集中質量を有するはりの音響放射効率

抄録

The radiation of sound from a mass-loaded, baffled beam has been studied. It is assumed that the beam is carrying a concentrated mass at its middle and is simply supported at both ends. Closed-form approximate expressions are developed for the radiation efficiency of a mass-loaded beam for a region below the coincidence frequency. It is shown that an extreme change of the radiation efficiency occurs due to attaching of a mass to the beam. The value of the change, does not depend on the mode number of the beam vibration but depends on the ratio of the acoustic wavenumber to the beam length, the phase relation between the response of the mass and that of near boundary, and the response of the mass. The assumption of a complete wave cancellation, except at the two ends and the mass point, is valid and useful in estimating, the radiation efficiency of a mass-loaded beam for a region well below the coincidence frequency region.