Revision 930599 of BiquadFilterNode

<p>{{APIRef("Web Audio API")}}</p>

<div>
<p><span class="seoSummary">The <code>BiquadFilterNode</code> interface represents a simple low-order filter, and is created using the {{ domxref("AudioContext.createBiquadFilter()") }} method. It is an {{domxref("AudioNode")}} that can represent different kinds of filters, tone control devices, and graphic equalizers.</span> A <code>BiquadFilterNode</code> always has exactly one input and one output.</p>
</div>

<table class="properties">
 <tbody>
  <tr>
   <th scope="row">Number of inputs</th>
   <td><code>1</code></td>
  </tr>
  <tr>
   <th scope="row">Number of outputs</th>
   <td><code>1</code></td>
  </tr>
  <tr>
   <th scope="row">Channel count mode</th>
   <td><code>"max"</code></td>
  </tr>
  <tr>
   <th scope="row">Channel count</th>
   <td><code>2</code> (not used in the default count mode)</td>
  </tr>
  <tr>
   <th scope="row">Channel interpretation</th>
   <td><code>"speakers"</code></td>
  </tr>
 </tbody>
</table>

<h2 id="Properties">Properties</h2>

<p><em>Inherits properties from its parent, </em><em>{{domxref("AudioNode")}}</em>.</p>

<dl>
 <dt>{{domxref("BiquadFilterNode.frequency")}}</dt>
 <dd>Is a {{k-rate}} {{domxref("AudioParam")}}, a double representing a frequency in the current filtering algorithm measured in hertz (Hz).</dd>
 <dt>{{domxref("BiquadFilterNode.detune")}}</dt>
 <dd>Is an {{a-rate}} {{domxref("AudioParam")}} representing detuning of the frequency in <a class="external external-icon" href="https://en.wikipedia.org/wiki/Cent_%28music%29">cents</a>.</dd>
 <dt>{{domxref("BiquadFilterNode.Q")}}</dt>
 <dd>Is a {{k-rate}} {{domxref("AudioParam")}}, a double representing a <a href="https://en.wikipedia.org/wiki/Q_factor" title="https://en.wikipedia.org/wiki/Q_factor">Q factor</a>, or <em>quality factor</em>.</dd>
 <dt>{{domxref("BiquadFilterNode.gain")}} {{readonlyInline}}</dt>
 <dd>Is a {{k-rate}} {{domxref("AudioParam")}}, a double representing the <a href="https://en.wikipedia.org/wiki/Gain" title="https://en.wikipedia.org/wiki/Gain">gain</a> used in the current filtering algorithm.</dd>
 <dt>{{domxref("BiquadFilterNode.type")}}</dt>
 <dd>Is a string value defining the kind of filtering algorithm the node is implementing.<br />
 &nbsp;
 <table class="standard-table">
  <caption>The meaning of the different parameters depending of the type of the filter (detune has the same meaning regardless, so isn't listed below)</caption>
  <thead>
   <tr>
    <th scope="row"><code>type</code></th>
    <th scope="col">Description</th>
    <th scope="col"><code>frequency</code></th>
    <th scope="col"><code>Q</code></th>
    <th scope="col"><code>gain</code></th>
   </tr>
  </thead>
  <tbody>
   <tr>
    <th scope="row"><code>lowpass</code></th>
    <td>Standard second-order resonant lowpass filter with 12dB/octave rolloff. Frequencies below the cutoff pass through; frequencies above it are attenuated.</td>
    <td>The cutoff frequency.</td>
    <td>Indicates how peaked the frequency is around the cutoff. The greater the value is, the greater is the peak.</td>
    <td><em>Not used</em></td>
   </tr>
   <tr>
    <th scope="row"><code>highpass</code></th>
    <td>Standard second-order resonant highpass filter with 12dB/octave rolloff. Frequencies below the cutoff are attenuated; frequencies above it pass through.</td>
    <td>The cutoff frequency.</td>
    <td>Indicates how peaked the frequency is around the cutoff. The greater the value, the greater the peak.</td>
    <td><em>Not used</em></td>
   </tr>
   <tr>
    <th scope="row"><code>bandpass</code></th>
    <td>Standard second-order bandpass filter. Frequencies outside the given range of frequencies are attenuated; the frequencies inside it pass through.</td>
    <td>The center of the range of frequencies.</td>
    <td>Controls the width of the frequency band. The greater the <code>Q</code> value, the smaller the frequency band.</td>
    <td><em>Not used</em></td>
   </tr>
   <tr>
    <th scope="row"><code>lowshelf</code></th>
    <td>Standard second-order lowshelf filer. Frequencies lower than the frequency get a boost, or an attenuation; frequencies over it are unchanged.</td>
    <td>The upper limit of the frequencies getting a boost or an attenuation.</td>
    <td><em>Not used</em></td>
    <td>The boost, in dB, to be applied; if negative, it will be an attenuation.</td>
   </tr>
   <tr>
    <th scope="row"><code>highshelf</code></th>
    <td>Standard second-order highshelf filer. Frequencies higher than the frequency get a boost or an attenuation; frequencies lower than it are unchanged.</td>
    <td>The lower limit of the frequencies getting a boost or an attenuation.</td>
    <td><em>Not used</em></td>
    <td>The boost, in dB, to be applied; if negative, it will be an attenuation.</td>
   </tr>
   <tr>
    <th scope="row"><code>peaking</code></th>
    <td>Frequencies inside the range get a boost or an attenuation; frequencies outside it are unchanged.</td>
    <td>The middle of the frequency range getting a boost or an attenuation.</td>
    <td>Controls the width of the frequency band. The greater the <code>Q</code> value, the smaller the frequency band.</td>
    <td>The boost, in dB, to be applied; if negative, it will be an attenuation.</td>
   </tr>
   <tr>
    <th scope="row"><code>notch</code></th>
    <td>Standard <a href="https://en.wikipedia.org/wiki/Band-stop_filter" title="/en-US/docs/">notch</a> filter, also called a <em>band-stop</em> or <em>band-rejection</em> filter. It is the opposite of a bandpass filter: frequencies outside the give range of frequencies pass through; frequencies inside it are attenuated.</td>
    <td>The center of the range of frequencies.</td>
    <td>Controls the width of the frequency band. The greater the <code>Q</code> value, the smaller the frequency band.</td>
    <td><em>Not used</em></td>
   </tr>
   <tr>
    <th scope="row"><code>allpass</code></th>
    <td>Standard second-order <a href="https://en.wikipedia.org/wiki/All-pass_filter#Digital_Implementation" title="/en-US/docs/">allpass</a> filter. It lets all frequencies through, but changes the phase-relationship between the various frequencies.</td>
    <td>The frequency with the maximal <a href="https://en.wikipedia.org/wiki/Group_delay_and_phase_delay" title="/en-US/docs/">group delay</a>, that is, the frequency where the center of the phase transition occurs.</td>
    <td>Controls how sharp the transition is at the medium frequency. The larger this parameter is, the sharper and larger the transition will be.</td>
    <td><em>Not used</em></td>
   </tr>
  </tbody>
 </table>
 </dd>
</dl>

