# US 11,910,150 B2 · Control of an electrostatic acoustic device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,910,150 B2 - Document ID: US11910150B2 - Status: Granted - Kind: B2 - Application number: 17/925,642 - Filed: 2021-05-11 - Published: 2023-06-01 - Granted: 2024-02-20 - Earliest claimed: 2020-05-18 - Assignees: Waves Audio Ltd. - Applicants: Waves Audio Ltd. - Inventors: Gabriel Zeltzer; Meir Shaashua - Web page: https://patentgrep.com/patent/US11910150B2 ## CPC - H04R 1/1041: {Mechanical or electronic switches, or control elements (switches in general H01H)} - G10K 11/17825: {Error signals} - G10K 11/17827: {Desired external signals, e.g. pass-through audio such as music or speech} - H04R 1/1016: {Earpieces of the intra-aural type} - H04R 1/1025: Accumulators specially adapted for earpieces; Arrangements specially adapted for charging thereof - H04R 1/1075: {Mountings of transducers in earphones or headphones} - H04R 3/06: of electrostatic transducers - H04R 7/04: Plane diaphragms - H04R 7/18: at the periphery - H04R 19/00: Electrostatic transducers - H04R 19/02: Loudspeakers (H04R19/01 takes precedence) - H04R 29/001: {for loudspeakers (H04R29/007 takes precedence)} - G10K 2210/3026: Feedback - H04R 3/007: {Protection circuits for transducers} - H04R 2400/01: Transducers used as a loudspeaker to generate sound aswell as a microphone to detect sound - H04R 2430/01: Aspects of volume control, not necessarily automatic, in sound systems - H04R 2460/01: Hearing devices using active noise cancellation - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) - G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR ## Abstract A control circuit for an electrostatic transducer including: an audio signal input, a detector configured to detect a current or charge signal from the electrostatic transducer. The detector is configured to produce an audio output signal varying at audio frequencies. A transform circuit is configured to transform the audio output signal to produce a feedback signal. A comparator is configured to compare an input audio signal at the audio signal input to the feedback signal to produce an error signal. A controller is configured to input a control signal to the electrostatic transducer, the control signal responsive to the error signal. The control signal is configured to control acoustic transparency of the electrostatic transducer, from outside space through through-holes of the first electrode, across the membrane and through through-holes of the second electrode. ## Claims ### Claim 1 A control circuit operable for an electrostatic acoustic device including a membrane, a first electrode and a second electrode, wherein the first electrode is disposed parallel to the membrane, wherein the membrane is configured to respond mechanically to a varying first electric field in accordance with an electric potential applied between the first electrode and the membrane, wherein the second electrode is disposed parallel to the membrane opposite from the first electrode; wherein the membrane is configured to respond mechanically to a varying second electric field in accordance with an electric potential applied between the second electrode and the membrane, wherein the first and second electrodes have through holes configured for acoustic transmission to and from the membrane, the control circuit comprising: an audio signal input; a detector configured to detect a current or charge signal from the electrostatic acoustic device responsive to motion of the membrane, the current or charge signal including an audio signal varying at audio frequencies, wherein the detector is configured to produce an audio output signal varying at audio frequencies; a transform circuit configured to transform the audio output signal to produce a feedback signal; a comparator configured to compare an input audio signal at the audio signal input to the feedback signal to produce an error signal; and a controller configured to input a control signal to the electrostatic acoustic device, the control signal responsive to the error signal; wherein the control signal is configured to control acoustic transparency of the electrostatic acoustic device, from outside space through the through-holes of the first electrode, across the membrane and through the through-holes of the second electrode. ### Claim 2 (depends on 1) The control circuit of claim 1, wherein acoustic transparency is controlled in accordance with a ratio between the control signal and the input audio signal at the audio signal input. ### Claim 3 (depends on 1) The control circuit of claim 1, wherein direct current (DC) bias voltages are applied on the electrodes and an audio voltage input responsive to the control signal is applied to the membrane. ### Claim 4 (depends on 1) The control circuit of claim 1, wherein responsive to the control signal, a non-inverted audio voltage input may be applied to one of the electrodes and an identical but inverted audio voltage input may be applied to the other electrode; and the membrane is biased with a DC bias voltage. ### Claim 5 (depends on 1) The control circuit of claim 1, wherein the first electrode includes a first conductive layer deposited on an electrically insulated substrate, the first