Longitudinal Vibration - Square Sound Source Radiation Characteristics

The system of longitudinal vibration transducer and thin rectangular plate has a wide range of application in practice in the acoustic technology.In the gas medium, the bending vibration can achieved with the gas medium a good match, thereby the bending vibration gaining a wide range of applications. One way to generate bending vibration is using the conversion of the different vibration mode. For example, use the longitudinal vibration transducer and rectangular plate make up of the composite system. This kind of composite system not only has the high efficiency of the longitudinal vibration transducer but also has the low impedance, large radiating characteristics of the bending vibration. Therefore, that transducer has wide range of application in the acoustic technology. However, the radiating surface of this composite system exists nodal line, the interference cancellation caused by the vibration displacement in the opposite direction on the two sides of nodal line, which will reduce the radiation efficiency of the composite system, in order to improve the radiation efficiency, the radiating surface, can be improved to stepped plate.In the underwater acoustic applications, the acoustic transducer is a key component. In the design of underwater weapons guidance systems, rectangular or square plate can be use as the radiating surface, if the longitudinal vibration of piezoelectric and the bending vibration mode of plate can taken together, we can improved sound radiation, receive frequency response characteristic and achieve high spatial gain.The longitudinal vibration as the excitation source connects plate on its center. In the actual application, the excitation source (The longitudinal vibration transducer) and the plate has the connected areas, location of the nodal line will change with the different excited area, different area will caused different distribution of the nodal line of the plate and caused different directivity pattern. We know that directivity pattern is important acoustic parameters that describe the characteristics of radiated acoustic field. Therefore, the study of the relationship between the excited areas and the nodal line, the relationship between the excited areas and directivity pattern are very important.The detailed work is fellow:(1) The resonant system composed of the longitudinal transducer and the thin square plate. The longitudinal vibration transducer as the excitation source connects square plate on its center, the excitation source (the longitudinal vibration transducer) and the plate has the connected areas. Use the finite element calculated the different between the nodal line on the square plate when no excited areas and have excited areas; design experiments, through the experimental results verify the correctness of the finite element calculation results.(2) Use frequency and a levy vibrating modal frequency is the same, but the different excited areas longitudinal vibration transducer excited the square plate. Research the rule of the distribution of nodal line and resonance frequency of system with the different excitation areas excited the plate. Research the different distribution of nodal line when use the same excited areas, the different frequency excited the square plate.(3) Use frequency and a levy vibrating modal frequency is the same and the different excited areas longitudinal vibration transducer excited the square plate, research the rule of the directivity pattern of the plate.