Could Submarine Sonar Kill a Diver?

A submarine’s sonar can be either passive, meaning it listens for sounds, or active, meaning it transmits sound pulses and listens for echoes. Passive sonar emits no sound, so it cannot acoustically injure a diver. Active sonar can produce intense sound, but whether it could harm someone depends on the exposure at the diver’s location—not simply on the submarine’s equipment or a headline sound-level number.

The practical answer is that active sonar could be hazardous under some close-range, high-intensity conditions, but ordinary sonar is not known as a reliable way to kill a diver. There is no single sonar level that can be used as a universal human fatality threshold.

Why “loud sonar” does not give a simple answer

Underwater sound level depends on the pressure wave that actually reaches a person. A sonar’s source level describes its output using a specified reference and measurement convention; it does not tell you the received level at a diver. Sound spreads through the water, and the level reaching a particular place depends on distance, direction, frequency, reflections, and the surrounding environment. Active transmissions may also be brief or intermittent rather than continuous.

Underwater sound levels are commonly stated in decibels relative to a reference pressure of 1 micropascal ($1\,\mu\text{Pa}$). For a sound pressure level of 180 dB re $1\,\mu\text{Pa}$, the corresponding root-mean-square pressure is:

$$p = 1\,\mu\text{Pa}\times 10^{180/20}=1{,}000\,\text{Pa}.$$

That is an illustrative conversion, not a claim about a particular submarine or the level at a diver. Without knowing where and how the pressure was measured, a decibel figure cannot establish the diver’s exposure. Underwater and airborne decibel figures also use different reference pressures, so they cannot be compared directly by reading the numbers alone.

What an intense exposure might do

Very intense sound can pose a risk to hearing. Depending on the exposure, possible effects could include pain, temporary or lasting hearing impairment, or disorientation. Human underwater sound exposure is not characterized by one simple threshold that predicts injury in every case; duration, frequency, and the way sound reaches the body matter. A sudden, unexpected transmission could also startle a diver, which may create an indirect danger if the diver is working, managing breathing equipment, or operating near an obstacle.

A sound wave is not the same thing as an underwater explosion. Explosions create powerful, abrupt pressure changes and can cause severe or fatal blast injuries. Sonar is a sound transmission; it should not be treated as a blast merely because it is described as loud. At extreme acoustic intensities, sound itself can be dangerous, but that does not mean normal sonar operation produces a lethal effect on a diver.

The factors that matter most

Factor	Why it matters
Active or passive operation	Passive sonar listens; only active sonar transmits.
Distance and direction	They affect the sound level that reaches the diver.
Frequency and pulse pattern	Different sounds and exposure durations can have different effects.
Measurement location	A source-level figure is not necessarily the received level.
Diver’s situation	Startle or disorientation may be hazardous even without direct physical injury.

A diver very close to a powerful active transducer could face a greater risk than someone far away or outside the beam. But without reliable information about the system and the diver’s actual exposure, it is not possible to calculate an individual risk or declare a particular transmission lethal.

Common mistakes

• Treating all sonar as active. Passive sonar only receives sound; it does not send a ping.
• Treating source level as the diver’s exposure. The source and received levels are different measurements.
• Comparing underwater and airborne decibels directly. Their reference pressures differ, and the surrounding medium matters.
• Confusing sonar with an explosion. A blast wave is a distinct hazard and has a much clearer potential for fatal injury.
• Assuming a precise human kill threshold exists. The effects depend on exposure conditions, and a single universal threshold is not appropriate.

If you are planning a dive near naval activity, do not rely on a general sound-level estimate to judge safety. Follow official exclusion zones, notices, and instructions from the relevant maritime or diving authority.