EP4677863A1

EP4677863A1 - Howling prevention

Info

Publication number: EP4677863A1
Application number: EP24734668.7A
Authority: EP
Inventors: Xiaoran FAN; Liyang Rui; Govind Kannan; Trausti Thormundsson
Original assignee: Google LLC
Current assignee: Google LLC
Priority date: 2024-05-24
Filing date: 2024-05-24
Publication date: 2026-01-14
Also published as: WO2025244651A1

Abstract

Techniques and apparatuses are described for performing howling prevention. In example aspects, a hearable (102) includes an acoustic circuit (116). The hearable (102) employs howling prevention (124) to monitor for one or more conditions that can lead to the unintentional generation of howling (122) via the acoustic circuit (116). Upon detecting a condition, the hearable (102) appropriately configures the acoustic circuit (116) to prevent howling (122) from occurring. Using various sensing techniques, the hearable (102) can quickly detect the condition and proactively adjust a gain of the acoustic circuit (116) to maintain stability of the acoustic circuit (116) and avoid howling (122). With howling prevention (124), an overall user experience with hearables (102) is improved while supporting features such as active noise cancellation and/or a transparency mode. Furthermore, some hearables (102) can be configured to perform howling prevention (124) without the need for additional hardware.

Description

HOWLING PREVENTION

BACKGROUND

[0001] Wireless technology has become prevalent in every day life, making communication and data readily accessible to users. One ty pe of wireless technology' are wireless hearables, examples of which include wireless earbuds and wireless headphones. Wireless hearables have allowed users freedom of movement while listening to audio content from music, audio books, podcasts, and videos. With the prevalence of wireless hearables, there is a market for adding additional features to existing hearables without introducing hardw are changes.

SUMMARY

[0002] Techniques and apparatuses are described for performing howling prevention. In example aspects, a hearable includes an acoustic circuit, which can perform active noise cancellation and/or can provide a transparency mode. The hearable employs howling prevention to monitor for one or more conditions that can lead to the unintentional generation of howling via the acoustic circuit. Upon detecting a condition, the hearable appropriately configures the acoustic circuit to prevent howling from occurring. Using various sensing techniques, the hearable can quickly detect the condition and proactively adjust a gain of the acoustic circuit to maintain stability' of the acoustic circuit and avoid howling. With howling prevention, an overall user experience with hearables is improved while supporting features such as active noise cancellation and/or a transparency mode. Furthermore, some hearables can be configured to perform howling prevention without the need for additional hardware.

[0003] Aspects described below include a method for performing howling prevention using a hearable that is positioned at an ear of a user. The method includes causing an acoustic circuit of the hearable to operate in accordance with a first state. The first state has a first amount of gain. The method also includes detecting, during a first time period and using at least one sensor of the hearable, movement of the hearable relative to the ear of the user. The method additionally includes causing, based on the detecting, the acoustic circuit to operate in accordance with a second state. The second state has a second amount of gain that is less than the first amount.

[0004] Aspects described below include a computer-readable storage medium comprising instructions that, responsive to execution by a processor, cause a hearable to perform any one of the methods described herein. [0005] Aspects described below include a device with at least one sensor, at least one acoustic circuit, and at least one processor. The device is configured to perform, using the at least one sensor and the at least one processor, any one of the methods described herein.

[0006] Aspects described below include a system with means for performing howling prevention.

BRIEF DESCRIPTION OF DRAWINGS

[0007] Apparatuses for and techniques that perform howling prevention are described with reference to the following drawings. The same numbers are used throughout the drawings to reference like features and components:

FIG. 1 illustrates an example environment in which how ling prevention can be implemented;

FIG. 2-1 illustrates example changes in a position of a hearable relative to a user's ear;

FIG. 2-2 illustrates an example feedback path that may cause an acoustic circuit to produce howling;

FIG. 3 illustrates example components of a computing device;

FIG. 4 illustrates example components of a hearable capable of performing howling prevention;

FIG. 5 illustrates an example scheme for performing aspects of howling prevention;

FIG. 6 illustrates an example implementation of a hearable;

FIG. 7 illustrates an example implementation of ho wling-prev ention logic;

FIG. 8 illustrates an example implementation of an acoustic sensor;

FIG. 9 illustrates example operations of two hearables performing active acoustic sensing;

FIG. 10 illustrates an example implementation of a hearable capable of performing howling prevention using active acoustic sensing;

FIG. 11 illustrates an example sensor signal of an acoustic sensor for performing aspects of howling prevention;

FIG. 12 illustrates an example sensor signal of an optical sensor for performing aspects of howling prevention;

FIG. 13 illustrates an example method for performing how ling prevention;

FIG. 14 illustrates another example method for performing howling prevention using active acoustic sensing; and

FIG. 15 illustrates an example computing system embodying, or in which techniques may be implemented that enable use of, howling prevention. DETAILED DESCRIPTION

[0008] Wireless hearables can provide users freedom of movement while listening to audio content. To further improve the user experience, some wireless hearables can provide additional features, such as active noise cancellation (ANC) or a transparency mode (TM). With active noise cancellation, a wireless hearable attenuates noise that is present in an external environment to make it easier for the user to hear the audio content. In contrast, the transparency mode enables sounds from the external environment to pass through the hearable to the user’s ear. In some cases, the transparency mode enables the hearable to function as a hearing aid and further amplify the sounds from the external environment to assist with a hearing impairment.

[0009] There can be several challenges, however, in implementing an acoustic circuit that performs the active noise cancellation and/or provides the transparency mode. One such challenge involves a susceptibility of the acoustic circuit to producing an undesired “howling’' (or “whistling”) sound. Generally speaking, howling is an audible, high-intensity signal that can cause some users discomfort. The howling can occur when a feedback loop of the acoustic circuit becomes unstable due to a sudden injection of noise at a microphone of the hearable. In some instances, this noise injection occurs as the user repositions the hearable. Left unchecked, the howling can continue to be amplified by the acoustic circuit to a level that can potentially damage the user’s hearing and/or can potentially damage components of the hearable 102 (e.g.. a speaker or the microphone).

[0010] To address this problem, some hearables can detect the howling and take steps to suppress it. The problem with these reactive techniques is that there is an inherent delay between when the howling starts and when it is adequately suppressed. During this delay, the user can experience discomfort while listening to the howling and waiting for it to subside. As the howling sound can, at the very least, be annoying to the user, its occurrence can degrade the overall user experience with the hearable.

[0011] In contrast to the reactive techniques described above, proactive techniques are described that perform howling prevention. In example aspects, a hearable includes an acoustic circuit, which can perform active noise cancellation and/or can provide a transparency mode. The hearable employs howling prevention to monitor for one or more conditions that can lead to the unintentional generation of howling via the acoustic circuit. Upon detecting a condition, the hearable appropriately configures the acoustic circuit to prevent howling from occurring. An example condition involves the user repositioning the hearable, which causes an insertion depth and/or an orientation of the hearable to change. Using various sensing techniques, the hearable can quickly detect the movement of the hearable and adjust a gain of the acoustic circuit to maintain stability of the acoustic circuit and avoid howling. With howling prevention, an overall user experience with hearables is improved while supporting features such as active noise cancellation and/or a transparency mode. Furthermore, some hearables can be configured to perform howling prevention without the need for additional hardware.

Operating Environment

[0012] FIG. 1 is an illustration of an example environment 100 in which howling prevention can be implemented. In the example environment 100, a hearable 102 is connected to a computing device 104 using a physical or wireless interface. The hearable 102 is a device that can play audio content provided by the computing device 104 and direct the audio content into a user 106’s ear 108. In this example, the hearable 102 operates together with the computing device 104. In other examples, the hearable 102 can operate or be implemented as a stand-alone device. Although depicted as a smartphone, the computing device 104 can include other types of devices, including those described with respect to FIG. 3.

[0013] To use the hearable 102, the user 106 positions the hearable 102 at the ear 108 in a manner that creates at least a partial seal 110 around or in the ear 108. Some parts of the ear 108 are shown in FIG. 1, including the ear canal 112 and an ear drum 114 (or tympanic membrane). While positioned at the user 106’s ear 108, the hearable 102 can render the audio content to the user 106 or perform additional functions, as further described below.

[0014] In this example, the hearable 102 includes at least one acoustic circuit 116 providing at least one of adaptive noise cancellation and/or transparency (e g., a transparency mode). Example acoustic circuits 116 include an active-noise-cancellation (ANC) circuit 118 (ANC circuit 118) and a transparency -mode circuit 120 (TM circuit 120). A single hybrid audio circuit can provide both adaptive noise cancellation and transparency. Using the active-noise-cancellation circuit 118, the hearable 102 performs active noise cancellation to reduce environmental sounds (e.g., background noise) at the ear 108. This can make it easier for the user 106 to hear the audio content. In contrast to the active-noise-cancellation circuit 118, the transparency-mode circuit 120 provides (and optionally amplifies) the environmental sounds for the user 106. This can make it easier for the user 106 to hear another person speaking while wearing the hearable 102.

[0015] A design of the acoustic circuit 116 can cause the acoustic circuit 116 to be susceptible to producing howling 122. Howling 122 is a high-intensity, audible sound that can cause some users 106 discomfort. The howling 122 can occur when a feedback loop of the acoustic circuit 116 becomes unstable due to a sudden injection of noise at a microphone of the hearable 102. Left unchecked, the howling 122 can be amplified by the acoustic circuit 116 to a level that can potentially damage the user 106’s hearing and/or can potentially damage components of the hearable 102 (e.g., a speaker or the microphone).

[0016] To avoid this situation, the hearable 102 performs howling prevention 124, which is a proactive technique that prevents howling 122 from occurring. Explained another way, howling prevention 124 enables the acoustic circuit 116 to maintain stability^ (e.g., maintain a stable condition or state) such that howling 122 is not generated by the acoustic circuit 1 16. To perform howling prevention 124, the hearable 102 can employ various sensing techniques to detect one or more conditions that can lead to the unintentional generation of the howling 122 based on a current operational state of acoustic circuit 116. In example implementations, the hearable 102 can use active acoustic sensing 126, optical sensing 128, capacitive sensing 130, or some combination thereof to detect a condition. Each of these sensing techniques occur at the ear 108 and are further described below.

