Integrated circuit for detecting proximity of earphone and earphone

Abstract

The present invention discloses an integrated circuit for proximity detection of headphones and headphones, the headphones including a headphone speaker, the integrated circuit including: a first input end for receiving a first signal from a first headphone microphone, the first signal indicating the headphone environment sound; a second input end for receiving a second signal from a second headphone microphone, the second signal indicating the sound present at the acoustic output end of the headphone speaker; and a circuit for comparing a first acoustic energy of the first signal with a second acoustic energy of the second signal to determine whether the headphone is on the user's ear.

Description

[0001] This application is a divisional application of application number 201980069297.8, filed on August 19, 2019, entitled "Auricular Proximity Detection". Technical Field

[0002] This disclosure generally relates to adaptive noise cancellation associated with acoustic transducers, and more specifically, to resetting the filter coefficients of an adaptive noise cancellation system in a manner that minimizes audible artifacts. Background Technology

[0003] Cordless phones (such as mobile / cellular phones), cordless phones, and other consumer audio devices (such as MP3 players) are widely used. Noise cancellation can be provided by using a microphone to measure ambient acoustic events and then using signal processing to insert an anti-noise signal into the device's output to eliminate the ambient acoustic events, thereby improving the clarity performance of such devices.

[0004] Active noise cancellation (ANC) systems suppress noise by using one or more microphones to observe ambient noise and processing the noise signal with a digital filter to generate an anti-noise signal (which is then played through a speaker). Applications of active noise cancellation in personal audio devices such as cordless phones and headphones aim to enhance the user's listening experience regarding clarity and isolation from ambient noise. Because the acoustic environment around personal audio devices can vary depending on the presence of noise sources and the device's location or installation conditions, adaptive filters can be used to implement active noise cancellation systems to adapt the anti-noise signal to account for these environmental variations.

[0005] In many situations, it is beneficial to detect when a user removes headphones from their ear. Auricular proximity detectors (PPDs) can detect such events. Auricular proximity detection has numerous applications and uses. For example, an audio system can be configured to play audio when the speaker is coupled to the ear and pause playback when the speaker is not coupled to the ear to enhance the user experience. As another example, an audio system can be configured to turn off headphones when they are not coupled to the ear to reduce power consumption and extend battery life.

[0006] Traditionally, ear proximity detection is performed by playing a single low-frequency tone (e.g., 20Hz) and measuring the amplitude of that tone at a microphone located on headphones positioned between the speaker and the user's ear. However, this method does not work well in noisy ambient audio environments with low-frequency noise, does not work well with large playback volumes, and does not work well in adaptive ANC systems. Furthermore, this traditional solution consumes a significant amount of power to continuously transmit low-frequency tones.

[0007] Therefore, a method is needed to reliably detect ear-distance conditions in all different acoustic scenarios, and to do so in ANC headphones, which presents a challenge to ear proximity detection, which is not possible in non-ANC headphones. Summary of the Invention

[0008] Based on the teachings of this disclosure, some of the drawbacks and problems associated with existing methods for detecting auricular proximity can be reduced or eliminated.

[0009] According to embodiments of this disclosure, an integrated circuit for implementing at least a portion of a personal audio device may include: an output for providing an output signal to a transducer, wherein the output signal includes a pilot signal; a microphone input for receiving a microphone signal indicating the output of the transducer from a microphone; and processing circuitry. The processing circuitry may be configured to implement pilot signal control to apply adjustments to the pilot signal as needed, thereby maintaining the pilot signal at a substantially constant amplitude, independent of the proximity of the transducer to the auricle, and to implement a proximity determination block configured to determine the proximity of the transducer to the auricle based on the adjustments.

[0010] According to these and embodiments of the present disclosure, a method may include: providing an output signal to a transducer, wherein the output signal includes a pilot signal; receiving a microphone signal from a microphone indicating the output of the transducer; applying an adjustment to the pilot signal as needed to maintain the pilot signal at a substantially constant amplitude, regardless of the proximity of the transducer to the auricle; and determining the proximity of the transducer to the auricle based on the adjustment.

[0011] The technical advantages of this disclosure will be apparent to those skilled in the art from the accompanying drawings, description, and claims included herein. The objects and advantages of the embodiments will be implemented and accomplished, at least by means of the elements, features, and combinations specifically pointed out in the claims.

[0012] It should be understood that the foregoing general description and the following detailed description are illustrative and exemplary, and do not limit the claims set forth in this disclosure. Attached Figure Description

[0013] A more complete understanding of this embodiment and its advantages can be obtained by referring to the following description in conjunction with the accompanying drawings, in which the same reference numerals denote the same features, and wherein:

[0014] Figure 1A This is an illustration of an example wireless mobile phone according to an embodiment of the present disclosure;

[0015] Figure 1B This is an illustration of an example wireless mobile phone having an earphone assembly coupled thereto according to an embodiment of the present disclosure;

[0016] Figure 2 According to embodiments of this disclosure Figure 1A A block diagram depicting selected circuitry within a wireless mobile phone;

[0017] Figure 3 This is a block diagram of a system according to an embodiment of the present disclosure, the system including Figure 2 Selected signal processing circuits and function blocks within the adaptive noise cancellation circuit and ear proximity detection circuit of the encoder-decoder integrated circuit;

[0018] Figure 4 According to embodiments of this disclosure Figure 3 The system block diagram, with additional details showing the selected functional components of the pilot level adjustment block;

[0019] Figure 5 A graph depicting example waveforms according to an embodiment of the present disclosure is provided, illustrating how an auricle proximity determination block can use a gain signal to determine the proximity of a speaker to the auricle of the ear.

[0020] Figure 6 According to embodiments of this disclosure Figure 4 The system block diagram includes a bandpass filter for isolating the sensed pilot signal;

[0021] Figure 7 A graph depicting an example waveform according to an embodiment of the present disclosure is provided, illustrating the operation of the auricle proximity determination block when a source audio signal is present near the frequency range of the pilot signal, with bandpass filtering and no bandwidth filtering applied to the error microphone signal err.

[0022] Figure 8 A graph depicting example waveforms according to embodiments of the present disclosure illustrates the operation of an auricle proximity determination block with delayed detection of on-ear and off-ear events;

[0023] Figure 9 This is a block diagram of selected components of a PID controller according to embodiments of the present disclosure;

[0024] Figure 10 A graph depicting an example waveform according to an embodiment of the present disclosure illustrates the operation of the auricle proximity determination block in the presence of clamping within the PID controller;

[0025] Figure 11 According to embodiments of this disclosure Figure 6 The system block diagram depicts the selected components of the system and the various control loops present within the system.

[0026] Figure 12 According to embodiments of this disclosure Figure 6The system block diagram includes a notch filter within an adaptive noise cancellation circuit.

[0027] Figure 13 According to embodiments of this disclosure Figure 12 The system block diagram includes an environmental noise estimator and a pilot reference calculator;

[0028] Figure 14 A graph depicting an example waveform according to an embodiment of the present disclosure is provided, illustrating the calculation of a reference pilot signal based on ambient noise.

[0029] Figure 15 A graph depicting an example waveform according to an embodiment of the present disclosure is provided, illustrating the calculation of a proximity detection threshold based on a reference pilot signal;

[0030] Figure 16 According to embodiments of this disclosure Figure 6 The system block diagram includes a programmable gain element for controlling the feedback noise immunity gain;

[0031] Figure 17A and Figure 17B Each is depicted as a graph of an example waveform according to an embodiment of the present disclosure, illustrating the calculation of the proximity detection threshold based on the feedback noise immunity gain;

[0032] Figure 18 According to embodiments of this disclosure Figure 3 The system block diagram includes circuitry for duty cycle ear proximity detection.

[0033] Figure 19 According to embodiments of this disclosure Figure 18 The system block diagram includes circuitry for ear proximity detection based on forward passive occlusion.

