140 can adjust the parameter information (e.g., frequency information, amplitude information, and / or phase information) of the noise (sound field) at the first spatial location obtained in step 810, so that the amplitude and frequency information of the updated noise-reduced signal are more consistent with the amplitude and frequency information of the ambient noise at the user's ear canal, and the phase information of the updated noise-reduced signal is more consistent with the anti-phase information of the ambient noise at the user's ear canal, thereby enabling the updated noise-reduced signal to eliminate ambient noise more accurately. The second microphone array 160 needs to monitor the sound field at the user's ear canal after the noise-reduced signal cancels out the ambient noise. The signal processor 140 can estimate the sound signal at the first spatial location (e.g., at the ear canal) based on the noise-reduced wave and ambient noise picked up by the second microphone array 160, thereby determining whether the noise-reduced wave and ambient noise at the ear canal are completely canceled out. The signal processor 140 estimates the sound field at the ear canal using the sound signal picked up by the second microphone array 160 to update the noise-reduced signal, which can further improve the noise reduction effect and the user's auditory experience.

[0096] In an open-type acoustic device, the loudspeaker is located near the user's ear canal. The transmission path of the noise-reduced wave output by the loudspeaker based on the noise-reducing signal is from the loudspeaker to the user's ear canal (i.e., the overall secondary path). Specifically, the transmission path from the loudspeaker to the user's ear canal can be divided into a first-level transmission path from the loudspeaker to the second microphone array and a second-level transmission path from the second microphone array to the user's ear canal. After the noise-reduced wave generated by the loudspeaker based on the noise-reducing signal (generated based on the noise signal at the ear canal) reaches the user's ear canal opening, the parameter information (e.g., phase information, amplitude information, etc.) of the noise-reduced wave changes, causing the noise-reduced wave to not completely cancel out the noise at the user's ear canal opening. To improve the noise reduction effect of the open-type acoustic device, in some embodiments, the signal processor can determine the overall secondary path transfer function between the loudspeaker and the user's ear canal based on the sound signal picked up by the second microphone array, and generate a noise-reducing signal based on the overall secondary path transfer function and the noise at the user's ear canal, so that the noise-reduced wave generated by the loudspeaker can completely cancel out the noise at the user's ear canal opening when it reaches the ear canal opening. For details on generating noise reduction signals based on noise signals from the user's ear canal, please refer to [link / reference]. Figures 9 to 12 And related content.

[0097] Figure 9 This is another exemplary flowchart illustrating the operation of a second microphone array 160 as shown in some embodiments of this specification. Figure 9 As shown, process 900 may include the following steps.

[0098] Step 910: Determine the overall secondary path transfer function between the speaker 150 and the user's ear canal based on the sound signal picked up by the second microphone array 160.

[0099] In some embodiments, this step may be performed by the signal processor 140. In some embodiments, the propagation path of the sound signal from the speaker 150 to the ear canal is referred to as the overall secondary path. The overall secondary path transfer function S(z) refers to the phase frequency response of the sound signal (e.g., the noise-reduced wave emitted by the speaker 150) from the speaker 150 to the user's ear canal, reflecting the influence of the overall secondary path on the sound signal. The signal processor 140 can estimate the noise-reduced signal based on the overall secondary path transfer function S(z) and the sound signal at the user's ear canal. For details on the overall secondary path transfer function S(z), please refer to [link to relevant documentation]. Figure 11 The process 1100 and its related descriptions will not be repeated here.

[0100] In some noise reduction scenarios, if the influence of the overall secondary path on the sound signal is not considered, the noise reduction effect of the noise-reducing wave emitted by the speaker 150 will be poor, resulting in the noise-reducing wave signal output by the speaker 150 at the ear canal failing to completely cancel out the ambient noise signal at the ear canal. To improve this problem, the overall secondary path transfer function S(z) is calculated to compensate for the noise-reducing wave emitted by the speaker 150, thereby enhancing the noise reduction effect of the noise-reducing wave emitted by the speaker 150 at the user's ear canal.

