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\begin{itemize}  \item No! They are measuring different things. Payam's $t_{\rm h}$ is considering the diffusion of momentum information about a particle (I think this is the characteristic time in the decay of the velocity autocorrelation). My $t_{\rm h}$ is about pure information flow.  \item Some reading about propagation of hydrodynamic information: information:\\  \citet{1995PhyA..214..185E},  \citet{Espanol_Rubio_Zuniga_1995} for evidence of sound-wave propagation;   \citet{Clercx_1997}; propagation;\\   \citet{Clercx_1997};\\  \citet{Kao_Yodh_Pine_1993} for high-speed experiment; experiment;\\  \citet{nderson_Mitchell_Bartlett_2002} describe an experiment where sonic communication is observed.  \item Sound speed shouldn't depend on viscosity at except for near-supersonic flow. (\href{http://iopscience.iop.org/0370-1301/66/5/303/pdf/0370-1301_66_5_303.pdf}{Or does it?} \href{http://www.engineeringtoolbox.com/sound-speed-water-d_598.html}{Speed of sound table}, \href{http://resource.npl.co.uk/acoustics/techguides/soundpurewater/content.html#LUBBERS}{$c(T,P)$ fits}.)