Echo canceler-suppressor speakerphone
AssigneeAT&T Bell Laboratories
InventorWilliam A. Ford
Life of this patent
Estimating the term…
Abstract
An echo canceler-suppressor speakerphone arrangement effectively addresses the limitations of regeneration and reverberant return echo inherent in the design of speakerphones. The tendency for regeneration is eliminated by employing adaptive echo cancellation in the receive path of the speakerphone arrangement to cancel speakerphone talker echo across a hybrid and thereby reduce the local loop gain to below unity. And the generation of a reverberant return echo to the far-end party is avoided by employing adaptive echo suppression in the transmit path of the speakerphone arrangement. Near-full and full duplex operation are regularly achieved since the receive path remains open at all times and the transmit path has its gain reduced only to the level necessary to suppress excessive reverberant return echo.
Claims13
An apparatus for processing speech signals for a communication line, the apparatus including a transmit signal path for transmitting speech signals to the communication line and a receive signal path for receiving speech signals from the communication line, the apparatus comprising:
- loss insertion means in the transmit signal path for attenuating the speech signals for transmission over the communication line;
- echo canceling means in the receive signal path for canceling transmit speech signals appearing in the receive signal path;
- receive speech level adjusting means for controlling the level of the speech signals in the receive signal path;
- means for measuring an estimate of both the level of speech signals received from the communication line and the level of transmit speech signals appearing in the receive signal path;
- and
- loss adjusting means operably responsive to the measuring means for proportionally adjusting the level of attenuation inserted by the loss insertion means into the transmit path in response to the estimate of the level of the speech signals received from the communication line, and the receive speech level adjusting means being operably responsive to both the echo canceling means and the measuring means for inserting attenuation into the receive signal path in response to uncanceled transmit speech signals appearing in the receive signal path.
A method of processing speech signals in a voice signal controller, the voice signal controller being connectable to a communication line and including a transmit signal path for transmitting speech signals to the communication line and a receive signal path for receiving speech signals from the communication line, the method comprising the steps of:
- inserting loss in the transmit signal path for attenuating the speech signals for transmission over the communication line;
- inserting a time variant signal in the receive signal path for canceling transmit speech signals appearing in the receive signal path;
- measuring an estimate of both the level of speech signals received from the communication line and the level of transmit speech signals appearing in the receive signal path;
- and
- adjusting the level of attenuation inserted by the loss insertion step into the transmit path responsive to the receive speech signals measuring step, and inserting attenuation into the receive signal path in response to uncanceled transmit speech signals appearing in the receive signal path.
Dependencies are inferred from the claim text.