Fleet owners and shipbuilders are reviewing noise regulations adopted this summer under the International Convention for the Safety of Life at Sea (SOLAS) to gauge the impact on their operations.
On July 1, SOLAS was amended with the “Code on Noise Levels on Board Ships,” applicable to new vessels. SOLAS regulation II-1/3-12 requires that ships be built to protect mariners from excessive noise. The code lays out noise limits for machinery spaces, workshops, control rooms, accommodations and other onboard spaces. It supersedes non-mandatory 1981 guidelines from the London-based International Maritime Organization.
Mariners are affected by a variety of mechanical, aerodynamic and hydro-acoustic noise. Main and auxiliary engines, pumps, turbochargers, compressors, fans, heating and air conditioning systems, and piping emit noise, as do propellers and thrusters. Engine air-intake and exhaust systems generate noise.
“In reducing a ship’s noise, the greatest challenges are machinery spaces and main propeller spaces,” said retired Rear Adm. Joe Carnevale, senior defense adviser at the Shipbuilders Council of America in Washington, D.C. “Auxiliary machinery spaces and smaller pieces of equipment also have to be addressed. Since steel is a good propagator of noise and because noise is airborne, a ship’s spaces have to be engineered to minimize sound.”
Commercial shipbuilders have made progress in noise reduction, Carnevale said, and very large diesel engines are less noisy than in the past. Advances in engine-mounting systems have lowered noise and kept it from traveling through a ship’s hull. Sound insulation is used more effectively in ships’ machine spaces than in the past.
In offshore oil vessels, the increased use of diesel-electric propulsion has cut noise and vibration. Isolation systems absorb an engine’s vibrations before they spread through the hull.
"You don’t want sailors or mariners wearing hearing protection while sitting in a dining room, rec room or sleeping compartment,” Carnevale said. “Certain Navy activities require single protection for hearing, and others need double protection. Today’s Navy ships aren’t all that noisy, however, and commercial ships are less so.”
So why has SOLAS issued these new rules? “SOLAS is evolutionary,” Carnevale said. “As it grows and evolves, SOLAS is taking a tougher stance on noise.”
He said noise is a significant issue for anyone spending his or her working life on ships. “Going into and coming out of a space may not present a noise problem,” he said. “But it’s different when you’re in that space for four-hour watches at a time for several months. What matters is the level and duration of the noise, the length of sailing time and a mariner’s years on the job.”
During the summer, U.K.-based Videotel, owned by KVH Industries Inc. in Rhode Island, introduced a training course to coincide with the new SOLAS noise requirements.
“Even moderate noise and vibration can not only affect comfort, but with increasing exposure can lead to a severe drop in performance in the workplace,” said Nigel Cleave, Videotel’s chief executive.
The company’s course, called “Noise and Vibration – The Forgotten Hazards,” can be accessed through an interactive CD-ROM, Videotel On Demand or a DVD with a workbook.
Besides protecting against hearing loss and improving mariners’ lives at sea, the new SOLAS rules take into account the need to communicate with shipmates, hear alarms and work in a place where clear-headed decisions can be made.
A related concern is cited by oceanographers, who for years have said noise radiated by ships threatens marine life. Noise from ships interferes with underwater instruments and equipment used by scientists and the offshore oil industry.