Effect of chronic and acute exposure to noise on physiological functions in man.

Physiological parameters have been compared in 75 normal healthy individuals exposed to occupational noise of 88-107 dB(A) (6-8h/day) for 10-15 years and in 36 normal non-exposed subjects. Blood pressure, both systolic (P less than 0.01) and diastolic (P less than 0.001), and heart rate (P less than 0.05) were found to be significantly higher in the exposed subjects. Irregularity in cardiac rhythm, both in amplitude and duration, was found in 18% of the exposed subjects as against 6% in the non-exposed group. Variation in the heart rate during acute noise exposure of 90 dB(A) has been shown to be related with the preponderance of tonicity of sympathetics and parasympathetics. Measurement of hand blood flow during the same exposure showed a lesser degree of vasoconstriction and a slower recovery rate in the exposed group. Altered observations in the exposed group could be attributed to changes in the mechanical property of blood vessels.