[0017] Active acoustic sensing 126 involves, at least in part, measuring properties associated with an acoustic circuit that fonns between the hearable 102, the ear canal 112, and the ear drum 1 14 due to the seal 110. The properties of the acoustic circuit can change due to a variety⁷ of different situations or actions, including movement of the hearable 102. In general, the repositioning of the hearable 102 at the ear 108 can modulate an amplitude and/or phase of an acoustic signal that propagates through the ear canal 112 and is received using active acoustic sensing 126. Active acoustic sensing 126 can be performed without the use of other auxiliary sensors, such as an optical sensor or an electrical sensor.

[0018] In some implementations, active acoustic sensing 126 can have a higher sensitivity to detecting movement of the hearable 102 compared to other sensing techniques. This is because a w avelength of an acoustic signal that is received using active acoustic sensing 126 can be, in some implementations, on-par with a distance the hearable 102 moves due to the repositioning. This causes characteristics of the acoustic signal to be modified by a significant amount (e.g., a readily detectable amount) compared to other motions that are much larger relative to the wavelength of the acoustic signal.

[0019] Optical sensing 128 can involve active and/or passive sensing techniques. In a first example implementation, optical sensing 128 involves detecting an optical signal that reflects off of some portion of the ear 108. In some cases, a distance can be measured based on an amount of time it takes the emitted light to be received. In a second example implementation, optical sensing 128 involves sensing an amount of light that is visible at the hearable 102. In other words, it determines a degree to which ambient light is blocked by the user 106’s ear 108. The optical signal can have frequencies associated with visible light, infrared, and/or ultraviolet light. Variations in the received optical signal can indicate movement of the hearable 102 relative to the ear 108.

[0020] Capacitive sensing 130 involves detecting a change in capacitive coupling between the user 106's ear 108 and a sensor. As the hearable 102 moves, the measured capacitance can change and this change can be detected to determine that the user 106 is repositioning the hearable 102.

[0021] To perform any of the described sensing techniques, the hearable 102 includes at least one sensor 132. Example sensors 132 are further described with respect to FIG. 4. In some implementations, the sensor 132 performs additional functions, such as on-head detection, biometric sensing, and so forth. In general, the sensor 132 can detect movement of the hearable 102 relative to the user 106’s ear 108. This movement can occur, for instance, while the user 106 repositions the hearable 102. An example repositioning of the hearable 102 is further described with respect to FIG. 2-1.

[0022] FIG. 2-1 illustrates example changes in a position of the hearable 102 relative to the user 106’s ear 108. While using and/or wearing a hearable 102, the user 106 may adjust a position of the hearable 102 relative to their ear 108. At 200-1, the user 106 changes an orientation of the hearable 102 by rotating and/or twisting the hearable 102 clockwise or counter-clockwise, as indicated at 202. At 200-2. the user 106 changes an insertion depth of the hearable 102 by pushing the hearable 102 farther into their ear 108 or pulling it farther out of their ear 108, as indicated at 204. Generally speaking, adjusting or re-adjusting a position of the hearable 102 can refer to changing an orientation of the hearable 102, rotating the hearable 102, changing an insertion depth of the hearable 102, changing a distance between the hearable 102 and the ear canal 112, and/or repositioning the hearable 102 at the ear 108.

[0023] An intentional repositioning of the hearable 102 by the user 106 can have a significantly greater impact on a signal generated by the sensor 132 compared to other body motions or activities (e.g., talking, w alking, runningjumping, or chewing), which may inadvertently change a position of the hearable 102. Sometimes signal fluctuations caused by the intentional repositioning of the hearable 102 by the user 106 can be on the order of several times greater than fluctuations indirectly caused by other activities (e g., two times greater, ten times greater, thi rty times greater, and so forth). Changing the position of the hearable 102 can sometimes lead to howling 122, as further described with respect to FIG. 2-2.

[0024] FIG. 2-2 illustrates an example feedback path that may cause the acoustic circuit 116 to produce howling 122. The hearable 102 is shown to include the acoustic circuit 116, at least one speaker 206, and at least one microphone 208. In the depicted configuration, the hearable 102 includes a first microphone 208-1 and a second microphone 208-2. The first microphone 208-1 represents a feedforward microphone, and the second microphone 208-2 represents a feedback microphone.

[0025] The first microphone 208-1 is oriented towards an external environment. In other words, the first microphone 208-1 is oriented away from the user 106's ear canal 112. For active noise cancellation and/or for the transparency mode, the first microphone 208-1 provides information regarding sounds that are present within the external environment.

[0026] The speaker 206 and the second microphone 208-2 are oriented towards the user 106’s ear canal 112. In other words, the speaker 206 and the second microphone 208-2 are oriented away from the external environment. For active noise cancellation and/or the transparency mode, the second microphone 208-2 provides information regarding the sounds that are present within the ear canal 112. This information can be used to tune the performance of the acoustic circuit 116. [0027] The acoustic circuit 116 is coupled to the speaker 206 and the microphones 208-1 and 208-2. A feedback path 210 exists from the speaker 206 to the second microphone 208-2. When the user 106 repositions the hearable 102 (as described with respect to FIG. 2-1), noise 212 is produced. More specifically, this noise 212 can occur from the hearable 102 moving against the user 106’s ear 108. The noise 212 can be sensed by the microphone 208-2 and injected into the feedback path 210 of the acoustic circuit 116. Left unchecked, this noise 212 can cause the acoustic circuit 116 to become unstable and generate howling 122.

[0028] The acoustic circuit 116 can selectively operate in one of multiple states 214-1 to 214-S, where S represents a positive integer that is greater than or equal to two. Each state 214 provides a different tradeoff between performance 216 and a howling risk 218 (e g., a risk of howling occurring due to movement of the hearable 102). Generally speaking, the acoustic circuit 116 can realize a higher level of performance 216 at the cost of a higher risk of howling 122. Alternatively, the acoustic circuit 116 can accept a lower level of performance 216 to decrease the howling risk 218.

[0029] For active noise cancellation, the performance 216 can indicate a degree to which the acoustic circuit 116 cancels environmental noise at the user 106’s ear 108. For the transparency mode, the performance 216 can indicate a degree to which the acoustic circuit 116 provides sounds from the external environment to the user 106’s ear 108. The performance 216 of the acoustic circuit 116 is based, at least in part, on a gain 220 of the acoustic circuit 116. For active noise cancellation, for instance, a higher gain 220 can enable the environmental noise to be attenuated by a larger amount at the user 106’s ear 108. For the transparency mode, a higher gain 220 can enable the sounds from the external environment to be presented at the user 106’s ear 108 with a higher amplitude. [0030] For explanation purposes, the gain 220 is considered to have a direct relationship between the gain 220 of the acoustic circuit 116 and the performance 216 of the acoustic circuit 116. This means that increasing the gain 220 improves the performance 216 of the acoustic circuit 116 while decreasing the gain 220 degrades the performance 216 of the acoustic circuit 116. Additionally, the gain 220 is considered to have a direct relationship between the gain 220 of the acoustic circuit 116 and the howling risk 218. This means that increasing the gain 220 increases the howling risk 218, and decreasing the gain 220 decreases the howling risk 218. Although defined in this manner, the concepts for howling prevention 124 can be readily adapted to other definitions of the gain 220 that may have an inverse relationship with the perfonnance 216 and the howling risk 218.

[0031] Consider an example in which the acoustic circuit 116 can operate in accordance with a first state, which is represented by state 214-1, or a second state, which is represented by state 214-S. The first state 214-1 represents a nonnal mode (or a responsive mode) in which the acoustic circuit 116 can quickly provide a signal with a desired amount of gain for active noise cancellation and/or for a transparency mode based on the information provided by the microphones 208-1 and/or 208-2. To provide the designed signal, the acoustic circuit 116 applies a first amount of gain 220. Due to the gain 220 of the first state 214-1, the acoustic circuit 116 has an increased risk of becoming unstable if noise 212 is injected into the feedback path 210. As such, the first state 214-1 has a significantly higher risk of generating howling 122 if the user 106 changes the position of the hearable 102.

[0032] In contrast, the second state 214-S represents a light mode (or a conservative mode) in which the acoustic circuit 116 provides a signal with less gain 220 for active noise cancellation and/or for to reduce the nsk of the acoustic circuit 116 becoming unstable due to noise 212. In particular, the acoustic circuit 116 applies a second amount of gain 220 that is less than the first amount associated with the first state 214-1. The smaller gain 220 of the second state 214-S enables the acoustic circuit 116 to maintain a stable condition (or improves a probability of the acoustic circuit 116 maintaining a stable condition) even if the noise 212 is injected into the feedback path 210. As such, the second state 214-S significantly decreases the risk of howling 122 if the user 106 changes the position of the hearable 102.

[0033] As explained above, the first state 214-1 is designed for improving the performance 216 of the acoustic circuit 116 while the second state 214-S is designed to avoid howling 122 by reducing the howling risk 218. In example implementations, the gain 220 of the first state 214-1 is several decibels greater than the gain 220 of the second state 214-S. For example, the gain 220 of the first state 214-1 can be approximately tw o, three, four, six, or ten decibels greater than the gain 220 of the second state 214-S. Although two example states are described above, the acoustic circuit 116 can be designed to operate with any quantity of states 214. For example, other states 214 can exist between the first state 214-1 and the second state 214-S to provide further options regarding the performance 216 and the howling risk 218.

[0034] In an example implementation, the acoustic circuit 116 includes at least one combiner 222 and at least one amplifier 224. The combiner 222 has inputs coupled to the microphones 208-1 and 208-2. The amplifier 224 is coupled between the combiner 222 and the speaker 206. Although not explicitly shown, the acoustic circuit 116 can include one or more components that are coupled between the combiner 222 and the microphones 208-1 and/or 208-2, coupled between the combiner 222 and the amplifier 224, coupled between the amplifier 224 and the speaker 206, or some combination thereof.

[0035] In this example, the amplifier 224 represents an output amplification stage of the acoustic circuit 116. Generally speaking, the gain 220 of the acoustic circuit 116 is at least partially dependent on a gain of the amplifier 224. In some cases, the gain 220 of the acoustic circuit 116 represents the gain of the amplifier 224. For instance, the various states 214-1 to 214-S can specify different gains of the amplifier 224 to realize the desired performance 216 and howling risk 218. [0036] In general, the gain 220 of the acoustic circuit 116 represents a gain of one or more amplifiers 224 that are coupled between the microphone 208-2 and the speaker 206. This means that the amplifier 224 is at least a part of the feedback path 210 and can amplify the noise 212 that is received by the microphone 208-2. Appropriately adjusting the gain of the amplifier 224 can enable the acoustic circuit 116 to realize the target performance 216 and howling risk 218 for a particular state 214.

