Core estimator and adaptive gains from signal to noise ratio in a hybrid speech enhancement system

A speech enhancement system, comprising:

• a noise adaptation module receiving noisy speech,
• the noisy speech being characterized by spectral coefficients spanning a plurality of frequency bins and containing an original noise,
• the noise adaptation module segmenting the noisy speech into noise-only frames and signal-containing frames, and
• the noise adaptation module determining a noise estimate and a probability of signal absence in each frequency bin;
• a signal-to-noise ratio estimator coupled to the noise adaptation module,
• the signal-to-noise ratio estimator determining a first signal-to-noise ratio and a second signal-to-noise ratio based on the noise estimate;
• and
• a core estimator coupled to the signal-to-noise ratio estimator and receiving the noisy speech,
• the core estimator applying to the spectral coefficients of the noisy speech a first set of gains in the frequency domain without discarding the noise-only frames to produce speech that contains a residual noise,
• wherein the first set of gains is determined based, at least in part, on the second signal-to-noise ratio and a level of aggression, and
• wherein the core estimator is operative to maintain the spectral density of the spectral coefficients of the residual noise below a proportion of the spectral density of the spectral coefficients of the original noise.