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Piezoelectric materials have been used in the past to reduce noise and vibration in several different applications, but the use of these materials to enhance noise reduction for automotive exhaust systems is a new application of this technology. The work detailed herein shows how an inductive shunt circuit may be used to improve the noise reduction performance of a baffle-less automotive muffler system. The absence of interior baffles in the muffler minimizes backpressure and improves fuel efficiency of the upstream engine system. We designed and built a prototype system utilizing an IM7/bismaleimide composite for the muffler body, stainless steel end caps and PZT 5A piezo-ceramic for the passive/adaptive element. By matching the acoustic resonance of the cavity inside the muffler with that of the structure surrounding it, a fully coupled system was achieved.