bluuebunny/crossref_metadata_2025 huggingface dataset:
Occlusion Effect: Unilateral Sensorineural Hearing Loss
Authors: Tyszka Frederic A. , Goldstein David P.
Published: September 2005

The discrepancy between the occlusion effect and a corresponding sound pressure, which arises in the external auditory canal, was compare for 10 normal-hearing subjects and 10 subjects with a unilateral sensorineural hearing loss. No significant differences were found between the mean occlusion effects of the two groups. The increase in level of sound in the auditory canal, which follows occlusion of the ear, was greater than the associated occlusion effect, and this discrepancy between these two measures was the same for both groups. The results of the experiment indicate that the discrepancy between the occlusion effect and canal sound pressure shift does not stem from a change from binaural to monaural hearing upon occlusion of the ear canal. Alternative hypotheses concerning why this discrepancy occurs are discussed.
Reply to “Comments on ‘Farfield Spectrum of the Sonic Boom’” [E. E. Zepler, J. Acoust. Soc. Am. 43, 374(L) (1968)]
Authors: Howes Walton L.
Published: September 2005

In Zepler and Harel's studies of auditory response to sonic booms the theoretical calculations should have been for N wave inputs and triangular-wave outputs from the ear, rather than for ramp functions. The test results may possess appreciable error because the perceived shock pressure-rise rate, which determines the loudness, was limited by earphones, rather than by the ear.
New Experimental Technique to Measure Ultrasonically Induced Mixing
Authors: Santhanam N. , Bakhshi N. N.
Published: September 2005

A new experimental technique has been developed to measure the mixing produced by ultrasonics in a flow system. The experimental studies were carried out in an ultrasonic tank coupled with an ultrasonic generator. The generator produces sound waves at 90 kc/sec at all average output of 80 W. Stimulus response technique was used to measure the residence time distributions. Water was allowed to flow through the tank at flow rates of 55, 125, 187, and 250 ml/min. Residence time distributions were measured for each flow rate under each of the following five conditions: (1) no stirrer, (2) insonation, (3) stirrer at 200 rpm, (4) stirrer at 260 rpm, (5) stirrer at 1800 rpm. A slug of sodium hydroxide solution was used as a tracer, and the tracer output was measured by a pH meter. From the mean residence times obtained with insonation, an equivalent Reynolds number was obtained at each flow rate. A correlation is developed for the mean residence time in terms of the equivalent Reynolds number. An index for mixing “sonomixing number” has been developed to estimate the degree of mixing produced by ultrasonics in equivalent rpm for a given flow. The results show that sonomixing number is significantly affected by the flow. As the flow decreases, the sonomixing number increases. It is postulated that sonomixing number may be related to the ultrasonic intensity.
Quality of Reverberation
Authors: Shankland R. S.
Published: September 2005

In observations and measurements on the acoustical properties of a number of rooms varying greatly in size, shape, ornament, and surface finish, several factors bearing on the quality of sound have been noted. The generally accepted requirements for the reverberation-time characteristic as a function of frequency are rather stringent. It has been especially evident that when the high-frequency reverberation times in a concert hall are significantly longer relative to those of the midfrequency and low-frequency range than would normally occur, the acoustical conditions are judged unsatisfactory. A specific example of this condition has recently been studied in a new concert hall. Other factors relate to directional characteristics. It is concluded that highly isotropic reverberant sound is not pleasant, but confusing. Conditions are greatly improved if the preponderance of the reverberant sound approaches the listener from directions near the plane that includes the source and the listener's ears. For longer reverberation times, the quality is enhanced when it is possible to make some judgments of distance and direction by the binaural hearing sense, provided there is ample diffusion to suppress echoing. Binaural effects produce a sense of spaciousness, and this, rather than simply a prolonged reverberation time, is probably the principal effect giving rise to the exceptional acoustical properties of many large churches.
Transverse Vibrations of a Moving Thin Rod
Authors: Barakat Richard
Published: September 2005