[0101] Step 920: Estimate the noise-reduced signal based on the noise signal at the user's ear canal and the overall secondary path transfer function S(z).

[0102] In some embodiments, this step may be performed by the signal processor 140.

[0103] In some embodiments, the signal processor 140 can compensate the noise-reduced signal based on the overall secondary path S(z) calculated in step 910, so that the noise-reduced wave finally emitted by the speaker can cancel the ambient noise in the ear canal after being adjusted by the overall secondary path transfer function. For example, the signal processor 140 can adjust the parameter information (e.g., frequency information, amplitude information, phase information) of the noise-reduced signal according to the ambient noise signal in the ear canal (e.g., sound pressure, sound frequency, sound amplitude, sound phase, sound source vibration velocity, or medium (e.g., air) density).

[0104] In some embodiments, step 920 may be included in step 440.

[0105] Figure 10 An exemplary flowchart for estimating the noise-reduced signal is shown in some embodiments of this specification, namely... Figure 10The following is an exemplary flowchart of step 920. Figure 10 As shown, process 1000 (step 920) may include the following steps.

[0106] Step 1010: Estimate the noise-reduced wave in the user's ear canal based on the noise signal in the user's ear canal.

[0107] In some embodiments, this step may be performed by the signal processor 140.

[0108] In some embodiments, the noise reduction signal at the user's ear canal can be estimated by performing the process similar to step 440, thereby estimating the noise reduction wave at the user's ear canal.

[0109] Step 1020: Generate a noise-reduced signal based on the noise-reduced wave at the user's ear canal and the overall secondary path transfer function S(z).

[0110] In some embodiments, this step may be performed by the signal processor 140.

[0111] In some embodiments, the signal processor 140 may adjust the parameter information (e.g., frequency information, amplitude information, phase information) of the noise reduction signal based on the estimated noise reduction wave at the user's ear canal (e.g., sound pressure, sound frequency, sound amplitude, sound phase, sound source vibration velocity, or medium (e.g., air) density).

[0112] It should be noted that the above description of process 1000 is for illustrative purposes only and does not limit the scope of this specification. Those skilled in the art can make various modifications and changes to process 1000 under the guidance of this specification. However, these modifications and changes remain within the scope of this specification.

[0113] Figure 11 The exemplary flowchart for determining the global secondary path transfer function S(z) is shown in some embodiments of this specification, namely... Figure 11 The following is an exemplary flowchart of step 910. Figure 11 As shown, process 1100 (step 910) may include the following steps.

[0114] Step 1110: Determine the first-order path transfer function between the speaker 150 and the second microphone array 160 based on the noise-reduced wave output by the speaker 150 and the sound signal picked up by the second microphone array 160.

[0115] In some embodiments, this step can be performed by the signal processor 140. Specifically, the propagation path of the sound signal (e.g., the noise-reduced wave output by the speaker 150) from the speaker 150 to the second microphone array 160 is called the first-order path. The first-order path transfer function S(z1) refers to the phase frequency response of the sound signal (e.g., the noise-reduced wave emitted by the speaker 150) from the speaker 150 to the second microphone array 160, which reflects the influence of the first-order path on the sound signal. Since faces reflect sound waves, different wearing methods will affect the first-order path transfer function. In some embodiments, the speaker 150 and the second microphone array 160 can respectively convert the output noise-reduced sound signal and the picked-up sound signal into electrical signals and transmit them to the signal processor 140. The signal processor 140 can process the two electrical signals to calculate the first-order path transfer function S(z1). For example, the first-order path transfer function S(z1) can be expressed as the ratio of the sound signal picked up by the second microphone array 160 to the noise-reduced sound signal output by the speaker 150.

[0116] Step 1120: Determine the overall secondary path transfer function based on the first-level path transfer function.

