Yahoo Finance Scientists develop paper-thin loudspeaker that can turn any surface into an audio source
Scientists have developed a paper-thin loudspeaker that can turn any surface into an active audio source.
The device that weighs just 2 grams and is the size of a human hand was made by researchers, including those from the Massachusetts Institute of Technology (MIT) in the US.
The tiny loudspeaker can potentially provide noise cancellation in critical environments like airplane cockpits and even three-dimensional audio in a theatre or theme park ride.
It produces sound with minimal distortion, using only a fraction of the energy required by a traditional loudspeaker.
The device, described recently in the IEEE Transactions on Industrial Electronics journal, can generate high-quality sound no matter what surface its film is bonded to, said the scientists.
“It feels remarkable to take what looks like a slender sheet of paper, attach two clips to it, plug it into the headphone port of your computer, and start hearing sounds emanating from it. It can be used anywhere. One just needs a smidgeon of electrical power to run it,” Vladimir BuloviÄ, senior author of the paper from MIT, said in a statement.
Scientists also pointed out that because the device is light weight and needs only a small amount of power to operate, it becomes well suited for applications on smart devices where battery life is limited.
“Ultra-thin, lightweight, high-performance, low-cost and energy-efficient loudspeakers that can be deployed over a wide area have become increasingly attractive to both traditional audio systems and emerging applications such as active noise control and immersive entertainment,” they wrote in the study.
A typical loudspeaker used in headphones and audio systems has electric current inputs pass through a coil of wire to generate a magnetic field that moves the speaker’s membrane and the air above it, forming the sound we hear.
The new loudspeaker instead has a simplified design that uses a thin film of a shaped piezoelectric material – a type of material in which electric charge accumulates – that converts pressure on it into electricity and moves when voltage is applied over it.
A new paper-thin loudspeaker can turn any surface into an active audio source. It produces sound with minimal distortion and weighs about as much as a dime. https://t.co/IvAVXuHGpz pic.twitter.com/O3NT8vf667
— Massachusetts Institute of Technology (MIT) (@MIT) April 26, 2022
This moves the air above it to generate sound.
Thin-film loudspeakers are usually designed to be freestanding since the film must bend freely to produce sound. But mounting these onto a surface would impede vibration and hamper their ability to generate sound.
The new design, in contrast, has tiny domes on a thin layer of the piezoelectric material that vibrate individually instead of having the entire material vibrate.
Scientists shaped up the new loudspeaker by using a laser to cut tiny holes into a thin sheet of lightweight PET plastic and laminated the underside of this layer with a very thin film of PVDF, a kind of piezoelectric material.
They then applied a vacuum above the bonded sheets and used a heat source at 80C under them.
The pressure difference created by the vacuum and heat source caused the ultrathin PVDF layer to bulge, causing tiny domes to protrude in areas where they aren’t blocked by PET.
Scientists then laminated the other side of the PVDF with another PET layer to act as a spacer between the domes and the bonding surface.
The domes are about 15 microns in height – about a sixth of the thickness of a human hair – and move up and down about half a micron when they vibrate, the study noted.
Each of these domes is a single sound-generation unit, and when thousands of these tiny domes vibrate together, it produces audible sound, the researchers explained.
In the study, scientists also developed a fabrication technique they said could be scaled up to produce ultrathin loudspeakers large enough to cover the inside of an automobile or to wallpaper a room.
“This is a very simple, straightforward process. It would allow us to produce these loudspeakers in a high-throughput fashion if we integrate it with a roll-to-roll process in the future. That means it could be fabricated in large amounts, like wallpaper to cover walls, cars, or aircraft interiors,” Jinchi Han, another co-author of the study, said.
Researchers tested the device by mounting it to a wall 30cm from a microphone to measure the sound pressure level, recorded in decibels.
When they passed about 25 volts of electricity through the device at 1 kilohertz – a rate of 1,000 cycles per second – the speaker produced high-quality sound at 66 decibels – a volume slightly above the normal speaking range.
Scientists said the device needs only about 100 milliwatts of power per square meter of speaker area.
In contrast, they said an average home speaker might consume “more than 1 watt of power to generate similar sound pressure at a comparable distance.”
There can also be applications for the technology in sectors other than audio.
If the vibrating domes of the thin film are covered with a reflective surface, it may be used to create patterns of light for future display technologies.
“The options of how to use this technology are limitless,” Dr Bulovic said.
