Define what the measurement must decide.
“Measure the ship underwater noise” is not yet a complete scope. The project may need a deep-water comparison, a shallow-water assessment, a source-level estimate, a class-notation submission, an owner baseline, a retrofit comparison, an environmental-management record, research data or troubleshooting evidence. The required quantity, method, operating condition, uncertainty and reviewer can differ for each purpose.
| Field | Required entry | Owner / source | Open question |
|---|---|---|---|
| Decision and report recipient | ___ | ___ | ___ |
| Required acoustic quantity | Radiated level / source level / spectrum / tonality / project output | ___ | ___ |
| Method, edition and amendment | ___ | ___ | ___ |
| Vessel state and configurations | ___ | ___ | ___ |
| Witness and acceptance route | ___ | ___ | ___ |
| Exclusions and limitations | ___ | ___ | ___ |
A standard can describe a measurement procedure without supplying the project acceptance limit. Record the exact contract, class notation, flag instruction, owner specification, research protocol or environmental programme that controls the decision. IACS does not approve service suppliers, and neither an ISO reference nor an IMO guideline creates blanket class or flag acceptance.
Use the canonical underwater-radiated-noise survey service to agree the vessel, location, reporting purpose and specialist-partner requirements. Use the pre-delivery and sea-trial measurement service where the URN run must be coordinated with a broader acceptance programme.
Choose the method before selecting the range.
ISO 17208-1:2016 covers precision comparison measurements in deep water and calls its result radiated noise level. It does not provide underwater-noise criteria or address biological effects. ISO 17208-2:2019 addresses determination of source levels from deep-water measurements. ISO 17208-3:2025 specifies shallow-water measurement procedures and calculations. A project-specific engineering survey can still be valuable, but its departures and decision limits must be explicit.
| Route | Typical purpose | Evidence that must be fixed | Boundary to state |
|---|---|---|---|
| ISO 17208-1 deep-water comparison | Comparable radiated-noise measurement under prescribed operation | Site qualification, geometry, prescribed run, acoustic chain and corrections | Not a universal pass limit or biological-impact assessment |
| ISO 17208-2 source-level determination | Source-level output derived from qualified deep-water measurement | Input measurement, calculation route and uncertainty | Do not label every normalised level as the same source quantity |
| ISO 17208-3 shallow-water route | Measurement where bottom and propagation conditions require the Part 3 procedure | Bathymetry, environment, geometry, processing and applicability | Not interchangeable with an unqualified deep-water result |
| Project engineering campaign | Baseline, retrofit comparison, research or diagnosis | Declared method, repeatability controls and limits | No ISO or class equivalence unless the evidence establishes it |
| IMO management context | URN management planning and reduction measures | Applicable revised guidance, vessel context and selected actions | The guideline does not invent one universal ship pass/fail number |
Confirm the current edition and any amendment with the report recipient. If the project changes from screening to contractual acceptance, stop and revalidate the method, range and evidence chain rather than relabelling an earlier engineering run.
Prove that the site can support the selected route.
Record charted and measured water depth, bathymetry along the track, seabed character where relevant, sound-speed profile, sea state, current, wind, precipitation, water temperature, salinity basis, ambient shipping, biological or construction noise and the practical ability to repeat runs. Document navigation restrictions, permits, safety zones, support craft, hydrophone deployment and recovery, and traffic windows.
| Control | Planned evidence | Observed evidence | Effect / disposition |
|---|---|---|---|
| Depth, bathymetry and seabed | ___ | ___ | ___ |
| Sound-speed and water conditions | ___ | ___ | ___ |
| Hydrophone depth / array geometry | ___ | ___ | ___ |
| Track, aspect and closest approach | ___ | ___ | ___ |
| Background and traffic window | ___ | ___ | ___ |
| Permit, safety and repeat-run feasibility | ___ | ___ | ___ |
A convenient harbour, anchorage or coastal lane may be unsuitable for a comparison campaign even when a recorder produces clean-looking spectra. Conversely, a constrained site can support a declared engineering investigation when propagation, background and comparison limits are documented honestly.
Freeze every state that can move the acoustic result.
Prepare run IDs before the trial. Record draught, trim, displacement basis, hull and propeller condition, heading, track, speed through water and over ground, shaft or propeller RPM, pitch, propulsion mode, engine load, generator lineup, pumps, thrusters, stabilisers, HVAC and other auxiliaries. Define stabilisation time, run direction, repetition count and the permitted tolerance for each control.
| Run / time | Draught / trim | STW / SOG | RPM / pitch / load | Auxiliary state | Track / aspect | Valid / repeat / qualify |
|---|---|---|---|---|---|---|
| URN-___ / ___ | ___ | ___ / ___ | ___ | ___ | ___ | ___ |
| URN-___ / ___ | ___ | ___ / ___ | ___ | ___ | ___ | ___ |
| URN-___ / ___ | ___ | ___ / ___ | ___ | ___ | ___ | ___ |
Retain the ordered run plan and the executed run log. A nominal speed label is insufficient when current changes speed through water, or when identical speed is achieved with different shaft RPM or pitch. Mark deviations at the time they occur; do not repair the log later from memory.
Link the hydrophone sample to vessel position and RPM.
