bluuebunny/crossref_metadata_2025 huggingface dataset:
Binaural-Discrimination Enhancement in Brainstem Neurons
Authors: Adams William B. , Edmonds Baird E. , Moushegian George
Published: November 2005

Binaural interactions at the neural level of cat have been investigated for single elements within or near the medial superior olivary nucleus (MSO) of cat. A type of neuron has been studied in the area of the MSO to which at least one ear contributes both excitatory and inhibitory components. This type of cell responds to both LE-monaural and RE-monaural stimulation. At some binaural-phase conditions, the response of the cell exceeds the sum of the monaurally produced responses. However, at some other phase angles, spike production is less than that produced monaurally. These cells are similar to those found by Rose et al. in the inferior colliculus. The complex excitatory-inhibitory interaction, as implied by the binaural-response characteristics, provides a mechanism for enhancement of binaural time-difference discrimination and also demonstrates the type of cell required for correlation models of frequency discrimination. [Research supported in part by National Science Foundation.]
Anatomical Distribution of Efferent Fibers in the 8th Cranial Nerve of the Bullfrog (Rana catesbeiana)
Authors: Robbins Ruth G. , Bauknight R. S. , Honrubia V.
Published: November 2005

The 8th cranial nerve of the bullfrog was surgically transected between the brain stem and sensory ganglion. Two to three weeks after section of the nerve the frogs were sacrificed and the Wallerian degeneration in the nerve was studied. It was possible to demonstrate the presence of efferent fibers going toward the sensory epithelium of all the recognized vestibular end organs, and also toward the papilla of the pars amphibiorum. However, no efferent fibers were seen at the level of the papilla basilaris. The ganglion cells of both the acoustic and vestibular afferent fibers appeared normal. Many degenerated fibers were seen around the sacculus wall among a group of fibers previously undescribed.
Hearing Impairment following Subtotal Electrolytic Lesions to the Auditory-Nerve Region of the Guinea Pig
Authors: Wilpizeski C. , Tanaka Y. , Liu J.-C. , Harbert F.
Published: November 2005

Guinea pigs were surgically prepared with permanent monopolar recording electrodes and bipolar lesion electrodes placed in the 8th nerve cochlear-nucleus region. Continuous-trace absolute-threshold recordings (visual-detection level) for 1, 50, 100, and 1000 clicks/second were made over 3-min measurement periods by means of a motor-driven recording attenuator. Neural equilibration at suprathreshold levels was evaluated in terms of evoked-potential amplitudes. Following subtotal electrolytic lesions to the nerve, threshold and amplitude changes were monitored regularly over a 13-week period. Parallel data were collected from additional guinea pigs trained to track absolute thresholds to discrete white-noise stimuli by means of an avoidance-conditioning procedure. Changes in auditory function are interpreted in terms of reversible and nonreversible neural damage. [Work supported in part by National Institute of Neurological Diseases and Blindness.]
Recent Developments in the Mathematical Theory of Quartz-Crystal Resonators
Authors: Mindlin R. D.
Published: November 2005

It was observed about 30 years ago, by Bechmann, that many of the undesirable overtones of a quartz resonator plate disappear as the area of the electrode plating is reduced. The cause of the phenomenon was discovered by Mortley and rediscovered recently by Shockley. Their explanation makes it possible to bring the matter within the framework of equations of motion of anisotropic plates. One-dimensional and two-dimensional solutions, with appropriate boundary conditions on a pair of parallel boundaries, lead to explicit formulas for Bechmann's Number—the ratio of length of electrode to thickness of plate below which certain overtones are absent. Other overtones, traceable to reflections from all four edges of a free, rectangular plate, are more difficult to treat mathematically owing to the usual obstacle which is present even in the elementary theories of plates. However, in an AT-cut, quartz plate, the modes that prevent a general solution are relatively unimportant and their omission makes it possible to obtain closed solutions that include some of the additional undesirable modes.
Approximations in Nonsymmetric Shell Vibrations
Authors: Ross Edward W.
Published: November 2005

The non-symmetric vibration of shells of revolution is studied by means of classical thin-shell theory. Approximations are found by asymptotic methods for the eight solutions of the system. The behavior of the solutions when the frequency is either high or low is discussed. The approximations are used to give general descriptions of the types of natural frequencies and modes that can be found. In particular, the occurrence of low natural frequencies associated with inextensional modes is shown to be impossible for many edge conditions and to be calculable solely from membrane theory in certain frequency ranges.
On High-Frequency Vibrations of Thin, Elastic Shells
Authors: Kalnins Arturs , Long Carl F.
Published: November 2005

The purpose of this paper is to investigate the limits of dynamic shell theory that are imposed by the frequency of vibration. For illustration, the free-vibration characteristics of a complete spherical shell, as predicted by various approximate shell theories given by Hildebrand, Reissner, and Thomas, are compared with the corresponding results as predicted by the theory of elasticity. The precise meaning of the approximations made in shell theory is investigated by identifying the types of modes of vibration which are, or are not, predicted and the range of frequency in which these modes occur. The conclusions can be applied to thin shells of arbitrary shape.
Mobility of a Long Cylindrical Shell
Authors: Palladino J. L. , Neubert V. H.
Published: November 2005

