Ear Attachment Transition Detection

Abstract

The present disclosure generally relates to an ear - on transition detection, and more particularly to an ear - on transition detection circuit, which includes: a monitoring unit operable to monitor a speaker current flowing through a speaker and / or a speaker voltage induced on the speaker, and generate a monitoring signal indicative of the speaker current and / or the speaker voltage; and an event detector operable to detect a qualified interference in a sensor signal indicative of a qualified pressure change occurring on the speaker caused by the speaker transitioning from an ear - on state to an ear - off state or vice versa, wherein the sensor signal is the monitoring signal or is derived from the monitoring signal.

Description

Technical Field

[0001] The present disclosure generally relates to ear - on transition detection and, more particularly, to a transducer such as a speaker or a microphone or an ear - on transition detection circuit (such as an audio circuit) configured to operate with the transducer.

[0002] Specifically, the present disclosure relates to a circuit used in a host device (such as a headset or a pair of earphones) having a speaker or a microphone. An in - ear headphone is an exemplary host device highlighted herein.

[0003] Such a circuit can be configured to detect a transition of the host device from a deployed state or an "ear - on" state (e.g., inserted or plugged into a user's ear canal or near the user's ear) to an undeployed state or an "ear - off" state (e.g., removed from the user's ear canal or removed from near the user's ear), or vice versa.

[0004] The present disclosure extends to such host devices including an ear - on transition detection circuit (such as an audio circuit) and corresponding methods. Background Art

[0005] Taking an audio circuit as a convenient example, such a circuit can be implemented (at least partially on an IC) within a host device, which can be considered an electrical or electronic device and can be a mobile device. Exemplary devices include portable and / or battery - powered host devices such as mobile phones, audio players, video players, PDAs, mobile computing platforms (such as laptop computers or tablet computers) and / or gaming devices. An exemplary host device particularly relevant to the present disclosure is a headphone, such as an in - ear headphone. In - ear headphones are sometimes referred to as in - ear transducers or "earbuds".

[0006] Headphones have traditionally referred to a pair of small speakers worn on or around the head, e.g., fitting around or over a user's ears, and a band over the head can be used to hold the speakers in place. Earbuds or earpieces are in - ear headphones that consist of individual units that are inserted into a user's ear canal. As with traditional headphones, in some arrangements, a pair of in - ear headphones can be provided that are physically connected together via an interconnecting band. In other arrangements, a pair of in - ear headphones can be provided as separate units rather than physically connected together.

[0007] The battery life of a host device is typically a key design constraint, which can be exacerbated in "small" host devices such as headphones. Thus, host devices are generally capable of entering a low - power state or "sleep mode". In such a low - power state, typically only a minimal amount of circuitry is active, and this minimal amount of circuitry includes components for sensing stimuli to activate a higher - power operating mode.

[0008] To reduce power consumption, many personal audio devices (host devices) have a dedicated "in-ear detection" (or "ear-to-ear detection") function that can operate to detect the presence or absence of an ear near the device. If no ear is detected, the device can be placed in a low-power state to save power; if an ear is detected, the device can be placed in a relatively high-power state.

[0009] The in-ear (ear-to-ear) detection function can also be used for other purposes. For example, when a mobile phone is placed near a user's ear, the mobile phone can use the in-ear detection function to lock the touch screen to prevent accidental touch input during a call. For example, a personal audio device can pause audio playback in response to detecting that the personal audio device has been removed from the user's ear, or cancel the pause of the audio when it is detected that the personal audio device has been applied to the user's ear. The in-ear detection function can thus be considered to include the ear-to-ear detection function and / or the near-ear detection function.

[0010] Taking in-ear headphones as an operating example, it is known to use an optical sensor to determine whether the in-ear headphones are in a deployed state or an ear-to-ear state (e.g., inserted or stuffed into the user's ear canal) or in an undeployed state or an ear-away state (removed from the user's ear canal), because this can determine whether the in-ear headphones are in a low-power state or "sleep mode", or in a high-power state or "active mode" or "wake-up mode". It is also known to use a combination of a speaker and a separate microphone provided in the in-ear headphones to determine the acoustic transfer function of the surrounding environment of the in-ear headphones in order to determine whether the in-ear headphones are in a deployed state or an undeployed state.

[0011] However, when considering power performance, such systems are considered to be improvable.

[0012] There is a desire to provide improved audio circuits and related host devices, for example, where the power performance reaches an acceptable level. Summary of the Invention

[0013] According to a first aspect of the present disclosure, there is provided an ear-to-ear transition detection circuit, comprising: a monitoring unit that can operate to monitor a speaker current flowing through a speaker and / or a speaker voltage induced on the speaker and generate a monitoring signal indicating the speaker current and / or the speaker voltage; and an event detector that can operate to detect a qualified interference in a sensor signal indicating a qualified pressure change occurring on the speaker caused by a transition of the speaker from an ear-to-ear state to an ear-away state or vice versa, wherein the sensor signal is the monitoring signal or derived from the monitoring signal.

[0014] According to a second aspect of the present disclosure, there is provided an audio circuit comprising: a monitoring unit operable to monitor a speaker current flowing through a speaker and / or a speaker voltage induced on the speaker, and to generate a monitoring signal indicative of the speaker current and / or the speaker voltage; and an event detector operable to detect a qualified interference in a sensor signal indicative of a qualified pressure change occurring on the speaker, wherein the sensor signal is the monitoring signal or derived from the monitoring signal.

[0015] According to a third aspect of the present disclosure, there is provided a transducer circuit comprising: a monitoring unit operable to monitor a transducer current flowing through a transducer and / or a transducer voltage induced on the transducer, and to generate a monitoring signal indicative of the transducer current and / or the transducer voltage; and an event detector operable to detect a qualified interference in a sensor signal indicative of a qualified pressure change occurring on the transducer, wherein the sensor signal is the monitoring signal or derived from the monitoring signal.

[0016] According to a fourth aspect of the present disclosure, there is provided a method of detecting a qualified pressure change occurring on a speaker, the method comprising: generating a monitoring signal indicative of a speaker current flowing through the speaker and / or a speaker voltage induced on the speaker; and detecting a qualified interference in a sensor signal indicative of a qualified pressure change occurring on the speaker, wherein the sensor signal is the monitoring signal or derived from the monitoring signal.

[0017] According to a fifth aspect of the present disclosure, there is provided a method of detecting insertion of an in-ear headphone into an ear canal or removal of the in-ear headphone from the ear canal, the in-ear headphone comprising a speaker, the method comprising: generating a monitoring signal indicative of a speaker current flowing through the speaker and / or a speaker voltage induced on the speaker; and detecting a qualified interference in a sensor signal indicative of a qualified pressure change occurring on the speaker, wherein the sensor signal is the monitoring signal or derived from the monitoring signal, and wherein the qualified pressure change corresponds to insertion of the in-ear headphone into the ear canal or removal of the in-ear headphone from the ear canal.

[0018] According to a sixth aspect of the present disclosure, there is provided a method of detecting insertion of an in-ear headphone into an ear canal or removal of the in-ear headphone from the ear canal, the in-ear headphone comprising a speaker, the method comprising: generating a monitoring signal indicative of a speaker current flowing through the speaker and / or a speaker voltage induced on the speaker; and detecting an interference in a sensor signal indicative of insertion of the in-ear headphone into the ear canal or removal of the in-ear headphone from the ear canal, wherein the sensor signal is the monitoring signal or derived from the monitoring signal.

[0019] According to a seventh aspect of the present disclosure, there is provided a method for detecting a transition of a loudspeaker from an ear - coupled state to an ear - decoupled state or vice versa, the method comprising: generating a monitoring signal indicative of a current flowing through the loudspeaker and / or a loudspeaker voltage induced on the loudspeaker; and detecting an interference in the sensor signal indicative of the transition, wherein the sensor signal is the monitoring signal or is derived from the monitoring signal.

[0020] Another aspect provides an electronic device or a host device, the electronic device or the host device comprising a processing circuit and a non - transitory machine - readable medium storing instructions which, when executed by the processing circuit, cause the electronic device to implement the method as described above.

[0021] Another aspect provides a non - transitory machine - readable medium storing instructions which, when executed by a processing circuit, cause an electronic device or a host device to implement the method as described above.

[0022] Another aspect provides instructions (e.g., a computer program) which, when executed by a processing circuit (e.g., a processor), cause an electronic device or a host device to implement the method as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Now, reference will be made to the drawings by way of example only, in which:

[0024] Figures 1a to 1e Examples of host devices are shown, which may be considered as personal audio devices;

[0025] Figure 2 is a schematic diagram of a host device;

[0026] Figure 3 is a schematic diagram of an audio circuit in the host device of FIG. 1;

[0027] Figure 4A is Figure 3 a schematic diagram of one embodiment of a microphone signal generator of

[0028] Figure 4B is Figure 3 a schematic diagram of another embodiment of a microphone signal generator of

[0029] Figure 5 is as Figure 3 a schematic diagram of an exemplary current monitoring unit as an embodiment of a current monitoring unit of

[0030] Figure 6 is as Figure 3 a schematic diagram of another exemplary current monitoring unit as an embodiment of a current monitoring unit of

[0031] Figure 7 is showingFigure 3 Part of the audio circuit and schematic diagram of the equivalent circuit;

[0032] Figure 8 Shows based on Figure 3 The simulation of the speaker generates a graph, where the ambient pressure p appearing on the speaker undergoes a series of step changes;

[0033] Figure 9 Indicates Figure 3 The voltage across the speaker may form a monitoring signal in some use cases;

[0034] Figure 10 Is Figure 3 The schematic diagram of the event detector, which is used to understand its potential uses in various audio circuit groups;

[0035] Figures 11 to 15 Is Figure 10 The schematic diagram of an exemplary embodiment of the event detector;

[0036] Figure 16 Is the schematic diagram of another host device;

[0037] Figures 17A to 17D Presents a method that can be executed by Figure 2 Or Figure 16 The host device;

[0038] Figure 18 Is the schematic diagram of the event detector according to the embodiments of the present disclosure; and

[0039] Figure 19 Shows the acquisition of the audio signal according to the embodiments of the present disclosure. Detailed Description

[0040] Embodiments of the present disclosure provide devices (such as host devices or circuits), systems, methods, and computer programs for detecting a change in the deployment state of a host device.

[0041] Specifically, the embodiments utilize a pressure change monitoring process to detect the transition of the host device from a deployed state or "ear - attached" state (e.g., inserted or stuffed into the user's ear canal, or near the user's ear) to an undeployed state or "ear - detached" state (e.g., removed from the user's ear canal, or removed from near the user's ear), or vice versa. Such embodiments utilize the pressure changes experienced during such transitions (referred to herein as "qualified pressure changes") and attempt to identify those pressure changes as occurring on transducers such as loudspeakers.

[0042] A useful example to keep in mind is that when an in-ear headphone is inserted into a user's ear canal (from an undeployed state to a deployed state), the loudspeaker of the in-ear headphone may experience a step change increase in the steady-state external pressure it experiences. The transition from the undeployed state to the deployed state can be referred to as an insertion event in this document. Similarly, when an in-ear headphone is removed from a user's ear canal (from a deployed state to an undeployed state), the loudspeaker of the in-ear headphone may experience a step change decrease in the steady-state external pressure it experiences. The transition from the deployed state to the undeployed state can be referred to as an insertion event in this document. During similar transitions, the loudspeakers of other host devices (such as other types of headphones or mobile phones) may experience similar pressure changes, and for simplicity, such transitions will also be referred to as insertion events and removal events.

[0043] Some embodiments also use biometric processes to detect the presence or absence of an ear based on one or more ear biometrics.

[0044] As used herein, the term "host device" is any electrical or electronic device suitable for or configurable to analyze pressure changes occurring on a transducer such as a speaker or a loudspeaker. Specific examples are suitable for providing audio playback essentially only to a single user and can be referred to as personal audio devices. A corresponding transducer analysis circuit or audio circuit may be provided as part of such a host device.

[0045] Figures 1a to 1e Some examples of suitable host devices are shown.

[0046] Figure 1a A schematic diagram of a user's ear is shown, including the (outer) earflap or auricle 12a, and the (inner) ear canal 12b. A host device 20 including an earcup headphone is worn by the user on the ear and is shown in an "on-ear" state. The headphone includes a housing that substantially surrounds and encloses the auricle 12a to provide a physical barrier between the user's ear and the external environment. A cushion or padding may be provided at the edge of the housing to increase user comfort and the acoustic coupling between the headphone and the user's skin (i.e., to provide a more effective barrier between the external environment and the user's ear).

[0047] The headphone includes one or more loudspeakers 22 that are located on the inner surface of the headphone and are arranged to generate an acoustic signal towards the user's ear (specifically, the ear canal 12b). The headphone also includes one or more (optional) microphones 24 that are also located on the inner surface of the headphone and are arranged to detect acoustic signals within the internal volume defined by the headphone, the auricle 12a, and the ear canal 12b. In some arrangements, it is not necessary to provide one or more microphones 24.

[0048] Figure 1bShows an alternative host device 30, including supra-aural headphones. The supra-aural headphones do not surround or enclose the user's ears, but are placed on the pinna 12a and are shown in a "on-ear" state. The headphones may include cushions or pads to reduce the impact of ambient noise. Similar to Figure 1a the over-ear headphones shown, the supra-aural headphones include one or more loudspeakers 32 and one or more optional microphones 34.

