Pilot-tone noise-reduction system using quantised control signals

A preliminary investigation has been made of a multiband noise-reduction system which uses a time-shared frequency-modulated narrow-band pilot tone. Signal-path delay allows anticipation of the control signal, and enables transient distortion to be eliminated. Discrete-level encoding is shown to have several important advantages, and, in the system described, the compression range is 24 dB in 6 dB steps. Crosstalk between the signal bands is minimised by dynamic adjustment of the filter bandwidths.