bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduction of Compressor Noise Radiation
Authors: Lowson M. V.
Published: September 2005

The mechanisms underlying compressor noise radiation are reviewed in detail with particular emphasis on potential methods for compressor noise reduction. It appears that many independent methods of reducing compressor noise are possible, so that large (20–30 dB) reductions of noise radiation may be practicable. Analyses of the effects of rotor-stator spacing and duct-mode directivity are presented. It is concluded that an increase in the number of rotor blades may be desirable from several points of view.
Particle Size-Amplitude Relations for the Ultrasonic Atomizer
Authors: Lobdell Donn D.
Published: September 2005

A relationship between capillary wave amplitude and the diameter of spherical particles ejected in an ultrasonic atomizer is developed. This relationship predicts a threshold amplitude for the generation of the aerosol and is based upon a bifurcation process to reduce surface energy. The most probable size of particles is found to be a diameter of 0.36λ, where λ is the wavelength of capillary waves for the system. This result is in excellent agreement with the previously reported empirical median particle diameter of 0.34λ.
Detection and Relative Discrimination of Auditory “Jitter”
Authors: Pollack Irwin
Published: September 2005

Thresholds for the minimal departure from periodicity and thresholds for discrimination of relative departures from periodicity were obtained in order to explore the limits of temporal resolution for auditory pulse trains. In a forced-choice test, listeners were presented pulse trains, one of which was subjected to more variability, or “jitter,” than the other three. His task was to select that pulse train that was different from the other three. The principal experimental variables examined were: the number of intervals; the mean interpulse interval; and, the jitter of the reference pulse train. Minimum thresholds for jitter, relative to the center interpulse interval, are less than 0.1% for large number of pulses. Threshold jitter decreases with shorter interpulse intervals for a large number of pulses. Jitter thresholds are minimal for interpulse intervals of 4–6 msec for a small number of pulses. Jitter discrimination is approximately independent of the reference jitter for a small number of pulses and is nearly directly proportional to the reference jitter for a large number of pulses. The temporal precision of the auditory system, in contrast to its precision of spectral analysis, appears to be insufficient to account for minimal jitter thresholds.
Hazardous Exposure to Impulse Noise
Authors: Coles R. Ross A. , Garinther Georges R. , Hodge David C. , Rice Christopher G.
Published: September 2005

This paper presents impulse-noise damage-risk criteria based on conclusions of independent British and American studies and on the work of other research workers in this field. Most of the studies that led to this criterion were performed with noise from small arms, but the criterion is general enough to permit assessment of most other types of impulse noise. The variables that must be considered in determining the potential hearing hazard and in the practical application of the criteria are presented, and the parameters that must be measured are defined. The measurement technique and type of transducers to be used are discussed.
Perception of the Range of a Sound Source of Unknown Strength
Authors: Hirsch Henry R.
Published: September 2005

The range of a sound source of unknown strength can be calculated from measured interaural differences in the time of arrival and intensity of a brief sound. The possibility that the brain performs this calculation is discussed, and an experiment to determine human range perception is proposed.
20-Hz Signals Observed in the Central Pacific
Authors: Northrop J. , Cummings W. C. , Thompson P. O.
Published: September 2005

Signals of 20 Hz were recorded at SOFAR depth hydrophones of the Pacific Missile Range at Midway, Wake, Oahu, and Eniwetok Islands in the North Pacific. The signal strength, source movement, and seasonal peak (in winter) suggest a biological source.
Passive Sonar Detection in the Presence of Interference
Authors: Schultheiss Peter M.
Published: September 2005

The paper deals with the detection of a passive sonar target in the presence of ambient noise and a plane-wave interference. Target signal, interference, and ambient noise are assumed to be Gaussian random processes, the ambient noise being statistically independent from hydrophone to hydrophone. The receiving array is linear and consists of equally spaced hydrophones. The performance of conventional and likelihood-ratio detectors is analyzed. In an interference-dominated environment, the likelihood-ratio detector can be superior by a substantial margin. Complete elimination of the interference can be accomplished at a cost of no more than one hydrophone.
Effect of Sodium Deficiency on Cochlear Potentials
Authors: Konishi Teruzo , Kelsey Elizabeth
Published: September 2005

The scala tympani in guinea pigs was prefused with mammalian Ringer-Locke's solution, in which NaCl was replaced with either choline chloride or sucrose. Cochlear potentials were recorded from the basal turn before, during, and subsequent to the perfusion. Complete replacement of the perilymph with Na+-free solution did not alter the endocochlear potential and the cochlear microphonic immediately, although the action potential was abolished rapidly. In most cases, the depression of the action potential was reversible. The mechanism underlying the generation of the receptor potential is discussed, and it is concluded that production of cochlear microphonic is not dependent on the concentration of Na+ in the perilymph but on the presence of high K+ concentration in the endolymph.
Detection of Auditory Signal in Restricted Sets of Reproducible Noise
Authors: Pfafflin Sheila M.
Published: September 2005

