Top plots: velocity profiles of simulated hydrodynamic shocks plotted versus linear depths under the quiet Sun (QS) photosphere for different times after beam injection (panel a) and versus time after the beam onset for different linear depths in the solar interior under the QS photosphere (panel b). Zero in the X-axis indicates the position of the QS photosphere, positive height is above and negative height is below the QS photosphere. The horizontal dashed lines in panel b represent the sound speed at 0.1, 0.5, 1 and 2 Mm. Bottom plot: distributions over depth z in the solar interior of a model acoustic cut-off frequency (top) and a sound speed (bottom) taken from Chirstensen-Dalsgaard’s model S (Christensen-Dalsgaard et al. 1996).