Touch gesture control of in-ear electrostatic acoustic device

Abstract

A headphone assembly including an electrostatic acoustic device. An audio signal is input to the electrostatic acoustic device. The membrane of the electrostatic acoustic device is configured to mechanically respond to a varying electric field responsive to an audio signal at the audio signal input. The detector is configured to detect a time-dependent displacement of the membrane in response to an external stimulus on the housing and to issue a command in accordance with the detected time-dependent displacement of the membrane and the corresponding external stimulus.

Description

background 1. Technical Field

[0002] The present invention relates to electrostatic audio devices, including headphones and loudspeakers.

[0003] 2. Description of Related Technology

[0004] In the field of high-fidelity sound reproduction, electrostatic speakers have attracted attention due to their inherently superior sound quality and smooth response over a wide frequency range. In such devices, a flexible sound-generating membrane is located near an electrode, or in the case of a push-pull arrangement, near a pair of electrodes, one on each side of the membrane. A polarization potential is applied between the membrane and the electrodes, and an audio signal is superimposed on the electrodes, causing the membrane to move in response to the audio signal. The electrodes are acoustically transparent so that the sound generated by the moving membrane radiates outward through the electrodes to the listening area.

[0005] Electrostatic devices are very efficient both electrically and mechanically. The electrical impedance is high and decreases as the acoustic frequency increases. The high electrical impedance results in very low operating currents and minimal electrical losses. Mechanically, there are no moving parts other than the very lightweight moving membrane. Electrostatic devices are therefore inherently more energy efficient than the electrodynamic acoustic devices currently used in battery-powered electronic devices. Brief Overview

[0007] Disclosed herein are various earphone assemblies for earphone assemblies including electrostatic acoustic devices and control methods thereof. An audio signal is input to the electrostatic acoustic device. The membrane of the electrostatic acoustic device is configured to mechanically respond to a changing electric field in response to an audio signal at an audio signal input terminal. The housing surrounds the electrostatic acoustic device and the detector. The detector is configured to detect the time-dependent displacement of the membrane in response to an external stimulus on the housing. A processor operably attached to the detector may be configured to issue a command selected from a set of previously defined commands. The selected command may be adapted to the time-dependent displacement of the detected membrane and the corresponding external stimulus. The processor may be configured to select an operating mode of the electrostatic acoustic device according to the time-dependent displacement of the detected membrane and the corresponding external stimulus. The housing may surround the electrostatic acoustic device and the detector. The housing may include a nozzle configured to be used for acoustic transmission from the membrane to the ear canal during in-ear operation. The processor may be configured to detect the displacement of the membrane in response to an external stimulus during in-ear operation, the external stimulus comprising a touch gesture on the housing that applies pressure toward the ear canal. The processor may be configured to detect a time-dependent displacement of the membrane as an impulse response to an external stimulus during in-ear operation, the external stimulus comprising a finger tap gesture on the shell. The processor may be configured to distinguish between a finger tap on the shell with a fingernail and a finger tap on the shell with a fingertip. The processor may be configured to detect a time-dependent displacement of the membrane in response to an external stimulus during in-ear operation, the external stimulus comprising a touch gesture of stroking the surface of the shell. The processor may be configured to distinguish at least two directions of stroking. The shell may include a surface having a roughness profile, the roughness profile being configured to produce different time-dependent displacements of the membrane when rubbed in different directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention is herein described, by way of example only, with reference to the accompanying drawings, in which:

[0010] Figure 1A schematically illustrates a cross-sectional view of an electrostatic device according to features of the present invention;

[0011] Figure 1B is an isometric view of a headset according to features of the present invention viewed from the back;

[0012] Figure 1C Shows and Figure 1B an earphone according to a further feature of the invention as viewed from the back, wherein the back cover is removed;

[0013] Figure 2is an electronic block diagram of a feedback control system for noise cancellation and / or adjustable acoustic transparency according to features of the present invention;

[0014] Figure 2A It shows that according to the conventional technology Figure 2 Electronic block diagram of a proportional-integral-derivative (PID) controller;

[0015] Figure 3 is a system diagram including an electrostatic acoustic device and its driver that serves dual purpose as a loudspeaker and a microphone;

[0016] Figure 4A Shown for Figure 2 and Figure 3 Electronic block diagram of the electrostatic acoustic device and its driver used in;

[0017] Figure 4B Shown for Figure 2 and Figure 3 An alternative block diagram driver of an electrostatic acoustic device and a driver according to features of the present invention used in;

[0018] Figure 5 is a flow chart illustrating a method that features the present invention.

