Building an anti-Tempest Device

Tempest used to be a surveillance system back in the 80s where a laser would be shone onto the window of a house and the vibrations of the window measured by the return beam. By measuring the vibrations and with a clean line of sight, this method could be used to listen in on conversations at a distance. The same principle is used more-or less, give or take a laser beam, for long-range microphones that are capable of folding their vantage point in order to listen at long distances.

Countering a Tempest device or long range microphones is probably not an easy task, but one can for sure make the surveillance operation more difficult or annoying. One way to do that is to use a vibration speaker, a speaker that is advertised to turn any surface into a speaker through resonance, and to glue the speaker onto the window. Any voice taking place within the house will then invariably end up being mingled with the sounds played through the speaker, and if the laser is pointed at the window onto which the speaker is glued, then more than likely the vibrations will overcome any speech taking place within the house.

These speakers are easy to wire up, requiring only two leads, one for ground and the other for the signal, with the main features of the vibration speaker being the face plate opposed to a small aperture on the other side that will act together like a pump by pressing onto the surface that the speaker is placed upon.

For best results, some thin double-sided sticky tape can be used in order to temporarily attach the speaker to a window. The speaker should preferably be connected to an amplifier in order to counter any impedance mismatch between the device that will output the sound and the speaker. Ideally, all the windows should have one of these speakers.