Patent ID: 7831035

Claim:
A method of digital signal processing at a near end of a two-way communication system for reducing echo for a remote end, the near end having a speaker for playing audio from the remote end and an array of microphones to capture near end speech, the method comprising: separately applying an acoustic echo cancellation process for canceling remote-end echo on each of a plurality of microphone channels from the microphone array; performing sound source localization and microphone array processing on the microphone channels to produce a source-localized speech channel for transmission to the remote end; performing center clipping on the source-localized speech channel, and wherein the center clipping comprises: for each of a plurality of frequency bands, computing an overall leak through estimate for the microphone channels, wherein said computing the overall leak through estimate comprises: computing separate leak through estimates at the frequency band for each of the microphone channels; filtering the separate leak through estimates across neighboring frequency bands; and combining the separate leak through estimates to produce the overall leak through estimate at the frequency band; computing an overall instantaneous microphone power estimate for the microphone channels; determining whether the overall leak through estimate exceeds a minimum of the overall instantaneous microphone power estimate and residual power at the frequency band on the source-localized speech channel; if so, then setting a residual value magnitude for the frequency band on the source-localized speech channel equal to the frequency band's magnitude for a background noise floor and a complex phase of a residual value for the frequency band on the source-localized speech channel equal to a random complex phasor; and if not, then passing the residual value for the frequency band on the source-localized speech channel unchanged, wherein said combining the leak through estimates comprises selecting a maximum of the leak through estimates of the microphone channels at the frequency band.