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futurity_medicine 00290.txt

#Tiny fly ear seesaw could boost hearing aids Engineers have developed a tiny, low-power device that mimics a fly ultra-sensitive hearing. The advance could lead to hypersensitive hearing aids. The new device could be used to build the next generation of hearing aids with intelligent microphones that adaptively focus only on those conversations or sounds that are of interest to the wearer. The researchers drew inspiration for the device from the yellow-colored Ormia ochracea fly. This species can pinpoint the location of a chirping cricket with remarkable accuracy because of its acute hearing. The fly relies upon a sophisticated sound-processing mechanism that resembles a teeter-totter to determine direction of sound within two degrees. Using the fly ear structure as a model, Neal Hall, an assistant professor of engineering at the University of Texas at Austin, and his graduate students built a miniature pressure-sensitive device out of silicon that replicates the fly super-evolved hearing structure. The 2-millimeter-wide device is nearly identical in size to the fly hearing organ. PRESSURE TO POWER Other researchers have built fly-inspired hearing devices, but current design is the first to include piezoelectric materials. These materials turn mechanical pressure into electric signals, or voltage, and allow the device to operate with very little power. Researchers allowed beetle larva to feast on antibiotic-treated leaves and natural leaves and found that on the antibiotic-treated leaves, the beetles suffered from the plant's anti-herbivore defense, but on the natural leaves the larva gained more weight and thrived. Credit: andriux-uk/Flickr) ecause hearing aids rely on batteries, minimizing power consumption is a critical consideration in moving hearing-aid device technology forward, Hall says. This technology may be a boon for people who are hearing impaired in the future. Currently, only two percent of Americans wear hearing aids, but as much as ten percent of the population could benefit from wearing one, Hall says. any believe that the major reason for this gap is patient dissatisfaction, Hall adds. urning up the volume to hear someone across from you also amplifies all of the surrounding background noiseesembling the sound of a cocktail party. PINPOINT SOUND Humans and other mammals have the ability to pinpoint sound sources because of the finite speed of sound combined with the separation between our ears. Insects generally lack this ability because their bodies are so small that sound waves essentially hit both sides simultaneously. O. ochracea is a notable exception. It can locate the direction of a cricket chirp even though its ears are less than 2 millimeters apart. In the four millionths of a second between the sound entering one ear and the other, the sound phase shifts slightly. The teeter-totter-style structure in the fly ear effectively amplifies the time delay and allows the fly to locate its cricket prey with remarkable accuracy. To replicate the fly hearing mechanism the researchers developed a flexible beam and integrated the piezoelectric materials. The use of piezoelectric materials allowed them to simultaneously measure the flexing and the rotation of the beam, which in turn allowed them to replicate the fly hearing. Hall credits the pioneering work of Ronald Miles at Binghamton University and Ronald Hoy at Cornell University, along with their teams, who discovered the fly unusual hearing mechanism, for inspiring this research and device. In addition to possibly improving hearing aids, the device could have military and defense applications as well. In dark environments, for instance, where visual cues are not available localizing events using sound may be critical. The Defense Advanced Research Projects Agency supported the research, which appears in Applied Physics Letters P

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