<!DOCTYPE html> <html class="client-nojs" lang="en" dir="ltr"> <head> <meta charset="UTF-8"/> <title>Noise Gate - Audacity Manual</title> <meta name="ResourceLoaderDynamicStyles" content=""/> <meta name="generator" content="MediaWiki 1.28.2"/> <link rel="shortcut icon" href="../favicon.ico"/> <link rel="search" type="application/opensearchdescription+xml" href="https://alphamanual.audacityteam.org/m/opensearch_desc.php" title="Audacity Development Manual (en)"/> <link rel="EditURI" type="application/rsd+xml" href="https://alphamanual.audacityteam.org/m/api.php?action=rsd"/> <link rel="copyright" href="http://creativecommons.org/licenses/by/3.0/"/> <link rel="stylesheet" href="../m/skins/monobook/main.css/303.css" media="screen" /> </head> <body class="mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject page-Noise_Gate rootpage-Noise_Gate skin-monobook action-view"><div id="globalWrapper"> <div id="column-content"> <div id="content" class="mw-body" role="main"> <a id="top"></a> <div class="mw-indicators"> </div> <h1 id="firstHeading" class="firstHeading" lang="en">Noise Gate</h1> <div id="bodyContent" class="mw-body-content"> <div id="siteSub">From Audacity Development Manual</div> <div id="contentSub"></div> <div id="jump-to-nav" class="mw-jump">Jump to: <a href="#column-one">navigation</a>, <a href="https://alphamanual.audacityteam.org/man/Noise_Gate#searchInput">search</a></div> <div id="mw-content-text" lang="en" dir="ltr" class="mw-content-ltr"> <p><br /> </p> <div class="intro"><p>Use the <i><b>Noise Gate</b></i> to reduce the level of sound below a specified threshold level.</p> <p>A noise gate is a kind of "dynamics processor" that allows audio above a specified threshold level to pass through unaffected (gate <i>"open"</i>), and stops or reduces sounds below the threshold level (gate <i>"closed"</i>).</p> <p>Noise Gates may be used to cut the level of residual noise between sections of a recording. While this is essentially a very simple effect, this Noise Gate has a number of features and settings that allow it to be both effective and unobtrusive and well suited to most types of audio.</p> <div style="margin-top:12px; margin-bottom:12px; margin-left:24px; margin-right:24px"> <table style="background:#FEFFD0; color:black; border:1px solid #999999; padding-left:12px; padding-right:12px" width="100%" align="center"> <tr> <td width="30px" valign="top" align="center"><img alt="Advice" src="../m/images/b/ba/warningicon.png" title="Advice" width="24" height="24" /> </td> <td align="left" valign="top">Note carefully that when you apply an effect to a <a href="audacity_tracks_and_clips.html#speed" title="Audacity Tracks and Clips"><b>time-stretched clip</b></a> the changed speed of the clip will be automatically <a href="edit_menu_clip_boundaries.html#render" title="Edit Menu: Clip Boundaries"><b>rendered</b></a>. <ul><li>If you apply an effect to a selection within a time-stretched clip then Audacity will <a href="audacity_tracks_and_clips.html#split" title="Audacity Tracks and Clips"><b>split the original clip</b></a> so that the selection can be rendered as part of applying the effect.</li></ul> </td></tr></table></div> <div style="margin-top:12px; margin-bottom:12px; margin-left:24px; margin-right:24px"> <table style="background:#FFCCCC; color:black; border:1px solid #CC0000; padding-left:12px; padding-right:12px" width="100%" align="center"> <tr> <td width="30px" valign="top" align="center"><img alt="Alert" src="../m/images/6/6c/stopicon.png" title="Alert" width="24" height="24" /> </td> <td align="left" valign="top">If you apply this effect with an <a href="envelope_tool.html" title="Envelope Tool"><b>envelope</b></a> present then there is a <a rel="nofollow" class="external text" href="https://github.com/audacity/audacity/issues/5099"><b>bug</b></a> whereby the envelope is removed and the audio reverts to its full amplitude state prior to the effect being applied. </td></tr></table> </div> </div> <dl><dd><b>Accessed by:</b> <span class="menu">Effect > Noise Removal and Repair > Noise Gate</span></dd> <dd><span title="Noise Gate dialog"><img alt="Noise Gate 3-5-0.png" src="../m/images/f/f8/noise_gate_3_5_0.png" width="465" height="376" /></span></dd></dl> <p><br /> </p> <div id="function"></div> <h2><span class="mw-headline" id="Select_Function">Select Function</span></h2> <p>Select whether you want to apply the noise gate, or analyze the noise level: </p> <ul><li><b>Gate:</b> Apply the noise gate.