Hum (recorded at home).
Around 50 Hz (recorded at home).
These pulses is made by my watch at 1,5 mt.
This noise is made by my PC monitor at 10 mt. In the center-left the monitor was off.
This picture (center) show the noise made by a little DC motor (at 4 mt).
This is the signal made by my cordless phone (DECT 1.8 GHz at 3 mt).
Traces made by two cars at 30 mt.