@inproceedings{ClauderMunkPfriem2022, author = {Clauder, Lothar and Munk, Christoph and Pfriem, Alexander}, title = {The influence of thermal modification on the initial material-brightness (L*), documented by in-situ measurements}, series = {European Conference on Wood Modification 2022}, booktitle = {European Conference on Wood Modification 2022}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-2801}, pages = {4}, year = {2022}, abstract = {In this study, the influence of the thermal modification on the characteristic brightness of the raw material Alder (Alnus rubra) and Maple (Acer pseudoplatanus) was investigated by spectral photometric in-situ analysis.}, language = {en} } @inproceedings{MunkClauderPfriem2018, author = {Munk, Christoph and Clauder, Lothar and Pfriem, Alexander}, title = {Acoustical comparison of two different guitars, made of untreated tropical wood and thermally modified wood, using a frequency response analysis}, series = {Northern European Network for Wood Science \& Engineering (WSE)}, booktitle = {Northern European Network for Wood Science \& Engineering (WSE)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-2850}, year = {2018}, abstract = {To this day, many guitar makers around the world use primarily tropical woods such as rosewood (Dalbergia spp.) for their production. Due to the current CITES regulation of January 2017 regarding the trade of tropical woods, it becomes inevitable to generate alternative materials with similar material properties to be generated and established. Part of this study is an acoustic comparison of two guitars. One made of untreated tropical wood [Dalbergia nigra Benth.)] and one made of European thermally modified wood (TMT) species. [Pyrus (L.) and Alnus (Mill.)]. The method used allows a significant statement about the acoustic radiation performance of stringed and plucked instruments. The experimental setup consists of an impulse hammer for excitation of a force in the center of the bridge and a microphone for recording the signal radiated by the guitar body at a distance of one meter from the sound hole. A front-end was used to record the data, and further processing was done using analysis software to determine frequency response functions (FRFs) of the two instruments. The FRFs determined can be subdivided into several ranges which contain the different acoustic information about bass range, loudness, clarity, brightness and sharpness of the instruments. Examination of the frequency ranges reveals an acoustic similarity between the two guitars. Slight differences can be seen in the bass and loudness areas, where the guitar from TMT has a higher average level. Clearer differences are offered by the areas of clarity, where the guitar made of tropical wood shows a higher average level. In summary, the method gives an efficient acoustic impression as a function of the natural frequencies of the two guitars. The measured data show similarities and thus comparable acoustic properties of the instruments. However, additional effects such as psychoacoustic sensations or musical taste for the complete acoustic impression of an instrument are also of importance. Therefore, further empirical and fundamental research is needed to obtain a more detailed acoustic impression of the instruments.}, language = {en} } @inproceedings{MunkClauderPfriem2019, author = {Munk, Christoph and Clauder, Lothar and Pfriem, Alexander}, title = {Sound absorption coefficient of thermally modified and unmodified wood species measured in an impedance tube}, series = {Northern European Network for Wood Science and Engineering (WSE) - 15th Annual Meeting 2019}, booktitle = {Northern European Network for Wood Science and Engineering (WSE) - 15th Annual Meeting 2019}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-2890}, year = {2019}, abstract = {Different parts of the guitar body are made of certain wood species, selected by their specific properties. The sound board, which is mainly made of spruce or cedar, transfers the vibration of the strings to the resonance body by means of the bridge. The sides and the back of the guitar rather reflect the sound of the acoustic vibrations and are predominantly made of tropical hardwoods like palisander, mahogany or ebony species. These species have limited availability and are listed on the CITES Annex I and II. To substitute tropical wood species, thermally modified European wood species with improved acoustic properties and dimensional stability may be used. Although the acoustic reflection of the sides and the back parts of a guitar body is an important property, there is not much knowledge about this reflection behaviour of wood. A few studies like the work of Hong (1989), Kang (2010) or Smardzewski et al. (2013) investigated the sound absorption properties of unmodified wood. Subsequently this study considers the sound absorption coefficients of unmodified and thermally modified European wood species in comparison to an unmodified tropical wood species.}, language = {en} } @inproceedings{MunkWohlertPfriem2021, author = {Munk, Christoph and Wohlert, Hauke and Pfriem, Alexander}, title = {Investigation of the influence of two different thermal treatment processes on the change of various material properties of spruce resonance wood (Picea abies (L.) Karst.)}, series = {Northern European Network for Wood Science and Engineering - 17th Annual Meeting 2021}, booktitle = {Northern European Network for Wood Science and Engineering - 17th Annual Meeting 2021}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-2909}, pages = {3}, year = {2021}, abstract = {In recent years, a large number of different studies have shown that a variety of positive property changes can be achieved by thermally treating spruce resonance wood. Various methods have been established, which differ mainly in the choice of treatment atmosphere, but also in the associated treatment duration and temperature. Part of the present investigation was to compare a thermal-vacuum process with a process which takes place in an oxygen-reduced atmosphere, with regard to various property changes. The results show that both processes achieved similar results in terms of dynamic acoustic property changes. Larger differences were found with regard to moisture behavior and color change.