How Listening Like a Fly Could Lead to Better Sound Detectors, by Charles Q Choi via popularmechanics
A new sound detector that mimics how a parasitic fly uses its extraordinary hearing to pinpoint its victims, could one day help soldiers track down snipers and lead to better phones and hearing aids that stifle background noise.
The new invention was inspired by the ear of a small yellow nocturnal fly, Ormia ochracea. The fly can identify the origin of sounds with uncanny accuracy—and uses that ability with deadly force. When a female of the species hears the mating song of a male cricket, she flies onto the back of the singer and deposits her offspring, which invade, consume and kill their host.
The fact that this fly can pinpoint sound so well is a bit of a surprise. We humans know where sounds are coming from because of the distance separating our ears—if a sound comes from one side, the ear on that side will hear it slightly before the ear on the other side. But because the yellow nocturnal fly is so tiny, sound waves hit both sides of its head at essentially the same time. Its ears are separated by about the width of a nickel, which means it takes sound about four millionths of a second to go from one ear to the other.
Nearly 20 years ago, engineer Ronald Miles at Binghamton University discovered the secret: The fly’s ear possesses a structure resembling a teeter-totter that’s about 1.5 millimeters long. When a sound reaches the insect from the side, one end of the teeter-totter starts tipping before the other, which tells the fly which side sound is coming from, says Neal Hall, an engineer at the University of Texas at Austin and coauthor on the new study.
The new sound detector Hall and his colleagues developed is essentially a silicon teeter-totter only 2 millimeters wide. Under both ends of the see-saw are springs made of piezoelectric materials, which turn mechanical force into electrical signals. Thanks to these springs, the researchers can measure how the seesaw beam flexes and rotates. “Doing so enabled us to fully emulate the mimic and replicate the fly’s special ability,” Hall says.
The research, funded by DARPA, could have military applications, Hall says. “One can imagine battlefield scenarios where being able to determine the location of an event based on sound alone is important—situations in which visual cues are denied. Finding a hidden sniper using sound emitted from the gunshot is an example.”
Or, imagine a smartphone that can filter our ambient noise. “We envision a smartphone app that uses directional microphones to focus only on a specific speaker of interest while rejecting all other ambient noise,” Hall says. “for example, plates dropping in the background, or screaming toddlers.”
This tech could lead to a new generation of smarter hearing aids that focus only on conversations or sounds of interest to wearers, instead of amplifying everything as current hearing aids do. The discomfort from this amplified background noise a major reason why only 2 percent of Americans wear hearing aids even though perhaps 10 percent of the population could benefit from wearing one, Hall says.