Audio signal component compensation system

Abstract

A system compensating audio signal components in a communication system is disclosed, the method comprising the steps of detecting, by a microphone, a sound signal, the sound signal comprising audio signal components resulting from reproducing an audio signal of an audio source, the sound signal further comprising speech signal components corresponding to a speech signal from a person, filtering the sound signal to whiten the sound signal, compensating the audio signal components in the whitened sound signal, and removing the whitening of the compensated sound signal, where the filtering of the audio signal is performed using at least two filters in an alternating way, each filter using time-dependent filter coefficients.

1 . A method for compensating an audio signal in a communication system comprising the steps of: 
 detecting a sound signal, the sound signal comprising a detected audio signal component from an audio signal and a speech signal component;    filtering the sound signal in order to create a whitened sound signal;    filtering the audio signal component in order to create a whitened audio signal component, where the step of filtering the audio signal component is performed using at least two filters in an alternating way, each filter using time-dependent filter coefficients;    compensating the audio signal component in the whitened sound signal; and    inverse filtering the compensated whitened sound signal.    
     
     
         2 . The method of  claim 1 , further comprising the step of calculating the time-dependent filter coefficients.  
     
     
         3 . The method of  claim 2 , where the step of filtering the sound signal is performed using the time-dependent filter coefficients.  
     
     
         4 . The method of  claim 3 , further comprising the step of renewing the time-dependent filter coefficients every N cycles.  
     
     
         5 . The method of  claim 3 , further comprising alternately supplying the time-dependent filter coefficients to a first filter and a second filter, where time-dependent filter coefficients calculated for a first set of N cycles are supplied to the first filter, and time-dependent filter coefficients calculated for a next set of N cycles are supplied to the second filter, such that the time-dependent filter coefficients for the first filter and the second filter, respectively, are renewed every 2N cycles.  
     
     
         6 . The method of  claim 1 , where the step of compensating the audio signal component in the whitened sound signal further comprises: simulating the whitened audio signal component to create a whitened simulated audio signal component; and determining a whitened error signal by subtracting the simulated audio signal component from the sound signal.  
     
     
         7 . The method of  claim 6 , further comprising determining an estimated sound signal component using the error signal as a feedback control signal.  
     
     
         8 . The method of  claim 7 , where the step of simulating the audio signal component of the sound signal is performed by an echo compensation filter having a length equal to N.  
     
     
         9 . The method of  claim 6 , where the step of determining a whitened error signal comprises alternately subtracting a first whitened simulated audio signal component from the whitened sound signal, and a second whitened simulated audio signal component from the whitened sound signal.  
     
     
         10 . The method of  claim 9 , further comprising inverse filtering the whitened simulated error signal, resulting in an error signal corresponding to an echo compensated sound signal.  
     
     
         11 . The method of  claim 9 , where the step of determining a whitened error signal comprises alternately subtracting a first whitened simulated audio signal component from the whitened sound signal for a first set of N cycles, and a second whitened simulated audio signal component from the whitened sound signal for a next set of N cycles.  
     
     
         12 . A method for compensating an audio signal comprising the steps of: 
 detecting a sound signal, the sound signal comprising a detected audio signal component from an audio signal, and a speech signal component;    calculating time dependent filter coefficients;    filtering the sound signal to create a whitened sound signal using a decorrelation filter, said decorrelation filter being supplied with the time dependent filter coefficients every N cycles;    filtering the audio signal component to create a whitened audio signal component where the step of filtering the audio signal component is performed using at least two filters in an alternate way, said two filters being supplied alternately every 2N cycles with said time dependent filter coefficients;    compensating the audio signal component in the whitened sound signal; and    inverse filtering the compensated whitened sound signal.    
     
     
         13 . An echo compensation system comprising: 
 at least one microphone for detecting a sound signal, the sound signal comprising a detected audio signal component from an audio signal and a speech signal component;    at least one loudspeaker for outputting the sound signal and the audio signal;    a filter unit comprising a first filter and a second filter used in an alternating way for filtering the audio signal component, where each filter uses time-dependent filter coefficients; and    an echo compensation unit for compensating the audio signal component received by the microphone.    
     
     
         14 . The echo compensation system of  claim 13 , further comprising a calculating unit for calculating the time-dependent filter coefficients.  
     
     
         15 . The echo compensation system of  claim 14 , further comprising a first switch in communication with the calculating unit and the first and second filters, for alternately supplying the time-dependent filter coefficients to the first filter and the second filter.  
     
     
         16 . The echo compensation system of  claim 15 , where the first switch switches between a first position and a second position every N cycles.  
     