[0049] Figure 1c Shows another alternative host device 40, including intra-aural headphones (or receivers). In use, the intra-aural headphones are located within the user's concha cavity and are shown in a "on-ear" state. The intra-aural headphones may fit loosely within the cavity, allowing air to flow into and out of the user's ear canal 12b.

[0050] Similar to Figure 1a and Figure 1b the devices shown in, the intra-aural headphones include one or more loudspeakers 42 and one or more optional microphones 44.

[0051] Figure 1d Shows another alternative host device 50, including in-ear headphones (or receivers), insert earphones, or earbuds, and is shown in a "on-ear" state. This headphone is configured to be partially or fully inserted into the ear canal 12b and can provide a relatively tight seal between the ear canal 12b and the external environment (i.e., it can be acoustically enclosed or sealed). Similar to the other devices described above, the headphone may include one or more loudspeakers 52 and one or more optional microphones 54.

[0052] Since the in-ear headphones can provide a relatively tight acoustic seal around the ear canal 12b, the external noise detected by the microphone 54 (i.e., from the external environment) may be very low. However, the pressure change associated with the deployment / undeployment state transition may be relatively large.

[0053] Figure 1e Shows another alternative host device 60, which is a mobile phone or cellular phone or handset, and is shown in a "on-ear" state. The handset 60 includes one or more loudspeakers 62 for playing audio to the user, and one or more optional microphones 64 similarly positioned.

[0054] In use, the handset 60 is placed near the user's ear (shown in the "ear - close" state as depicted) to provide audio playback (e.g., during a call). Although a tight acoustic seal is not achieved between the handset 60 and the user's ear, the handset 60 is typically held close enough such that acoustic stimulation applied to the ear via one or more speakers 62 generates a response from the ear, which can be detected by one or more microphones 64. There may also be detectable pressure changes associated with the deployed / undeployed state transition.

[0055] Combined with Figures 1a to 1e All of the host devices described can provide audio playback to substantially a single user in use. Each device includes one or more speakers and optionally one or more microphones, which can be used to generate biometric data related to the user's ear, such as described in US 2019 / 0294769 A1, the entire content of which is incorporated herein by reference.

[0056] Combined with Figures 1a to 1e All of the host devices described may be capable of performing active noise cancellation to reduce the amount of noise experienced by the headphone user. Active noise cancellation operates by detecting the noise (i.e., using a microphone) and generating a signal with the same amplitude but opposite phase to the noise signal (i.e., using a speaker).

[0057] Figure 2 is a schematic diagram of a host device 100, which can be considered an electrical or electronic device and can be a mobile device. The host device 100 can be considered a representative of any of the devices shown in Figures 1a to 1e and any of the devices can be used to implement aspects of the present disclosure.

[0058] The host device 100 includes an audio circuit 200 (not shown specifically), as will be explained in more detail in conjunction with Figure 2 The audio circuit 200 can be considered an example of an ear - close transition detection circuit. Although the host device 100 is schematically shown, it will be assumed that it can be a headphone, and in fact, an exemplary arrangement where the host device 100 is an in - ear headphone will be used as a running example.

[0059] As shown in FIG. 1, the host device 100 includes a controller 102, a memory 104, a radio transceiver 106, a user interface 108, at least one microphone 110, and at least one speaker unit 112. In some arrangements, the user interface 108 and the microphone 110 may be omitted. In some arrangements, the radio transceiver 106 may be omitted. In some arrangements, the speaker unit 112 may be replaced by another transducer, and the audio circuit 200 is referred to as a transducer circuit. Examples of transducers that can detect a pressure difference may be any capacitance-based transducer or coil-based transducer, such as an accelerometer. In view of detecting a transition of the host device 100 from a deployed (ear-mounted) state to an undeployed (ear-off) state or vice versa (as explained in more detail later), the audio circuit 200 may be referred to as an ear-mounted transition detection circuit.

[0060] The speaker unit 112 may correspond to any one of the loudspeakers 22, 32, 42, 52, 62. Similarly, the microphone 110 may correspond to any one of the microphones 24, 34, 44, 54, 64.

[0061] The host device may include an enclosure, i.e., any suitable housing, cover, or other enclosure for housing the various components of the host device 100. The enclosure may be constructed of plastic, metal, and / or any other suitable material. In addition, the enclosure may be adjusted (e.g., sized and shaped) such that the host device 100 is easy to carry by the user of the host device 100.

[0062] In the case of an in-ear headphone as in the running example, the enclosure may be adjusted (e.g., sized and shaped) to fit into the user's ear canal. It should be understood that the discussion herein of an in-ear headphone "fitting into" the user's ear canal (deployed state) may correspond to the in-ear headphone being at least partially or fully inserted or snapped or plugged into the ear canal, depending on the arrangement. For completeness, in the case of another type of host device 100, such as a mobile phone (such as a smart phone), an audio player, a video player, a PDA, a mobile computing platform (such as a laptop computer or a tablet computing device), a handheld computing device, or a gaming device, the enclosure may be appropriately adjusted for ergonomic use, and the deployed state may be, for example, near or against the user's ear (for examples, see Figures 1a to 1e ). As previously mentioned, the deployed state corresponds to the "ear-mounted" state, and the undeployed state corresponds to the "ear-off" state.

[0063] The controller 102 is housed within an enclosure and includes any system, apparatus, or device configured to interpret and / or execute program instructions and / or process data, and may include, but is not limited to, a microprocessor, a microcontroller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), or any other digital or analog circuitry configured to interpret and / or execute program instructions and / or process data. In some arrangements, the controller 102 interprets and / or executes program instructions and / or processes data stored in the memory 104 and / or other computer-readable media accessible to the controller 102.

[0064] The memory 104 may be housed within an enclosure, may be communicatively coupled to the controller 102, and includes any system, apparatus, or device (e.g., a computer-readable medium) configured to retain program instructions and / or data for a period of time. The memory 104 may include random access memory (RAM), electrically erasable programmable read-only memory (EEPROM), Personal Computer Memory Card International Association (PCMCIA) cards, flash memory, magnetic memory, magneto-optical memory, or any suitable series and / or array of volatile or non-volatile memory that retains data after power to the host device 100 is turned off.

[0065] The user interface 108 may be at least partially housed within an enclosure, may be communicatively coupled to the controller 102, and includes any tool or collection of tools by which a user may interact with the user host device 100. For example, the user interface 108 may allow a user to input data and / or instructions into the user host device 100 (e.g., via buttons, a keypad, and / or a touchscreen), and / or otherwise manipulate the host device 100 and its associated components. The user interface 108 may also allow the host device 100 to convey data to the user, for example, via a display device (e.g., a touchscreen or an LED).

[0066] The capacitive microphone 110 may be at least partially housed within the enclosure 101, may be communicatively coupled to the controller 102, and includes any system, apparatus, or device configured to convert sound occurring at the microphone 110 into an electrical signal that may be processed by the controller 102, where such sound is converted to an electrical signal using a diaphragm or membrane whose capacitance varies based on acoustic vibrations received on the diaphragm or membrane. The capacitive microphone 110 may include an electrostatic microphone, a condenser microphone, an electret microphone, a microelectromechanical systems (MEMs) microphone, or any other suitable capacitive microphone. In some arrangements, multiple capacitive microphones 110 may be provided and employed selectively or together. In some arrangements, the capacitive microphone 110 may not be provided, relying on the speaker unit 112 to function as a microphone, as explained later.

[0067] The radio transceiver 106 can be housed within an enclosure, can be communicatively coupled to the controller 102, and includes any system, apparatus, or device configured to generate and transmit radio frequency signals with the aid of an antenna and to receive radio frequency signals and convert the information carried by these received signals into a form usable by the controller 102. Of course, the radio transceiver 106 can be replaced by only a transmitter or only a receiver in some arrangements. The radio transceiver 106 can be configured to transmit and / or receive various types of radio frequency signals, including but not limited to cellular communications (e.g., 2G, 3G, 4G, LTE, etc.), short-range wireless communications (e.g., Bluetooth), commercial radio signals, television signals, satellite radio signals (e.g., GPS), Wi-Fi, etc.

[0068] The speaker unit 112 includes a speaker (possibly together with support circuitry) and can be at least partially housed within an enclosure or can be external to the enclosure (e.g., attachable to the enclosure in the case of headphones). Such a speaker can be referred to as a loudspeaker. As will be explained later, the audio circuit 200 described in conjunction with Figure 3 can be considered to correspond to the speaker unit 112 or the combination of the speaker unit 112 and the controller 102. It should be understood that in some arrangements, multiple speaker units 112 can be provided and used selectively or together. Similarly, the audio circuit 200 described in conjunction with Figure 2 can be considered to be provided multiple times, corresponding respectively to multiple speaker units 112, although it need not be provided for each of those speaker units 112. The present disclosure will be understood accordingly.

[0069] The speaker unit 112 can be communicatively coupled to the controller 102 and can include any system, apparatus, or device configured to generate sound in response to an electrical audio signal input. In some arrangements, the speaker unit 112 can include a dynamic loudspeaker as its speaker.

[0070] A dynamic loudspeaker can employ a lightweight diaphragm that is mechanically coupled via a flexible suspension to a rigid frame, and the flexible suspension constrains a voice coil to move axially through a cylindrical magnetic gap. When an electrical signal is applied to the voice coil, the current in the voice coil generates a magnetic field, making it a variable electromagnet. The magnetic systems of the coil and the driver interact, thereby generating a mechanical force that causes the coil (and thus the attached cone) to move back and forth, thereby reproducing sound under the control of an applied electrical signal from an amplifier.

[0071] In an arrangement where the host device 100 includes multiple speaker units 112, such speaker units 112 can provide different functions. For example, in some arrangements, when the second speaker unit 112 can play voice data (e.g., voice data of a phone call between the other party received by the radio transceiver 106 and the user of the host device 100 on this side), the first speaker unit 112 can play ringtones and / or other alerts.

[0072] Although specific exemplary components (e.g., the controller 102, the memory 104, the user interface 108, the microphone 110, the radio transceiver 106, the speaker unit 112) are described above as being integral with the host device 100, in some arrangements, the host device 100 can include one or more components not specifically listed above. In other arrangements, the host device 100 can include a subset of the components specifically listed above, for example, it may not include the radio transceiver 106 and / or the microphone 110 as described above. Figure 2 As described above, one or more speaker units 112 can be used as microphones. For example, the sound that appears on the diaphragm or other sound - generating components of the speaker unit 112 may cause the movement of this diaphragm, which in turn causes the movement of the voice coil of this speaker unit 112. This will induce a voltage on the voice coil, and the voltage can be sensed and transmitted to the controller 102 and / or other circuits for processing, thus effectively serving as a microphone. The sound detected by the speaker unit 112 used as a microphone can be used for many purposes.

[0073] For example, in some arrangements, the speaker unit 112 can be used as a microphone to sense voice commands and / or other audio stimuli. These can be used to perform predefined actions (e.g., a predefined voice command can be used to trigger a corresponding predefined action).

[0074] For example, in some arrangements, the speaker unit 112 can be used as a microphone to sense voice commands and / or other audio stimuli. These can be used to perform predefined actions (e.g., a predefined voice command can be used to trigger a corresponding predefined action).

[0075] Voice commands and / or other audio stimuli can be used to “wake up” the host device 100 from a low-power state and transition it to a higher power state. In such an arrangement, when the host device 100 is in the low-power state, the speaker unit 112 can transmit an electrical signal (a microphone signal) to the controller 102 for processing. The controller 102 can process such a signal and determine whether such a signal corresponds to a voice command and / or other stimuli for transitioning the host device 100 to a higher power state. If the controller 102 determines that such a signal corresponds to a voice command and / or other stimuli for transitioning the host device 100 to a higher power state, the controller 102 can activate one or more components of the host device 100 that may have been deactivated in the low-power state (e.g., the capacitive microphone 110, the user interface 108, the application processor forming part of the controller 102).

[0076] In some cases, the speaker unit 112 can be used as a microphone for sound pressure levels or volumes above a particular level, e.g., such as a recording of a live concert. At such higher sound levels, the speaker unit 112 may have a more reliable signal response to sound compared to the capacitive microphone 110. When using the speaker unit 112 as a microphone, the controller 102 and / or other components of the host device 100 can perform frequency equalization because the frequency response of the speaker unit 112 when used as a microphone may be different from that of the capacitive microphone 110. Such frequency equalization can be achieved using filters known in the art (e.g., a filter bank). In a particular arrangement, such filtering and frequency equalization can be adaptive, and during a period when the capacitive microphone 110 is active (but not overloaded by the volume of the sound present) and the speaker unit 112 is used as a microphone, the controller 102 performs an adaptive filtering algorithm. Once the frequency response is equalized, the controller 102 can smoothly transition between the two by cross-fading between the signals received from the capacitive microphone 110 and the speaker unit 112.