[0037] One aspect of howling prevention 124 involves dynamically adjusting an active state of the acoustic circuit 116 to manage the howling risk 218 and the performance 216 of the acoustic circuit 116, as further described with respect to FIGs. 5 and 6. The computing device 104 and the hearable 102 are further described with respect to FIGs. 3 and 4, respectively.

[0038] FIG. 3 illustrates an example implementation of the computing device 104. The computing device 104 is illustrated with various non-limiting example devices including a desktop computer 104-1, a tablet 104-2, a laptop 104-3, a television 104-4, a computing watch 104-5, computing glasses 104-6, a gaming system 104-7, a microwave 104-8, and a vehicle 104-9. Other devices may also be used, such as an augmented and/or virtual reality headset, a home service device, a smart speaker, a smart thermostat, a baby monitor, a Wi-Fi™ router, a drone, a trackpad, a drawing pad, a netbook, an e-reader, a home automation and control system, a wall display, and another home appliance. Note that the computing device 104 can be wearable, non-wearable but mobile, or relatively immobile (e.g., desktops and appliances).

[0039] The computing device 104 includes one or more computer processors 302 and at least one computer-readable medium 304, which includes memory media and storage media. Applications and/or an operating system (not shown) embodied as computer-readable instructions on the computer-readable medium 304 can be executed by the computer processor 302 to provide some of the functionalities described herein. The computer-readable medium 304 can optionally include an application 306. In example implementations, the application 306 can render audio content for the user. Other implementations are also possible in which the application 306 can control an operation of the hearable 102 to activate or deactivate certain features, such as active noise cancellation and/or a transparency mode.

[0040] The computing device 104 can also include a network interface 308 for communicating data over wired, wireless, or optical networks. For example, the network interface 308 may communicate data over a local-area-network (LAN), a wireless local-area-network (WLAN), a personal-area-network (PAN), a wire-area-network (WAN), an intranet, the Internet, a peer-to- peer network, point-to-point network, a mesh network, Bluetooth®, and the like. The computing device 104 may also include the display 310. Although not explicitly shown, the hearable 102 can be integrated within the computing device 104, or can connect physically or wirelessly to the computing device 104. The hearable 102 is further described with respect to FIG. 4.

[0041] FIG. 4 illustrates an example hearable 102. The hearable 102 is illustrated with various non-limiting example devices, including wireless earbuds 402-1, wired earbuds 402-2, and headphones 402-3. The earbuds 402-1 and 402-2 are a type of in-ear device that fits into the ear canal 112. Each earbud 402-1 or 402-2 can represent a hearable 102. Headphones 402-3 can rest on top of or over the ears 108. The headphones 402-3 can represent closed-back headphones, open-back headphones, on-ear headphones, or over-ear headphones. Each headphone 402-2 includes two hearables 102, which are physically packaged together. In general, there is one hearable 102 for each ear 108. The headphones 402-3 may be designed in some manner or may utilize techniques, such as beamforming, to assist with directing signals used for active acoustic sensing 126 into the ear canal 112. The hearable 102 can also represent a hearing aid (not shown). [0042] The hearable 102 includes at least one speaker 206, at least one microphone 208, and at least one acoustic circuit 116. In example implementations, the acoustic circuit 116 can be implemented using the active-noise-cancellation circuit 118 or the transparency -mode circuit 120. In some cases, the hearable 102 includes both the active-noise-cancellation circuit 118 and the transparency-mode circuit 120. [0043] The hearable 102 also includes a communication interface 404 to communicate with the computing device 104, though this need not be used when the hearable 102 is integrated within the computing device 104. The communication interface 404 can be a wired interface or a wireless interface, in which audio content is passed from the computing device 104 to the hearable 102. The hearable 102 can also use the communication interface 404 to pass data associated with howling prevention 124 to the computing device 104. In general, the data provided by the communication interface 404 is in a format usable by the application 306 or another application of the computing device 104. The communication interface 404 also enables the hearable 102 to communicate with another hearable 102.

[0044] Additionally, the hearable 102 includes at least one system processor 406 and at least one system medium 408 (e.g., one or more computer-readable storage media). In the depicted configuration, the system medium 408 includes howling-prevention logic 410. The howling- prevention logic 410 dynamically controls an active state 214 of the acoustic circuit 116 to enhance performance and to prevent howling 122 from occurring. Example implementations of the howling-prevention logic 410 are further described with respect to FIGs. 6 and 7. The howling-prevention logic 410 is also capable of detecting a condition that can cause the acoustic circuit 116 to produce howling 122 based on information provided by one or more sensors 132. [0045] As shown in FIG. 4, the hearable 102 also includes at least one sensor 132. The sensor 132 sensitive to movement of the hearable 102 that is caused by the user 106 repositioning the hearable 102 at their ear 108. In some implementations, the sensor 132 may not be particularly sensitive to other movements of the hearable 102 that are unintentionally caused by the user 106 performing another activity, such as walking, running, talking, and/or chewing. In addition to being able to detect the movement of the hearable 102, the sensor 132 is further able to detect the onset and the ending of the movement. By providing this information to the howling-prevention logic 410, the howling-prevention logic 410 and the sensor 132 operate together to perform aspects of howling prevention 124. In some implementations, the sensor 132 is also capable of performing on-head detection.

[0046] Example sensors 132 include an acoustic sensor 412, an optical sensor 414, and a capacitive sensor 416. The acoustic sensor 412 can perform active acoustic sensing 126 to detect if the hearable 102 is being repositioned by the user 106. Active acoustic sensing 126, also known as audioplethysmography, is capable of sensing subtle changes that are observable at the user 106’s outer and middle ear. To perform active acoustic sensing 126, the acoustic sensor 412 transmits and receives acoustic signals that at least partially propagate within the user 106’s ear canal 112. An example implementation and operation of the acoustic sensor 412 is further described with respect to FIGs. 8 and 9, respectively. In some implementations, the acoustic sensor 412 is implemented as an ultrasound sensor.

[0047] The acoustic sensor 412 can be implemented using existing hardware within the hearable 102. For example, the acoustic sensor 412 can be implemented using the speaker 206 and the microphone 208 of the hearable 102. In this case, howling prevention 124 can be implemented without the need for additional hardware. The acoustic sensor 412 can also be used to perform on-head detection. In some cases, the acoustic sensor 412 can have a faster sampling rate than another type of sensor, such as the optical sensor 414 and/or the capacitive sensor 416. This faster sampling rate can improve the reaction time for detecting the movement of the hearable 102 and appropriately configuring the acoustic circuit 116 to prevent howling 122.

[0048] The optical sensor 414 can perform optical sensing 128 to determine whether the hearable 102 is being repositioned by the user 106. In an example implementation, the optical sensor 414 is implemented using an infrared sensor. A footprint and cost of the infrared sensor can make it readily accessible for integrating within the hearable 102. Some implementations of the hearable 102 may already include an infrared sensor for on-head detection. In this case, the infrared sensor can also be used for howling prevention 124. Other example optical sensors 414, such as a camera or a photodetector, can also be implemented to perfomi aspects of howling prevention 124 for some hearables 102.

[0049] The capacitive sensor 416 can perform capacitive sensing 130 to determine whether the hearable 102 is being repositioned by the user 106. In an example implementation, the capacitive sensor 416 is implemented using a capacitor. A footprint and cost of the capacitive sensor 416 can make it readily accessible for integrating within the hearable 102. Some implementations of the hearable 102 may already include a capacitive sensor 416 for on-head detection. In this case, the capacitive sensor 416 can also be used for howling prevention 124.

[0050] Other types of sensors are also possible, such as an inertial measurement unit (IMU) and/or a radar sensor. The inertial measurement unit, however, can be sensitive to other movements that are made by the user 106, including those associated with certain activities. In this case, additional logic may be necessary' to distinguish between movements of the hearable 102 that are caused by normal activities and movements that are caused by the intentional repositioning of the hearable 102. An example operation of the howling-prevention logic 410 for performing howling prevention 124 is further described with respect to FIG. 5.

[0051] FIG. 5 illustrates an example scheme 500 implemented by the hearable 102 for performing howling prevention 124. At 502, the hearable 102 performs on-head detection. For example, the hearable 102 uses the sensor 132 (or another sensor) to determine whether the user 106 is wearing the hearable 102 (e.g., to determine whether the hearable 102 is at the user 106’s ear 108). At 504, the hearable 102 determines whether on-head detection is “true” or “false”. If on-head detection is false, the hearable 102 can wait a predetermine amount of time before returning to 502 and performing on-head detection. If on-head detection is true, the hearable 102 proceeds to 506.

[0052] In some implementations, the hearable 102 can optionally set an initial state of the acoustic circuit 116 at 508 prior to proceeding to 506. For example, the hearable 102 can configure the acoustic circuit 116 to be in the second state 214-S when activated. The second state 214-S can decrease the howling risk 218 of the acoustic circuit 116 relative to the first state 214-1, as explained with respect to FIG. 2-2. In situations in which the user 106 recently put the hearable 102 on and is more likely to readjust the hearable 102 to a more comfortable position, initializing the acoustic circuit 116 at the second state 214-S instead of the first state 214-1 can better configure the acoustic circuit 116 to prevent howling 122.

[0053] At 506, the hearable 102 detects if it is moving (e.g., determines if it is being adjusted or repositioned by the user 106). More specifically, the sensor 132 provides information that enables the howling-prevention logic 410 to determine if the hearable 102’s is moving. The movement of the hearable 102 can change its orientation and/or its insertion depth relative to the ear 108, as described with respect to FIG. 2-1. If the howling-prevention logic 410 determines that the hearable 102 is not moving (or is not moving by a sufficient amount to increase the risk of howling 122), the howling-prevention logic 410 causes the acoustic circuit 116 to operate in the first state 214-1, as shown at 510. The first state 214-1 enables the acoustic circuit 116 to enhance its performance 216. Alternatively, if the howling-prevention logic 410 detennines that the hearable 102 is moving (e.g., is moving by a sufficient amount to increase the risk of howling 122), the howling-prevention logic 410 causes the acoustic circuit 116 to operate in the second state 214-S, as shown at 512. The second state 214-S enables the acoustic circuit 116 to decrease its howling risk 218 and prevent howling 122 from occurring.

