Abstract: A piezoelectric hydrophone is designed with overload protectors (1a, 11a, 11b) which protects the hydrophone against internal and external overpressures. The hydrophone assembly proper and a first overload protector (1a) are made in one piece, while other overload protectors (11a, 11b) are mounted outside the hydrophone assembly (1) above the pressure sensitive diaphragms (4a, 4b).The separate metallic parts of the hydrophone are joined by means of laser welding which may be performed in a pressure chamber. Likewise the final sealing of the hydrophone assembly may take place in a pressure chamber under a pressure corresponding to the water depth at which the hydrophone is operated.