bluuebunny/crossref_metadata_2025 huggingface dataset:
Receiver-Operating Characteristics Determined by a Mechanical Analog to the Rating Scale
Authors: Watson Charles S. , Rilling Mark E. , Bourbon Walter T.
Published: September 2005

In one portion of a fixed-interval-observation experiment, observers indicated their certainty that a 500-cps signal had been presented in a thermal-noise background by positioning a slider after each interval. In a second portion of this experiment, the observers responded by making binary decisions. Slider positions were treated as typical confidence ratings; the conditional probability of a given rating or of one indicating greater confidence, given signal plus noise, was plotted against the probability of these ratings, given noise alone. Functions produced in this manner, for a rating scale divided into thirty-six positions, were fit closely by the receiver-operating characteristics (ROC's) of the theory of signal detectability. A psychophysical model using two straight-line segments did not provide a good approximation to these data. Values of d′ were generally lower for the rating procedure than for the binary-decision procedure. The use of a large number of rating categories did not result in large increases information transmitted by the observers, but it did provide the desired fine resolution of the ROC's.
Short-Time Spectrum and “Cepstrum” Techniques for Vocal-Pitch Detection
Authors: Noll A. Michael
Published: September 2005

A spectrum analyzer based on a definition of short-time power spectra has been designed and simulated on a digital computer. The analyzer is primarily intended for use in speech analysis. It has been designed to operate in real time, and to produce high-resolution spectra without utilizing either heterodyning methods or bandpass filter banks. The logarithm of each consecutive amplitude spectrum thus obtained can be used as the input to a second similar spectrum analyzer. The output of this analyzer is then the “cepstrum” or power spectrum of the logarithm spectrum. The cepstrum of a speech signal has a peak corresponding to the fundamental period for voiced speech but no peak for unvoiced speech. Thus, a cepstrum analyzer can function both as a pitch and as a voiced-unvoiced detector. Cepstral pitch detection has the important advantages that it is insensitive to phase distortion, and is also resistant to additive noise and amplitude distortion of the speech signal. The method does not require the presence of the fundamental frequency in the speech signal, and will give several separate cepstral peaks if several different pitch periods are present. Cepstral techniques appear to be even more reliable and efficient than visual methods for pitch detection. The short-time spectrum and cepstrum analyzers described in this paper were simulated by a sampled-data system on an IBM-7090 digital computer. The simulation was programmed with the assistance of a special block-diagram compiler.
Automatic Reduction of Vowel Spectra: An Analysis-by-Synthesis Method and Its Evaluation
Authors: Paul Allan P. , House Arthur S. , Stevens Kenneth N.
Published: September 2005

An analysis-by-synthesis procedure for the automatic reduction of vowel spectra is described. The scheme is realized as a program for a general-purpose digital computer. The output of the program specifies time samples of vocalic utterances in terms of parameters that characterize the transfer function of the vocal tract. The performance is described and evaluated in terms of deviations of formant-frequency values and magnitudes of error scores; manually derived data provided by a related scheme are used as criteria for comparison.
Scattering of Elastic Waves by Small Inhomogeneities
Authors: Knopoff L. , Hudson J. A.
Published: September 2005

The scattering of elastic waves by a randomly inhomogeneous medium has been studied. The mean-square amplitudes of the scattered waves averaged over a statistical ensemble of inhomogeneities are calculated. The space-correlation functions of the elastic parameters are assumed to be Gaussian and isotropic. Terms of the second order in the variation of the elastic parameters from their means are neglected. The theory has been applied to the scattering of plane P and S waves in an inhomogeneous medium of infinite extent. The results give the amount of the P wave that is transformed into shear waves and vice versa. The fluctuations in phase and amplitude of the transmitted waves are also computed.
Plate-Edge Admittances
Authors: Eichler Ewald
Published: September 2005

The response of a semi-infinite plate bounded by a straight edge and excited harmonically by a stud attached to its edge is presented in terms of an admittance matrix that relates the two in-plane rotatory velocities and the transverse velocity of the stud to the respective forces. The problem is solved by means of the classical theory of thin plates and by assuming a simple stress distribution along the plate edge. Numerical results for stud widths smaller than one-third of the flexural wavelengths and for a value of Poisson's ratio σ=0.3 are given. They are found to relate well to known results for the full infinite plate.
Approximate Expressions for the Mechanical Impedance and Transmissibility of Beams Vibrating in their Transverse Modes
Authors: Snowdon J. C.
Published: September 2005

Expressions for the driving-point impedance, transmissibility, and transfer impedance of damped beams excited transversely by a central force have been approximated and written in general form. These general expressions are applicable whether the ends of the beams are simply supported, simply clamped, or totally free; they apply accurately at all frequencies greater than about 0.7 times the fundamental resonant frequency of each beam. The general expressions obtained for driving-point impedance and transmissibility are remarkably simple in nature. Both graphical and tabular comparisons have been made between computations of the exact and approximate expressions for impedance and transmissibility.
Loudness Function in the Presence of Masking Noise
Authors: Gleiss Norman , Zwicker Eberhard
Published: September 2005

