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How loud is a ship underwater?

171–193dB re 1 µPa1 m (source level, back-calculated)

Large ships have broadband source levels of roughly 171 to 193 dB re 1 µPa at 1 m, from a tug and barge (171 dB) through a large tanker (186 dB) to icebreaking (193 dB), according to DOSITS. A big container ship at 21.7 knots can reach 188 dB. Shipping has raised low-frequency ocean noise by 10 to 15 dB over 50 years.

Level
171–193 dB re 1 µPadecibels relative to 1 micropascal, measured in water
Distance
1 m1 m (source level, back-calculated)
Daily limit
Underwater levelnot an air level

What the numbers mean

How it was measured. Underwater level in dB re 1 µPa. Underwater decibels are not comparable with in-air decibels: see "underwater-vs-air". Broadband source levels from DOSITS: tug and barge at 18 km/h 171 dB, large tanker 186 dB, icebreaking 193 dB; a 54,000 gross ton container ship at 21.7 knots up to 188 dB (20 to 1,000 Hz).

Much of a ship's noise comes from its propellers: as they rotate, bubbles form in the water (cavitation) and a loud sound is created when the bubbles collapse. DOSITS's table of broadband source levels lists a tug and barge at 18 km/h at 171 dB, a supply ship at 181 dB, a large tanker at 186 dB and icebreaking at 193 dB re 1 µPa at 1 m. It also cites source levels as high as 188 dB re 1 µPa at 1 m (20 to 1,000 Hz) for a 54,000 gross ton container ship travelling at 21.7 knots.

Individually, ships are far quieter than airguns or sonar, but there are a great many of them and they run constantly. DOSITS says low-frequency ambient noise has increased by 10 to 15 dB in the past 50 years with the growth of propeller-driven shipping. Measurements in the Northeast Pacific from 1950 to the early 1970s showed levels at 50 Hz rising by about 0.55 dB a year. The southern hemisphere has fewer ships, and its low-frequency ambient noise is generally at least 10 dB lower.

This low band overlaps the calls of the great whales, which is why ship noise is a conservation concern.

Is it dangerous?

Measured in water against a 1 µPa reference, so the number cannot be compared directly with levels in air. See the underwater note on the Scroll. Marine-mammal and diver exposure criteria use their own metrics and are outside the scope of this page.

Protecting your hearing

Not a hearing risk for people on board or in the water at normal distances. Ship-quieting measures (slower speeds, better propellers) mainly protect marine life.

Questions

How loud is a container ship underwater?

Up to about 188 dB re 1 µPa at 1 m for a 54,000 gross ton container ship at 21.7 knots, according to DOSITS.

Has the ocean got noisier?

Yes. DOSITS says low-frequency ambient noise has risen 10 to 15 dB in 50 years because of propeller-driven ships.

Sources

  1. What are common underwater sounds?, DOSITS, University of Rhode Island (Wayback Machine copy). Supports: dB_low: tug and barge 171 dB.Tug and Barge (18 km/hour) 171Checked 2026-11-02.
  2. What are common underwater sounds?, DOSITS, University of Rhode Island (Wayback Machine copy). Supports: Large tanker 186 dB.Large Tanker 186Checked 2026-11-02.
  3. What are common underwater sounds?, DOSITS, University of Rhode Island (Wayback Machine copy). Supports: dB_high: icebreaking 193 dB.Icebreaking 193Checked 2026-11-02.
  4. How does shipping affect ocean sound levels?, DOSITS, University of Rhode Island (Wayback Machine copy). Supports: Container ship 188 dB at 1 m.as high as 188 dB re 1µPa @ 1 m for a 54,000 gross ton container ship traveling at 21.7 knotsChecked 2026-11-02.
  5. How does shipping affect ocean sound levels?, DOSITS, University of Rhode Island (Wayback Machine copy). Supports: Long-term trend.sound levels at 50 Hz were increasing by about 0.55 dB/yearChecked 2026-11-02.
  6. Ship (Audio Gallery), DOSITS, University of Rhode Island (Wayback Machine copy). Supports: 10 to 15 dB rise.low-frequency ambient noise has increased 10-15 dB in the past 50 yearsChecked 2026-11-02.

This page is general information, not medical advice. If you have ringing in your ears, muffled hearing or any change in your hearing, see an audiologist or your doctor.