Noise reduction of passive and active hybrid panels

The transmitted noise reduction (NR) of passive and active hybrid panels is experimentally studied. The concept of hybrid panels is based on a combined approach for noise controls: a passive approach for mid and high frequencies and an active approach for low frequencies. Active and passive hybrid panels are demonstrated. An active-hybrid single panel is made with a plate structure on which piezoelectric sensor/actuators are bonded in conjunction with a simple controller. Sound absorbing material is bonded on the structure to effectively reduce the transmitted noise in mid frequencies. An active-hybrid double panel is also made by using another single plate to maintain an air gap. To prove the concept of hybrid panels, an acoustic measurement experiment is performed. Instead of using the active control system, a passive shunt damping is used for the NR in low frequencies. This is called a passive-hybrid panel. The use of sound absorbing material and an air gap is effective for noise control in mid and high frequencies. Meanwhile, the active approach and the passive shunt approach are useful for noise control at lower resonance modes. These hybrid panels demonstrate the potential for NR at broadband frequencies.