bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Electrophysiological Aspects of Hearing in the Bat Eptesicus fuscus
Authors: Dalland John , Vernon Jack , Peterson Ernest A.
Published: September 2005

For one bat, it was possible to ascertain the magnitude of cochlear-microphonic potentials elicited by pure-tone stimuli of threshold SPL. These potentials at the threshold of hearing varied from 0.008 μV at 70 kHz to 30 μV at 2.5 kHz. The function relating these “threshold potentials” to frequency was strikingly similar in shape to the curve depicting the way hearing thresholds varied with frequency; the covariation was great even in a region around 40 kHz, where the hearing threshold function displayed a large insensitivity peak. There appeared to be no single magnitude of hair-cell potential that inevitably gave rise to a just-perceptible hearing sensation. Thus, it is unlikely that density of cochlear stimulation (e.g., microvolts/millimeters of basilar membrane or microvolts/neural unit) bears any simple relation to the initiation of “threshold level” impulses in the auditory nerve. Data from other animals agree with the above.
Temporal Patterns of Response in Single Neural Units of the Auditory Nerve
Authors: Finck Alfred
Published: September 2005

Responses were taken by microelectrode from single elements in the auditory nerve of the golden hamster. The activity evoked by tones of various frequencies and intensities was analyzed according to the interval histogram. Temporal aspects of the spike responses were studied for units having different best frequencies. The results of these analyses indicated that the frequency of occurrence of particular time intervals between successive action potentials was constant over a wide range of stimulus intensities. The constant pattern of spike intervals was observed for units having low as well as high best frequencies. The data suggest that the density of intervals generated by a particular unit may be linearly related to the absolute value of the interval (in milliseconds). [Work supported by a grant from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Velocity Control
Authors: Carson David L.
Published: September 2005

NEL thinks of velocity control, in the broad sense, as any direct or indirect method that can ensure that a prescribed velocity distribution will exist for a transducer array. Force control may be thought of as an indirect method of obtaining velocity control. Provisions for velocity control in this broad sense must be included in any consistent array-design procedure. NEL believes that, to design, analyze, or evaluate properly many present-day transmitting or receiving arrays, one must have and use an adequate composite mathematical model that accounts for all components of the system, including the acoustic medium and boundary conditions. In practice, such an analysis frequently requires the numerical solution of a large system of linear equations. The characteristics and size of such a system can make it impractical to obtain the solution of the equations even with modern computer facilities. In these cases, velocity control may be used to make the diagonal terms of this system of equations dominant; in many cases, it will then be practical to solve the equations.
Uses of Power-Spectrum Analysis
Authors: Lang W. W.
Published: September 2005

The measurement of power spectra requires careful consideration of data-conversion methods, analysis procedures, and statistical estimates. As a technique for analyzing data, this type of measurement has application to a large number of physical situations. While the physical models are widely different, the techniques used in these several areas have much in common. To avoid obtaining incorrect results from power-spectrum measurements, the relationships among frequency resolution, accuracy, length of data record, and computation techniques must be fully appreciated. It is the purpose of this Workshop to explore the various uses of power-spectrum analysis in an effort to identify and arrive at a better understanding of common problems. Following the review paper, which summarizes current techniques of power spectrum analysis. panel members comment on the uses of such techniques in several areas. At the conclusion of the panel presentations. the Workshop is open to participation from the audience.
Temperature Dependence of Sound Velocity and Ratio of Specific Heats in Liquids at Ultrahigh Frequencies (UHF)
Authors: O'Connor C. Leonard , Schlupf Joseph P.
Published: September 2005

An experimental study of the central line and the Brillouin components in the molecular scattering of light has been made in several liquids using a 75 mW He-Ne gas laser as a light source. The scattered light from liquids was analyzed by a Fabry-Perot interferometer (pressure scanning) in conjunction with a dry-ice-cooled phototube detector and recorder output. Modifications in the optical system commonly used have resulted in an increased signal-to-noise ratio in the scattered radiation. In particular, a detailed study of the separation of the Brillouin doublets (to determine the UHF velocity of sound) and the ratio of the intensity of the central line to that of the doublet lines (to determine the ratio of specific heats) was made for water over a temperature range of 0° to 30°C. Correction factors for errors due to overlap of lines of central and Brillouin components are considered.
Effect on Detectability of Interaural Signal-Frequency Disparity
Authors: Robinson Donald E.
Published: September 2005

The function relating interaural signal-frequency difference (Δf) to masking level difference (MLD) was obtained using a two-alternative forced-choice procedure. The masking noise was presented diotically (N0) at a spectral level of 45 dB. The signals to the two ears were gated simultaneously and each was 1 sec in duration. For all sessions, the signal to one ear was 400 cps. In separate sessions, signal frequencies of 406, 420, 440, 460, 500, 550, 600, and 700 cps were presented to the other ear. The MLD was found to decrease from about 10 dB at Δf=6 cps to about 7 dB at Δf=150, 200, and 300 cps. This limiting value of the MLD is also the MLD for the 400-cps signal presented monaurally (N0-Sm). [Research partially supported by the U. S. Air Force Office of Scientific Research.]
Evaluation of the Performance of a Polarity Coincidence Correlator in an Active Sonar Application
Authors: Bartram James F.
Published: September 2005

