Editing Ambient noise level

{{Short description|Background sound pressure level}}
[[Image:Integrating Sound Level Meter dB(A) Brüel Kjær 2225.jpg|thumb|right|Integrating Sound Level Meter]]

In [[atmospheric sounding]] and [[noise pollution]], '''ambient noise level''' (sometimes called '''[[background noise]] level''', '''reference sound level''', or '''room noise level''') is the background [[sound pressure level]] at a given location, normally specified as a reference level to study a new intrusive sound source.<ref>{{cite web|url=https://gracey.co.uk/basics/background-noise-b1.htm|title=Sound and Vibration Instrument Hire and Calibration Background Noise Measurement|access-date=22 October 2021|publisher=Gracey & Associates}}</ref>

Ambient sound levels are often measured in order to map sound conditions over a spatial regime to understand their variation with locale.<ref>{{cite journal|issn=2006-0459|url=http://repository.futminna.edu.ng:8080/jspui/handle/123456789/12697|publisher=SCHOOL OF ENVIRONMENTAL TECHNOLOGY, FUT MINNA|title=SPATIAL ANALYSIS AND GEOGRAPHICAL INFORMATION SYSTEM (GIS) MAPPING OF NOISE POLLUTION IN BOSSO LOCAL GOVERNMENT COUNCIL, NIGER STATE, NIGERIA|first1=S.A|last1=Jonah|first2=A.N|last2=Baba-Kutigi|first3=U.E|last3=Uno|first4=M.L|last4=Dangana|first5=M.T|last5=Kolo|first6=N.P|last6=Ofor|first7=C.I|last7=Unuevho|first8=F.M|last8=Abba|first9=D.U|last9=Alhassan|first10=A.N|last10=Amadi|first11=M.O|last11=Umar|first12=M.I|last12=Kimpa|journal=Environmental Technology & Science Journal |date=2011}}</ref>  In this case the product of the investigation is a sound level [[contour line|contour map]].<ref>{{cite journal|url=https://web.s.ebscohost.com/abstract?direct=true&profile=ehost&scope=site&authtype=crawler&jrnl=15829596&AN=34525080&h=mw0NZuMmyhIpTu6JFbUaIeHMbta4i%2fUFwUQ%2fhcnJBxT51m8eWGsHEFySYISTZ2DHMZNZSi%2bCdYcgRwQXq2C6rA%3d%3d&crl=c&resultNs=AdminWebAuth&resultLocal=ErrCrlNotAuth&crlhashurl=login.aspx%3fdirect%3dtrue%26profile%3dehost%26scope%3dsite%26authtype%3dcrawler%26jrnl%3d15829596%26AN%3d34525080|journal=Environmental Engineering & Management Journal|first1=Cahit Tagi|last1=Celik|first2=Lale|last2=Guremen|title=Analytical Noise Contour Construction Using Inverse Square Law of Sound Propagation |date=2008|issue=4|volume=7|pages=423–426|doi=10.30638/eemj.2008.061 |bibcode=2008EEMJ....7..423C }}</ref>  Alternatively ambient noise levels may be measured to provide a reference point for analyzing an intrusive sound to a given environment.  For example, sometimes [[aircraft noise]] is studied by measuring ambient sound without presence of any overflights, and then studying the noise addition by measurement or [[computer simulation]] of overflight events.  Or [[roadway noise]] is measured as ambient sound, prior to introducing a hypothetical [[noise barrier]] intended to reduce that ambient noise level.  

Ambient [[Environmental noise|noise level]] is measured with a [[sound level meter]].<ref name="measurement"/> It is usually measured in [[decibel|dB]] relative to a reference pressure of 0.00002 Pa, ''i.e.,'' 20 μPa (micropascals) in [[International System of Units|SI units]].<ref name="db"/> This is because 20 μPa is the faintest sound the human ear can detect.<ref name="db">{{cite web|url=https://heartaudio.co.nz/what-decibels-pascals-means|publisher=HeartAudio|title=Decibels & Pascals|access-date=22 October 2021}}</ref> A pascal is a newton per square meter.  The centimeter-gram-second [[system]] of units, the reference sound pressure for measuring ambient noise level is 0.0002 dyn/cm<sup>2</sup>, or 0.00002 N/m<sup>2</sup>.<ref>{{cite web|url=https://www.justintools.com/unit-conversion/pressure.php?k1=micropascals&k2=newton-per-square-meter|publisher=Justin Tools|title=PRESSURE Units Conversion micropascals to newton-per-square-meter|access-date=22 October 2021}}</ref>  Most frequently ambient noise levels are measured using a frequency weighting filter, the most common being the [[A-weighting]] scale, such that resulting measurements are denoted dB(A), or decibels on the [[A-weighting]] scale.<ref name="measurement">{{cite web|url=https://www.nexflow.com/blog/what-does-dba-mean/|title=What does dBA mean when someone talks about noise levels?|date=November 6, 2018|publisher=Nex Flow|access-date=22 October 2021}}</ref>

==See also==
{{div col|colwidth=23em}}
*[[A-weighting]]
*[[Background noise]]
*[[Environmental noise]]
*[[Noise barrier]]
*[[Noise health effects]]
*[[Sonar#Performance_prediction_2|Noise level in the sonar equation]]
*[[Noise pollution]]
*[[Noise regulation]]
{{div col end}}

== References ==
{{Reflist}}
{{FS1037C MS188}}

[[Category:Noise]]
[[Category:Noise pollution]]
[[Category:Sound]]
[[Category:Acoustics]]

== Further reading ==
* [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3377030/ Assessment of Ambient Noise Levels]
[[de:Umgebungslärm]]