ArticlePublisher preview available

Extensively damaged trees tested with acoustic tomography considering tree stability in urban greenery

Authors:
Radovan Ostrovský at Slovak Academy of Sciences
Radovan Ostrovský
Marek Kobza at Slovak Academy of Sciences
Marek Kobza
Ján Gažo at Slovak University of Agriculture in Nitra
Ján Gažo
Read publisher preview
Download citation
To read the full-text of this research, you can request a copy directly from the authors.

Abstract and Figures

Key message Damaged area of five tree species was determined by acoustic tomography. Final accuracy of 83% was found as satisfactory and proven suitability for overall tree stability assessment. Abstract Objectives of study were to assess the accuracy and reliability of the acoustic tomography technique for detecting internal structural defects compared to visual assessment on extensively damaged trees of five species in urban greenery. Tomography was realized by Fakopp 3D acoustic tomograph tool. Several types of structural defects were determined, such as heartwood and sapwood decay, internal and lateral cracks, ring shake and hollow. Acoustic tomography inspection revealed correct detection of damage in all disc samples involved in study. Accuracy of damaged area determination reached 90%. Total accuracy determination for both area and location of damage was 83%. Overestimation of damaged area was observed in eight samples, contrary to seven underestimated samples. Difference in estimated false-positive area in comparison to false-negative area was minimal. Irregularity of cross section shape does not affect the final accuracy of tomograph. Accuracy is not influenced by diameter of tree trunk. We determined strong positive correlation between real area of damage and results of tomography (r = 0.75; p = 0.001). Acoustic tomography provides satisfactory accuracy in damage area determination inside tree trunk and for overall tree stability assessment on even extensively damaged trees in urban greenery.
Figures - available from: Trees
This content is subject to copyright. Terms and conditions apply.
A preview of this full-text is provided by Springer Nature.
Learn more
Content available from Trees
This content is subject to copyright. Terms and conditions apply.
Vol.:(0123456789)
1 3
Trees (2017) 31:1015–1023
DOI 10.1007/s00468-017-1526-6
ORIGINAL ARTICLE
Extensively damaged trees tested withacoustic tomography
considering tree stability inurban greenery
RadovanOstrovský1· MarekKobza1· JánGažo2
Received: 2 August 2016 / Accepted: 13 January 2017 / Published online: 7 February 2017
© Springer-Verlag Berlin Heidelberg 2017
damage area determination inside tree trunk and for overall
tree stability assessment on even extensively damaged trees
in urban greenery.
Keywords Acoustic tomography· Tree stability· Visual
assessment
Introduction
The failure of trees in an urban environment can endan-
ger lives and damage infrastructure. Schubert etal. (2009)
determine the main aspects of the stability of a tree: trunk
diameter, weight- and wind-loading, strength of trunk
wood, root anchorage as well as the location and geom-
etry of fungal decay or a cavity in the interior of a stem.
Acoustic tomography is a technique that has been explored
by many researchers in the area of urban tree decay detec-
tion as well as of determination of tree stability (Divos and
Szalai 2002; Nicolotti etal. 2003; Gilbert and Smiley 2004;
Wang etal. 2005, 2009; Liang etal. 2008; Wang and Alli-
son 2008; Johnstone 2010). As reported by Li etal. (2012),
investigations into urban trees showed great success using
acoustic tomography to detect moderate to severe inter-
nal decay within a trunk. Bucur (2005) consider acoustic
tomography as convenient for the inspection and defect
detection of standing trees from parks and public gardens
as well as for poles and other wooden structural elements.
It is possible to study visually the composition of the
stem and/or branches of different types of wood. This helps
to evaluate the location of potential hazard and its relation
to existing damage in tree stems and branches (Heikura
etal. 2008). To minimize the potential damage on one hand
and to avoid felling sound trees on the other, risk assess-
ment is crucial in managing urban trees. Decomposition of
Abstract
Key message Damaged area of five tree species was
determined by acoustic tomography. Final accuracy of
83% was found as satisfactory and proven suitability for
overall tree stability assessment.
Abstract Objectives of study were to assess the accu-
racy and reliability of the acoustic tomography technique
for detecting internal structural defects compared to visual
assessment on extensively damaged trees of five species in
urban greenery. Tomography was realized by Fakopp 3D
acoustic tomograph tool. Several types of structural defects
were determined, such as heartwood and sapwood decay,
internal and lateral cracks, ring shake and hollow. Acous-
tic tomography inspection revealed correct detection of
damage in all disc samples involved in study. Accuracy of
damaged area determination reached 90%. Total accuracy
determination for both area and location of damage was
83%. Overestimation of damaged area was observed in
eight samples, contrary to seven underestimated samples.
