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Modeling guitar distortion in Matlab

Module by: Brent Stephens, Neil Narayan, Rob Smith, Barron Stone. E-mail the authors

Summary: An implementation of distortion in Matlab

A very simple type of guitar distortion can be done with clipping of the signal. This is where a threshold value is set, and if the signal ever increases above this value, it is clipped off. This type of distortion adds a "fuzzy" sounding distortion. As is obvious from the picture of the frequency-domain effects of clipping, clipping the signal creates a more complex signal by adding more frequencies.

Figure 1: A picture of a sine wave after it has been processed with the Matlab function below
Distorted Sine Wave
Distorted Sine Wave (clippedsine.png)
Figure 2
FFT of a distorted sine wave
FFT of a distorted sine wave (fftafterdistortion.png)

The Matlab code that implements this algorithm is also very simple:

function [output]=fuzzy(sound, amount)

norms = norm(sound);
output = sound/norms;
amount = (1- amount)/100;

for i = 1:length(output)
    
  
  if ( output(i) > amount )
    output(i) = amount;
  end

  if ( output(i) < -amount)
     output(i) = -amount;
  end
 
end
 
output = output*norms;

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