bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation Loss as Predicted by Modified Ray Theory
Authors: Davis J. A.
Published: October 2005

Modified ray theory predicts a frequency-dependent distortion of the sound field which is obtained by ordinary ray theory [J. A. Davis and E. L. Murphy, J. Acoust. Soc. Amer. 50, 101 (1970)]. One qualitative consequence of this distortion is the introduction of a caustic in problems where ray theory predicts a shadow boundary. In order to test this approximate theory and determine the significance of such effects, a computer program has been developed which computes propagation loss for a variety of problems which, while simple, are pertinent to underwater sound propagation. The results of a numerical investigation of propagation loss versus range are presented as a function of frequency, material properties, and boundary conditions (unbounded, pressure release surface, rigid boundary). Comparisons are made with ray theory and available exact solutions. The accuracy of the method in determining propagation loss in the ray-theory shadow zone is strongly dependent upon the treatment of the caustic. The simplest (and most practical) treatment leads to a propagation loss that follows the exact answer to within 2 dB for at least two decades into the shadow region.
Some Curious Analytical Ray Paths for Some Interesting Velocity Profiles in Geometrical Acoustics
Authors: Barnes A. , Solomon L. P.
Published: October 2005

Geometrical acoustics problems in oceanic applications are solved using complicated computer codes. This paper presents some cases that may be used to verify these codes. The velocity profiles are depth dependent, range dependent, and depth and range dependent. The ray path solutions, as well as the velocity profiles, are all expressed in terms of analytical, closed-form, or, at worst, tabulated functions.
Transmission into a Basin Having a Bigradient Sound-Speed Profile
Authors: Smith P. W. , Jones Joie P.
Published: October 2005

A basin is idealized as a flat-bottom region of deeper water surrounded by a gentle, constant-slope transition to a flat-bottom region of shallower water (“shelf”). The speed profile is taken to have a constant negative gradient above a fixed axis depth and a constant positive gradient below, both independent of horizontal position. Analytical estimates for averaged sound transmission loss between a point in the basin and a point at variable range have been formulated from ray theory with lossy specular reflection from the surface and bottom. The approach is an adaptation to the bigradient case of earlier work [P. W. Smith, Jr., J. Acoust. Soc. Amer. 49, 96(A) (1971)]. The loss estimate can be very sensitive to frequency, the depth of the point in the basin, and range, as the variable point moves up the slope and over the shelf. A physical interpretation of this behavior, the dominant parameters, and comparisons with data are discussed. [Study supported by Office of Naval Research.]
The Integral Solution of the Sound Field in a Multilayered Liquid-Solid Half-Space with a Liquid Bottom
Authors: Kutschale Henry W.
Published: October 2005

The integral solution of the wave equation is derived by matrix methods for point sources of harmonic waves in a liquid layer of a multilayered half space of interbedded liquid and solid layers. The solution is in a form convenient for numerical computation on a high-speed digital computer. The integral over wavenumber has singularities in the integrand for guided propagation and is conveniently transformed into the complex plane. By a suitable choice of contours, complex poles are displaced to an unused sheet of the two-leaved Riemann surface, and the integral solution for the multilayered system reduces to a sum of normal modes plus the sum of two integrals, one along the real axis and the other along the imaginary axis. These integrals are evaluated by a Gaussian quadrature formula. Numerical computations are presented for propagation in the ice covered Arctic Ocean.
The Nature of Sound Fluctuation in Continuous, Statistically Isotropic Media
Authors: Neubert J. A.
Published: October 2005

An analytic procedure is developed for obtaining the Lagrangian measure function B(χ, ξ|s) from its characteristic function φ(k, ξ|s) for stochastic-Fermat media. This permits the calculation of the (Eulerian) ensemble average of the pressure wave, 〈p(χ)〉, as well as 〈|p|2〉, via a central limit theorem for stochastic Lagrangian functionals. This results in a coefficient of intensity variation V that evinces a frequency-dependent phase-dominance region and a frequency-independent amplitude-dominance region. The methods employed in this study are new to the problem of sound propagation through continuous stochastic media and avoid three common difficulties: (1) range limitations due to cumulative phase effects; (2) discrete scattering associations; and (3) restriction to an Eulerian path.
Loudspeaker Horn Theory—A Review
Authors: Salmon V.
Published: October 2005

The theoretical and applied contributions of Webster, Hanna, Bostwick, Olson, Salmon, Mawardi, and Klipsch (among others) will be reviewed, using the impedance concept as a unifying principle. The characteristics of the complete audio source-driver-horn-radiation field system will be examined from the points of view of steady-state and transient response.
Errors in the Measurement of Machine Noise
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 using a limited number of measuring points; and (3) the error in measuring sound pressure at each point. The magnitude of these errors for measurements made in ordinary rooms following the procedure of ISO Recommendation 1680 is discussed.
Human Cochlear Partition Stiffness
Authors: Allaire P. , Raynor S. , Billone M.
Published: October 2005

