Abstract: A noise cancelling system comprises two conventional noise cancelling microphones (1,2) spaced apart by a distance of one of up to 10 cms with use of the microphones (1) being arranged to be close to the mouth of a user for reception of speech and the other microphone (2) spaced therefrom and used as a reference microphone. The signals from the microphones are processed by means (7) which use a batch of signals derived from the reference microphone (2) to modify a signal derived from the speech microphone in accordance with the Widrow algorithm known in the art. This system enables effective noise cancellation to be achieved with a delay of only 0.1 sec.