Thick shrubs barely block noise because they act as a slower continuum
Evidence
Trees, shrubs, and low, round hills often help only a little. Recently, the author made measurements near a 15-foot-thick, 10-foot-high, and 100-m-long, dense, neatly trimmed shrub with squared sides near a busy highway. There was only a few dB difference on the highway side versus the “protected” side. Despite what our eyes tell us, such a shrub acts like a continuum region with a somewhat slower wave speed, at least for sound below about 2000 Hz in frequency, since the objects doing the scattering are packed closer together than a wavelength. — Eric J. Heller, Why You Hear What You Hear- An…, 2603
Categorization
Category: Contrarian or Surprising Claims
- XREF: Connects to the specular-reflection figure 2.8 logic for why rough surfaces look shiny to long-wavelength waves.
Related
- Dense vegetation barely reduces highway noise below 2000 Hz (similarity 0.84)
- Lower frequencies diffract more around obstacles than higher frequencies do (similarity 0.80)
- Sharp-edged phenomena require high-frequency waves far above human hearing (similarity 0.79)
- Flat surfaces reflect low-frequency sound specularly but scatter high-frequency sound (similarity 0.79)
- Denser materials slow sound while stiffer bonds speed it up (similarity 0.78)
Broader Connections
- Higher material density slows sound propagation speed
#corroborates(0.85) — David Howard, Jamie Angus, coustics and Psychoacoustics, 33 - Denser materials slow sound while stiffer bonds speed it up
#corroborates(0.82) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 57 - Lower frequencies diffract more around obstacles than higher frequencies do
#qualifies(0.72) — David Howard, Jamie Angus, coustics and Psychoacoustics, 418