Validation of a Harmonic Acoustic Model for Duct-borne Noise & Vibration onboard Maritime Vessels

Abstract

Noise & Vibration studies are one of the most important aspects of designing any dynamic system. Any machinery which has components having high inertia, rotating components, friction, losses and other random forces create excitations at various locations. Ducts are an excellent carrier of various types of vibrations which are created by these excitation forces and carry them to various locations. Thus, if excessive noise levels are generated and transmitted to different ship locations, there are possibilities of detrimental effects such as hearing disabilities for crew and passengers onboard, failure of equipments due to resonance, noise emission to surroundings, violation of stealth requirements etc. This paper primarily focuses on understanding the sources of noise & vibrations onboard marine vessels, transmission of these vibrations to various locations on ships via ducts and attenuation of the noise. Using the guidelines established by various classification societies such as American Bureau of Shipping, Bureau Veritas, Lloyd’s Register etc., a package written in Python is developed to calculate the theoretical attenuation across the duct system for a case under consideration. A harmonic acoustic model is created in ANSYS (R2022) software to replicate this noise & vibration scenario onboard ships for various duct subsystems. After the simulation is carried out, a comparison of the output of the Python package and ANSYS model is carried for attenuation of noise levels. This provides a basis for establishing the accuracy of the simulated model. It is found that the error is minimal and the 2 output results are in sync. Thus, this enables us to further improve these models for various ships and ensure the noise levels are restricted within the required limits.