Modeling guitar distortion in Matlab

Module by: Brent Stephens, Neil Narayan, Rob Smith, Barron Stone

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

Figure 2

FFT of a distorted sine wave

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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This work is licensed by Brent Stephens, Neil Narayan, Rob Smith, and Barron Stone under a Creative Commons Attribution License (CC-BY 2.0).

Last edited by Rob Smith on Dec 20, 2006 4:21 pm US/Central.