Editing Sonar (section)

===Scattering===
{{See also|Deep scattering layer}}
When active sonar is used, [[scattering]] occurs from small objects in the sea as well as from the bottom and surface.  This can be a major source of interference. This acoustic scattering is analogous to the scattering of the light from a car's headlights in fog: a high-intensity pencil beam will penetrate the fog to some extent, but broader-beam headlights emit much light in unwanted directions, much of which is scattered back to the observer, overwhelming that reflected from the target ("white-out").  For analogous reasons active sonar needs to transmit in a narrow beam to minimize scattering.
[[File:Undersea bubble clouds.jpg|thumb|Bubble clouds shown under the sea. From ref.<ref name="Leighton_et_al_Nature_2018">{{cite journal |author1=Leighton, T.G. |author2=Coles, D.C.H. |author3=Srokosz, M. |author4=White, P.R. |author5=Woolf, D.K. |title=Asymmetric transfer of CO2 across a broken sea surface|journal= Scientific Reports |year=2018 |volume=8 |issue=1 |pages=8301 |doi=10.1038/s41598-018-25818-6 |pmid=29844316 |pmc=5974314 |bibcode=2018NatSR...8.8301L}}</ref>]] 
The scattering of sonar from objects (mines, pipelines, zooplankton, geological features, fish etc.) is how active sonar detects them, but this ability can be masked by strong scattering from false targets, or 'clutter'. Where they occur (under breaking waves;<ref name="Woolf+Thorpe_1991">{{cite journal |author1= Woolf, D.K. |author2=Thorpe, S.A.  |title= Escape of methane gas from the seabed along the West Spitsbergen continental margin  |journal= J. Mar. Res.  |year=1991 |volume=49 |issue=3| pages= 435–466 |doi= 10.1357/002224091784995765 }}</ref> in ship wakes; in gas emitted from seabed seeps and leaks<ref name= "Westbrook_et_al_2009">{{cite journal |author1=Westbrook, G.K. |author2=Thatcher, K.E. |author3=Rohling, E.J. |author4=Piotrowski, A.M. |author5=Pälike, H. |author6=Osborne, A.H. |author7=Nisbet, E.G. |author8=Minshull, T.A. |author9=Lanoisellé, M. |author10=James, R.H. |author11= Hühnerbach, V. |author12=Green, D. |author13=Fisher, R.E. |author14=Crocker, A.J. |author15=Chabert, A. |author16=Bolton, C. |author17=Beszczynska-Möller, A. |author18=Berndt, C. |author19=Aquilina, A.  |title= Escape of methane gas from the seabed along the West Spitsbergen continental margin  |journal= J. Mar. Res.  |year=2009 |volume=36 |issue=15 |pages= L15608|bibcode= 2009GeoRL..3615608W |doi= 10.1029/2009GL039191 |url= http://nora.nerc.ac.uk/id/eprint/164607/1/2009gl039191%2Baux.pdf |doi-access=free }}</ref> etc.), gas bubbles are powerful sources of clutter, and can readily hide targets. TWIPS (Twin Inverted Pulse Sonar)<ref name="Leighton_et_al_2010_TWIPS">{{Cite journal | doi = 10.1098/rspa.2010.0154| title = Clutter suppression and classification using twin inverted pulse sonar (TWIPS)| journal = Proceedings of the Royal Society A| volume = 466| issue = 2124| pages = 3453–3478| year = 2010| last1 = Leighton | first1 = T. G.| last2 = Finfer | first2 = D. C.| last3 = White | first3 = P. R.| last4 = Chua | first4 = G. – H. | last5 = Dix | first5 = J. K.|bibcode = 2010RSPSA.466.3453L | s2cid = 111066936|url=http://resource.isvr.soton.ac.uk/staff/pubs/PubPDFs/2010%20Leighton%20et%20al%20(PRS)%20Clutter%20suppression%20and%20classification.pdf}}</ref><ref name="Leighton_et_al_2012_PRS_dolphins">{{Cite journal | doi= 10.1098/rspa.2012.0247| title = Do dolphins benefit from nonlinear mathematics when processing their sonar returns?| journal = Proceedings of the Royal Society A| volume = 468| issue = 2147| pages = 3517–3532| year = 2012| last1 = Leighton | first1 = T. G.| last2 = Chua | first2 = G. H.| last3 = White | first3 = P. R.| url= http://resource.isvr.soton.ac.uk/staff/pubs/PubPDFs/2012_Leighton_et_al_%20(PRS)_Do_dolphins_benefit.pdf|bibcode = 2012RSPSA.468.3517L | s2cid = 109255100| doi-access = free}}</ref><ref name="Leighton_et_al_2011_JASA_TWIPS">{{Cite journal| pmid = 22088017| year = 2011| last1 = Leighton| first1 = T. G.| title = Clutter suppression and classification using twin inverted pulse sonar in ship wakes| journal = The Journal of the Acoustical Society of America| volume = 130| issue = 5| pages = 3431–7| last2 = Finfer| first2 = D. C.| last3 = Chua| first3 = G. H.| last4 = White| first4 = P. R.| last5 = Dix| first5 = J. K.|url=http://resource.isvr.soton.ac.uk/staff/pubs/PubPDFs/Pub12669.pdf| doi = 10.1121/1.3626131| bibcode = 2011ASAJ..130.3431L}}</ref> is currently the only sonar that can overcome this clutter problem.[[File:TWIPS picture 2.png|thumb|Comparison of Standard Sonar and TWIPS in finding a target in bubbly water. Adapted from ref.<ref name="Leighton_et_al_2010_TWIPS"/>]] This is important as many recent conflicts have occurred in coastal waters, and the inability to detect whether mines are present or not present hazards and delays to military vessels, and also to aid convoys and merchant shipping trying to support the region long after the conflict has ceased.<ref name="Leighton_et_al_2010_TWIPS"/>