Study on the conservation state of wooden historical structures by means of acoustic attenuation and vacuum microbalance

Acoustic emission is a well-known noninvasive methodology for the study of defects in materials but still rarely applied in the field of cultural heritage diagnostic. How alteration products and degradation processes affect the acoustic emission signal still is an open issue. The proposed study concerns the utilization of such techniques to investigate the relations existing between the moisture content and the typology and amount of crystallized salts with the acoustic emission features. This work focuses on spruce wood logs belonging to an historical warehouse in Trondheim, Norway, since no strictly scientific studies exist on the conservation conditions of these big wooden structures. The methodology, also involving the moisture content measurement of structures and the samplings of portions analyzed through vacuum microbalance, allowed identifying a clear relationship between the amount of water in logs as a function of their distance from the ground and variations in the amplitude of the acoustic emission signals.