Code of Practice for Noise Levels in Ships

Contents

1  Scope of the Code
2  Purpose of the Code
3  Application of the Code
4  Measuring equipment
5  Method of measurement
6  Survey
7  Limits (acceptable maximum noise levels)
8  Exposure of personnel to potentially harmful noise
9  Methods of controlling noise exposure
10 Ear protection
11 Training of personnel
12 Responsibility
13 Definitions
Appendices
1 Format for presentation of ship noise survey results
2 Methods of calculating equivalent continuous sound level
3 Ear protectors
4 Method of converting octave band sound pressure levels to A-weighted sound level
5 Extract from the Merchant Shipping (Crew Accommodation) Regulations 1978
6 Requirements on protection against noise in machinery spaces in the Passenger and Cargo Ship Construction and Survey Regulations 1984
7 Extract from the Merchant Shipping (Protective Clothing and Equipment) Regulations 1985
8 Extract from the Merchant Shipping (Health and Safety: General Duties) Regulations 1984

Introduction
This revised Code of Practice represents a standard of good practice following on from the initial code, and takes the form of recommendations. These recommendations provide a basis to which those concerned with designing, building and owning or managing ships can work in order to protect the seafarer from the harmful effects of noise and to establish acceptable conditions in respect of noise on board ship at sea and in port.
It may be that, in the case of existing ships, especially small ships, strict compliance with some recommendations is impracticable. In such circumstances, every endeavour should be made to observe the intent of the code.
The original code was published in 1978 with the co-operation of the shipping industry in a working group on Noise Levels in Ships consisting of representatives of the shipowners, seafarers, shipbuilders, engine manufacturers, statutory authorities, classification societies and research organisations. This revision takes into account some of the provisions of the IMO: Code on Noise Levels on Board ships (1982) and other technical developments.
Although the Code is addressed to the health and working conditions of seafarers, under the Merchant Shipping (General Duties) Regulations 1984 shipowners and employees have a duty to ensure the health and safety of other persons aboard ship who are not engaged in the normal business of the ship. In this respect compliance with this code should satisfy the requirements of the Health and Safety Executive which were originally published in 1972 by the Department of Employment and entitled "Code of Practice for Reducing the Exposure of Employed Persons to Noise".
Extracts from some of the regulations currently in force relevant to noise in ships are appended to the code.

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1 Scope of the Code
1.1 The Code of Practice deals with:
    (a) The measurement of noise levels.
    (b) Recommendations for acceptable maximum noise levels for all spaces to which persons normally have access.
    (c) The means of protecting the seafarer from the risk of noiseinduced hearing loss under conditions where at the present time it is not technically feasible to limit the noise to a level that is not potentially harmful.
    (d) Noise abatement measures generally applicable on board ships.
1.2 Certain provisions may be relaxed for vessels designed for, and employed on, voyages of short duration. Provisions may be further relaxed for vessels without sleeping accommodation which are crewed on a shift basis eg certain ferries, dock and harbour craft etc. (See Section 3 for details of application of this Code).
1.3 The provisions of this Code are not intended to apply to passenger cabins and other passenger spaces except in so far as they are work spaces as covered by this Code.

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2 Purpose of the Code
2.1 The objectives of the Code are to limit noise levels on board ship and to reduce exposure to noise in order to:
    (a) Protect seafarers and others on board ship from noise levels which may give rise to a noise-induced hearing loss.
    (b) Provide the seafarer with an acceptable degree of comfort in rest, recreation and other spaces and also provide conditions for recuperation from the effects of exposure to high noise levels.
    (c) Make work places safer by facilitating speech communication in control stations, navigation and radio spaces, and manned machinery spaces so permitting decisions to be made without excessive distraction from noise.
    (d) Reflect the provisions of the Merchant Shipping (Health and Safety: General Duties) Regulations 1984. (SI 1984: No 408).
    (e) To raise the standards of environmental health and welfare by recommending noise levels in crew accommodation and recreational spaces.

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3 Application of the Code
3.1 All sections of this Code should apply to new ships (except private pleasure craft and fishing vessels) of 500 tons and over subject to the provisions of 3.4 to 3.6 below. This Code should also be applied to new ships below 500 tons where reasonable and practicable.
3.2 The provisions relating to potentially hazardous noise levels contained in the following sections of this Code should also apply to existing ships of 500 tons and over (except private pleasure craft and fishing vessels) subject to the provisions of 3.6 below, regardless of type, size or service: 7.3; 8; 9.1.1; 9.5; 9.6; 9.7; 9.10.1; 9.12; 10; 11.2; 12.
3.3 In order to apply the recommendations of 3.2 above some of the measurements detailed in sections 6 and 7 will be necessary.
3.4 For new ships intended for manning on a shift or daywork basis; such as dock and harbour craft, ferries on voyages of short duration, including those where sleeping accommodation is provided but not normally used, the recommendations contained in sections 7.2.7; 7.2.9; 7.2.10; 7.2.11 need not apply.
3.5 For vessels designed for and employed on voyages of short duration or on other service involving short periods of operation of the vessel, sections 7.2.7; 7.2.9; 7.2.10; and 7.2.11 may be applied with the vessel in the "in port" or "non-operational" condition only, provided that the per.iods under such conditions are suitable for personnel rest and recreation.
3.6 This Code applies to ships in service, ie in port or at sea with crew on board.

