ScriptProcessorNode: audioprocess event

This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

The audioprocess event of the ScriptProcessorNode interface is fired when an input buffer of a script processor is ready to be processed.

Bubbles No
Cancelable No
Default action None
Interface AudioProcessingEvent
Event handler property ScriptProcessorNode.onaudioprocess


scriptNode.addEventListener('audioprocess', function(audioProcessingEvent) {
  // The input buffer is a song we loaded earlier
  var inputBuffer = audioProcessingEvent.inputBuffer;

  // The output buffer contains the samples that will be modified and played
  var outputBuffer = audioProcessingEvent.outputBuffer;

  // Loop through the output channels (in this case there is only one)
  for (var channel = 0; channel < outputBuffer.numberOfChannels; channel++) {
    var inputData = inputBuffer.getChannelData(channel);
    var outputData = outputBuffer.getChannelData(channel);

    // Loop through the 4096 samples
    for (var sample = 0; sample < inputBuffer.length; sample++) {
      // make output equal to the same as the input
      outputData[sample] = inputData[sample];

      // add noise to each output sample
      outputData[sample] += ((Math.random() * 2) - 1) * 0.2;         

You could also set up the event handler using the ScriptProcessorNode.onaudioprocess property:

scriptNode.onaudioprocess = function(audioProcessingEvent) {


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

Browser compatibility

No compatibility data found. Please contribute data for "api.MediaStreamTrack.audioprocess_event" (depth: 1) to the MDN compatibility data repository.

See also

Document Tags and Contributors

Last updated by: chrisdavidmills,