Why are hulls on submarines covered with anechoic tiles or coatings?

• A. To improve hydrodynamic efficiency at high speed.
• B. To camouflage visually at sea.
• C. To protect against corrosion in saltwater.
• D. To reduce passive sonar detection by absorbing or deflecting sound.

Answer: (D)

Anechoic hull coatings are all about acoustic stealth. Submarines rely on sonar to sense or be sensed in the water, and sound waves interact strongly with the hull. Anechoic tiles are soft, rubbery tiles with embedded cavities that absorb much of the acoustic energy in the water, turning it into a tiny bit of heat instead of a strong echo. They also create a rough, irregular surface that scatters sonar signals, making any reflected sound weaker. This combination lowers the submarine’s acoustic signature, making it harder for sonar systems—especially passive listening—to detect it.

They aren’t primarily for visual camouflage, corrosion protection, or drag reduction, though those coatings can have their own roles. The tiles’ main purpose is reducing detection by absorbing or deflecting sound, which is why this item is the best choice.