You would think that blocking out the sounds of noisy neighbors or other distractions requires wearing headphones all day, but MIT researchers have developed a paper-thin speaker that can be put to practically any surface, such as wallpaper, transforming walls into enormous noise-cancelling speakers.
Take apart the speakers in practically any consumer sound gadget, and you'll find essentially the same hardware: a membrane linked with a coil of wire that generates a magnetic field (or other movement mechanism). When electricity is supplied to the membrane, it causes it to move back and forth and push air in certain patterns, resulting in sound waves reaching our ears. It's a basic formula that's worked for over 150 years, but it takes a certain amount of power and space to work. Take a glance at the big speakers on either side of the stage during a concert and you'll see why there's still room for advancement in speaker technology.
Researchers at MIT's Organic and Nanostructured Electronics Laboratory have developed a new type of thin-film speaker that is as thin and flexible as a sheet of paper but can produce clear, high-quality sound even when mounted to a stiff surface such as a wall. Researchers have attempted to construct ultra-thin lightweight speakers before, but prior attempts have resulted in a film that must be freestanding and unobstructed in order to make sound. Past thin speakers' ability to vibrate and move air is severely limited when mounted to a hard surface, limiting where and how they can be used. However, MIT researchers have developed a new manufacturing procedure that addresses this issue.
Rather than constructing a thin-film speaker that vibrates the entire panel, the researchers started with a sheet of lightweight PET plastic that was laser perforated with small holes. The researchers then bonded a layer of thin piezoelectric material called PVDF to the underside of the sheet, and then heated both layers to 80 degrees Celsius in a vacuum, causing the piezoelectric layer to expand and push through the laser-cut holes in the top layer.This resulted in a sequence of tiny domes that, regardless of whether the panel is connected to a rigid surface, can pulse and vibrate when an electric current is applied. The researchers also created a spacer out of a few extra layers of the tough PET plastic to ensure that the domes may vibrate freely and are protected from abrasion damage.
The domes are only "one-sixth the thickness of a human hair" in height and vibrate at a speed of half a micron. Thousands are required to make audible noises, but the researchers discovered that by altering the size of the laser-cut holes, which also varies the size of the domes formed, the thin-film panel's sound can be tweaked to be louder.Because the domes move so slowly, only 100 milliwatts of electricity were required to power a single square meter of the material, compared to more than a full watt for a normal speaker to provide the same level of sound pressure. Please sign up for our newsletter! If you don't give us your email address, the robot will receive it. Please enter your email address. Please register me. You agree to our Terms of Service and Privacy Policy by subscribing.
The possibilities for thin-film speaker technology are infinite. In addition to being used to cancel out unpleasant noises on interiors such as office walls or even the inside of an airplane, an entire car might be coated in a speaker, making it easier to inform passersby that an otherwise silent electric vehicle was coming. The researchers believe the technology might be utilized for ultrasonic imaging, tracking the motions of individuals in a specific space, or even as a futuristic display technology, similar to how Texas Instruments' DLP technology works. But one thing the experts can't predict is when this technology will be available for purchase.
