Rules for Classification and Construction I Ship Technology

1 Seagoing Ships

23 Harmony Class - Rules on Rating Noise and Vibration for Comfort, Cargo Ships

Edition 2009

The following Rules come into force on July 15th, 2009

Germanischer Lloyd Aktiengesellschaft

Head Office Vorsetzen 35, 20459 Hamburg, Germany

Phone: +49 40 36149-0 Fax: +49 40 36149-200

headoffice@gl-group.com

www.gl-group.com

"General Terms and Conditions" of the respective latest edition will be applicable (see Rules for Classification and Construction, I - Ship Technology, Part 0 - Classification and Surveys).

Reproduction by printing or photostatic means is only permissible with the consent of Germanischer Lloyd Aktiengesellschaft.

Published by: Germanischer Lloyd Aktiengesellschaft, Hamburg Printed by: Gebrüder Braasch GmbH, Hamburg

Table of Contents

Section 1 Classification

A. Scope .......................................................................................................................................... 1- 1 B. Harmony Categories (hc) ........................................................................................................... 1- 1 C. Class Notation ............................................................................................................................ 1- 1

Section 2 Noise and Vibration Limits

A. General ....................................................................................................................................... 2- 1 B. Noise Limits and Tolerances ...................................................................................................... 2- 1 C. Vibration Limits and Tolerances ................................................................................................ 2- 1

Section 3 Required Measurements

A. General ....................................................................................................................................... 3- 1 B. Measuring Conditions ................................................................................................................ 3- 1 C. Performance of Measurements ................................................................................................... 3- 1 D. Preparation and Documentation of Measurements ..................................................................... 3- 3

Annex A Standards

A. General ....................................................................................................................................... A- 1 B. Standards .................................................................................................................................... A- 1

Annex B Important Definitions

Annex C Recommendations to Reduce Noise and Vibration

A. General ....................................................................................................................................... C- 1 B. Considerations Regarding Excitation Forces ............................................................................. C- 1 C. Theoretical Investigations .......................................................................................................... C- 1 D. Secondary Measures ................................................................................................................... C- 1 E. Supplementary Measurements during Production Phase ............................................................ C- 2

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Table of Contents Chapter 23Page 3

Section 1

Classification

A. Scope

1. In general, these Rules are based on national and international standards listed in Annex A. They will be adapted to the latest editions of these standards when deemed necessary or will be modified to ac-count for the progress of knowledge. The Rules reflect the state of the art in vibration and acoustic technol-ogy.

2. Some important definitions for expressions used in these Rules are given in Annex B.

3. Various comfort-promoting factors like furni-ture and size of cabins, the indoor climate, ship mo-tions as well as the noise and vibration level decide on the well-being of the crew and officers. In these Rules only noise and vibration is dealt with.

4. In this context, noise and vibration are de-fined as follows:

4.1 Noise

Audible air pressure variations in the range of 16 Hz to 16 kHz

4.2 Vibration

Structural oscillations in the frequency range of 1 to 80 Hz

5. The influence of ship motions on human well-being (seasickness) is not considered in these Rules.

6. These Rules are intended to support owners and shipyards to specify requirements regarding the comfort of the crew on board seagoing cargo vessels.

7. Requirements according to current regula-tions of the responsible flag state regarding maximum noise and vibration levels in crew spaces are to be fulfilled independently of these Rules.

8. If the length between perpendiculars is less than 80 m, limit values given in these Rules do not apply. They shall be agreed upon separately after conferring with Germanischer Lloyd (GL).

9. The Rules do not give special requirements for vessels with additional passenger cabins, but a reasonable comfort level for this case is indicated.

10. To reflect the different situation of small and large cargo vessels with regard to noise and vibration the limit values distinguish between an aft and a more forward deck house position.

B. Harmony Categories (hc)

1. To allow for a graduation of noise and vibra-tion levels, 3 harmony categories hc are introduced:

hc = 1 =̂ ∗∗∗ high comfort

hc = 2 =̂ ∗∗ moderate comfort

hc = 3 =̂ ∗ acceptable comfort

2. Respective limit values of noise and vibration are defined in Section 2.

3. Compliance with criteria given in these Rules shall be verified through measurements performed under defined conditions at specified locations, see Section 3.

C. Class Notation

1. Upon request, ships complying with these Rules are granted the following special Notation of Harmony Class

HC (hc).

2. For a series of ships, the required noise measurements are to be conducted individually for each ship of the series. Regarding vibration measure-ments, a reduced measurement programme can be accepted for sister ships.

3. After modifications (e.g. conversions) that might influence the noise and vibration behaviour, the Class Notation is to be reconfirmed by GL.