[0077] In some cases, the speaker unit 112 can be used as a microphone to enable identification of a user of the host device 100. For example, the speaker unit 112 (e.g., implemented as headphones, earphones, or earbuds) can be used as a microphone while a speaker signal is being provided to the speaker (e.g., playing a sound such as music) or based on noise. In this case, the microphone signal may contain information about the user's ear canal, enabling the user to be identified by analyzing the microphone signal. For example, the microphone signal can indicate how the played sound or noise resonates in the ear canal, which may be specific to the relevant ear canal. Since the shape and size of each person's ear canal are unique, the resulting data can be used to distinguish a particular (e.g., "authorized") user from other users. Thus, the host device 100 (including the speaker unit 112) can be configured in this way to perform biometric checks similar to a fingerprint sensor or an eye scanner.

[0078] It should be understood that in some arrangements, the speaker unit 112 can be used as a microphone in those cases where it is not otherwise used to emit sound. For example, when the host device 100 is in a low-power state, the speaker unit 112 may not emit sound and can thus be used as a microphone (e.g., to assist in waking up the host device 100 from the low-power state in response to a voice activation command, as described above). As another example, when the host device 100 is in speakerphone mode, the speaker unit 112 is typically used to play voice data to the user, and when the host device 100 is not in speakerphone mode (e.g., the speaker unit 112 that a user typically holds next to his or her ear during a phone call), the speaker unit may be deactivated and not emit sound, and in this case can be used as a microphone.

[0079] However, in other arrangements (e.g., in the case of the biometric checks described above), the speaker unit 112 can be used as both a speaker and a microphone simultaneously, such that the speaker unit 112 can emit sound while capturing sound. In such an arrangement, the diaphragm and voice coil of the speaker unit 112 can vibrate in response to a voltage signal applied to the voice coil and other sounds present on the speaker unit 112. From Figure 2 It can be understood that the controller 102 and / or the speaker unit 112 can determine that current flows through the voice coil, which will exhibit the following effects: a voltage signal for driving the speaker (e.g., based on a signal from the controller 102); and a voltage induced by external sound present on the speaker unit 112. From Figure 2 It can be understood how, in this case, the audio circuit 200 enables the recovery of the microphone signal (attributable to external sound present on the speaker of the speaker unit 112).

[0080] In these and other arrangements, the host device 100 may include at least two speaker units 112, which may be selectively used to transmit sound or act as a microphone. In such an arrangement, each speaker unit 112 may be optimized for performance over a specific volume level range and / or frequency range, and the controller 102 may select which (if any) speaker units 112 are used to transmit sound and which (if any) speaker units 112 are used to receive sound based on the detected volume level and / or frequency range.

[0081] It should be understood that such detection of voice commands or ear biometrics may form a secondary part of detecting whether the host device should be "awakened" from a low-power state or, conversely, enter a "sleep mode", as mentioned later in this document. Embodiments may initially (or even only) utilize a pressure change monitoring process to detect a transition of the host device 100 from a deployed state to an undeployed state, or vice versa, to detect whether the host device should be "awakened" from a low-power state or, conversely, enter a "sleep mode".

[0082] Therefore, the focus will now be on how the speaker units 112 can be used to collect information about the surrounding environment of the host device 100, and thus effectively use the speaker units 112 (specifically the speakers of the speaker units 112) as sensors to detect a transition of the host device 100 from a deployed (ear-mounted) state to an undeployed (ear-detached) state, or vice versa. In some arrangements, such a sensor may be referred to as a pressure sensor or even a microphone. It should be understood later how such a sensor can be effectively used, particularly in the context of the host device 100 (such as the in-ear headphones in the running example).

[0083] Figure 3 is a schematic diagram of an audio circuit (ear-mounted transition detection circuit) 200. The audio circuit includes a speaker driver 210, a speaker 220, a current monitoring unit (or simply referred to as a monitoring unit) 230, a microphone signal generator 240, and an event detector 400.

[0084] For ease of explanation, the audio circuit 200 (including the speaker 220) will be considered hereinafter to correspond to Figure 2 the speaker unit 112 of Figure 3 (described later) where the signals SP and MI in

[0085] The speaker driver 210 is configured to drive the speaker 220 based on the speaker signal SP, specifically driving a given speaker voltage signal V on the signal line to which the speaker 220 is connected SThe speaker 220 is connected between the signal line and the ground, and the current monitoring unit 230 is connected such that the speaker current I flowing through the speaker 220 S is monitored by the current monitoring unit 230.

[0086] Of course, this arrangement is an example, and in another arrangement, the speaker 220 can be connected between the signal line and the power supply. Similarly, the current monitoring unit 230 is connected such that the speaker current I flowing through the speaker 220 S is monitored by the current monitoring unit 230. In yet another arrangement, the speaker driver 210 can be an H-bridge speaker driver, and then the speaker 220 is connected at both ends to be driven, for example, in antiphase. Similarly, the current monitoring unit 230 will be connected such that the speaker current I flowing through the speaker 220 S is monitored by the current monitoring unit 230. The present disclosure will be understood accordingly.

[0087] Return Figure 2 , the speaker driver 210 can be an amplifier, such as a power amplifier. In some arrangements, the speaker signal SP can be a digital signal, where the speaker driver 210 is controlled digitally. The voltage signal V S (which is actually the potential difference maintained across the combination of the speaker 220 and the current monitoring unit 230, indicating the potential difference maintained across the speaker 220) can be an analog voltage signal controlled based on the speaker signal SP. Of course, the speaker signal SP can also be an analog signal. In any case, the speaker signal SP indicates the voltage signal applied to the speaker. That is, the speaker driver 210 can be configured to maintain a given voltage level of the voltage signal V S for a given value of the speaker signal SP, such that the value of the voltage signal V S is controlled by or related to (e.g., proportional, at least within the linear operating range) the value of the speaker signal SP.

[0088] The speaker 220 can include a dynamic loudspeaker as described above. Similarly as described above, the speaker 220 can be considered any audio transducer, including a micro speaker, a loudspeaker, an ear speaker, headphones, earplugs or in-ear transducers, a piezoelectric speaker, and an electrostatic speaker, etc.

[0089] The current monitoring unit 230 is configured to monitor the speaker current I flowing through the speaker S and generate a monitoring signal MO indicating the current. The monitoring signal MO can be a current signal or can be a voltage signal or a digital signal, which indicates the speaker current I S (e.g., related to or proportional to the speaker current).

[0090] The microphone signal generator 240 is connected to receive the speaker signal SP and the monitoring signal MO. When an external sound appears on the speaker 220, the microphone signal generator 240 can operate to generate a microphone signal MI representative of the external sound based on the monitoring signal MO and the speaker signal SP. Of course, the speaker voltage signal V S is related to the speaker signal SP, and thus the microphone signal generator 240 can be connected to receive the speaker voltage signal V S instead of (or as well as) the speaker signal SP, and can operate to generate the microphone signal MI accordingly. The present disclosure will be understood accordingly.

[0091] The event detector 400 will be described in more detail later in this document Figures 9 to 14 which is connected to receive the monitoring signal MO and / or the microphone signal MI. The monitoring signal MO and / or the microphone signal MI or a signal derived therefrom may be referred to as a sensor signal SS.

[0092] The event detector 400 can operate to detect a qualified interference in the sensor signal SS indicating a qualified pressure change occurring on the speaker 220, where the sensor signal SS is the monitoring signal MO or derived from the monitoring signal MO. The event detector 400 can also operate to generate an event detection signal EDS indicative of the corresponding qualified pressure change in response to detecting the qualified interference.

[0093] The meaning of "qualified interference" and the corresponding "qualified pressure change" will become more apparent later in this document, but from the term "qualified" it will be obvious that not all interferences will be considered (i.e., qualified to be) "qualified interferences". In the context of the in-ear headphones in the running example, examples of qualified pressure changes may be pressure changes caused by inserting into and removing from the user's ear canal, and in fact these examples will be adopted more closely later in this document. These of course correspond to insertion (from off-ear to on-ear) and removal (from on-ear to off-ear) events respectively. The detected qualified pressure changes can be considered as "events" detected by the event detector 400.

[0094] The input connections of the event detector 400 are shown by dashed lines to indicate that it is not necessary for both the monitoring signal MO and the microphone signal MI to be provided to the event detector 400. In this regard, in some arrangements (where the microphone signal MI is not required), the microphone signal generator 240 can be omitted, and the sensor signal can be or derived from the monitoring signal MO (instead of the microphone signal MI). In other arrangements (where the microphone signal MI is required and the microphone signal generator 240 is provided), the sensor signal SS can be or derived from the microphone signal MI.

[0095] As described above, in the context of the host device 100, the speaker signal SP can be received from the controller 102, and the microphone signal MI can be provided to the controller 102. Similarly, the event detection signal EDS can be provided to the controller 102.

[0096] Figure 4A Yes Figure 3 Schematic diagram of an embodiment of the microphone signal generator 240. Figure 4A In the embodiment of, the microphone signal generator 240 includes a transfer function unit 250 and a converter 260.

[0097] The transfer function unit 250 is connected to receive the speaker signal SP and the monitoring signal MO, and defines and implements a transfer function that at least models (or represents or simulates) the speaker 220. The transfer function can additionally model the speaker driver 210 and / or the current monitoring unit 230.

[0098] Therefore, the transfer function particularly models the performance of the speaker. Specifically, the transfer function (transducer model) is for the expected speaker current I S Based on the speaker signal SP (or the speaker voltage signal V S ) and how any sound appearing on the speaker 220 changes. This is of course related to how the monitoring signal MO will change based on the same influencing factors.

[0099] By receiving the speaker signal SP and the monitoring signal MO, the transfer function unit 250 can adaptively define the transfer function. That is, the transfer function unit 250 is configured to determine the transfer function or the parameters of the transfer function based on the monitoring signal MO and the speaker signal SP. For example, the transfer function unit 250 can be configured to define, re - define, or update the transfer function or the parameters of the transfer function over time. This adaptive transfer function (such that the operation of the converter 260 can be adjusted as follows) can be adjusted slowly and also compensate for the delay and frequency response in the voltage signal applied to the speaker compared to the speaker signal SP.

[0100] As an example, a pilot tone significantly lower than the speaker resonance (through the corresponding speaker signal SP) can be used to adjust or train the transfer function. This may be useful for low - frequency response or overall gain. Pilot tones significantly higher than the speaker resonance (e.g., ultrasonic) can be similarly used for high - frequency response, while low - level noise signals can be used for the audible frequency band. Of course, audible sounds can be used to adjust or train the transfer function, for example, in the initial setup or calibration phase, such as in factory calibration.

[0101] This adaptive update of the transfer function unit 250 can be most easily operated when no (incoming) sound appears on the speaker 220. However, over time, even if sound (e.g., occasionally) appears on the speaker 220, the transfer function may iterate towards the "optimal" transfer function. Of course, an initial transfer function or initial parameters of the transfer function (e.g., from memory) corresponding to the "standard" speaker 220 can be provided to the transfer function unit 250 as a starting point for such adaptive updates.

[0102] For example, such an initial transfer function or initial parameters (i.e., parameter values) can be set in a factory calibration step or preset based on design / prototype characteristics. For example, the transfer function unit 250 can be implemented as a storage device for such parameters (e.g., coefficients). Another possibility is that the initial transfer function or initial parameters can be set based on extracting parameters in a separate process for speaker protection purposes and then deriving the initial transfer function or initial parameters based on those extracted parameters.

[0103] The converter 260 is connected to receive the control signal C from the transfer function unit 250, and the control signal C reflects the transfer function or the parameters of the transfer function such that it defines the operation of the converter 260. Thus, the transfer function unit 250 is configured to define, re - define, or update the operation of the converter 260 via the control signal C as the transfer function or the parameters of the transfer function change. For example, the transfer function of the transfer function unit 250 can be adjusted over time to better model at least the speaker 220.

[0104] The converter 260 (e.g., a filter) is configured to convert the monitoring signal MO into a microphone signal MI, effectively generating the microphone signal MI. As Figure 4A indicated by the dashed signal path in, the converter 260 (as defined by the control signal C) can be configured to generate the microphone signal MI based on the speaker signal SP and the monitoring signal MO.

[0105] It should be noted that the converter 260 is shown in Figure 4A as also providing a feedback signal F to the transfer function unit 250. Using the feedback signal F in this way is optional. It should be understood that the transfer function unit 250 can receive the feedback signal F from the converter 260 such that the transfer function modeled by the transfer function unit 250 can be adaptively updated or adjusted based on the feedback signal F, e.g., based on the error signal F received from the converter unit 260. Instead of or in addition to the monitoring signal MO, the feedback signal F can also be provided to the transfer function unit 250. In this regard, the detailed implementation of the microphone signal generator 240 will be explored later in conjunction with Figure 4B Explore the detailed implementation of the microphone signal generator 240.

[0106] It should be understood that there are four basic possibilities regarding the speaker 220 emitting sound and receiving incoming sound. These will be considered in turn. For convenience, when the intention is for the speaker to emit sound (such as playing music), the speaker signal SP will be represented as a "sounding" speaker signal, and when the intention is for the speaker not to or essentially not to emit sound (corresponding to the speaker being muted or seemingly off), the speaker signal SP will be represented as a "non-sounding" speaker signal. The sounding speaker signal can be referred to as an "active" or "on" speaker signal and has a value that causes the speaker to emit sound (such as playing music). The non-sounding speaker signal can be referred to as an "inactive" or "off" or "dormant" speaker signal and has one or more values that cause the speaker not to or essentially not to emit sound (corresponding to the speaker being silent or seemingly off).