Partly masked loudness curves given by different authors are compared. It is shown that the curves depend upon the spectrum of the masking should and so cannot be calculated in general from one simple formula.
Temperature Coefficients of Sound Velocity in Ethyl Alcohol
Authors: Wilson Wayne
Published: September 2005

The temperature coefficients of sound velocity in ethyl alcohol were used to evaluate Rao's empirical equation for temperatures and pressures in the range 0° to 60°C and 14.7 to 13 000 psi. It is shown that ethyl alcohol does not satisfy the equation in these ranges.
Diffraction of Ultrasound Radiating into an Elastically Anisotropic Medium
Authors: Papadakis Emmanuel P.
Published: September 2005

The diffraction loss-distance characteristics in crystals have been computed for the single-slit transducer geometry in ultrasonic pulse-echo measurements. The characteristics are functions of elastic anisotropy and show several local maxima and minima before becoming monotonic at large distances from the transducer. By applying scale factors to the ordinates and abscissas of the characteristics, they were made applicable to the case of a circular transducer. The scale factors were chosen to bring the computed single-slit characteristic for isotropic materials into coincidence with the well-known isotropic-diffraction characteristic for circular-piston sources. The scaled crystal characteristics served to predict the positions of the local loss maxima to 15% and their amplitudes to 25% or better in four experiments. Certain crystals produce less diffraction loss per unit length than others because of the dependence of diffraction on anisotropy. The scaled diffraction loss-distance characteristics can be used for computing diffraction corrections for ultrasonic attenuation.
Electromagnetic Reflection from Sound Waves. II
Authors: Schmitt Hans J. , Wu Tai Tsun
Published: September 2005

The reflection of electromagnetic waves normally incident on the surface of a liquid supporting a spherical sound wave is discussed theoretically. The effect of Bragg reflection is neglected, and only the microscopic movement of the liquid surface is taken into account. Because of the periodic nature of the sound wave, the reflected electromagnetic signal contains frequency components that correspond to both the sum and the difference of the electromagnetic and acoustic frequencies. These two frequency components have quite different properties. The problem is treated by perturbation theory, and two special cases are examined in detail.
Audiofrequency Compliances of Prestressed Quartz, Fused Silica, and Aluminum
Authors: Greenspan Martin , Tschiegg Carl E.
Published: September 2005

The anomalies in the audiofrequency compliances reported by Fitzgerald [J. Acoust. Soc. Am. 32, 1270 (1960)] were searched for in vain. In particular, the measured shear compliances were independent of frequency and prestress within the experimental error of about 4% over a range of these variables within which Fitzgerald reported a variation of one to two orders of magnitude. The present technique involves a vibrating duplex reed; the biasing steady stress is of either piezoelectric or thermal origin. An extension of the common theory of the “bimetallic strip” to anisotropic materials is presented.
Transverse Vibrations of Tapered Cantilever Beams with End Loads
Authors: Mabie H. H. , Rogers C. B.
Published: September 2005

Free vibrations of nonuniform cantilever beams with an end mass have been investigated, using the equations of Bernoulli-Euler. Two configurations of interest are treated: (a) constant width and linearly variable thickness; and (b) constant thickness and linearly variable width. Charts have been plotted for each case from which the fundamental frequency, the second harmonic, and the third harmonic can be easily determined for various taper ratios and ratios of end mass to beam mass. The Tables from which these charts were plotted are also included.
Flexural Vibrations of Cylindrically Aeolotropic Circular Plates
Authors: Minkarah I. A. , Hoppmann W. H.
Published: September 2005

Equations for the determination of the frequencies of flexural vibration and corresponding modal shapes for cylindrically aeolotropic circular plates are presented. A considerable analysis has been made of the case of symmetric vibrations, and results are tabulated. The theory is exemplified by an analysis of the vibration of a circular plate with circular stiffeners for which the effective elastic compliances had been determined in a previous investigation. Nodal patterns and corresponding frequencies were experimentally determined for the first five symmetric modes and the first four asymmetric modes of a simply supported stiffened plate. Comparison between the theoretical and experimental results for the first three symmetric modes is provided. Finally, some discussion given for the important problem of approximating plates with attached stiffeners by equivalent homogeneous uniformly thick aeolotropic plates.
On Vibrations of Spherical Shells
Authors: Prasad C.
Published: September 2005

By the use of suitable auxiliary variables, the equations of motion of nonshallow spherical shells are reduced to a system of two uncoupled and one partly coupled equations. The solution of these equations is given in terms of associated Legendre functions.
Intensity of Noise Exposure and the Time-Course of Recovery from Temporary Hearing Loss
Authors: Trittipoe William J. , Spieth Walter
Published: September 2005

