System and method for on-ear detection of a headset

Abstract

The described embodiments generally relate to a signal processing device for on-ear detection of an earbud. The device includes: a first microphone input for receiving a microphone signal from a first microphone configured to be positioned within a user's ear when the earbud is worn; a second microphone input for receiving a microphone signal from a second microphone configured to be positioned outside the user's ear when the earbud is worn; a signal generator configured to generate a signal for acoustic playback from a speaker configured to be positioned within the earbud; and a processor. The processor is configured to receive at least one first microphone signal from each of the first microphone input and the second microphone input, and compare the first microphone signals to determine an on-ear state of the earbud; determine that the on-ear state of the earbud cannot be sufficiently determined, generate a signal for acoustic playback from the speaker, receive a second microphone signal from the first microphone input, and compare the second microphone signal with the generated signal to determine the on-ear state of the earbud.

Description

Technical Field

[0001] Embodiments generally relate to systems and methods for determining whether a headset is on or in a user's ear, and to headsets configured to determine whether a headset is on or in a user's ear. Background Art

[0002] A headset is a popular device for delivering sound and audio to one or both ears of a user. For example, a headset can be used to deliver audio such as music, audio files, or playback of a telephone signal. A headset typically also captures sound from the surrounding environment. For example, a headset can capture a user's voice for voice recording or a voice call, or can capture background noise signals for enhancing signals processed by the device. A headset can provide a wide range of signal processing functions.

[0003] For example, one such function is active noise cancellation (ANC, also known as active noise control), which combines a noise cancellation signal with a playback signal and outputs the combined signal via a speaker such that the noise cancellation signal component acoustically cancels ambient noise and the user hears or mainly hears the playback signal of interest. ANC processing typically takes as input the ambient noise signal provided by a reference (feedforward) microphone and the playback signal provided by an error (feedback) microphone. Even when the headset is removed, ANC processing continues to consume a significant amount of power.

[0004] Thus, in ANC and similarly in many other signal processing functions of a headset, it is desirable to know whether the headset is worn at any given time. For example, it is desirable to know whether an on-ear headset is placed on or above a user's pinna, and whether an earbud-type headset has been placed in a user's ear canal or outer ear. Both of these usage scenarios are referred to herein as the respective headset being "on ear". An unused state such as when the headset is worn around the user's neck or is completely removed is referred to herein as being "off ear".

[0005] Previous methods for on ear detection include using dedicated sensors such as capacitive sensors, optical sensors or infrared sensors which can detect when a headset is worn on or near the ear. Another previous method for on ear detection is to provide a sensing microphone positioned to detect acoustic sounds inside the headset when worn, based on the fact that acoustic reverberation in the ear canal and / or pinna will result in a detectable rise in the power of the sensing microphone signal compared to when the headset is away from the ear. However, the power of the sensing microphone signal can be affected by significant ambient noise from noise sources such as traffic, so this method may output false positives for the headset being on ear when the headset is actually away from the ear and affected by noise. These and other methods for on ear detection may also output false positives when the headset is held in the user's hand, placed in a case, etc.

[0006] It is desirable to address or improve one or more drawbacks or disadvantages associated with prior systems and methods for determining whether a headset is located on or in a user's ear, or at least to provide a useful alternative.

[0007] Throughout this specification, the word "comprise" or variations such as "comprises" or "comprising" will be understood to imply the inclusion of the stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0008] In this specification, a statement that an element can be "at least one" of a list of options should be understood to mean that the element can be any one of the listed options, or any combination of two or more of the listed options.

[0009] Any discussion of documents, acts, materials, devices, articles, etc. included in this specification should not be taken as an admission that any or all of these matters form part of the prior art base or are common general knowledge in the field relevant to this disclosure, as they existed before the priority date of each of the appended claims. SUMMARY OF THE INVENTION

[0010] Some embodiments relate to a signal processing device for on ear detection of an earbud, the device comprising:

[0011] A first microphone input for receiving a microphone signal from a first microphone configured to be positioned within a user's ear when the earbud is worn;

[0012] A second microphone input for receiving a microphone signal from a second microphone, the second microphone being configured to be positioned outside the user's ear when the earbud is worn;

[0013] A signal generator configured to generate a signal for acoustic playback, the signal for acoustic playback being from a speaker configured to be positioned within the earbud; and

[0014] A processor configured to:

[0015] Receive at least one first microphone signal from each of the first microphone input and the second microphone input, and compare the first microphone signals to determine an on-ear state of the earbud;

[0016] Determine that the on-ear state of the earbud cannot be sufficiently determined, generate a signal for acoustic playback from the speaker, receive a second microphone signal from the first microphone input, and compare the second microphone signal with the generated signal to determine the on-ear state of the earbud.

[0017] Some embodiments further include a proximity sensor, and wherein the processor is further configured to receive at least one sensor signal from the proximity sensor indicating that the earbud is close to an object, and in response to receiving at least one sensor signal from the proximity sensor, perform the steps of receiving at least one first microphone signal and comparing the first microphone signals to determine the on-ear state of the earbud. According to some embodiments, the proximity sensor is an infrared sensor.

[0018] According to some embodiments, comparing the first microphone signals to determine the on-ear state of the earbud includes comparing power levels of the first microphone signals. In some embodiments, comparing the first microphone signals to determine the on-ear state of the earbud further includes determining that the earbud is on-ear if the power of the first microphone signal received from the first microphone is lower than a predetermined threshold than the power of the first microphone signal received from the second microphone.

[0019] In some embodiments, comparing the first microphone signals to determine the on-ear state of the earbud further includes determining that the earbud is off-ear if the power of the first microphone signal received from the first microphone is higher than a predetermined threshold than the power of the first microphone signal received from the second microphone.

[0020] In some embodiments, comparing the first microphone signals to determine the on-ear state of the earbud further includes determining that the on-ear state of the earbud cannot be sufficiently determined if the power level of each first microphone signal is lower than a predetermined threshold.

[0021] According to some embodiments, comparing at least one second microphone signal with the generated signal to determine an on-ear state of the earbud includes determining whether the at least one second microphone signal includes a resonance of the generated signal.

