OscillatorNode.setPeriodicWave()

The setPeriodicWave() method of the OscillatorNode interface is used to point to a PeriodicWave defining a periodic waveform that can be used to shape the oscillator's output, when type = "custom" is used.

Syntax

var oscillator = audioCtx.createOscillator();
oscillator.setPeriodicWave(wave);

Returns

void.

Example

The following example illustrates simple usage of createPeriodicWave(), recreating a sine wave from a periodic wave.

var real = new Float32Array(2);
var imag = new Float32Array(2);
var ac = new AudioContext();
var osc = ac.createOscillator();

real[0] = 0;
imag[0] = 0;
real[1] = 1;
imag[1] = 0;

var wave = ac.createPeriodicWave(real, imag);

osc.setPeriodicWave(wave);

osc.connect(ac.destination);

osc.start();
osc.stop(2);

This works because a sound that contains only a fundamental tone is by definition a sine wave.

Here, we create a Periodic Wave with two values. The first value is the DC offset, which is the value at which the oscillator starts. 0 is good here, because we want to start the curve at the middle of the [-1.0; 1.0] range.

The second and subsequent values are sine and cosine components. You can think of it as the result of a Fourier transform, where you get frequency domain values from time domain value. Here, with createPeriodicWave(), you specify the frequencies, and the browser performs a an inverse Fourier transform to get a time domain buffer for the frequency of the oscillator. Here, we only set one component at full volume (1.0) on the fundamental tone, so we get a sine wave.

Parameters

periodicWave

The PeriodicWave object you want to use to shape the oscillator's output.

Specifications

Browser compatibility

See also

• Using the Web Audio API