bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarity Coincidence Arrays
Authors: Clay C. S.
Published: October 2005

The purpose is to examine the performance of a multiple polarity signal-processing system for an array having a small number of channels. The system has a narrow directional response and small side lobes for CW signals. In the m-channel system, the instantaneous signals are sampled to determine the sign of the signals. If all m channels have the same sign, the output is 1 and otherwise the output is 0. The system performance is measured by the ratio of the mean output of system sN to the standard deviation of the output σN. Gaussian noise is assumed to be in each channel and is uncorrelated between channels. At small input-signal to noise-power ratios, sN/σN was proportional to the input-signal to noise-power ratio, N12 and f(m), where N is the number of independent observations and f(m) is a system function. f(m) has a maximum value at m = 6. The response of a six-receiver array was simulated on a delay line. The signals were delayed the times 0, T, 2T, 4T, 7T, and 13T. For a CW signal, the output was 1 at the frequency T−1, and the null-to-null width of the main lobe was (15T)−1. The side lobes were less than 0.1.
A PROCEDURE TO COMPUTE THE DEPTH OF A PRESSURE-SENSING DEVICE
Authors: Graefe Volker , Latham Richard
Published: October 2005

A method is described to take into consideration the variability of the specific volume of seawater when determining the depth of an instrument from the in situ pressure. The method is sufficiently accurate to eliminate all errors in the depth determination other than the error of the pressure sensor itself.
Toroidal Microphones
Authors: Sessler G. M. , West J. E. , Schroeder M. R.
Published: October 2005

“Toroidal” microphones are defined as microphones having toroid-shaped directional characteristics, i.e., they have minimum sensitivity along the rotational axis of the toroid and maximum sensitivity in the plane perpendicular to that axis. Several practical designs of toroidal microphones based on second-order gradient receivers are proposed and analyzed as to directional characteristics and frequency response. Experimental microphones are presented, some of which use a Helmholtz resonator tuned to the lower end of the frequency range to compensate the ω2 dependence of the second-order gradient receivers and to improve the over-all signal-to-noise ratio of the microphones. Measurements show that the microphone sensitivity in a plane through the rotational axis obeys approximately the expected cosine-squared law. In the direction of the rotational axis, the sensitivity at midfrequencies was found to be typically 20 dB lower than the sensitivity in the plane normal to that axis. The equalized frequency response in this plane is within ±3 dB from 0.3 to 2.5 kHz. Sensitivities are about −80 dBV/μbar. Using existing low-noise pre-amplifiers, this corresponds to a signal-to-noise ratio of about 35 dB for speech at conversational levels.
Measurement of the Phase of Vibrational Displacement by a Laser Interferometer
Authors: Serbyn M. R. , Andrews F. A.
Published: October 2005

A method of measuring the phase of vibrational displacement, utilizing a Michelson interferometer with a laser source, is described. Results of several applications are presented and discussed.
Optimum Passive Bearing Estimation in a Spatially Incoherent Noise Environment
Authors: MacDonald Verne H. , Schultheiss Peter M.
Published: October 2005

This paper studies the minimum bearing error attainable with a linear passive array. Signal and noise are stationary Gaussian processes with arbitrary power spectra, and the noise is assumed to be statistically independent from hydrophone to hydrophone. The Cramér-Rao technique is used to set a lower bound on the rms bearing error and the results are compared with the bearing error of a slightly modified split-beam tracker. The latter reaches the lower bound for a two-element array and comes very close to reaching it for a linear array with an arbitrary number of equally spaced hydrophones. Thus, the modified split-beam tracker is very nearly optimal for the uniformly spaced array. Comparisons of split-beam tracker error with the Cramér-Rao lower bound are also obtained for nonuniform hydrophone spacings.
Vibration in an Infinite Isotropic Elastic Plate Due to a Vertical Harmonic Load
Authors: Paul H. S. , Muthiyalu N.
Published: October 2005

Analysis and numerical results are presented for a problem in which a vertical harmonic load is applied to an infinite isotropic elastic plate. Two cases are analyzed: In the first case, an equal harmonic load is applied to the two bounding planes of the plate in a rectangular region, and in the second case, a harmonic load is applied to the bottom face equal and opposite to the harmonic load on the upper face of the plate. In each case, the vertical displacement at the center of the loaded area is derived and numerical results are presented.
Intensity Fluctuations in Reflections from the Ocean Surface
Authors: Brown M. Vertner
Published: October 2005

The fluctuations in energy occurring in successive reflections of acoustic pings from the ocean surface have been measured in the acoustic frequency range from 160 to 1360 Hz. The relations of these fluctuations to the independently measured statistics of the ocean waves indicate that the degree of fluctuation is proportional to the effective roughness ℛ up to a saturation roughness, the distribution of reflected energies departs more and more strongly from normal as the roughness increases, and only surface waves whose wavelength exceeds that of the impinging acoustic ping by a factor considerably greater than I will produce fluctuations in the reflected pings.
Acoustic Decoupling Properties of Onionskin Paper
Authors: Higgs R. W. , Eriksson L. J.
Published: October 2005

