As the world turns...
Central offices get quieter and quieter.
In days of old (I visited COs in the early 80's) there was a low level din of switching going on. Much was mechanical with relays and all that. It is now being replaced with smaller and smaller kit as the days go on. The only noise you get is the blowing air of the fans and the 60 (50) Hz hum of the power supplies in the back room, or the high pitched whine of the switchers being run from the -48 volt buss that is everywhere.
Of course the BIG NOISE is the gas powered turbine for standby power, but you don't expect that too often (it is in a separate room anyway).
Life goes on, but I really miss the step-by-step exchanges where you could SEE how a telephone call worked. Now days all you can do is say it came in from over there, and it goes out over yonder. Not very instructive.
Time marches on...