Well, I found the source of the false short ping readings. I had placed the 2 sensors 5 & 10 cm away from the Arduino Uno (with wav shield) on my pedestal. Something on the board emits a directional noise that the sensors heard and misreported the distance as short. When I moved the sensors 20 cm away and put a piece of wood between them and the computer, the noise no longer spoofed the Ping sensors. Thanks, everyone, for helping with suggestions. Tim - I am going to implement your new ping library next. I will post my results after testing.