Overview
ISO 4678:2024 - "Ships and marine technology - Noise measurement method for HVAC system in accommodation spaces" specifies instrumentation and procedures for measuring noise from shipboard HVAC systems in accommodation spaces. Measurements are made in third-octave bands from 63 Hz to 8 kHz and include correction for cabin reverberation. The standard targets spaces defined in ISO 2923 (cabins, offices, hospitals, messrooms, recreation rooms) and is intended for use during ship commissioning, troubleshooting and habitability assessments.
Key topics and technical requirements
- Frequency and metrics: Third-octave band analysis across 63 Hz–8 kHz; steady-state equivalent sound pressure levels using 30 s stable readings.
- Instrumentation:
- Class 1 sound level meters / recorders and data sampling compliant with IEC 61672-1.
- One-third-octave frequency analyser per IEC 61260-1 and ISO 266 centre frequencies.
- Calibration before and after tests using Class 1 acoustic calibrators per IEC 60942.
- Use of nose cones and windshields to reduce airflow effects; combined influence limited to ≤ 0.5 dB(A).
- Microphone arrangement: Preferred setup uses three microphones on tripods in one plane, equally spaced (β = 120°), at 1 m from the outlet edge with inclination angle α between 30°–45°. One or two mics are allowed where space is restricted.
- Procedure highlights:
- Measure outlet noise with HVAC running at design flowrates.
- Measure background noise with HVAC off; apply energetic averaging from the same microphone positions and correct outlet readings per the standard’s correction method.
- Measure reverberation time using interrupted source or integrated impulse response methods following ISO 3382-2, and apply reverberation correction when calculating vent noise levels.
- Document measurement uncertainties and produce a comprehensive measurement report (company/personnel, ship and HVAC particulars, instruments, conditions, raw data).
Applications and users
ISO 4678:2024 is practical for:
- Ship designers and naval architects verifying acoustic habitability of accommodation spaces.
- Shipbuilders and test teams performing commissioning and acceptance tests.
- HVAC and acoustic consultants diagnosing noisy outlets and recommending mitigation.
- Classification societies, operators and regulators assessing compliance with onboard noise criteria.
- Maintenance teams tracking performance changes and verifying retrofit effectiveness.
Related standards
Keywords: ISO 4678, HVAC noise measurement, ship accommodation, third-octave band, reverberation time, Class 1 sound level meter, marine HVAC acoustics.