Jordan J. Baruch

Industrial view of computer applications in the life sciences

The phenomenal growth of the use of digital computation in such fields as airline reservations, hotel-chain record keeping, banks and credit agencies overshadows its much slower growth in such areas as biomedical research, retail stores and architecture. To the researcher, to the government agencies that sponsor biomedical research and to the layman, it seems inequitable that the benefits of computation flow so easily to ease the pain of the air traveler but still contribute so little to the life sciences.

The IEEE Annals: An experiment in selective dissemination

Over the years, a great deal of attention has been paid to the cost of disseminating scientific and technical information. Unfortunately, a similar amount of effort has not been expended on determining the economic value of that information to the user. While Innumerable user preference surveys have been conducted, such surveys are notoriously useless in determining questions of price. For over a year now, the IEEE has been conducting an experiment aimed both at testing a selective dissemination system and, from the subscribe; behavior, determining the price elasticity of material presented via that system. Our initial data indicate that early adopters of such a system behave in a fashion analogous to that observed in early adopters of other technological innovations. Over approximately an 8-to-1 range, their price elasticity is essentially zero. Based on these early data, the program is being extended in order to determine price elasticity in an equilibrated system.

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Some Laminar Acoustical Materials

Recent developments in the lighting field, such as the use of large‐area illumination, have made the incorporation of reverberation control in ceiling design extremely difficult. By applying established principles to the design of a thin absorbing material, it has been possible to produce a system having high translucency to light as well as a reasonable acoustical absorption coefficient. Since the material is actually resistive in nature and does not depend on diaphragmatic action, a great deal of freedom is permissible in mounting, and the absorption‐frequency curve is broad rather than being sharply tuned. The basic material and several extensions and modifications of it show promise in the fields of functional absorbers, duct linings, large‐area ceiling treatments, and wall treatments.

An Automatic Data Reduction System

The problems involved in manually reducing acoustical data obtained on extensive field noise surveys make this phase of the job an exceedingly tedious one. Instrumentation has been developed to perform the reduction techniques automatically from tape‐recorded field data. Once the correction numbers for the recording system have been inserted, the system will plot a narrow band analysis, a 13 octave band analysis, or an octave band analysis of a sample of the noise. The ordinate may be either peak pressure level, rms pressure level, or average pressure level. Facilities have been provided for taking samples from several points (such as the equal area points on a grid) and averaging the squares of the pressures, thus yielding an average intensity over the grid. For the case where the areas are not equal, weighting functions may be introduced.

Tentative Criteria for Noise Control Design

Presented in this paper is a set of criteria that have been developed and applied on numerous noise control problems. A wide range of confirmatory evidence and experiences has led us to view these criteria with some confidence, although we recognize that they are subject to modification on the basis of additional data which are continuing to accumulate. An essential feature of the criteria is that they incorporate a specification of frequency dependence (usually expressed by octave bands) as well as over‐all sound pressure level. Tentative criterion curves are presented for: (a) risk of permanent damage to the hearing mechanism under habitual exposure to (i) continuous spectrum noises and (ii) single frequency components; (b) speech communication conditions in terms of percentage intelligibility, voice level, distance between talkers, and type of vocabulary; (c) risk of annoyance to residential areas as dependent on type and previous noise conditioning of the community, daytime vs nighttime exposure, and ...

A Large‐Scale Panel‐Driving Source

In testing the qualities of panels which contribute to the transmission‐loss phenomenon, the need for a driving source presents a large problem. At the M.I.T. Acoustics Laboratory, a large‐scale adjustable source has been built. The driver consist of a bank of 256 five‐inch loudspeakers arranged in a 16‐by‐16 array closely coupled to the panel under test. The speakers are essentially isolated, and act individually. The individual columns of speakers may be phased independently, allowing a simulation of various wave fronts, such as cylindrical waves and plane waves of various angles of incidence.

On the Design of Sound Absorbing Ducts

General design charts for square and circular sound absorbing ducts have been developed by an application of Morses theory for the transmission of sound inside pipes. These charts have been developed specifically for ducts with all four walls lined with an absorbing material with or without an air space behind it. Interesting results of this study are that attenuations of 15 to 20 db per wavelength can be obtained over a frequency range of about one‐half octave and that by scaling the size of the duct and the impedance of the acoustical material on the side walls this peak in attenuation may be placed at any desired frequency. Measurements on ducts ranging in size from 8×8 in. to 4×4 ft. show that the measured attenuation curves result in somewhat higher values of attenuation above and below the peak value and a slightly lower value at the peak than are calculated from the charts. For those ducts in which an air space is used behind the absorbing inner wall, the partitioning of the air space plays an imp...

Improving the sensitivity of switches with linear feedback

The sensitivity of reversible switches can be adjusted to varying degrees by using a suitable linear feedback coefficient. Maximum sensitivity depends on the characteristic curve of the switch, and methods are presented for determining this maximum and the feedback coefficient needed to achieve it.

An Automatic Sound‐Field Mapper

The field mapper consists of a mechanism for moving a microphone over a plane in the sound field and suitable equipment for automatically plotting its output. The path of the microphone consists of a number of horizontal lines forming a raster whose spacing may be adjusted from 4 in. to 12 in. The position of the microphone is converted into two electrical signals which control the position of a recording pen by means of a two‐dimensional servomechanism. The electrical signal from the microphone is recorded as a contour map of the sound field in the plane, the contours being isobaric lines (lines of constant sound‐pressure level) or isotemporal lines (lines of constant phase). The system will plot 5 contours simultaneously, covering a 7‐ft. by 7‐ft. plane in 11 minutes. The level represented by any contour is arbitrarily set at any integral decibel value in a 30 db range. Thus 5 contours spaced as closely as 1 db may be plotted at once. The resulting map is read directly in db re: 1 dyne/cm2. As many cont...