  We report new results obtained in calibrations of superheated liquid droplet
detectors used in dark matter searches with different radiation sources
(n,$\alpha$,$\gamma$). In particular, detectors were spiked with alpha-emitters
located inside and outside the droplets. It is shown that the responses are
different, depending on whether alpha particles or recoil nuclei create the
signals. The energy thresholds for $\alpha$-emitters are compared with test
beam measurements using mono-energetic neutrons, as well as with theoretical
predictions. Finally a model is presented which describes how the observed
intensities of particle induced acoustic signals can be related to the dynamics
of bubble growth in superheated liquids. An improved understanding of the
bubble dynamics is an important first step in obtaining better discrimination
between particle types interacting in detectors of this kind.