It has been previously determined that precompressed onionskin paper may be used as an acoustic decoupler. In our evaluation, compressional-wave measurements were made on various types of paper, and in particular onionskin typing paper, at 32 and 1000 kHz. At the lower frequency, a composite material technique was used to allow pressurization of the samples. The velocity of sound and attenuation were found to vary nonlinearly with pressure over the range from 0 to 2000 psi. This nonlinearity introduces a nonlinear acoustic loading of the transducer elements and is the main disadvantage of onionskin paper. However, it was confirmed that the onionskin paper should be more stable with pressure than the other papers, provided that it has been properly precompressed. Most of the insertion loss provided by onionskin paper is caused by the mismatch in acoustic impedance. Thus, a fairly wide variety of materials should provide equivalent acoustical properties.
Development of Simple Equations for Accurate and More Realistic Calculation of the Speed of Sound in Seawater
Authors: Leroy C. C.
Published: October 2005

Many equations for calculating the speed of sound in the sea suffer from a lack of accuracy in spite of their complexity. By taking an appropriate approach in the development of the equation and by limiting the data to be fitted to those that correspond to real seawater conditions, it is found that more simple and more accurate equations can be developed. A survey of the characteristics of all existing seawaters is first made. This leads to a substantial limitation in the existing data to be fitted and suggests the appropriate measurements for further research. Previous methods of formulation are then discussed and a new method presented. To illustrate the advantages of the latter method, two equations formulated in this way are given. One fits Wilson's second equation for seawater to within 0.1 m/sec in the domain described, and the other fits Wilson's corresponding data with a better accuracy than does Wilson's equation.
Experiments on the Acoustic Modulation of Large-Amplitude Waves
Authors: Muir T. G. , Blue J. E.
Published: October 2005

A series of experiments were preformed to study the parametric relationship between two high-frequency carrier waves and the difference-frequency wave created by their nonlinear interaction. The measurements were made in a freshwater lake in the farfield of all radiations. A split-face piston projector, 2 in. × 2 in., was driven by two pulsed power amplifiers, and the resulting acoustic fields were measured with three separate calibrated hydrophones. Before the experiments were conducted, the usefulness of a frequency selective acoustic filter (SOAB) in identifying pseudosound was established. In the first experiments, a 143 kHz difference-frequency wave having an extrapolated source level of 81 dB re 1 μbar at 1 yd was created from the nonlinear interaction of a 981-kHz and a 1124-kHz radiation whose source levels were 121 and 113 dB, respectively. The difference-frequency sound propagated according to the spherical spreading law, independently of the existence of the carriers, with a 1.7° half-power beamwidth. The difference-frequency SPL was found to be proportional to the product of carrier-wave amplitudes, except at high carrier-wave source levels, and proportional to the difference frequency to a power of 1.7. With few exceptions, the results showed good agreement with a mathematical model of the problem devised by Westervelt.
Underwater Acoustic Propagation Prediction by the Alternating-Direction Implicit-Explicit Computational Method
Authors: Smith M. C.
Published: October 2005

A computer solution of the wave-difference equations is found by using an interlacing implicit-explicit scheme. In the computation, the entire two-dimensional field is found as a function of time. The examples considered involve propagation in a homogeneous shallow-water channel, where the effect of superposition of discrete spectra produces characteristic modal patterns. The spatial sound-pressure fluctuations are represented as plot-density variations along the two-dimensional channel. Examples of discrete propagated modes as well as evanescent modes are presented. The size of the field that can be presented is limited by the size, accuracy, and speed of the computer.
Attenuation of Guided, Weak Sawtooth Waves
Authors: Temkin Samuel
Published: October 2005

This paper presents an analytical study of the decay of plane sawtooth waves traveling inside tubes. The analysis is based on energy considerations and takes into account the energy dissipated at the walls owing to heat and momentum transfer. The results are applicable to sawtooths with shock strengths δ in the range 0⩽δ≈0.1. Comparison with existing data [H. Medwin, J. Acoust. Soc. Amer. 36, 870–877 (1964)] shows good agreement within this range.
Interferometric Measurement of Ultrasonic Velocity in Liquids—Effect of Diffraction
Authors: Subrahmanyam S. V. , Khan V. Hyder , Raghavan C. V.
Published: October 2005

The effect of diffraction on Sound-velocity measurements in liquids was studied in the low frequency range, 0.6 to 3.0 MHz, using a single-crystal interferometer. The excess velocity ΔC over the plane-wave velocity C was found to follow the relation ΔC/C = 3.2λ32/2π2dD12 where λ is the wavelength, d the beam diameter, and D is the distance from the source at which measurements were made. The diffraction effects are 3.2 times the values envisaged theoretically [from Bass and Williams cited in H. J. McSkimin, J. Acoust. Soc. Amer. 33, 539 (L) (1961)].
Reply to “Comments on Two Letters by Neubauer on Creeping and Circumferential Waves” [J. Acoust. Soc. Amer. 46, 275(L) (1969)]
Authors: Neubauer Werner G.
Published: October 2005