<h2 id="Methods">Methods</h2>

<p><em>Inherits methods from its parent, </em><em>{{domxref("AudioNode")}}</em>.</p>

<dl>
 <dt>{{domxref("BiquadFilterNode.getFrequencyResponse()")}}</dt>
 <dd>From the current filter parameter settings this method calculates the frequency response for frequencies specified in the provided array of frequencies.</dd>
</dl>

<h2 id="Example">Example</h2>

<p>{{page("/en-US/docs/Web/API/AudioContext.createBiquadFilter","Example")}}</p>

<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', '#the-biquadfilternode-interface', 'BiquadFilterNode')}}</td>
   <td>{{Spec2('Web Audio API')}}</td>
   <td>&nbsp;</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari (WebKit)</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatChrome(10.0)}}{{property_prefix("webkit")}}</td>
   <td>{{CompatGeckoDesktop(25.0)}}&nbsp;</td>
   <td>{{CompatNo}}</td>
   <td>15.0{{property_prefix("webkit")}}<br />
    22 (unprefixed)</td>
   <td>6.0{{property_prefix("webkit")}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>Firefox OS</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
   <th>Chrome for Android</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatUnknown}}</td>
   <td>26.0</td>
   <td>1.2</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>33.0</td>
  </tr>
 </tbody>
</table>
</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>