[0107] The first possibility is that the speaker signal SP is a sounding speaker signal and no significant (incoming) sound appears on the speaker 220 (even sound due to reflection or echo). In this case, the speaker driver 210 is operable to drive the speaker 220 such that it emits the corresponding sound signal, and the expected monitoring signal MO includes a speaker component generated by (attributable to) the speaker signal but no microphone component generated by external sound (ideally). Of course, there may be other components, such as attributable to circuit noise. Assuming no microphone component caused by external sound, this first possibility may be particularly suitable for the transfer function unit 250 to define / redefine / update the transfer function based on the speaker signal SP and the monitoring signal MO. The converter 260 here (ideally) outputs a microphone signal MI such that it indicates no (incoming) sound appears on the speaker, i.e., silence. Of course, in practice, there may always be a microphone component, even if it is just a very small, negligible microphone component.

[0108] A second possibility is that the speaker signal SP is an audible speaker signal and there is an apparent (incoming) sound present at speaker 220 (possibly based on reflection or echo of sound). In this case, the speaker driver 210 is again operable to drive speaker 220 such that it emits a corresponding sound signal. However, here, it is expected that the monitoring signal MO includes a speaker component generated by (attributable to) the speaker signal, and an apparent microphone component generated by the external sound (in fact due to the back EMF caused when the sound exerts a force on the speaker diaphragm). There may of course be other components, such as those attributable to circuit noise. In this second possibility, the converter 260 outputs a microphone signal MI such that it represents the (incoming) sound present at the speaker. That is, the converter 260 effectively filters out the speaker component and / or equalizes and / or isolates the microphone component when converting the monitoring signal MO into the microphone signal MI.

[0109] A third possibility is that the speaker signal SP is a non - audible speaker signal and there is an apparent (incoming) sound present at speaker 220. In this case, the speaker driver 210 is operable to drive speaker 220 such that it emits substantially no sound signal. For example, the speaker driver 210 may drive speaker 220 with a speaker voltage signal V S which is substantially a DC signal, such as 0V with respect to ground. Here, it is expected that the monitoring signal MO includes an apparent microphone component caused by the external sound but no speaker component. There may of course be other components, such as those attributable to circuit noise. In the third possibility, the converter 260 again outputs a microphone signal MI such that it represents the (incoming) sound present at the speaker. In this case, the converter effectively isolates the microphone component when converting the monitoring signal MO into the microphone signal MI.

[0110] A fourth possibility is that the speaker signal SP is a non - audible speaker signal and no apparent (incoming) sound is present at speaker 220. In this case, the speaker driver 210 is again operable to drive speaker 220 such that it emits substantially no sound signal. Here, it is expected that the monitoring signal MO includes neither an apparent microphone component nor a speaker component. There may of course be other components, such as those attributable to circuit noise. In the fourth possibility, the converter 260 outputs a microphone signal MI such that it indicates that no (incoming) sound is present at the speaker, i.e., silence.

[0111] At this point, it should be noted that the monitoring signal MO indicates the speaker current I S rather than a voltage such as the speaker voltage signal V S etc., so it may also be referred to as such Figure 2 andFigure 3 The monitoring signal MO(I) in A indicates the speaker current (I) it indicates. Although in the case where the speaker driver 210 is effectively disconnected (such that the speaker 220 is not driven) and replaced by a sensing circuit (such as an analog-to-digital converter) (in which case the monitoring signal MO may be referred to as the monitoring signal MO(V)), the monitoring signal MO indicates a voltage such as the speaker voltage signal V S and so on voltages would be possible, but this mode of operation may be inappropriate or inaccurate in the case where the speaker 220 is driven by the speaker driver 210 (where the speaker signal SP is a non-sounding speaker signal and a sounding speaker signal) and there is a distinct sound present on the speaker 220.

[0112] In other words, when the transducer 220 (here the speaker 220) is driven with a voltage from the driver 210, the sensing circuit (e.g., Figure 3 the monitoring unit 230) operates in current mode to provide a corresponding monitoring signal MO(I). When the driver 210 is disabled, there is no circuit (in the driver 210) to force the voltage to be at Vs. Thus, if the node is floating (with respect to the driver 210), it can be operated in voltage mode and the back EMF across the transducer 220 can be directly measured and a corresponding monitoring signal MO(V) provided. In fact, in this mode, the voltage at Vs is driven by the transducer 220 itself.

[0113] The speaker driver 210 (when enabled or operating) effectively forces the speaker voltage signal V S to have a value based on the value of the speaker signal SP as described above. Thus, considering the possible driving capabilities of the speaker driver 210, any inductive voltage effects (Vemf due to diaphragm displacement) of the distinct sound present on the speaker 220 will be mostly or completely lost in, for example, the speaker voltage signal V S . However, in this case, the speaker current I S will exhibit components attributable to the speaker signal as well as any distinct external sound that appears, which will translate into corresponding components in the monitoring signal MO (where it indicates the speaker current I S ), as described above. Thus, as described above, having a monitoring signal MO that indicates the speaker current I S , i.e., as the monitoring signal MO(I), enables a common architecture to be employed for all four possibilities described above.

[0114] Although not shown in Figure 3Although not explicitly shown in A, the converter 260 may be configured to perform a conversion such that the microphone signal MI is output as a signal that more usefully represents the external sound (e.g., as a sound pressure level (SPL) signal). For example, such a conversion may involve a certain scaling and may involve a certain frequency equalization. Here, the monitoring signal MO indicates the current signal I S , and may even be the current signal itself. However, for a circuit such as the controller 102 to receive the microphone signal MI, the signal MI may be required to be a sound pressure level (SPL) signal. The converter 260 may be configured to perform the conversion according to a corresponding transfer function. Thus, the converter 260 may include a transfer function unit (not shown) that is equivalent to the transfer function unit 250 and is similarly configured to update, define, or redefine the transfer function implemented in an adaptive manner, e.g., based on any one or all of the monitoring signal MO, the speaker signal SP, the microphone signal MI, the feedback signal F, and the control signal C.

[0115] Those skilled in the art will understand that in the context of the speaker 220, the transfer function and / or the conversion function may be at least partially defined by Thiele - Small parameters. Such parameters may be reused from speaker protection or other processing. Thus, the operation of the transfer function unit 250, the converter 260, and / or the transfer function unit (not shown) may be at least partially defined by such Thiele - Small parameters. As is well known, Thiele - Small parameters (Thiele / Small parameters, TS parameters, or TSP) are a set of electromechanical parameters that define the specified low - frequency performance of a speaker. These parameters can be used to simulate the position, velocity, and acceleration of the diaphragm, model the input impedance and sound output of the system including the speaker and its enclosure.

[0116] Figure 4B is Figure 2 a schematic diagram of an embodiment of the microphone signal generator 240 (herein represented as 240') of Figure 4B In the embodiment of

[0117] the microphone signal generator 240' includes a first transfer function unit 252, an adder / subtractor 262, a second transfer function unit 264, and a TS parameter unit 254.

[0118] The first transfer function T1 can be considered to model at least the loudspeaker 220. The first transfer function unit 252 is connected to receive the loudspeaker signal SP (hereafter referred to as Vin), and outputs a loudspeaker current signal SPC indicative of the expected or predicted (modeled) loudspeaker current based on the loudspeaker signal SP.

[0119] An adder / subtractor 262 is connected to receive a monitoring signal MO (indicating the actual loudspeaker current IS, i.e., the monitoring signal MO(I)) and the loudspeaker current signal SPC, and outputs an error signal E, which indicates the residual current representative of the external sound occurring on the loudspeaker 220. As Figure 4B shown, the first transfer function unit 252 and thus the first transfer function T1 are configured to be adaptive based on the error signal E provided to the first transfer function unit 252. Figure 4B The error signal E in can be compared with Figure 4A the feedback signal F in.

[0120] A second transfer function T2 may be adapted to convert the error signal output by the adder / subtractor 262 into a suitable SPL signal (forming a microphone signal MI) as described above. The parameters or coefficients of the first transfer function T1 can be stored in the TS parameter unit 254 and applied to the second transfer function T2.

[0121] The first transfer function T1 can be referred to as an adaptive filter. Through the TS parameter unit 254, which can be a storage unit, the parameters or coefficients of the first transfer function T1 (in this case the Thiele - Small coefficients TS) can be extracted and applied to the second transfer function T2. The second transfer function T2 can be considered an equalization filter.

[0122] For example, looking at Figure 4B , T2 is the transfer function applied between E and MI, so T2 = (MI / E), or MI = T2 * E, where E = (MO – SPC). Similarly, T1 = (SPC / SP), or SPC = T1 * SP.

[0123] Exemplary transfer functions T1 and T2 derived from Thiele - Small modeling can include:

[0124]

[0125]

[0126] Where:

[0127] · Vin is the voltage level of the loudspeaker signal SP (or indicated thereby);

[0128] ·R is equivalent to Re, which is the DC resistance (DCR) of the voice coil in ohms (Ω), preferably measured with the speaker cone blocked or prevented from moving or vibrating;

[0129] ·L is equivalent to Le, which is the inductance of the voice coil in millihenries (mH);

[0130] ·Bl is called the force factor and is a measure of the force generated by a given current flowing through the speaker voice coil, in tesla meters (Tm);

[0131] ·Cms describes the compliance of the speaker suspension and is in meters per newton (m / N);

[0132] ·Rms is a measure of the losses or damping in the speaker suspension and moving system. The unit is usually not given but is in mechanical 'ohms';

[0133] ·Mms is the mass of the speaker cone, coil, and other moving parts of the driver, including the acoustic load imposed by the air in contact with the speaker cone, and is in grams (g) or kilograms (kg);

[0134] ·s is the Laplace variable; and

[0135] ·Generally, for Thiele - Small parameters, reference can be made to Beranek, Leo L. (1954). Acoustics. NY: McGraw - Hill.

[0136] Figure 5 is a schematic diagram of an exemplary current monitoring unit 230A, which can be considered as Figure 3 an embodiment of the current monitoring unit 230. Thus, the current monitoring unit 230A can be used in place of the current monitoring unit 230.

[0137] The current monitoring unit 230A includes an impedance 270 and an analog - to - digital converter (ADC) 280. The impedance 270 is a resistor with a monitoring resistance R MO in this arrangement, and is connected in series in the current path carrying the speaker current I S . Thus, a monitoring voltage V MO is generated across the resistor 270 such that:

[0138] V MO = I S × R MO

[0139] Therefore, with the monitoring resistance R MO of the resistor 270 fixed, the monitoring voltage V MO is proportional to the speaker current I Sis proportional. In fact, as can be understood from the above equation, when R MO is known, the speaker current I S can be easily obtained from the monitored voltage V MO .

[0140] The ADC 280 is connected to receive the monitored voltage V MO as an analog input signal and output a monitoring signal MO as a digital signal. The microphone signal generator 240 (including the transfer function unit 250 and the converter 260) can be implemented digitally such that the speaker signal SP, the monitoring signal MO, and the microphone signal MI are digital signals.

[0141] Figure 6 is a schematic diagram of an exemplary current monitoring unit 230B, which can be considered as Figure 3 an implementation of the current monitoring unit 230. Therefore, the current monitoring unit 230B can be used instead of the current monitoring unit 230 and can actually be used together with the elements of the current monitoring unit 230A, as will be apparent. Other known active sensing techniques can be used, such as a current mirror with drain-source voltage matching.

[0142] The current monitoring unit 230B includes a first transistor 290 and a second transistor 300 connected in a current mirror arrangement. The first transistor 290 is connected in series in the current path carrying the speaker current I S such that a mirror current I MIR is generated in the second transistor 300. MIR The mirror current I S can be proportional to the speaker current I MIR depending on the current mirror arrangement (e.g., the relative sizes of the first transistor 290 and the second transistor 300). For example, the current mirror arrangement can be configured such that the mirror current I S is equal to the speaker current I Figure 6 . In

[0143] the first transistor 290 and the second transistor 300 are shown as MOSFETs, but it should be understood that other types of transistors (such as bipolar junction transistors) can be used. The current monitoring unit 230B is configured to generate a monitoring signal MO based on the mirror current I MIR . For example, the impedance in the path of the mirror current I MIR and the ADC (equivalent to Figure 5 the impedance 270 and the ADC 280) can be used to generate the monitoring signal MO based on the mirror current I MIR , and repeated description is omitted.

[0144] From Figure 3It can be understood that the audio circuit 200 can be provided without the speaker 220 to be connected to such a speaker 220. The audio circuit 220 can also be provided with a controller 102 or other processing circuits, which are connected to provide a speaker signal SP and / or receive a microphone signal MI. Such a processing circuit can act as a speaker signal generator that can operate to generate the speaker signal SP. Such a processing circuit can act as a microphone signal analyzer that can operate to analyze the microphone signal MI.

[0145] Now the focus will return to Figure 3 the event detector 400 to better understand its function in the audio circuit (transducer circuit) 200. Recall that the event detector 400 can operate to detect a qualified interference in the sensor signal SS that indicates a qualified pressure change occurring on the speaker 220, where the sensor signal SS is the monitoring signal MO or derived from the monitoring signal MO. Additionally, in the case of in-ear headphones, an example of a qualified pressure change can be the pressure change caused by inserting the in-ear headphones into the user's ear canal and removing the in-ear headphones from the user's ear canal. Recall that these correspond to the insertion event and the removal event, as well as the transition between the deployed state and the undeployed state (the on-ear state and the off-ear state).

