Based Audio Directional System Of Cylindrical Corrugated Shell Pvdf Piezoelectric Transducer Dynamic Characteristics

Audio Beam is a revolutionary way of projecting audio signal in a highly directional manner to the listener. With the nonlinear interaction of ultrasound in air, the system can generate a narrow beam of sound, which features a highly directional propagation in a specified region innovatively. The main target of this thesis is to analyze vibration characteristics of corrugated cylindrical shell PVDF piezoelectric transducer which is one of the most important part of audio beam system, to optimize the structural parameters, design and fabricate a corrugated cylindrical transducer with low distortion, high directivity and loud sound pressure level based on the above theoretical analysis results.According to classical piezoelectric shell theory, a theoretical model on coupled extensional and flexural vibration of a infinite-width corrugated cylindrical shell piezoelectric transducer is produced. The vibration characteristics of transducer at low frequency range are analyzed. There is a resonant frequency which is insensitive to the pieces N. As N becomes larger, the flexural displacement is considerably smaller for pieces near the center of the transducer than for the pieces near the edges. By considering the shear deformation and rotatory intertia, a theoretical analysis on coupled extensional and flexural vibration of a one-dimensional infinite-width corrugated cylindrical shell piezoelectric transducer at higher frequency rang is performed. Shear deformation and rotatory intertia make the resonant frequency lower and flexural displacement larger. The higher resonant frequencies are affected more than lower resonant frequencies. Based on the one-dimensional theoretical model, a theoretical model on coupled extensional and flexural vibration of a finite-width corrugated cylindrical shell piezoelectric transducer is produced and effects of the edge constraints on the basic vibration characteristics of transducer are analyzed. Resonant frequency of transducer increases with decreasing width/length ratio due to a stronger influence from the two transversal edges on the vibrations of corrugated shells. It is observed that flexural displacement approaches a constant in the middle portion with increasing width/length ratio, while violent change happens only near the two edges at β/ l=0and 1. The axial force distributions in the transducer are all in compression for larger width/length ratio and become larger in the central portion of the shell. The coupled extensional and flexural vibrations of axially-symmetrical annular corrugated shell piezoelectric transducer is studied and basic vibration characteristics of resonant frequencies, mode shapes are calculated and examined. According to the theoretical analysis results, a corrugated cylindrical PVDF transducer is designed and fabricated. It is found that the resonant frequency of transducer is 43kHz (designed 40kHz), the maximal sound pressure level (SPL) of transducer was 125dB, -3dB beam width is approximately±15oand -10dB beam width is approximately±30o.