The detectability of auditory signals in reproducible random noise was studied under two conditions: a single noise used throughout a block of 288 trials, and 12 noises occurring at random, but with equal frequency, throughout a block of trials. Both two-interval forced-choice judgments and judgments of the presence or absence of the signal in single-noise samples were obtained in separate blocks of trials. On individual trials of the forced-choice judgments, the same noise appeared in both intervals. Signal detectability was found to be significantly better when a single noise was present in a block of trials. Introducing variability in the stimulus by altering the number of different signal levels presented during a block of trials did not affect detection. The results support the importance of memory for the noise from trial to trial in the detection process.
Perceptual Study of Vocal Fry
Authors: Hollien Harry , Wendahl Ronald W.
Published: September 2005

Three assumptions constitute the basis for a research program of which this study is a part. Vocal fry (1) is a normal mode of laryngeal production; (2) it consists of a register of very low fundamental frequencies, and (3) it consists of a train of relatively discrete laryngeal pulses with nearly complete damping between successive glottal excitations. In order to obtain perceptual evidence relevant to the latter point, listeners were asked to match the repetition rate of a variable pulse train (electronically produced) to the fundamental of eight samples of vocal fry. The resultant data supported the hypothesis that repetition rate can be successfully assigned to vocal fry. In addition, evidence was obtained indicating that vocal fry occurs within a low-frequency phonatory register, is perceived similarly in relation to single or double glottic pulses, and is regular, rather than aperiodic, in nature.
Vibrational Relaxation in CO2/D2O Mixtures
Authors: Shields F. Douglas , Burks James Alton
Published: September 2005

Sound absorption and velocity measurements have been made in CO2/D2O mixtures at 300°, 400°, and 500°K. The results show that D2O is from 13 to 15 as efficient as H2O in de-exciting the bending-mode vibration of CO2 in a molecular collision. The collision efficiency of D2O for de-exciting CO2 decreases with temperature at an even greater rate than does that of H2O. The large difference between D2O and H2O invalidates the chemical affinity explanation of effect of H2O on CO2. An approximate semiclassical calculation of the transition probability indicates that it is possible to attribute the relaxation to an interchange between the vibration of the CO2 and the rotation of the H2O or D2O.
Relation between Absolute Threshold and Duration-of-Tone Pulses in the Bottlenosed Porpoise
Authors: Johnson C. Scott
Published: September 2005

Results of a study of absolute threshold and duration-of-tone pulses in the bottlenosed porpoise indicated that the animal, in detecting pure-tone stimuli, integrated the acoustic energy in essentially the same way as humans. Pure-tone thresholds were determined at 0.25, 1, 4, 20, 45, and 100 kHz for a wide range of pulse durations. Least-squares fits to the data yielded time constants that were in general agreement with those obtained in experiments with humans. The data for very short pulses at 20 and 40 kHz indicated the presence of critical-frequency bands, for which rough estimates were obtained.
Digital-Formant Synthesizer for Speech-Synthesis Studies
Authors: Rabiner Lawrence R.
Published: September 2005

Recent work on speech synthesis by rule has led to the design and evaluation of a new digital-formant synthesizer. The synthesizer was simulated on a digital computer at a 20-kHz sampling frequency. The improvements over previous synthesizers include: an excitation source for the unvoiced component of voiced fricatives; a method for producing a voice bar for the closure period of voiced stops; and a simple design for the higher pole correction network that exploits the properties of sampled data systems. Spectrographic examples of synthetic speech are shown in order to illustrate these improvements. A brief discussion of some advantages and disadvantages of serial and parallel synthesizers is presented.
Reply to “Comment on ‘Sound Transmission through a Finite, Closed, Cylindrical Shell’” [J. E. Manning, J. Acoust. Soc. Am. 43, 886–887 (L) (1968)]
Authors: White Pritchard H.
Published: September 2005

The statistical-energy method of analysis is appropriate for many sound-transmission problems. Continued research and usage have led to improved accuracy, especially for cylindrical structures.
Vibration Analysis of Stiffened Cylinders including Inter-Ring Motion
Authors: Wah Thein , Hu William C. L.
Published: September 2005

An analytic method is presented for the determination of the vibrational characteristics of ring-stiffened cylindrical shells. The stiffening rings, which are assumed to be uniform and evenly spaced, are treated as discrete members, and the inter-ring shell motions are fully and exactly accounted for within the linear shell theory used in the analysis. The flexural, extensional, and torsional rigidities of the rings are retained in the analysis as well as all in-plane inertia terms. Numerical comparison made with the results from existing energy methods and orthotropic model approach. It is found that for high circumferential wavenumbers, the inter-ring displacements may become very pronounced.
Two-Tone Inhibition in Auditory-Nerve Fibers
Authors: Sachs Murray B. , Kiang Nelson Y. S.
Published: September 2005

Spike discharges from single fibers in the auditory nerve of anesthetized cats were recorded with micro-electrodes. Rates of discharge were measured as functions of the frequencies and levels of either single tones or two tones presented simultaneously. We found that the presence of a second tone diminishes the responses to the first tone if appropriate stimulus parameters are chosen. All fibers tested showed this two-tone inhibition. Response areas and inhibitory areas were defined from isorate contours. The general characteristics of the inhibitory areas are found to be similar for a population of over 300 fibers.
Analysis of the Electromechanical Piston Used in Calibrating Infrasonic Sensors and of the Modified Moore Variometer Used in Infrasound Studies
Authors: Fehr Uri , Ben-Ary B. , Redekopp L. G.
Published: September 2005