}, language = {en} } @inproceedings{MunkPfriem2022, author = {Munk, Christoph and Pfriem, Alexander}, title = {Influence of thermal modification and subsequent linseed oil impregnation on the sound propagation velocity and related acoustic properties of various wood species}, series = {Tenth European Conference on Wood Modification}, booktitle = {Tenth European Conference on Wood Modification}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-2916}, year = {2022}, abstract = {In the field of instrument making, the use of indigenous wood species is becoming more and more important due to the increasing environmental awareness of instrument makers and their customers. As the properties of some of these wood species cannot meet the high demands of this field of application, processes are being sought that can achieve improvements. In recent years, many studies have shown that different modification methods, such as furfurylation, thermal treatment, densification or impregnation methods, can partly improve wood properties such as elasticity, strength values, damping behaviour, but also moisture behaviour and wood moisture content significantly. The extent to which different modification processes and their positive changes in properties can be combined with each other and thus achieve further improvements will become increasingly important in the future, not only in instrument making but also in other areas of application. Therefore, this study investigated the influence of thermal treatment followed by linseed oil impregnation of wood on its sound propagation velocity and the associated acoustic properties of characteristic impedance and acoustic radiation.}, language = {en} } @inproceedings{MunkPfriem2022, author = {Munk, Christoph and Pfriem, Alexander}, title = {Influence of residual oxygen content during thermal modification process on mass loss, brightness colour and dynamic Young´s modulus of Fagus sylvatica (L.)}, series = {18th Annual Meeting of the Northern European Network for Wood Science and Engineering, 21-22 September 2022, G{\"o}ttingen, Germany}, booktitle = {18th Annual Meeting of the Northern European Network for Wood Science and Engineering, 21-22 September 2022, G{\"o}ttingen, Germany}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-3582}, pages = {1 -- 3}, year = {2022}, abstract = {The thermal modification of wood is considered to be an environmentally friendly and cost-effective treatment process, which has been able to establish itself in many areas of application due to its positive effect on a whole range of different material properties through a wide variety of process designs. In addition to heat transfer and pressure, closed and open systems differ primarily in the choice of treatment atmosphere mainly used to prevent combustion (Sandberg et al. 2021). Although many studies in recent years have investigated influencing process parameters such as temperature, pressure or treatment duration, there exists a knowledge gap regarding the influence of the treatment atmosphere or its behaviour during the treatment process (Candelier et al. 2016). Therefore, this study aims to analyse different oxygen-nitrogen concentrations in the treatment atmosphere at different residual oxygen levels during the process duration and their influence on different property parameters of Fagus sylvatica (L.).}, language = {en} } @inproceedings{BenderMunkDamayetal.2022, author = {Bender, Tobias and Munk, Christoph and Damay, J{\´e}r{\´e}mie and Jousserand, Michael and G{\´e}rardin, Philippe and Pfriem, Alexander}, title = {The Effect of Thermal Treatment of Sycamore Maple (Acer Pseudoplatanus L.) prior to Impregnation with Furfuryl Alcohol, regarding Homogeneity and Swelling Behaviour}, series = {18th Annual Meeting of the Northern European Network for Wood Science and Engineering, 21-22 September 2022, G{\"o}ttingen, Germany}, booktitle = {18th Annual Meeting of the Northern European Network for Wood Science and Engineering, 21-22 September 2022, G{\"o}ttingen, Germany}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-3597}, pages = {1 -- 1}, year = {2022}, abstract = {Impregnation of wood with certain chemical compounds is a well established method to improve its physical and mechanical properties. However, the result is often not quite homogeneous. This study examines the effect of two varying thermal treatments on the impregnability of sycamore maple (Acer Pseudoplatanus L.) with furfuryl alcohol (FA), and on the resulting Anti-Swelling-Efficiency (ASE).}, language = {en} } @inproceedings{MunkBiewerDamayetal.2024, author = {Munk, Christoph and Biewer, Raphael and Damay, J{\´e}r{\´e}mie and Jousserand, Michael and G{\´e}rardin, Philippe and Pfriem, Alexander}, title = {Acoustic properties of thermally treated and furfurylated European hardwood species}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-9864}, pages = {1 -- 3}, year = {2024}, abstract = {Three hardwood species, including alder (Alnus glutinosa), sycamore maple (Acer pseudoplatanus) and hornbeam (Carpinus betulus), were analyzed for changes in their acoustic properties due to thermal treatment (TM), furfurylation (FU) and a combination of both types of treatment (TF). TM was carried out in a nitrogen atmosphere at 200 °C for 4 hours. For FU, a solution of 85\% furfuryl alcohol, 10\% water and 5\% tartaric acid was used, which was impregnated in a vacuum pressure process, followed by polymerization at 120 °C for 16 hours. For each wood species, one test group was left as an untreated reference, the other groups were treated according to the treatment types TM, FU and TF. Per group 10 samples were tested using experimental modal analysis. Due to the orthotropy of the wood, the acoustic parameters dynamic modulus of elasticity (E), damping and sound radiation coefficient were determined in both the longitudinal and radial directions. The results show that TM slightly decreases longitudinal E for all three species and slightly increases radial E for maple and hornbeam. FU and TF strongly increase the E in the radial direction, especially for maple and alder. For all three species the damping is reduced by TM, more in the radial direction than in the longitudinal direction. FU and TF increase the damping in the longitudinal direction, mainly for maple and alder, but also reduce it in the radial direction. The sound radiation coefficient is reduced by FU and TF for all three species, particularly in the longitudinal direction. However, in both the longitudinal and radial directions, TM slightly increases the sound radiation coefficient for all three species. The anisotropy ratio of the longitudinal/radial E of all three species is reduced by FU and TF, whereas TM has no significant effect on it.}, language = {en} }