Noise is one of the most effective exogenous factors affecting the processing mechanisms of the human brain, which has a major role in the occurrence of human error and occupational accidents. Low frequency noise is usually produced by sources such as ventilation systems, pumps, compressors, diesel engines and gas turbines, and so on. For this reason, the sound is in addition to industrial environments such as control rooms, in residential, office, etc., and compared to high-frequency sounds, low frequency sound is less attention and the rules associated with its control Not satisfactory Low-frequency sound is one of the most important sources of sound-producing in the environment, and it is even annoying at low levels and affecting the cognitive function of individuals. These sounds are seen in both industrial and public environments. Because the levels of exposure to this sound are usually not very high, it does not attract much attention. Some of the individual differences, such as superiority, extroversion, neuroticism, and audible sensitivity, can reduce or increase the effect of sound on cognitive functions. The purpose of this study was to investigate the effect of handicapping on cognitive functions in the presence of low frequency noise.
The present study is an interventional type. The research population was Hamedan University of Medical Sciences students. 120 of them were selected through purposeful sampling (40 right, 40 doubly capable and 40 lepers). All tests were carried out at the Faculty of Health of Hamedan University of Medical Sciences in a room with acoustic and physical control in March 2012. The conditions for entry to the study include: Being between the ages of 20 and 30 years, not taking any drug that reduces the level of consciousness during the test, no color blindness, hearing loss (hearing loss below 25 dB), lack of background Cardiovascular disease, respiratory problems, and sleep disorders. In order to eliminate the interfering factors, an audiometric test was conducted at the Faculty of Health and Ishihara Blind test. Individual information and medical records were collected by a questionnaire and, if they did not have the criteria for entering the study, were removed from the community under study. After the final selection of eligible individuals, all tests were fully explained to the subjects. It should be noted that all the subjects participating in this study were verbally and oral.Chapman's hand-breaking questionnaire was used to determine the supreme hand. By simulating the real environment of each subject, exposure to high-frequency audibility in the industry (45 and 65dB) was exposed for 40 minutes. The environmental conditions were maintained under thermal comfort conditions, with an equivalent temperature of 18 ° C and a relative humidity of 50%, without constant disturbance of air flow. Also, with 500 lux and fluorescent lamps, the brightness level of the surfaces was well maintained and maintained during all experiments. In this study, the recorded sound of the industrial air conditioning system was used in the work environment using the Cool Edit Program In the desired frequency band, it was edited. This program is a powerful software for producing sound at different frequencies, especially low-frequency noise. When playing sound, the level of sound pressure level was measured at the ears of the subjects tested and sitting. The benchmark used in the SVANTEK research is the 971-based Polish-American company, which operates according to the IEC 61672 standard, which has the ability to analyze 1.1 and one-third of the octave band. Spherical shaped speakers with a SWA-100 amplifier to amplify low-frequency noise that produces similar sound to the work environment. And during exposure to IVA PLUS CPT, the cognitive functions (reaction time, attention, balance, concentration, and processing speed) of the subjects were examined. The cognitive performance tests lasted 10 minutes, from the minute 30 to 40 people responded. After the implementation of each step, the groups changed to eliminate the effect of the exposure sequence, and the interval between each experiment was 24 hours in order to prevent cumulative fatigue at the second level. Data were analyzed using SPSS v.20 software, Kruskal-Wallis test and variance analysis.
The mean age of the subjects was 23.94 with a standard deviation of 3.35. The distribution of the tested subjects was only male, 85% of them were single and the rest were married. Most of the participants in the study were from health sciences and 80% of them were undergraduate. The results showed that there is a significant difference between cognitive functions of individuals with increasing voice level from 45 to 65 dB. Also, there is a significant difference between the components of cognitive function and hand holding (p <0.05), so that the right subjects of the components Better cognitive listening, and leftover subjects had better visual cognitive components than others, and the two-way performance was higher at the higher level than the other two groups (p <0.05).
The results of this study indicate that there is a significant relationship between side advantage and cognitive functions, thus, it was observed that during exposure to voice in leftover subjects, visual components of cognitive functions are more than right ones. Voice is effective on the mental activity of individuals, so that the differences between the components of cognitive functions when exposed to two levels of sound 45 and 65 dB with sound are quite obvious. According to the findings of this study, it can be concluded that by increasing the level of sound from 45 to 65 dB, the low-frequency sound (the intensities in the industry) can improve the cognitive functions in all three groups (right hand, left hand and two-way power). Slowly In the meanwhile, the performance of the two shafts is higher than the right-handed and left-handed ones. The results of this study indicate that exposure to low frequency noise was effective in the components of the cognitive functions of participants, and there was a significant relationship between the increase in noise and cognitive function components with hand holding. During the exposure to sound, the two sides had higher components of cognitive function. Accordingly, in work posts and sensitive occupational tasks requiring the use of cognitive functions, the effect of handicapping should be considered.
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