A mathematical model of the human cochlear partition is developed to investigate in depth the partition's stiffness. To date, no experiment has been performed on the partition to determine the difference between the dynamic stiffness and the statically measured stiffness. Nonlinearities observed in the partition's dynamic motions and dynamic stiffness measurements on bone and muscle tissue indicate that previous studies of the cochlear partition's stiffness may not be conclusive. In this study, the cochlear partition is modeled by a series of composite beams whose stiffness is due to linear bending rigidity at normal amplitudes at motion. At larger amplitudes (in the nonlinear range near the threshold of pain), the model's stiffness is increased due to the nonlinear stretching of the basilar membrane. The nonlinear model may account for the observed nonlinearity. The model also includes the increase in stiffness, above the static stiffness, due to dynamic loading as observed in the studies of bone and muscle tissue. The dynamic cochlear partition stiffness predicted by the model varies approximately 100 fold from base to apex. Except near the stapes, the model's stiffness in the linear range at 100 Hz is approximately the same as the statically measured stiffness. At 10 000 Hz the model's stiffness in the linear range is nearly double the statically measured stiffness.
Neural Phase Locking to Combination Tones Predicted by Simple Transducer Models
Authors: Goldstein Julius L.
Published: October 2005

Conceptual distinctions can be made between nonlinearities arising in stimulus processing prior to transduction and those arising during transduction to neural events. The class of model transducers is considered for which a memoryless nonlinear transformation generates from the processed stimulus X a non negative signal R(X), which then in direct proportion determines the instantaneous probability of a neural event. For X comprising the incoherent tones a cosω1t+b cosω2t, the expected period histogram referenced in cosine phase to the combination frequency pω1+qω2, for p and q integral, nonzero and possessing no common integral factor greater than one, is proportional to P(pω1+qω2, Θ) = 12π  ∫ 02π R {a cosqφ+b cos(pφ − Θ/q)}dφ⋯. (1) For R(X) = exp(X), the expected histogram for any integral p and q is proportional to P(pω1+qω2, Θ) = I0(a)I0(b)+2  ∑ n−1∞ Inp(a)Inq(b) cos n Θ⋯, (2) where Im(z) is the mth-order modified Bessel function of the first kind. Application of this theory to auditory-nerve data clarifies some aspects of nonlinear stimulus processing prior to transduction. [Work supported by a grant from the National Institutes of Health.]
Detection of a Missing Harmonic in a Continuous or Pulsed Harmonic Complex
Authors: Viemeister Neal F. , Green David M.
Published: October 2005

The masker was a complex of harmonically related sinusolds with the mth harmonic missing. The signal was the mth harmonic and its threshold was determined with the masker either continuously presented or pulsed, i.e., gated simultaneously with the signal. The missing harmonic is always more detectable with the continuous rather than the pulsed masker. Differences in thresholds between the two conditions range from 2 to 25 dB. With a continuous masker the phase of the signal influences the threshold by as much as 15 dB. No such phase effects were observed with pulsed maskers. The difference between continuous and pulse thresholds also depends on signal frequency, number and spacing of the components, relative phases of the components, and masker level. [This research was supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare; and by a Special Traineeship from NINDS.]
Effects of Choline Salicylate on the AC Cochlear Potential in Guinea Pigs
Authors: McPherson D. L. , Miller J. M.
Published: October 2005

AC cochlear potentials were recorded from the round window of guinea pigs anesthetized with Nembutal. Following placement of the electrode, the auditory bulla was closed and pure tones were presented via a speaker located 5 cm from the ear. Intensities were determined with calibrated Brüel & Kjær probe tubes and condenser microphones at the opening of the external auditory meatus. One microvolt contours examined with a General Radio wave analyzer (3-Hz bandwidth) across frequency (0.2 to 20 kHz) were found to agree with accepted guinea pig sensitivity curves. Following oral administration of choline salicylate, a rapid and significant decrease in the AC cochlear potential was observed. Following a peak effect (at 3–4 h) and plateau, initial recovery was noted. The effect was drug dose dependent. The effect was frequency specific, with the greatest influence on the middle-frequency range. The maximum amplitude at the point of nonlinearity of the AC cochlear potential was reduced with drug. Also the point of nonlinearity was reached at a higher intensity of tonal stimulation following drug administration. Detailed findings on the cochlear effects of choline salicylate will be described. The interpretation of these effects on generation of the AC cochlear potential will be discussed. [This research was supported by an NIH grant and by the Deafness Research Foundation.]
Ototoxicity of Lead: VDL and AP Changes in Chronically Poisoned Guinea Pigs
Authors: Wilpizeski Chester , Vogel Wolfgang
Published: October 2005

