Scientists and researchers at Binghamton University are looking to nature for possible improvements to hearing aids.
Ron Miles, distinguished professor and mechanical engineering department chair, and Jian Zhou, a Ph.D. candidate in mechanical engineering, have found evidence that spider silk, the material spiderwebs are composed of, could be used to aid those with eardrum impairment.
“Spider silk came to my mind when I walked in the nature preserve, and it is proved to work amazingly by following the fluctuating airflow with almost full fidelity from infrasound to ultrasound,” Zhou wrote in an email.
The majority of animals pick up sounds by detecting subtle air motion through fine hairs, the researchers said. Eardrums, on the other hand, rely on sound pressure. The pair’s research examined how spiders sense direction using their silk, which can identify exactly where a sound comes from. Knowing this, Miles and Zhou theorized spider silk can be used in the microphones within hearing aids to identify exactly where the desired sound is coming from.
Zhou first learned about Miles and his research while he was working toward his master’s degree. He was intrigued by Miles’ work on microelectro-mechanical systems microphones in relation to the directional hearing of Ormia ochracea, a type of parasitic fly that uses the sense to detect the location of crickets and lay larvae inside of them.
Zhou said he was inspired to conduct this research while taking Miles’ advanced acoustics class in fall 2014. When Miles taught about pressure in microphones, Zhou said he realized that tiny hair-like structures were ideal for detecting sound because they can effectively move with airflow. Acoustic fiber sensors can be used to detect sounds. Most animals hear through flow sensing using hairs, but humans use pressure sensing eardrums. Flow sensing can detect infrasound waves, which have a frequency lower than what humans can hear.
“We discussed the fiber sensor, which detecting sound by flow sensing instead of pressure sensing,” Zhou wrote. “Professor Miles figured that sub-micron fiber will move with airflow exactly in a broadband frequency range. To prove this, a thin, strong and handy fiber will help a lot.”
Since animals are able to use their hairs to detect sound, Miles said he thought it’d be possible to mimic the effect using thin fiber. In order to figure out how thin it had to be, Miles assembled a model by plating spider silk with gold and applying a magnetic field to it, thereby producing an electric signal. The frequency of this signal showed that spider silk is just the right size to lead to a possible solution. According to Miles, this means that their research might lead to better hearing aids than the ones currently available.
“I believe this work could lead to much better miniature microphones to be used in hearing aids,” Miles wrote. “Our microphone can do a much better job of detecting sounds than can be done with a pair of current hearing aid microphones. This should make hearing aids sound much better when they are used in noisy places.”