Several previously published results on creeping wave and circumferential wave phenomena have been criticized by R. E. Bunney. This Letter is a reply to those criticisms.
Effects of Signal Quantization on the Performance of Multichannel Processing Systems
Authors: Vural A. M.
Published: October 2005

This paper determines the effects of amplitude quantizing on the performance of conventional or optimum multichannel space, time signal-processing systems, with emphasis on underwater acoustic applications. The system output signal-to-disturbance ratio is chosen as the performance criterion. The selection of proper analog-to-digital conversion parameters is influenced both by the characteristics of the system and the characteristics of external fields in which the system is operating. The external disturbance is assumed to consist of sonar self-noise, which included ambient sea noise and noise generated by nearfield noise sources, plane-wave interference, reverberation, or, in general, any combination of these. Through the use of representative assumptions on the statistical properties of external fields in space and time domain, some useful criteria for selecting the parameters of quantization are derived.
Comparison of ROC Curves from One- and Two-Interval Rating-Scale Procedures
Authors: Leshowitz Barry
Published: October 2005

The detection of a brief (40 msec) 1000-Hz sinusoid in the presence of narrow-band noise was investigated using a rating-scale procedure. Signals were added either to noise alone (simple detection) or to noise plus sinusoidal pedestal (pedestal detection). In the simple-detection experiment, the noise masker was presented in one condition as a steady background and in another as a gated burst for a duration equal to the observation interval. In the pedestal-detection experiment, the masker, consisting of noise plus pedestal, was gated on only during the observation interval. Receiver operating characteristics (ROC curves) were determined utilizing both a one-interval and a two-interval observation period. A comparison of performance measures estimated from ROC's for one- and two-interval paradigms showed that detectability was superior for the two-interval paradigm. The slopes of the ROC's for two-interval detection were slightly larger than unity and were greater than those obtained in comparable one-interval experiments.
Comments on “A Plea for Conformity” [J. Backus, J. Acoust. Soc. Amer. 44, 285 (L) (1968)]
Authors: Chapline Joseph
Published: October 2005

This is a defense of the existing system of notation in organbuilding.
Reply to “Comments on ‘A Plea for Conformity’ ” [J. Chapline, J. Acoust. Soc. Amer. 46, 475–476 (L) (1969)]
Authors: Backus John
Published: October 2005

The organbuilder's system of octave notation has too many disadvantages to justify substituting it for the present American Standards Terminology.
Sound Radiation from the Mouth of an Organ Pipe
Authors: Coltman John W.
Published: October 2005

A double-ended organ pipe, symmetrical about its midplane, was blown at one of its mouthpieces and radiation patterns were observed in an anechoic chamber. The sharp nulls on the midplane show that the unexcited end is very nearly as strong a source as the blown end. Thus, the blowing jet current, even though chopped by the switching action, does not contribute materially to the radiated sound. This also implies that the jet current does not contribute directly to sustaining oscillations in the pipe.
Approximating the Frequencies of the Musical Scale with Digital Counter Circuits
Authors: Stapelfeldt Roelif
Published: October 2005

All 12 frequencies of an even-tempered scale can be approximated by frequency division of the output of a single, stable, high-frequency oscillator. Digital integrated circuits have now become a convenient means for dividing by a different integer for each note. The 12 integer divisors giving the smallest attainable maximum frequency error are tabulated for binary counters ranging from 6–12 stages.
Influence of Vowel Environment upon the Duration of /s/ and /∫/
Authors: Schwartz Martin F.
Published: October 2005

The duration of /s/ and /∫/ in VCV utterances is differentially affected by the final vowel.
Effect of Random Noise on Plant Growth
Authors: Woodlief C. B. , Royster L. H. , Huang B. K.
Published: October 2005

The effect of random noise on the growth rate of 12 tobacco plants is presented. During a two-week period of exposure, the average growth rate of the plants decreased by 40.6%.
Resonance-Bar Damping Measurements by the Resonance-Buildup Technique
Authors: Fiore N. F. , Brach R. M.
Published: October 2005

Resonance-bar damping measurements are usually made with the sample vibrating at steady-state resonance or in free decay from resonance. Solution of the equation of motion of the damped harmonic oscillator indicates that the damping can be determined, also, by the rate at which a sample, initially at rest, builds up to resonance. This method allows damping measurements as a function of amplitude and frequency in times of the order of 10−3 sec. In addition, the damping is determined in the earliest possible stage of vibration, so damping phenomena sensitive to vibration, such as solute redistribution in the vicinity of dislocations, can be studied.
Use of Dispersive Delay Lines for Signal Processing in Underwater Acoustics
Authors: Tournois P. , Bertheas J.
Published: October 2005

Signal processors incorporating dispersive delay lines can be designed for matched filters in active sonars, for spectrum analyzers in passive listening, and for generators of frequency-modulated codes. Depending upon its bandwidth and its duration, the signal to be processed is fed into a dispersive delay line that is matched to it in the case of wide-band systems, or matched to an homothetic signal (a signal having the same modulation characteristics, the same time-bandwidth product as the original signal, but having a frequency scale multiplied or divided by a factor k and a time scale divided or multiplied by the same factor k) with a larger bandwidth in the case of narrow-band systems. In this last case, the signal is previously time compressed with an appropriate unit, such as a recirculating memory or a magnetic recorder.
Combining Sound-Pressure Levels of Unequal Frequencies
Authors: Lou S. C.
Published: October 2005