The linearized transverse vibrations of a moving thin rod between two supports is investigated. Since the governing differential equation in the steady state is not self adjoint, the vibration frequencies and mode shapes are obtained via infinite systems of simultaneous equations using the mode functions of the corresponding stationary rod. Detailed calculations are performed for both end supports fixed and for both end supports simply supported. The energy of vibration is also investigated.
Response of the Bilinear Hysteretic System to Stationary Random Excitation
Authors: Iwan W. D. , Lutes L. D.
Published: September 2005

Time-average statistics of the response of the bilinear hysteretic system to an excitation with approximately white-power spectral density and approximately Gaussian probability distribution are determined, using electronic-analog techniques. Results are presented for the mean-squared amplitude, the power spectral density, and the probability distribution of the response. The applicability of the Krylov-Bogoliubov method of equivalent linearization to this problem is investigated by comparing predicted and experimentally measured values of the mean-squared level of response.
Power Flow between a Class of Coupled Oscillators
Authors: Newland D. E.
Published: September 2005

The equation of mean power flow between two groups of randomly excited oscillators is derived from first principles. Subject to the coupling satisfying certain requirements, it is shown that a new parameter—the average natural frequency shift of the oscillators owing to the coupling—determines the power flow between the two groups. Power flow is directly proportional to the natural frequency shifts and to the oscillator densities (modal densities) in each group. It is suggested that this formulation has advantages over the conventional “coupling-loss-factor” equation of the statistical energy approach to noise-transmission problems.
Focusing Properties of Cylindrical Liquid-Filled Acoustic Lenses with Large Diameter-to-Wavelength Ratios
Authors: Folds D. L. , Brown D. H.
Published: September 2005

The focusing properties of liquid-filled cylindrical acoustic lenses are investigated theoretically and experimentally for lens diameter to wavelength (d/λ) ratios greater than 15. Geometrical aberration theory is used to determine the optimum index of refraction of the lens fluid and the maximum d/λ at which acceptable focusing in the Strehl sense will be maintained. A mathematical model that includes the effects of the lens shell is described and used to predict theoretical directivity patterns. A cylindrical lens 40 cm in diameter and 4 cm in height was constructed and tested at frequencies ranging from 25 to 900 kc/sec. Experimental directivity patterns are presented and compared with those predicted theoretically. The results of this investigation indicate that cylindrical lenses are practical at d/λ values up to 138, which is a factor of 10 greater than previously reported.
Volume Reverberation as a Function of Single Frequency Pulse Lengths and FM Sweep Rates
Authors: Keane John J.
Published: September 2005

Volume-reverberation tests were conducted with a vertically directional transducer at a frequency of 15.4 kHz. For each of two source levels, the system was capable of transmitting single frequency (SF) pulses of 10-, 50-, 100-, 300-, and 1000-msec duration and 1000-msec frequency-modulated (FM) pulses swept 100, 200, and 400 cycles. The relationship between volume reverberation level and pulse length is investigated. The data show a less than linear dependence of volume reverberation on pulse length and a linear dependence on source level. Reverberation levels for FM and SF pulses of 1000-msec duration are discussed. Although the amplitudes of the deviations from the mean reverberation are lower in the FM mode than the SF mode, no significant difference in mean levels is observed.
Stress Sensitivity of Piezoelectric Ceramics: Part 2. Heat Treatment
Authors: Krueger Helmut H. A.
Published: September 2005

The large rise in permittivity experienced by transducer ceramics when subjected to stress parallel to the polar axis can reduce the utility of these materials. Measurements are described on PZT-4 and PZT-8, representative of ceramics useful for high-power high-stress applications, for which a stabilizing heat treatment has reduced the change in permittivity. It is shown that the stabilizing effect is permanent. Several stress cycles to 10 or 20 kpsi also stabilize these ceramics. It is shown that the stabilization with stress for stress cycles to 10 kpsi is not permanent. Measurements were made over an aging range from one day to six months.
Stress Sensitivity of Piezoelectric Ceramics: Part 3. Sensitivity to Compressive Stress Perpendicular to the Polar Axis
Authors: Krueger Helmut H. A.
Published: September 2005