[0117] In some embodiments, this step may be performed by the signal processor 140. In some embodiments, the signal processor 140 is configured to calculate and determine the overall secondary path transfer function S(z) based on the first-level path transfer function S(z1). In some embodiments, determining the overall secondary path transfer function based on the first-level path transfer function may include determining the second-level path transfer function between the second microphone array and the user's ear canal based on the first-level path transfer function, and determining the overall secondary path transfer function based on the first-level path transfer function and the second-level path transfer function. The propagation path of the sound signal from the second microphone array 160 to the user's ear canal is called the second-level path. The second-level path transfer function S(z2) refers to the phase frequency response of the sound signal (e.g., the noise-reduced wave emitted by the speaker 150) from the second microphone array 160 to the user's ear canal, reflecting the influence of the second-level path on the sound signal. The first-level path transfer function S(z1) and the second-level path transfer function S(z2) have a certain relationship (e.g., the second-level path transfer function S(z2) = f(S(z1))), and the second-level path transfer function S(z2) can be determined from the first-level path transfer function S(z1). In some embodiments, the second-level path transfer function can be determined based on the first-level path transfer function using a trained machine learning model or a pre-defined model. Specifically, by inputting the first-level path transfer function S(z1) into a trained machine learning model or a pre-defined model, the second-level path transfer function S(z2) can be output. In some embodiments, the machine learning model can be, but is not limited to, any one of Gaussian mixture models, deep neural network models, etc.

[0118] In some embodiments, the pre-set model can be obtained through manual testing and statistics. In this case, the second-order path transfer function S(z2) can be determined without using the first-order path transfer function S(z1). In some embodiments, in order to achieve the purpose of open-ear acoustic devices without blocking the user's ear canals, the second microphone array 160 cannot be placed in the user's ear canal. Therefore, the second-order path transfer function S(z2) in the open-ear acoustic device 100 is not fixed. In this case, during the product debugging stage, one or more signal generating devices can be set at the location of the second microphone array 160, and one or more sensors can be set at the ear canal. Then, the sound signal emitted by the signal generating device can be received by the one or more sensors set at the ear canal. Finally, the sound signal output by the signal generating device and the sound signal picked up by the one or more sensors set at the ear canal can be converted into electrical signals and transmitted to the signal processor 140. The signal processor 140 can analyze the two electrical signals and calculate the second-order path transfer function S(z2). Furthermore, the signal processor 140 can calculate the relationship between the second-stage path transfer function S(z2) and the first-stage path transfer function S(z1): S(z2) = f(S(z1)).

[0119] In some embodiments, the overall secondary path transfer function S(z) can be calculated based on the first-level path transfer function S(z1) and the second-level path transfer function S(z2). For example, considering that the overall secondary path transfer function, the first-level path transfer function S(z1), and the second-level path transfer function S(z2) are all affected by the surrounding environment of the open acoustic device 100 (e.g., the face of the person wearing the open acoustic device 100), the overall secondary path transfer function satisfies a certain functional relationship with the first-level path transfer function S(z1) and the second-level path transfer function S(z2) (e.g., S(z) = f(S(z1), S(z2)). The signal processor 140 can obtain the overall secondary path transfer function in actual use by calling this functional relationship.

[0120] It should be noted that the above description of process 1100 is for illustrative purposes only and does not limit the scope of this specification. Those skilled in the art can make various modifications and changes to process 1100 under the guidance of this specification. However, these modifications and changes remain within the scope of this specification.

[0121] Figure 12 An exemplary flowchart illustrating the determination of the first-stage path transfer function based on the noise-reduced wave output by speaker 150 and the sound signal picked up by the second microphone array 160, as shown in some embodiments of this specification, is as follows: Figure 12 The following is an exemplary flowchart of step 1110. Figure 12 As shown, process 1200 (step 1110) may include the following steps.

[0122] Step 1210: Obtain the noise-reduced wave picked up by the second microphone array 160 based on the sound signal picked up by the second microphone array 160.

