Web/API/PeriodicWave

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 object 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 methods.

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 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. <math display="inline">\left( {a + bi} \right)e^{i},\left( {c + di} \right)e^{2i},\left( {f + gi} \right)e^{3i}</math>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 APIThe definition of 'PeriodicWave' in that specification.	Working Draft

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`PeriodicWave`	Chrome Full support 14	Edge Full support ≤18	Firefox Full support 25	IE No support No	Opera Full support 15	Safari Full support 6	WebView Android Full support Yes	Chrome Android Full support 18	Firefox Android Full support 26	Opera Android Full support 14	Safari iOS Full support Yes	Samsung Internet Android Full support 1.0
`PeriodicWave()` constructor	Chrome Full support 55 Notes' Full support 55 Notes' Notes' Before Chrome 59, the default values were not supported.	Edge Full support ≤79	Firefox Full support 53	IE No support No	Opera Full support 42	Safari ?	WebView Android Full support 55 Notes' Full support 55 Notes' Notes' Before Chrome 59, the default values were not supported.	Chrome Android Full support 55 Notes' Full support 55 Notes' Notes' Before Chrome 59, the default values were not supported.	Firefox Android Full support 53	Opera Android Full support 42	Safari iOS ?	Samsung Internet Android Full support 6.0 Notes' Full support 6.0 Notes' Notes' Before Samsung Internet 7.0, the default values were not supported.

Legend

Full support: Full support
No support: No support
Compatibility unknown: Compatibility unknown
See implementation notes.': See implementation notes.