Measurements are reported of the change in permittivity, loss, and the piezoelectric constants, d31 and d32, for piezoelectric ceramic transducer materials subjected to high stress perpendicular to the polar axis (T1) Ceramics useful for high-power applications (PZT-4 and PZT-8) and some donor-doped ceramics of high sensitivity but with high losses that make such applications unwise (PZT-5A and PZT-5H) were tested. Permittivity generally decreased with stress, T1, opposite to results with parallel stress, T3. The piezo-electric coefficient d31 (in the direction of stress application) decreases markedly with stress, while d32 (in the direction perpendicular to the stress and the polarization) generally rises. The effects are less severe for the “hard” ceramics. A permanent change in pseudocrystal symmetry from ∝ m to 2mm is observed for the donor-doped ceramics, even at relatively low stress levels (5 kpsi).
Design of Spherical Radiators Capable of Producing Prescribed Directivity Patterns
Authors: Molloy Charles T.
Published: September 2005

Formulas are given that permit the calculation of the radial velocity at the surface of a spherical radiator, such that a prescribed pressure distribution will be achieved over the surface of any sphere, concentric with, and exterior to, the radiator. Formulas valid in the nearfield and the farfield are given. Both symmetrical and unsymmetrical pressure distributions are considered. A special class of symmetrical pressure distributions described by Chebyshev polynomials are discussed in detail. In particular, it is shown how these can be used to independently specify beam width and lobe suppression. Formulas and curves are also given for their directivity indices. A series of numerical cases were selected in which the beam width ranged from 10° through 90° and the side-lobe suppressions ranged from 10 through 40 dB. The distribution (continuous) of radiator surface velocity required to produce each of these was calculated on a high-speed digital computer. In addition, one of these continuous velocity distributions was approximated by discrete sets of radiating pistons having different sizes, and the pressure fields due to these arrays were compared to the pressure field that was originally specified. Some of the piston arrays reproduced the specified pressure pattern quite well.
Noise-Damage Criterion using A Weighting Levels
Authors: Mercer Derwent M. A.
Published: September 2005

The use of the single dBA level as a hearing-damage criterion was stated by Flanagan and Guttman [J. Acoust. Soc. Am. 36, 1654–1658 1964)] to be inapplicable. It is shown by consideration of a number of industrial noise spectra that dBA levels can be satisfactorily used in practice. A level of 81 dBA or less is safe, and over 88 dBA dangerous; intermediate levels need checking by analysis.
Films on Acoustics and Wave Motion
Authors: Stumpf F. B.
Published: September 2005

Films and film loops are listed for those teachers invested in presenting material relating to acoustics and wave motion. The source for obtaining these films are also given.
Four-Pole Parameters for Impedance Analyses of Conical and Cylindrical Shells under Axial Excitations
Authors: Hu William C. L. , Kana Daniel D.
Published: September 2005

A combined analytical and experimental study is presented to demonstrate that the four-pole parameters of a truncated, thin conical shell, under axial excitations, may be accurately obtained by applying membrane shell theory. A general calculation procedure is described, and the numerical results are applied to determine the mechanical impedances of shell-mass systems, and then compared with test data for three shell models with semivertex angles 0°, 15°, and 30° over a frequency range from 20 to 600 cps. The exce lent agreement indicates that the four-pole parameters calculated through the present analysis are adequate for vibration analyses, if the input excitation frequency is appreciably lower than a theoretical singularity, on the frequency spectrum inherent to the membrane shell theory. If the excitation frequency is near or above this singularity, a more accurate bending shell theory must be used.
Acoustical Design and Testing of the Centenary Auditorium of Madras University
Authors: Ramakrishna B. S.
Published: September 2005

The paper describes the acoustical design and testing of a 3250-seat multipurpose auditorium. Among the problems discussed here is the question of what reverberation time is optimal for a hall that uses a sound-reinforcement system to augment the direct sound. The design and performance of a sound-reinforcement system for the hall is also described. The hall has a volume of about 800 000 ft3 and a midfrequency RT of 2.3 sec when empty and 1.7 sec when full. The bass ratio is approximately 1.3. The maximum variation of the sound level over the seating area is 4.5 dB. The noise level (on C weighting) in the fully occupied hall is 42±1 dB without air conditioning and 52±1 dB with air conditioning.
Temporal and Intensive Factors in Binaural Lateralization of Auditory Transients
Authors: Elfner Lloyd F. , Tomsic Richard T.
Published: September 2005

