Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Revised comfort class rules

Proposals for revised comfort class rules:
Based on the findings of this study it was decided to revise the comfort class criteria for high-speed vessels to a more realistic level than what appears in the current edition of the comfort class.

It may be worthwhile considering an area-wise distribution of noise levels instead of dividing between different size vessels. Two alternative proposals are therefore presented.

Based on the statistical analysis of the DNV database for noise levels onboard high-speed vessels two alternative proposals for maximum levels have been made and specific new limits have been proposed in the referenced technical note.

Description of changes:
- An area-wise division may be considered instead of a length division. Alternatively, the length division should be increased from 50m to 100m. The influence of size on noise levels is not felt to be significant before the vessels become very large. Both short and long vessels have problems reducing aftship levels.

- If an area-wise distinction is allowed, the new maximum levels will be in line with the IMO requirements or slightly stricter for comfort rating 1 in the aftship. For the forward areas, the new maximum levels will be roughly in line with the previous requirements for vessels exceeding 50 m overall length (slightly less strict for rating 3).

- If a length division is kept, the maximum noise levels for Passenger localities have been raised, except for comfort rating 3, which is already at the minimum requirement specified by IMO. The noise level requirements have been increased by 2 - 5dB(A) based on experience from measurements onboard new buildings, in order to make the requirements realistically attainable. The requirements are still strict compared to the experience from vessels in service today.

However, it is believed that advances in noise reduction technology will make the requirements more easily achievable in the future. It is also felt that comfort rating 1 represents a noise requirement that most builders will have to stretch themselves to their utmost capability in order to achieve. It is also felt that vessels achieving the comfort class requirements will have a high level of comfort. Particularly, if the novel requirement to tonal noise is accepted.

- The maximum levels for navigation bridge is increased from 60dB(A) to 63dB(A) for comfort ratings 1 and 2. It is felt that 63dB(A) on a bridge environment will be good enough. A noise level of 63dB(A) will enable clear and undisturbed communication and should not stress the crew. The bridge is often exposed to aerodynamic flow noise and noise from internal navigation equipment. Noise control for these sources may be difficult as well impractical.

- The noise levels for service areas are reduced from 78dB(A) to 75dB(A) for comfort rating 3 in order to bring this requirement in line with the IMO maximum levels. For vessels longer than 100m the noise requirement is increased from 65 to 68dB(A) for practical reasons and to harmonise the requirement to the requirement for passenger localities.

- New requirements have been added for outdoor passenger areas. Such areas have become common for vessels operating in hot climates. Hence, in order to keep in line with the market, noise requirements for such areas should be included in the comfort class. Noise on open deck areas is hard to attenuate and will often be influenced by noise from the sea in particular the wake, but also airflow. The suggested requirements have therefore been kept in line with the IMO requirements with a slight reduction for the higher comfort rating(s).

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