| In this dissertation low frequency sound radiation prediction models for vibro-acoustic problems which are based on acoustic impedance are presented.; A method based on the use of the acoustic radiation resistance matrix is presented. This matrix can be combined with the volume velocity vector on a discretized vibration surface to predict the total sound power radiated from the structure. In order to do so, the vibrating structure is simulated by a finite number of small piston sources mounted flush on the surface.; The resistance matrix is absolutely uncoupled from the vibration problem, and it just depends on the geometry of the structure. Thus, this approach has some advantages when used for design purposes, since the information on the resistance matrix of a particular structure can be stored on a computer, and can be used for different velocity distributions.; Since it can be difficult to determine the individual elements of the resistance matrix in certain cases, an experimental method is presented as well. The theory of the measurement is based on the transfer function between the voltage signals from two small microphones. The analysis has been validated through measurement of the self- and cross-resistance for a small piston mounted flush in a baffle.; The application of the acoustic radiation resistance matrix is presented for several cases, involving one-dimensional and two-dimensional geometries. The one-dimensional cases reported correspond to the determination of the input resistance in a pipe and in a simple expansion chamber.; The two-dimensional cases studied in this dissertation correspond to the sound radiation from a rectangular baffled plate, (1) subjected to simply-supported and (2) subjected to clamped boundary conditions.; Both numerical and experimental results are presented for rectangular plates and they show very good agreement with classical results reported in the literature.; Finally, in the application of the resistance matrix the calculation of the acoustic field has been avoided, giving a degree of accuracy comparable to the classical approaches. Therefore, for highly reactive sound fields, or in the presence of high background noise, the method presented here appears to be very useful for the determination of the sound radiated from structures. (Abstract shortened by UMI.)... |
