Donald G. Albert, Michelle E. Swearingen, Frank E. Perron, and David L. Carbee — Low Frequency Acoustic Pulse Propagation in Temperate Forests

28 published claims from this book.

• A cluttered pine forest reverberates longer than a concert hall
• A uniformly planted spruce forest functions acoustically like a sonic crystal.
• Advance site preparation dramatically shortens field acoustic measurement time
• Echoes off terrain behind a source reveal landscape features the direct path hides.
• Evenly spaced tree grids produce the weakest reverberation of any forest layout.
• Field acoustic arrays can be assembled as one tractor-towed cable package
• Forest cover shifts impulsive sound energy to lower peak frequencies than grass
• Forest floor clutter and roughness are treated as distinct acoustic variables from canopy structure.
• Forest sound propagation depends on ground porosity, scattering, and foliage absorption
• Forest structure reshapes sound propagation, affecting animal communication and sensor performance
• Ground flow resistivity is far lower in forests than in grassland.
• Ground snow cover alters outdoor sound propagation enough to warrant seasonal retesting.
• Impedance-matching a microphone lets an ordinary seismograph record acoustic signals undistorted.
• Litter depth changes seasonally, so acoustic measurements must record sampling date.
• Loud direct arrivals must be windowed out before fitting a decay model.
• Low-frequency sound scatters less off tree trunks because wavelengths exceed trunk diameter.
• Mounting an accelerometer on the source pistol gives precise shot timing for impulse tests.
• Paired summer-winter measurements isolate seasonal effects on forest acoustics
• Research questions shape measurement choices and thereby restrict results to narrow applications
• Reverberation decay is measured from the third signal peak to the noise floor.
• Reverberation time in forests is measured as T30 decay using Schroeder buildup curves.
• Seismographs built for earthquakes also capture pistol shots in forests
• Snow cover suppresses low-frequency reverberation by absorbing sound and smoothing terrain.
• Sparse mixed forests and bamboo groves acoustically resemble concert halls
• Understory roughness governs forest reverberation more than season
• Uniform thin-stemmed stands produce comparable sound decay times
• Water content measured against total sample weight can exceed 100 percent
• Wavelength relative to obstacle size governs sound decay in forests