The electromechanical piston used as a generator of infrasound in the calibration facility is evaluated. It is concluded from theory that the system can generate efficiently infrasonic waves in an environment of 800 litres covering the frequency range of 0.001–1 cps and pressure amplitudes of 10−2 to 103 dyn/cm2. This agrees well with empirical studies. The Modified Moore Variometer, a sensor for infrasonic pressure variations utilizing thermistor-bead elements that sense variation in fluid flow, is also evaluated. The analysis gives a physical explanation for the principle involved in the sensing-elements configuration and shows the dependence of the high-frequency cutoff on heat-transfer efficiency between the fluid flow and the thermistor-bead elements.
Measurement of Vocal Fold Motion Using an Ultrasonic Doppler Velocity Monitor
Authors: Minifie Fred D. , Kelsey Charles A. , Hixon Thomas J.
Published: September 2005

A technique is described for using the ultrasonic Doppler frequency shift as a means of continuously monitoring the velocity of vocal fold motion during voice production. The basic instrumentation employed and the theoretical principles underlying the technique are discussed. The results of a series of experiments using excised animal larynges are presented to demonstrate that a characteristic laryngeal Doppler pattern is obtained during phonation and is the result of vocal fold motion. Finally, the Doppler velocity monitor is used with human subjects. Vocal fold displacement patterns derived from the Doppler signal appear to have very good agreement with previously reported displacement values using high-speed motion-picture films.
Strength of Caustics
Authors: Ludwig Donald
Published: September 2005

The ratio of amplitudes on and away from a smooth convex caustic is computed, using a uniformly valid asymptotic theory. This ratio may be used to measure the strength of a caustic. Caustic strengths are limited by the requirement that (ka)12 be large, where ka/2π is the radius of curvature of the caustic measured in wavelengths.
Resonant Properties of Piezoelectric Ceramic Rectangular Parallelepipeds
Authors: Holland Richard
Published: September 2005

This paper is concerned with the resonant properties of free, piezoelectric ceramic rectangular parallelepipeds, such as cubes. By means of the calculus of variations, the electroelastic differential equations are transformed into an approximate matrix characteristic value problem. Solution of this problem yields the resonant frequencies, the particle displacement patterns at resonance, and the equivalent circuit parameters such as the motional capacitances. Structures of the present type possess eight distinct symmetry families of modes; however, only one of these is excitable piezoelectrically with two opposite faces completely electroded. The resonant frequencies of the first 50 modes of this family are presented graphically versus Poisson's ratio for the special case of an isotropic cube. The frequency and dynamic capacitance of the first 30 modes of the same family are given for a piezoelectric ceramic square cylinder as the thickness-to-width ratio is varied from zero (thin square plate case) to unity (cube case). This result demonstrates the fact that the so-called thickness mode of a thin plate is actually a composite of many high contour-extensional overtones. Numerous modal displacement patterns are sketched for the square cylinder and cube special cases. Lastly, experimental results are reported that correspond reasonably well with the theory: Agreement is on the order of 3% for resonant frequency values and 20% for other quantities.
Wave Propagation in a Sandwich Ring
Authors: Sagartz M. J. , Keer L. M. , Herrmann G.
Published: September 2005

The propagation of small-amplitude free harmonic waves in an elastic sandwich ring is studied by using a Timoshenko-type theory, which takes into account the effects of radial shear deformation, rotatory inertia, and extension of the neutral axis. The form of the equations of motion is the same for both homogeneous and sandwich rings, but the range of values for the parameters involved in the latter case can lead to qualitative changes in the wave propagation characteristics of the system. It is shown that the ratio of the ring's extensional stiffness to its shear stiffness has an important influence on the frequencies and group velocities of sandwich rings. When this ratio becomes large, two of the three modes of wave propagation become less dispersive. Numerical examples are presented and discussed.
Effects of Interaural Time Delays on Masking by Two Competing Signals
Authors: Carhart Raymond , Tillman Tom W. , Johnson Kenneth R.
Published: September 2005

Interference with thresholds for spondees and intelligibility of monosyllabic words (at 60 dB SPL) produced by combining modulated white noise (4 mod/sec, − 10 dB interburst ratio) and connected speech as simultaneous maskers was studied under a variety of interaural listening conditions at each of three masker levels (66, 72, and 78 dB sound-pressure level). Monaural performance in the presence of both maskers (CmNmSm) was 7.8–10.5 dB poorer than with either masker alone (NmSm or CmSm). Thus, the two maskers produced added interference substantially in excess of the approximately 3-dB increase to be expected on the basis of the summing of their powers alone. Very little release from masking was achieved in the transition from monaural (CmNmSm) to homophasic listening (C0N0S0). During antiphasic (CτNπS0) presentation, approximately 5 dB of release from masking occurred (re C0N0S0). A little less than half as much release from masking appeared when the maskers were given 0.8 msec interaural time delays, while the test material remained in phase at the two ears. Performance with opposing interaural delays (C0.8N 0.8S0) was no better than with parallel time delays (C0.8N0.8S0). Since neither of these conditions yielded as large masking-level difference as did the antiphasic, even though the sources of signals were lateralized (localized) much more sharply by the subject during time-delay conditions, this study offers further evidence that localization (separation of source azimuths) and the capacity to understand speech against competing sounds are separate capacities. Various implications of the finding are discussed.
“Polyacusis,” a Hearing Anomaly
Authors: Corliss Edith L. R. , Burnett Edwin D. , Stimson Harold F.
Published: September 2005

