Imagine if someone were having difficulties hearing and all they needed to do was turn up their shirt. Engineers from MIT and partners at the Rhode Island School of Design came up with the notion for a new "acoustic fabric." The researchers created a material that operates like a microphone, translating sound into vibrations and then electrical signals in the same way that human ears do.

Fabrics vibrate in response to audible sounds, albeit these vibrations are on the nanometer scale and are too small to be perceived normally. The research team developed a pliable fiber that, when interlaced into a fabric, bends with it like seaweed on the ocean's surface, capturing these inaudible vibrations.

The fiber is made of a "piezoelectric" material that, when bent or mechanically distorted, provides an electrical signal, allowing the fabric to transform sound vibrations into electrical data.

From whispers to jet planes

The fabric can detect an astounding range of sounds and determine the precise direction of unexpected sounds such as clapping. The fabric can identify a wearer's faint heartbeat when sewn into the lining of a shirt. The fibers can also be made to produce sound, such as a recording of words or phrases that can be recognized by another fabric.

The team's findings are detailed in a study published this month in Nature. Wei Yan, the lead author andThe acoustic fiber can be woven with conventional yarns. Source: Fink LabThe acoustic fiber can be woven with conventional yarns. Source: Fink Lab MIT postdoc who helped design the fiber, envisions numerous possibilities for fabrics that can hear.

“Wearing an acoustic garment, you might talk through it to answer phone calls and communicate with others,” said Yan, currently an assistant professor at the Nanyang Technological University in Singapore. “In addition, this fabric can imperceptibly interface with the human skin, enabling wearers to monitor their heart and respiratory condition in a comfortable, continuous, real-time, and long-term manner.”

The research team believes that a directional sound-sensing material could help those who suffer from hearing loss to better hear conversations in noisy atmospheres.

Beyond wearable garments

“It can be integrated with spacecraft skin to listen to (accumulating) space dust, or embedded into buildings to detect cracks or strains,” Yan suggested. “It can even be woven into a smart net to monitor fish in the ocean. The fiber is opening widespread opportunities.”

The research was supported in part by the U.S. Army Research Office through the Institute for Soldier Nanotechnologies, National Science Foundation, Sea Grant NOAA.

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