Editing Dynamic range compression (section)

== Types ==
{{multiple image
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   | header    = '''Two methods of dynamic range compression'''
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   | image1    = Audio-level-compresion-diagram-01.svg
   | height1   = 160
   | alt1      = Downward compression diagram
   | caption1  = Downward compression
   | image2    = Upward compression.svg
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   | alt2      = Upward compression diagram
   | caption2  = Upward compression
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There are two types of compression: downward and upward. Both types of compression reduce the [[Dynamic range#Audio|dynamic range]] of an audio signal.<ref name="Reese">{{Cite book|last1=Reese|first1=David E|url=https://archive.org/details/audioproductionw0000rees|title=Audio Production Worktext: Concepts, Techniques, and Equipment|last2=Gross|first2=Lynne S|last3=Gross|first3=Brian|publisher=Focal Press|year=2009|isbn=978-0-240-81098-0|pages=[https://archive.org/details/audioproductionw0000rees/page/149 149]|oclc=1011721139|url-access=registration|via=Internet Archive}}</ref>

''Downward'' compression reduces the volume of loud sounds ''above'' a certain threshold. The quiet sounds ''below'' the threshold remain unaffected. This is the most common type of compressor. A [[limiter]] can be thought of as an extreme form of downward compression as it compresses the sounds over the threshold especially hard. 

''Upward'' compression increases the volume of quiet sounds ''below'' a certain threshold. The louder sounds ''above'' the threshold remain unaffected. 

Some compressors also have the ability to do the ''opposite'' of compression, namely ''expansion''. Expansion ''increases'' the dynamic range of the audio signal.<ref>{{Cite web |url=https://ccrma.stanford.edu/courses/192b/192b_Lecture_1_18.pdf |title=Dynamic Range Processing and Digital Effects |last=Kadis |first=Jay }}{{Cite web |url=https://ccrma.stanford.edu/courses/192b/192b_Lecture_1_18.pdf |title=Dynamic Range Processing and Digital Effects |last=Kadis |first=Jay }}</ref> Like compression, expansion comes in two types, downward and upward. 

''Downward'' expansion makes the quiet sounds below the threshold even quieter. A [[noise gate]] can be thought of as an extreme form of downward expansion as the noise gate make the quiet sounds (for instance: noise) quieter or even silent, depending on the floor setting.<ref name="Reese" />

''Upward'' expansion makes the louder sounds above the threshold even louder.
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