A Novel Loop Stabilisation Technique for Full-Duplex Speakerphones

Closed electro-acoustic loops can become unstable when the total loop gain is positive at some frequencies, resulting in a phenomenon referred to as howling (also known as squealing or singing). In this article, we discuss the problem of loop stabilization in full-duplex speakerphones. After a brief overview of known techniques, we introduce a novel approach based on an algorithmic structure with two adaptive transversal filters in parallel. This structure is shown to be effective, non-intrusive with respect to speech in either direction, and efficient in terms of computational complexity. It can also be combined easily with any of the existing techniques for additional protection against howling