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Nov 1982

Volume 72, Issue S1, pp. S1-S108

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back to top Session EE: Education in Acoustics: Special Session on the Use of Computers in Acoustics Education
Invited Papers
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Classroom exercise programs for numerically predicting and graphically displaying propagation characteristics of sound (A)

Joseph A. Clark

J. Acoust. Soc. Am. Volume 72, Issue S1, pp. S50-S50 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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Several computer programs will be described which were developed for an introductory graduate course in underwater acoustics that was offered at a government laboratory (DTNSRDC) where Tektronix or H.P. graphics computers were available to most of the students. One program numerically solves the acoustic field equations in one dimension by a finite difference method. This program has been used to illustrate the reflection of sound at boundaries and effects of transmission into a second (or third) medium where the acoustic impedance and sound speed might differ. A second program numerically solves the acoustic field equations in two spatial dimensions. A ray tracing program will be described which illustrates the major features of sound propagation in inhomogeneous media and a program which plots beam patterns for an array with an arbitrary number of elements spaced at arbitrary distances apart will also be presented. The programs are written in BASIC and include interactive features which allow the students to explore a variety of propagation and radiation conditions on their own. The programs were found to provide a third useful way to develop a physical intuition for sound propagation characterstics when they were used in conjunction with studies of approximate analytical solutions of the field equations and laboratory demonstrations.
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A Fourier‐synthesis system with audible and visible ouput (A)

W. James Hadden, Jr.

J. Acoust. Soc. Am. Volume 72, Issue S1, pp. S50-S50 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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All too often, when teaching Fourier analysis in vibrations and acoustics courses, one encounters a spurious resistance (from students) partially attributable to the absence of illustrations with tangible results. This paper describes the use of a commercially available digital/analog converter and microcomputer to provide demonstrations of Fourier series in which the usual time‐ and frequency‐domain representations are supplemented by an audible output. Several versions of the driving software will be discussed. In one, the user may alter amplitudes of spectral components “on the fly” and soon thereafter hear the change in the acoustic signal while choosing between graphic displays of waveform or Fourier spectrum. In another, the user may enter spectral amplitudes and phases or fill in parameters in formulas for Fourier series—this information is then processed and stored for display as in the previous case. Convergence of Fourier sums to simple periodic functions, effects of relative phase changes, and responses of resonant systems to periodic excitation are among the topics that can be illustrated using this system. A brief demonstration is planned.
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Some experiments with broadband ultrasonic pulses (A)

M. Paul Hagelberg

J. Acoust. Soc. Am. Volume 72, Issue S1, pp. S50-S50 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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Several broadband ultrasonic pulse experiments will be presented which are suitable for use in the undergraduate laboratories. A brief description will be given of a set which requires only time domain measurements and for which the analysis is conceptually easy. Attention will be concentrated on a group which requires frequency domain analysis and for which digital data acquisition techniques are particularly suited. While these may be performed with relatively unsophisticated equipment they are readily adapted for microcomputer control and analysis.
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Computer based laboratory instruction in acoustics and noise control (A)

David K. Holger

J. Acoust. Soc. Am. Volume 72, Issue S1, pp. S50-S51 (1982); (2 pages)

Online Publication Date: 12 Aug 2005

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A computer based instructional laboratory in acoustics and noise control is described. The semester length laboratory, which is currently being developed, is based upon analog to digital (A to D) conversion of transducer signals followed by micro‐ and/or main frame‐computer analysis of the digitized signals. The proposed laboratory is compared with traditional laboratories in acoustics which normally require a number of stand‐alone instruments. Extensions of the microcomputer based laboratory using the “micro” as a “smart” terminal in a main frame time sharing system are also discussed. The progression of experiments in the laboratory evolves through these phases. First phase experiments are designed to familiarize the student with transducers, A to D conversion and simple, stand alone, micro‐computer analysis. Second phase experiments involve multichannel data acquisition and more extensive micro‐computer analysis. Third phase experiments involve main frame software and data storage using the micro‐computer as a “smart” terminal in a time sharing system. A phase two experiment pertaining to acoustic parameters describing the impulsive response of a room will be described and discussed in detail.
back to top Session EE. Education in Acoustics: Special Session on the Use of Computers in Acoustics Education
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The development of a local micro‐computer network for an acoustics laboratory (A)

J. E. Kerivan and C. I. Holmer

J. Acoust. Soc. Am. Volume 72, Issue S1, pp. S51-S51 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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Local computer networks (LCN's) lend themselves as a cost‐efficient, growth‐oriented, powerful answer to the problem of real‐time control and processing of acoustic signals in a laboratory. The availability of inexpensive scientific and engineering “off‐the‐shelf” software which can be structurally integrated in a shared resource environment permits the realization of large data‐base management systems with micro‐computers. The comparison of LCN alternatives, both hardware and software options, as it relates to specific acoustic measurement problems will be contrasted in showing E‐A‐R's solution for a mini/micro‐computer network. Modal analysis, reverberation‐time measurements, damping data reduction, hearing protection attenuation, and analytical modeling are some of the tasks which are integrated in the system. In this presentation we will discuss in detail some of the alternatives considered to date in our system development and their perceived advantages and limitations. Listings of structured programs currently under development will be provided.
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Computers in acoustics education at Lehigh (A)

John B. Ochs

J. Acoust. Soc. Am. Volume 72, Issue S1, pp. S51-S51 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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In the late 1970's the Industrial Engineering Department and the Mechanical Engineering Department of Lehigh University joined forces to develop and promote an integrated approach to the progression from mechanical design to manufacturing with computer graphics systems providing the man/machine interface. The primary focus of the CAD/CAM program is the education of the approximately 600 undergraduates in the two departments with the emphasis on the design and manufacturability of products so that an engineer can understand the ramifications of his design decision in an integrated CAD/CAM environment. The aim of the program is to provide state‐of‐the‐art computer graphics systems as tools to improve design and manufacturing innovation. Educationally the goal is to implement the computer graphics technology into every undergraduate course in the two departments, which include such diverse topics as statics/dynamics, thermodynamics, mechanical vibration, statistics, operation research as well as the classical design and manufacturing. Some courses stress extensive use of these computer systems and the means to manage them, while others use the facilities for projects or homework assignments. By hard wiring the CAD and CAM laboratories to classrooms, the color real‐time dynamic displays can be used as dynamic blackboards to visualize complex three‐dimensional geometry or to illustrate multi‐dimensional mathematical relationships. Growing from a strong undergraduate base the program has attracted graduate research from several engineering disciplines supported mainly by Lehigh's industrial partners.
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Approaches for digital processing acoustic and vibration data in a teaching laboratory (A)

Wolfgang Sachse, R. Cochran, S. Yu, C. P. Chen, and C. Chang

J. Acoust. Soc. Am. Volume 72, Issue S1, pp. S51-S51 (1982); (1 page)

Online Publication Date: 12 Aug 2005

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In this paper we describe the signal acquisition and processing approaches we have implemented using a portable mini‐computer system in laboratory experiments of acoustics and vibrations courses. Also described will be examples of programs we have developed to data which include the simulation of 1‐ and 2‐degree‐of‐freedom vibrating systems, the analysis of displacement, velocity, or acceleration signals of such systems; the digital processing of speech and other transient acoustic signals to obtain spectrograms; the determination of reverberation time; two‐dimensional ray tracing in homogeneous and inhomogeneous layered media; and a general data acquisition, processing, and display program in which any one of more than 70 commands can be called with a three‐letter mnemonic. Key to all the examples is the versatility of the system and the ease with which new experiments or examples can be implemented by inexperienced users.
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