Attenuation of Ultrasound in Solid Wood

A method of evaluating the attenuation of ultrasound in wood over a range of frequencies and angle of incidence with respect to the three principal 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 and shear waves. Attenuation coefficients were deduced as a ratio of the amplitude of the received signal when the transducers were in contact to the amplitude when the ultrasonic pulse has travelled through the sample. Results are reported on horse chesnut, with a density of 510 kg m−3 and 12% moisture content. For out-of-axis propagation the longitudinal direction of wood displays the most dispersion with respect to frequency, while the tangential propagation direction displays the least dispersion. Attenuation is generally greater for out-of-axis propagation.