A previously unrecognized anomaly of pitch perception was discovered by H. F. Stimson while testing his hearing. Signals above 3500 Hz did not produce the same pitch in each ear; the right ear's sensation was that of a sound at a lower frequency, for which he also had normal pitch perception. Between 3700 and 5200 Hz, the pitch perceived in the right ear was independent of the frequency of the stimulus. As intensity was raised, additional pitches appeared; and for an intense sound, a chord was heard whose constituents were not harmonically related. Stimson can match these anomalous pitches with sinusoidal stimuli of the appropriate lower frequency within about 2%; part of this variation is a change of pitch with intensity. Tones in his normal pitch range having a pronounced overtone structure are perceived as multiple. Overtones falling in the anomalous range give rise to the anomalous pitch. This would indicate a Fourier type of analysis before pitch recognition. Beats are not excited by interference between the pitches evoked by signals in the anomalous range and those heard normally. Loudness studies show signal powers to be additive. Tone-masking and loudness summation experiments yield data suggesting that the pitch recognition mechanism lies in that part of the auditory system in which loudness is perceived—i.e., beyond the cochlea.
Toward the Specification of Normal Bone-Conduction Threshold
Authors: Dirks Donald D. , Malmquist Carolyn W. , Bower Deborah R.
Published: September 2005

Monaural bone-conduction thresholds at the mastoid process and frontal bone were obtained on several groups of young adults with normal hearing. The results are reported in force thresholds (decibels re 1.0 dyn rms) from calibrations made on a Beltone artificial mastoid. The data at the mastoid are in close agreement with the HAIC interim norm and the results of Weston et al. (1967). These results confirm the clinical usefulness of the HAIC interim norm. Likewise, the similarity between the current data obtained at the frontal bone and that reported by Weston et al. (1967) provides a basis for an interim norm until the International Organization for Standardization has completed its deliberations.
Localization of Tonal Stimuli in the Vertical Plane
Authors: Roffler Suzanne K. , Butler Robert A.
Published: September 2005

Listeners, when requested to judge the location of tone bursts on the vertical plane, tended to place the stimuli on a vertical scale in accordance with their respective pitch. Higher-pitched sounds were perceived as originating above lower-pitched sounds. This phenomenon was also observed in congenitally blind persons and in young children who presumably were unaware of the use of the words high and low in describing differently pitched sounds. In additional tests, visual cues were found to influence the range of the scale within which listeners perceived the sound sources and they could even bias the location judgments of high-pitched tone bursts despite contrary binaural cues. But the main implication of the data is that tonal stimuli have intrinsic spatial characteristics, which result in the perception of frequencies with shorter periods as being higher in space than those with longer periods.
Resonance Frequencies of the Clarinet
Authors: Backus John
Published: September 2005

Equipment has been constructed that will automatically plot on a chart the resonance curve for a clarinet as produced by external excitation with sound of constant pressure amplitude. On the same chart are plotted for comparison the frequencies of the harmonics of the lowest resonance. The harmonic structure of the sound pressure in the mouthpiece of the instrument when sounded by blowing with an artificial embouchure is also plotted for further comparison. It is found for the lowest notes on the clarinets used that the resonances lie at frequencies progressively lower than the harmonic frequencies. Even harmonics are present in the standing wave in the instrument when sounded, although the odd ones predominate out to the fifth harmonic; only the second is completely absent. As the scale is ascended, the resonances get more out of tune with the harmonics and decrease in number until for the (written) note B♭4, before the change to the next register, there are only two strong resonances. In the next register, the resonances appear to bear only a fortuitous relationship to the harmonics, and the second harmonic is present. Comparison of resonance curves for instruments of different manufacture shows them to be remarkably similar.
Study of a System of Minimal Speech-Reproducing Units for Italian Speech
Authors: Francini G. L. , Debiasi G. B. , Spinabelli R. D.
Published: September 2005

A language maybe synthesized by combining, in a suitable way, elementary speech segments that have been extracted from the utterances of a native speaker of that language. The main criteria for the choice of these elements are discussed. The discussion leads to the definition of a new set of physically determinate linguistic elements that can be obtained by experiment. A preliminary list is reported for the Italian language. From experimental tests, it appears that it is possible to synthesize Italian speech with a small number of elements. These elements may form the basis for research in speech recognition.
Absorption of Sound in Oxygen Containing Hydrogen, Carbon Dioxide, or Water Vapor as Impurity
Authors: Harlow R. George , Nolan M. E.
Published: September 2005

Measurements of the attenuation of sound are reported for oxygen containing up to 2.6% of hydrogen, carbon dioxide or water vapour as impurity. The measurements cover the f/p range from 80 to 1700 Hz/atm and were made with a resonance tube system. The least-squares fits to the results are given below, where 103h is the mole fraction of the impurity, and f0 is the frequency of maximum absorption.