[0019] The above and / or other aspects will become apparent from the following detailed description when considered in conjunction with the accompanying drawings. Detailed Description

[0021] Reference will now be made in detail to the features of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. These features are described below to explain the present invention by referring to the drawings.

[0022] By way of introduction, different aspects of the invention may relate to an in-ear electrostatic acoustic device that may be used in different operating modes. The in-ear electrostatic acoustic device may be configured as an in-ear headphone and may include or be interfaced with an audio player and include functions such as play, stop, move forward or backward in a playlist. Alternatively, the in-ear device may be operated as a hearing aid. According to an embodiment of the invention, touch gestures on the housing of the in-ear electrostatic acoustic device during in-ear operation may be detected and used to control the operation of the device.

[0023] Features of the invention may include an earphone housing having one or more small holes to provide an acoustically transparent back, an integrated power source (e.g., a battery with power circuitry and audio circuitry integrated within the in-ear housing). Two main operating modes are available: i) a closed-loop control mode, which includes 1) a noise cancellation mode, in which feedback to the electroacoustic device can be configured to cancel ambient sound or noise, and / or 2) an adjustable acoustically transparent mode, i.e., the extent to which the user hears ambient sound can be adjusted by adjusting the feedback in the control circuit. The second main operating mode is ii) an open-loop mode, which allows extraction of a signal responsive to the time-dependent displacement of the membrane of the electrostatic speaker. In mode ii), the electrostatic speaker can be used as both a microphone and a speaker, and sound can be generated by touch gestures on the housing of the in-ear device to control the operation of the device. In accordance with features of the invention, touch gestures can be used to switch the device between main operating modes i) and ii).

[0024] Referring now to the drawings, Figure 1A , Figure 1A An electrostatic acoustic device 10 according to features of the present invention is schematically shown. A vertical axis Z is shown passing through the center of the acoustic device 10. A tensioned membrane 15 is supported by the edges of an electrode 11, substantially in a plane perpendicular to the vertical axis Z. The membrane 15 may be impregnated with a conductive, resistive and / or electrostatic material so that the membrane 15 mechanically responds to a changing electric field. The central region of the electrode 11 is nominally equidistantly mounted near the membrane 15 (e.g., parallel to the membrane 15) at a distance d (e.g., 20 microns to 500 microns) from the membrane 15. The electrode 11 as shown may be provided with a small hole 12 that transmits sound waves emitted from the membrane 15 when the electrostatic acoustic device 10 is operating. Alternatively or additionally, one or more side ports 13 may transmit sound waves from the air surrounding the membrane 15 to the outside of the device 10.

[0025] During operation of the electrostatic acoustic device 10, a constant direct current (DC) bias voltage (e.g., +V DC = +100 volts to +1000 volts) is applied to the membrane 15. The non-inverting voltage signal +V i can be applied to one of the electrodes 11, while the same but inverted voltage signal -V i can be applied to the other electrode 11. Alternatively, the voltage signal V i can be applied to the membrane 15, and the electrode 11 can be biased to ±V DC / 2. Voltage signal ±V i may vary at audio frequencies (nominal between 20 Hz and 20,000 Hz). The dashed lines schematically show the response of the membrane 15 to the voltage signal ±V i Causes the voltage to change and moves.

[0026] Now also refer to Figure 1B , Figure 1B 1 is an isometric view of an earphone 101 according to a feature of the present invention viewed from the back of the earphone. The housing of the earphone 101 includes one or more assembly components, a rear housing 17 and a front housing 18. The rear housing 17 may include one or more apertures 14 or through holes that provide acoustic transparency from the environment through the apertures 14, through the apertures 12 of the electrode 11 to the membrane 15 of the electroacoustic device 10.

[0027] Now also refer to Figure 1C , Figure 1C An earphone 101 is shown with the rear housing 17 removed in accordance with features of the present invention. An acoustic seal 19 may be removably mounted over the nozzle 16. The acoustic seal 19 is designed to fit inside the ear canal of a user and to acoustically seal inside the ear canal of the user. Inside the nozzle 16 is a passage leading to an electrostatic acoustic device 10 including a membrane 15 (not shown) sealed therein. The circuit board 29 may include a DC-DC converter that provides a direct current (DC) bias voltage V from a voltage input from a battery 280. DC The circuit board 29 may include a circuit board for providing an audio voltage signal ±V i circuits, and other circuits as disclosed herein or otherwise desired.

