What does a sonobuoy primarily use for detection?

• A. Sounds
• B. Radio waves
• C. Light
• D. Magnetic fields

Answer: (A)

Underwater acoustic sensing is what a sonobuoy relies on. It uses hydrophones to pick up sound waves traveling through water, allowing it to detect noise from submarines, ships, or other underwater sources. Passive configurations simply listen for existing sounds, while active ones send out a ping and listen for the returning echoes. Sound propagates well in water, and its speed and attenuation depend on factors like temperature, salinity, and depth, which helps determine range and bearing.

Radio waves don’t travel far underwater because seawater conducts electricity and quickly attenuates RF signals, making them ineffective for practical underwater detection. Light is rapidly absorbed and scattered in water, especially in turbid or deep environments, so it cannot provide reliable long-range detection. Magnetic fields are not the primary detection method for standard sonobuoys; while magnetic sensing exists in other ASW tools, the core detection method for a sonobuoy is acoustic sensing.