OscillatorNode - Web APIs 编辑

The OscillatorNode interface represents a periodic waveform, such as a sine wave. It is an AudioScheduledSourceNode audio-processing module that causes a specified frequency of a given wave to be created—in effect, a constant tone.

An OscillatorNode is created using the BaseAudioContext.createOscillator() method. It always has exactly one output and no inputs. Its basic property defaults (see AudioNode for definitions) are:

Constructor

OscillatorNode()

Creates a new instance of an OscillatorNode object, optionally providing an object specifying default values for the node's properties.  If the default values are acceptable, you can call the BaseAudioContext.createOscillator() factory method.

Properties

Inherits properties from its parent, AudioScheduledSourceNode, and adds the following properties:

OscillatorNode.frequency

An a-rate AudioParam representing the frequency of oscillation in hertz (though the AudioParam returned is read-only, the value it represents is not). The default value is 440 Hz (a standard middle-A note).

OscillatorNode.detune

An a-rate AudioParam representing detuning of oscillation in cents (though the AudioParam returned is read-only, the value it represents is not). The default value is 0.

OscillatorNode.type

A string which specifies the shape of waveform to play; this can be one of a number of standard values, or custom to use a PeriodicWave to describe a custom waveform. Different waves will produce different tones. Standard values are "sine", "square", "sawtooth", "triangle" and "custom". The default is "sine".

Event handlers

OscillatorNode.onended

Sets the event handler for the ended event, which fires when the tone has stopped playing.

Methods

Inherits methods from its parent, AudioScheduledSourceNode, and adds the following:

OscillatorNode.setPeriodicWave()

Sets a PeriodicWave which describes a periodic waveform to be used instead of one of the standard waveforms; calling this sets the type to custom. This replaces the now-obsolete OscillatorNode.setWaveTable() method.

OscillatorNode.start()

Specifies the exact time to start playing the tone.

OscillatorNode.stop()

Specifies the time to stop playing the tone.

Examples

The following example shows basic usage of an AudioContext to create an oscillator node and to start playing a tone on it. For an applied example, check out our Violent Theremin demo (see app.js for relevant code).

// create web audio api context
var audioCtx = new (window.AudioContext || window.webkitAudioContext)();

// create Oscillator node
var oscillator = audioCtx.createOscillator();

oscillator.type = 'square';
oscillator.frequency.setValueAtTime(440, audioCtx.currentTime); // value in hertz
oscillator.connect(audioCtx.destination);
oscillator.start();

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Using the Web Audio API