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.

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 Inherits properties from its parent, AudioNode.

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 volume as a floating point value; initially set to the value of AudioParam.defaultValue. Though it can be set, any modifications happening while there are automation events scheduled — that is events scheduled using the methods of the AudioParam — are ignored, without raising any exception.

Methods

AudioParam Inherits methods from its parent, AudioNode.

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 BiquadFilterNode having some values set. These are examples of k-rate AudioParam's, as the values are set for the entire audio block at once.

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

var biquadFilter = audioCtx.createBiquadFilter();

biquadFilter.type = "lowshelf";
biquadFilter.frequency.value = 1000;
biquadFilter.gain.value = 25;

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 AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic supportChrome Full support 14Edge Full support YesFirefox Full support 25IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Full support 18Edge Mobile Full support YesFirefox Android Full support 26Opera Android Full support 15Safari iOS ? Samsung Internet Android Full support Yes
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 18Edge Mobile Full support YesFirefox Android Full support 26Opera Android Full support 15Safari iOS ? Samsung Internet Android Full support Yes
maxValueChrome Full support 52Edge Full support YesFirefox Full support 53IE No support NoOpera Full support 39Safari Full support 6WebView Android Full support 52Chrome Android Full support 52Edge Mobile Full support YesFirefox Android Full support 53Opera Android Full support 39Safari iOS ? Samsung Internet Android Full support 6.0
minValueChrome Full support 52Edge Full support YesFirefox Full support 53IE No support NoOpera Full support 39Safari Full support 6WebView Android Full support 52Chrome Android Full support 52Edge Mobile Full support YesFirefox Android Full support 53Opera Android Full support 39Safari iOS ? Samsung Internet Android Full support 6.0
valueChrome 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 18Edge Mobile Full support YesFirefox Android Full support 26Opera Android Full support 15Safari iOS ? Samsung Internet Android Full support Yes
cancelAndHoldAtTimeChrome Full support 57
Full support 57
No support ? — 56
Alternate Name
Alternate Name Uses the non-standard name: cancelValuesAndHoldAtTime()
Edge ? Firefox No support NoIE No support NoOpera Full support 44
Full support 44
No support ? — 43
Alternate Name
Alternate Name Uses the non-standard name: cancelValuesAndHoldAtTime()
Safari No support NoWebView Android Full support 57
Full support 57
No support ? — 56
Alternate Name
Alternate Name Uses the non-standard name: cancelValuesAndHoldAtTime()
Chrome Android Full support 57
Full support 57
No support ? — 56
Alternate Name
Alternate Name Uses the non-standard name: cancelValuesAndHoldAtTime()
Edge Mobile Full support YesFirefox Android No support NoOpera Android Full support 44
Full support 44
No support ? — 43
Alternate Name
Alternate Name Uses the non-standard name: cancelValuesAndHoldAtTime()
Safari 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 18Edge Mobile Full support YesFirefox Android Full support 26Opera Android Full support 15Safari iOS ? Samsung Internet Android Full support Yes
exponentialRampToValueAtTimeChrome 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 18Edge Mobile Full support YesFirefox Android Full support 26Opera Android Full support 15Safari iOS ? Samsung Internet Android Full support Yes
linearRampToValueAtTimeChrome 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 18Edge Mobile Full support YesFirefox Android Full support 26Opera Android Full support 15Safari iOS ? Samsung Internet Android Full support Yes
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 18Edge Mobile Full support YesFirefox Android Full support 26Opera Android Full support 15Safari iOS ? Samsung Internet Android Full support Yes
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 18Edge Mobile Full support YesFirefox Android Full support 26Opera Android Full support 15Safari iOS ? Samsung Internet Android Full support Yes
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 18Edge Mobile Full support YesFirefox Android Full support 26Opera Android Full support 15Safari iOS ? Samsung Internet Android Full support Yes

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Uses a non-standard name.
Uses a non-standard name.

See also

Document Tags and Contributors

Last updated by: chrisdavidmills,