The rolloffFactor
property of the PannerNode
interface is a double value describing how quickly the volume is reduced as the source moves away from the listener. This value is used by all distance models.
The rolloffFactor
property's default value is 1
.
var audioCtx = new AudioContext(); var panner = audioCtx.createPanner(); panner.rolloffFactor = 1;
A double.
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.value = 1; panner.orientationY.value = 0; panner.orientationZ.value = 0; } else { panner.setOrientation(1,0,0); } var listener = audioCtx.listener; if(listener.forwardX) { listener.forwardX.value = 0; listener.forwardY.value = 0; listener.forwardZ.value = -1; listener.upX.value = 0; listener.upY.value = 1; listener.upZ.value = 0; } 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.value = xPos; listener.positionY.value = yPos; listener.positionZ.value = 300; } 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.value = xPos; panner.positionY.value = yPos; panner.positionZ.value = zPos; } 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.
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'rolloffFactor' in that specification. | Working Draft |
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 14 | Yes | 25 | No | 15 | 6 |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | Yes | 14 | Yes | 26 | No | 15 | ? |
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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/PannerNode/rolloffFactor