bluuebunny/crossref_metadata_2025 huggingface dataset:
Some characteristics of the glottal sound source of deaf children
Authors: Monsen R. B. , Engebretson A. M. , Fisher W. M.
Published: October 2005

The glottal source of 28 hearing-impaired and five normally hearing adolescents is compared with respect to the waveshape produced and the spectrum. The measurement device used employs a uniform reflectionless tube, recently described by M. M. Sondhi [J. Acoust. Soc. Am. 55, 396 (1974)]. Among the variety of glottal waveshapes produced by normal talkers, the opening phase of the wave appears typically less steep and is longer than the closing phase. In contrast, many of the deaf subjects commonly produce a waveshape reversed in phase with respect to normal: the opening phase is shorter and steeper than the closing phase. Such phase differences need not be a primary factor in abnormal voice quality. However, the abnormal laryngeal control necessary to produce the observed waveshapes may adversely affect the normal production of speech sounds. [Supported by NINDS Grant NS 03856.]
Auditory evoked responses to simultaneous syllables and chords
Authors: Benson P. J. , Shand M. , Smith T. S.
Published: October 2005

Schulman et al. (1974) report at this meeting they have found significant differences between the auditory evoked responses (AER) to syllables and pure tones in the P3 wave. Using a similar paradigm, we presented subjects a sequence of CV syllables /ba/ and /da/ and musical chords (C major and minor) with speech and chords mixed binaurally. Subjects attended to either the speech or chords in any one run and counted the infrequent target stimuli. The target stimulus, e.g., /da/ occurred in a 1:4 ratio with the nontarget /ba/. Both of the unattended stimuli occurred equally often. AERs were recorded at the vertex and symmetric left and right temproparietal locations for targets and nontargets. Preliminary results for six subjects show consistent differences between syllable and chord conditions.
Dependence of human brainstem evoked potentials on signal duration and rise-fall time
Authors: Hecox K. , Squires N. , Galambos R.
Published: October 2005

This report extends observations presented by Hecox and Galambos at the 1973 Los Angeles Meeting of this Society on the acoustical dependencies of the human brainstem evoked potential. We report here on the latency and amplitude dependency of wave V, the most reliably elicited response component, as a function of signal duration and rise-fall time. Increasing the rise time of a 30-msec noise burst produces a striking increase in response latency and no change in response amplitude. With rise time held constant, changing stimulus fall time alters neither response latency nor amplitude. Longer latencies and smaller amplitudes occur whenever stimulus duration (the ontime, 0.5–30 msec) increases with a silent period (off-time) under 60 msec, and whenever off-time shortens with on-time held constant. The sensitivity of these responses to signal rise time, and their relative insensitivity to fall time and duration, demonstrate that the human brainstem evoked potential is an onset response.
Most comfortable loudness for pure tones sad speech in the presence of masking noise
Authors: Richards Alan M. , Lehman Herbert H.
Published: October 2005

Pure-tone and speech most-comfortable-loudness levels (MCLs) were determined in noise and quiet. A Békésy-type tracking task was used to determine the MCLs under all conditions. During the first phase, the subjects (N = 12) tracked their MCLs for five pure-tone frequencies (250, 500, 1000, 2000, and 4000 Hz) in the presence of four white-noise levels (55, 65, 75, and 85 dB SPL) and in quiet. During the second phase, speech MCLs were tracked under the noise conditions identical to those of the tones. The results indicated that the mean MCLs for tones between 500–4000 Hz, and for the speech stimuli, systematically increased as a function of the masker level. The rate of this increase was about 7 dB/10-dB noise increment for both stimulus modes when the level of the noise exceeded 65 dB. At noise levels below 65 dB SPL, pure-tone MCL increases were only about 3 dB/10-dB noise increment, while the slope of the speech MCL function remained relatively unchanged. The results further indicated that the variability of MCL judgments for both stimulus modes decreased as a function of increased masking. The present MCL data were related to other investigations of loudness growth in noise.
Wave propagation in a piezoelectric crystal shell
Authors: Dökmeci M. Cengiz
Published: October 2005

In this study, we first present a two-dimensional theory of high-frequency vibrations of piezoelectric crystal surfaces, coated with thin electrodes. The theory is systematically and consistently extracted using a method of direct integration [cf. M. C. Dökmeci, J. Acoust. Soc. Am. 54, 292 (1973) and L. Al, Nuovo Cimento 7, 449–454 (1973)] appropriate to the linear expansions of the mechanical and electric displacement fields, from the three-dimensional field equations. The interactions between crystal plate and electrodes are taken into account through the usual continuity conditions. Next, we use logarithmic convexity arguments to enumerate a set of sufficient conditions for uniqueness in the theory [cf. M. C. Dökmeci, “On the Higher-order Theories of Piezoelectric Crystal Surfaces,” to appear in J. Math. Phys. 15, (1974)]. Further, we exhibit some applications of the theory, and, in particular, study wave propagations in an infinite circular cylindrical anisotropic thin shell of uniform thickness, with its inner and outer faces being both traction free and completely coated with electrodes. The transcendental equations of resonant frequencies are obtained and the dispersion curves are calculated for a rotated Y-cut quartz shell. The results are compared with those of unplated shell, and considerable deviations in the dispersion spectrum are found. [Work supported by the Turkish Office of Naval Research.]
M61A1 gunfire environmental effects on F-14A aircraft structure and AN/AWG-9 equipment
Authors: Popolo J. J. , Curtis A. J.
Published: October 2005

