Noise level prediction to attain a vessel with an acceptable acoustic environment

Purpose

To determine in which areas of the vessel the noise levels may be excessive, and how much the levels must be reduced in order to comply with relevant noise requirements. The propeller may cause uncomfortable noise levels in cabins and public spaces in the aft-ship. In the area above the propulsion machinery, annoying low frequency noise generated by the engines firing impulses as well as noise in the higher frequency range have been experienced. Further, in all parts of the vessel where the background levels are low, sufficient sound insulation for acoustic privacy is important.

Benefits

DNV has leading-edge competence and tools to analyse the noise in and acoustics of ship structures. The results may serve as a basis for the design specifications of a newbuilding or as a basis for modifications to an existing vessel. Based on our extensive experience, we will propose a possible modification to the design in order to attain a vessel with an acceptable acoustic environment, thus improving the safety and operability of the vessel.

Features

The analyses are based on DNV Semi-empirical Noise Analysis Programme (NV5850). This program calculates the contribution to air- and structure-borne sound induced by the main noise sources. With reference to the HVAC systems in general, the noise control is assumed to be taken care of by the HVAC suppliers, based on given noise criteria specified by the yard. The above analyses will be carried out for a normal service transit condition of the vessel. On request, the operating condition with the bow thrusters in operation (DP-condition) may also be included. The results are presented as dB(A)-levels for the various accommodation spaces, open deck areas and engine room/working spaces. The predicted levels are compared to the specified noise limits. Where the required noise levels are not met, noise reducing measures are proposed.