響板の振動・音響特性 : ピアノの音響学的研究 第3報

抄録

The soundboard without strings in the low frequency region vibrates nearly equal to the isotropic plate for correcting the anisotropy of the wood plate by ribs. In the higher freuency region the local character of the soundboard appears. The boundary condition in the low frequency region lies between fixing and support. The higher the frequency is, the more the boundary condition closes to fixing. The influence of stretching strings is that the resonance frequency of each mode becomes high and Q becomes low. The character of the soundboard is shown in quantity by measuring the driving point character at the positions of string support on the bridge. Moreover it is important factor for finding the influence on the strings. In the low frequency region the fundamental mode is put down and many partials are built up. In the middle frequency region the higher mode vibration than the fundamental vibration of the soundboard is used, so that the fundamental mode is no matter what it may be. In the high frequency region the admittance becomes high by taking the vibration between ribs. The acoustical character when the soundboard is driven with a constant current is studied. The directivity of sound pressure is considered.