It would be reasonable to expect that temporary threshold shift (TTS) following exposure to higher sound levels would be an increasing function of the exposure level. However, numerous investigators have observed that when duration of exposure is held constant, a greater TTS may occur after exposure to a less intense level than after a more intense level. This is frequently observed when the TTS is measured soon after exposure, but less frequently observed when the TTS is measured 3 min or longer after exposure. Thus, Miller found that 3 min of white noise at 115 db produced more TTS than at 120 db (measured 6 min later at 4000 cps). In the present study TTS was measured by the Békésy method at 4000 and 6000 cy for 10 min following exposure to 3 min durations of thermal noise. Five different noise levels were used. They ranged, in 5 db steps, from 108 to 128 db. Each of 9 ears was run twice on each noise condition. Only 1 ear showed a definite pattern of decreasing TTS with increasing intensity.
Binaural versus Monaural Auditory Fatigue
Authors: Hirsh Ira J.
Published: September 2005

Theoretical considerations regarding the interaction between the two ears suggest the possibility that the amount of auditory fatigue (threshold elevation) in one ear following exposure to sound will depend, in part, upon whether the exposure was directed at that ear only or at both ears. Exposures to noise and to tone were directed at either ear and at both ears of five observers, and continuous threshold recording of the absolute threshold for one ear was made following each exposure. The results indicate no significant difference in the fatiguing effect in one ear between exposures on that ear and exposures to both ears. (This research was supported in whole or in part by the U. S. Air Force under Contract No. AF33(616)-3505, monitored by Aero Medical Laboratory.)
On Torsional Oscillations in a Finite Circular Cylinder
Authors: Wainwright W. L.
Published: September 2005

This paper deals with some aspects, which do not seem to have received previous attention, of the torsional oscillations in a finite circular cylinder of elastic isotropic materials. The general solution for the nonvanishing displacement includes the higher modes of motion; both free and forced torsional oscillations are discussed.
Hydroacoustic Scattering from a Pair of Fluid Spheres
Authors: Knollman G. C. , Hartog J. J.
Published: September 2005

Experimental results are presented concerning the scattering of plane underwater sound waves from an identical pair of liquid spheres spaced apart up to distances of many acoustic wavelengths. Sphere sizes on the order of and larger than the wavelength are considered for two different acoustic-impedance contrasts between spheres and surrounding water. Typical azimuth-scattering patterns are depicted for sphere line-of-centers both colinear with and orthogonal to the direction of wave propagation. Forward scattering is studied for these two orientations as well as for two additional arrangements of the line-of-centers. A pair of identical fluid spheres oriented normal to the propagation direction and spaced less than a wavelength apart exhibits major side lobes in the azimuth pattern. For separations exceeding a few acoustic wavelengths, azimuth patterns can, in general, be obtained from those associated with each sphere alone. An alignment of one sphere behind the other in the sound field results in rather prominent interference effects, these interferences being the more marked the smaller the separation between spheres. No large-scale differences in forward scattering are evidenced when sphere sizes are doubled, provided sphere separation exceeds a few wavelengths.
Performance of Open Ferroelectric Ceramic Cylinders in Underwater Transducers
Authors: McMahon G. W.
Published: September 2005

The behavior of the cavity resonance in open tubes of barium titanate and lead zirconate titanate ceramic immersed in water has been studied both experimentally and theoretically for a range of length-to-radius ratios (h/a). Particular emphasis is given to tubes of small h/a where the cavity-resonant frequency is near the ring-resonant frequency of the tube, and close coupling is observed between the two modes. A coaxial line array of such elements, which has been built and tested, exhibits a high efficiency over a wide frequency band. Since no pressure release is used in its construction, this transducer is promising as a lightweight, high-power sound source for operation at great depths in the ocean.
Instrumentation of a Random Vibration System to Meet Current Test Specifications
Authors: Priest Dorman E.
Published: September 2005

Common random test specifications include a shaped random vibration level in g2 per cps, a load in pounds, and a frequency region in which equalization for irregularities of response are specified. By a straightforward process the size and characteristics of the shaker and other system components can be determined which will satisfy most of the important factors involved. Important limitations imposed by the nonlinear resonant load reactions, the high-frequency resonances of the shaker armature structures, and the peak voltage limit of the power amplifier make a new approach to part of the specifications desirable. A revision of the usual test method is suggested which avoids impractical attempts to equalize for these load reactions and deletes certain high-frequency regions. In these, a complex pattern of standing waves in the shaker table, fixture, and specimen does not allow the usual definition of the acceleration level.
Fluctuating Wall Pressure under a Separated Supersonic Flow
Authors: Kistler A. L.
Published: September 2005

Measurements have been obtained of the pressure fluctuations under the turbulent, separated region ahead of a forward-facing step at Mach numbers 3.01 and 4.54. These pressures are significantly larger than the pressures produced by an attached boundary layer. The data can be interpreted as showing that the pressure fluctuations originate from two distinct causes: fluctuations due to changes in the geometry of the separated region and fluctuations due to the turbulent, free shear layer. The levels to be expected from each cause can be estimated from a simple model.
Reliability of Measures Obtained with the Zwislocki Acoustic Bride
Authors: Tillman Tom W. , Dallos Peter J. , Kuruvilla Thomas
Published: September 2005

