Acoustic neutrino detectors in water may complement the Cherenkov arrays now under construction (KM3NeT and Baikal) extending the sensitivity of such apparatuses to the Ultra high energy regime.
In such view the KM3NeT-Italia project has developed acoustic sensors and read-out electronics sensitive to micro-Pascal scale acoustic pulses in the range 5-70 kHz. Read-out and data transmission electronics is completely embedded in the Cherenkov detector one, making the array acoustic time synchronised with the Cherenkov one. The acoustic arrays streams the acoustic data flow continuously from all the sensors to shore. Each sensor has a standard and a high (+30 dB gain) to match three main field of science and technology: detector positioning system, bioacoustics and oceanography, study for acoustic neutrino detection.
The same hydrophone, with proper modifications of the front-end electronics, is used in the KM3NeT ARCA detector.
The first KM3NeT Italia tower-structure will be deployed in May 2016. The tower is composed by 14 floors, each being a 8 m long bar structure, vertically spaced by 20 m. Hydrophones are placed close to the end of each floor and one hydrophone is placed on the tower base at about 3 m from the seafloor. Results on system qualification, test and calibration will be presented together with first acoustic data from deep sea.