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<title>Audio normalization</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Audio normalization</span></span>

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</p><p><b>Audio normalization</b> is the application of a constant amount of gain to an <a href="Audio_recording" class="mw-redirect" title="Audio recording">audio recording</a> to bring the amplitude to a target level (the norm). Because the same amount of gain is applied across the entire recording, the <a href="Signal-to-noise_ratio" title="Signal-to-noise ratio">signal-to-noise ratio</a> and <a href="Dynamics_(music)" title="Dynamics (music)">relative dynamics</a> are unchanged. Normalization is one of the functions commonly provided by a <a href="Digital_audio_workstation" title="Digital audio workstation">digital audio workstation</a>.

</p><p>Two principal types of audio normalization exist. <b>Peak normalization</b> adjusts the recording based on the highest signal level present in the recording. <b>Loudness normalization</b> adjusts the recording based on perceived <a href="Loudness" title="Loudness">loudness</a>.

</p><p>Normalization differs from <a href="Dynamic_range_compression" title="Dynamic range compression">dynamic range compression</a>, which applies varying levels of gain over a recording to fit the level within a minimum and maximum range. Normalization adjusts the gain by a constant value across the entire recording.

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<div class="mw-heading mw-heading2"><h2 id="Peak_normalization">Peak normalization</h2></div>

<p>One type of normalization is peak normalization, wherein the gain is changed to bring the highest <a href="Pulse-code_modulation" title="Pulse-code modulation">PCM</a> sample value or analog signal peak to a given level – usually 0 <a href="DBFS" title="DBFS">dBFS</a>, the loudest level allowed in a digital system.<sup id="cite_ref-Myths_1-0" class="reference"><a href="#cite_note-Myths-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

</p><p>Since it searches only for the highest level, peak normalization alone does not account for the apparent loudness of the content. As such, peak normalization is generally used to change the volume in such a way to ensure optimal use of available dynamic range during the mastering stage of a <a href="Digital_recording" title="Digital recording">digital recording</a>. When combined with compression/limiting, however, peak normalization becomes a feature that can provide a loudness advantage over non–peak-normalized material. This feature of digital recording systems, compression and limiting followed by peak normalization, enables contemporary trends in program loudness.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Loudness_normalization">Loudness normalization</h2></div>

<p>Another type of normalization is based on a measure of loudness, wherein the gain is changed to bring the average loudness to a target level. This average may be approximate, such as a simple measurement of average power (e.g. <a href="Root_mean_square" title="Root mean square">RMS</a>), or more accurate, such as a measure that addresses human perception e.g. that defined by <a href="EBU_R128" class="mw-redirect" title="EBU R128">EBU R128</a> and offered by <a href="ReplayGain" title="ReplayGain">ReplayGain</a>, <a href="Sound_Check_(iTunes_feature)" class="mw-redirect" title="Sound Check (iTunes feature)">Sound Check</a> and <a href="GoldWave" title="GoldWave">GoldWave</a>.

</p><p>For example, <a href="YouTube" title="YouTube">YouTube</a>'s preferred loudness level is −14 <a href="LKFS" class="mw-redirect" title="LKFS">LUFS</a>, so if an audio program is analyzed to be −10 LUFS, YouTube will lower the loudness by 4 dB to bring it to the preferred level.

</p><p>Loudness normalization combats varying loudness when listening to multiple songs in a sequence. Before loudness normalization, one song in a playlist might be quieter than the rest, so the listener would have to turn a volume knob up to adjust the playback volume.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

</p><p>Depending on the dynamic range of the content and the target level, loudness normalization can result in peaks that exceed the recording medium's limits, causing clipping. Software offering loudness normalization typically provides the option of <a href="Dynamic_range_compression" title="Dynamic range compression">dynamic range compression</a> to prevent <a href="Clipping_(audio)" title="Clipping (audio)">clipping</a> when this happens. In this situation, signal-to-noise ratio and relative dynamics are altered.

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<div class="mw-heading mw-heading3"><h3 id="Loudness_standards">Loudness standards</h3></div>

<p>Standardised normalized loudness levels vary by territory and application.<sup id="cite_ref-pro-vid_5-0" class="reference"><a href="#cite_note-pro-vid-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup>

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<ul><li>−24<span class="nowrap"> </span>LUFS: <a href="ATSC" class="mw-redirect" title="ATSC">ATSC</a> <a rel="nofollow" class="external text" href="https://www.atsc.org/atsc-documents/a85-techniques-for-establishing-and-maintaining-audio-loudness-for-digital-television/">A/85</a> (US TV), NPRSS, and <a href="Public_Radio_Exchange" title="Public Radio Exchange">PRX</a> radio broadcast<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-pro-vid_5-1" class="reference"><a href="#cite_note-pro-vid-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></li>

