Whale Orca’s ears inspire ultrasensitive mike

June 26th, 2011 - 10:35 pm ICT by IANS  

Washington, June 26 (IANS) Orca whale’s ears have inspired researchers to develop a microphone so sensitive that it can be used at any ocean depth, capable of recording anything from a whisper in a library to a huge explosion.

The undersea pea-sized microphone can capture the whole range of ocean sounds. It also can hear sound frequencies across a span of 17 octaves, spanning pitches far higher than the whine of a mosquito and far lower than a rumbling foghorn.

“It is a very high dynamic range microphone, able to sense everything from the weakest sounds to those 100 million times stronger,” said Onur Kilic, postdoctoral researcher in electrical engineering at Stanford University, who led the study.

For most people, listening to the ocean means contemplating the soothing sound of waves breaking gently on a sandy beach.

But for researchers tackling underwater mapping to guiding robots trying to repair leaking undersea oil wells, listening to the ocean from the other side, underwater, can reveal volumes of valuable data, reports the Journal of the Acoustic Society of America.

Existing underwater microphones — called hydrophones — have much more limited ranges of sensitivity and do not perform well at depth, where the pressure can be extremely large, making it difficult to detect faint sounds, according to a Stanford statement.

Sonar — using sound to locate and map — is critical to underwater communication and
exploration, because radio signals can travel only a centimetre or two before they dissipate in seawater and light can’t penetrate the depths below about 100 metres.

“Orcas had millions of years to optimise their sonar and it shows. They can sense sounds over a tremendous range of frequencies and that was what we wanted to do,” Kilic said.

In the ocean, for every 10 metres you descend below the surface, the water pressure around you increases by the equivalent of 1 atmosphere — the air pressure we feel at the earth’s surface.

The deepest point on the planet, the Challenger Deep in the Mariana Trench in the South Pacific, lies approximately 11,000 metres below sea level. At that depth, the pressure is approximately 1,100 times the air pressure at the earth’s surface.

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