Active noise cancellation system and method

Abstract

An active noise cancellation system and method includes: a feedforward path configured to receive a reference signal including external noise and adaptively generate an anti-noise signal to cancel the external noise, and including an adaptive gain component configured to adaptively adjust the gain of the anti-noise signal; and a logic device configured to determine a leakage profile based on the adaptive gain component. The feedforward path includes a feedforward adaptive filter tuned to generate an anti-noise signal corresponding to the reference signal according to the determined leakage profile. The leakage profile is selected from a plurality of stored leakage profiles tuned for corresponding gains, and corresponds to an ear coupling condition associated with the cooperation between the active noise cancellation system and the user. An adaptive transparency filter receives the reference signal and generates an externally included signal for output to the user.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to U.S. non-provisional patent application No. 17 / 098,270, filed November 13, 2020, entitled "ACTIVE NOISE CANCELLATION SYSTEMS AND METHODS," and U.S. provisional patent application No. 63 / 001,205, filed March 27, 2020, entitled "ACTIVE NOISE CANCELLATION SYSTEMS AND METHODS," which are hereby incorporated by reference in their entirety. Technical Field

[0003] This application relates generally to noise cancellation systems and methods, and more specifically, for example, to active noise cancellation (ANC) systems and methods used in headphones (e.g., circum-aural, supra-aural, and in-ear types), earbuds, hearing aids, and other personal hearing devices. Background Technology

[0004] Active noise cancellation systems typically operate by sensing noise via a reference microphone and generating a corresponding anti-noise signal that is approximately equal in amplitude but opposite in phase to the sensed noise. The noise and anti-noise signal audibly cancel each other out, allowing the user to hear only the desired audio signal. To achieve this effect, a low-latency filter path can be implemented from the reference microphone to the speaker that outputs the anti-noise signal. In operation, conventional anti-noise filtering systems do not completely eliminate all noise, leaving residual noise and / or generating audible artifacts that may distract the user. In some implementations, the user may wish to selectively listen to certain external noises that can affect ANC adaptation and other processing. The performance of these active noise cancellation systems can be further degraded due to leakage, which can vary from person to person and from device to device due to the various ways in which the listening device is coupled to the user's configuration.

[0005] In view of the foregoing, there is a continued need for improved active noise cancellation systems and methods for headphones, earphones and other personal listening devices. Summary of the Invention

[0006] Systems and methods for improved active noise cancellation in personal listening devices are disclosed. In various embodiments, for example, the active noise cancellation systems and methods provide improved leakage control and / or improved transparency processing.

[0007] In one or more embodiments, an active noise cancellation system includes: a reference sensor configured to sense ambient noise and generate a corresponding reference signal; an error sensor configured to sense noise in a noise cancellation region and generate a corresponding error signal; and a noise cancellation path including a noise cancellation filter and an adaptive gain filter. The noise cancellation path (such as a feedforward ANC path) is configured to receive the reference signal and generate a corresponding anti-noise signal to cancel ambient noise at a tympanic membrane reference point. An adaptation engine is configured to receive the reference signal and the error signal and control various components of the active noise cancellation system, including adaptively adjusting the weights of the noise cancellation filter and / or the adaptive gain filter.

[0008] In some embodiments, the adaptation engine includes adaptive gain control logic configured to update an adaptive gain filter. A programmable filter can be used to adjust the inputs to the adaptive gain control logic, operable to protect against low-frequency transients and / or high-frequency distractors in ambient noise. The programmable filter may include: a low-pass filter that filters out high frequencies determined to create constructive interference between the noise cancellation region and the tympanic membrane reference point; and / or a high-pass filter that filters out low frequencies determined to be inaudible to the user of the noise cancellation system. An error signal sensed in the noise cancellation region can be used to tune the adaptation engine to cancel noise at the tympanic membrane reference point.

[0009] In various embodiments, the adaptation engine includes leakage control logic configured to track the adaptive gain value of the adaptive gain filter and select optimal leakage control settings based on the adaptive gain value. In some embodiments, the adaptation engine is configured with multiple leakage profiles adapted to corresponding leakage conditions related to the positioning and / or fit of a personal listening device relative to a user's construction. For example, a leakage profile may include modeling a tight seal between the personal listening device and the user's ear structure, and modeling one or more leakage scenarios associated with inappropriate headset positioning and / or leakage fit conditions. In various embodiments, the adaptation engine is configured to track the adaptive gain value and switch between leakage profiles based on changes in the adaptive gain value of the adaptive gain filter.

[0010] In various embodiments, the ANC system further includes a second processing path configured to generate a transparency output representing ambient noise detected by a reference microphone for the user. The second processing path is configured to process the transparency output in parallel with the feedforward processing path of the ANC system. In some embodiments, the transparency output path includes an adaptive transparency processing filter configured to generate the transparency output based on one or more conditions, including but not limited to settings associated with an active leakage profile. An adaptation engine or other control module is configured to detect user input selection of a listening mode associated with a transparency mode and / or an ANC mode, and selectively enable or disable the transparency output.

[0011] In one or more embodiments, a method includes: receiving a reference signal from a first sensor, the reference signal representing external noise; processing the reference signal through a noise cancellation path including an adaptive noise cancellation filter and a van adaptive gain filter to generate an anti-noise signal; receiving an error signal from a second sensor, the error signal representing noise in a noise cancellation region; and adaptively adjusting an adaptive noise cancellation filter in response to the reference signal, the error signal, and an adaptive gain control process to eliminate external noise at a tympanic membrane reference point.

