ISO 4678:2024

International
Standard
ISO 4678
First edition
Ships and marine technology —
2024-01
Noise measurement method for
HVAC system in accommodation
spaces
Navires et technologie maritime — Méthode pour le mesurage du
bruit du système CVCA dans les locaux
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Instrumentation . 2
4.1 Microphone with sound level meter or other microphone amplifier .2
4.2 Microphone cable .2
4.3 Frequency analyser .2
4.4 Nose cone and windshield .3
4.5 Sound level recorder or other data sampling devices .3
4.6 Calibration of instruments.3
5 General requirements . 3
6 Measurement procedure . 3
6.1 Outlet noise measurement .3
6.2 Background noise measurement and outlet noise correction .4
6.3 Reverberation time measurement .5
6.4 Result processing .5
6.4.1 Exhaust outlet noise level .5
6.4.2 Calculation of the cabin sound absorption .6
6.4.3 Determination of the vent noise levels .6
6.5 Measurement uncertainties . .7
7 Measurement report . 7
7.1 Measurement company and personnel .7
7.2 Ship particulars .7
7.3 HVAC particulars .7
7.4 Measuring instruments .8
7.5 Measuring conditions .8
7.6 Measurement data .8
Bibliography . 9

iii
Foreword
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iv
Introduction
Heating, ventilation and air conditioning (HVAC) is one of the most serious noise sources, especially for ship
accommodation spaces that are far from the machinery spaces. This noise source affects the habitability
comfort of crews and passengers on a ship. Although some standards exist for measuring noise on board
vessels, for example ISO 2923, no special attention has been paid to measure noise arising from the HVAC.
Other standards such as ISO 3740 are more accurate for quantifying measurement of a noise source.
However, the methods specified in other standards require more measurement instruments, are more time-
consuming than the method presented in this document and are difficult to use in the noise measurement of
HVAC system onboard ships, which has many outlets distributed in hundreds of cabins.
This document specifies a method of noise measurement of HVAC systems in ship accommodation spaces by
placing three microphones around the vent outlets to reduce airflow interference and space inhomogeneity,
and by correcting the noise result by measuring the reverberation time of the cabin. The noise measurement
method for the HVAC system is a compromise, which is more precise, but less laborious, compared to the
previous methods.
The measurement should be performed for ship accommodation spaces, where noise exceeds the required
limits according to existing regulations. The measurement and analysis results could be used to detect the
causes of the higher noise level of the HVAC system, further enabling objective measures to be taken to
mitigate these causes.
v
International Standard ISO 4678:2024(en)
Ships and marine technology — Noise measurement method
for HVAC system in accommodation spaces
1 Scope
This document provides the instrumentation requirements and measurement procedures for measuring
noise from HVAC systems in ship accommodation spaces.
Accommodation spaces are defined according to ISO 2923, and include cabins, offices (for carrying out ship’s
business), hospitals, messrooms and recreation rooms.
Measurement of noise levels in HVAC systems in ship accommodation is performed in the third octave band
over the frequency range from 63 Hz to 8 kHz, taking into account the correction of cabin reverberation.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 266, Acoustics — Preferred frequencies
ISO 3382-2, Acoustics — Measurement of room acoustic parameters — Part 2: Reverberation time in ordinary
rooms
IEC 60942, Electroacoustics — Sound calibrators
IEC 61260-1, Electroacoustics — Octave-band and fractional-octave-band filters — Part 1: Specifications
IEC 61672-1, Electroacoustics — Sound level meters — Part 1: Specifications
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
nose cone
microphone shield designed to substitute the normal protection grid of the microphone and used in high-
velocity air flows with low turbulence and little swirl having a streamlined shape with the least possible
resistance to airflow and a fine wire mesh around its periphery allowing sound pr
...