<li>−23<span class="nowrap"> </span>LUFS: <a href="EBU_R_128" title="EBU R 128">EBU R 128</a> broadcast<sup id="cite_ref-pro-vid_5-2" class="reference"><a href="#cite_note-pro-vid-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></li>

<li>−19 to −16 LUFS: PRX podcasts<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup></li>

<li>−14<span class="nowrap"> </span>LUFS: <a href="Spotify" title="Spotify">Spotify</a>, <a href="YouTube" title="YouTube">YouTube</a> and other <a href="Streaming_media" title="Streaming media">streaming</a> platforms<sup id="cite_ref-pro-vid_5-3" class="reference"><a href="#cite_note-pro-vid-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></li></ul>

<ul><li><a href="Alignment_level" title="Alignment level">Alignment level</a></li>

<li><a href="Dialnorm" title="Dialnorm">Dialnorm</a></li>

<li><a href="Loudness_war" title="Loudness war">Loudness war</a></li>

<li><a href="Normalization_(image_processing)" title="Normalization (image processing)">Normalization (image processing)</a>, image analog</li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite id="CITEREFDes2008" class="citation web cs1">Des (20 April 2008). <a rel="nofollow" class="external text" href="http://www.hometracked.com/2008/04/20/10-myths-about-normalization/">"10 Myths About Normalization"</a>. Hometracked<span class="reference-accessdate">. Retrieved <span class="nowrap">10 June</span> 2012</span>.</cite></span>

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<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><cite id="CITEREFShelvock2012" class="citation book cs1">Shelvock, Matt (2012). <a rel="nofollow" class="external text" href="http://ir.lib.uwo.ca/cgi/viewcontent.cgi?article=1709&context=etd"><i>Audio Mastering as Musical Practice</i></a>. London: University of Western Ontario: EDT. p. 26.</cite><span class="cs1-maint citation-comment"><code class="cs1-code">{{cite book}}</code>: CS1 maint: publisher location (link)</span></span>

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<li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><cite id="CITEREFKatz2007" class="citation book cs1">Katz, Bob (2007). <span class="id-lock-limited" title="Free access subject to limited trial, subscription normally required"><a rel="nofollow" class="external text" href="https://archive.org/details/masteringaudioar00katz"><i>Mastering Audio: The Art and the Science</i></a></span>. Focal Press. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/masteringaudioar00katz/page/n159">168</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-240-80837-6</bdi>.</cite></span>

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<li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20180627230633/https://www.hybridstudiosca.com/mastering/">"What are the "loudness wars" and loudness normalization?"</a>. <i>Hybrid Studios</i>. Archived from <a rel="nofollow" class="external text" href="https://www.hybridstudiosca.com/mastering/">the original</a> on 27 June 2018<span class="reference-accessdate">. Retrieved <span class="nowrap">1 July</span> 2018</span>.</cite></span>

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<li id="cite_note-pro-vid-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-pro-vid_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-pro-vid_5-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-pro-vid_5-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-pro-vid_5-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><cite id="CITEREFTépper2018" class="citation web cs1">Tépper, Allan (23 March 2018). <a rel="nofollow" class="external text" href="https://www.provideocoalition.com/how-many-lufs-for-ideal-audio-loudness-why-cant-we-be-friends/">"How many LUFS for ideal audio loudness? Why can't we be friends?"</a>. <i>Pro Video Coalition</i><span class="reference-accessdate">. Retrieved <span class="nowrap">11 July</span> 2019</span>.</cite></span>

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<li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://help.prx.org/hc/en-us/articles/360003516334-Formatting-Audio-Files-for-Broadcast">"Formatting Audio Files for Broadcast"</a>. <i>PRX – Help Desk</i>. <a href="Public_Radio_Exchange" title="Public Radio Exchange">PRX</a><span class="reference-accessdate">. Retrieved <span class="nowrap">21 March</span> 2022</span>. <q>Loudness at -24 LUFS, ± 2 LU (recommended)</q></cite></span>

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<li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://help.prx.org/hc/en-us/articles/360022234293-How-should-I-format-my-audio-files-for-Publish-">"How should I format my audio files for Publish?"</a>. <i>PRX – Help Desk</i>. <a href="Public_Radio_Exchange" title="Public Radio Exchange">PRX</a><span class="reference-accessdate">. Retrieved <span class="nowrap">21 March</span> 2022</span>. <q>Set your loudness between -16db LUFS and -19db LUFS. There is no set industry standard, [...]</q></cite></span>

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<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><a rel="nofollow" class="external text" href="http://www.hydrogenaud.io/forums/index.php?showtopic=85571">Discussion of inter-sample clipping when normalizing to 0 dBFS peaks</a></li>

<li><a rel="nofollow" class="external text" href="http://transom.org/?p=16413">Detailed article about levels by Jeff Towne</a></li></ul></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2024-05-29" href="https://en.wikipedia.org/wiki/?title=Audio_normalization&oldid=1226272112">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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