Noise suppression system

An improved noise suppression system for attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal, said noise suppression system comprising:

• means for separating the input signal into a plurality of pre-processed signals representative of selected frequency channels;
• means for generating and storing an estimate of the background noise power spectral density of said pre-processed signals, said background noise estimate generating means including means for modifying said background noise estimate in response to a timing parameter indicative of the time interval since the previous background noise estimate modification;
• means for generating an estimate of the signal-to-noise ratio (SNR) in each individual channel based upon said modified background noise estimates;
• means for producing a gain value for each individual channel in response to said channel SNR estimates;
• and
• means for modifying the gain of each of said plurality of pre-processed signals in response to said gain values to provide a plurality of post-procesed signals.

An improved noise suppression system for attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal, said noise suppression system comprising:

• means for separating the input signal into a plurality of pre-processed signals representative of a number N of selected frequency channels
• means for generating an estimate of the energy in each individual channel;
• means for monitoring said channel energy estimates and for distinguishing narrowband noise bursts from speech energy and background noise energy, thereby producing a modification signal;
• means for selectively modifying said channel energy estimates in response to said modification signal such that channel energy estimates representative of narrowband noise bursts are modified;
• means for producing a gain value for each individual channel in response to each modified channel energy estimate;
• and
• means for modifying the gain of each of said plurality of pre-processed signals in response to said gain values to provide a plurality of post-processed signals.

An improved method of attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal in a noise suppression system comprising the steps of:

• separating the input signal into a plurality of preprocessed signals representative of a number N of selected frequency channels;
• generating an estimate of the energy in each individual channel;
• generating and storing an estimate of the background noise power spectral density of said pre-processed signals;
• generating an estimate of the signal-to-noise ratio (SNR) in each individual channel based upon said background noise estimates and said channel energy estimates;
• producing a gain value for each individual channel in response to said channel SNR estimates, said gain values having a range of minimal values, said gain value producing step including the steps of providing a predefined SNR threshold and comparing said channel SNR estimates to said predefined SNR threshold such that channels having SNR estimates below said SNR threshold produce gain values within said minimal range;
• and
• modifying the gain of each of said plurality of preprocessed signals in response to said gain values to provide a plurality of post-processed signals.