Results of an experimental and theoretical study of mobility of a long, moderately thick-walled, pipelike, cylindrical shell are reported. Experimental data for mobility are compared, over a wide frequency range not previously investigated, with analytical predictions based on thin-shell theory. Existing solutions for free vibrations of thin shells are extended to predict vibration response to a point force that varies sinusoidally with time, based on a normal-mode series solution. Practical convergence of the series is of special interest. The long, pipelike shell was chosen to make this convergence problem more severe since the resonances in some frequency ranges are very closely spaced. For most of the study, the ends of the experimental shell were free to move laterally but the end cross section was restrained to maintain a circular shape, so the shell was treated as free for the n=1 or beam modes and freely supported for the n=2 or lobar modes. Some resonant frequencies are also included for the shell with completely free ends. Boundary conditions for the free-free shell are discussed based on Vlasov's equations.
On Matching the Speech Signal to Mechanisms of Production
Authors: Abramson Arthur S.
Published: November 2005

The traditional phonetician practices the art of describing speech sounds in auditory-articulatory terms. This description may furnish the data for the phonological analysis of a language. In acoustic phonetics, the major concern is with the speech signal itself. For some this means refined instrumental analysis to find characterizing features of phonemes; for others it also means determining the perceptual relevance of acoustic features. In both basic and applied speech research, investigators have been reluctant to give up hope of finding acoustic invariants for phonemes, at least for those of a single speaker's system. Certain approximations to acoustic invariance have been found for some phonemes, but in general this search has been more successful in the nonacoustic domain. While work on neuromuscular dimensions has not yet yielded a clear set of phonemic invariants, there seem to be rather stable correlations between articulatory events and phonemes. With the help of experimental findings from several laboratories, a multidimensional approach to an important phonological feature, voicing, is presented to illustrate this thesis.
Speech Pathology and Basic Research on Speech
Authors: Curtis James F.
Published: November 2005

Speech pathology is concerned with deviations in speaking behavior that significantly reduce communication effectiveness. Organic causes of speech disorders include defects of peripheral speech organs, neuromuscular defects, and sensory defects—for example, significant hearing loss. In many cases, there is no apparent organic defect sufficient to explain the speech disorder. An understanding of abnormal speech obviously presupposes knowledge concerning the normal processes of speech and language. Thus, the speech pathologist has a particular interest in research concerning the speech-generating processes and their relationships to the nature of the speech output. Recent work concerning speech articulation and the probable relationships of underlying neural events to the control of articulatory processes is of special significance to speech pathology. Studies directed toward better understanding of the fundamental time segments of the speech stream is of particular interest because of implications concerning the behavioral units with which the speech pathologist must deal. Other research areas of special interest include study of the aerodynamic relationships required for speech generation and further research into the functioning of the larynx as a sound source.
Some Graphical Methods to Speed-Up Routine Acoustical Calculations
Authors: Ver I. L.
Published: November 2005

Graphical methods showing the principal relationship between sound power and sound pressure for different characteristic environments, as well as the relation between average vibration level of wall surfaces and radiated sound power, will be discussed and illustrated on practical problems.
Impulsive Noises in Restaurants
Authors: Harris A. S. , Watters B. G.
Published: November 2005

In work reported earlier, the authors examined the speech component of the restaurant-noise environment and developed a design method for achieving the required acoustic criteria. In the recent work presented here, they have expanded their analysis of the noise environment to include sounds such as dish and silverware clatter and other impact sounds.
On the Quality of Reverberation
Authors: Shankland R. S.
Published: November 2005

In observations and measurements on the acoustical properties of a number of rooms varying greatly in size, shape and decoration, features bearing on the quality of reverberation are noted. In addition to accepted requirements for reverberation times as a function of frequency, some additional factors seem desirable. When high-frequency reverberation times in a concert hall are greater relative to the midfrequency reverberation than normally found in concert halls, the acoustical conditions are universally judged as unsatisfactory. A specific example of this condition has recently been corrected in the Kulas Hall of the Cleveland Institute of Music. Other factors relate to directional characteristics. It is believed that highly isotropic reverberant sound is not pleasant, but confusing. This condition is greatly improved if the preponderance of the reverberant sound approaches the listener in the horizontal plane. When the reverberation time is long, its pleasing quality is enhanced if it is possible to make judgments of distance and direction by the binaural-hearing sense. This latter sensation, rather than a prolonged reverberation time, is probably the principal effect, giving rise to the familiar acoustical properties of large churches.
Approach to Recreating a Sound Field
Authors: Camras Marvin
Published: November 2005

