Section 4 Testing

4.1.1 These requirements take precedence where quoted standards may differ.

4.1.2 Prior to survey, a noise and vibration measurement plan is to be agreed by the Owner, Builder and LR.

4.1.3 The trial measurements may be undertaken by an approved technical organisation as defined in Vol 3, Pt 2, Ch 7, 4.1 Measurement procedures or by LR. In the former case, the measurements shall be witnessed by an LR Surveyor.

4.2.1 Test conditions for the surveys are to be in accordance with those detailed in ISO 2923 and 20283-5 as applicable.

4.2.2 The intended operating conditions of the ship during assessment surveys are to be submitted to LR for agreement, prior to commencement of surveys.

4.2.3 Surveys will only be conducted when the ship is fully outfitted, and all systems contributing to noise and vibration levels are fully operational.

4.2.4 The test conditions required for the vibration and noise measurements are to be in accordance with the following conditions:

1. Propulsion machinery operating profiles are to be submitted prior to the trials and an operating condition agreed between the Owner and LR. Noise and vibration measurements will be taken at this agreed operating condition and the comfort level assigned. This condition, or conditions, should include as a minimum the operational modes, defined in the System Operational Concept document, for the propulsion systems which provide the normal ship service speed, or normal cruising speed, see Vol 2, Pt 1, Ch 3, 3.4 System operational concept. The power absorbed by the propeller(s) should preferably not be less than 85 per cent of the maximum continuous rating of the propulsion machinery.
2. All propulsion and auxiliary machinery, including HVAC systems, are to be running in their normal sea-going mode during the noise and vibration trials. Combinations of auxiliary machinery operation may be necessary in order to establish the worst case measurement scenario.
3. Measurements are to be taken with the ship proceeding ahead, at a constant speed and course, in a depth of water not less than five times the deep draught of the ship.
4. Trials are to be conducted in sea conditions not greater than sea state 3 on the WMO sea state code.
5. The ship is to be at a displacement and trim corresponding to the normal operating condition.
6. Rudder angle variations are to be limited to ±2º of the midship position and rudder movements are to be kept to a minimum throughout the measurement periods.
7. Intermittently run equipment such as transverse thrust or dynamic positioning units are not required to be operated, unless the vessel operates for a substantial period of time (>8hrs) in this mode, in which case they are to be operated at 40 per cent of their rated power for additional measurements in surrounding ship areas.
8. In addition, for ships which are designed to spend a considerable period of time in harbour, the noise and vibration levels are to be measured for this condition, with the auxiliary machinery and HVAC systems running at their normal rated capacity.
9. Care is needed to ensure that external sources of noise, due to aircraft for example, do not influence the noise measurement results.

4.2.5 Prior to survey, a test programme is to be submitted for approval by LR. This programme is to contain details of the following:

1. measurement locations, indicated on a general arrangement of the ship, for sound pressure levels, vibration levels and sound insulation;
2. the ship’s outfit condition during survey;
3. the machinery operating condition, including HVAC system, during survey;
4. noise and vibration measuring equipment; and
5. test site water depth.

4.3.1 Noise measurements are to be conducted in accordance with ISO 2923 and 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). Measurements of noise levels are to be carried out using precision grade sound level meters conforming to IEC 61672, Type 1 or 2. Subject to demonstration, equivalent standards are acceptable. The calibration of the measurement equipment shall be verified on-site before and after the measurements.

4.3.2 Where the measured noise exceeds the relevant criteria, or contains subjectively annoying low frequency noise, or obvious tonal components, octave band readings are to be taken, with centre frequencies from 31,5 Hz to 8 kHz.

4.3.3 Measurements are to be performed to evaluate the ship with respect to sound insulation. When outfitting is complete, and all soft furnishings are in place, sound reduction indices for crew and embarked personnel spaces are to be determined in accordance with ISO 16283-1 and presented in accordance with ISO 717-1.

4.4.1 Measurement locations are to be chosen so that assessment represents the overall noise environment on board the ship. All working areas and at least 50 per cent of the normally occupied accommodation areas in the after third of the vessel, and at least 25 per cent elsewhere, are to be surveyed. Distribution of the measurement locations is to be agreed by LR.

4.4.2 During measurement trials, recognised noise sources are to be operated at their normal level of noise output (e.g. machinery at design rating).

4.4.3 In larger sized spaces, where noise levels may vary considerably, measurements are to be taken at locations not greater than 7 m apart.

4.4.4 The extent and number of partitions to be measured for the determination of sound reduction indices should be agreed with LR before testing (typical extent 10–20 partitions). If the partition surface area is less than 10 m², an area of 10 m² shall be used in the calculations, unless otherwise agreed.

4.5.1 Vibration measurements are to be conducted in accordance with ISO 20283-5.

4.5.2 Measurements are to be made with instrumentation meeting the requirements of ISO 8041. The calibration of the measurement equipment shall be verified on-site before and after the measurements.

4.6.1 Measurement locations are to be chosen so that the assessment represents the overall vibration environment on board the ship. To minimise survey times, readings may be taken at the locations previously defined for the noise assessment part of the survey.

4.6.2 In cabins, vibration readings are to be taken in the centre of the floor area. The measurements are to indicate the vibration of the deck structure. In large spaces, such as mess rooms, sufficient measurements are required to define the vibration profile.

4.6.3 Where deck coverings make transducer attachment impracticable, use of a small steel plate having a mass of at least 1 kg is permissible.

4.6.4 At all locations, vibrations in the vertical direction are to be assessed. Sufficient measurements in the longitudinal and transverse directions are to be taken to define global vibrations, in at least two locations on each deck.

4.7.1 An approved technical organisation for the purposes of these Rules is one that is acceptable to the Owner and LR with proven capability in noise and vibration measurement and satisfies all the criteria set out below:

1. Have instrumentation whose calibration, both before and after the measurements, can be traced back to National Standards.
2. Personnel with knowledge in the field of noise, vibration, measurement techniques, equipment handling and relevant standards and Codes (including these Rules)
3. Have analysis procedures capable of data reduction to the requirements and standards set out in these Rules.
4. Be able to provide a written report in English with contents as defined by Vol 3, Pt 2, Ch 7, 5 Survey reporting.