AudioListener.speedOfSound

Deprecated
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 speedOfSound property of the AudioListener interface is a double value representing the speed of sound, in meters per second.

The speedOfSound property's default value is 343.3 m/s and is used to calculate the doppler shift appropriate for the speed the panner is travelling at (as defined by PannerNode.setVelocity.)

Note: Bear in mind that no propagation delay is automatically applied to a sound far from the listener.

Syntax

var audioCtx = new AudioContext();
var myListener = audioCtx.listener;
myListener.speedOfSound = 343.3;

Value

A double.

Example

In the following example, you can see an example of how the createPanner() method, AudioListener and PannerNode would be used to control audio spatialisation. Generally you will define the position in 3D space that your audio listener and panner (source) occupy initially, and then update the position of one or both of these as the application is used. You might be moving a character around inside a game world for example, and wanting delivery of audio to change realistically as your character moves closer to or further away from a music player such as a stereo. In the example you can see this being controlled by the functions moveRight(), moveLeft(), etc., which set new values for the panner position via the PositionPanner() function.

To see a complete implementation, check out our panner-node example (view the source code) — this demo transports you to the 2.5D "Room of metal", where you can play a track on a boom box and then walk around the boom box to see how the sound changes!

Note how we have used some feature detection to either give the browser the newer property values (like AudioListener.forwardX) for setting position, etc. if it supports those, or older methods (like AudioListener.setOrientation()) if it still supports those but not the new properties.

// set up listener and panner position information
var WIDTH = window.innerWidth;
var HEIGHT = window.innerHeight;

var xPos = Math.floor(WIDTH/2);
var yPos = Math.floor(HEIGHT/2);
var zPos = 295;

// define other variables

var AudioContext = window.AudioContext || window.webkitAudioContext;
var audioCtx = new AudioContext();

var panner = audioCtx.createPanner();
panner.panningModel = 'HRTF';
panner.distanceModel = 'inverse';
panner.refDistance = 1;
panner.maxDistance = 10000;
panner.rolloffFactor = 1;
panner.coneInnerAngle = 360;
panner.coneOuterAngle = 0;
panner.coneOuterGain = 0;

if(panner.orientationX) {
  panner.orientationX.setValueAtTime(1, audioCtx.currentTime);
  panner.orientationY.setValueAtTime(0, audioCtx.currentTime);
  panner.orientationZ.setValueAtTime(0, audioCtx.currentTime);
} else {
  panner.setOrientation(1,0,0);
}

var listener = audioCtx.listener;

if(listener.forwardX) {
  listener.forwardX.setValueAtTime(0, audioCtx.currentTime);
  listener.forwardY.setValueAtTime(0, audioCtx.currentTime);
  listener.forwardZ.setValueAtTime(-1, audioCtx.currentTime);
  listener.upX.setValueAtTime(0, audioCtx.currentTime);
  listener.upY.setValueAtTime(1, audioCtx.currentTime);
  listener.upZ.setValueAtTime(0, audioCtx.currentTime);
} else {
  listener.setOrientation(0,0,-1,0,1,0);
}

var source;

var play = document.querySelector('.play');
var stop = document.querySelector('.stop');

var boomBox = document.querySelector('.boom-box');

var listenerData = document.querySelector('.listener-data');
var pannerData = document.querySelector('.panner-data');

leftBound = (-xPos) + 50;
rightBound = xPos - 50;

xIterator = WIDTH/150;

// listener will always be in the same place for this demo

if(listener.positionX) {
  listener.positionX.setValueAtTime(xPos, audioCtx.currentTime);
  listener.positionY.setValueAtTime(yPos, audioCtx.currentTime);
  listener.positionZ.setValueAtTime(300, audioCtx.currentTime);
} else {
  listener.setPosition(xPos,yPos,300);
}

listenerData.innerHTML = 'Listener data: X ' + xPos + ' Y ' + yPos + ' Z ' + 300;

// panner will move as the boombox graphic moves around on the screen
function positionPanner() {
  if(panner.positionX) {
    panner.positionX.setValueAtTime(xPos, audioCtx.currentTime);
    panner.positionY.setValueAtTime(yPos, audioCtx.currentTime);
    panner.positionZ.setValueAtTime(zPos, audioCtx.currentTime);
  } else {
    panner.setPosition(xPos,yPos,zPos);
  }
  pannerData.innerHTML = 'Panner data: X ' + xPos + ' Y ' + yPos + ' Z ' + zPos;
}

Note: In terms of working out what position values to apply to the listener and panner, to make the sound appropriate to what the visuals are doing on screen, there is quite a bit of math involved, but you will soon get used to it with a bit of experimentation.

Browser compatibility

DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
speedOfSound
Deprecated
Chrome No support 14 — 56Edge No support 12 — 79Firefox No support 25 — 63IE No support NoOpera No support 15 — 43Safari Full support 6WebView Android No support ? — 56Chrome Android No support 18 — 56Firefox Android No support 26 — 63Opera Android No support 14 — 43Safari iOS ? Samsung Internet Android No support 1.0 — 6.0

Legend

Full support
Full support
No support
No support
Compatibility unknown
Compatibility unknown
Deprecated. Not for use in new websites.
Deprecated. Not for use in new websites.

See also