Recent Trends On Application Of Piezoactive Polymers To Acoustics

摘要

Superposition of the direct and inverse piezoelectric effects is realized by means of simple circuits employing an operational amplifier. The remarkable change of the elastic constant of piezoelectric materials can be induced. The acoustic impedance of piezoelectric films can be also controlled by this technique. Employing a curved structure of piezoelectric PVDF film, controllable sound shielding systems have been demonstrated. The transmission loss can be increased or decreased under control at any frequency. The remarkable feature of the proposed sound shielding system is that the transmission loss increases with decreasing frequency of sound. In most ordinary sound absorbing materials, the transmission loss decreases with decreasing frequency. Therefore, the shielding of low frequency noise has been a difficult task in engineering. The present work describes some basic knowledge and experimental results on PVDF films with a small area 4 X 4 cm. Future studies should be directed to the construction of sound shielding systems with a much larger area. The distinctive features of such completed systems would be low weight, low cost and high efficiency at low frequencies.