In combining many sound-pressure levels of different frequencies, the usual method of combining two at a time is tedious and prone to mistakes. The new method described, employing a table of antilog values, simplifies this procedure considerably. This method can also be used to find the average sound-pressure level from values measured at a standard array of points.
Thermal Relaxation in Humid Air
Authors: Monk Robin G.
Published: October 2005

A theoretical and experimental investigation of the molecular absorption process in air has been carried out with particular reference to the variation of Napier frequency (fmax) with water-vapor concentration (h′). It turns out that the relationship between these two quantities is a quadratic only at very low humidities and that, over the rest of the humidity range, the general relationship derived here is best approximated by an equation of the form fmax = const h′x, where 1 < x < 2. Critical examination of previous theoretical relationships shows that the rate of resonant interchange of energy between oxygen and water vapor has been underestimated because of the quadratic approximation. Reassessment of this quantity on the basis of the analysis herein yields a more realistic value that is more consistent with previous experimental findings in oxygen and closer to what one would expect from theoretical calculations. Details are also given of a numerical method of calculating Napier frequency directly from measured values of molecular absorption.
Subharmonic and Other Low-Frequency Emission from Bubbles in Sound-Irradiated Liquids
Authors: Neppiras E. A.
Published: October 2005

This paper presents measurements of the acoustic emission from gas bubbles of controlled sizes “seeded” into water and glycerol-water mixtures and subjected to sound fields over a wide range of frequencies and intensities up to, and beyond, the transient cavitation threshold. The emission from unprepared liquids was also recorded for comparison. A mechanical device has been developed for generating small bubbles of uniform sizes at controlled rates. The results suggest that there are at least two mechanisms for generating signals below the excitation frequency (f0): (1) Subharmonics of f0 may be produced by forced oscillations of bubbles whose radial resonance frequencies are submultiples of f0; (2) bubbles of any size may be shock excited to emit signals at their radial resonance frequencies. Large bubbles of certain preferred sizes are normally present, and their resonances probably account for many low-frequency signals that are not integral submultiples of f0. It also seems certain that some other mechanism unconnected with resonant bubbles contributes to the relatively strong signals observed at the first subharmonic (f0/2).
Rôle of the Vibrational Relaxation of Nitrogen in the Absorption of Sound in Air
Authors: Piercy J. E.
Published: October 2005

The vibrational relaxation of nitrogen is proposed for the mechanism of the anomalously large absorption of sound found at low frequency and high relative humidity in air.
Propagation of Sinusoidal Small-Amplitude Waves in a Deformed Viscoelastic Solid. I
Authors: Hayes M. A. , Rivlin R. S.
Published: October 2005

The propagation of a sinusoidal wave of small amplitude in an initially isotropic viscoelastic solid, which is subjected to a static pure homogeneous deformation, is discussed. The secular equation for a plane wave propagating an arbitrary direction with respect to the principal directions of the static deformation is derived. The complex slownesses corresponding to propagation along the principal axes of the static strain are found. Relations are obtained between these and the principal stresses associated with the static deformation, which generalize earlier formulas obtained by Ericksen for elastic materials.
Wave Propagation in Anisotropic Bars of Rectangular Cross Section. II. Flexural Wave Propagation
Authors: Nigro Nicholas J. , Andrews Richard
Published: October 2005

An approximate method is employed to obtain the solution for the problem of steady-state flexural wave propagation in anisotropic bars of infinite length and rectangular cross section. The first three dispersion curves are obtained for bars of orthotropic, tetragonal, hexagonal, cubic, and isotropic material with several different values of S (ratio of lateral dimensions). The work represents an extension of a previous study of the longitudinal wave-propagation problem that is discussed by Nigro [J. Acoust. Soc. Amer. 43, 958–965 (1968)].
Stability of Nonlinear Oscillations of Stretched Strings
Authors: Anand G. V.
Published: October 2005

The stability of damped forced vibrations and undamped free vibrations of stretched strings is investigated. The regions of stability for the forced vibrations are plotted in the amplitude-frequency plane. It is shown that undamped planar free vibrations are unstable.
Response of Linear Structures to Classes of Pressure Fields. I. Deterministic Nonconvecting Fields
Authors: Cottis M. G. , Collas P.
Published: October 2005

Pressure fields are classified according to the analyticity of the input-function wavenumber and frequency spectrum. This property is sufficiently general to allow for grouping of a host of different input functions into a class, and yet provides sufficient information for the calculation of the response. A methodology thus results for the theoretical prediction of the linear response of structures. Within the framework of this methodology, a detailed mathematical description of the excitation is not required; rather, knowledge of the nature of the singularities of the input-function spectrum suffices. This paper considers the important class of input functions whose spectra are meromorphic functions of wavenumber and frequency. The methodology and computational procedure are exemplified by the calculation of the response of simply supported uniform beams and plates to deterministic excitation; the excitation is described by input functions of the foregoing class. With a single calculation, response solutions result that are applicable to a variety of input functions. It is shown that the dependence of the response on the physical parameters of interest is dictated by the location and order of the poles of the input-function spectrum. The usefulness of the derived solutions in engineering applications is shown through a simple example.
Constants of a Trapped-Energy Electromechanical Transducer Made by Evaporating a Thin Layer of a Piezoelectric Crystal on Each Side of a Quartz Plate
Authors: Mason W. P.
Published: October 2005

