AudioParam

The Web Audio API's AudioParam interface represents an audio-related parameter, usually a parameter of an AudioNode (such as GainNode.gain). An AudioParam can be set to a specific value or a change in value, and can be scheduled to happen at a specific time and following a specific pattern.

There are two kinds of AudioParam, a-rate and k-rate parameters:

  • An a-rate AudioParam takes the current audio parameter value for each sample frame of the audio signal.
  • A k-rate AudioParam uses the same initial audio parameter value for the whole block processed, that is 128 sample frames. In other words, the same value applies to every frame in the audio as it's processed by the node.

Each AudioNode defines which of its parameters are a-rate or k-rate in the spec.

Each AudioParam has a list of events, initially empty, that define when and how values change. When this list is not empty, changes using the AudioParam.value attributes are ignored. This list of events allows us to schedule changes that have to happen at very precise times, using arbitrary timelime-based automation curves. The time used is the one defined in AudioContext.currentTime.

Properties

AudioParam.defaultValue Read only
Represents the initial volume of the attribute as defined by the specific AudioNode creating the AudioParam.
AudioParam.maxValue Read only
Represents the maximum possible value for the parameter's nominal (effective) range. 
AudioParam.minValue Read only
Represents the minimum possible value for the parameter's nominal (effective) range. 
AudioParam.value
Represents the parameter's current value as of the current time; initially set to the value of defaultValue.

Methods

AudioParam.setValueAtTime()
Schedules an instant change to the value of the AudioParam at a precise time, as measured against AudioContext.currentTime. The new value is given by the value parameter.
AudioParam.linearRampToValueAtTime()
Schedules a gradual linear change in the value of the AudioParam. The change starts at the time specified for the previous event, follows a linear ramp to the new value given in the value parameter, and reaches the new value at the time given in the endTime parameter.
AudioParam.exponentialRampToValueAtTime()
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.
AudioParam.setTargetAtTime()
Schedules the start of a change to the value of the AudioParam. The change starts at the time specified in startTime and exponentially moves towards the value given by the target parameter. The exponential decay rate is defined by the timeConstant parameter, which is a time measured in seconds.
AudioParam.setValueCurveAtTime()
Schedules the values of the AudioParam to follow a set of values, defined by an array of floating-point numbers scaled to fit into the given interval, starting at a given start time and spanning a given duration of time.
AudioParam.cancelScheduledValues()
Cancels all scheduled future changes to the AudioParam.
AudioParam.cancelAndHoldAtTime()
Cancels all scheduled future changes to the AudioParam but holds its value at a given time until further changes are made using other methods.

Examples

First, a basic example showing a GainNode having its gain value set. gain is an example of an a-rate AudioParam, as the value can potentially be set differently for each sample frame of the audio.

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

var gainNode = audioCtx.createGain();
gainNode.gain.value = 0;

Next, an example showing a DynamicsCompressorNode having some param values maniuplated. These are examples of k-rate AudioParam's, as the values are set for the entire audio block at once.

var compressor = audioCtx.createDynamicsCompressor();
compressor.threshold.setValueAtTime(-50, audioCtx.currentTime);
compressor.knee.setValueAtTime(40, audioCtx.currentTime);
compressor.ratio.setValueAtTime(12, audioCtx.currentTime);
compressor.attack.setValueAtTime(0, audioCtx.currentTime);
compressor.release.setValueAtTime(0.25, audioCtx.currentTime);

