Effect of Shear on the Transmission Loss of Thick Panels

Abstract

One of the problems associated with concrete and masonry structures is their relatively poor acoustical performance in relation to their mass. A principal reason for this result lies in the fact that the critical frequency for these types of structures occurs at very low frequencies, sometimes as low as 100 Hz. The effect of coincidence, and the corresponding reduction in transmission loss in the vicinity of the critical frequency, results in the poor performance at low and medium frequencies. However, in the frequency region above the critical frequency, the theoretical transmission loss curve indicates values in excess of the theoretical mass law, whereas measurements show values that are substantially lower and that lie in a line essentially parallel to the mass law line. This presentation will briefly review the theory of the transmission loss of single panels including the effect of shear relating to the behavior of thick panels. Theoretical curves and experimental verification of the results for concrete and masonry structures will be presented. The application of the theory to the case of sandwich panels is discussed in connection with previous work by other authors. [This work was conducted under contract to the Department of Housing and Urban Development.]