[0034] Figure 20 According to embodiments of this disclosure Figure 19 The system block diagram shows that circuitry for auricular proximity detection based on reverse passive occlusion has been added to replace the circuitry for auricular proximity detection based on forward passive occlusion.

[0035] Figure 21 According to embodiments of this disclosure Figure 19 The system block diagram shows that circuitry for ear proximity detection based on active noise cancellation effect has been added to replace the circuitry for ear proximity detection based on forward passive occlusion.

[0036] Figure 22This is a flowchart of an example method for selecting and combining auricle proximity detection techniques based on system operating parameters, according to embodiments of the present disclosure;

[0037] Figure 23 This is a system block diagram of a system that replaces the foregoing figures according to embodiments of the present disclosure. The system of the foregoing figures includes... Figure 2 Selected signal processing circuits and function blocks within the adaptive noise cancellation circuit and ear proximity detection circuit of the encoder-decoder integrated circuit;

[0038] Figure 24 Similar to embodiments of this disclosure Figure 24 System block diagram of a system without adaptive gain control elements; and

[0039] Figure 25 This is a block diagram of an example environmental noise estimator according to an embodiment of the present disclosure. Detailed Implementation

[0040] This disclosure includes noise cancellation techniques and circuitry that can be implemented in personal audio devices such as wireless telephones. The personal audio device includes ANC circuitry that measures the surrounding acoustic environment and generates a signal that is injected into the output of a speaker (or other transducer) to cancel ambient sound events. A reference microphone may be provided to measure the surrounding acoustic environment, and an error microphone may be included for controlling the adaptation of the noise cancellation signal to cancel ambient audio sounds and for correcting the electroacoustic path from the output of the processing circuitry through the transducer.

[0041] Now refer to Figure 1A The personal audio device 10 shown according to an embodiment of this disclosure is depicted as being close to the ear 5. The personal audio device 10 is an example of a device in which the technology according to embodiments of this disclosure may be employed; however, it should be understood that it is not required that all elements or configurations presented in the illustrated personal audio device 10 or in the circuitry depicted in the following figures practice the features claimed. The personal audio device 10 may include transducers, such as a speaker SPKR, that reproduce remote voice received by the personal audio device 10, as well as injections of other local audio events (e.g., ringtones, stored audio program data, near-end speech (i.e., the voice of the user of the personal audio device 10)) to provide balanced conversational awareness, and other audio that the personal audio device 10 is required to reproduce, such as sources from web pages or other network communications received by the personal audio device 10, and audio indications such as low battery indications and other system event notifications. A near-end speech microphone NS may be provided to capture near-end speech, which is transmitted from the personal audio device 10 to one or more other conversation participants.

[0042] Personal audio device 10 may include ANC circuitry and features that inject noise-resistant signals into the speaker SPKR to improve the clarity of distant speech and other audio reproduced by the speaker SPKR. A reference microphone R may be provided to measure the surrounding acoustic environment and may be placed in a typical location away from the user's mouth, thereby minimizing near-end speech in the signal generated by the reference microphone R. Another microphone (error microphone E) may be provided to further improve ANC operation by providing a measure of ambient audio combined with the audio reproduced by the speaker SPKR near the ear 5 when the personal audio device 10 is close to the ear 5. In some embodiments, additional reference and / or error microphones may be used. In yet another embodiment, the ANC system may include the error microphone E but not the reference microphone R.

[0043] The circuitry 14 within the personal audio device 10 may include an audio codec integrated circuit (IC) 20 that receives signals from a reference microphone R, a proximity microphone NS, and an error microphone E, and interfaces with other integrated circuits such as a radio frequency (RF) integrated circuit 12 having a wireless telephone transceiver. In some embodiments of this disclosure, the circuitry and techniques disclosed herein may be incorporated into a single integrated circuit that includes control circuitry and other functions for implementing the entire personal audio device, such as an integrated circuit on an MP3 player chip. In these and other embodiments, the circuitry and techniques disclosed herein may be implemented, in part or entirely, in software and / or firmware that is presented in a computer-readable medium and is executable by a controller or other processing device.

[0044] Generally, the ANC technology of this disclosure can measure ambient sound events (opposite to the output of the speaker SPKR and / or near-end speech) impinging on a reference microphone R (in embodiments where a reference microphone R is present), and also by measuring the same ambient sound events impinging on an error microphone E, the ANC processing circuitry of the personal audio device 10 adapts the noise-resistant signal generated from the output of the reference microphone R to have the characteristic of minimizing the amplitude of the ambient sound events at the error microphone E. Because the acoustic path P(z) extends from the reference microphone R to the error microphone E, the ANC circuitry can effectively estimate the acoustic path P(z) while removing the electroacoustic path S(z) representing the response of the audio output circuitry of the codec (CODEC) IC 20 and the influence of the acoustic / electrical transfer function of the speaker SPKR, which includes the coupling between the speaker SPKR and the error microphone E in a particular acoustic environment, which may be affected by the proximity and structure of the ear 5 and other physical objects, as well as the head structure that may be close to the personal audio device 10, when the personal audio device 10 is not firmly pressed against the ear 5. Although the illustrated personal audio device 10 includes a dual-microphone ANC system with a third proximity microphone NS, some aspects of this disclosure can be implemented in wireless telephone systems that do not include separate error microphones and reference microphones or use the proximity microphone NS to perform the function of a reference microphone R. Furthermore, in personal audio devices designed solely for audio playback, the proximity microphone NS is generally not included, and the proximity signal path in the circuitry described in further detail below can be omitted without altering the scope of this disclosure, except for limiting the options provided for microphone input.

[0045] Now refer to Figure 1B Personal audio device 10 is depicted having a headphone assembly 13 coupled thereto via an audio port 15. The audio port 15 is communicatively coupled to an RF integrated circuit 12 and / or a CODEC IC 20, thereby allowing communication between components of the headphone assembly 13 and one or more of the RF integrated circuit 12 and / or the CODEC IC 20. Figure 1B As shown, the headphone assembly 13 may include a combo box 16, a left earpiece 18A, and a right earpiece 18B. In some embodiments, the headphone assembly 13 may include a wireless headphone assembly, in which case all or part of the CODEC IC 20 may be present in the headphone assembly 13, and the headphone assembly 13 may include a wireless communication interface (e.g., Bluetooth) for communication between the headphone assembly 13 and the personal audio device 10.

[0046] As used in this disclosure, the term "headphones" broadly includes any speaker and associated structure designed to be mechanically held in a position close to the listener's ear canal, and includes, but is not limited to, headphones, earplugs, and other similar devices. As a more specific example, "headphones" may refer to intra-concha headphones, supra-concha headphones, and supra-aural headphones.

[0047] Another portion of the combination box 16 or the headphone assembly 13 may have a proximity microphone NS to capture near-end speech in addition to or in lieu of the proximity microphone NS of the personal audio device 10. Additionally, each headset 18A, 18B may include a transducer such as a speaker SPKR that reproduces remote speech received by the personal audio device 10, as well as injections of other local audio events (e.g., ringtones, stored audio program data, near-end speech (i.e., the user's voice of the personal audio device 10)) to provide balanced conversational awareness, and other audio that the personal audio device 10 is required to reproduce, such as sources from web pages or other network communications received by the personal audio device 10, and audio indications such as low battery indicators and other system event notifications. Each headset 18A, 18B may include a reference microphone R for measuring the ambient sound environment and an error microphone E for measuring ambient audio combined with the audio reproduced by the speaker SPKR near the listener's ear (when such headsets 18A, 18B are engaged with the listener's ear). In some embodiments, the CODEC IC 20 may receive signals from the reference microphone R and error microphone E of each earpiece, as well as the proximity microphone NS, and perform adaptive noise cancellation for each earpiece as described herein. In other embodiments, a CODEC IC or another circuit may be present within the earpiece assembly 13, communicatively coupled to the reference microphone R, the proximity microphone NS, and the error microphone E, and configured to perform adaptive noise cancellation as described herein. Figure 1A As shown, in some embodiments, Figure 1B The configuration shown may include an error microphone E, but not a reference microphone R.

