Acoustics - Measurement of airborne sound emitted by vessels on inland waterways and harbours
1Key Takeaways
This document specifies the conditions for obtaining reproducible and comparable measurement results of the airborne sound emitted by vessels of all kinds, on inland waterways and in ports and harbours, except powered recreational craft as specified in the ISO 14509 series. This document is applicable to sea-going vess…
2Expert Interpretation
Comprehensive analysis of ISO 2922:2020 technical requirements for air noise measurement for inland waterways and ports, including measurement equipment specifications, test environment requirements, operating condition control and data correction methods, applicable to noise compliance detection and monitoring of various types of ships.
Interpretation of the core content of the standard
The third edition of ISO 2922:2020 replaces the 2000 edition of the standard. The main updates include: clarifying that it is applicable to ships of all speeds and sizes; adding sound pressure level response requirements (slow response); specifying the background noise integration time (5 minutes); and adding a sound pressure level calculation formula for a reference distance of 25 meters.
| Measurement type | Key parameters | Allowance deviation |
|---|---|---|
| Mobile ship | Microphone distance | 25m±5m |
| Stationary ship | Microphone height | 3.5m±0.5m |
| Background noise | Signal-to-noise ratio requirement | ≥10dB(acceptance)/≥6dB(monitoring) |
Technical requirements for measurement equipment
The standard requires the use of IEC 6001-compliant equipment. 61672-1 Class 1 sound level meter, key equipment parameters include:
- Anemometer error ≤±10%
- Tachometer error ≤±50r/min
- Windshield must keep the whole system at Class 1 accuracy
Calibration requirements:A Class 1 sound calibrator must be used before and after each measurement, and the difference between two consecutive readings must be ≤0.5dB.
Key points of environmental control
Case:When measuring an inland cargo ship, the wind speed was 6m/s, and the test needed to be terminated according to clause 6.3.1 of the standard. Practical solutions include:
- Select a leeward measurement location
- Use multiple windbreaks
- Post-data correction (to be noted in the report)
Implementation recommendations
1. Acceptance test preparation: Ensure that the ship is at minimum loading and the engine speed is ≥95% of the rated value
2. Distance correction formula: When the actual distance d≠25m, correct according to LpASmax,25 = LpASmax,d + 20lg(d/25)
3. Uncertainty control: The total standard deviation σtot should be controlled within 2.6dB (95% confidence level)