Specifications

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

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
AudioParamChrome Full support 14Edge Full support 12Firefox Full support 25IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Full support 18Firefox Android Full support 26Opera Android Full support 14Safari iOS Full support YesSamsung Internet Android Full support 1.0
automationRateChrome Full support 68Edge Full support ≤79Firefox No support NoIE No support NoOpera Full support 55Safari No support NoWebView Android Full support 68Chrome Android Full support 68Firefox Android No support NoOpera Android Full support 48Safari iOS No support NoSamsung Internet Android Full support 10.0
cancelAndHoldAtTimeChrome Full support 57Edge Full support ≤79Firefox No support NoIE No support NoOpera Full support 44Safari No support NoWebView Android Full support 57Chrome Android Full support 57Firefox Android No support NoOpera Android Full support 43Safari iOS No support NoSamsung Internet Android Full support 7.0
cancelScheduledValuesChrome Full support 14Edge Full support 12Firefox Full support 25IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Full support 18Firefox Android Full support 26Opera Android Full support 14Safari iOS Full support YesSamsung Internet Android Full support 1.0
defaultValueChrome Full support 14Edge Full support 12Firefox Full support 25IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Full support 18Firefox Android Full support 26Opera Android Full support 14Safari iOS Full support YesSamsung Internet Android Full support 1.0
exponentialRampToValueAtTimeChrome Full support 14Edge Full support 12Firefox Partial support 25
Notes
Partial support 25
Notes
Notes Does not work (see bug 1171438 and bug 1567777).
IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Partial support 18
Notes
Partial support 18
Notes
Notes This sets the target volume at the specified time, but it doesn’t ramp to it, causing this function to behave like setValueAtTime().
Firefox Android Partial support 26
Notes
Partial support 26
Notes
Notes Does not work (see bug 1171438 and bug 1567777).
Opera Android Full support 14Safari iOS Full support YesSamsung Internet Android Full support 1.0
linearRampToValueAtTimeChrome Full support 14Edge Full support 12Firefox Partial support 25
Notes
Partial support 25
Notes
Notes Does not work (see bug 1171438 and bug 1567777).
IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Partial support 18
Notes
Partial support 18
Notes
Notes This sets the target volume at the specified time, but it doesn’t ramp to it, causing this function to behave like setValueAtTime().
Firefox Android Partial support 26
Notes
Partial support 26
Notes
Notes Does not work (see bug 1171438 and bug 1567777).
Opera Android Full support 14Safari iOS ? Samsung Internet Android Full support 1.0
maxValueChrome Full support 52Edge Full support ≤18Firefox Full support 53IE No support NoOpera Full support 39Safari Full support 6WebView Android Full support 52Chrome Android Full support 52Firefox Android Full support 53Opera Android Full support 41Safari iOS Full support YesSamsung Internet Android Full support 6.0
minValueChrome Full support 52Edge Full support ≤18Firefox Full support 53IE No support NoOpera Full support 39Safari Full support 6WebView Android Full support 52Chrome Android Full support 52Firefox Android Full support 53Opera Android Full support 41Safari iOS Full support YesSamsung Internet Android Full support 6.0
setTargetAtTimeChrome Full support 14Edge Full support 12Firefox Full support 25IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Full support 18Firefox Android Full support 26Opera Android Full support 14Safari iOS Full support YesSamsung Internet Android Full support 1.0
setValueAtTimeChrome Full support 14Edge Full support 12Firefox Full support 25IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Full support 18Firefox Android Full support 26Opera Android Full support 14Safari iOS Full support YesSamsung Internet Android Full support 1.0
setValueCurveAtTimeChrome Full support 14Edge Full support 12Firefox Full support 25IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Full support 18Firefox Android Full support 26Opera Android Full support 14Safari iOS Full support YesSamsung Internet Android Full support 1.0
valueChrome Full support 14Edge Full support 12Firefox Full support 25
Notes
Full support 25
Notes
Notes Prior to Firefox 69, value did not take into account scheduled or gradiated changes to the parameter's value; instead, only explicitly set values were returned.
IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Full support 18Firefox Android Full support 26
Notes
Full support 26
Notes
Notes Firefox for Android does not currently take into account scheduled or gradiated changes to the parameter's value; only the initial value or the most recent explicitly set value is returned.
Opera Android Full support 14Safari iOS Full support YesSamsung Internet Android Full support 1.0

Legend

Full support  
Full support
Partial support  
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No support  
No support
Compatibility unknown  
Compatibility unknown
See implementation notes.
See implementation notes.

See also