[0054] With the scheme 500 described above, the active state of the acoustic circuit 116 can be dynamically set to enhance performance 216 or to enhance howling prevention 124. For instance, upon detecting the condition, the howling-prevention logic 410 causes the acoustic circuit 116 to operate in accordance with the second state 214-S to enhance howling prevention 124. After the condition subsides or is no longer present, howling-prevention logic 410 causes the acoustic circuit 116 to operate in accordance with the first state 214-1 to prioritize performance 216. In contrast to reactive techniques, these techniques are proactive in preventing howling 122 from occurring and are proactive in enhancing performance 216 when the conditions indicate that howling 122 is less likely to occur. In this way, an overall experience of the user 106 is improved. An example relationship between the sensor 132, the howling-prevention logic 410, and the acoustic circuit 116 is further described with respect to FIG. 6.

[0055] FIG. 6 illustrates an example implementation of the hearable 102, which is capable of performing howling prevention 124. In the depicted configuration, the hearable 102 includes the acoustic circuit 116, the howling-prevention logic 410, and the multiple sensors 132-1 to 132-S. The multiple sensors 132-1 to 132-S include sensors that perform different sensing techniques, such as active acoustic sensing 126, optical sensing 128, capacitive sensing 130, or some combination thereof. The howling-prevention logic 410 is coupled to outputs of the sensors 132-1 to 132-S. Additionally, the howling-prevention logic 410 is coupled to an input of the acoustic circuit 116.

[0056] The howling-prevention logic 410 can be implemented using a variety of different ways. In a first example, the howling-prevention logic 410 is implemented using a signal processor, which uses signal-processing techniques to analyze signals provided by the sensors 132-1 to 132-S and to detect the one or more conditions that can cause the acoustic circuit 116 to generate howling 122. An example implementation of the howling-prevention logic 410 using the signal processor 602 is further described with respect to FIG. 7.

[0057] In a second example, the howling-prevention logic 410 is implemented using a machine- learned model 604. The machine-learned model 604 is composed of one or more neural networks. A neural network includes a group of connected nodes (e.g., neurons or perceptrons), w hich are organized into one or more layers. As an example, the machine-learned model 604 includes a deep neural network, which includes an input layer, an output layer, and one or more hidden layers positioned between the input layer and the output layers. The nodes of the deep neural network can be partially-connected or fully-connected between the layers.

[0058] In some implementations, the neural network is a recurrent neural network (e.g., a long short-term memory (LSTM) neural network) with connections between nodes forming a cycle to retain infonnation from a previous portion of an input data sequence for a subsequent portion of the input data sequence. In other cases, the neural network is a feed-forward neural network in which the connections between the nodes do not form a cycle. Additionally or alternatively, the machine-learned model 604 includes another type of neural network, such as a convolutional neural network. The machine-learned model 604 can also include one or more types of classification models. In example implementations, the machine-learned model 604 can be implemented using a single-channel -input machine-learned model or a multi-channel-input machine-learned model. The single-channel-input machine-learned model accepts information from a single sensor 132. The multi-channel-input machine-learned model accepts information from multiple sensors 132. In some implementations, an output of the machine-learned model 604 can indicate whether or not a condition that can cause howling 122 is detected (e.g., indicate whether or not the hearable 102 is moving by a significant amount that can lead to howling 122). [0059] In general, the machine-learned model 604 is trained using supervised learning to extract features from signals provided by the one or more sensors 132 and to determine whether the hearable 102 is moving by a sufficient amount based on these extracted features. The supervised learning can use simulated (e.g., synthetic) data or measured (e.g., real) data for training purposes. The supervised learning can include data that accounts for different positions of the hearable 102 relative to the ear canal 112. In this way. the machine-learned model 604 can successfully perform aspects of howling prevention 124 regardless of an insertion depth and/or an orientation of the hearable 102.

[0060] During operation, the acoustic circuit 116 is in an active state and operates to perform some function of the hearable 102. For example, the acoustic circuit 116 can operate to perform active noise cancellation and/or to provide a transparency mode. The sensors 132-1 to 132-S respectively generate sensor signals 608-1 to 608-S. The information provided by the sensor signals 608-1 to 608-S can indicate whether or not the hearable 102 is moving. In some implementations, the sensor signals 608-1 to 608-S represent signals having an amplitude and/or a phase. In this case, fluctuations in the amplitude and/or the phase of the signals can indicate that the hearable 102 is being repositioned by the user 106. Example signals are further described with respect to FIGs. 11 and 12.

[0061] The howling-prevention logic 410 analyzes the sensor signals 608-1 to 608-S to determine whether or not the hearable 102 is moving, as indicated at 506 in FIG. 5. The howling-prevention logic 410 generates a control signal 610, which controls an active state 612 of the acoustic circuit 116 based on this determination. In general, the control signal 610 causes the acoustic circuit 116 to operate in accordance with one of the states 214-1 to 214-S. If the howling- prevention logic 410 determines that the hearable 102 is not moving (or is not moving by a significant amount), the howling-prevention logic 410 generates the control signal 610 to cause the acoustic circuit 1 16 to be in the first state 214-1, as described at 510 in FIG. 5. Alternatively, if the howling-prevention logic 410 determines that the hearable 102 is moving (or is moving by a significant amount), the howling-prevention logic 410 generates the control signal 610 to cause the acoustic circuit 116 to be in the second state 214-S, as described at 512 in FIG. 5. An example implementation of the howling-prevention logic 410 is further described with respect to FIG. 7.

[0062] FIG. 7 illustrates an example implementation of the howling-prevention logic 410. In the depicted configuration, the howling-prevention logic 410 uses signal processing techniques to determine whether the hearable 102 is being repositioned. The howling-prevention logic 410 includes at least one buffer 702, at least one calculator, and at least one comparator. In the example shown, the one or more calculators can include a mean calculator 704, a variance calculator 706, and/or a cumulative sum calculator 708. The howling-prevention logic 410 also includes a comparator for each calculator. In this example, the howling-prevention logic 410 includes three comparators 710, 712, and 714, which are respectively coupled to the calculators 704, 706, and 708.

[0063] In this example, the howling-prevention logic 410 evaluates the sensor signal 608 in three different ways to determine whether the hearable 102 is moving. In particular, the howling- prevention logic 410 evaluates a mean, a variance, and a cumulative sum of the sensor signal 608. Other implementations of the howling-prevention logic 410 can utilize other techniques in addition to or instead of any of the described techniques. Still other implementations of the howling-prevention logic 410 can implement one of the described techniques (e.g., evaluates the cumulative sum of the sensor signal 608 but does not evaluate the mean and the variance) or can implement some other combination of the described techniques (e g., evaluates the mean and the variance but does not evaluate the cumulative sum). To evaluate the mean, the howling- prevention logic 410 also includes at least one subtractor 716, whose operation is further described below.

[0064] The howling-prevention logic 410 additionally includes a control signal generator 718. The control signal generator 718 generates the control signal 610 based on the information provided by the one or more comparators 710, 712, and/or 714. In some implementations, the control signal generator 718 can be implemented using one or more logic gates, including an AND gate and/or an OR gate.

[0065] During operation, the buffer 702 accepts time-domain samples of the sensor signal 608. The buffer 702 provides samples 720 of the sensor signal 608 that correspond with a predetermined window- size. In effect, the buffer 702 performs a windowing function such that the calculators 704 and 706 can be designed to operate on a particular quantity of samples. In some implementations, the buffer 702 functions as a moving window.

[0066] The mean calculator 704 computes a mean 722 of the samples 720. The subtractor 718 computes a difference 724 between the mean 722 and a base value 726 (e.g., a previously- computed mean 722 or a predetermined value). The variance calculator 706 calculates a variance 728 of the samples 720. The cumulative sum calculator 708 computes a cumulative sum 730 of the sensor signal 608. The outputs of the subtractor 718 and the calculators 706 and 708 are respectively evaluated by the comparators 710, 712, and 714. [0067] The comparator 710 compares the difference 724 to a first threshold 732 and generates a first result 734. The comparator 712 compares the variance 728 to a second threshold 736 and generates a second result 738. Likewise, the comparator 714 compares the cumulative sum 730 to a third threshold 740 and generates a third result 742. The results 734, 738, and 742 indicate whether the inputs to the comparators 710, 712, and 714 are greater than or less than the corresponding thresholds 732, 736, and 740, respectively. In many cases, an indication that the hearable 102 is moving is based on one or more of the results 734, 738, and 742 indicating that the corresponding input 724, 728, or 730 is greater than the corresponding threshold 732, 736, or 740.

[0068] The control signal generator 718 evaluates the results 734, 738, and 742 and appropriately generates the control signal 610. The control signal generator 718 can be designed in various ways to achieve a desired degree of howling prevention 124. In some cases, the control signal generator 718 can generate the control signal 610 to cause the acoustic circuit 116 to operate in the second state 214-S responsive to at least one of the results 734, 738, and 742 indicating that the corresponding threshold 732, 736, and 740 is exceeded. Also, the control signal generator 718 can generate the control signal 610 to cause the acoustic circuit 116 to operate in the first state 214-1 responsive to all of the results 734, 738, and 742 indicating that the corresponding thresholds 732. 736, and 740 are not exceeded. In this case, the howling-prevention logic 410 can quickly react to a potential howling-inducing condition and can be slower to return the acoustic circuit 116 to a high-performing state when the howling-inducing condition is no longer detected. [0069] In situations in which the acoustic circuit 116 can operate in accordance with more than two states 214, the control signal generator 718 can generate the control signal 610 in a different manner. For example, the control signal generator 718 can generate the control signal 610 to cause the acoustic circuit 116 to operate in any one of three different states depending on how many of the results 734, 738, and 742 indicate that the corresponding thresholds 732, 736, and 740 are exceeded. For example, if none of the results 734, 738, and 742 indicate that the corresponding thresholds 732, 736. and 740 are exceeded, the control signal 610 causes the acoustic circuit 1 16 to operate in a first state 214 associated with a highest gain 220. If one of the results 734, 738, or 742 indicate that the corresponding threshold 732, 736, or 740 is exceeded, the control signal 610 causes the acoustic circuit 116 to operate in another state 214 associated with a second-highest gain 220. If two of the results 734. 738, and/or 742 indicate that the corresponding thresholds 732, 736, and/or 740 is exceeded, the control signal 610 causes the acoustic circuit 116 to operate in another state 214 associated with a third-highest gain 220. In this manner, the howling-prevention logic 410 causes the acoustic circuit 116 to gradually decrease the gain 220 over time, thereby decreasing the performance 216 and reducing the howling risk 218, as more conditions (or results) indicate that the hearable 102 is moving within the wearer's ear 108. This technique of controlling the acoustic circuit 116 can further enable the hearable 102 to enhance the performance of the acoustic circuit 116 while performing howling prevention 124.

