Scientists Create Wallpaper-Thin Speakers

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Every few decades, speakers get a little more immersive thanks to advances in sound processing technologies and cheaper access to surround sound components.

What if you could literally turn every wall in your house into one giant speaker?

This could be possible in the years to come. Researchers at MIT has developped a new kind of paper-thin speaker that’s light and durable enough to attach to all kinds of surfaces.

That all sounds good, but fancy tech doesn’t mean much if it’s too complicated and expensive to bring to market. But this state-of-the-art speaker promises the opposite: MIT News says the speaker paper can be built with a three-step process that is apparently easier than traditional speakers.

It should be noted here that this thin speaker business is not entirely new. Planar magnetic and electrostatic the speakers also rely on thin, flat vibrating material, leading to unusually thin speaker designs.

But even the material described in the MIT article is not unheard of: the speakers use polyvinylidene fluoride (PVDF) film, which has piezoelectric properties and has been used for loudspeakers since at least the 70s.

Traditionally, PVDF loudspeakers have faced many design challenges that have prevented their commercial viability, including problematic durability and limited frequency response. They also required a strong support structure and ultimately didn’t offer much advantage over traditional pilots.

MIT’s main innovation here seems to be to strengthen the material by reshaping it. A perforated layer of PET plastic is applied to the PVDF sheet which, when heat treated under vacuum, forces the PVDF through the perforations, creating a myriad of tiny domes.

Credit: MIT News
Credit: MIT News

It’s kind of like a super tiny bubble wrap that can make more than just a popping sound.

Rather than just vibrating the entire sheet of PVDF material in unison, it’s the domes that vibrate. Meanwhile, layers of PET surrounding the domes add the structural integrity required so the material can bend and attach to surfaces without impeding sound reproduction.

Manufacturers can then modify the acoustic properties of the material by resizing and rearranging the domes, leading to all sorts of interesting applications. Domes could be arranged to concentrate sound at specific locations in a room, for use in ultrasound imaging, or even to “provide a new method of chemical agitation”. Sure why not.

Going back to the text of this article, the weight and flexibility of the material also means that it could be used as wallpaper. Besides the immersive implications of such a design, the ability to cover large areas and precisely shape sound means you could theoretically turn your walls into noise-cancelling surfaces. working much like noise canceling headphones to prevent outside noise from filtering into your home.

This idea also works with regular speakers, but positioning limitations make it essentially impossible in a practical sense.

But enough talk – listen for yourself.

Well, that doesn’t sound very good. But I mean, when did you hear something the size of a post-it note go off?

The fact that it’s capable of producing audible sound in such a form factor is quite remarkable, especially considering the design looks pretty efficient. One square meter of speaker material uses about one-tenth (100 milliwatts) of the electricity as the “average home speaker” (1 watt) for similar decibel output.

Granted, most home loudspeakers don’t have a square meter of radiating surfaces – all things being equal, the larger the radiating surface, the more efficient the loudspeaker – but such loudspeakers would be so large that they would be impractical. The compelling part of PVDF speakers is that you can line your home – or the interiors of cars and playhouses – with the material without taking up virtually any space.

If the technology expands into commercial use, I can see that being a boon for mobile devices. It is fundamentally difficult to install large traditional drivers on laptops and phones. The speakers and their associated magnets simply take up too much space (not to mention the added weight). PVDF speakers, on the other hand, could take up the entire surface of your phone or laptop without adding much to the overall volume or power demand.

Researchers will have a lot to prove before these PVDF enclosures hit the market. For one thing, they’ll likely struggle to reproduce bass in large quantities, and it remains to be seen how cost-effective the design will become, compared to proven speaker designs.

Still, I think it’s one of the coolest innovations in the speaker world in quite some time. I’d like to imagine a world where speakers can be easily and invisibly integrated into our homes, rather than trying to find the perfect place to stick massive wooden boxes. I hope I can get wallpaper speakers from Home Depot in the years to come.

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