bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of End Conditions on the Lateral Frequencies of Uniform Straight Columns
Authors: Amba-Rao Chintakindi L.
Published: September 2005

Calculations of fundamental frequencies in lateral vibration are made for straight bars under compressive loads for various fractions (less than one) of the Euler load for a number of boundary conditions. As the compressive load on the bar increases, the fundamental natural frequency decreases. The rate of decrease increases as one proceeds in the following order; clamped free, hinged/hinged. clamped/hinged, and clamped/clamped. Besides their usefulness for design purposes, the results find an application in problems, of dynamic stability.
Effect of Boundary Conditions on Flexural Vibrations of Thin Orthogonally Stiffened Cylindrical Shells
Authors: Penzes Leslie E.
Published: September 2005

A set of Donnell-type equations of motion were formulated for arthotropic cylindrical shells in three partial differential equations. The approximate solutions of these equations were investigated for relatively long cylinders. The following three boundary conditions were applied: clamped-clamped, clamped-simply supported, and both edges simply supported.
Ambient-Noise Levels in Selected Shallow Water off Miami, Florida
Authors: Widener M. Ward
Published: September 2005

Noise-level measurements have been made in shallow water off Miami, Florida. Areas containing snapping shrimp have been calibrated for noise levels in excess of 30 dB over Sea State 1 up to 50 kHz. Spectral components were observed to 150 kHz with lower frequencies extending down to 4 kHz.
Influence of Attenuation upon the Frequency Content of a Stress Wave Packet in Graphite
Authors: Serabian Steven
Published: September 2005

This paper presents experimental data concerning the distortion of the frequency spectrum of a stress wave packet as produced by attenuation effects in graphite.
Detection of an Incoherent Finite Signal Using a Number of Sensors
Authors: Hinich Melvin J.
Published: September 2005

Consider a collection of m sensors, immersed in an isotropic noise field, that is designed to detect the arrival of an unknown time-limited signal of length T seconds. However, the power spectrum S(ω) of the signal is known. Asssume that the direction of the signal propagation is known approximately, but due to local perturbations of the medium or motions of the sensors, the precise arrival time of the signal at each sensor is unknown, and the signals cannot be added coherently. Time adjustments can be made for each sensor channel so that the signal is assumed to arrive during a sampling window of T seconds if some part or all of the signal is within the window for each sensor. If the noise is white, the weak-signal optimal detection procedure is to compute U = Δπ ∫ 0π/Δ Ŝ(ω) S(ω) dω, where S(ω) is the observed power spectrum averaged over all the sensors and Δ is the interval between discrete observations, and then to compare U with a threshold. The signal is claimed to be present if U exceeds the threshold. This procedure is equivalent to a certain type of weighted power detection. It has a greater signal-to-noise ratio gain (called signal detectability) than that obtained by using simple power detection. The end effects due to loss of part of the signal in the finite window prohibit the use of power spectrum comparisons.
The Hertz
Authors: Fitzpatrick Hugh M.
Published: September 2005

The hertz is the reciprocal of the second and, hence, a suitable unit for expressing the value of any quantity having the dimensionality of the reciprocal of a time. As commonly employed, “cycle per second” and “radian per second” are two more names for the same unit.
Radiation Pressure on a Small Rigid Sphere
Authors: Nyborg Wesley L.
Published: September 2005

Simple expressions are derived for the acoustic radiation force F on a small rigid sphere of radius a, volume v and density ρ suspended In a liquid or gas of density ρ0. Effects of viscosity are neglected; use is made of methods developed by King and Embleton. Results are expressed in terms of the time-averaged densities T̄a and V̄a of kinetic and potential energies, respectively, in the incident sound field. Letting β be ρ0/ρ it is found. as an approximation when a is much less than the sonic wavelength, that F = v[B∇T̄a − ∇V̄a]+Δ, B − 3 1 − β /(2+β), where Δ is given by a relatively complicated expression. The quantity Δ is important primarily in progressive waves of relatively uniform amplitude, as exist in the field of a large source; here ∇T̄a and ∇V̄a, may be relatively small while gradients of the phase exist. In a standing wave or in the neighborhood of a small source, Δ is negligible. When Δ = 0, the above expression for F agrees with one given previously by Gor'kov.
Anharmonic, Thickness-Twist Overtones of Thickness-Shear and Flexural Vibrations of Rectangular, AT-Cut Quartz Plates
Authors: Mindlin R. D. , Spencer W. J.
Published: September 2005

Equations of motion accommodating thickness-twist overtones of thickness-shear and flexural vibrations of rectangular, AT-cut, quartz plates are obtained. The equations are solved in closed form for plates with all four edges free. The predicted frequencies are compared with measured resonances. X-ray topographs of typical thickness-twist overtone modes are exhibited which verify that the mode shapes correspond to those predicted.
Shapes of Tuning Curves for Single Auditory-Nerve Fibers
Authors: Kiang N. Y. S. , Sachs M. B. , Peake W. T.
Published: September 2005

When threshold for single auditory-nerve fibers are plotted in terms of stapes displacement, the tuning curves rise monotonically on both sides of the characteristic frequency.
Conversion Relations for Isotropic and Ferroelectric Ceramic Elasticity Formulations
Authors: Holland Richard
Published: September 2005

