How does TNM compute tree zone attenuation?
TNM computes tree attenuation per the International Standards Organization (ISO 9613-2, “Acoustics – Attenuation of Sound During Propagation Outdoors – Part 2). This standard requires that trees be sufficiently dense to completely block the view along the propagation path. This requires dense undergrowth as well as dense tree-top foliage. Do not include a TNM tree zone unless its vegetation is sufficiently dense.