     
         17 . The echo compensation system of  claim 13 , where the filter unit further comprises a third filter for filtering the sound signal and outputting a whitened sound signal component, where the third filter receives the time-dependent filter coefficients calculated by the calculating unit, and the time-dependent filter coefficients received by the third filter are refreshed every N cycles.  
     
     
         18 . The echo compensation system of  claim 13 , where the echo compensation unit comprises a first echo compensation filter in communication with the first filter and a second echo compensation filter in communication with the second filter, where the first echo compensation filter receives a first whitened audio signal component from the first filter and outputs a first whitened simulated audio signal component, and the second echo compensation filter receives a second whitened audio signal component from the second filter and outputs a second whitened simulated audio signal component.  
     
     
         19 . The echo compensation system of  claim 18 , where the echo compensation unit further comprises a subtracting unit where the first and second whitened simulated audio signal components are subtracted from the whitened sound signal component, resulting in a whitened error signal.  
     
     
         20 . The echo compensation unit of  claim 19 , where the whitened error signal is used as a feedback control signal for the echo compensation filters.  
     
     
         21 . The echo compensation unit of  claim 13 , further comprising an inverse filter for inverse filtering the whitened error signal, and outputting an echo compensated sound signal.  
     
     
         22 . The echo compensation unit of  13 , further comprising a third filter and a fourth filter, where the first and third filters correspond to a first audio signal component, and the second and fourth filters correspond to a second audio signal component; and four echo compensation filters, where two of the echo compensations filters correspond to the first audio signal component and the other two echo compensation filters correspond to the second audio signal component.  
     
     
         23 . The echo compensation unit of  claim 18 , further comprising a switch for alternately supplying the first whitened simulated audio signal component and the second whitened simulated audio signal component to the subtracting unit, the switch alternating every N cycles.  
     
     
         24 . An echo compensation system comprising: 
 at least one microphone for detecting a sound signal, the sound signal comprising a detected audio signal component from an audio signal and a speech signal component;    at least one loudspeaker for outputting the sound signal and the audio signal;    a calculating unit for calculating time dependent filter coefficients based on the audio signal;    at least two filters for alternately filtering the audio signal, said filters being alternately supplied with said time-dependent filter coefficients every 2N cycles;    a sound signal filter for filtering the sound signal, the sound signal filter being supplied with said time dependent filter coefficients every N cycles;    an echo compensation unit for compensating the audio signal component.    
     
     
         25 . A method for compensating audio signal components comprising the steps of: 
 detecting a sound signal, the sound signal comprising a detected audio signal component from an audio signal comprising a first channel and a second channel, and a speech signal component;    generating an echo compensated sound signal to compensate acoustic echoes in the sound signal due to the detected audio signal component in the sound signal, where the generating step comprises the steps of:    supplying the first channel of the audio signal to a mono echo compensation unit;    supplying the first and second channels of the audio signal to a multi channel echo compensation unit;    outputting a first output associated with a first signal power from the mono echo compensation unit, and a second output associated with a second signal power from the multi channel echo compensation unit;    comparing the first signal power and the second signal power;    selecting the first output if the first signal power is smaller than the second signal power; and    selecting the second output if the second signal power is smaller than the first signal power.    
     
     
         26 . The method of  claim 25 , further comprising the step of filtering the sound signal in order to obtain a whitened sound signal before the step of generating the echo compensated sound signal, and inverse filtering the selected output.  
     
     
         27 . The method of  claim 25 , where the step of generating an echo compensated sound signal further comprises: generating a first simulated audio signal component for the first channel and a second simulated audio signal component for the second channel using the multi channel echo compensation unit; and adding the first and second simulated audio signals to obtain a combined simulated audio signal component.  
     
     
         28 . The method of  claim 26 , further comprising calculating time-dependent filter coefficients to be used for obtaining the whitened sound signal.  
     
     
         29 . The method of  claim 27 , further comprising subtracting a mono simulated audio signal component from the sound signal to obtain the first output, and subtracting the combined simulated audio signal component from the sound signal to obtain the second output.  
     
     
         30 . A method for compensating audio signal components comprising the steps of: 
 detecting a sound signal, the sound signal comprising a detected audio signal component from an audio signal comprising a first channel and a second channel, and a speech signal component;    filtering the sound signal to obtain a whitened sound signal;    filtering the first channel to obtain a first whitened audio signal component;    filtering the second channel to obtain a second whitened audio signal component;    supplying the first whitened audio signal component and the whitened sound signal to a mono echo compensation unit;    outputting a first output having a first signal power from the mono echo compensation unit;    supplying the first whitened audio signal component, the second whitened audio signal component, and the whitened sound signal to a multi channel echo compensation unit;    outputting a second output having a second signal power from the multi channel echo compensation unit;    comparing the first signal power and the second signal power;    selecting the first output if the first signal power is smaller than the second signal power; and    selecting the second output if the second signal power is smaller than the first signal power.    
     
