The intelligibility of voice transmission through a telephone can be severely affected by the presence of excessive background noise. Accordingly, a system was designed to incorporate an auxiliary microphone into the receiver of an ordinary telephone handset. This microphone is strategically placed to pick up ambient noise. The signal from this microphone is subtracted from that of the receiver through a circuit incorporating three op-amps to produce a signal that contains significantly less background noise than the original signal. The corrected signal is then relayed through the telephone in the same manner as that for the receiver in an ordinary telephone.