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Inspired by the human ear, a new acoustic fabric converts audible sounds into electrical signals.

Hearing Help

Acoustic fabric converts audible sounds into electrical signals, Wow!

Tech Explore Home/Engineering March 16, 2022

Author:  Ms. Jennifer Chu, Massachusetts Institute of Technology

So, you are having trouble hearing.  Well then, just turn up your shirt.

What?  I must have misheard you.  Turn up my shirt?  Is this Star Trek?  Should I tap my communicator?

Interesting that you mention SciFi.  Many inventions were first discussed in science fiction.  However, that is a topic for another day.  Yes, I did say turn up your shirt.  That is the idea behind a new “acoustic fabric” developed by engineers at MIT and collaborators at Rhode Island School of Design.  There is an interesting pairing:  MIT and an art/design school.  Could it be a match made in audiologic heaven?

Apparently, all fabrics vibrate in response to audible sounds; something I did not know.

These vibrations are on the scale of nanometers- far too small to ordinarily be sensed.  To capture these imperceptible signals, the researchers created a flexible fiber that, when woven into a fabric, bends with the fabric like seaweed on the ocean’s surface.

The fabric can capture sounds ranging in decibel from a quiet library to heavy road traffic, and determine the precise direction of sudden sounds like handclaps.  When woven into a shirt’s lining, the fabric can detect a wearer’s subtle heartbeat features.  The fibers can also be made to generate sound, such as a recording of spoken words, that another fabric can detect.

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

Inspired by the human auditory system, the team sought to create a fabric “ear” that would be soft, durable, comfortable, and able to detect sound.

Their research led to two important discoveries:  Such a fabric would have to incorporate stiff fibers to effectively convert sound waves into vibrations.  And, the team would have to design a fiber that could bend with the fabric and produce an electrical output in the process.

The researchers tested the fiber’s sensitivity to sound.

Next, the team wove the fiber with conventional yarns to produce panels of drapable, machine-washable fabric.  “It feels almost like a lightweight jacket-lighter than denim, but heavier than a dress shirt”, says Elizabeth Meiklejohn, an RISD graduate student who wove the fabric using a standard loom.  “The fabric was able to detect the angle of the sound to with 1 degree at a distance of 3 meters away”, says Noel.

The team stitched a fiber into a shirt’s inner lining, just over the chest, and found it accurately detected the heartbeat of a healthy volunteer; including subtle variations of the heart’s S1 and S2 features (those make the “lub-dub sounds of the heartbeat).  The researchers envision that a directional sound-sensing fabric could help those with hearing loss to tune into a speaker amid noisy surroundings.  In addition to wearable hearing aids, clothes that communicate, and garments that track vital signs, the team sees applications beyond clothing.

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

I guess this was a match made in acoustic heaven.  If you have questions about this article or would like to read it in its entirety, contact us at Hears to U Audiology.

 

Yan’s co-authors include Grace Noel, Gabriel Loke, Tural Khudiyevm Juliette Marion, Julianna Cherston, Atharva Sahasrabudhe, Joao Wilbert, Irmandy Wicasksono, and professors John Joannopoulos and Yoel Fink at MIT along with collaborators from the Rhode Island School of Design, Lei Zhu from Case Western Reserve University, Chu Ma from the University of Wisconsin at Madison, and Reed Hoyt of the US Army Research Institute of Environmental Medicine.

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