Audio enhancement system and method

Abstract

A system and method for enhancing the sound signal produced by an audio system in a listening environment by compensating for ambient sound in the listening environment, comprises producing an audio sound in the time domain from an electrical sound signal in the time domain. The electrical sound signal in the time domain is transformed into an electrical sound signal in the frequency domain and the electrical sound signal in the frequency domain is retransformed into an audio sound in the time domain. The total sound level in the environment is measured and a signal representative thereof is generated. The audio sound signal and the total sound signal are processed to extract a signal representing the ambient sound level within the environment, and equalization is performed in the frequency domain to adjust the output from the audio sound signal to compensate for the ambient noise level.

1 . An audio enhancement system for compensating for ambient noise in a listening environment, comprising:
 means for producing an electrical sound signal in the time domain and generating a sound output from the electrical sound signal, comprising
 time-to-frequency transformation means responsive to the electrical sound signal in the time domain for generating an electrical sound signal in the frequency domain; 
 frequency-to-time transformation means responsive to the electrical sound signal in the frequency domain for generating a re-transformed electrical sound signal in the time domain for generating the sound output; 
   a sensor that obtains a sound signal representative of the total sound level in the environment, where the total sound level comprises both the sound output from the means for producing and the ambient noise within the environment;   means, responsive to the total sound signal and to the electrical sound signal, for extracting an ambient noise signal representative of the ambient noise in the environment from the total sound signal, where spectral voice signal components in the total sound signal are suppressed; and   means, responsive to the ambient noise signal and the electrical sound signal in the frequency domain, for equalizing according to the spectral distribution of the noise signal and adjusting in the frequency domain the sound output of the means for producing to compensate for the ambient noise level.   
     
     
         2 . The audio enhancement system of  claim 1 , where the means for equalizing and adjusting comprises a gain shaping unit for performing an equalizing function in the frequency domain. 
     
     
         3 . The audio enhancement system of  claim 2 , where the means for equalizing and adjusting comprises a voice activity detector for detecting and suppressing spectral voice components in the total sound signal. 
     
     
         4 . The audio enhancement system of  claim 3 , where the means for equalizing and adjusting comprises a mean value calculation unit. 
     
     
         5 . The audio enhancement system of  claim 4 , where the means for equalizing and adjusting comprises a time-to-frequency transformation unit connected to the sensor for transforming the total sound signal in the time domain into a total sound signal in the frequency domain. 
     
     
         6 . The audio enhancement system of  claims 5 , where the means for extracting comprises a noise estimation unit operated in the frequency domain. 
     
     
         7 . The audio enhancement system of  claim 6 , where the noise estimation unit comprises a frequency domain adaptive filter. 
     
     
         8 . The audio enhancement system of  claims 7 , where the frequency domain adaptive filter comprises an overlap-save frequency domain adaptive filter. 
     
     
         9 . The audio enhancement system of  claims 5 , where the means for extracting comprises a noise estimation unit operated in the time domain, the noise estimation unit being connected between the sensor and the means for equalizing and adjusting. 
     
     
         10 . The audio enhancement system of  claim 9 , where the noise estimation unit operated in the time domain comprises at least one adaptive filter. 
     
     
         11 . The audio enhancement system of  claim 1 , where the means for equalizing and adjusting performs a linear predictive coding in the frequency domain. 
     
     
         12 . The audio enhancement system of  claim 2 , where the gain shaping unit performs a psycho-acoustically motivated gain shaping function. 
     
     
         13 . The audio enhancement system of  claim 12 , where the gain shaping unit has a frequency scale according to psycho-acoustic frequency groups. 
     
     
         14 . The audio enhancement system of  claim 12 , where the gain shaping unit has a warped frequency scale. 
     
     
         15 . The audio enhancement system of  claim 12 , where the gain shaping unit performs psycho-acoustic masking. 
     
     
         16 . The audio enhancement system of  claim 15 , where the psycho-acoustic masking is performed in the MPEG format. 
     
     
         17 . The audio enhancement system of  claim 15 , where the psycho-acoustic masking is performed according to the Johnston model. 
     
