Devices for Protection of Information from Interception.

When we talk acoustic waves propagate freely and reach the walls, windows, doors and other building structures. The most of wave's energy is reflected and absorbed. The rest of this energy creates the vibration in the building structure (f.e., in the wall) and is partly reradiated outside the room (see Figure 1). These processes can occur in all kinds of rooms and are the main reason of acoustic information leakage. Acoustic information can be intercepted by 'reading' from window glass, room partition walls, heating and water supply pipes. Sometimes such an interception doesn't need any special technical means. And if special equipment is used - interception is possible even through the main walls. The common and cheap 'folk' methods like loud music, water noise, etc. can't prevent interception if up-to-date technologies are used. If the espionage equipment is outside, even the fact of interception can't be established.

Building of an initially soundproof room is rather expensive. And if room was not initially soundproof, measures taken to improve these properties can cost a vast sum of money.

vibration of the Wall

But how do we prevent the leakage of information via acoustic and vibro-acoustic channels in another way?

The costs of interception prevention can be considerably reduced if the 'Active Protection' methods are used. 'Active Protection' method's main idea is to create an acoustic noise in all building constructions that can become the channels of acoustic information leakage.