EVALUATION OF THE ATTENUATION OF BROAD-BAND SOUND BY A NON-UNIFORM STILL ATMOSPHERE

This Item provides a means of estimating the attenuation of sound across a frequency band, referred to as band attenuation, by the atmosphere in which the temperature and relative humidity vary along the propagation path. The band attenuation rate is estimated by integrating the discrete frequency attenuation over the appropriate frequency range. Values of discrete frequency attenuation are found using Item No. 78002 which is based on the prediction method given in Derivation 1. Allowance is made for spectrum shape, and guidance is given on the use of a layering technique for the estimation of attenuation when atmospheric properties vary with altitude. The atmospheric layering technique should be used only, when the variation of the atmospheric parameters with altitude is known with sufficient confidence to enable the division of the atmosphere into layers within which temperature and relative humidity vary linearly with altitude. When considering horizontal propagation of sound where the temperature and relative humidity vary along the propagation path, the suggested layering technique can be used by substituting linear distance for altitude. In this case any change in pressure between the layers due to variations in temperature is extremely small and should be neglected. A numerical method for the estimation of the band atmospheric attenuation rate, assuming an ideal filter shape, is given as the recommended prediction procedure. Listings of the programmed method in both Basic and Fortran are provided. To enable a rapid estimate of the one-third octave band atmospheric attenuation rate to be made, an alternative graphical procedure is provided in Appendix A. A typical application is the correction of aircraft noise measurements to standard atmospheric conditions. (Copyright (c) Engineering Sciences Data Unit Ltd, 1978.)

  • Supplemental Notes:
    • For information on availability of series, sub-series, and other individual data items, write NTIS, Attn: ESDU, Springfield, VA. 22161.
  • Corporate Authors:

    Engineering Sciences Data Unit Limited

    251-259 Regent Street
    London W1R 7AD,   England 
  • Publication Date: 1978

Media Info

  • Pagination: 65 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00305058
  • Record Type: Publication
  • Source Agency: National Technical Information Service
  • Report/Paper Numbers: ISBN-0-85679-228-4
  • Files: TRIS
  • Created Date: Feb 11 1980 12:00AM