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4 Measuring Equipment
4.1 In order to ascertain the amount of noise to which employees are being subjected, it is necessary to carry out a noise survey. Noise level instruments are designed to respond in approximately the same way as the human ear, and to give objective reproducible measurements of sound pressure level. Given that an increase of only 3 dB(A) should halve the permitted period of exposure, it is important that noise measurements are accurate.
Measurement of sound pressure levels should be carried out using meters manufactured to:
    (i) British Standard 5969: 1981 (IEC 651: 1979) suitable for field use. Type 1 sound level meter is a precision grade meter and type 2 is an industrial grade meter.
 or (ii) British Standard 6698: 1986 (IEC 804: 1985) suitable for measurement of the equivalent continuous sound pressure level of impulse noise.
 or (iii) Sound level meters meeting other specifications provided their performance is known to be at least equivalent to that required by BS 5969: 1981 for the noise situations met with on the ship.
4.2   Octave filter set
When used alone or in conjunction with a sound level meter, as appropriate, an octave filter set should conform to British Standard 2475: 1964 octave and one-third octave band-pass filters or IEC publication 225: 1966 Octave, half-octave and third-octave band filters intended for the analysis of sounds and vibrations. Octave filter sets meeting other specifications may be accepted provided their performance is known to be at least equivalent.
4.3   Impulse noise measurement
Impulse noise may be defined as a noise event of short duration which occurs as an isolated event or as one of a series of events with a repetition rate of less than 15 per second. (An example of impulse noise aboard a ship is the starting air release on some slow speed engines, or the blow of a hammer.) (See 5.3.) To measure peak levels for compliance with 7.3.1, a sound level meter equipped with a circuit for measuring the peak value of the sound will be required. This facility is not to be confused with the impulse or I time weighting characteristic provided on some sound level meters.
4.4   Measurement of equivalent continuous sound level
If the sound level variation is discrete, varying in steps, the equivalent continuous sound level can be calculated using the formula in the definitions or using one of the methods in Appendix 2. If the variation is irregular or erratic, an integrating sound level meter manufactured to IEC Standard Publication 804: 1985 Integrating-averaging sound level meters may be used. Type 1 is a precision grade meter and Type 2 is an industrial grade meter. These meters calculate and give the equivalent continuous sound level over the required period automatically. The measuring period over which averaging is carried out may have one or more preset values or the meter may be equipped to measure and display the averaged values over the time elapsed since the beginning of measurement extending to a few hours. If impact noise is involved, the specification of the meter should be consulted to ensure that its dynamic range is suitable.
4.5   Choice of equipment
Sound level meters vary considerably in cost, depending on whether they are industrial grade or precision grade, and depending on the extra facilities they offer, such as measurement of peak value and equivalent continuous sound level. For octave band analysis, octave band filter sets may be an integral part of or may be separate units to be used with the sound level meters.
When purchasing a sound level meter the first decision which must be made is between industrial and precision grade. The main difference between the grades is in the tolerance band which is allowed on the Aweighting filter networks. The tolerances allowed are wider at low and high frequencies than at mid frequencies. In consequence, for noise emitted by typical medium sized machines the accuracy of measurement with a precision grade meter is about:+/- 1 dB(A) and with an industrial grade meter about:+/- 3 dB(A).
It is recommended that precision grade instruments should be used where noise levels are likely to be close to the limits given in this document, and in any cases of dispute.
Where an industrial grade meter is used a factor of 3 dB should be added to the readings to allow for the reduced accuracy of this type of instrument.
4.6   Calibration
A suitable calibrator, approved by the manufacturer of the particular sound level meter should be used. Calibrators for use with precision grade sound level meters should be accurate to within +/- 0.3 dB, and for use with industrial grade meters accurate to within +/- 0.5 dB.
The sound measuring instrument and calibrator should be returned to the manufacturer or other competent organisation capable of providing a calibration check traceable to a national standard laboratory at intervals not exceeding two years. This is to ensure that the instrument continues to comply with the relevant sections of the appropriate national and international standards related to such equipment and quoted in Sections 4.1, 4.2 and 4.3.
4.7   Microphone wind screen
A microphone windscreen should be used when taking readings on bridge wings or on deck, and below decks where there is any substantial air movement. The windscreen should not appreciably affect the calibration of the instrument, and in general the nylon mesh and plastic foam types obtainable from the major instrument suppliers are suitable.
Windscreens do not completely prevent interference by wind. To make reliable measurements the apparent sound level caused by the wind should be at least 10 dB below the sound level which it is desired to measure. The manufacturer of the windscreen and microphone being used should be consulted for advice on the apparent noise levels generated by wind of various velocities blowing over the windscreen. One prominent manufacturer states that wind speeds of 25 to 30 km/hour (about 13 to 16 knots) blowing over the windscreen produce an apparent noise level of about 45 dB(A), so measurements of 55 dB(A) (or greater) noise levels could be made in this situation. Most wind conditions are gusty, so it is recommended that if the noise measurements have to be taken under these conditions, and if the noise is subjectively steady, the lowest reading (disregarding rapid swings of the meter needle) should be taken. If the noise to be measured is not subjectively steady reliable measurements cannot be made with a sound level meter in gusty wind conditions.
4.8   Safety when using measuring equipment
The measuring equipment specified in this Code may present an ignition hazard if used in areas where flammable gas/air mixtures may be present. Therefore the equipment should not be used in such areas unless it has been appropriately certified intrinsically safe by BASEEFA to Standard Ex ia for the gases which may be encountered, or, it has been appropriately certified by other National Testing Authorities to an equivalent standard.

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5 Method of Measurement
5.1   Measurement procedure
The batteries and calibration of the measuring instrument should be checked immediately before and after each period of use.
In general, the microphone should be located with its direction of greatest sensitivity (or direction for which it is calibrated) towards the noise source. This usually means pointing the microphone directly at  the noise source, but the makers' instructions should be consulted beforehand. In spaces which do not contain predominant noise sources, the microphone should be pointed upwards. Measurement positions are given in Section 6.
During noise measurement only those persons necessary for the operation of the ship and those persons taking the measurements should be present in the space concerned.
The spaces should generally be furnished to the normal seagoing standard.
Unless specifically required the measurements should not normally be taken closer than 1 metre from decks, bulkheads, or other major surfaces.
In spaces such as Radio and Radar rooms, care should be taken to ensure that any electrical interference present does not give rise to a false indication of noise level.
5.2   Reasonably steady noise and fluctuating (non-impulsive) noise Sound level readings should be taken in dB(A) and if necessary also in octave bands between 31.5 and 8000 Hz in order to determine the noise rating (NR) number as required by Section 7, or to assess the suitability of ear protectors as required by Section 10.
The meter should be set to the "slow" response, and readings only made to the nearest decibel. A measuring time of at least 5 seconds should be allowed. If the meter reading fluctuates no more than 5dB, an estimate of the mean level should be made.
If the fluctuations are in excess of 5 dB, or the noise source is cyclic, irregular or intermittent in operation, an integrating meter should be used set to A-weighting. Integration should be made over a period of at least 30 seconds.
5.3   Impulsive noise
When an impulsive noise with a level approaching the overriding limit given in 7.3.1 is apparent, measurement should be made in accordance with 4.3.
Note
Measurement of this type is unlikely to be necessary in many ships.
5.4   Overriding limits
With the meter set to "fast response" spot checks should be made at positions of high noise level in accordance with 7.3.1 and 7.3.2 before commencement of measurements.

