shows two electromagnetic waves, one in the form of a dashed line that
perceives wood as a transparent material and the other in the form of a solid line
that is influenced by the wood material properties. The disturbed wave is
attenuated and makes a phase change relative to the undisturbed wave as it is
transmitted through the wood material. A phase change is the displacement
between reference points on each wave and is usually expressed in an angular
displacement I (figure 8). The size of the phase shift and the attenuation depend
on the mc and the dry density