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The objective of the study was to analyze the influence of coating treatments on sound propagation speeds in thin boards, along the longitudinal and radial directions of resonance wood. The samples studied were thin boards made of spruce and maple wood with dimensions of 240 mm × 80 mm × 4 mm (length × width × thickness) subjected to different coating treatments (oil-based varnish and alcohol varnish) as well as unvarnished samples, exposed to radiation UV, and specimens treated in the saline fog. The test method consisted of evaluating the propagation speeds of Lamb waves applied to thin plates, according to a semicircular test model, so that the results highlighted both the acoustic response in the longitudinal and radial directions as well as the variation in the anisotropy of the samples with the change in the sound propagation direction relative to wood fibers. Based on the statistical analysis, sound propagation speed profiles were obtained in each of the 38 directions analyzed for all wood samples. The results highlighted that the oil-based varnish led to a decrease in the speed of propagation in the radial direction, compared to the alcoholic varnish, whose major effect was in the longitudinal direction, on the spruce wood. On maple wood, increasing the number of varnish layers, regardless of the type of varnish, led to a decrease in the anisotropy ratio between the longitudinal and radial directions. [ABSTRACT FROM AUTHOR]

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Copyright of Buletinul AGIR is the property of Asociatia Generala a Inginerilor din Romania and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Classical guitar necks were submitted to 40, 65 and 80% relative humidity (RH) during time periods ranging from 24 h to several months, and moisture-induced deformations were observed. Different types of classical guitar necks were investigated in terms of structure and reinforcement. The influences of the wood species and the neck reinforcements on the moisture content (MC)-induced deformation were in focus. First, before humidity exposure in the climatic chamber, the relative positions of three points marked on each sample were measured with a control ruler and noted. After exposure, the displacement of the reference points on the samples were verified periodically. The differences between the measurements in different stages and reference positions were calculated, resulting in relative displacement data of the measured points. During the experiments, the MC of the sample was monitored by weighing. The variation of RH leads to dimensional instability and moisture-induced stresses of the guitar necks, which affect the acoustic quality of a guitar. Steel enforcement of the guitar neck improves this situation. [ABSTRACT FROM AUTHOR]

The present study envisaged the modal analysis of the top and back plate of violins, in order to establish the first natural frequency and the damping factor of each plate as individual violin part. The differences between the wood species involved (resonance spruce wood - used for the top plates and curly maple wood - used for the back plates), but also the influence of the wood characteristics specific to four different quality classes of violins upon were investigated by a dynamical test, using excitation of the plate by means of a hammer and signal acquisitioning by means of an accelerometer. The results revealed that the first natural frequency of resonance spruce wood lies at about 140Hz and that of curly wood at 327Hz. The damping factor has the lowest value for the spruce top plate of maestro-class violins. [ABSTRACT FROM AUTHOR]

Numerous studies highlight the analysis and modeling of the characteristics of the musical timbre of violins, obtained on the basis of the acoustic perception of the experienced subjects, the acoustic quality of the violins being interpreted on the basis of the statistical analysis of the psycho-acoustic impressions. Also, there are studies on the structural behavior of the violin to determine signature modes. However, the analysis of the radiated frequency response in three overlapping regions, as described in the literature, have been less studied. In this sense, the paper presents the study of the behavior of a historical violin, on the entire audio range, examining the frequency response function. The acoustic signal is produced by the excitation of the strings by the violinist, and the recording of the acoustic signals was made both in a concert hall and in an anechoic chamber. The results in the form of acoustic spectrograms, frequency spectrum, magnitude, and power spectrum density for each receiver were analyzed comparatively between the two acoustic spaces, the sounds emitted by the violins are amplified or dampened. [ABSTRACT FROM AUTHOR]

The acoustic quality of a violin is closely related to the quality of the material, the geometric parameters of the violin body, the type of varnish and last but not least the time factor expressed by the aging of the wood. In the current study, the investigations regarding the influence of the artificial aging of the wood on the acoustic and dynamic properties of the resonance wood are presented. The researches were carried out on rectangular wooden boards - spruce and maple from the musical instrument factory. All the physical, acoustic and dynamic parameters of the samples were determined before the artificial aging and after accelerated aging with UV and thermal radiation, about 300 hours. Comparing the sound propagation speeds and the modal frequency spectrum of the boards before and after UV exposure, quantitative and qualitative changes in the acoustic and dynamic parameters are emphasized. [ABSTRACT FROM AUTHOR]