Primary sources of acoustic fluctuations are mechanical oscillatory systems, for example organs of speech of the person, and secondary - converters of various type, including electro-acoustic. The last represent the devices intended for transformation of acoustic fluctuations in electric and back. Piezoelements, microphones, phones, loudspeakers and other devices concern to them.
For receiving the generator calibrated on noise level use the special rustling vacuum diodes. The spectral density of power of the generated noise is proportional to anode current of the diode. Noise diodes of two types 2DZB and 2D2S were widely adopted. The first generates noise to a strip to 30 MHz, and the second - to 600 MHz. The schematic diagram of the generator of noise is given in the rustling vacuum diodes on rice
For obtaining real efficiency it is necessary to consider existence in the car of windows which cannot be replaced with the equivalent steel screen. Therefore it is necessary to calculate efficiency of shielding of the equivalent glass screen.
Thus, if the malefactor has at the order of 3 statistically independent channels with verbal legibility 2, at data processing received from these channels he will possess information with legibility 0,4
Physical essence electromagnetic the considered from the point of view of the theory of an field and the theory of electric chains, to that under the influence of a source of energy on the party of the screen turned to a source, there are charges, and in its walls - currents, fields in external space on intensity are close to a source field, and in the direction are opposite to it and therefore there is mutual compensation of fields.
The simplest method of receiving white noise is use of the rustling electronic elements (lamps, transistors, various the diode with strengthening of tension of noise. The schematic diagram of the simple generator of noise is provided on rice
Reflection of electromagnetic energy is caused by discrepancy of wave characteristics of dielectric within which the screen, and screen material is located. Than more this discrepancy, the wave resistance of the screen and dielectric, the more intensively partial effect of shielding determined by reflection of electromagnetic waves more.
Project purpose: definition and consideration of technical channels of information leakage from salon of the car, calculation of methods of counteraction to information leakage, the analysis of the obtained data and identification of the most expedient means of protection of the protected information.
The intercepted speech message contains the number of correctly understood words sufficient only for drawing up the short reference summary reflecting a subject, a problem, the purpose and the general sense of the intercepted conversation;
For increase of efficiency of shielding of salon possibly car case inside covering thin layer of aluminum. Thus we receive the multilayered screen which efficiency of shielding is calculated on a formula:
For engineering calculations use the simplified expressions received in the analysis of many designs of screens of different function. Let's calculate efficiency of shielding of the car without use of additional resources.