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6 Survey
6.1   General
6.1.1 Ultimate responsibility for measurement of noise levels rests with the shipowner as the employer of the seafarers the Code is designed to protect. In practice, for new ships the responsibility should be defined in the contractual agreement between shipbuilder and shipowner and the measurements required by 6.1.2 and 6.1.3 below should in general be the responsibility of the shipbuilder in the case of new ships.
6.1.2 When a new ship to which this code applies, is completed, or as soon as practicable thereafter, measurement of noise levels in all spaces specified in Section 7 should take place under the operating conditions specified in 6.3 and 6.4 below and be suitably recorded. Surveys already completed in accordance with the previous edition of the code will continue to be accepted provided no major modifications have been made. Existing ships coming onto UK Register for the first time should be similarly surveyed unless they were previously surveyed and the survey report is considered acceptable. Surveys should also be conducted when a ship has been re-engined, or when changes in a ships' structural arrangement have been made which are likely to affect noise.
6.1.3 In all ships sufficient measurement of noise levels should take place under the operating conditions specified in 6.3 and 6.4 to ensure that the recommendations of Section 3 are met. Facilities should be made available for a surveyor representing the Department of Transport or Ife., the certifying authority to attend these tests when deemed appropriate.
6.1.4 A copy of the survey report should be forwarded to DSG2 Division, Marine Directorate, Sunley House, 90 High Holborn, London WCIV 6LP.
6.1.5 Appendix 1 gives the recommended format and guidance notes on the compilation of noise survey reports. A copy of the report should be carried on board.
6.2   Records
6.2.1 The records of the measurements should be accompanied with a plan of the ship in which the positions at which the measurements were made are indicated. (See Appendix 1 Section S8(a) and (c)).
6.2.2 The dB(A) level should be recorded and if it is necessary to determine the noise rating (NR) number (as required by Section 7 or Section 10) then the octave band sound pressure levels measured and the NR number should be recorded. (See Appendix 1 Section S8(b) and (d)).
6.3   Operating conditions-at sea
6.3.1 Measurements should be taken with the ship loaded or in ballast or an intermediate condition by agreement with the Owners. Alternatively if a subjective or substantial increase in noise is noticed or expected under another condition, measurements should be taken under this condition. Unless specified otherwise in this Code (ie Section 7.2.5(2)). the main propulsion machinery should be run at normal service speed. Air conditioning and ventilation plant should be operated at full capacity. All auxiliary machinery, navigation instruments, radio and radar sets, etc normally, or likely to be, in use at anyone time, should operate throughout the measurement period. If these conditions cannot be achieved, or special conditions prevail, an explanation should be provided in the survey report.
6.3.2 Spaces containing emergency diesel engines driving generators, fire pumps or other emergency equiupment that would normally be run only in an emergency, or for drill purposes, should be measured with the equipment operating. Adjoining spaces need not be measured with such equipment operating unless it is likely that the equipment be operated for periods other than those mentioned above.
6.3.3 Ships fitted with bow thrusters, stabilizers, etc may be subject to high noise levels when these are operating. Measurements should be taken at positions around such machinery and in adjacent spaces when they are operating. Particular attention should be paid to ascertaining noise levels in accommodation spaces located above or adjacent to bow thrusters and propellers.
6.3.4 Spaces used in the operational aspects of berthing the ship should be measured to ensure that speech communication does not become incoherent (see 9.4.1).
6.4   Operating conditions in port
6.4.1 Measurements as specified in 6.4.2, 6.4.3 and 6.4.4 should be taken with the ship in the "in port" condition.
6.4.2 Holds and deck areas, other non-specified work spaces, certain machinery spaces and other spaces specified in Section 7 (including accommodation spaces) may be subjected to high noise levels when the ship is loading or discharging. When this is the case measurements in such spaces should be taken with the ships own cargo handling equipment in operation. Noise originating from sources external to the ship should be discounted.
6.4.3 When the ship is a vehicle carrier and noise during loading and discharging originates from the vehicles being carried the noise level in the vehicle spaces and the duration should be measured and the exposure of personnel considered in conjunction with Section 8.
6.4.4  It will be necessary to take measurements in machinery spaces with the auxiliary machinery operating in the "in port" condition if the recommendations of Section 8.2 in respect of ear protection are to be met in lieu of the recommendations of Section 8.1, during maintenance, overhaul or similar "in port" periods.
6.5   Environmental conditions
6.5.1 The depth of water under the ship's keel and the presence of large reflecting surfaces in the ship's vicinity may affect the readings obtained and should therefore be noted in the survey record.
6.5.2 The meteorological conditions such as wind and rain, as well as sea state, should be such that they do not influence the measurements. Wind force 4 and sea state 3 should not be exceeded. If this cannot be achieved, the actual conditions should be reported.
6.5.3 Care should be taken to see that noise from external sound sources, such as people, construction and repair work, does not influence the noise level on board the ship at the positions of measurement. If necessary, readings may be corrected for steady state background noise.
6.6   Measurement positions
6.6.1 Accommodation spaces and other spaces not containing machinery - general requirements
At least one measurement should be taken in every occupied space, and this should be taken at the normal ear height (1.2 to 1.6 metre).  The microphone should be moved horizontally and/or vertically over a distance of 1 metre and the mean reading recorded. In cabins, day rooms, offices and similarly sized spaces, the readings should normally be taken in the centre of the room with windows and doors closed.  Additional measurements should be performed at other points if appreciable differences ie 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. The distance between two measurement points, however, should be at least 2 metre. In larger sized spaces, such as bridges, wheelhouses, messes, galleys, recreation rooms, when noise levels may vary considerably within the space, readings should be taken at intervals of not greater than 7 metre throughout the space, including positions of maximum noise level.
In order to avoid an unnecessarily large number of measurements and recordings, noise levels need not be recorded for normally unoccupied spaces, holds, deck areas and other spaces, which are remote from sources of noise and where a rough check shows that the noise levels are well below the limit laid down in Section 7.2.8. However see Section 6.4.2.
6.6.2 Machinery Spaces-General Requirements
Readings should not normally be taken closer than 1 metre from operating machinery, or from decks, bulkheads, or other major surfaces, or from inlets or exhausts. Where this is not possible measurement should be taken at a position mid-way between the machine and adjacent reflecting surface.
Measurements of noise from inlet and exhaust openings should be taken at positions located at 30° to the direction of flow at a distance of 1 metre from the edge of the opening to avoid influencing the readings by low frequency turbulence in the gas stream.
Measurements of noise from machines which constitute noise sources should be taken at 1 metre from the machine at ear height (1.2 to 1.6 metre) above the deck, platform or walkway.
6.6.3 Machinery Spaces-Specific Requirements
Measurement should be made at a height of 1.2 to 1.6 metre above the deck, platform or walkway as follows:
    (a) At a distance of 1 metre from and at invervals not greater than 3 metre in a path around the following machinery:
         (i) main turbines or engines at each level
         (ii) main gearing
         (iii) turbo-blower(s)
         (iv) purifiers
         (v) alternators or generators
         (vi) boiler firing platform
         (vii) forced and/or induced draught fans
         (viii) compressors
         (ix) cargo pumps (including their driving motors or turbines).
(In order to avoid an unnecessarily large and impractical number of measurements and recordings in the case of large engines and machinery spaces, where the measured sound 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 level should however be made and recorded, subject to at least four measurements being recorded at each level) .
    (b) Local control stations, eg the main manoeuvring or emergency manoeuvring stand on the main engine.
    (c) All other locations not specified above which would normally be visited during routine inspection, adjustment and maintenance of machinery.
    (d) Points on all normally used access routes, unless covered by positions already specified above, at intervals not greater then 10 metre.
(In order to avoid an unnecessarily large and impractical number of measurements and recordings, the number of recordings can be reduced as in (a) above, subject to a total of at least four measurements (including those specified in (a), (b) and (c) above) being recorded at each engine room level up to upper deck).