An acoustic-impedance bridge designed by Zwislocki recently became available. The bridge allows the specification of the absolute acoustic impedance of the human car by yielding independent measures of acoustic reactance and resistance. This measurement of absolute impedance requires an accurate measure of the volume of the external ear. The test-retest reliability of volume measures, as well as those of resistance and reactance, was examined. Three examiners obtained volume measures by using two different techniques as well as measures of resistance and compliance (reactance) on 10 subjects in test and retest sessions. Results suggest that measurement of the volume of the ear canal is sufficiently repeatable to allow this procedure to serve as a first step in the measurement of absolute impedance with the Zwislocki bridge. Test-retest reliability of the compliance measures was also high. Test-retest measures of resistance yielded low correlations in spite of high interexaminer correlation in both sessions. It is postulated that unknown factors caused a real but nonsystematic shift in acoustic resistance over subjects, thus destroying test-retest correlation while preserving high interexaminer correlation. Further investigation is required to establish the validity of this hypothesis, but it can be concluded that the bridge itself is a reliable measuring device.
Preliminary Investigation of Some Blanket Damping Treatment Variables
Authors: Barnett N. E. , Kushner S. S.
Published: September 2005

An investigation of the dependence of vibration damping capacity on frequency, septum weight, blanket density, and blanket thickness was carried out by means of thick plate decay rate apparatus for several fibrous-glass-blanket-septum configurations. Correlations between these parameters will be presented.
Audiogram-Average Methods and SRT Scores
Authors: Siegenthaler Bruce M. , Strand Richard
Published: September 2005

Pure-tone audiograms and SRT scores on 535 audiology patients were utilized. Binaural percent hearing loss and audiogram summary or average according to several methods were computed for each subject. Each subject had an SRT score obtained with a common clinical test. Product-moment correlations were computed between each pure-tone audiogram percent or summary method and SRT scores, with subjects categorized according to SRT test given and audiogram shape. Most between-test correlations were over 0.70 and many were over 0.85. In general, the AMA and the Fowler methods had less high correlations with SRT than the other methods. The two-frequency average had a general superiority over other methods and may be considered the method of choice for relating pure-tone audiograms to SRT. However, the differences among methods, including the Fowler and AMA percent methods, were small.
Sound Propagation through the Atmosphere
Authors: Burkhard M. D.
Published: September 2005

The propagation of sound from an airborne source to the ground has been studied. The source was a propeller type airplane flown at altitudes up to 4800 ft and distances up to 9600 ft. Angles of elevation of the source with respect to the earth's surface were 2°, 5°, 15°, 30°, and 90°. The weather varied to include typical year-round conditions in the Chicago, Illinois, area and winter in Phoenix, Arizona. The noise propagated to the earth was analyzed to determine the variation in attenuation as a function of frequency and the relative position of the noise source. A statistical analysis was made to determine the effects of various weather parameters on propagation of the sound. Average values of sound attenuation were obtained. In addition, the effects of temperature, temperature gradient, humidity, wind, and wind gradient are given in an empirical formula. Propagation does not vary significantly for elevation angles between 5° and 90°, but for the 2° angle there is evidence of ground surface effects. The most important factor for minimizing the noise on the ground on a particular day was wind direction. Other meteorological conditions do not appear to be significant for controlling noise from flight operations around an airport. (Sponsored by the Aero Medical Laboratory, WCRDB, Wright-Patterson Air Force Base, Ohio.)
Sonic-Pulse Compression in Bats and People: A Comment
Authors: van Bergeijk Willem A.
Published: September 2005

Bats have been reported to be extremely resistant to noise jamming. Since they navigate on a sonar consisting of FM chirps, G. K. Strother suggested that their auditory system contains “collapsing filter” similar in principle to that used in chirp radars. This paper examines that possibility in more detail and reports on some informal experiments with people; the conclusion is reached that people do not have collapsing filters, and that bats very probably don't either. It is further concluded, on the basis of an analysis of basilar-membrane responses, that at the hair-cell level the time order in the stimulus is preserved and that the basilar membrane as a whole preserves the envelope structure of a complex stimulus. Concerning the question of why, then, the bat chirps, the suggestion is made that an FM signal acts as a feature-extracting probe signal, informing the bat not only of the location but also of the size, and possibly texture, of objects in its environment.
Near Field Jet Engine Noise Contours
Authors: Kirchman E. J. , Owen A. L.
Published: September 2005

Using the method of near field jet noise prediction developed by Bolt Beranek and Newman, a dual pod installation of after burning engines has been investigated for the following cases: (1) inboard 100% power, (2) inboard with afterburner, (3) outboard 100% power, (4) outboard with afterburner, (5) inboard 100% and outboard 100%, (6) inboard afterburner and outboard 100%, (7) inboard 100% and outboard afterburner, and (8) inboard afterburner and outboard afterburner. A comparison is given between the predicted data and measured data. In the case of single engines, the experimental results indicate that, in the very high intensity areas at least, sufficiently close predictions can be made for design purposes. A modified method has been developed to approximate the experimental results for multiengine configurations.
Effect of Auditory Deprivation
Authors: Batkin Stanley , Ansberry Merle
Published: September 2005

