AudioContext.createGain()

Syntax

var gainNode = AudioContext.createGain();

Return value

A GainNode which takes as input one or more audio sources and outputs audio whose volume has been adjusted in gain (volume) to a level specified by the node's GainNode.gain a-rate parameter.

Example

The following example shows basic usage of an AudioContext to create a GainNode, which is then used to mute and unmute the audio when a Mute button is clicked by changing the gain property value.

The below snippet wouldn't work as is — for a complete working example, check out our Voice-change-O-matic demo (view source.)

<div>
  <a class="mute">Mute button</a>
</div>

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var gainNode = audioCtx.createGain();
var mute = document.querySelector('.mute');
var source;
if (navigator.mediaDevices.getUserMedia) {
 navigator.mediaDevices.getUserMedia (
   // constraints - only audio needed for this app
   {
     audio: true
   },
   // Success callback
   function(stream) {
     source = audioCtx.createMediaStreamSource(stream);
   },
   // Error callback
   function(err) {
     console.log('The following gUM error occured: ' + err);
   }
  );
} else {
   console.log('getUserMedia not supported on your browser!');
}
source.connect(gainNode);
gainNode.connect(audioCtx.destination);
  ...
mute.onclick = voiceMute;
function voiceMute() {
  if(mute.id == "") {
    gainNode.gain.value = 0;
    mute.id = "activated";
    mute.innerHTML = "Unmute";
  } else {
    gainNode.gain.value = 1;
    mute.id = "";
    mute.innerHTML = "Mute";
  }
}

Specifications

Browser compatibility

See also

• Using the Web Audio API