conductive layer assembled proximate to the membrane; wherein the second electrode includes a second conductive layer deposited on an electrically insulated substrate, the second conductive layer assembled proximate to the membrane. ### Claim 6 (depends on 1) The control circuit of any of claim 1, wherein the control signal is configured to cancel at least in part a mechanical response of the membrane due to ambient noise. ### Claim 7 (depends on 1) The control circuit of claim 1, wherein the control signal is configured to limit mechanical displacement of the membrane. ### Claim 8 (depends on 1) The control circuit of claim 1, wherein a probe signal varying at radio frequency is injected into the electrode, wherein the current or charge signal is detected by converting the current or charge signal to a modulated voltage signal, wherein the current or charge signal includes the input audio signal modulating the radio frequency of the probe signal. ### Claim 9 (depends on 8) The control circuit of claim 8, wherein the audio output signal is obtained by homodyne detection of the modulated voltage signal at radio frequency. ### Claim 10 (depends on 8) The control circuit of claim 8, further comprising: a phase-locked loop configured to phase and frequency lock the modulated voltage signal at radio frequency and a radio frequency carrier signal responsive to the probe signal at radio frequency. ### Claim 11 A method performable to control an electrostatic acoustic device including an audio signal input, a membrane, a first electrode and a second electrode, wherein the first electrode is disposed parallel to the membrane, wherein the membrane is configured to respond mechanically to a varying first electric field in accordance with an electric potential applied between the first electrode and the membrane, wherein the second electrode is disposed parallel to the membrane opposite from the first electrode, wherein the membrane is configured to respond mechanically to a varying second electric field in accordance with an electric potential applied between the second electrode and the membrane; wherein the first and second electrodes have through-holes configured for acoustic transmission to and from the membrane, the method comprising: detecting a current or charge signal from the electrostatic acoustic device, the current or charge signal including an audio signal varying at audio frequencies, thereby producing an audio output signal varying at audio frequencies; transforming the audio output signal to produce a feedback signal; comparing an input audio signal at the audio signal input to the feedback signal to produce an error signal; responsive to the error signal, inputting a control signal to the electrostatic acoustic device and controlling thereby acoustic transparency of the electrostatic acoustic device, from outside space through the through-holes of the first electrode, across the membrane and through the through-holes of the second electrode. ### Claim 12 (depends on 11) The method of claim 11, further comprising: controlling acoustic transparency in accordance with a ratio between the control signal and the input audio signal at the audio signal input. ### Claim 13 (depends on 11) The method of claim 11, further comprising: applying DC bias voltages on the electrodes and applying to the membrane an audio voltage input responsive to the control signal. ### Claim 14 (depends on 11) The method of claim 11, further comprising: responsive to the control signal, applying a non-inverted audio voltage input to one of the electrodes and an identical but inverted audio signal input to the other electrode and biasing the membrane with a DC bias voltage. ### Claim 15 (depends on 11) The method of any of claim 11, further comprising: configuring the control signal to cancel at least in part a mechanical response of the membrane due to ambient noise. ### Claim 16 (depends on 11) The method of any of claim 11, further comprising: configuring the control signal to limit mechanical displacement of the membrane. ### Claim 17 (depends on 11) The method of claim 11, further comprising: injecting a probe signal varying at radio frequency into an input of the electrostatic acoustic device; detecting a current or charge signal by converting the current or charge signal to a modulated voltage signal, wherein the current or charge signal includes the input audio signal varying at audio frequencies modulating the radio frequency of the probe signal; demodulating the modulated voltage signal to produce the audio output signal. ### Claim 18 (depends on 17) The method of claim 17, further comprising: obtaining the audio output signal varying at audio frequency by homodyne detection of the modulated voltage signal at radio frequency. ### Claim 19 (depends on 17) The method of claim 17, further comprising: phase and frequency locking the modulated voltage signal at radio frequency and a radio frequency carrier signal responsive to the probe signal at radio frequency. ### Claim 20 (depends on 17) The method of claim 17, further comprising: configuring a local oscillator to generate a sinusoid at radio frequency; inputting the sinusoid at radio frequency; and outputting the probe signal with frequency corresponding to the sinusoid.