Broad-spectrum instability detection and mitigation

Abstract

A method is provided for an audio output device to detect instability and take mitigating action. Specifically, an A-weighted dBA level of the raw feedback signal exceeding a threshold level at least triggers muting of the driver. The described method is applied to detect instability over a wide frequency spectrum.

Description

[Technical Field]

[0001] This application claims priority to and the benefit of U.S. Patent Application No. 17 / 460,865, filed August 30, 2021, the contents of which are incorporated herein by reference in their entirety as if fully set forth below.

[0002] Aspects of the present disclosure generally relate to detecting instability in a wearable audio output device and taking steps to mitigate the instability. Detection occurs across the human audible frequency spectrum. Mitigating the instability reduces the likelihood of an unstable condition causing the device to produce loud noises that are unpleasant to the user. [Background technology]

[0003] Various audio devices incorporate active noise reduction (ANR) functionality, also known as active noise control or cancellation (ANC), in which one or more microphones detect sounds, such as external sounds captured by a feedforward microphone or internal sounds captured by a feedback microphone. Signals from the feedforward and / or feedback microphones are processed to provide anti-noise signals to be sent to sound transducers (e.g., speakers, drivers) to cancel noise that would otherwise be heard by the user. Certain instabilities can arise that can be unpleasant for the user. Therefore, it is desirable to detect instabilities and take steps to mitigate the instabilities. Summary of the Invention

[0004] All examples and features mentioned in this specification can be combined in any technically possible manner. [Means for solving the problem]

[0005] An aspect provides a method performed by an audio output device, the method including receiving, by an instability detector, a feedback signal from a feedback microphone of the audio output device, and muting a driver of the audio output device based at least in part on characteristics of the feedback signal.

[0006] In an embodiment, the characteristic of the feedback signal includes the feedback signal exceeding a threshold A-weighted decibel (dBA) level. In an embodiment, the feedback signal exceeds the threshold A-weighted decibel (dBA) level for a predetermined period of time.

[0007] In an embodiment, the feedback microphone detects signals between 20 Hz and 24 kHz.

[0008] In aspects, muting the driver includes muting the driver for a predetermined amount of time.

[0009] In an aspect, the method further includes triggering a restart of the audio output device based at least in part on a characteristic of the feedback signal. In an aspect, the method further includes triggering the restart when the driver is muted a threshold number of times over a defined period of time based at least in part on a characteristic of the feedback signal.

[0010] In an aspect, the method further includes turning off at least one of the feedback microphone or the feedforward microphone based at least in part on a characteristic of the feedback signal.

[0011] An aspect provides an audio output device comprising: a memory in a first earpiece coupled to at least one processor, the memory having stored thereon instructions for causing the audio output device to receive, by the at least one processor, a first feedback signal from a first feedback microphone and mute a first driver of the audio output device based at least in part on a characteristic of the first feedback signal.

[0012] In an aspect, the characteristic of the first feedback signal includes the first feedback signal exceeding a threshold A-weighted decibel (dBA) level. In an aspect, the feedback signal exceeds the threshold A-weighted decibel (dBA) level for a predetermined period of time.

[0013] In an embodiment, the first feedback microphone detects signals between 20 Hz and 24 kHz.

[0014] In aspects, the instructions to mute include instructions to mute the driver for a predetermined amount of time.

[0015] In an aspect, the instructions further cause the audio output device to trigger a restart of the audio output device based at least in part on a characteristic of the first feedback signal. In an aspect, the instructions further include instructions for causing the audio output device to trigger a restart when the first driver is muted a threshold number of times over a defined period of time based at least in part on a characteristic of the first feedback signal.

[0016] In an aspect, the instructions further include instructions to cause the audio output device to turn off at least one of a first feedback microphone or a first feedforward microphone in the first earpiece based at least in part on a characteristic of the first feedback signal.

[0017] In an aspect, the audio output device further comprises at least one processor in the second earpiece, and the memory has stored therein instructions for causing the audio output device to receive, by the processor in the second earpiece, a second feedback signal from the second feedback microphone and mute a second driver of the audio output device based at least in part on a characteristic of the second feedback signal.

[0018] In an aspect, the instructions cause the audio output device to independently mute the first driver and the second driver.

