The propeller of the little 9-row airplane that flies from Phoenix to Flagstaff Arizona hums low, the fan warbles at a mid-range pitch, and then the whole plane shakes like the butt-kickers at the IMAX theater as we take off.

As we rise higher, the puddle-jumper thrums a pumping pulse about 60 beats/minutes until it levels out at a steady higher pitch. Then the overhead compartments rattle and buzz loudly. Quite a drum set.

After the plane lands, all the phones make their little startup calls. Unlike birds, they’re not talking to each other.