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7 Limits (acceptable maximum noise levels)
7.1   Recommended limits
7.1.1 The limits set out in this section should be regarded as maximum levels and not as desirable levels. Where it is reasonably practicable to do so the sound should be reduced to low levels.
7.1.2 Limits are specified in terms of dB(A) sound levels but in cases where the dB(A) criteria are exceeded or where there is a subjectively.annoying low frequency noise or obvious tonal components (eg turbo- ";1' charger whine) the noise rating (NR) number (see Appendix 1 Section S8(d)) should be determined.
7.1.3 Criteria may be considered as satisfied if the noise rating number is numerically no higher than 5 below the dB(A) limit. For example, a limit of 90 dB(A) would be met by an NR 85 level or less.
7.2   Limits for specified spaces
7.2.1 Machinery spaces A
These comprise machinery spaces, associated workshops and stores in any part of the ship, used for any purpose and which are intended to be continuously manned, or which normally require long periods of attendance for maintenance or other purposes.
The recommended limits are 90 dB(A) (or NR 85). (See 9.6.2, 8.1 and 8.2), except for workshops for which the recommended limits are 85 dB(A) (or NR 80).
Note
Machinery space noise will usually be found to be reasonably steady. Where this is not the case an equivalent continuous sound level (L_eq) should be determined to compare with the limits. (See 5.2).
7.2.2 Machinery spaces B
These comprise machinery spaces which are not intended to be continuously manned or which do not normally require long periods of attendance within the space under any sailing conditions including manoeuvring, eg machinery spaces supervised from a control room, fan rooms, refrigerator machinery spaces, pump rooms, and spaces containing emergency diesel engines, bow thrust units, stabilizers, controllable pitch propeller machinery, etc.
The recommended limits are 110 dB(A) (or NR 105).
Note
These limits have been set from hearing damage risk considerations, allowing for the attenuation provided by suitable ear protectors. (See 10 and Appendix 3).
7.2.3 Machinery control rooms
This includes all machinery control rooms or cargo control rooms occupied during the normal running, operation, or manoeuvring of the vessel.
The recommended limits are 75 dB(A) (or NR 70).
Note
These limits have been set with speech communication and the facility to make decisions without distraction by noise. Face to face conversation should be satisfactory at a distance of approximately 0.75m using a raised voice. As telephone usage is likely to be slightly difficult, consideration should be given to the provision of telephone amplifiers.
7.2.4 Wheelhouse or roofed bridge, chart room and radar room measurements should be taken with all auxiliary equipment such as radar, echo-sounder, clear view windows, etc, in operation, and with the weather side door and windows closed and the lee side door and windows opened and then closed.
The recommended limits are 65 dB(A) (or NR 60).
Note
These limits have been set with speech communication in mind. Face to face conversation should be satisfactory at distances of up to about 1.2m for normal voice effort and up to about 9m when shouting. Telephone and radio usage should be acceptable.
Readings are required with the leeside window or door first open and then closed as situations have been encountered where noise sources immediately outside the wheelhouse (usually engine room ventilation fans) have caused a higher level inside with the window or door in the open position. Alternatively, situations have been encountered where high noise levels have occurred with windows or doors shut, and which were reduced when windows or doors were opened.
7.2.5 Bridge wings and at windows of roofed bridges and other listening posts.
(1) Measurements should be taken on both bridge wings when the bridge wing to be measured is on the leeside of the ship with the ship at normal speed as specified in 6.3.
The recommended limits are 70 dB(A) (or NR 65).
(2) In addition to the above measurements and in accordance with the IMO Recommendation on methods of measuring noise levels at listening posts (IMO RES A343 (IX)), noise levels should also be measured at t speed as follows:
    (a) The average of the maximum values observed during a period of ten seconds will be regarded as the prevailing noise level.
    (b) The microphone should, if possible, be separated by a distance of at least 1.5m from any substantial reflecting or obstructing surface;
    (c) An average value should be determined in the area of the usual listening position from measurements made in at least three different microphone positions separated by at least 0.5m from one another and approximately at the average height of ear of normal listeners;
    (d) (i) as far as is practicable, measurements should be made in conditions of wind speed between 5 knots and 10 knots:
         (1) with the wind ahead,
         (2) with the wind astern, and
         (3) with the apparent wind successively on both beams and the listening position on the corresponding lee-side of the vessel;
    (d) (ii) whether or not these recommended conditions can be achieved, the prevailing wind speed and direction and the course of the vessel should be recorded.
The provisional guide lines in the Appendix to the IMO Recommendation state that it is desirable that the background noise levels at listening posts should not on average exceed the noise level defined by octave band levels as follows:
    (1) 68 dB in the band centred on 250 Hz;
     (2) 63 dB in the band centred on 500 Hz.
Note
