A group of engineers and designers from MIT and Rhode Island School of Design have developed acoustic fabric that can convert sound pressure waves to electrical signals. The team detailed the technology in a study published in Nature. Potential applications for sound sensitive fabric include shirts that are also hearing aids, apparel that monitors your heart sounds, clothes that enable two-way communications, and even structural stability monitoring for buildings, bridges, and ships.

The team created a fiber from piezoelectric material that converts mechanical energy to electrical energy when the material is moved or stressed. The engineers wove the fiber into fabric that bends in response to sound. The fabric movements are tiny: measured in nanometers or one-billionth of a meter. That tiny movement is enough, according to the study, for the fabric to detect sounds that range from “a quiet library to heavy road traffic.” The sound-sensitive fabric can also detect the precise direction of sounds.

This technology potentially enables diverse applications. The conversion between sound vibrations and electrical signals works both ways. Wei Yan is the lead author of the study; he was an MIT postdoc student when he worked on the technology. According to Yan, a person wearing an acoustic garment made from the fabric could use the garment to have phone conversations. Now an assistant professor at the Nanyang Technological University in Singapore, he also points out that “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.”

Testing the sound-sensitive fabric, the MIT-based team found that a single fiber stitched inside a shirt worn over the chest detected a healthy volunteer’s heartbeat accurately. Study co-author Yoel Fink from MIT said that a pregnant woman could possibly monitor her baby’s fetal heartbeat by wearing maternity clothes made with the acoustic fabric.