Editing Standing wave (section)

=== Acoustic resonance ===
{{Main|Acoustic resonance}}

[[File:Rotatingsaturnhexagon gif.ogv|frame|right|[[Saturn's hexagon|The hexagonal cloud feature]] at the north pole of Saturn was initially thought to be standing [[Rossby wave]]s.<ref>[http://pubs.giss.nasa.gov/docs/1990/1990_Allison_etal.pdf A Wave Dynamical Interpretation of Saturn's Polar Region] {{webarchive|url=https://web.archive.org/web/20111021145109/http://pubs.giss.nasa.gov/docs/1990/1990_Allison_etal.pdf |date=2011-10-21 }}, M. Allison, D. A. Godfrey, R. F. Beebe, Science vol. 247, pg. 1061 (1990)</ref> However, this explanation has recently been disputed.<ref>{{cite journal | doi = 10.1016/j.icarus.2009.10.022 | bibcode=2010Icar..206..755B | volume=206 | issue=2 | title=A laboratory model of Saturn's North Polar Hexagon | year=2010 | journal=Icarus | pages=755–763 | last1 = Barbosa Aguiar | first1 = Ana C.}}</ref>]]
Standing waves are also observed in physical media such as strings and columns of air. Any waves traveling along the medium will reflect back when they reach the end. This effect is most noticeable in musical instruments where, at various multiples of a [[vibrating string]] or [[air column]]'s [[natural frequency]], a standing wave is created, allowing [[harmonics]] to be identified. Nodes occur at fixed ends and anti-nodes at open ends. If fixed at only one end, only odd-numbered harmonics are available. At the open end of a pipe the anti-node will not be exactly at the end as it is altered by its contact with the air and so [[end correction]] is used to place it exactly. The density of a string will affect the frequency at which harmonics will be produced; the greater the density the lower the frequency needs to be to produce a standing wave of the same harmonic.