The purpose of the study was to analyze the influence of the quality class and the orthotropy of wood upon the sound absorption coefficient, the reflection and the impedance ratio of two species widely used for stringed musical instruments, namely spruce (Picea abies L. Karst) and maple (Acer pseudoplatanus L.). An impedance tube for the frequency range 100–6400 Hz was used in these experimental determinations. Knowing the influence of porosity and tortuosity on the acoustic absorption, these properties were also determined, as well as the sound reduction coefficient and the maximum values of the acoustic absorption coefficients in relation to frequency. The main results highlighted the differences between the anatomical quality class of the wood within each species, but also concerning the sound direction relative to the three main sections of wood, as an orthotropic material. The article highlights the acoustic performance parameters related to the frequency of the wooden material and its relationship to density, porosity and quality class. The results represent useful information for musical instruments manufacturers and more.

This research investigated the potential of some European wood species for use in the manufacturing of the back plates of violins as an alternative to the quite rare curly maple wood. An experimental modal analysis was employed for this purpose using the impact hammer method. The modal analysis was performed both on the top and back plates, as individual structures, and then after being integrated into the violin body. The modal analysis envisaged the determination of the eigenfrequencies (natural frequencies), the number of spectral components, and the quality factor, as important indicators of the acoustic performances of a musical instrument. A multi-criteria analysis based on the values obtained for these indicators allowed interesting findings concerning the acoustic properties of the selected wood species (hornbeam, willow, ash, bird-eye maple, walnut, and poplar). Same as curly maple, they all have special aesthetics, but only hornbeam, willow, and ash wood proved to have acoustic potential as well.

This paper presents the results of an experimental study performed on seven violins obtained from a top plate made of resonance spruce and a back plate made of curly maple. Each pair of plates had a different modification to its thickness profile. Some were thickened and others were thinned compared to the classical thickness profile. Then, a soloist played a musical sequence on each violin and the acoustic signals were recorded. The sound quality of the signals was evaluated with a psycho-acoustic evaluation based on a blind questionnaire completed by listeners. It turned out that: (1) respondents with more musical experience (especially those with over 26 years of experience) were more demanding in assessing sound clarity and offered the widest range of scores in assessing this quality; (2) the musical experience of the respondents influenced to the highest degree the appreciation of the warm sound quality; (3) the scores for the violins with thinned plates were weaker, especially according to the psycho-acoustic analysis; and (4) the highest score was obtained by the violin with the thickest plates, which can be correlated with the two dominant frequencies extracted from the FFT analysis, whose values coincide with the frequencies of the B1− and B1+ modes.