Patent ID: 8705754

Claim:
A method of measuring displacement of a moving diaphragm in an electroacoustic transducer having a magnetic structure and a voice coil assembly comprising at least a voice coil aligned with the magnetic structure, one of the magnetic structure or the voice coil assembly coupled to the diaphragm, the method comprising: producing a modulated electrical signal by modulating an electrical signal based on changes in capacitance between the voice coil and the magnetic structure resulting from motion of the voice coil relative to the magnetic structure; and demodulating the modulated electrical signal to produce an output signal having a value proportional to the displacement, wherein: producing a modulated electrical signal comprises applying a carrier signal having a frequency above an operating range of the electroacoustic transducer to a first input terminal of the voice coil such that changes in capacitance between the voice coil assembly and the magnetic structure of the transducer caused by motion of the voice coil assembly relative to the magnetic structure modulates the amplitude of the carrier signal.