RF Capacitor Microphone

An alternative form of capacitor microphone which uses the capacitive capsule as the tuning element of a radio-frequency oscillator. Sound waves arriving at the capsule change its capacitance, which varies the frequency of the RF oscillator to produce an FM signal. This is immediately demodulated by the microphone's internal circuitry to produce the audio output. The advantage of this approach is that the capsule works in a very low-impedance environment (as opposed to the very high-impedance environment of a traditional DC-biased and Electret capacitor mics), making it immune to the effects of humidity which can cause unwanted noise in conventional capacitor mics. This technology was invented by Sennheiser and is used in their MKH range of microphones.