Identification of Design Drivers for Reducing Ship Radiated Underwater Noise and the Airborne Noise Levels on Tug’s

The most widespread and pervasive kind of anthropogenic energy is underwater sound. Shipping noise is a major contributor to the ambient noise levels of the oceans and a major source for adverse effects on marine mammals. Proper design considerations need to be studied on noise sources on ships to reduce airborne and underwater noise levels and improve safety.

There is a need to identify the various noise sources (propeller, machinery and flow around ship) on ship and check alternatives means to dampen each noise source propagations, so has to have considerable damping in overall airborne and underwater noise levels in the initial design stages.

Measurements of airborne noise have been carried out in various location of different propulsion type tugs in the channel of Visakhapatnam and a comparison of the results is tabulated. The measurements of the airborne noise levels on five tugs are noted during regular towing operation.  The noise levels in the Engine room are well below the permissible limits but in other locations the noise levels are above the limits. The reason for the noise limits to be above the acceptable limits in upper deck regions being the position of the ventilation blower unit in the above deck and the windows in open condition during measurements. Also the average noise levels of Voith Schneider propulsion (VSP) and Schottel Rudder propulsion (SRP) is 103 dB.  The vessel traffic noise levels at the entrance of the channel is around 69 dB.

The most widespread and pervasive kind of anthropogenic energy is underwater sound. Shipping noise is a major contributor to the ambient noise levels of the oceans and a major source for adverse effects on marine mammals. Proper design considerations need to be studied on noise sources on ships to reduce airborne and underwater noise levels and improve safety.

There is a need to identify the various noise sources (propeller, machinery and flow around ship) on ship and check alternatives means to dampen each noise source propagations, so has to have considerable damping in overall airborne and underwater noise levels in the initial design stages.

Measurements of airborne noise have been carried out in various location of different propulsion type tugs in the channel of Visakhapatnam and a comparison of the results is tabulated. The measurements of the airborne noise levels on five tugs are noted during regular towing operation.  The noise levels in the Engine room are well below the permissible limits but in other locations the noise levels are above the limits. The reason for the noise limits to be above the acceptable limits in upper deck regions being the position of the ventilation blower unit in the above deck and the windows in open condition during measurements. Also the average noise levels of Voith Schneider propulsion (VSP) and Schottel Rudder propulsion (SRP) is 103 dB.  The vessel traffic noise levels at the entrance of the channel is around 69 dB.