AudioListener
The AudioListener
interface represents the position and orientation of the unique person listening to the audio scene, and is used in audio spatialization. All PannerNode
s spatialize in relation to the AudioListener
stored in the AudioContext.listener
attribute.
It is important to note that there is only one listener per context and that it isn't an AudioNode
.
Properties
Inherits properties from its parent, AudioNode
.
The position, forward, and up value are set and retrieved using different syntaxes. Retrieval is done by accessing, for example, AudioListener.positionX
, while setting the same property is done with AudioListener.positionX.value
. This is why these values are not marked read only, which is how they appear in the specification's IDL.
AudioListener.dopplerFactor
- A double value representing the amount of pitch shift to use when rendering a doppler effect. See Deprecated features to learn why this property was removed.
AudioListener.positionX
- Represents the horizontal position of the listener in a right-hand cartesian coordinate sytem. The default is 0.
AudioListener.positionY
- Represents the vertical position of the listener in a right-hand cartesian coordinate sytem. The default is 0.
AudioListener.positionZ
- Represents the longitudinal (back and forth) position of the listener in a right-hand cartesian coordinate sytem. The default is 0.
AudioListener.forwardX
- Represents the horizontal position of the listener's forward direction in the same cartesian coordinate sytem as the position (
positionX
,positionY
, andpositionZ
) values. The forward and up values are linearly independent of each other. The default is 0. AudioListener.forwardY
- Represents the vertical position of the listener's forward direction in the same cartesian coordinate sytem as the position (
positionX
,positionY
, andpositionZ
) values. The forward and up values are linearly independent of each other. The default is 0. AudioListener.forwardZ
- Represents the longitudinal (back and forth) position of the listener's forward direction in the same cartesian coordinate sytem as the position (
positionX
,positionY
, andpositionZ
) values. The forward and up values are linearly independent of each other. The default is 0. AudioListener.speedOfSound
- Is a double value representing the speed of sound, in meters per second. See Deprecated features to learn why this property was removed.
AudioListener.upX
- Represents the horizontal position of the top of the listener's head in the same cartesian coordinate sytem as the position (
positionX
,positionY
, andpositionZ
) values. The forward and up values are linearly independent of each other. The default is 0. AudioListener.upY
- Represents the vertical position of the top of the listener's head in the same cartesian coordinate sytem as the position (
positionX
,positionY
, andpositionZ
) values. The forward and up values are linearly independent of each other. The default is 0. AudioListener.upZ
- Represents the longitudinal (back and forth) position of the top of the listener's head in the same cartesian coordinate sytem as the position (
positionX
,positionY
, andpositionZ
) values. The forward and up values are linearly independent of each other. The default is 0.
Methods
Inherits methods from its parent, AudioNode
.
AudioListener.setOrientation()
- Sets the orientation of the listener.
AudioListener.setPosition()
- Sets the position of the listener. See Deprecated features to learn why this method was removed.
Deprecated features
In a previous version of the specification, the dopplerFactor
and speedOfSound
properties and the setPosition()
method could be used to control the doppler effect applied to AudioBufferSourceNode
s connected downstream — these would be pitched up and down according to the relative speed of the PannerNode
and the AudioListener
. These features had a number of problems:
- Only
AudioBufferSourceNode
s were pitched up or down, not other source nodes. - The behavior to adopt when an
AudioBufferSourceNode
was connected to multiplePannerNode
s was unclear. - Because the velocity of the panner and the listener were not
AudioParam
s, the pitch modification could not be smoothly applied, resulting in audio glitches.
Because of these issues, these properties and methods have been removed.
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!
// Define Web Audio API objects 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; panner.orientationX.value = 1; panner.orientationY.value = 0; panner.orientationZ.value = 0; var listener = audioCtx.listener; listener.orientationX.value = 0; listener.orientationY.value = 0; listener.orientationZ.value = -1; listener.upX.value = 0; listener.upY.value = 1; listener.upZ.value = 0; var source; var boomBox = document.querySelector('.boom-box'); // set up listener and panner position information var WIDTH = window.innerWidth; var HEIGHT = window.innerHeight; var xPos = WIDTH/2; var yPos = HEIGHT/2; var zPos = 295; leftBound = (-xPos) + 50; rightBound = xPos - 50; xIterator = WIDTH/150; // listener will always be in the same place for this demo listener.positionX.value = xPos; listener.positionY.value = yPos; listener.positionZ.value = zPos; listenerData.innerHTML = 'Listener data: X ' + xPos + ' Y ' + yPos + ' Z ' + 300; // panner will move as the boombox graphic moves around on the screen function positionPanner() { panner.positionX.value = xPos; panner.positionY.value = yPos; panner.positionZ.value = zPos; pannerData.innerHTML = 'Panner data: X ' + xPos + ' Y ' + yPos + ' Z ' + zPos; } // controls to move left and right past the boom box // and zoom in and out // only right movement code shown in this listing to save space // look at the source code for full listing var leftButton = document.querySelector('.left'); var rightButton = document.querySelector('.right'); var zoomInButton = document.querySelector('.zoom-in'); var zoomOutButton = document.querySelector('.zoom-out'); var boomX = 0; var boomY = 0; var boomZoom = 0.25; var zoomInLoop; var zoomOutLoop function moveRight() { boomX += -xIterator; xPos += -0.066; if(boomX <= leftBound) { boomX = leftBound; xPos = (WIDTH/2) - 5; } boomBox.style.transform = "translate(" + boomX + "px , " + boomY + "px) scale(" + boomZoom + ")"; positionPanner(); rightLoop = requestAnimationFrame(moveRight); return rightLoop; } rightButton.onmousedown = moveRight; rightButton.onmouseup = function () { window.cancelAnimationFrame(rightLoop); }
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 fiddly math involved, but you will soon get used to it with a bit of experimentation.
Specifications
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'AudioListener' in that specification. |
Working Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | 10.0webkit (Yes) (unprefixed) |
25.0 (25.0) | No support | 15.0webkit 22 (unprefixed) |
6.0webkit |
Position, forward, and up properties | 52.0 | 39 |
Feature | Android | Android Webview | Firefox Mobile (Gecko) | Firefox OS | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|---|
Basic support | ? | (Yes) (Yes) (unprefixed) |
26.0 | 1.2 | ? | ? | ? | 33.0 (Yes) (unprefixed) |
Position, forward, and up properties | No support | 52.0 | 39 | 52.0 |
See also
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/api/audiolistener