Ground and vegetation attenuate noise in complementary frequency ranges.

Evidence

Foliage, stems, and ground conditions are all important in the attenuation of noise transmitted near the ground, and together their effects span most acoustically important frequencies. Depending upon the particular annoyance, some one or all of these factors may be effective. For example, while a strip of soft ground would be most effective in reducing the lowfrequency noise from trucks starting up at toll booths, a band of dense foliage would better reduce the noise from high-speed traffic. — Donald Aylor, Noise Reduction by Vegetation and Ground, 122

Categorization

• SHARE: The practical application split (soft ground for low-frequency idling truck rumble, foliage for high-speed traffic hiss) is a nice concrete hook for anyone teaching the frequency-band logic.
• ADDENDUM: Sits directly under the leaf-off hypothesis thread: ground dominates low band, foliage the high band.
• XREF: connects to: Ground impedance, not foliage, governs low-band attenuation by vegetation. — Donald Aylor, Noise Reduction by Vegetation and Ground, 2; Trunk scatter cannot alone explain forest high-frequency sound attenuation — Margaret A. Price, Keith Attenborough, and Nicholas W. Heap, Sound Attenuation through Trees:…, 87; Snow is the most sound-absorbent natural ground cover — Donald G. Albert, Acoustic Waveform Inversion with…, 5 (+7 more)

Related

• Ground impedance, not foliage, governs low-band attenuation by vegetation. (similarity 0.91)
• Dense vegetation barely reduces highway noise below 2000 Hz (similarity 0.89)
• Prior noise studies conflicted after omitting ground attenuation as a variable. (similarity 0.86)
• Vegetation attenuation thresholds differ measurably across cover types and soil states (similarity 0.86)
• Leaf width and canopy leaf area drive sound scattering in dense vegetation (similarity 0.86)
• Trunk scatter cannot alone explain forest high-frequency sound attenuation (similarity 0.83)
• Ground-effect interference fades at higher frequencies and longer ranges (similarity 0.82)
• Excess attenuation increases with frequency in vegetated habitats (similarity 0.82)
• Low-frequency attenuation depends critically on proper seal and construction (similarity 0.82)
• Woodland attenuation shows a characteristic peak-dip-rise spectral shape (similarity 0.81)
• Snow is the most sound-absorbent natural ground cover (similarity 0.80)
• Dense multi-layered jungle vegetation makes hearing more efficient than sight (similarity 0.80)
• Mature woodland humus layers do not behave as locally reacting acoustic grounds (similarity 0.80)
• Effective flow resistivity is the dominant ground absorption parameter. (similarity 0.79)
• Vegetation substrate type shapes the spectral character of wind noise (similarity 0.79)

Broader Connections

• Excess attenuation increases with frequency in vegetated habitats #expands (0.85) — Almo Farina, Soundscape Ecology, 418
• Dense vegetation barely reduces highway noise below 2000 Hz #exemplifies (0.80) — Eric J. Heller, Why You Hear What You Hear- An…, 2603