Trunk scatter cannot alone explain forest high-frequency sound attenuation

Evidence

The conclusion may be drawn that scattering by trunks is not the only factor involved in the high-frequency attenuation, even for the spruce monoculture (site 2). Branches and leaves must also contribute. Moreover, the results of data fitting indicate that scattering by trunks accounts for a considerably higher proportion of the attenuation for the spruce monoculture (site 2) and the mixed woodland (site 1 in winter) than for the mixed coniferous (site 3) or the mixed woodland (site 1 ) in summer. This is consistent with the physical differences in the foliage between the various sites since the mixed woodland has considerably more undergrowth and foliage (in summer) than the spruce monoculture, an• the mixed coniferous woodland forms a denser barrier of branches and foliage than that offered by the other two sites. — Margaret A. Price, Keith Attenborough, and Nicholas W. Heap, Sound Attenuation through Trees, 87

Categorization

• XREF: Core evidence for the leaf-off hypothesis: foliage is an independent attenuator proportional to foliage density, so measuring the same site leaf-on vs leaf-off isolates foliage. — connects to: Woodland attenuation shows a characteristic peak-dip-rise spectral shape — Margaret A. Price, Keith Attenborough, and Nicholas W. Heap, Sound Attenuation through Trees:…, 105; Branch transverse vibrations are the active oscillators in tree sound absorption. — T. F. W. Embleton, Sound Propagation in Homogeneous…, 2; Tree branches, not leaves or twigs, resonate as forced acoustic oscillators near 275-450 cps. — T. F. W. Embleton, Sound Propagation in Homogeneous…, 49 (+6 more)
• QUESTION: Could the leaf-off leaf-on contrast at one site map onto site-to-site foliage-density gradations reported here as a validity check?

Related

• Woodland attenuation shows a characteristic peak-dip-rise spectral shape (similarity 0.89)
• Leaf width and canopy leaf area drive sound scattering in dense vegetation (similarity 0.88)
• Tree branches, not leaves or twigs, resonate as forced acoustic oscillators near 275-450 cps. (similarity 0.86)
• Branch transverse vibrations are the active oscillators in tree sound absorption. (similarity 0.85)
• Woods sound attenuation stays near constant regardless of optical visibility through the canopy. (similarity 0.85)
• Ground and vegetation attenuate noise in complementary frequency ranges. (similarity 0.83)
• Excess attenuation increases with frequency in vegetated habitats (similarity 0.83)
• Margaret A. Price, Keith Attenborough, and Nicholas W. Heap — Sound Attenuation through Trees Measurements and Models (similarity 0.82)
• Rayleigh attributed a forest echo’s octave rise to size-dependent scattering of high frequencies (similarity 0.82)
• Ground impedance, not foliage, governs low-band attenuation by vegetation. (similarity 0.82)
• Vegetation attenuation thresholds differ measurably across cover types and soil states (similarity 0.82)
• Ground-effect interference fades at higher frequencies and longer ranges (similarity 0.81)
• A source at a wood’s edge creates large boundary effects on forest sound attenuation. (similarity 0.80)
• Open and dense forest canopies create distinct sound atmospheres (similarity 0.79)
• Mature woodland humus layers do not behave as locally reacting acoustic grounds (similarity 0.78)

Broader Connections

• Leaf width and canopy leaf area drive sound scattering in dense vegetation #expands (0.85) — Almo Farina, Soundscape Ecology, 321
• Excess attenuation increases with frequency in vegetated habitats #corroborates (0.80) — Almo Farina, Soundscape Ecology, 418
• Flat surfaces reflect low-frequency sound specularly but scatter high-frequency sound #expands (0.80)
• Rayleigh attributed a forest echo’s octave rise to size-dependent scattering of high frequencies #expands (0.75) — Eric J. Heller, Why You Hear What You Hear- An…, 2639
• Ground and vegetation attenuate noise in complementary frequency ranges. #expands (0.75) — Donald Aylor, Noise Reduction by Vegetation and Ground, 122