Hydrophone

A hydrophone is a sound-to-electricity transducer for use in water or another liquid, analogous to the use of a microphone in air. A hydrophone can also be used as an emitter, but not all hydrophones have this capability.

History

The first operational sonar was built by Reginald Fessenden in the United States in 1914. This device used an electromagnetic copper oscillator that emitted a low-frequency noise, then switched to a listening mode to receive the echo. Due to this crude mode of operation it was not very precise in determining the direction of the target.

The first device called a hydrophone was developed when the technology matured and ultrasonic waves were used to improve detection capacity. Ultrasounds are generated by a mosaic of thin quartz crystals glued together by steel sheets so that resonance frequencies above 150 kHz are obtained.

Los idiófonos son una parte importante del sonar usado para detectar submarinos tanto por barcos de superficie como por otros submarinos.

Directional hydrophones

A single cylindrical ceramic transducer can achieve almost perfect omnidirectional reception. Directional hydrophones improve sensitivity in one direction using basically two techniques:

Reflector

This method uses a single transducer element with a cone-shaped acoustic reflector or disc to further focus the signals. This type of hydrophone can be made from inexpensive omnidirectional hydrophones, but must be used stationary, since the reflector prevents its movement through the water.

Matrices

Several hydrophones can be mounted in a cluster so that they can add signals in one direction while canceling out in others.

Uses

Geophysics

Hydrophones are used by geologists and geophysicists for the detection of seismic energy.

Military uses

There are hydrophones capable of detecting an enemy submarine from a distance. There are several listening networks such as the SOSUS network or the Azorian project.