[0028] Thus, in an embodiment of the present invention comprising an electrostatic acoustic device 10 used as an earphone and sealed into the ear canal, the mechanical displacement of the eardrum can be coupled with the mechanical displacement of the membrane 15. The user's voice can be transmitted internally via bone conduction to the eardrum and by internal coupling to the membrane 15, enabling the membrane 15 to function as a microphone. When used as a microphone, the membrane 15 is sensitive to ambient sounds as well as sounds generated by touch gestures on the housing 17, 18.

[0029] Reference now Figure 2 , Figure 2 21. In the forward path, G(s) represents the open loop gain of the control circuit comprising the system 21, where s may be a representation of A is a complex variable of an AC voltage signal of the form , where A represents the amplitude, ω = 2πf represents the angular frequency, where f represents the frequency (in Hertz), and Represents the phase shift in radians.

[0030] Now also refer to Figure 2A , Figure 2AA proportional, integral and derivative (PID) block 24 is shown according to conventional techniques. The feedback loop may include a proportional, integral and derivative (PID) block 24 in the forward path G(s). The block 24 may include a linear combination of proportional gain, derivative and / or integral and frequency filtering performed on the error signal 25 to output a control signal 26.

[0031] Return to reference Figure 2 , in the feedback path, block 22 represents the output voltage signal V o The feedback path output from the feedback block 22 can output a feedback signal 27, which can be converted from the input signal v by the comparator 230. i The feedback signal 27 is subtracted to generate an error signal 25. In response to the error signal 25, the PID controller 24 outputs a control signal 26 to the controller block 21 to make the output signal V o The overall transfer function of the system 20 (the voltage output V of the controller 21) is o Divide by the voltage input v i ) can be modeled by Equation 1:

[0032]

[0033] When the input signal v i At nominally zero, the feedback signal 27 becomes the error signal 25. Alternatively, in place of the comparator 23, a signal combiner 23 may be equivalently used, and the feedback block 22 converts the voltage output signal V o The error signal 25 is appropriately converted (eg, inverted) into a feedback signal 27 which is incorporated into the error signal 25 .

[0034] The stability of the control system 20 depends on the denominator 1+G(s)·H(s) having a sufficiently large absolute value and / or being non-zero. It is well known that in a resonant system 21 comprising a damped harmonic oscillator and an external drive, for drive frequencies well below the resonant frequency, the response of the oscillator is in phase with the external drive (i.e., ), for a drive frequency at the resonant frequency, the oscillator's response is in phase quadrature with the external drive (i.e., ), and for frequencies well above the resonant frequency, the oscillator's response is out of phase with the external drive (i.e., ). If the control system 21 includes a resonant and oscillating energy source, then to maintain stability, the oscillating energy source is operated below or above the resonant frequency without crossing the resonant frequency. In the case of crossing the resonant frequency, a phase shift filter can be added to mitigate phase response discontinuities.

[0035] Reference now Figure 3 , Figure 3is a simplified electronic system block diagram including an electrostatic acoustic device 10 in an open loop operation mode to operate as a loudspeaker and a microphone simultaneously. Block 21 represents a driver or electronic circuit whose input voltage signal V i The reference signal 28 can be derived from the input audio signal V i Block 21 detects a signal proportional to or responsive to the mechanical movement of membrane 15 and outputs a signal responsive to the movement of membrane 15, such as a voltage V o . Voltage output signal V o is the second input of the comparator 23. The comparator 23 is configured to output the voltage signal V o Compared with the reference signal 21 (for example, the output voltage signal V o A reference signal 21 is subtracted, and by appropriate signal processing, a microphone signal 250 may be extracted in response to membrane vibrations caused by ambient sounds or sounds generated by touch gestures on the housing 17 , 18 of the in-ear device 101 .

[0036] A signal proportional to or responsive to the mechanical movement of the membrane 15 may be detected by various detection methods known in the art. Detecting changes in electrostatic current or changes in capacitance between the membrane 15 and the electrode 11 is described herein. Other detection methods for measuring the movement of the membrane 15 may be used according to different embodiments of the present invention, including optical sensors, external field gradient (force) detection (such as electrostatic field gradient or magnetic field gradient) using, for example, a Hall effect magnetic sensor.