The present experiment employed three experienced listeners. The primary purpose was to investigate the ability of the listener to detect a just noticeable shift from center of a dichotically produced auditory image. Thresholds were determined using a modification of Fechner's Method of Right and Wrong Cases. Thresholds were evaluated by means of an oscilloscope and camera. All combinations of a 600-Hz and a 6000-Hz tone and rise times of 10, 50, and 250 msec were used. Individual threshold plots are shown for each experimental condition. Tables are presented showing the intensity levels of the lead signal and the intensity differences between the two signals during the rise-time portion of the signal complex for the various values employed. A frequency-dependent relationship was indicated only for the 10-msec rise-time signal. It was also noted that time differences between equal intensity portions (of the two signals) are not constant throughout the rise time of the signals.
Detection of Monaural Signals as a Function of Interaural Noise Correlation and Signal Frequency
Authors: Wilbanks W. A. , Whitmore John K.
Published: September 2005

The effects of varying the interaural correlation for the masking noise on the detection of monaural signals between 150 Hz and 4000 Hz were investigated. A rating-scale procedure was used to obtain ROC curves, from which measures of detection (ds) and masking level differences (MLD's) were calculated. The results show that: (1) The magnitude of the advantage for binaural over monaural detection depends on the interaural correlation for the masker and the frequency of the signal; (2) the effect of signal frequency on MLD can be portrayed as a simple reduction in the interaural correlation for noise; (3) any sizeable binaural assistance in detecting monaural signals in noise of moderate intensity is confined to frequencies between 225 and 1200 Hz; (4) additive acoustic noise produced in the ear canal is not a sufficient explanation for the dramatic reduction in binaural assistance found for signals below 250 Hz; (5) the striking dependence of low-frequency MLD's on noise level suggests that the speed of propagation of the traveling wave, and the basal spread of neural excitation on the basilar membrane are the major determiners of binaural unmasking for these signals; (6) the consistent agreement of ROC curves for human observers with the appropriate theoretical curves for the degraded amplitude detector provides no evidence for believing that the stimulus distributions for binaural detection differ markedly in form from the amplitude distributions for monaural detection; and, (7) as long as care is taken in the training of observers, the Jeffress conversion from one value of ds and signal level to another is an efficient means of obtaining differences among interaural conditions.
Period Histogram and Product Spectrum: New Methods for Fundamental-Frequency Measurement
Authors: Schroeder M. R.
Published: September 2005

The fundamental frequency of a periodic signal whose fundamental component is not available for measurement can be determined by measuring the frequencies of its higher harmonic components and computing the largest common divider of these frequencies. Similarly, the fundamental period can be determined by measuring the periods of individual harmonics and finding their smallest common multiple. Several methods of fundamental frequency and period measurement, based on these concepts, are described in this paper. The results of computer simulations and analog instrumentations indicate that these new methods. at a considerable reduction in complexity, compare favorably with, and in some cases exceed, the capabilities of cepstrum analysis.
Elastic, Piezoelectric, and Dielectric Properties of Ammonium Dihydrogen Arsenate (ADA). I
Authors: Adhav R. S.
Published: September 2005

The elastic, piezoelectric, and dielectric constants of single crystals of ammonium dihydrogen arsenate (ADA) have been measured in the temperature range 20°–80°C. While the six elastic constants and their temperature coefficients are similar to those of ADP, the piezoelectric and the dielectric constants are somewhat different. The relative dielectric constants K11 and K33 are 85 and 22, respectively, at 25°C. The piezoelectric constants d14 and d36 are 36.5×10−12 and 27.5×10−12 C/N, respectively, at 25°C. The loss tangents tanδ11 and tanδ33 are high, and are 1.2 and 9 at 1 kHz frequency. The specific resistivities ρ11 and ρ33 are low and are in the range 5×107 Ω cm measured at 25°C.
Electromechanical Conversion Efficiency of Biased Semiconductor Transducers
Authors: Adler E. L.
Published: September 2005