The above mentioned figures are set in order to ensure an adequate probability of hearing other ships whistles at the appropriate ranges given in Annex III of the Revision of the International Regulations for Preventing Collisions at Sea, 1972. As indicated above they have only been set provisionally by IMO as guidelines and it is possible that they will be altered in the light of further experience; but they should be met so far as it is practicable. (See also 7.2.13)
7.2.6 Radio room
Measurements should be made in the centre of the room and at an appropriate height at the normal work station of the operator. The radio equipment should be in operation, but without audible signals being reproduced.
The recommended limits are 60 dB(A) (or NR 55).
7.2.7 Galleys, serveries and pantries
This includes all spaces associated with the preparation and serving of food.
With ventilation arrangements on, but other food processing equipment not operating, the recommended limits are 75 dB(A) (or NR 70).
Equipment installed within the galley should not individually produce noise levels exceeding 80 dB(A) (or NR 75) measured at a distance of 1m from the equipment.
Note
These limits are set to allow a reasonable standard of communication and with the comfort of crew members in mind when operating galley equipment. See also Appendix 5 "Extract from the Merchant Shipping (Crew Accommodation) Regulations 1978."
7.2.8 Normally unoccupied spaces
This includes holds, deck areas and other spaces where verbal communication is not of prime importance. Where there is a defined work station, measurements should be taken at this position. Measurements should also be taken at the position of maximum sound level. Should there be a noise source within the space, levels should be taken at a distance of 1 metre from the noise source. (See 6.4.2 and 6.5.1). In large cargo holds, no more than three measurements need be taken.
The recommended limits are 90 dB(A) (or NR 85).
Note
In certain circumstances such as during cargo discharge in port eg on road vehicle carriers, the noise level may not be steady. Where this is the case an equivalent continuous sound level (L_eq) may be determined to compare with the limit of 90 dB(A). (See 5.2).
7.2.9 Sleeping cabins, Day cabins and Hospital
Measurements should be made in the centre of the room and in addition if there is a subjectively appreciable variation of noise level within the cabin, measurements should be taken in areas where this is apparent and the maximum level recorded. (See 6.6.1).
The recommended limits are 60 dB (A) (or NR 55)
Note
These criteria are set at a level 5 dB(A) above the level which is known to cause changes in sleep state in some individuals in a normal population. The difference should take some account of a self-selected population habituated to its surroundings, and allows a realistic and attainable criterion. It is known that sea-going personnel apparently sleep satisfactorily in higher noise levels, but the long-term effect on their general health has not been quantified. The limits also allow recovery from the effects of noise.
See also Appendix 5 "Extract from the Merchant Shipping (Crew Accommodation) Regulations, 1978."
Consideration should be given to the siting of possible noise annoyance sources within recreation and mess rooms and other sources of intermittent noise away from sleeping spaces.
7.2.10 Offices, Conference rooms etc
Measurements should be made in the centre of the room, and in addition if there is a subjectively appreciable variation of noise level within the room, measurements should be taken in areas where this is apparent and the maximum level recorded. (See 6.6.1).
The recommended limits are 65 dB(A) (or NR 60).
Note
These limits have been set to allow recovery from the effects of noise and to allow reasonable speech communication.
See also Appendix 5 "Extract from the Merchant Shipping (Crew Accommodation) Regulations, 1978."
7.2.11 Mess rooms, Recreation rooms, Recreation areas, etc
This includes smoke rooms, lounges, hobby and sports rooms, and deck areas specifically intended for recreation purposes.
The recommended limits are 65 dB(A) (or NR 60) within accommodation and 75 dB(A) (or NR 70) on open decks.
Note
These limits have been set to allow recovery from the effects of noise and to allow reasonable speech communication.
See also Appendix 5 "Extract from the Merchant Shipping (Crew Accommodation) Regulations, 1978."
7.2.12 Corridors, Changing rooms, Bathrooms, Lockers and similar spaces
This includes other areas not specified which are visited for short periods and where speech communication is not critical.
The recommended limits are 80 dB(A) (or NR 75).
Note
These criteria have been set fairly high as such areas can often be used as "buffer zones" between noise sources and noise-sensitive areas, thereby avoiding the penalties of heavy or double-skinned constructions. See also Appendix 5 "Extract from the Merchant Shipping (Crew Accommodation) Regulations, 1978."
7.2.13 Ship's whistle
The ship's whistle should be positioned so as to minimise hearing damage risk to personnel. The sound pressure level at listening posts (bridge wings, forecastle when the whistle is sounding not exceed 110 dB (A) and so far as practicable should not exceed 100 dB(A).
Note
The above are requirements under the Merchant Shipping (Distress Signals and Prevention of Collisions) Regulations 1983. Annex III paragraph 1 (e).
7.3   Overriding limits
7.3.1 The unprotected ear should not be exposed to a sound pressure level, measured with an instrument set to the "fast" response, exceeding 135 dB, or in the case of impulse noise an instantaneous sound pressure exceeding 150 dB. (See 4.4, 5.3, 5.4).
7.3.2 Other parts of the body should not be exposed to a sound pressure level, measured with an instrument set to the "fast" response, exceeding 150 dB. (See 5.4).
7.3.3 Measures recommended in Section 9 should be taken to ensure that the above overriding limits are not exceeded under any normal circumstances.

