Active Structural Acoustic Control with Emphasis on Characterizatoin of Sensing Techniques

Problem Statement
Radiation of structure-borne sound can be controlled with piezoelectric actuators located on the surface of the structure; however, sensing techniques have been limited primarily to microphones located in the radiated field. In an effort to develop an adaptive structure with the sensors embedded within or bonded to the surface of the structure both the structural response and the acoustic near-field response must be studied to gain physical insight into the mechanisms of sound radiation.

Physical quantities such as the structural response, acoustic intensity and pressure are readily computed, but the quantity of information can be overwhelming. In the majority of studies performed, the time averaged quantities are presented to show the total flow of power away from the structure. While this informaton is useful, the physical insight gained from the transient dynamics of the problem are lost. Instantaneous representation of these quantities is often discussed; however, without animaton, a clear graphical interpretation of the problem is difficult. The thrust of this work is to animate the instantaneous acoustic and structural response of a simply supported plate in an effort to better understand the mechanisms of sound radiation for designing shaped PVDF sensors in active structural acoustic control approaches.

Visual Insight
Upon viewing the animated instantaneous acoustic and structural response of the plate, the method of sound radiation becomes evident. As the plate passes through zero displacement, corresponding to maximum velocity, the pressure wave is launched from the surface of the plate. The instantaneous energy exchange between regions of the plate out of phase with other regions is also clearly presented in the animated response.

Viewing the acoustic response in conjunction with the structural response leaves the viewer with a physical interpretation of the physical interaction between the structure and the fluid. This physical insight assists in the initial choice of optimal shape and location of PVDF sensors for controlling sound radiation.

Select original 300DPI image by clicking on figures above.