5.4 Matlab eq: approach: time-domain and effects

Approach: time-domain and effects

Once the Inverse Fast Fourier Transform (IFFT) has taken place, we are able to apply our time-domain effects: Reverb, Flange, and Distortion. When the effects have been implemented, we then output our modified signal into a plot where we are able to analyze the new spectrum of our signal. The last two effects, Gain and Volume, are included at the end.

Flange

Flanging is another time-domain audio effect which happens when two audio signals are mixed together, with the requirement that one of the signals is time-delayed by a very small amount of time. An analogy we like is the simultaneous playing of two tape recorders playing the same track. Then if we pause one of them for a small amount of time and then hit play, the combined audio of the two tape recorders is flanging.

In our coding, we used 15 refresh periods.

Reverb

By definition, reverberation is the lingering of sound in a given space once the original sound is removed. It is not necessarily termed “echo” as reverb is the decay of a large number of echoes when the sound is absorbed. Thus, once the sound signal stops, the reverberated reflections carry on and gradually decrease in amplitude until they zero out.

In our implementation, we used 15 consecutive refresh periods. This wasn’t incredibly realistic as we could have modified our design to produce a better reverb, but this allowed our program to function smoothly without memory overflows in MATLAB.

The main visual difference between flange and reverb was the persistence of sound once the song/audio clip ended.

Distortion

A distortion that we introduced in our equalizer can also be referred to as “audio clipping” as we cut off signals above a certain amplitude.

This is also called hard clipping. Distortion is usually an unwanted effect except in music, such as Gabber (150-220 beats-per-minute hardcore techno) or as an electric guitar effect.

In order to guarantee a visual representation, we went ahead and clipped our signals at the 0.5 mark in amplitude.

Gain

In our equalizer, we implemented a gain control which provided for the increase of our input signal’s amplitude for a given frequency band. We had 10 frequency bands of which we could modify the gain levels.

Volume

Volume is the implementation of gain for all frequencies.