Page 46: of Marine Technology Magazine (July 2005)

www,seadiscovery.com Marine Technology Reporter 47 was also critical to the overall success."

Aside from the treatments themselves, the NOAA con- tract included an extensive sound and vibration testing program that was carried out by both equipment vendors and Noise Control Engineering. All noise critical machinery had sound and vibration measured both in the factory and as installed in the ship. This included the ASI

Propulsion Motors, all Caterpillar diesel generators, air compressor, hydraulic power units, pumps and HVAC equipment. VT Halter Marine conducted about 10 underway sea trials events. Noise Control Engineering attended seven different underway trips measuring noise and vibration. This ranged from quick one day trips where underwater noise was measured using the Oscar

Dyson RHIB to the full at-sea underwater noise survey.

Final at-sea measurement of underwater noise was con- ducted on September 10-11, 2004 in the Gulf of Mexico.

Noise Control Engineering deployed its entire office to conduct this test. They were joined by the crew of the

Tyson B., an offshore supply boat out of Dauphin Island,

Alabama, VT Halter Test & Trials, NOAA on-site per- sonnel and Naval Surface Warfare Center (NSWC) per- sonnel.

The Gulf of Mexico survey was performed five days before Hurricane Ivan, the huge storm that hit Mobile and Florida panhandle last year. High ambient underwa- ter noise interfered with the sound from the Oscar Dyson and definitive underwater sound data was not collected below 80 Hertz. As a result, the government did not accept the NCE/VT Halter radiated noise test and required the shipyard to bring the Oscar Dyson to the

Navy's AUTEC Range for further testing. The Navy test was performed in mid December with similar results to those found by the shipbuilder. The Navy and NOAA gave its final approval in early 2005 and subsequently the ship was delivered on January 5.

Is the Oscar Dyson the quietest RV in the world?

According to NOAA's Madden, "I think this vessel far exceeds what is available in the rest of the world".

According to NCE's Fischer, "It is certainly among the quietest. This vessel also had a requirement for low nar- rowband (tonal) sound, which has not been a requirement

The government designed, acoustically quieted propeller for the Oscar Dyson. (Photo by Noise Control Engineering, Inc.)

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