Wood selection for musical instrument making is usually based on visual estimation and on manual mechanical and vibrational subjective testing. The method proposed uses TV holography and holographic interferometry with a double-pulsed laser to visualize the standing acoustic waves and the impact generated by transient waves as inspection testing tools. The theory of bending waves in orthotropic plates is used to interpret the experimental results. This enables us to estimate Young’s moduli parallel to and perpendicular to the grain and the in-plane shear modulus in wood. The testing is nondestructive, so the expensive wooden plates can be used in production. Properly modified, the test can be applied to the judgment of any wooden and wooden composite plates. The 3-D charts for a set of the physicoacoustical characteristics—density, modulus of elasticity, and acoustic constant on the axes—are confirmed as a useful procedure that can help to provide more objective results in wood grading for materials selection in the design of musical instruments, mainly bowed string instruments and pianos.
"Grading of wooden plates for musical instrument making by means of holographic interferometry," Optical Engineering 37(7), (1 July 1998). https://doi.org/10.1117/1.601702