Difference in estimated false-positive area in comparison to
false-negative area was minimal. Irregularity of cross sec-
tion shape does not affect the final accuracy of tomograph.
Accuracy is not influenced by diameter of tree trunk. We
determined strong positive correlation between real area
of damage and results of tomography (r = 0.75; p = 0.001).
Acoustic tomography provides satisfactory accuracy in
Communicated by J. Lin.
* Radovan Ostrovský
radovan.ostrovsky@savzv.sk
1 Branch forWoody Plants Biology, Institute ofForest Ecology
oftheSlovak Academy ofSciences, Nitra, Slovakia
2 Department ofGenetics andPlant Breeding, Slovak
University ofAgriculture inNitra, Nitra, Slovakia
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Subsequently, the drilling resistance method will be used to test resistance amplitude variation profiles on the trunks, to assess the extent and location of decayed and nondecayed regions. Finally, visual inspections of disks Gilbert et al. 2016;Karlinasari et al. 2016;Ostrovský et al. 2017). Acoustic tomography is still influenced by the characteristics of wood in different tree species. ...
... Additionally, using hardness mapping and sonic tomography to detect decay in the heartwood area of the trunk shows that sonic tomography underestimates the area of decay (Liang et al. 2008). The frequency of the stress wave is influenced by various factors, including the wood material, the applied sensor, and the geometry, such as the distance between the source and the receiver (Ostrovský et al. 2017). When tomography is used to assess structural defects in a trunk, the presence of internal cracks or ring cracks can lead to an overestimation of the defect area. ...
... Essentially, the accuracy of tomography is dependent on the correct setup of these parameters to avoid misrepresenting the size and extent of structural defects. Defects or decay areas can only be detected when they account for more than 2.8% to 5% of the cross-sectional area (Ostrovský et al. 2017). Therefore, to better assess the internal condition and decay of trees, other more effective methods should be combined, such as using more probe sensors to improve resolution. ...
Detection of Ganoderma australe Decay in Three Acacia confusa Trees: A Case Study
Article
  • Feb 2025
Background This study aims to utilize various nondestructive methods to assess the internal trunks of 3 Acacia confusa trees affected by Ganoderma australe decay. Methods Visual Tree Assessment (VTA) was employed to examine the trees, selecting 3 Taiwan acacia ( Acacia confusa ) trees at the base of which G. australe fungal fruiting bodies were growing, identified as severely damaged and classified as having an immediate hazard level. Subsequently, a stress wave device was used to detect the cross-sectional area of these trees at the locations where G. australe fungus was growing in order to obtain 2D tomographies of stress wave velocity. Following this, a resistance drilling instrument was used to examine the same cross-sectional areas, acquiring resistance drilling amplitude data. Finally, the 3 trees were felled, and 15-cm thick discs were cut from the same cross-sectional areas for laboratory testing. Results Using 2D sonic tomography and a corresponding velocity grid map of stress wave velocity revealed areas with varying velocities across the trunk cross sections. Drill resistance profile curves depicted changes in resistance strength, while visual inspections of disk cross sections indicated the location and severity of decay. Additionally, pilodyn penetration testing showed different penetration depths on the surfaces of the disk cross sections. Conclusion The study discusses the use of these detective methods to discover the location and extent of decay within tree trunks and assesses the percentage of decay in cross-sectional areas, providing a reference for tree risk assessment levels.
View
... In 2022, the use of the dynamic modulus of elasticity was found to improve the acoustic tomographic evaluation of standing trees, demonstrating that sound velocity is related to the mechanical parameters of wood [24]. The inspection of standing trees in China and Panama showed that acoustic tomography is an effective, non-invasive method for assessing internal decay, cavities, and structural integrity, even in irregularly shaped trees [4,28,29]. Other studies have used tomography for the numerical simulation of wave propagation to determine the size of the cavity and for developing a new approach to the quantitative analysis of acoustic tomography images, demonstrating the effectiveness of the method relative to others [30]. ...
... The sensor transmitted the sound waves and formed the data matrix. The sound velocity was automatically calculated in the software, and a tomogram was generated [29,46,48]. ...
... The sens transmitted the sound waves and formed the data matrix. The sound velocity was au matically calculated in the software, and a tomogram was generated [29,46,48]. ...