[0048] Now refer to Figure 2The block diagram shows selected circuitry within the personal audio device 10. In other embodiments, the selected circuitry may be placed, in whole or in part, in other locations such as one or more headphones or earbuds. In embodiments where a reference microphone R is present, the CODEC IC 20 may include an analog-to-digital converter (ADC) 21A for receiving a reference microphone signal from the microphone R and generating a digital representation of the reference microphone signal ref. The CODEC IC 20 may also include: an ADC 21B for receiving an error microphone signal from an error microphone E and generating a digital representation of the error microphone signal err; and an ADC 21C for receiving a near-speech microphone signal from a near-speech microphone NS and generating a digital representation of the near-speech microphone signal ns. The CODEC IC 20 may generate an output from an amplifier A1 for driving a speaker SPKR, which may amplify the output of a digital-to-analog converter (DAC) 23 that receives the output of a combiner 26. Combiner 26 can combine an audio signal ia from internal audio source 24, a pilot signal PILOT generated by a pincushion proximity detector (PPD) 32, an anti-noise signal generated by ANC circuit 30 (which, by convention, has the same polarity as the noise in the reference microphone signal ref and is therefore subtracted by combiner 26), and a portion of the proximity microphone signal ns, so that the user of personal audio device 10 can hear his or her own voice, appropriately correlated with downlink voice ds, which can be received from radio frequency (RF) integrated circuit 22 and can also be combined by combiner 26. The proximity microphone signal ns can also be provided to RF integrated circuit 22 and can be transmitted as uplink voice to the service provider via antenna ANT.

[0049] Now refer to Figure 3 The embodiments of this disclosure illustrate details of a system 40 including selected components of the CODEC IC 20 (including ANC circuitry 30 and PPD 32). Figure 3 The ANC circuit 30 shown does not include an input for the reference microphone signal, and therefore relies on feedback ANC based on the error microphone signal from the error microphone E.

[0050] The ANC circuit 30 may include an adaptive filter 34 for estimating the response of path S(z), which may have coefficients controlled by an SE coefficient control block 33, which may compare a source audio signal (e.g., downlink audio signal ds and / or internal audio signal ia) with a playback correction error signal PBCE to generate such coefficients. The playback correction error signal PBCE may include an error microphone signal err after removing the source audio signal, downlink audio signal ds, and / or internal audio signal ia, which has been filtered by the adaptive filter 34 to represent the expected downlink audio delivered to the error microphone E, and an error signal PBCE removed by the combiner 36 from the output of the adaptive filter 34 to generate the playback correction error signal PBCE. The SE coefficient control block 33 may correlate the source audio signal (e.g., the actual downlink audio signal ds and / or internal audio signal ia) with components of the source audio signal. In operation, the SE coefficient control block 33 can implement an adaptive algorithm, such as the least mean square algorithm, which can accept the source audio signal as a training signal and the playback correction error signal PBCE as another input, and can attempt to adjust the coefficients of the adaptive filter 34 to minimize the playback correction error signal PBCE (e.g., in a mean square sense). In minimizing the playback correction error signal PBCE, the adaptive filter 34 can approximate the transfer function of the electroacoustic path S(z), which can be the coupling function between the loudspeaker SPKR and the auricle of the ear 5. Therefore, the adaptive filter 34 and the SE coefficient control block 33 effectively implement an adaptive loudspeaker-to-auricle model to help the feedback loop, including the feedback filter 44, not to eliminate the playback audio, but only to eliminate the ambient noise entering the auricle of the ear 5 through the headphones, as observed by the error microphone E.

[0051] The adaptive filter 34 can therefore be adapted to generate a signal from the source audio signal that, when subtracted from the error microphone signal err, includes the contents of the error microphone signal err that are not caused by the source audio signal, in order to generate a playback correction error signal PBCE.

[0052] exist Figure 3 middle, Figure 2 The function of combiner 26 is performed by combiners 26A and 26B. Combiner 26A can combine a source audio signal (e.g., downlink audio signal ds and / or internal audio signal ia) with a pilot signal PILOT generated by PPD 32. This source audio signal combined with the pilot signal PILOT can be processed by ANC circuit 30. Combiner 26B can combine the signal obtained by combiner 26A with an anti-noise signal ANTI-NOISE to generate an audio output signal to be played back to speaker SPKR.

[0053] like Figure 3 As shown, the ANC circuit 30 may further include a feedback filter 44. The feedback filter 44 can receive the playback correction error signal PBCE and can apply the response FB(z) to generate a feedback noise immunity signal ANTI-NOISE based on the playback correction error. The feedback signal ANTI-NOISE can be combined by combiner 26B with the source audio signal and pilot signal PILOT for reproduction by the loudspeaker SPKR.

[0054] The ear proximity detection performed by PPD 32 can begin with pilot signal generator 52, which generates a raw pilot signal. This raw pilot signal may include a single low-frequency tone, a set of tones, or a narrow band of non-replay audio with sufficiently large amplitude variations when the speaker SPKR is near rather than far from the ear. Gain element 54 can apply gain to the raw pilot signal to generate an ideally inaudible pilot signal, PILOT. This pilot signal PILOT can be combined with the source audio signal via combiner 26A and subsequently added to the anti-noise signal ANTI-NOISE via combiner 26B. The resulting audio output signal (including the pilot signal PILOT) can be converted to the analog domain by DAC 23, amplified by amplifier A1, and reproduced by the speaker SPKR. Error microphone E can receive the combined acoustic signal reproduced by loudspeaker SPKR (which may include pilot signal PILOT), and after converting the combined acoustic signal into the digital domain to generate error microphone signal err, pilot tracker 56 of PPD 32 can isolate pilot signal PILOT from error microphone signal err to generate sensed pilot signal PILOT'. The pilot level adjustment block is tuned to have a bandwidth smaller than the bandwidth of the pilot tracker. Specifically, the pilot level adjustment block is tuned to have a bandwidth approximately ten times smaller than the bandwidth of the pilot tracker.

[0055] Pilot level adjustment block 58 can receive the sensed pilot signal PILOT' and generate a gain control signal GAIN to control the gain of gain element 54 so as to maintain the sensed pilot signal PILOT' at a predetermined constant level. When the speaker SPKR is not near the auricle of the ear 5, the auricle proximity determination block 60 can receive the gain control signal GAIN generated by the pilot level adjustment block 58 and compare the gain indicated by the gain control signal GAIN with the gain required to maintain a constant pilot level. Based on this comparison, the auricle proximity determination block 60 can determine the proximity between the auricle of the ear 5 and the speaker SPKR. To illustrate, when the speaker SPKR is close to the auricle, the acoustic load allows the speaker SPKR to effectively drive the pilot signal PILOT, and the gain element 54 does not need to provide much (if any) gain to maintain the pilot level at the desired predetermined level. However, when the speaker SPKR is not near the auricle, the acoustic load will be different, and the speaker SPKR may be inefficient, which means that the gain element 54 must provide more gain to maintain the desired predetermined level of the pilot signal PILOT observed at the error microphone E.

[0056] Figure 4 According to embodiments of this disclosure Figure 3 The block diagram of system 40 depicted in the figure shows, with additional details illustrating the selected functional components of pilot level adjustment block 58. Pilot level adjustment block 58 can implement a proportional-integral-derivative (PID) based adaptive gain control (AGC) loop to automatically and robustly maintain a constant pilot level.

[0057] To protect the AGC loop of the pilot level adjustment block 58 from the DC signal components that may incorrectly drive the PID control, a high-pass filter 62 (e.g., with a cutoff frequency one-tenth of the center of the pilot signal PILOT) can filter out the low-frequency components of the pilot signal PILOT.