The program to define and assess the environmental effects on the F-14A aircraft structure and the AN/AWG-9 avionics equipment due to firing of the M61A1 rapid-fire gun is described. An initial assessment was made from acoustic and vibration data obtained from a ground test article which consisted of a mock-up of the forward fuselage of the aircraft, with the gun and simulated equipment installed, cantilevered from a strong back. The final assessment and verification of M61A1/F-14A and M61A1/AWG-9 compatibility was obtained from vibration measurements and observation of system performance during firing of the gun in a production aircraft, both on the ground and during a range of flight conditions. The F-14A M61A1 gun blast tube, gas diffuser, and support structure were specifically designed to withstand the gun blast and recoil loads. The M61A1 acoustic and vibration input to the equipment was attenuated by the installation of an absorptive acoustic liner and damping tape applied to the equipment shelves. To define the vibration environment for the avionics, a statistical analysis of the data was performed. The results of this analysis compare favorably to the design and test requirements imposed on the equipment, based on a prediction made at the inception of the F-14A program in early 1969.
Characteristics of 20-mm gunfire on the A-7 weapons system
Authors: Hancock R. N.
Published: October 2005

Four versions of 20-mm guns have been utilized on the A-7 aircraft, encompassing firing rates from 960 rounds per minute to 6000, and both fuselage and pod mountings. Muzzle blast pressures rather than recoil loads have proved to be most severe for nearby equipment operation. These pressures, with peak to rms ratios in excess of 6, and resulting vibrations are described in terms of waveforms and statistical properties. Studies of methods to control both noise and vibrations and the limitations encountered are briefly discussed. A technique developed for laboratory simulation employing a series of shock pulses for equipment response testing is discussed.
Anomalous vibrations of rotating wire stranding machinery
Authors: Pierce Allan D.
Published: October 2005

A recent design of a large rotating wire strander exhibited large anomalous vibrations at a frequency twice that of the rotation speed. The present paper discusses the author's opinion as to the cause of these vibrations. The principal part of the strander consists of a horizontal hollow steel cylinder which rotates about its axis. Windows (i.e., holes) of dimensions comparable to the cylinder radius are spaced along two sides of the cylinder. The natural tendency of the cylinder to sag under its own weight is therefore asymmetric, because of the unequal average bending stiffness when the holes are up and down as contrasted to when they are on the sides. Perturbation treatment of the appropriate equations leads to a model roughly describable as a rotating beam with an axially distributed hypothetical centrifugal force rotating at twice beam rotation frequency. The magnitude of the force per unit length is proportional to the weight per unit length times the bending stiffness fluctuation divided by average bending stiffness. Numerical computations based on the model corroborated observed amplitudes of vibration. [Work supported by Southwire Co.]
Vibration propagation in frame structure
Authors: Gan W. S.
Published: October 2005

We consider propagation of longitudinal and transverse sound waves along T-shaped concrete frame structures which are combinations of walls and ceilings. The formulation of Morse [J. Acoust. Soc. Am. 22, 219 (1950)] and Muskat et al. [Geophysics V, 115 (1940)] is followed throughout, though not in detail. For the horizontal part of the structure, the boundary condition of the vanishing of the normal components of stresses over the bounding surfaces is used. Both a plane longitudinal wave and a transverse wave when incident on a solid/vacuum interface produce both a reflected longitudinal wave and a reflected transverse wave. For propagation along the vertical part of the structure, we use the boundary conditions that both the displacements and the stresses at the solid/solid interface shall be continuous. Transmission coefficients are plotted as functions of the incident frequencies and the angles of incidence. They are compared with the theoretical works of Cremer [Acustica 3, 317 (1953)] and Arenberg [J. Acoust. Soc. Am. 20, 1 (1948)] because no previous experimental work has been done for this type of structure. Comparison shows reasonable agreement on the shape of transmission coefficient curves.
Comments on “Rytov's method and large fluctuations” [L. R. Brownlee, J. Acoust. Soc. Am. 53, 156–161 (1973)]
Authors: de Wolf D. A.
Published: October 2005

Rytov's approximation has been studied extensively by workers concerned with waves in random media, although this fact appears not to be appreciated by researchers in acoustics. This letter indicates that the approximation is not equivalent to the Born approximation in its domain of validity. A guide to recent literature is given.
Influence of interaural phase on forward masking
Authors: Punch Jerry , Carhart Raymond
Published: October 2005

