Echo canceller for non-linear circuits
AssigneeEricsson Inc.
InventorEric Douglas Romesburg
Life of this patent
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Abstract
A system and a method for echo suppression which use two or more microphones for beamforming of an echo signal corresponding to an incoming speech signal that is output by a loudspeaker. The outputs of the microphones are appropriately filtered and then linearly combined to cancel the echo signal, even if the incoming speech signal has been non-linearly distorted. Also, the microphones may be selectively positioned or pointed to allow the linear cancellation of ambient noise.
Claims68
In an audio circuit comprising a microphone and a loudspeaker, said microphone detecting a speech signal from a near-end user, said loudspeaker receiving a far-end speech signal and generating a corresponding echo signal that is also detected by said microphone, a method of cancelling the echo signal comprising the steps of:
- providing at least one other microphone in said audio circuit for detecting said echo signal, said at least one other microphone also detecting said near-end speech signal;
- estimating a plurality of acoustic transfer functions in a plurality of adaptive filters each having a plurality of coefficients, at least one of said adaptive filters using the far-end speech signal as a reference signal for adjusting its coefficients;
- filtering the outputs of one or more of said microphones using the coefficients of one or more of said adaptive filters;
- and
- combining the filtered and any unfiltered microphone outputs so as to substantially cancel said echo signal while substantially preserving said near-end speech signal.
A circuit for cancelling an echo signal from an audio source comprising:
- a first microphone for detecting said echo signal along a first path defined by a first acoustic transfer function H.sub.1 ;
- a second microphone for detecting said echo signal along a second path defined by a second acoustic transfer function H.sub.2 ;
- a first adaptive filter for estimating H.sub.1 ;
- a second adaptive filter for estimating H.sub.2 ;
- a first fixed filter for filtering the output of said first microphone using the estimate of H.sub.2 ;
- a second fixed filter for filtering the output of said second microphone using the estimate of H.sub.1 ;
- and
- means for subtracting the output of said second fixed filter from the output of said first fixed filter so as to cancel said echo signal.
A circuit for cancelling an echo signal from an audio source comprising:
- a first microphone for detecting said echo signal along a first path defined by a first acoustic transfer function H.sub.1 ;
- a second microphone for detecting said echo signal along a second path defined by a second acoustic transfer function H.sub.2 ;
- a first adaptive filter for estimating H.sub.1 ;
- a second adaptive filter for estimating H.sub.2 ;
- a fixed filter for filtering the output of said second microphone using an acoustic transfer function H.sub.1 /H.sub.2 based on the estimates of H.sub.1 and H.sub.2 ;
- and
- means for subtracting the output of said fixed filter from the output of said first microphone so as to cancel said echo signal.
A circuit for cancelling an echo signal from an audio source comprising:
- a first microphone for detecting said echo signal along a first path defined by a first acoustic transfer function H.sub.1 ;
- a second microphone for detecting said echo signal along a second path defined by a second acoustic transfer function H.sub.2 ;
- a first adaptive filter for estimating 1/H.sub.1 and for filtering the output of said first microphone;
- a second adaptive filter for estimating 1/H.sub.2 and for filtering the output of said second microphone;
- and
- means for subtracting the output of said second adaptive filter from the output of said first adaptive filter so as to cancel said echo signal.
A circuit for cancelling an echo signal from an audio source comprising:
- a first microphone for detecting said echo signal along a first path defined by a first acoustic transfer function H.sub.1 ;
- a second microphone for detecting said echo signal along a second path defined by a second acoustic transfer function H.sub.2 ;
- a first adaptive filter for estimating H.sub.1 ;
- a second adaptive filter for estimating 1/H.sub.2 and for filtering the output of said second microphone;
- a fixed filter for filtering the output of said second adaptive filter using the estimate of H.sub.1 ;
- and
- means for subtracting the output of said fixed filter from the output of said first microphone so as to cancel said echo signal.
A circuit for cancelling an echo signal from an audio source comprising:
- a first microphone for detecting said echo signal along a first path defined by a first acoustic transfer function H.sub.1 ;
- a second microphone for detecting said echo signal along a second path defined by a second acoustic transfer function H.sub.2 ;
- a first adaptive filter for estimating H.sub.1 ;
- a second adaptive filter for estimating H.sub.1 /H.sub.2 and for filtering the output of said second microphone;
- and
- means for subtracting the output of said second adaptive filter from the output of said first microphone so as to cancel said echo signal.
In a speech communications system including a loudspeaker which generates an echo signal from an incoming signal, an echo cancellation circuit comprising:
- a plurality of microphones for detecting said echo signal from said loudspeaker;
- means for estimating a plurality of acoustic transfer functions using the incoming signal as a reference signal;
- means for filtering one or more of the outputs of said microphones using one or more of the estimated acoustic transfer functions;
- and
- means for combining the filtered outputs of the microphones so as to cancel said echo signal.
Dependencies are inferred from the claim text.