[0058] Additionally, the high-pass filtered pilot signal PILOT can be extracted by decimation filter 64 to allow the AGC loop of pilot level adjustment block 58 to operate at a significantly reduced rate, which can reduce the processing requirements of the AGC loop.

[0059] Pilot level adjustment block 58 may include a linear-to-decibel converter 66 to convert the sensed pilot signal PILOT' into a value PILOT given in decibels relative to the full-scale amplitude of the sensed pilot signal PILOT'. dB Operation in the decibel domain can enable the dynamic range of the compressed pilot signal PILOT while preserving a reasonable number of fixed-point signals.

[0060] Combiner 68 can detect the pilot signal PILOT dB 'Subtract the reference pilot signal PILOT from the middle REF This generates an error signal ERROR. The PID controller 70 can receive the error signal and generate a gain signal GAIN in decibels based on it. dB This is to adaptively minimize the error signal ERROR. The decibel-to-linear converter 72 can convert the gain signal GAIN in the decibel domain. dB It is converted into a linear scaling equivalent, and this converted linear scaling equivalent can be interpolated by interpolator 74 to have the same sampling frequency as ADC 21B in order to generate the gain signal GAIN.

[0061] Figure 5 A graph depicting an example waveform according to an embodiment of the present disclosure is shown, illustrating how the ear proximity determination block 60 can use the decibel-domain gain signal GAIN. dB To determine the proximity of the speaker SPKR to the auricle of ear 5. Figure 5 The top waveform depicts the decibel-domain gain signal GAIN over a period of time. dB From this point onward, the user puts the earphones on their ears, then briefly removes them, and then puts them back on. The ear proximity determination block 60 can determine this by using the decibel domain gain signal GAIN. dB The speaker SPKR is compared with a pair of thresholds to determine whether it is on or off the ear: (i) when the decibel domain gain signal GAIN dB When the upper threshold is exceeded, the speaker SPKR can be declared "at the ear"; and (ii) when the decibel domain gain signal GAIN dB When the threshold drops below the lower threshold, the speaker SPKR can be declared "off-ear".

[0062] Figure 6 According to embodiments of this disclosure, as follows Figure 4 The block diagram of system 40 shown includes a bandpass filter 76 for isolating the sensed pilot signal PILOT' from the source audio signal. Because the signal content of the source audio reproduced by the speaker SPKR and captured by the error microphone E may be near the frequency region of the pilot signal PILOT, the bandpass filter 76 can filter the error microphone signal err in the frequency range near the frequency region of the pilot signal PILOT, thereby minimizing the impact of the source audio signal on the functionality of PPD 32 and allowing the pilot tracker 56 to focus on the pilot signal PILOT. Figure 7A graph depicting an example waveform according to an embodiment of the present disclosure illustrates the operation of the ear proximity determination block 60 when a source audio signal is present near the frequency range of the pilot signal PILOT, with and without bandpass filtering of the error microphone signal err. Figure 7 As shown, without bandpass filtering of the error microphone signal err, the ear proximity determination block 60 may have difficulty distinguishing between the sensed pilot signal PILOT′ and the source audio signal, and may be able to effectively track the sensed pilot signal PILOT′ even with bandpass filtering of the error microphone signal err.

[0063] When the speaker SPKR is pulled out of the ear 5, there is typically a brief moment during which the earphone including the speaker SPKR forms a tighter seal, and the speaker forms a stronger acoustic coupling with the error microphone E. In this situation, the gain required within the gain element 54 to maintain the pilot signal PILOT at the desired level may be very small. Similarly, when the earphone including the speaker SPKR is pushed back onto the ear 5, a tighter seal may be formed briefly. In these cases, the PPD 32 may need to take longer to make a correct judgment about the proximity of the speaker SPKR to the ear 5, because the gain signal GAIN may be temporarily pushed away from its value to which it should stabilize, and thus away from the threshold it must cross to indicate an ear-off event. Figure 8 A graph depicting an example waveform illustrating this phenomenon according to an embodiment of the present disclosure is provided.

[0064] To mitigate this phenomenon, the PID controller 70 may include features not typically found in a PID controller, particularly signal clamping. Figure 9 This is a block diagram of selected components of a PID controller 70 according to an embodiment of the present disclosure. Figure 9 As shown, clamp 78 can be added to the integrated components of a typical PID controller so that if the input signal INPUT drops below the threshold CLAMP_THRESHOLD, the output signal OUTPUT of the PID controller 70 (which may correspond to the decibel domain gain signal GAIN) will be clamped. dB Maintain at the CLAMP_THRESHOLD level, such as Figure 10 As described. For example Figure 10 As shown, the gain signal GAIN in the decibel domain dB Compared to the unclamped case, the clamped decibel domain gain signal GAIN dB This allows the gain signal GAIN in the decibel domain to be increased. dB The settling time at the distance from the ear is shortened, thus allowing for faster detection of distance from the ear and on-ear events.

[0065] Figure 11 According to embodiments of this disclosure, as follows Figure 6 The block diagram of system 40 shown depicts the selected components of system 40 and the various control loops existing within the system. Specifically, Figure 11 The loudspeaker-to-error microphone modeling loop, noise immunity feedback loop, and adaptive gain control loop are depicted. For clarity and illustration purposes, Figure 6 Some components of the system 40 presented in the text are not in Figure 11 It is displayed in the middle.

[0066] It might be desirable to control the level of the pilot signal PILOT solely through the adaptive gain control of PPD 32. However, as seen with error microphone E, the level of the pilot signal PILOT can also be affected by the interaction of the noise immunity feedback loop and the speaker-to-error microphone modeling loop. Since the adaptive speaker-to-error microphone modeling loop attempts to model the acoustic coupling between the speaker SPKR and the error microphone E, such modeling at low frequencies in the narrow band close to the pilot signal PILOT can be poorly performed. This poor modeling can then lead to significant variations in the pilot signal at the output of combiner 36. The remainder of this variation in the pilot signal PILOT may end in the feedback loop, where it can be eliminated or amplified in different ways when reproduced by the speaker SPKR and sensed by the error microphone E. The AGC loop may then attempt to automatically adjust the level of the pilot signal PILOT. In this case, the AGC loop may not be the only mechanism for controlling the pilot signal PILOT, and therefore the AGC loop may overcompensate or undercompensate, potentially becoming unstable. As a result, not only may PPD 32 make incorrect decisions, but the adaptive speaker-error microphone modeling loop may also adapt to strong pilot signals, and the resulting incorrect adaptation may cause the adaptive speaker-error microphone modeling loop to become unstable.

[0067] To mitigate this problem, a band-stop or notch filter 80A with a response SE_NOTCH(z) centered at the center frequency of the pilot signal PILOT can be added to the output of the adaptive filter 34, such as... Figure 12 As shown. Furthermore, due to the least mean square stability criterion, the equivalent phase effect of the notch filter 80A should be placed in conjunction with the training signal input to the SE coefficient control block 33. Therefore, a copy 80B of the notch filter 80A can be placed before the training signal input of the SE coefficient control block 33. For example... Figure 12As shown, in the presence of notch filters 80A and 80B, the adaptive speaker-to-error microphone modeling loop and the noise immunity feedback loop may not interact to change the level of the pilot signal PILOT, and only the AGC loop implemented by PPD 32 can control the level of the pilot signal PILOT. Therefore, the level of the pilot signal PILOT may change only in response to changes in the speaker-to-error microphone coupling when the headphones are adjusted on or away from the auricle of ear 5. Furthermore, the adaptive speaker-to-error microphone loop may not be adapted to the pilot signal PILOT itself, because the pilot signal PILOT is not part of the training signal for the speaker-to-error microphone loop.

