Inboard Noise of Fishing Training Ship Nansei-maru

It is important to improve the noise environment of fishing training ships in order to secure the health of crews and maintain safe navigation. Therefore, 23 observation points were set for clarifying the actual condition of the inboard noise of a ship named Nansei-maru, and the measurement of the noise level (equivalent continuous A-weighted sound pressure level) and frequency analyses were carried out. The main sources of Nansei-maru's inboard noise were its main engine, generator, turbocharger, pumps and propeller shaft. The line spectra of their fundamental frequencies and harmonics were analyzed in detail. The inboard noise level increased with increase of the revolution of the main engine. The inboard noise at 700 rpm, which is the maximum revolution of the main engine, is described as follows. The highest level of the inboard noise was 100 dB in the engine room, the second was 70 dB in the engine watch room, and the lowest was 51 dB in the Professor room. The mean value of the 22 observation points, excluding the engine room, was 59 dB. In the accommodation space, the highest noise level was 61 dB in the No. 4 cadet room, the lowest was 51 dB in the Professor room, and the average was 56 dB. Noise level was higher on the main engine-installed deck, and lower on the upper floor. The sound insulation quantity of the engine watch room was lesser in the low frequency band up to 750 Hz, and the attenuation level in the higher frequency band was 30-40 dB