For many of you, the term magnetostriction might sound just like any word in a language you neither understand nor have ever heard of; yet things are rather simple and easy to figure out. In few words, magnetostriction refers to special materials which behave in particular ways when either strain or electricity is induce onto them.[admark=1]
Pretty much like the quartz crystals, which emit electricity when they undergo pressure, magnetostrictive materials can also behave the opposite way, namely modify shape or structure as electricity passes through; such materials are called smart materials and they have become more and more used with numerous applications.
It's the very special case of the recent Terfenol-D, a smart material which promises to change the way we are used to experience audio, on the streets and in shops, as well as in our very own homes. Terfenol-D is a compound material made from rare earths and sports extraordinary magnetic properties; a composite made from Terbium, Iron and Dysprosium, the Terfenol-D is one of the most promising smart materials to have so far been created and used in the audio industry.
Well, indeed, "industry" might sound a bit too much as things are moving rather slowly in this field; nevertheless there are already numerous applications using this technology and making possible things no one thought of some 20 or 30 years ago. One of the sound applications for the Terfenol-D is the resonant audio domain; using Terfenol-D as a transducer, the new "solid-drive" audio tools can bring music in places most unlikely to have anything to do with it.
Even though the inner mechanics of smart materials such as the Terfenol-D might be quite hard to understand for those with lesses physics preparation, the principle used to generate sound is quite easy to understand. Given the fact that the Terfenol-D has been engineered very seriously, it can respond with dynamics which are considered "giant" among smart materials; this is why this particular one can actually resonate, by moving with very fast speeds, in microseconds, expanding and contracting.
Having no moving coils like traditional speakers do, these drivers are infinitely less susceptible to heath build-up and can therefore work for prolonged periods of time with out failure, even close to their maximal parameters. Specialized manufacturers have already designed a wide range of Terfenol-D-based drivers with various frequency responses and even a subwoofer; easy to retrofit in any spaces because these units use existing materials, such "speakers" are also convenient for presentation purposes and are more than portable. At the same time, these units are simply perfect for no-fuss distributed audio over large spaces where redecoration is highly impractical.
We're talking gear like the FeONIC Whispering Windows or the S3i SolidDrive Desktop: using the magnetostrictive smart materials, one can instantly turn the very tabletop of his/her work desk in a neat loudspeaker or even the windows! Extensive experiments have already been set in practice with shop windows and the results have been at least spectacular: imagine having the entire window of your large shop spreading music on the sidewalk, with clarity and warmth - wouldn't you stop or at least slow down and take a peek at what's inside?
All that's needed in the classic amplifier and some flat surface to stick your Terfenol-D drivers to it: then press "play" and there you go, that surface will resonate to the music! Even more, FeONIC have developed audio gadgets for everyday use, such as the SoundBug: a portable magnetostriction-powered audio gadget you can hook up to your MP3 player or iPod. Just have a cable in the headphone jack of your portable digital player and the SoundBug stuck on a window using the convenient suction cup, and you've got a speaker and music coming form it...even though there isn't actually any speaker there.
Another cool thing coming with the Terfenol-D drivers is the fact that in their case, having audio and water in the same equation will not result anymore in damaged audio technology: water has actually nothing to do with the proper drivers, therefore you can have them installed on your very bathtub or shower cabin glass walls and enjoy the nifty sound of your fav tracks without fear you'll wreck your audio gear.
So far, fun-oriented Terfenol-D gadgetry, like the FeONIC SoundBug, retails for affordable prices under $200, but extensive sound systems with dedicated resonant subwoofers and tweeters sell for prices starting at $2,000-$4,000. Get more extensive data in these locations and here. If you're looking for the Terfenol-D specs, there you go.
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Terfenol-D: No Speakers = Great Sound!
Magnetostriction explained, and working for you: a possible future for your audio
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