[0022] In some embodiments, the generated signal is an audible detection signal. According to some embodiments, the generated signal has a frequency known to produce a resonance in a human ear canal.

[0023] In some embodiments, the processor is further configured to perform an audio processing function in response to the determined on-ear state of the earbud.

[0024] Some embodiments relate to a method for on-ear detection of an earbud, the method including:

[0025] Receiving a first microphone signal from a first microphone and a first microphone signal from a second microphone, wherein the first microphone is configured to be positioned within a user's ear when the earbud is worn, and the second microphone is configured to be positioned outside the user's ear when the earbud is worn;

[0026] Comparing the first microphone signal to determine the on-ear state of the earbud;

[0027] Determining that the on-ear state of the earbud cannot be sufficiently determined, generating a signal for acoustic playback, receiving a second microphone signal from the first microphone, and comparing the second microphone signal with the generated signal to determine the on-ear state of the earbud, the signal for acoustic playback being from a speaker configured to be positioned within the earbud.

[0028] Some embodiments further include receiving at least one sensor signal from a proximity sensor indicating that the earbud is close to an object, and performing the steps of receiving at least one first microphone signal and comparing the first microphone signal to determine the on-ear state of the earbud in response to receiving the at least one sensor signal from the proximity sensor.

[0029] According to some embodiments, comparing the first microphone signal to determine the on-ear state of the earbud includes comparing power levels of the first microphone signal. In some embodiments, comparing the first microphone signal to determine the on-ear state of the earbud further includes determining that the earbud is on-ear if the power of the first microphone signal received from the first microphone is lower than a predetermined threshold than the power of the first microphone signal received from the second microphone.

[0030] According to some embodiments, comparing the first microphone signal to determine the on-ear state of the earbud further includes determining that the earbud is off-ear if the power of the first microphone signal received from the first microphone is higher than a predetermined threshold than the first microphone signal received from the second microphone.

[0031] In some embodiments, comparing the first microphone signal to determine the on-ear state of the earbud further includes determining that the on-ear state of the earbud cannot be determined sufficiently if the power level of each first microphone signal is lower than a predetermined threshold.

[0032] In some embodiments, comparing at least one second microphone signal with the generated signal to determine the on-ear state of the earbud includes determining whether the at least one second microphone signal includes a resonance of the generated signal.

[0033] According to some embodiments, the generated signal is an audible detection signal. In some embodiments, the generated signal has a frequency known to produce resonance in a human ear canal.

[0034] Some embodiments further include performing an audio processing function in response to the determined on-ear state of the earbud.

[0035] Some embodiments relate to a signal processing device for on-ear detection of an earbud, the device including:

[0036] A first microphone input for receiving a microphone signal from a first microphone configured to be positioned within a user's ear when the earbud is worn;

[0037] A second microphone input for receiving a microphone signal from a second microphone configured to be positioned outside a user's ear when the earbud is worn;

[0038] A signal generator configured to generate a signal for acoustic playback, the signal for acoustic playback being from a speaker configured to be positioned within the earbud; and

[0039] A processor configured to:

[0040] Generate a signal for acoustic playback from the speaker;

[0041] Cause the signal to be played by the speaker;

[0042] Receive at least one microphone signal from each of the first microphone input and the second microphone input, and compare the received microphone signals with the signal generated by the speaker for playback to detect a resonance of the generated signal; and

[0043] Determine the on-ear state of the earbud;

[0044] Wherein, the earbud is determined to be on-ear only when resonance is detected in the signal input from the first microphone but not in the signal input from the second microphone.

[0045] According to some embodiments, the generated signal is an audible detection signal. According to some embodiments, the generated signal has a frequency known to produce resonance in a human ear canal.

[0046] In some embodiments, the processor is further configured to filter the received microphone signals using a band-pass filter before comparing the received microphone signals. In some embodiments, the band-pass filter is matched to the frequency of the generated signal.

[0047] According to some embodiments, the processor is configured to compare the filtered signals only after a predetermined time period has elapsed since the time when the generated signal was emitted from the speaker.

[0048] In some embodiments, comparing the received microphone signals with the generated signal played by the speaker to detect resonance of the generated signal includes subtracting the power level of the microphone signal received from the second microphone and the power level of the generated signal from the power level of the microphone signal received from the first microphone, and comparing the resulting power level with a predetermined threshold.

[0049] According to some embodiments, the processor is further configured to perform an audio processing function in response to the determined on-ear state of the earbud.

[0050] Some embodiments relate to a method for on-ear detection of an earbud, the method comprising:

[0051] Generating a signal for acoustic playback, the signal for acoustic playback being from a speaker configured to be located within the earbud;

[0052] Causing the signal to be played by the speaker;

[0053] Receiving at least one microphone signal from a first microphone and a second microphone, wherein the first microphone is configured to be located within a user's ear when the earbud is worn, and the second microphone is configured to be located outside the user's ear when the earbud is worn;

[0054] Comparing the received microphone signals with the generated signal played by the speaker to detect resonance of the generated signal; and

[0055] Determine an on-ear state of the earbud, wherein the earbud is determined to be on-ear only when resonance is detected in the signal from the first microphone input but not in the signal from the second microphone input.

[0056] In some embodiments, the generated signal is an audible detection signal. According to some embodiments, the generated signal has a frequency known to produce resonance in a human ear canal.

[0057] Some embodiments further include filtering the received microphone signals using a bandpass filter before comparing the received microphone signals. In some embodiments, the bandpass filter is matched to the frequency of the generated signal.

[0058] Some embodiments further include comparing the filtered signals only after a predetermined time period has elapsed since the time the generated signal was emitted from the speaker.

[0059] According to some embodiments, comparing the received microphone signals with the generated signal played by the speaker to detect resonance of the generated signal includes subtracting the power level of the microphone signal received from the second microphone and the power level of the generated signal from the power level of the microphone signal received from the first microphone, and comparing the resulting power level with a predetermined threshold.

[0060] Some embodiments further include performing an audio processing function in response to the determined on-ear state of the earbud.

[0061] Some embodiments relate to a machine-readable medium storing non-transitory instructions that, when executed by one or more processors, cause an electronic device to perform the methods of some other embodiments.