[0037] For any detection method that responds to the movement of the membrane 15, the membrane 15 can be detected by subtracting the response of the membrane 15 to the audio input signal V i The microphone signal 250 is extracted by comparing with the time-dependent motion of the signal. The subtraction can be performed in the time domain by digital signal processing and appropriate level adjustment and / or time delay. Alternatively, the microphone signal can be extracted by transforming the signal in the frequency domain (e.g., by a short-time Fourier transform, performing the subtraction in the frequency domain) and then performing, for example, an inverse Fourier transform back to the time domain.

[0038] Reference now Figure 4A , Figure 4A According to a feature of the present invention, a circuit 21A is schematically shown in more detail. Figure 2 and Figure 3 The driver 21A includes an electrostatic acoustic device 10 which may be configured to receive a high voltage audio input +V at a first electrode 11. iAnd receives the inverted high voltage audio input -V at the second electrode 11 i , the voltage audio input varies at an audio frequency for conversion into sound by the electrostatic acoustic device 10.

[0039] A radio frequency (eg, 0.1 MHz to 20 MHz) probe signal from a local oscillator (LO) 51 may be coupled between the primary winding P of the transformer T. Audio signal +V i and inverted audio signal -V i The audio signal ±V can be fed to the electrode 11 through the series-connected secondary windings S1 and S2 of the transformer T, respectively. i Can be a high voltage signal. Alternatively, the audio signal ±V i Can be a low voltage signal up to about ±20V. DC voltage bias +V DC can be applied to the membrane 15. The detection signal generates a current whose magnitude is determined by the characteristic reactance of the circuit formed by the membrane 15 and the electrode 11 (essentially a variable capacitor). The detection signal from the local oscillator (LO) 51 can also be combined with the voltage output of the amplifier 30 at the signal combiner / multiplier 32. The signal combiner / multiplier 32 outputs to the low pass filter 34, which demodulates and sends a voltage output signal V o , voltage output signal V o System 21B is a homodyne detection circuit that uses a local oscillator 51 as a reference that is multiplied by the measured signal output of amplifier 30 at the same frequency. The baseband or DC component of this multiplication includes a signal frequency converted from a narrow band around the LO 51 frequency that is detected at a very high signal-to-noise ratio.

[0040] When the device 10 can act as a microphone, the membrane 15 can mechanically respond to ambient sound waves. In response to the ambient sound, the distance d (Figure 1) between the membrane 15 and the electrode 11 changes, causing the capacitance C of the electrostatic acoustic device 10 to change. A transimpedance amplifier 30 can be used to sense the changed current i(t) due to the ambient sound, which is approximated by:

[0041]

[0042] Alternatively, a charge amplifier 30 may be considered instead of a transimpedance amplifier, which integrates the current i(t) to sense the charge Q(t), which changes as the capacitance of the electrostatic acoustic device 10 changes, and the sensed charge is converted into an output voltage signal V o .

[0043] Amplifier 30 may be configured as inverting or non-inverting, and may have a passband that includes audio frequencies (20 Hz - 20,000 Hz).

[0044] The advantage of using radio frequency is that radio frequency does not produce perceptible mechanical movement, but is modulated by electrical changes in capacitance that are related to the mechanical movement produced when an audio signal and / or ambient sound is present. In addition, the RF AM signal has a higher signal-to-noise ratio relative to the total capacitance change of the device when compared to the current induced by the direct capacitance change as shown in relation (2).

[0045] Reference now Figure 4B , Figure 4B Schematically shows different features of the invention. Figure 2 and Figure 3 Another alternative to block 21 in 21B. In controller 21B, the audio voltage V i can be applied to the membrane 15. The detection signal from the local oscillator 51 can also be induced to the membrane 15 using a transformer T having a primary P connected in parallel with the local oscillator 51 and a secondary P connected in series with the audio voltage V i The secondary S between the film 15 and the bias voltage V DC can be applied symmetrically to the electrodes 11, where -V DC / 2 is applied to the first electrode 11, and +V DC / 2 is applied to the second electrode 11. The differential amplifier 31 can be used with the input terminals capacitively coupled to the electrodes 11, respectively. The voltage output of the differential amplifier 31 varies with the capacitance of the device 10. The detection signal from the local oscillator (LO) 51 can also be combined with the voltage output of the differential amplifier 31 at the signal combiner / multiplier 32. The signal combiner / multiplier 32 outputs to the low pass filter 34, which demodulates and sends a voltage output signal V o , voltage output signal V o The differential amplifier 31 can be made from a Texas Instruments / Burr-Brown TM INA105 is implemented. According to the features of the present invention, controller 21B has advantages over controller 21A because when a single high voltage audio signal V i , one high voltage input amplifier is required instead of two.

