Editing Sound power (section)

==Sound power level ''L''<sub>WA</sub>==

[[File:Atlas Copco XAHS 347-pic7-Max. sound power level.jpg|thumb|Maximum sound power level ([[A-weighting|''L''<sub>WA</sub>]]) related to a portable [[air compressor]]]]Regulations often specify a method for measurement<ref>{{cite web | url = https://www.iso.org/obp/ui/#iso:std:iso:3744:ed-3:v1:en | title = ISO 3744:2010(en) Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Engineering methods for an essentially free field over a reflecting plane | publisher = [ISO] | access-date = 22 December 2017 }}</ref> that integrates sound pressure over a surface enclosing the source. ''L''<sub>WA</sub> specifies the power delivered to that surface in decibels relative to one picowatt. Devices (e.g., a vacuum cleaner) often have labeling requirements and maximum amounts they are allowed to produce. The [[A-weighting]] scale is used in the calculation as the metric is concerned with the loudness as perceived by the human ear. Measurements<ref>{{cite web | url = http://blog.nti-audio.com/measurement/eu-sound-power-regulation-vacuum-cleaners | title = EU Sound Power Regulation for Vacuum Cleaners | date = 19 December 2017 | publisher = [NTi Audio] | access-date = 22 December 2017 }}</ref> in accordance with ISO 3744 are taken at 6 to 12 defined points around the device in a hemi-anechoic space. The test environment can be located indoors or outdoors. The required environment is on hard ground in a large open space or hemi-anechoic chamber (free-field over a reflecting plane.)

===Table of selected sound sources===
Here is a table of some examples, from an on-line source.<ref>{{cite web | url = http://www.engineeringtoolbox.com/sound-power-level-d_58.html | title = Sound Power | publisher = The Engineering Toolbox | access-date = 28 November 2013 }}</ref> For omnidirectional point sources in free space, sound power in ''L''<sub>wA</sub> is equal to [[sound pressure level]] in dB above 20 micropascals at a distance of 0.2821 m<ref>{{cite web | url = http://www.sengpielaudio.com/calculator-soundpower.htm | title = Sound Power Level}}</ref>

{| class="wikitable"
! Situation and<br>sound source !! Sound power<br>([[Watt|W]]) !! Sound power level<br>([[Decibel|dB]] ref 10<sup>−12</sup> W)
|-
| [[Saturn V]] rocket<ref>{{Cite journal|title=NASA Technical Reports Server (NTRS)|url=https://ntrs.nasa.gov/citations/20120003777|access-date=2021-03-24|website=NASA|date=15 February 2012|quote=the largest sound power levels ever experienced at NASA Stennis was approximately 204dB, which corresponded to the Saturn S‐IC stage on the B‐2 test stand.|last1=Allgood|first1=Daniel C.}}</ref>|| align="right" | {{val|100000000}} || align="right" | 200
|-
| [[Turbojet]] engine || align="right" | {{val|100000}} || align="right" | 170
|-
| [[Turbofan]] aircraft at take-off || align="right" | {{val|1000}} || align="right" | 150
|-
| [[Turboprop]] aircraft at take-off || align="right" | {{val|100}} || align="right" | 140
|-
| [[Machine gun]] <br>Large [[pipe organ]]|| align="right" | {{val|10}} || align="right" | 130
|-
| [[Symphony orchestra]]<br>Heavy [[thunder]]<br>[[Sonic boom]] || align="right" | {{val|1}} || align="right" | 120
|-
| [[Rock concert]] (1970s)<br>[[Chain saw]]<br>Accelerating [[motorcycle]]|| align="right" | {{val|0.1}} || align="right" | 110
|-
| [[Lawn mower]]<br>Car at highway speed<br>[[Rapid transit|Subway steel wheels]] || align="right" | {{val|0.01}} || align="right" | 100
|-
| Large [[Diesel engine|diesel vehicle]] || align="right" | {{val|0.001}} || align="right" | 90
|-
| Loud [[alarm clock]] || align="right" | {{val|0.0001}} || align="right" | 80
|-
| Relatively quiet [[vacuum cleaner]] || align="right" | {{val|e=-5}} || align="right" | 70
|-
| [[Hair dryer]] || align="right" | {{val|e=-6}} || align="right" | 60
|-
| Radio or TV || align="right" | {{val|e=-7}} || align="right" | 50
|-
| [[Refrigerator]]<br/>Low voice || align="right" | {{val|e=-8}} || align="right" | 40
|-
| Quiet conversation || align="right" | {{val|e=-9}} || align="right" | 30
|-
| Whisper of one person<br>Wristwatch ticking|| align="right" | {{val|e=-10}} || align="right" | 20
|-
| Human breath of one person || align="right" | {{val|e=-11}} || align="right" | 10
|-
| Reference value || align="right" | {{val|e=-12}} || align="right" | 0
|}