[0062] Some embodiments relate to a device including a processing circuit and a non-transitory machine-readable medium that, when executed by the processing circuit, causes the device to perform the methods of some other embodiments.

[0063] Some embodiments relate to a system for on-ear detection of an earbud, the system including a processor and a memory containing instructions executable by the processor, and wherein the system is operable to perform the methods of some other embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Embodiments are further described in detail below by way of examples and with reference to the accompanying drawings, in which:

[0065] Figure 1Illustrated is a signal processing system including a headset, in which on-ear detection according to some embodiments is implemented;

[0066] Figure 2 Shows a block diagram of the hardware components of an earbud of a headset; Figure 1

[0067] Figure 3 Shows a block diagram of the software modules of an earbud of a headset; Figure 1

[0068] Figure 4 Shows a flowchart of a method for determining whether a headset is on or in a user's ear, as exemplified by a system; Figure 1

[0069] Figure 5 Shows a block diagram of the active on-ear detection process of the method, shown in further detail; Figure 4

[0070] Figures 6A to 6C Shows a graph of the signal measured by the internal microphone of a system; and Figure 1

[0071] Figures 7A to 7B Shows a graph of the signals measured by the internal and external microphones of a system; Figure 1 DETAILED DESCRIPTION

[0072] This embodiment generally relates to systems and methods for determining whether a headset is on or in a user's ear, and to a headset configured to determine whether a headset is on or in a user's ear.

[0073] Some embodiments relate to hybrid on-ear detection techniques, in which a headset first operates in a low-power listening mode or a passive mode and makes a first attempt to make an on-ear determination. If a determination cannot be made, for example if the surrounding acoustic environment is too quiet, the headset moves to a relatively high-power active mode where a probe signal needs to be generated, and then makes a second attempt to make an on-ear determination. This hybrid technique can allow for greater certainty by using the active detection technique as a last resort and not requiring continuous probe signals to be emitted, compared to using proximity sensors or passive detection techniques alone.

[0074] ​​​​​​Some embodiments further relate to a high-power or active on-ear detection technique that reduces false positive results that may occur when the earbuds are contained within a small enclosed environment (e.g., held in the user's hand) by comparing an internal microphone signal and an external microphone signal in response to the application of an audible resonance detection signal rather than looking at the internal microphone signal alone.

[0075] Figure 1 An example of a headset 100 in which on-ear detection is implemented is illustrated. The headset 100 includes two earbuds 120 and 150, each earbud including two microphones 121, 122 and 151, 152, respectively. The headset 100 may be configured to determine whether each earbud 120, 150 is located within or on the user's ear.

[0076] Figure 2 FIG. is a system diagram that further shows in detail the hardware components of the earbud 120. The earbud 150 includes components that are substantially the same as those of the earbud 120 and are configured in substantially the same manner. Accordingly, the earbud 150 is not shown or described separately.

[0077] In addition to the microphones 121 and 122, the earbud 120 further includes a digital signal processor 124 that is configured to receive microphone signals from the earbud microphones 121 and 122. The microphone 121 is an external microphone or a reference microphone and is positioned to sense ambient noise from outside the ear canal and outside the earbud when the earbud 120 is positioned within or on the user's ear. In contrast, the microphone 122 is an internal microphone or an error microphone and is positioned within the ear canal such that when the earbud 120 is positioned within or on the user's ear, it senses the acoustic sound within the ear canal.

[0078] The earbud 120 further includes a speaker 128 for delivering audio to the user's ear canal when the earbud 120 is positioned within or on the user's ear. When the earbud 120 is positioned within the ear canal, the microphone 122 is at least partially blocked from the external ambient acoustic environment but remains in good coupling with the output of the speaker 128. In contrast, when the earbud 120 is positioned within or on the user's ear, the microphone 121 is at least partially blocked from the output of the speaker 128 but remains in good coupling with the external ambient acoustic environment. The headset 100 may be configured to deliver music or audio to the user, allow the user to make phone calls, deliver voice commands to a voice recognition system, and other such audio processing functions.

[0079] The processor 124 is also configured to adapt the manipulation of such audio processing functions in response to one or both of the earbuds 120, 150 being positioned on or removed from the ears. For example, the processor 124 may be configured to pause the audio being played through the headset 100 when the processor 124 detects that one or more of the earbuds 120, 150 have been removed from the user's ears. The processor 124 may also be configured to resume the audio being played through the headset 100 when the processor 124 detects that one or more of the earbuds 120, 150 have been placed on or within the user's ears.

[0080] The earbud 120 also includes a memory 125, which may actually be provided as a single component or multiple components. The memory 125 is provided for storing data and program instructions that can be read and executed by the processor 124 to cause the processor 124 to perform functions such as those described above. The earbud 120 also includes a transceiver 126 that allows the earbud 120 to communicate with external devices. According to some embodiments, the earbuds 120, 150 may be wireless earbuds, and the transceiver 126 may facilitate wireless communication between the earbud 120 and the earbud 150, as well as wireless communication between the earbuds 120, 150 and external devices such as a music player or a smart phone. According to some embodiments, the earbuds 120, 150 may be wired earbuds, and the transceiver 126 may facilitate wired communication between the earbud 120 and the earbud 150 directly (such as within an overhead band) or via an intermediate device such as a smart phone. According to some embodiments, the earbud 120 may also include a proximity sensor 129 that is configured to send a signal indicating whether the earbud 120 is in a position proximate to an object to the processor 124 and / or measure the proximity of the object. In some embodiments, the proximity sensor 129 may be an infrared sensor or a subsonic sensor. According to some embodiments, the earbud 120 may have other sensors such as a motion sensor or an accelerometer. The earbud 120 also includes a power source 123, which may be a battery according to some embodiments.

