Editing Ferrofluid (section)

====Loudspeakers====
Starting in 1973, ferrofluids have been used in [[loudspeaker]]s to remove heat from the [[voice coil]], and to passively [[Damping ratio|damp]] the movement of the cone. They reside in what would normally be the air gap around the voice coil, held in place by the speaker's magnet. Since ferrofluids are paramagnetic, they obey [[Curie's law]] and thus become less magnetic at higher temperatures. A strong magnet placed near the voice coil (which produces heat) will attract cold ferrofluid more than hot ferrofluid thus pushing the heated ferrofluid away from the electric voice coil and toward a [[heat sink]]. This is a relatively efficient cooling method which requires no additional energy input.<ref>{{cite journal|author=Rlums, Elmars|url=http://www.sbfisica.org.br/bjp/download/v25/v25a10.pdf|journal=Brazilian Journal of Physics|volume=25|issue=2|date=1995|title=New Applications of Heat and Mass Transfer Processes in Temperature Sensitive Magnetic Fluids}}</ref>

Bob Berkowitz of [[Acoustic Research]] began studying ferrofluid in 1972, using it to damp resonance of a tweeter. Dana Hathaway of Epicure in Massachusetts was using ferrofluid for tweeter damping in 1974, and he noticed the cooling mechanism. Fred Becker and Lou Melillo of Becker Electronics were also early adopters in 1976, with Melillo joining Ferrofluidics and publishing a paper in 1980.<ref>{{cite journal | last1=Melillo | first1=Louis | last2=Raj | first2=K. | title=Ferrofluids as a Means of Controlling Woofer Design Parameters | journal=Journal of the Audio Engineering Society | publisher=Audio Engineering Society | volume=29 | issue=3 | date=1981-03-01 | pages=132–139 }}</ref> In concert sound, [[Showco]] began using ferrofluid in 1979 for cooling woofers.<ref>{{cite magazine |url=https://books.google.com/books?id=fAEAAAAAMBAJ&pg=PA61 |page=61 |date=June 1979 |title=Magnetic Fluids |last=Free |first=John |magazine=[[Popular Science]] }}</ref> [[Panasonic]] was the first Asian manufacturer to put ferrofluid in commercial loudspeakers, in 1979. The field grew rapidly in the early 1980s. Today, some 300&nbsp;million sound-generating transducers per year are produced with ferrofluid inside, including speakers installed in laptops, cell phones, headphones and earbuds.<ref>{{Cite web|url=https://www.czferro.com/ferrofluid-history|title=Brief History of Ferrofluid|website=Ferrofluid Displays, Art, and Sculptures &#124; Concept Zero}}</ref>