A table of formulas is presented for interrelating the coefficient systems of an isotropic solid: Young's modulus and Poisson's ratio; the Lamé constants; and tensor and matrix stiffness, compliance, and planar stiffness.
Optical Imaging of the Cross Section of a Microwave Acoustic Beam in Rutile by Bragg Diffraction of a Laser Beam
Authors: Tsai Chen S. , Hance Harold V.
Published: September 2005

This letter reports some results of an analysis, based on a wave-optical formulation, of the farfield Bragg diffraction from a cylindrical line source light beam by a line-source acoustic wave. The properties of the diffracted light that are relevant to the problem of optically viewing or imaging the acoustic fields of plane or cylindrical transducers are discussed. The most important of these properties are as follows: (1) A line light source exists for the diffracted light and is either real or virtual depending upon the location of the acoustic source relative to the light source; (2) the location of this line source for the diffracted light has a geometrical correspondence to the acoustic source location; and (3) the phase and amplitude of the acoustic source is preserved in the diffracted line source. As the field of a plane or cylindrical transducer can be represented as a superposition of a set of line-source waves, it follows that the total diffracted field is either a real or virtual image of the acoustic field. In either case, a real, enlarged image can be formed by the used of proper lenses. A description and examples of results are given for an experiment in imaging the transverse section of two parallel but physically separated 923 MHz microwave acoustic beams in a rutile crystal. The image resolution obtainable is discussed and compared for the experimental conditions with that obtained using a finely focused, mechanically scanned light probe.
A SONIC TEST SYSTEM FOR NONDESTRUCTIVELY EVALUATING COMPOSITE STRUCTURES
Authors: Botsco Ron
Published: September 2005

A sonic test system has been developed by North American Aviation, Inc., for nondestructively evaluating composite structures throughout their entire depth while requiring access to only one surface. Applications include adhesive-bonded, diffusion-bonded, and brazed honeycomb structures. Also, the system has been successfully utilized for testing laminated and corrugated-core composites. Structural defects such as unbonds, core crushing, and core rupturing are detectable.
Acquisition of Successive Auditory Discrimination in Monkeys
Authors: Dewson James H. , Wertheim George A. , Lynch James C.
Published: September 2005

Six monkeys, conditioned with positive reinforcement techniques on a successive auditory discrimination, required about 1100 trials for acquisition (range; 950–1200 trials). The discriminative stimuli were a tone and a noise of equal intensity and duration. Retention was measured after a 30-day layoff. The procedure described in this letter is unique in auditory conditioning methodology in that an “OBSERVING” response is required of the animal in order for him to gain access to the stimuli.
New Laryngoscopic Technique by use of Fiber Optics
Authors: Sawashima Masayuki , Hirose Hajime
Published: September 2005

A fiberscope with a thin flexible fiber-optics cable is inserted through the nasal passage in order to observe the laryngeal states and movements during various phonatory and articulatory conditions. Sample photographs of this procedure are presented.
Effect of Masking Noise upon Syllable Duration in Oral and Whispered Reading
Authors: Schwartz M. F.
Published: September 2005

In an earlier study. the whispered syllable was found to be of significantly greater duration than the oral. The present study, concerned with the effect of various levels of masking noise upon this performance, finds no effect for noise upon the magnitude of the oral-whisper difference.
Sound Scattering by Elastic Cylinders
Authors: Doolittle R. D. , Überall H. , Uginčius P.
Published: September 2005

The problem of steady-state sound scattering by an infinite elastic circular cylinder is treated by performing a Sommerfeld-Watson transformation on the normal-mode series. The complex velocities of the ensuing circumferential waves are found by obtaining zeroes of a 3 × 3 determinant in the complex plane, identical to that used by Goodman and Grace in the theory of free vibrations of an elastic cylinder. We find numerically two kinds of zeroes: (α) Franz-type zeroes, similar to (and for aluminum cylinders, almost identical with) those appearing in scattering from rigid cylinders; (β) Rayleigh-type zeroes, as found by Goodman and Grace, which for large cylinders tend to the Rayleigh and Stoneley wave velocities, and which enter the cylinder surface at a certain critical angle. These two types correspond to the “diffracted” and the ordinary surface waves conjectured by Keller and Karal. We also consider the causality relations of sound pulses and show mathematically that they lead to arrival times in accord with the (complex) ray paths of Keller's theory. Finally, the trajectories of the zeroes in the complex plane for variations of ka and the group velocities of circumferential sound pulses have been obtained.
Asynchrony II: Perception of Temporal Gaps within Periodic and Jittered Pulse Patterns
Authors: Pollack Irwin
Published: September 2005