One of the problems in making overtone monolithic crystal filters is that the electrodes become so small and the electromechanical coupling so low that the impedance becomes so high and the bandwidth so low that useful filters are not obtained. It is suggested in this paper that both of these difficulties can be removed by evaporating thin films of a high-electromechanical-coupled crystal such as lithium tantalate on both sides of a quartz-crystal substrate. An alternate construction is to cement thin single crystals on each side and decrease their thickness by grinding or sputtering. The thickness of the thin transducers are in the order of R times the quartz-crystal thicknesses where R is the plate-back parameter for a monolithic filter. It is shown that such a structure has a resonant frequency determined by the sum of the thickness of the quartz crystal and evaporated piezoelectric layer and a coupling coefficient given by kc2 = (h/b)k2, where k2 is the square of the coupling coefficient of the evaporated film, h is the thickness of one film, and b is half the thickness of the quartz crystal. For k = 0.6, as in lithium tantalate, the composite coupling kc is in the same order as for a quartz crystal. For an overtone mode, the composite coupling kc does not vary, whereas it varies as 1/n for an overtone quartz crystal. Since the impedance is very low, the filter impedance can be matched by standard transformers.
Phase and Amplitude Fluctuations in Propagating through a Layered Ocean
Authors: Kennedy Robert M.
Published: October 2005

A propagation experiment was conducted over a 25-mile wholly refracted (RRR) path for 48 h in October 1967. The data recorded during the experiment consisted of both the arrival time and the amplitude of acoustic pulses at 11 vertically spaced hydrophones. The source and the receivers were fixed, and the medium was sampled every tenth of an hour with a 10-msec pulse at 800 Hz. The propagation path between source and receiver was purely refractive and amounted to a complete cycle of RRR type of propagation. The means, variances, autocorrelation, autospectral density, cross correlation, and coherence function were estimated for both the amplitude and phase data. The probability distribution function for both amplitude and phase is demonstrated to be nearly Gaussian. An interrelationship between the time and space characteristics of the random inhomogeneities of the medium is illustrated. Wherever possible, the measured results are compared with the theoretical values of Chernov (1960). A comparison of the theory, which is based on a statistically homogeneous medium, with the measured values, obtained in a layered medium, is discussed.
Maximum Side-Aspect Target Strength of an Individual Fish
Authors: Love Richard H.
Published: October 2005

Experiments are described in which the target strengths of a number of individual fish were measured at various frequencies. The results of these experiments are combined with results from six other sources and an empirical equation approximating the maximum side-aspect target strength of an individual fish determined for 1 ⩽ L/λ ⩽ 100, where L is the fish length and λ is the acoustic wavelength. This result is combined with a theoretical estimate of the resonance of a fish containing a swimbladder, to produce a curve approximating the maximum side-aspect target strength of an individual bladder fish for L/λ⩽100.
Volume Scattering-Strength Profiles in the Northeast Pacific Ocean
Authors: Scrimger J. A. , Turner R. G.
Published: October 2005

A technique is described that permits the determination of the acoustic scattering strength of the ocean volume in terms of depth, frequency, and time. A pod of charges is lowered together with a hydrophone to various depths in the ocean and, by observing the amount of scattered energy produced by detonating units of the explosive charge pod, a profile of good resolution of the scattering strength versus depths obtained. The broad-band acoustic characteristics of the charges permit the spectral characteristics of the scattered returns to be determined. Observations made over an extended time period yield the time dependence of scattering. Measurements made in the northeast Pacific Ocean are given.
Intensity Summation of Modes and Images in Shallow-Water Sound Transmission
Authors: Urick R. J.
Published: October 2005

The modes and images of wave and ray theories for the propagation of sound in shallow isovelocity water with lossy boundaries have been summed and integrated without regard to phase that is, by summing and integrating mode and image intensities. This is equivalent to averaging over range and over source and receiver depths. A computer summation of both mode and image models gives the same result : cylindrical spreading for zero loss and a spreading equivalent to a −32 power of the range for all finite boundary losses when the ratio of water depth to wavelength is large. For the lossy case, the transmission loss is found to be proportional to the square root of the reflection coefficient at the boundaries. The same results are shown to be obtained by integrating a continuous distribution of images and modes. The theory leads to a series of curves of transmission anomaly plotted against normalized range that are useful for the prediction of loss in near-isovelocity shallow water, once values for the boundary-loss coefficient and volume-attenuation coefficient have been selected.
Scattering by Liquid-Coated Prolate Spheroids
Authors: Yeh C.
Published: October 2005