[0081] Figure 3 A block diagram of an executable software module stored in the memory 125 of the earbud 120 is shown in further detail, and a process for on-ear monitoring according to some embodiments is further illustrated. Figure 3 The microphones 121 and 122, and the speaker 128 and the proximity sensor 129 are shown. The proximity sensor 129 may be an optional component in some embodiments. When audio is not being played through the speaker 128, the reference microphone 121 generates a passive signal X based on the detected ambient sound RPWhen playing audio via the speaker 128, the reference microphone 121 generates an active signal X based on the detected sound, which may include ambient sound and the sound emitted through the speaker 128. When not playing audio via the speaker 128, the error microphone 122 generates a passive signal X based on the detected ambient sound. RA When playing audio via the speaker 128, the error microphone 122 generates an active signal X based on the detected sound, which may include ambient sound and the sound emitted through the speaker 128. EP When playing audio via the speaker 128, the error microphone 122 generates an active signal X based on the detected sound, which may include ambient sound and the sound emitted through the speaker 128. EA When playing audio via the speaker 128, the error microphone 122 generates an active signal X based on the detected sound, which may include ambient sound and the sound emitted through the speaker 128.

[0082] The memory 125 stores a passive on-ear detection module 310 executable by the processor 124 to determine whether the earbud 120 is on or in the user's ear using passive on-ear detection. Passive on-ear detection refers to an on-ear detection process that does not require audio to be emitted via the speaker 128 but instead uses the sound detected in the ambient acoustic environment to make an on-ear determination. The passive on-ear detection module 310 is configured to receive a signal from the proximity sensor 129 and the passive signals X and X from the microphones 121 and 122. RP and X EP The signal received from the proximity sensor 129 may indicate whether the earbud 120 is close to an object. If the signal received from the proximity sensor 129 indicates that the earbud 120 is close to an object, the passive on-ear detection module 310 may be configured to cause the processor 124 to process the passive signals X and X to determine whether the earbud 120 is in or on the user's ear. In some embodiments where the earbud 120 does not include a proximity sensor 129, the earbud 120 may alternatively perform passive on-ear detection continuously or periodically based on a predetermined time period or based on some other input signal being received. RP and X EP The processor 124 may perform passive on-ear detection by measuring and comparing the powers of the passive signals X and X. If the power of the passive signal X received from the reference microphone 121 is high, but the power of the passive signal X received from the error microphone 122 is low, the processor 124 may determine that the earbud 120 is in or on the user's ear. According to some embodiments, the processor 124 may consider the power of the passive signal X received from the reference microphone 121 to be high, while the power of the passive signal X received from the error microphone 122

[0083] The processor 124 may perform passive on-ear detection by measuring and comparing the powers of the passive signals X and X. RP and X EP If the power of the passive signal X received from the reference microphone 121 is high, but the power of the passive signal X received from the error microphone 122 is low, the processor 124 may determine that the earbud 120 is in or on the user's ear. According to some embodiments, the processor 124 may consider the power of the passive signal X received from the reference microphone 121 to be high, while the power of the passive signal X received from the error microphone 122 RP is low, then the processor 124 may determine that the earbud 120 is in or on the user's ear. According to some embodiments, the processor 124 may consider the power of the passive signal X received from the reference microphone 121 to be high, while the power of the passive signal X received from the error microphone 122 EP is low, then the processor 124 may determine that the earbud 120 is in or on the user's ear. According to some embodiments, the processor 124 may consider the power of the passive signal X received from the reference microphone 121 to be high, while the power of the passive signal X received from the error microphone 122 RP is high, while the power of the passive signal X received from the error microphone 122 EPThe power is low, for example if the threshold difference between the two signals is greater than 8 dB. This may correspond to a situation where the reference microphone 121 is detecting ambient noise, but since the error microphone 122 is located within the ear canal, this ambient noise is blocked by the microphone 122. If the passive signal X received from the reference microphone 121 RP has high power, and the passive signal X received from the error microphone EP also has high power, then the processor 124 may determine that the earbud 120 is outside the user's ear. According to some embodiments, the processor 124 may consider the passive signal X received from the reference microphone 121 RP to have high power, and the passive signal X received from the error microphone 122 EP also to have high power, for example if the threshold difference between the two signals is less than 8 dB and the power of the two signals is higher than a predetermined threshold (which may be approximately 70 dB SPL). This may correspond to a situation where both the reference microphone 121 and the error microphone 122 are detecting ambient noise. The result of this determination may be sent to the decision module 340 for further processing. However, if the passive signal X received from the reference microphone 121 RP has low power, then the processor 124 may not be able to make a determination about the on-ear state of the earbud 120. This may correspond to a situation where there is little or no ambient noise, and thus both microphones 121 and 122 may generate low signals. For example, a low signal may be a signal below 70 dB SPL.

[0084] If the passive on-ear detection module 310 cannot make a determination, the passive on-ear detection module 310 may send a signal to the active on-ear detection module 320 to indicate that the passive on-ear detection was not successful. According to some embodiments, even if the passive on-ear detection module 310 can make a determination, the passive on-ear detection module 310 may also send a signal to the active on-ear detection module 320 to initiate active on-ear detection, which may be used, for example, to confirm the determination made by the passive on-ear detection module 310.

[0085] The active on-ear detection module 320 may be executed by the processor 124 to use active on-ear detection to determine whether the earbud 120 is on or in the user's ear. Active on-ear detection refers to an on-ear detection process that requires an audio tone to be emitted via the speaker 128 to make an on-ear determination. The active on-ear detection module 320 may be configured to cause the speaker 128 to play a sound, receive the active signal X from the error microphone 122 in response to the played sound EA , and cause the processor 124 to process the active signal X with reference to the played sound EA, to determine whether the earbud 120 is in or on the user's ear. According to some embodiments, the active on-ear detection module 320 may also optionally receive and process an active signal X from the reference microphone 121 RA , as described further below with reference to Figures 5 to 7B .

[0086] The processor 124 that executes the active on-ear detection module 320 may first be configured to instruct the signal generation module 330 to generate a detection signal that will be emitted by the speaker 128. According to some embodiments, the generated detection signal may be an audible detection signal and may be, for example, a chime signal. According to some embodiments, the detection signal may be a signal having a frequency known to resonate in a human ear canal. For example, according to some embodiments, the frequency of the signal may be between 100 Hz and 2 kHz. According to some embodiments, the frequency of the signal may be between 200 Hz and 400 Hz. According to some embodiments, the signal may include the notes C, D, and G and is a Csus2 chord.

[0087] The microphone 121 may generate the active signal X during the period when the speaker 128 is emitting the detection signal EA . The active signal X EA may include a signal that at least partially corresponds to the detection signal emitted by the speaker 128.

