An analysis is made of thermal fluctuations on the premelting exotherm
ics of materials with different types of chemical bond (KCI, Ge, Sb, a
nd Cu). Statistical and spectral parameters of the thermal fluctuation
s are introduced. It is shown that for these materials under certain c
onditions the thermal fluctuations may be identified as two-level ther
mal flicker noise. (C) 1998 American Institute of Physics.