# 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]);

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