Sound transmission through multi-element flexible barriers is studied. Configurations analyzed include panels with different thickness and elastic modulus in different regions and layered structures connected by an elastic suspension. The purpose of the research is to see if flexibility and controlled resonant behavior can be used to block sound transmission even when structural damping is very low. Strategies are considered to alter vibrating surface wavenumber spectra to reduce coupling between the structure and the acoustic field. Another approach that can be employed is the utilization of structural wave cut-off with multi-element materials. Finally, multiple differentially tuned subsidiary elements acting as resonators can be used to greatly reduce the structural response. Examples of acoustic transmission loss through panel barriers using different strategies are presented, and the potential advantages and possible shortcomings of various approaches are evaluated. Copyright © 2008 by ASME.