Adaptive bass processing system

Abstract

An effective and simple psychoacoustic bass generation system generates a harmonic signal having inter-modulation controllable to remain below a threshold level and includes a high-pass filter configured to pass harmonics which are reproducible with fidelity by the loudspeaker or other transducer and a loudness matching block configured to compensate the loudness of the desired harmonics to match the loudness of the original signal.

What is claimed is: 
     
         1 . A bass enhancement system comprising:
 an adaptive low frequency signal extractor;   an adaptive adjustor of harmonic decay pattern;   a nonlinear processor configured to generate a harmonic signals having inter-modulation controllable to remain below a threshold level;   a high-pass filter configured to pass harmonics which are reproducible by the output transducer; and   an output mixer which sums the high-pass filtered raw input data with the psychoacoustic bass corresponding to the post processed harmonics generated by the nonlinear processor.   
     
     
         2 . The system as recited in  claim 1  further comprising a loudness matching block configured to compensate the loudness of the desired harmonics to match the loudness of the original low frequency signal. 
     
     
         3 . The system as recited in  claim 2  wherein the adaptive adjustor generates a harmonic decay rate that is implemented by an automatic gain related to at least one of the input level or the cut-off frequency of the speaker. 
     
     
         4 . The system as recited in  claim 1  wherein the adaptive adjustor generates full-harmonic generation and inaudible inter-modulation. 
     
     
         5 . The system as recited in  claim 1  wherein the nonlinear processor generates both even and odd harmonics. 
     
     
         6 . The system as recited in  claim 1  wherein the nonlinear processor is designed as a fifth order polynomial. 
     
     
         7 . The system as recited in  claim 2  wherein the output path from the nonlinear processor to the output mixer does not include a low pass filter. 
     
     
         8 . The system as recited in  claim 1  wherein the system filters out low frequency signals from the audio input signal by subtracting the output of the low frequency extractor from the audio input signal. 
     
     
         9 . The system as recited in  claim 2  wherein the loudness matching is performed by a loudness compressor. 
     
     
         10 . The system as recited in  claim 9  wherein the loudness compressor operates on a high pass filtered output from the nonlinear processor. 
     
     
         11 . The system as recited in  claim 2  configured to adjust the harmonic decay rate optionally by controlling the adaptive adjustor of harmonic decay pattern or by altering the coefficients of the nonlinear processor. 
     
     
         12 . The system as recited in  claim 2  wherein the audio signal comprises at least a first and second channel and the output mixer comprises a first and second channel output mixer, and wherein the low frequency extraction is applied to a combination of the first and second channels and the harmonics passed by the high pass filter are added to both the first and second output mixers. 
     
     
         13 . A method for enhancing bass perception from an audio signal, the method comprising:
 extracting the low frequency components from the audio signal;   adjusting the harmonic decay pattern adaptively; and   generating harmonic signals using a nonlinear processing method that controls inter-modulation to remain below a threshold value.   
     
     
         14 . The method recited in  claim 13  further comprising compensating the loudness of the desired harmonic signals to match the loudness of the original extracted low frequency signal. 
     
     
         15 . A computer program product for enhancing bass perception of an audio signal reproducible on a loudspeaker in a listening space, the computer program product being embodied in a non-transitory computer readable medium and comprising computer executable instructions for:
 receiving the audio signal;   extracting the low frequency components from the audio signal;   adjusting the harmonic decay pattern adaptively; and   
       generating harmonic signals using a nonlinear processing method that controls inter-modulation to remain below a threshold value.