Time-distance diagrams of (a) the perturbed hydrodynamic wave energy flux parallel to the magnetic field along field line 3 at an azimuthal slice φ = 0 for the driven simulation and (b) the total hydrodynamic wave energy flux along field line 1 for the undriven simulation. In both plots the transition region (T = 40 000 K) is denoted by the grey contour whereas the green contour outlines the β = 1 layer. The local sound speed (dashed line) and local Alfvén speed (dotted line) are also plotted on each field line.