The passive control of tonal sound radiation from vibrating structures

Low-frequency sound radiation from harmonic vibrating structures such as po wer transformers poses a serious noise problem to nearby residents. In this paper, a passive method is outlined for attenuating the tonal noise radiat ion by suppressing the harmonic structural vibration. This method utilises mechanical constraints to break down uniform vibrating shapes into irregula r ones and to reduce the total vibration level resulting in an attenuation of sound radiation. Both the theoretical analysis and laboratory experiment s have demonstrated the effectiveness of this method in controlling the ton al noise radiation from vibrating structures. For a fixed number of constra ints, the efficiency for controlling fluid-borne harmonic vibration and sou nd radiation is lower than that for a point excited harmonic vibration. (C) 2000 Elsevier Science Ltd. All rights reserved.