SOUND-PROPAGATION THROUGH ATMOSPHERIC-TURBULENCE - MULTIFRACTAL PHASE FLUCTUATIONS

Phase fluctuations of sound propagating through turbulent air show frequency spectra following an F(-β) power law (β= const.) over several decades. This is consistent with a simple fractal description involving the dimension D = (5 — β)/2. However, many similar natural phenomena have been shown to be multifractal. Universal multifractals are characterized by two additional parameters: The Lévy index 0α2 for the type of multifractal and the codimension 0C1l for the intermittence. These parameters are a statistical measure of the nonlinear dynamics. Analysis of experimental data obtained at 5 kHz, range 4 m and wind speed 12 m/s is reported here and results indicate that phase fluctuations are “hard multifractal” (α>l). The actual estimate is near the limiting value α=2, which is consistent with Kolmogorov's lognormal model for turbulence. © 1995, Acoustical Society of America. All rights reserved.