Researchers at MIT have developed a paper-thin speaker that can be applied to almost any surface, turning objects like walls into giant noise-cancelling speakers.
If you tear apart the speakers in almost any consumer device that produces sound, you will find the same hardware: a coil of wire that produces a magnetic field. When electricity is applied, the air moves back and forth and creates sound waves that reach our ears. It is a simple formula that has worked well for over 150 years, but requires a certain amount of power and space to work. There is room for improvement when it comes to speaker tech, and you will understand why if you look at the tower of massive speakers on either side of the stage at a concert.
A new kind of thin-film speaker that is as thin and flexible as a sheet of paper is able to generate clear, high-quality sound even when it's stuck to a rigid object. Previous attempts have resulted in a film that needs to be freestanding and able to produce sound. The ability to vibrate and move air is limited when mounted to a rigid surface. MIT researchers have come up with a new manufacturing process that can solve that problem.
Instead of designing a thin-film speaker that requires the entire panel to vibrate, the researchers started with a sheet of lightweight plastic that they cut with a laser. A layer of thin piezoelectric material called PVDF was laminated to the underside of the sheet, and then the researchers subjected both layers to a vacuum and 80 degrees Celsius heat, which caused the piezoelectric layer to bulge and push through the laser-cut holes in the top layer. A series of tiny domes that are able to vibrate and pulse when an electric current is applied, regardless of whether or not the panel is bonding to a rigid surface. The domes can vibrate freely, and be protected from damage, if the researchers add a few extra layers of the durable plastic.
The domes are one-sixth the thickness of a human hair and only half the size. The researchers found that changing the size of the laser-cut holes allowed the sound produced by the thin-film panel to be louder. Because the domes have such minute movement, it takes less electricity to power a single square meter of material than it does to power a standard speaker.
There are many applications for the thin-film speaker material. In addition to being applied to interiors like office walls or even the inside of an airplane to cancel out unwanted noises, an entire car could be wrapped in a speaker, making it easier to alert pedestrians that an otherwise silent electric vehicle was approaching. The technology could be used for a variety of purposes, from tracking the movements of people in a given space to covering all those tiny domes in reflective surfaces. When we might actually see this technology hit the market is one thing the researchers can't predict.
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