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Abstract |
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In the ship hull structure, there are a lot of noise sources such as propulsion engines, diesel generators, pumps
and air conditioning machinery, etc.Noise generated by these sources propagates through the decks and bulkheads
in the hull structure, and becomes noise in compartments such as cabins and workrooms. It is necessary to predict
the noise levels and determine appropriate noise control approaches in order to reduce the noise levels in compartments.
However, in order to get accurate results for noise prediction, an effective prediction model is needed.
Therefore noise transmission characteristics from various sources and source levels must be obtained properly.
This paper describes the noise transmission characteristics from the sources to the cabins when the one diesel
generator is running on the Tokai University research and training ship“BOSEI MARU”,and an effective and simple
noise prediction model using these transmission characteristics is proposed. The noise transmission characteristics
are obtained by using the distance between the diesel generator and the cabin.Then the attenuation of the noise level
is expressed as coefficients of damping proportional to the number of frames and decks.The source level of the diesel
generator is obtained by using these transmission characteristics and noise measurement in adjacent compartments.
The noise predictions for 20 cabins are performed using both the source levels and transmission characteristics.It is
shown that the accuracy of these predictions is within 5 dB in about 60 % of the cabins. It is also found that the
accuracy of the predicted noise spectrum levels is typically within 5 dB using the frequency dependent damping
coefficients.
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