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DSP System Toolbox

Audio Special Effects

This example shows three audio effects applied to music read from a file: flanging, reverberation, and the simulation of synthetic stereo from a mono source.

Some of the concepts shown by this model include:

  • Demonstration of audio sound effects

  • Easy and intuitive implementation of sound effects using DSP System Toolbox™ blocks

  • Implementation of control flow for a model using subsystems, masks, and the Simulink® Switch Case and Switch Case Action blocks

Exploring the Example

Select a sound effect by setting the Audio effect parameter of the Effect block. Run the example. Listen to the original sound or the enhanced sound by using the switch before the 'To Audio Device' block. Change the Audio effect parameter and listen to the difference.

The Example Model

Right-click the Effect block, select "Mask" and click "Look Under Mask"

There are three action subsystems. Each implements one of the three effects. The active subsystem is controlled by a Simulink Switch Case block. The Effect parameter of the parent block drives the switch, which in turn activates one of the three audio effects subsystems.

To view the implementation of an effect, double-click on its subsystem. The contents of each subsystem are shown below.


Flanging is a time-based audio effect created by mixing a signal with a delayed version of itself. The amount of delay is time-varying. In the example, this is accomplished by using the DSP System Toolbox™ Variable Fractional Delay block. Use a time-varying signal on the block's optimal Delay port to create a time-varying flanging effect.


Reverberation is a property of sound in an enclosed space such as an auditorium. Reflections of the sound source from various surfaces create multiple echoes of lesser magnitude that decay in time.

A simple but effective means of simulating reverberation is a feedback loop. The feedback loop is recognized as a single-pole IIR filter. You can modify the parameters of each block to change the characteristics of the reverberation.

Synthetic Stereo

One way of creating the sensation of stereo from a mono source is to add a delayed version of the signal to itself. This is shown in the Stereo subsystem.


More information on audio effects can be found on the Harmony Central website.