Sonar Domes
Some warships specialized for anti-submarine warfare use a specifically shaped bulb as a hydrodynamic housing for a sonar transducer, which resembles a bulbous bow but the hydrodynamic effects are only incidental. The transducer is a large cylinder or sphere composed of a phased array of acoustic transducers. The entire compartment is flooded with water and the acoustic window of the bulb is made of fiber-reinforced plastic or another material (such as rubber) transparent to underwater sounds as they are transmitted and received. The transducer bulb places the sonar equipment at the greatest possible distance from the ship's own noise-generating propulsion system.
Read more about this topic: Bulbous Bow