Motorola Corporation

Continental Automotive Systems Corporation

Temic Automotive of North America, Inc.

Christopher W Springfield

James Brian Piket

Keith L Owens

William Chunhung Yip

Ernest Pei-Ching Chen

An echo canceler circuit () and method attenuates at least post-echo canceler uplink data () to produce attenuated uplink data () in response to uplink echo return loss based attenuation data (). The echo canceler circuit () includes an echo return loss based attenuation data generator () and at least an uplink data attenuator (). The echo return loss based attenuation data generator () produces the uplink echo return loss based attenuation data () in response to echo return loss data (). The echo return loss data () is based on at least one of: attenuated downlink data (), pre-echo canceler uplink data (), and/or amplifier gain data (). The uplink data attenuator () attenuates the post-echo canceler uplink data () to produce attenuated uplink data () based on the uplink echo return loss based attenuation data ().

Echo canceler circuit and method

A double talk activity detector () and method for an echo canceler circuit () improves the probability of detecting a double talk condition based on at least pre-echo canceler uplink data (). The echo canceler circuit () includes a double talk activity probability data generator () and an echo canceler stage (). The double talk activity probability data generator () receives pre-echo canceler uplink data () and in response produces double talk activity probability data (). The echo canceler stage () is coupled to the double talk activity probability data generator () and receives downlink data (), pre-echo canceler uplink data () and the double talk activity probability data () and in response produces attenuated uplink data ().

Double talk activity detector and method for an echo canceler circuit

A bi-directional hands-free communication device includes a microphone for transmitting a signal along a transmit path and a speaker receiving a signal transmitted along a receive path and outputting a corresponding output signal. An echo canceller, positioned in the transmit path and the receive path, cancels echo signals induced by the microphone from the speaker and outputs a corresponding cancelled signal along the transmit path, and a transparency circuit distributes state-dependent additional loss derived from the noise floor margin to the transmit path and the receive path to reduce residual echo signals output from the echo canceller. The transparency circuit measures a noise floor and inserts an artificial noise signal to the transmit path, and optionally to the receive path, at a predetermined level in relation to the measured noise floor, and dynamically adjusts the speaker to compensate for changing environmental conditions by dividing a range of an expected ambient noise power into adjacent consecutive bins, and controlling a volume of the speaker responsive to ambient noise changes only when measured noise power moves into an adjacent bin.

Full-duplex hands-free transparency circuit and method therefor

A communications transmitter which operates as a mobile telephone incorporates a noise suppressor ( FIG. ) which reduces the background noise in the transmitted voice signal. An external voice activity detector ( ), which operates in conjunction with a noise suppressor ( ) estimates the signal power of the incoming voice signal and compares this to an estimated noise floor. As a result of this comparison, a voice activity factor is applied to an updated noise floor estimate to create a voice activity threshold estimate. The voice activity threshold estimate is then used to decide whether or not to the force noise suppressor ( ) to perform an update of a noise content estimate of the incoming voice signal.

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Chandler, AZ, United States of America

Christopher W Springfield