Abstract: A mechanism (1000) for classifying logs based on a combination of transit time technology and resonance-based technology is provided. Pressure impulses are applied to a log (4) so as to produce acoustic waves in the log. Acoustic measurements are performed using transit time technology and resonance-based technology, respectively, to obtain a maximum and an average impulse velocity, respectively, of the log. The log quality is evaluated based on the different impulse velocities, forming a radial impulse velocity gradient of the log. The quality algorithm can include a combination of MOE and radial wood gradients to improve the accuracy further. Other parameters, such as log shape, weight, temperature, may also be included. The system can utilize impulses separated in space and time, where differences in impulse velocities between transmitter-receiver paths reflect internal wood defects. The log is classified (and sorted) using criteria or thresholds dependent on the log quality.