Thresholds for temporal gaps within periodic and jittered pulse patterns were determined. Gap thresholds within periodic pulse trains are in close agreement with those obtained in a previous study. Extremely fine temporal gap detection (10–20 μsec) is achieved for high-frequency pulse trains consisting of many intervals. Reduction in the number of intervals, or introduction of jitter to the pulse train, sharply increases temporal-gap thresholds for high-frequency pulse trains. By contrast, temporal-gap sensitivity for low-frequency pulse trains is relatively independent of the number of intervals or of the amount of jitter. Acute temporal-gap sensitivity is apparently achieved at high pulse frequencies by a spectral analysis of the temporal information, rather than by a direct temporal analysis.
Thickness-Shear Vibration in Rectangular AT-Cut Quartz Plates with Partial Electrodes
Authors: Byrne R. J. , Lloyd P. , Spencer W. J.
Published: September 2005

The thickness-shear vibrations in AT-cut quartz plates with partial electrodes including the effects of a pair of free edges are discussed in a qualitative manner. The frequencies and mode shapes as a function of plate and electrode dimensions are determined from an analysis similar to that of Mindlin and Lee. These results are compared with measured values obtained from rectangular quartz plates with rectangular electrodes. The ratio of capacitances of thickness-shear vibrations are calculated from an expression given by Lewis. These calculations indicate that the ratio of electrode length to plate length is equally as important in the suppression of anharmonic thickness-shear vibrations in finite quartz plates as is the ratio of electrode length to plate thickness (Bechmann's number).
Statistical Theory of the Speech Discrimination Score
Authors: Boothroyd A.
Published: September 2005

A mathematical analysis is developed that relates to scores obtained in discrimination tests using consonant-vowel-consonant words. Account is taken of the fact that recognition of a speech sound depends on “intrinsic” and “contextual” factors. The intrinsic factors are the acoustical properties of the sound and its probability of occurrence. Two contextual factors are introduced: a “second-order” factor, including acoustic influences in adjacent sounds and second order phoneme probabilities, and a “vocabulary” factor. The theory is applied to the results of discrimination tests given to two groups of children, one normally hearing, the other partially hearing. The vocabulary factor is found to be related to age only, while the second-order factor is related to high-frequency hearing loss. This implies that the second-order factor is primarily an acoustical one. Comparisons are shown between measured discrimination scores and the scores which would theoretically be obtained if only intrinsic factors contributed to discrimination. These show that a score based on the percentage of recognized phonemes is more valid as a measure of the ability to make phonemic classifications from intrinsic acoustical clues, than is a score based on the percentage of recognized words.
Acoustic Field in a Luneberg Lens
Authors: Lord Gary E.
Published: September 2005

A wave solution is presented for plane acoustic radiation incident on a particular spherical, omnidirectional, perfectly focusing fluid lens.
Monaural Phase Effects in Auditory Signal Detection
Authors: Fricke J. E.
Published: September 2005

A complex signal composed of a fundamental (525 cps) and a second harmonic (1050 cps) was created by systematically altering the phase of the second with respect to the first through six relative-phase relationships (0°, 30°, 60°, 90°, 120°, and 150°). Four 100-msec bursts of noise, one of which contained the complex waveform, were presented to four subjects; and they were forced to choose which of the four contained the signal. Ten different signal-to-noise ratios (S/N), covering a range of 10 dB around a subjective “threshold” value, were utilized. Forty judgments at each of these S/N ratios were made in each phase condition. The data revealed differences with regard to the detectability of the complex signal as a function of the relative phase of the components.
Prediction of Monaural Detection
Authors: Mulligan B. E. , Adams J. C. , Mulligan M. J. , Burwinkle R. E.
Published: September 2005

The optimum receiver for the case where signal is known except for phase has been suggested as a model for auditory detection of sinusoidal signals in noise. We have furthered application of this model in an effort to evaluate some of the parameters of monaural detection that are important for prediction. Of particular interest is bandwidth, or “critical band,” which was found to decrease as signal-to-noise ratio increases, the rate of decrease being a function of frequency. Bandwidths were derived from the parametric values of the ROC's that describe the detection performance of our observers. It was found that human ROC's are closely matched by ideal ROC's. The ROC's of our observers were obtained with a six-category rating scale and our measure of detection was ds. Values of ds were obtained at 500, 800, 1300, 2500, and 4000 Hz over a range of signal-to-noise (S/N) ratios. It was found that the relationship of ds to S/N ratio at all signal frequencies could be summarized by a single equation, the psychometric function. Other equations are also given so that the psychometric function for any signal frequency may be determined simply from a knowledge of the power per unit bandwidth of the masking noise.
Finite-Amplitude Standing Waves in Rigid-Walled Tubes
Authors: Coppens Alan B. , Sanders James V.
Published: September 2005

A perturbation expansion is formulated for the one-dimensional, nonlinear, acoustic-wave equation with dissipative term describing the viscous and thermal energy losses encountered in a rigid-walled, closed tube with large length-to-diameter ratio. The resulting set of iterative, linear equations is solved for a finite-amplitude standing wave. Solutions lead to a steady-state distribution of harmonics of the fundamental, the amplitude and phase of each term being strong functions of frequency and the absorptive process. Necessary features of the approach include characterizing all absorptive processes by a bulk absorption coefficient and requiring a boundary-layer depth much less than the tube diameter. The solution, while strictly limited to the preshock régime, can be used to predict certain features of the onset of shock. Intense longitudinal standing waves were generated within a rigid-walled tube of 6-ft length and 212-in. diam. The tube contained air, at ambient pressure and temperature, which was excited into vibration by a piston at one end. A microphone at the rigid end of the tube was used to observe the pressure as a function of time. For input frequencies around either the fundamental or the first overtone of the tube, the amplitudes of the second and third harmonics of the finite-amplitude wave were in excellent agreement with the predictions of the theory. Waveforms reconstructed from the predicted amplitudes and phase angles of the solution compared very well with the observed microphone output. An extension of the theory to the shock régime provided qualitative agreement with observations of the frequency dependence of both the intensity needed to produce shock and the phase of the onset of shock.
Effect of Lateral Motion on the Longitudinal Vibration of Tapered Bars
Authors: Chehil D. S. , Heaps H. S.
Published: September 2005

