Anyone watching a wood cutter in the distance should recognize that the sound of chopping arrives slower than the sight of the chopping.
Would this speed of sound delay affect Hermetic spells?
eg listening to distant whispers?
Projecting your voice into another's hearing?
Rego can move people, animals and things instantly or - biblically speaking - in the blink of an eye. See e. g. ArM5 p.134 box Rego Corpus Guidelines, TME p. 107 box New Guidelines for Instant Transportation (with the relevant errata for some levels) and TME p.108ff Travel in the Blink of an Eye. There is even an option for troupes wishing to limit this instantaneity in p.106 box Optional Rule: Limits on Instant Transportation.
But barring the use of that optional rule, also magically transporting images and species could be instantaneous.
Anyway, Peripatetics knew of the different speed at which sound travels through different material, and the different changes of pitch this does cause. This is analyzed in De Audibilibus. a text surviving only as fragments in a commentary from Porphyry, namely his Commentary on Ptolemy's Harmonics. See here for a quick analysis.
Interesting question regarding voice range- being able to react when you see them casting before the sound of their voice arrives. Not much time, but...