BaseAudioContext: createPeriodicWave() method
=============================================

 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
------


```js
createPeriodicWave(real, imag)
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`.



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

### Return value

A `PeriodicWave`.

Examples
--------

 The following example illustrates simple usage of `createPeriodicWave()`, to
 create a `PeriodicWave` object containing a simple sine wave.


```js
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, { 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. Bear in mind the
 fundamental tone is the oscillator's frequency (which, by default, is 440 Hz).
 Thus, by altering the oscillator's frequency we are in effect shifting the frequency
 of this periodic wave along with it.

 The coefficients of the Fourier transform should be given in *ascending* order
 (i.e. 


(

a
+
b
i

)

e
i

,

(

c
+
d
i

)

e

2
i

,

(

f
+
g
i

)

e

3
i

 \left(a+bi\right)e^{i} , \left(c+di\right)e^{2i} ,
 \left(f+gi\right)e^{3i} 


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 |
| --- |
| Web Audio API # dom-baseaudiocontext-createperiodicwave |

Browser compatibility
---------------------

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See also
--------

* Using the Web Audio API