California Coast & Ocean

Building Quieter Ships
Some shipping industry representatives also believe that the issue deserves serious consideration now rather than later. Kathy Metcalf, director of maritime affairs for the Chamber of Shipping of America, which represents owners and operators of large commercial vessels of all flags that have offices in the United States, has participated in gatherings where scientists, engineers, and others have met to discuss the scope of the problem and possible responses. “While we recognize there is some impact now, we just don’t know the degree and whether it rises to the level of 'significant,'" she said. “One thing is certain: at some point, with the expected increase in the number and size of vessels, there will be a significant impact.”

Vessel-quieting technologies already exist, developed by the Navy to hide its own ships and by others for use on research vessels, though not all of these technologies are relevant to commercial ships. To be widely adopted, quieting technologies must be cost-effective for shipowners, Metcalf said. “We’ve had naval architects that said yes, it can be done economically, and others that say no, it can’t,” she said. “At this point, it’s too early to tell whether or not it’s feasible.”

Most of the technologies developed to reduce ship noise have focused on ways to decrease propeller cavitation, a process that is the biggest source of underwater noise from ships. As they spin, propellers generate vacuum bubbles in the water. The bubbles collapse almost as fast as they are generated, making a loud rumbling sound. “It is my hope that you can reduce propeller cavitation in a way that increases fuel efficiency,” Metcalf said. “In that case, we’d be stupid not to do it.”

In May 2007, Southall coordinated a NOAA-sponsored international symposium of scientists, engineers, industry representatives, and others in Silver Springs, Maryland, to assess the feasibility, costs, and benefits of various vessel-quieting options. The evidence presented suggests that “there are certainly technologies that could be applied, and they very likely could quiet really big ships to some degree,” Southall said. “The question is, how much do you want to quiet them, and how much do you want to spend?” Some quieting at a fairly reasonable cost seems possible. The key will be to give shipbuilders and -owners incentives to adopt them.

Sharon Young, marine issues field director of the Humane Society of the United States, who led a working group at the symposium, said afterward that she was “very heartened by the reaction of the engineers and other industry representatives. They were very receptive [to working on solutions]. Many of them just had no idea that vessel noise was such a problem. I thought it was a very promising beginning.”

Metcalf, who also participated in the symposium, said that her next step will be to bring together some private-sector experts to see how they might spur action at the international level. “If you’re really going to do something about ambient noise, it has to be international,” she said. “The International Maritime Organization (IMO) is the only entity that could feasibly regulate it.”