[0088] Once the speaker 128 has emitted the signal generated by the signal generation module 330 and the microphone 122 has generated the active signal X EA (the signal X EA is generated based on the audio sensed by the microphone 122 during the emission of the generated signal by the speaker 128), the signal X EA is processed by the processor 124 that executes the active on-ear detection module 320 to determine whether the earbud 120 is on or in the user's ear. The processor 124 may perform active on-ear detection by detecting whether the error microphone 122 detects the resonance of the detection signal emitted by the speaker 128, by comparing the detection signal with the active signal X EA . This may include determining whether the resonance gain of the detection signal exceeds a predetermined threshold. If the processor 124 determines that the active signal X EA is related to the resonance of the detection signal, the processor 124 may determine that the microphone 122 is located within the user's ear canal and, thus, the earbud 120 is on or in the user's ear. If the processor 124 determines that the active signal X EAIrrespective of the resonance of the detection signal, the processor 124 can determine that the microphone 122 is not located within the user's ear canal, and thus the earbud 120 is not on or in the user's ear. The result of this determination can be sent to the decision module 340 for further processing.

[0089] Once an on-ear decision is generated by one of the passive on-ear detection module 310 and the active on-ear detection module 320 and transmitted to the decision module 340, the processor 124 can execute the decision module 340 to determine whether any action needs to be taken as a result of this determination. According to some embodiments, the decision module 340 can also store historical data of the previous state of the earbud 120 to assist in determining whether any action needs to be taken. For example, if it is determined that the earbud 120 is now in the in-ear position, while the previously stored data indicates that the earbud 120 was previously in the out-of-ear position, the decision module 340 can determine that audio should now be delivered to the earbud 120.

[0090] Figure 4 is a flowchart illustrating a method 400 for on-ear detection using the earbud 120. The method 400 is performed by the processor 124 executing the code of the passive on-ear detection module 310, the active on-ear detection module 320, the signal generation module 330, and the decision module 340 stored in the memory 125.

[0091] The method 400 begins at step 405, where the processor 124 receives a signal from the proximity sensor 129. At step 410, the processor 124 analyzes the received signal to determine whether the signal indicates that the earbud 120 is close to an object. This analysis can include comparing the received signal with a predetermined threshold, which can be a distance value in some embodiments. If the processor 124 determines that the received signal does not indicate that the earbud 120 is close to an object, the processor 124 determines that the earbud 120 is not in or on the user's ear, and thus continues to wait for further signals received from the proximity sensor 129.

[0092] On the other hand, if the processor 124 determines from the signal received from the proximity sensor 129 that the earbud 120 is close to an object, the processor 124 continues to execute the method 400 and proceeds to step 415. In embodiments where the earbud 120 does not include a proximity sensor 129, steps 405 and 410 of the method 400 can be skipped, and the processor 124 can start executing the method from step 415. According to some embodiments, different sensors (such as motion sensors) can be used to trigger the execution of the method 400 from step 415.

[0093] At step 415, the processor 124 executes the passive on-ear detection module 310 to determine whether the earbud 120 is in or on the user's ear. As referred to aboveFigure 3 As described in further detail, performing the passive on-ear detection module 310 can include the processor 124 receiving and comparing the passive signals X generated by the microphones 121 and 122 in response to the received ambient noise RP and X EP for power.

[0094] At step 420, the processor 124 checks whether the passive on-ear detection process is successful. If the processor 124 can determine whether the earbud 120 is in or on the user's ear based on the passive signals X RP and X EP then at step 425, the result is output to the decision module 340 for further processing. If the processor 124 cannot determine whether the earbud 120 is in or on the user's ear based on the passive signals X RP and X EP then the processor 124 continues to perform the active on-ear detection process by moving to step 430.

[0095] At step 430, the processor 124 executes the signal generation module 330 to cause a probe signal to be generated and sent to the speaker 128 for emission. At step 435, the processor 124 further executes the active on-ear detection module 320. As described above with reference to Figure 3 As described in further detail, performing the active on-ear detection module 320 can include the processor 124 receiving the active signal X generated by the microphone 122 in response to the emitted probe signal EA , and determining whether the received signal corresponds to the resonance of the probe signal. According to some embodiments, as described below with reference to Figures 5 to As described in further detail, performing the active on-ear detection module 320 can further include the processor 124 receiving the active signal X generated by the microphone 121 in response to the emitted probe signal RA , and determining whether the received signal corresponds to the resonance of the probe signal. At step 425, the result of the active on-ear detection process is output to the decision module 340 for further processing.

[0096] ​ FIG. shows a block diagram further detailing the components of the earbud 120, specifically referring to an alternative method for performing active in-ear detection that can be executed by the processor 124 of the active on-ear detection module 320. As described below with reference to ​ Some prior art techniques for active on-ear detection only look for resonances on the internal microphone (i.e., the error microphone 122), and thus may be prone to false positives in certain situations, such as when the earbud 120 is held in a resonant cavity (such as a tightly held hand or other small enclosed environment). ​The method shown also takes into account the resonance of the external microphone (i.e., reference microphone 121), which can avoid false positives in some cases.

[0097] ​ Microphones 121 and 122 and speaker 128 are shown. When audio is played via speaker 128, reference microphone 121 generates an active signal X based on the detected sound (which may include ambient sound as well as the sound emitted by speaker 128) RA while error microphone 122 generates an active signal X based on the detected sound (which may include ambient sound as well as the sound emitted by speaker 128) EA .

[0098] The audio played by speaker 128 is generated by signal generation module 330. According to some embodiments, for the active in-ear detection method to be performed, signal generation module 330 can generate a probe signal. The probe signal can be an audible probe signal and can be, for example, a bell signal. According to some embodiments, the probe signal can be a signal having a frequency known to resonate in a human ear canal. For example, according to some embodiments, the frequency of the signal can be between 100 Hz and 2 kHz. According to some embodiments, the frequency of the signal can be between 200 Hz and 400 Hz. According to some embodiments, the signal can include the notes C, D, and G, i.e., the Csus2 chord.

