Section 1 General requirements

1.1.1 These Rules set down the criteria for the assessment of noise and vibration levels on naval ships and are applied in addition to the other relevant requirements of the Rules and Regulations for the Classification of Naval Ships, January 2023.

1.1.2 These Rules apply to surface ships when engaged in peace-time mission profiles.

1.1.3 For NS2, NS3 or NS(SSC) vessels, higher noise and vibration levels will be permitted as allowed by 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) for vessels of between 1600 gt and 10,000 gt. Limits for these ships are identified within the text of these Rules.

1.1.4 The limits provided in these Rules do not take account of any external influences on noise or vibration such as weapons firing, aircraft operations or replenishment at sea activities.

1.1.5 These Rules recognise existing National and International Standards and specify levels of noise and vibration currently achievable using good engineering practice. Compliance with these requirements will be assessed by review of procedures, inspection and measurement of the relevant parameters. Pre-survey reviews, inspections and measurements will be conducted, witnessed or assessed by LR Surveyors.

1.1.6 These Rules present values of noise and vibration which should be verified by measurements following completion of the ship. It is recommended that the Builders undertake calculations of noise and vibration so that any potential problem areas can be identified and control measures implemented.

1.1.7 The sound pressure levels for audible alarms and public address systems fitted in accordance with other Sections of the Rules are to satisfy IMO Resolution A.1021(26) – Code on Alerts and Indicators, 2009 – (Adopted on 2 December 2009) or other specified arrangements.

1.2.1 Crew and embarked personnel spaces are defined as all areas intended for crew and embarked personnel use, and include the following:

1. accommodation spaces (e.g. cabins, corridors, offices, mess rooms, recreation rooms);
2. work spaces;
3. navigation spaces.

1.2.2 Noise level is defined as the A-weighted energy equivalent sound pressure level measured in accordance with ISO 2923.

1.2.3 Vibration level is defined by application of ISO 20283-5, as the overall frequency weighted r.m.s. value of deck structure vibration during a period of steady-state operation over the frequency range 1 to 80 Hz.

1.3.1 In addition to the hull and machinery class notations defined in Vol 1, Pt 1, Ch 2, 3 Character of Classification and Class notations, ships verified as compliant with these requirements will be assigned the optional notation:

• CEPAC1 Crew and Embarked Personnel Accommodation Comfort Level 1; or
• CEPAC2 Crew and Embarked Personnel Accommodation Comfort Level 2

1.3.2 These notations indicate that the crew and embarked personnel accommodation and work areas meet the respective acceptance criteria and provide ship Operators with an objective assessment of a ship’s noise and vibration levels in accommodation and work areas throughout its life.

1.3.3 Assignment of the notation is subject to the requirements of this Chapter being complied with and maintained through-life in accordance with the requirements of Vol 3, Pt 2, Ch 7, 7 Survey requirements.

1.3.4 The impact of any subsequent modifications to the ship’s structure or equipment resulting in any alteration to the data specified in Vol 3, Pt 2, Ch 7, 1.4 Information and documentation required for submission including the noise and vibration measurement results are to be submitted for review of ongoing compliance.

1.4.1 The following documents are to be submitted for review and agreement prior to the noise and vibration trials being undertaken:

1. trials condition specification (including agreed machinery settings);
2. compartment designation and agreed assessment criteria for each space;
3. test measurement plan, including trials conditions, test locations, instrumentation and operator competence;
4. relevant specification requirements;
5. acoustic insulation plan; and
6. noise and vibration predictions and analysis techniques (optional).

1.4.2 The compartment designations, criteria and test conditions are to be agreed by the Shipyard and Owner.

1.4.3 On completion of the noise and vibration trials being undertaken, a survey report is to be submitted for acceptance in accordance with the requirements of Vol 3, Pt 2, Ch 7, 5 Survey reporting.