[0070] Although the howling-prevention logic 410 of FIG. 7 is shown to process a single sensor signal 608, the implementation shown in FIG. 7 can be modified to support the processing of multiple sensor signals 608-1 to 608-S. Other implementations are also possible in which the howling-prevention logic 410 uses an expiration of a timer, or another mechanism besides the sensor 132, to control when to cause the acoustic circuit 116 to transition back to a high- performance state 214 after movement of the hearable 102 is detected. In some example implementations, at least one of the sensors 132 includes the acoustic sensor 412. In another example implementation, one of the sensors 132 includes the acoustic sensor 412, such as an ultrasound sensor, and another one of the sensors 132 includes the optical sensor 414, such as an infrared sensor. An example implementation of the acoustic sensor 412 is further described with respect to FIG. 8.

Active Acoustic Sensing

[0071] FIG. 8 illustrates an example implementation of an acoustic sensor 412. In the depicted configuration, the acoustic sensor 412 includes at least one transducer 802 that can convert electrical signals into sound waves. The transducer 802 can also detect and convert sound waves into electrical signals. These sound waves may include ultrasonic frequencies and/or audible frequencies, either of which may be used for active acoustic sensing 126. In particular, a frequency spectrum (e.g., range of frequencies) that the transducer 802 uses to generate an acoustic signal can include frequencies from a low-end of the audible range to a high-end of the ultrasonic range, e.g., between 20 hertz (Hz) to 2 megahertz (MHz). Other example frequency spectrums for active acoustic sensing 126 can encompass frequencies between 20 Hz and 20 kilohertz (kHz), between 20 kHz and 2 MHz, between 20 and 60 kHz, or betw een 30 and 40 kHz.

[0072] In an example implementation, the transducer 802 has a monostatic topology. With this topology, the transducer 802 can convert the electrical signals into sound waves and convert sound waves into electrical signals (e.g., can transmit or receive acoustic signals). Example monostatic transducers may include piezoelectric transducers, capacitive transducers, and micro-machined ultrasonic transducers (MUTs) that use microelectromechanical systems (MEMS) technology. [0073] Alternatively, the transducer 802 can be implemented with a bistatic topology, which includes multiple transducers that are physically separate. In this case, a first transducer converts the electrical signal into sound waves (e.g., transmits acoustic signals), and a second transducer converts sound waves into an electrical signal (e.g., receives the acoustic signals). An example bistatic topology can be implemented using at least one speaker 804 and at least one microphone 806. The speaker 804 and the microphone 806 can be dedicated for active acoustic sensing 126 or can be used for both active acoustic sensing 126 and other functions of the hearable 102 (e.g., active noise cancellation, a transparency mode, passive audio sensing, presenting audio content to the user 106, or capturing the user 106’s voice). In some example implementations, the speaker 804 and the microphone 806 represent the speaker 206 and the microphone 208 that are coupled to the acoustic circuit 116.

[0074] During bistatic sensing, the acoustic sensor 412 can use the communication interface 404 to coordinate with another acoustic sensor 412 of another hearable 102 to support two-ear active acoustic sensing 126, as further described with respect to FIG. 9. In particular, the transmitting acoustic sensor 412 can communicate timing and waveform information to the receiving acoustic sensor 412 to enable the receiving acoustic sensor 412 to appropriately demodulate a received acoustic signal.

[0075] In general, the speaker 804 and the microphone 806 of the acoustic sensor 412 are directed towards the ear canal 112 (e g., oriented towards the ear canal 112). Accordingly, the speaker 804 can direct acoustic signals towards the ear canal 112, and the microphone 806 is responsive to receiving acoustic signals from the direction associated with the ear canal 112.

[0076] The hearable 102 includes at least one analog circuit 808, which includes circuitry and logic for conditioning electrical signals in an analog domain. The analog circuit 808 can include analog-to-digital converters, digital-to-analog converters, amplifiers, filters, mixers, and switches for generating and modifying electrical signals. In some implementations, the analog circuit 808 includes other hardware circuitry associated with the speaker 804 or microphone 806

[0077] The acoustic sensor 412 also includes at least one system processor 810 and at least one system medium 812 (e.g., one or more computer-readable storage media). In the depicted configuration, the system medium 812 includes a pre-processing module 814 and optionally includes a calibration module 816. The pre-processing module 814 and the calibration module 816 can be implemented using hardware, software, firmware, or a combination thereof. In this example, the system processor 810 implements the pre-processing module 814 and the calibration module 816. In an alternative example, the system processor 406 of the hearable 102 can implement at least a portion of the pre-processing module 814 and the calibration module 816. Operations of the pre-processing module 814 and the calibration module 816 are further described with respect to FIG. 10.

[0078] During active acoustic sensing 126, the repositioning of the hearable 102 changes a position of the transducer 802 relative to the ear canal 112. As such, acoustic signals that propagate through the ear canal 112 can travel along different paths relative to a previous position of the hearable 102. The acoustic sensor 412 can detect changes to the characteristics of the acoustic signal, as further described with respect to FIG. 11. This enables active acoustic sensing 126 to readily distinguish between the user 106 adjusting the hearable 102 and the user 106 performing some other activity. Different types of active acoustic sensing 126 are further described with respect to FIG. 9.

[0079] FIG. 9 illustrates example operations of two hearables 102-1 and 102-2. In a first example operation, the hearables 102-1 and 102-2 perform single-ear active acoustic sensing 126. This means that the hearables 102-1 and 102-2 independently perform active acoustic sensing 126 on different ears 108 of the user 106. In this case, the first hearable 102-1 is proximate to (arranged at) the user 106’s right ear 108, and the second hearable 102-2 is proximate to (arranged at) the user 106‘s left ear 108. Each hearable 102-1 and 102-2 includes an acoustic sensor 412-1 and 412-2. The hearables 102-1 and 102-2 can operate in a monostatic manner during the same time period or during different time periods. In other words, each hearable 102-1 and 102-2 can independently transmit and receive ultrasound signals.

[0080] For example, the first hearable 102-1 uses the acoustic sensor 412-1 to transmit a first acoustic transmit 902-1, which propagates within at least a portion of the user 106’s right ear canal 112. The first hearable 102-1 uses the acoustic sensor 412-1 to receive a first acoustic receive signal 904-1. The first acoustic receive signal 904-1 represents a version of the first acoustic transmit signal 902-1 that is modified, at least in part, by the acoustic circuit associated with the right ear canal 112. This modification can change an amplitude, phase, and/or frequency of the first acoustic receive signal 904-1 relative to the first acoustic transmit signal 902-1.

[0081] Similarly, the second hearable 102-2 uses the acoustic sensor 412-2 to transmit a second acoustic transmit signal 902-2, which propagates within at least a portion of the user 106’s left ear canal 112. The second hearable 102-2 uses the acoustic sensor 412-2 to receive a second acoustic receive signal 904-2. The second acoustic receive signal 904-2 represents a version of the second acoustic transmit signal 902-2 that is modified by the acoustic circuit associated with the left ear canal 112. This modification can change an amplitude, phase, and/or frequency of the second acoustic receive signal 904-2 relative to the second acoustic transmit signal 902-2. [0082] In a second example operation, the two hearables 102-1 and 102-2 perform two-ear active acoustic sensing 126. This means that the hearables 102-1 and 102-2 jointly perform acoustic sensing 126 across two ears 108 of the user 106. The hearables 102-1 and 102-2 operate together in a bistatic manner during the same time period.

[0083] During operation, the first hearable 102-1 transmits a third acoustic transmit 902-3 using the acoustic sensor 412-1. The third acoustic transmit signal 902-3 propagates through the user 106’s right ear canal 112. The third acoustic transmit signal 902-3 also propagates through an acoustic channel that exists between the right and left ears 108. In the left ear 108, the third acoustic transmit signal 902-3 propagates through the user 106's left ear canal 112 and is represented as a third acoustic receive signal 904-3. The second hearable 102-2 receives the third acoustic receive signal 904-3 using the acoustic sensor 412-2. The third acoustic receive signal 904-3 represents a version of the third acoustic transmit signal 902-3 that is modified by the acoustic circuit associated with the right ear canal 112. modified by the acoustic channel associated with the user 106’s face, and modified by the acoustic circuit associated with the left ear canal 1 12. This modification can change an amplitude, phase, and/or frequency of the third acoustic receive signal 904-3 relative to the third acoustic transmit signal 902-3. In some cases, the hearable 102-2 measures the time-of-flight (ToF) associated with the propagation from the first hearable 102-1 to the second hearable 102-2. Sometimes a combination of single-ear and two-ear active acoustic sensing 126 are applied to further improve measurement confidence.

[0084] The acoustic transmit signals 902 of FIG. 9 can represent a variety of different types of signals as described above with respect to FIG. 8. In example implementations, the acoustic transmit signal 902 can be a continuous-wave signal (e.g., a sinusoidal signal) or a pulsed signal. Some acoustic transmit signals 902 can have a particular tone (or frequency). Other acoustic transmit signals 902 can have multiple tones (or multiple frequencies). A variety' of modulations can be applied to generate the acoustic transmit signal 902. Example modulations include linear frequency modulations, triangular frequency modulations, stepped frequency modulations, phase modulations, or amplitude modulations. The acoustic transmit signal 902 can be transmitted as part of a calibration procedure or a measurement procedure, as further described as part of FIG. 10. [0085] FIG. 10 illustrates an example implementation of the hearable 102 capable of performing howling prevention 124 using active acoustic sensing 126. In the depicted configuration, the hearable 102 includes the acoustic sensor 412, which is coupled to the howling-prevention logic 410. The acoustic sensor 412 includes the speaker 804, the microphone 806, the analog circuit 808, the pre-processing module 814, and the calibration module 816. Other implementations of the hearable 102 are also possible in which the hearable 102 does not include the calibration module 816 to reduce processing power requirements. In this case, the preprocessing module 814 can perform aspects of frequency selection as further described below to improve the signal-to-noise ratio for active acoustic sensing 126.

