Effect of soaking process in water on the acoustical quality of wood for traditional musical instruments

Abstract

The damping coefficient of the first mode in the longitudinal vibration of mulberry and walnut woods was characterized to find justifications for the water soaking of woods in traditional musical instrument industries in Iran. Visually clear and sound beams were prepared from Morus alba and Juglans regia, and the damping coefficient in the temporal field was evaluated before and after three continuous cycles of soaking of specimens in distilled water (24 hours, pH 7, and temperature 50 oC). Experiments were conducted with free longitudinal vibration using the free-free bar method in 360 × 20 × 20 (L ×R ×T) dimensions. Soaking cycles homogenized and decreased the damping coefficient in both species. On the basis of such results, the suitability of water soaked specimens is discussed in traditional musical instrument industries in Iran, taking into the account the longitudinal sound velocity, modulus of elasticity, and density affecting the acoustic limits. These two series of testing specimens were suitable in resonators and xylophone bars for backs, sides, and ribs and not for top plates, unless as the outstanding piece, since they marginally meet the density, sound velocity and damping coefficient limits qualified for those applications.