[0012] The method may also include using programmable filters to adjust the input to the adaptive gain control process for protection against low-frequency transients and / or high-frequency interference in external noise. Adjustment may also include low-pass filtering of high frequencies defined as falling within: (i) the range that creates constructive interference between the noise cancellation region and the tympanic membrane reference point, and (ii) the range of differences in noise cancellation performance between the noise cancellation region and the tympanic membrane reference point; and / or high-pass filtering defined as low frequencies falling within a range inaudible to the user. The method may also include using an error signal sensed in the noise cancellation region to tune the noise cancellation path to eliminate noise at the tympanic membrane reference point.

[0013] In various embodiments, the method further includes a leakage control process that includes tracking an adaptive gain value of an adaptive gain filter and selecting leakage control settings based on the adaptive gain value. In some embodiments, the leakage control process further includes configuring a plurality of leakage profiles adapted to corresponding leakage conditions related to the positioning and / or engagement of the listening device relative to a user's configuration. The configuration of the plurality of leakage profiles may include modeling various headset positioning and / or engagement conditions and defining associated leakage profiles. The method may also include tracking adaptive gain values ​​and switching between leakage profiles based on changes in the adaptive gain value of the adaptive gain filter.

[0014] In various embodiments, the method further includes processing a transparency processing path representing external noise detected by a reference microphone for a user, in parallel with the feedforward processing path of the ANC system. In some embodiments, the method includes updating filter values ​​of a transparency processing filter and generating a transparency output based on one or more conditions, including but not limited to settings associated with an active leakage profile. The method also includes detecting and / or receiving a user input selection of a listening mode associated with a transparency mode and / or an ANC mode, and selectively enabling and / or disabling the transparency output.

[0015] The scope of this invention is defined by the claims, which are incorporated herein by reference. A more complete understanding of embodiments of this disclosure and the implementation of its additional advantages will be provided to those skilled in the art by considering the following detailed description of one or more embodiments. Reference will be made to the accompanying drawings, which will first be briefly described. Attached Figure Description

[0016] A better understanding of the aspects and advantages of this disclosure can be achieved by referring to the following accompanying drawings and the detailed description that follows. It should be understood that the same reference numerals are used to identify the same elements illustrated in one or more of the drawings, wherein the illustrations in the drawings are for the purpose of illustrating embodiments of the disclosure and not for the purpose of limiting embodiments of the disclosure. The components in the drawings are not necessarily to scale, but rather the emphasis is on clearly illustrating the principles of the disclosure.

[0017] Figure 1 An active noise cancellation device according to one or more embodiments of the present disclosure is illustrated.

[0018] Figure 2 An active noise cancellation system according to one or more embodiments of the present disclosure is illustrated, including an adaptive gain filter, profile switching, and parallel transparency processing.

[0019] Figure 3A , 3B The 3C and 3D illustrations depict the ear coupling of a personal listening device according to one or more embodiments of the present disclosure.

[0020] Figure 4A and 4B The illustration shows an example of adaptive gain control tuning and usage implementation according to one or more embodiments.

[0021] Figure 5A This is a flowchart illustrating an example process for creating a leak profile according to one or more embodiments.

[0022] Figure 5B This is a flowchart illustrating an example process for profile switching for gain adjustment according to one or more embodiments.

[0023] Figure 6 This is a state diagram illustrating an example profile switching process according to one or more embodiments.

[0024] Figure 7 An example implementation of a hybrid ANC system according to one or more embodiments is illustrated. Detailed Implementation

[0025] According to various embodiments, improved active noise cancellation (ANC) systems and methods are disclosed. An ANC system for headphones, earbuds, or other personal listening devices may include: a noise sensing reference microphone for sensing ambient noise outside the personal listening device; an error microphone for sensing the acoustic mixture of noise generated by the ANC system and anti-noise; and a low latency signal processing subsystem that generates anti-noise to cancel the sensed ambient noise. The signal processing subsystem may be configured to adapt the anti-noise signal in real time to ambient noise, coupling of the personal listening device relative to the user, user-selectable modes, and other factors to achieve consistent noise cancellation performance. In various embodiments, the systems and methods disclosed herein improve ambient noise cancellation under various ear coupling and leakage scenarios; improve the handling of ambient noise in a transparent mode that allows some or all of the ambient noise to pass through to the user; and reduce associated adaptation pseudomorphs perceptible to the user.

[0026] It is recognized that high leakage can lead to a decline in ANC performance. For example, feedback ANC path tracking and adaptation to error microphone signals can generally provide a good measurement of ANC performance at the user's eardrum. However, in the presence of high leakage, the speaker may physically be unable to push enough air to achieve the desired performance at the eardrum. This disclosure addresses these and other leakage problems by allowing a fixed ANC profile to be tuned for different leakage scenarios. Leakage is tracked by tracking the gain value of an adaptive gain control block, which is then used to select an appropriate leakage profile.

[0027] The improved adaptive systems and methods disclosed herein include an adaptive gain filter in the feedforward path to generate a robust noise-resistant signal. An adaptive engine is configured to receive a reference signal and an error signal and control various components of the active noise cancellation system, including adaptively adjusting the weights of the feedforward adaptive noise cancellation filter and / or the adaptive gain filter. In various embodiments, leakage control logic is configured to track parameters related to the adaptive gain filter and provide improved leakage control.