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8 Exposure of personnel to potentially harmful noise
8.1   In the circumstances that occur on board ship, where personnel move from one place to another and the length of time spent in each place may vary, it is not generally practicable to effectively control the duration of exposure to potentially harmful noise. Therefore personnel should not be exposed to a sound level exceeding 85 dB(A) unless they are using ear protectors which effectively reduce the sound level at the user's ear to or below the limit for unprotected ears. (But see Section 8.2 and 10). This limit is based on an exposure of 8 hours in anyone day to a reasonably steady sound level. Exposure to 85 dB(A) over 8 hrs is equivalent to a continuous sound level of 80 dB(A) over 24 hrs. The remaining portion of the day spent in spaces with substantially lower noise levels (eg sleeping cabins, day cabins, mess rooms, recreation rooms, see 7.2.9, 7.2.11 and Appendix 2) does not make a significant contribution to a harmful exposure and may be ignored.
8.2   In special cases in lieu of the method of protection of personnel given in 8.1 above, the shipowner may consider it practicable to control the duration of exposure to potentially harmful noise. If this method is to be used it is necessary for the control of the duration of exposure to noise to be effectively exercised. If exposure is for a period of other than 8 hours, or if the sound level is fluctuating, an equivalent continuous sound level over 8 hours should be calculated and this value should not exceed 85 dB(A) or an L_eq (24) of 80 dB(A) should not be exceeded. (See Appendix 2).
8.3   Following figures illustrate the acceptable maximum daily noise doses for unprotected ears, based on dB(A) sound energy received.

