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DynamicsCompressorNode.attack

The attack property of the DynamicsCompressorNode interface is a k-rate AudioParam representing the amount of time, in seconds, required to reduce the gain by 10 dB. It defines how quickly the signal is adapted when its volume is increased.

The attack property's default value is 0.003 and it can be set between 0 and 1.

Syntax

var audioCtx = new AudioContext();
var compressor = audioCtx.createDynamicsCompressor();
compressor.attack.value = 0;

Value

An AudioParam.

Note: Though the AudioParam returned is read-only, the value it represents is not.

Example

The below code demonstrates a simple usage of createDynamicsCompressor() to add compression to an audio track. For a more complete example, have a look at our basic Compressor example (view the source code).

// Create a MediaElementAudioSourceNode
// Feed the HTMLMediaElement into it
var source = audioCtx.createMediaElementSource(myAudio);

// Create a compressor node
var compressor = audioCtx.createDynamicsCompressor();
compressor.threshold.value = -50;
compressor.knee.value = 40;
compressor.ratio.value = 12;
compressor.reduction.value = -20;
compressor.attack.value = 0;
compressor.release.value = 0.25;

// connect the AudioBufferSourceNode to the destination
source.connect(audioCtx.destination);

button.onclick = function() {
  var active = button.getAttribute('data-active');
  if(active == 'false') {
    button.setAttribute('data-active', 'true');
    button.innerHTML = 'Remove compression';

    source.disconnect(audioCtx.destination);
    source.connect(compressor);
    compressor.connect(audioCtx.destination);
  } else if(active == 'true') {
    button.setAttribute('data-active', 'false');
    button.innerHTML = 'Add compression';

    source.disconnect(compressor);
    compressor.disconnect(audioCtx.destination);
    source.connect(audioCtx.destination);
  }
}

Specifications

Specification	Status	Comment
Web Audio API The definition of 'attack' in that specification.	Working Draft

Browser compatibility

Feature	Chrome	Edge	Firefox (Gecko)	Internet Explorer	Opera	Safari (WebKit)
Basic support	10.0webkit	(Yes)	25.0 (25.0)	No support	15.0webkit 22 (unprefixed)	6.0webkit