     
         31 . An echo compensation system comprising: 
 at least one microphone for detecting a sound signal, the sound signal comprising a detected audio signal component from an audio signal comprising a first channel and a second channel, and a speech signal component;    at least one loudspeaker for outputting the sound signal;    a mono echo compensation unit for receiving the first channel of the audio signal and outputting first output having a first signal power;    a multi channel echo compensation unit for receiving the first and second channels of the audio signal and outputting a second output having a second signal power; and    a comparison unit for comparing the first signal power and the second signal power; and    selecting the first output if the first signal power is lower than the second signal power, or the second output if the second signal power is lower than the first signal power.    
     
     
         32 . The echo compensation system of  claim 31 , further comprising a plurality of filters to whiten the audio signal and the sound signal, and an inverse filter for inverse filtering at least one of the first output and the second output.  
     
     
         33 . The echo compensation system of  claim 32 , where the plurality of filters includes at least one filter for the first channel and at least one filter for the second channel.  
     
     
         34 . An echo compensation system comprising: 
 at least one microphone for detecting a sound signal, the sound signal comprising a detected audio signal component from an audio signal comprising a first channel and a second channel, and a speech signal component;    at least one loudspeaker for outputting the sound signal;    a filter unit for generating a whitened sound signal;    a plurality of filter units for generating a whitened audio signal, the whitened audio signal comprising a first whitened audio signal corresponding to the first channel and a second whitened audio signal corresponding to the second channel;    a mono echo compensation unit being supplied with the first whitened audio signal and with the whitened sound signal, and outputting a first output;    a multi channel echo compensation unit being supplied with the first whitened audio signal, the second audio signal, and the whitened sound signal, and outputting a second output; and    a comparison unit for comparing a signal power of the first output and a signal power of the second output, and selecting whichever of the first output or second output has a lower signal power.    
     
     
         35 . An echo compensation system comprising: 
 an audio source for generating an audio signal having a first channel with a first time delay and a second channel with a second time delay, where the first and second time delays are adjustable relative to each other;    at least one microphone for detecting a sound signal, the sound signal comprising a detected audio signal component from the audio signal, and a speech signal;    a loudspeaker unit for outputting the audio signal and the sound signal;    an echo compensation unit for simulating the audio signal component to obtain a simulated audio signal component, and subtracting the simulated audio signal component from the sound signal, the echo compensation unit comprising:    a filter for filtering the audio signal to obtain a pulse response of the audio signal, the pulse response having a maximum value;    a plurality of filter coefficients corresponding to the filter;    a delay element for introducing a variable time delay corresponding to the audio signal; and    a delay control unit for controlling the delay element so that the maximum value of the pulse response is located within a predetermined range of the filter coefficients.    
     
     
         36 . The echo compensation system of  claim 35 , where the delay element comprises a delay memory having a variable length.  
     
     
         37 . The echo compensation system of  claim 36 , where the delay element is in communication with a signal memory, the signal memory of the filter having a constant length.  
     
     
         38 . The echo compensation system of  claim 35 , where a filter coefficient corresponding to the maximum value of the pulse response is located between a tenth and a twentieth filter coefficient.  
     
     
         39 . The echo compensation system of  claim 35 , where the maximum value of the pulse response is located between a twentieth and a fortieth filter coefficient  
     
     
         40 . The echo compensation system of  claim 35 , where the maximum value of the pulse response is located between a twenty-fifth and a thirty-fifth filter coefficient.  
     
     
         41 . The echo compensation system of  claim 35 , where the maximum value of the pulse response is located between a twenty-eighth and a thirty-second filter coefficient.  
     
     
         42 . The echo compensation system of  claim 35 , where the delay control unit determines at which filter coefficient the maximum value of the impulse response is positioned.  
     