This study investigated the degree to which masking level differences (MLDs) obtained by six normal-hearing subjects during simultaneous masking continue to be manifest during the forward masking that follows termination of the masker. Thresholds for 500-Hz probe tones of 745 msec were obtained in quiet and in a 1000-msec narrow-band noise centered at 500 Hz. Probe tones were increased to as much as 945 msec when forward masking was measured. The interaural conditions compared were SmNm, SmN0, SmNπ, S0N0, SπNπ, S0Nπ, and SπN0. MLDs obtained during simultaneous masking were comparable to those reported by earlier investigators. The same hierarchy among interaural conditions characterizing simultaneous masking persisted during forward masking for about the first 5.5 to 7.5 msec. Thereafter, the two antiphasic conditions (S0Nπ and SπN0) continued to exhibit modest MLDs. These were observed even at the longest postmasker interval (Δt = 200 msec) employed, where the mean MLD was 3.3 dB. Forward masking does not appear to represent merely the residuum of processes occurring during simultaneous masking. Instead, nonidentical neural processes which are at least to some degree central in origin seem involved in two masking phenomena.
Noise measurement in reverberant rooms
Authors: Waterhouse Richard
Published: October 2005

A short review is given of the acoustics of the reverberation chamber. Earlier work by Sabine, Bolt, and Cook is discussed, and the effects of moving the position of the source, the receiver, and a reflecting vane are considered. The statistical properties of reverberant sound fields without time-varying elements are reviewed, and the space-variances obtained by averaging at discrete points and along a continuous traverse are compared. The case of the reverberant sound field produced by a band of noise is then taken up, and finally some areas needing further study are mentioned. These include the accurate measurement of the power output of a pure-tone source, and the theory and practice of moving reflectors.
Analysis of errors in measuring machine noise under free-field conditions
Authors: Hübner Gerhard
Published: October 2005

Even under free-field conditions there are three types of errors in the measurement of machine noise: (1) the nearfield error, (2) the error caused by suing a limited number of measuring points, and (3) the error in measuring sound pressure at each point. The magnitude of these errors is discussed.
Noise from aerial bursts of fireworks
Authors: Maglieri Domenic J. , Henderson Herbert R.
Published: October 2005

As part of a broad study relating to sonic-boom exposures and their effects on people and building structures, measurements were made of the shock-wave pressure time histories resulting from aerial bursts during a professional fireworks display. The information derived from these tests may be of general interest in regard to community noise exposure criteria. Data were obtained using standard NASA sonic-boom instrumentation located at two positions near the ground almost directly under the air burst which occurred at about 300 ft altitude. Ground-launch motors varied in size from 4 to 6 in. in diameter and had composition charges of from 2 to 3 lb. Peak overpressures of up to 15 psf were observed. Signature durations were about 12 msec, as compared to normal sonic-boom signatures having overpressures and durations varying from about 1 to 3 psf and 100 to 300 msec, respectively. Also included information relating to the frequency spectra and impulses, and comparisons are made with available hearing damage criteria.
Upstream and downstream sound radiation into a moving fluid
Authors: Ingard Uno , Singhal Vijay K.
Published: October 2005

An experimental demonstration of the influence of fluid motion in a duct on the sound pressure field radiated in the upstream and downstream directions from a stationary sound source is presented. The measured ratio between the upstream and downstream sound pressure amplitudes in the duct is presented as a function of the flow Mach number in the range M = 0–0.5. The results are discussed in the light of a mathematical analysis of the problem.
Some beam-steering properties of discretely phased symmetric arrays
Authors: Sjoding Theodore W.
Published: October 2005

It is shown that a beam formed from a uniformly shaded receiving array that can be partitioned into a symmetric array pair and which uses uniform incremental electrical delays is steerable in almost uniform pointing increments over small angles. This result assumes that the beam pointing direction is defined by the difference beam null. A specific discrete beam spacing is achieved by a unique choice of beamformer delay increment or integer submultiples of that delay increment. A relationship is derived for determining that delay increment.
Formal solution of the surface Helmholtz integral equation at a nondegenerate characteristic frequency
Authors: Rogers Peter H.
Published: October 2005

The surface Helmholtz integral equation (SHIE) for the acoustic pressure on an object whose surface S vibrates harmonically with a given normal velocity, is known to fail by nonuniqueness at certain “characteristic” frequencies. These frequencies are identical to the eigenfrequencies of the homogeneous Dirichlet problem for a volume of fluid enclosed by the surface S. This paper deals with nondegenerate characteristic frequencies, that is, frequencies at which exactly one independent solution of the interior homogeneous Dirichlet problem exists but no nontrivial solutions of the interior homogeneous Neuman problem exist. The problem is reformulated in terms of operators on the Hilbert space of functions which are square integrable over S. The eigenvectors of the (skew-Hermitian) Green's function operator for the interior Neumann problem provide an orthonormal basis for the space and, hence, the unknown Green's function operator for the exterior Dirichlet problem can be completely specified by its matrix elements with respect to these eigenvectors. The nonuniqueness failure of the SHIE is found to result from the indeterminacy of a single element of this infinite matrix. An expression for the indeterminate matrix element is obtained directly from the SHIE by a perturbation technique yielding a formal solution of the problem.
Transverse-vibration responses of nonuniform, internally damped cantilever beams. I
Authors: Kerlin R. L.
Published: October 2005