[0028] In various embodiments, the adaptation engine includes leakage control logic configured to track adaptive gain parameters of the adaptive gain filter and select optimal leakage control settings based on the adaptive gain values. In some embodiments, the adaptation engine is configured with multiple pre-configured user leakage profiles adapted to multiple corresponding leakage conditions related to the positioning and / or fit of the listening device relative to the user's configuration. The user leakage profiles may include modeling of a tight seal between the personal listening device and the user's ear, and modeling of one or more leakage paths associated with leakage device location and / or fit conditions. In various embodiments, the adaptation engine is configured to track one or more adaptive gain parameters and automatically switch between user leakage profiles based on changes detected in the adaptive gain parameters for optimal filtering.

[0029] In various embodiments, the ANC system further includes a second feedforward processing path configured to generate a transparency output. The transparency mode can be user-selectable to allow certain external noise to pass through the system for playback by a personal listening device and can be used with and / or without ANC processing. This transparency processing path is configured to process the transparency output in parallel with the feedforward processing path of the ANC system. In some embodiments, the transparency processing path includes an adaptive transparency filter configured to generate the transparency output based on one or more conditions, including but not limited to settings associated with an active leakage profile. An adaptation engine and / or other control logic is configured to detect user input selection of a listening mode associated with the transparency mode and / or ANC mode and selectively enable or disable the transparency output.

[0030] Example embodiments of the active noise cancellation system of this disclosure will now be described with reference to the accompanying drawings. (Refer to...) Figure 1 The active noise cancellation system 100 includes a personal listening device 110 and an audio processing component, which may include a low latency engine (LLE) 120, a digital-to-analog converter (DAC) 130, an amplifier 132, a reference audio sensor 140, a speaker 150, an error sensor 162 and / or other components.

[0031] In operation, the listener can hear external noise d(n), which can be heard through the housing and components of the personal listening device 110. To cancel the noise d(n), a reference audio sensor 140 senses the external noise, thereby generating a reference signal x(n) fed to the LLE 120 via an analog-to-digital converter (ADC) 142. The LLE 120 may include hardware and / or software configured to generate an anti-noise signal y(n), which is fed to a speaker 150 via a DAC 130 and an amplifier 132 to generate anti-noise in a noise cancellation zone 160. When the anti-noise is equal in amplitude and opposite in phase to the noise d(n) in the noise cancellation zone 160, the noise d(n) will be canceled in the noise cancellation zone 160. The resulting mixture of noise and anti-noise is captured by an error sensor 162, which generates an error signal e(n) to measure the effectiveness of noise cancellation. The error signal e(n) is fed to the LLE 120 via the ADC 164, which is adapted to the noise immunity signal y(n) to minimize the error signal e(n) within the cancellation region 162 (e.g., drive the error signal e(n) to zero). In some embodiments, the speaker 150 may also generate desired audio (e.g., music), which is received by the error sensor 162 and removed from the error signal e(n) during processing.

[0032] In various embodiments, the personal listening device 110 may include headphones (e.g., over-ear, on-ear, and in-ear types), earphones, hearing aids, and other personal listening devices. The personal listening device 110 may be a standalone device (such as a hearing aid) or an audio listening device implemented as (e.g., physically and / or wirelessly) connected to one or more external devices, such as computers (e.g., desktop, laptop, notebook, tablet), mobile phones, audio playback devices (e.g., MP3 players), video game systems, or other devices. The reference audio sensor 140 and error sensor 162 may include one or more audio sensors, transducers, microphones, or other components configured to detect sound and convert the detected sound into an electrical audio signal.

[0033] LLE 120 may include a single sample processor, digital signal processor, controller, central processing unit with program instructions stored in memory, and / or other logic devices configured to perform one or more processes disclosed herein. LLE 120 may include programmable logic and / or hardware components for causing LLE 120 to perform certain processes, including (e.g., ANC processing via ANC logic 122), profile switching (e.g., profile switching logic 124), detection of ear coupling states (such as leakage) (e.g., ear coupling detection logic 126), and enabling and disabling of transparency modes (e.g., transparency logic 128). LLE 120 may receive instructions such as ANC and / or transparency mode selection from user control 170, which may include one or more physical buttons, sliders, dial pads or other physical input components, touchscreens or other user input devices with associated graphical user interfaces, components, or logic.

[0034] What will be understood is... Figure 1 The embodiment described herein is one example of an active noise cancellation system, and the systems and methods disclosed herein can be implemented using other active noise cancellation implementations that include a reference microphone and an error microphone. It will also be understood that... Figure 1 The embodiments can be used with additional components in various embodiments, including an audio playback component for receiving and generating playback signals for output through speaker 150 (e.g., music, audio from a voice conference).

[0035] refer to Figure 2 Example embodiments of ANC processing, including ear coupling detection, profile switching, adaptive leakage compensation, and improved transparency signal processing, will now be described. The active noise cancellation system 200 is configured to use an external microphone 212 (e.g., Figure 1 External noise is sensed at a reference sensor (e.g., a reference audio sensor 140), which generates an external noise signal x(n). The external noise also travels along a noise path (e.g., a main path P(z)), which may include the housing and components of a personal listening device, and is received at an error sensor 234 (e.g., an error microphone 162). As used herein, the main path P(z) represents the transfer function modeling the acoustic path between the reference sensor 212 and the error sensor 234.

[0036] The ANC system 200 includes a feedforward path configured to generate an anti-noise signal from a received external noise signal x(n), including a decimator 214 configured to downsample the external noise signal x(n) for processing by the ANC system 200; and a feedforward adaptive filter 216 (W ff(z)), which is configured to adaptively estimate the main path P(z) to generate an anti-noise signal y(n) for eliminating external noise signals (e.g., d(n)). In various embodiments, one or more adaptive filters of this embodiment may be constructed using a least mean square (LMS) process, a filtered LMS (FxLMS) process, an infinite impulse response filter, a finite impulse response filter, and other filter types as known in the art.