To re-create a “concert hall in a telephone booth,” a smaller volume is delineated within the original environment. The surfaces of this sound-transparent volume are covered with microphones, all having a directional pattern facing outwards from the volume. The sampled space is reproduced with an array of loudspeakers corresponding to the microphones, but with their directional pattern pointed inwards. Since the listeners can move freely within the re-created environment, some basic limitations associated with binaural listening are removed. Experiments were made with a 12-channel system. Studies included (a) effects of sampled-volume size, (b) microphone spacing and distribution, (c) space “magnification,” (d) use of small inexpensive speakers for the multiple channels with fewer large speakers for bass, (e) high-absorption listening environments, (f) effects of a finite number of channels.
Ultrasonic Relaxation in the Carboxylic Acids
Authors: Piercy J. E. , Rao M. G. Seshagiri
Published: November 2005

The ultrasonic absorption in formic, butyric, and octanoic acids has been measured at frequencies of 1, 3, 5, 15, and 45 Mc/sec over a temperature range of 20–100°C. Analysis of these measurements reveals a large single relaxation in each acid similar to the classic one in acetic acid, which has previously been attributed to monomer-dimer association. However, the activation energy of the relaxation in formic acid is 8.2±0.8 kcal/mole, which is in good agreement with the barrier of 8.9 kcal/mole for internal rotation about the C–O bond in the monomer obtained from spectroscopic measurements, and which is close to the activation energy of 8.7 kcal/mole for the similar relaxation in methyl and ethyl formates, where the mechanism of internal rotation is well established. It is argued, from this comparison and from solution measurements, that the mechanism for the large relaxation in this homologous acid series, including acetic acid, is internal rotation about the C–O bond.
Density Dependence of the Bulk Viscosity in Argon
Authors: Madigosky W. M.
Published: November 2005

The coefficient of ultrasonic attenuation in dense gaseous argon was measured as a function of frequency, from 5 to 85 MHz, and as a function of density, from 0.5 to 1.0 gm/cm3 at −38.6°C. The attenuation was found to be in excess of that attributed to the shear viscosity and thermal conductivity and was ascribed to the existence of a significant bulk viscosity. The magnitude of the bulk viscosity was found to be less than the hard-sphere calculation of 5/3 the shear viscosity, and essentially proportional to the density squared. The results are in excellent agreement with the predictions of Gray and Rice.
Visualization of Quasilongitudinal and Quasitransverse Elastic Waves
Authors: Staudte Juergen H. , Cook Bill D.
Published: November 2005

An optical method that permits the visualization of the deviation of energy flux from the wave normal of elastic waves in transparent crystals is described. Both the wavefronts and the direction of energy flux are simultaneously rendered visible by spatial filtering (Schlieren technique). Its application and comparison with other optical methods are discussed. [Supported by the National Science Foundation and the U. S. Navy Office of Naval Research.]
Characterization of Speech Sources in Terms of Genetic Operating Characteristics
Authors: Smith Caldwell P.
Published: November 2005

It was established that speech sources can be characterized in terms of genetic operating characteristics of the form 〈e〉=k/N, where 〈e〉 is the expected value of spectrum error in decibels, or a “fidelity” factor, N is the number of speech-spectra categories that are contained in a pattern library constructed from analysis of the properties of specified speech sources, and k is an experimentally determined constant that varies in accordance with the entropy of different speech sources. A genetic operating characteristic (GOC) so established predicts the number of pattern categories and information in bits required to specify a multidimensional information source to any desired level of fidelity. [This research was supported in part by the Laboratory Director's Fund.]
Optimum Linear Speech Filter
Authors: Griffiths John D.
Published: November 2005

A common speech-communications problem involves a noisy channel and a peak-power-limited transmitter. Many empirically derived devices have been proposed and used, such as amplitude limiters and peak clippers, to attain higher intelligibility. By accepting the French and Steinberg Articulation Index, as modified by Beranek and Kryter, as a valid description of the performance of a linear speech system in the presence of noise, it is possible to analytically derive an optimum linear time-invariant pretransmission filter to maximize the intelligibility of speech over a noisy channel. Such a filter was built and shown, by intelligibility tests, to be significantly more intelligible than other filters that bounded the optimum filter. The transfer function of this filter is dependent on the noise spectrum. The filter results in an increase in intelligibility equivalent to a transmitter power increase of 64%.
Omnidirectional Scattering of Acoustic Waves from Time-Varying Rough Surfaces
Authors: Parkins B. E.
Published: November 2005

The fading of monochromatic acoustic plane waves reradiated by moving rough surfaces is described using the far-zone spectral density of the reradiated pressure. This quantity is calculated using the method of physical optics and specialized to the cases of slightly rough and very rough wind-generated seas. The dependence of the spectrum upon wind speed and the angles of incidence and observation relative to the wind direction is shown. [Work was supported by the U. S. Office of Naval Research.]
Microbubbles as a Source of Diffuse Scatter
Authors: Turner William R.
Published: November 2005

