Mature woodland humus layers do not behave as locally reacting acoustic grounds

Evidence

The humus layer of decomposing matter that forms beneath mature forest stands tends to have high porosity and low flow resistivity. Consequently, the assumption of local reaction in Eqs. (2)-(6) may not be valid. The possibility of extended reaction may be taken into account computationally by using suitable theory. 27’28 On the other hand, this refinement has been found to offer only marginal gain, 22 and its neglect is of small importance when compared with the simplifying assumptions made already in applying such crude models for the ground structure. — Margaret A. Price, Keith Attenborough, and Nicholas W. Heap, Sound Attenuation through Trees, 52

Categorization

• QUESTION: Useful acoustic ecology note: a forest floor is not a standardized grass impedance surface; the double-layer (porous humus over soil) structure shifts ground-effect peaks. Worth chasing for soundscape methodology.
• XREF: connects to: Ground-effect interference fades at higher frequencies and longer ranges — Margaret A. Price, Keith Attenborough, and Nicholas W. Heap, Sound Attenuation through Trees:…, 79; Wood’s anisotropy makes sound radiation direction- and frequency-dependent; Vegetation substrate type shapes the spectral character of wind noise — Almo Farina, Soundscape Ecology: Principles,…, 1255

Related

• Ground-effect interference fades at higher frequencies and longer ranges (similarity 0.83)
• Vegetation substrate type shapes the spectral character of wind noise (similarity 0.82)
• Margaret A. Price, Keith Attenborough, and Nicholas W. Heap — Sound Attenuation through Trees Measurements and Models (similarity 0.81)
• Ground and vegetation attenuate noise in complementary frequency ranges. (similarity 0.80)
• Ground impedance, not foliage, governs low-band attenuation by vegetation. (similarity 0.80)
• Woodland attenuation shows a characteristic peak-dip-rise spectral shape (similarity 0.79)
• Open and dense forest canopies create distinct sound atmospheres (similarity 0.78)
• Trunk scatter cannot alone explain forest high-frequency sound attenuation (similarity 0.78)

Broader Connections

• Wood’s anisotropy makes sound radiation direction- and frequency-dependent #corroborates (0.72)
• Vegetation substrate type shapes the spectral character of wind noise #complicates (0.72) — Almo Farina, Soundscape Ecology, 1255