Longitudinal vibration of a bar of general taper is analyzed subject to the inclusion of the effect of Poisson's ratio. The resulting differential equation may be used to treat bars of general taper. Numerical results are presented for bars of conical taper. It is found that if the length of the bar exceeds the diameter then inclusion of a value of Poisson's ratio equal to 0.3 leads to the prediction of fundamental resonant frequencies and velocity gains that are only a few percent less than the predicted values that result when Poisson's ratio is ignored.
Damping and Pulsation of Large Nitrogen Bubbles in Water
Authors: Koger H. G. , Houghton G.
Published: September 2005

Decay constants and pulsation frequencies of nitrogen bubbles (2–20-mm diam) in water have been determined by oscilloscope photography of the transduced and amplified sound pulses emitted by bubbles formed at submerged jets. The sound decay of single bubbles has been studied over the pulsation frequency range of 0.3–3.0 kHz, and a technique of time-exposure photography has been developed whereby differences in the decay patterns between individual bubbles can be smoothed by the use of an ensemble of consecutively formed bubbles of the same size. Within experimental error, the decay constants and pulsation frequencies have been found to agree with those predicted theoretically by linear pulsation theory.
Location and Enumeration of Underwater Explosions in the North Pacific
Authors: Spiess F. N. , Northrop John , Werner E. W.
Published: September 2005

Hydroacoustic signals from underwater explosions were documented from analog recordings of 20 widely spaced SOFAR depth hydrophones in the North Pacific for a year. The number of shots per month ranged from 300 in winter to 4000 in summer. Source solutions, of accuracy between 10 and 30 miles, were grouped off the west coast of North America, north of Hawaii, and seaward of the Japanese and Kuril Islands.
Controlled Dispersion of Axisymmetric Waves in Composite Rods
Authors: McNiven H. D. , Mengi Y.
Published: September 2005

In an earlier paper dealing with dispersion of waves in composite rods, it was noted that the dispersive properties of one rod were quite different from those of another with different properties. This observation prompted the speculation that the dispersive properties of a composite rod could be controlled through a choice of the geometric and material parameters of the rod. In this paper, we show how the dispersive properties can be controlled; that is, we show the influence of each of the parameters on the dispersive characteristics of a rod. Our previous study had led us to suppose that if we were sufficiently adroit, we could choose the rod parameters so that the resulting composite rod would be nondispersive. Our study here shows that this is impossible and that a rod will always be dispersive, at least if it has a traction-free surface. We show that, with a very restricted, theoretical exception, the least dispersive composite rod is the degenerate one: the one-material rod.
Effect of Phase Errors on the Direction-Finding Precision of Hydrophone Arrays
Authors: Bell Thaddeus G.
Published: September 2005

One limit to the precision of finding the direction of an underwater sound source with an electrically steered array is the phase error in each hydrophone output signal. A theoretical relation between the standard deviation of hydrophone phase error and the standard deviation of array direction-finding error is derived in this paper. Supporting experimental evidence is presented from measurements on two multielement, scanning-sonar-type, circular arrays.
Wave Theory of an Acoustic Luneberg Lens
Authors: Boyles C. A.
Published: September 2005

The wave theory of an underwater, spherical Luneberg lens is discussed in terms of a generalized wave equation, which differs from the ordinary wave equation in that it contains a term involving the gradient of the density of the lens. The special case where the density of the lens has a constant value (to a first approximation) is studied in detail. This case is of some importance since it corresponds to the compliant-tubing lens built and tested by W. J. Toulis [J. Acoust. Soc. Am. 35, 286–292 (1963)]. For this case, we determine the analytic solution of the wave equation when the lens is being irradiated by plane waves and then present the results of a numerical evaluation of that solution. In particular, we calculate the acoustic pressure field along the axis of the lens and the pressure receiving patterns. These results give us the gain and beamwidths for the range 1⩽k0a⩽30 (k0 being the wavenumber in water, a the radius of the lens). Finally, the theory is compared with Toulis's experimental results, and the agreement is found to be quite good.
Coherence of Convergence Zone Sound
Authors: Urick R. J. , Lund G. R.
Published: September 2005