The report should trace each acoustic file through the hydrophone, preamplifier or conditioning chain, recorder, channel settings, sensitivity, bandwidth, sample rate, dynamic range, gain state, calibration evidence and field checks. Retain positioning equipment, clock source and synchronisation method. If onboard tachometer, torque, vibration or cavitation observations support interpretation, synchronise those files to the same time base.
| Channel | Instrument / serial | Sensitivity / range | Calibration / field check | Clock / position source | Raw file |
|---|---|---|---|---|---|
| HYD-___ | ___ | ___ | ___ | ___ | ___ |
| REC-___ | ___ | ___ | ___ | ___ | ___ |
| NAV-___ | ___ | ___ | ___ | ___ | ___ |
| RPM / AUX-___ | ___ | ___ | ___ | ___ | ___ |
Calibration status alone does not establish a valid chain. Check overload, clipping, dropout, self-noise, cable or connector faults, gain changes and time drift. Preserve original files and processing configuration so a reviewer can reproduce the reported bands, spectra and corrections.
Reject or qualify weak runs before averaging.
- Compare pre-run and post-run background with the vessel-pass data using the selected method.
- Check closest approach, aspect, hydrophone depth, track tolerance and acoustic-window timing.
- Review sea state, current, traffic, support-craft movement and transient interference.
- Confirm the vessel reached the required state before the usable window and held it throughout.
- Compare repeated runs before presenting a combined result; investigate outliers rather than hiding them.
- State measurement, geometry, environmental, processing and operating-condition contributions to uncertainty.
- Retain excluded records with the reason, author and consequence of exclusion.
A clean spectral plot can still be invalid for the contractual decision. The release decision belongs to the declared method and acceptance owner, not to visual smoothness or a single low value.
Make every reported quantity auditable.
| Run | Vessel state | Site / geometry | Background | Reported quantity | Uncertainty | Deviation / acceptance owner |
|---|---|---|---|---|---|---|
| URN-___ | ___ | ___ | ___ | ___ | ___ | ___ |
| URN-___ | ___ | ___ | ___ | ___ | ___ |
Identify vessel, date, site, method and edition; instrument and calibration chain; run plan and actual states; background and environmental evidence; processing and corrections; reported units and reference quantities; uncertainty; deviations; excluded runs; reviewer; and the exact comparison criterion where one applies. Separate measured facts, calculated quantities, acceptance statements and engineering interpretations.
A radiated result does not identify the source by itself.
A tone or speed-related change can suggest propeller, shaft, gear, engine, generator, pump or structural contributions, but attribution needs corroborating evidence. Useful additions can include synchronised RPM/order data, onboard machinery vibration, hull response, airborne noise, operating-state substitutions, controlled speed or pitch changes and specialist cavitation observations. Record hypotheses and untested alternatives.
When the decision is fault isolation rather than only reporting, connect the campaign to the noise and vibration troubleshooting service. Do not promise that one hydrophone pass will locate a defect, prove cavitation or demonstrate a corrective action without an equivalent-condition comparison.
Prepare real project proof without inventing a vessel or result.
Decision and basis
What question, method, edition and acceptance route governed the campaign?
Site and run controls
Which water-area, geometry, vessel-state and background controls made the data comparable?
Measurement chain
Which instruments, calibration evidence, clocks, positions and raw files preserved traceability?
Finding boundary
What did the reported quantity support, and which sources or effects remained untested?
Matched verification
Which conditions were repeated after a design, maintenance or operating change?
Publication permission
Who authorised disclosure, and which vessel, client, values, plots and images may be used?
This is an empty evidence structure. Do not add a vessel name, customer, class society, flag, acoustic value, pass result, improvement percentage, testimonial or environmental outcome without contemporaneous records and written publication permission.
Resolve feasibility before the test window.
Provide vessel particulars and IMO number; general arrangement and propulsion details; draught and trial loading; purpose and required quantity; method, notation or specification; candidate water area; planned speeds, RPM, pitch and auxiliary states; navigation and support-craft plan; hydrophone deployment arrangement; witness route; raw-data expectations; report deadline; and known confidentiality restrictions.
Attendance in Singapore, Malaysia, India, Sri Lanka, Indonesia, Thailand, the Philippines, the Middle East, wider Asia-Pacific or worldwide remains subject to specialist availability, equipment movement, permits, site suitability and a confirmed technical scope. No office location, guaranteed attendance or turnaround is implied.
Confirm the edition and project basis before use.
- ISO 17208-1:2016 remains current after its 2021 review and covers precision deep-water comparison measurements.
- ISO 17208-2:2019 addresses determination of source levels from deep-water measurements.
- ISO 17208-3:2025 covers shallow-water measurement procedures and calculations.
- IMO MEPC.1/Circ.906/Rev.1 provides revised guidance for reducing underwater noise from commercial shipping.
Official catalogue records establish document identity and broad scope. They do not determine the applicable acceptance limit, class notation, contract or flag process for a particular ship.
Turn the checklist into a controlled URN trial plan.
Send the vessel, decision, candidate range, operating configurations, governing document and required report outcome. The specialist team can then confirm feasibility, instruments, partners, run controls and evidence before mobilisation.
Request a URN scopeReview the URN serviceCoordinate a sea trial