[0037] The noise-resistant signal y(n) is gain-adjusted by the adaptive gain filter 218 and compared with the playback signal 222 (e.g., voice communication, music, recorded voice, audio accompanying video, etc. in a VoIP call) and the transparent signal generated by the adaptive transparency filter 290 (B AI (z)) and / or the error signal generated by the feedback adaptive filter 270 ((W) fb (z) The signal is mixed (at box 220) and / or further modified by the above signal to generate the output signal. An adaptive transparency filter 290 is adapted in parallel to the reference signal to generate a transparency signal for playback through speaker 230, allowing the user to hear all or part of the external noise when transparency is enabled. The output signal is upsampled by interpolator 224 for output to speaker 230. The adaptation engine may also use an adaptive playback compensation filter 223 to adapt the playback signal (from playback 222). In one or more embodiments, the playback compensation filter 223 is an equalizer that adapts the playback signal (e.g., gain adjustment) based on the detected leakage scenario.

[0038] Error sensor 234 receives a mixture of output signals, including desired audio (e.g., playback signal, externally contained signals from the transparency processing path) and noise-resistant signals, as well as external noise d(n) through the main path P(z). Playback signal 222 (and transparency signal, if the transparency mode is active) is adjusted to account for the secondary path through adaptive filter 272 and removed from the error signal at block 274. As used herein, the secondary path S(z) represents the transfer function modeling the acoustic and electrical paths (e.g., D / A, A / D, etc.) between the speaker and error sensor. Residual error is downsampled for processing by ANC system 200 via decimator 276 and provided as input to feedback adaptive filter 270, which outputs an error correction signal to minimize residual error.

[0039] In the illustrated embodiment, the adaptation engine 280 receives a residual error signal and a copy of a reference signal, the residual error signal being filtered by a filter 278 (G(z)) that models the transfer function between the speaker 230 and the error sensor 234, and the copy of the reference signal being filtered by an estimation and signal conditioning filter 292 (H(z)) of the secondary path 291.

[0040] The ANC system 200 also includes an adaptation engine 280, which includes logic components for adaptive gain control (ADG) 282, ear coupling and profile switching 284, and transparency management 286. In various embodiments, ADG 282 is configured to minimize broadband ripples in the noise immunity path, ear coupling and profile switching 284 is configured to continuously track and compensate for various ear coupling and leakage scenarios and switch to an appropriate filter profile to optimize ANC performance, and transparency management 286 is configured to adapt transparency performance in a parallel transparency path. In some embodiments, ear coupling and profile switching 284 tracks current gain parameters from adaptive gain control 218 and modifies feedforward processing at one or more adaptive filters in the feedforward path to adapt to current leakage scenarios.

[0041] In one or more embodiments, the hybrid ANC system 200 is tuned to achieve certain noise cancellation performance. For example, in the feedforward path, adaptive filters 216 and 218 are pre-tuned and then adapted during operation based on the audio signal received from reference sensor 212 to maximize noise cancellation. In some embodiments, the tuning of the ANC system 200 may be established based on a tight seal between the personal listening device and the user's ear, such that there is little to no leakage. If more leakage exists (e.g., ear coupling between the personal listening device and the ear is inconsistent with the modeled tuning), less low-frequency sound can be sensed, and the adaptive gain control 218 will adapt by increasing the gain. It is also recognized that a detected increase in gain in the feedforward path generally corresponds to less coupling and more leakage than expected. In some embodiments, the adaptive gain filter may be placed on the feedback path (see, e.g., Figure 7 ), and is monitored to detect coupling states and leaks.

[0042] Typically, the adaptation engine 280 includes logic for detecting, tracking, and adapting to user-related conditions and external conditions. User-related conditions may include, for example, tracking gain adaptation to determine leakage mechanisms and modifying filter parameters based on the determined leakage mechanisms. External conditions may include, for example, classifying external conditions detected by reference sensors (e.g., using a neural network classifier) ​​and optimizing filter performance based on the classified external conditions. For example, when classified, known external conditions including low-frequency noise and / or voice may be modeled and optimized.

[0043] Now refer to Figures 3A to 7 A more detailed description of an embodiment incorporating ear coupling detection and profile switching is provided. (See references.) Figure 3A -D, a personal listening device such as a wireless earbud 310 is adapted to fit into the ear 320 of a user 300. In operation, the wireless earbud 310 is operable to wirelessly communicate with a host system such as a mobile device 330. The wireless earbud 310 is designed to insert into (or be adjacent to) the user's ear canal 322, where audio output from the wireless earbud 310 is sensed at the user's eardrum 324. The personal listening device 310 includes a wireless transceiver for transmitting and receiving communications (e.g., audio streams) between the wireless earbud 310 and the mobile device 330.

[0044] User 300 will freely insert and remove the wireless earbuds 310 into and from the user's ear 320 to listen to audio from the mobile device 330. During this process, the wireless earbuds 310 pass between an exposed first position 314 and a second position 316, in which the wireless earbuds 310 are securely positioned in the ear 320. In various embodiments, the wireless earbuds 310 include a flexible end (e.g., silicone, memory foam) designed to conform to the shape of the ear to create a tight seal that controls leakage. However, in practice, when the wireless earbuds 310 are positioned in the second position 316, one or more gaps 326 and / or loose coupling / seal may form between the construction of the wireless earbuds 310 and the user's ear 320, resulting in leakage.

