Ultra-thin speakers spin as wallpaper for sound surfaces

Engineers at the Massachusetts Institute of Technology have developed an ultra-thin speaker that could be used to ensure that all surfaces create sound. The unique design should be energy efficient and easy to manufacture on a scale, the team says.

Basically, the speakers work by vibrating a membrane that manipulates the air above it, creating sound waves. In speakers, which are commonly found in audio systems or headphones, this is done using electric currents and magnetic fields.

But in recent years, scientists have developed ways to achieve similar results in much more subtle devices. Thin-film speakers operate using piezoelectric materials that vibrate in response to voltage applications. They were used in phones and TVsand even experimentally create columns from things like unusual as flags.

The problem is that these thin speakers must be either freestanding or have some separation from another surface – their mounting reduces their ability to vibrate and create sound. But in a new study, researchers at the Massachusetts Institute of Technology redesigned thin columns so they could be mounted on a variety of surfaces.

Instead of vibrating the entire surface of the membrane, the team formed a material into a network of raised domes that vibrate independently of each other. This is done by sandwiching a thin layer of piezoelectric material with a thickness of only 8 micrometers between two layers of PET plastic. One layer of PET has a network of tiny holes through which the piezoelectric material protrudes. The bottom layer of PET protects the membrane and allows you to install the speaker on the surface.

“It’s a very simple and straightforward process,” said Ginchi Khan, lead author of the study. “This will allow us to produce these high-bandwidth speakers if we integrate them with the roll-to-roll process in the future. This means that it can be produced in large quantities, such as wallpaper for walls, cars or airplanes.

The resulting speaker is only 120 mm (4.7 inches) thick and weighs just 2 g (0.07 ounces), with thousands of tiny domes 15 micrometers high. To test the device, the researchers attached it to the wall and measured its output with a microphone at a distance of 30 cm (11.8 inches). The speaker was capable of producing sound up to 66 decibels (dB) at 25 V at 1 kHz and 86 dB at 10 kHz. The device is also energy efficient, consuming just 100 milliwatts of power per square centimeter of speaker.

Along with mountable thin-film speakers, the team says the device can be used as ultrasonic detectors or covered with reflective material to create unique light displays.

The team showcases the speakers in the video below. The study is published in the journal IEEE Transactions of Industrial Electronics.

Source: MIT