Mixture Equation Standard error

O 2 - H 2  f0/p=−0.3+64.2h Hz/atm 9 Hz/atm

O 2 - CO 2  f0/p=9+ 45h Hz/atm 70 Hz/atm

O 2 - H 2 O  f0/p=9+162h+144h2 Hz/atm 26 Hz/atm

The results are compared with those of other workers, and in particular, it is suggested that the results of Harlow and Kitching are probably in error because they ignored the adsorption of water vapor on the walls of the tube.
Turbulent Wall-Pressure Fluctuations on a Body of Revolution
Authors: Bakewell Henry P.
Published: September 2005

Measurements of the statistical properties of the fluctuating pressure at the wall were obtained in the turbulent boundary layer on a body of revolution in a water medium using flush-mounted hydrophones. The nondimensionalized spectral and correlation data are in good agreement with zero and nearly zero pressure gradient data obtained on flat plates and in fully developed turbulent pipe flow, respectively. In addition to longitudinal and lateral correlation data, correlations were obtained for hydrophone separations oriented at angles of 26.5° and 45° to the flow axis. These data confirm Corcos' assumption that the magnitude of the general cross-spectral density function is closely represented by the product of the magnitudes of the streamwise and lateral cross-spectral density functions.
Effect of Compliant-Tube Arrays on the Radiation Impedance of Small Sonar Transducers at an Air-Water Interface
Authors: Crum L. A. , Stumpf F. B.
Published: September 2005

Measurements of some fundamental aspects of compliant-tube arrays as well as their effect on the acoustic interaction between sonar-array elements at an air-water interface are presented. A theoretical analysis of the effect of an array of compliant tubes on the interaction radiation-resistance ratio is derived, and comparison made between theoretical and experimental results. It is concluded that compliant tubes can be used to influence greatly the acoustic interaction between sonar-array elements but they may change the radiation pattern.
Transmission Loss of Multiple Panels in a Random Incidence Field
Authors: Mulholland K. A. , Price A. J. , Parbrook H. D.
Published: September 2005

In this paper, the method of predicting the transmission loss of multilayer panels first proposed by Beranek and Work is used and developed to the point where the method can be applied under conditions where sound is incident on the panel from any angle or from many angles simultaneously as in the random incidence field. Doubts expressed recently about the accuracy of the theory are removed, and the method is shown to be a powerful tool for the prediction of transmission loss.
TTS and Recovery from TTS after Use of Powerful Hearing Aids
Authors: Macrae J. H.
Published: September 2005

Powerful hearing aids can cause temporary threshold shifts in the aided ears of children with sensorineural deafness, and recovery from TTS in these children may be at an unusually slow rate.
Effect of Surface Roughness on the Error in Calculated Ultrasonic Sound Velocities
Authors: Moment R. L.
Published: September 2005

The effect of surface roughness on the error in calculated sound velocities has been measured. The error in the calculated velocity varies linearly with the ratio of the surface roughness to the specimen thickness, above some minimum roughness value. The linear behavior is as expected, but cannot be calculated theoretically because of the nonlinear relationship during early stages of roughening. The data, while given for etched Al, should be qualitatively applicable to other metals.
BEATING SINUSOIDS AND PITCH CHANGES
Authors: Jeffress Lloyd A.
Published: September 2005

When two sinusoids of unequal frequency and amplitude are added, there is a frequency shift of the average tone during the moment when the beat cycle goes through a minimum. This fact is well known, but attempts to hear the corresponding change of pitch have generally been unsuccessful. By gating the tone and listening to only a short section, it is possible to hear the pitch difference between a sample taken during the minimum and one taken during the maximum.
Domed Sonar System
Authors: Maidanik G.
Published: September 2005

An analysis of the changes that are induced by a dome in the signal to-noise (S/N) ratio of a sonar system is performed. Both the transducer system and the dome are idealized in this analysis. A blanket dome and a plate dome are considered. It is shown that a properly designed dome can be made transparent to supersonic spectral components in the external pressure field and can reduce the response of the transducer system to subsonic spectral components in this pressure field. A dome can thus be emp oyed to increase the S/N ratio of a sonar system that is subjected to noise-pressure fields that possess high density of subsonic spectral components. The external pressure field considered in this paper is composed of the blocked pressure field induced by an incident plane acoustic-pressure field (the signal-pressure field) and the blocked pressure field of a subsonic turbulent boundary layer (the noise-pressure field).
External-Ear Acoustic Models with Simple Geometry
Authors: Teranishi R. , Shaw E. A. G.
Published: September 2005