The Bernoulli-Euler theory of transverse beam vibration, suitably extended to take into account internal beam damping, is used to derive closed-form expressions for the mechanical driving-point impedance and force transmissibility of two types of nonuniform cantilever beams that are driven at their free ends by a sinusoidally varying point force. The beams are truncated and of rectangular cross section; they have a linearly tapered depth and have either (1) constant breadth or (2) parabolically varying breadth. Representative computations of the frequency dependence of impedance and transmissibility are plotted for beams having the same length and mass as an equally long and equally massive uniform reference beam. Significant attenuation or amplification of force transmissibility is observed, depending on the proportions of the beams and on whether their depth tapers towards their fixed or free end. The measured resonance frequencies of a set of nonuniform aluminum (6061-T651) cantilever beams agree closely with the predictions of theory.
Vibratory patterns examined by real-time and time-averaged holography
Authors: Khanna S. M. , Tonndorf J. , Janecka I.
Published: October 2005

The vibratory patterns of a circular plate were studied systematically by means of real-time holography and also by time-averaged holography. The present real-time method, an extension of the original method of Stetson and Powell (1965), allows one to view reconstructions of vibratory patterns directly and observe their changes as the frequency and/or amplitude of the signal are being varied. The contrast obtained is much poorer than that given by the time-averaged method. Nevertheless, the real-time method permits one to pinpoint specific mode patterns for later recording by time-averaged holography. In a given situation, time-averaged holography records approximately twice as many alternate bright and dark fringes as the real-time method.
Numerical method for computing multipath interference in a time-varying medium
Authors: DeFerrari Harry A.
Published: October 2005

Ray-model simulations of multipath interference of CW signals require precise computation of travel times along the paths between source and receiver. The travel times for each ray path must be known with sufficient precision to resolve the phase of the arrival. The effects of time-varying sound-speed profiles can then be simulated by allowing the state of the medium to change slightly for each multipath summation. This letter is concerned with a numerical method for making such computations.
Fundamental-frequency component of a finite-amplitude plane wave
Authors: Merklinger Harold M.
Published: October 2005

A method due to Westervelt [Proceedings of the Third International Congress on Acoustics, Stuttgart 1959 (Elsevier, Amsterdam, 1961), Vol. 1, pp. 316–321] is used to describe the fundamental frequency component of an initially sinusoidal finite-amplitude plane wave. The result, expressed in terms of the extra loss (in decibels) introduced by nonlinearity, is given as 10 log10[1 + Γ2(1 − e−2σ/Γ)2/16] where Γ is the acoustic Reynold's number and σ is range normalized to the shock formation distance. This relation is shown to lie within 1 dB of Blackstock's results obtained from Burgers' equation [D. T. Blackstock, J. Acoust. Soc. Am. 36, 534–542 (1964)].
Feasibility of rapid critical bandwidth estimates
Authors: Haggard Mark P.
Published: October 2005

While partly influenced by critical bandwidth (CB), direct measures of auditory sensitivity such as pure-tone masked threshold and frequency-difference threshold reflect other factors as well. In an attempt to find a rapid direct estimation of CB, two experimental tasks were explored. The difference threshold for frequency modulation of a narrow stop band in a noise spectrum was found not to provide a good estimator as the task showed the variability over subjects usual with measures of performance level. The second task, threshold frequency difference required for a partly masked tone to achieve a pitch separate from that of a higher-frequency masking tone, furnished absolute values and functions over frequency very similar to the classical CB.
Effect of vowel environment on the duration of consonants in the speech of three-, six-, and nine-year-old children
Authors: DiSimoni Frank G.
Published: October 2005

The effect of vowel environment on consonant duration previously noted for adults is not present in the speech of three-, six-, or nine-year-old children.
Nonlinear forced and free vibrations in acoustic waveguides
Authors: Keller Joseph B.
Published: October 2005

Nonlinear acoustic theory is used to show that the cutoff frequencies and the resonant frequencies of modes in acoustic waveguides of finite length depend upon the mode amplitude. The amplitude εn, of mode n > 0, produced by a periodic piston motion of amplitude δn, is also determined. It is found that at and near a resonant frequency, εn≏δn1/3 while at and near the cutoff frequency εn≏δn1/2. Away from these frequencies εn≏δn, as linear theory predicts. Thus the infinite amplitude, which linear theory yields at cutoff and resonance, is avoided. The results are obtained simply by using the result for the propagation constant as a function of mode amplitude given by J. B. Keller and M. H. Millman [J. Acoust. Soc. Am. 49, 329–333(1971)].
Parametric detection of low-frequency acoustic waves in the nearfield of an arbitrary directional pump transducer
Authors: Rogers Peter H. , Van Buren A. L. , Williams A. O. , Barber J. M.
Published: October 2005