Using Acoustic Tomography to Model Wood Deterioration in Cedrelinga cateniformis Ducke in the Peruvian Amazon
Article
Full-text available
  • Apr 2024
Forest plantations can be established in order to restore degraded areas. Acoustic tomography, which is of increasing importance in forest management, was used in the present study to obtain information for managing plantations of Cedrelinga cateniformis Ducke in the Peruvian Amazon. The species is valuable in the timber sector of Peru, but the core wood tends to deteriorate and develop cavities. The main objective of the study was to model wood deterioration in Cedrelinga cateniformis Ducke using the data obtained through acoustic tomography. Eight plantations of varying ages were analyzed using acoustic tomography in order to obtain indicators of wood deterioration. Biometric, climatic, and edaphic data (explanatory variables) were also measured in each plantation. The indicator variables and explanatory variables were compared and evaluated using correlation and principal component analysis. Wood deterioration was modelled using stepwise regression. The indicator variables differed significantly between plantations and were mainly correlated with the biometric variables (age and diameter at breast height). The models explained 81% of the variability of pith rot. The percentage rotten area was minimal in young plantations (1%), and the opposite was observed in mature trees (21.5 to 25.6%). The study findings provide valuable information, enabling foresters to determine the optimal age and diameter for felling Cedrelinga cateniformis in plantations in the Peruvian Amazon.
View
... In 2022, the use of the dynamic modulus of elasticity was found to improve the acoustic tomographic evaluation of standing trees, demonstrating that sound velocity is related to the mechanical parameters of wood [24]. The inspection of standing trees in China and Panama showed that acoustic tomography is an effective, non-invasive method for assessing internal decay, cavities, and structural integrity, even in irregularly shaped trees [4,28,29]. Other studies have used tomography for the numerical simulation of wave propagation to determine the size of the cavity and for developing a new approach to the quantitative analysis of acoustic tomography images, demonstrating the effectiveness of the method relative to others [30]. ...
... The sensor transmitted the sound waves and formed the data matrix. The sound velocity was automatically calculated in the software, and a tomogram was generated [29,46,48]. ...
... The sens transmitted the sound waves and formed the data matrix. The sound velocity was au matically calculated in the software, and a tomogram was generated [29,46,48]. ...
View
... Ez természetesen hosszabb ideig tart [32]; [4]; [3]. Ha az egészséges faanyagban mért átlagsebesség 85-90 %-os értékre csökken, az már utalhat korhadásra [12]; [35]. Ezen az elven alapul ennek a műszernek a működése (2. ...
Városi fák vizsgálati módszerei
Article
  • Jan 2024
Az utóbbi években a megváltozott klíma komoly kihívások elé állította a zöldfelületeken megtalálható növényállományt. A fokozódó növényegészségügyi problémák mellett az időjárás extrém jelenségei is nehezítik a fák életét a városban. A lakosság aggódva figyeli az orkán erejű szélben mozgó lombkoronát, vagy a törzsön kialakuló odvasodásokat. Ugyanakkor társadalmi ’elvárás’ – valamint a fenntarthatóság szempontjából is fontos érdek – a városi fák életének meghosszabbítása a kivágásuk helyett. Mit tehetünk? Elsőként a probléma ’gyökerét’ kell feltárnunk, melyre – többek között – az alábbiakban ismertetett módszerek állnak a faápoló szakemberek rendelkezésére.
View
Acoustics of Trees
Chapter
  • Feb 2025
Acoustic technology is appropriated for quality assessment of a very large range of tree’s size and quality such as for trees belonging to the cultural heritage, for forest trees, for trees in plantations, for urban trees, for seedlings and even for forest seeds. Acoustic non-destructive methodology allows to study the characteristics of the standing trees and to detect some of the particularities of their living structure such as the pith, the juvenile wood, the reaction wood, the ring shake, the slope of grain, the cavities and the decay. The major effects of the sylvicultural treatments of forest trees in plantations such as thinning, pruning, etc., can be detected with acoustic technology.
