Ultrasonic Ears

Hello,

Is it possible to hear an electric motor in ultrasonic frequencies? I remember seeing somewhere that motors and gears are VERY noisy at the ultrasonic level, but I am not sure. If so, can you make two separate bat detector circuits, put the two microphones facing opposite directions and be able to "hear" a motor spinning for a significant distance...and tell the direction?

Does this sound feasible, or would I just be waisting my time?

Thanks,

George L.

A simple heterodyneing process might work. Figure out how to make a set of headphones that play back a 50khz sine wave and place them directly over the ear. Any sound entering the ear canal where the 50khz wave should mix with it and heterodyne allowing you to hear between 50 and 70khz or so. A wider frequency range would require frequency compressors of some kind, though I don't know how to approach.