Hydrophones are essentially devices that are configured to pick up underwater sound and convert it into audio signals that can be translated into measurable data. This form of underwater microphone makes exploration of large bodies of water much easier, even at depths and in circumstances that rule out the use of scuba diving as a means of exploration. Constructed as a piezoelectric transducer, the hydrophone converts the audio into an electrical signal that can be documented and plotted.
The hydrophone relies on the generation of electricity to work. Piezoelectric materials such as transducer that is watertight are used in the construction of the device. The transducer that is used to power a hydrophone may also often also drive the function of various types of sonar equipment, such as a side scan sonar device. Unlike sonar equipment, a hydrophone will function as a receiver only, and not emit any type of signal that is bounced back when encountering some sort of solid object.
In many cases, the hydrophone is encased in some sort of material that will provide protection for the device, but also not interfere with the reception of audio input. The casing is usually in the form of a long tube that is flexible in design, and can be towed behind a survey ship. The hydrophone and casing may be lowered to just about any depth and continue to function.
As data is collected, the hydrophone transmits the information to a control panel on the ship. Software converts the data into graphs and other images that can be studied in more detail. Depending on the spacing and frequency of the audio signals picked up by the hydrophone, the results may identify an area that the survey ship wishes to explore in more detail.
One application of the hydrophone is to monitor for the incidence of underwater echoes that indicate the presence of explosives in the immediate area. This application can help a survey ship to locate old mines that need to be deactivated, as well as be an important tool during wartime to avoid the destruction of a ship or submarine by enemy weapons.