[0086] Outputs of the speaker 804 and the microphone 806 are coupled to inputs of the analog circuit 808. The pre-processing module 814 has inputs that are coupled to outputs of the analog circuit 808. The pre-processing module 814 also has an output that is coupled to inputs of the howling-prevention logic 410 and the calibration module 816. In an example implementation, the pre-processing module 814 includes at least one in-phase and quadrature mixer (I/Q mixer) and at least one filter. The in-phase and quadrature mixer performs frequency down-conversion and can be implemented using at least two mixers, at least one phase shifter, and at least one combiner (e.g., a summation circuit). The filter attenuates intermodulation products that are generated by the in-phase and quadrature mixer. In an example implementation, the filter is implemented using a low-pass filter.

[0087] The pre-processing module 814 can optionally include at least one frequency selector. The frequency selector can identify and select one or more tones (or carrier frequencies) that provide a high-quality signal for later processing. The frequency selector can further pass the selected tones to other processing modules (e.g., the howling-prevention logic 410) and filter (or attenuate) other tones that are not selected. The frequency selector can be implemented in a similar manner as the calibration module 816, which is further described below'.

[0088] The calibration module 816 has an output that is coupled to the speaker 804. The calibration module 816 includes at least one frequency selector. The frequency selector can include at least one amplitude detector, at least one phase detector, at least one quality detector, and at least one comparator. Using the frequency selector, the calibration module 816 can perform a calibration procedure that determines appropriate characteristics (e.g., waveform or signal characteristics) of acoustic transmit signals 902 to improve active acoustic sensing 126 (e.g., to enhance the perfomiance of howling prevention 124). The calibration procedure enables active acoustic sensing 126 to take into account the wear of the hearable 102 (e.g., the position of the hearable 102 relative to the ear canal 112) and the physical structure of the ear canal 112 to determine a transmission frequency that can increase sensitivity.

[0089] Consider an example operation of the hearable 102 in accordance with single-ear active acoustic sensing 126. In this example, the hearable 102 includes the calibration module 816. With the calibration module 816, the hearable 102 can perform a calibration procedure prior to performing a measurement procedure. In some circumstances, the acoustic sensor 412 can perform on-head detection (or in-ear detection) by detecting the presence of the seal 110 and initiating the calibration procedure and/or the measurement procedure based on a determination that on-head detection is “true.” In other circumstances, the acoustic sensor 412 can initiate the calibration procedure based on a specified schedule or a timer, which can be controlled by the user 106 via the computing device 104 or the hearable 102. The calibration procedure and the measurement procedure are further descnbed below.

[0090] During both the calibration procedure and the measurement procedure, the speaker 804 transmits the acoustic transmit signal 902 and the microphone 806 receives the acoustic receive signal 904. During the calibration procedure, the acoustic transmit signal 902 and the acoustic receive signal 904 can have tones 1002-1 to 1002-M, where M represents a positive integer. The multiple tones 1002-1 to 1002-M can be transmitted in parallel or in series over a given time interval. In this case, the acoustic transmit signal 902 can have a particular bandwidth on the order of several kilohertz. For example, the acoustic transmit signal 902 can have a bandwidth of approximately 4. 5, 6, 8, 10, 16, or 20 kHz. In example implementations, the acoustic transmit signal 902 is transmitted over multiple seconds, such as 2, 3, 4, 6, or more seconds. A duration of each tone 1002 can be evenly divided over a total duration of the acoustic transmit signal 902. [0091] In an example implementation, the acoustic transmit signal 902 for the calibration procedure can have seven tones 1002 (e.g., equals 7). In some cases, the tones 1002 are evenly distributed across an interval. For example, the tones 1002 can be in 1 kHz increments between 32 kHz and 38 kHz (e.g., at approximately 32, 33, 34, 35, 36, 37, and 38 kHz). The term “approximately” means that the tones 1002 can be within 5% of a given value or less (e.g., within 3%, 2%, or 1% of the given value).

[0092] An amplitude of the calibration procedure’s acoustic transmit signal 902 can be approximately the same across the tones 1002-1 to 1002-M. In this manner, power is evenly distributed across each tone 1002. The quantity of tones 1002 (e.g., M) can be determined based on an output power of the speaker 804. Increasing the quantity of tones 1002 can increase a likelihood that the hearable 102 can support howling prevention 124 across various conditions including user wear and a physical structure of the user 106’s ear canal 112. However, an amplitude of the acoustic transmit signal 902 can be limited across these tones 1002 based on the output power of the speaker 804. Thus, the quantity of tones 1002 can be optimized based on an amount of output power that is available for active acoustic sensing 126.

[0093] During the measurement procedure, the acoustic transmit signal 902 and the acoustic receive signal 904 can have selected tones 1004-1 to 1004-N, where /V represents a positive integer that is less than or equal to M. The selected tones 1004-1 to 1004-N can represent a subset (sometimes a proper subset) of the tones 1002-1 to 1002-M. The selected tones 1004 can be transmitted in parallel or in series over a given time interval.

[0094] An amplitude of the measurement procedure’s acoustic transmit signal 902 can be approximately the same across the selected tones 1004-1 to 1004-N. In this manner, power is evenly distributed across each selected tone. The amplitude of the measurement procedure’s acoustic transmit signal 902 can be higher than the amplitude of the calibration procedure’s acoustic transmit signal 902 because the available output power is distributed across fewer tones. Additionally or alternatively, a duration of each of the selected tones 1004 of the measurement procedure’s acoustic transmit signal 902 can be longer than the duration of the tones 1002 of the calibration procedure’s acoustic transmit signal 902. The higher amplitude and/or the longer duration can further improve the signal-to-noise ratio performance of the acoustic sensor 412 for active acoustic sensing 126. By using a few selected tones 1004 that were determined to improve signal-to-noise ratio performance, the measurement procedure can achieve a higher level of accuracy and sensitivity for howling prevention 124.

[0095] The analog circuit 808 performs analog-to-digital conversion to generate a digital transmit signal 1006 and a digital receive signal 1008 based on the acoustic transmit signal 902 and the acoustic receive signal 904, respectively. The pre-processing module 814 perfonns frequency downconversion and demodulation to generate at least one pre-processed signal 1010 based on the digital transmit signal 1006 and the digital receive signal 1008. The pre-processing module 814 can also apply filtering to generate the pre-processed signal 1010.

[0096] Optionally, as part of the calibration procedure, the calibration module 816 processes the pre-processed signal 1010 to determine the selected tones 1004-1 to 1004-N. The selected tones 1004-1 to 1004-N can improve performance of active acoustic sensing 126 during the measurement procedure. To determine the selected tones 1004-1 to 1004-N, the calibration module 816 extracts the amplitude and/or phase of the pre-processed signal 1010 using the amplitude detector and the phase detector, respectively. The quality detector of the calibration module 816 measures quality metrics for each tone (or frequency) of the pre-processed signal 1010 and for each of the characteristics (e g., amplitude and/or phase). Example quality metrics can include peak-to-average ratios and/or signal-to-noise ratios. The peak-to-average ratio represents a peak intensity within a frequency range of interest divided by an average intensity within this frequency range. A higher quality metric indicates a higher-quality signal, or more generally, better performance for active acoustic sensing 126.

[0097] The comparator of the calibration module 816 can evaluate the quality metrics with respect to a threshold. In an example implementation, the comparator determines the selected tones 1004-1 to 1004-N for a subsequent measurement procedure based on the frequencies associated with the quality metrics that are greater than or equal to a threshold. Additionally or alternatively, the comparator can evaluate the quality metrics with respect to each other. In an example implementation, the comparator determines one of the selected tones based on a frequency with the highest quality metric across the amplitude. Also, the comparator can determine one of the selected tones 1004-1 to 1004-N based on a frequency with the highest quality metric across the phase. In other implementations, the comparator can determine a single selected tone based on a frequency having the highest quality metric associated with either the amplitude or the phase.

[0098] In general, the calibration module 816 enables the selected tones 1004-1 to 1004-N to be dynamically adjusted prior to the measurement procedure based on a current environment, which can account for a wear of the hearable 102 (e.g., a current insertion depth and/or rotation), a physical structure of the user 106’s ear canal 112, and a response characteristic of the hearable 102 (e.g., speaker, microphone, and/or housing). In this manner, the calibration module 816 can improve the signal-to-noise ratio performance of the acoustic sensor 412 for the measurement procedure. The calibration module 816 can also determine which tones 1004 generate acoustic receive signals 904 with desired characteristics for howling prevention 124. In general, the calibration procedure can be performed whether or not the user 106 is speaking.

[0099] The calibration module 816 communicates the selected tones 1004-1 to 1004-N to the speaker 804 using a control signal. The speaker 804 accepts the control signal that identifies the selected tones 1004-1 to 1004-N and can transmit a subsequent acoustic transmit signal 902 for howling prevention 124 using the selected tones 1004-1 to 1004-N. With the calibration procedure, the hearable 102 can dynamically adjust the transmission frequency (e.g., one or more carrier frequencies) each time the seal 110 is formed (e.g., based on the wear of the hearable 102) and based on the unique physical structure of the ear 108. Through this calibration procedure, the hearables 102 on different ears 108 may operate with one or more different ultrasound frequencies. [0100] As part of the measurement procedure, the howling-prevention logic 410 can perform aspects of howling prevention 124 using the pre-processed signal 1010 to generate the control signal 610. In this example, the pre-processed signal 1010 represents the sensor signal 608 of FIG. 6.

[0101] To perfonn howling prevention 124, the howling-prevention logic 410 analyzes the pre- processed signal 1010 and detects a significant variation or fluctuation in an amplitude and/or phase of the pre-processed signal 1010. This variation is caused by the movement of the hearable 102 as the user 106 repositions the hearable 102 at the ear 108. The how ling-prevention logic 410 can be implemented in a variety of ways to detect the variation in the pre-processed signal 1010, as described with respect to FIGs. 6 and 7.