A method is devised for evaluating and comparing the performance of receivers used in an active sonar application. The basis of comparison is the level of background noise that will just bring the maximum signal excess, after system adjustment, to zero, given a propagation loss. The better system is the one that can withstand the higher level of background noise before the maximum signal excess goes to zero. This method is applied to the polarity coincidence correlator and, for comparison, a classical audio/visual receiver. In evaluating the polarity coincidence correlator in the active sonar environment, it has been found that, because of the effects of reverberation, attention must be paid to transmit waveform design, transmit-and-receive array design, and postdetection filter design. In the last instance, direct-current blocking has been found to be effective, and its use is assumed in the performance evaluation. When all the proper steps have been taken, it is found that the polarity coincidence correlator compares favorably with current audio/visual receiver.
Formation of Difference Patterns in Transducer Arrays with an Odd Number of Elements
Authors: Wilson Geoffrey L.
Published: September 2005

A combination of sum and difference patterns is often used when a hydrophone is used to determine bearing. Usually, an array containing an even number of elements is employed. However, it may be desirable to use an odd number of elements so that an element at the geometrical center can be available for a phase reference. It is shown that the modified Dolph-Chebyshef method due to Kendig [V. M. Albers, Underwater Acoustics Handbook (The Pennsylvania State University Press, University Park, 1960), Chap. 11] is equally applicable to odd-ordered arrays. Experimental data are shown, comparing the patterns from a 7×7 array with those from an 8×8 array of similar characteristics.
Amplitude Distributions for the Shaded Line Array in Terms of Hypergeometric Polynomials
Authors: Simmons Bernard D.
Published: September 2005

The functions that represent directional properties of a line array of acoustic elements can be related to a general class of polynomials that includes those of Jacobi, Gegenbauer, Chebyshev, Legendre, Laguerre, and Hermite. The significance of these polynomials for array design is that the response amplitudes are given in terms of parameters that varied continuously, produce continuous and predictable changes in the directivity pattern. For a symmetrical distribution of amplitudes, the functions are essentially Gegenbauer polynomials that, expanded in a trigonometric series, give amplitudes explicitly in terms of a single parameter. With proper normalization, this parameter can be varied from zero to infinity, producing the pattern of an unshaded line for value unity; the Chebyshev distribution, with equal side lobes, for zero value; and the binomial distribution, with vanishing side lobes, in the limit of large values. A value of one-half gives Legendre polynomials. Choosing a representative pattern with a particular distribution of side lobes, the introduction of an additional parameter, which amounts to a change of scale, permits a uniform reduction of all side lobes by a fixed ratio relative to the main beam.
Theoretical Investigation of Finite-Amplitude Effects for Acoustic Standing Waves in Cavities
Authors: Coppens A. B. , Sanders J. V.
Published: September 2005

The generation of overtones by finite-amplitude processes in rigid-walled cylindrical cavities with large length-to-diameter ratios is studied. An extension of the Keck-Beyer perturbation technique leads to a set of iterative equations valid for standing waves that can be applied to cavities with energy losses occurring at the walls. Necessary features of the theory include assuming one-dimensional motion, characterizing all absorptive processes by a bulk absorption coefficient, and requiring a boundary-layer depth much less than the tube diameter. Solutions lead to a steady-state distribution of harmonics of the fundamental, the relative amplitude of each overtone being inversely proportional to the absorption coefficient characteristic of the relevant normal mode of the cavity. [Work supported in part by the U. S. Office of Naval Research and the U. S. Bureau of Ships.]
Shock-Producing Excitation in a Viscous Fluid
Authors: Rodin Ervin Y.
Published: September 2005

If Burgers' equation, vt+vvx=δvxx, is used as a descriptor of the propagation of waves of finite amplitude in a viscous fluid, one can give a characterization of the set of boundary functions that are shock-producing. The boundary conditions assumed are v(0,t)=a(t), vx(0,t)=b(t). Conditions for the appearance of shocks are given in terms of the quadratic form a2(t)−2δb(t) by means of the concept of complete monotonicity. The results obtained are an extension of those obtained by the author in “Mathematical Advances in the Theory of One Dimensional Flow,” in Symposium on Apollo Applications, Huntsville, Alabama, January 1966. [Work supported by the National Aeronautics and Space Administration.]
Acoustic Visualization of Transient Inhomogeneities Induced by Intense Focused Ultrasound in Lucite
Authors: Okuyama Daitaro , Fry William J. , Fry Francis J. , Leichner Gene H. , Kelly Elizabeth
Published: September 2005

