  Acoustic neutrino detection is a promising approach to instrument the large
detector volumes needed for the detection of the small neutrino fluxes expected
at ultra-high energies (E > 1 EeV). We report on several studies investigating
the feasibility of such an acoustic detector. High-precision lab measurements
using laser and proton beams aiming at the verification of the thermo-acoustic
model have been performed. Different types of acoustic sensors have been
developed and characterized. An autonomous acoustic system, attached to the
ANTARES prototype string "Line0", has been deployed and operated successfully
at 2400 m depth, allowing for in-situ studies of the acoustic background in the
Mediterranean Sea.
