A room can be many things: a place to work, a place to talk, a place to sleep. The brief was a single unit that could stay polite to all three.
Quiet mode on the Heat-pump 12k runs at 27 dB(A). That is, by measurement, quieter than a library at midnight (30 dB) and quieter than a soft whisper at three metres (35 dB).
The trade-off is throughput: in Quiet mode, the indoor fan runs at 700 rpm, about half its Super-mode speed. Cooling is slower; the room takes ten or fifteen minutes longer to come down. The view from the start was that this is the right trade.
You do not need to slam the room to a temperature. You need to hold it there. Quiet mode is for the second hour of use, not the first.