4. The Class Notation is granted on basis of the measurement results attainted during the sea trials or a later voyage on ballast draft by GL's own experts or authorised companies.

If other loading conditions yield a substantially higher noise or vibration level an additional measurement voyage is required. If the noise or vibration level does not meet the Class Notation, the Notation can be downgraded, withdrawn or - provided that abatement measures are foreseen - limited as to time.

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Section 2

Noise and Vibration Limits

A. General

1. Requirements given in these Rules refer to human wellbeing only. However, to achieve a certain level of noise and vibra-tion comfort it shall be ensured that main and auxiliary machinery do not vibrate heavily. To closely cover these vibration excitation sources corresponding measurements are performed. The results, however, are not subject to the HC-rating. The influence of external sources on the wellbeing of the crew is not considered. However, it is pointed out that loading/unloading of the vessel herself as well as harbour activities in general may substantially impair the recreation of the crew.

2. Requirements regarding acoustic privacy are given in addition to those for noise and vibration. The ship should be designed in a way that the acoustic privacy levels stated in Table 2.2 are maintained. Noise measurements will be conducted only in case complaints from the crew occur.

3. The ship should be designed in a way that the speech interference levels (SIL) maintain the limits given in footnote of Table 2.1. Noise measurements will be conducted only in case complaints from the crew occur.

4. The personal noise protection has to be con-form to Chapter 5 "Noise exposure limits" and Chap-ter 7 "Ear protection and warning information" of IMO resolution A.468 (XII), 1982.

5. Noise limits given are valid for Sea Mode and under loading/unloading condition, vibration limits are valid for Sea Mode only.

6. The noise and vibration limits given for Sea Mode Operation form an upper bound for any operation mode.

7. Different requirements are valid for ships with deck houses positioned aft and more forward, where "aft position" is defined by a distance of the propeller plane to aft deckhouse bulkhead < 20 % Lpp. All other cases correspond to a "forward position".

8. Noise and vibration caused by charging or dis-charging of the vessel are not subject to these rules as such operation is not practicable within the scope of sea trials.

B. Noise Limits and Tolerances

1. Most relevant standards are ISO 2923, ISO 717/1, ISO 717/2 and IMO Resolution A.468 (XII).

2. The noise limit values depending on the harmo-ny category number (hc) are listed in Tables 2.1 and 2.2.

3. The noise measurement procedures are de-scribed in Section 3.

4. Following tolerances may be applied in com-paring the measured noise levels with the limit values.

4.1 Sea Mode and loading/unloading condition

4.1.1 Machinery, work, service and navigating spaces

In case that the HC-criterion (Table 2.1) is exceeded by max. 1 dB, this will be tolerated as long as the corresponding Noise Rating curve (NR) is maintained.

4.1.2 Accommodation spaces

For day and sleeping rooms the average noise level per deck is to comply with the limits of Table 2.1 provided that not more than 15 % per deck exceed the relevant HC-criterion and by not more than 2 dB(A) each.

For mess and recreation rooms as well as offices ex-ceedances are not granted in any case.

4.1.3 Other spaces

Noise levels higher than specified for hospital, treat-ment room, corridors, open recreation deck, gymna-sium, hobby room, indoor swimming hall, sauna etc. are acceptable as long as not more than 30 per cent of these spaces exceed the relevant HC-criterion and by not more than 2 dB(A) each. IMO Res. A.468 (XII) has to be fulfilled in any case.

4.2 Acoustic privacy

Verification of acoustic privacy has to be proved ei-ther with a certificate (Rw-value) by the supplier of interior systems combined with a site inspection or by measurements. Taking sound flanking paths into con-sideration the certified Rw-value shall be 5 dB higher than the specified limits in Table 2.2.

C. Vibration Limits and Tolerances

1. The most relevant vibration standard is ISO 6954, edition 2000. The limit values refer, conse-quently, to the overall frequency-weighted rms value in the range of 1 to 80 Hz. The vibration velocities are given in mm/s.

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2. Required vibration limit values depending on the harmony category (hc) are listed in Table 2.3.

3. The vibration measurement procedure is de-scribed in Section 3.

4. Following tolerances may be applied in compar-ing the measured vibration levels with the limit values.

4.1 No tolerance is granted for global longitudi-nal and transverse measurement points on decks form-ing the floor of living, working or recreation spaces.

4.2 Maximum 15% of all vertical measurement points on floors in living, working or recreation spaces may exceed the limit value given for the respective target-hc by max. 0,3 mm/s.