We analyze by first-order perturbation theory the manner in which a low-frequency acoustic wave and a high-frequency pump beam interact nonlinearly to produce a sum- and a difference-frequency component. Provided that its acoustic beam is well collimated, the pump source can be of arbitrary shape, with arbitrary acoustic distribution over its surface. For the case where the incident low-frequency wave is plane, we derive the following result: To a close approximation, the acoustic particle velocity at the difference frequency is proportional to the product of (a) the velocity potential of the pump beam, calculated at the difference frequency, and (b) the response function, at the low frequency, of an endfire array stretching from the pump source to the plane of a receiver. The result also holds for the sum frequency. We also prove that the result holds—with a modified endfire response function—when the low-frequency source is at a finite distance. For a circular plane piston as pump source, we discuss the achievable directivity in detail; also, we show that focusing the pump beam to obtain a stronger signal can succeed only at the expense of good directivity.
Amplitude fluctuations of low-frequency underwater acoustic pulses reflected from the ocean surface
Authors: Nichols R. H. , Senko A.
Published: October 2005

Measurements made with a fixed-bottomed source and fixed-bottomed receivers in water 2400 f deep show that for small ocean wave heights, up to about 3 ft, the fluctuations in amplitude of surface-reflected sine-wave signals at frequencies of 400, 750, 1000, and 1500 Hz at grazing angles of 18°, 31°, and 85° are in general agreement with theoretical predictions. In this wave height range, the coefficient of variation increased with increasing frequency, grazing angle, and wave height, reaching a maximum at about 5-ft wave height for each combination of frequency and grazing angle. As the wave height increased further, up to 30 ft, the coefficient for a given combination of frequency and grazing angle generally decreased. For a given combination of frequency and grazing angle, the average peak level of the reflected pulses does not appear to depend strongly upon wave height.
Effect of the forcing function on the vibratory modes of circular membranes
Authors: Ropper Allan
Published: October 2005

The descriptive mathematics of a clamped circular membrane, driven at its center, is reviewed. This classical analysis of Rayleigh is extended to include the effect of elliptical off-center forcing functions. A digital computer was used to solve the equation describing these vibratory modes and to plot the results. Stable patterns are shown to exist at frequencies between those of the classical vibratory modes, and to be formed by a vector sum of these patterns. The mathematically calculated vibration patterns are compared to those observed by holographic techniques. Close agreement was found between the observed and calculated results.
Reflection and transmission of Rayleigh waves by the edge of a deposited thin film
Authors: Yoneyama Tsukasa , Nishida Shigeo
Published: October 2005

The reflection and transmission of Rayleigh waves by the edge of an isotropic thin film deposited on an isotropic substrate is solved within the first-order approximation relying on the Wiener-Hopf technique under the assumption that the film is thin enough compared to the wavelength. Straight-crested Rayleigh waves are assumed to impinge on the edge of the film perpendicularly from the unplated side of the substrate. In formulating the problem mathematically, Tiersten's boundary condition is employed to take into account the effects which the deposited film imposes on the elastic waves in the substrate. Expressions for the radiation coefficients of both of the bulk waves, longitudinal and transverse, and for the reflection coefficient of the Rayleigh wave are derived and evaluated numerically for gold, aluminum, nickel, and copper films deposited on the fused-silica substrate. It is found that the radiation coefficients, especially the one for the transverse bulk wave, exceed the reflection coefficient by a factor of 10 or more in magnitude. The reflection and transmission of the Rayleigh wave is influenced mainly by the shear velocity and shear modulus μ′ of the film material, whereas the Lamé constant λ′ of the film does not have as much effect on both the reflection and transmission.
Natural frequencies of monoclinic circular plates
Authors: Padovan J. , Lestingi J.
Published: October 2005

The present paper studies the effects of material anisotropy on the frequency eigenvalues of fiber reinforced circular plates. A general solution is developed by means of an integral transformation of the plate equations together with the subsequent use of power series expansions to solve the resultant transformed equation. In terms of this solution, the effects of fiber orientation on the frequency eigenvalues are discussed at length.
Effects of prestress on the acoustic behavior of panels
Authors: Dym Clive L.
Published: October 2005

The vibrational and acoustical behavior of one- and two-dimensional walls is examined, in the presence of a constant compressive prestress. It is shown that the resonance frequencies are lowered, and that the critical frequency is raised, by the presence of the prestress. Further, a mass-law approximation is derived for the transmission loss, and it is shown to give higher values of the transmission loss than are found for an unstressed panel.
Variations of sound intensity for mistuned consonances
Authors: Rigden John S.
Published: October 2005

The intensity of sound resulting from the combination of two sinusoidal components whose frequencies are very nearly ratios of small integers (mistuned consonances) varies periodically with a frequency equal to that of the perceived beats. As the mistuning of a consonance increases the intensity variations likewise increase.
Plane wave propagation in stratified anisotropic media
Authors: Schoenberg M.
Published: October 2005