[0019] An aspect provides an audio output device comprising: a feedback microphone; a driver; and an instability detector, the instability detector configured to receive a feedback signal from the feedback microphone of the audio output device and to trigger muting of the driver based at least in part on characteristics of the feedback signal.

[0020] In an aspect, the characteristic of the feedback signal includes the feedback signal exceeding a threshold A-weighted decibel (dBA) level for a predetermined amount of time.

[0021] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. [Brief explanation of the drawings]

[0022] [Figure 1] 1 illustrates an exemplary audio output device in which aspects of the present disclosure may be implemented. [Figure 2] 1 illustrates exemplary components of an instability detector, according to aspects of the present disclosure. [Figure 3] 1 illustrates example operations performed to detect and mitigate instability, according to aspects of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0023] Aspects of the present disclosure provide an audio output device and a method performed by the audio output device for detecting and mitigating instabilities within the audio output device. Currently, a specific subset of instabilities that result in vibrations can be detected. In one embodiment, at least a portion of a feedback signal is processed to detect a tonal signature of an unstable condition within a portion of the signal captured by a feedback (e.g., internal) microphone. If the tonal signature is indicative of an unstable condition, the audio output device generates one or more control signals to adjust an ANC system such that the unstable condition is mitigated.

[0024] Current methods can be limited because they attempt to detect and respond to a subset of known or otherwise pre-identified instabilities. Furthermore, it is desirable to reduce or stop instabilities as quickly as possible to reduce discomfort and potential hearing damage. The audio output devices and methods described herein detect instabilities across a wide frequency spectrum in a lightweight manner. Instabilities can be detected before vibrations reach a point that damages the listener's hearing.

[0025] Any change in the transfer function between either the feedback microphone and the driver, or the feedforward microphone and the driver, can create instability. Exemplary causes of instability across the audio frequency spectrum include the nozzle of the in-ear tip being blocked, removing the earcup cover of the feedback microphone 150, cupping the earcup opening by the user's hand, and crushing or damaging the housing and electronics within the device.

[0026] FIG. 1 illustrates an example of an ANC system 100 deployed in headphones 110. The headphones 110 include earcups 120 on each side that fit over, around, or above the user's ears. The earcups 120 may include a layer 130 of soft material (e.g., soft foam) for a comfortable fit over the user's ears. The ANC system on the headphones 110 includes a feedforward microphone (external microphone) 140 positioned outside or near the earcups 120 to detect ambient noise in the user's environment. The ANC system also includes a feedback microphone (or internal microphone) 150 that may be positioned in close proximity (e.g., within a few millimeters) to the user's ear canal and / or driver 160. The driver 160 may be an acoustic transducer for converting electrical signals into acoustic signals that the user can hear. In an aspect, the driver 160 emits an audio signal from an audio source device to which the headphones 110 are connected. The feedforward microphone 140 , the feedback microphone 150 and the driver 160 are connected to an active noise control engine 170 .

[0027] The ANC system 100 operates to reduce audio noise components heard by a user of an audio output device. A noise cancellation system may include a feedforward system and / or a feedback system. In a feedforward system, the feedforward microphone 140 detects noise external to the headphones 110. The active noise control engine 170 provides an anti-noise signal to counteract the external noise expected to be transmitted to the user's ear. In a feedback system, the feedback microphone 150 detects acoustic signals reaching the user's ear. The active noise control engine 170 processes the detected signal to cancel any signal components not intended to be part of the user's acoustic experience.

[0028] In an embodiment, the active noise control engine 170 includes an instability detector 180. The instability detector 180 detects a feedback signal from the feedback microphone 150. Based on characteristics of the feedback signal, the instability detector 180 takes action to mitigate the instability. In an embodiment, the instability detector 180 identifies instability in the feedback signal output by the feedback microphone 150 and takes action to mute at least the driver 160.

[0029] Figure 1 illustrates some example components of headphones 110. There may be other components for the functioning of headphones 110 that are not illustrated in Figure 1. Headphones 110 may further include hardware and circuitry, including a processor / processing system and memory, configured to implement one or more sound management or other capabilities, including, but not limited to, the described ANC and methods for detecting and mitigating instability.

[0030] For example, headphones 110 include (or are coupled to) a processor, a memory that stores instructions for operating the headphones, and methods described herein.