[0068] In environments with high ambient noise (e.g., outside the headphones including the speaker SPKR), the pilot tracker 56 may have difficulty following the pilot signal, and therefore the PPD 32 may make incorrect judgments about the proximity of the speaker SPKR to the auricle of the ear 5. To solve this problem, as Figure 13 As shown, the ambient noise estimator 82 of the PPD 32 can estimate the amount of ambient noise present in the sensed pilot signal PILOT'. Methods for generating estimates of ambient noise are described elsewhere in this disclosure. Based on the amount of ambient noise present in the sensed pilot signal PILOT', the pilot reference calculator 84 of the PPD 32 can determine a reference pilot signal PILOT. REF For example, in some embodiments, once the ambient noise has increased to exceed a minimum noise threshold, the reference pilot signal PILOT is activated. REF It can increase per decibel with the increase of ambient noise, for example, Figure 14 As shown. Additionally, the ear proximity determination block 60 can be configured to modify the determination threshold used to detect events of ear displacement and ear insertion to address the fact that any increase in the gain signal GAIN will be at least partially caused by the reference pilot signal PILOT. REF The increase is caused by, for example, such as Figure 15 As shown.

[0069] Figure 16 According to embodiments of this disclosure Figure 6 The system block diagram includes a programmable gain element 46 for controlling the programmable feedback noise immunity gain. (See diagram for example.) Figure 16As shown, the feedback noise immunity path can have a programmable gain element 46 connected in series with the feedback filter 44, thereby applying the product of the response FB(z) and the gain of the programmable gain element 46 to the playback correction error signal PBCE to generate the noise immunity signal ANTI-NOISE. The gain of the programmable gain element 46 can be modified according to user settings input by the user of the personal audio device 10. Although the feedback filter 44 and the gain element 46 are shown as separate components of the ANC circuit 30, in some embodiments, some structures and / or functions of the feedback filter 44 and the gain element 46 can be combined. For example, in some such embodiments, the effective gain of the feedback filter 44 can be changed by controlling one or more filter coefficients of the feedback filter 44. To the extent that the gain element 46 has a variable gain, the combination of the feedback filter 44 and the gain element 46 can be regarded as an adaptive filter, wherein the gain of the gain element 46 is similar to the filter coefficients of the feedback filter 44.

[0070] By partially eliminating and / or amplifying the pilot signal PILOT, the varying noise immunity caused by changes in the programmable feedback noise immunity gain may affect the level of the pilot signal PILOT detected at the error microphone E. Because the programmable feedback noise immunity gain can be modified by the user and may not be anticipated during product design, the ear proximity determination block 60 can dynamically compensate for the programmable feedback noise immunity gain to make an accurate speaker-to-ear proximity determination, regardless of the programmable feedback noise immunity gain, as shown in the example where the programmable feedback gain is transmitted to the ear proximity determination block 60. Figure 16 As shown.

[0071] The proximity detection threshold used by the ear proximity determination block 60 can be adjusted in response to changes in the programmable feedback noise immunity gain, based on whether increasing the programmable feedback noise immunity gain partially eliminates or enhances the pilot signal PILOT. For example, in the product design of the personal audio device 10, the test equipment can measure how much influence (if any) the noise immunity feedback loop has on the pilot signal PILOT when the programmable feedback noise immunity gain is set to its maximum value. In the case where the noise immunity feedback loop partially eliminates the pilot signal PILOT, the determination threshold of the ear proximity determination block 60 can increase with the increase of the programmable feedback noise immunity gain, such as... Figure 17A As shown. On the other hand, when the pilot signal PILOT is partially enhanced by the noise immunity feedback loop, the determination threshold of the ear proximity determination block 60 can decrease as the programmable feedback noise immunity gain increases, such as... Figure 17B As shown.

[0072] Figure 18 According to embodiments of this disclosure Figure 3The block diagram of system 40 shown includes circuitry for duty cycle loop ear proximity detection. In the absence of audio playback and noise cancellation, the PPD 32 may still be necessary. However, to reduce power consumption and maximize battery life, the duty cycle functionality of the PPD 32 may be desirable.

[0073] like Figure 18 As shown, PPD 32 may include a ramp scaler 86 and a duty cycle timer 88. In operation, the duty cycle timer 88 may be activated for short periods at regular intervals (e.g., 1 second out of every 10-second period is active). The duty cycle timer 88 may generate the operation used to enable the pilot level adjustment block 58 (in... Figure 18 The operation of enabling the ear proximity determination block 60 is indicated by the "Adjustment Enable" instruction. Figure 18 The operation of enabling the ramp calibrator 86 (indicated by the "determination enable" instruction) and enabling the ramp calibrator 86 (in Figure 18 The control signal is indicated by the "ramp activation" indicator. Therefore, as... Figure 18 As shown in the waveform depicted at the bottom, when the duty cycle timer 88 is activated, it enables the operation of the pilot level adjustment block 58, the ear proximity determination block 60, and the ramp scaler 86. When activated, the ramp scaler 86 can tilt the gain of the signal to be applied to the pilot signal generator 52 from a minimum gain (e.g., zero) to a maximum gain (e.g., one) at the beginning of each duty cycle activation period, and tilt the gain of the signal to be applied to the pilot signal generator 52 from a maximum gain to a minimum gain at the end of each duty cycle activation period. Such tilting can minimize the occurrence of audio artifacts caused by the application of periodic pilot signals.

[0074] During the duration of the gradual increase and decrease of the gain of the ramp calibrator 86, the AGC loop of the PPD 32 is not responsible for the pilot level; therefore, ear proximity detection should be frozen, and adjustment of the pilot level should be disabled. Figure 18 As shown. When the pilot signal PILOT is muted by the ramp scaler 86, the most recent proximity determination can be maintained until the next activation cycle of the duty cycle timer 88.

[0075] Therefore, the pilot signal PILOT can be non-zero for short periods of time at regular intervals, and power savings can be achieved by not giving the drive amplifier A1 and the speaker SPKR continuous signals.

[0076] Figure 19 According to embodiments of this disclosure, as follows Figure 18 The block diagram of system 40 shown includes circuitry for detecting auricular proximity based on forward passive occlusion. (See above reference...) Figure 1AAs mentioned in 1B and 2, the personal audio device 10 may include a reference microphone for sensing ambient sound. Adding the reference microphone R to system 40 can enable additional auricular proximity detection via a technique known as forward passive occlusion. By comparing the acoustic energy of both the reference microphone R and the error microphone E in a specific frequency band, the PPD 32 can utilize headphones (e.g., [earphones]). Figure 1B The physical characteristics of the headphones (18A, 18B) and the significant differences that can occur at higher frequencies (e.g., in the 2kHz to 5kHz band) when the headphones are on and off the ears (due to the noise isolation of the headphones) can be considered. This additional information can be used in place of pilot-based decisions, or it can supplement pilot-based decisions to build more confidence in the final decision.

[0077] like Figure 19 As shown, the PPD 32 may further include: a frequency range isolation filter 90 configured to receive and bandpass-filter a reference microphone signal ref; an envelope detector 92 configured to detect the signal envelope of the reference microphone signal ref within the bandpass-filtered range; and a linear-to-decibel converter 94 configured to convert the detected envelope, bandpass-filtered reference microphone signal into a value REF given in decibels relative to the full-scale amplitude of the reference microphone signal ref. dB Similarly, PPD 32 may also include: a frequency range isolation filter 96 configured to receive and bandpass-filter the error microphone signal err; an envelope detector 98 for detecting the signal envelope of the error microphone signal err within the bandpass-filtered range; and a linear-to-decibel converter 100 configured to convert the detected envelope, bandpass-filtered error microphone signal into a value ERR given in decibels relative to the full-scale amplitude of the error microphone signal err. dB Auxiliary decision block 102 can compare the value REF. dB and ERR dB The difference between the two values ​​is compared with the threshold TH_FPO, and the signal is transmitted to the ear proximity determination block 60, which can overturn or supplement the proximity determination made by the ear proximity determination block 60.

