Sound transmission loss of corrugated panels

Corrugated panels are often used in the construction of industrial buildings as they have a high strength to weight ratio. However, the Sound Transmission Loss (TL) of a corrugated panel tends to be poorer and more difficult to understand than that of a comparable flat panel. In the present paper this issue is studied both experimentally and theoretically. The TL of three sinusoidal and three trapezoidal panels with different corrugation periods and heights was measured in the laboratory. In addition, calculated values were obtained by various methods, by an analytical approximation which consider the corrugated panel as a thin orthotropic flat plate of infinite extent with appropriate mass per area and "equivalent" bending stiffnesses and by a combination of Finite Elements for the panels and Boundary Elements for the sending and receiving rooms of the testing facility. Meaningful comparison between measured and calculated results faces several difficulties, in particular the uncertainty in the boundary conditions originating from the mounting of the panels in the test opening and the limitation of the calculations for finite panels to frequencies considerably lower than the highest measured (5 kHz or 8 kHz). Consequently, the theoretical modeling of the measured TL is still incomplete or unsatisfactory. Nevertheless, some features related to the corrugation period or - due to strong anisotropy - to the wide range of coincidence frequencies can be identified.