Sound insulation of brick diaphragm walls—II. Vibrational energy flow through the cross-ribs

A description of an investigation of the sound insulation of brick diaphragm walls by scale-model measurement and Statistical Energy Analysis was given in an earlier companion paper [B. M. Gibbs and J. Lewis, Building and Environment 26, 165–172 (1991)]. In the present paper, the acoustic bridging effect of the cross-ribs is considered. It is shown that existing simple theory for bridged cavity structures is inappropriate. Statistical Energy Analysis is again invoked where various system definitions and associated coupling loss factors are considered. Predicted vibrational level difference across the leaves is compared with measurement of full scale diaphragm walls. It is shown that the best agreement is obtained when the cross-ribs are included as separate vibrating sub-systems in the Statistical Energy Analysis.