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.
Design charts for the selection of acoustical enclosures for diesel engine generator sets
Abstract It has been realized that attenuation of the noise radiated from diesel engine generating sets is a challenge for the designer. The enclosure, which may be designed for noise reduction, has to allow for the flow of the necessary amount of air. The present work is an attempt to tackle such a contradictory problem. A mathematical model is developed to predict the enclosure design configuration. The parameters affecting the insertion loss, such as enclosure and silencer dimensions, number of baffles, and sound absorption material specifications are taken into account. To verify the developed model, experimental measurements based on ISO 8528 part 10 are conducted. Four different generating sets covering a wide range of power rating are employed. The effect of changing each parameter on the insertion loss is studied separately for the chosen range. Design charts, based on the results of the present investigation, are constructed to facilitate the section of a proper acoustical enclosure configuration at the preliminary design stage.
Proposed beam diagnostics instrumentation for the LANSCE refurbishment project
Presently, the Los Alamos National Laboratory is in the process of planning a refurbishment of various subsystems within its Los Alamos Neutron Science Center accelerator facility. A part of this LANSCE facility refurbishment will include some replacement of and improvement to existing older beam-diagnostics instrumentation. While plans are still being discussed, some instrumentation that is under improvement or replacement consideration are beam phase and position measurements within the 805-MHz side-coupled cavity linac, slow wire profile measurements, typically known as wire scanners, and possibly additional installation of fast ionization-chamber loss monitors. This paper will briefly describe the requirements for these beam measurements, what we have done thus far to answer these requirements, and some of the technical issues related to the implementation of the instrumentation.