Section 2 Noise
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Naval Ships, January 2023 - Volume 3 Additional Class Notations - Part 2 Naval Ship Safety - Chapter 7 Noise and Vibration Levels in Personnel Spaces - Section 2 Noise

Section 2 Noise

Parent topic: Chapter 7 Noise and Vibration Levels in Personnel Spaces

2.1 Maximum noise levels

2.1.1 Where the measured noise level exceeds the applicable maximum noise level in Table 7.2.1 Accommodation - maximum noise levels, in dB(A) and Table 7.2.2 Work areas - maximum noise levels, in dB(A) by 3 dB(A), or contains subjectively annoying low frequency or tonal components, the noise rating (NR) number is to be established in accordance with Figure 7.2.1 Noise rating curves. This is achieved by plotting the linear octave band levels on the graph; the NR number is that NR curve to which the highest plotted octave band level is anywhere tangent. The specified criterion may be considered satisfied if the NR number does not exceed the specified A-weighted value minus 5 dB(A).

2.1.2 Guidance on maximum acceptable sound pressure levels and noise exposure limits is given in IMO Resolution MSC.337(91) – Adoption of the Code on Noise Levels on Board Ships – (Adopted on 30 November 2012)The Annex below is consolidated into Resolution MSC.337(91).

2.2 Crew and embarked personnel accommodation and work areas

2.2.1 When the ship is proceeding in its agreed operating condition and in accordance with the provisions specified in Vol 3, Pt 2, Ch 7, 4.2 Test conditions, the noise levels specified in Table 7.2.1 Accommodation - maximum noise levels, in dB(A) and Table 7.2.2 Work areas - maximum noise levels, in dB(A) are not to be exceeded.

2.2.2 The noise levels should preferably be predicted at design stage (optional). The predictions should include both airborne noise, structure-borne noise and noise from the ventilation system (HVAC). Where performed, the predictions should be provided to LR for information.

2.2.3 Noise predictions are recommended to be performed in accordance with ISO 9613-2 (outdoor airborne noise), ISO/TR 11690 (indoor airborne noise), statistical energy analysis (SEA) or, if appropriate, simplified methods (structure-borne noise) and the ASHRAE Applications Handbook methodologies (HVAC noise). Alternate standards or techniques may also be appropriate.

Table 7.2.1 Accommodation - maximum noise levels, in dB(A)

Location NS1 and NS(SR) vessels NS2, NS3 and NS(SSC) vessels
Comfort Level
1 2 1 2
Sleeping cabins, medical spaces (see Note 1) 52 55 55 60
Recreation areas, offices, conference rooms 55 60 60 65
Mess rooms 57 60 60 65
Open deck recreation areas (see Note 2) 72 75 72 75
Passageways within accommodation areas, changing rooms, communal washrooms 70 70 75 75
Note 1. Medical spaces not including beds or patient treatment facilities may be considered as offices in agreement with the Owner/Naval Administration
Note 2. The levels may be exceeded by 5 dB(A) within 3 m of a ventilation inlet/outlet or machinery intake/uptake on open decks.
Note 3. In austere/temporary accommodation higher levels could be accepted in agreement with the Owner/Naval Administration

Table 7.2.2 Work areas - maximum noise levels, in dB(A)

Location dB(A) level
Machinery spaces (e.g. engine room, pump room, refrigeration space, thruster space or fan room) (see Note 1) 110
Workshops, hangars, passageways within work areas, stairwells, non-specified work spaces and open deck work spaces 85
Machinery control rooms 75
Bridge, chart rooms, conning positions, operational control rooms, and radar rooms 65
Look-out posts e.g. at bridge wing or window

Additional limits: (measured according to IMO A.343(IX))

70
—250 Hz band 68
—500 Hz band 63
Communication compartments (with comms equipment operating but not producing audio signals) 60
Laundries, galleys and pantries:  
Equipment not working 75
Individual items at 1 m 85
Normally unoccupied spaces (e.g. stores, magazines, holds, decks) 90
Ship's whistle, on bridge wings, forecastle (see COLREGS, Annex III 1.e) 110
Note 1. Where machinery spaces are continuously or periodically manned, maximum noise levels are to be consistent with the requirements for personal daily exposure limits as agreed with the Owner.


Figure 7.2.1 Noise rating curves

2.3 Acoustic insulation

2.3.1 The airborne sound insulation properties for bulkheads and decks within the accommodation area shall comply with the apparent sound reduction index (R′w) given in Table 7.2.3 Minimum apparent sound reduction index (R′w) according to the standard ISO 717-1.

Table 7.2.3 Minimum apparent sound reduction index (R′w)

Location R′w
Comfort Level
1 2
Between sleeping cabins; cabins to hospitals 35 32
Mess rooms, recreation rooms, public spaces to sleeping cabins and hospitals 45 42
Corridor to sleeping cabin 30 27
Work areas to accommodation areas 45 42

2.3.2 The acoustic insulation plan shall be submitted to LR at design stage and the required sound reduction index for all relevant partitions shall be defined. Where partitions have certified Rw values and installed under survey in accordance with the manufacturer’s instructions no R′w measurements are required; the certified Rw values shall be 3 dB(A) higher than the R’w values as per Table 7.2.3 Minimum apparent sound reduction index (R′w).

2.3.3  In other cases, or where there is doubt regarding the achievement of the certified Rw values, the airborne sound insulation properties shall be determined according to the field measurements standard ISO 16283-1 for representative partitions.

2.3.4 The sound reduction index for the partitions should preferably be predicted at design stage (optional). The predictions are recommended to be performed according to the methodology described in ISO 12354-1. Where performed, the predictions should be provided to LR for information.

2.4 General alarm and crew and embarked personnel address systems

2.4.1 The general alarm and crew and embarked personnel address systems are to comply with Vol 3, Pt 2, Ch 7, 2.4 General alarm and crew and embarked personnel address systems 2.4.2 to Vol 3, Pt 2, Ch 7, 2.4 General alarm and crew and embarked personnel address systems 2.4.5 together with Vol 2, Pt 9, Ch 10, 5.1 Emergency alarm system and Vol 2, Pt 9, Ch 10, 4.1 Crew and embarked personnel address system.

2.4.2 During the noise measurement programme the general alarm and crew address systems are to be demonstrated by tests. These tests are to be undertaken under the trial conditions as described in Vol 3, Pt 2, Ch 7, 4.2 Test conditions.

2.4.3 When the ship is proceeding in its agreed operating condition, the minimum sound pressure levels of the public-address system for broadcasting emergency announcements are to comply with the following:

  1. In interior spaces:
    • 75 dB(A); and
    • at least 20 dB(A) above the speech interference level.
  2. In exterior spaces:
    • 80 dB(A); and
    • at least 15 dB(A) above the speech interference level.
Note The speech interference level is defined as the arithmetic average of the sound pressure level of the ambient noise in the four octave bands: 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz.

2.4.4 The sound pressure level from the general alarm and public address system is not to exceed 120 dB(A) and should be limited to 100 dB(A) where possible.

2.4.5 If the speech interference level exceeds 90 dB(A), flashing light beacons are to be installed in the area sufficient to alert Operators to the nature of the alarm. In large spaces, or during times when machinery is not running, multiple audible calling devices should be installed to avoid shock to persons close to the source of the sound and to ensure uniform sound levels over all the space. See also IMO Resolution A.1021(26) – Code on Alerts and Indicators, 2009 – (Adopted on 2 December 2009)
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