Table 2.1 Noise limits, crew accommodation and work spaces

DH aft position (see A.7.) DH forward position Sea mode and loading/ unloading operation 1

Sea mode and loading/ unloading operation 1

HC HC Maximum noise level in dB(A)

1 2 3 1 2 3 Machinery and work spaces

Machinery spaces (continuously manned) 1, 2 85 90 90 85 90 90 Machinery spaces (not continuously manned) 1, 2 108 110 110 108 110 110 Workshops 1, 2, 5 82 85 85 82 85 85 Crane indoor working places (cockpit) 85 85 Laundries and changing rooms 1 80 80 Open deck working areas and rescue stations 2, 3, 4, 5 85 85 Control rooms located in and/or adjacent to engine rooms 1, 3 70 73 75 70 73 75 On car decks of RoRo and RoPax vessels 2, 5 85 90 90 85 90 90 Stores and work spaces not specified 2 90 90

Service spaces Galleys 1, 5 70 73 75 70 73 75 Pantries, shops, etc. 1, 5 70 70 75 70 70 75

Navigation spaces Navigation bridge and chart rooms 1, 3 62 65 65 62 65 65 Radio rooms 1, 3 60 60 Listing posts, including outdoor bridge wings 6 70 70

Accommodation spaces Day and sleeping rooms 1 55 58 60 52 56 60 Crew's and officer's mess 1, 3 and recreation rooms 1, 3, offices 1 60 63 65 57 60 65 Gymnasiums, hobby rooms, indoor swimming halls, saunas etc. 1 65 70 70 60 65 70 Hospital 1 57 60 60 57 60 60 Treatment rooms 1 65 65 Corridors adjacent to accommodation spaces 67 67 Open deck recreation areas 72 75 75 72 75 75 1 The noise level generated only by air-conditioning and/or mechanical ventilation systems are to be limited to at least 7 dB(A) below the

required HC noise limit value. 2 Reference is made to COLREG, Annex II and IMO Resolution A.468 (XII), 1982 – ear protectors should be worn when the noise level is

above 85 dB(A). 3 For spaces requiring verbal communication when berthing the ship and during normal seagoing condition of the vessel (wheelhouse,

control rooms, mess and recreation rooms) the corresponding SIL level is to be maintained on board. Acceptance measurements are to be conducted on board only in case that complaint of the crew occurs. The corresponding SIL level is determined as follow: SIL = (HC Noise limit) minus 7 dB.

4 Open deck working spaces which are normally occupied during loading and discharging of the vessel are included, e.g. between container cells, refrigerating containers, at pump stations, etc. (see also Annex B).

5 With mechanical ventilation in normal operation. 6 Reference is made to IMO Resolution A.343 (IX), 1975 – which also requires that the noise level at ¾ of max. vessel’s speed does not

exceed 68 dB in the 1/1 octave band at 250 Hz and does not exceed 63 dB in the 1/1 octave band at 500 Hz.

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Table 2.2 Noise limits for acoustic privacy

On board acoustic privacy – sound insulation (minimum required weighted apparent sound insulation index in dB

according to ISO 717/1 and ISO 140/4)

HC Arrangements

1 2 3 Cabin to cabin 1 35 Cabin to mess and recreation rooms 1 45 Cabin to hospitals, gymnasiums, service spaces etc. 1 45

On board acoustic privacy – impact sound insulation (maximum permissible normalized sound pressure level in dB

according to ISO 717/2, ISO 140/7)

HC Arrangements

1 2 3 Cabin below and/or adjacent to gymnasiums, passageways on open deck 1 58 Cabin below bridge wings and wheelhouse 1 60 Cabin below service spaces (galleys, pantries etc.) 1 65

1 Acoustic privacy levels are to be maintained on board. Acceptance measurements are to be conducted only in case that complaint of the

crew occurs.

Table 2.3 Vibration level limits

DH aft position (see A.7.) DH fwd position HC HC Vibration level limits in mm/s

(overall frequency- weighted rms value 1 to 80 Hz) 1 2 3 1 2 3

Accommodation and recreation spaces Day & sleeping rooms, hospital 2,7 3,0 3,2 2,2 2,7 3,2 Mess and recreation rooms 3,0 3,3 3,5 2,5 3,0 3,5 Gymnasium 3,5 3,8 4,0 3,0 3,5 4,0 Open deck recreation areas 4,0 4,8 5,0 3,0 4,0 5,0

Work and nav. spaces, permanently manned Nav. bridge, chart & radio room 3,5 3,8 4,0 3,0 3,5 4,0 Engine control room 4,0 4,3 4,5 3,5 4,0 4,5 Galley 4,0 4,3 4,5 3,5 4,0 4,5 Offices 3,5 3,8 4,0 3,0 3,5 4,0

Work and nav. spaces, sometimes manned Offices 4,0 4,3 4,5 3,5 4,0 4,5 Navigation bridge wing 5,0 5,3 5,5 4,5 5,0 5,5 Workshops 5,0 5,0 5,0 5,0 5,0 5,0

Spaces, not manned Machinery spaces 6,0 6,0 6,0 6,0 6,0 6,0 Stores 6,0 6,0 6,0 6,0 6,0 6,0

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Section 3

Required Measurements

A. General

1. Noise and vibration measurements and their evaluation have to be carried out by GL experts or companies accepted by GL.

