AnalyserNode: smoothingTimeConstant property

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.

ThesmoothingTimeConstant property of theAnalyserNode interface is a double value representing the averaging constant with the last analysis frame. It's basically an average between the current buffer and the last buffer theAnalyserNode processed, and results in a much smoother set of value changes over time.

Value

A double within the range0 to1 (0 meaning no time averaging). The default value is0.8.

If 0 is set, there is no averaging done, whereas a value of 1 means "overlap the previous and current buffer quite a lot while computing the value", which essentially smooths the changes acrossAnalyserNode.getFloatFrequencyData/AnalyserNode.getByteFrequencyData calls.

In technical terms, we apply aBlackman window and smooth the values over time. The default value is good enough for most cases.

Note:If a value outside the range 0–1 is set, anINDEX_SIZE_ERR exception is thrown.

Examples

The following example shows basic usage of anAudioContext to create anAnalyserNode, thenrequestAnimationFrame and<canvas> to collect frequency data repeatedly and draw a "winamp bar graph style" output of the current audio input.For more complete applied examples/information, check out ourVoice-change-O-matic demo (seeapp.js lines 108–193 for relevant code).

If you are curious about the effect thesmoothingTimeConstant() has, try cloning the above example and settinganalyser.smoothingTimeConstant = 0; instead. You'll notice that the value changes are much more jarring.

const audioCtx = new AudioContext();const analyser = audioCtx.createAnalyser();analyser.minDecibels = -90;analyser.maxDecibels = -10;analyser.smoothingTimeConstant = 0.85;// …analyser.fftSize = 256;const bufferLength = analyser.frequencyBinCount;console.log(bufferLength);const dataArray = new Uint8Array(bufferLength);canvasCtx.clearRect(0, 0, WIDTH, HEIGHT);function draw() {  drawVisual = requestAnimationFrame(draw);  analyser.getByteFrequencyData(dataArray);  canvasCtx.fillStyle = "rgb(0 0 0)";  canvasCtx.fillRect(0, 0, WIDTH, HEIGHT);  const barWidth = (WIDTH / bufferLength) * 2.5;  let barHeight;  let x = 0;  for (let i = 0; i < bufferLength; i++) {    barHeight = dataArray[i];    canvasCtx.fillStyle = `rgb(${barHeight + 100} 50 50)`;    canvasCtx.fillRect(x, HEIGHT - barHeight / 2, barWidth, barHeight / 2);    x += barWidth + 1;  }}draw();