BS ISO 4678:2024
Ships and marine technology. Noise measurement method for HVAC system in accommodation spaces

Standard No.

BS ISO 4678:2024

Release Date

2024

Published By

British Standards Institution (BSI)  GB  /  BSI

Latest

BS ISO 4678:2024

Introduction

Analysis of the core content of the standard

BS ISO 4678:2024 proposes a special method for the noise measurement of HVAC systems in ship cabins for the first time, solving the applicability problem of traditional standards (such as ISO 2923) in the measurement of ventilation system noise. The standard innovatively adopts a three-microphone array arrangement scheme, combined with a reverberation time correction algorithm, to control the measurement accuracy to ±1.5dB (frequency band above 100Hz).

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Comparison of key technical requirements

Dimensions	ISO 4678:2024	Traditional method (ISO 3740)
Measurement points	3 microphones 120° circular array	Single point measurement
Airflow interference processing	Nose cone + windscreen combination (≤0.5dB impact)	No special provisions
Data processing	Reverberation time energy correction (Formula 3-7)	Simple background noise subtraction
Applicable scenarios	Small space in ship cabins	General acoustic environment

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Key points for measurement implementation

Instrument configuration specifications

The standard requires the use of an IEC 61672-1 Class 1 sound level meter in conjunction with a one-third octave band analyzer (in accordance with IEC 61260-1), where:

• The microphone cable must be temperature stable
• The nose cone shape should conform to the streamlined design shown in Figure 1
• The windshield diameter ≥ 60mm (see Figure 2)

Typical measurement process

1. Shut down other mechanical equipment when the HVAC system is running at full load
2. Arrange the microphone array as shown in Figure 3 (α=30°-45°, l=1m)
3. Collect at least 30 seconds of steady-state noise data
4. Perform background noise correction (refer to Table 1)
5. Repeat the reverberation time measurement 5 times
6. Calculate the final vent noise level according to Formula 7

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Engineering application suggestions

Based on the experience of standard implementation, the following optimization suggestions are put forward:

Ship design stage

It is recommended to preset the measurement point spatial analysis module in the cabin 3D model to ensure that all vents meet the following requirements:

• Distance to bulkhead ≥0.5m
• Tripod unfolded diameter ≥2.5m

Measurement implementation stage

For complex cabins such as passenger ships, it is recommended to:

• Prioritize the use of shore power supply when berthing
• Use infrared synchronous trigger device to coordinate multiple groups of measurement equipment
• Use a simplified dual-microphone solution for corner vents

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Standard Evolution Analysis

Compared with the IMO MSC.337(91) noise specification, the technical breakthroughs of this standard are reflected in:

• Frequency range: extended to 63Hz-8kHz (the original standard only required 125Hz-4kHz)
• Uncertainty control: The low frequency band of small cabins below 30m³ is allowed to be relaxed to 3dB
• Data traceability: It is mandatory to record the instrument serial number and calibration validity period

BS ISO 4678:2024 Referenced Document

• IEC 60942 Electroacoustics - Sound calibrators
• IEC 61260-1 IEC 61260-1: Electroacoustics - Octave-band and fractional-octave-band filters - Part 1: Specifications
• IEC 61672-1 Electroacoustics - Sound level meters - Part 1: Specifications
• ISO 266 Acoustics - Preferred frequencies
• ISO 3382-2 Acoustics - Measurement of room acoustic parameters - Part 2: Reverberation time in ordinary rooms; Technical Corrigendum 1

BS ISO 4678:2024 history

• 2024 BS ISO 4678:2024 Ships and marine technology. Noise measurement method for HVAC system in accommodation spaces

Standard and Specification