The exact solution of the diffraction of plane sound waves by a rigid prolate spheroid coated with a confocal sheath of penetrable acoustic material is obtained. Results are given in terms of spheroidal functions. Detailed numerical computations for the radiation patterns of the scattered wave are carried out for certain acoustic parameters. It is found that the coating alters quite significantly the scattering characteristics of an incident wave. Furthermore, because of the coupling between each expansion coefficient for the scattered wave with all expansion coefficients for the incident wave for the coated spheroid case, the Watson transformation technique cannot be used directly to yield expressions that are applicable at high frequencies.
Ultrasonic Radiation Field of a Focusing Spherical Source at Finite Amplitudes
Authors: Smith Carl W. , Beyer Robert T.
Published: October 2005

A PZT-4 ceramic spherical cap with a radius of curvature of 30 cm has been used to produce a finite-amplitude ultrasonic field in water at a frequency of 2.3 MHz. The field has been observed by a nonresonant probe with an active face of 18 in. diam. The fundamental, second, third, and fourth harmonics have been studied both along the axis of the beam and transverse to the axis. The axial values are compared with various theoretical analyses.
Thermal Relaxation in Nitrogen with CH4 and CD4 Admixtures
Authors: Henderson M. C. , Burbank L. J. , Glatzel J. J.
Published: October 2005

Using the pressurized acoustic-resonance tube developed in this laboratory, the shift in the napier (relaxation) frequency of nitrogen at 168°C has been measured as a function of percent of added methane, both normal and fully deuterated. The shift is linear up to 2% of impurity in each case, but is by far the greater with the deuterated methane: 1350 Hz/1% vs 240 Hz/1% for the ordinary. The degenerate unsymmetrical stretching mode of vibration at 2259 cm−1 in deuterated methane differs by only 72 cm−1 from nitrogen's vibration at 2331 cm−1, and a resonance interchange of energy is clearly probable. The symmetrical stretch at 2109 cm−1 is also within 10% of nitrogen. In the case of ordinary methane and nitrogen, there are no such near approaches. Precisely the reverse obtains in the case of oxygen and the two methanes.
Concentration and Temperature Dependence of the Molecular Sound Velocity and Compressibility in Aqueous Mixtures of Glycerol at 0.6 Mc/sec
Authors: Rajagopalan S.
Published: October 2005

The molecular sound velocity R and molecular compressibility B have been calculated at 0.6 Mc/sec in the complex-forming aqueous mixtures of glycerol at various concentrations and temperatures. A nonlinear variation of R and B with concentration has been found, confirming similar behavior noted previously in most of the aqueous mixtures.
Reflection of Ultrasonic Third-Harmonic Waves in NaCl
Authors: Scorey C. R.
Published: October 2005

The reflection at a stress-free boundary of the third harmonic of an ultrasonic wave has been observed. A maximum in the amplitude of the third harmonic is observed after four reflections from the stress-free boundary, contrary to theoretical expectations. Measurements under vacuum indicate that this is not due to a loading effect of the air in the capacitance detector used to measure the harmonic amplitude. It is noted that the harmonic generation is due almost entirely to dislocations in the crystal.
First-Branch Dispersion of Torsional Waves in Bimaterial Rods
Authors: Reuter Robert C.
Published: October 2005

Dispersion curves are presented for the first branch of torsional wave propagation in a rod consisting of two concentric circular cylinders of dissimilar materials. Conditions under which either or both constituent cylinders rotate as a whole are discussed.
Comments on “Finite Radial Oscillations of a Spinning Thick-Walled Cylinder” [J. L. Nowinski and S. D. Wang, J. Acoust. Soc. Amer. 40, 1548–1553 (1966)]
Authors: Bharatha S.
Published: October 2005

It is shown that contrary to the implication of the subject paper, finite radial oscillations of a spinning cylinder are dynamically inadmissible.
Tentative Method of Producing Diffuse Sound Fields
Authors: Raes Auguste C.
Published: October 2005

This paper describes a new method of approximating diffuse sound fields such as are needed, for example, in the measurement of sound insulation between rooms. The method is found to be a substantial improvement over conventional procedures, especially for field measurements.
System for Algorithmic Construction of Signal Waveforms with Optimal Autocovariance Properties
Authors: Lord Norman W.
Published: October 2005

A system for sorting and representing all possible waveforms has been developed for those classed as finite duration, balanced, constant amplitude, and frequency modulated. They are first categorized according to their frequency-time schedules into subclasses that are ranked in terms of the ratio between average and midrange frequencies. By representing successive intervals between time-axis crossings as elements of isosum integer partitions, it is then possible through primitively recursive relations to enumerate and generate in a well-ordered manner all possible waveforms in unambiguously defined subclassses. The waveforms can then be examined in sequence for optimal attainment of desired signal-processing properties. Furthermore, the subclasses themselves have a natural order that permits the entire parent class to be surveyed. The technique is applied to the problem of measuring an unknown clustered multipath distribution by replica cross-correlation. In each category of waveforms, an optimal subset is found which occupies a limited area of the map of isosum integer partitions. Relationships are developed among multipath distribution extent, waveform autocovariance features, and the computation time required for the resolution process. One example is to seek waveforms whose autocovariance has maximum lag in which it does not vary more than a specified amount. In a particular class, this yields waveforms whose autocovariance has essentially only one isolated sidelobe in addition to the central peak. This permits an explicit resolution of the multipath structure using Rank 3 sets of linear equations. As measured by the number of digital computer cycles required in the calculation, these optimal waveforms are 10 times more effective than linear FM or pseudorandom noise pulses of equal time-bandwidth product.
Effective Density of Flexible Polyurethane Foam When Considered as an Acoustic Fluid
Authors: West M.
Published: October 2005

