  The acoustic neutrino detection technique is a promising approach for future
large-scale detectors with the aim of measuring the small expected flux of
neutrinos at energies in the EeV-range and above. The technique is based on the
thermo-acoustic model, which implies that the energy deposition by a particle
cascade - resulting from a neutrino interaction in a medium with suitable
thermal and acoustic properties - leads to a local heating and a subsequent
characteristic pressure pulse that propagates in the surrounding medium.
Current or recent test setups for acoustic neutrino detection have either been
add-ons to optical neutrino telescopes or have been using acoustic arrays built
for other purposes, typically for military use. While these arrays have been
too small to derive competitive limits on neutrino fluxes, they allowed for
detailed studies of the experimental technique. With the advent of the research
infrastructure KM3NeT in the Mediterranean Sea, new possibilities will arise
for acoustic neutrino detection. In this article, results from the "first
generation" of acoustic arrays will be summarized and implications for the
future of acoustic neutrino detection will be discussed.
