  A promising approach to measure the expected low flux of cosmic neutrinos at
the highest energies (E > 1 EeV) is acoustic detection. There are different
in-situ test installations worldwide in water and ice to measure the acoustic
properties of the medium with regard to the feasibility of acoustic neutrino
detection. The parameters of interest include attenuation length, sound speed
profile, background noise level and transient backgrounds. The South Pole
Acoustic Test Setup (SPATS) has been deployed in the upper 500 m of drill holes
for the IceCube neutrino observatory at the geographic South Pole. In-situ
calibration of sensors under the combined influence of low temperature, high
ambient pressure, and ice-sensor acoustic coupling is difficult. We discuss
laboratory calibrations in water and ice. Two new laboratory facilities, the
Aachen Acoustic Laboratory (AAL) and the Wuppertal Water Tank Test Facility,
have been set up. They offer large volumes of bubble free ice (3 m^3) and water
(11 m^3) for the development, testing, and calibration of acoustic sensors.
Furthermore, these facilities allow for verification of the thermoacoustic
model of sound generation through energy deposition in the ice by a pulsed
laser. Results from laboratory measurements to disentangle the effects of the
different environmental influences and to test the thermoacoustic model are
presented.
