Automatic gain selector for a 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, each of said plurality of pre-processed signals comprised of a plurality of frames, each frame comprised of a plurality of samples of said input signal;
• means for modifying an operating parameter of each of said plurality of pre-processed signals provided by said signal separating means to provide a plurality of post-processed signals;
• and
• means responsive to said plurality of pre-processed signals for generating a modification signal for application to said modifying means to enable the operating parameter to be modified, said modification signal generating means including means for smoothing said modification signal multiple times per frame.

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 an estimate of the signal-to-noise ratio (SNR) in each individual channel;
• means for producing a gain value for each channel by automatically selecting one of a plurality of gain tables in response to a multi-channel noise parameter, and selecting one of a plurality of gain values from the selected gain table in response to said channel SNR estimates and the channel number;
• and
• means for modifying the gain of each of said plurality of pre-processed signals provided by said signal separating means in response to said gain values to provide a plurality of post-processed 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 selected frequency channels, each of said plurality of pre-processed signals comprised of a plurality of frames, each frame comprised of a plurality of samples of said input signal;
• means for generating an estimate of the signal-to-noise ratio (SNR) in each individual channel once each frame;
• means for producing a raw gain value for each channel in response to said SNR estimates once each frame;
• means for smoothing said raw gain values multiple times per frame;
• and
• means for modifying the gain of each of said plurality of pre-processed signals provided by said signal separating means in response to said smoothed gain values to provide a plurality of post-processed signals.

An improved noise suppression system for attenuating the background noise from a noisy pre-processed input signal to produce a noise-suppressed post-processed output signal by spectral gain modification, said noise suppression system comprising:

• signal dividing means for separating the pre-processed input signal into a plurality of selected frequency bands, thereby producing a plurality of pre-processed channels;
• channel energy estimation means for generating an estimate of the energy in each of said plurality of pre-processed channels;
• channel noise estimation means for generating an estimate of the signal-to-noise ratio (SNR) of each individual channel based upon said channel energy estimates and an estimate of the current background noise energy for that individual channel;
• channel gain controlling means for providing channel gain values, said channel gain controlling means having a plurality of gain tables, each gain table having predetermined individual channel gain values corresponding to various individual channel SNR estimates, said channel gain controlling means further having gain table selection means for automatically selecting one of said plurality of gain tables according to the overall average background noise level of said input signal;
• channel gain modifying means for adjusting the gain of each of said plurality of pre-processed channels provided by said signal dividing means according to said channel gain values, thereby producing a plurality of post-processed channels;
• and
• channel combination means for recombining said plurality of post-processed channels to produce said post-processed output signal.

The method of attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal comprising the steps of:

• separating the input signal into a plurality of pre-processed signals representative of selected frequency channels;
• modifying an operating parameter of each of said plurality of pre-processed signals to provide a plurality of post-processed signals;
• and
• generating a modification signal responsive to said plurality of pre-processed signals, said modification signal having a selected modification value for each channel to enable the operating parameter to be modified, said modification signal generated by automatically selecting a modification value for each channel from one of a plurality of sets of modification values for that channel.

The 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 pre-processed signals representative of selected frequency channels, each of said plurality of pre-processed signals comprised of a plurality of frames, each frame comprised of a plurality of samples of said input signal;
• modifying an operating parameter of each of said plurality of pre-processed signals to provide a plurality of post-processed signals;
• and
• generating a modification signal responsive to said plurality of pre-processed signals, said modification signal having a selected modification value for each channel to enable the operating parameter to be modified, said modification values being smoothed multiple times per frame to reduce discontinuities in said modification signal.

The method of attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal by spectral gain modification, comprising the steps of:

• separating the input signal into a plurality of pre-processed signals representative of selected frequency channels;
• generating an estimate of the signal-to-noise ratio (SNR) in each individual channel;
• producing a gain value for each channel by automatically selecting one of a plurality of gain tables in response to a multi-channel noise parameter, and selecting one of a plurality of gain values from the selected gain table in response to said channel SNR estimates and the channel number;
• and
• 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.

The method of attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal by spectral gain modification, comprising the steps of:

• separating the input signal into a plurality of pre-processed signals representative of selected frequency channels, each of said plurality of pre-processed signals comprised of a plurality of frames, each frame comprised of a plurality of samples of said input signal;
• generating an estimate of the signal-to-noise ratio (SNR) in each individual channel once each frame;
• producing a raw gain value for each channel in response to said SNR estimates once each frame;
• smoothing said raw gain values multiple times per frame;
• and
• modifying the gain of each of said plurality of pre-processed signals in response to said smoothed gain values to provide a plurality of post-processed signals.