[0146] Figure 7 is a schematic diagram showing Figure 3 a part of the audio circuit (transducer circuit) 200 and an equivalent circuit. As an example, the current monitoring unit 230 is represented as Figure 5 the embodiment 230A. In the equivalent circuit, the speaker (transducer) 220 is specifically shown as an equivalent circuit including a series connection of a voltage source 221, a resistance Re, and an inductance Le.

[0147] Figure 7 also indicates the influence of the ambient pressure p on the speaker 220. According to Faraday's law, and considering the speaker as a (dynamic) loudspeaker where the voice coil and the magnet move relative to each other, the movement of the speaker diaphragm under the applied force induces a back EMF in the speaker, which will be manifested as a voltage V at the voltage source 221 as follows EMF :

[0148]

[0149] where is the rate of change of the magnetic flux at the voice coil with respect to time. Since the rate of change of the magnetic flux is proportional to the rate of change of the ambient pressure p occurring on the speaker, it can be concluded that:

[0150]

[0151] The reference current monitoring unit 230A, in the case where the speaker 220 is not driven, the back-EMF voltage V EMF can be considered to appear across the resistor 270, such that:

[0152]

[0153] Therefore, it can also be said (for the DC step response):

[0154]

[0155] Taking the above into account, referring to Figure 8 , which shows a graph generated based on the simulation of the speaker 220, where the ambient pressure p appearing on the speaker undergoes a series of step changes that affect the speaker current I S .

[0156] As Figure 8 shown, the ambient pressure p undergoes a first step change, where the pressure p increases, and then undergoes a second step change, where the pressure p drops back to its original value. The pressure p is plotted as an SPL signal, in pascals. Although the pressure p signal is shown as a DC signal that steps from one value to another and back again, this is of course for simplicity. It should be understood that in an actual implementation, the pressure p signal can have a DC component (corresponding to the signal shown in Figure 8 ), and an AC component (corresponding to, for example, the sound signal that appears) is superimposed on the DC component. Therefore, Figure 8 the step change in the pressure p in

[0157] can be considered to represent a step change in the DC or steady-state value. Figure 8 Similarly as S shown, the speaker current I S is disturbed due to the two step changes in the pressure p. These disturbances can each be referred to as ringing (e.g., including spikes) in the speaker current I S . In fact, the speaker current I S is proportional to the rate of change of the pressure p with respect to time, as shown in the above equation. It should be noted that the polarities of the first step change and the second step change of the pressure p are different (opposite to each other), so the polarities of the corresponding spikes or ringing in the speaker current I Figure 7 are also different (opposite to each other). It can be understood from S that the speaker current I Figure 3 )).

[0158] Returning to the in-ear headphone operation example, the first step change and the second step change are examples of qualified pressure changes and can be considered to correspond, respectively, to inserting the in-ear headphone into the user's ear canal and removing the in-ear headphone from the user's ear canal. These correspond to the insertion event and the removal event, and the transition between the deployed state and the undeployed state (the on-ear state and the off-ear state). In short, when inserting the in-ear headphone into the user's ear canal (from off-ear to on-ear), the ambient pressure appearing on its speaker may increase according to Figure 8 the first step change. Similarly, when removing the in-ear headphone from the user's ear canal (from on-ear to off-ear), the ambient pressure appearing on its speaker may decrease according to Figure 8 the second step change.

[0159] Figure 9 is a schematic diagram of a situation where the speaker 220 is in a state not being driven by the speaker driver 210. For example, if the speaker driver 210 is powered off and the voltage V S is effectively driven by the speaker 220 instead of the driver 210, the back EMF induced in the speaker 220 by the change in pressure p can be measured as the voltage signal across the speaker 220 (actually V EMF ). This voltage signal (actually V EMF ) itself can be used as the monitoring signal MO, which is MO(V) in this case. Based on the above equations, in response to a step change in pressure p, interference may occur in the monitoring signal MO(V) corresponding to the interference in the speaker current I Figure 8 shown in S .

[0160] Therefore, Figure 3 a variant of the audio circuit 200 can include the speaker 220 connected to the event detector 400 in accordance with Figure 9 , where the (current) monitoring unit 230 is replaced by a (voltage) monitoring unit effectively implemented as a tap point at the upper terminal of the speaker 220 (where the signal V S is shown), and the microphone signal generator 240 is omitted (in some cases, the speaker driver 210 is also omitted).

[0161] In view of the above and referring to Figure 10 , the event detector 400 is operable to detect qualified interference in the sensor signal SS, where exemplary qualified interference corresponds to the speaker current I Figure 8 shown in SOne of the interferences in. The sensor signal SS can be or derived from a microphone signal MI or a monitoring signal MO (whether the monitoring signal MO(I) or MO(V)). Then, such a qualified interference is regarded as indicating a qualified pressure change occurring on the speaker 220, for example corresponding to Figure 7 one of the step changes in pressure p shown.

[0162] The qualified interference in the sensor signal SS (and thus the corresponding qualified pressure change) can be detected by comparing the sensor signal SS with a corresponding qualified specification that defines at least one qualified interference and determining whether a candidate interference in the sensor signal SS conforms to or meets the qualified specification. Thus, the qualified specification can include at least one of the following: the definition of one or more qualified criteria; the configuration of a neural network or classifier implemented by an event detector; thresholds, such as amplitude values or rate-of-change values; average values, such as running average values; peak amplitudes; rise times; time constants; settling times; and frequency response values. The qualified specification can include configuration settings / details / parameters related to any cepstral techniques (including MFCC); statistical distance metrics, such as KL divergence or statistical distance metrics derived from ECDF; simple distance metrics, such as Euclidean distance, Mahalanobis distance; and UBM-based techniques (Universal Background Model) or GMM (Gaussian Mixture Model).

[0163] See Figure 8 , and the event detector 400 can thus be implemented as a spike or ring or peak detector consistent with the exemplary embodiment 400A of Figure 11 .

[0164] Those skilled in the art will understand that a spike, peak or ring detector can be configured to distinguish a qualified interference in the sensor signal SS from other (non-qualified) interferences (e.g., such as those attributable to ambient noise or minute "ripples" in the presence of sound). A spike, peak or ring detector can also be configured to distinguish one qualified interference in the sensor signal SS from another qualified interference, for example with opposite polarities according to Figure 8 shown.

[0165] For example, a spike, peak or ring detector can be configured to determine the presence of a qualified interference in the sensor signal SS based on comparing the signal with a threshold (such as an amplitude value, rate-of-change value, average value, running average value, peak amplitude, rise or fall time, time constant, settling time, and / or frequency response value).

[0166] The resulting Event Detection Signal EDS can thus indicate only that a qualified interference (and thus a qualified pressure change) has been detected, or that a specific type of qualified interference (and thus the corresponding specific type of qualified pressure change) has been detected. In the latter case, taking an in-ear headphone as an example of operation, one type might correspond to insertion into the user's ear canal (insertion event - transition from off-ear to on-ear), while another type might correspond to removal from the ear canal (removal event - transition from on-ear to off-ear).

[0167] As another example, the event detector 400 can be implemented as a neural network or other classifier consistent with the exemplary implementation 400B of Figure 12 Similar to the above, those skilled in the art should understand that the neural network can be configured (e.g., through training or through stored configuration settings / parameters) to distinguish qualified interferences in the sensor signal SS from other (non-qualified) interferences, and / or to distinguish one type of qualified interference in the sensor signal SS from another type of qualified interference, where the Event Detection Signal EDS is configured accordingly.

[0168] Figure 13 is a schematic diagram of an exemplary implementation 400C of the event detector 400, where it is configured as a "spike" (ringing) detector. In the case where the sensor signal SS is a digital signal representing the speaker current I S (e.g., output by the ADC 280), it is assumed that the sensor signal is the monitoring signal MO(I).

[0169] The delay block 402 and the adder 404 are configured to find the difference between consecutive samples of the sensor signal SS, and then this difference is compared with a threshold TH by the comparator 406. If the threshold TH is exceeded, a spike (i.e., a sudden increase or decrease in the sensor signal SS) has been detected, and the Event Detection Signal EDS indicates the detection of a spike. The threshold TH can be set accordingly, and in fact, different thresholds TH can be used to detect different types of spikes, such as spikes of different polarities (see Figure 8 ).

[0170] Figure 14 is a schematic diagram of an exemplary implementation 400D of the event detector 400, where it is configured as a peak detector. In the case where the sensor signal SS is an analog voltage signal representing the induced back-EMF in the speaker 220 (see Figure 9 ), it is assumed that the sensor signal is the monitoring signal MO(V).

[0171] The sensor signal SS and the threshold voltage signal V TH are applied to a comparator preferably having hysteresis. If the threshold voltage V TH, then a peak has been detected, and the event detection signal EDS indicates that a peak has been detected. The threshold voltage V can be set accordingly TH , and in fact different threshold voltages V can be used TH to detect different types of peaks, such as peaks of different polarities (see Figure 8 ).

[0172] Figure 15 is a schematic diagram of an exemplary embodiment 400E of the event detector 400, where the event detector is configured as a peak detector, enhanced compared to that in Figure 14 (e.g., for high precision and in the case of narrow spikes occurring). In the case where the sensor signal SS is an analog voltage signal representing the induced back-EMF in the speaker 220 (see Figure 9 ), again assume that the sensor signal is the monitoring signal MO(V).

[0173] Those skilled in the art will understand that the peak detector of the embodiment 400E is merely an example of a series of peak detector circuits, and its operation is generally known. However, for the sake of completeness, in the peak detector of Figure 14 , the op-amps (operational amplifiers) 410 and 418 are configured as voltage followers, and the intermediate diodes 412 and the capacitor 416 act as peak detectors. The diode 412 acts as a rectifier, such that the voltage stored on the capacitor 416 tracks and stores the increasing peak in the sensor signal SS, and the peak subsequently appears as the output signal, which is the event detection signal EDS in this case. The op-amp 418 acts as a comparator.

[0174] As described above, the event detection signal EDS can be provided to the controller 102, and in response, the controller 120 can control the operation of the host device 100.

[0175] Figure 16 is a schematic diagram of the host device 500, which can be described as (or include) an audio processing system. The host device 500 corresponds to the host device 100, so the host device 100 can also be described as (or include) an audio processing system. The host device 500 will be regarded as an in-ear headphone here, consistent with the running example (although this is just an example). However, for simplicity, Figure 16 the elements of the host device 500 explicitly shown in

[0176] The host device 500 is organized into an "always-on" domain 501A and a "main" domain 501M. An "always-on" controller 502A is provided in the domain 501A and a "main" controller 502M is provided in the domain 501M. The controllers 502A and 502M can be considered equivalent to Figure 2 controller 102.

[0177] As previously described, the host device 500 can operate in a low-power state, where the components of the "always-on" domain 501A are active and the components of the "main" domain 501M are inactive (e.g., turned off or in a low-power state). The host 500 can be "awakened" to a higher-power state where the components of the "main" domain 501M are active.

[0178] The host device 500 includes an input / output unit 520, which can include one or more components corresponding to Figure 2 components 106, 108, 110, and 112. Specifically, as shown, the input / output unit 520 includes at least one set of audio circuits 200, which correspond to Figure 2 the speaker unit 112.

[0179] As Figure 16 shown, audio and / or control signals can be exchanged between the "always-on" controller 502A and the "main" controller 502M. Additionally, one or both of the controllers 502A and 502M can be connected to receive an event detection signal EDS from the audio circuits 200. Although not shown, one or both of the controllers 502A and 502M can be connected to provide a speaker signal SP to the audio circuits 200.

[0180] For example, the "always-on" controller 502A can be configured to operate an insertion detection algorithm (detecting the insertion of in-ear headphones into the user's ear canal, or an insertion event, or a transition from an off-ear state to an on-ear state) based on analyzing or processing the event detection signal EDS, and wake up the "main" controller 502M via a control signal as shown when a suitable event detection signal EDS is received. As an example, the event detection signal EDS can initially be processed by the "always-on" controller 502A and routed through this controller to the "main" controller 502M until the "main" controller 502M can receive the event detection signal EDS directly. In one example use case, the host device 500 can be located on a table, in a pocket, or in a storage container (i.e., not in the user's ear canal), and it may be desired to use the speaker 220 as a sensor to detect the insertion of in-ear headphones into the ear canal. Such detection can be performed by the "always-on" controller 502A, which monitors the event detection signal EDS when the host device 500 is in its low-power state.

[0181] As another example use case, the "master" controller 502M, once awakened - for example because the host device 500 is being deployed (inserted into the user's ear canal) - can be configured to play audio (such as music) in response to corresponding controls from the user. The "master" controller can also operate a removal detection algorithm based on analyzing or processing an event detection signal EDS (detecting the removal of the in-ear headphones from the user's ear canal or a removal event, or a transition from an on-ear state to an off-ear state), and enter a low-power state when a suitable event detection signal EDS is received. In this case, it may be desirable to use the speaker 220 as a microphone (such that the microphone signal MI can be used as a sensor signal SS) to detect the removal of the in-ear headphones from the user's ear canal, even while audio is being played.

