Background-noise reduction

摘要

Interference by siren background-noise with speech transmitted from radio equipment 3 of an emergency-service vehicle, is reduced by apparatus 1 that subtracts an estimate of the correlated siren-noise component from the contaminated signal yk supplied by the cab-microphone 2. The estimate is computed by FIR (finite impulse response) filtering of a siren-reference signal xk supplied by a unit 4 from one or more microphones located on or near the siren, or from the electric waveform driving the siren. The filter-coefficients wk are adjusted according to an LMS (least mean square) adaptive algorithm that is applied to an error signal ek of the correlated-noise component of the fed-back noise-reduced signal, so as to bring about iterative cancellation with close frequency-tracking, of the siren noise.