Recognized sources of acoustic scatter in the ocean are fishes and other biological life containing swim bladders or air pockets. Such sources are in sufficiently low volume concentration that they are identifiable as discrete scatterers and contribute to volume reverberation principally at frequencies approaching the resonances of the air cavities for which the scatter cross sections exceed physical cross sections by one to two orders of magnitude. A review of reverberation data obtained with high-resolution depth sensors discloses instances of significant diffuse scatter. The hypothesis is advanced that this scatter arises from stabilized microbubbles, and further, that these populations of microbubbles are also responsible for a reduction of acoustic velocity measured in situ, as compared with computed values based on temperature, depth, and salinity.
Acoustics of Rooms for Classical Recordings
Authors: Beranek L. L. , Schultz T. J.
Published: November 2005

One of the tasks of the producer of classical recordings is to select the acoustical environment and the placement of microphones to achieve the result that he and the conductor feel fulfills the composer's intent. For organ and choir music, fullness of tone is sought. For music of the Baroque period, a drier quality is usually preferred. Much of the music of the Classical and Romantic periods is satisfactorily produced in one type of environment. Excerpts from recordings of the major record companies are played to demonstrate the results achieved. Several examples of the same composition performed by the same orchestra and conductor in two different halls are presented. One asks whether listeners' tastes for the acoustics of live music might be influenced by the “standardized” environment heard on many recordings.
Study of Sound Decay Using Ray-Tracing Techniques on a Digital Computer
Authors: Atal B. S. , Schroeder M. R.
Published: November 2005

Reverberation times calculated on the basis of existing ray acoustical theories often differ considerably from measured results. In order to develop an accurate theory of reverberation based on ray acoustics, sound decays in rooms of different shapes and sizes are obtained by simulating the propagation of rays on a digital computer. The path of each ray, radiated from a point source in the enclosure, is traced and its energy is computed as a function of time by taking into account the effect of any absorbing materials on the boundaries. Sufficient conditions for the sound decay to be exponential are formulated. Reverberation-time formulas based on the results of this study depend on the shape of the enclosure and the distribution of the absorbing material.
Critical Review of Sound-System Design Concepts, Applied to “Difficult” Reinforcement Situations
Authors: Figwer J. Jacek
Published: November 2005

In addition to fulfilling the traditional objectives in the performance of sound-amplification systems, which include the increase of sound level or the improvement of sound coverage throughout the audience areas, sound systems can also be considered devices aimed at increasing the early-to-reverberant energy ratio. (T. J. Schultz, “Acoustics of the Concert Hall,” IEEE Spectrum 56–57 (June 1965).) This approach seems to be particularly important in large multi-purpose halls with long reverberation characteristics, when used for drama. Not only are directional loudspeaker systems needed in such halls to preserve a high ratio of direct to reverberant energy, but equally strict requirements should be set for an acoustically “dry” microphone pickup. This unfortunately is difficult to achieve, since the occasion usually calls for inconspicuous reinforcement with microphones hidden at remote locations. The analysis of the microphone setup for adequate coverage of a theatrical stage leads one to conclude that the development of a new type of wireless personal microphone could ease the situation considerably.
Systems and Methods in Statistical Analysis and Reduction of Geoacoustical and Geomagnetic Data
Authors: Tolman Wallace F. , Crolene Robert , Fehr Uri
Published: November 2005

Geoacoustical and geomagnetic wave-phenomena data are collected by an array of sensors and are recorded on magnetic tape in frequency-modulated form. The accumulated data are assumed to be a realization from a nonstationary stochastic process, but subgroups of this process are assumed to be stationary in the wide sense. The data are digitized by a unique method not requiring demodulation, reduced and adjusted (or “recolored”) using a numerical-analysis technique which corrects for frequency attenuation due to the frequency-response characteristics of the sensor and field recording equipment. A statistical time-series analysis is performed on subgroups of the adjusted data. The analysis consists of describing the observations in terms of amplitude, phase, “significant” frequencies, and coherence between series, resulting in an easy determination of velocities and source locations. Physical properties can then be deduced. The mathematical techniques involved in “recoloring” and filtering are explained and the statistical techniques (i.e., autocovariance, cross covariance, etc.) used in the time series analysis are discussed. An explanation and description of systems used in handling the data is summarized. Samples of the analysis related to the Saturn rocket test firings are presented.
Analytical Review of the Electromechanical Piston and the Modified Moore Variometer Used in Infrasound Studies
Authors: Ben-Ary B. , Fehr Uri
Published: November 2005