[0031] 1 also illustrates the right portion of the headphones. The corresponding, not shown, left portion of the headphones 110 includes similar features to those illustrated in FIG. 1. In particular, the left side may also include a feedforward microphone, a feedback microphone, a driver, an active noise control engine, and an instability detector. Similar to the right portion of the headphones, the left instability detector detects a feedback signal from the feedback microphone, which is positioned in close proximity (e.g., within a few millimeters) to the driver in the user's left ear canal and / or left earcup. Based on the characteristics of the feedback signal, the instability detector takes action to mitigate the instability, such as muting the driver in the left earcup.

[0032] In an aspect, the right and left sides of headphones 110 each independently determine whether instability is detected in their respective earcups. An instability detector in the right earcup controls the driver on the same side (e.g., right side) of headphones 110. Similarly, an instability detector in the left earcup controls the driver on the same side (e.g., left side) of headphones 110. As such, the raw feedback signals from each feedback microphone are independently processed to identify instability on each side of headphones 110. Based on the respective feedback signals, one or more of the drivers are independently controlled and / or muted.

[0033] Although FIG. 1 illustrates an embodiment in which the ANC system 100 is deployed in around-ear headphones 110, the ANC system 100 may also be deployed in other form factors, including in-ear headphones, on-ear headphones, and audio glasses or frames.

[0034] FIG. 2 illustrates exemplary components of the instability detector 180 according to an embodiment of the present disclosure. The instability detector 180 receives a raw feedback signal from the feedback microphone 150. The instability detector 180 performs A-weighting (A-frequency weighting) to weight audio frequencies to reflect the response or sensitivity of the human ear to noise. The A-weighting filter 190 encompasses the entire audio frequency range from 20 Hz to 24 kHz, and its output approximates the frequency sensitivity of the human ear. A-weighting accounts for the relative loudness perceived by the human ear, as the human ear is less sensitive to low audio frequencies. The n-second averaging filter 210 averages the A-weighted signal over a predetermined period. The threshold detector 220 compares the averaged A-weighted signal to a threshold dBA level. As described below, if the threshold detector 220 determines that the averaged A-weighted signal exceeds the threshold dBA level, a control signal is output to mute at least the driver 160.

[0035] The instability detector 180 detects instability when the averaged A-weighted signal from the feedback microphone exceeds a threshold A-weighted level (dBA) for a predetermined period of time. In response to detecting instability, the instability detector 180 sends a control signal to mute the driver 160 for a period of time. After that period of time has elapsed, the driver unmutes. The instability detector does not take any action affecting the driver unless instability is detected. Temporarily muting the driver protects the user by blocking sound from the driver and allowing the user to move the headphones away from the user's ears.

[0036] The International Telecommunication Union standard ITU-T H.870, "Guidelines for safe listening devices / systems," describes requirements for safe listening devices and systems, including personal and portable audio systems, to protect people from hearing loss. The purpose of this standard is to provide a means of determining when a listener experiences maximum volume over a given period of time. ITU-T H.870 specifies a minimum sound level of 1.6 Pa per week for adults for a given A-weighted level (dBA), as shown in the table below. 2 The time it takes to reach a volume of 110 dBA is specified. Generally, the time is halved for every 3 dBA. At 110 dBA, it is 1.6 Pa / week for an adult. 2 The time to reach a volume of 100 dBA is approximately 2.25 minutes, while for 120 dBA it is a few seconds. Given the short amount of time it takes to reach maximum volume, it is important that people are not unnecessarily exposed to high dBA levels, and that such exposure is limited as much as possible.

[0037] [Table 1]

[0038] In an embodiment, the threshold A-weighted level is 110 dBA. In an embodiment, averaging filter 210 is a 1-second averaging filter. Thus, in one embodiment, the A-weighted signal must exceed 110 dBA for 1 second for the instability detector to detect instability.

[0039] In an embodiment, upon detecting instability, the instability detector mutes the driver for 3 seconds, after which the driver unmutes.

