Method and apparatus for audio signal processing

Abstract

A sampled digital audio signal is displayed on a spectrogram, in terms of frequency vs. time. An unwanted noise in the signal is visible in the spectrogram and the portion of the signal containing the unwanted noise can be selected using time and frequency constraints. An estimate for the signal within the selected portion is then interpolated on the basis of desired portions of the signal outside the time constraints defining the selected portion. The interpolated estimate can then be used to attenuate or remove the unwanted sound

1 . A method for audio signal processing comprising:
 displaying a spectrogram representing a recorded audio signal;   selecting a region on the spectrogram representing a selected portion of the audio signal, the selected portion of the audio signal being constrained in time and frequency, and the selected portion of the audio signal containing an unwanted sound; and   replacing the selected portion of the audio signal such that the unwanted sound is attenuated or removed.   
     
     
         2 . The method according to  claim 1 , wherein replacing the selected portion of the audio signal comprises utilising a further portion of the audio signal outside the selected region on the spectrogram. 
     
     
         3 . The method according to  claim 1 , wherein the selected portion of the audio signal is constrained between two selected times. 
     
     
         4 . The method according to  claim 1 , wherein the selected portion of the audio signal is constrained between two selected frequencies. 
     
     
         5 . The method according to  claim 1 , wherein the region on the spectrogram is in the form of a rectangle. 
     
     
         6 . The method according to  claim 1 , wherein the region on the spectrogram is in the form of a non-rectangular shape. 
     
     
         7 . The method according to  claim 1 , further comprising selecting an additional region on the spectrogram for use in replacing the selected portion of the audio signal. 
     
     
         8 . The method according to  claim 1 , further comprising displaying a revised spectrogram after the unwanted sound has been attenuated or removed. 
     
     
         9 . The method according to  claim 1 , wherein selecting the region on the spectrogram comprises selecting one or more subregions on the spectrogram representing a corresponding one or more subportions of the selected portion of the audio signal, the one or more subportions of the selected portion of the audio signal containing a corresponding one or more subparts of the unwanted sound. 
     
     
         10 . The method according to  claim 1 , wherein the audio signal outside the selected portion of the audio signal is not adversely affected. 
     
     
         11 . The method according to  claim 1 , wherein the audio signal outside the selected portion of the audio signal is affected. 
     
     
         12 . The method according to  claim 1 , wherein replacing the selected portion of the audio signal comprises replacing the selected portion of the audio signal with replacement audio. 
     
     
         13 . The method according to  claim 2 , wherein replacing the selected portion of the audio signal comprises replacing the selected portion of the audio signal with an interpolated estimate. 
     
     
         14 . The method according to  claim 13 , wherein the interpolated estimate is constrained to converge to a chosen template signal. 
     
     
         15 . The method according to  claim 13 , wherein interpolating the estimate comprises simultaneously interpolating two or more selected subportions of the audio signal. 
     
     
         16 . The method according to  claim 1 , wherein replacing the selected portion of the audio signal comprises replacing the selected portion of the audio signal with a template signal. 
     
     
         17 . The method according to  claim 1 , wherein the audio signal is a digital audio signal. 
     
     
         18 . The method according to  claim 17 , wherein the spectrogram is used to define a set of samples to be replaced. 
     
     
         19 . The method according to  claim 1 , further comprising selecting at least one additional region on the spectrogram representing a corresponding at least one additional portion of the audio signal, each of the at least one additional portion of the audio signal containing a respective unwanted sound of a corresponding at least one additional unwanted sound. 
     
     
         20 . The method according to  claim 19 , wherein one or more of the at least one additional unwanted sound is a harmonic of the unwanted sound. 
     
     
         21 . A method for audio signal processing comprising:
 displaying a spectrogram representing a digitally-recorded audio signal;   selecting a region on the spectrogram representing a selected portion of the digitally-recorded audio signal, the selected portion of the digitally-recorded audio signal being constrained in time and being constrained in frequency, and the selected portion of the digitally-recorded audio signal containing an unwanted sound; and   attenuating or removing the unwanted sound within the selected portion of the digitally-recorded audio signal.   
     
     
         22 . A computer program for implementing the method defined in any of  claim 1 . 
     
     
         23 . A computer program for implementing the method of  claim 21 .