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\subsection{First Sound}  For first sound it can be seen from figure 3 that there is a slow decrease in $C_1$ from T=0 onward except at the $\lambda$ point where there is a acusp due to theromodynamic behovior close to a transition temperature [1]. First sound also experiences attenuation peaks at $T_\lambda$ and near 1 K.   \subsection{Second Sound}  The second sound mode is special to the superfluid state of helium 4 in that its a propagating temperature and entropy wave, different from normal liquids where waves are diffuse. Here the normal fluid and superfluid move in opposite directions so that $J=0$ so $v_s=-(\frac{\rho_n}{\rho_s})v_n$ Second sound can be detected using a transducer with small pores in it where only the superfluid component, having zero viscosity, can move through the pores.