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INTRODUCTION NOISE is an unwanted sound that is detrimental to our auditory system. Low frequency noise (LFN) which is also called infrasound has a frequency range between 10 Hz to 500 Hz. One such disease that is caused due to long term exposure of LFN is vibroacoustic disease (VAD). Excessive exposure to LFN results in abnormal growth of extracellular matrices (collagen and elastic )which may thickens blood vessels and hence less blood flow to the brain which may cause dizziness,vertigo, headaches, depression, lack of concentration, unusual tiredness, disturbed sleep etc. VAD is generally prevalent among workers where they are exposed to LFN for example:-restaurant workers, disc jockeys, aircraft technicians ,military pilots, commercial pilots, cabin-crew members and recently among employees working at metro stations. Pressure in eardrum increases due to LFN which results in unpleasant sensations in the ear and thus affects the auditory system. Greater the time of exposure to LFN greater will be the severity of the symptoms of VAD. A recent study also reported that VAD also had an adverse effect on voice and may also lead to throat infection due to presence of LFN which lead to the vocal abuse (Branco et al., 2002). Aim: Present study aims to identify the effect of LFN on voice, hearing and human body metabolism. METHODS: PARTICIPANTS A total of 40 male participants with minimum of 5 years working experience were included in present , 20 were working in LFN situation with age range of 18-54 years(mean age of 36.5 years) and other 20 age matched subjects were working in non-noisy situation with age range of 21-50 years (mean age of 38.2 years ) . Participants with psychological, behavioural and neurological issues were excluded from the study. TOOLS AND INSTRUMENT To find out the complete profile of VAD complete case history was taken which includes the information regarding the duration of work, exposure to noise per day, presence of tinnitus, vertigo, nausea and other health related issues. A pure tone audiometry was done using Elkon Audiometer. To identify the effect of LFN on voice, acoustic analysis was done using PRAAT software and Perceptual analysis was done using Buffallo III voice profile. To assess the effect of voice impairment on quality of life “Voice related quality of life (VRQOL)” was assessed. Phonation duration and s/z ratio was also calculated as aerodynamic measure of voice. Blood pressure and cardiac rate was also measured using Omron HEM 7113. Hamilton anxiety rating scale was also assessed to find out the level of anxiety due to noise exposure. RESULT The subjects used to work on an average 10 hours per day in noisy situation. Noise level was approximately 85 dBA which was measured using SLM. All participants had high Blood Pressure (i.e. mean systolic B.P = 134.95, mean diastolic = 85.9). On Pure Tone Audiometry all participants had high frequency hearing loss. However only 3 participants had a notch at 4KHz. On vocal profile most of all the subjects were not able to produced |z| and their s/z ratio was more than 1.04 which is indicative of vocal pathology. On acoustic analysis, significant difference was observed at Jitter local (p = 0.02). On VRQOL , average 14.41 score was obtained which is indicative of “a small amount of adverse effect on quality of life”. We also observed that prolonged exposure of LFN was directly correlated with the amount of hearing loss and voice impairment. CONCLUSION From present study, we can conclude that LFN had an adverse effect on human metabolism, hearing level and voice. This is preliminary study and to understand the effect of LFN on human body, we need more detailed and extensive studies.
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