Comparing the potential of acoustic parameters for the assessment of the strength of timber

The article compares the potential of acoustic parameters for the assessment of the strength of timber. Acoustic NDT parameters were evaluated during tests on 33 controlled-homogeneity beam specimens cut from 12-layer laminated veneer panels and three solid wood beams. The LF and ultrasonic TOF velocities were also measured. Holes were then drilled through the beams and filled with dowels to simulate knots. These holes were then re-drilled and larger dowels inserted. The number of 25 mm simulated knots was progressively increased along the beam while avoiding drilling at the anti- nodal positions of the eighth harmonic. The eighth harmonic underwent little change until holes were drilled at its anti- nodal points because harmonic frequencies are derived, not from a measurement of the whole specimen, but from discrete points along it.