How loud is military sonar?
US Navy mid-frequency hull sonars have nominal source levels of 223 dB (AN/SQS-56) to 235 dB (AN/SQS-53C) re 1 µPa at 1 m, according to the joint NOAA and Navy report on the 2000 Bahamas whale strandings. Guinness World Records also cites 235 dB for military sonar pulses.
- Level
- 223–235 dB re 1 µPadecibels relative to 1 micropascal, measured in water
- Distance
- 1 m1 m (nominal source level)
- 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". Nominal source levels of US Navy mid-frequency tactical sonars from the NOAA/Navy report on the March 2000 Bahamas strandings: AN/SQS-56 223 dB, AN/SQS-53C 235 dB re 1 µPa at 1 m. Nominal levels are calculated as if from a single point source.
The figures come from the official investigation into the stranding of beaked whales and other marine mammals in the Bahamas on 15 and 16 March 2000, during a Navy exercise. The report gives the nominal source level of the AN/SQS-53C sonars as 235 dB, with centre frequencies of 2.6 and 3.3 kHz, and of the AN/SQS-56 as 223 dB referenced to 1 micropascal at 1 m.
A nominal source level is a simplification. The report explains that an array operated at a nominal 235 dB does not reach 235 dB anywhere; the sound simply propagates as if it came from a single point source at that level. It also notes that no calibration measurements were made during the exercise, so actual levels could have been lower than the nominal figures but not higher.
Guinness World Records describes military sonar pulses measured at 235 dB re 1 µPa at 1 m and notes that sonar is far narrower in bandwidth than airgun arrays.
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
Navies set exclusion zones around active sonar exercises; divers should follow them. For marine mammals, the concern is behavioural disruption and, in rare cases, strandings.
Questions
How loud is navy sonar?
US Navy mid-frequency hull sonars have nominal source levels of 223 to 235 dB re 1 µPa at 1 m.
Is sonar louder than a sperm whale?
The nominal 235 dB of an AN/SQS-53C is about the same as a sperm whale click's 236 dB re 1 µPa, though the two are measured differently.
Sources
- Joint Interim Report: Bahamas Marine Mammal Stranding Event of 15-16 March 2000, NOAA / National Marine Fisheries Service and US Navy (2001). Supports: dB_high: 235 dB re 1 µPa at 1 m.
The nominal source level of the AN/SQS-53C sonars was 235 dB
Checked 2026-11-02. - Joint Interim Report: Bahamas Marine Mammal Stranding Event of 15-16 March 2000, NOAA / National Marine Fisheries Service and US Navy (2001). Supports: dB_low: 223 dB re 1 µPa at 1 m.
The nominal source level (in terms of sound pressure level or SPL) produced by the AN/SQS-56 sonars was 223 dB referenced to 1 micro Pascal at one meter distance
Checked 2026-11-02. - Joint Interim Report: Bahamas Marine Mammal Stranding Event of 15-16 March 2000, NOAA / National Marine Fisheries Service and US Navy (2001). Supports: What nominal level means.
an array operated at a nominal level of 235 dB does not in fact attain 235 dB in any place
Checked 2026-11-02. - Loudest industrial ocean noise pollution, Guinness World Records. Supports: Independent 235 dB figure.
military sonar, which typically uses pulses of sound that have been measured at 235 dB (re 1 μPa at 1 m)
Checked 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.