Sound propagation in a turbulent atmosphere near the ground: an approach based on the spectral representation of refractive-index fluctuations.
A new, rigorous approach is presented for the computation of the fluctuating field of a monopole source in a nonrefracting, turbulent atmosphere above a ground surface. The time-averaged sound pressure level is considered, as well as statistical distributions of the sound pressure level. The computation is based on the Rytov solution of the wave equation for a turbulent medium, evaluated for the half-space above the ground surface. The solution takes into account the ground reflection of scattered waves, which has been neglected in previous work on this subject. The present approach is based on a Fourier-Stieltjes representation of refractive-index fluctuations, and makes use of a turbulent image atmosphere to account for the ground reflection of scattered waves. This approach is rigorous only for a rigid ground surface, but it is shown that it also yields a good approximation for a finite-impedance ground surface. The accuracy of the solution is demonstrated by comparison with results of numerical computations with the parabolic equation method for a turbulent atmosphere. The assumption of a nonrefracting atmosphere implies that direct application of the solution is limited to propagation over relatively small distances. However, this study can also be considered as a basis for a generalized solution for a downward refracting atmosphere, which can be applied for larger propagation distances.
Salomons
E M
EM
TNO Institute of Applied Physics, Delft, The Netherlands. salomons@tpd.tno.nl
Ostashev
V E
VE
Clifford
S F
SF
Lataitis
R J
RJ