CLASS GUIDELINE
DNVGL-CG-0493
Edition May 2016
Criteria for handling of excessive noise and
vibration levels
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FOREWORD
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Changes - current
CHANGES – CURRENT
This is a new document.
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Changes – current.................................................................................................. 3
Section 1 Introduction............................................................................................ 5
1 Objective..............................................................................................5
Section 2 Vibration levels....................................................................................... 6
1 General................................................................................................ 6
2 Maximum number of deviations.......................................................... 6
3 Distribution of deviations.................................................................... 6
4 Example............................................................................................... 6
Section 3 Noise levels............................................................................................. 8
1 General................................................................................................ 8
2 Maximum number of deviations.......................................................... 8
3 Distribution of deviations.................................................................... 8
4 Example............................................................................................... 8
Historic changes................................................................................................... 10
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Contents
CONTENTS
1 Objective
In order to assign the comfort class notation, COMF, see RU SHIP Pt.6 Ch.8 Sec.1, all the locations on board
shall comply with the relevant comfort class noise and vibration limits. However, small deviations from the
requirements may be accepted on a case by case basis, depending on the reason for the deviation, type
of location and by how much the criteria are exceeded. This class guideline provides information on how
moderate excesses to the comfort class noise and vibration criteria are handled.
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Section 1
SECTION 1 INTRODUCTION
1 General
This section details how to handle excessive vibration levels in the comfort class. The procedure is valid for
qualifiers crn 1, crn 2 and crn 3.
2 Maximum number of deviations
Measured vibration levels exceeding the specified comfort class limits will not be allowed in more than:
— 15% of all the sleeping cabins and public spaces
— 25% of the measurements on the open deck areas.
3 Distribution of deviations
The excessive vibration levels shall not exceed the distribution shown in Table 1. The limits in this table are
based on a one-sided normal distribution of the excessive vibration levels with a standard deviation of 0.5
mm/s for cabins/public spaces and 1 mm/s for open deck areas.
Table 1 Distribution of excessive vibration levels
Range
Magnitude of vibration level
in excess of limiting value
[mm/s]
Maximum number of cabins/public
spaces exceeding limiting values
Maximum number of open deck
locations exceeding limiting values
Normal
Maximum
Normal
Maximum
I
0.1 to 0.5
11%
(15%)
11%
(25%)
II
0.6 to 1.0
4%
(4%)
7%
(14%)
III
1.1 to 1.5
None
None
4%
(7%)
IV
1.6 to 2.0
None
None
3%
(3%)
The number of locations within the lower allowable ranges of values may be increased at the expense of the
number of locations within the higher vibration level ranges, but such that all the locations with excessive
vibration levels shall not exceed the total maximum of 15% in cabins/public spaces and 25% of open deck
areas. The increased number of locations is shown inside the parentheses in Table 1.
4 Example
The following example may illustrate the permissible deviations from the normal distribution. One of nine
measuring positions in the open deck areas has an exceeding value of 1.0 mm/s of the criteria, while the
other positions are within the criteria, i.e. 11% exceeding values in range II. This is regarded as acceptable
(See Table 1).
Table 1 is illustrated in Figure 1 and Figure 2 below:
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Section 2
SECTION 2 VIBRATION LEVELS
Section 2
Figure 1 Allowable excessive vibration levels, cabins and public spaces
Figure 2 Allowable excessive vibration levels, open deck areas
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1 General
This section details how to handle excessive noise levels in the comfort class. Deviations shall be treated
according the procedures given in the subsections below.
Dispensations for excesses of the crn 3 noise criteria for cargo vessel cabins shall only be granted in special
circumstances if it is documented that compliance will not be possible despite inclusion of relevant and
reasonable technical noise reducing measures. If this is documented, the excessive levels shall be treated
according to the procedures given in the subsequent sections.
In machinery spaces and non-specified work spaces, reference is given to chapter 5 in the MSC.337(91)
resolution. Excesses in these areas may be handled by reducing the worker’s exposure time and using
hearing protectors.
2 Maximum number of deviations
Measured noise levels exceeding the specified comfort class limits will not be allowed in more than:
— 15% of all the sleeping cabins
— 30% of all the public spaces (recreation rooms, restaurants, cinemas, open deck recreation areas, etc.).
3 Distribution of deviations
The distribution of excessive noise levels shall not exceed the distribution shown in Table 1. The limits in this
table are based on a one-sided normal distribution of the excessive noise levels.
Table 1 Distribution of excessive noise levels in cabins and public spaces
Magnitude of noise
level in excess
of limiting value
[dB(A)]
Normal
Maximum
Normal
Maximum
I
1 to 3
14%
(15%)
23%
(30%)
II
4 to 6
1%
(1%)
6%
(7%)
III
7 to 10
None
None
1%
(1%)
IV
>10
None
None
None
None
Range
Maximum number of cabins
exceeding limiting values
Maximum number of public
spaces exceeding limiting values
The distribution of excessive noise levels for cabins (passenger and crew cabins) is stricter than for public
spaces. The limits for cabins and public spaces are based on a normal distribution where the mean value is
zero (i.e. no deviation from the noise limit), and with a standard deviation of 2 dB(A) for cabins and 3 dB(A)
for public spaces.
The number of locations within the two lowest ranges may be increased on the expense of the number of
locations within the higher ranges, but such that all the locations with excessive noise levels shall not exceed
the total maximum (15% of cabins, and 30% of public spaces). The increased limits are shown inside the
parentheses in Table 1.
4 Example
The following example may illustrate the permissible deviations from the normal distribution. 25% of the
public spaces have noise levels in excess of the relevant comfort class noise limits, but none of the public
spaces have higher noise levels than 3 dB(A) in excess of the limits. Then the limit within parentheses in
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Section 3
SECTION 3 NOISE LEVELS
Table 1 is illustrated in Figure 1 and Figure 2 below:
Figure 1 Allowable excessive noise levels, cabins
Figure 2 Allowable excessive noise levels, public spaces
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Section 3
range I Table 1 for public spaces apply, i.e. up to 30% of the total public spaces may have excessive noise
levels in the range 1 to 3 dB(A) higher than the given limit, and consequently the public spaces will comply
with the comfort noise criteria in question.
Historic changes
HISTORIC CHANGES
There are currently no historical changes for this document.
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