On the basis of analytical considerations, it was first indicated by one of the authors (W.J.F.) that transient inhomogeneities in sound speed induced in media by pulsed acoustic energy of appropriate level would be detectable by standard ultrasonic reflection techniques. [Ultrasonic Energy, Biological Investigations and Medical Applications, Elizabeth Kelly, Ed. (University of Illinois Press, Urbana, 1965)]. This presentation is concerned with describing conditions appropriate for demonstrating such effects in Lucite by employing 3-Me/sec ultrasound for durations over the range 0.3–1.6 sec. The results obtained indicate that the total energy applied for heating is the significant parameter (for the range of pulse durations employed) whose values can be used to characterize the observed effects. [Investigation supported in part by the National Cancer Institute, National Institutes of Health. Public Health Service, U. S. Department of Health, Education, and Welfare.]
Free Expansion of a Gas Bubble in a Highly Porous Medium
Authors: Epstein David
Published: September 2005

In a previous report [D. Epstein, J. Acoust. Soc. Am. 37, 1182 (1965)], the influence of the ocean bottom on an underwater-explosion waveform was discussed in terms of a generalized method of images. A one-parameter, or liquid model, of the upper sedimentary layers was assumed; the density of the layer was obtained from formulas quoted in the literature. More realistically, however, the sediments should behave as a porous, rather than liquid, layer; for our purposes, a porous medium is described by two parameters: porosity (φ) and permeability (k). Here, general two-parameter flow. or flow in a homogeneous porous medium, induced by an explosion, is treated; approximate formulas valid for the free expansion of the gas bubble in a high-porosity, high-permeability medium are developed. These results show that ideal flow is strongly modified in a porous medium; the flow is characterized in terms of a parameter βto, where β=μφ/kρ, and to is a characteristic time of the explosion; examples are discussed.
Signal Distortion Caused by Bottom Reflection
Authors: Nuttall Albert H. , Cron Benjamin F.
Published: September 2005

The acoustic theory for the reflection of a single-frequency plane wave from a fluid layer lying between two semiinfinite fluid media, where the layer and the bottom medium are subject to attenuation, is reviewed. Applying the experimental fact that the attenuation is proportional to the first power of frequency to this theoretical model, it is shown that the effect on impingent plane waves may be treated as a parallel linear filtering operation with a typical transfer function of the basic form H(f)=exp[−2πb|f|+iεsgn(f)]. Here f is the frequency in cycles per second, 2πb is the attenuation in nepers/cycles per second, ε is the phase shift in radians, and sgn (f) = {1, f>0−1 f<0}. For this basic type of transfer function, the reflected pulse is first derived generally in terms of incident pulse, attenuation, and phase shift. Reflected pulse shapes for some specific incident pulses are then derived and numerically evaluated. The correlation loss for a random function with flat finite bandwidth is also obtained. In general, the distortion of waveform and crosscorrelation loss is significant only for low values of Q or large values of attenuation across the band.
Immediate Sound Generation
Authors: Mathews M. V.
Published: September 2005

Procedures are described for the immediate synthesis of sounds by means of a small computer (Packard-Bell 250) attached to a large computer (IBM-7094) with an electrical data connection. In a typical use, a score stored in the disk memory of the large machine is edited according to instructious entered ou the typewriter keyboard of the small machine; the resulting sounds are played by a digital-analog converter and loudspeaker attached to the small computer; the sounds are automatically recorded on an analog tape recorder. The whole process typically requires only minutes; previous methods needed hours to a day. This speed has made possible studies that could not have been otherwise attempted. Possibilities of even more-rapid synthesis that will allow improvization are discussed.
Computer Music: Analysis, Synthesis, and Composition
Authors: Strang Gerald
Published: September 2005

Adaptation of the Bell Telephone Laboratories “Music IV” program for use at UCLA is described. Topics included are (a) advantages of higher sample rates; (b) some applications of random number techniques; and (c) problems of Fourier synthesis of tones having partials with inharmonic frequencies—synthesis involving continuous generation of each partial is compared with synthesis based on a stored composite waveform. A synthetic approach to certain studies of ethnic music is discussed.
Exploration and Organization of Sound with the Computer
Authors: Ferretti Ercolino
Published: September 2005

The use of the computer as a tool for the creative musician presents an entirely new set of initial conditions for the exploration and organization of sound. The art of relating the parameters of electrical waveforms to sound, the understanding of computers and coding, and the sensitivity of the artist are the basic elements that develop within a single individual for creative expression. To generate complex sounds requires a large amount of data-processing. To achieve a high degree of flexibility requires a relatively small amount of input data. These two conditions can be met if the coding techniques relate the inherent characteristics of the computer to musical parameters, and if the coding techniques are geared to individual style and requirements. An alphabet based on the parameters of waveforms in contrast to a general dictionary of musical sounds offers a wider range of possibilities for expression. Some computer-music samples are presented.
Effect of Duration upon Detection with Gated Noise and Signal
Authors: Tucker Ann , Evans Rand B. , Jeffress Lloyd A.
Published: September 2005