The effect of drifting carriers on the electromechanical-conversion efficiency of a thin-film piezoelectric transducer deposited onto a delay rod is analyzed. When the acoustic loss in the transducer is due to the carriers only, significant improvement in the efficiency occurs near the half-wavelength or quarter-wavelength frequencies of the transducer, depending on whether the mechanical load presented by the delay rod is small or large. For supersonic carrier velocities, electromechanical-conversion gain is obtained near the mechanical resonances. A linear theory based on the acoustic-amplification mechanism is outlined and the extent of this electromechanical amplification illustrated by computations for a 2-μ-thick ZnO film.
Effects of Ultrasonic Waves on Gaussian Light Beams with Diameter Comparable to Ultrasonic Wavelength
Authors: Hargrove L. E.
Published: September 2005

A theory is developed for diffraction of a Gaussian light beam by arbitrary periodic ultrasonic waves. Special attention is given the case of light beam diameter comparable to ultrasonic wavelength. The approach is essentially an extension of the simplified Raman-Nath theory for normal incidence of light and sound, but the results should predict the general behavior under conditions other than Raman-Nath and/or normal incidence. Criteria for considering the sound beam to be “thin” are considered.
Representation of Viscosity by Translational Relaxation in Sound Waves
Authors: Morgan Edward J. , Kern Robert A.
Published: September 2005

A method is given for representing the effects of viscosity by means of translational relaxation. When applied to the absorption and dispersion of a sound wave in a monatomic gas, the relaxation theory gives a dominant root that is identical to, at low frequencies, and very similar to, at other frequencies, the dominant root of classical theory. Over all, the roots of the relaxation theory are very similar to the roots of the Burnett theory.
Frequency Discrimination and Masking Effectiveness
Authors: Nielsen Donald W. , Elliott Donald N.
Published: September 2005

Previous research has shown a positive relationship, across frequencies, between frequency discrimination limens and critical-ratio size; these were based upon data obtained from groups of subjects (S's). The question was therefore raised as to whether or not the critical ratio was related to the frequency-discrimination ability of individual S's. The present study shows a complete lack of relationship between critical ratios and frequency discrimination limens of individual S's at a frequency of 1000 Hz.
Detection and Localization Experiment: Comments on a Paper by Hershman and Lichtenstein [J. Acoust. Soc. Am. 42, 446–452 (1967)] and a Note on a Table of d′ for k = 2
Authors: Taylor M. M.
Published: September 2005

The probability of a correct answer, P(C), is not a valid index of sensitivity in the detection and localization (DAL) experiment although the DAL experiment is itself valuable. A table of d' exists for the DAL experiment with k = 2. In the construction of the table, Gaussian distributions of the critical variable were assumed, but no assumption was necessary about the relative variance of noise-alone and of signal-plus-noise distributions.
Comment on “Sound Transmission through a Finite, Closed, Cylindrical Shell” [P. H. White, J. Acoust. Soc. Am. 40, 1192–1193 (L) (1966)]
Authors: Manning Jerome E.
Published: September 2005

Recently, White presented a theoretical and experimental analysis of the noise reduction by a cylindrical shell [“Sound Transmission through a Finite, Closed, Cylindrical Shell,” J. Acoust. Soc. Am. 40, 1192–1193 (1966)]. His analyses correctly indicate that minima in the noise reduction occur at the ring frequency and the critical frequency. White's theoretical analysis attributes the minima in noise reduction at the ring frequency to increased modal density and at the critical frequency to an increased radiation resistance. In fact, the minima in the noise reduction at both the ring frequency and the critical frequency are governed by increased radiation resistance.
Noise Measurements of Turbulent Natural-Gas Diffusion Flames of 120 000- to 750 000-Btu/h Output
Authors: Putnam Abbott A.
Published: September 2005

