Absorption of Low-Frequency Sound Energy by Vegetation: A Laboratory Investigation

Many field research projects have been conducted to study the effects of natural foliage on the propagation and attenuation of sound. This research takes natural foliage into a controlled laboratory setting to test its low-frequency acoustic characteristics. Absorption of low-frequency components of unwanted noise is of interest to the Army, but has been an unsolved problem due in part to the cumbersome and expensive testing facilities needed to study long wavelengths. In this research, low-frequency absorption and reflection coefficients were found reliably and consistently. Due to study of the steady state conditions, the methods presented here could constitute a more consistent method than ever before. The procedures described in this paper can serve as a handbook for future research; recommendations are included. Prepared in collaboration with University of Illinois, Urbana, IL. The original document contains color images.