perturbations in sound speed (temperature), magnetic field (fast wave speed), and flow (doppler shift). Flow is isolated by contrasting travel times between two points in opposite directions. There is no background flow in our simulations.

However, phase shifts are also produced by wave reflection and mode conversion [@Cal09aa; @TraKauBri03aa]. It is a difficult (and inexact) task to theoretically determine shifts due to a single mode conversion process, but our modelled system consists of several occurring sequentially. It is further complicated by the shallow wave generation layer that excites both acoustic and magnetic waves directly, thereby differing from the model of @CalGoo08aa where care was taken to inject only acoustic waves from the bottom of the computational region [ (see Section \[sec:BVP\])]{}. The stochastic driving layer is however more solar-relevant, and so is of more practical relevance.

To enumerate, the mode transmissions/conversions consist of: fast-to-slow (acoustic) transmission at $a=c$; the resulting slow wave may then either escape upward or be reflected by the acoustic cutoff, depending on frequency and magnetic field inclination; the converted fast wave continues upward to be reflected near where its horizontal phase speed matches the Alfvén speed; conversion to upgoing and downgoing Alfvén waves occurs near this 