Noise reduction of an acoustical enclosure --- Mechanisms and prediction accuracy
Noise reduction (NR) of an acoustical enclosure with flexible boundary walls has been predicted using t he Statistical Energy Analysis (SEA) method by several authors. Although it is useful for a rough NR estimation, a lar ge discrepancy often exists between the predicted and measured NR levels. Moreover, some physical mechanisms which may affect NR prediction were not addressed in the e xisting SEA models. The sources of the discrepancy were identified by investigating the limitation of SEA f or system energy transfer in the entire frequency r ange of noise transmission, and the effect of enclosure wall coup ling and sound-structural coupling on the NR and its prediction accuracy. This paper presents a modified SEA model, which includes the non-resonant response and more accurate transmission coefficient of finite panels, and comp ares the model prediction with experimental results . A reasonable agreement between the prediction and experiment was observed.
Study on Noise Prediction and Reduction in Coupled Workshops Using SEA Method
A theoretical model for predicting noise reduction in coupled workshops is presented by using statistical energy analysis (SEA) method. An opening between the coupled workshops is considered into the theoretical model properly. The leakage issue is dealt with in the process of SEA modeling. An experiment is also carried out. A reasonable agreement between the prediction of noise reduction and the experimental data is observed. Moreover, it is concluded from the simulations that the sound energy transmit through the opening was the most important way to affect the noise reduction and the leakage is a significant element to influence the effect of noise treatment.
Explicit solutions for N-dimensional Schrödinger equations with position-dependent mass
With the consideration of spherical symmetry for the potential and mass function, one-dimensional solutions of nonrelativistic Schrodinger equations with spatially varying effective mass are successfully extended to arbitrary dimensions within the frame of recently developed elegant nonperturbative technique, where the BenDaniel-Duke effective Hamiltonian in one dimension is assumed like the unperturbed piece, leading to well-known solutions, whereas the modification term due to possible use of other effective Hamiltonians in one dimension and, together with the corrections coming from the treatments in higher dimensions, are considered as an additional term like the perturbation. Application of the model and its generalization for the completeness are discussed.