The electromechanical system, which is an integral part of the infrasonic calibration and testing facility at the Institute of Geophysics and Planetary Physics at the University of California, has been studied analytically. An equation taking into account the electrical and mechanical parts as a closed system has been formulated, and the resulting frequency response and sensitivity curves compared with those obtained experimentally. A similar study was conducted on the fluid dynamics involved with the infrasonic sensor (the modified Moore Variometer) used in our infrasound studies. The results yielded a better understanding of capabilities of this device and verified its evaluation. The calibration facility itself has the capability of testing and evaluating the behavior of any infrasonic sensor in the frequency range of 1/1000–1000 cps, and pressure variations of 10−2–103 μbar, in the ambient atmosphere. The facility has also the capability of testing and calibrating the infrasonic sensors under high-altitude conditions, enabling the simulation of atmospheric density up to 90 km and of varied temperature conditions.
Continuous Surface-Pressure Waves and Troposphere Dynamics
Authors: Young J. M. , Bowman H. S.
Published: November 2005

Certain spatially coherent traveling atmospheric pressure waves were recorded at the earth's surface in the Washington, D. C. area. These waves occurred almost continuously during a period of one week in December 1965. The occurrences of these waves have been related to the dynamics of the upper troposphere. These waves have periods of between 6 and 11 min and horizontal speeds of between 40 and 70 m/sec. Experimental data are presented that tend to confirm the previously suggested existence of a functional relationship between the long-period surface-pressure wave phenomena and local tropospheric jetstream behavior.
Seismic Waves Generated by Sonic Booms—A Geoacoustical Problem
Authors: Espinosa A. F. , Mickey W. V. , Sierra P. J.
Published: November 2005

Low- and very-low-frequency air-coupled seismic waves were efficiently excited on different occasions by jet fighter planes flying at high altitudes at Mach numbers greater than 1.2. The experiments presented in this investigation were clearly recorded on a geophone array containing up to 12 short-period vertical-component stations, and a singular station recording the transverse and radial type of motion. Correlation is made between the acoustical signal registered at the microphone stations in Cape Kennedy and the first impulsive onset of the air-coupled seismic waves recorded at the array setup. Fourier-transform techniques are applied to some of the seismograms, and some interesting features are delineated.
Velocity Dispersion Measurements in Benzene and Carbon Tetrachloride
Authors: Carome E. F. , Singal S. P. , Kunsitis C. R.
Published: November 2005

Measurements of the velocity of sound in benzene and carbon tetrachloride have been made at 25°C in the frequency range from 1.5 to about 5 kMc/sec using laser light-scattering techniques. In benzene, there is striking confirmation that the observed ultrasonic absorption and hypersonic velocity data may be interpreted in terms of double relaxation of the vibrational specific heat. In carbon tetrachloride, though the observed variation of velocity with frequency may be explained in terms of relaxation of the entire vibrational specific heat, with τ″=5.4×10−11 sec, it is shown that this is not a unique interpretation. [Supported in part by the Advanced Research Projects Agency and the Office of Naval Research.]
Brillouin Scattering in Viscoelastic Liquids
Authors: Candau S. , Montrose C. J. , Pinnow D. , Litovitz T. A.
Published: November 2005

The complex elastic modulus Mc of a viscoelastic medium can be determined from the attenuation coefficient α and the phase velocity Vs (or wave vector k) of a longitudinal wave of propagation factor exp [i(wt−kx)−αx]. The real and imaginary parts of Mc (M′ and M″, respectively) are then computed using standard expressions involving α and Vs. In a Brillouin scattering experiment, one observes light scattered by a Fourier component of a decaying density fluctuation. Here the propagation factor involved is exp [i(Ωt−κx)−Γt], and the measured quantities are Ω and Γ. These can be used also to calculate M′ and M″. In liquids where the loss per cycle is of order unity, the difference in the experiments becomes apparent. For example, Vs≠Ω/κ, as is usually assumed for low-loss liquids. Moreover, the presence of a relatively broad unshifted spectral component [R. D. Mountain, J. Res. Natl. Bur. Std. 70A, 207–220 (1966)], which “overlaps” the Brillouin line causing the peak of the latter to appear at a shifted frequency different from Ω, must be taken into account. The correction for this deviation can be obtained in terms of the measured quantities: The case of glycerol is treated in this light and the data are compared with those previously obtained from ultrasonic techniques. [Supported by the National Science Foundation.]
On the Relation of the Intensity of Scattered Light to the Viscoelastic Properties of Liquids and Glasses
Authors: Pinnow D. , Candau S. , LaMacchia J. , Litovitz T. A.
Published: November 2005

It has long been recognized that the position of the Brillouin peak in the spectra of scattered light could be a useful tool for the measurement of the velocity of hypersonic waves. Only recently has the intensity of the scattered light been rigorously related to the viscoelastic parameters of a fluid. In this paper, the rigorous theory of Mountain, and also, useful phenomenological theory describing the relative spectra of the scattered light, are considered. These theories will be applied to the spectrum of glycerol, which has been measured as a function of temperature from −70° to +150°C using a He-Ne laser source. The results show that a suitably defined Landau-Placzek ratio and the relative Brillouin intensity can be used to gain information about the relaxational behavior of the longitudinal modulus of elasticity and hypersonic velocity both in the liquid and in the glassy state. [Supported by National Science Foundation.]
Resonance Effects on Human Hearing Threshold Sensitivity
Authors: Castle Diane Sklar
Published: November 2005

