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---
title: AudioParam
slug: Web/API/AudioParam
tags:
- API
- Audio
- AudioParam
- Interface
- NeedsTranslation
- Parameter
- Reference
- TopicStub
- Web Audio API
- sound
translation_of: Web/API/AudioParam
---
<div>{{APIRef("Web Audio API")}}</div>
<p><span class="seoSummary">The Web Audio API's <code>AudioParam</code> interface represents an audio-related parameter, usually a parameter of an {{domxref("AudioNode")}} (such as {{ domxref("GainNode.gain") }}).</span> An <code>AudioParam</code> 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.</p>
<p>There are two kinds of <code>AudioParam</code>, <em>a-rate</em> and <em>k-rate</em> parameters:</p>
<ul>
<li id="a-rate">An <em>a-rate</em> <code>AudioParam</code> takes the current audio parameter value for each <a href="https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API/Basic_concepts_behind_Web_Audio_API#Audio_buffers.3A_frames.2C_samples_and_channels">sample frame</a> of the audio signal.</li>
<li id="k-rate">A <em>k-rate</em> <code>AudioParam</code> 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.</li>
</ul>
<p>Each {{domxref("AudioNode")}} defines which of its parameters are <em>a-rate</em> or <em>k-rate</em> in the spec.</p>
<p>Each <code>AudioParam</code> has a list of events, initially empty, that define when and how values change. When this list is not empty, changes using the <code>AudioParam.value</code> 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 {{domxref("AudioContext.currentTime")}}.</p>
<h2 id="Properties">Properties</h2>
<dl>
<dt>{{domxref("AudioParam.defaultValue")}} {{readonlyInline}}</dt>
<dd>Represents the initial volume of the attribute as defined by the specific {{domxref("AudioNode")}} creating the <code>AudioParam</code>.</dd>
<dt>{{domxref("AudioParam.maxValue")}} {{readonlyInline}}</dt>
<dd>Represents the maximum possible value for the parameter's nominal (effective) range. </dd>
<dt>{{domxref("AudioParam.minValue")}} {{readonlyinline}}</dt>
<dd>Represents the minimum possible value for the parameter's nominal (effective) range. </dd>
<dt>{{domxref("AudioParam.value")}}</dt>
<dd>Represents the parameter's current value as of the current time; initially set to the value of {{domxref("AudioParam.defaultValue", "defaultValue")}}.</dd>
</dl>
<h2 id="Methods">Methods</h2>
<dl>
<dt>{{domxref("AudioParam.setValueAtTime()")}}</dt>
<dd>Schedules an instant change to the value of the <code>AudioParam</code> at a precise time, as measured against {{domxref("AudioContext.currentTime")}}. The new value is given by the <code>value</code> parameter.</dd>
<dt>{{domxref("AudioParam.linearRampToValueAtTime()")}}</dt>
<dd>Schedules a gradual linear change in the value of the <code>AudioParam</code>. The change starts at the time specified for the <em>previous</em> event, follows a linear ramp to the new value given in the <code>value</code> parameter, and reaches the new value at the time given in the <code>endTime</code> parameter.</dd>
<dt>{{domxref("AudioParam.exponentialRampToValueAtTime()")}}</dt>
<dd>Schedules a gradual exponential change in the value of the <code>AudioParam</code>. The change starts at the time specified for the <em>previous</em> event, follows an exponential ramp to the new value given in the <code>value</code> parameter, and reaches the new value at the time given in the <code>endTime</code> parameter.</dd>
<dt>{{domxref("AudioParam.setTargetAtTime()")}}</dt>
<dd>Schedules the start of a change to the value of the <code>AudioParam</code>. The change starts at the time specified in <code>startTime</code> and exponentially moves towards the value given by the <code>target</code> parameter. The exponential decay rate is defined by the <code>timeConstant</code> parameter, which is a time measured in seconds.</dd>
<dt>{{domxref("AudioParam.setValueCurveAtTime()")}}</dt>
<dd>Schedules the values of the <code>AudioParam</code> 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.</dd>
<dt>{{domxref("AudioParam.cancelScheduledValues()")}}</dt>
<dd>Cancels all scheduled future changes to the <code>AudioParam</code>.</dd>
<dt>{{domxref("AudioParam.cancelAndHoldAtTime()")}}</dt>
<dd>Cancels all scheduled future changes to the <code>AudioParam</code> but holds its value at a given time until further changes are made using other methods.</dd>
</dl>
<h2 id="Examples">Examples</h2>
<p>First, a basic example showing a {{domxref("GainNode")}} having its <code>gain</code> value set. <code>gain</code> is an example of an a-rate AudioParam, as the value can potentially be set differently for each sample frame of the audio.</p>
<pre class="brush: js">var AudioContext = window.AudioContext || window.webkitAudioContext;
var audioCtx = new AudioContext();
var gainNode = audioCtx.createGain();
gainNode.gain.value = 0;</pre>
<p>Next, an example showing a {{ domxref("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.</p>
<pre class="brush: js">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);</pre>
<h2 id="Specifications">Specifications</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
</tr>
<tr>
<td>{{SpecName('Web Audio API', '#AudioParam', 'AudioParam')}}</td>
<td>{{Spec2('Web Audio API')}}</td>
<td></td>
</tr>
</tbody>
</table>
<h2 id="Browser_compatibility">Browser compatibility</h2>
<div>
<p>{{Compat("api.AudioParam")}}</p>
</div>
<h2 id="See_also">See also</h2>
<ul>
<li><a href="/en-US/docs/Web_Audio_API/Using_Web_Audio_API">Using the Web Audio API</a></li>
</ul>
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