A preliminary study of attenuated auditory and motor stimulation in the guinea pig from birth to the age of four months has suggested associated decreased hearing responses and absence of the pinna reflex.
Comments on “Sensory Thresholds and Response Bias”
Authors: Taylor M. M.
Published: September 2005

Auditory-detection data presented by Norman [J. Acoust. Soc. Am. 35, 1432 (1963)] are shown to be compatible with the continuous model of signal-detectability theory and not to require the assumption of a low threshold.
Circumaural Earphone Coupling with Improved Performance as an Ear Defender
Authors: Shaw E. A. G. , Thiessen G. J.
Published: September 2005

It is customary to use a relatively small coupling volume (typically 15–50 cm3) to provide maximum earphone sensitivity at speech frequencies, although a much greater volume is desirable to minimize the penetration of extraneous noise, particularly at low frequencies. This dilemma is resolved by making the effective coupling volume frequency dependent. For example the cavity may be divided into two parts coupled by an acoustic resistance, both parts then being effective at low frequencies but only one above a transition frequency (300 cps in a typical case). Alternatively, the two cavities may be coupled by an acoustic mass. When a large total coupling volume is used, it is desirable to damp out high-frequency standing waves with suitable porous material. The introduction of such material is also beneficial at low frequencies where the wave motion tends to be isothermal thus further increasing the effective cavity size.
Theory of Pulse Jet Noise Generation
Authors: Westervelt Peter J. , McQuillin Richard J.
Published: September 2005

Pulse jet noise arises from three separate and distinct mechanisms. The pulsating air flow at the inlet and exhaust constitute simple monopole souces whose source strengths can be related to the instantaneous volume flow. The fact that the exhaust flow is directed causes a large periodic flux of momentum to be directed along the axis of the jet giving rise to a dipole or force source. The strength of this force source is clearly related to the thrust of the jet. Finally, the jet, mixing with the surrounding air, will produce noise of the Lighthill variety stemming from the convected quadripole sources. One problem consists in determing the proper admixture of the three fundamental sources necessary to reproduce the measured far-field directivity. Another problem consists in relating the three source strengths to the measured flow and thrust characteristics of the jet. Both of these problems are currently being studied. Preliminary analysis indicates that the fundamental frequency is generated by a monopole and that the higher harmonics contain monopole, dipole, and quadripole radiation. (Work supported by the Wright Air Development Command.)
Correlations and Spectra of Pressure Fluctuations on the Wall Adjacent to a Turbulent Boundary Layer
Authors: Harrison Mark
Published: September 2005

A fully developed turbulent boundary layer with a zero pressure gradient has been studied. A subsonic wind tunnel was used. The pressure fluctuations on the wall of the wind tunnel were measured by small flush mounted microphones about 132 of an inch in radius. Data for the dimensionless spectral density of the pressure fluctuations, P(f)/ρ2U03δ*, as a function of the frequency parameter fδ*/U0, will be presented; P (f), ρ, U0, δ*, and f are, respectively the spectral density, fluid density, free stream velocity, boundary layer displacement thickness, and frequency. Data for the coefficient (p(t)2)/ρ2U04 will be presented. The longitudinal and transverse cross correlations for the pressure fluctuation were studied by using two flush mounted microphones. These correlations were measured for the total pressure fluctuation and as a function of frequency. Data for the latter will be presented as a function of f0x/U0 and x/δ*; x is the distance between the two microphones and f0 is the midfrequency of a sufficiently narrow tunable filter. Based upon these measurements, an evaluation of the concept of frozen lamellae of turbulence convected at a local mean flow velocity will be presented
Farfield-Noise Prediction from Nearfield-Spectrum Measurements
Authors: Greenspon Joshua E.
Published: September 2005

A theory is presented for computing farfield noise radiation from nearfield measurements. The relations are given for a spheroidal surface. It turns out that the same mathematical development in spheroidal functions can be used both for single frequency and for noise spectrum.
Ultrasonic-Wave Propagation in Pure Silicon and Germanium
Authors: Mason Warren P. , Bateman T. B.
Published: September 2005

Ultrasonic attenuation and velocity measurements have been made in pure germanium and silicon (doping <1014 impurity atoms per cc) and in doped n-type germanium and p-type silicon. The attenuation in pure materials shows a continuous decrease as the temperature is decreased and a very low attenuation below 20°K. These results indicate that the energy losses are accounted for entirely by phonon-phonon interactions. A calculation has been made of these losses, using a model based on the Akheiser effect and incorporating the recently measured third-order elastic moduli of silicon and germanium. For both materials, the calculated values predict correctly the large difference between longitudinal and shear waves and agree quantitatively within 50% with the measured values over the whole temperature range.
Propagation of Axisymmetric Waves in a Circular Semiinfinite Elastic Rod
Authors: Kaul R. K. , McCoy J. J.
Published: September 2005

