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.textContent = `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.textContent = `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
BCD tables only load in the browser