View
Reliability of Noninvasive Sonic Tomography for Detection and Quantification of Internal Defects in Yoshino Cherry
Article
  • Mar 2024
Preventive maintenance through monitoring and early detection is important for trees that are structurally weak due to internal decay. Once internal decay has occurred, recovery of lost strength is irreversible. The decaying tree becomes vulnerable to external impacts, which may lead to breakage or windthrow. The Yoshino cherry (Cerasus×yedoensis (Matsum.) “Somei-yoshino”) accounts for a high proportion of landscape trees in Asia. Testing the reliability of noninvasive sonic tomography (SoT) to estimate internal defects could facilitate structural stability evaluation and proactive preventive management. We performed noninvasive SoT and invasive resistance microdrilling to detect and quantify internal defects in old and large Yoshino cherry trees. Generally, SoT reflected the areas and location of severe structural defects, showing a correlation with the resistance microdrilling results (R² = 0.542, p < .001). However, when cracks were present in disks, the SoT overestimated defects and errors mainly observed in the transition zone (green). Based on these findings, when evaluating the SoT, careful decisions are needed to distinguish between actual defects and broad sonic shadows. Furthermore, additional evidence from drilling resistance is required to differentiate between incipient decay and cracks. The results of this study provide valuable insights for enhancing the interpretation of sonic tomograms. Study Implications: We suggest defect boundaries in sonic tomograms should be redefined to improve the accuracy of interpretation for any new species being studied. Careful drilling resistance measurements should be taken, especially in transition zones (green areas in tomogram) and incipient decay zone (light brown areas). Noninvasive sonic tomograms only reflect acoustic properties of the tested cross-section of a tree and cannot be considered an actual representation of the internal conditions until the readings are calibrated to destructive sampling results.
View
Non-destructive detection of tree deterioration due to termite attack in plant conservation areas
Article
Full-text available
  • Dec 2023
Cibodas Botanic Gardens (CBG) is an ex-situ conservation area in tropical highlands. Termites are one of the nuisance organisms in the collection that have conservation value. The number of attacks and the intensity of termite attacks require more strict attention. The main problem in tree health analysis is the difficulty in detecting internal weathering due to attacks by wood-destroying organisms which causes damage to the tree’s core (heart rot) and butt rot. Arborsonic is a tool used and developed to detect and assess tree damage, especially to the trunk. This study aimed to analyze the deterioration of the main trunk of a living tree with visual signs of termite attack using a non-destructive method. Termite observation plots were made in 4 replications to determine the type of termites that attack. Observations on termite baits in 4 plots showed no attack on the baits. Observations on 12 sample trees tested in 4 plots showed low-intensity damage. Visual signs of termite attack can be used as a sign of wood decay, but the effect is minor.
View
Tree Failure Assessment of London Plane (Platanus × acerifolia (Aiton) Willd.) Street Trees in Nanjing City
Article
Full-text available
  • Aug 2023
The London plane (Platanus × acerifolia (Aiton) Willd.) street tree is a symbolic tree species in Nanjing City, which is known as the “city card”. However, accidents such as street trees falling over cars, affecting traffic, and hurting people have seriously affected the daily lives of citizens. Thus, it is of vital significance to accurately assess the potential for tree failure in London plane street trees in Nanjing City. This study comprehensively considers the growth condition of London plane street trees and their impact on traffic, establishes a scientific street tree failure assessment scheme that contains eight characteristics, creates a tree failure assessment database by thoroughly collecting data on trees, and develops a tree failure assessment model based on factor analysis and k-means clustering. The assessment results show that street trees that pose a high or medium potential for failure are present in proportions of 4.47% and 34.85%, respectively, and are mostly found in Gulou District, Xuanwu District, and Qinhuai District. The average tree failure score of London plane street trees on Changjiang Road in Xuanwu District is the highest, while the road with the lowest tree failure score is Mufu East Road in Gulou District. The results will provide a scientific basis for the maintenance of London plane street trees in Nanjing City and have reference significance for other street tree failure assessment studies.
View
Acoustic Tomography as a Supporting Tool in the Sustainable Management of Historic Greenery: Example of the Church Garden in Horostyta (Poland)
Article
Full-text available
  • May 2023
Senile trees in historic church gardens have natural, aesthetic, historical, and cultural value. Cutting them down too hastily annihilates the achievements of entire generations. We should try to preserve the greenery surrounding historic churches and integrate it into a clear compositional arrangement with the sacral architecture. The primary purpose of the paper was to describe the process of inventorying 200-year-old trees and to present the revalorization project for the garden around the historic Orthodox church in Horostyta, located in the Lublin Voivodeship, in southeastern Poland. The church complex consists of a wooden 18th-century building, bell tower, garden, and cemetery. Within the church garden’s boundaries, there are 15 trees, with two predominant species: Acer pseudoplatanus L. and Tilia cordata Mill. These trees are of varying ages and health conditions. We used acoustic tomography to perform tree health diagnostics. Three trees, for which the initial visual assessment was disturbing, were examined thanks to detailed tomography tests. Then, through a project adapting the church garden to the health conditions of the ancient trees, they were separated from users by flowerbeds and no small architectural objects were placed around them. The presented development concept forms a compromise between tradition and the modern user’s needs. In 2007, a general renovation of the temple building was completed. Currently, the presented project for the church garden is being implemented.
