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Noise Headlines and Top Story- Updated November 16, 2017
Vermont Imposes Noise Limits on Wind Turbine Noise
- BART Lowers Rail Noise with Reduced-Contact Wheel Profile
- Noise Linked with Increased Health Risk for Pregnant Women
- Research Vessel to Feature Low Underwater Radiated Noise
- Oysters Shut Down When Exposed to Low-Frequency Noise
- Acoustical Society of America to Showcase Latest Noise Research
- Spider Webs Inspire New Type of Labyrinthine Acoustic Metamaterials
- New Smart-Phone Application Targets Community Noise 
- Noise Impairs Productivity of Millions of Office Workers
- Bureau of Labor Statistics Gauges Noise at Work 

Maritime Industry Looks to Reduce Vessel Noise
Among the mounting evidence that anthropogenic noise has palpable negative impacts on marine life, new research is demonstrating that noise in the marine environment not only impairs marine mammals, but fish, cephalopods, and invertebrates as well, all while the world’s oceans are getting noisier. Analysis by Scripps Institution of Oceanography of declassified Navy documents in 2006 concluded that underwater sound levels off the coast of southern California increased three decibels per decade between 1964 and 2004.

While Navy sonar and its impact on marine mammals has received much attention over the past decade or more, there is increased awareness of commercial shipping’s contribution to rising ocean noise levels, with vessel builders, owners, and operators—along with their consultants—continuing to develop and implement methods of modeling, measuring, and mitigating underwater radiated noise (URN) from ship propulsion and machinery.  

  “Most of the noise ships produce is at low frequencies (roughly 20–500 Hz),” according to the University of Rhode Island. “In the frequency range of roughly 500–100,000 Hz, however, ambient noise is mostly due to breaking waves, rather than shipping. At low frequencies the background sound level in many places in the ocean is dominated by noise from distant ships, even when there is no nearby ship.”

The Ship Operations Cooperative Program (SOCP), a non-profit organization of maritime industry professionals, examined the issue at its latest meeting earlier this month, where Jason Gedamke, director of NOAA’s Ocean Acoustics program, provided background and the current picture. Also at the meeting, Yanran Wang, senior engineer at DNV GL, explained her organization’s SILENT Class Notations, voluntary standards for URN emissions from vessels. 

  Jesse Spence, president of Noise Control Engineering, LLC, described how reductions in noise of 3-5 dB for individual ships can be achieved through measures taken during the design, engineering, manufacturing, and installation stages—something Gedamke said would signal a great improvement if applied across the fleet. Decreasing vessel speed also has the potential to reduce noise. “Depending on how much you reduce speed, you could achieve a 3-5 dB reduction in noise, or more; it just depends on how much you reduce your speed,” said Spence.

“My big picture takeaway is that noise is becoming a greater concern, and shipping vessels (and other vessels, including ferries, tugs, and other workboats) will likely be required to meet underwater noise specifications in the future,” Spence told NRR. “However, the ‘line in the sand’ will be tough to identify since there are so many different species out there with differing sensitivities to noise.
“It may be more practical to approach the question of noise requirements or limits, reducing noise not from a biological perspective but from an engineering perspective. We know today how to reduce noise from ships, so it would be possible to identify realistic targets for ships. We probably cannot go back to noise levels that existed before motorized ships, but we can limit the increase in noise and potentially reduce noise worldwide.”

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