A 2AFC procedure was used to study the effect of duration on signal detectability, with noise and signal gated simultaneously. Durations employed were 10, 20, 50, 100, 200, and 500 msec. The data do not show the near constancy of detection with duration for constant signal energy over the range found by Green, Birdsall, and Tanner [J. Acoust. Soc. Am. 29, 523–531 (1957)] for gated signal and continuous noise. Instead, for constant signal energy, they indicate a tendency to peak at about 20 msec (reciprocal of the critical bandwidth?). [Work supported through a contract with the U. S. Bureau of Ships and a grant from the National Aeronautics and Space Administration.]
Effect of Stimulus Duration on the Detection of Sinusoids Added to Continuous Pedestals
Authors: Leshowitz Barry , Raab David H.
Published: September 2005

The effect of stimulus duration on the phenomenon of “negative masking” was investigated in two studies. Gated 1000-Hz sinusolds were added in phase to continuous pedestals in the presence of a steady background noise at durations between 10 and 500 msec. Plots of signal intensity necessary for approximately 75%-correct detections as a function of duration revealed enhanced detectability and an intensity-duration reciprocity factor of 14 dB per log unit of time. In the second experiment, signal energy was held constant as duration of the probe was varied betxveen 10 and 100 msec and the proportion of correct responses was measured in a two-interval forced-choice procedure. Marked improvement in detectability obtained as signal duration was increased. When increment energy was held constant, discriminability remained unchanged in the face of an 8.5-dB decrease in signal energy. After correcting an energy-detection model for internal noise, the model accurately predicted P(c). Finally, it is argued that a description of detection data in terms of increment energy renders pedestal results simpler and more understandable.
Frequency Discrimination in Noise
Authors: Henning G. Bruce
Published: September 2005

The relation between frequency discrimination and the ratio of signal-energy to noise-power density (E/No) was investigated at three frequencies—250, 1000, and 4000 cps. On each trial of the experiment, two tones of equa energy were presented one after the other in a background of continuous white noise (32–dB spectrum level). The observers were required to judge whether the first or the second tone had been the higher-frequency tone. The higher-frequency tone was equally likely to precede or follow the lower-frequency tone. Discrimination performance for tones of different frequency separation (ΔF) was measured as the percentage of correct responses in 200 trials. Discrimination performance at all frequencies and all frequency separations increases with increasing E/No until E/No reaches 40 dB. No further increase in performance was apparent with a further increase in E/No of more than 40 dB. The limiting performance levels are not due to amplitude-limiting in the auditory system, since lowering the background-noise level has no effect on the ultimate performance limits. The implications of these data for some models of the auditory process are discussed. [Research supported in part by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Turbulence Measurements Relevant to Jet Noise
Authors: Chu Wing T.
Published: September 2005

Two-point space-time correlations of both the turbulent velocities and the square of these velocities have been measured in the mixing region of a 4-in. low-speed model jet (about 140 fps) with constant temperature hot-wire anemometers. These measurements include the ordinary u component of the turbulent velocity and also the components at 45° and 60° to the jet axis. Using the moving axis transformations of these space-time correlation functions together with the mean velocity measurements, an attempt has been made to estimate the basic directivity, the intensity, and the spectrum of both the “shear” and the “self”-noise generated by a unit volume of jet turbulence. The calculations are based on the Proudman form of Lighthill's integral for aerodynamic noise and Ribner's notion of “shear” and “self”-noise. The present attempt entails more experimental precision and is more advanced than previous work: very few generalizations and assumptions have been made concerning the complex velocity correlations that constitute the integrand of Lighthill's integral.
Measurements of the Spectral and Cross Spectral Density of Pressure on a Rigid Pipe Wall Owing to Turbulent Air Flow
Authors: DeMetz Fred C. , Jorgensen Donald W. , Devin Charles
Published: September 2005

Pressure fluctuations in a turbulent airflow inside a rigid pipe have been measured on the pipe wall for the frequency range from 10 to 10 000 Hz, using two small pressure transducers separated by various longitudinal and transverse spacing. The measurements were obtained over the wide range of Reynolds number from 20 000 to 400 000, based on pipe diameter. Spectral density and two-point cross-spectral density of the pressure were obtained by using conventional analog methods of data analysis and a digital computer. An extensive study was made to determine and reduce the low-frequency background noise frequently suspected of influencing measurements of boundary-layer pressure fluctuations performed in flow facilities. These results tend to confirm certain results of earlier investigators, e.g., a slowly increasing power spectrum with decreasing frequency, down to a Strouhal number of 0.01 (based on pipe diameter and centerline velocity).
Laboratory Simulation of Sonic Booms
Authors: Parnell John
Published: September 2005

