Some shield simply to prevent advanced hacking.  Others feel weapons or surveillance systems are targeting them.  Others feel something is communicating with their body or brain.

Shielding is the activity or material which protects an area from electric or magnetic fields.

There are three primary ways in which things can reach or affect your safe space.  One or all of these may be affecting you:

* Electric fields and high-frequency electromagnetic radiation

* Magnetic fields and low-frequency electromagnetic radiation

* Sound and physical vibrations (may be inaudible)

To learn more, pursue classes in physics, electronics engineering, and electromagnetic compatibility.

Most information is transmitted by electric fields and high-frequency electromagnetic radiation nowadays.  This covers light and microwaves.  It is blocked by covering an area in continuous conductive material, with no holes or gaps of any sort, not even seams.