A single reverberation-time number is the first thing every acoustics brief asks for, and it is also the easiest number to hit while still getting the room wrong.
RT60 describes how long sound takes to decay by 60 decibels, averaged across the room. It says nothing about where the early reflections arrive, whether they arrive from a useful direction, or whether a handful of parallel surfaces are quietly building a flutter echo underneath a perfectly respectable average. We have measured rooms with textbook RT60 figures that still sound wrong the moment you clap your hands in them, because the problem was never really about decay time — it was about the first thirty milliseconds.
The fix is not a better single number. It is looking at the actual arrival pattern — the same kind of plot our room simulator draws on the homepage — rather than trusting a summary statistic to stand in for the whole shape of a room’s response.