The solution for plane harmonic waves propagating in a stratified region, where each layer is homogeneous, elastic, and fully anisotropic (21 constants of elasticity) is presented. The treatment of various boundary and or radiation conditions at the top and bottom of the layered region is discussed.
Frequency spectra information on storm-related infrasound
Authors: Bowman H. S.
Published: October 2005

Infrasonic data were collected and associated with various severe storms. The local and/or distant storm phenomena occurred in a variety of geographic locations having numerous terrain from orographical to plane. Acoustic spectral characteristics of some of the infrasonic signatures were studied in order to possibly assort the various storms. Preliminary results indicate an apparent procedure for classification via spectral analysis of infrasound propagation data.
Wave propagation in elastic rings and helical coils of small pitch
Authors: Haines D. W. , Chang N. , Huang C. H.
Published: October 2005

The problem of harmonic waves propagating around an elastic ring is formulated in generalized plane stress and solved. Three dispersion curves can be described. The wavenumber of the first branch is always real, but the second and third possess segments of real, imaginary, and complex wavenumbers. The third branch has a narrow range at low frequencies, for which the phase and group velocities are of opposite sign. As the wavelengths become progressively shorter, the dispersion curves approach their counterparts for straight bars. The solution is also valid for helical coils of small pitch and, when converted to plane strain, for similar waves in cylindrical shells and cylinders.
Rayleigh-wave reflection from groove and step discontinuities
Authors: Tuan Hang-Sheng , Li Robert C. M.
Published: October 2005

In an important new class of signal-processing devices using elastic surface waves, the reflection of a Rayleigh wave from grooves is a key feature. In the present paper, a boundary-perturbation technique is employed to determine the reflection of a Rayleigh wave from either a shallow groove or a low step in the surface of an isotropic elastic half-space. Comparison with available experimental data for the case of the rectangular groove and step yields excellent agreement.
A comparison of ray theory, modified ray theory, and normal-mode theory for a deep-ocean arbitrary-velocity profile
Authors: Blatstein I. M. , Newman A. V. , Überall H.
Published: October 2005

For a typical sound-velocity profile arbitrary shape in the deep ocean, the validity of ray theory, modified ray theory, and normal-mode theory is assessed by a mutual comparison of their predictions in the shadow zone, caustic region, and double-arrival regions of the first convergence zone caustic. Modified ray theory is found to constitute a reasonable approximation to the more exact normal-mode theory.
Influence of utterance length upon bilabial closure duration for /p/ in three-, six-, and nine-year-old children
Authors: Di Simoni Frank G.
Published: October 2005

The effect of utterance length on phoneme duration, previously noted for adults, is present in the speech of children three years of age.
Speech Power and Its Measurement
Authors: Sivian L. J.
Published: September 2005

The paper is chiefly concerned with the important speech power quantities—frequency spectra, distributions of instantaneous, average, syllabic and peak amplitudes, etc.—as they obtain in actual speech for a large range of voices, talking levels, and subject matters. The analysis is not nearly so complete nor so fine-grained as that which, in principle, can be derived from oscillographic records of individual speech sounds. Its advantage is in the speed with which data can be secured, under widely varying conditions and on a scale which warrants statistical conclusions. Some of the methods in use for measurements of this type are described. A “level analyzer” has been developed, primarily for the measurement of average and peak pressure amplitudes in speech and music, both as to magnitude and as to position in the frequency spectrum. Illustrative results are given for samples of speech, music and noise.
Articulation Testing Methods
Authors: Fletcher H. , Steinberg J. C.
Published: September 2005

This paper is chiefly concerned with the technique of making articulation tests. The construction of a syllabic testing list, the selection of a testing crew, the methods of comparing articulation data for various crews, and the significance of the test as a measure of the speech capabilities of a system are discussed. Various types of lists for different uses are also discussed.
Elimination of Noise in Machinery
Authors: Kimball Arthur L.
Published: September 2005

Direct and indirect noise.

Three ways of treating problems:

(1) Elimination at source.

(2) Screening.

(3) Elastic Suspension.

Brief discussion of these with illustrations.

Remarks on theory of elastic suspension.

Further illustrations from practice.
The Binaural Localization of Pure Tones
Authors: Wightman E. R. , Firestone F. A.
Published: September 2005

Measurements of phase difference and amplitude ratio of the sound entering the ears of a man-shaped wax dummy were taken with the source at varying azimuths around the head; at 256, 1024 and 1944 cycles per second; and at distances of 20, 50, 100 and 400 cm. from the head. The measurements at the two frequencies agree with the values published by Hartley and Fry computed on the assumption that the head is a rigid sphere in free space, except that the observed values of amplitude ratio are about 13 per cent. less than the computed values on account of the interference of the neck. The observed values at 1944 cycles are quite different from the computed values.

