Forest sound propagation depends on ground porosity, scattering, and foliage absorption

Evidence

At relatively short propagation distances (tens to hundreds of meters), past studies have revealed three frequencydependent forest effects: the effect of the porous ground surface, scattering from tree trunks, branches, and foliage, and absorption by the foliage. Ground impedance can have a large effect on horizontally propagating acoustic waves, and the porous litter layer is expected to produce a different acoustic response compared to an open field. — Donald G. Albert, Michelle E. Swearingen, Frank E. Perron, and David L. Carbee, Low Frequency Acoustic Pulse…, 22

Categorization

• DEFINE: Cleanly enumerates the three physical mechanisms that govern acoustic behavior in forests at short range.
• ADDENDUM: Extends the ‘trees as infrastructure’ idea into an acoustic register: leaf litter and canopy as material systems doing measurable work.