View
Wood Decay Measurement of Shiitake Cultivation Logs Based on Spin Relaxation Times Obtained using Magnetic Resonance Imaging
Preprint
Full-text available
  • May 2023
To harvest large shiitake mushrooms ( Lentinula edodes ), it is important to adjust the suitable cultivation environment for shiitake mycelium so that it can extend throughout an entire log, maximizing wood decomposition and nutrient absorption. We attempted to measure the degree of wood decay of cultivation logs noninvasively by Magnetic Resonance Imaging (MRI). The cultivation logs were sourced from konara oak ( Quercus serrata ), which was inoculated with shiitake mycelium for 0.6 to 4 years. After MRI measurements, the logs were cut into wood pieces between 1 to 2 cm in length, and the degree of wood decay of the individual pieces was evaluated using the dry wood density. NMR signals were measured using a long echo time, TE = 11 ms, to obtain T 1 and T 2 relaxation times of free water in the logs. The results showed that wood decay of the cultivation logs correlated well with T 2 values and poorly with T 1 values. In addition, based on the obtained T 2 map, the spatial distribution of wood decay within cultivation logs 1.6 years after inoculation could be visualized.
View
View
Horticultural evaluation of woody plants in the National Cemetery Martin, Slovakia
Article
Full-text available
  • Jan 2007
In this article we present the results of horticultural evaluation of woody plants in the National Cemetery in Martin. There have been evaluated 486 woody plants, representing 43 taxons from 25 species. The obtained data reveal that 265 woody plants are of a very low horticultural value, corresponding to the degrees 1 and 2; 192 of them are acceptable (degree 3), and 29 are of a high value (degree 5). The Pearson's correlation coefficient (r) was used for expressing the relation between the horticultural value and size of the woody plants evaluated.
View
Can the impulse propagation speed from cross-section tomography explain the conditioned density of wood?
Article
Full-text available
  • Jul 2014
Tomography is a wave-based technique used to depicture tree cross-sections; specifically, impulse tomography uses data given by the passage of impulse waves, which were primarily influenced by density, modulus of elasticity, and moisture content of wood. The influence of wood characteristics on various kinds of waves has been extensively studied, allowing the establishment of statistical correlations between wave behavior and wood properties. In this context, the relationship between impulse speed from cross-section tomography and conditioned density that was obtained on diametrical sample by X-ray densitometry was analyzed using logs of three tree species with different densities that were air dried to 12 % moisture content. For each species, means from 5 mm length intervals of conditioned density profile graph (ρ 12%) and impulse speed distribution graph (S 12%) on the same diametrical sample are used to fit models. Joining data from all species, the exponential model ln⁡ρ12%=−4.32822+1.67894∗ln⁡S12% \ln \rho_{12\% } = - 4.32822 + 1.67894 *\ln S_{12\% } was obtained with correlation coefficient of 0.85 and highly significant parameters. The results indicate that conditioned density could be explained by impulse speed on the cross-section, but research is necessary to make a useful tool out of it.
View
The Measurement of Wood Decay in Landscape Trees
Article
Full-text available
  • May 2010
The evaluation of wood in a tree trunk is essential for tree risk assessment, however the accurate measurement of decay is still in its infancy. A review of the current methods used for the field measurement of wood decay in landscape trees is presented. The methods are compared in terms of the damage caused to tree tissues, ease of use and the level of accuracy. Moderately invasive decay detecting devices, such as constant feed drills, are accurate for locating wood decay in a tree. In contrast computerized tomography devices are less damaging to tree tissues, but results may be difficult to interpret.
View
Application and Comparison of Three Tomographic Techniques for Detection of Decay in Trees
Article
Full-text available
  • Mar 2003
This paper reports application of electric, ultrasonic, and georadar tomography for detection of decay in trees and their comparison with the traditional penetrom- eter. Their feasibility in arboriculture is also evaluated, critically considering some "open problems." The experi- ments were carried out in an urban environment on two plane (Platanus hybrida Brot.) trees. Both trees, after felling, showed extensive white rot in the central cylinder. The electric tomography revealed low resistivity zones roughly centered in the trunk. A comparison with the successively cut sections showed a fine correspondence to decayed areas and a strong correspondence between high moisture zones and low resistivity zones. Ultrasonic tomography demonstrated to be a very effective tool for the detection of internal decay, accurately locating the position of the anomalies and estimating their size, shape, and characteris- tic in terms of mechanical properties. With the georadar technique, the high contrast of electromagnetic impedance measured between the inner decayed section and the outside sound section allowed the detection of the interface between the sound and decayed section of the tree, using radar acquisition in reflection modality. The penetrometer profiles detected the low-resistance areas inside the two trunks.
