2. In the case that it is possible to carry out the measurement with the sister ship or the similar ship mentioned before though the parameters of those ship are unknown, the procedure of the calculation must be as follows:

(1) The measurement and the calculation are carried out with the sister ship or the similar ship.

(2) The parameters necessary for the calculation is obtained from the comparison between the measurement and the calculation in (1). The work described in this step is referred to as "the matching work" hereafter.

(3) The calculation of the ship concerned is carried out using parameters obtained in the step (2).

3. In the case that there is not the parameter, nor the measurement can be carried out, the parameters of the ship which has the most same specifications as the ship concerned is used in the calculation.

In any of above cases, the measurement of the ship concerned should be carried out and evaluate the validity of the parameters if possible.

The authors had an opportunity to carry out the calculation corresponding to the above case 2. The ship concerned is the cargo ship which is Ship No.1 in Table 1 and the similar ship is Ship No.2 in Table 1. Put another way, the measurement and also the calculation were carried out with Ship No.2 and the parameters were obtained by the matching work with these results. Then the calculation was carried out with Ship No.1 using the parameters obtained at the previous stage.

　

Table 1 Objects

　

5.2 Case for KNOISE to be Applied

5.2.1 Measurement at the Real Ship

The purpose of the measurement is to obtain parameters necessary for the calculation and to verify the calculated results. In the following three measurement, while the first and the second measurements were applied to only Ship No.1, the third measurement was applied to both Ship No. 1 and Ship No,2.

Case1; This is the measurement of the conventional reverberation time to determine the mean absorbent rate of the accommodation space and the engine room. A starting pistol is used as the impulsive sound source. The internal loss factor of the room is calculated from this.

Case2; In this case, the transmission of the sound or the vibration are measured using the noise source for the test. While the tapping machine is used as the test source in the accommodation space above the upper deck, the diesel engine for the generator is used as the test source when the energy transmission from the engine room to the accommodation spce. is measured because the power of the tapping machine is insufficient. The coupling loss factor is calculated from the result of this measurement.

Case3; The aim of this measurement is to get the data for the evaluation of the calculation. The measurement is carried out during the operation of the continuous service condition at the sea trial. The measuring point is the center of each element of the SEA model with both the sound and vibration.

Ship service condition are shown in Table 2.

　

Table 2 Ship Service Condition

　

5.2.2 Calculation of Similar Ship (Ship No.2)

This calculation of the prediction described below is carried out for the comparison with the result of the measurement. The scale of the model used in this calculation was set to be proper for the purpose of this calculation which is to compare the result of this calculation with the result of the measurement. In the accommodation space, parameters in the standard spec. tables described in 4.2 for rooms whose acoustic specifications of the interior were not clear at the design stage. However, because there is no standard data of the parameter in the machinery space, the standard for the room of each layer were determined using the result of the measurement. Consequently, standard specifications for the room are divided into 28 groups.

It has been found through the matching work that the difference between the calculation and the measurement could not be decreased within the sufficient range both in the accommodation space and the machinery space simultaneously, if same parameters are used for these two spaces. The cause of this seems that the energy loss during the transmission becomes large above the upper deck. Therefore, two kinds of the correction factor for the energy loss are used for the accommodation space and the machinery space respectively.

The condition of the sound source such as the main diesel engine, the auxiliary engine for the generator and the air conditioning unit must be necessary for the calculation. In many cases, these condition is given such a manner that the sound pressure level corresponding to the sound source is given at the position of the sound source concerned. But the condition generated by this way may be much different from the true condition in the case that the influence of the acoustic environment around the sound source must be considered. Therefore, the sound power level is used as the condition of the sound source instead of the sound pressure level. Sound power of the main engine and the auxiliary engine obtained from the measurement at the real ship were used.

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