Effect of moisture content on the ultrasonic acoustic properties of wood

We determined the ultrasonic velocity and energy attenuation value of three tree species (basswood, elm, and fir) 1 per tree in different moisture content levels, using RSM-SY5 ultrasonic testing instrument, and analyzed the regularity of ultrasonic velocity and energy attenuation values with moisture content, respectively. The ultrasonic velocity of the three species decreased as moisture content increased, with the turning point at 32 % of moisture content. When the moisture content was more than 32 %, the growth curve of ultrasonic wave velocity was flattened. The moisture contents of all three species increased under the any point moisture content of 1-60 %. The differentiation degrees of energy attenuation value of three species were higher than the corresponding ultrasonic wave velocity, when the moisture content was less than 15 %. The differentiation degrees of the energy attenuation value of three species was higher than the corresponding ultrasonic velocity, when the moisture content was more than 15 %.