[0078] Figure 20 According to embodiments of this disclosure, as follows Figure 19 The block diagram of system 40 shown adds circuitry for auricular proximity detection based on reverse passive occlusion, replacing the circuitry for auricular proximity detection based on forward passive occlusion. The presence of a reference microphone R in system 40 enables additional auricular proximity detection via a technique called reverse passive occlusion. By comparing the acoustic energy of both the reference microphone R and the error microphone E in a specific frequency band, the PPD 32 can utilize the headphones (e.g., Figure 1B The physical characteristics of the headphones (18A, 18B) and the low-frequency characteristics (e.g., below 100Hz) when the headphones are on the ear (e.g., bone conduction due to jaw movement, intracranial joint vibration due to neck movement) and away from the ear may show significant differences. For example, the error microphone E may receive the bone conduction effect, while the reference microphone R may not, and the bone conduction effect may only occur when the headphones are on the ear. Therefore, this additional information can be used in place of pilot-based decisions and / or forward passive blockage-based decisions, or it can supplement pilot-based decisions and / or forward passive blockage-based decisions to build greater confidence in the final decision.

[0079] like Figure 20 As shown, the PPD 32 may further include: a frequency range isolation filter 104 configured to receive and low-pass filter a reference microphone signal ref; an envelope detector 106 for detecting the signal envelope of the reference microphone signal ref within the low-pass filtered range; and a linear-to-decibel converter 108 configured to convert the detected envelope, low-pass filtered reference microphone signal into a value REF given in decibels relative to the full-scale amplitude of the reference microphone signal ref. dB Similarly, PPD 32 may also include: a frequency range isolation filter 110 configured to receive and low-pass filter the error microphone signal err; an envelope detector 112 configured to detect the signal envelope of the error microphone signal err within the low-pass filtered range; and a linear-to-decibel converter 114 configured to convert the detected envelope, low-pass filtered error microphone signal into a value ERR given in decibels relative to the full-scale amplitude of the error microphone signal err. dB The supplementary decision block 116 can adjust the value REF. dB and ERR dB The difference between them is compared, and this difference is compared with the threshold TH_RPO. The signal is then transmitted to the ear proximity determination block 60, which can overturn or supplement the proximity determination made by the ear proximity determination block 60 and / or the supplement determination block 102.

[0080] Figure 21 According to embodiments of this disclosure, as follows Figure 19 The block diagram of system 40 shown adds circuitry for ear proximity detection based on active noise cancellation effect instead of circuitry for ear proximity detection based on forward passive occlusion. The presence of a reference microphone R in system 40 enables additional ear proximity detection via a technique called active noise cancellation effect. By comparing the acoustic energy in a specific frequency band at the reference microphone R and the error microphone E, the PPD32 can utilize the headphones (e.g., Figure 1BThe physical characteristics and mid-frequency (e.g., from 300Hz to 2kHz) of headphones 18A, 18B may show significant differences when the headphones are on the ear (e.g., due to active noise cancellation effects) and off the ear. Therefore, this additional information can be used to replace, or supplement, pilot-based, forward-passive-masking-based, and / or reverse-passive-masking-based decisions, to build greater confidence in the final decision.

[0081] like Figure 21 As shown, the PPD 32 may further include: a frequency range isolation filter 118 configured to receive and bandpass-filter a reference microphone signal ref; an envelope detector 120 for detecting the signal envelope of the reference microphone signal ref within the bandpass-filtered range; and a linear-to-decibel converter 122 configured to convert the detected enveloped, bandpass-filtered reference microphone signal into a value REF given in decibels relative to the full-scale amplitude of the reference microphone signal ref. dB Similarly, PPD 32 may also include: a frequency range isolation filter 124 configured to receive and bandpass-filter the error microphone signal err; an envelope detector 126 for detecting the signal envelope of the error microphone signal err within the bandpass-filtered range; and a linear-to-decibel converter 128 configured to convert the detected envelope, bandpass-filtered error microphone signal into a value ERR given in decibels relative to the full-scale amplitude of the error microphone signal err. dB Supplementary decision block 130 can adjust the value REF. dB and ERR dB The difference between them is compared, and the difference is compared with the threshold TH_ANCE. The signal is then transmitted to the ear proximity determination block 60, which can overturn or supplement the proximity determination made by the ear proximity determination block 60, the supplementary determination block 102 and / or the supplementary determination block 116.

[0082] By employing multiple ear proximity methods (based on pilot signals, forward passive occlusion, reverse passive occlusion, and active noise cancellation effects) depending on the environment and / or listening scenario (e.g., the presence of source audio, whether ANC is enabled), the PPD 32 can utilize the optimal detector for the scenario. Furthermore, the PPD 32 can combine detector decisions with the product to achieve potentially more robust ear proximity assessments. Figure 22 This is a flowchart of an example method 132 for selecting and combining auricular proximity detection techniques based on system operating parameters, according to embodiments of the present disclosure. In some embodiments, method 132 may be performed by another component of auricular proximity determination block 60 or PPD 32.

[0083] Method 132 may begin at step 134, where PPD 32 determines whether a source audio signal is present. If a source audio signal is present, method 132 may proceed to step 146. If a source audio signal is not present, method 132 may proceed to step 136.

[0084] In step 136, PPD 32 determines whether the ambient sound contains higher frequency content (e.g., between 2kHz and 5kHz). If the ambient sound contains higher frequency content, method 132 can proceed to step 138. Otherwise, if the ambient sound does not contain higher frequency content, method 132 can proceed to step 140.

[0085] In step 138, PPD 32 can activate forward passive occlusion detection. After completing step 138, method 132 can proceed to step 148.

[0086] In step 140, PPD 32 determines whether adaptive noise cancellation is activated in system 40. If adaptive noise cancellation is activated, method 132 can proceed to step 142. If adaptive noise cancellation is deactivated, method 132 can proceed to step 146.

[0087] In step 142, PPD 32 can determine whether the ambient sound has mid-frequency content (e.g., between 300 Hz and 2 kHz). If the ambient sound has mid-frequency content, method 132 can proceed to step 144. Otherwise, if the ambient sound does not have mid-frequency content, method 132 can proceed to step 146.

[0088] In step 144, PPD 32 can activate active noise cancellation effect detection. After completing step 144, method 132 can proceed to step 148.

[0089] In step 146, PPD 32 can activate pilot signal-based detection. After completing step 146, method 132 can proceed to step 148.

[0090] In step 148, PPD 32 can activate reverse passive occlusion detection. After completing step 148, method 132 can proceed to step 150.

[0091] In step 150, PPD 32 can combine the detector determinations of the activated proximity detection method to provide an auricular proximity detection determination. After step 150 is completed, method 132 can end.

[0092] In addition to the steps described above for selecting and combining ear proximity detection methods, other parameters can be used to select which ear proximity detection method to employ. For example, some detection methods may consume more battery power than others (e.g., when the pilot detector plays a strong pilot without source audio or noise immunity, this method consumes considerable power to drive the pilot signal PILOT through the speaker SPKR). In such cases, if an alternative detection method is available that is well-suited to the environment / listening scenario, the PPD 32 can select it instead.

[0093] Figure 23 This is a block diagram of a system 40A including selected components (including ANC circuit 30 and PPD 32A) of a CODEC IC 20 according to an embodiment of the present disclosure. Figure 23 System 40A is in many ways similar to Figure 3 Similar to System 40, therefore, only the key differences between System 40A and System 40 will be described below. A key difference between System 40A and System 40 is that System 40A includes PPD 32A instead of PPD 32. Unlike PPD 32, PPD 32A can perform auricular proximity detection without using pilot signals. Instead, when source audio is present, the source audio signal can provide training signals for an adaptive gain-based auricular proximity detector. Figure 23 As shown, PPD 32A may include low-pass filters 152 and 154. Low-pass filters 152 and 154 can respectively low-pass filter the error microphone signal err and the source audio signal to focus on the analysis of the low-frequency response of the acoustic coupling between the speaker SPKR and the error microphone E. PPD 32A may also include two filters 156 and 158, each having a response S_OE_LP(z) that represents the a priori low-frequency coupling between the speaker SPKR and the error microphone E when the headphones are not near the auricle of the ear 5 (away from the ear). Filter 158 may be needed to maintain the phase balance of the two inputs of the gain control block 160.

