Listening to what’s going on under the sea matters greatly. Mapping the ocean floor, monitoring whale migrations, repairing the next Deepwater Horizon: each of these tasks relies on or can be aided by an underwater microphone. Eavesdropping on the ocean, though, is more complicated, on a technological level, than listening to the world up above, because the amount of pressure a microphone must withstand differs greatly depending on how deep it dives. In the ocean, descending another 10 meters means adding an atmosphere of pressure; the Marianas Trench, for instance, has a surrounding pressure well over 1,000 times greater than that of the surface.
Stanford researchers mulling this problem decided to study the orca. “Orcas had millions of years to optimize their sonar, and it shows,” Onur Kilic, a postdoctoral researcher in electrical engineering at Stanford, recently said. “They can sense sounds over a tremendous range of frequencies, and that was what we wanted to do.” The orca-inspired microphone he and his team produced is only the size of a pea, but it can plunge to the ocean’s greatest depths and pick up a huge range of sounds, from the faintest whisper to the most deafening explosion.
The first insight that Kilic and a team of engineers (plus one applied physicist) had was this: to make a truly versatile underwater microphone would require the ability to flood the microphone itself. “The only way to make a sensor that can detect very small fluctuations in pressure against such immense range in background pressure is to fill the sensor with water,” Kilic recently told Stanford Report. If you can’t beat 1,000 atmospheres of pressure, join ‘em.
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