</li> <li><b>Analyze Noise Level:</b> Analyze the level of the selected audio. All other controls are ignored when this option is selected.</li></ul> <p>When analyzing the noise level, ensure that the start of the selection lies within a region of noise only. The measurement is taken from the first half second of the selection. The analysis displays the measured level, and suggests a setting for the <a href="#threshold">Gate threshold</a> setting. </p><p><br /> </p> <div id="linking"></div> <h2><span class="mw-headline" id="Stereo_Linking">Stereo Linking</span></h2> <p>When <b>Link Stereo Tracks</b> is selected (the default), the gate will work on the channels of a stereo track as a pair and change the level of both channels by the same amount when the level in <i>both</i> channels fall below the threshold. This option is generally recommended, but will leave low level noise un-gated if there is sound above the threshold in the other channel. </p><p>When <b>Don't Link Stereo</b> is selected, the gate will adjust the amplitude separately for the left and right channels of a stereo track. This may be preferred when left and right channels have unrelated sounds, such as perhaps two sides of a conversation. For conventional stereo tracks it may cause a peculiar sensation of sound moving across the stereo field. </p><p><br /> </p> <div id="threshold"> <h2><span class="mw-headline" id="Gate_threshold">Gate threshold</span></h2> <p>When the audio level drops below this threshold the gate will 'close' and the output level will be reduced. When the audio level rises above this threshold the gate will 'open' and the output will return to the same level as the input. </p><p><br /> </p> <div id="gate"></div> <h2><span class="mw-headline" id="Gate_frequencies_above">Gate frequencies above</span></h2> <p>This slider control has a range up to 10 kHz (default = 0). </p> <ul><li>When set to zero, the gate acts on all of the audio. </li> <li>When set above zero, the gate acts on audio frequencies above the set kHz level, and lower frequencies pass through the gate unaffected.</li></ul> <p>This option may be useful in cases where there is substantial high frequency hiss, but relatively little noise at lower frequencies. </p><p><br /> </p> <div id="level"></div> <h2><span class="mw-headline" id="Level_reduction">Level reduction</span></h2> <p>Some noise gates refer to this control as "Range" or "Ratio". </p><p>This slider control determines the amount of attenuation (negative amplification) that is applied when the gate is "closed" (below the threshold level). At <b>-100 dB</b>, the gate stops the sound completely when closed, unless the "Gate frequencies above" is set higher than zero. If "Gate frequencies above" is higher than zero, the frequencies above the specified kHz level are stopped completely when the amplitude level is below the threshold. </p><p>Lower (more negative) setting attenuate the signal more, resulting in less noise passing through the closed gate, but may also produce noticeable <i>pumping</i> of the audio as the gate opens and closes. See the section on <a href="#workflow">Suggested Workflow</a> below. </p><p><br /> </p> <div id="attack"></div> <h2><span class="mw-headline" id="Attack">Attack</span></h2> <p>This setting controls how quickly the gate opens once the signal level exceeds the <a href="#threshold"><b>Gate threshold</b></a> level. </p><p>Unlike most hardware noise gates, this effect is able to look ahead and begin opening the gate so that the gate is open by the time that the threshold has been exceeded. This feature helps to avoid clipping the start of sounds even with relatively long <b>Attack</b> settings. </p> <ul><li>At the minimum (1 ms) the gate will fully open almost instantly as the audio level crosses the threshold.</li> <li>At the maximum (1000 ms), the gate will begin to slowly open (fade-in) 1 second before the sound level exceeds the threshold.