As we have seen, the main source of noise is the propulsion mechanism, and therefore the highest levels of noise are found in its vicinity. In most ships, the noise is greater than 100 dB(A), and can sometimes be as high as 110 dB(A).

 

Location

dB(A)

Low-speed diesel engine

Medium-speed diesel engine

Electricity generator

Turbo generator

Steam turbine

Main boiler

Reducer

Auxiliary boiler

Compressor

Water pump

100-105

105

95-105

90-95

85-95

90-95

80-90

95

85-100

80

 

Table.1: Mean noise levels in various types of engine room

 

In other locations, however, noise levels are generally between 60 and 75 dB(A). Technological progress has ensured that on passenger ships, particularly cruise ships, cabin noise levels are around 40 dB(A).

Fishing vessels are generally smaller than merchant ships, and fishermen spend much longer on board over the course of a year than merchant seafarers do. These vessels pose more acute noise problems. The above noise sources on merchant ships are obviously also present on fishing vessels. In addition, there is the noise of winches used for launch and for lifting fishing equipment. We have reproduced below the noise levels found on board various fishing vessels of the same tonnage:

 

 

55 m tuna boat

55 m trawler

24 m trawler

Gangway

Cabins

Galley

Engine room

Fishing deck

74 dB

68 – 70 dB

76 dB

109 dB

74 dB

76 – 85 dB

78 – 81 dB

110 dB

81 – 95 dB

76 dB

80 – 85 dB

81 dB

106 dB

86 dB

 

Table 2: Noise levels in different compartments of fishing vessels

Noise in engine rooms exceeds 105 dB and is perceptually equivalent to levels found on board merchant ships of any size. The difference between merchant ships and fishing vessels is that there is not always a soundproofed control cabin on smaller fishing vessels. Noise levels in sleeping quarters in fishing vessels less than 30 m in length are very high (because the crew quarters and engine room are so close together). There is also a high level of noise on the fishing deck. Modern fishing trawlers have covered fishing decks, which provide greater safety and comfort than outside work, but which increase noise levels as they act as resonance chambers.  

Some authors (7) have measured median noise levels for ships (it is best not to use the term “mean”, as decibels are logarithmic values which cannot be added arithmetically). For a common type of 24-metre trawler, median noise levels were 76 dB on the gangway, 80 dB in the wardroom, 86 dB in the steerage compartment, 84 dB on the fishing deck, 82 dB in the crew quarters and 106 dB in the engine room.

The most relevant audiometry finding in relation to risks to hearing is the equivalent continuous level (Leq) to which the crew members are subjected during one day and during one trip. Data recorded in situ show that in 55-60 m trawlers, there are equivalent average noise levels of around 85 dB over a 14-day trip.

Equivalent noise level (Leq) considers not only the intensity of noise, but also duration of exposure. Generally, in industry, we calculate the Leq for a period of 8 hours per day, which is a normal working hours in Western countries. The Leq (8h) is regarded as a source of hearing loss when it exceeds 80 dB (A). However, on ships, seafarers are exposed to noise 24 hours on 24. Therefore, we now calculate the Leq (24hrs) for seafarers, which produce a more precise idea of exposure.

As fishermen are on board for 24 hours a day over several days, levels that would be considered to be disease-causing in workers on land cannot easily be applied to them. Much also depends on the job an individual carries out on board.

 

Skipper

First mate

Engineer

Cook

Deckhands

Trawler 1

72.9 dB(A)

79.5 dB(A)

92 dB(A)

82.4 dB(A)

82.3 dB(A)

Trawler 2

69.9 dB(A)

83.3 dB(A)

92.5 dB(A)

84.4 dB(A)

85.9 dB(A)

Trawler 3

76.3 dB(A)

83.6 dB(A)

95.4 dB(A)

84.8 dB(A)

85.9 dB(A)

Trawler 4

73.2 dB(A)

86.6 dB(A)

95.4 dB(A)

83.8 dB(A)

84.4 dB(A)

 

Table 3: Average equivalent levels for a while trip for crews of four semi-industrial 34- metre fishing trawlers ( l7)

             

The only fisherman who is not exposed to a level of noise that causes trauma to the auditory system is the skipper. All other crewmembers are. The recognised threshold above which there is a risk of hearing loss is 80 dB(A), 8 hours per day. However, if the formula for calculating equivalent continuous levels is used, we notice that a Leq(24h) of 82 dB(A) corresponds to a Leq(8h) of 95 dB(A), according to energy equivalence laws. This means that a seafarer who is exposed to a noise level of 82 dB(A) over 24 hours is exposed to a stressor and a risk to hearing that is equivalent to that of a worker who is exposed to 95 dB(A) for 8 hours a day. In this type of fishing, engineers are subject to highly traumatic levels of noise. If we study, as we are currently, the noisiest times of the work day, we see that length of stay on deck (handling fishing equipment, mending nets, processing the catch) means that fishermen are exposed to 85 dB(A) for an average of 13 hours per day. Then there is time spent in the crew quarters (during sleeping periods, around 5-6 hours per day) exposed to 83 dB(A), and meals in the wardroom (81dB for three hours) and gangway watch (73 dB) for 2 hours. For a conventional trawler of between 15 and 25 metres in length, the equivalent continuous noise level over 24 hours has been calculated as Leq(24h) = 83.6 dB(A).

Therefore, we have to consider that fishermen, apart from skippers of large industrial trawlers, are at high risk of hearing damage due to noise, whatever job they do on board.