Ships at berth cause noise which can be avoided if power is supplied from the electric grid instead of using auxiliary engines generators. Also, noise attenuation is achievable by installing silencers to reduce sound impact from diesel generator engine exhaust.
In addition to diesel generator engine exhaust, other sources of noise from ships at berth include ventilation inlets/outlets from engines room, and other secondary noise sources such as refrigerated containers ‘reefers’, air conditionate, pumps, internal ramps operations, etc.
Port areas are subject to spatial planning along with local noise delimitation where noise level limits are to be respected. Noise planning in ports including data collection by noise measurements, analysis, elaboration of port noise maps and corresponding appropriate measures, is an obligation set out in Directive 2002/49/CE. In Spain, Royal Decree 1367/2007 transposes Directive 2002/49/CE, and many municipal governments in port cities have already approved their respective noise plans. Finally, local by-laws specifically set maximum admissible noise limits.
Ships are obliged to fulfill IMO noise limits established by Resolution A.468 (XII) Code on noise level on board ships, 1981. This regulation limits noise to 75 dB(A) at external onboard leisure areas where 5 dB(A) less is recommended. Thus, if this limit is used to estimate sound power of auxiliary engines, and -after corresponding propagation exercise- 45 dB(A) noise level is to be respected at night in residential areas, the resulted minimum required buffer from these areas can reach relevant distances.
Therefore on-shore power supply at berth is recognized as a valid solution to reduce impact of noise from ships. Because of using shore power GREENPORTS estimated noise reductions ranging from 0 (Tankers/RoRo) to 16dB (Bulk). Many other factors influence final decision to be taken on a cases by case bases upon considering alternatives or complementary options the main ones are the following related either on ships and by port management,
- adaptation on board consisting of silences on the diesel generator exhaust or rerouting exhaust via main engine exhaust, adding mineral wool to fan rooms walls, modify procedures to operate internal ramps,
- rearrange allocation of berth slots or relocation of ship berthing spatially (remoteness or shift ship side), port infrastructure charging differentiation as suggested by EU study and NoMEPorts project.
PUERTOS DEL ESTADO commissioned a study to specifically estimate reduction of noise impact from auxiliary engines of ships at berth, the summary of which can be found here.