The fact, that the crew find 50-90% of troubles of the marine diesel engine in the MO ship, implies the human sense of hearing plays a crucial role in the diagnosis of the engine. And the hearing ability to diagnose is improved by experience in hearing the abnormal sounds. But now the crew have little opportunity for hearing abnormal sounds.
It is proposed the training system for the improvement in the hearing ability using artificial sythetic sounds in place of original sounds which is very difficult to collect. In this paper, the normal and abnormal sounds of a four-stroke diesel engine are sythesized by means of the frequency modulation synthesis and the addition synthesis.
The synthetic sounds simulate the original sounds exactly, as the result of the comparison of the synthetic and original sounds by hearing and observation of the waveforms.

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The author has analysed statistically on damage data of propulsive engines for the classed ships following the previous study on propulsive shaf tings. Data base of 139 ships collected with survey reports in the period of 8 years were used. Degrees of damages in engine parts were converted into amount of maintenance in the same procedure as the mentioned study. Then the relation between the amount of maintenance and other factors were investigated by application of quantification theory. Main conclusions obtained are as follows;
(1) Locations in which damages occur in main engines are closely connected with engine type and engine performance such as Pmax.
(2) Maintenance mode which means how frequently damages occur or maintenance work is done through 8 years examined in this study was investigated. And it was found that it has close correlation with engine type, revolution and ship's nationality.
(3) Constitutional factors of propulsive engine systems which influence the amount of maintenance are revolution, engine type and ship's kind in descending order. Ship's nationality has little influence on it.
(4) Membership functions regarding influential factors and their categories relating amount of maintenance were introduced. By using these Fuzzy functions the trend of the amount of maintenance in one propulsive engine system can be easily compared with another system.

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Today, it is very important to establish the technology for extracting energy from Solar Heat and Ocean Powers.
We made and placed the air chamber in the experimental tank of the wave simulator. The wave height and the air pressure in the chamber were measured by the combination of nine different diameters orifices wave periods.
The efficiency of energy conversion from the average wave oscillation to the average air blowing through the orifice was examined in relation to the effect of the wave period and the area ratio (the orifice area/the air chamber cross sectional area) .
The followings are main conclusion ;
1. The method fo wave simulation was completed and arbitrary wave periods and wave heights were generated in the experimental tank.
2. The pressure in the air chamber oscillates because of the interaction between the inertia of water and the compressibility of air.
3. The efficiency of energy conversion, ηbecomes worst at the point of that the crest of natural vibration of the experimental tank and the air chamber meets the trough of forced vibration.

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A support ship “Yokosuka” for a 6500m deep research submersible is provided with many underwater acoustic instruments. To get full performances of such instrments, it was necessary to reduce the underwater radiation noise from “Yokosuka” herself to the sea. For this purpose, from her initial planning stage until the completion, the authors carried out a thorough noise control, taking the underwatet radiation noise to be the most impotant problem to be solved. As a result, the underwater radiation noise from “ Yokosuka” drastically reduced and cleared the target level which was set at the design stage, and the underwater acoustic instruments could develop their performances to their full extent.
This paper introduces the method of noise control applied to “Yokosuka”.

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With years to elapse, ships undergo an unfavorable operationg condition-over-torque of main engine, by their speeds being decreased due to the deterioration of the performance by aging of hull, main engine and propeller.
There are several measures available against such over-torque condition:
—applying a margin to the propeller speed at a propeller designing stage,
—recoditioning main engine,
—cleaning up fouled hull surface,
—polishihng propeller surface,
—modifying propeller particulars, etc.
Among these measures, the modifying of propeller particulars is usually practiced from viewpoints of workability, economy and effectiveness.
This paper describes modifying methods of propeller particulars, with effects on shafting, etc., which will be a useful guide to ship operators and shipbuilders.

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