[0045] In practice, small changes in coupling are expected when a user inserts and removes the wireless earbuds, which can be addressed by an adaptive gain control filter. However, a larger gap 326 may form, resulting in leakage that cannot be accounted for by gain adjustment. This leakage may be due to factors such as the user's specific configuration, the positioning of the wireless earbuds 310 (e.g., misalignment of the earbuds relative to the ear, inappropriate insertion depth, etc.), the size and shape of the wireless earbuds 310, changes in the shape of the earbuds due to use, the user's lack of awareness of when proper coupling is achieved, and / or other factors.

[0046] The wireless earbuds 310 include an ANC system 312 to cancel ambient noise and / or allow certain ambient noise to pass through in a transparency mode. During operation, adaptive components of the ANC system 312 are adapted to optimize ANC performance. In various embodiments, the ANC system 312 includes an adaptive gain control filter (e.g., adaptive gain filter 218) and adaptive gain control logic (e.g., ADG 282) to adjust the gain of the noise-canceling signal to optimize cancellation. It is observed that the gain parameter of the adaptive gain control filter is related to the leakage level due to the position and / or fit of the wireless earbuds 310 in the user's ear 320. The ADG 282 tracks one or more gain parameters to determine the current gain applied to the noise-canceling signal to identify leakage scenarios.

[0047] The correlation between gain and leakage conditions can be modeled, for example, by using virtual head test locations and matching scenarios and optimizing ANC parameters for the leakage conditions detected, by testing people in a general population, by modeling the parameters of the ANC system, and / or other methods. It has been observed that for a sample of potential user populations, leakage scenarios typically fall into two or three clusters, and in most cases, four or five clusters are sufficient for acceptable performance. These clusters or other groupings can be used to define leakage profiles, including adaptive filters tuned for leakage scenarios. Because the leakage corresponding to the gain is known, the feedforward path (e.g., W...) ff (z)), feedback path (e.g., W) fb (z)), Transparent Path (e.g., B) AI (z)) and / or playback path (e.g., S) PL The filters in (z) can, for example, be switched to certain pre-tuned filters representing the leakage scenario based on the detected gain.

[0048] In some embodiments, the gain value can be used to detect other conditions (such as outdoor conditions detected during insertion or removal activities) and to trigger changes in the operation of the wireless earbuds 310, such as entering a low-power mode, adjusting the output volume, and activating or disabling certain functions.

[0049] refer to Figure 4A An embodiment of an adaptive LMS system 422 is disclosed. The adaptive LMS system 422 continuously updates the coefficients of the feedforward ANC filter 402 to adjust for changes in the coupling path. The input to the LMS system can be a programmable filter B. G (z) is adjusted by the programmable filter B. G (z) is designed to protect against low-frequency transients in the environment. (Reference) Figure 4B An embodiment of an adaptive gain (ADG) subsystem 400 is disclosed. Adaptive gain control logic 420 continuously updates an adjustable gain filter 404 to adjust for changes in the coupling path. A programmable filter B can be used. G (z) (e.g., programmable filters 408 and 410) to adjust the input to ADG 420, the programmable filter B G (z) is designed to protect against low-frequency transients and high-frequency interference in the environment. In some embodiments, filter B G (z) may include a low-pass filter and / or a band-pass filter, which also filters out very low frequencies (e.g., <20Hz that cannot be heard from a loudspeaker).

[0050] As discussed earlier, variations in the physical geometry of a personal listening device and human-to-human interaction can affect noise cancellation performance. For example, the shape of the outer ear and the length of the ear canal can alter the acoustic transfer function of interest in an ANC system. In some embodiments, the ANC system in a personal listening device (e.g., Figure 1 The system uses a noise sensing reference microphone, an error microphone, and a DSP subsystem to generate appropriate anti-noise to cancel the noise field as measured by the error microphone. This results in a cancellation region where the degree of cancellation is maximized at the error microphone location and degrades inversely proportional to wavelength. Therefore, for higher frequencies (lower wavelengths), the cancellation performance degrades significantly at the tympanic membrane (approximately 25 mm away from the error microphone), resulting in a loss of cancellation bandwidth, as perceived by the user of the noise cancellation system. Figure 4A The -B embodiment addresses these and other issues by maximizing the cancellation bandwidth at the tympanic membrane during the tuning phase and formulating an adaptive method that uses an error microphone during operation to adapt to user-specific characteristics.

[0051] For the purposes of this embodiment, the error microphone location is referred to as the ERP (Error Reference Point) and the tympanic membrane location as the DRP (Drum Reference Point). For an ANC system tuned at the DRP, the error microphone is a good indicator of low-frequency cancellation at the DRP, and therefore a robust error correction signal can be derived from the low-pass version of the error microphone signal. This correction signal can then be used to adapt the gain in the noise immunity signal path.

[0052] To maximize cancellation, the ideal placement of the error microphone would be at the eardrum, but this location is impractical for many consumer devices. Therefore, the error ERP is used to provide a practical signal that roughly indicates the cancellation performance at the DRP. Adaptive algorithms attempt to minimize the ERP signal, which leads to (i) reduced cancellation at high-frequency signals at the DRP and (ii) a higher probability of hissing artifacts due to constructive interference at high frequencies at the DRP. Conventional methods employ adaptive algorithms that use a transfer function from the ERP to the DRP. These methods suffer from several drawbacks, including inaccurate transfer function estimation at high frequencies, low estimation accuracy affecting broadband cancellation performance and leading to transient hissing levels, high computational cost, and difficulty in tuning and calibrating for all usage conditions, making deployment impractical for many devices. Figure 4A The -B embodiment provides a computationally inexpensive method that overcomes many of the drawbacks of conventional systems, is easy to tune, for example, by measuring certain transfer functions during system design, and is self-calibrating.