This study was designed to explore whether resonance characteristics of the ear can affect threshold sensitivity more markedly than previous observations suggest. Discrete frequency thresholds were obtained with a Békésy audiometer for 10 male and nine female normal-hearing listeners using two testing procedures, one experimenter-controlled, the other subject-controlled. Pulsed-tone test stimuli were presented through an Audivox 9C earphone in conjunction with an individual ear impression at 100-cycle intervals between 400 and 3000 cps, and at smaller frequency intervals whenever adjacent test frequencies differed by 5 dB or more. Reproducible threshold contours were obtained by both testing procedures which showed sizeable prominences of sensitivity at such frequency locations as have been associated often in the literature with middle ear resonances. For some listeners, a 12–15-dB variation in threshold level occurs within frequency intervals of less than 100 cycles. All listeners showed at least two prominences of sensitivity, and one showed as many as eight. Such evidence suggests that there may be reflections of resonances in the threshold contour which are both sharp and numerous, depending on the listener.
Attenuation Characteristics of Earmuffs at Low Audio and Infrasonic Frequencies
Authors: Hille Harald K. , Nixon Charles W. , Kettler L. Keith
Published: November 2005

Progress in the development of newer and larger propulsion systems has resulted in the generation of greater acoustic energy in the low-audio and infrasonic frequency ranges. The efficiency of muff-type ear protectors in intense acoustic exposures of this type has been questioned. For this purpose, a study was initiated to evaluate the effective noise reduction of present-day earmuffs in this frequency range. Subjective attenuation and noise reduction of three different earmuffs are described. These characteristics were determined (1) by physical measurements of discrete frequency signals in the range from 1 to 500 Hz inside and outside earmuffs worn by subjects and (2) by psychoacoustical or subjective measurements similar to the USASI “Real Ear Attenuation at Threshold Method.” Measurements were performed using nine subjects; and the data, including correlation between the two measurement methods, are presented in terms of mean attenuation and as a function of frequency. Results show that good present-day earmuffs provide some attenuation in the frequency range from 20 to 100 Hz and very little protection below 20 Hz. Similar evaluations using earplugs and earplug-earmuff combinations are contemplated.
Impairment and Recovery in Time Required for Tonal Sensation in 57 Patients Selected for Vertebral Artery Surgery
Authors: Boomsliter Paul C. , Powers Samuel R. , Creel Warren
Published: November 2005

Time requirements for achieving tonal sensation have been shown to be affected by the state of the blood supply to the brain stem. Of 57 patients selected for vertebral artery surgery, a fortuitous instance of a subclavian steal produced by automobile accident in a normal 23-year-old man was closely studied audiologically immediately after the trauma. The test for tonal sensation was grossly abnormal; all other audiological tests were normal. Following surgical repair of the steal, time scores returned to near normal; cortical-evoked potentials became more complex. Other audiologic test results remained unchanged. Arteriograms are presented. The presentation illustrates pre- and postoperative test results in 57 cases selected for vertebral artery surgery and current work utilizing specific brain-stem destruction in rhesus monkeys. [Supported in part by a United Cerebral Palsy grant and by the National Institutes of Health, U. S. Public Health Service, Department of Health, Education, and Welfare.]
Temporal Summation in the Hearing-Impaired Listener
Authors: Wright H. N.
Published: November 2005

Temporal summation was measured at the threshold of audibility in listeners with moderate sensorineural hearing loss. The results indicate that while the conventional analysis of threshold-duration functions is appropriate for listeners with normal hearing, it does not seem appropriate for the hearing-impaired listener. Because of this, a revised method of analysis for threshold-duration functions is proposed that appears appropriate for both normal and hearing-impaired listeners. Further analysis of the results showed that the deviant results that were obtained are consistent with the theory of temporal auditory summation. They also suggested that threshold-duration functions may be an extremely sensitive psychophysical index of a physiological disturbance at the level of the cochlea. [Research supported in part by the Bureau of State Service, U. S. Public Health Service, Department of Health, Education and Welfare.]
Torque on a Finite Disk Executing Damped Harmonic Oscillations in a Viscous Fluid Near a Rigid Boundary
Authors: De Metz F. C.
Published: November 2005

Expressions are derived for the torque exerted on a finite cylindrical disk that executes torsional oscillations about its cylindrical axis while immersed in a viscous fluid parallel to a rigid plane boundary. The relations for the total torque of the fluid on the oscillating disk are given in terms of the period and decrement of the disk's oscillation for small, large, and intermediate separation distances between the disk and the rigid plane boundary. Theoretical relations for the torque of the fluid on the disk are found, assuming that the disk oscillates slowly and that the force per unit area on the plane and cylindrical surfaces of the disk is equal to that for an infinite disk and cylinder, respectively. An empirical correction is used to account for the torque which is due to the effects of the sharp corners of the disk. The effects of the bounding plane on the reactive and dissipative components of the torque are given in terms of the depth of penetration of a decaying transverse wave propagated into the fluid.
Piston-Type Spherical Radiation
Authors: Molloy C. T. , Miller K. L.
Published: November 2005

