Last fall I bought a Fab Echo pedal to liven up my Pignose 7-100. Recently I was playing through them, and the pedal started to emit a warbling noise that sounded just like a '50s-era "flying saucer" sound effect. My wife even called upstairs to make sure I was OK, and not getting probed. I removed the 9v battery and tested it with my multimeter: 6.2v. When I installed a fresh battery in the pedal, the noise was gone. Is that what the Fab Echo does when its battery is running low?