When flexible polyurethane foam is considered as an effective fluid, the density calculated with the model is much less than the physical density of the absorbent. The inference is that the structure plays little part in the absorptive behaviour. This is consumed by considering the more elaborate two-fluid model.
Nearfield Pressure Distributions for a Rigid and a Flexing Piston in an Infinite Soft Baffle
Authors: Kuhn G. E. , Andrews F. A.
Published: October 2005

The nearfield pressures of a rigid piston (ka = 0.906 at f = 7.55 kHz) and a flexing piston (ka = 2.4 at f = 20.0 kHz) in an infinite soft baffle were measured in a tank by means of a toneburst technique. The resulting pressure profiles are presented as isobaric contours, comparable to those for pistons in a rigid baffle derived analytically by H. Stenzel [Handbook for the Calculation of Sound Propagation Phenomena, A. R. Stickney, Trans. (Springer-Verlag, Berlin, 1939)].
Automatic Speaker Verification Using Cepstral Measurements
Authors: Luck James E.
Published: October 2005

Automatic speaker verification was accomplished in this study using cepstral measurements to characterize short segments in each of the first two vowels of the standard test phrase “My code is .” The length of the word “my” and the speaker's pitch were used as additional parameters. The verification decision is treated as a two-class problem, the speaker being either the authorized speaker or an impostor. Reference data is used only for the authorized speaker. The decision is based on the test sample's distance to the nearest reference sample. Data is presented to show that, if reference samples are collected over a period of many days, then verification is possible more than two months later, whereas, if reference data is collected at one sitting, verification is highly inaccurate as little as 1 h later. Four authorized speakers and 30 impostors were examined, with error rates obtained from 6% to 13%. Impostors attempting to mimic the authorized speaker could not improve their ability to deceive the system significantly.
Identification of the “Shift” between Vocal Registers
Authors: McGlone Robert E. , Brown William S.
Published: October 2005

This study investigated the ability of listeners to identify the point where speakers indicated that they shifted from one register to another during phonation. Nine females and 10 males phonated an ascending and descending series of tones, identifying the level at which they perceived a shift between registers. These phonations were recorded and played back to judges, who made the same identifications on a perceptual basis. The results indicated that (1) females were slightly less variable in self-judgment of their shift between registers than were males and (2) greater variation in register-shift identification was found for judges listening to the recording than for the speakers' self-judgments while phonating. It was concluded that registers should be more rigorously defined—perhaps on both a perceptual and physiological basis—in order to account for the difficulty in perceptual identification.
Laser-Induced Acoustic Transients in the Mammalian Eye
Authors: Cleary Stephen F. , Hamrick Philip E.
Published: October 2005

Acoustic transients resulting from the absorption of normal mode and Q-switched laser pulses in the mammalian eye have been implicated in damage to retinal tissue. A theoretical analysis indicated that acoustic transients with durations of the same order as the laser pulse (e.g., 100 msec for a Q-switched pulse) and amplitudes of greater than 100 atm could be produced in model systems that simulate the retina. Piezoelectric transducers and a schlieren optical system were used to verify experimentally the theoretical predictions. By the use of these devices, studies were made of the production of laser-induced acoustic transients in the rabbit eye. An 18-mJ Q-switched ruby-laser pulse produced acoustic transients with amplitudes of 1000 atm in the immediate vicinity of the site of absorption, a 750-μ-diam spot on the retina. Normal-mode laser pulses of the same energy but with durations of 0.5 msec produced a train of pulses with amplitudes 500–1000 times less than the Q-switched pulse. The biological significance of these findings is discussed.
Reply to “Comments on ‘Monaural Loudness Functions Under Masking’ ” [Rhona P. Hellman, J. Acoust. Soc. Amer. 45, 1564(L) (1969)]
Authors: Richards Alan M.
Published: October 2005

Some comments are made with reference to Dr. Hellman's letter.
Ultrasonic Doppler Monitoring of Vocal-Fold Velocity and Displacement
Authors: Beach J. L. , Kelsey C. A.
Published: October 2005

