ISO 4678:2024 船舶と海洋技術 | ページ 2

Foreword

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This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology, Subcommittee SC 8, Ship design.

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 ここで, 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.

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.

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:

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 pressure transmission to the microphone diaphragm, whilst a truncated cone behind the mesh reduces the air volume in the form of the diaphragm

Note 1 to entry: See Figure 1.

Figure 1 — Schematic diagram of a nose cone

3.2

windshield

device designed for the insertion of the microphone and preamplifier, taking the form of a ball of open-pored foam with a cylindrical hole of appropriate diameter and not to affect the directivity of the microphone

Note 1 to entry: A minimum size of the wind shield is suggested to diameter of 60 mm.

Note 2 to entry: See Figure 2.

Figure 2 — Schematic diagram of a windshield

Bibliography