Abstract: A method of environmental noise compensation a speech audio signal is provided that includes estimating a fast audio energy level and a slow audio energy level in an audio environment, wherein the speech audio signal is not part of the audio environment, and applying a gain to the speech audio signal to generate an environment compensated speech audio signal, wherein the gain is updated based on the estimated slow audio energy level when the estimated fast audio energy level is not indicative of an audio event in the audio environment and the estimated gain is not updated when the estimated fast audio energy level is indicative an audio event in the audio environment.

Abstract: A method and apparatus for cross-talk resistant adaptive noise cancellation.

Abstract: A method of voice activity detection is provided that includes measuring a first signal level in a first sample of a first audio signal from a first audio capture device and a second signal level in a second sample of a second audio signal from a second audio capture device, and detecting voice activity based on the first signal level, the second signal level, and an activity threshold.

Abstract: A method and apparatus for cross-talk resistant adaptive noise cancellation.

Abstract: Hands-free phones with echo cancellation using dual filters, one fast adapting filter and one slow adapting filter; the choice of filters includes switching with hysteresis from recent performance, and the fast adapting filter has step size control to limit relative filter update energy and the slow adapting filter limits filter divergence.

Abstract: Hands-free phones with voice activity detection using a comparison of frame power estimate with an adaptive frame noise power estimate, automatic gain control with fast adaptation and minimal speech distortion, echo cancellation updated in the frequency domain with stepsize optimization and smoothed spectral whitening, and echo suppression with adaptive talking-state transitions.

Abstract: Layered code-excited linear prediction (CELP) speech encoders have progressively weaker perceptual weighting filters for each of the successive enhancement layers and decoders have progressively weaker short-term postfilters for increased bit rates (increased number of enhancement layers decoded) and a long-term postfilter for all bit rates.

Abstract: A decoder for code excited LP encoded frames with both adaptive and fixed codebooks; erased frame concealment uses repetitive excitation plus a smoothing of pitch gain in the next good frame, plus multilevel voicing classification with multiple thresholds of correlations determining linear interpolated adaptive and fixed codebook excitation contributions.

Abstract: Acoustic echo control for hands-free phone has acoustic echo cancellation and echo suppression with a voice activity detection for the echo suppression based on near-end input power together with an estimate for acoustic echo cancellation gain.

Abstract: Speech noise gating for gain control functions such as automatic gain control, dynamic range compression, and digital volume control scales the gain control function gain according to the ratio of noise energy to input energy.

Abstract: Speech-free noise estimation by cancellation of speech content from an audio input where the speech content is estimated by noise suppression. Adaptive noise cancellation with primary and noise-reference inputs and an adaptive noise cancellation filter from estimating primary noise from noise-reference input. Speech Suppressor (Noise Estimation) applied to noise-reference input provides speech-free noise estimates for noise cancellation in the primary input.

Abstract: Noise suppression (speech enhancement) by spectral amplitude filtering using a gain determined with a quantized estimated signal-to-noise ratio plus, optionally, prior frame suppression. The relation between signal-to-noise ratio and filter gain derives from a codebook mapping with a training set constructed from clean speech and noise conditions.

Abstract: Hands-free phones with echo cancellation using dual filters, one fast adapting filter and one slow adapting filter; the choice of filters includes switching with hysteresis from recent performance, and the fast adapting filter has stepsize control to limit relative filter update energy and the slow adapting filter limits filter divergence.

Abstract: Hands-free phones with voice activity detection using a comparison of frame power estimate with an adaptive frame noise power estimate, automatic gain control with fast adaptation and minimal speech distortion, echo cancellation updated in the frequency domain with stepsize optimization and smoothed spectral whitening, and echo suppression with adaptive talking-state transitions.

Abstract: Hands-free phones with voice activity detection using a comparison of frame power estimate with an adaptive frame noise power estimate, automatic gain control with fast adaptation and minimal speech distortion, echo cancellation updated in the frequency domain with stepsize optimization and smoothed spectral whitening, and echo suppression with adaptive talking-state transitions.

Abstract: A decoder for code excited LP encoded frames with both adaptive and fixed codebooks; erased frame concealment uses muted repetitive excitation, threshold-adapted bandwidth expanded repetitive synthesis filter, and jittered repetitive pitch lag.

Abstract: Fixed-point representation of impulse response coefficients by partitioning the sequence of coefficients into bins according to sequence index intervals, and within each bin quantizing to the fixed-point format providing the greatest resolution without overflow; then computing the total fixed-point quantization error; lastly, optimizing the partitioning to minimize the total fixed-point quantization error and thereby define the fixed-point representation.

Abstract: A system and method for enhancing the speech quality of the mixed excitation linear predictive (MELP) coder and other low bit-rate speech coders. The system and method employ a plosive analysis/synthesis method, which detects the frame containing a plosive signal, applies a simple model to synthesize the plosive signal, and adds the synthesized plosive to the coded speech. The system and method remains compatible with the existing MELP coder bit stream.

Abstract: A decoder for code excited LP encoded frames with both adaptive and fixed codebooks; erased frame concealment uses repetitive excitation plus a smoothing of pitch gain in the next good frame, plus multilevel voicing classification with multiple thresholds of correlations determining linear interpolated adaptive and fixed codebook excitation contributions.

Abstract: Layered code-excited linear prediction speech encoders/decoders with progressively weakening perceptual weighting filters for the enhancement layers in the encoder and progressively weakening short-term postfilters for increased bit rates (enhancement layers) and a long-term postfilter for all bit rates.