  Already more than 30 years ago the acoustic particle detection method has
been considered to be one possibility to measure signals from ultra-high
energetic neutrinos. The present status and problems of corresponding model
predictions are discussed in comparison with existing experimental
measurements. Available acoustic sensors and transmitters are described and new
ideas for corresponding applications are mentioned. Different methods for
in-situ calibrations are discussed. Results of measurements of acoustic test
arrays at different sites are presented in some detail. Future activities for
applications of the technology in large size detectors are evaluated.
