  We show that when a drop of water is maintained in its Leidenfrost regime, a
sound in the form of periodic beats emits from the drop. The process of beat
emission involves two distinct frequencies. One component is the frequency of
beats itself and second is the frequency of sound in every beat which is
emitted when one oscillation in the drop occurs. Experiments have been
performed by placing a drop of water over a concave metallic surface and the
beats of the drop were recorded by fixing a microphone above the drop. A video
camera was also fixed above the drop to record its oscillations. Simple
analytical techniques like Fourier and wavelet transforms of the audio signals
and image processing of the videos of the drop have been used to gain insight
about mechanism of beat emission process. This analysis also helped us in
studying the dependence of frequencies, if any, on the radius of the drop and
the substrate temperature.