The Mindlin-McNiven equations for axially symmetric waves are used to determine the radial strains in a circular, semiinfinite, isotropic, elastic rod for both pure and mixed end conditions when a constant pressure is suddenly applied to its end. Using double-integral transforms, the solution is obtained in terms of three Fourier integrals, each one representing one mode of propagation. These integrals are too complex to be evaluated exactly and, therefore, an asymptotic solution, valid for large distance of travel, is obtained for the head of the pulse by using the method of steepest descent. The results predict the existence of edge resonance and further demonstrate its influence on the strain field.
Elastic Waves along a Cylindrical Bore
Authors: White J. E.
Published: September 2005

This paper discusses axially symmetric solutions for elastic waves propagating along an infinite cylinder, namely those which can be expressed as F(r) eikz e−iwt. M. A. Biot [J. Appl. Phys. 23, 997–1005 (1952)] presented results for phase velo|cities along the axis less than shear velocity in the solid and indicated that for higher phase velocities, the waves cannot propagate without attenuation. The present paper gives solutions for higher phase velocities, showing that no attenuation in the direction of the axis is required. Special attention is given to the limiting case of phase velocity equal to the speed of compressional waves in the solid, which yields the coupling of a fluid-filled borehole to a plane compressional wave in the surrounding solid. In the low-frequency limit, this coupling agrees with an approximate expression published earlier [J. Acoust. Soc. Am. 25, 906–915 (1953)].
Dynamic Absorbers Applied to a Bar That Has Solid Damping
Authors: Neubert V. H.
Published: September 2005

The theoretical steady-state response of an axially excited bar having solid damping is determined. The effect of adding one or two dynamic absorbers is considered, as well as the effect of adding concentrated mass only. Tuning of the absorbers and optimization of damping are discussed.
Wave Propagation in a Medium with Random, Spheroidal Inhomogeneities
Authors: Knollman G. C.
Published: September 2005

An acoustic or electromagnetic wave propagating in a material medium experiences fluctuations in amplitude and phase that can be attributed in part to scattering from inhomogeneities due to variations in the refractive index of the transmission medium. Since such “patches of inhomogeneity” are often regarded as lenticular in shape, it is the purpose of this paper to extend, for both plane and spherical sound waves, contemporary wave-fluctuation theory (based on a Gaussian correlation function for refractive index) to include the circumstance of spheroidal inhomogeneities. Mean-square amplitude and phase fluctuations are considered for acoustic waves propagating in a statistically isotropic medium in which random deviations of the refractive index are small. Large-scale inhomogeneities of arbitrary spheroidal shape are treated, and the influence of transmitter-to-receiver range, acoustic wavelength, and “patch” dimensions on variations in wave amplitude and phase is derived for this general case. Particular attention is given the high-frequency ray limit (Bergmann region) and the low-frequency (Fraunhofer diffraction) region. The significant effects on wave fluctuations of both spherical and nonspherical inhomogeneities are compared for plane and spherical acoustic waves.
Masking of English Words by Prolonged Vowel Sounds
Authors: Moser Henry M. , Dreher John J. , O'Neill John J.
Published: September 2005

One-hundred and ten monosyllabic words selected from the Thorndike list of 1000 most frequently occurring words in English to represent equally each of 10 vowels were presented to 300 American listeners in an articulation test. Also tested were 72 spondee words, half selected from those in use in audiological tests and half from those in frequent use in air traffic control, further to represent the same vowel sounds. Masking of the stimuli was accomplished by separately recording each of nine prolonged vowels intoned by a trio of male voices. Results indicate that vowels of equal sound pressure levels differ considerably in masking effectiveness, that words containing a specific vowel are not masked optimally by the same vowel, and that spondees are masked by prolonged vowels in the same rank order as are the monosyllables. Prolonged vowel sounds with relatively high concentrations of energy between 700 and 1000 cps are most effective as masking agents. Rank order correlation of observed masking effectiveness with masking effectiveness predicted by the Strassberg method is 0.52, the Beranek method is 0.59, and by the Pickett-Kryter method, 0.69. Some observations on resistance of words to masking are made in relation to phonemic transition areas with words. [Done in connection with contract AF 19(604)-1577, monitored by the Operational Applications Laboratory, Air Research and Development Command, Bolling Air Force Base, Washington 25, D.C.]
Sensitivity of Liquid-Filled, End-Capped, Cylindrical, Ceramic Hydrophones
Authors: McMahon G. W.
Published: September 2005

A theoretical expression is developed for the sensitivity of liquid-filled, cylindrical, ceramic hydrophones having rigid and semirigid end caps. The theory gives good agreement with experimental measurements on a lead zirconate-titanate hydrophone with two end-cap conditions and three different enclosed fluids.
Effect of Boundary Flexibility on the Response of a String to Convected Random Loading
Authors: White Pritchard H.
Published: September 2005

