Robust and high quality howling suppressor for real time hands-free communication systems

This paper presents high quality and robust Infinite Impulse Response (IIR) adaptive howling suppressor (AHS) developed based on adaptive notch filters (ANF) with regularisation. The proposed method uses Normalised Least Mean Square (NLMS) adaptation algorithm with leakage factor based on moving-average technique. The proposed system uses combination of front end de-correlation and modified NLMS adaptation. This is to ensure faster howling detection and very robust performance under different types of input signals and at different power levels. The proposed leakage factor introduced during adaptation, ensures stability of operation even when howling build-up frequency is oscillating in the neighbourhood bands. The performance test results obtained with the proposed system demonstrates quick detection and stable operation when compared to the recent techniques. The additional complexity involved with the proposed system compared to traditional methods is marginal or negligible.