The vertical coherence of underwater sound in a convergence zone has been investigated by means of a vertical receiving array of six hydrophones spaced 212 ft apart and hung at a depth of 3800 ft from a surface ship. A second ship towed a 1120-Hz CW source outward in range from 28 to 43 miles. The outputs of the different hydrophones, when correlated together, yield correlation coefficients equal to nearly unity when in the convergence half-zones at 30 and 38 miles, and show only a slow falloff with increasing separation. In between zones, where bottom-reflected paths occur, the correlation coefficient was much smaller and was found to fall off faster with increasing separation. It may therefore be concluded that a vertical array located in the convergence zone of a distant source will experience a higher signal-to-noise ratio as a result of two effects: an increased signal level due to convergence, amounting to 10 dB in one experiment, and an increased array gain due to the greater coherence of the received sound.
Metamorphosis of a Critical Interval: Age-Linked Changes in the Delay in Auditory Feedback that Produces Maximal Disruption of Speech
Authors: MacKay Donald G.
Published: September 2005

A developmental study of delayed auditory feedback (DAF) indicated that: (1) DAF disrupts the speech of children more than adults, for all delays in feedback; (2) The delay for maximal interference varies with age. The older a subject, the shorter the delay producing maximal interference with his speech; (3) The peak interference delay remains at 0.2 sec, when adults reduce their rate of speech by drawing out speech sounds. This finding suggested that the critical DAF interval is independent of the duration of speech sounds in the returning auditory signal; (4) Slowing down the rate of speech as described above, reduced the amount of stuttering under DAF; (5) However, a subject's maximum rate of speech was significantly correlated with the duration of the delay producing maximal interference with his speech. The slower the subject's maximum rate of speech, the longer the peak interference delay. A correlation of maximum speech rate and frequency of DAF stuttering was also significant. The slower a subject's maximum speech rate, the more he tended to stutter under DAF. Since voluntary prolongation of speech sounds had the opposite effect, decreasing rather than increasing stuttering, it was suggested that: (l) Mechanisms determining the maximum speech rate are to some extent different from those governing the prolongation of speech sounds; (2) both the amount of stuttering under DAF and the peak interference delay are related to some as yet unknown factor or set of factors determining the maximum rate of speech, and, (3) this factor is age-linked since the maximum rate of speech varies inversely with age.
Attenuation of Longitudinal Ultrasonic Waves in Insulators at Room Temperature
Authors: Lewis M. F.
Published: September 2005

It is possible to distinguish between two intrinsic loss mechanisms for longitudinal ultrasonic waves propagating in dielectric single crystals, viz., the thermoelastic loss mechanism and the Akhiezer mechanism. In the normal derivation of the theoretical expressions of the attenuation coefficients for these mechanisms, the former involves the thermal conductivity and the thermal expansion coefficients, while the latter involves the thermal conductivity and the Grüneisen numbers of the thermal phonon modes. These Grüneisen numbers can only be deduced from a knowledge of the third-order elastic constants. We have found experimentally that, for the 15 materials for which sufficient data are available, the attenuation from the Akhiezer mechanism exceeds that from the thermoelastic mechanism by a factor of about 40. This result is shown to be a consequence of the distribution of the Grüneisen numbers of the thermal phonon modes about the mean value. It is suggested that our conclusions can be used to predict the total ultrasonic attenuation in other materials from a knowledge of a few macroscopic properties, even if the third-order elastic constants are unknown. Such predictions are made for GaAs, InSb, and diamond. The third-order elastic constants of GaAs, InSb, and LiF have also been used to compute the ultrasonic attenuation in these materials, and to compute the volume Grüneisen constants. The latter are found to be in good agreement with experimental values except for InSb.
Ultrasonic Diffraction of Light by Short Acoustic Pulses
Authors: Zitter R. N.
Published: September 2005

A theoretical analysis of the Raman-Nath diffraction of light by short acoustic pulses has been developed. “Short” means a pulse whose length in the medium is of the order of, or less than, the diameter of the light beam. Expressions are derived that give the angle and time dependence of diffracted intensity for pulse trains as well as single acoustic pulses. With pulse trains, each diffracted order becomes broadened by a “suborder” structure, which may be resolved under appropriate conditions. In the time domain, calculated curves are presented comparing the shape of diffracted light pulses to the originating acoustic pulses.
Scattering by Penetrable Spheroids
Authors: Burke J. E.
Published: September 2005

The exact spheroidal-function series solution for the scattering of a plane wave by a penetrable spheroid is used to obtain explicit low-frequency (long-wavelength) approximations in ascending powers of k = 2π/λ, where λ is the wavelength. The farfield scattering amplitude is given to the sixth power of k, and the fields near and inside the spheroid are given to the second and first power, respectively. The results are valid for prolate and oblate spheroids and arbitrary angles of incidence and observation.
Creeping-Wave Analysis of Acoustic Scattering by Elastic Cylindrical Shells
Authors: Uginčius P. , Überall H.
Published: September 2005

The Sommerfeld-Watson transformation is applied to the normal-mode solution of a plane sound wave being scattered by an infinite elastic cylindrical shell immersed in a fluid and containing another fluid. The resulting residue series is generated by poles that are the complex zeroes of a 6×6 determinant. These zeroes are found numerically by an extension of the Newton-Raphson method for complex functions. As in our previous work on sound scattering by a solid cylinder, it is found that besides the infinity of the well-known rigid zeroes, there exists a set of additional zeroes that gives rise to generalized Rayleigh and Stoneley waves. The behavior of these zeroes has been studied as function of the wavenumber and also of the shell thickness. The bistatic cross section was evaluated numerically and compared with experiments.
Direct Comparison of Subglottal and Esophageal Pressure during Speech
Authors: Lieberman Philip
Published: September 2005

