Ground impedance, not foliage, governs low-band attenuation by vegetation.
Evidence
On the other hand, the stems of the hemlock, pine, and brush all reduced noise by only about 5 dB/100 ft at 4000 Hz. Bare ground attenuates frequencies of 200-1000 Hz, and the frequency of maximum attenuation depends on the soil permeability to air. Thus, tilling the soil reduced the frequency of peak attenuation from 700 to 350 Hz and increased maximum attenuation at 52 m from the source by nearly 80%. — Donald Aylor, Noise Reduction by Vegetation and Ground, 2
Categorization
- ADDENDUM: Directly feeds the leaf-off hypothesis thread: ground effect dominates low-frequency attenuation and persists regardless of overhead foliage — the mechanism that operates below ~200-1000 Hz in autumn.
- SHARE: Send to Paul Bogard: tilling shifts peak ground attenuation frequency from 700 to 350 Hz because tillage opens air-filled pores — a striking acoustic fingerprint of soil management.
- XREF: connects to: Prior noise studies conflicted after omitting ground attenuation as a variable. — Donald Aylor, Noise Reduction by Vegetation and Ground, 4; Ground and vegetation attenuate noise in complementary frequency ranges. — Donald Aylor, Noise Reduction by Vegetation and Ground, 122; Effective flow resistivity is the dominant ground absorption parameter. — Donald G. Albert and John A. Orcutt, Acoustic Pulse Propagation Above…, 73 (+7 more)
Broader Connections
- Thick shrubs barely block noise because they act as a slower continuum
#corroborates(0.82) - Dense vegetation barely reduces highway noise below 2000 Hz
#corroborates(0.80) — Eric J. Heller, Why You Hear What You Hear- An…, 2603 - Low-frequency sound passes through ordinary walls because impedance shifts with frequency
#corroborates(0.78) — Eric J. Heller, Why You Hear What You Hear- An…, 2441 - Small rooms alter source impedance and reduce sound radiation at low frequencies
#corroborates(0.75) - Low-frequency attenuation depends critically on proper seal and construction
#corroborates(0.75) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 2703 - Dense multi-layered jungle vegetation makes hearing more efficient than sight
#expands(0.72) — Almo Farina, Soundscape Ecology, 341 - Leaf width and canopy leaf area drive sound scattering in dense vegetation
#expands(0.70) — Almo Farina, Soundscape Ecology, 321