System and method for narrow bandwidth digital signal processing

Abstract

The present invention provides methods and systems for narrow bandwidth digital processing of an input audio signal. Particularly, the present invention includes a high pass filter configured to filter the input audio signal. A first compressor then modulates the filtered signal in order to create a partially processed signal. In some embodiments, a clipping module further limits the gain of the partially processed signal. A splitter is configured to split the partially processed signal into a first signal and a second signal. A low pass filter is configured to filter the first signal. A pass through module is configured to adjust the gain of the second signal. A mixer then combines the filtered first signal and the gain-adjusted second signal in order to output a combined signal. In some embodiments, a tone control module further processes the combined signal, and a second compressor further modulates the processed signal.

What is claimed is: 
     
         1 . A system for narrow bandwidth digital signal processing comprising:
 a splitter configured to split the an least partially processed audio signal into a first signal and a second signal;   a low pass filter configured to filter said first signal;   a pass through module configured to adjust a gain of said second signal; and   a second processing module configured to process said filtered first signal and said gain-adjusted second signal to create an output signal, said second processing module including at least a mixer configured to combine said filtered first signal and said gain-adjusted second signal, creating a combined signal.   
     
     
         2 . The system as recited in  claim 1  wherein said second processing module comprises a tone control module configured to process said combined signal, creating a controlled signal; and a second compressor configured to modulate said controlled signal to create an output signal. 
     
     
         3 . A system as recited in  claim 1  further comprising a first processing module including a first compressor configured to modulate an input audio signal, creating said partially processed signal. 
     
     
         4 . A system as recited in  claim 3  wherein said first processing module further comprises a clipping module configured to adjust the gain of said modulated signal, creating said partially processed signal. 
     
     
         5 . A system as recited in  claim 3  further comprising a high pass filter configured to filter said input audio signal to create a filtered signal based on a first frequency. 
     
     
         6 . A system as recited in  claim 5  wherein said first frequency is tunable. 
     
     
         7 . A system as recited in  claim 5  wherein said first frequency is selected from the range between 2.5 kHz and 3.2 kHz. 
     
     
         8 . A system as recited in  claim 1  wherein said low pass filter is configured to filter said first signal based on a second frequency. 
     
     
         9 . A system as recited in  claim 8  wherein said second frequency is tunable. 
     
     
         10 . A system as recited in  claim 8  wherein said second frequency is lower than said first frequency. 
     
     
         11 . A system as recited in  claim 8  wherein said second frequency is selected from the range between 700 Hz and 1000 Hz. 
     
     
         12 . A system as recited in  claim 2  wherein said tone control module comprises a parametric equalizer. 
     
     
         13 . A method for narrow bandwidth digital signal processing of an input audio signal comprising:
 processing the input audio signal with a pre-transmission module, creating a partially processed signal;   transmitting the partially processed signal to a receiver;   splitting the received signal into a first signal and a second signal;   filtering the first signal to create a filtered first signal;   adjusting the gain of the second signal to create a gain-adjusted second signal;   combining the filtered first signal and gain-adjusted second signal to create a combined signal; and   modulating the controlled signal to create an output signal.   
     
     
         14 . The method as recited in  claim 13  further comprising filtering the input audio signal to create a filtered signal; processing the filtered signal to create the partially processed signal. 
     
     
         15 . The method as recited in  claim 14  further comprising modulating the filtered signal with a first compressor to create a modulated signal. 
     
     
         16 . The method as recited in  claim 15  further comprising adjusting the gain of the modulated signal to create the partially processed signal. 
     
     
         17 . A system as recited in  claim 13  further comprising filtering the input audio signal using a high pass filter based on a first frequency, creating a first signal. 
     
     
         18 . The method as recited in  claim 17  wherein the first frequency is selected from the range between 2.5 kHz and 3.2 kHz. 
     
     
         19 . A system as recited in  claim 17  further comprising filtering the first signal with a low pass filter configured to filter the first signal based on a second frequency. 
     
     
         20 . A system as recited in  claim 19  wherein the second frequency is lower than the first frequency.