Subglottal air pressure during speech was measured by two methods: (1) by recording from a tracheal catheter, and (2) by recording from a 10-cm-long balloon positioned in the middle third of the esophagus and correcting for the pressure developed by the elastic recoil of the lungs. A simple linear elastic-recoil correction factor was devised. The two measures of subglottal air pressure yielded similar results. Some of the conditions that can produce pressure artifacts in esophageal balloons are discussed. The data also show that peaks in subglottal air pressure are not always associated with phonetic prominence, particularly when several noncontiguous words are emphasized in the same breath group.
Identification of Speaker Sex from Isolated, Voiceless Fricatives
Authors: Schwartz Martin F.
Published: September 2005

A study was designed to investigate the ability of listeners to identify speaker sex from isolated productions of /f/, /θ/, /s/, and /∫/. Nine females and nine males recorded the four fricatives in isolation. The stimuli were randomized and presented via loudspeaker to 10 listeners for sex identifications. The results indicated that the listeners could identify the sex of the speakers from the isolated productions of /s/ and /∫/, but could not from the /f/ and /θ/ productions. Subsequent spectrographic analysis of the /s/ and /∫/ stimuli revealed that the female spectra tended generally to be higher in frequency than the male.
Acoustic Radiation from a Finite Line Source with N-Wave Excitation
Authors: Wright Wayne M. , Medendorp Nicholas W.
Published: September 2005

A shock wave with an N-shaped pressure profile is propagated in the equatorial plane of a weak spark in air. In the present work, the directional dependence of the acoustic waveform is examined for 0.5- and 1.0-cm sparks having discharge energies between 0.01 and 0.1 J. The transient signals are detected with a wide-band capacitor microphone that has a rise time of less than 1 μsec. As the spark axis is approached, an interval with no acoustic disturbance appears near the center of the waveform. The angular dependence of both the shock amplitude and the length of this central interval is found to be in qualitative agreement with the results of a linear analysis in which it is assumed that each point along the spark acts as a source of N waves.
Prediction of Finite-Amplitude Waveform Distortion with Dissipation and Spreading Loss
Authors: Cary Boyd B.
Published: September 2005

A new technique recently used for solution of the plane-wave Burgers' equation in a lossless medium has led to the development of an approximate analytical solution to Burgers' equation with dissipation for plane, cylindrical, and spherical sinusoidal waves. The solution is valid for the initial propagation zone prior to sawtooth formation for Gol'dberg numbers larger than 5 as indicated by comparison with a previous numerical solution of Burgers' equation for a plane wave. The approximate solution is expressed as a series that converges rapidly enough to permit calculations of harmonic levels by hand. For more viscous cases, where the approximate solution fails, the above technique leads easily to a numerical solution of Burgers' equation. By comparing the harmonic levels predicted by the numerical solution with empirical data taken on distorting spherical waves, it is concluded that numerical results tend to be below the measured values. It is felt that the numerical method can be of use in predicting distortion levels for practical underwater systems that exploit finite-amplitude effects.
Speech Recognition as a Function of Channel Capacity in a Discrete Set of Channels
Authors: Hill F. J. , McRae L. P. , McClellan R. P.
Published: September 2005

There have been many attempts to perform a frequency analysis of speech and to use the outputs of this analysis to provide cutaneous stimulation. The results of these tests have left in doubt the issue of whether or not cutaneous recognition of speech is actually possible. In addition to other difficulties, an optimum frequency analysis has never been achieved. Instead, filtering configurations have been chosen essentially arbitrarily. The systems considered may well have had insufficient channel capacity for speech recognition even in the event that the tactile stimulators were arranged in an optimum manner. In this paper, several sets of finite frequency band to discrete channels filters were considered. The frequency of each discrete channel was constrained to the fixed center frequency of the corresponding band so as to be directly translatable to the position of a tactile stimulator. Tests were conducted to measure the auditory recognition rate of speech, resynthesized as the sum of these discrete channel signals. From these measurements with different numbers of channels, a representation of recognition rate as a function channel capacity was obtained. It is anticipated that these results will be helpful in the choice of the optimum filtering configuration for test in actual tactile recognition.
Transient Response of a Rigid Sphere to a Plane Acoustic Step Wave
Authors: Tang Sing-chih
Published: September 2005

The transient response of a rigid sphere in an acoustic medium to a plane step shock wave is analyzed. The velocity response of the rigid sphere is found to be dependent upon the ratio of the mass of the sphere to that of the displaced fluid medium. The long-time asymptotic velocity of the sphere is identical to that of the particles in the incident shock wave only in the special case of the ratio equal to 1. The velocity responses of rigid spheres with various masses versus time after the shock wave arrives are plotted.
Structure of Confusions in Short-Term Memory between English Consonants
Authors: Klatt Dennis H.
Published: September 2005