As an alternative illustration and equivalent to the above figures, the maximum daily noise dose for unprotected ears is halved for each increase of 3 dB(A).
eg   85 dB(A) for 8 hours
     88 dB(A) for 4 hours
     91 dB(A) for 2 hours, etc
8.4   Examples of noise levels in different locations are given below in order to enable personnel to appreciate when and where a potentially harmful noise exposure may exist:

These levels are only approximate and engine noise can vary considerably with the type of installation.

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9 Methods of controlling noise exposure
9.1   General
9.1.1 The code is designed to provide standards to prevent the occurrence of potentially hazardous noise levels on board ships, and to provide standards for an acceptable environment for seafarers.
9.1.2 The need for noise control should be taken into account in the design stage when deciding which of different designs of engines and machinery are to be installed, the method of installation, and the siting of the machinery in relation to other spaces and the acoustic insulation and siting of the accommodation.
9.1.3 Due to the normal methods of ship construction it is most probable that noise originating from machinery and propellers and reaching the accommodation and other spaces outside the machinery spaces will be of the structure borne type.
9.1.4 Some of the measures which can be taken to control the sound level or reduce the exposure of personnel to potentially harmful noise are indicated in 9.2 to 9.8 below. This Code does not provide the detailed technical information needed for putting constructional noise control measures into effect, or for deciding which measures are appropriate in particular circumstances. For detailed information on these aspects, reference may be made to the "Ship Design Manual-Noise" (produced in 1982 by the British Ship Research Association, now British Maritime Technology, Wallsend Research Station).
9.1.5 It should be noted that when designing efficient and economic measures for noise control of existing machinery installations the measurement of the sound produced in terms of A-weighted sound level dB (A) will need to be supplemented by some form of frequency analysis (eg octave band analysis such as that necessary for the determination of NR-numbers).
9.1.6 It is recommended that design and construction of noise control measures should be supervised by a person skilled in noise control techniques.
9.1.7 When introducing noise control measures care should be taken to ensure that regulations concerning ship structure, accommodation and other safety matters are not infringed and where sound reduction material is used it is such that a fire or health hazard is not introduced.
9.2   Selection and installation of machinery
9.2.1 In the design stage the noise produced by each item of machinery to be fitted should be taken into account.
9.2.2 Manufacturers should be requested to supply information on the noise produced by their machinery and also to supply recommended methods of installation in order to keep noise levels to a minimum.
9.2.3 Where appropriate machines should be supported on correctly designed and applied vibration isolating mountings.
9.2.4 Where structureborne sound from auxiliary machinery, compressors, hydraulic units, generating sets, vents, exhaust pipes and silencers produces unacceptable noise levels in accommodation spaces or on the navigating bridge, resilient mountings should be fitted.
9.3   Separation of noise sources
9.3.1 Where practicable engines or machinery producing sound levels in excess of the limits set out in Section 7.2.1 should be installed in compartments that do not require continuous attendance. (See also 9.6.1).
9.3.2 Suitable partitions, bulkheads, decks, etc may be needed to prevent the spread of noise. It is important that these be of the correct construction and location in relation to the noise source and the frequency of the noise to be attenuated.
9.3.3 Where a space, such as an engine room, is being divided into noisy (not continuously manned) and less noisy (capable of being continuously manned) compartments it is preferable for the separation to be as complete as possible by ensuring that there are a minimum of openings in the partition consistent with the need to supervise the space and provide the required means of escape.
9.3.4 It may be advisable to provide sound absorbing material in certain spaces in order to prevent increase of sound level due to reflection from partitions, bulkheads, decks, etc.
9.3.5 Consideration may be given where applicable to separation of accommodation from machinery spaces by unoccupied spaces, effective bulkheads and decks, or by vibration isolators.
9.3.6 Accommodation should be sited both horizontally and vertically as far away as is practicable from sources of noise such as propellers and propulsion machinery.
9.3.7 Machinery casings should, where practicable, be arranged outside superstructures and deckhouses containing accommodation spaces. Where this is not feasible, passageways should be arranged between the casings and accommodation spaces, if practicable.
9.3.8 Consideration should be given, where practicable, to the placing of accommodation spaces in deck houses not in superstructures extending to the ship's side. (Also see 9.9.1)
9.4   Exhaust and intake silencing
9.4.1 Exhaust systems from internal combustion engines, air intake systems to machinery spaces, accommodation spaces and other spaces should be arranged so that the inflow or discharges are remote from places frequented by personnel or are fitted with effective silencers or attenuators.
9.4.2 Silencers or attenuators should be regularly inspected, cleaned and maintained.
9.4.3 To minimise accommodation noise levels it is normally necessary to isolate exhaust systems and certain pipework and ductwork from casings, bulkheads, etc.
9.5   Machinery enclosure
9.5.1 In continuously manned spaces or spaces where personnel might reasonably be expected to spend lengthy periods of time on maintenance or overhaul work, and where separation as detailed in 9.3 is not practicable consideration may have to be given to the fitting of sound insulating enclosures or partial enclosures to engines or machinery producing sound levels in excess of the limits set out in Section 7.2.1.
9.5.2 Where the sound level produced by engines or machinery installed in spaces as in 9.5.1 above is higher than the overriding limits specified in Section 7.3, it is essential that sound insulating enclosures or other noise reduction measures are provided.
9.5.3 When sound insulating enclosures ("acoustic hoods") are fitted it is desirable that the machine should be resilient mounted and that all pipe, trunk and cable connections to it should be flexible. This is because much of the noise from the machine may be structure borne (see 9.1.4). For maximum noise reduction it is also important that the hood entirely encloses the machine. Care should be taken to ensure that the fire extinguishing systems will be effective and that materials used in the construction of sound insulating enclosures are such that a fire or health hazard is not introduced.
9.6   Enclosure of the operator
9.6.1 In most machinery spaces it would be desirable and advisable to protect the operating or watchkeeping personnel by providing a sound reducing control room or other similar space (see 9.3.1).
9.6.2 In the continuously manned machinery spaces of small ships and of existing ships where sound levels are higher than those specified in 7.2.1 a noise refuge at the control station or manoeuvring platform should be provided where the watchkeeper might be expected to spend the major part of his time.
9.7   Use of ear protectors
9.7.1 Where the noise level in any space is above 85 dB(A) (see 7.2.1, 7.2.2 and 7.2.8) ear protectors should be provided for the use of personnel manning that space. Ear protectors should also be provided for the use of personnel when making routine inspections, working in, or otherwise being required to enter such spaces. (See Section 10).
9.8   Reduction of noise in the aft body
9.8.1 To reduce the noise influence in the aft body of the ship, especially to the accommodation spaces, consideration should be given to noise emission problems during the design procedures relating to the aft body, propeller, etc.
9.9   Accommodation spaces
9.9.1 To reduce noise levels in accommodation spaces, it may be necessary to consider the isolation of deckhouses containing such spaces from the remaining structure of the ship by fitting resilient mountings.
9.9.2 Consideration may also be given to the provision of flexible connections to bulkheads, linings and ceilings and the installation of floating floors within accommodation spaces.
9.9.3 The provision of curtains and the use of carpets within accommodation spaces assists in absorbing noise.
9.10   Inspection and maintenance
9.10.1 All items of machinery, equipment and their associated working spaces should be regularly inspected by a competent person such as the Chief Engineer (or other senior officer) with respect to noise. Should such inspection reveal defects in the means for noise control, or other defects causing excessive noise, these should be rectified as soon as practicable (ear protection should be worn as appropriate until the defect is rectified (see 9.7.1)).
9.11   Complaints of excessive noise levels
9.11.1 If noise levels become the cause of complaint, noise measurement in the relevant spaces should be undertaken by the owners, eg the Chief Engineer (or other Senior Officer), with the ship in service. If the complaint is found to be reasonable after assessment of the results, the owner should endeavour to reduce the noise to the level recommended in Section 7 of this Code as appropriate to the space concerned.
9.12   Warning notices
Where noise in machinery spaces (or other spaces) exceeds 85 dB(A) all entrances to such spaces should carry a warning sign (comprising symbol and supplementary sign) complying with BS 5378: Safety Signs and colours as shown below in Fig 1.
Sign with symbol: The background colour should be blue and the symbol should be white and placed centrally on the background. Blue should cover at least 50% of the area of the sign. The diameter should be 150 mm or 300 mm.
Supplementary sign: This should be rectangular. The background colour should be white with black letters or alternatively the background may be the same colour blue as the sign with the symbol and have white letters. The height of the letters should be a minimum of 20 mm.

Sign with Symbol:
Supplementary sign:	HIGH NOISE LEVELS USE EAR PROTECTORS

Fig 1  Sign for warning that ear protection is required
Reference should be made to BS 5378 for colormetric and photometric properties of the materials.
Where hand tools and other portable equipment produce noise levels above 85 dB(A) in normal working conditions suitable warning information should be provided.

