Evaluation of sound perception and its cardiovascular implications

Abstract

Background: Sound is a vibration from a particular machine, place or material which can be heard clearly whereas noise is mixed vibrations that will come to us from all directions. A sound can be clear and heard but noise will not be clear and cannot be heard. Noise is a known stress that affects various physiological responses of individual exposed to it and its pollution is increasingly being recognized as a physical factor in the environment that is injurious to many aspects of our health. Aim: To assess the effects of environmental noise on sound perception and cardiovascular system of those exposed to noise over a period of time. Materials and Methods: The study group included 50 subjects from a noisy environment (≥80 dB). This group was further divided into group Ia (those that have developed Noise Induced Hearing Impairment) and group Ib (those without Noise Induced Hearing Impairment). The control group consists of 50 subjects from a non-noisy environment (≤60 dB). An audio-visual scale which was marked between 0 and 10 cm and calibrated for differing sound levels was used as a tool for the determination of sound perception. Heart rate and blood pressure was measured using digital sphygmomanometer at rest and after exposure to noise at 60 dB, 90 dB, and 102 dB for 5 minutes each. All data were expressed as mean ± SEM. All the results were analyzed using one-way ANOVA. P ≤ 0.05 was considered as statistically significant. Results/Discussion: Noise exposure over a period of time produced a cardio-protective mechanism against arterial blood pressure in group Ia but produced a very significantly high arterial blood pressure in sub-group Ib and control subjects. There was also a very poor sound perception among those that have developed noise-induced hearing impairment unlike in sub-group Ib and control. Conclusion: Environmental noise is a possible contributing factor in the development of high arterial blood pressure and significantly affects individual's sound perception.