Data on confusions in short-term memory between English consonants [W. A. Wickelgren, J. Acoust. Soc. Am. 39, 388–398 (1966)] have been reanalyzed within the framework of binary features. A new method of analysis is described that involves a similarity metric. The method produces an evaluation of individual features and associates a confidence level with each statement made about the data. With a confidence level greater than 0.99, it is shown that long frication, continuant, sonorant, sibilant, and voiced are features present in the data of Wickelgren. The issues of feature independence, completeness of a feature system, and the derivation of optimal features are treated. The advantages of the similarity metric over rank-order statistics, multidimensional scaling, and information transfer are discussed.
On the Propagation of Sound Waves in a Cylindrical Conduit
Authors: Benade A. H.
Published: September 2005

The series impedance and shunt admittance of an acoustic line is calculated from the linearized acoustic equations. Exact and limiting formulas for small and large tubes are provided for R, L, G, C, the real and imaginary parts of the characteristic impedance Z0, as well as the phase velocity v and attenuation constant α. All results are presented in convenient form for quick computation on the basis of tables and graphs. A self-consistent set of molecular data is presented. Accuracies of formulas and of the data are discussed in detail.
Measurement of Acoustic Intensity and Reflection Coefficient with Cardioid Microphones
Authors: Bauer Benjamin B.
Published: September 2005

The acoustic intensity In along a unit vector n̂ can easily be determined by using a cardioid microphone and a voltmeter. If an rms voltage e+ is generated with the microphone oriented against n̂, and e− with the microphone directed with n̂, then In = (e+2 − e−2)/(k12ρc), where k1 is the voltage sensitivity of the microphone and ρc is the specific acoustic resistance. In a plane wave reflected from a boundary (as in an impedance tube), the quantity e+2/(k12ρc) represents the intensity of the forward traveling wave and the quantity e−2/(k12ρc) that of the reflected wave. Thus the power reflection coefficient αr = (e−/e+)2.
Mechanism for the Optical-Acoustic Effect at Interfaces
Authors: Porter J. W.
Published: September 2005

An analysis is made of the production of acoustic disturbances at solid-gas and liquid-vapor interfaces that are subject to transient thermal radiation. The interaction of radiation with phase-exchange rate processes at the interfaces is the mechanism by which acoustic disturbances are produced. General expressions are derived for the perturbation velocity of the gas or vapor in terms of an arbitrary time-dependent radiant heat flux. Explicit solutions are derived for the case of a stepwise pulse of radiation. Results are applied to tungsten-oxygen, glass-nitrogen, and mercury liquid-vapor interfaces.
Normal-Mode Reverberation in Channels or Ducts
Authors: Bucker H. P. , Morris Halcyon E.
Published: September 2005

Equations are derived for calculation of sonar reverberation in terms of quantities used in a normal-mode propagation calculation. The equations are suitable for moderate to long ranges and for both surface ducts and shallow water channels.
Spikes on Sonic-Boom Pressure Waveforms
Authors: Pierce Allan D.
Published: September 2005

The cause of the spikes or peaks frequently observed on sonic-boom pressure waveforms is generally attributed to small-scale atmospheric variations representing deviations of the atmosphere from a stratified medium. A detailed mechanism consistent with this theory is proposed that interprets the spikes as being due to the simultaneous focusing and diffraction of a nearly planar N wave by an inhomogeneous layer in the atmosphere. Spikes appear on the waveform in regions where a ray analysis indicates a magnification due to focusing. That the mechanism does lead to spiked waveforms is exemplified quantitatively by analysis of a simple model. Examination of a limited number of data showing very pronounced spikes at one site and showing gradually vanishing spikes at adjacent sites during a given experiment suggests that the scale of the atmospheric irregularities should be of the order of 200 m, which is compatible with turbulence correlation coefficients derived by Panofsky for unstable air. The width of the spikes is related somewhat simply to the travel delay time of waves diffracted around the “edges” of irregularities. Estimates based on the data and the mechanism suggest that the dominant scattering layer should be of the order of 1–3 km above the ground. The mechanism appears capable of explaining the rounded category of sonic-boom waveforms as well as the peaked category.
Longitudinal Distribution of the Cochlear Microphonics inside the Cochlear Duct (Guinea Pig)
Authors: Honrubia Vicente , Ward Paul H.
Published: September 2005

Cochlear microphonics (CM) were recorded with glass micropipet electrodes inserted in the scala media in the four turns of the guinea pig's cochlea. From the data acquired, the longitudinal distribution of the cochlear microphonics were determined. The points of maximum sensitivity for different frequencies along the cochlear partition were 2 mm apart for a change of 1 oct. By increasing the intensity of the stimuli, there was a shift of 4 mm of the point of maximum voltage of the CM toward the base of the cochlea. The slope of the proximal side of the envelope was steeper than that of the distal side. Both proximal and distal slopes doubled their magnitude for a change from 300 to 3000 Hz. At moderate sound-pressure levels (i.e., 70 dB), the voltages of the CM were the same for all frequencies at the point of maximum stimulation.
Manifestations of Task-Induced Stress in the Acoustic Speech Signal
Authors: Hecker Michael H. L. , Stevens Kenneth N. , von Bismarck Gottfried , Williams Carl E.
Published: September 2005

