残響応答によるピアノ音とギター音の減衰分析

抄録

Piano and guitar tone decay analysis has been carried out using reverberation responses calculated by Wigner distributions. The responses are investigated in comparison with record of the conventional short time spectra. The reverberation responses which are intimately related with the internal energy of instrumens represent 1) the envelope of tone decay without fluctuation induced by interference, reflect 2) mutual load effect associated with the oscillators, thus, clearly show 3) the gradients of energy decay curves, and are 4) less influenced by window function length. A guitar under investigation is shown to provide 1) two-step tone decay curve not caused by difference between decay rates of horizontal and vertical vibration modes of the strings (single string tone), and 2) multi-step energy curve with each step having much longer duration than the interference period (two string tone).
On the other hand, the analysis of a grand piano reveals the following features:
1) two power peaks in the spectra of aftersound are caused by different reasons from each other, 2) multistep energy decay curve is altered by performance style or piano condition, and 3) the partials are exhausted after absorbing energy of the other vibration modes.