[0040] The 1-second averaged dBA level, A-weighted, that triggers the 3-second mitigation action is based on many factors. As shown in the table above, ITU-T H.870 specifies that the average adult's listening time is 40 hours per week at 80 dBA, decreasing dramatically at higher SPLs (e.g., listening time is only 4.5 minutes per week at 107 dBA). The average adult should be exposed to no more than 2.25 minutes per week at 110 dBA. Using a 1-second average dBA level trigger to detect instability is significantly faster than outlined by the standard, while still preventing very short-duration transient noise from triggering instability. Additionally, the 1-second averaging allows for the processing time required for the instability detector to perform the A-weighting and verify that the threshold dBA level has been met. Therefore, an A-weighted level of 110 dBA for 1 second is a balance value for a short amount of time of excessively loud signals to minimize annoyance and hearing damage, and to avoid short transient noise causing instability.

[0041] Muting the drivers for three seconds allows the user to take action to stop the instability by removing the headphones from the user's head or moving the headphones away from the user's ears. Muting for three seconds also allows the user to turn the device back on and resume listening, or to turn the headphones off if the user is unable to stop the instability. While muting is one action that may be taken based on detected instability, other actions may be taken, as described in more detail with respect to FIG. 3.

[0042] 3 illustrates example operations 300 performed by an audio output device to detect and mitigate instability. An instability detector of the audio output device receives a feedback signal from a feedback microphone of the audio output device at 310. Based on characteristics of the feedback signal, a driver is muted at 320. In an aspect, the instability detector sends a control signal to mute the driver.

[0043] The feedback microphone detects signals between 20 Hz and 24 kHz, so that instability detection occurs across the human audible frequency spectrum, generally up to 20 kHz. Additionally, instability detection is not limited to a particular subset of known instabilities. In an embodiment, the characteristics of the feedback signal include an A-weighted dBA level that exceeds a threshold level. In one embodiment, the feedback signal exceeds the threshold dBA level for a predetermined period of time.

[0044] Although the examples describe using a 110 dBA level threshold, instability detection may use other threshold levels greater than or less than 110 dBA. Similarly, although the examples describe averaging the A-weighted feedback signal above the threshold for 1 second, other periods greater than or less than 1 second may be used in accordance with the methods described herein. Generally, a high average dBA level for a short amount of time will identify instability quickly enough to minimize discomfort and avoid hearing loss.

[0045] In an aspect, the driver is muted for a predetermined amount of time. According to the example described above, the driver is muted for three seconds. The user may assume that the audio device stopped outputting sound due to instability, as opposed to a loss of connection to the source device, in part due to a momentarily loud sound the user heard before the driver muted. In an aspect, the instability detector sends a control signal to mute the driver for a configured amount of time. The driver may be muted for any amount of time (longer or shorter than three seconds), as long as the length of time the driver is muted allows the user to turn off the audio output device or otherwise move the audio output device away from the user's ear.

[0046] In aspects, the instability detector tracks the number of instabilities or the number of times the instability detector sends an instruction to mute the driver. In aspects, the audio output device forces a device restart after a configured number of instabilities are detected over a period of time. For example, if n instabilities are detected over a period of time (e.g., one day), or if y control signals are sent to mute the driver in response to instability over a period of time (e.g., four hours), the audio output device may trigger a device restart in an attempt to refresh the system and / or install updates to help address any issues that may be causing the frequent instability.

[0047] In aspects, the feedback microphone and / or the feedforward microphone are turned off after a configured number of instabilities over a period of time are detected. Turning off the feedback microphone interrupts the signal path between the feedback microphone and the driver, thereby preventing the driver from outputting a further excessively loud signal. Turning off the feedforward microphone will stop oscillations and instabilities that may be caused by the feedforward signal. Muting, forced restart, turning off the feedback microphone, and turning off the feedback microphone may be performed singly or in any combination.

[0048] The detection and mitigation methods described herein are advantageously not limited to a subset of instabilities. Instead, the methods detect instabilities across a wide frequency spectrum. In aspects, instability triggers muting the driver. In addition to or instead of muting the driver, instability (i.e., some instability over a given amount of time) may cause the device to reboot. In addition to or instead of muting and / or rebooting the device, the feedback microphone and / or feedforward microphone may be turned off so that no feedback or feedforward signals are sent to the driver and output to the user.

