Abstract: An automatic adjusting threshold microphone squelch system for use in aircraft or other high noise environments including digital drop-out timer and voice detector connected directly to an analog composite signal processor. The processor is comprised of two channels including a microphone audio channel and an aircraft noise detection channel. The channels, driven from a common microphone, are arranged in parallel with the noise detector feeding its noise-dependent output forwardly to a variable-threshold microphone audio post-amplifier. The composite audio from this amplifier is automatically maintained below a first digital "zero" level when voice is absent while containing peaks above a second digital "one" level when audio is present. This composite audio directly feeds the digital detector/timer without further wave-shaping or other signal processing.