Measurements of noise generated by natural gas/air turbulent-diffusion flames indicated two predominant frequency ranges. The less intense corresponds to a moderate amplification of the jet noise from the fuel sources during burning. The principal intensity was in the 100 to 500-Hz range and appeared to correspond to the output of monopole-type sources. Thermal efficiencies were in line with previously reported data at lower firing rates.
Spoiler-Generated Flow Noise. I. The Experiment
Authors: Gordon Colin G.
Published: September 2005

We discuss the growing importance of forms of aerodynamic noise other than classical jet noise in the modern gas-turbine engine. An experiment is described in which, on a model scale, the sound-generating capabilities of a flow spoiler within the environment of a pipe have been studied. A selection of results is presented. These show some of the principal findings of the study and the appearance of a correlation scheme for spoiler noise based on the total pressure drop across the spoiler.
Source Size as a Theoretical Limitation on the Determination of Wave Vectors by Detector Arrays
Authors: Posmentier Eric S.
Published: September 2005

An important class of infrasonic waves in the atmosphere and seismic waves in the earth's crust are generated by ocean waves in marine storms. The determination of wave vectors from such large sources by detector arrays is limited by the systematic errors introduced by the large sources, as well as by the resolving power and ambiguities associated with any given array configuration. The apparent phase lag and coherency between two detectors, each receiving signals from the multitude of mutually incoherent oscillators comprising a large source, is discussed as a function of source size and source-detector configuration. It is found that the apparent phase lags between two detectors may deviate from the phase lag of a ray from the source center. As a result, the apparent phase lags among the detectors in an array may lead to an apparent wave vector discrepant with the wave vector from the source center. Empirical results are presented to confirm the validity of this approach in the case of microbarom generation by ocean waves.
Discrimination of Mean Temporal Interval within Jittered Auditory Pulse Trains
Authors: Pollack Irwin
Published: September 2005

Thresholds for the auditory discrimination of mean interpulse interval were determined as a function of the number of intervals and of temporal variability, or “jitter.” Interval discrimination at low pulse frequencies is relatively independent of the number of pulses and of jitter. By contrast, interval discrimination at high pulse frequencies is extremely dependent upon the number of pulses and the level of jitter. The precision of interval discrimination achieved suggests that pulse interval discrimination for high pulse frequencies is carried out by a spectral analysis, rather than by a temporal analysis, of auditory information.
Periodicity Discrimination for Auditory Pulse Trains
Authors: Pollack Irwin
Published: September 2005

Two forms of periodicity are distinguished for auditory pulse trains in which information is coded in terms of the interval between successive pulses. Internal periodicity refers to the precision of reproducing adjacent intervals between successive pulses. External periodicity refers to the reproduction of a repeated pattern of successive pulses. Two variables were manipulated to study the discrimination of pulse trains of controlled internal and external periodicity: the number of successive presentations of a given pattern of interpulse intervals and the deviation of the intervals from strict internal periodicity. Equivalent results are obtained with both variables. Periodicity discrimination improves as the number of interpulse intervals within the pattern is increased and as the average interpulse interval is decreased. Acute periodicity discrimination is developed at high pulse frequencies with a large number of interpulse intervals. Periodicity discrimination at low pulse frequencies is relatively poor and is relatively independent of the number of interpulse intervals. Two quantitative models, based upon informational measures, are examined with respect to their rank orderings of conditions for auditory periodicity discrimination.
Study of Acoustical Treatments for Jet-Engine Nacelles
Authors: Marsh Alan H.
Published: September 2005

Preliminary experimental studies were conducted by the Douglas Aircraft Company, with assistance from the Pratt & Whitney Aircraft Company, to determine designs for nacelle treatments suitable for the P&WA JT3D turbofan engine, considering aerodynamic and acoustical criteria. The studies consisted of (1) evaluation of inlets with light-bulb-shaped center bodies by analytical aerodynamic studies and wind-tunnel model tests; (2) measurement of duct-wall sound-pressure levels during a ground runup of a JT3D engine; (3) measurement of airflow resistances, acoustical impedances, and absorption coefficients of various duct-lining treatment configurations; and (4) the determination of the attenuation achieved by several configurations of inlet and fan-discharge duct models for duct airflow velocities ranging from 75 to 465 ft/sec. From these studies, a nacelle treatment employing a broad-band resonator concept was developed, offering the potential for high absorptivity over a wide frequency range, with minimal weight and drag penalties.
Elastic Axial Shear Vibrations of a Hollow Cylinder Bonded to a Thin Shell
Authors: Anderson G.
Published: September 2005