Evidence for lead-induced auditory impairment was obtained by recording VDLs and AP input-output functions for click stimuli presented to guinea pigs having permanently implanted electrodes located in the auditory nerve-cochlear nucleus region. Six animals were fed approximately 1 g of lead acetate per day mixed with powdered food rations for a 3-month period following weaning (chronic lead poisoning). Six additional animals served initially as a control group but were later injected intraperitoneally daily with 10 mg/kg of lead acetate in an aqueous solution. Mean VDLs recorded from the chronic group were raised 14 dB above control values for continuous and interrupted trains of 100 clicks per second. Input-output functions showed a flattening of slope at higher click intensities. Acutely poisoned animals died within 2 weeks without demonstrable shifts or AP changes attributable to lead effects. [Supported in part by USPHS.]
The World of Nonlinearity
Authors: Beyer R. T.
Published: October 2005

As we attempt to describe the physical world more accurately, we find that linear relations among the variables of interest, and linear differential equations become inadequate. For want of a positive term, we cover all such situations with the word nonlinear. In particular, sound propagation in a particular substance will be nonlinear in character whenever the intensity of sound is sufficiently high, or when there are nonlinear terms in the equations describing the medium, or when there are nonlinearities involved in the boundary conditions. The term nonlinearity of the medium may involve the simple relation of the adiabatic equation for an ideal gas, the third-order elastic constants in solids or the characteristics of a vortex or a plasma. Our knowledge of sound propagation can both contribute to and benefit from our knowledge of these nonlinearities.
Ultrasonic Second-Harmonic Generation in Resonant Nonlinear Elastic Solids
Authors: Peters R. D.
Published: October 2005

Second-harmonic and fundamental standing wave amplitudes have been measured to see if nonlinearity parameters (combinations of third-order elastic constants) can be determined from measurements made on resonant samples. Measurements were made on five different materials, all single crystals except for a sample of isotropic fused quartz. Data were taken for fundamental frequencies in the range 5–30 MHz, all amplitudes being measured with capacitive detectors. Agreement with pulse results is surprisingly good in some cases, rather poor in others. A model is given in an attempt to explain the presence or absence of agreement between the two systems.
Generation and Propagation of Finite-Amplitude Waves in Flexible Tubes
Authors: Bjørnø L.
Published: October 2005

Highly reproducible finite-amplitude waves, generated by a modified electromagnetic plane-wave generator, characterized by a rise time <0.5 μsec, peak pressures of 20–100 bar, and time constants of 5–10 μsec in the exponential pressure decay behind the front, are propagated along the axes of water-filled steel, perspex, and natural rubber tubes (30–50 mm i.d., 40–100 mm o.d.). Using new, very small piezoelectric transducers with a high natural frequency, pressure-time functions are measured at different axial and radial tube positions. The frequency domain equation for wave propagation in elastic fluid-filled tubes is developed and solved numerically on an IBM 360/75 computer for water-filled tubes of steel and perspex in the frequency range 1 kHz–1 MHz, giving dispersion curves for phase and group velocities of the first six propagation modes. Using the fast Fourier transform technique on the initial finite-amplitude waves together with (1) the dispersion relationship for the Fourier components, (2) a mode selection procedure, and (3) a new expression for choosing the interval of integration, the waves are “synthesized” again at different tube positions. Surprisingly good agreement between measured and calculated pressure—time functions is found. The work throws new light on the distribution of energy in the modes of propagation and on the influence of parameters of the materials considered on finite-amplitude wave propagation.
Nonlinearity Considerations in Bragg Imaging of Ultrasonic Waves
Authors: Breazeale M. A. , Martin Franklin D. , Adler Laszlo
Published: October 2005

Two fundamentally different techniques exist for the study of the diffraction of light by finite amplitude ultrasonic waves: (1) Diffraction of light at normal incidence can be used to determine the ultrasonic waveform. (2) Diffraction of light incident at the Bragg angle gives detailed information of a completely different nature. Each diffraction order contains an image of the ultrasonic wavefront. Therefore, objects placed within the ultrasonic field are imaged in the diffraction orders. When a finite amplitude ultrasonic wave is used, an ultrasonic wave transmission filter allows one to distinguish the images produced by the second harmonic from those produced by the fundamental. The image produced by the second harmonic is twice as large as that produced by the fundamental and appears at the position of the fundamental's second order. In addition, at large amplitudes, multiple scattering of light by the fundamental ultrasonic wave can produce higher Bragg diffraction orders. These higher orders contain multiple images. Two images appear in the second order, three in the third, etc. [Research supported by the Office of Naval Research.]
Spectral Effects of Subglottal Cavity System
Authors: Fant G. , Ishizaka K. , Lindqvist J. , Sundberg J.
Published: October 2005

Aspirated sounds display shifts of formant frequencies and new formants are added. These can typically be observed in the aspirative part of stop consonant bursts. A quantitative modeling of this influence has been performed on the basis of subglottal impedance data and simple geometry approximations of the subglottal system. The influence of subglottal coupling on voice-source characteristics is discussed.
Some Statistical Characteristics of Voice Fundamental Frequency
Authors: Horii Yoshiyuki
Published: October 2005

