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

A method for canceling electromagnetic noise in a microphone communications path, comprising:

• converting speech from the microphone to an electrical voice signal;
• producing a signal free reference signal from an electrical equivalence circuit in close proximity to and electrically matching the microphone;
• switching alternately from the microphone to the electrical equivalence circuit to produce a multiplexed signal comprising the voice signal and the signal free reference signal;
• carrying the multiplexed signal through an electromagnetic noise intensive environment such that the multiplexed signal acquires an electromagnetic noise component;
• digitizing the multiplexed signal having the noise component to produce a plurality of voice samples and a plurality of noise samples;
• and
• applying a noise suppression procedure to the plurality of noise samples and the plurality of voice samples to reproduce the voice signal with the electromagnetic noise component suppressed.

An apparatus for canceling electromagnetic noise in a microphone system, comprising:

• a microphone configured to convert speech to an electrical voice signal;
• an electrical equivalence circuit, in close proximity to and electrically matching the microphone, configured to produce a signal free reference signal;
• a first communications path for carrying the voice signal from the microphone to an analog multiplexer,
• a second communications path for carrying the signal free reference signal from the electrical equivalence circuit to the analog multiplexer, the first and second communications paths being carried through an electromagnetic noise intensive environment such that the voice signal and the signal free reference signal both acquire an electromagnetic noise component;
• said analog multiplexer, connected to the first and second communications paths, configured to alternately switch between the microphone and the electrical equivalence circuit to produce a multiplexed signal comprising the voice-laden component voice signal and the noise-laden component signal free reference signal;
• an A/D converter coupled to the analog multiplexer for converting the multiplexed signal having the noise component to a plurality of voice samples and a plurality of noise samples;
• and
• a noise cancellation unit applying a noise suppression procedure to the plurality of noise samples and the plurality of voice samples to reproduce the voice signal with the electromagnetic noise component suppressed.