Accurate FFT-based hankel transforms for predictions of outdoor sound propagation
✍ Scribed by T.L. Richards; K. Attenborough
- Publisher
- Elsevier Science
- Year
- 1986
- Tongue
- English
- Weight
- 593 KB
- Volume
- 109
- Category
- Article
- ISSN
- 0022-460X
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✦ Synopsis
Without modification, the FFT-based Hankel Transform that is used in the Fast Field Program developed for applications in underwater acoustics, is not sufficiently accurate for predictions of outdoor sound propagation near to finite impedance boundaries. Numerical problems arise from singularities in the integrand and from representation of an infinite integral by a finite sum. Modifications to the basic algorithm are proposed to improve its accuracy. These modifications include integration below the real axis, subtraction of an analytic function and, addition of terms to represent the ditterence between the finite sum and the sum to infinity. Predictions of the modified algorithm of propagation in a calm, isothermal atmosphere from a point source near to a boundary are compared both with those of the unmodified algorithm and with exact solutions or analytic approximatio.ns.