The mean-square displacement of a uniform, stretched string, restrained against lateral movement at the boundaries by springs, to a convected, random-loading field has been investigated. A modal-analysis technique based on Powell's method has been used, all crosscoupling terms being retained. The response is strongly affected by two parameters: the ratio of convection velocity to the wave velocity of the string (u/a) and the ratio of wavenumber of the excitation to wavenumber of the eigenfunction of the string (ke/ks). Modal response to a harmonic convected wave is greatest for all modes, except the first, when the ratios are both unity. For the first mode, the response is greatest when (u/a) approaches +∞ and (ke/ks) approaches 0 so that the product remains unity. The response is strongly affected by crossproduct terms, even though orthogonal eigenfunctions are used. Inclusion of the crossproduct terms in the calculations results in a mean-square displacement that is less peaked at the center of the string but correspondingly higher toward the outer ends than if these terms had been neglected. The effect of the boundary flexibility is to increase the mean-square displacement at all points of the string, and also to make the distribution of this displacement more uniform over the length.
Sound Insulation and the Apartment Dweller
Authors: Northwood T. D.
Published: September 2005

Most of the existing sound-insulation requirements are based on experience with traditional construction, and this is reflected in the shape of the standard grading curve. Since nontraditional constructions frequently have quite different sound-insulation characteristics, the desired shape of insulation curve, i.e., the relative importance of the various frequency bands, becomes an important consideration. To gain insight on this point, the problem was approached by considering directly the activities and needs of apartment dwellers. The tentative conclusion is that the most common type of grading curves, including the ASTM Sound Transmission Class curve, are of approximately the correct shape for rating sound insulation between dwellings.
Owner's Viewpoint in Residential Acoustical Control
Authors: Rose Frederick P.
Published: September 2005

Stress is laid on the lack of adequate acoustical treatment in the design and construction of multiple dwellings in the United States of America.
Integration of Energy at Threshold with Gradual Rise-Fall Tone Pips
Authors: Dallos Peter J. , Olsen Wayne O.
Published: September 2005

Short-tone thresholds were tested with an array of ten stimuli so chosen to incorporate a wide range of parameter variations. It was shown that the average data could be very well fitted with the function (I−I0)T = k, where I is the stimulus intensity at threshold, I0 and k are constants, while T is the equivalent stimulus duration. This equivalent duration was derived for gradually rising and falling tone pips, and was shown to be computable as T = 2r/3+P, where r is the rise-fall time and P is the peak time. It was shown that the above model predicted individual thresholds with considerably greater accuracy than other alternative descriptions. The theoretical implications of the model are the existence of a definite lower limit of stimulus intensity (I0), below which the stimulus power does not contribute toward threshold recognition, and the constancy of the effective utilizable energy at threshold (k). This latter quantity did not vary more than 0.5 dB from stimulus to stimulus.
Explanation of Limens of Loudness
Authors: Pierce J. R.
Published: September 2005

It is proposed that the limen of loudness ΔS is equal or proportional to the root mean square deviation in the number of pulses produced by the sound in the time T of observation. By making a plausible assumption concerning the deviation and by assuming that loudness S is proportional to the pulse rate one obtains ΔS = A−1/2T−1/2S1/2. Here A is a constant which must be a function of frequency if the equation is to fit experimental data. The fit is encouraging but not completely convincing. If valid, the hypothesis might be used to explain other acoustic phenomena.
Comments on “Radiation Impedance of a Source near Reflectors” by R. V. Waterhouse
Authors: Maling George C.
Published: September 2005

The increase in acoustic power output of a constant-strength point monopole caused by boundaries can be found directly from the value of the imaginary part of the reflected pressure at the source. Waterhouse obtained an expression for the power output of a source by assuming that the plane could be specified by a pressure-reflection coefficient (R) that is Independent of the angle of incidence. It is shown here that for some geometries the power output is independent of the angular dependence of R. When the source is located over an infinite plane, the increase in acoustic power output can also be found by using admittance boundary conditions. Some solutions are presented for this configuration and are compared with the results obtained by Waterhouse.
Aural Azimuth Discrimination Ability of a Human Observer
Authors: Frazier F. , Johnson J. C. , Fitzpatrick R. C.
Published: September 2005

A preliminary study has been made for the purpose of determining the ability of an individual to accurately estimate the direction of sound arrival. The observers were shielded such that no visual aids could be used. A limited statistical analysis has been applied to the data from this study, and significant though not conclusive, results were obtained. [Parts of this research were supported by Tri-service Contract No. DA-36-039-sc-52654.]
On the Estimation of the Generalized Force due to Random Pressure and on Necessary Modes
Authors: Powell Alan
Published: September 2005

Under certain conditions of major practical interest, the double surface integral giving the generalized force due to a random pressure field for a mode of vibration can be reduced to the product of two double line integrals. For sinusoidal mode shapes, the double line integral further reduces to a single integral, easily evaluated for any correlation function. It is also pointed out that for cylindrical structures, lacking a boundary condition of zero deflection for the circumferential modes, the modes cos (nθ) and sin (nθ) must both be considered.
Detection of Beats in Repeated Bursts of Tone
Authors: Goldstein M. H. , Sandel T. T.
Published: September 2005

