. Bulletin. Forests and forestry -- United States. RESONANCE. 25 sound be produced by a direct blow, but a thin board may be set vibra- ting and be made to give a tone by merely producing a suitable tone in its vicinity. Tbe vibrations of the air, caused by the motion of the strings of the piano, communicate themselves to the board, which vibrates in the same intervals as the string and reeuforces the note. The note which a given piece of wood may emit varies in pitch directly with the elasticity, and indirectly with the weight, of the wood. The ability of a properly shaped sounding board to r
. Bulletin. Forests and forestry -- United States. RESONANCE. 25 sound be produced by a direct blow, but a thin board may be set vibra- ting and be made to give a tone by merely producing a suitable tone in its vicinity. Tbe vibrations of the air, caused by the motion of the strings of the piano, communicate themselves to the board, which vibrates in the same intervals as the string and reeuforces the note. The note which a given piece of wood may emit varies in pitch directly with the elasticity, and indirectly with the weight, of the wood. The ability of a properly shaped sounding board to respond freely to all the notes within the range of an instrument, as well as to reflect the character of the notes thus emitted (i. e., whether melodious or not), depends, first, on the structure of the wood and next on the uniformity of the same throughout the board. In the manufacture of musical instruments all wood containing defects, knots, cross grain, resinous tracts, alternations of wide and narrow rings, and all wood in which summer and spring wood are strongly contrasted in structure and vari- able in their proportions, is rejected, and only radial sections (quarter sawed, or split) of wood of uniform structure and growth are used. The irregularity in structure, due to the presence of relatively large pores and pith rays, excludes almost all our broad-leaved woods from such use, while the number of eligible woods among conifers is limited by the necessity of combining sufficient strength with uniformity in structure, absence of too pronounced bands of summer wood, and relative freedom from resin. Spruce is the favored resonance wood; it is used for sounding boards both in pianos and violins, while for the resistant back and sides of the latter, the highly elastic hard maple is used. Preferably resonance wood is not FlG> bent to assume the final form; the belly of the violin is section of a shaped from a thicker piece, so that every fiber is in the f^erl °
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