The decay rate of the partial vibration of a piano string, with its frequency near the natural frequency of the soundboard vibration, is larger than that with its frequency far from the natural frequency of the soundboard vibration. The existence of this phenomena is examined in this paper both experimentally with an actual upright piano and theoretically with a coupled vibration model of a string and a sounboard.
This paper presents the characteristic extraction of violin bowing based upon the information on the spectral structure and the sound pressure. A professional violinist and the beginners served as subjects. Each of them played a simple scale on d^1 string. In this case, each pitch is played twice by martele with down bow and up bow without vibrato. Although there will be several factors which characterize the bowing of violin, two factors of bow pressure and sound pressure are selected among them. Firstly, an experiment as to bow pressure is done and it is proved that relatively high order harmonics get strong with the higher bow pressure. On the other hand, the strength of relatively high order harmonics of each beginner's playing is measured and compared with that of the professional's. It is concluded that the beginners' pressure are higher than the professional's on the whole. Secondly, the gradient of sound pressure of each monotone is measured. The consistency is found, in the case of professional, that the gradient of the tone by down is somewhat greater than that of the same pitch by the successive up bow. It shows that the professional regards two monotones played in a certain pitch as one musical group separated from another pitch.
With the aim of being able to predict the noise radiation from machine elements, numerical methods for estimation of acoustic radiation from vibrating structures in arbitrary modes were investigated, and results for fundamental structures were examined. Numerical Helmholtz integral formulation was applied and formulae for calculating radiation efficiency and radiation loss factor were derived to represent the frequency characteristics of radiation. A practical method for estimating field pressure patterns was also developed that uses plane wave approximation at high frequencies. The lower limit of this plane wave approximation is given by the break frequency of the estimated radiation efficiency curve. Numerical solutions for spherical sources in breathing and oscillating modes agree well with the analytical solutions. In addition, radiation factores for cylindrical bars undergoing flexural vibratin were calculated and compared with analytical solutions for infinite bar.
This paper investigates the dynamic response of rectangular foundation-soil system for the case that the ground is regarded as homogeneous, isotropic half-space with internal dissipation. First, the approximate expressions of the transfer function between a vibration source and the surface wave are introduced. The expression for normal direction has been compared with the experimental results, and it has been shown that the expression can be applicable over the range 2. 5 wavelengths away from the source. Next, the experimental results have been presented, and the following results have been obtained. The relative amplitude of the wave radiated from square source coincides with the one from circular source which has the same area with the square source. Radiated wave from rectangular source has directivity away from the transition point, and the directivity for the direction perpendicular to the longer side is more intensive than the direction perpendicular side of the shorter side. The relative amplitude for the direction 45 degree from the side of the source roughly coincides with the one from circular source which has the same area as the rectangular source.