The properties of the human ear are duplicated in simple physical models that may be accurately specified. A shallow cylindrical cavity set in an infinite plane that represents the concha has a depth resonance with values of gain and bandwidth in agreement with those observed in typical real ears under “meatus-blocked” conditions. To represent the human pinna, a rectangular flange is added to an inclined cylindrical concha. A cylindrical canal with a two-element network to simulate the eardrum impedance completes the model. Response curves with hard and soft eardrums, measured at eardrum position, at canal entrance and with blocked meatus, all have identical angular dependence up to 7 kHz and very similar angular dependence up to at least 12 kHz. The response of the model with blocked meatus and with open canal is in good agreement with real-ear data up to 7 kHz at normal and oblique incidence. Pressure distributions in the model ear for the first two modes (M1 and M2) are in excellent agreement with replica data.
International Standard Reference Zero for Audiometers
Authors: Weissler Pearl G.
Published: September 2005

This is a detailed report on the technical activities of ISO's Technical Committee on Acoustics No. 43, Working Group on Threshold of Hearing, which led to the ISO Recommendation R389, “Standard Reference Zero for the Calibration of Pure-Tone Audiometers,” November 1964. The activities described are the determinations of the transfer factors from loudness balancing experiments between the five earphone-coupler combinations R389, the incorporation of the transfer data into the computation of the reference equivalent threshold sound-pressure levels (RETSPL) in R389, and the details of the weighting of the original threshold determinations. A statistical analysis estimates the average standard deviation of the RETSPL in R389 to be 2 dB due in large part to the variance in the transfer factors. The present USASI standards are definitely outside the ISO uncertainty limits at all frequencies. The standard deviation of the differences between adjacent columns in R389 (or the equivalence of the RETSPL for the different earphone-coupler combinations) was estimated to be 2.5 dB. To improve accuracy in audiometry, it is suggested that the variance due to the transfer factors be eliminated by agreement on one standard earphone type.
Nonlinear Shift of Relaxation Rates by Admixtures — Comments on a Paper by A. A. Monkewicz [J. Acoust. Soc. Am. 42, 258–266 (1967)]
Authors: Bauer Hans-Jörg
Published: September 2005

For the power series expansion of the shift of the relaxation rates of a gas by admixtures, new coefficients are given. They were applied on measurements of Monkewicz [J. Acoust. Soc. Am. 42, 258–266 (1967)] in methane with water vapor admixed. The resulting rate constants differ considerably from those obtained by the use of the Tuesday-Boudart coefficients.
Fundamental Results Concerning Integral Representations in Acoustic Radiation
Authors: Copley Lawrence G.
Published: September 2005

Attention has of late been drawn to the use of integral equations for obtaining numerical solutions to problems of steady-state harmonic acoustic radiation. Essentially, three distinct methods have been reported: the Simple Source Method, the Surface Helmholtz Integral Equation, and the Interior Helmholtz Integral Relation. The present paper contains two major theoretical results. Firstly, nonexistence failure at certain frequencies of the simple-source method is clearly indicated. Secondly, it is shown that the surface Helmholtz integral equation fails by nonuniqueness at the same frequencies. In both cases, failure occurs at each of the discrete Dirichlet eigenfrequencies for the region enclosed by the vibrating surface. Physical interpretations and examples of the theoretical results are included.
Reflection of Extensional Waves at the End of a Thin Cylindrical Shell
Authors: Tasi J.
Published: September 2005

Simple formulas are given for the frequency, wavenumbers, and molal amplitudes of end resonance in a thin cylindrical shell as functions of the material and geometric properties of the shell. Differences in behavior are found between the results for a thin shell and those for analogous motion in plates and rods.
Experimental Measurement of “Creeping” Waves on Solid Aluminum Cylinders in Water Using Pulses
Authors: Neubauer Werner G.
Published: September 2005

The results of experiments of scattering of a pulse by a solid cylinder are presented that demonstrate the existence of “Franz-type” or “creeping” waves traveling outside the circumferential boundary of an aluminum cylinder.
Energy Spectral Density of the Sonic Boom
Authors: Lee Jhong S. , Peterson H. L. , McCoy C.
Published: September 2005

The spectral density of the sonic-boom N-wave pressure time function is derived simply. The analysis method employed herein is one that avoids the usual method of integration by parts in computing the Fourier transform of any function made up of straight line segments such as an ideal N-wave pressure signature. The dominant first peaks of the normalized energy spectral density are plotted for different sonic-boom durations. The results modify those given earlier by Young [J. Acoust. Soc. Am. 40, 496–498 (L) (1966)].
Acoustic-Wave Propagation past a Sinusoidal Surface
Authors: Salant Richard F.
Published: September 2005

The acoustic field produced by a plane wave propagating in a direction parallel to a sinusoidal surface is examined analytically. When the surface wavenumber is larger than twice the acoustic wavenumber, it is found that the disturbance produced by the surface decays exponentially with distance from the surface. However, when the surface wavenumber is smaller than twice the acoustic wavenumber, it is found that a portion of the disturbance propagates to infinity.
Response of an Elastic Plate to a Cyclic Longitudinal Force
Authors: Torvik Peter J. , McClatchey Jay J.
Published: September 2005