[0182] Of course, these are just example use cases for the host device 500 (and similarly for the host device 100). Based on this disclosure, those skilled in the art will envision other exemplary use cases.

[0183] Those skilled in the art will understand that by using the speaker 220 as a sensor to detect a qualified interference in the sensor signal SS (indicating a qualified pressure change occurring on the speaker 220), insertion and removal events can be detected with relatively low associated power requirements. For example, Figures 13 to 15 the event detector has particularly low power requirements. In the case of detecting an insertion event, the power requirements can be particularly important because the host device 500 (or 100) may be in a particularly low-power state awaiting deployment. Figure 14 and Figure 15 the event detector may be particularly useful in this regard.

[0184] Figure 17A is a schematic diagram of a method 600 that can be performed by the host device 100 or 500 (such as by its controller and / or audio circuitry). The method includes: detecting (step S2) a qualified interference in the sensor signal SS indicating a qualified pressure change occurring on the speaker 220, and controlling (step S4) the host device in response to the detection. Such control can include transitioning from a low-power operation mode to a high-power operation mode, or vice versa. The method 600 can then return to step S2 and continue to loop until, for example, the host device is powered off.

[0185] Figure 17BIt is a schematic diagram of a method 700 that can be executed by a host device 100 or 500 (e.g., by its controller and / or audio circuit). The method includes: detecting (step S6) a qualified interference in the sensor signal SS that indicates a qualified pressure change occurring on the speaker 220; differentiating (step S8) the type of the qualified interference and thus the type of the detected qualified pressure change; and in response to the detection, controlling (step S10) the host device according to which type of qualified interference has been detected. Such control may include entering a high-power operation mode from a low-power operation mode, or vice versa, depending on which type of qualified interference has been detected. The method 700 can then return to step S6 and continue to loop until, for example, the host device is powered off.

[0186] Figure 17C It is a schematic diagram of a method 800 that can be executed by a host device 100 or 500 (e.g., by its controller and / or audio circuit) when the host device is an in-ear headphone. The method includes: detecting (step S12) a qualified interference in the sensor signal SS that indicates a qualified pressure change occurring on the speaker 220; and differentiating (step S14) the type of the qualified interference and thus the type of the detected qualified pressure change, where the types are respectively related to an insertion event and a removal event. If an insertion event is detected, the method proceeds to step S16, and controls the host device to enter or continue to operate in a high-power mode. If a removal event is detected, the method proceeds to step S18, and controls the host device to enter or continue to operate in a low-power mode. The method 800 can then return from step S16 or step S18 to step S12 and continue to loop until, for example, the host device is powered off.

[0187] Figure 17D It is a schematic diagram of a method 900 that can be executed by a host device 100 or 500 (e.g., by its controller and / or audio circuit) when the host device is an in-ear headphone.

[0188] The method includes detecting (step S20) a qualified interference in the sensor signal SS that indicates a qualified pressure change occurring on the speaker 220, the qualified interference corresponding to an insertion event; and if an insertion event is detected, controlling (S22) the host to enter or continue to operate in a high-power mode. Once operating in the high-power mode, the method includes: detecting (step S24) a qualified interference in the sensor signal SS that indicates a qualified pressure change occurring on the speaker 220, the qualified interference corresponding to a removal event; and if a removal event is detected, controlling (S26) the host to enter or continue to operate in a low-power mode. Once in the low-power mode, the method returns to step S20.

[0189] It is possible that the event detector 400 operates in a different manner in step S20 than in step S24. For example, it is assumed that the host device may be in a low-power mode in step S20 and in a high-power mode in step S24. For example, the event detector may operate according to embodiment 400B or 400C in step S20, and according to embodiment 400D or 400E in step S24. Operating the neural network according to embodiment 400B may consume more power than operating the peak / spike detector based on the analog voltage signal MO(V) according to embodiment 400D or 400E.

[0190] Method 900 can start from any of its steps and continue to loop until, for example, the host device is powered off.

[0191] As previously mentioned, the detection of voice commands or ear biometrics can form a secondary part of detecting whether the host device 100 should be "awakened" from a low-power state or, conversely, enter the "sleep mode".

[0192] For example, detecting an insertion event (transition from the off-ear state to the on-ear state) or a removal event (transition from the on-ear state to the off-ear state) by detecting a steady-state ambient pressure shift that appears on the speaker (only) may allow the detection to have a certain confidence level. By performing a secondary detection in response to detecting a shift in the steady-state ambient pressure, such as detecting ear biometrics, it is possible to increase this confidence level. This can avoid deciding that the host device should be "awakened" from a low-power state or, conversely, enter the "sleep mode" when, in fact, the transition from the off-ear state to the on-ear state or from the on-ear state to the off-ear state has not occurred.

[0193] Secondary (second-stage) detection can be used to detect the presence of any ear (transition from the off-ear state to the on-ear state) or the absence of any ear (transition from the on-ear state to the off-ear state), i.e., regardless of whose ear it is. After this secondary detection, a tertiary (third-stage) detection of the presence of a specific user's ear (transition from the off-ear state to the on-ear state) or the absence of a specific user's ear (transition from the on-ear state to the off-ear state) can be performed, i.e., increasing the complexity of determining whose ear it is.

[0194] The decision regarding whether the host device should be "awakened" (e.g., partially or in stages) from a low-power state or, conversely, enter the "sleep mode" (e.g., partially or in stages) can then depend on the secondary and / or tertiary detections. The tertiary detection can be considered part of the secondary detection.

[0195] Taking this into account and returning to the reference Figure 3 , the event detector 400 can be considered to include: a first-stage detector 400-1, which can operate to perform as previously described (see Figure 8)Detection of eligible interference in the sensor signal; and a second-stage detector 400-2 operable to perform a second-stage detection to determine (with greater confidence) whether the detected eligible interference indicates a given event in response to the detection of eligible interference by the first-stage detector 400-1. Figure 18 Is a schematic diagram of such an event detector.

[0196] For simplicity, the second-stage detector 400-2 can be configured to perform the second-stage detection and / or third-stage detection as described above, optionally in an order such that, for example, the third-stage detection depends on the second-stage detection. That is, in some arrangements, the second-stage detector 400-2 can be considered to represent a combination of the second-stage detector and the third-stage detector.

[0197] In terms of the method, the detection of a given event (ear attachment transition detection) can include a first-stage detection (detecting eligible interference in the sensor signal SS as described above), followed by at least a second-stage detection in the case where eligible interference is detected. If the second-stage detection is successful, for example, an ear is detected, then a third-stage detection, such as detecting the ear of a specific user, can be performed. The event detection signal EDS can be issued after any one of these detections. These detections can be performed in parallel, in which case the event detection signal EDS can be issued based on the result of any one of these detections or any combination thereof.

[0198] As described above, the host device 100 can have a series of different power levels. For example, with respect to the insertion event, the host device 100 can transition from the lowest power "sleep" mode to the medium power "partial wake" mode when a shift in the steady-state ambient pressure is detected, and then perform a secondary (second-stage) detection in this "partial wake" mode, for example, because the secondary detection may have a higher power requirement than detecting the shift in the steady-state ambient pressure. In this way, energy can be saved and the power is only increased to the extent required. That is, the first-stage detection (shift in the steady-state ambient pressure) can effectively be used as a kind of power gating method, not continuing with the second-stage detection unless needed - that is, the success of the first-stage detection triggers the second-stage detection. If the second-stage detection is successful (e.g., detecting the presence of any ear using ear biometrics), then the host device 100 can transition from the medium power "partial wake" mode to a higher power "fully wake" or "more fully wake" mode. There may even be power gating here before the third-stage detection of a specific ear - that is, the success of the second-stage detection triggers the third-stage detection. For simplicity, the following description will focus on the "sleep" and "wake" modes, but it should be remembered that a series of different power levels can be employed.

[0199] As an exemplary implementation of the second-stage and / or third-stage detection, biometric authentication will be considered.

[0200] As described above, biometric authentication generally involves comparing a biometric input signal (in particular, one or more features extracted from the input signal) with a template stored for an authorized user. Any of the signals MO, MI, and SS described above can be used as the input signal. As described above, the stored template is typically obtained during a "registration" process. Some biometric authentication processes may also involve comparing the biometric input signal (or features extracted therefrom) with a "generic model" that describes the biometrics of the general population (rather than a specific authorized user).

[0201] The output of the biometric authentication process is a score indicating the likelihood that the biometric input signal is the signal of an authorized user. For example, a relatively high score may indicate a relatively high likelihood that the biometric input signal matches an authorized user; a relatively low score may indicate a relatively low likelihood that the biometric input signal matches an authorized user. The biometric processor can decide whether to authenticate a particular user as an authorized user by comparing the biometric score with a threshold. For example, if the biometric score exceeds the threshold, the user can be authenticated; if the biometric score is below the threshold, the user may not be authenticated. The value of the threshold can be constant or can vary (e.g., vary according to the required security level). The event detector 400 can be considered to include such a biometric processor.

[0202] Figure 19 FIG. is a schematic diagram showing an example of obtaining and using the audio signal 1500 for in-ear detection and ear biometric authentication according to an embodiment of the present disclosure. More details can be found in US 2019 / 0294769 A1, the entire content of which is incorporated herein by reference.

[0203] Due to the relatively low amplitude of ear biometrics, the audio signal (as an exemplary input signal) obtained by the personal audio device (host device) described herein may have an inherently low signal-to-noise ratio. To reliably distinguish the ears of an authorized user from those of an unauthorized user, the biometric algorithm may require a relatively large amount of data. This is because ear biometrics have a relatively low amplitude and also because ear biometrics vary only slightly between different individuals.

[0204] Conversely, the difference between the biometric input signal indicating the presence of any ear and the biometric input signal indicating the absence of any ear is more significant. Thus, the systems and methods according to embodiments of the present disclosure may be able to reliably distinguish the presence and absence of any ear based on relatively little data. In other words, the in-ear (ear-touching) detection according to embodiments of the present disclosure can be performed quickly and consume relatively little power.

[0205] In a practical system, it is conceivable to reliably determine the presence or absence of any ear based on 5 to 10 data frames, while determining the presence of a specific ear (e.g., the ear of an authorized user) can be reliably based on approximately 100 data frames. This concept is shown in Figure 19 where the input audio signal 1500 includes a series of data frames 1502 - n (where n is an integer). Each data frame may include one or more data samples.

[0206] illustrates three different scenarios. In each scenario, a biometric algorithm is performed on the audio signal, including comparing the biometric features extracted from the audio signal 1500 with the template or earprint of an authorized user, and generating a biometric score indicating the likelihood of the presence of the ear of the authorized user. The biometric score may be based on the cumulative data in the audio signal 500 and thus may evolve and converge over time towards the "true" value. The biometric algorithm may include one or more different types of ear biometric features, in which case the ear biometric scores or decisions are fused as described above.

[0207] In the illustrated embodiment, the biometric module first determines whether the audio signal 500 includes an ear biometric feature indicating the presence of any ear. The determination may be based on relatively little data. In the illustrated example, the biometric module 416 makes the determination based on a single data frame; however, any number of data frames may be used for the determination. The determination may involve comparing the current biometric score with a threshold T1.

[0208] In Scenario 1, the biometric module 416 determines that there is no ear, so the biometric algorithm ends without further calculation after data frame 502 - 1. This may be considered the second-stage detection as described above. Specifically, the biometric module 416 does not continue to determine whether the audio signal 500 includes an ear biometric feature corresponding to the ear biometric feature of an authorized user. Of course, the algorithm may be repeated in the future, for example, periodically or in response to the detection of a certain event.

[0209] In scenario 2, the biometric module 416 determines the presence of an ear after data frame 502-1 (second-stage detection), and in response to that determination, continues to execute a "full" biometric algorithm (third-stage detection) to determine whether the ear belongs to an authorized user. This process may require relatively more data, and thus in the illustrated embodiment, the authentication decision can only be reliably made after data frame 502-5. In scenario 2, this determination is negative (i.e., the user is not authorized). Scenario 3 basically corresponds to scenario 2, but the authentication device is affirmative (i.e., the user is authorized). In either case, the data on which the authentication decision is based can include more data frames than the data on which the in-ear (ear-touching) detection decision is based. For example, the data can be averaged over all data frames. The determination can involve a comparison of the current biometric score with a threshold T2.

[0210] Accordingly, the present disclosure provides methods, devices, and systems for performing in-ear detection using a biometric processor or module.

[0211] Another exemplary implementation of the second-stage detection and / or third-stage detection, biometric authentication can be understood according to US6697299, the entire content of which is incorporated herein by reference. Specifically refer to the Figure 5 and Figure 6 .

[0212] In this example, the impedance of the loudspeaker 220 (of the speaker unit) is measured within a frequency range (e.g., when a sound with a frequency of 100 Hz to 500 Hz is sent from the loudspeaker), for example, when the host device 100 is in an ear-touching state. Then the obtained impedance is plotted on a coordinate where one axis is the real number and the other axis is the imaginary number.

[0213] It is found that such impedance plots vary from person to person, i.e., based on the different characteristics of people's ears. In the range of 100 Hz to 500 Hz, the lower frequencies make the differences more obvious, indicating that the use of the low-frequency region is suitable for personal authentication.

