An efficient hybrid transfer matrix-statistical energy analysis approach for predicting the sound transmission through thick and layered walls
In this work, an efficient method is developed for computing the diffuse sound transmission of walls and floors that consist of layers of solid, fluid and/or poroelastic material. This is achieved by coupling a transfer matrix model of the wall or floor to statistical energy analysis subsystem models of the adjacent room volumes, which obviates the need for numerically integrating the plane wave transmission coefficient for all possible angles of incidence. The modal behavior of the wall is approximately accounted for by projecting the wall displacement onto a set of sinusoidal lateral basis functions. The method is applied for predicting the airborne sound insulation of a thin plate, a thick wall and a sandwich panel. The predictions are compared with alternative predictions and with measured values. A good overall agreement is observed.
Acoustic and vibration response of a structure with added noise control treatment under various excitations.
The evaluation of the acoustic performance of noise control treatments is of great importance in many engineering applications, e.g., aircraft, automotive, and building acoustics applications. Numerical methods such as finite- and boundary elements allow for the study of complex structures with added noise control treatment. However, these methods are computationally expensive when used for complex structures. At an early stage of the acoustic trim design process, many industries look for simple and easy to use tools that provide sufficient physical insight that can help to formulate design criteria. The paper presents a simple and tractable approach for the acoustic design of noise control treatments. It presents and compares two transfer matrix-based methods to investigate the vibroacoustic behavior of noise control treatments. The first is based on a modal approach, while the second is based on wave-number space decomposition. In addition to the classical rain-on-the-roof and diffuse acoustic field excitations, the paper also addresses turbulent boundary layer and point source (monopole) excitations. Various examples are presented and compared to a finite element calculation to validate the methodology and to confirm its relevance along with its limitations.
Numerical and experimental validation of variance prediction in the statistical energy analysis of built-up systems
In the statistical energy analysis (SEA) approach to vibration modeling, a complex system is represented as an assembly of coupled subsystems, and the method leads to the prediction of the vibrational energy level of each subsystem. The averaging procedures implicit in the technique imply that the predicted energy is the mean value taken over an ensemble of random structures, such as a set of vehicles leaving a production line. Recently, a new method has been developed to allow the ensemble variance, in addition to the mean, to be predicted within the context of SEA, and the present paper concerns further extension and validation of this work. The theoretical extension concerns the variance of the energy density at a single point in any of the subsystems, and the validation includes both simulation and experimental studies. The simulation results concern plate assemblies, while experimental results are presented both for a single-plate and for a cylinder-plate structure. In each case an ensemble of random structures has been generated by adding small point masses at random locations on the structure. In general, good agreement between the predictions and the validation results is observed.