組立矩形ダクト内流体中の低周波数音速

概要

論文の詳細を見る
The longitudinal wave propagation in a liquid contained in a duct is generally effected by the compliance of the duct walls, causing a reduction of the wave speed. If the duct is rectangular, and is constructed with separate pieces of metal plate, which are assembled together with screws, the wave speed in it is difficult to predict, because the wall motion is unpredictable, caused by location or number or fastening forces of screws or other factors. In this paper, the sound wave speed in low frequencies in a liquid-filled square duct was investigated. Two models were developed for the duct walls, and transmission line theory was used to predict the wave speed. The duct consists of four pieces of aluminum sheet, which were joined together with brass screws. Acoustical impedance at the driving point for open-ended water-filled duct system was measured for the determination of the sound speed. The simply supported beam model for the duct walls predicted wave speed slightly lower than measured values. The more constrained model gave higher values. Thus, the two models should predict the extremes of the wave speed for practical square ducts.