Propagation of sound in water. A molecular-dynamics study

TLDR: In this paper, a system of 216 water molecules, studied by molecular dynamics at 1 g and 10 g, was found to exhibit a secondary maximum at a much higher frequency than the normal frequency of sound propagation and it was suggested that experiments should be directed to the region of this "high-frequency sound."

Abstract: Fluctuation phenomena occurring in a system of 216 water molecules, studied by molecular dynamics at 1 g ${\mathrm{cm}}^{\ensuremath{-}3}$ and 10 \ifmmode^\circ\else\textdegree\fi{}C, indicate that (i) transverse currents persist in the form of propagating collective coordinates even for a wavelength of about 20 \AA{}, with indications that the same will happen for much longer wavelengths. The velocity of propagation is 1.05 \ifmmode\times\else\texttimes\fi{} ${10}^{5}$ cm ${\mathrm{sec}}^{\ensuremath{-}1}$. In the region of 20 \AA{} the lifetime of the fluctuation appears to increase linearly with increasing wavelength. (ii) Density fluctuations at 20 \AA{} are found to be propagating but only marginally; the corresponding velocity of sound is 1.8 \ifmmode\times\else\texttimes\fi{} ${10}^{5}$ cm ${\mathrm{sec}}^{\ensuremath{-}1}$. (iii) The spectrum of density fluctuations exhibits a secondary maximum at a much higher frequency than the normal frequency of sound propagation and it is suggested that experiments should be directed to the region of this "high-frequency sound."