[0049] Although the description of the embodiments of the present disclosure has been presented above for purposes of illustration, it may be noted that the embodiments of the present disclosure are not intended to be limited to any of the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0050] Reference has been made above to aspects of the present disclosure. However, the scope of the present disclosure is not limited to the particular described aspects. Aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which may be generally referred to herein as "components," "circuits," "modules," or "systems." Furthermore, aspects of the present disclosure may take the form of a computer program product, such as a computer program tangibly embodied in one or more information carriers, such as non-transitory computer-readable mediums or storage devices, having readable program code embodied thereon.

[0051] Any combination of one or more computer-readable media may be utilized. The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. The computer-readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media include an electrical connection having one or more wires, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the present context, a computer-readable storage medium may be any tangible medium capable of storing a program.

[0052] The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various aspects. In this regard, each block in the flowcharts or block diagrams may correspond to a module, segment, or portion of instructions, including one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions described in the blocks may occur out of the order depicted in the figures. For example, two blocks shown in succession may in fact be executed substantially simultaneously, or in some cases, the blocks may be executed in the reverse order, depending on the functionality involved. It should also be noted that each block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, may be implemented in a dedicated hardware-based system performing a particular function or operating a combination of dedicated hardware and computer instructions.

Claims

1. 1. A method performed by an audio output device, comprising: receiving, by an instability detector, a feedback signal from a feedback microphone of the audio output device; muting a driver of the audio output device based at least in part on a characteristic of the feedback signal; and triggering a restart of the audio output device when the driver is muted a threshold number of times over a defined period of time based at least in part on the characteristic of the feedback signal.

2. The method of claim 1 , wherein the characteristic of the feedback signal comprises the feedback signal exceeding a threshold A-weighted decibel (dBA) level.

3. The method of claim 2 , wherein the feedback signal exceeds the threshold A-weighted decibel (dBA) level for a predetermined period of time.

4. The method of claim 1 , wherein the feedback microphone detects signals between 20 Hz and 24 kHz.

5. The method of claim 1 , wherein muting the driver comprises muting the driver for a predetermined amount of time.

6. turning off at least one of the feedback microphone or the feedforward microphone based at least in part on the characteristic of the feedback signal; The method of claim 1 further comprising:

7. 1. An audio output device, comprising: a memory in a first earpiece coupled to at least one processor, the memory including: causing the at least one processor to receive a first feedback signal from a first feedback microphone; muting a first driver of the audio output device based at least in part on a characteristic of the first feedback signal; an audio output device having stored thereon instructions for triggering a restart of the audio output device when the first driver is muted a threshold number of times over a defined period of time based at least in part on the characteristic of the first feedback signal.

8. 8. The audio output device of claim 7, wherein the characteristic of the first feedback signal includes the first feedback signal exceeding a threshold A-weighted decibel (dBA) level.

9. 9. The audio output device of claim 8, wherein the first feedback signal exceeds the threshold A-weighted decibel (dBA) level for a predetermined period of time.

10. The audio output device of claim 7 , wherein the first feedback microphone detects signals between 20 Hz and 24 kHz.

11. 8. The audio output device of claim 7, wherein the instructions to mute include instructions to mute the first driver for a predetermined amount of time.

12. The audio output device:

8. The audio output device of claim 7, further comprising instructions to turn off at least one of the first feedback microphone or a first feedforward microphone in the first earpiece based at least in part on the characteristic of the first feedback signal.

13. and at least one processor in the second earpiece, the memory including: receiving, by the processor in the second earpiece, a second feedback signal from a second feedback microphone; 8. The audio output device of claim 7, further comprising stored instructions for muting a second driver of the audio output device based at least in part on a characteristic of the second feedback signal.

14. The audio output device of claim 13 , wherein the instructions cause the audio output device to independently mute the first driver and the second driver.

15. 1. An audio output device, comprising: a feedback microphone, a driver, and an instability detector, the instability detector comprising: receiving a feedback signal from the feedback microphone of the audio output device; triggering a mute of the driver based at least in part on a characteristic of the feedback signal; an audio output device configured to trigger a restart of the audio output device when the driver is muted a threshold number of times over a defined period of time based at least in part on the characteristic of the feedback signal.

16. 16. The audio output device of claim 15, wherein the characteristic of the feedback signal comprises the feedback signal exceeding a threshold A-weighted decibel (dBA) level for a predetermined amount of time.

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