Energy supplied to the edge of a semi-infinite plate by a sinusoidal in-plane force, uniform across the thickness, is found to be divided among the various propagating modes in such a manner that one type of mode receives most of the energy. Because the mode shapes change with frequency, the same mode is not dominant at all frequencies. The dominant mode, at any frequency, is that mode that most closely resembles the symmetrical Goodier-Bishop wave having a dilatational portion independent of the thickness coordinate. Computations were performed over a range of frequencies, extending to frequencies where five propagating modes are involved, and graphs of results are presented.
Isopreference Method for Speech Evaluation
Authors: Rothauser E. H. , Urbanek G. E. , Pachl W. P.
Published: September 2005

A study of speech-quality measurement procedures requires a working definition of the over-all concept of speech quality. It is assumed that speech quality can be described in terms of intelligibility, preference, loudness, and speaker recognizability. A utilitarian approach to the measurement of preference, the isopreference method, is presented and discussed. In this method, preference is evaluated in a forced pair-comparison test and is described in terms of a continuously variable reference signal. The results of extensive testing and test repetitions indicate that the accuracy of preference evaluations is not limited by the proposed method, but by variety and variability of listeners and by training and accommodation effects for given sets of test signals.
Ultrasonic Velocity Dispersion in Ethane-Argon Mixtures
Authors: Amme Robert C. , Warren Bruce E.
Published: September 2005

A crystal ultrasonic interferometer has been utilized to measure velocity dispersion in ethane-argon mixtures at 304.1°K and up to f/P values of about 108 cps/atm. The double-relaxation characteristic of ethane persists, and relaxation times are only slightly affected by the addition of argon. Treatment of the relaxations as parallel processes gives relaxation times for ethane argon collisions. Considering the argon atoms as a Lennard-Jones 6:12 “probe” yields a value for the ethane repulsive range that is in excellent agreement with the Schwartz Slawsky Herzfeld theory for a 6:12 relaxing gas.
Reflections of Harmonics Generated by Finite-Amplitude Waves
Authors: Thompson D. O. , Tennison M. A. , Buck O.
Published: September 2005

Ultrasonic measurements which were designed to test the theory of reflections of harmonics generated by finite amplitude waves at stress free boundaries in solids have been made. The results are found to be in agreement with theoretical expectations.
Propagation of Weak Waves in Liquid Crystals of Nematic Type
Authors: Ericksen J. L.
Published: September 2005

We discuss conditions under which relatively weak discontinuities can propagate in liquid crystals, assuming these are incompressible and neglecting temperature variations. Loosely speaking, these assumptions tend to suppress waves that would occur in simpler liquids, thus they emphasize the waves that are peculair to liquid crystals. A primary feature is that they involve disturbances in orientation. As a general rule, there are accompanying perturbations of the motion.
Reflection and Transmission of Acoustic Waves from and through a Transition Zone
Authors: Nakamura Yosio
Published: September 2005

The transimssion of plane harmonic waves normally incident on a transition zone with arbitrary velocity and density variations in a fluid or an elastic medium is studied theoretically. The general solution for a one-dimensionally heterogeneous, isotropic medium is obtained in a series form by integrating the Volterra integral equation for the particle displacement. The reflection and transmission coefficients are derived from this solution.
Scattering of Acoustic Waves from a Moving Elastic Nonlinearity
Authors: Tsai C. S.
Published: September 2005

A Doppler-like phenomenon for acoustic waves is investigated by studying the scattering of a plane acoustic wave from a moving elastic nonlinearity in a nonlinear acoustic medium. By using the Green's-function technique, the first-order waves scattered in both forward and backward directions are calculated in terms of radiations arising from secondary sources induced in the region of the moving elastic nonlinearity. Three typical profiles of the moving elastic nonlinearity (rectangular, sawtooth, and trapezoidal) are considered. A Doppler-frequency shift similar to that in the electromagnetic-wave case is found in the backward-scattered wave but not in the forward-scattered wave. This frequency shift depends on the phase velocity of the acoustic wave in the unperturbed medium and the velocity of the moving elastic nonlinearity but not on the detail profile of the elastic nonlinearity. The intensity of the frequency-shifted scattered wave depends very strongly on the wavenumber of the incident wave, width and detail profile of the elastic nonlinearity, and less strongly on the velocity of the elastic nonlinearity. A possible experimental structure for investigating the Doppler-like phenomenon is suggested. The application of the Doppler-like phenomenon as a tool for investigating dynamical properties of a moving elastic nonlinearity or an elastic shock wave in liquids or solids is also indicated.
Method for Computing the Electrical and Acoustical Behavior of Free-Flooding Cylindrical Transducer Arrays
Authors: Porter David T.
Published: September 2005

