Overview
ISO 2923:1996 - "Acoustics - Measurement of noise on board vessels" specifies standardized techniques and conditions to obtain reproducible, comparable measurements of ship noise. It covers inland and seagoing vessels and defines what to measure, instrumentation requirements, test environments and operating conditions, measurement procedures, and minimum test-report content. Typical outputs include equivalent continuous A‑weighted sound pressure levels, octave‑band spectra and assessments of impulsive or tonal noise for use in acceptance testing, regulatory compliance and noise‑abatement planning.
Key topics and technical requirements
- Quantities to measure
- Equivalent continuous A‑weighted sound pressure level (LAeq)
- C‑weighted peak level when risk of >130 dB exists
- Octave‑band LAeq from 31.5 Hz to 8 000 Hz (if required)
- Presence of impulsive noise and tonal sounds
- Instrumentation
- Type‑1 sound level meters (IEC 651) or integrating‑averaging meters (IEC 804)
- Microphone with diffuse‑field flat response; windscreen that does not alter A‑weighted level by >0.5 dB (in no‑wind)
- Calibrator Class 1 (IEC 942) applied before and after measurement series; calibrator verification at least annually
- Instrument verification at least every 2 years
- Measurement procedure
- Microphone height: 1.2 m (seated) to 1.6 m (standing); no closer than 0.5 m to boundaries
- Minimum measurement time: 10 s (longer as needed for stated uncertainty)
- Multiple positions in large spaces (e.g., cargo holds: ≥3 positions)
- Octave‑band measurements at representative highest‑level positions
- Test environment and vessel operating conditions
- Report water depth, nearby reflecting surfaces, meteorological conditions (wind, rain, sea state)
- At sea: propulsion at normal service speed and ≥80% MCR (inland vessels ≥95% MCR); auxiliary systems in normal operation
- In port: cargo‑handling noise measured when equipment is operating
- Uncertainty
- Measurements conforming to ISO 2923 typically achieve reproducibility standard deviation ≤ 1.5 dB
Applications and users
ISO 2923 is used to:
- Compare vessel designs and layouts for ship noise performance
- Support delivery/acceptance testing against national/international limits
- Monitor operational noise and evaluate crew exposure (health & safety)
- Assess speech intelligibility and audibility of alarms for bridge and duty stations
- Provide baseline data for noise‑abatement engineering and retrofits
Primary users:
- Marine acoustic consultants, naval architects, shipbuilders
- Classification societies, port authorities, regulators
- Ship operators, environmental & occupational health teams
Related standards
- IEC 651 (Sound level meters), IEC 804 (Integrating‑averaging meters)
- IEC 942 (Sound calibrators), IEC 1260 (Octave‑band filters)
- IMO Resolution 468 (XII) - Code on Noise Levels On Board Ships
Keywords: ISO 2923:1996, measurement of noise on board vessels, ship noise measurement, marine acoustics, A‑weighted sound pressure level, octave‑band, impulsive noise, tonal sound, sound level meter.