View
Picus Sonic Tomography For The Quantification Of Decay In White Oak (Quercus Alba) And Hickory (Carya Spp.)
Article
Full-text available
  • Sep 2004
The Picus Sonic Tomograph is a noninvasive tool for assessing decay in trees. It works on the principle that sound waves passing through decay move more slowly than sound waves transversing solid wood. By sending sound waves from a number of points around a tree trunk to the same number of receiving points, the relative speed of the sound can be calculated, and a two-dimensional image of the cross-section of the tree, a tomogram, can be generated. Picus tomography and visual inspection were used to evaluate 27 cross-sections from 13 trees. The tomograms correlated closely with the visual assessment of decay. In 10 samples where no decay was present, Picus found no decay. In the remaining 17 samples, Picus detected less decay than was observed visually. Differences in most cases were small (average of 5% of total area). In terms of predicting the location of decay, on average 3% of the total area was a false positive (where the tomogram showed that decay was present but the cross- section did not), and an average of 8% of the area was false negative (the cross-section showed decay that was not seen on the tomogram).
View
Nondestructive evaluation of wood
Article
  • Jan 1998
Our forests are an extremely valuable resource. In addition to their value for aesthetics and recreation, the forest serves as a renewable source of raw material for an ever-increasing list of wood and fiber products.
View
Field guide for visual tree assessment (VTA)
Article
  • Feb 1994
The VTA-Method (VISUAL TREE ASSESSMENT) consists in three steps. Visual control of the tree in order to find external symptoms of internal defects. If the constant stress distribution in a tree is disturbed due to the presence of a defect the tree attaches more wood at the overloaded spot. So bulges or dents are formed near decayed hollows and ribs near cracks etc.If symptoms are detected the related defect has to be confirmed and measured by deeper inspection. This can be done by measuring the velocity of a sound wave traveling through the cross-section and by drilling methods. The strength of the remaining healthy wood is determined now with the FRACTOMETER, a wood testing device in pocket-size.If defect size and wood quality is known failure criteria are used to decide whether the tree is dangerous or not.VTA is nondestructive for healthy trees. Only if there is a reason for increasing concern the tree is subject of deeper inspection but also in this case the wounding of the tree has to be kept minimum.
View
Acoustic wood tomography on trees and the challenge of wood heterogeneity
Article
The assessment of tree stability requires information about the location and the geometry of fungal decay or of a cavity in the interior of the trunk. This work aims at specifying which size of decay or cavity can be detected non-destructively by acoustic wood tomography. In the present work, the elastic waves that propagate in a trunk during a tomographic measurement were visualized by numerical simulations. The numerical model enabled to systematically investigate the influence of fungal decay on tomographic measurements neglecting the heterogeneity of wood. The influence of wood heterogeneity was studied in laboratory experiments on trunks. The experiments indicated that the waveforms of the measured signals are by far more sensitive to the natural heterogeneity of trunk wood than the travel times, thereby making waveforms unsuitable for decay detection. Thus, it is recommended to further develop the travel time inversion algorithms for trunks and to neglect the information in waveforms or amplitudes. Fungal decay is detectable if the influence of the decay is distinguishable from the influence of the heterogeneity. It was found from the numerical analysis that the cross-section of a cavity, which is larger than 5% of the total cross-section of the trunk, can be detected by acoustic wood tomography.
View
A simple anisotropy correction procedure for acoustic wood tomography
Article
Anisotropy of acoustic propagation velocities is a ubiquitous feature of wood. This needs to be considered for successful application of travel time tomography, an increasingly popular technique for non-destructive testing of living trees. We have developed a simple correction scheme that removes first-order anisotropy effects. The corrected travel-time data can be inverted with isotropic inversion codes that are commercially available. Using a numerical experiment, we demonstrate the consequences of ignoring anisotropy effects and outline the performance of our correction scheme. The new technique has been applied to two spruce samples. Subsequent inspection of the samples revealed a good match with the tomograms.
View