Methods And Apparatus For Adaptive Gain Control In A Communication System

Abstract

Methods and apparatus for a communication system having microphones and loudspeakers to determine a noise and speech level estimate for a transformed signal, determine a SNR from the noise and speech level estimates, and determine a gain for the transformed signal to achieve a selected SNR range at a given position. In one embodiment, the gain is determined by adapting an actual gain to follow a target gain, wherein the target gain is adjusted to achieve the selected SNR range.

1 . A method, comprising:
 for a communication system having microphones and loudspeakers, transforming a signal received by a first one of the microphones to the frequency domain;   determining a noise level estimate for the transformed signal;   determining a speech level estimate for the transformed signal;   determining a SNR from the noise and speech level estimates; and   determining a gain for the transformed signal to achieve a selected SNR range at a given position, wherein determining the gain comprises:
 adapting an actual gain to follow a target gain, wherein the target gain is adjusted to achieve the selected SNR range; 
 comparing the target gain and the actual gain to determine a gain change increment; 
 increasing the actual gain if the SNR at the given position is lower than a minimum SNR in the SNR range; and 
 decreasing the actual gain if the SNR at the given position is higher than a maximum SNR in the SNR range. 
   
     
     
         2 . The method according to  claim 1 , further including adapting the SNR range in response to a change in the noise level. 
     
     
         3 . The method according to  claim 1 , further including using a psychoacoustic measure for determining the noise and/or speech level estimate. 
     
     
         4 . The method according to  claim 3 , further including determining a noise level estimate for the transformed signal using spectral weights based upon the psychoacoustic measure. 
     
     
         5 . The method according to  claim 1 , further including performing voice activity detection on the transformed signal and generating weighting factors from the voice activity detection to detect an active speaker. 
     
     
         6 . The method according to  claim 5 , further including determining mixer weights to select a speaker-specific gain for the active speaker. 
     
     
         7 . The method according to  claim 5 , further including attenuating the gain during speech pauses detected by the voice activity detection. 
     
     
         8 . The method according to  claim 1 , further including determining the gain for different frequencies. 
     
     
         9 . The method according to  claim 1 , further including, in a bi-directional system, setting a maximum gain to block a loudspeaker output of an inactive communication system. 
     
     
         10 . The method according to  claim 9 , further including using a first one of the microphones to determine the SNR at the given position. 
     
     
         11 . The method according to  claim 1 , wherein the given position corresponds to a position proximate an expected location of a user ear. 
     
     
         12 . An article, comprising:
 a non-transitory computer-readable medium having stored instructions than enable a machine to:   for a communication system having microphones and loudspeakers, transform a signal received by a first one of the microphones to the frequency domain;   determine a noise level estimate for the transformed signal;   determine a speech level estimate for the transformed signal;   determine a SNR from the noise and speech level estimates; and   determine a gain for the transformed signal to achieve a selected SNR range at a given position, wherein determining the gain comprises:
 adapt an actual gain to follow a target gain, wherein the target gain is adjusted to achieve the selected SNR range; 
 compare the target gain and the actual gain to determine a gain change increment; 
 increase the actual gain if the SNR at the given position is lower than a minimum SNR in the SNR range; and 
 decrease the actual gain if the SNR at the given position is higher than a maximum SNR in the SNR range. 
   
     
     
         13 . The article according to  claim 12 , further including instructions to adapt the SNR range in response to a change in the noise level. 
     
     
         14 . The article according to  claim 12 , further including instructions to use a psychoacoustic measure for determining the noise and/or speech level estimate. 
     
     
         15 . The article according to  claim 12 , further including instructions to perform voice activity detection on the transformed signal and generate weighting factors from the voice activity detection to detect an active speaker. 
     
     
         16 . The article according to  claim 15 , further including instructions to determine mixer weights to select a speaker-specific gain for the active speaker. 
     
     
         17 . The article according to  claim 12 , further including, in a bi-directional system, instructions to set a maximum gain to block a loudspeaker output of an inactive communication system. 
     
     
         18 . A communication system, comprising:
 microphones to receive sound in an enclosed environment;   loudspeakers to generate sound into the enclosed environment;   a sound processing module to transform a signal received by a first one of the microphones to the frequency domain;   a noise estimate module to determine a noise level estimate for the transformed signal;   a speech estimate module to determine a speech level estimate for the transformed signal;   a gain control module comprising:
 a SNR module to determine a SNR from the noise and speech level estimates; and 
 a gain module to determine a gain for the transformed signal to achieve a selected SNR range at a given position, the gain module including a processor configured to:
 adapt an actual gain to follow a target gain, wherein the target gain is adjusted to achieve the selected SNR range; 
 compare the target gain and the actual gain to determine a gain change increment; 
 increase the actual gain if the SNR at the given position is lower than a minimum SNR in the SNR range; and 
 decrease the actual gain if the SNR at the given position is higher than a maximum SNR in the SNR range. 
 
   
     
     
         19 . The system according to  claim 18 , wherein the gain module is further configured to adapt the SNR range in response to a change in the noise level. 
     
     
         20 . The system according to  claim 18 , wherein the noise estimate module is configured to use a psychoacoustic measure for determining the noise level estimate.