The dynamic Young's modulus and the internal friction of many specimens made of a trunk of Akaezomatsu and that of Kuroezomatsu were measured using a flexural vibration method, and the comparison in these properties between Akaezomatsu and Kuroezomatsu was made. In order to find out the difference in dynamic properties of the wood classified by the experience of piano industry, these specimens were classified into the high grade wood used for grand piano soundboards, the medium grade wood used for upright piano soundboards and the low grade wood which is not used for soundboards, and their properties were investigated statistically.
The main results obtained are as follows:
(1) It was observed that in acoustical properties Kuroezomatsu was not inferior to Akaezomatsu when used for the soundboards of musical instruments, and that the percentage of the low grade wood of the former was about twice that of the latter. It was also found that such a high percentage of the low grade wood was mainly caused by the colour of Kuroezomatsu. Consequently, it seems that the reason why Kuroezomatsu is not used for the soundboards is not because of its acoustical properties, but because of its low yield.
(2) The results of the statistical investigation on the properties of the classified wood agreed with the general opinion on the physical properties which are desirable for the wood for soundboards. Consequently, it was found that the selection method of the wood for soundboards used in piano industry, which was learned through experience, was marvelous.