Listeners report hearing beats in repeated bursts of tone of low intensity provided the burst rate stands in a nearly harmonic relation to the frequency of the tone and provided that certain conditions of rise time of the bursts and frequency of the tone (carrier) are met. A typical signal that will give rise to beats at a rate of 2/sec might be one in which bursts of a tone of 2001 cps are repeated at a rate of 200 per second; the bursts of tone are presented at a level of 35 db above threshold with a rise time of 0.25 msec for each burst, and a sound-time fraction of 0.5. In these experiments, listeners were asked to report the presence or absence of beats as the frequency of the carrier was slowly changed. For a given test, repetition rate, sound-time fraction, and rise time were held constant. For a nearly harmonic situation the probability of detection of beats is greater for short rise times, and carriers of relatively low frequency. Data on the masking of the beats with wide-band noise, high-pass filtered noise, and low-pass filtered noise are also presented. These experiments permit comparison of various mathematical representations of these stimuli with respect to their ability to predict the listeners responses. [This work was supported by the U. S. Army (Signal Corps), The U. S. Air Force (Office of Scientific Research, Air Research and Development Command), and the U. S. Navy (Office of Naval Research).]
Example of the Dependence of Sound Absorption on the Area of Sample
Authors: Young Robert W.
Published: September 2005

The sound absorption in a solid concrete room was measured by the reverberation method, first with the room entirely bare, then with a “border” of 114-in. Acousti-Celotex (46 ft2 in area) around the ceiling, then with a “border” added around the top of the walls (total acoustical tile 112 ft2), and finally with the entire ceiling and one-third of the side walls covered (265 ft2 of acoustical tile). The test sound, generated by mechanical impact, was filtered on reception into third-octave and half-octave bands. The volume of the rectangular room was 1350 ft3 and its area 793 ft2. With the border of 46 ft2 the coefficients determined in the customary fashion by the Sabine reverberation equation were near those published for 114 in. Acousti-Celotex. At 125 and 8000 cps the coefficients changed little with the area of sample. At 1000 cps, however, the measured coefficient dropped from 0.93 to 0.44, to 0.25 as the sample area was increased. This is possible evidence for a change in effective mean free path and for the need of an appropriate adjustment in the reverberation formula. The name Sabine absorption coefficient is suggested for the usual coefficient computed by the reverberation technique, to distinguish it from the energy absorption coefficient that does not exceed unity.
Acoustical-Impedance Characteristics of Sintered Stainless Steel
Authors: Anderson John E.
Published: September 2005

Impedance characteristics of various sintered stainless-steel resistance elements were measured. These elements are essentially pure resistances, exhibiting a linear relationship between sound-flow velocity and normalized-flow resistance. Processing parameters that permit consistent attainment of desired stable acoustical characteristics were discovered.
Definition Measurement Apparatus
Authors: Collins J. L. , Anderson C. D.
Published: September 2005

A laboratory apparatus for the measurement of acoustic “definition” or “clearness” as proposed by Professor Erwin Meyer [J. Acoust. Soc. Am. 26, 630–636 (1954)] has been built and used to determine the definition of several school classrooms. This paper will describe the instrumentation used for making these measurements and discuss a few of the typical readings. Further results of the definition measurements will be presented in the paper “Acoustic Measurements in School Classrooms” by Mr. R. N. Lane et al.
Effects of Shading on Minor-Lobe Level and Beamwidth in Symmetrical Uniformly Spaced 6- and 4-Element Arrays
Authors: Karbo Donald J.
Published: September 2005

The effects of shading on number of minor lobes, level of minor lobes with respect to the principal lobe, and beamwidth are analyzed for symmetrically shaded, uniformly spaced 6- and 4-element arrays. For a 6-element array shaded 1:a:b:b:a:1, there are no minor lobes above the parabola 125−30 a+a2−20b=0. Between this parabola and 5−2 a+a2−4b=0, there is one minor lobe, while between the second parabola and the straight line b−3a+5=0 there are two minor lobes, which may or may not be equal in amplitude. Below the straight line, there is again only one minor lobe. Curves in the a-b plane for constant first and second minor-lobe levels are presented, as well as curves of constant beamwidth for the half-wavelength spacing. For the 4-element array shaded 1:c:c:1, there are no minor lobes when c is greater than 3. Curves for minor-lobe level and beamwidths for the half-wavelength spacing as a function of c are presented.
Propagation of Displacement Waves in the Sea
Authors: Liebermann L. N. , Rasmussen R. A.
Published: September 2005

In the past, underwater acoustic data have been obtained with pressure-sensitive hydrophones, which neglect the particle displacement in an acoustic wave. Displacement reception possesses certain advantages, among which are the possibilities of direction finding and also of acoustic observations at the sea surface. The theory of operation of a displacement hydrophone is discussed and the technique is given for constructing instruments sensitive to a displacement of 0.1 Å at 1000 cps. The propagation of displacement observed at sea is compared with theoretical predictions. The vertical component of displacement is found to be maximum on the sea surface as predicted; the horizontal component vanishes at the sea surface, but at greater depths can be used to observe the wave-propagation direction. At short ranges, the acoustic-displacement field is closely approximated by a dipole source; at longer ranges, the displacement field diminishes less rapidly (1/r dependence) than is predicted by the dipole theory.