2. Propulsion machinery power shall be verified during measurements.

3. Measurements shall be witnessed by a GL expert.

B. Measuring Conditions

1. Sea Mode

1.1 Propulsion machinery shall produce the nec-essary power to reach the service speed of the vessel as contractually agreed on. Power shall not be less than 85 % MCR.

1.2 The minimum water depth during measure-ments shall be at least five times the aft draught. For ships normally operating in shallow waters, corre-sponding conditions have to be chosen for measure-ments.

1.3 Sea state 3 (significant wave height approx. 1,2 m) and a wind speed of 4 Bft shall not be ex-ceeded. For more severe weather conditions, the ac-ceptance of measurements will be decided by GL on a case-by-case basis.

1.4 The course of the vessel shall be as straight as possible. Minimum rudder movement is imperative. Rudder angles shall not exceed ± 2 degrees.

1.5 The ship shall be fully outfitted, and all sys-tems contributing to noise and vibration shall be in normal seagoing condition, i.e. all auxiliary machin-ery, navigation instruments, radar sets, etc. shall be in normal operation.

Mechanical ventilation and air-conditioning equip-ment shall be in normal operation (capacity to be in accordance with design conditions). All air-condition-ing systems shall be adjusted prior to measurements.

1.6 Doors and windows shall, in general, be closed.

C. Performance of Measurements

1. Noise

1.1 Instrumentation

The measuring instrumentation has to fulfil the re-quirement according to ISO 2923. Basically an inte-grating sound level meter with 1/3-octave filters shall be applied.

A measuring device suitable for storing time signals, sound (booming) or obvious tonal components is to be provided.

1.2 Measurement locations

The measurement locations have to be chosen accord-ing to ISO 2923. All measurement positions shall be documented traceable in a measurement location plan.

1.3 Measurement procedure

The general measurement procedure is described in ISO 2923.

During each measurement, the microphone is to be slowly moved horizontally and/or vertically over a distance of approximately ± 0,5 m (averaging over time and space).

Wind noise, e.g. wind trash, singing or similar effects have to be reported for outdoor spaces surveyed.

The overall sound pressure level (LAeq), file number of the data storage (ID number), measurement loca-tion, noise limit according to hc target and subjective noise impression are to be recorded and immediately noted in measurement protocol sheets after recording.

1.3.1 Acoustic privacy

Acoustic privacy measurements shall be carried out if:

– no adequate certificate is available

– proper workmanship during outfitting is not approved

– the sound or impact insulation keeps obviously not the limits (subjective impressions) or com-plaints occur

Required measurements shall be performed following the standards ISO 140/4, ISO 140/7, ISO 717/1 and ISO 717/2.

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1.3.2 Presence of secondary noise sources

In general, secondary noise sources (e.g. rattling, knocking and squeaking noises from doors, panels, furniture, fittings or fixtures etc.) are to be eliminated in crew accommodation space.

1.3.3 Presence of obvious tonal components

1.3.3.1 In general, obvious tonal components in crew accommodation spaces will not be accepted for Sea Mode or Harbour Mode. Obvious tonal components audible in crew spaces are to be subjectively judged and reported.

1.3.3.2 If measured noise contains obviously tonal components, third-octave band readings are to be taken and stored, with centre frequencies from 20 Hz to 10 kHz. In addition, narrow band readings should be measured and stored in the frequency range of interest.

1.3.3.3 The octave band levels in dB are to be calcu-lated based on the third-octave band measurements as described in 1.3.4.2. The octave band levels in dB are to be compared against the corresponding NR curves.

1.3.4 Presence of booming effects

1.3.4.1 In general, the presence of annoying low-frequency sound (booming effects) occurring in crew spaces during Sea or Harbour Mode will not be ac-cepted. Annoying low-frequency sound audible in crew spaces are to be subjectively judged and re-ported.

1.3.4.2 Where the measured noise levels contain annoying low-frequency sound (booming effects), third-octave band readings are to be taken and stored, with centre frequencies from 20 Hz to 10 kHz. In addition, narrow band readings should be measured and stored in the frequency range of interest.

