Research of Ultrasonic Suppression of Recording Devices

The article discusses the main types of dictaphone suppressors to protect acoustic information. The physics of the propagation of ultrasonic waves and their effect on electronic devices for secretly obtaining information are described. A prototype of an ultrasonic suppressor of cellular phones and voice recorders was developed, the limits of applicability of this device were determined. The dependence of the efficiency of suppression on the distance between the radiators is investigated. Circuit solutions are presented with the rationale for the proposed approaches, as well as the optimal signal for noise suppressed devices. Experimental measurements were carried out for a number of typical recording devices and appropriate conclusions were made.