mcbem-2014-01-submission-wwf-en

For the future, the IMO Energy Efficiency Design Index (EEDI) and Ship Energy Efficiency Management
Plan (SEEMP) should be carried out in concert with noise reduction, as noise measurements may point
to energy efficiency issues. Model tank testing also should incorporate noise as matter of routine. A
requirement to measure each ship’s noise output would help to bring noise considerations to the fore.
Research needs include comparing model tank tests with real at-sea measurements of ships in typical
operating conditions.
Figure 14. The main source of underwater noise on most vessels is due to propeller cavitation. Courtesy
of Lindy Weilgart.
To reduce their noise impact, ships could minimize the time spent near shore, where noise propagates
into the deep sound channel. IMO guidelines will provide a checklist for ship designers to consider noise.
Noise compliance could be achieved through port authorities, ship classification and green certification
programs, regulations, and economic incentives. A menu of quieting options for future consideration
and action would be helpful, as would funds for modelling basin research.
For pile driving, quieting options include piling with a sound shield, the Hydro Sound Damper,
dewatered cofferdams (noise reductions of around 20 dB), and bubbling curtains. However, sound
transmission also occurs through the substrate, so rather than reducing noise after it is produced,
quieter piling sources are recommended, such as the Multiple Linked Hydraulic Vibratory Hammer
System (MLHVH) or drilled foundations using excavation machines, which are more than 40 dB under
the German government noise limit (160 dB (SEL) / 184 dB (peak) @ 750m).
48