[0094] Gain control block 160 (which may use the least mean square method) adaptively controls the gain of gain element 162 to attempt to minimize the differential signal (as generated by combiner 164) between the low-pass filtered error microphone signal and the output of filter 156. When the output of combiner 164 is minimized, the combination of the adaptive gain of gain element 162 and filter 158 adequately simulates the low-frequency coupling response between speaker SPKR and error microphone E. This gain can approach unity when speaker SPKR is away from the ear. When speaker SPKR is on the ear, this gain may be much smaller than unity. Auricular proximity determination block 60A can use this gain to make a determination regarding the proximity between speaker SPKR and the auricle of ear 5.

[0095] When the source audio is available, proximity detection can be performed by removing the adaptive gain-based component from the PPD 32A. Figure 24 This is a block diagram of a system 40B according to an embodiment of the present disclosure, the system 40B including selected components of a CODEC IC 20, including an ANC circuit 30 and a PPD 32B. Figure 24 System 40B is in many ways similar to Figure 23 Similar to System 40A, the following describes only the key differences between System 40B and 40A. A key difference between System 40B and System 40A is that System 40B includes PPD 32B instead of PPD 32A. Unlike PPD 32A, PPD 32B can perform ear proximity detection without using adaptive gain control circuitry. When the speaker SPKR is away from the ear, the difference between the energy of the low-pass filtered error microphone signal and the output of filter 156 (generated by combiner 164) may be small, while this difference may be significantly larger when the speaker SPKR is on the ear. Therefore, the ear proximity determination block 60B can utilize this difference to make an ear proximity determination.

[0096] Back Figure 13 In this system 40, an ambient noise estimator 82 is used. Figure 25 This is a block diagram of an example ambient noise estimator 82 according to an embodiment of the present disclosure. To effectively estimate ambient noise, it is necessary to remove as much of the sensed pilot signal PILOT' as possible from the bandpass-filtered error microphone signal. This removal can be achieved by... Figure 13 The pilot tracker 56 described in the document is used to perform this action, or it can be performed by, for example, the pilot tracker 56 described in the document. Figure 25The additional pilot tracker 166 shown is used to perform this function in order to predict the sensed pilot signal PILOT'. The combiner 168 can subtract the predicted pilot signal from the bandpass-filtered error microphone signal to obtain the unfiltered error microphone signal. The envelope detector 170 and the linear-to-decibel converter 172 can further process the unfiltered error microphone signal to generate an estimate of the ambient noise, which the ambient noise estimator 82 can then transmit to the pilot reference calculator 84.

[0097] As used herein, when two or more elements are referred to as “coupled” to each other, the term indicates that the two or more elements are in electronic or mechanical communication, if applicable, whether indirect or direct, with or without intervening elements.

[0098] This disclosure includes all changes, substitutions, variations, alterations, and modifications to the exemplary embodiments herein that will be understood by those skilled in the art. Similarly, where appropriate, the appended claims cover all changes, substitutions, variations, alterations, and modifications to the exemplary embodiments herein that will be understood by those skilled in the art. Furthermore, references in the appended claims to means or systems adapted to, arranged to, capable of, configured to, enabled, operable to, or operated to perform a particular function, or components of such means or systems, include that means or system, whether or not it or the particular function is activated, turned on, or unlocked, provided that the means or system is so adapted, arranged, capable of, configured to, enabled, operable to, or operated. Therefore, modifications, additions, or omissions may be made to the systems, means, and methods described herein without departing from the scope of this disclosure. For example, components of systems and means may be integrated or separated. Furthermore, the operation of the systems and means disclosed herein may be performed by more, fewer, or other components, and the described methods may include more, fewer, or other steps. Additionally, the steps may be performed in any suitable order. As used in this document, “each” means each member of a set or each member of a subset of a set.

[0099] Although exemplary embodiments are shown in the accompanying drawings and described below, the principles of this disclosure can be implemented using any number of techniques, whether currently known or not. This disclosure should in no way be limited to the exemplary embodiments and techniques shown in the drawings and described above.

[0100] Unless otherwise specified, the items depicted in the accompanying drawings are not necessarily drawn to scale.

[0101] All examples and conditional language described herein are intended for educational purposes to aid the reader's understanding of this disclosure and the concepts contributed by the inventors to further develop the technology, and are not to be construed as being limited to such specific examples and conditions. Although embodiments of this disclosure have been described in detail, it should be understood that various changes, substitutions, and modifications can be made thereto without departing from the spirit and scope of this disclosure.

[0102] While specific advantages have been listed above, various embodiments may include some, none, or all of the listed advantages. Furthermore, other technical advantages will become apparent to those skilled in the art after reviewing the foregoing figures and description.

[0103] In order to help the Patent Office and any reader of any patent published under this application to interpret its appended claims, the applicant wishes to note that they have no intention of referencing 35 U.SC §112(f) in any appended claim or claim element, unless the words “means for…” or “steps for…” are used expressly in a particular claim.

Claims

1. An integrated circuit for proximity detection of headphones, the headphones including a speaker, the integrated circuit comprising: A first input terminal is used to receive a first signal from a reference microphone of the headphones, the first signal indicating ambient sound of the headphones; The second input terminal is used to receive a second signal from the error microphone of the headphones, the second signal indicating the sound present at the acoustic output terminal of the headphone speaker; as well as Circuitry used to compare the first acoustic energy of the first signal and the second acoustic energy of the second signal to determine whether the earphones are on the user's ears. Wherein, the first acoustic energy and the second acoustic energy are within a frequency band, and wherein the frequency band is from 2KHz to 5KHz.

2. The integrated circuit according to claim 1, further comprising: A frequency range isolation filter configured to receive the first signal and perform bandpass filtering on the first signal; An envelope detector is used to detect the signal envelope of a first signal within a bandpass filter range. as well as A linear-to-decibel converter configured to convert a detected enveloped, bandpass-filtered first signal into a value given in decibels relative to the full-scale amplitude of the first signal.

3. The integrated circuit according to claim 1, further comprising: A frequency range isolation filter configured to receive the second signal and perform bandpass filtering on the second signal; An envelope detector is used to detect the signal envelope of a second signal within a bandpass filter range. as well as A linear-to-decibel converter configured to convert a detected enveloped, bandpass-filtered second signal into a value given in decibels relative to the full-scale amplitude of the second signal.

4. The integrated circuit according to claim 1, further comprising: A first frequency range isolation filter is configured to receive the first signal and perform bandpass filtering on the first signal; A first envelope detector is used to detect the signal envelope of a first signal within the bandpass filtering range; A first linear-to-decibel converter is configured to convert the detected envelope, bandpass-filtered first signal into a value given in decibels relative to the full-scale amplitude of the first signal; A second frequency range isolation filter is configured to receive the second signal and perform bandpass filtering on the second signal; The second envelope detector is used to detect the signal envelope of the second signal within the bandpass filtering range; as well as A second linear-decibel converter is configured to convert the detected envelope, bandpass-filtered second signal into a value given in decibels relative to the full-scale amplitude of the second signal.

