Classification of log based on sound analysis and its application for grading system and drying process control

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The modulus of elasticity (Et) of log was determined by measuring the natural frequency of longitudinal wave due to sound when hitting cross section. The Et of laminae and post-sized lumber with pith produced by the log were also measured. Results were as follows: (1) Et was recognized to be highly linear to the modulus of elasticity due to static bending test(Es).The third-term natural frequency of longitudinal wave was hardly affected by piling in stock yard as compared to the first or second ones,thus longitudinal wave sound analysis could be considered as a reasonable material selection and control system. (2) Since the Et of post-sized lumber and the average value of Et of laminae was recognized to be highly linear to Et of the original log, this rough classification of log could be useful in the selection of raw materials for structural lumber and glue-laminated lumber. (3) Since changing of natural frequency during drying process was affected by the increase of Et and weight loss due to desorption of water,it might be effective as rough quality control of drying within a well-known increase of Et. (4) In the glue-laminated lumber mill, the classification of log was conducted by longitudinal wave sound analysis. It could be efficient as a reasonable selection system for laminae.