Gruppenhorchgerät

The Gruppenhorchgerät ('group listening device', abbreviated GHG) was a hydrophone array which was used on vessels of the German Kriegsmarine in World War II.

The individual receivers were mostly placed in the front part of the vessel along the hull sides to have enough distance from the screw and the noise they emitted.

The quartz crystals generate electric voltage depending on the pressure acting on it.

In collaboration with the Imperial German Navy, Atlas Werke AG in Bremen and Electroacustik (ELAC) in Kiel worked on piezoelectric transducers and the development of detectors and amplifiers in general.

These 48 low frequency signals were then routed to a switching matrix in the main unit.

The sonar operator could determine the ship's side and the exact direction of the sound source.