Transmission of Random Sound and Vibration through a Rectangular Double Wall

The existence of many modes of vibration in a complex system makes a detailed classical analysis almost intractable. However, when excited by broad-band random noise, the detailed response characteristics may be overlooked and statistical properties such as mean-square values and power spectra provide a measure of the vibration. The existence of classes of similarly excited modes allows theories of room acoustics and thermodynamics to be applied successfully. For sound transmission through a rectangular double wall, this technique gives results that agree within experimental error of measured transmission loss, much better than do conventional loss estimates. Both theory and experiment confirm that the product of modal density, average joint acceptance of the first panel, and the ratio of radiation to total resistance of the second panel are the most important characteristics in determining the transmission characteristics of the wall.