1.3.4.3 The octave band levels in dB are to be calcu-lated based on the third-octave band measurements as described in 1.3.5.2. The octave band levels in dB are to be compared against the corresponding NR curves.

1.3.5 Presence of impulse noise

1.3.5.1 In general, impulse noise in crew spaces will not be accepted for Sea or Harbour Mode Impulse noise audible in crew spaces are to be reported.

1.3.5.2 Impulse noise is to be determined following the procedure described in ISO 2923.

1.3.6 SIL-Levels

SIL-levels mentioned in Section 2, Table 2.1 foot-note 3 are to be calculated by arithmetic averaging the octave-band levels 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz.

2. Vibration

2.1 Instrumentation

2.1.1 The equipment shall be calibrated at periodic intervals of not more than two years. Calibration sheets shall be provided.

2.1.2 On non-magnetic floors, measuring sensors should preferably be mounted on a three-legged plate with a minimum weight of 1500 g.

2.1.3 The instrumentation shall allow for calcula-tion of the weighted rms value in terms of vibration velocity according to ISO 6954.

2.1.4 Provision shall be made for the storage of all spectra and a limited number of time records.

2.1.5 The instrumentation shall comply with re-quirements of ISO 8041.

2.2 Measurement Locations and Directions

2.2.1 The required number of measurement loca-tions depends on the vibration direction to be meas-ured (longitudinal, transverse or vertical).

2.2.2 Measurement locations for assessing longitu-dinal vibrations shall be chosen in a way that meas-urement results adequately reflect the global longitu-dinal deck house vibration level. At least following positions should be included:

– weather deck level , deckhouse front wall, ps or sb

– nav. deck level in way of ps and sb deckhouse walls

– nav. deck level outer edge of ps or sb bridge wing

– compass deck level, main mast foundation

– top of main mast

2.2.3 Measurement positions for assessing trans-verse vibration shall be chosen in a way that results adequately reflect the global transverse hull and deck-house vibration level. At least following measurement positions should be included:

– weather deck level, transom ps or sb

– weather deck level , deckhouse front wall ps or sb

– nav. deck level, in way of aft and front deck-house walls

– compass deck level, main mast foundation

– top of main mast.

2.2.4 Measurement positions for assessing vertical vibration shall be chosen in a way that results ade-quately reflect local vibration levels of deck panels in

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accommodation and working spaces. At least follow-ing measurement positions should be included:

– all crew and, if present, passenger cabins. For com-bined living and sleeping rooms one position, for separate rooms two measurement positions

– all working, navigation, accommodation spaces and offices which are permanently or frequently occupied

– inner and outer deck recreation spaces

– nav. deck level outer edge of ps or sb bridge wing

– sample measurements in non-occupied spaces as machinery rooms and stores.

– compass deck level, main mast foundation

2.3 Measurement procedure

2.3.1 Provision shall be made that amplitude spec-tra of the measured time signals can be made available during sea trials for diagnostic purposes, i.e. identifi-cation of frequency content.

2.3.2 If desired by GL experts, for instance if beat-ing occurs, time records of selected measurement positions shall be recorded and stored.

2.3.3 To ensure comparability of the spectra, the following parameters shall be applied for data acquisi-tion and signal processing:

– measurement time per point: ≥ 1 min

– sampling rate: ≥ 300 1/s

– spectral frequency range: 1 Hz to 80 Hz

– minimum spectral resolution: 0,2 Hz

– FFT window function: flat top (if not available, Hanning window)

– FFT averaging mode: linear averaging (stable mean)

2.3.4 The results shall be presented as weighted rms values in terms of vibration velocity

D. Preparation and Documentation of Meas-urements

1. Survey Programme

Measurements shall be planned in due time before conducting the measurements, be documented in a Survey Programme containing all relevant informa-tion. The Survey Programme has to be submitted to GL at least two months before sea trials or measure-ments.

2. Survey Report

The measurement results as well as the resulting HC-Class Notation shall be documented in a report based on the Survey Program. Each deviation from the Pro-gramme shall be explicitly stated.

An electronic standard form containing all information to be filled in can be submitted on request.

