Absorption of acoustic energy by plant leaves

Abstract

We investigated the vibration of leaves of four plant species in a sound field using a laser-Doppler-vibrometer system. All leaves behave as linear mechanical systems when driven by sound and noise at sound pressure levels (SPL) of up to 100 dB re 20 μPa. The modes of vibration are complex in the investigated frequencies (0.5-5.5 kHz), and change with the orientation of the leaf in the sound field. The vibration velocities of the leaves varied between 10–5 and 3 X 10–4 m/s, while the vibration velocity of the air particles is 5 X 10–3m/s at 100 dB SPL. Although the amount of sound energy absorbed in this way by a single leaf is very small, this mechanism may anyhow contribute to sound attenuation by plants and plant communities, since the number of leaves of one fullgrown tree equals 2 X105. © 1981, Acoustical Society of America. All rights reserved.