[0046] Now also refer to Figure 5 , Figure 5 is a flow chart illustrating a method 50 that features the present invention. Figure 2 and Figure 3, the detector circuit 75 is shown connected to a processor 77 which is configured to monitor (step 52) the time-dependent displacement of the membrane 15. The time-dependent displacement results in a time-dependent change in capacitance which can be detected by processing the corresponding output of the detector 75 and / or as described above. Figure 3 A microphone signal 250 is shown to be detected.

[0047] The processor 77 may be configured to classify (step 53) the time-dependent displacement as corresponding to one of a set of previously defined touch gestures. The processor 77 and the detector 75 may be configured to detect (decision block 54) a pressure gesture on the housings 17, 18 of the in-ear device 101 during operation. Pressure in the direction of the inner ear during, for example, 100 milliseconds to 1000 milliseconds may cause the membrane 15 to be displaced outward on average because the in-ear device 101 is gently pushed into the ear with both the eardrum and the membrane 15 sealed in the ear canal and the small hole 14 in the rear housing 17 enabling pressure equalization between the membrane and the surrounding atmosphere. According to a feature of the present invention, if a pressure gesture is detected (decision block 54), the operating mode of the in-ear device 101 may be switched between the following modes (step 55): (i) noise cancellation / adjusting acoustic transparency ( Figure 2 ); and (ii) operate simultaneously as a microphone and a speaker ( Figure 3 ). When in mode (ii), the microphone signal may be processed by the processor 77, and the processor 77 may issue (step 56) a corresponding command based on the classified microphone signal, which is derived from a specific sound generated by the user through a touch gesture.

[0048] Now refer to it again Figure 1B , Figure 1B Further features of the present invention are shown. The processor 77 can be configured to detect a time-dependent displacement of the membrane in response to an external stimulus (including a touch gesture in which a user strokes the surface of the shell 17 or 18) during in-ear operation. Various touch gestures may include impulses, for example, a finger tap gesture on the outer shell 17. The processor 77 may be configured (i.e., pre-trained) to distinguish between a finger tap on the shell with a fingernail and a finger tap on the shell with the pad of the finger. The shell 17 and / or 18 may include a roughness or spatial periodicity 71, 73 that emits a characteristic sound when stroked, which characteristic sound may cause a characteristic time-dependent displacement of the membrane 15, which may be sensed by the detector 75 and classified by the processor 77 as a control command. As Figure 1BAs shown in the device 101, the housing 17 is shown as two examples of surface roughness 71 and 73 with different periodicities and different periodic directions. The periodicity or amount of roughness changes the frequency composition of the characteristic sound caused by stroking the housing 17, 18. The user's stroking of the housing 17 is optionally in different places 71 and 73 and in different directions, which can cause the processor 77 to issue two different commands.

[0049] The term "homodyne" as used herein refers to a method of detecting / demodulating a signal that is phase and / or frequency modulated on an oscillating signal by combining it with a reference oscillation.

[0050] The term "ambient" as used herein refers to the vicinity of the membrane of the electrostatic acoustic device.

[0051] The term "driver" as used herein is an electronic circuit configured to electrically bias, input and / or output signals to and from an electrostatic acoustic device.

[0052] As used herein, the term "transimpedance amplifier" converts current into voltage. A transimpedance amplifier can be used to process the current output of a sensor into a voltage signal output.

[0053] The term "charge amplifier" as used herein generally converts a time-varying charge to a voltage output by integrating a time-varying current signal.

[0054] The terms "audio frequency" or "audio frequency" refer to the rate of oscillation of an alternating current or voltage or a magnetic, electric or electromagnetic field or a mechanical system, in the frequency range of 0 Hz to 20,000 Hz.

[0055] As used herein, the terms "audio signal", "audio output", "audio output signal" refer to an electrical signal that varies substantially at audio frequencies.

[0056] The term "radio frequency" (RF) is the oscillation rate of an alternating current or voltage or a magnetic, electric or electromagnetic field or a mechanical system, ranging in frequency from about 20,000 times per second (20 kHz) to about 300 billion times per second (300 GHz).

[0057] As used herein, the transitional term "comprising" is synonymous with "including" and is inclusive or open-ended and does not exclude additional elements or method steps not explicitly recited. The articles "a", "an" are used herein, such as "a circuit" or "an electrode" have the meaning of "one or more", i.e., "one or more circuits", "one or more electrodes".

