Fine fibres such as spider silk could lead to new and better microphones that sense airflow fluctuations rather than pressure changes.
Some insects, including mosquitos, flies and spiders, sense sound using fine hairs on their bodies that move with the sound waves travelling through the air. “We use our eardrums which pick up the direction of sound based on pressure, but most insects actually hear with their hairs,” explained Ron Miles, a professor at Binghamton University in New York.
Working alongside graduate student Jian Zhou, Miles recreated a similar system inside a microphone, which had better directional sensing across a wider range of frequencies than traditional models. It could give hearing aid or smartphone users the ability to cancel out background noise more effectively when having a conversation in a crowed area.
To create their microphone, Miles and Zhou used spider silk, which is thin enough that it moves with the air when hit by soundwaves. “This can even happen with infrasound at frequencies as low as 3 Hertz,” said Miles – that’s the equivalent of hearing the normally inaudible rumble of tectonic plates moving in an earthquake.
To translate the movement of the spider silk into an electronic signal, the researchers coated it with gold and placed it in a magnetic field. “It’s actually a fairly simple way to make an extremely effective microphone that microphone that has better directional capabilities across a wide range of frequencies,” said Miles.
Rob Malkin, an expert in bio-inspired acoustic devices from the University of Bristol, told Professional Engineering that the research demonstrated yet again “how a beautiful design from the insect world can lead to advancements in microphone engineering”.
He called the work a “step change” in how microphones could function in the future, as it expanded the narrow range of frequencies that insects can hear at, into a spectrum broad enough for humans. “The work is very encouraging as it shows that the physical process being exploited by many insects – that is hearing with hairs – is relatively simple, and should make the manufacture of broadband devices finally possible,” Malkin added.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.
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