  In this paper, we report the detection of amplitude modulation in a delta
Scuti star HD118660. We found that the p-mode frequency at 24.3837 c/d varies
periodically in amplitude with frequency 0.0558 c/d. However, all other modes
are stable in both amplitude and phase which is clear evidence of
non-conservation of visible pulsation mode energy. We constructed a
two-frequency model by superimposing two sinusoids with frequencies n1 =
24.3837 c/d and n2 = 24.4420 c/d and corresponding phases f1 = 0:5211 rad and
f2 = 0:9481 rad to mimic the observed variations of amplitude and phase with
time. The plausible explanation of the amplitude modulation in HD118660 is due
to beating of two unresolved closed frequencies n1 and n2.
