Woods sound attenuation stays near constant regardless of optical visibility through the canopy.

Evidence

Recognizing that results for the first 50 ft of woods are not comparable with the remainder, the values of attenuation calculated from the remaining three sections of the woods are shown as a function of visibility in Fig. 4. The results from three adjacent frequencies, 250, 320, and 400 cps, were averaged in order to provide a more reliable value. Eyring •’ implies a monotonic curve passing through the point of zero attenuation and infinite visibility—his values recalculated for 320 cps are represented by the dashed curve of Fig. 4. The present work shows no very obvious correlation, though what little correlation there is appears to favor an attenuation independent of visibility and having a value of 6 or 7 dB/100 ft. — T. F. W. Embleton, Sound Propagation in Homogeneous…, 46

Categorization

• XREF: Challenges the intuition that ‘thicker/denser foliage’ governs how much woods muffle sound — relevant to the reader’s use of leaf-on vs leaf-off contrasts. — connects to: Tree branches, not leaves or twigs, resonate as forced acoustic oscillators near 275-450 cps. — T. F. W. Embleton, Sound Propagation in Homogeneous…, 49
• QUESTION: How does this visibility-independence reconcile with the reader’s deciduous/evergreen framing? If attenuation is independent of foliage visibility, what does leaf loss actually change?

Related

• Tree branches, not leaves or twigs, resonate as forced acoustic oscillators near 275-450 cps. (similarity 0.85)
• Trunk scatter cannot alone explain forest high-frequency sound attenuation (similarity 0.85)
• Woodland attenuation shows a characteristic peak-dip-rise spectral shape (similarity 0.84)
• T. F. W. Embleton — Sound Propagation in Homogeneous Deciduous and Evergreen Woods (similarity 0.84)
• Leaf width and canopy leaf area drive sound scattering in dense vegetation (similarity 0.83)
• A source at a wood’s edge creates large boundary effects on forest sound attenuation. (similarity 0.81)
• Branch transverse vibrations are the active oscillators in tree sound absorption. (similarity 0.81)
• Open and dense forest canopies create distinct sound atmospheres (similarity 0.81)
• Excess attenuation increases with frequency in vegetated habitats (similarity 0.81)
• Ground-effect interference fades at higher frequencies and longer ranges (similarity 0.80)
• Dense multi-layered jungle vegetation makes hearing more efficient than sight (similarity 0.80)
• Ground impedance, not foliage, governs low-band attenuation by vegetation. (similarity 0.80)
• Vegetation attenuation thresholds differ measurably across cover types and soil states (similarity 0.80)
• Prior noise studies conflicted after omitting ground attenuation as a variable. (similarity 0.79)