Orca Ears Inspire New Microphone Design

Using the ultra-sensitive ears of killer whales as inspiration, researchers at the Stanford University have created a new underwater microphone. Their device is significantly more responsive to sound than other similar device on the market today.

One of the advantages this microphone has is that it can be used at any depth in the ocean without fear of damage. It works even under pressure levels that would force other underwater microphones to implode, and can still remain sensitive to a wide array of sounds even under these conditions.

Killer whales – also called orcas – have an extraordinarily acute sense of hearing, and Stanford postdoctoral researcher Onur Kilic decided to replicate it in an artificial device. With this microphone, experts will be able to get a clearer view of what's going on underneath the waves.

For the common folk, listening to the oceans is resumed to the sound of crashing waves, but for experts the real treasure trove is located under the waves. They use complex array of submerged microphones to collect data on whale and fish migrations, as well as on drilling activities and much more.

Orcas can hear even better than our most sensitive microphones can. Even the new device, which perceives a range of approximately 160 decibels, cannot hope to rival with the nearly-perfect hearing of a killer whale.

The sound frequencies the Stanford microphone can detect span 17 octaves. For comparison, a piano has only 8 octaves, which encompass all the sounds it's capable of. This means the microphone can perceive both ultrasound, and the high part of infrasonic frequencies.

“Orcas had millions of years to optimize their sonar and it shows. They can sense sounds over a tremendous range of frequencies and that was what we wanted to do,” explains Kilic, a postdoctoral researcher in electrical engineering at Stanford.

He is also the lead author of a new paper detailing the way his microphone is constructed. The work is published in a recent issue of the esteemed Journal of the Acoustic Society of America.

“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 says of the innovation that allows his microphone to function in the harshest aquatic conditions.

Funds for the new study were provided by Litton Systems Inc., which is a wholly owned subsidiary of the Northrop Grumman Corporation.