     
         18 . The audio enhancement system of  claim 1 , where the means for producing comprises a bypass path for higher frequencies, the bypass path having a controllable gain controlled by the means for equalizing and adjusting. 
     
     
         19 . The audio enhancement system of  claim 18 , where the bypass path comprises a delay unit. 
     
     
         20 . The audio enhancement system of  claim 18 , where the means for equalizing and adjusting is operated in an undersampled mode. 
     
     
         21 . A method for enhancing the sound signal produced by an audio system in a listening environment by compensating for ambient noise in the listening environment, comprising the steps of:
 producing an audio sound in the time domain from an electrical sound signal in the time domain, the electrical sound signal in the time domain being transformed into electrical sound signal in the frequency domain and the electrical sound signal in the frequency domain being retransformed into audio sound in the time domain to provide an audio sound signal;   measuring the sound level in the environment and generating a total sound signal representative thereof;   processing the audio sound signal and the total sound signal to extract a signal representing the ambient noise level within the environment, where spectral voice signal components in the total sound signal are suppressed; and   performing an equalization according to the spectral distribution of the signal representing the ambient noise level in the frequency domain and adjusting the output from the audio sound signal to compensate for the ambient noise level.   
     
     
         22 . The method of  claim 21 , where equalizing comprises gain shaping in the frequency domain. 
     
     
         23 . The method of  claim 22 , where equalizing comprises detecting a voice activity. 
     
     
         24 . The method of  claim 23 , where equalizing comprises calculating a mean value. 
     
     
         25 . The method of  claim 21 , where equalizing comprises a time-to-frequency transformation step for transforming the total sound signal in the time domain into a total sound signal in the frequency domain. 
     
     
         26 . The method of  claim 25 , where the processing to extract comprises estimating noise estimation in the frequency domain. 
     
     
         27 . The method of  claim 26 , where estimating the noise comprises adaptive filtering in the frequency domain. 
     
     
         28 . The method of  claim 27 , where the adaptive filtering comprises an overlap-save adaptive filtering in the frequency domain. 
     
     
         29 . The method of  claim 25 , where the extraction step comprises a noise estimation step in the time domain. 
     
     
         30 . The method of  claim 29 , where the noise estimation step in the time domain comprises at least one adaptive filtering step. 
     
     
         31 . The method of  claim 30 , where the equalizing comprises linear predictive coding in the frequency domain. 
     
     
         32 . The method of  claim 22 , where the gain shaping step comprises psycho-acoustical gain shaping. 
     
     
         33 . The method of  claim 32 , where the gain shaping step comprises frequency scaling according to psycho-acoustic frequency groups. 
     
     
         34 . The method of  claim 32 , where the gain shaping step comprises a warped frequency scaling. 
     
     
         35 . The method of  claim 32 , where the gain shaping step performs psycho-acoustic masking. 
     
     
         36 . The method of  claim 35 , where the psycho-acoustic masking is performed in the MPEG format. 
     
     
         37 . The method of  claim 35 , where the psycho-acoustic masking is performed according to the Johnston model. 
     
     
         38 . The audio enhancement system of  claim 1 , where the means for producing comprises a bypass path for higher frequencies, the bypass path having a controllable gain controlled by the means for equalizing and adjusting. 
     
     
         39 . The audio enhancement system of  claim 38 , where the bypass path comprises a delay step. 
     
     
         40 . The audio enhancement system of  claim 38 , where the means for equalizing and adjusting operates in an undersampled mode. 
     
     
         41 . An audio enhancement system for compensating for ambient noise in a listening environment, comprising:
 a time to frequency domain transformation unit that receives an input signal and provides a frequency domain output signal;   a multiplier that receives the frequency domain output signal and an equalizing signal and provides a multiplier output signal;   a frequency to time domain transformation unit that receives the multiplier output signal and provides an equalized signal;   a loudspeaker that receives the equalized signal and outputs an audio signal indicative thereof to a listening environment;   a transducer that senses audio within the listening environment and provides a sensed audio signal indicative thereof;   means responsive to the sensed audio signal and the frequency domain output signal for providing the equalizing signal.