Sonic-boom signatures, including measurements from existing aircraft and predicted waveforms for the supersonic transport, have been reproduced in a laboratory facility. The facility is used to obtain judgments from human subjects on various subjective parameters of sonic booms. This simulation was accomplished using an array of loudspeakers coupled to a 70-ft3 a sealed chamber to produce the appropriate pressure field inside at the subject position. An electronic analog of the sonic-boom pressure wave, recorded on magnetic tape, is delivered to shaping networks and dc amplifiers, which in turn drive the loudspeakers. Signal-conditioning in the system includes the response compensation necessary to achieve rise times (associated with the abrupt pressure gradients of the bow and tail waves) of the order of 1–2 msec. The techniques used to generate the electronic analogs of the sonic-boom pressure waves make it possible to reproduce any waveform for use with the simulator system. Judgment tests comparing the perceived loudness of sonic booms have been carried out for identical signatures, different nearfield waveforms, and signatures differing only in duration.
Movies of Simulated Basilar-Membrane Motion
Authors: Lummis Robert C. , Noll A. Michael , Sondhi Man Mohan
Published: September 2005

Two movies are shown of the simulated motion of the human basilar membrane in response to various acoustic-input signals. One movie is a stereographic projection of the membrane depicted as a spiral in three dimensions while the other is a conventional two-dimensional representation of the same motion. Both movies are the results of a sampled data representation of J. L. Flanagan's model of basilar-membrane deflection based upon measurements made by yon Békésy. The sampled-data calculations were performed on a digital computer, which also produced the instructions for automatically generating the movies on a microfilm plotter.
Input-Output Relations of Neurons in the Anteroventral Cochlear Nucleus, Based on Component Analysis of Waveform
Authors: Pfeiffer Russel R.
Published: September 2005

Each neuron in the anterior part of the anteroventral cochlear nucleus receives input from one to perhaps four auditory-nerve fibers by means of very large synaptic endings—the bulbs or calyces of Held. The electrical activity recorded extracellularly in this region, with metal as well as fluid-filled microelectrodes, exhibits a distinctive waveform that can be interpreted as being composed of a presynaptic component (a primary fiber input) and a postsynaptic component (neuron discharge). The interpretation above leads one to conclude that these neurons discharge in response to every primary fiber input, except those occurring within a refractory time associated with the neuron. Therefore, except for the refractoriness, the times of occurrence of output discharges of these neurons are superpositions of the times of occurrences of the inputs of the individual primary auditory-nerve fibers that innervate them. [Work supported in part by the Joint Services Electronics Program, by the National Science Foundation, by the National Institutes of Health, U. S. Department of Health, Education, and Welfare, and by the National Aeronautics and Space Administration.]
Displacement Amplitudes of Middle-Ear Structures in Cats as a Function of the Sound-Pressure Levels at the Eardrum
Authors: Tonndorf Juergen , Khanna S. M.
Published: September 2005

Displacement amplitudes of middle-ear structures in response to given sound-pressure levels have been determined previously. The availability of improved methods of small-amplitude measurement made it possible to obtain such values directly in living cats. With the cochlear-microphonic output serving as reference, SPL's at the eardrum and corresponding displacement levels of malleus and stapes were measured. Varying with signal frequency (range: 25 to 10000 Hz), SPL's ranging from 40 to 100 dB and displacement amplitudes betxveen 3×10−8 and 3×10−5 cm were utilized in these experiments. The results permitted determination (or redetermination) of the following properties of the cat's ear: (a) the displacement amplitudes of malleus and stapes at the threshold of hearing; (b) the leverage ratio of the ossicular chain; (c) the function of the incudomallar joint. Furthermore, the middle-ear impedance was calculated from the measured values. The results obtained are compared to those of earlier writers. [Work supported by grants from the Public Health Service. U. S. Department of Health, Education, and Welfare.]
Origin of the Middle Ear
Authors: van Bergeijk Willem A.
Published: September 2005

The evolution of the middle ear, especially the eardrum, has been shrouded in uncertainty for many years. It is first found in the primitive Stegocephalian amphibians. In these animals, it was already quite highly developed, but there has been no hint of a transitional stage between fish and amphibian. Among the extinct Rhipidistian fishes, from which, for many comparative-anatomical reasons, the amphibians are believed to have arisen, were a few species that appear to represent this “missing link.” These fishes, notably Eusthenopteron and Osteolepis, had a diverticulum of the first pharyngeal pouch that probably developed in the first instance as an auxiliary respiratory organ. The diverticulum came to the surface of the fish in close association with a superficial ligament, with which it formed a narrow drum membrane. The endothelium of the drum was intimately attached to the hyomandibular bone, which is the homolog of the stapes and articulates with the otic capsule. It can be shown that the entire system was compatible with aquatic as well as terrestrial hearing, the threshold sensitivity in air being about 45 dB SPL at 100 cps.
Temporal Masking: Neural Lesions
Authors: Oesterreich Roger E.
Published: September 2005

Cats were trained to respond to a 10-msec burst of filtered noise using a shock-avoidance procedure in a double-grill box. Forward, backward, and simultaneous masking by a 500-msec burst of wide-band noise at 75 dB SPL was measured. One or more cortical or subcortical lesions were made in the central auditory system and masking curves determined after each operation. Extensive cortical removals including AI, AII, I-T, and adjacent areas had no effect on masking curves. A hemineodecortication plus a contralateral section of the brachium of the inferior colliculus produced a marked increase in both backward and forward masking. Similar effects on backward and forward masking were found after removal of the inferior colliculi alone or in combination with cortical removals. Simultaneous masking was reduced in both cases owing to elevated absolute thresholds. An extra-lemniscal pathway projecting to “nonauditory” cortex can apparently maintain normal signal discrimination in the absence of the auditory projection areas. [Work supported by Mental Health Funds, State of Illinois, the National Institutes of Health, U. S. Department of Health, Education, and Welfare, and the Research Foundation, State University of New York.]
Complex Auditory Discrimination and Lesions of Temporal Cortex in the Monkey: A Progress Report
Authors: Dewson James H.
Published: September 2005

