Vibrational and acoustical experiments on logs of spruce

This paper presents the results of some vibro-acoustical experiments conducted on logs of spruce. The aim from this study was in the beginning to study the possibilities of investigating acoustically the presence of decay in the stems of standing trees, and for assessing the strength of wood in the shape of logs. First, a brief review is made for the different experimental techniques used in studying the response of mechanical systems in general with emphasis on an efficient technique used for evaluating the impulse response of vibrating systems. Then a literature survey on the effects of decay on the strength and on the damping properties of wood are presented with some practical general implications regarding decay inspection of wood composites. Lastly some experiments using vibrations and sound which were conducted on two specimens of wood logs, one sound and one decayed, are presented with some discussions regarding the implementations of these methods for the quality grading and defect detection in wood logs and standing trees.