Distributional measures such as mean, median, standard deviation, 90% range, and 50% range of fundamental frequency have been often used to characterize voices. This study reports behavior of such statistical measures for each of six talkers as a function of sample size (from 3.6 up to 200 sec). Fundamental frequencies were obtained by a computer program that used a peak-picking method. The results showed that, for each script reading hy a given talker, the standard deviations of the means converge fairly quickly—that is, to within about 2 Hz of the total mean at a sample size of about 1 min. However, when all the various readings from even a single talker are used to get the total mean, the convergence was much slower, indicating that differences among the scripts and day-to-day variations in repeated readings are significant and must be taken into account when interpreting statistical measures of fundamental-frequency variation. Median convergence behavior was the same. Implications of these findings to studies of normal and disordered speech are discussed. [This research was supported in part by the Air Force Cambridge Research Laboratories.]
An Electronic Violin
Authors: Kohut J. , Mathews M. V.
Published: October 2005

The electronic violin described here was developed from data obtained in previous studies in which the resonances of a violin body were simulated electronically. The mechanical part of the electronic instrument consists of a violin without a body. Transducers, sensitive to string motions at the bridge, drive 28 electrical resonances which substitute for those of the normal violin body. The filtered, amplified voltages are applied to a loudspeaker. Violinists report the electronic instrument is easier to play than a conventional one because it responds faster and its strings are easier to bow. By changing the amplitudes of various resonances, the instrument can be quickly adjusted to produce a wide range of tone qualities. Nonlinear enhancements of responsiveness and tone quality are possible.
Real-Time Music Analysis for the Performer
Authors: Titze Ingo R. , Strong William J.
Published: October 2005

Waveform, pitch, dynamics, and 32 harmonic components of a tone with a specified nominal pitch are displayed on a computer-driven CRT. The rate of display is approximately 10/sec, thus presenting essentially real-time analysis. The nominal pitch and the expected pitch deviation are specified by the performer. The pitch deviation can range from a quarter step to a whole step above and below the nominal pitch. The performer can visually adjust his average pitch, monitor his vibrato rate and range, check his dynamics, and observe his spectrum while he sings or plays into the microphone. As an additional feature, the spectrum may be averaged over any specified time interval. The spectrum is obtained by taking a 64 point FFT over a single period of the waveform. The period is determined by sweeping the pitch over the specified range and selecting the best value on the basis of the minimum of a one-cycle average of the waveform and a “fractional period correlation” of adjacent cycles. The present system is comprised of a 30-kHz A/D converter and a PDP-15 computer system with associated graphics.
Acoustic Impedance of Perforated Plate Liners with Two-Frequency Excitation
Authors: Abdelhamid A. N.
Published: October 2005

The acoustic impedance of a lining material has been previously shown to be dependent on the noise spectrum impressed upon the liner and several analytical models for its determination have been recently proposed. The results of these models, however, seem to be in very good agreement with experimental data for single-frequency excitation, but not as good with the limited available data for two-frequency excitation. In this paper, an impedance tube with two sound drivers at one end is used to investigate the performance of perforated plate liners under two-frequency excitation. The two frequencies varied from 800 to 2000 Hz with SPLs at the liner up to 145 dB. The plate thickness varied from 0.05 to 0.20 in. with open area ratio ranging from 0.05 to 0.10. The experimental results indicate that, for the same SPL at the liner, the effect of excitation at the liner resonant frequency on the acoustic resistance at other frequencies is considerably higher than the reverse effect. Based on the experimental data obtained, modifications to the previously proposed impedance models are discussed.
Acoustic Propagation in a Waveguide with a Transverse Concentration Gradient
Authors: Salant Richard F.
Published: October 2005

Acoustic propagation in a two-dimensional waveguide containing a two-component gaseous mixture with transverse concentration gradient, has been investigated analytically. It has been shown that if the steady density is uniform, the sole effect of a concentration gradient is to produce a variable sound speed. However, if the steady temperature is uniform, the medium must be treated as a two-component mixture. For the latter case, the eigenvalues and eigenfunctions have been computed.
The Effect of the Rotating Vane on the Averaged Sound Pressure in Reverberation Chamber
Authors: Tichy Jiri , Andersen Douglas
Published: October 2005

The modulation effect of the rotating vane in the reverberation chamber and the consequences on the sound-power measurement at single frequencies [J. Tichy, “The Effect of Boundary Conditions on the Statistical Properties of the Sound Field in Enclosures,” J. Acoust. Soc. Amer. 50, 98(A) (1971)] has been further studied. The vane causes the amplitude and frequency modulation of the sound field, which results in line frequency spectrum of the sound in the chamber. Therefore, several modes or modal groups can be excited. The time average value of the sound pressure at a certain point depends on the vane speed. The statistical properties of the sound-pressure amplitude have been studied as a function of microphone location and damping of the chamber for various vane speeds.
Differential Equation Approximation to the Expansion of an Underwater Cylindrical Gas Bubble
Authors: Epstein David
Published: October 2005