Frequency equations and displacement ratios for elastic axial shear vibrations of an infinitely long hollow elastic cylinder bonded on its outer curved surface to a thin elastic casing are derived and compared with similar equations appropriate for hollow cylinders with (i) traction free surfaces and (ii) one traction-free and one clamped surface. Various plots of the natural circular frequency coefficients and displacement ratios have been made in order to display their dependence on shell thickness, core thickness, mass density, and elastic properties.
Comment on Papers Concerning Rectified Diffusion of Cavitation Bubbles
Authors: Safar M. H.
Published: September 2005

It is shown that the threshold of rectified diffusion according to the Hsieh and Plesset solution is in fact frequency dependent when the inertial terms in the equation of motion of the bubble are not neglected. A comparison is made between the threshold calculated from the modified Hsieh and Plesset solution and that obtained by Eller and Flynn, using numerically computed radius-time curves.
Wave Propagation in Anisotropic Bars of Rectangular Cross Section. Part I. Longitudinal Wave Propagation
Authors: Nigro Nicholas J.
Published: September 2005

An approximate solution is obtained for the problem of steady-state longitudinal-wave propagation in anisotropic bars of infinite length and rectangular cross section by employing the variational method of Ritz. The first three dispersion curves are presented for orthotropic, tetragonal, hexagonal, cubic, and isotropic systems.
Growth of Acceleration Waves in Isotropic Elastic Materials
Authors: Chen Peter J.
Published: September 2005

The growth of acceleration waves propagating in an isotropic elastic material is examined. The underlying assumption made is that the material is at rest in its reference configuration. First, we establish that only longitudinal or transverse acceleration waves may propagate, and the wave speeds are determined. Then, we derive the differential equation governing the growth of the amplitude of longitudinal acceleration waves and obtain explicit solutions for plane, cylindrically or spherically expanding waves. These results indicate that the amplitude of acceleration waves may either decay to zero in infinite time or become infinite (shock formation) in finite time; the radius effect on the amplitudes of cylindrical or spherical acceleration waves are not of the form 1/r12 or 1/r, as predicted by lineary theory. On the other hand, the behavior of transverse waves is similar to that obtained by linear theory.
High-Temperature Shear Ultrasonic Interferometer Using Sensitive Phase-Lock Detection System
Authors: Simmons J. H. , Macedo P. B.
Published: September 2005

A high-temperature ultrasonic interferometer for the study of propagation properties of shear waves through molten glasses below 1600°C and between 3 and 23 MHz is described. Techniques for measuring velocity and absorption of the transmitted echoes are presented with special emphasis on the study of shear waves in the relaxation region of a molten glass. In this case, an absorption per wavelength as high as 5.4 Np/cycle was measured; this is more than twice the capability of previously reported equipment. The use of a lock-in amplifier in the video circuit made this work possible. This method of handling the transmitted echoes not only suppressed noise by 25 dB, but also permitted measurements of pulse heights to better than 0.1 dB. The video circuit is not sensitive to rf values and can be used with most existing pulsed ultrasonic systems.
Numerical Prediction of Response-Peak Statistics of Linear Systems Excited by Impulsive Noise
Authors: Hedin G. L. , Lambert R. F.
Published: September 2005

Two methods of predicting response peak statistics (crests, positive maxima, and rises) for linear systems excited by Poisson impulsive noise are developed. One scheme yields good predictions for the statistics of fairly elementary systems. The other scheme extends these results to more complex systems, suggesting a method of approximating the complex system by an elementary one on the basis of basic system parameters. Empirical results obtained on a bimodal system are presented and agree well with the predictions.
Optimum Sizes and Shapes of Electrodes for Quartz Resonators
Authors: Mindlin R. D.
Published: September 2005

