Web/API/BaseAudioContext/createPeriodicWave

The createPeriodicWave() method of the BaseAudioContext Interface is used to create a PeriodicWave, which is used to define a periodic waveform that can be used to shape the output of an OscillatorNode.

Syntax

var wave = AudioContext.createPeriodicWave(real, imag[, constraints]);

Returns

A PeriodicWave.

Parameters

real: An array of cosine terms (traditionally the A terms).
imag: An array of sine terms (traditionally the B terms).

The real and imag arrays have to have the same length, otherwise an error is thrown.

constraints Optional: An dictionary object that specifies whether normalization should be disabled (if not specified, normalization is enabled by default.) It takes one property:

disableNormalization

If set to true, normalization is disabled for the periodic wave. The default is false.

If normalized, the resulting wave will have a maximum absolute peak value of 1.

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 'createPeriodicWave' 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
`createPeriodicWave`	Chrome Full support 59 Notes' Full support 59 Notes' Notes' Default values supported Full support 57 Full support 10 Prefixed' Prefixed' Implemented with the vendor prefix: webkit	Edge Full support ≤18	Firefox Full support 53 Notes' Full support 53 Notes' Notes' Originally implemented on `AudioContext` in Firefox 25.	IE No support No	Opera Full support 22 Full support 22 Full support 15 Prefixed' Prefixed' Implemented with the vendor prefix: webkit	Safari Full support 6 Prefixed' Full support 6 Prefixed' Prefixed' Implemented with the vendor prefix: webkit	WebView Android Full support 59 Notes' Full support 59 Notes' Notes' Default values supported Full support 57 Full support 4.4.3 Prefixed' Prefixed' Implemented with the vendor prefix: webkit	Chrome Android Full support 59 Notes' Full support 59 Notes' Notes' Default values supported Full support 57 Full support 33 Prefixed' Prefixed' Implemented with the vendor prefix: webkit	Firefox Android Full support 53 Notes' Full support 53 Notes' Notes' Originally implemented on `AudioContext` in Firefox Android 26.	Opera Android Full support 22 Full support 22 Full support 14 Prefixed' Prefixed' Implemented with the vendor prefix: webkit	Safari iOS Full support 6 Prefixed' Full support 6 Prefixed' Prefixed' Implemented with the vendor prefix: webkit	Samsung Internet Android Full support 7.0 Notes' Full support 7.0 Notes' Notes' Default values supported Full support 7.0 Full support 2.0 Prefixed' Prefixed' Implemented with the vendor prefix: webkit
Possible to disable normalisation	Chrome Full support Yes	Edge Full support ≤18	Firefox No support No	IE No support No	Opera ?	Safari No support No	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android No support No	Opera Android ?	Safari iOS No support No	Samsung Internet Android Full support Yes

Legend

Full support: Full support
No support: No support
Compatibility unknown: Compatibility unknown
See implementation notes.': See implementation notes.
Requires a vendor prefix or different name for use.': Requires a vendor prefix or different name for use.