Acoustic emission monitoring of micro-damage in wooden art objects to assess climate management strategies

Acoustic emission (AE) is a method with great potential for monitoring the development of micro-damage in objects exposed to the potentially harmful conditions of temperature (T) and relative humidity (RH). It allows one to directly record damage growth while changes remain invisible to those caring for the collection, as opposed to monitoring and inferring damage indirectly due to undesired interactions with local climates or waiting for visible damage to develop. As a consequence, AE can be used to record environmentally-induced physical changes directly in historic materials and, hence, can support the assessment of strategies for the indoor climate management of museums. However, applying AE to museum collections requires specific measures to deal with issues such as the uniqueness and fragility of the monitored objects, the diversity of construction materials and the measurement of signals in an often noisy environment. Systematic tests of the propagation and attenuation of AE signals in wood were performed to better understand the monitoring results in terms of damage location and to assess the ability of various high-pass filters to reduce the background noise. This paper offers an insight into monitoring methodologies for wooden art objects to effectively manage the museum climate.