I'm setting in Frisco, and have been monitoring Plano on the SDR radios after the Collin County P25 Simulcast goes quiet from the days' testing. I don't know the normal volume, but I'm certainly seeing quiet periods on the system (the nice thing about the SDR is I can see all the channels light up, even if I'm only getting audio for 1 or 2). As I type this (22:20 CDT, Friday night) I'm only seeing 3 or 4 concurrent conversations max, and several are encrypted (Plano NCIC seems to be really active right now, but I don't see anything on the talkaround groups at the moment).