Spider silk could pave the way for powerful microphones

The best microphone in the world might have an unexpected source: spider silk. Spiders weave webs to trap insects, but the sticky strands also help spiders hear. 

Spider silk and sound detection

Unlike human eardrums and conventional microphones that detect sound pressure waves, spider silk responds to changes in the velocities of air particles as they move through a sound field. 

This sound velocity detection method remains largely underexplored compared to pressure sensing, but it holds great potential for high-sensitivity, long-distance sound detection.

Wide range of sound frequencies 

By investigating how spiders listen to their environments through webs, a team of researchers from Binghamton  University found that spider webs match the acoustic particle velocity for a wide range of sound frequencies. 

“Most insects that can hear sound use fine hairs or their antennae, which don’t respond to sound pressure,” said Ronald Miles, a professor of mechanical engineering at Binghamton. “Instead, these thin structures respond to the motion of the air in a sound field. I wondered how to make an engineered device that would also be able to respond to sound-driven airflow. 

“We tried various man-made fibers that were very thin, but they were also very fragile and difficult to work with. Then, Dr. Jian Zhou was walking in our campus nature preserve and saw a spider web blowing in the breeze. He thought spider silk might be a great thing to try.”

How bridge spiders detect their prey

Before building such a device, the team needed to prove that spider webs truly respond to sound-driven airflow. To test this hypothesis, they simply opened their lab windows to observe the Larinioides sclopetarius, or bridge spiders, that live on windowsills. 

Bridge spiders are particularly known for their affinity for man-made structures, where they build their large, circular webs to catch flying insects such as moths and flies.

The researchers played sound ranging from 1 Hz to 50 kHz for the spiders and measured the spider silk motion with a laser vibrometer. 

The experiment revealed that the sound-induced velocity of the silk was the same as the particles in the air surrounding it, confirming the mechanism that these spiders use to detect their prey.

Spider silk inspires new microphones 

“Because spider silk is, of course, created by spiders, it isn’t practical to incorporate it into the billions of microphones that are made each year,” Miles said. “It does, however, teach us a lot about what mechanical properties are desirable in a microphone and may inspire entirely new designs.”

Thus, the innovative use of spider silk to detect sound velocities may pave the way for improved audio detection devices that surpass the capabilities of current pressure-sensitive microphones.

More about spider silk

Spider silk is renowned for its impressive mechanical properties, which include high tensile strength and elasticity. This makes it stronger, by weight, than steel and almost as stretchy as rubber. 

Sound technology 

Recent research, such as the Binghamton University study, has explored how spider silk could also have applications in sound technology. The fine threads can carry vibrations across their span, and some types of spiders use the vibrations traveling through their webs as a way to communicate and detect prey or mates.

Maximum sound performance 

The properties of spider silk could make it useful for creating new types of sound sensors or acoustic devices. For instance, because spider silk can be fine-tuned during its production – by adjusting its thickness and tension – it might be adapted for use in highly sensitive microphones or speakers that require minimal material mass but maximum performance. 

Hearing aids 

Researchers are also investigating if spider silk can improve the quality of microphones for hearing aids, potentially providing clearer sound than traditional materials. This intersection of natural material science with technology highlights the potential of biomimicry – using designs inspired by nature to solve human problems.

The Binghamton study was presented by Ronald Miles on May 16 as part of a joint meeting of the Acoustical Society of America and the Canadian Acoustical Association.

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