MDN’s new design is in Beta! A sneak peek: https://blog.mozilla.org/opendesign/mdns-new-design-beta/

The PeriodicWave interface defines a periodic waveform that can be used to shape the output of an OscillatorNode.

PeriodicWave has no inputs or outputs; it is used to define custom oscillators when calling OscillatorNode.setPeriodicWave(). The PeriodicWave itself is created/returned by AudioContext.createPeriodicWave().

Constructor

PeriodicWave.PeriodicWave()
Creates a new PeriodicWave instance using the default values for all properties. If you wish to establish custom property values at the outset, use the AudioContext.createPeriodicWave() factory method instead.

Properties

None; also, PeriodicWave doesn't inherit any properties.

Methods

None; also, PeriodicWave doesn't inherit any properties.

Example

The following example illustrates simple usage of createPeriodicWave(), to create a PeriodicWave object containing a simple sine 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, {disableNormalization: true});

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 PeriodicWave 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.

The coefficients of the Fourier transform should be given in ascending order (i.e. (a+bi)ei,(c+di)e2i,(f+gi)e3i\left(a+bi\right)e^{i} , \left(c+di\right)e^{2i} , \left(f+gi\right)e^{3i}   etc.) and can be positive or negative.  A simple way of manually obtaining such coefficients (though not the best) is to use a graphing calculator.

Specifications

Specification Status Comment
Web Audio API
The definition of 'PeriodicWave' in that specification.
Working Draft  

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 10.0webkit (Yes) 25.0 (25.0)  No support 15.0webkit
22 (unprefixed)
6.0webkit
Constructor (Yes) ? No support No support ? No support
Feature Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support ? (Yes) 25.0 (25.0) ? ? ? 33.0
Constructor No support ? No support No support ? No support (Yes)

See also

Document Tags and Contributors

 Contributors to this page: Sheppy, abbycar, chrisdavidmills, teoli
 Last updated by: Sheppy,