Posts Tagged ‘Sonar’

Scientists See Squid Attack Squid

June 18, 2008

It was like a scene from a grade-B horror film. On a gently rocking vessel in the warm waters of the Sea of Cortez, a young oceanographer earnestly watches her computer screen while colleagues lower a cable into the water. Instruments aboard the ship, the Pacific Storm, ping sound waves toward the cable. The oceanographer’s eyes flicker across the screen to make sure the signal is clear. Tethered to the cable is a 5-pound Humboldt squid, and the sound waves, set at 38 kilohertz, bounce off the squid. An image shows up on the screen.

The oceanographer raises her fist in triumph. It marks the first time scientists had clearly picked up a strong sonar signal for squid, which lack the bones and swim bladders that give away other marine creatures.

Suddenly a second image appears, darting up from below. The acoustic signal tracks it from the depths toward the cable — and the tethered squid. It is another squid, larger than the first, and it attacks the tethered animal. The oceanographer screams.

Fade to black.

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Roaring Bats: New Scientific Results Show Bats Emitting More Decibels Than A Rock Concert

May 3, 2008

Researchers studying the echolocation behavior in bats have discovered that the diminutive flying mammals emit exceptionally loud sounds — louder than any known animal in air.

Annemarie Surlykke from the Institute of Biology, SDU, Denmark, and her colleague, Elisabeth Kalko, from the University of Ulm, Germany, studied the echolocation behavior in 11 species of insect-eating tropical bats from Panamá, the findings of which are reported in this weeks’ PLoS ONE.

The researchers used microphone arrays and photographic methods to reconstruct flight paths of the bats in the field when these nocturnal hunters find and capture their insect prey in air using their sonar system. Surlykke and Kalko took this information as a base to estimate the emitted sound intensity and found that bats emit exceptionally loud sounds exceeding 140 dB SPL (at 10 cm from the bat’s mouth), which is the highest level reported so far for any animal in air. For comparison, the level at a loud rock concert is 115-120 dB and for humans, the threshold of pain is around 120 dB.

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Navy releases extensive marine impact study

April 5, 2008

After losing a series of lawsuits, the Navy for the first time today will release a massive study that examines the potential collateral damage to wildlife when training sailors to use sonar, drop bombs, fire missiles and help Marines storm beaches in Southern California.

The environmental impact statement, fatter than the Los Angeles phone book, comes after federal judges have repeatedly ruled that the Navy failed to do a proper assessment on how to protect whales and dolphins from sonar used to hunt submarines.

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