Working with The Cornell Hawai'i program

~~~~~ By Adam S. Frankel

Admittedly, three days is a short time in which to introduce someone to the world of marine mammal passive acoustics. Even so, the Cornell University students who signed up to spend a semester in Hawai‘i learning the Big Island’s natural history, culture and ecology, readily immersed themselves in underwater sound-recording techniques, progressing from an appreciation to a fair understanding of the process in the time we had together.

            The instructional team—University of Hawai‘i, Department of Zoology graduate students, Tim Clark and Marc Lammers, and myself—put students to work deploying sonobuoys right away. We assembled about mid-morning at Honokohau harbor, adjacent to Kaloko-Honokohau National. After introductions from both students and staff, half of the class boarded Tim’s boat, a retired NOAA research vessel, and steered toward our designated recording site in waters just off the national park. Students placed our three U. S. Navy surplus SQS-57B sonobuoys in a straight line several hundred feet offshore, parallel to the shoreline, approximately one kilometer away from each other.

            The sonobuoys weigh about 10 pounds in air and consist of a hydrophone, radio transmitter, salt-water battery and inflatable white-plastic float that houses a transmission antenna. To ensure that the sonobuoys remained afloat, each was moored with a small anchor and safety float. Nothing sank, but one of the sonobuoy’s built-in floats didn’t inflate, resulting in a non-functional antenna. So we immediately deployed a spare sonobuoy in its place. However, back at the shore station where our Dell laptop was set up to receive and record sonobuoy transmissions, the other half of the class could see the evidence: the spare itself was a bust. No audio signal. No visual sonogram. Field recording data for this session would be generated from two, not three sonobuoys.

            Our operational goal had been to collect and record ocean sound for use as pilot data as part of an eventual statistical description of ambient underwater noise conditions around Kaloko-Honokohau National Park. The sonobuoys succeeded in transmitting typical 21^st century undersea sounds: a steady mix of natural and man-made. At the shore station, students both heard and viewed those transmissions on our digital recording system.

Consisting of the car battery-powered Dell laptop with built-in speakers, plus a National Instruments multi-channel analog-to-digital converter card and Ishmael ⁽²⁾ sound-recording software, students documented the roars, snaps, crunches and songs made by the following sources: small boats from constant traffic moving in and out of the mouth of the harbor; snapping shrimp; different species of fish, including those that make crunching sounds when they bite the coral reef; and the distant but distinctive songs of humpback whales. By that first day’s end, we had collected and recorded four hours of useable data.

We spent the remaining two days of our mini-course at the foot of the beautiful Kohala Mountains in the village of Waimea on the 100-acre Hawai‘i Preparatory Academy (HPA) campus. In HPA’s computer lab, students learned more about sound analysis and the biology of humpback whales. First, students analyzed acoustical data recorded by Marc’s portable array of hydrophones that Tim’s boat had towed during our field session. Using new software developed at the Hawai‘i Institute of Marine Biology (HIMB), students explored localization theory as one way to determine locations of sound sources. Later that second day, I had the pleasure of spending a good part of the afternoon talking and answering student questions about the natural history of humpback whales.

Taking place in early March, the students’ mini-course coincided with humpback whale migration from feeding grounds in cool, high-altitude waters of places like Alaska, to mating and calving grounds in warmer, low-latitude waters off Hawai‘i. This is a prime time to see and hear young and adult humpback whales. 

But students learned that passive acoustical localization of whales isn’t always easy, even when the animals are present in great numbers. To better understand the limitations as well as the advantages of acoustical localization, we reviewed the physics and the proper measurement of sound. Using a new statistical technique (involving a genetic search algorithm) developed by Cornell University’s Bioacoustics Research Program (BRP) ⁽³⁾, we explored how the ways that sound propagates through the ocean can sometimes make it challenging to acoustically pinpoint an animal’s location.

Perhaps the highlight for those of us working as instructors on behalf of HMMC, was seeing the excitement of students when they recognized animal and man-made sounds transmitted in real time by the sonobuoys they helped deploy. Personally, it was gratifying to hear students’ insightful questions about marine mammal research and to realize the leaps in understanding they had made about bioacoustics and the physics of sound in just a few days. It was also satisfying to help HMMC fulfill its goals of fostering an appreciation and awareness of marine mammal life in and around the islands of Hawai‘i.

(1) To learn more about Cornell University’s Department of Earth and Atmospheric Sciences Hawai‘i-based *Marine Ecosystems Field Course, taught by Associate Professor and Director of the Ocean Resources and Ecosystems Program, Chuck Greene, and Senior Research Associate, Bruce Monger (Ph.D. 1993, University of Hawai‘i), go to:  http://www.eas.cornell.edu/eas/index.html  (select "Featured Pages")

(2) Ishmael, developed by HMMC friend, David Mellinger, Ph. D., is a multi-purpose sound analysis tool that includes automatic call recognition (ACR) and the capability to process sound from real time, files, or a sequence of files. To learn more about Ishmael and other bioacoustics software programs, visit the MobySoft: Bioacoustics Software Library:

http://cetus.pmel.noaa.gov/cgi-bin/search.pl