The performance for the transmitted noise reduction of smart panels is experimentallytested. A smart panel is a plate on which piezoelectric patches are bonded withelectrical shunt circuits so as to absorb the acoustic energy at the circuit. Fourpiezoelectric patches are bonded on the host panel along with resonant shunt circuits.The resonant shunt circuit is composed of a resistor and an inductor in series,and the optimal resistance and inductance are determined by maximizing theabsorbed energy through the circuit. To be able to perform the transmitted noisereduction at low resonance frequencies, a multiple-shunt damping is investigatedby using a tuning method based on the measured electrical impedance model.Three types of smart panels are tested: a bare smart panel, a single smart panel,and a double smart panel. It is found that the use of sound absorbing materialand air gap can effectively absorb the sound transmitted at the mid-frequencyregion while the use of piezoelectric shunt damping can reduce the noise at lowresonance frequencies of the panel structure. The transmitted noise of smart panels istested in an acoustic tunnel. When the multiple-shunt damping is applied topanels, a remarkable transmitted noise reduction at the low frequency region isachieved. The double panel exhibits better noise reduction than the other panels do.