</li></ul> <p><br /> </p> <div id="hold"></div> <h2><span class="mw-headline" id="Hold">Hold</span></h2> <p>This is the length of time that the gate remains open after the signal has dropped below the <b>Gate threshold</b>, before the gate starts to close. </p> <ul><li> When gating low frequency sounds, <b>Hold</b> should normally be set long enough to prevent the gate from closing between the waveform's peaks.</li> <li> When gating percussive sounds such as a snare drum, <b>Hold</b> may be set long enough to allow the natural decay of the sound before the gate closes.</li></ul> <p><br /> </p> <div id="decay"></div> <h2><span class="mw-headline" id="Decay">Decay</span></h2> <p>Some noise gates refer to this as "Release time". </p><p>This is the complement of <a href="#attack"><b>Attack</b></a>. Whereas <b>Attack</b> sets the time taken for the gate to open, <b>Decay</b> sets the time taken for the gate to close. The gate will begin to close after the signal has dropped below the <a href="#threshold"><b>Gate threshold</b></a> and the <a href="#hold"><b>Hold</b></a> time (if any) has been used. Longer <b>Decay</b> times close the gate more gradually. </p> <div id="levels"> <dl><dd><span title="The Attack, Hold and Decay times of the noise gate"><img alt="Noise Gate levels.png" src="../m/images/1/13/noise_gate_levels.png" width="523" height="307" /></span></dd></dl> <p><br /> </p> <div id="workflow"> <h2><span class="mw-headline" id="Suggested_Workflow">Suggested Workflow</span></h2> <div class="note">It is highly recommended to use the "Preview" button frequently when setting the controls.</div> <ol><li> Analyze the noise level</li> <li> Test the gate on a short selection with the Level Reduction set to -100 dB</li> <li> Adjust the <b>Gate threshold</b> if necessary and retest.</li> <li> Adjust the <b>Level reduction</b> slider and test. For the most 'transparent' results avoid setting the Level reduction any lower than absolutely necessary.</li> <li> When the settings are correct, apply the effect to the entire song.</li></ol> <p><br /> </p> <div id="limitations"> <h2><span class="mw-headline" id="Limitations">Limitations</span></h2> <p>Due to Nyquist restrictions the maximum amount of audio that can be acted upon with Noise Gate is 2,137,483,647 samples, which is about 13.5 hours of stereo at 44,100 Hz default rate. </p><p>If you try with a selection longer than that you will get the following error message: </p> <dl><dd><span title="Error message: Selection too long , limit is about 13.5 hours stereo"><img alt="Noise Gate Nyquist Error Selection too long.png" src="../m/images/2/24/noise_gate_nyquist_error_selection_too_long.png" width="352" height="148" /></span></dd></dl> <div style="margin-top:12px; margin-bottom:12px; margin-left:24px; margin-right:24px"> <table style="background:#FEFFD0; color:black; border:1px solid #999999; padding-left:12px; padding-right:12px" width="100%" align="center"> <tr> <td width="30px" valign="top" align="center"><img alt="Tip" src="../m/images/d/d7/bulbicon.png" title="Tip" width="32" height="32" /> </td> <td align="left" valign="top">the workaround for longer audio is to split it into smaller selections for Noise Gate to work on. </td></tr></table> </div> <p><br /> </p> <h2><span class="mw-headline" id="Links">Links</span></h2> <p><a href="index_of_effects_generators_and_analyzers.html" title="Index of Effects, Generators and Analyzers"><b>|<</b> Index of Effects, Generators and Analyzers</a> <br /> </p> <a href="effect_menu.html" title="Effect Menu"><b>|<</b> Effect Menu</a></div> </div> </div> </div> </div> <div class="visualClear"></div> </div> </div> </div> <div id="column-one"> <div class="portlet" id="p-logo" role="banner"> <a href="../index.html" class="mw-wiki-logo" title="Visit the main page"></a> </div> <div class="generated-sidebar portlet" id="p-Navigation" role="navigation"> <h3>Navigation</h3> <div class='pBody'> <ul><li> <a href="../index.html" title="Main Page"><span title="Front page, complete with clickable image of Audacity screen.">Manual Home Page</span></a></li> <li> <a href="how_to_use_audacity.html" title="How to use Audacity"><span title="Quick Help, Audacity Foundations, Editing with Audacity, Help with Advanced Topics">Using Audacity</span></a> <ul><li> <a href="audacity_tour_guide.html" title="Audacity Tour Guide"><span title="A quick tour of selected features of Audacity. 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