The hydrophone and projector elements are housed within the submersible unit or transducer. Seismic wave fields are recorded by a seismometer, hydrophone (in water), or accelerometer. Both bottom-mounted hydrophone arrays and towed streamer systems are in use. The ships were also equipped with a Model 93 sonar and a Type 93 hydrophone. SOSUS systems consisted of bottom-mounted hydrophone arrays connected by underwater cables to facilities ashore. Upsweep is an unidentified sound detected on the American NOAA's equatorial autonomous hydrophone arrays. The vocalizations are recorded by a single hydrophone. Sound pressure can be measured using a microphone in air and a hydrophone in water. Additional torpedo tubes and hydrophone installation was ordered. It was recorded using an autonomous hydrophone array. Her anti-submarine features included ASDIC, a hydrophone, and four depth-charge throwers. They developed an improved directional hydrophone, which convinced the Admiralty of their usefulness. In one embodiment there is a further processing of each hydrophone signal. In the study, recordings of boat noise were made by using a hydrophone. The use of hydrophone networks allows volcanic eruptions to be detected.