In a previous paper, it has been shown that it is possible to specify a desired acoustic pressure pattern and to calculate the continuous velocity distribution on the surface of a spherical transducer that will produce it. A computer program has been written to yield the transducer velocity distribution required to produce a prescribed pressure pattern. A program has also been developed that permits the acoustical field pressure to be calculated when a velocity distribution is prescribed over the surface of the transducer. These two programs are the basic tools in this research. A desired far-field pressure pattern is selected and the continuous transducer velocity distribution computed. This distribution is then approximated by an array of piston lying in a spherical surface and the pressure pattern which the array produces is calculated. This is compared with the original desired pattern. The present paper discusses the problem of approximating the continuous velocity distribution by an array of pistons. In particular the effects of piston size, signal frequency, and transducer radius are discussed. [Work supported by U. S. Navy Ordnance Systems Command.]
Maximum Array Gain Versus Optimum Pattern
Authors: Becker Clair J.
Published: November 2005

In the design of arrays, there is a tradeoff between obtaining the maximum array gain on one hand and an optimum pattern on the other. An array was chosen, and the amplitude shading coefficients were calculated to produce the maximum array gain. Next the Tchebyscheff polynomials were used to obtain the amplitude shading coefficients which result in an optimum intensity pattern. Then the array gains and intensity patterns were calculated for each procedure and for a surface generated ambient and an isotropic noise field. The beam width of the patterns (for the same side lobe levels) and the array gains, as obtained by the two methods, were compared at each element spacing. For the cases of a linear, five-element, evenly spaced array at spacings of d/λ=1/8, 2/8, ⋯, 6/8 and both noise models, the two procedures produced minor differences. The maximum differences were that the Tchebyscheff procedure produced a main beam about 112° narrower but resulted in 12 dB less of array gain. For d/λ=7/8 and 1, differences were greater.
Extremely-Low-Noise Preamplifier for Audio Frequencies
Authors: Truchard J. J. , Stockton J. E.
Published: November 2005

A low-frequency low-noise preamplifier has been designed around a recently developed field-effect transistor (FET). Data are presented on the noise performance of this FET circuit as compared with a state-of-the-art bipolar transistor circuit. The theoretical source noise for the FET circuit is computed and compared with measured values. The noise characteristics of this circuit approach its theoretical source noise in the frequency range 10–100 Hz. The self-noise spectrum level at 10 Hz is below 140 dB//V2/ Hz as measured with a simulated hydrophone capacitance across the input. The low noise performance from 10 Hz to 20 kHz and its other characteristics such as high input impedance, wide dynamic range, low distortion, low current drain, small size, and low cost suggest many potential applications in underwater acoustics as well as possible applications in other acoustical fields.
Active End Correction of Pipes and Resonators
Authors: Elder S. A.
Published: November 2005

When a pipe is sounded by blowing across the mouth, the sounding frequency can be varied by adjustment of the stream speed so as to be either above or below the natural pipe frequency, an effect observed but not explained by Rayleigh [Phil. Mag. Set. 5, 13, 340–343 (1882)]. As a pipe is “blown up” to pitch, the pipe-mouth end correction may be considered to have an active component, due to the presence of the jet, whose reactive part varies from positive to negative as jet-feedback control shifts from edge to pipe. The positive reactance derives from the edge-induced “dipole” field while the negative component can be determined from the pipe-jet transfer function. Experimental data are presented. [Work supported by the Office of Naval Research.]
Program for Automatically Plotting the Scores of Computer Sound Sequences
Authors: Chang Jih-Jie , Mathews Max V.
Published: November 2005

A graphical language for the scores of computer generated sounds has been described. The language was intended for a composer; it makes possible drawing scores with a light pen on a cathode-ray tube attached to a small computer. It is difficult to follow these scores while listening to the sounds because of the repetitions and algebra inherent in the language. A program to output an easy-to-read score is described. Frequency (in a logarithmic scale) and intensity (going from pp to ff) are plotted as functions of time (measured in beats). The frequency function is divided into dashes corresponding to note durations. Four voices may be plotted simultaneously. The functions are drawn by a computer on a cathode-ray tube and are recorded photographically on microfilm. For computer sounds, these scores are easier to follow than standard scores and more general than standard scores; it is easy to learn to read them.
Jet Engine Sideline Noise Measurements
Authors: O'Keefe J. V. , Bielak G. W.
Published: November 2005

