Parametric array: Difference between revisions

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{{Citation style|date=September 2009}}

In the field of [[acoustics]], a '''parametric array''' is a nonlinear [[transducer|transduction]] mechanism that generates narrow, nearly [[side lobe]]-free beams of low frequency sound, through the mixing and interaction of high frequency [[sound wave]]s, effectively overcoming the [[diffraction limit]] (a kind of spatial 'uncertainty principle') associated with linear acoustics.<ref>{{cite book| last=Beyer| first=Robert T| title=Nonlinear Acoustics| chapter=Preface to the Original Edition| url=http://asa.aip.org/books/nonlinear.html#Preface1}}</ref> Parametric arrays can be formed in water,<ref name=nonlinear-underwater-acoustics-book>{{cite book| last1=Novikov| first1=B. K.| last2=Rudenko| firstfirst2=O. V.| last3=Timoshenko| first3=V. I.| others= Translated by Robert T. Beyer| title=Nonlinear Underwater Acoustics| url=http://asa.aip.org/books/nonuw.html}}</ref> air,<ref>[http://dx.doi.org/10.1121/1.384959 Experimental study of a saturated parametric array in air]</ref> and earth materials/rock.<ref>[http://dx.doi.org/10.1121/1.403453 Finite amplitude wave studies in earth materials]</ref><ref>[http://www.lanl.gov/orgs/ees/ees11/geophysics/nonlinear/pubs/parabeam.html Parametric Beam Formation in Rock]</ref>

== History ==

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* medical [[ultrasound]] <ref>[http://dx.doi.org/10.1088/0031-9155/46/11/314 A focused ultrasound method for simultaneous diagnostic and therapeutic applications<!-- Bot generated title -->]</ref>

* and tomography [http://dx.doi.org/10.1121/1.1344160]

* underground seismic prospecting <ref>[http://dx.doi.org/10.1121/1.2022023],</ref>

* active noise control <ref>[http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=378],</ref>

* and directional high-fidelity commercial audio systems ([[Sound from ultrasound]])<ref>[[n:Elwood Norris receives 2005 Lemelson-MIT Prize for invention.]]</ref>

Parametric ''receiving'' arrays can also be formed for directional reception.<ref>[http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1170632].</ref> In 2005, Elwood Norris won the $500,000 [[Lemelson-MIT Prize|MIT-Lemelson Prize]] for his application of the parametric array to commercial high-fidelity loudspeakers.

==References==