  Prompted by intriguing events observed in certain particle-physics searches
for rare events, we study light and acoustic emission simultaneously in some
inorganic scintillators subject to mechanical stress. We observe
mechanoluminescence in ${Bi}_4{Ge}_{3}{O}_{12}$, ${CdWO}_{4}$ and ${ZnWO}_{4}$,
in various mechanical configurations at room temperature and ambient pressure.
We analyze how the light emission is correlated to acoustic emission during
fracture. For ${Bi}_4{Ge}_{3}{O}_{12}$, we set a lower bound on the energy of
the emitted light, and deduce that the fraction of elastic energy converted to
light is at least $3 \times 10^{-5}$.