A method is described for computing the electrical and acoustical behavior of arrays of free-flooding, thin, cylindrical transducers. Each of the gaps between transducers is divided into a small number of “water rings,” which are acoustically driven by the vibrations of the transducers and other water rings. Several water rings are also added at each end of the array. Mutual impedance coefficients between transducer rings and water rings can then be determined from expressions for mutual impedance between bands on the inside and outside of an infinite rigid cylinder. Comparisons of theoretical predictions and measured data are made for an actual four-element array. The theoretical and measured admittance plots agreed very well with respect to size, shape, and frequency. For the two trandsucers in the middle of the array, the input conductance (and resistance) were negative over a small band for both theory and measurement. The theoretical and measured transmit voltage responses agreed well over most of the band considered. However, the measured beam patterns had deep nulls on the cylindrical axis that were not reproduced in the theoretical results.
Sound Scattering into the the Shadow Zone below an Isothermal Layer
Authors: Schweitzer Britt J.
Published: September 2005

A mathematical model is developed to describe sound propagation into the shadow zone below an isothermal layer by means of scattering from a rough surface. The model incorporates formula that describes the propagation losses within the duct to points from which the sound is scattered. The Beckmann theory is then used to estimate the scattered intensities at the various angles that correspond to ray paths leading from the surface to a point in the shadow zone. Reasonable agreement is found between the theoretical results and observations made at 5 kHz in a moderately rough sea. The theory indicates that most of the scattering occurs in a narrow region of the surface between 200 and 1200 yd from the point of observation in the shadow zone.
Adaptive Threshold Procedures: BUDTIF
Authors: Campbell Richard A. , Lasky Elaine Z.
Published: September 2005

Consideration of recent psychoacoustic research reveals that, independent of the general acceptance of the theory of signal detectability, threshold methodology continues to play a major rôle in the acquisition of psychoacoustic data. Although adaptive methods are widely used, the newer, finite-trial, adaptive methods are not—possibly owing to a misconception regarding the impossibility of obtaining psychometric function slopes and information other than threshold with such methods. The simplest of the finite-trial adaptive methods, the Block Up-and-Down, Two-Interval Forced-Choice (BUDTIF) method is investigated, and an attempt is made to show the feasibility and efficiency of obtaining such information with an adaptive method. Specifically, the variability and bias of repeated thresholds obtained using human subjects with two-, four-. and eight-trial block sizes and from 16 to 144 per threshold were determined. Results indicate that, for a target performance level of 75%, a block of four trials leads to minimal between-threshold variability. Although between-threshold variability is indirectly related to the number of trials per threshold, if greater precision is necessary it would seem preferable to invest the subject's time in more short threshold runs than fewer long threshold runs. An adaptive stopping rule is suggested.
On the Perception of Direction of Echo
Authors: Ebata M. , Sone T. , Nimura T.
Published: September 2005

The minimum time differences over which same two sounds coming from different directions in succession are heard separately in direction are obtained. When two clicks are used as stimuli, the second click is lateralized separately from the first click if the former lags more than 10 msec behind the latter and the second click is less than 20 dB smaller as compared with the first one. If an accessory click is inserted between these two clicks, the minimum time difference over which two stimuli are separately lateralized is longer than that in the case without an accessory click and its value amounts to 20∼30 msec. Such a minimum difference is 100∼200 msec in the case that the space between the first click and the second one is filled up with some stimuli. As one of the results, it is shown that this time difference is smaller for a sound containing more high-frequency component than for one containing less. Moreover, when two sounds with same duration are given to each ear with an interaural time difference, the minimum duration over which a sound image moves from side to center on the head is obtained. These data are discussed in regard to physiological facts.
Two-Image Lateralization of Tones and Clicks
Authors: Hafter Ervin R. , Jeffress Lloyd A.
Published: September 2005

When interaural differences of time and level are set into opposition, subjects may report a single image that is determined in its lateralization largely by the interaural level difference. Such images show a fairly large “trading-ratio.” They may report hearing an image that is little affected by the difference of level, but is dependent largely upon the interaural difference of time. Such images show a very small trading-ratio. With practice, subjects can learn to hear and respond to both images, and center either at will. The present study is concerned with both images as they arise from tonal stimuli of various durations and rise fall times, and from high-pass clicks.
Pure-Tone Intensity Discrimination and Energy Detection
Authors: McGill W. J. , Goldberg J. P.
Published: September 2005

A study of 1000-Hz intensity discrimination is reported in which single tones were identified as the louder or softer of two alternatives differing slightly in energy. Tones were phase locked and fixed in duration (150 msec). Feedback was given following each judgment. Psychometric functions are presented and a masking curve is computed. The masking curve is found to be linear above 25-dB sensation level, and the slope is computed as 15/16. These results are interpreted as reflecting a form of energy discrimination similar to that proposed in noise masking.
Auditory Pulsed Doppler Discrimination
Authors: Pollack Irwin
Published: September 2005

Detection and relative discrimination thresholds were determined for auditory pulsed Doppler sequences. Doppler thresholds rival the extremely acute interval, or pitch, thresholds of the ear. Doppler threshold changes of less than 1 μsec/interval are readily obtained. Doppler thresholds suffer when temporal uncertainty, or jitter, is introduced, especially at high pulse frequencies. An attempt was made to obtain a “pure” measure of auditory interval gradient discrimination. Under experimental procedures that lessen the contribution of component variables, auditory interval gradient discrimination is relatively poor: interval gradient thresholds of about 25% compare with pulse number thresholds of about 10%, and with interpulse interval thresholds of about 0.1%.