As a converse experiment, pure tones of frequency 256 cycles were presented binaurally to eight different observers, the phase difference and amplitude ratio of the acoustical pressures at the two ears being known and adjustable. The observers were asked to state the direction and distance of the apparent source of sound. Only three of the eight observers were influenced in their judgment of direction by the phase difference and even they were rather inaccurate. All were influenced more or less in judging direction by the amplitude ratio. None was able to tell the distance of the source by the amplitude ratio.
The Two Points of View in Teaching the Control of the Human Voice in Speech and Song
Authors: Simmions Louis
Published: September 2005

First: The School of the control of the vowels. This includes the teaching of the Bell Canto. The Old Italian School where the human voice is treated purely as an instrument where beautiful sound predominates.

Second: The Consonantal School of dramatic recitation in speech and in song where beautiful sound in voice development is not a prime consideration. This school belongs to the German and French.

The speaker, through practical demonstration, believes he can prove that the constant struggle between these two schools can be eliminated and coordinated through scientific investigation of the action of the Ventricles of Morgagni—two air spaces situated in the throat between the true and false vocal chords. According to some authorities and the speaker's own investigation these two ventricles or air pockets act as a valve and control the air pressure above the oscillation of the vocal chords, consequently controlling the binding of the two elements in speech and in song.
II. Theory of the Horn Type Loud Speaker
Authors: Hanna C. R.
Published: September 2005

In the electromagnetic driver the force per unit current has been shown to be a function of the inductance and the negative stiffness resulting from the presence of the steady magnetic field. In this paper it is proven that the force per unit voltage in the electrostatic device is a similar function of the capacity and the negative stiffness due to the steady electrostatic field.

A new concept called Motional Admittance is introduced for the electrostatic loud speaker and this is shown to be similar in its mathematical form to the Motional Impedance of the electromagnetic driver.

A calculation of the ultimate theoretical efficiency that may be obtained with an electrostatic speaker having a pure resistance radiator and covering a given frequency range is given. It appears that efficiencies between 5 and 10% may some day be obtainable with good fidelity of reproduction.
Are Acoustical Materials a Menace in the Hospital?
Authors: Neergaard Charles F.
Published: September 2005

Hospitals must be made quiet. To determine what would best meet their exacting requirements as to cleanliness, maintenance, permanance and cost, a series of tests were undertaken on the various acoustical treatments available. To determine further whether these materials would act as abiding and breeding places for bacteria and so present a menace in hospital construction, experiments were carried out at the bacteriological laboratories of Yale University on three felt materials, Celotex, and an acoustical plaster. A culture of B. prodigiosus, an easily recognizable organism, was first brushed, then sprayed on, and the materials examined microscopically every 48 hours or so, at the surface and three different depths. The results of the two methods of application were almost identical, and varied very little for the five materials. After two days in only the outer layers were bacteria found and after eight days they had disappeared entirely. The tests were made under severe conditions and ordinarily bacteria could probably not penetrate so deeply. It would appear that acoustical materials presented no greater menace than the structural surfaces they would replace. They are generally used on ceilings only, so that the chance of contamination is slight, and the washing and fumigating done routinely should safely disinfect them along with the walls, furnishings, etc. Acoustical engineers are alive to the peculiar needs of hospitals and since these tests, several new and better methods of acoutical treatment have been devised.
Area and Pattern Effects in Absorption Measurements
Authors: Parkinson John S.
Published: September 2005

The coefficient of absorption of an acoustical material as obtained by the reverberation chamber method varies with the area tested and the shape of the sample. A theoretical explanation of this phenomenon is outlined, showing that the results cannot be attributed entirely to edge affects, and explaining the discrepancies which appeared when the diffraction theory was applied to the tests.

Test results show the efficiency of various patterns and arrangements of treatment. It can be shown that the absorption coefficient isproportional to K(p/A)where p is the perimeter of the individual sample and A the area. It can be shown also that the absorption per square foot of total pattern area is always proportional to the ratio of treated to untreated area, regardless of the pattern arrangement. This relation is formed to hold good for all frequencies with the same material, but not for different materials. Typical questions of construction and design can be answered as a result of the data.
Recent Advances in Sound Absorption Measurements
Authors: Chrisler V. L. , Snyder W. F.
Published: September 2005

Part I. Measurement of Sound Absorption by Oscillograph Records. The method is much the same as that described in the previous paper except the decay is measured through as much as 50 decibels. The results agree very closely with those obtained by the ear using the usual reverberation method. The coefficients for a few materials are given as determined by both methods.

Part II. Absorption of an audience. The absorption of an audience has been determined when seated in different kinds of chairs. The results of these measurements are given with the suggestion that they should be checked by other observers.
Measurement and Calculation of Sound Insulation
Authors: Knudsen Vern O.
Published: September 2005