This study amplifies and extends to the primate the findings for the cat reported at these meetings in 1963 [J. Acoust. Soc. Am. 35, 1907(A) (1963)]. Five monkeys have been trained to make complex auditory (vowel sound, glissando, etc.) and visual discriminations. After discrete bilateral lesions of superior temporal gyrus (sparing primary auditory cortex), simple auditory and complex visual discriminations are unaffected; relearning of complex auditory discriminations requires more trials than original learning.
Effect of Sodium Salicylate on Conditioned Absolute Threshold in the Guinea Pig
Authors: Wilpizeski C. R.
Published: September 2005

By means of an automated single-lever shock-avoidance procedure, guinea pigs were conditioned to track absolute thresholds to a thermal noise stimulus. Threshold measurements were made under control conditions and 1–2 h following a single intraperitoneal injection of sodium salicylate. A temporary threshold-shift function was obtained for dose levels from 50 to 250 ms/ks of salicylate. Contrary to expectation, threshold shifts were not produced when salicylate doses below lethal amounts were cumulated over 4 days' time. Failure to demonstrate drug-induced TTS under chronic-dose conditions is discussed in terms of blood salicylate levels. Data are presented that suggest that the analgesic property of salicylate can account in part for the hearing-loss function obtained with avoidance-conditioning procedures. [Work supported in part by the National Institute of Neurological Diseases and Blindness, U. S. Department of Health, Education, and Welfare.]
Technical Aspects of a Rocket-Noise Monitoring System
Authors: Bringier William
Published: September 2005

This paper describes the design philosophy of a system to monitor rocket noise in communities located miles from the site of the test vehicle. Pole-mounted remote units are designed for continuous operation with high stability and reliability over varying ambient conditions. Commercial leased telephone lines are used to transmit a data band of 0.1–350 cps. Equipment protection against transient voltages on telephone lines is a primary requirement. The use of a temperature-controlled microphone and a preamplifier with an input impedance of over 25 000 MΩ permits utilization of a commercially available piezoelectric microphone cartridge in an outdoor environment with low-frequency response to 0.1 cps. The Base Station accepts up to eight inputs and provides signal conditioning for direct record of all channels simultaneously, permitting analysis at a later time. Continuous monitoring of any input and real-time demodulation with meter readout directly in sound-pressure level are featured in this versatile system.
Lateral Differences in Perception of Dichotically Presented Synthetic CV Syllables and Steady-State Vowels
Authors: Shankweiler D. , Studdert-Kennedy M.
Published: September 2005

Previous studies have shown that if random sequences of digits are dichotically presented, listeners recall digits presented to the right ear more accurately than those presented to the left. If the stimuli are brief melodies or sonar signals, however, listeners recall more-accurately those presented to the left ear. These results suggest that speech and nonspeech auditory patterns are processed in different portions of the nervous system. One may question, however, whether all acoustic features of the speech signal are processed by the same perceptual apparatus. The present study compared identifications of dichotically presented pairs of synthetic syllables consisting of six stop consonants (/b,d,g,p,t,k/) followed by the vowel /a/, and pairs of steady-state vowels (/i,ɛ,æ,a,u/). The results show a right-ear advantage for both CV syllables and vowels, but a significantly larger advantage for CV syllables, suggesting a difference in the degree of lateralization within the perceptual apparatus for different kinds of speech sounds, here stop consonants and stead-state vowels.
Study of Pitch-Variation Rates
Authors: Phillips Nathan D.
Published: September 2005

Several previous investigations have shown that visual, rather than auditory, feedback can be used to teach pitch inflections. In the present study, the extent of the ability to follow specific pitch patterns was investigated. The voiced signal was peak-detected to obtain a signal proportional to pitch. A frequency generator was used to produce a standard pattern of frequency versus time on a storage oscilloscope. Subjects were then asked to match their pitch patterns with the standard. The maximum rate of change that could be tracked was determined by the ability of the subjects to match patterns of increasing pitch inflection. Experimental results are presented. [Research supported by the U. S. Department of Health, Education, and Welfare, Office of Education, and Vocational Rehabilitation Administration.]
Masking Transforms the Power Function for Loudness
Authors: Stevens S. S. , Guirao Miguelina
Published: September 2005