[0214] The impedance can be obtained by measuring the voltage and current of a measurement circuit (e.g., a speaker) (using the above monitoring unit), and can be represented by the absolute value and phase of the impedance. Similar to the example combined above Figure 19 with, the plot of any ear against no ear is easier to distinguish than the plot of one ear against another ear. Therefore, similar considerations apply to the initial detection of any ear, and then the detection of a specific ear (if required).

[0215] As another exemplary implementation of the second-stage detection and / or the third-stage detection, the second-stage detection / third-stage detection may involve detecting qualified interference in the sensor signal SS, as described above but in a different manner from the first-stage detection. The second-stage detection / third-stage detection may even involve detecting qualified interference in the sensor signal SS, as described above and using the same method as the first-stage detection. Both of these methods can be considered a form of "double-check". In these cases, the second-stage detection / third-stage detection may be performed on the same data as the first-stage detection, such as a snapshot or (time-based) segment or portion of the sensor signal SS.

[0216] For example, where the second-stage detection / third-stage detection involves detecting qualified interference in the sensor signal SS, but in a different manner from the first-stage detection, the first-stage detection may involve using Figure 11 a detector 400A (spike or peak or ringing detector) to detect, while the second-stage detection may involve using Figure 12 a detector 400B (neural network or classifier) to detect. In this example, the power requirement of the first-stage detection may be greater than that of the second-stage detection, so it may be appropriate to "power-gate" the second-stage detection based on the result of the first-stage detection (i.e., trigger the second-stage detection only if the first-stage detection is successful). Of course, different / same detections of qualified interference can be performed any number of times, sequentially and / or in parallel.

[0217] Embodiments of the present disclosure may be implemented in an electronic, portable, and / or battery-powered host device (such as a smart phone, audio player, mobile phone or cellular phone, handset). Embodiments may be implemented on one or more integrated circuits disposed within such a host device. Embodiments may be implemented in a personal audio device configurable to provide audio playback to a single individual, such as a smart phone, mobile phone or cellular phone, headphones, earphones, etc. See Figures 1a to 1e . Similarly, embodiments may be implemented on one or more integrated circuits disposed within such a personal audio device. In yet another alternative, embodiments may be implemented in a combination of a host device and a personal audio device. For example, embodiments may be implemented in one or more integrated circuits disposed within a personal audio device and one or more integrated circuits disposed within a host device.

[0218] It should be understood - especially by those of ordinary skill in the art who benefit from this disclosure - that the various operations described herein, especially in connection with the figures, can be implemented by other circuits or other hardware components. The order of each operation of a given method can be changed, and various elements of the systems described herein can be added, reordered, combined, omitted, modified, etc. This disclosure is intended to cover all such modifications and changes, and thus, the above description should be considered illustrative rather than restrictive.

[0219] Similarly, although this disclosure refers to specific embodiments, certain modifications and changes can be made to those embodiments without departing from the scope and coverage of this disclosure. Additionally, any benefits, advantages, or solutions to problems described herein with respect to specific embodiments are not intended to be construed as critical, essential, or necessary features or elements.

[0220] Likewise, additional embodiments and implementations that benefit from this disclosure will be apparent to those of ordinary skill in the art, and such embodiments should be considered to be included herein. Additionally, those of ordinary skill in the art will recognize that various equivalent techniques can be applied instead of or in combination with the embodiments discussed, and all such equivalents should be considered to be covered by this disclosure.

[0221] Those skilled in the art will recognize that some aspects of the above-described devices (circuits) and methods can be embodied as processor control code (e.g., a computer program) located on a non-volatile carrier medium such as a disk, a CD- or DVD-ROM, a programmed memory (such as read-only memory (firmware)), etc., or on a data carrier such as an optical or electrical signal carrier. For example, the microphone signal generator 240 (and its subunits 250, 260) can be implemented as a processor operating based on processor control code. As another example, the controllers 102, 502A, 502B can be implemented as processors operating based on processor control code. As another example, the event detector can in some cases be implemented as a processor operating based on processor control code (e.g., when implementing a neural network or classifier).

[0222] For some applications, such aspects will be implemented on a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field Programmable Gate Array). Thus, the code can include conventional program code or microcode, or (for example) code for setting up or controlling an ASIC or FPGA. The code can also include code for dynamically configuring a reconfigurable device, such as a reprogrammable logic gate array. Similarly, the code can include code for a hardware description language, such as Verilog TM or VHDL. Those skilled in the art will appreciate that the code can be distributed among multiple coupled components that communicate with each other. Where appropriate, code that runs on a (reprogrammable) programmable analog array or similar device in the field to configure analog hardware can also be used to implement these aspects.

[0223] Some embodiments of the invention can be arranged as part of an audio processing circuit. For example, it can be provided in an audio circuit (such as a codec, etc.) in the host device as discussed above. The circuit according to an embodiment of the invention can be (at least partially) implemented as an integrated circuit (IC), for example, implemented on an IC chip. One or more input or output transducers (such as speaker 220) can be connected to the integrated circuit in use.

[0224] It should be noted that the above embodiments illustrate the invention and do not limit the invention, and those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in the claims, "a" or "an" does not exclude a plurality, and a single feature or other unit can implement the functions of several units recited in the claims. Any reference signs or labels in the claims should not be construed as limiting their scope.

[0225] As used herein, when two or more elements are referred to as being "coupled" to each other, this term indicates that the two or more elements are in electrical or mechanical communication, as applicable, whether indirectly or directly connected, with or without intermediate elements.

[0226] This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the exemplary embodiments herein that would be understood by a person of ordinary skill in the art. Similarly, to the extent appropriate, the appended claims cover all changes, substitutions, variations, alterations, and modifications to the exemplary embodiments herein that would be understood by a person of ordinary skill in the art. Additionally, references in the appended claims to a device or system, or a component of a device or system, that is adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function cover such device, system, or component, whether or not the device, system, or component or the particular function is activated, turned on, or unlocked, so long as the device, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Accordingly, the systems, devices, and methods described herein may be modified, augmented, or omitted without departing from the scope of this disclosure. For example, components of the systems and devices may be integrated or separated. Additionally, the operations of the systems and devices disclosed herein may be performed by more, fewer, or other components, and the methods described may include more, fewer, or other steps. Further, the steps may be performed in any suitable order. As used in this document, "each" refers to each member of a set or each member of a subset of a set.

[0227] Although the exemplary embodiments are illustrated in the drawings and described below, the principles of this disclosure may be implemented using any number of technologies, whether currently known or not. This disclosure should not in any way be limited to the exemplary embodiments and technologies shown in the drawings and described above.

[0228] Unless otherwise specifically stated, the items depicted in the drawings are not necessarily drawn to scale.

[0229] All of the examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the disclosure and the concepts contributed by the inventors to further the art, and are to be construed as not limiting to such specifically recited examples and conditions. Although the embodiments of this disclosure have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of this disclosure.

[0230] Although specific advantages have been enumerated above, various embodiments may include some of all of the enumerated advantages, none of the recited advantages, or all of the recited advantages. Additionally, other technical advantages may become apparent to a person of ordinary skill in the art after reading the foregoing drawings and description.

[0231] This disclosure extends to the following statements.

[0232] S1. An audio circuit, comprising:

[0233] A monitoring unit, operable to monitor a speaker current flowing through a speaker and / or a speaker voltage induced on the speaker, and to generate a monitoring signal indicative of the speaker current and / or the speaker voltage; and

[0234] An event detector, operable to detect a qualified interference in a sensor signal indicative of a qualified pressure change occurring on the speaker, wherein the sensor signal is the monitoring signal or derived from the monitoring signal.

[0235] S2. The audio circuit according to statement S1, wherein:

[0236] The audio circuit is or includes an ear - on / ear - off transition detection circuit;

[0237] Each qualified pressure change includes a shift of a steady - state, running average, or baseline ambient pressure occurring on the speaker; and / or

[0238] Each qualified pressure change includes a change in a steady - state value of the ambient pressure occurring on the speaker; and / or

[0239] Each qualified pressure change is a qualified steady - state pressure change; and / or

[0240] Each qualified pressure change is a pressure change caused by the speaker transitioning from an ear - on state to an ear - off state or vice versa; and / or

[0241] For each qualified pressure change, the corresponding qualified interference includes or is a change, step response, spike, or ring in the sensor signal.

[0242] S3. The audio circuit according to statement S2, wherein:

[0243] Each said shift includes a step change; and / or

[0244] Each said qualified interference is transient or substantially time - limited; and / or

[0245] Each said qualified interference responds to or is generated by a corresponding qualified pressure change; and / or

[0246] Each said qualified interference meets a given or stored or predefined qualified definition or specification.

[0247] S4. The audio circuit according to any of the foregoing statements, wherein the event detector is operable to perform the following operations to detect each qualified interference indicative of a corresponding qualified pressure change: compare the sensor signal with a corresponding qualified specification defining the qualified interference (and if a candidate interference in the sensor signal meets the qualified specification, determine that the candidate interference is the qualified interference).

[0248] S5. The audio circuit according to statement S4, wherein each qualification criterion includes at least one of the following:

[0249] Definition of one or more qualification criteria;

[0250] Configuration of a neural network or classifier implemented by the event detector; and

[0251] Threshold values, such as amplitude values, rate of change values, average values, running average values, peak amplitudes, rise or fall times, time constants, settling times, and / or frequency response values.

[0252] S6. The audio circuit according to any one of the foregoing statements, wherein the event detector includes:

[0253] A controller configured as a neural network or classifier and operative to detect qualified interference in the sensor signal based on the sensor signal; and / or

[0254] A peak detector configured to detect qualified peaks in the sensor signal; and / or

[0255] A spike detector configured to detect qualified spikes in the sensor signal.

[0256] S7. The audio circuit according to any one of the foregoing statements, wherein the event detector is operative to detect a plurality of different qualified interferences corresponding to a plurality of different qualified pressure changes respectively based on the sensor signal.

[0257] S8. The audio circuit according to statement S7, wherein:

[0258] The plurality of different qualified interferences include a first qualified interference and a second qualified interference corresponding to a first qualified pressure change and a second qualified pressure change respectively;

[0259] The polarities of the first qualified pressure change and the second qualified pressure change are substantially opposite to each other, such that the polarities of the first interference and the second interference in the sensor signal are also substantially opposite to each other; and

[0260] The event detector is configured to distinguish the first qualified pressure change and the second qualified pressure change at least in part by detecting the polarities of the relevant interferences detected in the sensor signal,

[0261] Optionally, wherein the first qualified pressure change corresponds to the transition of the speaker from the ear - attached state to the ear - detached state, and the second qualified pressure change corresponds to the transition of the speaker from the ear - detached state to the ear - attached state.

[0262] S9. The audio circuit according to any one of the foregoing statements further includes a speaker driver that is operable to drive the speaker based on a speaker signal,

[0263] wherein:

[0264] the event detector includes a microphone signal generator;

[0265] the microphone signal generator is operable to generate a microphone signal representative of the candidate pressure change based on the monitoring signal and the speaker signal when a candidate pressure change occurs on the speaker; and

[0266] the sensor signal is or is derived from the microphone signal.

[0267] S10. The audio circuit according to statement S9, wherein the event detector is operable to detect when the candidate pressure change is or includes a qualified pressure change based on the sensor signal.

[0268] S11. The audio circuit according to statement S9 or S10, wherein the candidate pressure change includes an external sound occurring on the speaker.

[0269] S12. The audio circuit according to any one of statements S9 to S11, wherein the microphone signal generator includes a converter configured to convert the monitoring signal into the microphone signal based on the speaker signal, and the converter is at least partially defined by a transfer function that models at least the speaker.

[0270] S13. The audio circuit according to statement S12, wherein the transfer function also models at least one of the speaker driver and the monitoring unit or both the speaker driver and the monitoring unit.

[0271] S14. The audio circuit according to statement S12 or S13, wherein:

[0272] the speaker driver is operable to drive the speaker when the speaker signal is a sounding speaker signal such that it emits a corresponding sound signal;

[0273] when the candidate pressure change occurs on the speaker and the speaker signal is a sounding speaker signal, the monitoring signal includes a speaker component generated by the speaker signal and a microphone component generated by the candidate pressure change; and

[0274] The transducer is defined such that when the candidate pressure change occurs on the loudspeaker and the loudspeaker signal is an active loudspeaker signal, it filters out the loudspeaker component and / or equalizes the microphone component and / or isolates the microphone component when converting the monitoring signal into the microphone signal.

[0275] S15. The audio circuit according to any one of statements S12 to S14, wherein:

[0276] The loudspeaker driver is operable to drive the loudspeaker such that it emits substantially no sound signal when the loudspeaker signal is an inactive loudspeaker signal;

[0277] When the candidate pressure change occurs on the loudspeaker and the loudspeaker signal is an inactive loudspeaker signal, the monitoring signal includes a microphone component generated by the candidate pressure change; and

[0278] The transducer is defined such that when the candidate pressure change occurs on the loudspeaker and the loudspeaker signal is an inactive loudspeaker signal, it equalizes the microphone component and / or isolates the microphone component when converting the monitoring signal into the microphone signal.