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Annex A

Standards

A. General

1. If these Rules contain procedures deviating from the relevant standards, these Rules shall have priority.

B. Standards

1. Noise standards

– IMO Resolution A.468 (XII): 1982, "Code on noise levels on board ship"

– IMO Resolution A.343 (IX): 1975-11, "Recommendation on Methods of Measuring

Noise Levels at Listening Posts"

– ISO 2923, 1996-12, "Acoustics – Measurement of noise on board

vessels"

– ISO 31-7: 1992-09, "Quantities and units of acoustics"

– IEC 61672 / 2003-10, "Electroacoustics - Sound level meters - Part 1:

Specifications"

– IEC 61260: 1995-08 and IEC 61260-Am 1: 2001-09,

"Electroacoustics - Octave-band and fractional-octave-band filters"

– IEC 60942: 2003-11, "Sound calibrators"

– ISO/DIS 20283-3: 2005, "Pre-installation vibratory noise measurement of

shipboard equipment"

– ISO 717/1: 1996-12, "Acoustics – Rating of sound insulation in

buildings and of building elements – Part 1: Airborne sound insulation in buildings and inte-rior elements"

– ISO 717/2: 1996-12, "Acoustics – Rating of sound insulation in

buildings and of building elements – Part 2: Im-pact sound insulation"

– ISO 140/4: 1998-12, "Acoustics – Measurement of sound insulation

in buildings and of building elements – Part 4:

Field measurements of airborne sound insulation between rooms"

– ISO 140/6: 1978-07, "Acoustics – Measurement of sound insulation

in buildings and of building elements – Part 4: Laboratory measurements of impact sound insu-lation of floors",

here: “4 Equipment….tapping machines with rubber coated hammers…”

– ISO 140/7: 1998-12, "Acoustics – Measurement of sound insulation

in buildings and of building elements – Part 7: Field measurements of impact sound insulation of floors"

– ISO 9921: 2003/10, "Ergonomics – Assessment of speech communi-

cation"

– ISO 1999: 1990-01, "Acoustics – Determination of occupational

noise exposure and estimation of noise-induced hearing impairment"

2. Vibration standards

– ISO 6954: 2000E, "Mechanical vibration – Guidelines for the measurement, reporting and evaluation of vibration with regard to habitabil-ity on passenger and merchant ships"

– ISO 2631-1: 1997 (E), "Mechanical vibration and shock – Evaluation of human exposure to whole-body vibration – Part 1: General require-ments"

– ISO 2631-2: 1989 (E), "Mechanical vibration and shock – Evaluation of human exposure to whole-body vibration – Part 2: Continuous and shock induced vibration in buildings (1 - 80 Hz)"

– ISO 4867: 1984 (E), "Code for the measurement and reporting of shipboard vibration data"

– ISO 4868: 1984 (E), "Code for the measurement and reporting of local vibration data of ship structures and equipment"

– ISO 8041: 1990 (E), "Human response to vibra-tion – Measuring instrumentation"

– GL Rules Machinery Installations (I-1-2)

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Annex B

Important Definitions

1. Angular frequency, circular frequency

ω [rad/s] is the product of the frequency of a sinusoi-dal quantity and the factor 2 π:

ω = 2 π ⋅ f

2. Acoustic privacy

"Privacy" from an acoustical point of view, i.e. the state of being alone and relatively undisturbed with regard to noise emissions from neighbouring cabins, sanitary cells, corridors, public spaces, open deck recreation spaces, service spaces etc. (sound and im-pact sound insulation).

3. Acoustic privacy plan

Drawings showing the arrangement of all cabin types including noise limit values to be kept. See also "cabin type".

4. Auxiliary machinery

Machinery, other than main propulsion machinery, operating when the ship is in normal service, e.g. auxiliary diesel engines, turbo-generators, hydraulic motors and pumps, compressors, boilers, ventilation fans, gears, pumps.

5. Abatement measures

Noise and/or vibration control measures, e.g. with the aim of reducing the airborne and/or structure-borne noise emission as well as of vibration levels of struc-tures, equipment etc.

6. A-weighted sound pressure level LAeq or LAeq,T

The A-weighted equivalent continuous sound pressure level using the frequency weighting "A" as specified in the IEC publication 60651 within a measurement time interval T.

7. Beat, beating

Periodic amplitude variations of an oscillation result-ing from the superposition of two excitation sources of slightly different frequencies. Beating which occurs in the audible frequency range is experienced as being annoying.

8. Boom, booming

Deep, hollow resonant low-frequency sound in the range between 16 and 125 Hz. Booming is mainly due to one or more discrete tonal components of signifi-cantly greater amplitudes than those of the adjacent spectrum level. Booming is experienced as being annoying and can only be detected subjectively. See also "steady noise with audible discrete tones".

9. Booming rating procedure

Procedure for measuring and assessing the occurrence of audible discrete tones below 125 Hz (booming effect). The procedure developed by GL is based on experimental investigations on board ships.

As result of this procedure a booming adjustment (CB in dB(A)) is established. The noise rating level has to be used for further evaluation.

10. Cabin type

Cabins with different types of interior systems (lining walls, ceilings, doors, etc.), floor constructions, floor coverings etc. See also "Acoustic Privacy Plan".