[0053] Figure 4A The diagram illustrates the calibration and tuning arrangement for the adaptive gain subsystem. In this arrangement, the ANC filter 402 is optimized to eliminate noise at the DRP during the initial tuning phase. In one embodiment, the device is placed on a head and torso simulator that has a second error microphone at the DRP. E2D (z), S E2D (z) The ERP-DRP transfer function is modeled in the indicated acoustic path. Then, the system can be optimized using the minimum mean square block 422 based on the error signal e'(n) to perform ANC tuning to derive the optimal W. DRP(z) Tuning in this manner helps achieve extended bandwidth elimination and better performance in the high-frequency band. In various embodiments, the device is placed in various locations (e.g., secure fit, misalignment, inappropriate insertion depth, etc.), fits (e.g., different head and ear constructions), configurations (e.g., removable ends on in-ear headphones), and wear scenarios to tune ANC performance for different leakage conditions. In various embodiments, the various scenarios can be grouped by associated adaptive gain values ​​to create profiles for optimizing ANC performance for various leakage scenarios.

[0054] like Figure 4B As illustrated, an adaptive algorithm is established to continuously update the gain element 404, G, which enables the system to adjust for variations in various coupling paths. In some embodiments, the signal is low-pass filtered and gain adjustment is performed for good low-frequency cancellation. A programmable filter B can be used. G (z) is used to adjust the input to the adaptive algorithm; the programmable filter B G (z) is programmed so that the ERP signal can mimic the cancellation performance at DRP. Additionally, B can be... G (z) Programming to optimize performance during low-frequency transients and high-frequency interference in the environment. It will be understood that... Figure 4A -B's embodiments are exemplary implementations, and the methods disclosed therein can be modified for adaptive versions of feedback, feedforward, and hybrid ANC solutions.

[0055] refer to Figure 5A and 5B The operation of an ANC system (e.g., according to one or more embodiments) will now be described. Figure 1-4B and Figure 7 The system employs adaptive gain control parameters to detect ear coupling and select from available leakage profiles. The configuration process 500 begins in step 502 by estimating transfer functions for the primary path P(z) and secondary path S(z) across a population range for individual listening devices and using different device customizations (e.g., different sizes of the ends of in-ear headphones). In step 504, a model of the device's leakage behavior is generated, which may include one or more gain parameters and coefficients for one or more adaptive filters for tuning. In step 506, the process acquires data from a supervisory detector used for the adaptation engine and determines tuning parameters. In some embodiments, a fixed number of profiles (e.g., four profiles) are generated, representing variations in coupling between the individual listening device and the person's ear or head. Profiles can be selected to cover a range of leakage factors and / or a range of common individual listening device configurations and locations / fits, such as tightly coupled configurations, exposed (or highly leaky) configurations, and intermediate leakage scenarios.

[0056] In step 508, gain and threshold values ​​are determined for different leakage scenarios. In one embodiment, a profile representing the tight coupling between the personal listening device and the user's ear / head can be associated with gain values ​​and threshold values ​​that can be used to trigger profile changes. For example, when the gain value is above a first predetermined threshold, the profile switches to a second profile associated with a second (e.g., higher) gain factor. The second profile may have an upper threshold above which the profile switches to a third profile associated with a third (e.g., higher) gain factor. The second profile may also have a lower threshold below which the profile switches back to the first profile. Additional profiles are defined in a similar manner using gain values ​​associated with the tuned leakage profile and a threshold range within which the filter provides acceptable (e.g., as determined by system requirements) performance. In one embodiment, the gain range defines a range of ANC performance that meets or exceeds the performance standards of the personal listening device. For example, when the gain value deviates more from the profile gain value, performance degrades, and a new profile is defined and tuned by the new gain value and the upper and lower threshold values.

[0057] Method 550 for operating an ANC system includes, in step 552, tracking the current profile state, including upper and lower threshold values ​​and gain values ​​available for the current profile. In step 554, method 550 tracks the gain parameters of an adaptive gain controller in the feedforward path. In step 556, the tracked gain parameters are compared with current thresholds to determine if a change has occurred in the leakage profile. If the tracked gain value is higher than the current upper threshold or lower than the lower threshold, the process switches to the appropriate profile. In step 558, the parameters of the adaptive filter for the ANC system are updated to the facility current leakage profile.

[0058] refer to Figure 6 The example profile switching process 600 according to one or more embodiments will be described in more detail. The profile switching process 600 switches between four predefined profiles, numbered 1-4 in the illustrated embodiment. A first profile (e.g., profile 1) is tuned for the tightest seal, where coupling is highest, and a fourth profile (e.g., profile 4) is tuned for leakage scenarios, such as when the device is substantially out of place. The remaining two profiles cover intermediate leakage scenarios. It will be understood that although four profiles are used in the illustrated embodiment, the number of profiles used may be more or less in certain implementations.

[0059] In various embodiments, each profile is tuned for a specific gain / leakage scenario and includes a high (H) threshold and a low (L) threshold, thereby defining the range of operation for each profile. A profile is valid when the detected gain is within the high (H) and low (L) thresholds of the profile. The threshold ranges for predefined profiles together span a range of gain values ​​that may be encountered during use. In some embodiments, each profile is tuned to provide acceptable ANC performance near a baseline gain value, and the thresholds are defined as falling within the range of gain values ​​that produce acceptable ANC performance for the tuned profile.

