This example shows how to apply a flanging effect and a stereo panning effect to an audio stream. A User Interface (UI) is used to control the audio effects. This interface plays the audio stream that contains the flanging and stereo panning effects. It displays the spectrograms of original and flanging audio streams.
This example also shows you how to process a continuous stream of data in MATLAB®. Processing frames of data avoids having to load the complete data at one time.
Flanging, or "whooshing" sound is a type of phasing effect. To create it, you add the input signal to its delayed version while varying the delay over time. The following figure shows a block diagram implementation of flanging.
The stereo panner adds the effect of the audio signal moving from one speaker to the other.
See more information on audio effects [ 1 ].
audioFlangerExampleApp is the function containing the algorithm's implementation. It instantiates, initializes and steps through the components forming the algorithm.
Execute audioFlangerExampleApp to run the simulation and plot the results on scopes. Note that the simulation runs for as long as the user does not explicitly stop it.
audioFlangerExampleApp launches a User Interface (UI) designed to interact with the simulation. The UI allows you to tune parameters and the results are reflected in the simulation instantly. For example, moving the slider for the 'Frequency of delay for flanging' to the right while the simulation is running, increases the frequency of the sine wave used to change the variable fractional delay over time. Similarly, moving the slider for the 'Stereo Panning' moves the audio signal from one speaker to the other. For more information on the UI, please refer to HelperCreateParamTuningGUI.
There are three buttons on the UI - The 'Reset' button resets the state of the variable fractional delay to its initial condition. 'Pause simulation' will hold the simulation until you press it again. 'Stop simulation' ends the simulation.
We can clearly see the frequency changing over time in the spectrogram of the audio signal with flanging.
This example shows you how to implement the flanging audio effect using variable fractional delay applied to streaming data.
DAFX: Digital Audio Effects, edited by Udo Zölzer, John Wiley & Sons, 2002.