◆ SpookStack

Approved For rei eoododett : CIA-RDP96-00788R001300020001-6 S$T-CS-01-169-72 July 1972 3. (U) Alekseyev and Suvarov (265) studied the speed and intensity of acoustic and visual reactions in subjects exposed to noise from thirty minutes to four hours. Using 70 to 90 db noise intensities in a soundproof chamber, the investigators recorded vocal and motor reaction response times after varying exposure durations. Prolonged (3-4 hour) testing at either db level caused fatigue of. the central nervous system, reduced effective response, and disturbed relation- ships between motor responses and strength of stimulus. Noise of 70 db produced no essential changes in responses within the first hour of testing, while 90 db noise caused changes in vision dependent reactions and slowing of reaction times. 4. (U) Strakhov (267) has investigated the effect of high intensity noise (95-100 db, 1500-3000 Hz) on EEG pattems. In human subjects a gradually increasing desynchronization of cortical rhythms was noted together with the appearance of slow waves. In rabbits and cats, both desynchronized and synchronized rhythms occurred. The general character of noise induced changes, the considerable after effect of noise, accompanying changes in respiratory function, and the presence of a cardiovascular reaction suggested that subcortical brain structures (especially the reticular formation of the medulla oblongata) were primarily responsible for the genesis and development of these changes. This hypothesis was confirmed by electrophysio~ logical studies with potentials taken directly from subcortical structures. In addition, histological examination showed pronounced changes in medullary nerve cells. In a later report (267), Strakhov reported that a generalized alpha rhythm depression develops during a period of several minutes as a result of exposure to 95-100 db noise, but that if photic stimulation were applied at the beginning of the noise, alpha rhythm bursts appeared which weakened, then completely disappeared as the noise action continued. Discontinuation of the noise first brought about new bursts of alpha rhythm in response to photic stimulation, and subsequently led to its complete restoration. The administration of scopolamine delayed the development of the changes. The results were regarded to be due to development of an inhibitory state in the cerebral cortex due to the activation by noise of the reticular structures of the inferior parts of the brain stem and the release of inhibitory mechanisms of the nonspecific thalamus. Other EEG work has been reported by Korzh (268) and by Doroshenko et al (269). 5. (U) On a more subjective psychological level, Vogel (270), classifies effects into three categories: gross, annoyance, and subtle, arranged roughly according to decreasing sound intensity. Subtle involves sounds used to instill fear, anxiety, confusion, panic, etc., examples of which would be the bugles played by 94 UNCLASSIFIED