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10 Ear Protection
10.1   General
10.1.1 When the application of means for controlling sound at source does not reduce the noise level in any space to 85 dB(A), personnel who are required to enter such spaces should be supplied with effective ear protection on an individual basis.
10.1.2 The provision of ear protectors should not be considered to be a substitute for effective noise control. They should normally be regarded as an interim measure until other means of control of noise exposure have been developed.
10.2   Selection and use of ear protectors
10.2.1 It is important to ensure that protectors will provide the majority of wearers with reliable and adequate protection. Suppliers should be instructed to provide full information on the average sound reduction likely to be provided, the standard deviation, the methods used for testing the protectors and details of the laboratory carrying out the test. Appendix 3 describes current test methods, and a procedure for using the test data for predicting the reduction of sound level. The suitability of ear protectors for a given ship should be assessed from the results of the noise survey (Section 6) and according to Appendix3. Ear protectors normally give better attenuation of noise at higher frequencies and great care will be needed in the selection of suitable ear protectors to reduce noise level at the ear to below 85 DB(A) particularly if lower frequencies are involved.
10.2.2 At the highest noise levels in machinery spaces (B) in 7.2.2, ie up to 110 dB(A), ear muffs must be chosen which will give at least 25 dB(A) of "assumed" protection, (ie the mean less one standard deviation) against actual shipboard noise spectra in the machinery space. A number of proprietary ear muffs are unable to provide sufficient attentuation against the highest noise levels and most of the earplugs cannot be relied upon to provide more than about 12 dB(A) of "assumed" protection against actual shipboard noise spectra.
10.2.3 Earplugs of the permanent or re-usable types are not recommended because of the need for skilled personnel to initially size and fit prospective users. So called "universal" fitting ear plugs of the permanent type do not provide an effective seal in the ear canal of a significant proportion of users and are also not recommended. In addition, there are likely to be serious hygiene problems associated with the use of ear plugs in the environment of ships engine rooms and other machinery spaces, as the ear canal is especially sensitive to dermatitic agents which may be transferred from the hands during fitting. Therefore the hands must be cleaned before fitting any type of ear plug to avoid the introduction of contaminents into the ear canal.
10.2.4 Disposable or semi-disposable ear plugs, eg those fashioned from glass down or plastic foam, may be found suitable for shipboard use subject to Sections 10.2.2 and 10.2.5.
10.2.5 Ear plugs of any type should not be used in certain ear conditions. Therefore if a user is suffering from ear trouble in the absence of medical advice, ear plugs should not be used and ear muff's used instead.
10.2.6 Ear protectors should be used only by the person to whom they are issued (see 10.1.1). Disposable ear plugs should only be used once. Semi-disposable and permanent ear plugs should be kept clean by regular washing with soap and water. The seals of ear muffs should be kept clean by sponging with soap and water. Before used ear muffs are re-issued to other persons they should be sterilized by immersion in a solution of disinfectant recommended for such purposes and the seals and noise absorbent inserts renewed. Proper provision should be made for clean storage of reusable protectors when not in use. This may include storage bags for ear muffs or clean lockers in which they can be stored with other clothing.
10.3   Supervision
10.3.1 Supervision is required on board ship to ensure the availability of ear protection, and to enforce its usage. This should be the responsibility of the Safety Officer or a senior member of the crew, such as the Chief Engineer. A record of ear muffs issued for use should be kept on board the ship. The arrangements should also include a system for employees to report damaged, defective or lost protectors to the person responsible for repair or replacement.
10.3.2 Provision should be made for warning seafarers of the hazards of excessive noise exposure and of the correct usage of personal ear protection. This may be through the Safety Officer or by way of warning notices, posters, films, talks, personal hand-outs, in-house magazines, etc, and any other industrial persuasion techniques. (See Appendix 7).
10.4   Communication when using ear protectors
10.4.1 When ear protection is required under 10.1.1 above, it is recommended that sets of ear protectors should be provided, for at least two persons, which incorporate means of speech communication between personnel when in a high noise level space.
10.4.2 Where personnel may be required to remain within a high noise level space in order to control or operate machinery, the provision of ear protectors fitted with means of communication with a control room or similar station should be considered.
10.4.3 Ear protectors incorporating means of communication may not be intrinsically safe and should not be used in hazardous areas where flammable gases or vapours may be present.

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11 Training of personnel
11.1   Training of Engineers and Shipbuilders
11.1.1 The need for noise control should be taken into account at the design stage when deciding which of different designs of engines and machinery are to be installed, the method of installation and the siting of machinery in relation to other spaces, and the acoustic insulation and siting of the accommodation spaces.
The measurements required by 6.1.1 and 6.1.2 should in general be the responsibility of the shipbuilder in the case of new ships and the shipowner in the case of existing ships. In either case persons skilled in noise control techniques should supervise the noise survey.
11.2   Training of Seafarers
11.2.1 Seafarers, especially engine room personnel and Safety Officers, should receive any necessary training in the correct use and maintenance of machinery and silencers or attenuators in order to avoid the production of unnecessary noise.
11.2.2 Seafarers should be instructed in the hazards of high and long duration noise exposures and the risk of noise induced hearing loss.  Instruction should be provided by the shipowner to all seafarers on initial employment and periodically thereafter to those regularly working in spaces with noise levels in excess of 85 dB(A). Instruction in the provisions of the code should include:
    (a) noise level limits and the use of warning notices
    (b) the types of ear protectors provided, their approximate attenuation and their proper use, fitting and risk effects experienced when first wearing such protection
    (c) the legal duty to wear ear protectors where appropriate (The Merchant Shipping (Protective Clothing and Equipment) Regulations 1985)
    (d) any hearing conservation programme including audiometric testing which may be available
    (e) some of the possible signs of hearing loss such as ringing in the ear, dead ear or fullness in the ear.

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12 Responsibility
12.1   Responsibility of the Shipowner
12.1.1 The shipowner is responsible for ensuring as far as is reasonably practical, the best means for reducing and controlling noise levels, and that they are applied and maintained.
12.1.2 Where noise levels in any space exceed the limit of 85 dB(A), the shipowner should ensure that:
    (a) the space is identified and the warning notice described in Section 9.11 is displayed.
    (b) the Master and Senior Officers of the ship are notified as to the importance of controlling entry into the space and the importance of the use of suitable ear protectors.
    (c) suitable ear protectors are provided in sufficient numbers for distribution on an individual basis.
    (d) adequate training is given to all seafarers in accordance with the provisions in para 11.2.2.

12.2   Responsibility of the Seafarer

12.2.1 The seafarer is responsible for ensuring that:
     (a) measures adopted for noise control are used and maintained.
     (b) defective noise control equipment is reported to a responsible person.
     (c) spaces where ear protectors are required are not entered under normal circumstances except by personnel wearing suitable ear protectors which should not then be removed even for short periods.
    (d) ear protectors are not wilfully damaged or misused and are maintained in a clean condition.

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13 Definitions

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