Trans RINA, Vol 157, Part A3, Intl J Maritime Eng, Jul-Sep 2015
aft, in the same ballast condition during speed trials and with the engine operating at maximum rpm. Average values are presented in Table 6.
experimental study of existing noise and vibration on eleven tankers ranging in size from 18,000 to 200,000 GRT.
The results for two representative types of vessels are summarized below: one of 200,000 GRT sailing at full load, and another of 70,000 GRT in ballast. On the 200,000 GRT vessel, a large difference in the noise level was registered between the Engine Room (105 dB) and Accommodation (68 dB), this difference increasing with increasing
frequency frequencies).
A significant low frequency component existed in the crew cabins, dropping to 23 dB in the 31.5 to 250 Hz frequency range. A peak appears at 500 Hz which raises the noise figure (NF) to 67, practically coinciding with the sound pressure level of 68 dB(A).
Figure 3. Histogram distribution of noise in 1,360 cabins on 45 different ships.
Table 6. Average noise levels in dB(A) of a group of 14 bulk carriers.
Workshop Galley (with extractor fan)
Galley (without extractor fan)
Cabin (main deck) Cabin (lower deck) Cabin (officers’ deck) Cabin (bridge deck) Control Room Wheelhouse Engine (top)
NF 94 82 69
65 57 56 54 75
dB(A) 98 84 74
67 61 61 59 79
- 68 98
SIL 91 77 68
55 50 47 49 71 -
103 96
Engine Room.- The average noise level in the Engine Room was 104 dB(A), so it is essential to have an Engine Control Room. The average value in these was 79 dB(A), which exceeds the recommended level of 75 dB(A). Outside the control room, average values of 103 dB(A) were obtained at the top of the engine, so it is not possible to hold a conversation here without shouting. The recommended level in the Engine Room workshop was 85 dB(A), while the measured value was 98 dB(A) and hence too high. Understanding what is said here is hence very difficult.
Wheelhouse.- The average level was 68 dB(A), while the recommended limit is 65 dB(A).
It can be seen that the limits are generally exceeded in almost all spaces on board.
d) Experimental levels of noise on tankers, Buiten [19] obtained the
results discussed below from ©2015: The Royal Institution of Naval Architects an
Third octave band frequency analysis of the noise and vibration on board reveals dominant frequencies. A peak appears at 5 Hz attributable to the propeller, which was rotating at 5.4 Hz at the time of measurement. At frequencies between 10 and 63 Hz, a band of relatively constant noise was observed that was attributed to structural transmission of the engine noise which is partly radiated through the air to the cabin.
As for the 70,000 GRT vessel, the characteristic peak of propeller noise is clearly observed at a frequency of around 8 Hz, the propeller rotating at 7.9 Hz at the time of measurement.
The bridge crew was subjected to an equivalent continuous sound level of 66 dB(A), and to 71dB (A) in the mess and 68 dB(A) in their cabins. Similar values were found for the rest of the deck crew.
e) Summary of noise levels for various types and sizes of vessels from the DNV CS [20], of average noise levels
in dB(A) for different vessels (table 7).
Table 7 shows that the higher the deck is with respect to the engine
room, the lower the level of noise.
Nevertheless, in almost no case does it exceed 65 dB(A) (except in vessels of less than 1000 DWT), when the cabin is located above the superstructure. This value is exceeded, however, when the cabin is located below the superstructure.
The values recommended by the IMO are 60 dB(A) for smaller vessels and 55 dB(A) for larger vessels. These limits are met in cargo ships from deck B (second deck starting from the main deck). The vessels that most fail to meet the recommendation are small container ships. Clearly, the sound insulation of cabins located on the main deck, and those below it needs to be improved, or accommodation should be located exclusively from the lower deck with respect to the main one.
types and sizes of (greater difference at
higher
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