Please cite this article in press as: M. Kloiber, et al., Comparative evaluation of acoustic techniques for detection of damages in historical wood, Journal of Cultural Heritage (2016), http://dx.doi.org/10.1016/j.culher.2016.02.009 ARTICLE IN PRESS G Model CULHER-3040; No. of Pages 10 Journal of Cultural Heritage xxx (2016) xxx–xxx Available online at ScienceDirect www.sciencedirect.com Original article Comparative evaluation of acoustic techniques for detection of damages in historical wood Michal Kloiber a , Ladislav Reinprecht b,∗ , Jaroslav Hrivnák a , Jan Tippner c a Czech Academy of Sciences, Institute of Theoretical and Applied Mechanics, v. v. i., Centre of Excellence ARCchip Telˇ c, 588 56 Telˇ c, Czech Republic b Technical University of Zvolen, Faculty of Wood Sciences and Technology, 960 53 Zvolen, Slovak Republic c Mendel University in Brno, Faculty of Forestry and Wood Technology, Department of Wood Science, 613 00 Brno, Czech Republic a r t i c l e i n f o Article history: Received 28 July 2015 Accepted 22 February 2016 Available online xxx Keywords: Historical wood Damages Inspection Acoustic techniques Mechanical properties a b s t r a c t This study assesses the suitability and sensitivity of select acoustic devices (Arborsonic Decay Detector, Fakopp Ultrasonic Timer with two types of sensors–TD45 and US10, and Fakopp 2D) for identification of damage in seven approximately 315 year old fir joining beams acquired during the reconstruction of the Baroque truss in the St. Mary of the Assumption Church in Vranov nad Dyjí, Czech Republic. The particular acoustic devices did not always provide similar results. However, brown rot and other inner damages in fir beams, located closer to their endings situated on masonry and connected with rafters, were determined with all acoustic devices. The possibility of indirect prediction of the strength, elasticity and hardness of the historical wood by means of the acoustic method was verified by correlation analyses, however, not seldom without higher significance. Generally, the results obtained indicate that it is not possible to fully rely on in situ acoustic methods for inspection of defects in wooden elements of historical structures, and therefore they should be combined with visual inspection and some other instrumental method(s). © 2016 Elsevier Masson SAS. All rights reserved. 1. Research aims Detection of inner decay and other damage in wooden ele- ments of historical structures is an important task to enable their reconstruction. Study of the sensitivity of selected acoustic nonde- structive techniques (NDT) in localization of damage in old joining beams at various distances from their visually damaged ends and correlation of these in situ analyses with mechanical properties of wood determined in vitro should give a realistic view on the use of acoustic techniques for inspection of wooden monuments. 2. Introduction Historical timber structures are frequently exposed to environ- mental conditions which result in their damage by abiotic and biological agents–temperature and moisture gradients, water with aggressive chemicals, sunlight, insects, wood-destroying fungi, moulds, etc. [1–3]. Some types of damage are detectable and quantifiable in extent and degree through preliminary visual sur- vey by the naked eye using only simple instruments [4,5]. These results can be classified by convenient ratings, e.g. by Italian ∗ Corresponding author. E-mail address: reinprecht@tuzvo.sk (L. Reinprecht). standard UNI 11119: 2004 [6]. The findings achieved at preliminary inspections are important to evaluate the integrity and mechani- cal performance of the historical timber structures needed for their stabilization, and also before their detailed survey and the complex restoration [5]. During visual inspections of timber structures, there some types of rot, insect damages or other failures in the inner parts of wood elements that can remain more or less hidden. Therefore, in practice, the in situ diagnoses of biodamages, cracks, or other defects in roofs, ceilings and other wooden structures are prefer- entially performed by a combination of visual methods [7,8] with selected instrumental nondestructive (NDT) or semi-destructive (SDT) techniques [4,9–15]. When carrying out the assessment of historical wooden elements, their surfaces and inner parts should not be injured (convenient are NDT), or the injuries should be reduced to a minimum (convenient are also SDT–e.g. the resistance drilling or pin penetration devices [16]). From among the NDT, usually the ultrasonic and other acous- tic methods are used for the analysis of timber structures [17–21]. By Marˇ cok et al. [22] or Raczkowski et al. [23], they are also able to determine early stages of wood damage. Acoustic methods are sim- pler, quicker and cheaper in comparison with other NDT, e.g. the radiographic, microwave, thermographic, molecular or computer- tomographic ones [15]. The ultrasonic measurements can on the whole detect the location and degree of failures in the ends and http://dx.doi.org/10.1016/j.culher.2016.02.009 1296-2074/© 2016 Elsevier Masson SAS. All rights reserved.