Young's modulus E and internal friction Q -1 in longitudinal (L) direction and specific gravity γ were measured for numerous specimens of 25 softwood species. There was a high correlation between Q -1/(E/γ) and E/γ, and the suitability of wood for musical instruments can be evaluated by using the value of E/γ. Furthermore, effects of grain angle in the longitudinal-radial plane on Young's modulus and internal friction of wood were investigated. From these results, it is concluded that the value of internal friction as well as Young's modulus of wood is determined in large part by microfibril angle in the S2 layer of tracheid against the L direction.

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In order to develop criteria for the physical evaluation of wood for soundboards of musical instruments, measurements were made of dynamic Young's modulus E', static Young's modulus E, internal friction Q-1 in longitudinal direction, and.specific gravity ~, for numerous species of broad-leaved wood. From the results obtained, including those of our previous paper on coniferous wood [1], it was found that the suitability of wood for soundboards could be evaluated by the quantity of Q-I/(E'/7), and that there were very high correlations between Q-~/(E'/7) and E'/7, and between E' and E, regardless of wood species. Consequently, it becomes pbssible to select practically any wood suitable for soundboards by using the value of E/)J, which can be measured easily, and it was derived that the relation between E'/7 and Q-1 of wood could be expressed by an exponential equation regardless of wood species.