OscillatorNode
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
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.
| Number of inputs | 0 |
|---|---|
| Number of outputs | 1 |
| Channel count mode | max |
| Channel count | 2 (not used in the default count mode) |
| Channel interpretation | speakers |
Constructor
OscillatorNode()-
Creates a new instance of an
OscillatorNodeobject, optionally providing an object specifying default values for the node's properties. As an alternative, you can use theBaseAudioContext.createOscillator()factory method; see Creating an AudioNode.
Instance properties
Also inherits properties from its parent, AudioScheduledSourceNode.
OscillatorNode.frequency-
An a-rate
AudioParamrepresenting the frequency of oscillation in hertz (though theAudioParamreturned 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
AudioParamrepresenting detuning of oscillation in cents (though theAudioParamreturned 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
customto use aPeriodicWaveto describe a custom waveform. Different waves will produce different tones. Standard values are"sine","square","sawtooth","triangle"and"custom". The default is"sine".
Instance methods
Also inherits methods from its parent, AudioScheduledSourceNode.
OscillatorNode.setPeriodicWave()-
Sets a
PeriodicWavewhich describes a periodic waveform to be used instead of one of the standard waveforms; calling this sets thetypetocustom. AudioScheduledSourceNode.start()-
Specifies the exact time to start playing the tone.
AudioScheduledSourceNode.stop()-
Specifies the time to stop playing the tone.
Events
Also inherits events from its parent, AudioScheduledSourceNode.
Examples
Using an OscillatorNode
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 const audioCtx = new AudioContext(); // create Oscillator node const oscillator = audioCtx.createOscillator(); oscillator.type = "square"; oscillator.frequency.setValueAtTime(440, audioCtx.currentTime); // value in hertz oscillator.connect(audioCtx.destination); oscillator.start(); Different oscillator node types
The four built-in oscillator types are sine, square, triangle and sawtooth. They are the shape of the waveform generated by an oscillator. Fun fact: These are the defaults for most synths because they are waveforms which are easy to generate electronically. This example visualizes the waveforms for the different types at different frequencies.
<div class="controls"> <label for="type-select"> Oscillator type <select id="type-select"> <option>sine</option> <option>square</option> <option>triangle</option> <option>sawtooth</option> </select> </label> <label for="freq-range"> Frequency <input type="range" min="100" max="800" step="10" value="250" id="freq-range" /> </label> <button data-playing="init" id="play-button">Play</button> </div> <canvas id="wave-graph"></canvas> The code is in two parts: in the first part, we set up the sound stuff.
const typeSelect = document.getElementById("type-select"); const frequencyControl = document.getElementById("freq-range"); const playButton = document.getElementById("play-button"); const audioCtx = new AudioContext(); const osc = new OscillatorNode(audioCtx, { type: typeSelect.value, frequency: frequencyControl.valueAsNumber, }); // Rather than creating a new oscillator for every start and stop // which you would do in an audio application, we are just going // to mute/un-mute for demo purposes - this means we need a gain node const gain = new GainNode(audioCtx); const analyser = new AnalyserNode(audioCtx, { fftSize: 1024, smoothingTimeConstant: 0.8, }); osc.connect(gain).connect(analyser).connect(audioCtx.destination); typeSelect.addEventListener("change", () => { osc.type = typeSelect.value; }); frequencyControl.addEventListener("input", () => { osc.frequency.value = frequencyControl.valueAsNumber; }); playButton.addEventListener("click", () => { if (audioCtx.state === "suspended") { audioCtx.resume(); } if (playButton.dataset.playing === "init") { osc.start(audioCtx.currentTime); playButton.dataset.playing = "true"; playButton.innerText = "Pause"; } else if (playButton.dataset.playing === "false") { gain.gain.linearRampToValueAtTime(1, audioCtx.currentTime + 0.2); playButton.dataset.playing = "true"; playButton.innerText = "Pause"; } else if (playButton.dataset.playing === "true") { gain.gain.linearRampToValueAtTime(0.0001, audioCtx.currentTime + 0.2); playButton.dataset.playing = "false"; playButton.innerText = "Play"; } }); As for the second part, we draw the waveform on a canvas using the AnalyserNode we created above.
const dpr = window.devicePixelRatio; const w = 500 * dpr; const h = 300 * dpr; const canvasEl = document.getElementById("wave-graph"); canvasEl.width = w; canvasEl.height = h; const canvasCtx = canvasEl.getContext("2d"); const bufferLength = analyser.frequencyBinCount; const dataArray = new Uint8Array(bufferLength); analyser.getByteTimeDomainData(dataArray); // draw an oscilloscope of the current oscillator function draw() { analyser.getByteTimeDomainData(dataArray); canvasCtx.fillStyle = "white"; canvasCtx.fillRect(0, 0, w, h); canvasCtx.lineWidth = 4.0; canvasCtx.strokeStyle = "black"; canvasCtx.beginPath(); const sliceWidth = (w * 1.0) / bufferLength; let x = 0; for (let i = 0; i < bufferLength; i++) { const v = dataArray[i] / 128.0; const y = (v * h) / 2; if (i === 0) { canvasCtx.moveTo(x, y); } else { canvasCtx.lineTo(x, y); } x += sliceWidth; } canvasCtx.lineTo(w, h / 2); canvasCtx.stroke(); requestAnimationFrame(draw); } draw(); Warning: This example makes a noise!
Specifications
| Specification |
|---|
| Web Audio API # OscillatorNode |