[0123] In some embodiments, this step may be performed by the signal processor 140. In some embodiments, the signal processor 140 may determine the noise-reduced wave picked up by the second microphone array 160 based on the sound signal picked up by the second microphone array 160. The execution method of step 1210 is similar to that of step 1010, and will not be described again here.

[0124] Step 1220: Determine the first-order path transfer function S(z1) based on the noise-reduced wave output by the speaker 150 and the noise-reduced wave picked up by the second microphone array 160.

[0125] In some embodiments, this step can be performed by the signal processor 140. The signal processor 140 can calculate the first-order path transfer function S(z1) from the speaker 150 to the second microphone array 160 based on the noise-reduced wave emitted by the speaker 150 and the noise-reduced wave picked up by the second microphone array 160. Specifically, for example, the speaker 150 can play a standard sound, and the second microphone array 160 picks up the standard sound signal emitted by the speaker 150. The signal processor 140 can calculate the first-order path transfer function S(z1) from the speaker 150 to the second microphone array 160 by comparing the relevant parameters (e.g., frequency information, amplitude information, phase information) of the sound signal emitted by the speaker 150 with the relevant parameters (e.g., frequency information, amplitude information, phase information) of the sound signal received by the second microphone array 160. In some embodiments, the speaker 150 can play a prompt tone or a sound signal that is not likely to attract the user's attention, such as infrasound, in order to obtain the first-order path transfer function S(z1).

[0126] It should be noted that the above description of process 1200 is for illustrative purposes only and does not limit the scope of this specification. Those skilled in the art can make various modifications and changes to process 1200 under the guidance of this specification. However, these modifications and changes remain within the scope of this specification.

[0127] Figures 13A-13D This is a schematic diagram illustrating an exemplary arrangement of a microphone array (e.g., a first microphone array 130) according to some embodiments of this specification. In some embodiments, the microphone array arrangement may be a regular geometric shape. Figure 13AAs shown, the microphone array can be a linear array. In some embodiments, the microphone array can also be arranged in other shapes. For example, as... Figure 13B As shown, the microphone array can be a cross-shaped array. For example, such as... Figure 13C As shown, the microphone array can be a circular array. In some embodiments, the microphone array can also be arranged in an irregular geometric shape. For example, as... Figure 13D As shown, the microphone array can be an irregular array. It should be noted that the arrangement of the microphone array is not limited to... Figures 13A-13D The linear array, cross array, circular array, and irregular array shown can also be arrays of other shapes, such as triangular arrays, spiral arrays, planar arrays, three-dimensional arrays, radial arrays, etc. This specification does not limit them.

[0128] In some embodiments, Figures 13A-13D Each short solid line in the diagram can be considered a microphone or a group of microphones. When each short solid line is considered a group of microphones, the number of microphones in each group can be the same or different, the type of microphones in each group can be the same or different, and the orientation of each group of microphones can be the same or different. The type, number, and orientation of the microphones can be adapted to the actual application, and this manual does not limit this.

[0129] In some embodiments, the microphones in the microphone array may be uniformly distributed. Uniform distribution here means that the spacing between any two adjacent microphones in the microphone array is the same. In some embodiments, the microphones in the microphone array may also be non-uniformly distributed. Non-uniform distribution here means that the spacing between any two adjacent microphones in the microphone array is different. The spacing between the microphones in the microphone array can be adjusted adaptively according to actual conditions, and this specification does not limit this.

[0130] Figure 14A and Figure 14B This is a schematic diagram illustrating an exemplary arrangement of a microphone array (e.g., a first microphone array 130) according to some embodiments of this application. Figure 14A As shown, when a user wears an acoustic device with a microphone array, the microphone array is arranged in a semi-circular pattern at or around the user's ear, such as... Figure 14B As shown, the microphone array is arranged in a linear pattern at the ear level. It should be noted that the arrangement of the microphone array is not limited to this. Figure 14A and Figure 14B The semi-circular and linear microphone arrays shown are not limited to specific placement positions. Figure 14A and Figure 14B The locations shown, including the semicircles, lines, and microphone array placement, are for illustrative purposes only.

