A-weighted sound pressure level calculation in the dissipative atmosphere

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Authors

  • Krystyna BEREZOWSKA-APOLINARSKA Institute of Acoustics, A. Mickiewicz University, Poland
  • Rufin MAKAREWICZ Institute of Acoustics, A. Mickiewicz University, Poland

Abstract

During propagation of sound in the atmosphere a certain fraction of acoustical energy is absorbed by air. Thus, acoustical pressure decreases exponentially with distance. The rate of this drop is expressed by coefficient a which depends on frequency and meteorological conditions. Absorption coefficient α(f) is approximated in this study by binominal function of frequency with two coefficients depending on temperature and relative humidity. The A-weighted sound pressure level is expressed by the function depending on parameters which describe absorption and the distance between the source and the point of observation. Thus the integration is substituted for summation over frequency. bands. Calculations are made and charts are drawn to show differences in A-weighted pressure level calculation which result from α(f) approximation by binominal function.

References

[1] American National Standards Institute, Methods for the calculation of the absorption of sound by the atmosphere, ANSI SI 26, New York 1978.

[2] American National Standards Institute, Specification for sound level meters, ANSI SI 4, New York 1983.

[3] H. E. BASS, L. C. SUTHERLAND, J. E. PIERCY, L. EVANS, Absorption of sound by the atmosphere, in: Physical Acoustics, [Ed.] W. P. Mason, 17, Academic Press, Orlando 1984.

[4] K. BEREZOWSKA-APOLINARSKA, J. JARZECKI, R. MAKAREWICZ, The effect of sound absorption by the air on noise propagation. Archives of Acoustics, 10, 3, 241 -252 (1985).

[5] I. S. GRADSHTEYN, I. M. RYZHIK, Table of Integrals, Series and products, Academic Press, New York 1980.

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