The underwater cylindrical gas-bubble-expansion problem has been discussed in earlier reports [D. Epstein and J. B. Keller, J. Acoust. Soc. Amer. 44, 395(A) (1968); J. Acoust. Soc. Amer. 46, 117 (A) (1969)]. It was solved in the acoustic approximation, by treating the water as slightly compressible, and a system of nonlinear integrodifferential equations for the bubble radius was derived. In recent studies, a differential equation (DE) approximation was applied to the problem [R. A. Wentzell et al., J. Acoust. Soc. Amer. 48, 1283–1286 (1970); A. I. Joffe et. al., Sov. Phys.—Acoust. 13, 180–183 (1967)]. Here it is shown that by making certain approximations, a single DE, similar to those used in the papers cited above, may indeed be formally derived from the set of integrodifferential equations. The DE has a logarithmic term that causes the bubble pulsations to increase eventually without bound. However, in the early stages of the expansion, the DE solution compares favorably with the rigorous one. Thus, for certain purposes, it may be expected to yield useful results.
Thresholds for Surface Waves and Subharmonics Associated with a Single Bubble
Authors: Storm D. L.
Published: October 2005

When a gas bubble is subjected to an acoustic field, waves are seen on its surface after the pressure amplitude P of the ambient field increases beyond some threshold W. Similarly, a threshold pressure amplitude S has been observed for excitation of a subharmonic response of order one-half. For the work reported here, the thresholds W and S were measured in the frequency range 0.1 to 3 kHz. In a typical experiment, a rather large single bubble, with frequency f0 of volume resonance in the range 0.5–1.5 kHz, was subject to a plane standing wave in a liquid, while prevented from rising by a thin plastic film. Studies were made over a range of frequencies f extending above and below f0. The behavior of the air-liquid interface was observed, and a hydrophone in the liquid near the bubble monitored the pressure at f/2. The output of another hydrophone placed some distance away from the bubble indicated P. Both thresholds W and S were found to exhibit minima for f = f0. For a bubble in water resonant near 1 kHz, the lowest value for W was several millibars, and that for S was somewhat greater.
Light Scattering by Ultrasonic Cavitation in Liquid Helium II
Authors: Greene D. B. , Marston P. L.
Published: October 2005

Microscopic bubbles have been generated in liquid helium II with 50-kHz ultrasonic sound. We have observed that light is scattered from these bubbles and is intensity modulated at the fundamental, harmonics, and subharmonics of the driving frequency. The SPL for the onset of scattering coincides with the second audible threshold described by Jarman and Taylor [P. D. Jarman and K. T. Taylor, J. Acoust. Soc. Amer. 39, 584 (1956)]. Apparatus is now being constructed to photograph bubbles and to refine our original scattering measurements in order to measure their size distribution. We also hope to study the interaction of bubbles with quantized vorticies.
Optimal Performance of Physical Systems Subject to Impact
Authors: Pilkev W. D. , Wang B. P.
Published: October 2005

A computational capability for the evaluation of the limiting performance of transient dynamic systems is described. This capability permits the peak response (acceleration, force, displacement, or stress) of a system to be computed if portions of the system are optimally controlled or isolated. Thus, the worst occurrence to a human or vehicle can be determined under prescribed impact conditions if restraints such as seat belts or bumpers were to react in a time-optimal fashion and if response constraints on the system were not violated. No design configurations of the controllers or isolators are specified. Several specific applications of the capability to human and transportation systems are presented. In terms of design, this capability allows the designer to ascertain on the basis of response specifications alone the feasibility of a proposed design; in addition, he can measure and monitor his success during the design process. This is possible because the capability provides characteristics of the theoretically best, i.e., the limiting, design concept. Without the characteristics of the limiting design, the evaluation of proposed designs can be made only by performing a multitude of analyses for each candidate design. The problem is formulated in terms of linear programming. The controllers can be nonlinear, linear, active, or passive, while the remainder of the system must be linear. The linear programming formulation permits the use of off-the-shelf computer programs for the solution and, because of the capability of standard linear programs, means that multidegree-of-freedom, multi-isolator problems subjected to multiple, alternative sets of transient loading can be treated.
Response of an Infinite Strip of Structure to Fluctuating Pressure Fields
Authors: Morrow Charles T.
Published: October 2005

The best-known method of predicting the response of aerospace structure to intense noise fields is statistical energy analysis (SEA). This is an approximate analysis of a complicated structure. It is proposed to supplement this by a simplified model analysis—an exact analysis of a simple model to be used as a basis for inferences about real structure. The simplest model is a strip of infinite length with one-dimensional propagation characteristics for transverse vibration defined by a velocity and an attenuation constant which may depend on frequency. Responses are derived for several flight pressure fields and for a reverberant field.
Eigenvalues for Wave Motion in Irregularly Shaped Regions
Authors: Shaw Richard Paul , Tai George
Published: October 2005

Eigenvalues are obtained by means of a Helmholtz integral equation formulation for wave resonances in two- and three-dimensional enclosed regions. Examples of circular and spherical regions are given to compare this approach to the simpler but less general separation of variables method. An example of a triangularly shaped two-dimensional region is given to illustrate the advantages of this approach, i.e., that only surface values of the dependent variables appear, allowing a fine grid to be used with relatively few points, as compared to a standard finite difference approach for a nonseparable geometry.
Experimental Observation of Monastatic Reflection by Elastic Spheres in Water
Authors: Vogt Richard H. , Dragonette Louis R. , Neubauer Werner G.
Published: October 2005