[0131] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

Claims

1. An open acoustic device, comprising: A fixing structure is configured to fix the acoustic device in a position near the user's ear without obstructing the user's ear canal; The first microphone array is configured to pick up ambient noise; The signal processor is configured as follows: The primary path transfer function between the first microphone array and the user's ear canal is determined based on the ambient noise. Based on the environmental noise and the primary path transfer function, estimate the noise signal at the user's ear canal; as well as A noise reduction signal is generated based on the noise signal at the user's ear canal; as well as A speaker is configured to output a noise-canceling wave according to the noise-canceling signal, the noise-canceling wave being used to eliminate the noise signal at the user's ear canal; The second microphone array is configured to pick up ambient noise and the noise-reduced wave; The signal processor is further configured to: estimate noise at a first spatial location based on ambient noise picked up by the second microphone array and the noise-reduced wave, the first spatial location being closer to the user's ear canal than any microphone in the second microphone array; and update the noise-reduced signal based on the sound signal at the first spatial location; and / or, the signal processor is further configured to: determine the overall secondary transfer function between the speaker and the user's ear canal based on the sound signal picked up by the second microphone array, and generate the noise-reduced signal based on the noise signal at the user's ear canal by: estimating the noise-reduced signal based on the noise signal at the user's ear canal and the overall secondary transfer function.

2. The open acoustic device according to claim 1, wherein, The noise reduction depth of the open acoustic device is 5 dB to 25 dB in the frequency range of 150 Hz to 2000 Hz.

3. The open acoustic device according to claim 1, wherein, Determining the primary path transfer function between the first microphone array and the user's ear canal based on the ambient noise includes: The direction of the noise source is estimated based on the environmental noise. The primary path transfer function is determined based on the ambient noise, the direction of the noise source, and the position information of the first microphone array and the user's ear canal.

4. The open acoustic device according to claim 3, wherein, The positional information of the first microphone array and the user's ear canal includes the distance between the first microphone array and the user's ear canal. Determining the primary path transfer function based on the ambient noise, the direction of the noise source, and the positional information of the first microphone array and the user's ear canal includes: The primary path transfer function is determined based on the frequency of the ambient noise, the direction of the noise source, and the distance between the first microphone array and the user's ear canal.

5. The open acoustic device according to claim 1, wherein, The step of estimating the noise-reduced signal based on the noise signal at the user's ear canal and the overall secondary transfer function includes: The noise-reduced wave at the user's ear canal is estimated based on the noise signal at the user's ear canal; The noise-reduced signal is generated based on the noise-reduced wave at the user's ear canal and the overall secondary transfer function.

6. The open acoustic device according to claim 1, wherein, The determination of the overall secondary path transfer function based on the sound signal picked up by the second microphone array includes: The first-order path transfer function between the speaker and the second microphone array is determined based on the noise-reduced wave output by the speaker and the sound signal picked up by the second microphone array. The overall secondary path transfer function is determined based on the first-level path transfer function.

7. The open acoustic device according to claim 6, wherein, The determination of the first-level path transfer function based on the noise-reduced wave output by the speaker and the sound signal picked up by the second microphone array includes: The noise-reduced wave picked up by the second microphone array is obtained based on the sound signal picked up by the second microphone array; The first-order path transfer function is determined based on the noise-reduced wave output by the speaker and the noise-reduced wave picked up by the second microphone array.

8. The open acoustic device according to claim 6, wherein, The determination of the overall secondary path transfer function based on the first-level path transfer function includes: The second-level path transfer function between the second microphone array and the user's ear canal is determined based on the first-level path transfer function. The overall secondary path transfer function is determined based on the first-level path transfer function and the second-level path transfer function.

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