Method and apparatus for canceling noise in a microphone communications path using an electrical equivalence reference signal

摘要

In a technique for canceling noise from a microphone communications path, an electrical equivalence circuit which is positioned close to and electrically matched to the microphone produces a signal free reference signal. The microphone converts speech to a voice signal. An analog multiplexer alternately switches from the microphone to the electrical equivalence circuit to produce a multiplexed analog signal composed of the voice signal from the microphone and the signal free reference signal from the electrical equivalence circuit. A wire connects the output of the analog multiplexer switch to an A/D converter. The wire picks up noise from the surrounding environment. The A/D converter converts the multiplexed signal having the noise to a plurality of voice samples taken from the voice signal portion of the multiplexed signal and a plurality of noise samples taken from the signal free reference signal portion of the multiplexed signal. A noise cancellation unit applies a noise suppression algorithm (e.g., spectral subtraction) to the plurality of noise samples and the plurality of voice samples to reproduce the voice signal with the noise suppressed.