Trends in Acoustic Feedback Suppression Methods

Abstract: In audio amplifier systems, the acoustic feedback causes howling noise, which affects the quality of the audio signal. Detection and suppression of this howling noise is a requirement in Public Addressing (PA) systems, hearing aids, and telecommunication systems. The nature of howling signals, their spectrum, and effects on speech signal have been studied and presented in this paper. This paper also reviews the methods used for howling detection, and suppression in an acoustic environment. By adjusting the gain and altering the positions of the microphone, and speakers are the manual methods used to avoid howling. Automatically adjusting the parameters of the system, and not allowing it to enter into an unstable state is a crucial thing in audio system. Howling can be identified from the input signal using its temporal & spatial parameters. The commonly used method makes use of notch filters for suppressing the howling noise. Other methods include automatic equalization, automatic gain control, etc.

Keywords: Acoustic feedback, Howling, Adaptive filter.