5. The integrated circuit according to claim 1, further comprising: A first frequency range isolation filter is configured to receive the first signal and perform bandpass filtering on the first signal; A first envelope detector is used to detect the signal envelope of a first signal within the bandpass filtering range; A first linear-to-decibel converter is configured to convert the detected envelope, bandpass-filtered first signal into a value given in decibels relative to the full-scale amplitude of the first signal; A second frequency range isolation filter is configured to receive the second signal and perform bandpass filtering on the second signal; The second envelope detector is used to detect the signal envelope of the second signal within the bandpass filtering range; A second linear-decibel converter is configured to convert the detected envelope, bandpass-filtered second signal into a value given in decibels relative to the full-scale amplitude of the second signal; A circuit for comparing the difference between the decibel values ​​of the first signal and the second signal, comparing the difference with a threshold, and outputting a control signal; as well as A proximity determination block, in response to the control signal and configured to determine whether the earphone is on the user's ear.

6. An earphone, comprising: Headphones and speakers; Reference microphone; Error microphone; as well as An integrated circuit for proximity detection of headphones includes: A first input terminal is used to receive a first signal from the reference microphone, the first signal indicating ambient sound in the headphones; The second input terminal is used to receive a second signal from the error microphone, the second signal indicating the sound present at the acoustic output terminal of the headphone speaker; Circuitry used to compare the first acoustic energy of the first signal and the second acoustic energy of the second signal to determine whether the earphones are on the user's ears. Wherein, the first acoustic energy and the second acoustic energy are within a frequency band, and wherein the frequency band is from 2KHz to 5KHz.

7. The earphone according to claim 6, further comprising: A frequency range isolation filter configured to receive the first signal and perform bandpass filtering on the first signal; An envelope detector is used to detect the signal envelope of a first signal within a bandpass filter range. as well as A linear-to-decibel converter configured to convert a detected enveloped, bandpass-filtered first signal into a value given in decibels relative to the full-scale amplitude of the first signal.

8. The earphone according to claim 6, further comprising: A frequency range isolation filter configured to receive the second signal and perform bandpass filtering on the second signal; An envelope detector is used to detect the signal envelope of a second signal within a bandpass filter range. as well as A linear-to-decibel converter configured to convert a detected enveloped, bandpass-filtered second signal into a value given in decibels relative to the full-scale amplitude of the second signal.

9. The earphone according to claim 6, further comprising: A first frequency range isolation filter is configured to receive the first signal and perform bandpass filtering on the first signal; A first envelope detector is used to detect the signal envelope of a first signal within the bandpass filtering range; A first linear-to-decibel converter is configured to convert the detected envelope, bandpass-filtered first signal into a value given in decibels relative to the full-scale amplitude of the first signal; A second frequency range isolation filter is configured to receive the second signal and perform bandpass filtering on the second signal; The second envelope detector is used to detect the signal envelope of the second signal within the bandpass filtering range; as well as A second linear-to-decibel converter is configured to convert the detected envelope, bandpass-filtered second signal into a value given in decibels relative to the full-scale amplitude of the second signal.

10. The earphone according to claim 6, further comprising: A first frequency range isolation filter is configured to receive the first signal and perform bandpass filtering on the first signal; A first envelope detector is used to detect the signal envelope of a first signal within the bandpass filtering range; A first linear-decibel converter is configured to convert the detected envelope, bandpass-filtered first signal into a value given in decibels relative to the full-scale amplitude of the first signal; A second frequency range isolation filter is configured to receive the second signal and perform bandpass filtering on the second signal; The second envelope detector is used to detect the signal envelope of the second signal within the bandpass filtering range; A second linear-to-decibel converter is configured to convert the detected envelope, bandpass-filtered second signal into a value given in decibels relative to the full-scale amplitude of the second signal; A circuit for comparing the difference between the decibel values ​​of the first signal and the second signal, comparing the difference with a threshold, and outputting a control signal; as well as A proximity determination block, in response to the control signal and configured to determine whether the earphone is on the user's ear.

11. The headphones according to claim 6, wherein, The headphones are wired headphones used for communicatively coupling to an audio device.

12. The headphones according to claim 6, wherein, The headphones are wireless headphones used for communicatively coupling to audio devices.

13. The headphones according to claim 6, wherein, The headphones are wireless earbuds used for communicatively coupling to an audio device.

14. An integrated circuit for proximity detection of headphones, the headphones including a first headphone speaker and a second headphone speaker, the integrated circuit comprising: A first input terminal is used to receive a first signal from a first reference microphone, the first signal indicating ambient sound of the first earphone; The second input terminal is used to receive a second signal from the first error microphone, the second signal indicating the sound present at the acoustic output terminal of the first headphone speaker; The third input terminal is used to receive a third signal from the second reference microphone, the third signal indicating ambient sound in the second earphone; A fourth input terminal is used to receive a fourth signal from the second error microphone, the fourth signal indicating the sound present at the acoustic output terminal of the second headphone speaker; as well as; Circuitry used to compare the first acoustic energy of the first signal with the second acoustic energy of the second signal, and to compare the third acoustic energy of the third signal with the fourth acoustic energy of the fourth signal, to determine whether the earphone is on the user's ear. Wherein, the first acoustic energy and the second acoustic energy are within a frequency band, and wherein the frequency band is from 2KHz to 5KHz.

15. The integrated circuit according to claim 14, further comprising: A frequency range isolation filter configured to receive the first signal and perform bandpass filtering on the first signal; An envelope detector is used to detect the signal envelope of a first signal within a bandpass filter range. as well as A linear-to-decibel converter configured to convert a detected enveloped, bandpass-filtered first signal into a value given in decibels relative to the full-scale amplitude of the first signal.

16. The integrated circuit of claim 14, further comprising: A frequency range isolation filter configured to receive the second signal and perform bandpass filtering on the second signal; An envelope detector is used to detect the signal envelope of a second signal within a bandpass filter range. as well as A linear-to-decibel converter configured to convert a detected enveloped, bandpass-filtered second signal into a value given in decibels relative to the full-scale amplitude of the second signal.

17. The integrated circuit according to claim 14, further comprising: A first frequency range isolation filter is configured to receive the first signal and perform bandpass filtering on the first signal; A first envelope detector is used to detect the signal envelope of a first signal within the bandpass filtering range; A first linear-decibel converter is configured to convert the detected envelope, bandpass-filtered first signal into a value given in decibels relative to the full-scale amplitude of the first signal; A second frequency range isolation filter is configured to receive the second signal and perform bandpass filtering on the second signal; The second envelope detector is used to detect the signal envelope of the second signal within the bandpass filtering range; as well as A second linear-to-decibel converter is configured to convert the detected envelope, bandpass-filtered second signal into a value given in decibels relative to the full-scale amplitude of the second signal.

18. The integrated circuit according to claim 14, further comprising: A first frequency range isolation filter is configured to receive the first signal and perform bandpass filtering on the first signal; A first envelope detector is used to detect the signal envelope of a first signal within the bandpass filtering range; A first linear-decibel converter is configured to convert the detected envelope, bandpass-filtered first signal into a value given in decibels relative to the full-scale amplitude of the first signal; A second frequency range isolation filter is configured to receive the second signal and perform bandpass filtering on the second signal; The second envelope detector is used to detect the signal envelope of the second signal within the bandpass filtering range; A second linear-to-decibel converter is configured to convert the detected envelope, bandpass-filtered second signal into a value given in decibels relative to the full-scale amplitude of the second signal; A circuit for comparing the difference between the decibel values ​​of the first signal and the second signal, comparing the difference with a threshold, and outputting a control signal; as well as A proximity determination block, in response to the control signal and configured to determine whether the earphone is on the user's ear.

19. The integrated circuit according to claim 14, wherein, The headphones are wired headphones used for communicatively coupling to an audio device.

20. The integrated circuit according to claim 14, wherein, The headphones are wireless headphones used for communicatively coupling to audio devices.

21. The integrated circuit according to claim 14, wherein, The headphones are a pair of wireless earbuds used for communicatively coupling to an audio device.

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