A moving medium shifts sound speed, and speed gradients bend waves by refraction

Evidence

Motion of medium. Last, if in some region the messengers are moving en masse in the same direction, the wave propagates slower or faster (over the ground) according to whether it is moving with or against the mass movement. This will speed up or slow down the wave arrival merely by a fraction, except if the speed variation differs from place to place, in which case the variations also cause refraction of the waves. — Eric J. Heller, Why You Hear What You Hear- An…, 176

Categorization

• XREF: Connects to why sound carries downwind (or upwind) differently outdoors — ties to the reader’s earlier noise/soundscape reading about wind affecting how far noise travels.