A masking stimulus, either visual or auditory, raises the exponent of the psychophysical function relating sensation to stimulus. This power transformation applies only to the part of the function that is influenced by the masking stimulus. Since a given masking noise affects only weaker stimuli, the result is a discontinuous loudness function, which resembles the discontinuous brightness function produced by a glare. The loudness functions for low-frequency stimuli resemble those obtained under masking, as do also the recruitment functions in hard-of-hearing ears. The matching of the apparent brightness of a visual target to a masking surround can be done with relatively high precision, as in standard photometry. In an analogous fashion, the loudness of a pure tone immersed in a white masking noise can be matched to the loudness of the noise. As with visual stimuli, the mutual inhibition between tone and noise improves the precision of the loudness matching, though it still remains quite variable.
Mental Tasks and Auditory Fatigue—Again
Authors: Fricke James E.
Published: September 2005

Twenty subjects, both male and female, were exposed monaurally to Gaussian noise at intensity levels of 100, 110, and 120 dB SPL for 3-min duration. Békésy-type threshold tracings at 2000, 4000, 6000, and 8000 cps were determined for each subject and a comparison between pre- and post-fatigue thresholds constituted a measure of temporary threshold shift (TTS). Each subject participated under conditions of (a) listening to the noise in one ear, and counting the “breaks” in the noise field during the 3-min test period; and (b) hearing noise in the one ear but also listening to a story being told in the opposite ear, with the knowledge that each would be tested on the passage following the 3-min period. The amount of auditory fatigue was shown to vary as a result of “focusing” in the opposite ear at the 110-db-SPL condition. It was shown that more TTS resulted in the test ear when the subjects were concentrating on the message being presented in the opposite ear.
Speech Intelligibility by Head Contact as Function of Location on Head
Authors: Abbagnaro Louis A. , Rosenheck A. , DiMattia A.
Published: September 2005

A study was made to determine the level, spectrum, and intelligibility of speech available for contact transducers, as a function of head location. A specially designed head-contact microphone was developed for use in these tests. The output of the head-contact microphone and that of a “flat” acoustical microphone were simultaneously recorded for 10 talkers reciting phonetically-balanced test sentences. The recorded data were then played back, and trained listeners subjectively evaluated the intelligibility of the contact speech versus the acoustically received speech. Several head areas showed highly intelligible speech with good consonantal pickup, while other regions were notably poor even when equalization techniques were employed. Spectral analysis showed that regions that had adequate high-frequency energy generally corresponded to those that had exhibited good intelligibility in the listening tests. The head was grouped into four regions—forehead, ear, cheek, and top and back of head. The over-all intelligibility of each area was evaluated. The forehead region gave the most desirable output for contact pickup. Over-all output level available at each area was measured and a statistical analysis showed only modest level differences for most regions of the head. [Work supported by the U. S. Army Electronics Command.]
Head-Contact Microphone for Efficient Speech Transmission
Authors: Rosenheck A. , DiMattia A. , Bauer B. B.
Published: September 2005

Work was undertaken to develop a microphone that would provide highly intelligible speech reception by direct contact with the head. Since investigation (Paper 7D4) showed that the forehead provided the bighest quality speech, efforts were concentrated in this region. In order to avoid a loss of high-frequency response owing to flesh compliance, the total mass of the transducer had to be limited to below 1 g for a unit of small size. This was most readily accomplished with a miniature, inertial-type transducer, which, additionally, provides the proper response-frequency characteristics. Articulation tests, with the microphone located on the forehead, indicated an average PB word score of 90% in quiet surroundings. Good rejection of ambient acoustical noise was observed. The ultimate noise rejection is limited by noise-induced vibrations transmitted through the head. The microphone totally frees the mouth area of obstacles located in front of the lips, and its miniature size suggests several applications. [Work supported by the U. S. Army Electronics Command.]
Measurement of Specific Acoustic Impedance
Authors: Rogers Joseph Woos
Published: September 2005

The theory for a very simple procedure that can be used to measure the specific acoustic impedance of any termination of an acoustic transmission tube is described. The virtues of this method are that there are no moving parts and there is no need to calibrate the transfer properties of a microphone and coupling. The only precision measurements concern the frequency and the location of two holes necessary for the detection of pressure in the tube. The holes are located equidistantly from the center of the tube. A source is affixed to one end and the termination to the other. Frequency is adjusted until a relative minimum in the standing-wave pattern appears at the microphone closer to the termination. The voltage from each microphone is recorded. Then the source and termination are interchanged while the microphones are left undisturbed. The above process is repeated. The product of the voltage ratios is the same as the square of the pressure ratio. With this information, it is possible to calculate without too much difficulty the specific acoustic impedance of the termination.
Calculation of the Acoustic-Power Output of a Monopole in a Reverberation Chamber
Authors: Maling George C.
Published: September 2005

