Pseudo-shear universal actuator driving flextensional panel diaphragm low frequency acoustic source

Acoustic source used for Active Noise Control (ANC) at low frequency (80-250 Hz) is designed and developed by using a piezoelectric ceramic actuator and a flextensional panel diaphragm. In order to reach the vibration magnitude and radiation area needed for high and flat sound pressure level in the low frequency range. Pseudo-Shear Universal (PSU) actuator has been used as the driving part which is a new type of multilayer piezoelectric actuator originated from MRL offering the advantages of large displacement and high blocking force; on the other hand, Carbon Fiber Reinforced Composite has been used as the diaphragm material which provides a more rigid structure than conventional loudspeaker paper. A prototype device was fabricated which has the following characterizations: 40 layers PSU actuator with a compact dimension: 38 mm x 50 mm x 23.6 mm. Two of them are needed for a device. Diaphragm area is 126mm x 152 mm. At quasistatic condition (5 Hz) and at the 0.84 kV/cm electric field, 344 mu m displacement could be achieved at the apex of the diaphragm resulted from the flextensional amplifying mechanism with an amplification factor more than ii. The sound pressure level in the frequency range 100-250 Hz shows better flat behaviour than the acoustic sources studied earlier such as Double Amplifier and PANEL air transducers which exhibit a significant reduction of sound pressure level in the low frequency range. By a slight modification, it is likely to make this device in a total thickness of 10 - 15 mm range. High and stable sound pressure level as well as thin flat structure make it much more competitive in the whole area of applications for low frequency active noise control.