Careful comparison of steady-state theory and experiment has shown that outstanding features such as nulls in the reflection solution vs ka for spheres can be identified with precision by pulse experiments. The systematic influence of experimental parameters such as elastic constants and ambient temperature is discussed. A persistent discrepancy of 0.05% in wavenumber between theory and experiment has been observed.
Observations of Acoustic Radiation Resulting from Incidence at the Critical Angles and the Rayleigh Angle for Plane Surfaces
Authors: Neubauer Werner G.
Published: October 2005

The resulting radiated field is observed by sehlieren methods for an ultrasonic beam generated in water incident on a solid interface. Radiation outside the specular region has been observed at the longitudinal and shear critical angles and at the Rayleigh angle. A periodic spatial variation in acoustic amplitude occurs in this radiated field at the Rayleigh angle. This effect will be discussed.
An Exact Solution for the Impulse Response of a Baffled Rectangular Piston
Authors: Lockwood J. C. , Berktav H. O.
Published: October 2005

An exact solution for the pressure at any point in the field of an impulsively accelerated rectangular piston is obtained. This is a closed-form time-domain solution obtained by a geometrical approach similar to that used by Farn and Huang [J. Acoust. Soc. Amer. 43, 252–257 (1968)] for the case of a circular piston. It is expected that the impulse response obtained in the present case will be useful in calculating the nearfield for arbitrary motion of a rectangular piston. [This work was sponsored by the Office of Naval Research.]
Measurement of Axial Velocity Profiles and Resulting Acoustical Fields of a Rod
Authors: Nowotny L. J. , Hixson E. L.
Published: October 2005

Sinusoidal stress waves over the frequency range 10.0-85.8 kHz were transmitted down a cylindrical aluminum rod 12 ft long with a radius of 0.75 in. Using a modified Twyman-Green interferometer and a high-sensitivity fast rise time, photodiode radial distributions of peak-to-peak axial displacement were measured at the radiating face of the rod while it was under CW excitation. Measurements verified the almost pistonlike displacement profiles for low frequencies and indicated increased distortion of the face with increasing frequency. Nodal cylinders of axial displacement were found to occur beginning at about 29 kHz with only the lowest symmetric mode propagating in the rod. Directivity patterns of the radiating rod were measured over the specified frequency range in a laboratory pool. Only the radiating rod face was exposed to water at the plane surface of a 5-ft-square aluminum baffle. Measurements taken with pulsed sinuosidal excitation applied were compared with calculations for an ideal piston in an infinite baffle.
Radiation from an Array of Transducers on a Finite Cylinder
Authors: Porter D. T. , Rogers P. H.
Published: October 2005

It is difficult to obtain valid solutions for a large finite cylindrical array using the Helmholtz integral or source-density formulations because of the density of the eigenfrequencies of the interior of the body. Near these eigenfrequencies, it is difficult to obtain valid solutions. If a hole is drilled through the cylinder, the interior eigenfrequencies of the resulting finite annular cylinder can easily be found. If the hole is large enough so that the resulting wall thickness is less than a half wavelength, then there will be no eigenfrequencies below the sonar frequency and the eigenfrequency problem is avoided. An example is given showing that this hole has negligible effects on the radiated pattern. Beam patterns for an array of six bands on a finite annular cylinder three wavelengths high, 10 wavelengths in diameter, and 14 wavelength in wall thickness are compared with patterns for the same array on an infinite cylinder, for various depression angles. The finite and infinite cylinder patterns looked much alike, with diffraction oscillations added. The diffraction oscillations were seen on the main lobe only for depression angles deeper than 30°.
Subjective Study of Tire and Engine-Exhaust Noise
Authors: Akay Adnan , Reiter William F. , Cohen Harvey
Published: October 2005

Effective enforcement of noise regulations governing ground transportation vehicles depends on a valid noise rating scale for monitoring the noises involved. Previous investigations have shown that the dBA rating is acceptable for tire noise and engine noise. This investigation was aimed at evaluating rating scales for comparison of tire and engine-exhaust noise. The method of paired comparisons was used to evaluate subjectively noise composed predominantly of truck tire noise compared to diesel engine-exhaust noise at three different vehicle and engine speeds. The tests were conducted in a simulated home environment. Recordings obtained under actual field conditions were used as stimuli and were presented at two different sound pressure levels to a total of 85 subjects in groups of 10 or fewer. The stimuli presented were rated objectively in PNdB, EPNdB, SAE Phons, A-weighted SPL, and according to the Stevens Mark VII criteria. A correlation analysis was carried out to determine the relative validity of the these ratings. [NASA is acknowledged for partial sponsorship of this work.]
Noise Reduction of a Residential Air Conditioner
Authors: Seybert Andrew F. , Crocker Malcom J.
Published: October 2005