[0060] Profile switching process 600 begins by loading parameters associated with profile 2 at step 602. Control moves to step 614, where the ANC system uses profile 2 to process the noise immunity signal. The ANC system includes an adaptive gain filter in the feedforward path that converges to the current gain value. The current gain is tracked and compared with an upper threshold T2,H and a lower threshold T2,L. When the gain is within the threshold range, the process state remains at step 614. If the gain falls below the lower threshold (T2,L), profile 1 is loaded at step 612, and control moves to step 610 to use profile 1 to process the noise immunity signal when the gain is less than the upper threshold (e.g., the gain is less than or equal to T1,H). If the gain exceeds the upper threshold T1,H, control returns to step 602, profile 2 is loaded, and control returns to step 614, as previously discussed.

[0061] As in step 614, if the gain value exceeds the upper threshold limit (e.g., T2, H), control proceeds to step 616 to load profile 3, and then to step 618, where ANC processing is performed when the adaptive gain value is between the lower threshold limit T3, L and the upper threshold limit T3, H. If the gain is below the lower threshold limit T3, L, control returns to step 602 to load profile 2. If the gain exceeds the upper threshold limit T3, H, control proceeds to step 606, where profile 6 is loaded, and then to step 620, where ANC processing continues using profile 4 when the gain exceeds the lower threshold limit T4, L. If the gain falls below the lower threshold limit T4, L, control returns to step 616 to load profile 3 for ANC processing.

[0062] refer to Figure 7Example implementations of a low-latency hybrid ANC system 700, which can be used in one or more embodiments of this disclosure, will now be described. The hybrid ANC system 700 includes a reference microphone 702 and an error microphone 704 that convert sensed sound into an electronic analog signal. The reference microphone signal is converted to digital by an analog-to-digital converter 706, and the error microphone signal is converted to digital by an analog-to-digital converter 708. The microphones may include any device that senses sound waves and converts the sensed sound into an electronic signal, such as a piezoelectric microphone, a microelectromechanical system (MEMS) microphone, an audio transducer, or similar device. In various embodiments, the hybrid ANC system may include one or more additional microphones, which may include digital microphones that generate digital audio signals (e.g., thereby eliminating the need for a separate analog-to-digital converter), and / or other modifications consistent with the teachings of this disclosure may be made.

[0063] Hardware decimation unit 710 receives and downsamples digital audio signals for processing by the ANC system. In the illustrated embodiment, a reference microphone signal is downsampled by low latency decimation circuit 712, and an error microphone signal is downsampled by low latency decimation circuit 714. The signals are then passed to low latency router 716, which routes them to various components of the hybrid ANC system 700 for processing.

[0064] In the illustrated embodiment, the hybrid ANC system 700 includes a low latency engine 720, which includes a feedforward ANC path, a parallel transparency path, and a feedback ANC path. The low latency engine 720 can be implemented in hardware, software, or a combination of both. In some embodiments, the low latency engine 720 can be implemented as a single-sample processor, a digital signal processor, a controller, a processor, and a memory storing instructions, and / or other logic devices capable of performing the low latency ANC processing described herein. As illustrated, the feedforward path includes a processing profile 722 (which includes tuning and other parameters for generating a noise-resistant signal from a reference signal), an optional finite impulse response filter 724, and an adaptive gain component 726.

[0065] The feedback path receives the error microphone signal and is configured to remove the playback signal (e.g., at component 742), which is filtered by the secondary path filter 740 to account for the secondary path effect. The feedback path also includes a plurality of BiQuads 744 (e.g., 12 BiQuads) and a gain component 746 configured to function as an infinite impulse response filter.

[0066] The low latency engine 720 also includes a transparency signal processing path that receives a reference microphone signal, adaptively (e.g., via transparency processing unit 732) filters the reference microphone signal, and applies a gain 734. In the illustrated embodiment, the transparency processing unit operates in parallel with ANC processing and can operate with ANC enabled or disabled. The outputs of the feedforward path, feedback path, and transparency path (if transparency mode is activated) are combined at mixing unit 730 to generate an anti-noise signal. A low latency router 770 routes the signal between the low latency engine, a hardware interpolation unit 780 that adapts to upsample the anti-noise signal for output, and an adaptation engine 750. The hardware interpolation unit 780 includes low latency circuitry 782 for anti-noise signal upsampling and high-quality upsampling circuitry 784 configured to receive playback signals and generate high-quality audio signals for output. The upsampled noise-resistant signal and the playback signal are combined at component 786 and fed to digital-to-analog converter and amplifier 790, which drives the output (e.g., for output through a speaker).

[0067] The hardware interpolation unit 780 also includes a downsampler 788 for feeding the playback signal to the low latency engine 720 and an adaptation engine 750 for further processing (e.g., removing the playback signal from the received error microphone signal).

[0068] The adaptation engine 750 supervises ANC processing during operation and controls one or more components of the low latency engine 720 to optimize ANC performance. The adaptation engine 750 can be implemented using a single sample processor, digital processing unit, digital signal processor, or other logic device and / or processing system. In the illustrated embodiment, the adaptation engine 750 includes components for adaptive secondary path processing 752, estimated secondary path filter 754, adaptive profile processing 756, and profile selection 758. The adaptation engine 750 can be configured to provide adaptive leakage compensation by tracking and compensating for leakage differences (e.g., by selectively switching profiles). In various embodiments, the adaptation engine 750 may include additional processing components and controls, such as whistling control, wind control, external control, and other control logic. In some embodiments, additional detectors (e.g., whistling detectors, wind detectors, etc.) may be included to provide input to one or more detectors, and control elements may provide compensation for detected conditions by modifying one or more parameters of the adaptation profile and adaptive filter (e.g., gain control for whistling compensation).

