DSP Audio Effects Project

Distortion is a non-linear audio effect that changes the shape of a sound wave or content of a signal. Usually, distortion is consequence of imperfect conditions or equipment and is unwanted and degrading to the sound. However, it can be used to enhance certain sounds to improve the overall quality of a piece. The most common use of distortion as an enhancer can be found in rock music, specifically applied to guitars. This type of distortion changes the amplitude of the signal to make it sound less crisp and clear. There are many ways to implement various types of distortion into a signal, but we chose to use two functions, (atan (1) and tanh (2) ). In this way, the signal is used as an input of the function, and then multiplied by a gain factor, and the output is a distorted version of the original signal, with variable gain to determine how much distortion is applied. Both of these functions are soft limiter distortion functions. Another approach we found is  to use a function like equation 3 below. Using the atan and tanh functions, the output is the sound with distortion added. Using the exponential, the output is purely distortion so to get a distorted version of the original signal this output should be scaled and added to it.   

 

For the first 2 equations C1 is a constant that will control the amplitude and consequently the volume of the output. Additionally, C2 is a gain constant that will change the amount of distortion that is added to the original signal. This provides a variability to change just how much distortion is applied to the input signal. The constant C, in equation 3, acts in the same way as C2, in that it controls the amount of distortion applied to the signal.