Patent ID: 8199927

Claim:
A conferencing system with echo cancelling that detects muting and unmuting of push-to-talk (PTT) microphones, comprising: a receive port coupled to a speaker and to a source of distant audio that receives an incoming participant signal; a transmit port coupled to a distant listener of local audio that provides an outgoing participant signal; a PTT microphone coupled to a microphone port to receive microphone audio; electronics operable to provide said incoming participant signal as audio by way of said speaker, said electronics being further operable to receive microphone audio from said PTT microphone and to transmit microphone audio through said transmit port; an acoustic echo canceller having a set of converging variables, said echo canceller receiving as an input said incoming participant signal, said echo canceller being operable to provide echo cancellation for said PTT microphone to said outgoing participant signal only if a PTT detector does not indicate the muting of said PTT microphone; wherein said PTT detector detects the muting and unmuting of said PTT microphone, said PTT detector provides an indication to said echo canceller that an echo signal is no longer being received at said PTT microphone, and said PTT detector further includes an amplitude detector, a transient filter, and a zero-crossing detector; wherein said PTT detector considers an amplitude of a first set of frequencies under active microphone conditions and another set of frequencies at a period of time following detection of a transient event; wherein said zero-crossing detector determines said transient event using as a condition that a zero-crossing event was not detected in the microphone audio for a time greater than a period of a low-frequency limit; wherein said echo canceller is configured to receive said indication from said PTT detector, and further wherein said echo canceller is configured to halt convergence of said converging variables on condition that said indication is being received; and wherein detection of a muting event is dependent on a determination by said amplitude detector that a volume level of said microphone audio is less than a preselected threshold.