An acoustic waveguide system contains a trunk waveguide and a number of branch waveguides. The trunk waveguide section defines an interior passage and includes at least one open end. A number of branch waveguide sections define an interior passage and include a junction end and a terminal end, with the junction end coupled to the trunk waveguide. One or more cavities can be coupled to at least one of the trunk or branch sections and communicate therewith through a vent for damping the resonance peak of a target standing wave.