Electroacoustic transducers include loudspeakers, microphones, particle velocity sensors, hydrophones and sonar projectors. Optical fibers are used as hydrophones for seismic and sonar applications. GHG' () passive hydrophones were fitted to detect submarines. "Indianapolis" was not equipped with sonar or hydrophones, or provided with an escort. She was given a complete set of the latest radar, hydrophones and sonar. Some applications of PVDF are pressure sensors, hydrophones, and shock wave sensors. Sound travels far in water, and underwater loudspeakers and hydrophones can cover quite a gap. The ALC finds use as an adaptive beam former for arrays of hydrophones or antennas. They concluded that the best hope was to use hydrophones to listen for submarines. This reduction gearing was very noisy, and made the submarine easier to detect with hydrophones. Without boiling sounds, deep-sea volcanoes can be difficult to detect at great distances using hydrophones. It employed two cables, each with a dozen hydrophones attached. At roughly offshore, the hydrophones detected a ship. The bulbous bow contained five sensitive hydrophones and the lightened conning tower was also well-streamlined. Bottom mounted hydrophones can also be used, with land based processing.