The major sources of noise in a residential air-conditioner were studied. SPL and acceleration spectra were measured in an anechoic room. The noise sources were found to be the condenser fan motor, the evaporator fan motor, and the compressor. Measurements revealed that the fan motors were vibrating predominantly at twice line frequency, 120 Hz, and the vibration was being transmitted to the air-conidtioner panels. The research was concentrated on reducing this 120-Hz hum. The effectiveness of the fan-motor-isolation systems was studied by varying the frequency of the current supplied to one motor. The motor acceleration and the SPL at twice line frequency were both monitored. The acceleration frequency plot revealed a fan-motor-isolation system resonance frequency close to the operating frequency of 120 Hz. By reducing the stiffness of the mounting brackets of each of the fan motors, the SPL at 120 Hz was reduced by 12.5 dB. [Work supported by American Standard.]
Genetic Features of Deafness
Authors: Brown Kenneth S.
Published: October 2005

The pattern of hearing loss of children in schools for the deaf provides little information regarding etiology, but it is possible to evaluate the relative contribution of several etiologic factors by study of medical histories and family records. Traits such as thyroid or pigment anomalies can be used to identify particular genetic defects in a small proportion of deaf children; however, family data suggest that over half of all cases are the result of inheritance. Although most of the responsible genes are not now recognizable, pedigree data give excellent fit to simple genetic models. Thus we are able to estimate the minimum number of genes causing deafness and predict risks of deafness in offspring. Using experimental animals with patterns of hereditary deafness similar to man, we can observe development and anatomy which suggest important directions for the study of deaf children.
Anatomical Correlates of Deafness
Authors: Smith Catherine A.
Published: October 2005

Structural defects associated with deafness may be divided into two classes. The first class is associated with structures of the external and middle ear with the result that conduction of sound is impeded. Deformities of the external auditory canal and the ossicles may be hereditary and present at birth. Middle-ear infections, otosclerosis, etc., acquired later may alter normal ossicular chain function. If properly diagnosed, for the most part these can be repaired by surgery. In the second class, the pathology is restricted to the inner ear. If the defect is congenital, it may have been inherited, or occurred “in utero” such as with rubella infections. After birth, an individual may be exposed to any number of situations which cause destruction of the hair cells and the cochlear nerve fibers. If the loss is extensive enough, a defective receptor organ results, with partial or complete deafness of the individual. It is not clear at present precisely what percentage of hair cells and nerve fibers are necessary for adequate social communication, but there is no replacement of degenerated receptor cells or sensory nerve fibers.
Laryngeal-Disorder Detection through Speech Analysis
Authors: Crystal T. H.
Published: October 2005

This talk reports on a study into the feasibility of using automatic voice analysis for the detection of laryngeal disorder. Over 200 normal and pathological subjects were examined and had their voices recorded at the Massachusetts Eye and Ear Infirmary. The first stage of the automatic analysis was a highly accurate peak detection and pitch tracking on a throat microphone signal [CRYSTAL, T. H., and C. L. JACKSON (1970), J. Acoust. Soc. Amer. 48, 118(A)]. Lieberman's pitch perturbation technique [P. LIEBERMAN (1963). J. Acoust. Soc. Amer. 35, 334–353] was extended to amplitudes. Our analysis was made on “jitter” defined as the difference between smoothed data and actual data. The normalized mean-square jitter was then used as an index of vocal quality. A set of such indices, obtained by using different smoothing algorithms, was used in a multivariate discriminant analysis of the data. Linear discrimination on the training data allowed the separation of 83% of the male pathologicals when the decision threshold was set to misclassify less than 7% of the male normals. Less separation was obtained with females. This performance has also been compared to the effectiveness of a voice-evaluation procedure, which was specially introduced into the physician's examination. A review of the procedures and data together with the rate of incidence of laryngeal disorder suggests certain directions for the continuation of this work. [The original work was supported under the Neurological and Sensory Disease Control Program, U. S. Public Health Service, whose personnel contributed to the project.].
Acoustic and Perceptual Characteristics of the Speech of Deaf Children
Authors: Levitt Harry
Published: October 2005

The speech of deaf children differs from that of normal children in many ways. There are articulatory errors such as omission of consonants, insertion of adventitious sounds (typically between syllables and in consonant clusters), substitutions of one phoneme for another, moderate distortions in which the intended phoneme is still recognizable, and severe distortions in which there is no recognizable phoneme. In addition to articulatory errors involving individual phonemes, there are suprasegmental errors such as incorrect rhythm, stress, intonation, phrasing, and errors involving other prosodic features. There are also problems of voice quality such as excessive harshness, breathiness, nasality, and problems of pitch, i.e., average pitch too high, too low, or excessively variable. Acoustic measurements correlate reasonably well with these perceptual observations. On average, the fundamental frequency contours of deaf children tend to be higher than for normal children of the same age and sex, but there are notable exceptions in which the fundamental frequency contour is very low, or exhibits sudden changes from one extreme to the other. Formant frequencies during vowel sounds are similar to those for normal children, but are biased towards values typical of the schwa vowel. Substitution of the schwa for other vowels is a common error. Experiments involving measurements on other acoustic parameters, such as formant transitions and fricative spectra are currently in progress.
Some Acoustic Aspects of Stuttered Speech
Authors: Agnello J. G. , Wingate M. E.
Published: October 2005

