ln Part I of this paper sound transmission through double leaf lightweight partitions was examined. It was shown that an important part of the overall transmission is determined by structure--borne sound transmission between the two leaves of the wall. In this report, Part II of the paper, structural coupling is examined in more detail. Two theories are presented. One is appropriate where the connection behaves as a series of points and the other where the connection behaves as a continuous line. It was found that an appropriate transition frequency between these two theories was where a half bending wavelength on the plate fitted between the nails or screws that form the coupling. In the most common forms of construction the connection will behave as a series of independent points for most of the frequency range. The continuous line model included the frame either as a beam or as a short plate. It was found that the agreement with the experimental data was better when the frame was modelled as a plate. There was good agreement between the measured and predicted data for transmission between the two leaves of the wall for a wide variety of structures. These theories can be incorporated into a statistical energy analysis model to enable the sound transmission throughout the entire structure to be predicted as was shown in Part I of this paper.
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