Prior noise studies conflicted after omitting ground attenuation as a variable.

Evidence

For example, Embleton found that vegetation reduced sound equally for all frequencies between 200 and 2000 Hz, while both Eyring and Wiener and Keast reported attenuation that increased monotonically with frequency. Also Eyring found a positive correlation between visibility and attenuation, while Embleton did not. — Donald Aylor, Noise Reduction by Vegetation and Ground, 4

Categorization

• XREF: A miniature case study in how replication conflicts resolve when a hidden third variable (here ground impedance) is accounted for — parallels the methodological thread across the polyad about identifying what’s actually doing the work in observational data. — connects to: Ground impedance, not foliage, governs low-band attenuation by vegetation. — Donald Aylor, Noise Reduction by Vegetation and Ground, 2; Vegetation attenuation thresholds differ measurably across cover types and soil states — Almo Farina, Soundscape Ecology: Principles,…, 331

Related

• Vegetation attenuation thresholds differ measurably across cover types and soil states (similarity 0.88)
• Ground impedance, not foliage, governs low-band attenuation by vegetation. (similarity 0.88)
• Ground and vegetation attenuate noise in complementary frequency ranges. (similarity 0.86)
• Donald Aylor — Noise Reduction by Vegetation and Ground (similarity 0.84)
• Leaf width and canopy leaf area drive sound scattering in dense vegetation (similarity 0.83)
• Excess attenuation increases with frequency in vegetated habitats (similarity 0.82)
• Dense vegetation barely reduces highway noise below 2000 Hz (similarity 0.82)
• Low-frequency attenuation depends critically on proper seal and construction (similarity 0.81)
• Sound degradation has three measurable concurrent aspects en route through habitat (similarity 0.81)
• Dense multi-layered jungle vegetation makes hearing more efficient than sight (similarity 0.80)
• Effective flow resistivity is the dominant ground absorption parameter. (similarity 0.79)
• Each degradation aspect traces to specific physical mechanisms in habitat (similarity 0.79)
• Ground-effect interference fades at higher frequencies and longer ranges (similarity 0.79)
• Woods sound attenuation stays near constant regardless of optical visibility through the canopy. (similarity 0.79)
• Woodland attenuation shows a characteristic peak-dip-rise spectral shape (similarity 0.79)