In order to induce stress in an experimental subject, a task involving the addition of numbers under time pressure was developed. The subject was required to read six meters and to announce the sum of his readings, together with a test phrase. By controlling the duration of the meter display, the experimenter could vary the level of stress induced in the subject. For each of 10 subjects, numerous verbal responses were obtained while the subject was under stress and while he was relaxed. Contrasting responses containing the same test phrase were assembled into paired-comparison listening tests. Listeners could identify the stressful responses of some subjects with better than 90% accuracy and of others only at chance level. The test phrases from contrasting responses were analyzed with respect to level and fundamental frequency, and spectrograms of these test phrases were examined. The results indicate that task-induced stress can produce a number of characteristic changes in the acoustic speech signal. Most of these changes are attributable to modifications in the amplitude, frequency, and detailed waveform of the glottal pulses. Other changes result from differences in articulation. Although the manifestations of stress varied considerably from subject to subject, the test phrases of most subjects exhibited some consistent effects.
Effect of the Skull in Degrading the Display of Echoencephalographic B and C Scans
Authors: White D. N. , Clark J. M. , Chesebrough J. N. , White M. N. , Campbell J. K.
Published: September 2005

The skull causes topographical mislocalization in range of images of the brain due to the increased velocity of sound through its varying thickness. It also causes mislocalization in azimuth by refraction. Similarly, mislocalization in azimuth may result from echoes off the central axis of the transducer but distant to sonolucent areas of the skull, being displayed as if they lay in the central axis. Resolving power is degraded in range by the display of ringing due to either increased amplitude from strong echoes or reinforcing reverberation with the skull. Resolving power is degraded in azimuth because the varying attenuation at different parts of the skull will cause uniform point reflectors sometimes to return strong echoes, which will be displayed as a large image.
Effect of Harmonic Components on Frequency Discrimination
Authors: Henning G. Bruce , Grosberg Sheila L.
Published: September 2005

The effect of the presence of harmonics on frequency discrimination is measured as a function of the frequency of the fundamental component of the signal. For signals of fundamental frequency greater than approximately 2000 cps, harmonic components have little or no effect on the ability of observers to discriminate differences in frequency. Below approximately 2000 cps, however, differences in the frequency of signals containing harmonically related components are more readily discriminated than differences in the frequency of sinusoidal signals. These findings relate to the dependence of frequency discriminability on frequency.
Buffer-Rod System for Ultrasonic Attenuation Measurements
Authors: Papadakis Emmanuel P.
Published: September 2005

A method has been developed for making ultrasonic attenuation measurements in a large sample by means of a solid buffer rod temporarily bonded to the sample. A piezoelectric transducer is permanently bonded to the other end of the buffer rod. The ratios of the amplitudes of certain echoes are used to find the ultrasonic attenuation in the sample and the reflection coefficient at the buffer-sample interface at various frequencies across the band of the transducer. The echo-amplitude ratios are not affected by operating the transducer away from its resonant frequency, because none of the echoes considered arise from reflections at the buffer-transducer interface. A numerical analysis of the echo amplitudes is presented in which the reflection coefficient is assumed constant and the ultrasonic attenuation is taken as a power of the frequency. Experimental data are given on shear waves in a glass buffer rod on a fused-silica sample. The reflection coefficient varies little while the ultrasonic attenuation increases with frequency, fluctuating near 30 MHz.
Study of Tinnitus Induced Temporarily by Noise
Authors: Atherley G. R. C. , Hempstock T. I. , Noble W. G.
Published: September 2005

Subjects were exposed in one ear for 5 min to 13-oct band noise centered at either 2, 3, 4, or 6 kHz at 110 dB SPL. The resulting aftersensation, called “noise-induced short-duration tinnitus” (NIST) was matched for pitch and loudness in the nonstimulated ear. It was found that the pitch of NIST bears a constant relation to the frequency of the stimulus and that the difference between the equivalent frequency of NIST and the frequency of maximum threshold shift was equivalent to one critical band.
Frequency-Response Characteristic of Auditory Observers Detecting Signals of a Single Frequency in Noise: The Probe-Signal Method
Authors: Greenberg Gordon Z. , Larkin Willard D.
Published: September 2005

Four experiments were conducted to develop and test a method of determining the frequency-response characteristic of the observer when he listens for single-frequency signals presented against a continuous background of wide-band noise. After observers were trained to detect primary signals of a single frequency, probe signals of various other frequencies were presented infrequently, in lieu of the primary signal. Primary signals and all probe signals were presented with very similar amplitudes that would be expected to render them all equally detectable if presented alone in single-frequency experiments. Estimates of the detectability of the signals of the various frequencies were obtained concurrently in a two-alternative forced-choice procedure. The results from 14 observers were quite similar and show differences in detection as a function of signal frequency when the primary signal was of 1000 or of 1100 Hz. In general, the primary signal was correctly detected 75%–90% of the time while signals with frequencies at approximately 150 to 200 Hz on either side of the primary-signal frequency were detected at the chance level, 50% correct. In as few as three experimental sessions, the observer's frequency-response characteristic was obtained using the probe-signal method.