[0099] Microphones 121 and 122 can detect the signal emitted by speaker 128, as well as any other background noise or ambient noise. Microphones 121 and 122 can generate active signals X RA and X EA based on the detected sound, and transmit these signals to reference signal bandpass filter 510 and error signal bandpass filter 540 respectively. Bandpass filters 510 and 540 can apply bandpass filters to the received signals X RA and X EA , which can be narrow bandpass filters in some embodiments. According to some embodiments, filters 510 and 540 can apply 4th-order narrow bandpass filters. According to some embodiments, the parameters of bandpass filters 510 and 540 can be set based on the frequency of the probe signal generated by signal generation module 330. For example, according to some embodiments, filters 510 and 540 can apply a bandpass filter of 260 Hz to 300 Hz to the signals X RA and X EA , which can match the probe signal including the notes C and D. Using a matching filter can reduce the sensitivity of the system to external noise to avoid detecting high power readings based on external sounds that may occur simultaneously with the emission of the probe signal.

[0100] The filtered signals can be transmitted to the reference signal power meter 530 and the error signal power meter 560 via switches 520 and 550 respectively. Switches 520 and 550 can be configured to close only after a predetermined period of time has elapsed since the speaker 128 first starts emitting the generated probe signal. This can allow the signals detected and generated by microphones 121 and 122 to stabilize. For example, according to some embodiments, switches 520 and 550 can be configured to close 100 ms after the speaker 128 starts emitting the probe signal.

[0101] Once switches 520 and 550 are closed, the filtered signals generated by band-pass filters 510 and 540 are transmitted to power meters 530 and 560. Power meters 530 and 560 are configured to measure and output the power levels of the received filtered signals. The measured power levels are provided to the summing node 585. The summing node 585 subtracts the power level value determined by the power meter 530 from the measured power level determined by the power meter 560. The result is transmitted to the summing node 580, which also receives the power level value from the generated signal power meter 570, which is configured to measure and output the power level of the probe signal generated by the signal generation module 330 and emitted by the speaker 128. The summing node 580 adds the output of the summing node 585 to the measured power level determined by the power meter 560, and subtracts the power level value determined by the generated signal power meter 570. In some embodiments, the measured power level determined by the power meter 560 can be added at the summing node 585 with a gain of 2, rather than at the summing node 580, which will achieve the same result.

[0102] The result of the summing node 580 is transmitted to the active in-ear detection decision module 590. The decision module 590 compares the received result with a predetermined threshold to determine whether the earbud 120 is on or inside the user's ear. Specifically, if the received result is equal to or higher than the predetermined threshold, it is determined that the earbud 120 is on or inside the user's ear, and if the received result is lower than the predetermined threshold, it is determined that the earbud 120 is off-ear.

[0103] In practice, when the earbud 120 is in or on the user's ear such that the error microphone 122 is in the ear canal of the ear, the error microphone 122 will detect a high-power signal that is generated due to the probing signal emitted by the speaker 128 and resonates through the ear canal. The reference microphone 121 is blocked by the speaker 128 and will only detect a low-power signal. Therefore, subtracting the signal received by the reference microphone 121 from the signal received by the microphone 122 will produce a relatively high signal level that will be higher than the predetermined threshold to allow the processor 124 to correctly determine that the earbud 120 is in or on the user's ear.

[0104] When the earbud 120 is outside the user's ear and in an open space such that both the reference microphone 121 and the error microphone 122 are outside the ear canal or any other resonant cavity of the ear, neither the reference microphone 121 nor the error microphone 122 will detect a high-power signal that is generated due to the probing signal emitted by the speaker 128 because this signal will not resonate before reaching the microphones 121 and 122. The signals received by the microphones 121 and 122 may be substantially equal, so subtracting the signal received by the reference microphone 121 from the signal received by the microphone 122 will produce a relatively low signal level that will be lower than the predetermined threshold to allow the processor 124 to correctly determine that the earbud 120 is outside the user's ear.

[0105] When the earbud 120 is outside the user's ear but within a resonant cavity (such as within the user's closed hand) such that both the reference microphone 121 and the error microphone 122 are within the resonant cavity, both the reference microphone 121 and the error microphone 122 will detect a high-power signal that is generated due to the probing signal emitted by the speaker 128 because this signal will resonate within the cavity. The signals received by the microphones 121 and 122 may be substantially equal, so subtracting the signal received by the reference microphone 121 from the signal received by the microphone 122 will produce a relatively low signal level that will be lower than the predetermined threshold to allow the processor 124 to correctly determine that the earbud 120 is outside the user's ear. Therefore, this method can reduce false positives that are caused by placing the earbud 120 in a resonant cavity or resonant area outside the ear.

[0106] ​ is a graph that respectively illustrates the signals measured by microphones placed in an open space, in the ear, and in a closed hand.

[0107] ​Shows graph 600, showing signal 615 relative to X-axis 610 and Y-axis 605. The X-axis 610 shows frequency in kHz, while the Y-axis 605 shows power spectral density in dBm / Hz. When earbud 120 is in open space and speaker 128 is emitting a detection signal, signal 615 is generated by an internal earbud microphone such as microphone 122 of earbud 120. Signal 615 is sampled at a sampling rate of 16 kHz with a resolution bandwidth of 7.81 Hz.

[0108] In contrast, ​ Shows graph 630, showing signal 645 relative to X-axis 640 and Y-axis 635. The X-axis 640 shows frequency in kHz, while the Y-axis 635 shows power spectral density in dBm / Hz. When earbud 120 is in the user's ear and speaker 128 is emitting a detection signal, signal 645 is generated by an internal earbud microphone such as microphone 122 of earbud 120. Signal 615 is sampled at a sampling rate of 16 kHz with a resolution bandwidth of 7.81 Hz. As can be seen when comparing graph 630 with graph 600, there are many differences in the recorded signals when earbud 120 is in the ear compared to when it is in open space. For example, as illustrated by feature 655, signal 645 experiences a horizontal increase between 100 Hz and 1 kHz compared to signal 615. As illustrated by feature 650, signal 645 also experiences a peak around 2.5 kHz, followed by a trough around 3.5 kHz.