     
         43 . The echo compensation system of  claim 35 , further comprising: 
 a filter for generating a whitened sound signal using time-dependent filter coefficients;    a plurality of filter units for generating a whitened delayed audio signal, where at least one filter unit comprises two audio signal filters, each audio signal filter using time-dependent filter coefficients for generating corresponding whitened delayed audio signals, said at least two audio signal filters being used in an alternating way for generating the whitened delayed audio signals;    a mono echo compensation unit comprising at least two echo compensation filters alternately receiving the whitened delayed audio signals from the audio signal filters, and outputting a mono compensated sound signal having a first signal power;    a multi channel echo compensation unit comprising at least two echo compensation filters alternately receiving the whitened delayed audio signals from the audio signal filters, and outputting a multi channel compensated sound signal having a second signal power; and    a comparison unit for comparing the first signal power and the second signal power, and selecting whichever of the mono compensated sound signal and the multi channel compensated sound signal has a lower signal power.    
     
     
         44 . An echo compensation system comprising: 
 an audio source for generating an audio signal having a first channel with a first time delay and a second channel with a second time delay, where the first and second time delays are adjustable relative to each other;    at least one microphone for detecting a sound signal, the sound signal comprising a detected audio signal component from the audio signal, and a speech signal;    a loudspeaker unit for outputting the audio signal and the sound signal;    a delay element comprising a delay memory for generating a delayed audio signal;    a calculating unit for calculating a pulse response corresponding to the delayed audio signal and the sound signal, the pulse response having a maximum value;    an echo compensation unit for obtaining a compensated audio signal component and    a delay control unit for controlling the delay element so that the maximum value of the pulse response is located within a predetermined range of filter coefficients.    
     
     
         45 . A method for compensating audio signal components comprising the steps of: 
 reproducing an audio signal, the audio signal having a first channel with a first time delay and a second channel with a second time delay, where the first and second time delays are adjustable relative to each other;    outputting the audio signal;    detecting a sound signal, the sound signal comprising a detected audio signal component from the audio signal, and a speech signal component;    outputting the sound signal;    generating a simulated audio signal component;    subtracting the simulated audio signal components from the sound signal;    simulating a signal path of the audio signal from the loudspeaker to the microphone by determining a pulse response of the audio signal; the pulse response having a maximum value; and    introducing a variable time delay selected so that the maximum value of the pulse response is located within a predetermined range of filter coefficients of the filter.    
     
     
         46 . The method of  claim 45 , further comprising the step of adding a variable time delay to the audio signal by supplying the audio signal to a delay element of variable length.  
     
     
         47 . The method of  claim 45 , further comprising the step of determining the maximum value of the pulse response and determining at which filter coefficient the determined maximum value is located.  
     
     
         48 . The method of  claim 47  where the step of determining the maximum value of the pulse response comprises determining the maximum value of a weighted modulus of the pulse response.  
     
     
         49 . The method of  claim 45 , further comprising varying the length of a delay element.  
     
     
         50 . The method of  claim 49 , further comprising increasing the delay element when it is determined that the maximum value of the pulse response is positioned at a filter coefficient having a number larger than the predetermined range.  
     
     
         51 . The method of  claim 50 , further comprising decreasing the delay element when it is determined that the maximum value of the pulse response is positioned at a filter coefficient having a number smaller than the predetermined range.  
     
     
         52 . The method of  claim 45 , further comprising shifting the pulse response so that the maximum of the pulse response is located within the predetermined range of filter coefficients, if the determined pulse response is not located within a predetermined range of filter coefficients.  
     
     
         53 . The method of  claim 45 , further comprising the steps of: 
 filtering the sound signal to obtain a whitened sound signal;    filtering the first channel and the second channel to obtain a first whitened delayed channel and a second whitened delayed channel, where the filtering of the first and second channels is performed using at least two audio filters per channel in an alternating way, each audio filter using time-dependent filter coefficients;    obtaining a compensated mono sound signal having a first signal power using a mono echo compensation unit;    obtaining a compensated multi channel sound signal having a second signal power using a multi channel echo compensation unit;    comparing the compensated first signal power and the second signal power; and    selecting whichever of the mono sound signal and the compensated multi channel sound signal has a lower signal power.    
     
     
         54 . A method for compensating audio signal components comprising the steps of: 
 reproducing an audio signal, the audio signal having a first channel with a first time delay and a second channel with a second time delay, where the first and second time delays are adjustable relative to each other;    outputting the audio signal;    detecting a sound signal, the sound signal comprising a detected audio signal component from the audio signal, and a speech signal component;    outputting the sound signal;    delaying the audio signal using a delay element;    calculating a pulse response from the delayed audio signal and the sound signal, the pulse response having a maximum value;    generating a simulated audio component using the delayed audio signal and a filter, said filter using the calculated pulse response as filter coefficients;    controlling a delay introduced by the delay element so that the maximum value of the pulse response is positioned within a predetermined range of filter coefficients; and    subtracting the simulated audio component from the sound signal.