[0102] In general, the term “significantly'’ can mean that the values of the amplitude and/or the phase can change by 20% or more relative to a previous value (e.g., relative to an average of a set of previous values). Additionally or alternatively, a slope of the amplitude and/or the phase can vary significantly. Sometimes the slope of the amplitude and/or the phase can change signs (e.g., from a positive slope to a negative slope, or vice versa). A magnitude of the slope of the amplitude and/or the phase can sometimes change by approximately 10% or more.

[0103] In FIG. 10. the calibration procedure and the measurement procedure are described as individual procedures that occur at different time intervals. In particular, the calibration procedure occurs before the measurement procedure. This enables the acoustic transmit signal 902 for the measurement procedure to be transmitted with fewer tones than the acoustic transmit signal 902 used for the calibration procedure, which can increase signal-to-noise ratio performance for active acoustic sensing 126. In some implementations, however, the hearable 102 can have sufficient output power to perform the measurement procedure with the multiple tones 1002-1 to 1002-M using a single acoustic transmit signal 902. In this case, aspects of the calibration module 816 can be integrated within the pre-processing module 814 via a frequency selector. This frequency selector can effectively pass the selected tones 1004-1 to 1004-N to the howling-prevention logic 410.

Sensor Signals

[0104] FIGs. 11 and 12 illustrate an impact of a user 106’s repositioning the hearable 102 on different types of sensor signals 608. As shown below, the repositioning of the hearable 102 can significantly impact an amplitude (or an intensity) and/or a phase of the sensor signal 608. In some instances, the change in the amplitude and/or the phase can be relative to a previous state or relative to a previous trend in the amplitude and/or the phase. The previous state can refer to values of the amplitude and/or the phase during which the user 106 does not intentionally move the hearable 102. The user 106 may or may not be performing other activities during this time. [0105] FIG. 11 includes a graph 1100 of an amplitude 1102 and a phase 1104 of a sensor signal 608 that is generated by an acoustic sensor 412. In the graph 1100, time is depicted along the horizontal axis. Between time TO and time Tl, the user 106 repositions the hearable 102, as indicated at 1106. This causes the amplitude 1102 and/or the phase 1104 of the acoustic receive signal 904 to change significantly relative to a previous state (e.g., a state prior to time TO). [0106] Prior to time TO and after time Tl, the user 106 does not intentionally move the hearable 102. With active acoustic sensing 126, the howling-prevention logic 410 can detect that the user 106 is repositioning the hearable 102 based on the change in the amplitude 1102 and/or the phase 1104 of the sensor signal 608.

[0107] FIG. 12 includes a graph 1200 of an intensity 1202 of a sensor signal 608 that is generated by an optical sensor 414. In this case, the optical sensor 414 is an infrared sensor. In the graph 1200, time is depicted along the horizontal axis. Between time TO and time Tl, the user 106 repositions the hearable 102, as indicated at 1204. This causes the intensity of the sensor signal 608 to change significantly relative to a previous state (e.g., a state prior to time TO).

[0108] Prior to time TO and after time 77, the user 106 does not intentionally move the hearable 102. With optical sensing 128, the howling-prevention logic 410 can detect that the user 106 is repositioning the hearable 102 based on the change in the intensity of the sensor signal 608.

Example Methods

[0109] FIGs. 13 and 14 depict example methods 1300 and 1400 for implementing aspects of howling prevention 124. Methods 1300 and 1400 are shown as sets of operations (or acts) performed but not necessarily limited to the order or combinations in which the operations are shown herein. Further, any of one or more of the operations may be repeated, combined, reorganized, or linked to provide a wide array of additional and/or alternate methods. In portions of the following discussion, reference may be made to the environment 100 of FIG. 1 and entities detailed in FIGs. 3 and 4, reference to which is made for example only. The techniques are not limited to performance by one entity or multiple entities operating on one device.

[0110] At 1302, an acoustic circuit of a hearable is caused to operate in accordance with a first state. The first state has a first amount of gain. For example, the howling-prevention logic 410 causes the acoustic circuit 116 to operate in accordance with the first state 214-1, which has a first amount of gain 220. In an example implementation, the first state 214-1 can represent a state 214 with the largest gain 220, and thereby the highest performance 216 and the highest howling risk 218. In some implementations, the gain 220 represents a gain of an amplifier 224 that is positioned within at least the feedback path 210 of the acoustic circuit 11 . The amplifier 22 can be part of an output amplification stage of the acoustic circuit 116 in some cases.

[0111] At 1304, movement of the hearable relative to an ear of a user is detected during a first time period and using at least one sensor of the hearable. For example, the howling-prevention logic 410 detects, during a first time period and using at least one sensor 132 of the hearable 102, movement of the hearable 102 relative to the ear 108 of the user 106. The movement can involve a change in an orientation of the hearable 102, as shown at 200-1 in FIG. 2-1, and/or a change in an insertion depth of the hearable 102, as shown at 200-2 in FIG. 2-1. The at least one sensor 132 can be implemented using an acoustic sensor 412 (e.g., an ultrasound sensor), an optical sensor 414 (e.g., an infrared sensor), a capacitive sensor 416, or some combination thereof.

[0112] At 1306, the acoustic circuit is caused to operate in accordance with a second state based on the detecting. The second state has a second amount of gain that is less than the first amount. For example, the howling-prevention logic 410 causes the acoustic circuit 116 to operate in accordance with a second state 214-S based on the detecting. The second state 214-S has a second amount of gain 220 that is less than the first amount. In some cases, a difference between the second amount and the first amount is at least one decibel. For example, the difference can be equal to approximately 1, 2, 4, or 6 decibels. In an example implementation, the second state 214-S can represent a state 214 with the smallest gain 220, and thereby the lowest performance 216 and the lowest howling risk 218.

[0113] At 1402 in FIG. 14, active acoustic sensing is performed to detect movement of the hearable. The movement is caused by a user repositioning the hearable at their ear. For example, the hearable 102 performs active acoustic sensing 126 using the acoustic sensor 412 to detect movement of the hearable 102, which is caused by the user 106 repositioning the hearable 102 at their ear 108. To perform active acoustic sensing 126, the hearable 102 transmits and receives an acoustic signal (e.g., transmits the acoustic transmit signal 902 and receives the acoustic receive signal 904).

[0114] At 1404, the hearable is determined to have moved based on the active acoustic sensing. For example, the hearable 102 uses the howling- prevent! on logic 410 to determine that the hearable 102 moved (or is moving) based on the active acoustic sensing 126. The howling- prevention logic 410 can make this determination by analyzing the acoustic receive signal 904 using signal-processing techniques or using machine-learning techniques. In some examples, the howling-prevention logic 410 analyzes the mean 722, the variance 728, and/or the cumulative sum 730 of the acoustic receive signal 904 to make this determination.

[0115] At 1406, an active state of an acoustic circuit is controlled based on the determination. For example, the howling-prevention logic 410 generates the control signal 610, which controls the active state 612 of the acoustic circuit 116. The active state 612 of the acoustic circuit 116 is controlled in a manner so as to prevent howling 122 from occurring or at least to significantly decrease a probability of howling 122 occurring due to the movement of the hearable 102. Example Computing System

[0116] FIG. 15 illustrates various components of an example computing system 1500 that can be implemented as any ty pe of client, server, and/or computing device as described with reference to the previous FIGs. 3 and 4 to implement aspects of howling prevention 124 using a hearable 102. The computing system 1500 includes communication devices 1502 that enable wired and/or wireless communication of device data 1504 (e.g., received data, data that is being received, data scheduled for broadcast, or data packets of the data). The communication devices 1502 or the computing system 1500 can include one or more hearables 102. The device data 1504 or other device content can include configuration settings of the device, media content stored on the device, and/or information associated with a user of the device. Media content stored on the computing system 1500 can include any ty pe of audio, video, and/or image data. The computing system 1500 includes one or more data inputs 1506 via which any ty pe of data, media content, and/or inputs can be received, such as human utterances, user-selectable inputs (explicit or implicit), messages, music, television media content, recorded video content, and any other type of audio, video, and/or image data received from any content and/or data source.

[0117] The computing system 1500 also includes communication interfaces 1508, which can be implemented as any one or more of a serial and/or parallel interface, a wireless interface, any type of network interface, a modem, and as any other type of communication interface. The communication interfaces 1508 provide a connection and/or communication links between the computing system 1500 and a communication network by which other electronic, computing, and communication devices communicate data with the computing system 1500.

[0118] The computing system 1500 includes one or more processors 1510 (e.g., any of microprocessors, controllers, and the like), which process various computer-executable instructions to control the operation of the computing system 1500. Alternatively or in addition, the computing system 1500 can be implemented with any one or combination of hardware, firmware, or fixed logic circuitry' that is implemented in connection with processing and control circuits which are generally identified at 1512. Although not shown, the computing system 1500 can include a system bus or data transfer system that couples the various components within the device. A system bus can include any one or combination of different bus structures, such as a memory' bus or memory controller, a peripheral bus, a universal serial bus, and/or a processor or local bus that utilizes any of a variety of bus architectures.

[0119] The computing system 1500 also includes a computer-readable medium 1514, such as one or more memory devices that enable persistent and/or non-transitory data storage (i.e., in contrast to mere signal transmission), examples of which include random access memory' (RAM), non-volatile memory (e.g., any one or more of a read-only memory (ROM), flash memory, EPROM, EEPROM, etc.), and a disk storage device. The disk storage device may be implemented as any ty pe of magnetic or optical storage device, such as a hard disk drive, a recordable and/or rewriteable compact disc (CD), any type of a digital versatile disc (DVD), and the like. The computing system 1500 can also include a mass storage medium device (storage medium) 1516. [0120] The computer-readable medium 1514 provides data storage mechanisms to store the device data 1504, as well as various device applications 1518 and any other types of information and/or data related to operational aspects of the computing system 1500. For example, an operating system 1520 can be maintained as a computer application with the computer-readable medium 1514 and executed on the processors 1510. The device applications 1518 may include a device manager, such as any form of a control application, software application, signal-processing and control module, code that is native to a particular device, a hardware abstraction layer for a particular device, and so on.

