Control of an electrostatic acoustic device

A control circuit for controlling operation of an electrostatic acoustic device including a membrane and an electrode disposed proximate to the membrane, wherein the membrane is configured to respond mechanically to a varying electric field emanating from the electrode when a varying audio signal voltage is applied to the electrode, the control circuit comprising:

• an oscillator configured to inject a probe signal varying at radio frequency into the electrostatic acoustic device;
• a detector configured to detect a current or charge signal, the current or charge signal including an audio signal varying at audio frequencies modulating the radio frequency, wherein the detector is configured to convert the current or charge signal to a modulated voltage signal;
• a demodulator configured to demodulate the modulated voltage signal to produce an audio output signal varying at audio frequency;
• a transform circuit configured to transform the audio output signal to produce an error signal;
• and wherein phase and amplitude of the control signal are configured to cancel at least in part a mechanical response of the membrane due to ambient noise
• a controller configured to input a control signal to the electrostatic acoustic device, responsive to the error signal.