We have compared ultrasonic Doppler signals from the region of the vocal folds with the actual motion of the folds in order to determine the reliability of using the ultrasonic Doppler system suggested by Minifie et al. [J. Acoust. Soc. Amer. 43, 1165–1169 (1968)] for monitoring the folds during phonation. Frame-by-frame analysis of high-speed split-image laryngeal film-showed that velocities and displacements calculated from the Doppler signals do not always correlate with the motions of the folds. Significant errors were found in the timing, magnitude, and general shape of the calculated velocity and displacement pattern. Furthermore, the relationship between recognizable Doppler frequency patterns and the corresponding motions of the folds was both inconsistent and ambiguous. Because of this ambiguity, the Doppler system proposed by Minifie et al. has proven unsatisfactory as a continuous monitor of vocal-fold velocity and displacement. Tests of this Doppler technique using a flat-surface phantom moving at typical vocal-fold displacement and frequencies resulted in an accurate correlation between the velocity and displacement patterns calculated from the Doppler signal and those measured from the film. The complex motions of the folds during phonation is postulated as the primary reason for the unreliability of this Doppler technique in vivo.
Airborne Measurements of the Acoustic Characteristics of a Sperm Whale
Authors: Dunn J. L.
Published: October 2005

Target strengths of a submerged target, believed to be a sperm whale, Physeter catodon, were measured with the use of a calibrated passive sonobuoy and explosive charges. Measurements of 148 sperm whale echolocation clicks in a 13-oct band having a center frequency of 1 kHz resulted in an average source level of 73.5 dB // 1 dyn/cm2 with a standard deviation of 3.51 dB.
Acoustic Radiation Patterns for the Echolocating Bats Chilonycteris rubiginosa and Eptesicus fuscus
Authors: Simmons James A.
Published: October 2005

The echolocation signals used by two species of bats, Chilonycteris rubiginosa and Eptesicus fuscus, were recorded with four microphones in an array about the bat's head. The bats were trained to broadcast their sounds at a small. Stationary target, and the microphones were arranged in the horizontal plane at angles of 0°, 22.5°, 43°, and 90° with respect to the direction in which the bat pointed its head. The signals produced by both species were directional, with most of the energy projected straight ahead. The sound pressures recorded 22.5° away from the main axis of the broadcasts were about half as great as those recorded from directly in front of each bat. Chilonycteris appears to use a slightly more directional beam than Eptesicus.
Binaural Interaction of Transients: Interaural Intensity Asymmetry
Authors: Babkoff Harvey , Sutton Samuel
Published: October 2005

A parametric study of the ΔI jnd for the lateralization of transients (i.e., the smallest change in intensity of a transient at one ear required to displace a click image from some referent ΔI position) was performed. Referent ΔI's were generated by presenting a click to one ear and a less intense click to the other ear. The ΔI jnd was determined by a further attenuation of the less intense click. The results indicate that click sensation level and the referent ΔI interact in determining the ΔI jnd. These results do not conform with predictions made by the latency-intensity conversion hypothesis, which has been advanced as a model for the lateralization of transients. An alternative model based on the premise that the ΔI jnd for the lateralization of transients is related to the monotic jnd for intensity was tested and confirmed.
Continuity in Alternately Sounded Tone and Noise Signals in a Free Field
Authors: Elfner L. F.
Published: October 2005

Two experiments are reported that employed 10 normally hearing listeners who demonstrated an ability to concentrate on an interrupted white noise that alternated with a tonal burst. The purpose of the study was to demonstrate continuity effects in a free field situation and to investigate the effects of frequency and level of the signal component, the duration of the noise component, and the angular separation of the two components. The results showed that the level and the duration variables effected changes in continuity thresholds. Angular separation did not appreciably affect the perception of continuity in the noise.
Masking with Continuous and Pulsed Sinusoids
Authors: Green David M.
Published: October 2005

The detectability of a brief 10-msec sinusoidal signal was measured in the presence of a sinusoidal masker. The frequency of the masker was varied while the frequency of the signal was fixed at either 250, 1000, or 2800 Hz. In the first study, the masker was either continuous or gated; when gated, it was also 10 msec in duration and occurred simultaneously with the signal. When the masker was continuous, the data agreed essentially with those reported by Wegel and Lane in their classic paper. If the masker was gated and near the signal in frequency, there was little difference in the amount of masking produced by the gated and the continuous conditions, although gating the maskers produced somewhat more masking, about 5 dB. When the frequency of the signal and masker differed, for example, in the case of a masker at 1200 cps with a signal at 1000 cps, the gated condition produced substantially more masking, about 40 dB. A second study measured how the signal level must be changed to compensate for an increase or decrease in the masker level. In the third study, the signal was presented at various delays after the onset of the maskers to determine how long the masker must be present to achieve, effectively, a continuous-masker condition.
Depth of Sequential Auditory Information Processing
Authors: Pollack Irwin
Published: October 2005

Higher-order Markov sequences were constructed by a digital computer, converted into electrical pulse trains, and transduced to a high-speed auditory display by earphones. Under appropriate conditions, the depth of sequential information processing available to the auditory system is virtually without limit.
Click-Intensity Discrimination with and without a Background Masking Noise
Authors: Raab David H. , Taub Harvey B.
Published: October 2005

A study of intensity discrimination employing click stimuli revealed three unusual effects. First, clicks are difficult to differentiate with respect to intensity. Second, the Weber function differs from those usually obtained with stimuli of longer duration. Third, click-intensity discrimination is, improved by the addition of a continuous background noise. Since click stimuli have virtually no energy variations, these results cannot be explained by stimulus-oriented theories of detection and discrimination.