Statistical estimates of the influence of the source divergence angle on the characteristics of acoustic radiation transmitted through the atmosphere

The method of statistical simulation (Monte Carlo) is used for the first time to study the influence of the angular source divergence on the characteristics of transmitted acoustic radiation with allowance for the multiple scattering contribution. Results of calculations for a point source of unit power with divergence angles φ = 5, 10, 15, 20, and 25° at frequencies F = 1, 2, 3, and 4 kHz are presented for the outer scale of turbulence L ₀ = 10, 15, 20, 40, 60, and 80 m. It is established that for F = 2 kHz the multiple scattering contribution to the transmitted radiation intensity increases with the outer scale of turbulence from ∼10% (for L ₀ = 10 m) to 90% (for L ₀ = 60 m); for L ₀ = 80 m, the transmitted radiation intensity is virtually completely determined by the contribution of multiple scattering. When the width of the source directivity pattern (2φ) increases from 10 to 50°, the intensity of transmitted acoustic radiation decreases by 96%. Based on the results of statistical simulation, analytical dependences of the transmitted radiation intensity on the sound source divergence angle are suggested for typical sodar frequencies.