The term “reduction factor” has been given different meanings. Architects, builders and even many acoustical engineers, are not aware of these different meanings, and consequently unnecessary confusion arises whenever insulation data from different laboratories are compared. Thus, the “reduction factors” for the same type of panel measured at the Bureau of Standards and at the Riverbank Laboratories may differ as much as fifteen decibels. Buckingham and also Davis have shown that the quantities measured at different laboratories cannot be directly compared. However, these quantities may be converted into quantities—the coefficients of transmission for the panel—which do admit of direct comparison. Under suitable test conditions these coefficients should be independent of the test room and also of the method of testing. The writer has made some insulation measurements by three different methods—typical of the methods now in use at different laboratories—and obtains good agreement for the coefficients of transmission by all three methods. By assigning reasonable properties to the test rooms at the Riverbank Laboratories it is shown that Sabine's results on the insulation of rigid partitions are in essential agreement with Chrisler's results. A simple formula is suggested for calculating the insulation properties of rooms.
THEORY OF THE HORN-TYPE LOUD SPEAKER
Authors: Hanna C. R.
Published: September 2005

A brief review of the properties of horns as described in recent years by various writers is given. Reasons for the small throat, the large mouth, and the exponential shape are discussed.
THE PHASE DIFFERENCE AND AMPLITUDE RATIO AT THE EARS DUE TO A SOURCE OF PURE TONE
Authors: Firestone F. A.
Published: September 2005

Measurements of phase difference and amplitude ratio of the sound entering the ears of a man-shaped wax dummy were taken with the source at varying azimuths around the head; at 256, 1024, and 1944 cycles per second; and at distances of 20, 50, 100, and 400 cm. from the head. The measurements at the two lower frequencies agree with the values published by Hartley and Fry computed on the assumption that the head is a rigid sphere in free space, except that the observed values of amplitude ratio are about 13 percent less than the computed values on account of the interference of the neck. The observed values at 1944 cycles are quite different from the computed values.
A NEW ACOUSTIC ANALYZER—DETERMINATION OF THE SOUND SPECTRA PRODUCED BY AIRCRAFT IN FLIGHT
Authors: Delsasso L. P.
Published: September 2005

An Electro-Mechanical Frequency Analyzer has been adapted to the determination of the sound spectra of aircraft in flight. The complex source of sound is converted into potential fluctuations by a microphone and high quality amplifier. The output of the amplifier is applied to a modified quadrant electrometer, the needle of which forms part of a sharply resonant mechanical circuit. The natural period of the mechanical circuit is made continuously variable by a tri-filar suspension and can be determined from a single micrometer reading. An analysis of a complex source is made by observing the amplitude of vibration and natural period of the mechanical circuit for each component. By a previous calibration of the instrument these observations are sufficient to determine the amplitude and frequency components of the complex sound. The instrument has been used to measure the sound spectra of typical passenger and military planes in flight.
PLANE SOUND WAVES OF FINITE AMPLITUDE
Authors: Fay R. D.
Published: September 2005

The principal object of the analysis is to find the change in type of periodic plane waves of sound of finite amplitude propagated in free air.

A solution of the exact equation of motion is obtained as a Fourier series. Due to the nonlinear relation between pressure and specific volume there is found to be a gradual transfer of energy from components of lower frequency to those of higher frequency. Since the effect of viscosity is to attenuate the higher frequency components more than the lower, there is always a wave form having the harmonic components in a stable relation such that the decrease in relative magnitude of any component due to viscosity is compensated by the relative increase due to nonlinearity. The conditions for stability vary with intensity. There is therefore no permanent wave form, but the stable wave will change its form more gradually than any other wave of the same intensity and wave length. The change in type of any wave is toward this stable form. There is a marked departure from the sinusoidal in the stable type even for waves of very moderate amplitude.
THEORY OF SUPERSONIC INTERFEROMETERS
Authors: Hershberger W. D.
Published: September 2005

The theory of the supersonic interferometer is developed by deriving an expression for the impedance of the mechanical system to which the instrument may be reduced. The impedance is found to be a function of the crystal constants, frequency, length of fluid column, acoustic resistance of the medium, and sound absorption in it. The principal features of the behavior of the device are thereby explained and its possible usefulness in the measurement of sound absorption coefficients pointed out.
Some Physical Characteristics of Speech and Music
Authors: Fletcher Harvey
Published: September 2005

Kinematic and statistical descriptions of the physical aspects of speech and music are given in this paper. As the speech or music proceeds, the kinematic description consists in giving the principal melodic stream, namely, the pitch variation and also the intensity and the quality variations. For speech and song, the quality changes are principally described by giving, besides the main melodic stream, two secondary melodic streams corresponding, respectively, to the resonant pitches of the throat and mouth cavities. To this must also be added the positions of the stops and the high pitched components of the fricative consonant sounds as functions of the time. The statistical description consists in giving the average, the peak, and the probable variations of the power involved as the various kinds of speech and music proceed. These general ideas are illustrated by numerous experimental data taken by various instrumental devices which have been evolved in the Laboratories during the past fifteen years.
COMMENTS ON THE THEORY OF HORNS
Authors: Hall William M.
Published: September 2005

The present theory of horns makes a number of assumptions and approximations relative to the nature of the motion within the horns. This paper discusses these assumptions and presents the results of an experimental investigation of the sound fields within a conical and an exponential horn. These results show the conditions actually existing in these particular cases, and therefore indicate to a certain extent the validity of the above assumptions and approximations.