[0109] ​ Shows graph 660, showing signal 675 relative to X-axis 670 and Y-axis 665. The X-axis 670 shows frequency in kHz, while the Y-axis 665 shows power spectral density in dBm / Hz. When earbud 120 is in a resonant cavity such as a clenched hand and speaker 128 is emitting a detection signal, signal 675 is generated by an internal earbud microphone such as microphone 122 of earbud 120. Signal 675 is sampled at a sampling rate of 16 kHz with a resolution bandwidth of 7.81 Hz. As can be seen when comparing graph 660 with graph 600 or graph 630, placing earbud 120 in a clenched hand can produce features similar to those associated with earbud 120 being in the ear as visible in signal 645. Specifically, as illustrated by feature 685, signal 675 also experiences a horizontal increase between 100 Hz and 1 kHz, and as illustrated by feature 680, signal 675 also experiences a small peak around 2.5 kHz, followed by a small trough around 3.5 kHz.

[0110] As described above, this can also be resolved by looking at the signals generated by external microphone 121. ​ and ​Graphs are respectively illustrative of signals measured by microphones placed in an ear and in a closed hand, but show signals from an internal microphone and an external microphone.

[0111] ​ Graph 700 is shown, showing signal 715 relative to X-axis 710 and Y-axis 705. The X-axis 710 shows frequency in kHz, while the Y-axis 705 shows power spectral density in dBm / Hz. When earbud 120 is in the user's ear and speaker 128 is emitting a probe signal, signal 715 is generated by an internal earbud microphone such as microphone 122 of earbud 120. Graph 700 also shows signal 720, which is generated by an external earbud microphone such as microphone 121 of earbud 120 when earbud 120 is in the user's ear and speaker 128 is emitting a probe signal. Signals 715 and 720 are sampled at a sampling rate of 16 kHz with a resolution bandwidth of 7.81 Hz.

[0112] ​ Graph 750 is shown, showing signal 765 relative to X-axis 760 and Y-axis 755. The X-axis 760 shows frequency in kHz, while the Y-axis 755 shows power spectral density in dBm / Hz. When earbud 120 is in a resonance cavity such as a clenched hand and speaker 128 is emitting a probe signal, signal 765 is generated by an internal earbud microphone such as microphone 122 of earbud 120. Graph 700 also shows signal 770, which is generated by an external earbud microphone such as microphone 121 of earbud 120 when earbud 120 is in a resonance cavity such as a clenched hand and speaker 128 is emitting a probe signal. Signals 765 and 770 are sampled at a sampling rate of 16 kHz with a resolution bandwidth of 7.81 Hz.

[0113] As can be seen when comparing Graph 700 and Graph 750, there are similarities between signals 715 and 765, making it difficult to determine whether earbud 120 is in the ear or in a clenched hand based solely on internal microphone 122. However, signals 720 and 770 are more significantly different, and the increased level of signal 770 shows that in the situation shown in Graph 750, earbud 120 may not actually be in the ear.

[0114] Those skilled in the art will understand that various changes and / or modifications can be made to the embodiments described above without departing from the broad general scope of the disclosure. Accordingly, the embodiments are to be considered in all respects as illustrative and not restrictive.

Claims

1. A signal processing device for on-ear detection of an earbud, the device comprising: A first microphone input for receiving a microphone signal from a first microphone configured to be positioned within a user's ear when the earbud is worn; A second microphone input for receiving a microphone signal from a second microphone configured to be positioned outside the user's ear when the earbud is worn; A signal generator configured to generate a signal for acoustic playback, the signal for acoustic playback being from a speaker configured to be positioned within the earbud; And A processor configured to: Receive at least one first microphone signal from each of the first microphone input and the second microphone input and compare the first microphone signals to determine an on-ear state of the earbud, wherein the first microphone signals are generated when audio is not being played via the speaker; Determine that the on-ear state of the earbud cannot be adequately determined, generate the signal for acoustic playback from the speaker, receive a second microphone signal from the first microphone input, and compare the second microphone signal with the generated signal to determine the on-ear state of the earbud.

2. The signal processing device according to claim 1, further comprising a proximity sensor, and wherein the processor is further configured to receive at least one sensor signal from the proximity sensor indicating that the earbud is close to an object, and in response to receiving the at least one sensor signal from the proximity sensor, perform the steps of receiving at least one first microphone signal and comparing the first microphone signals to determine the on-ear state of the earbud.

3. The signal processing device according to claim 2, wherein the proximity sensor is an infrared sensor.

4. The signal processing device according to any one of claims 1 to 3, wherein comparing the first microphone signals to determine the on-ear state of the earbud comprises comparing power levels of the first microphone signals.

5. The signal processing device according to claim 4, wherein comparing the first microphone signals to determine the on-ear state of the earbud further comprises determining that the earbud is on-ear if the power of the first microphone signal received from the first microphone is lower than a predetermined threshold than the power of the first microphone signal received from the second microphone.

6. The signal processing device according to claim 4, wherein comparing the first microphone signals to determine the on-ear state of the earbud further comprises determining that the earbud is off-ear if the power of the first microphone signal received from the first microphone is higher than a predetermined threshold than the power of the first microphone signal received from the second microphone.

7. The signal processing device according to claim 4, wherein comparing the first microphone signals to determine the on-ear state of the earbud further comprises determining that the on-ear state of the earbud cannot be adequately determined if the power level of each of the first microphone signals is below a predetermined threshold.

8. The signal processing device according to any one of claims 1 to 3, wherein comparing the second microphone signal with the generated signal to determine the on-ear state of the earbud includes determining whether the second microphone signal includes a resonance of the generated signal.

9. The signal processing device according to any one of claims 1 to 3, wherein the generated signal is an audible detection signal.

10. The signal processing device according to claim 9, wherein the generated signal has a frequency known to generate resonance in a human ear canal.

11. The signal processing device according to any one of claims 1 to 3, wherein the processor is further configured to perform an audio processing function in response to the determined on-ear state of the earbud.

12. A method for on-ear detection of an earbud, the method comprising: Receiving a first microphone signal from a first microphone and a first microphone signal from a second microphone, wherein the first microphone signal is generated when audio is not being played via a speaker, wherein the speaker is configured to be located within the earbud, wherein the first microphone is configured to be located within a user's ear when the earbud is worn, and the second microphone is configured to be located outside the user's ear when the earbud is worn; Comparing the first microphone signal to determine the on-ear state of the earbud; Determining that the on-ear state of the earbud cannot be sufficiently determined, generating a signal for acoustic playback, receiving a second microphone signal from the first microphone, and comparing the second microphone signal with the generated signal to determine the on-ear state of the earbud, the signal for acoustic playback being from the speaker.

