Regularized adaptive notch filters for acoustic howling suppression

A method for the suppression of acoustic howling is developed, based on adaptive notch filters (ANF) with regularization (RANF). The method features three RANFs working in parallel to achieve frequency tracking, howling detection and suppression. The ANF-based approach to howling suppression introduces minimal processing delay and minimal complexity, in contrast to non-parametric frame-based methods featuring a non-parametric frequency analysis. Compared to existing ANF-based howling suppression methods, the proposed method allows for a more advanced howling detection such that tonal components in the source signal are not affected. The RANFs proposed in this paper are implemented in direct form and are updated using a gradient descent type algorithm. Results show that, under certain conditions, the level of suppression and sound quality are similar to what is obtained with frame-based methods.