[0279] S16. The audio circuit according to any one of statements S12 to S15, wherein the microphone signal generator is configured to determine or update the transfer function or the parameters of the transfer function based on the monitoring signal and the loudspeaker signal when the loudspeaker signal is an active loudspeaker signal that drives the loudspeaker to emit a corresponding sound signal.

[0280] S17. The audio circuit according to any one of statements S12 to S16, wherein the microphone signal generator is configured to determine or update the transfer function or the parameters of the transfer function based on the microphone signal.

[0281] S18. The audio circuit according to statement S16 or S17, wherein the microphone signal generator is configured to redefine the transducer as the transfer function or the parameters of the transfer function change.

[0282] S19. The audio circuit according to any one of statements S12 to S18, wherein the transducer is configured to perform a conversion such that the microphone signal is output as a sound pressure level signal.

[0283] S20. The audio circuit according to any one of statements S12 to S19, wherein the transfer function and / or the transducer are at least partially defined by Thiele - Small parameters.

[0284] S21. The audio circuit according to any one of the foregoing statements, wherein:

[0285] The speaker signal indicates a voltage signal applied to the speaker or is related to or proportional to the voltage signal; and / or

[0286] The monitoring signal is related to or proportional to the speaker current flowing through the speaker; and / or

[0287] The monitoring signal is related to or proportional to the voltage signal induced on the speaker.

[0288] S22. The audio circuit according to statement S21, wherein the speaker driver is operable to control the voltage signal applied to the speaker to maintain or tend to maintain a given relationship between the speaker signal and the applied voltage signal.

[0289] S23. The audio circuit according to any one of the foregoing statements, wherein the monitoring unit includes an impedance connected such that the speaker current flows through the impedance, and wherein the monitoring signal is generated based on the voltage across the impedance,

[0290] Optionally, wherein the impedance is a resistor.

[0291] S24. The audio circuit according to any one of the foregoing statements, wherein the monitoring unit includes a current mirror arrangement of transistors, the transistors being connected to mirror the speaker current to generate a mirror current, and wherein the monitoring signal is generated based on the mirror current.

[0292] S25. The audio circuit according to any one of the foregoing statements, which includes the speaker.

[0293] S26. The audio circuit according to any one of the foregoing statements, which includes a speaker signal generator operable to generate the speaker signal and / or a microphone signal analyzer operable to analyze the microphone signal.

[0294] S27. The audio circuit according to any one of the foregoing statements, wherein the event detector is operable to generate an event detection signal indicating a corresponding qualified pressure change in response to detecting a qualified interference.

[0295] S28. The audio circuit according to any one of the foregoing statements, wherein the event detector includes:

[0296] A first-stage detector operable to perform the detection of the qualified interference in the sensor signal; and

[0297] A second-stage detector that is operable to perform a second-stage detection to determine whether the detected qualified interference indicates a given event in response to (only) the qualified interference detected by the first-stage detector.

[0298] Wherein the second-stage detector is operable to generate an event detection signal indicating the given event based on the result of the second-stage detection.

[0299] S29. The audio circuit according to statement S27 or S28, comprising an event controller operable to analyze the event detection signal and output a control signal based on the analysis.

[0300] The event detection signal can be used to control the power level of the host device, for example, between different power usage levels (such as any one of sleep mode, wake-up mode, low-power mode, medium-power mode, high-power mode, wake-up mode, etc.).

[0301] The audio circuit can be referred to as a transducer circuit (for example, if the speaker is replaced by a transducer, not necessarily a speaker). Examples of transducers that can detect pressure differences can be any capacitance-based transducer or coil-based transducer, such as an accelerometer. For example, the reference to the speaker can be replaced by a reference to an accelerometer or a microphone or a pressure / force sensor. The audio circuit can be referred to as an ear-attached transition detection circuit (for example, if the qualified pressure change occurring on the speaker is caused by the speaker transitioning from an ear-attached state to an ear-detached state or vice versa).

[0302] S30. The audio circuit according to any of the foregoing statements, comprising an analog-to-digital converter configured to output the monitoring signal and / or the sensor signal as digital signals based on the speaker current and / or the speaker voltage.

[0303] S31. An audio processing system, comprising:

[0304] The audio circuit according to any of the foregoing statements; and

[0305] A processor configured to control the operation of the audio processing system based on the detection.

[0306] S32. The audio processing system according to statement S31, wherein the processor is configured to:

[0307] Transition from a low-power state to a higher power state in response to the detection; and / or

[0308] Transition from a high-power state to a lower power state in response to the detection.

[0309] S33. A host device comprising an audio circuit according to any one of statements 1 to 29 or an audio processing system according to statement S31 or S32.

[0310] S34. The host device according to statement S33, which is a headphone such as an in-ear headphone and includes a speaker.

[0311] S34. A transducer circuit comprising:

[0312] A monitoring unit operable to monitor a transducer current flowing through the transducer and / or a transducer voltage induced on the transducer and to generate a monitoring signal indicative of the transducer current and / or the transducer voltage; and

[0313] An event detector operable to detect a qualified interference in a sensor signal indicative of a qualified pressure change occurring on the transducer, wherein the sensor signal is the monitoring signal or derived from the monitoring signal.

[0314] S35. A method of detecting a qualified pressure change occurring on a speaker, the method comprising:

[0315] Generating a monitoring signal indicative of a speaker current flowing through the speaker and / or a speaker voltage induced on the speaker; and

[0316] Detecting a qualified interference in a sensor signal indicative of a qualified pressure change occurring on the speaker, wherein the sensor signal is the monitoring signal or derived from the monitoring signal.

[0317] S36. A method of detecting insertion of an in-ear headphone into or removal of the in-ear headphone from an ear canal, the in-ear headphone including a speaker, the method comprising:

[0318] Generating a monitoring signal indicative of a speaker current flowing through the speaker and / or a speaker voltage induced on the speaker; and

[0319] Detecting a qualified interference in a sensor signal indicative of a qualified pressure change occurring on the speaker, wherein the sensor signal is or derived from the monitoring signal, and wherein the qualified pressure change corresponds to insertion of the in-ear headphone into the ear canal or removal of the in-ear headphone from the ear canal.

[0320] S37. A method of detecting insertion of an in-ear headphone into or removal of the in-ear headphone from an ear canal, the in-ear headphone including a speaker, the method comprising:

[0321] Generating a monitoring signal indicative of a speaker current flowing through the speaker and / or a speaker voltage induced on the speaker; and

[0322] Detect an interference in a sensor signal indicative of insertion of the in-ear headphone into or removal from the ear canal, wherein the sensor signal is the monitoring signal or derived from the monitoring signal.

[0323] S38. A method for detecting a transition of a speaker from an ear-attached state to an ear-detached state or vice versa, the method comprising:

[0324] Generating a monitoring signal indicative of a speaker current flowing through the speaker and / or a speaker voltage induced on the speaker; and

[0325] Detecting an interference in a sensor signal indicative of the transition, wherein the sensor signal is the monitoring signal or derived from the monitoring signal.

Claims

1. An ear - attachment transition detection circuit, comprising: A monitoring unit that is operable to monitor a speaker current flowing through a speaker and / or a speaker voltage induced on the speaker, and generate a monitoring signal indicative of the speaker current and / or the speaker voltage; And An event detector that is operable to detect a qualified interference in a sensor signal indicative of a qualified pressure change occurring on the speaker caused by the speaker transitioning from an ear - attached state to an ear - detached state or from an ear - detached state to an ear - attached state, wherein the sensor signal is the monitoring signal or derived from the monitoring signal, Wherein: The event detector is operable to detect a first qualified interference and a second qualified interference corresponding to different first qualified pressure changes and second qualified pressure changes respectively based on the sensor signal; The polarities of the first qualified pressure change and the second qualified pressure change are opposite to each other, such that the polarities of the first qualified interference and the second qualified interference in the sensor signal are also opposite to each other; and The event detector is configured to distinguish the first qualified pressure change and the second qualified pressure change at least in part by detecting the polarities of the relevant interferences detected in the sensor signal.

2. The ear - attachment transition detection circuit according to claim 1, wherein: Each qualified pressure change includes a shift or change in a steady - state ambient pressure occurring on the speaker; and / or For each qualified pressure change, the corresponding qualified interference includes a step response or ringing in the sensor signal.

3. The ear - attachment transition detection circuit according to claim 2, wherein each of the qualified interferences satisfies a given or stored or predetermined qualified definition or specification.

4. The ear - attachment transition detection circuit according to any one of the preceding claims, wherein the event detector is operable to perform the following operations to detect each qualified interference indicative of a corresponding qualified pressure change: Compare the sensor signal with a corresponding qualified specification defining the qualified interference; and If a candidate interference in the sensor signal meets the qualified specification, determine that the candidate interference is the qualified interference.

5. The ear - attachment transition detection circuit according to claim 4, wherein each qualified specification includes at least one of the following: The definition of one or more qualified criteria; The configuration of a neural network or classifier implemented by the event detector; and A threshold.

6. The ear - attachment transition detection circuit according to any one of claims 1 - 3, wherein the event detector includes: A controller configured as a neural network or classifier and operable to detect qualified interferences in the sensor signal based on the sensor signal; And / or A peak detector configured to detect qualified peaks in the sensor signal; And / or A spike detector configured to detect qualified spikes in the sensor signal.

7. The ear - attachment transition detection circuit according to any one of claims 1 - 3, further comprising a speaker driver that is operable to drive the speaker based on a speaker signal, Wherein: The event detector includes a microphone signal generator; The microphone signal generator is operable to generate a microphone signal representative of the candidate pressure change based on the monitoring signal and the speaker signal when a candidate pressure change occurs on the speaker; and the sensor signal is or is derived from the microphone signal.

8. The ear - on transition detection circuit according to claim 7, wherein the event detector is operable to detect when the candidate pressure change is or includes a qualified pressure change based on the sensor signal.

9. The ear-attached conversion detection circuit according to claim 7, comprising: A speaker signal generator, the speaker signal generator being operable to generate the speaker signal, and / or a microphone signal analyzer, the microphone signal analyzer being operable to analyze the microphone signal.

10. The ear - on transition detection circuit according to any one of the preceding claims 1 - 3, comprising the speaker.

11. The ear - on transition detection circuit according to any one of the preceding claims 1 - 3, wherein the event detector is operable to generate an event detection signal indicating the corresponding qualified pressure change in response to detecting a qualified interference.

12. The ear - on transition detection circuit according to any one of the preceding claims 1 - 3, wherein the event detector comprises: A first - stage detector, which is operable to perform the detection of the qualified interference in the sensor signal; and A second - stage detector, which is operable to perform a second - stage detection to determine whether the detected qualified interference indicates a given event in response to the first - stage detector detecting a qualified interference, wherein the second - stage detector is operable to generate an event detection signal indicating the given event according to the result of the second - stage detection.

13. The ear - on transition detection circuit according to claim 11, comprising an event controller, the event controller being operable to analyze the event detection signal and output a control signal according to the analysis.

14. The ear - on transition detection circuit according to any one of the preceding claims 1 - 3, comprising an analog - to - digital converter, the analog - to - digital converter being configured to output the monitoring signal and / or the sensor signal as digital signals based on the speaker current and / or the speaker voltage.

15. The ear - on transition detection circuit according to claim 5, wherein the threshold is an amplitude value, a rate - of - change value, an average value, a rise or fall time, a time constant, and / or a frequency - response value.

16. The ear - on transition detection circuit according to claim 15, wherein the amplitude value is a peak amplitude, and / or the average value is a running average, and / or the time constant is a settling time.

17. The ear - on transition detection circuit according to claim 1, wherein the first qualified pressure change corresponds to the transition of the speaker from the ear - on state to the ear - off state, and the second qualified pressure change corresponds to the transition of the speaker from the ear - off state to the ear - on state.

18. An audio processing system, comprising: The ear - on transition detection circuit according to any one of the preceding claims; and A processor, the processor being configured to control the operation of the audio processing system based on the detection.

19. The audio processing system according to claim 18, wherein the processor is configured to: transition from a low power state to a high power state in response to the detection; and / or transition from a high power state to a low power state in response to the detection.

20. A host device comprising the ear-attached transition detection circuit according to any one of claims 1 to 17 or the audio processing system according to claim 18 or 19.

21. The host device according to claim 20, wherein the host device is a headset and comprises the speaker.

22. The host device according to claim 20, wherein the host device is an in-ear headset and comprises the speaker.

23. A method for detecting a transition of a speaker from an ear-attached state to an ear-detached state or from an ear-detached state to an ear-attached state, the method comprising: generating a monitoring signal indicative of a speaker current flowing through the speaker and / or a speaker voltage induced on the speaker; and detecting an interference in the sensor signal indicative of the transition, wherein the sensor signal is the monitoring signal or derived from the monitoring signal, wherein: the method comprises detecting a first qualified interference and a second qualified interference respectively corresponding to different first qualified pressure changes and second qualified pressure changes based on the sensor signal; the polarities of the first qualified pressure change and the second qualified pressure change are opposite to each other, such that the polarities of the first qualified interference and the second qualified interference in the sensor signal are also opposite to each other; and the method comprises differentiating the first qualified pressure change and the second qualified pressure change at least in part by detecting the polarities of the relevant interferences detected in the sensor signal.

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