[0058] All optional and preferred features and modifications of the described embodiments and the dependent claims are available in all aspects of the invention taught herein. In addition, the individual features of the dependent claims and all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with each other.

[0059] Although selected features of the present invention have been shown and described, it is to be understood that the invention is not limited to the described features.

Claims

1. An earphone assembly, comprising: an electrostatic acoustic device, the electrostatic acoustic device comprising a membrane; an audio signal input to the electrostatic acoustic device, wherein the membrane is configured to mechanically respond to a changing electric field in response to an audio signal at the audio signal input; detector; and a housing enclosing the electrostatic acoustic device and the detector; Therein, the detector is configured to detect a time-dependent displacement of the membrane in response to an external stimulus on the housing.

2. The earphone assembly according to claim 1, further comprising: A processor is operably attached to the detector, wherein the processor is configured to issue a command selected from a group consisting of previously defined commands, the selected command being adapted to the detected time-dependent displacement of the membrane and the corresponding external stimulus.

3. The earphone assembly according to claim 1, further comprising: A processor is operably attached to the detector, wherein the processor is configured to select an operating mode of the electrostatic acoustic device based on the detected displacement of the membrane and a corresponding external stimulus.

4. The earphone assembly according to any one of claims 1 to 3, further comprising: in, The housing also includes a nozzle configured for acoustic transmission from the membrane to the ear canal during in-ear operation.

5. The earphone assembly according to claim 4, wherein: The processor is configured to detect a time-dependent displacement of the membrane in response to the external stimulus during the in-ear operation, the external stimulus comprising a touch gesture applying pressure on the housing toward the ear canal.

6. The earphone assembly according to claim 4, wherein: The processor is configured to detect a time-dependent displacement of the membrane as an impulse response to the external stimulus during operation of the in-ear, the external stimulus comprising a finger tap gesture on the housing.

7. The earphone assembly according to claim 6, wherein: The processor is configured to distinguish between a finger tap with a nail on the housing and a finger tap with the pad of the finger on the housing.

8. The earphone assembly according to claim 4, wherein: The processor is configured to detect a time-dependent displacement of the membrane in response to the external stimulus during operation of the in-ear, the external stimulus comprising a touch gesture stroking a surface of the housing.

9. The earphone assembly according to claim 8, wherein: The processor is configured to distinguish at least two directions of the stroke.

10. The earphone assembly according to claim 9, wherein: The housing includes a surface having a roughness profile configured to produce different time-dependent membrane displacements when rubbed in different directions.

11. A method for implementing control of an earphone assembly, the earphone assembly comprising an electrostatic acoustic device, a detector and a housing, wherein: The electrostatic acoustic device comprises a membrane and an audio signal input, wherein the housing surrounds the electrostatic acoustic device and the detector, the method comprising: inputting an audio signal to the electrostatic acoustic device at the audio signal input terminal; configuring the membrane to mechanically respond to a changing electric field in response to the audio signal; and A time-dependent displacement of the membrane in response to an external stimulus on the housing is detected.

12. The method according to claim 11, further comprising: A command selected from the group consisting of previously defined commands is issued, the selected command being adapted to the detected time-dependent displacement of the membrane and the corresponding external stimulus.

13. The method according to claim 11, further comprising: An operating mode of the electrostatic acoustic device is selected based on the detected displacement of the membrane and the corresponding external stimulus.

14. The method according to any one of claims 11 to 13, further comprising: in, The housing includes a nozzle configured for acoustic transmission from the membrane to the ear canal during in-ear operation.

15. The method according to claim 14, further comprising: During the in-ear operation, a time-dependent displacement of the membrane in response to the external stimulus is detected, the external stimulus comprising a touch gesture applying pressure on the housing toward the ear canal.

16. The method according to claim 14, further comprising: During the in-ear operation, a time-dependent displacement of the membrane is detected as an impulse response to the external stimulus, the external stimulus comprising a finger tap gesture on the housing.

17. The method according to claim 16, further comprising: A distinction is made between finger tapping with the nail on the housing and finger tapping with the ball of the finger on the housing.

18. The method according to claim 14, further comprising: During the in-ear operation, a time-dependent displacement of the membrane in response to the external stimulus is detected, the external stimulus comprising a touch gesture stroking a surface of the housing.

19. The method according to claim 18, further comprising: At least two directions of the stroking are distinguished.

20. The method according to claim 19, wherein: The housing includes a surface having a roughness profile configured to produce different membrane displacements when rubbed in different directions.

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