Sound transmission via structural connections in cavity walls

This paper investigates the similarities and differences between three theories for predicting the sound transmission due to the structural connections of a double leaf cavity wall. The first of the theories does not include the effects of the resonant vibration of the wall leaves below the critical frequency. Above the critical frequency, this theory does include the effects of resonant vibration in both wall leaves. The second of the theories does by accident effectively include an empirical correction factor which accounts for some of the effects of the resonant vibration below the critical frequency, but the theory itself is not valid above the critical frequency. The third of the theories does include the effects of the resonant vibration of the wall leaves across the whole frequency range. It is shown that the first and third theories, although very different, are in very good agreement with regard to the radiation of sound from the receiving room side wall leaf above the critical frequency. This validates this aspect of these two theories. The amount by which ignoring the resonant vibration of the wall leaves alters the predicted sound transmission depends on the damping loss factor of the walls.