ATTENUATION OF ULTRASOUND IN SOLID WOOD

A method of evaluating the attenuation of ultrasound in wood over a ra nge of frequencies and angle of incidence with respect to the three pr incipal elastic directions of the material is described. The influence was considered on velocity. A continuous wave transmission technique was used to measure ultrasonic velocities and attenuation coefficients at 100 kHz, 250 kHz, 500 kHz, 1 MHz and 1.5 MHz, using longitudinal a nd shear waves. Attenuation coefficients were deduced as a ratio of th e amplitude of the received signal when the transducers were in contac t to the amplitude when the ultrasonic pulse has travelled through the sample. Results are reported on horse chestnut, with a density of 510 kg m-3 and 12% moisture content. For out-of-axis propagation the long itudinal direction of wood displays the most dispersion with respect t o frequency, while the tangential propagation direction displays the l east dispersion. Attenuation is generally greater for out-of-axis prop agation.