[0121] The device applications 1518 also include any system components, engines, or managers to implement howling prevention 124. In this example, the device applications 1518 include the howling-prevention logic 410.

Conclusion

[0122] Although techniques using, and apparatuses including, howling prevention have been described in language specific to features and/or methods, it is to be understood that the subject of the appended examples is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as example implementations of howling prevention.

[0123] Some examples are described below.

[0124] Example 1 : A method performed by a hearable that is positioned at an ear of a user, the method comprising: causing an acoustic circuit of the hearable to operate in accordance with a first state, the first state having a first amount of gain; detecting, during a first time period and using at least one sensor of the hearable, movement of the hearable relative to the ear of the user; and causing, based on the detecting, the acoustic circuit to operate in accordance with a second state, the second state having a second amount of gain that is less than the first amount. [0125] Example 2: The method of example 1, wherein: the causing of the acoustic circuit to operate in accordance with the second state results in preventing the acoustic circuit from generating howling.

[0126] Example 3: The method of any previous example, wherein the movement of the hearable is caused by the user repositioning the hearable at their ear during the first time period.

[0127] Example 4: The method of example 3, wherein the detecting of the movement of the hearable comprises at least one of the following: detecting, during the first time period and using the at least one sensor, a change in an orientation of the hearable relative to the ear of the user; and/or detecting, during the first time period and using the at least one sensor, a change in an insertion depth of the hearable relative to the ear of the user.

[0128] Example 5: The method of any previous example, further comprising: detecting, during a second time period and using the at least one sensor, cessation of the movement of the hearable; and causing, based on the detecting, the acoustic circuit to operate in the first state.

[0129] Example 6: The method of example 5, further comprising: detecting, during a third time period and using the at least one sensor of the hearable, that the hearable is relatively stationary, the user performing an activity during the third time period; and causing, based on the detecting, the acoustic circuit to remain in the first state.

[0130] Example 7 : The method of example 6, wherein the activity comprises the user performing at least one of the following: talking; walking; running; or chewing. [0131] Example 8: The method of any previous example, further comprising at least one of the following: performing, using the at least one sensor, active acoustic sensing to detect the movement of the hearable; performing, using the at least one sensor, optical sensing to detect the movement of the hearable; and/or performing, using the at least one sensor, capacitive sensing to detect the movement of the hearable.

[0132] Example 9: The method of example 8, wherein: the at least one sensor comprises a first sensor; the performing of the active acoustic sensing comprises: transmitting, using the first sensor, an acoustic transmit signal that propagates within at least a portion of an ear canal of the user; and receiving, using the first sensor, an acoustic receive signal, the acoustic receive signal representing a version of the acoustic transmit signal with one or more characteristics modified based on the propagation within the ear canal and based on the movement of the hearable relative to the ear of the user; and the detecting of the movement of the hearable comprises detecting the movement of the hearable based on the acoustic receive signal.

[0133] Example 10: The method of example 9, wherein the detecting of the movement of the hearable comprises one or more of the following: detecting the movement of the hearable based on a change in a mean of an amplitude and/or a phase of the acoustic receive signal being greater than a first threshold; detecting the movement of the hearable based on a variance of the amplitude and/or the phase of the acoustic receive signal being greater than a second threshold; and/or detecting the movement of the hearable based on a cumulative summation of the amplitude and/or the phase of the acoustic receive signal being greater than a third threshold. [0134] Example 11 : The method of example 9 or 10, wherein: the at least one sensor further comprises a second sensor; the performing of the optical sensing comprises generating, using the second sensor, a signal having an intensity that varies based on an amount of light that is sensed by the second sensor; and the detecting the movement of the hearable comprises detecting the movement of the hearable based on a fluctuation in the acoustic receive signal and based on a fluctuation in the intensity of the signal.

[0135] Example 12: The method of any previous example, further comprising: prior to causing the acoustic circuit to operate in accordance with the first state, determining, using the at least one sensor, that the hearable is relatively stationary, wherein the causing the acoustic circuit to operate in accordance with the first state is based on the determining that the hearable is relatively stationary.

[0136] Example 13: The method of example 12, further comprising: prior to detennining that the hearable is relatively stationary', determining, using the at least one sensor, that the hearable is being worn by the user.

[0137] Example 14: The method of any previous example, further comprising: performing active noise cancellation using the acoustic circuit; or providing a transparency mode using the acoustic circuit.

[0138] Example 15: A non-transitory computer-readable storage medium comprising instructions that, responsive to execution by a processor, cause a hearable to perform any one of the methods of examples 1 to 14.

[0139] Example 16: A hearable comprising: at least one sensor; at least one acoustic circuit; and at least one processor, the hearable configured to perform, using the at least one sensor and the at least one processor, any one of the methods of examples 1 to 14. [0140] Example 17: The hearable of example 16, wherein the at least one sensor comprises at least one of the following: an acoustic sensor; an infrared sensor; or a capacitive sensor.

[0141] Example 18: The hearable of example 17, further comprising: a speaker coupled to the at least one acoustic circuit; and a microphone coupled to the at least one acoustic circuit, wherein: the at least one sensor comprises the acoustic sensor; and the acoustic sensor is coupled to the speaker and the microphone.

[0142] Example 19: The hearable of any one of examples 16 to 18, wherein the at least one acoustic circuit comprises at least one of the following: an active-noise-cancellation circuit; or a transparency-mode circuit.

[0143] Example 20: The hearable of any one of examples 16 to 19, wherein the device comprises at least one earbud.

Claims

CLAIMS What is claimed is:

1. A method performed by a hearable that is positioned at an ear of a user, the method comprising: causing an acoustic circuit of the hearable to operate in accordance with a first state, the first state having a first amount of gain; detecting, during a first time period and using at least one sensor of the hearable, movement of the hearable relative to the ear of the user; and causing, based on the detecting, the acoustic circuit to operate in accordance with a second state, the second state having a second amount of gain that is less than the first amount.

2. The method of claim 1, wherein: the causing of the acoustic circuit to operate in accordance with the second state results in preventing the acoustic circuit from generating howling.

3. The method of any previous claim, wherein the movement of the hearable is caused by the user repositioning the hearable at their ear during the first time period.

4. The method of claim 3, wherein the detecting of the movement of the hearable comprises at least one of the following: detecting, during the first time period and using the at least one sensor, a change in an orientation of the hearable relative to the ear of the user; and/or detecting, during the first time period and using the at least one sensor, a change in an insertion depth of the hearable relative to the ear of the user.

5. The method of any previous claim, further comprising: detecting, during a second time period and using the at least one sensor, cessation of the movement of the hearable; and causing, based on the detecting, the acoustic circuit to operate in the first state.

6. The method of claim 5, further comprising: detecting, during a third time period and using the at least one sensor of the hearable, that the hearable is relatively stationary', the user performing an activity' during the third time period; and causing, based on the detecting, the acoustic circuit to remain in the first state.

7. The method of claim 6, wherein the activity comprises the user performing at least one of the following: talking; walking; running; or chewing.

8. The method of any previous claim, further comprising at least one of the following: performing, using the at least one sensor, active acoustic sensing to detect the movement of the hearable; performing, using the at least one sensor, optical sensing to detect the movement of the hearable; and/or performing, using the at least one sensor, capacitive sensing to detect the movement of the hearable.

9. The method of claim 8, wherein: the at least one sensor comprises a first sensor; the performing of the active acoustic sensing comprises: transmitting, using the first sensor, an acoustic transmit signal that propagates within at least a portion of an ear canal of the user; and receiving, using the first sensor, an acoustic receive signal, the acoustic receive signal representing a version of the acoustic transmit signal with one or more characteristics modified based on the propagation within the ear canal and based on the movement of the hearable relative to the ear of the user; and the detecting of the movement of the hearable comprises detecting the movement of the hearable based on the acoustic receive signal.

10. The method of claim 9, wherein the detecting of the movement of the hearable comprises one or more of the following: detecting the movement of the hearable based on a change in a mean of an amplitude and/or a phase of the acoustic receive signal being greater than a first threshold; detecting the movement of the hearable based on a variance of the amplitude and/or the phase of the acoustic receive signal being greater than a second threshold; and/or detecting the movement of the hearable based on a cumulative summation of the amplitude and/or the phase of the acoustic receive signal being greater than a third threshold.

11. The method of claim 9 or 10, wherein: the at least one sensor further comprises a second sensor; the performing of the optical sensing comprises generating, using the second sensor, a signal having an intensity that varies based on an amount of light that is sensed by the second sensor; and the detecting the movement of the hearable comprises detecting the movement of the hearable based on a fluctuation in the acoustic receive signal and based on a fluctuation in the intensity of the signal.

12. The method of any previous claim, further comprising: prior to causing the acoustic circuit to operate in accordance with the first state, determining, using the at least one sensor, that the hearable is relatively stationary, wherein the causing the acoustic circuit to operate in accordance with the first state is based on the determining that the hearable is relatively stationary.

13. The method of claim 12, further comprising: prior to detennining that the hearable is relatively stationary', determining, using the at least one sensor, that the hearable is being worn by the user.

14. The method of any previous claim, further comprising: performing active noise cancellation using the acoustic circuit; or providing a transparency mode using the acoustic circuit.

15. A non-transitory computer-readable storage medium comprising instructions that, responsive to execution by a processor, cause a hearable to perform any one of the methods of claims 1 to 14.

16. A hearable comprising: at least one sensor; at least one acoustic circuit; and at least one processor, the hearable configured to perform, using the at least one sensor and the at least one processor, any one of the methods of claims 1 to 14.

17. The hearable of claim 16, wherein the at least one sensor comprises at least one of the following: an acoustic sensor; an infrared sensor; or a capacitive sensor.

18. The hearable of claim 17, further comprising: a speaker coupled to the at least one acoustic circuit; and a microphone coupled to the at least one acoustic circuit, wherein: the at least one sensor comprises the acoustic sensor; and the acoustic sensor is coupled to the speaker and the microphone.

19. The hearable of any one of claims 16 to 18, wherein the at least one acoustic circuit comprises at least one of the following: an active-noise-cancellation circuit; or a transparency-mode circuit.

20. The hearable of any one of claims 16 to 19, wherein the hearable comprises at least one earbud.