Editing Dynamic range compression (section)

== Objective influence on the signal ==

In an article published in January 2014 by the ''Journal of the Audio Engineering Society'', Emmanuel Deruty and Damien Tardieu performed a systematic study describing the influence of compressors and brickwall limiters on the musical audio signal. The experiment involved four software limiters: Waves L2, Sonnox Oxford Limiter, Thomas Mundt's Loudmax, Blue Cat's Protector, as well as four software compressors: Waves H-Comp, Sonnox Oxford Dynamics, Sonalksis SV-3157, and URS 1970. The study provides objective data on what limiters and compressors do to the audio signal.<ref name="DerutyTardieuAES">{{Cite journal |last1=Deruty |first1=Emmanuel |last2=Tardieu |first2=Damien |date=2014-02-03 |title=About Dynamic Processing in Mainstream Music |journal=Journal of the Audio Engineering Society |language=en |volume=62 |issue=1/2 |pages=42–55 |doi=10.17743/jaes.2014.0001 }}</ref>

Five signal descriptors were considered: [[RMS power]], [[EBU R 128]] integrated loudness,<ref name="EBU3341" /> [[crest factor]], R 128 LRA,<ref name="EBU3342" /> and density of clipped samples. RMS power accounts for the signal's physical level, R 128 loudness for the perceived level.<ref name="EBU3341" /> The crest factor, which is the difference between the signal's peak and its average power,<ref name="DerutyTardieuAES" /> is on occasions considered as a basis for the measure of micro-dynamics, for instance in the ''TT Dynamic Range Meter'' plug-in.<ref>{{Cite conference |last=Vickers |first=Earl |date=4–7 November 2010 |title=The Loudness War: Background, Speculation and Recommendations |url=http://www.sfxmachine.com/docs/loudnesswar/loudness_war.pdf |conference=129th AES Convention |location=San Francisco |publisher=[[Audio Engineering Society]] |access-date=July 14, 2011}}</ref> Finally, R 128 LRA has been repeatedly considered as a measure of macro-dynamics or dynamics in the musical sense.<ref name="DerutyTardieuAES" /><ref name="SOS_Dynamic_Range">{{Cite magazine |last=Deruty |first=Emmanuel |date=September 2011 |title='Dynamic Range' & The Loudness War |url=https://www.soundonsound.com/sound-advice/dynamic-range-loudness-war |magazine=Sound on Sound |access-date=2013-10-24}}</ref><ref>{{Cite journal |last1=Serrà |first1=J |last2=Corral |first2=A |last3=Boguñá |first3=M |last4=Haro |first4=M |last5=Arcos |first5=JL |date=26 July 2012 |title=Measuring the Evolution of Contemporary Western Popular Music |journal=Scientific Reports |volume=2 |page=521 |arxiv=1205.5651 |bibcode=2012NatSR...2E.521S |doi=10.1038/srep00521 |pmc=3405292 |pmid=22837813 }}</ref><ref>{{Cite journal |last1=Hjortkjær |first1=Jens |last2=Walther-Hansen |first2=Mads |date=2014-02-03 |title=Perceptual Effects of Dynamic Range Compression in Popular Music Recordings |journal=Journal of the Audio Engineering Society |volume=62 |issue=1/2 |pages=37–41 |doi=10.17743/jaes.2014.0003 }}</ref><ref>{{Cite journal |last=Skovenborg |first=Esben |date=2012-04-26 |title=Loudness Range (LRA) - Design and Evaluation |url=http://www.aes.org/e-lib/browse.cfm?elib=16254 |language=en |publisher=Audio Engineering Society |url-access=subscription |access-date=2019-11-04 |via=AES E-Library}}</ref>

=== Limiters ===

The tested limiters had the following influence on the signal:
* increase of RMS power,
* increase of EBU R 128 loudness,
* decrease of crest factor,
* decrease of EBU R 128  LRA, but only for high amounts of limiting,
* increase of clipped sample density.

In other words, limiters increase both physical and perceptual levels, increase the density of clipped samples, decrease the crest factor and decrease macro-dynamics (LRA) given that the amount of limiting is substantial.

=== Compressors ===

As far as the compressors are concerned, the authors performed two processing sessions, using a fast attack (0.5&nbsp;ms) in one case, and a slow attack (50&nbsp;ms) in the other. Make-up gain is deactivated, but the resulting file is normalized.

Set with a fast attack, the tested compressors had the following influence on the signal:
* slight increase of RMS power,
* slight increase of EBU R 128 loudness,
* decrease of crest factor,
* decrease of EBU R 128 LRA,
* slight decrease of clipped sample density.

In other words, fast-attack compressors increase both physical and perceptual levels, but only slightly. They decrease the density of clipped samples, and decrease both crest factor and macro-dynamics.

Set with a slow attack, the tested compressors had the following influence on the signal:
* decrease of RMS power,
* decrease of EBU R 128 loudness,
* no influence on crest factor,
* decrease of EBU R 128 LRA,
* no influence on clipped sample density.

In other words, slow-attack compressors decrease both physical and perceptual levels, decrease macro-dynamics, but have no influence on crest factor and clipped sample density.