11. Crew spaces

Cabins, offices (for carrying out the ship's business), hospitals, mess rooms, recreation rooms (such as lounges, smoke rooms, cinemas, libraries, hobby and game rooms) and open recreation areas used by offi-cers and crew.

12. Corridors

Passageways/alleyways arranged in crew and passen-ger spaces.

13. Displacement (Δ)

Displacement of the vessel in metric tonnes.

14. Engine or shaft speed

Number of revolutions per minute [rpm]

15. Equivalent continuous sound pressure level Leq or Leq,T

Unweighted sound pressure level of a continuous steady sound. Within a measurement time interval T this sound has the same mean square sound pressure as a sound under consideration that varies with time. It is expressed in decibels by the following equation:

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Annex B Important Definitions Chapter 23Page B–1

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( )

( ) 2t

eq eq T 10t2 1 o

2

1

p t1L L , 10 log dtt t p

⎡ ⎤⎛ ⎞⎢ ⎥= = ⋅⎜ ⎟∫ ⎜ ⎟⎢ ⎥− ⎝ ⎠⎣ ⎦

where:

(t2 – t1) = is the period T over which the average is taken, starting at t1 and ending at t2

p (t) = unweighted instantaneous rms sound pres-sure between 16 and 16 000 Hz

p0 = 2 ⋅ 10–5 Pa (reference level)

16. Fluctuating noise

The measured sound pressure level (e.g. pointer of the display) varies more than ± 3 decibels with the "slow" meter characteristic switched on. Impulse noise shall be excluded.

17. HVAC

Heating, venting and air-conditioning system

18. Impulse noise

Noise of less than one second duration that occurs as an isolated event or as one of a series of events with a repetition rate of less than 15 times per second. The presence of impulse noise shall be determined by obtaining the difference between the equivalent con-tinuous sound pressure level measured with time weighting "impulse" and "fast". If the difference is more than 2 dB, the presence of impulse noise may be assumed. As result of this GL procedure an impulse adjustment (CI in dB(A)) is established. The noise rating level has to be used for further evaluation.

19. Integrating sound level meter

A sound level meter designed or adapted to measure the level of the mean squared time averaged A-weighted sound pressure level (IEC 804).

20. ISO noise rating (NR) number

The number found by plotting the 1/1 octave band spectrum of the NR curves given in ISO Standard R 1996-1967 and selecting the highest noise rating curve tangent to the spectrum .

21. Machinery spaces

All spaces containing propulsion machinery, boilers, steam and internal combustion engines, generators and major electrical machinery, oil filling stations, refrig-erating, stabilizing, hydraulic units, air-conditioning cooling compressors, etc.

22. Maximum continuous rating (MCR)

Designed maximum continuous power rating of main engines.

23. Measured SPL

The sound pressure level measured with a sound level meter or sound measurement instrumentation. The measured SPL shall be expressed to one decimal place.

24. Noise level

See "A-weighted sound pressure level".

25. NRC

Noise rating curve, see "ISO noise rating (NR) num-ber".

26. Noise rating level

The noise rating level LA, r is defined as follows:

A, r Aeq T I BL L C C C= + + + in dB(A)

LA, r is the noise rating level in dB(A)

LAeq is the measured overall A-weighted sound pressure level

CT, CI, CB are adjustments as result of the tone, im-pulse and booming rating procedure

27. Normal service speed

Shaft speed and propulsion power corresponding to service speed contractually agreed on, at least at 85 % MCR.

28. Overall frequency-weighted rms value

The overall frequency-weighted rms value has to be determined according to ISO 6954.

29. RMS value

The rms value of a single-valued function, f(t), over an interval between t1 and t2 is

( )

1 22

2 1

t2t1

f t dtrms value

t t

⎡ ⎤∫⎢ ⎥

= ⎢ ⎥−⎢ ⎥⎢ ⎥⎣ ⎦

30. Room space

Total room area of an individual public space in square metres.

31. Sound pressure level "L"

A measure of sound level on logarithmic scale given by:

[ ]100

pL 20 log dBp

⎛ ⎞= ⎜ ⎟

⎝ ⎠

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where:

p = rms value of measured sound pressure be-tween 16 and 16 000 Hz

p0 = 2 ⋅ 10–5 Pa reference level

32. Steady noise without audible discrete tones

Level fluctuations equal to or less than ± 3 decibels. This type of noise is frequently referred to as "broad-band" noise. Obvious tonal components of noise (tonality and/ or booming) in the whole audible frequency range be-tween 16 and 16 000 Hz are absent or negligibly small.