[0069] The hybrid ANC system 700 is transmitted via technologies such as I 2An audio interface 760, such as S-Video, PCM, or other interface protocols, receives audio playback from a separate device. The received playback signal is processed by an audio processing unit 762, which may include an audio codec and other components configured to modify the playback signal for output.

[0070] The foregoing disclosure is not intended to limit this disclosure to the precise form disclosed or a particular field of use. Therefore, it is contemplated that various alternative embodiments and / or modifications to this disclosure are possible, whether expressly described or implied herein. Given that embodiments of this disclosure have been described as such, those skilled in the art will recognize that changes in form and detail may be made without departing from the scope of this disclosure. Therefore, this disclosure is limited only by the claims.

Claims

1. An active noise cancellation system, comprising: A feedforward path is configured to receive a reference signal including external noise and adaptively generate an anti-noise signal to eliminate the external noise. The feedforward path includes an adaptive gain component configured to adaptively adjust the gain of the anti-noise signal. as well as A logic device configured to determine a leakage profile selected from multiple leakage profiles based on parameters of the adaptive gain component, the multiple leakage profiles being generated by tuning the active noise cancellation system according to sound received by a microphone at a tympanic membrane reference point. The feedforward path includes a feedforward adaptive filter that is tuned to generate the noise immunity signal corresponding to the reference signal based on the determined leakage profile.

2. The active noise cancellation system according to claim 1 further includes a memory that stores multiple leakage profiles.

3. The active noise cancellation system of claim 2, wherein each of the plurality of leakage profiles is tuned for a corresponding gain.

4. The active noise cancellation system of claim 2, wherein each of the plurality of leakage profiles has an associated threshold range, and wherein the logic device is configured to determine the leakage profile by determining whether the parameter is within the associated threshold range.

5. The active noise cancellation system of claim 1, wherein the determined leakage profile includes a filter tuned for a feedforward adaptive active noise cancellation filter, a feedback adaptive noise cancellation filter, a playback compensation filter, an adaptive active noise cancellation auxiliary path filter, and / or a transparency filter operating in parallel with the feedforward path.

6. The active noise cancellation system of claim 1, wherein the determined leakage profile corresponds to an ear coupling condition associated with the interaction between the active noise cancellation system and the user.

7. The active noise cancellation system of claim 1 further includes an adaptive transparency filter configured to receive the reference signal and generate an external inclusion signal for use as an output to a user of the active noise cancellation system.

8. The active noise cancellation system of claim 7, wherein the adaptive transparency filter operates in parallel with the feedforward path; and wherein the external environment includes signals that are mixed with the noise-resistant signal in the transparency mode.

9. The active noise cancellation system according to claim 8 further includes: A low latency engine is configured to provide low latency processing for the adaptive transparency filter, the adaptive gain component, the feedforward adaptive filter, and the feedback adaptive filter. and An adaptation engine, configured to supervise and control one or more adaptations of the low latency engine, the adaptation engine including the logic device.

10. The active noise cancellation system according to claim 1, further comprising: A reference sensor is configured to sense the external noise and generate a corresponding reference signal; and An error sensor is configured to sense the mixture of the external noise and the anti-noise signal in the noise cancellation zone and generate a corresponding error signal.

11. The active noise cancellation system of claim 1, wherein the leakage profile includes stored coefficients for at least one adaptive filter; and wherein the logic device is further configured to modify the filter coefficients of at least one adaptive filter in the feedforward path.

12. A method for performing active noise cancellation, comprising: A reference signal representing external noise is processed through a feedforward active noise cancellation path to adaptively generate an anti-noise signal to cancel the external noise, wherein the processing includes: An adaptive gain is applied to the noise immunity signal, wherein the gain is adapted to one or more leakage conditions; and A leakage profile is determined, which is selected from a plurality of leakage profiles based at least in part on the adaptive gain. These multiple leakage profiles are generated by tuning the feedforward active noise cancellation path according to the sound received by a microphone at a tympanic membrane reference point. The processing of the reference signal further includes applying an adaptive filter according to the determined leakage profile to generate the noise-resistant signal corresponding to the reference signal.

13. The method of claim 12, wherein determining the leakage profile based at least in part on the adaptive gain further includes storing a plurality of leakage profiles.

14. The method of claim 13, further comprising tuning each of the plurality of leakage profiles for a corresponding adaptive gain value.

15. The method of claim 14, wherein tuning each of the plurality of leak profiles further comprises: Measurements were taken for the main and secondary paths of an active noise cancellation system spanning multiple users; Construct a model for the leakage behavior of the active noise cancellation system; Acquire data for the supervisory detector and determine the tuning parameters; as well as For each of the multiple leakage profiles, a gain and threshold are determined.

16. The method of claim 15, further comprising determining a threshold range for each of the plurality of leakage profiles, and determining whether the gain value is within the threshold range of one of the plurality of leakage profiles.

17. The method of claim 12, wherein determining the leakage profile further comprises applying filters for a feedforward adaptive active noise cancellation filter, a feedback adaptive noise cancellation filter, a playback compensation filter, an adaptive active noise cancellation auxiliary path filter, and / or a transparency filter operating in parallel with the feedforward active noise cancellation path.

18. The method of claim 12, wherein the determined leakage profile corresponds to an ear coupling condition associated with the cooperation between the active noise cancellation device and the user.

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