2.8.1Points of measurement
If not otherwise stated, measurements should be performed with the microphone at a height of between 1.2 and 1.6 m from the deck. The distance between two measurement points should be at least 2 m, and in large spaces not containing machinery, measurements should be taken at intervals not greater than 7 m throughout the space including positions of maximum noise level. In large cargo holds no more than three measurements need be taken. In no case should measurements be taken closer than 0.5 m from the boundaries of a space. The microphone positions should be as specified in 2.8.2 to 2.8.8.
One measurement should be made in the middle of the space. The microphone should be moved slowly horizontally and/or vertically over a distance of 1 m and the mean reading recorded. Additional measurements should be performed at other points if appreciable differences, i.e. greater than 10 dB(A), in the level of sound inside the room occur, especially near the head positions of a sitting or lying person.
2.8.3Machinery spaces 220.127.116.11
Measurements should be made at the principal working and control stations of the seafarers in the machinery spaces and in the adjacent control rooms, if any, special attention being paid to telephone locations and to positions where voice communication and audible signals are important.
Readings should not normally be taken closer than 1 m from operating machinery, or from decks, bulkheads or other large surfaces, or from air inlets. Where this is possible, measurements should be taken at a position midway between the machinery and adjacent reflecting surface.
Measurements from machinery which constitutes a sound source should be taken at 1 m from the machinery. Measurement should me made at a height of 1.2 m to 1.6 m above the deck, platform or walkway as follows:
2.8.4 Duty stations
- at a distance of 1 m from, and at intervals not greater than 3 m around, all sources such as:
- main turbines or engines at each level;
- main gearing;
- exhaust-gas turbines;
- generators and aggregates;
- boiler firing platform;
- forced and/or induced draught fans;
- compressors; and
- cargo pumps (including their driving motors or turbines).
In order to avoid an unnessarily large and impractical number of measurements and recordings in the case of large engines and of machinery spaces where the measured sound pressure level in dB(A) at the intervals above does not vary significantly, it will not be necessary to record each position. Full measurement at representative positions and at the positions of maximum sound pressure level should, however, be made and recorded, subject to at least four measurements being recorded at each level;
- at local control stations, e.g. the main manoeuvring or emergency manoeuvring stand on the main engine and the machinery control rooms;
- at all other locations not specified in .1 and .2 which would normally be visited during routine inspection, adjustment and maintenance;
- at points on all normally used access routes, unless covered by positions specified under .1, .2 or .3 at intervals not greater than 10 m;
- in rooms within the machinery space, e.g. workshops. In order to restrict the number of measurements and recordings, the number of recordings can be reduced as in .1, subject to a total of at least four measurements (including those specified in this paragraph) being recorded at each machinery space level up to upper deck.
The noise level should be measured at all points where the work is carried out. Additional measurements should be performed in spaces containing duty stations if variations in noise level are thought to occur in the vicinity of the duty stations.
2.8.5Normally unoccupied spaces 18.104.22.168
In addition to the spaces referred to in 2.8.2 to 2.8.4, measurements should be made in all locations with unusually high noise levels where seafarers may be exposed, even for relatively short periods, and at intermittently used machinery locations, for example cargo discharge pumps.
In order to restrict the number of measurements and recordings, noise levels need not be measured for normally unoccupied spaces, holds, deck areas and other spaces which are remote from sources of noise and where a preliminary survey shows that the noise levels are well below the limit specified in Chapter 4.
Measurements should be taken in any areas provided for the purpose of recreation and additionally where a preliminary survey indicates that the limits specified in 5.3.1 may be exceeded.
2.8.7Intake and exhaust openings
When measuring noise levels at the intake and exhaust of engines and near ventilation, air-conditiong and cooler systems, the microphone should, where possible, be placed outside the gas stream at a distance of 1 m from the edge of the intake or exhaust opening and at a 30° angle away from the direction of the gas stream and as far as possible from reflecting surfaces.
2.8.8Navigating bridge wings
Measurements should be taken on both navigating bridge wings but should only be taken when the navigating bridge wing to be measured is on the lee side of the ship.