33. Steady noise with audible discrete tones This type of noise has components at one or more discrete frequencies having significantly greater am-plitudes than those of the adjacent spectrum level. Audible discrete tonal components of noise (tonality and/or booming) can occur in the whole audible fre-quency range between 16 and 16 000 Hz.

34. Tonality, annoying discrete tone A sound wave whose instantaneous sound pressure varies essentially as a simple sinusoidal function of time (pure tone). Tonality is experienced as being annoying and can only be detected subjectively. To-nality is defined in the frequency range between 125 and 16 000 Hz. It is mainly caused by main reduc-tion gears, pumps, air-conditioning cooling compres-sor units, thruster gears, HVAC inlet and outlet open-ings etc.

35. Tone rating procedure Procedure for measuring and evaluating the occur-rence of tonality. It is described in DIN 45681 "De-termination of tonal components of noise and determi-nation of a tone adjustment for the assessment of noise immissions" As a result of this procedure, a tone adjustment (CT in dB(A)) is established. The noise rating level has to be used for further evaluation.

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Annex C

Recommendations to Reduce Noise and Vibration

A. General

To maintain the required noise and vibration levels various investigations and reduction measures are recommended. This concerns the planning, design, fabrication and testing phase of a newbuilding.

B. Considerations Regarding Excitation Forces

By nature, the reduction of noise and vibration excita-tion forces is the most effective way to reduce the noise and vibration levels. Therefore it is recom-mended:

– to optimise the ship's lines by model tests in order to achieve an appropriate wake distribu-tion

– to optimise the propeller design with regard to noise and vibration excitation by cavitation tank tests

– to take into account the noise and vibration excitation characteristics of main and auxiliary machinery, gear, bow thruster etc. by appropri-ate choice of suppliers

C. Theoretical Investigations

1. Noise and vibration aspects should be con-sidered as early as possible in the design process.

2. The extent of the theoretical investigations necessary depends on the experience of the yard with the relevant ship type. As a guideline the analyses summarised in Table C.1 are recommended.

The following types of investigations are distin-guished:

2.1 Review of general arrangement plan

Prior to detailed investigations, the general arrange-ment plan is reviewed with regard to noise and vibra-tion. This should take place as early as possible in the design process.

2.2 Local vibration calculation

Natural frequencies of plate fields, stiffeners and small regularly stiffened panels are estimated by means of empirical formulas. The objective is to avoid reso-nance with main excitation frequencies. Added masses

as well as hydrodynamic masses have to be consid-ered. Attention should focus on deck structures situ-ated in the deckhouse and on living and working spaces close to the propeller and main engine. Natural frequencies of all structural components shall be cho-sen to have a sufficient margin to main excitation frequencies.

2.3 Noise prediction

A noise prediction is conducted at an early design stage. Semi-empirical noise prediction programmes are applied to predict the average airborne noise lev-els. Noise limits specified for passenger and crew spaces are compared with predicted values.

2.4 Global vibration level prediction

In a global vibration level prediction, the vibration level at "global" points of the ship structure is esti-mated on the basis of a forced vibration calculation in the lower frequency range (~ 1 Hz to 20 Hz). Dynamic magnification due to local resonances of plate fields, stiffeners or panels is not considered. These local structural systems are investigated separately (see ‘Local Vibration Calculation’).

The vibration level is estimated for relevant loading conditions at representative points of the ship struc-ture.

If the predicted vibration levels are expected to exceed the specified limits, modifications of the steel struc-ture, a different number of propeller blades, arrange-ment of compensators, etc. might be proposed as pos-sible means of improvement.

D. Secondary Measures

If the theoretical investigations reveal that the required noise and vibration levels probably can not be main-tained secondary measures should be provided, i.e.

– isolation (resilient supports for instance)

– insulation, encapsulation

– damping (floating floors for instance)

– compensation of vibration excitation forces

– silencing

– structural modifications

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E. Supplementary Measurements during Production Phase

1. It is recommended to carry out test bed noise and vibration measurements for machinery compo-nents in order to check the adherence to noise specifi-cations agreed on with suppliers.

2. During outfitting stage the local vibrations of deck structures should be measured (impact or/and ex-citer measurements) to verify calculation results and to identify and rectify local structural deficiencies.

3. During outfitting stage the impedance of ma-chinery foundations should be measured to verify cal-culation results and to identify and rectify local struc-tural deficiencies.

Table C.1 Recommended theoretical investigations for seagoing cargo vessels

Deckhouse position forward

Deckhouse position aft

hc hc

1 2 3 1 2 3

Review of general arrangement

Local vibration calculation

Noise prediction

Global vibration level prediction

= Strongly recommended

= Recommended

= Recommended only if experience with similar ships is not available

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