13. The method according to claim 12, further comprising receiving at least one sensor signal from a proximity sensor indicating that the earbud is close to an object, and performing the steps of receiving at least one first microphone signal and comparing the first microphone signal to determine the on-ear state of the earbud in response to receiving the at least one sensor signal from the proximity sensor.

14. The method according to claim 12 or claim 13, wherein comparing the first microphone signal to determine the on-ear state of the earbud includes comparing the power levels of the first microphone signal.

15. The method according to claim 14, wherein comparing the first microphone signal to determine the on-ear state of the earbud further includes determining that the earbud is on-ear if the power of the first microphone signal received from the first microphone is lower than a predetermined threshold than the power of the first microphone signal received from the second microphone.

16. The method according to claim 14, wherein comparing the first microphone signal to determine the on-ear state of the earbud further includes determining that the earbud is off-ear if the power of the first microphone signal received from the first microphone is higher than a predetermined threshold than the power of the first microphone signal received from the second microphone.

17. The method according to claim 14, wherein comparing the first microphone signals to determine the on-ear state of the earbud further comprises determining that the on-ear state of the earbud cannot be adequately determined if the power level of each first microphone signal is below a predetermined threshold.

18. The method according to claim 12 or 13, wherein comparing at least one second microphone signal with the generated signal to determine the on-ear state of the earbud comprises determining whether the at least one second microphone signal includes a resonance of the generated signal.

19. The method according to claim 12 or 13, wherein the generated signal is an audible probe signal.

20. The method according to claim 19, wherein the generated signal has a frequency known to produce a resonance in a human ear canal.

21. The method according to claim 12 or 13, further comprising performing an audio processing function in response to the determined on-ear state of the earbud.

22. A signal processing device for on-ear detection of an earbud, the device comprising: a first microphone input for receiving a microphone signal from a first microphone configured to be positioned within a user's ear when the earbud is worn; a second microphone input for receiving a microphone signal from a second microphone configured to be positioned outside the user's ear when the earbud is worn; a signal generator configured to generate a signal for acoustic playback, the signal for acoustic playback being from a speaker configured to be positioned within the earbud; and a processor configured to: generate a signal for acoustic playback from the speaker; cause the signal to be played by the speaker; receive at least one microphone signal from each of the first microphone input and the second microphone input, and compare the received microphone signals with the signal generated for playback by the speaker to detect a resonance of the generated signal; and determine the on-ear state of the earbud; wherein the earbud is determined to be on-ear only when a resonance is detected in the signal from the first microphone input but not in the signal from the second microphone input.

23. The signal processing device according to claim 22, wherein the generated signal is an audible probe signal.

24. The signal processing device according to claim 23, wherein the generated signal has a frequency known to produce a resonance in a human ear canal.

25. The signal processing device according to any one of claims 22 to 24, wherein the processor is further configured to filter the received microphone signals using a band-pass filter before comparing the received microphone signals.

26. The signal processing device according to claim 25, wherein the band-pass filter is matched to the frequency of the generated signal.

27. The signal processing device according to claim 25, wherein the processor is configured to compare the filtered signals only after a predetermined time period has elapsed since the time the generated signal was emitted from the speaker.

28. The signal processing device according to any one of claims 22 to 24, wherein comparing the received microphone signal with the signal generated by speaker playback to detect resonance of the generated signal includes subtracting the power level of the microphone signal received from the second microphone and the power level of the generated signal from the power level of the microphone signal received from the first microphone, and comparing the resulting power level with a predetermined threshold.

29. The signal processing device according to any one of claims 22 to 24, wherein the processor is further configured to perform an audio processing function in response to the determined on-ear state of the earbud.

30. A method for on-ear detection of an earbud, the method comprising: generating a signal for acoustic playback, the signal for acoustic playback being from a speaker configured to be positioned within the earbud; causing the signal to be played by the speaker; receiving at least one microphone signal from a first microphone and a second microphone, wherein the first microphone is configured to be positioned within a user's ear when the earbud is worn, and the second microphone is configured to be positioned outside the user's ear when the earbud is worn; comparing the received microphone signal with the signal generated by speaker playback to detect resonance of the generated signal; and determining the on-ear state of the earbud, wherein it is determined that the earbud is on-ear only when resonance is detected in the signal input from the first microphone but not in the signal input from the second microphone.

31. The method according to claim 30, wherein the generated signal is an audible detection signal.

32. The method according to claim 31, wherein the generated signal has a frequency known to produce resonance in a human ear canal.

33. The method according to any one of claims 30 to 32, further comprising filtering the received microphone signal using a band-pass filter before comparing the received microphone signals.

34. The method according to claim 33, wherein the band-pass filter is matched to the frequency of the generated signal.

35. The method according to claim 33, further comprising comparing the filtered signals only after a predetermined time period has elapsed since the generated signal was emitted from the speaker.

36. The method according to any one of claims 30 to 32, wherein comparing the received microphone signal with the signal generated by speaker playback to detect resonance of the generated signal includes subtracting the power level of the microphone signal received from the second microphone and the power level of the generated signal from the power level of the microphone signal received from the first microphone, and comparing the resulting power level with a predetermined threshold.

37. The method according to any one of claims 30 to 32, further comprising performing an audio processing function in response to the determined on-ear state of the earbud.

38. A machine-readable medium storing non-transitory instructions that, when executed by one or more processors, cause an electronic device to perform the method of any one of claims 12 to 21 and claims 30 to 37.

39. An apparatus comprising a processing circuit and a non-transitory machine-readable medium that, when executed by the processing circuit, cause the apparatus to perform the method of any one of claims 12 to 21 and claims 30 to 37.

40. A system for on-ear detection for earbuds, the system comprising a processor and a memory containing instructions executable by the processor, wherein the system is operable to perform the method of any one of claims 12 to 21 and claims 30 to 37.

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