Three extensive studies have been conducted on the acoustic features of stuttered speech. One study examined the temporal properties and formants of speech having various degrees of fluency. Another study reports on the coarticulation patterns across two languages (Italian-English) of stutterers and nonstutterers. The third study (discussed more extensively) is on the spectrographic patterns of simultaneous intraoral air pressure and formant patterns of stutterers and nonstutterers. Stutterers and normal speakers produced a series of syllables of /pa, ba, ap, ab, apa, aba/ and some short phrases. Simultaneous measures of intraoral air pressure and formant patterns of these utterances reflected the transitional features of labial release to glottal onset patterns, e.g., plosive to vowel. Also, vowel and plosive measurements reflected the manner of glottal termination followed by labial closure. Standard spectrographic tracings illustrate only the acoustic events of speech and pose certain problems of accurate temporal measurements for stutterers, since a great deal of their speech efforts are essentially nonacoustical. A system is presented that yields a more discrete pattern of the articulatory events in terms of formant patterns and intraoral air pressure. The transitional features in the fluent and nonfluent production of syllables uttered by stutterers and nonstutterers will be illustrated. The difference is shown to be within the transitional aspects of segmental units. The transitional features within the syllabic structure of the stuttered speech point to a disruption of coarticulated events. This transitional failure is the phenomenal core of stuttering. Implications will be discussed, particularly that voice control is the core element in stuttering behavior.
Dynamic Testing of Biological Materials
Authors: McElhaney James , Melvin John
Published: October 2005

Because the mechanical properties of biological materials exhibit strong rate dependence, special care must be exercised in their measurement. This paper describes a variety of measurement techniques to determine the dynamic mechanical properties of hard and soft tissues. Results of these tests on bone, scalp, brain, and dura are presented. Viscoelastic models, modeling techniques, and difficulties are discussed for these materials. Materials from both human and subhuman primates have been studied and comparisons made. The effect of post-mortem test times and storage and specimen preparation methods is discussed.
Code Design for a Transmit Beam Scanning Sonar
Authors: Ross J. M.
Published: October 2005

A scanned parametric transmitter is being constructed at Birmingham University. The receiver associated with the system is tuned to the difference frequency obtained from the interaction in water of the two transmitted primary frequencies. The transmitter scans a sector about 15° in width with a beam approximately 1.5° wide. One means of coding the transmitted beam is by sending a different code word into each subsector (1.5°) of the scanned sector. The code words considered each consist of a sequence of A pulses, each pulse of which can have one of N carrier frequencies. The target bearing is identified by correctly identifying the received code word. A two-threshold receiver provides better reduction of ambiguities caused from overlapping signal bandwidths than a one-threshold receiver. One means of reducing false alarms due to ambiguities is to rotate code words with each transmission. Bearing resolution can be improved by scanning the transmit beam less than one subsector beamwidth for each code word transmitted.
A Method for High-Speed Calculation of the Exact Solution for the Pressure in the Nearfield of a Circular Baffled Piston
Authors: Willette J. G. , Lockwood J. C.
Published: October 2005

A high-speed method has been developed for calculating from the exact integral solution the pressure at each point in the nearfield of a sinusoidally excited circular piston in an infinite baffle. Previously the exact nearfield pressure has been calculated by means of a double numerical integration over all source points on the piston face. The phase of the signal arriving at a field point from each point on the piston must be taken into account precisely. One investigation in which the double integration was employed is that of Zemanek, who published three-dimensional and contour plots of data obtained by this method [J. Acoust. Soc. Amer. 49, 181–191 (1971)]. We have reduced the calculation to a single numerical integration by starting with the known exact solution for the field produced by impulse motion of the piston. For each field point, we compute, at the frequency of interest, the Fourier transform of the impulse response. Thus, we obtain the transfer function, a complex quantity that, when expressed in polar form, gives us the amplitude and phase of the pressure variation. We have made three-dimensional and contour plots that compare favorably with those published by Zemanek. The high speed of our method makes possible the efficient calculation of the difference frequency source function. (See J. G. Willette, Paper F9 of this meeting.) [This work was sponsored by the Office of Naval Research.]
Closed-Form Solution for the Radiation from a Continuous End-Fire Line Array
Authors: Berktay H. O. , Shooter J. A.
Published: October 2005

An “exact” closed-form solution for the acoustic field from a continuous end-fire line array is presented. Interactions between the array elements are ignored, but no approximations are made regarding the position of the field point. (This model lends itself particularly well to the study of the response of parametric receivers.) The results are presented in the form of beam patterns as a function of range. It is shown that the range where the farfield response is obtained depends only on the length of the array and that the beam patterns within the nearfield can be substantially more narrow than the farfield beam patterns. [This work was sponsored by the Office of Naval Research.]