Measurements of vibrational power transmission from ship main engine

This experimental study belongs to the VÄRE subproject Vibration and noise control of transport equipment and mobile work machines. Literature review, which preceded this experimental study, was aimed to find methods for the characterisation of diesel engine of a ship as structure-borne sound source and to find design methods to minimise the sound transmission from machine via foundation to the ship structure. The aim of this experimental study was to apply and take into use the characterisation methods found in literature. Method was selected after literature survey without any experimental pre-tests. With this method it is possible to determine vibrational power transmission from vibrating source to the surrounding structure using measured vibration data. Method is based on measured mechanical driving-point mobility, transfer mobility and vibration velocities of the surrounding structure in the "far-field". Vibrational power transmission was successfully calculated from measured signals. However, quite large discrepancy existed between powers calculated with two different ways. According to the literature review this method has been applied to rather small structures. Large discrepancy mentioned above might be due to large and complicated real-life structure. However, the method seems to be promising and probably results could be improved by optimising excitation equipment for large and heavy structures.