A simple phase-reversal tone disabler

This paper describes the design and implementation of a phase-reversal, tone disabler for a multichannel digital echo canceller. The algorithm employs a fixed sample delay unit, an adaptive phase corrector, two low-pass filters for energy estimation and a simple phase discriminator. The algorithm has been implemented in a multichannel form using the NEC 7720 DSP chip. Results from both computer simulations and real-time implementation are presented for both noise-free and noisy conditions.