AID TO HEARING SPEECH IN A NOISY ENVIRONMENT

A signal processing circuit is incorporated into an audio reproducing device for suppressing noise while preserving distinctive features of speech. A noise detecting circuit includes a low pass filtering circuit (12) and a level detector (14). An output signal (C) from the detecting circuit controls a variable high pass filtering circuit (20) to attenuate a range of low frequencies of an input signal (A) proportional to the detected level of noise. The variable high pass filtering circuit exhibits a family of variable response curves (22, 24, and 26) that vary in slope below a common cut-off frequency (28) that is below a range of frequencies that convey a majority of second formant transitions between consonants and vowels.