The acoustic power (W) radiated by a harmonic monopole of strength Q located in a rectangular reverberation chamber has been calculated by using an eigenfunction expansion of the Green's function. An expression for the sound intensity valid for small normal admittance (β) has been integrated over the chamber surfaces to determine the power output. The results are within approximately ±2 dB of the results obtained by Waterhouse and Cook [J. Acoust. Soc. Am. 37, 424–428 (1965)] when the source is near one or more reflecting surfaces. At low frequencies, the ratio of W to the free-space power output (W0) varies with source position within the chamber and has been treated statistically. The space-averaged value of W/W0 is generally greater than unity, but values in the range 0.1–10.0 occur for particular values of frequency and β. The normalized standard deviation of W/W0 is 0.25–0.35 for β=0.05, and increases as β decreases. Application of the results to the choice of an optimum absorption characteristic for low frequency puretone power measurements is discussed.
Dissipation Associated with Gas-Pumping in Joint Structures
Authors: Maidanik Gideon , Carbonell Jaime R.
Published: September 2005

In recent experimental work dealing with the vibratory energy dissipation of plates with beams riveted to them, it was deduced that air-pumping, in the space between the plate and the beam, may be the mechanism that dominates the damping. A semiphenomenological theory based on this deduction is developed and is shown to predict satisfactorily not only the order of magnitude of the loss factors but also their dependence on frequency and on gas pressure. This theory attributes the damping to viscous forces associated with gas motion tangential to the plate, resulting from the relative flexural motions between the adjacent plate and beam surfaces. The present theory is limited to the high-frequency range, where a typical plate flexural wavelength is smaller than the rivet spacing. [Research supported by the National Aeronautics and Space Administration.]
Reduction of Turbomachinery Noise by Absorption and Choked Flow
Authors: Sperry William C.
Published: September 2005

Various configurations of materials suitable for use on surfaces of engine ducts, guide vanes, and splitters were investigated for sound absorption. The development and screening process began with basic tests in standing-wave-tube and dc-flow-resistance facilities. Promising configurations were then progressively studied in traveling-wave tubes, rectangular and annular ducts with air flow, and, ultimately, in rotating pressure fields with model compressors. Theoretical and empirical relationships were developed for the resistive and reactive acoustic absorption, including the effects of air flow, sound intensity, and sound source (electromagnetic, aerodynamic, or spinning modes). The effect of air flow on the reduction of sound was studied with a two-dimensional choked-flow facility containing vanes simulating engine inlet ducts and guide vanes. Theoretical and empirical relationships were developed for the noise reduction as a function of velocity and guide-vane setting angle, with and without acoustic-absorption treatment on the surfaces of the vanes and duct. [Work supported by the Federal Aviation Agency.]
Bubble Nucleation by Vortices in a Liquid-Helium II Bubble Chamber
Authors: Edwards M. H.
Published: September 2005

Persistent vortices in a liquid-helium II bubble chamber have been detected by photographic observation of transient bubbles produced by expansions. Stereoscopic 35-mm still pictures of the bubbles were taken, as well as nonstereoscopic 16-mm movies at framing speeds to 6000 frames/sec. A 100-cm3 cylindrical glass chamber was used, with a Teflon® piston and sleeve. Expansions with the “empty” glass chamber showed no bubbles below the λ point. Expansions with a vortex generator (a thin-walled brass cylinder with three small holes in the top, which, it was hoped, would produce quantized vortex rings) in the glass chamber, resulted in many bubbles. We believe that vorticity remaining from earlier expansions (and persisting up to 134 h at 1.73°K), or produced during the “current” expansion, can nucleate bubbles. The circulation of the vortices which acted as bubble nuclei was not measured.
Frequencies Dominant in the Perception of Pitch of Complex Sounds
Authors: Ritsma Roelof J.
Published: September 2005

In an investigation of the pitch of complex sounds, the relative importance of selected bands of frequencies was evaluated by determining the minimum sensation levels (SL) at which the bands govern over-all pitch. The stimulus consisted of the sum of (1) a low-frequency band of fundamental frequency f0 and upper cutoff frequency fc and (2) a high-frequency band of fundamental frequency f0±Δf and lower cutoff frequency fc. The parameters used were f0, fc, Δf, and the SL's of the two bands. In most of the experiments, f0 was 200 Hz, Δf/f0 was either 3% or 6%, and over-all SL was between 30 and 50 dB. Dominance for pitch sensation was determined in terms of the “crossover” frequency fc as a function of relative level of the bands. It was found that, for a given fc, the low band tended to dominate the pitch sensation as long as its amplitude exceeded a minimum absolute level of 10–15 dB SL. Dominance was found to be independent of Δf. It is concluded that the most effective frequencies influencing pitch correspond to the third, fourth, and fifth harmonics for fundamental frequencies in the range of 100–400 Hz.
Vocoder System for Commercial Telephone Speech
Authors: Miller R. L.
Published: September 2005

A flexible vocoder system of the channel type is described that will operate correctly on both wide-band speech and speech in which the fundamental as well as high-frequency components have been removed. A forward-acting pitch-monitoring system prevents major pitch errors in the pitch-extraction arrangement for either male or female talkers. A simple voiced-unvoiced decision arrangement makes use of both amplitude and axis-crossing information. Pulse-shaping and phase-equalization are utilized in the excitation signal to produce more-natural speech. Digital rates can be in the range of 2400–3500 bit/sec.