Acoustic Diode Only Lets Sound Travel in One Direction (Read: True Soundproofing)

By Clay Dillow Posted 07.27.2011 at 10:15 am 5 Comments

The Acoustic Diode By tuning the elastic spheres in certain ways--by changing their sizes and shapes from one end of the chain to the other, for instance--it's possible to manipulate a sound wave as it travels down the chain, downshifting the frequency or making it possible for sounds to travel in one direction but not the other. Chiara Daraio/Caltech

Anyone who has ever tried to record that first feature-length album in his or her dad’s garage knows that reflecting, suppressing, and otherwise manipulating sound isn’t as simple as it might seems. We’ve got that egg-carton foam that offers some soundproofing, but beyond such muting materials we have few mature technologies that let us control the way sound travels. But Caltech researchers are working to change that via the first tunable, acoustic diode that can be used to let sound flow in one direction only.

The acoustic diode works much like the electrical component of the same name, letting current (or, in this case, sound waves) pass in one direction but blocking it in the other. Composed of a structured arrangement of elastic spheres that ferry the sound through the material, the diode can be tuned to work only at certain frequencies or to downshift the frequencies moving through the material to lower frequencies as needed.

That opens the technology up to several potential applications. In the case of soundproofing, the technology could enable true one-way transmission of sound (rather than the simple dispersion and muting performed by “soundproofing” foams). But perhaps more interestingly, the material could be used to harvest energy from sound waves.

For instance, the tunable diode could scavenge energy from noisy machinery and channel it back into a transducer that converts those sound vibrations into electricity that could be fed back to the machine, reducing net energy consumption. It could also downshift sound frequencies to ranges that are optimal for energy conversion.

All that’s a long way off, but the notion is pretty intriguing. In the meantime, the Caltech team is also exploring a range of other technological applications for their wave-manipulating technology, including medical uses (ultrasound), architectural acoustics, and insulating materials that regulate temperature.

[PhysOrg]

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5 Comments

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sacridias

07/27/11 at 11:16 am

Technology is only discovered after the idea is presented in a movie (That is why technology before movies were so slow to become reality). Need proof, look at the speed of technology growth before and after movies and TV, I promise this is why.

You see shows with Lasers, Time Travel, Race cars, long range communication, teleportation, etc... The only movie I know of with sound reduction technology is get smart (Cone of Silence). All other movies are about making sound louder, and loader we have made it.

More proof that movies make technology. Too bad there are not more time travel movies, then we may have found a way to time travel instead of a limitation to it.

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Ancient Astronaut

07/27/11 at 12:27 pm

@sacridias - It's not Hollywood that is powering scientific discovery, but our imaginations. Throughout history science has been hindered due to people's lack of imagination, unwillingness to look at things differently. Look at all the "impossibles" that are now facts. There is no limit on how much imagination Hollywood can have, but the science community has a point where anything too imaginative is cast aside and labeled "science fiction" and "impossible". I must say this level has been rising in recent years, thanks to the weirdness of quantum theory.

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sacridias

07/27/11 at 2:19 pm

So now your going to tell me that global warming is not related to the drop in the number of pirates (Especially those that say argh)? :D
Sorry, if anyone actually thinks I believe the sharp increase in technology is related to movies or tv. The truth is I believe progress has always been accelerating, as our ability to expand our imagination and find better means to communicate those ideas to each other. Couple this with better means to define processes and tools to analyze our ideas means great science. My last statement was purely sarcastic.

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drchuck1

07/27/11 at 5:30 pm

technology builds upon itself, an increase in scientific discoveries over time should be no surprise, just the simple fact we have a much larger study area (did that make sense?) makes new discoveries much more likey

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BubbaGump

07/29/11 at 5:46 pm

@drchuck1, one of the great mysteries of building the great Egyptian pyramids is technology DID NOT build upon itself. Once these monolithic structures were built, the technology did not trickle out to the average builder “how to make gigantic granite blocks cut preciously to 1/1000 of inch accuracy or even small granite blocks. The blocks require diamond hardness tools. The technology just died with the pharaohs and tiny local supporting folk. The builders also left no tools of this event either. Still by the great size and scope of construction, the local community had to be involved.

But, yes typical at times in history, technology does seem to build on itself and the associated tooling, at least in our observed life time.

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