AudioParam.exponentialRampToValueAtTime()

The exponentialRampToValueAtTime() method of the AudioParam Interface schedules a gradual exponential change in the value of the AudioParam. The change starts at the time specified for the previous event, follows an exponential ramp to the new value given in the value parameter, and reaches the new value at the time given in the endTime parameter.

Note: Exponential ramps are considered more useful when changing frequencies or playback rates than linear ramps because of the way the human ear works.

Syntax

var AudioParam = AudioParam.exponentialRampToValueAtTime(value, endTime)

Parameters

value
A floating point number representing the value the AudioParam will ramp to by the given time.
endTime
A double representing the exact time (in seconds) after the ramping starts that the changing of the value will stop.

Returns

A reference to this AudioParam object. In some browsers older implementations of this interface return void.

Examples

In this example, we have a media source with two control buttons (see the audio-param repo for the source code, or view the example live.) When these buttons are pressed, exponentialRampToValueAtTime() is used to fade the gain value up to 1.0, and down to 0, respectively. This is pretty useful for fade in/fade out effects:

// create audio context
var AudioContext = window.AudioContext || window.webkitAudioContext;
var audioCtx = new AudioContext();

// set basic variables for example
var myAudio = document.querySelector('audio');
var pre = document.querySelector('pre');
var myScript = document.querySelector('script');

pre.innerHTML = myScript.innerHTML;

var expRampPlus = document.querySelector('.exp-ramp-plus');
var expRampMinus = document.querySelector('.exp-ramp-minus');

// Create a MediaElementAudioSourceNode
// Feed the HTMLMediaElement into it
var source = audioCtx.createMediaElementSource(myAudio);

// Create a gain node and set its gain value to 0.5
var gainNode = audioCtx.createGain();

// connect the AudioBufferSourceNode to the gainNode
// and the gainNode to the destination
gainNode.gain.setValueAtTime(0, audioCtx.currentTime);
source.connect(gainNode);
gainNode.connect(audioCtx.destination);

// set buttons to do something onclick
expRampPlus.onclick = function() {
  gainNode.gain.exponentialRampToValueAtTime(1.0, audioCtx.currentTime + 2);
}

expRampMinus.onclick = function() {
  gainNode.gain.exponentialRampToValueAtTime(0.01, audioCtx.currentTime + 2);
}

Note: A value of 0.01 was used for the value to ramp down to in the last function rather than 0, as an invalid or illegal string error is thrown if 0 is used — the value needs to be positive.

Specifications

Specification Status Comment
Web Audio API
The definition of 'exponentialRampToValueAtTime' in that specification.
Working Draft  

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 14 webkit 23 No support 15 webkit
22 (unprefixed)
6 webkit
Unprefixed (Yes)        
Feature Android Chrome Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile Chrome for Android
Basic support No support ? 25 1.2 No support No support webkit 28 webkit
Unprefixed ? (Yes)           (Yes)

See also

Document Tags and Contributors

 Contributors to this page: ffxsam, jpmedley, lcrespom, fscholz, chrisdavidmills
 Last updated by: ffxsam,