Evergreen forest wood occupies only about one part in 1000 of total volume.

Evidence

In the theory given in the Appendix, it is assumed that the oscillators are separated from each other, and between them is air in which the sound field is propagated. To make a comparison with the measured results, it is convenient to assume that the oscillators may be dispersed as a tenuous cloud filling all the space, retaining the same properties though with a strength inversely proportional to their diffuseness. One then requires the fraction of the total volume taken up by the volume of the branches; by measurement, this is roughly I part in 103 of reasonably dense evergreen forests. — T. F. W. Embleton, Sound Propagation in Homogeneous…, 59

Categorization

• CANDY: A striking image: a ‘dense’ evergreen forest is, by solid volume, only 0.1% tree — almost all air.

Related

• T. F. W. Embleton — Sound Propagation in Homogeneous Deciduous and Evergreen Woods (similarity 0.79)
• Open and dense forest canopies create distinct sound atmospheres (similarity 0.79)