title: Influence of a forest edge on acoustical propagation: experimental results.
abstract: Acoustic propagation through a forest edge can produce complicated pressure time histories because of scattering from the trees and changes in the microclimate and ground parameters of the two regions. To better understand these effects, a field experiment was conducted to measure low-frequency acoustic pulses propagating in an open field, a forest, and passing through a forest edge in both directions. Waveforms measured in the open field were simple impulses with very low scattering, whereas waveforms at the edge and within the forest had stronger reverberations after the direct arrival. The direct wave pulse shapes increased in duration in accordance with the path length in the forest, which had an effective flow resistivity 12 to 13 that of the grassy open field. The measurements exhibit different rates of attenuation in the two regions, with relatively lower attenuation in the open field than higher rates in the forest. Decay of SEL transmitted into the forest was 4 dB more per tenfold distance than for outbound transmission. Stronger attenuation in the 1-2 kHz range occurs when propagating into the forest. While the measured meteorological profiles revealed three distinct microclimates, meteorological effects are not sufficient to explain the apparent non-reciprocal propagation.
authors: Construction Engineering Research Laboratory, U.S. Army Engineer Research and Development Center, Champaign, Illinois 61826, USA. michelle.e.swearingen@usace.army.mil
authors: Michelle E
authors: ME
authors: Swearingen
authors: Michael J
authors: MJ
authors: White
authors: Patrick J
authors: PJ
authors: Guertin
authors: Donald G
authors: DG
authors: Albert
authors: Arnold
authors: A
authors: Tunick
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D002980:Climate; D004867:Equipment Design; D009038:Motion; D011312:Pressure; D012542:Scattering, Radiation; D012987:Soil / Q000737:chemistry; D013016:Sound; D013018:Sound Spectrography; D013997:Time Factors; D014160:Transducers, Pressure; D014197:Trees / Q000502:physiology*
chemical_list: D012987:Soil