Editing Decibel (section)

=== Acoustics ===
Probably the most common usage of "decibels" in reference to sound level is dB{{sub| SPL}}, sound pressure level referenced to the nominal threshold of human hearing:<ref>
{{cite book
 | title = Audio postproduction for digital video
 | first = Jay  | last = Rose
 | publisher = Focal Press
 | year = 2002
 | isbn = 978-1-57820-116-7
 | page = 25
 | url = {{Google books |plainurl=yes |id=sUcRegHAXdkC |page=25 }}
}}</ref>  The measures of pressure (a root-power quantity) use the factor of 20, and the measures of power (e.g. dB{{sub| SIL}} and dB{{sub| SWL}}) use the factor of 10.
; dB{{sub| SPL}} : dB{{sub| SPL}} (sound pressure level) – for sound in air and other gases, relative to 20&nbsp;micropascals (μPa), or {{val|2|e=-5|u=Pa}}, a level of 0&nbsp;dB{{sub| SPL}} is approximately the quietest sound a human can hear. For [[Underwater acoustics|sound in water]] and other liquids, a reference pressure of 1&nbsp;μPa is used.<ref>Morfey, C. L. (2001). Dictionary of Acoustics. Academic Press, San Diego.</ref>{{paragraphbreak}} An RMS sound pressure of one pascal corresponds to a level of 94&nbsp;dB&nbsp;SPL.
; dB{{sub| SIL}} : dB [[sound intensity level]] – relative to 10<sup>−12</sup>&nbsp;W/m<sup>2</sup>, which is roughly the [[threshold of human hearing]] in air.
; dB{{sub| SWL}} : dB [[sound power level]] – relative to 10<sup>−12</sup>&nbsp;W.
; dB{{sub| A}}, dB{{sub| B}}, and dB{{sub| C}} : These symbols are often used to denote the use of different [[weighting filter]]s, used to approximate the human ear's [[stimulus (psychology)|response]] to sound, although the measurement is still in dB&nbsp;(SPL). These measurements usually refer to noise and its effects on humans and other animals, and they are widely used in industry while discussing noise control issues, regulations and environmental standards. Other variations that may be seen are dB{{sub| A}} or dB(A). According to standards from the International Electro-technical Committee ([[IEC 61672|IEC 61672-2013]])<ref>{{cite book |title=IEC 61672-1:2013 Electroacoustics - Sound Level meters - Part 1: Specifications |date=2013 |publisher=International Electrotechnical Committee |location=Geneva}}</ref> and the American National Standards Institute, [[ANSI S1.4]],<ref>[[ANSI]] [https://law.resource.org/pub/us/cfr/ibr/002/ansi.s1.4.1983.pdf S1.4-19823 Specification for Sound Level Meters], 2.3 Sound Level, p. 2–3.</ref> the preferred usage is to write {{nobr| {{mvar|L}}{{sub| A}} {{=}} {{mvar|x}}&nbsp;dB .}} Nevertheless, the units dB{{sub| A}} and dB(A) are still commonly used as a shorthand for A{{nbhyph}}weighted measurements. Compare [[dBc|dB{{sub| c}}]], used in telecommunications.
; dB{{sub| HL}} : dB [[hearing level]] is used in [[audiogram]]s as a measure of hearing loss. The reference level varies with frequency according to a [[minimum audibility curve]] as defined in ANSI and other standards, such that the resulting audiogram shows deviation from what is regarded as 'normal' hearing.{{Citation needed|date=March 2008}}
; dB{{sub| Q}} : sometimes used to denote weighted noise level, commonly using the [[ITU-R 468 noise weighting]]{{Citation needed|date=March 2008}}
; dB{{sub| pp}} : relative to the peak to peak sound pressure.<ref>{{cite journal |last1=Zimmer |first1=Walter M.X. |first2=Mark P. |last2=Johnson |first3=Peter T. |last3=Madsen |first4=Peter L. |last4=Tyack |year=2005 |title=Echolocation clicks of free-ranging Cuvier's beaked whales (''Ziphius cavirostris'') |journal=[[The Journal of the Acoustical Society of America]] |volume=117 |issue=6 |pages=3919–3927 |doi=10.1121/1.1910225 |pmid=16018493 |bibcode=2005ASAJ..117.3919Z |hdl=1912/2358 |hdl-access=free }}</ref>
; dB{{sub| G}} : G‑weighted spectrum<ref>{{cite web | title = Turbine sound measurements |via=wustl.edu | url = http://oto2.wustl.edu/cochlea/wt4.html | url-status = dead | archive-url = https://web.archive.org/web/20101212221829/http://oto2.wustl.edu/cochlea/wt4.html | archive-date = 12 December 2010 }}</ref>