Frequency-domain Adaptive Echo Cancellation as a Special Case of Subband Echo Suppression 1 Frequency-domain Adaptive Echo Cancellation as a Special Case of Subband Echo Suppression

|Modelling acoustic impulse responses with lengths up to 250 ms is required for high quality echo cancellation in strongly reverberating environments , leading to FIR adaptive lters with several thousands of taps. Classical LMS-based solutions then clearly fail as they exceed the computational capabilities of present-day DSPs. Cheaper alternative solutions have been proposed and are mainly based on either subband or frequency-domain techniques. Both the subband and the frequency-domain approach turn out to have their strong and weak points. Subband lter implementations have many interesting properties and apparently allow to achieve the lowest possible computational cost. However, their inherent delay and residual errors have made them unattractive for real-time applications up till now. On the other hand, it is known that frequency-domain adaptive lters do not suuer from these problems despite being (nearly) equivalent to subband adaptive lters with`poor' lter banks. In this paper we explain the operation of the frequency-domain techniques in thèsubband jargon' and make an attempt at pointing out how to enhance subband performance. This latter is a subject of current research.