ACOUSTICAL PROPERTIES OF 10 AMAZONIAN HARDWOODS

Among the various wood forestry species only a few are employed on manufacturing musical instruments due to the outstanding performance of theirs physical and mechanical properties. This study aimed to evaluate the acoustics properties of ten tropical Amazonian Hardwoods. The forest species were representatives of groups of low, medium and high specific gravity and produced 10 samples of each in the dimensions of 3 x 20 x 300 (thickness x width x length). The acoustic evaluation was performed using the method of free-free flexural vibration testing according to ASTM E1875 and evaluated the frequency of resonance, the damping ratio and the speed of sound propagation. The studied hard-woods were compared with spruce and maple woods which are traditional materials em-ployed in the manufacture of musical instruments. A satisfactory acoustic result was ob-served when compared with traditionally known species. The frequency of resonance varied between 125.1 and 205.2Hz while the speed of sound propagation and logarithmic decrement ranged between 3910-4840 m/s and 0.026-0.037, respectively. It was possible to observe that significant acoustic variations occurred within the same species, while damp-ing ratio was the characteristic that most varied within the same species. This result may have occurred due to differences in cutting position of the boards and even due to phenotypic characteristics of wood specie. The results indicated that the native Amazonian Hardwood species are potentially suitable to produce high quality musical instruments. However, for a better elucidation of the results it is necessary to manufacture some musical instruments with several possible combinations of species by parts of the instruments, as well as practical tests with musicians. It should be emphasized that this selection is not a definitive criterion for choosing a species for the manufacture of the instrument, but rather an indication of their potentiality.