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 theAudioContext.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. 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
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
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
| Edge Full support ≤79 | Firefox Full support 53 | IE No support No | Opera Full support 42 | Safari ? | WebView Android
Full support
55
| Chrome Android
Full support
55
| Firefox Android Full support 53 | Opera Android Full support 42 | Safari iOS ? | Samsung Internet Android
Full support
6.0
|
Legend
- Full support
- Full support
- No support
- No support
- Compatibility unknown
- Compatibility unknown
- See implementation notes.
- See implementation notes.