files/en-us/web/api/oscillatornode/setperiodicwave/index.md
{{ APIRef("Web Audio API") }}
The setPeriodicWave() method of the {{domxref("OscillatorNode")}} interface is used to point to a {{domxref("PeriodicWave")}}
defining a periodic waveform that can be used to shape the oscillator's output, when
{{domxref("OscillatorNode.type", "type")}} is custom.
setPeriodicWave(wave)
wave
None ({{jsxref("undefined")}}).
The following example illustrates simple usage of createPeriodicWave(),
recreating a sine wave from a periodic wave.
const real = new Float32Array(2);
const imag = new Float32Array(2);
const ac = new AudioContext();
const osc = ac.createOscillator();
real[0] = 0;
imag[0] = 0;
real[1] = 1;
imag[1] = 0;
const wave = ac.createPeriodicWave(real, imag);
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 {{domxref("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.
{{Specifications}}
{{Compat}}