ABSTRACT
Laboratory measurements of sound propagation through vegetation have confirmed that vegetation behaves as a low pass filter giving attenuation between 2 and 8 kHz. Beneath mature trees, shrubs and hedges, fallen and decaying leaves have an important influence on the acoustical properties of ground. During measurements of sound transmission through 16 m tall red pine trees with mean trunk diameter 0.23 m and spacing 3.3 m it was that leaves falling from the red pine trees had created a 0.025 m deep layer of decaying foliage above the soil. D. E. Aylor measured sound transmission loss through dense corn, hemlock, red pine trees, hardwood brush and planted reeds in water and observed that the measured attenuation was greater than that attributable to viscous and thermal losses for a vegetation density. The amplitude of fluctuations in sound level caused by turbulence initially increases with increasing distance of propagation, sound frequency and strength of turbulence but it reach a limiting value.