Results of acoustic measurements of a YJ-75 turbojet with afterburner are analyzed and reported. Measurements have been made by the standard 200 ft polar method and also on an 800-ft and 1500-ft parallel line. Mobile equipment recorded acoustic data for the parallel-line test points. Airport jet-engine-sideline-noise levels associated with aircraft ground roll are usually rated at a sideline distance parallel to the aircraft centerline. Jet-noise levels measured at standard, polar, fixed-position-microphone test points must, therefore, be extrapolated to the designated sideline distance for airport-noise evaluation. Attenuation values have been determined for extrapolation of jet-noise levels to sideline-noise levels. Acoustic data were collected at the Boeing Test Site. Boardman, Oregon, for the purpose of making jet-noise suppressor-design evaluations. Terrain in this area is flat and the ground cover is low and uniform. Direct eye-level engine-noise measurements may be made at distances as far as 4000 ft for over an arc of 270° from the engine inlet. Ideal atmospheric conditions also assure excellent acoustic testing environment and data validity.
Propagation of Sound from Airport Ground Operations
Authors: Franken Peter A. , Bishop Dwight E.
Published: November 2005

An experimental study has been performed to investigate the sound-propagation losses associated with aircraft ground operations. Downwind propagation was emphasized in this study, because the highest levels observed on the ground generally occur when the receiver is downwind from the source. The noise from the initial part of jet-aircraft takeoff roll was found to be the most reliable high-level source for the study. The results show a pronounced increase in low-frequency range of 125–250 Hz. They indicate also that the “standard” values of atmospheric absorption are too large above 1000 Hz. A simple engineering procedure for estimating downwind propagation is given. [Work supported by the National Aeronautics and Space Administration.]
Quiet Wind-Tunnel Facility for Investigating Flow Noise
Authors: Hanson Carl E. , Leehey Patrick
Published: November 2005

A low-noise, low-turbulence, subsonic wind tunnel was designed for investigation of both wide- and narrow-band flow-noise processes. The open-circuit design incorporates such innovations as interchangeable open-jet and closed-duct test sections within a sealed test chamber that can be either reverberant or anechoic by the use of removable wall treatment. Low noise level at the test section is achieved by using upstream treatments, such as anechoic wedges off the face of the inlet and a honeycomb of soda straws, and by using downstream treatments, such as a combination muffler-diffuser and another honeycomb of soda straws. The design concept, the aerodynamic performance, and the acoustical performance are presented.
Effects of Stator Pitch and Removal on Axial-Flow Compressor-Noise Generation
Authors: King Robert J.
Published: November 2005

This paper presents the results of a series of tests to determine the characteristics of compressor noise emitted from a particular gas turbine. The machine tested was a General Electric Frame 5 industrial gas turbine, which is in the 18 000 hp class. Of primary interest in the test series were the changes in intensity of discrete-frequency, compressor-blade-passage noise caused by varying the pitch of the inlet-guide vanes and by removing the vanes. Removal of the vanes resulted in substantial increases in harmonic noise levels, which would seem to be contrary to current theory. This apparent incongruity is explained, however. The perturbation of the flow field into the first rotor stage that had originally been caused by the stator blading was now caused by the bearing-support struts, which, although farther upstream, were larger in cross section. The number of struts allowed greater propagation of the spinning-duct modes. Removal of the vanes resulted in increased power consumption of the compressor, also, as the rotor blading was not modified to operate without stators.
Application of the Fast Fourier Transform to Third-Octave and Octave-Band Analysis of Noise Produced by Business Machines
Authors: Maling G. C. , Morrey W. T. , Lang W. W.
Published: November 2005

A computer subroutine prepared by J. W. Cooley has been used together with additional programs to analyze the acoustical noise produced by typical business machines. The subroutine utilizes the Cooley-Tukey algorithm for the rapid computation of the Fourier coefficients of a discrete time series. The digital recording system described in an earlier paper [J. Acoust. Soc. Am. 40, 1273(A) (1966)] has been used to acquire data in a format suitable for computer processing. Emphasis is placed on computation of third-octave band levels from the Fourier coefficients, the filter characteristic or “window” associated with the analysis, and the spectral fluctuations that occur in short (100–250 msec) samples of the noise. The digital spectral estimates are in good agreement with analog measurements. For one machine studied, the spectral fluctuations are larger than would be expected for samples of random noise. Analysis of successive bursts from a second machine has indicated that spectral fluctuations occur even when the envelope of the pressure-time pattern is observed to be repetitive.
Central Masking: Temporal Decay at 1000 Hz
Authors: Newman R. A. , Zwislocki J. J.
Published: November 2005

According to experiments reported at the preceding meeting of the Society, central masking produced by a 1000-Hz tone and by a critical-band noise decays as the time delay from the masker onset increases. It reaches an asymptote between 100 and 200 msec. The decay is expotential with a time constant of approximately 50 msec independent of the masker intensity level. Recent experiments have extended the generality of the time constant to broadband noise. Earlier investigations have also revealed a slower masking decay for pure-tone stimulation. This decay extends over several minutes and appears to be complex. We now have found, in agreement with early pilot studies, that broadband noise does not produce any such decay. Both the fast and the slow decays parallel corresponding firing patterns of single units in the 8th nerve of the cat.