Scholarly Works, Mechanical Engineering
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Browsing Scholarly Works, Mechanical Engineering by Content Type "Abstract"
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- Computer-aided, interactive design routine for the prediction of sound levels in irregularly shaped factory spacesBlanding, James M.; Mitchell, Larry D.; Hurst, Charles J. (Acoustical Society of America, 1977)An interactive computer algorithm is presented which utilizes modified room acoustics theory to predict dBA sound pressure levels in regularly- and irregularly-shaped factory spaces. Irregularly positioned and nonuniform room absorptions are treated. The user-oriented algorithm, suited to remote interactive terminal operation, employs a conversational format to facilitate input of room dimensions, of absorption data, and of locations and noise levels of machinery. A redesign feature is included which employs three options. These allow the user to change sound source data and acoustic treatments in the process of finding the most economical accommodation of OSHA regulations during any phase of the factory design or redesign. [Work supported by NSF.]
- Prediction of sound pressure levels in irregularly shaped factory spacesZinskie, John H.; Mitchell, Larry D.; Hurst, Charles J. (Acoustical Society of America, 1976)The prediction of sound pressure levels in irregularly shaped factory spaces is approached through an analysis of acoustically coupled rooms. Previous work has indicated that room surface sound absorption characteristics create a theoretical interdependence between the sound pressure fields in each coupled volume. Whenever a barrier is interposed between a sound source and observer, the effects of diffraction must also be considered. A computer algorithm was developed to predict sound pressure levels in irregularly shaped rooms using a modified statistical acoustic theory. The program is based on a conversational technique and requires the user to enter information regarding room geometry, surface absorptions, receiver placements, and source sound power and placement information. Several output options are provided, among which is a plan view print-plot of sound pressure level contours in the analysis room. [Work supported by NSF.]
- Prediction of the sound diffracted around barriers in large rooms using an extension of Maekawa's approachJohnson, R. A.; Hurst, Charles J.; Mitchell, Larry D. (Acoustical Society of America, 1977)A computer program has been developed for the prediction of sound pressure levels in large, irregular rooms utilizing a geometric acoustics approach. Experiments indicated that the program gave good predictive accuracy when receiver positions were in the line of sight of the sound source. However, the accuracy was poor when the receiver was out of the line of sight. The present discussion reports on the further development of the program to include diffraction effects using an extension of Maekawa's approach for thin screens and right angle wedges. The program is capable of finding all valid diffracted rays which undergo three or fewer reflections before diffraction and three or fewer reflections after diffraction. Limited experimental work indicates good predictive accuracy.
- Sound transmission between absorbing parallel planesHurst, Charles J.; Mitchell, Larry D. (Acoustical Society of America, 1976)Partially absorbing parallel surfaces can be dominant acoustical feature of many rooms. The sound fields in such rooms are not diffuse, which causes difficulty in predicting sound pressure levels. A method is developed for predicted sound pressure levels in these rooms. It rests on the prediction of sound pressure levels caused by a nondirectional source of known sound power radiating between absorbing parallel planes. The development proceeds from a geometrical acoustics viewpoint. Good correlation has been found between predicted and measured levels in existing rooms having simple geometries. [Work supported by NSF.]