In this paper, formulas are given for sizes and shapes of electrode coatings, on quartz-crystal resonator plates, satisfying the criterion for Bechmann's number in all directions.
System-Reliability Prediction in Impulsive-Noise Environments, Based on Wear-Dependent Failure Rates, Using Response “Peak” Statistics
Authors: Smits T. I. , Lambert R. F.
Published: September 2005

An approach to system reliability under wearout and overload failure is outlined, where conventional models for these mechanisms are used to define wear-dependent failure rates in terms of response “peak” statistics. System-failure rates are seen to be bounded above, making predictions based on the Weibull distribution too conservative at the “tail”, while certain normal-derived predictions are too optimistic. However, Weibull distributions are found quite useful in approximating the various response peak statistics for certain impulsive-noise environments encountered in random vibrations and elsewhere. The pitfalls of misusing “normalized” curves of reliability are cited and the need for future investigations is expressed.
Angle-of-Arrival Measurements from Two Plane-Wave Tone Sources
Authors: Igarashi Yoshiya , Beck Lloyd
Published: September 2005

The theory describing the direction of the apparent angle of arrival from two plane wave sources impinging on two receiver elements is examined experimentally. Initially, the theory was verified in the laboratory, using an electrical analogy of the acoustical configuration. Sea tests were also conducted to examine the validity of the theory. The results of these experiments are interpreted and are found to be consistent with the theory. The frequency of occurrence of angles that were outside of the geometrical limits of the two sources was in good agreement with the theory, based on the assumption that the difference in phase between the arrivals from the two sources is uniformly distributed.
Response of a System of Point Transducers to Turbulent Boundary-Layer Pressure Field
Authors: Jorgensen D. W. , Maidanik G.
Published: September 2005

A system of flush-mounted transducers has the properties of a spatial filter whose properties can be varied by varying the sensitivities and separations between the constituent transducers of the system. It is shown that, by properly adjusting the sensitivities and the separations, substantial reduction in the response of the system to the pressure field in a turbulent boundary layer can be achieved. Provided that the flow velocities are subsonic, this reduction can be achieved without substantially affecting the response of the transducer system to an incident acoustic pressure field. Particular examples are presented for systems consisting of two- and three-point transducers. Comparison is made of the responses of these systems with the response of a uniform transducer of finite size.
Aerodynamic Sound Generated by a Rotating Cylinder
Authors: Lauvstad V. R.
Published: September 2005

The flow generated by a sinusoidally rotating cylinder immersed in a viscous and slightly compressible fluid is calculated as a singular perturbation problem (in the Mach number). It is found that the transverse waves in the boundary layer are not sufficient to satisfy all conditions of the problem but that longitudinal waves have to be added. The latter escape the flow field as sound and are used as a basis for the discussion of certain aspects of aerodynamically generated sound from boundary layers. The expression obtained for the intensity of the radiated sound seems contrary to dimensional arguments common to the literature, which advocates an enhancement of the sound level above the free flow estimate due to the boundary. Here it is shown that, if the boundary-layer thickness is small as compared with the cylinder radius, the surface brings about a reduced rate of momentum exchange within the boundary layer, resulting in an essential reduction in the sound intensity. The technique adopted is to devise two separate, locally valid expansions of the dependent variables developed for the regions close to and far from the cylinder. These expansions display features closely related to boundary-layer theory, subject to modifications by compressibility effects, together with the subsequent slightly induced changes in the acoustic environment. Thus, the flow field is separated into an inner and outer régime. In the inner, the incompressible flow patterns are largely retained, whereas in the outer the compressibility effects are dominant. The two régimes are related by a matching that uniquely yields the necessary boundary conditions for each expansion.
Approach to Recreating a Sound Field
Authors: Camras Marvin
Published: September 2005

To recreate a “concert hall in a telephone booth,” a smaller volume is delineated within the original environment. The surfaces of this sound-transparent volume are covered with microphones, all having a directional pattern facing outwards from the volume. The sampled space is reproduced with an array of loudspeakers corresponding to the microphones but with their directional pattern pointed inwards. Since the listeners can move freely within the recreated environment, some basic limitations associated with binaural listening are removed. Experiments were made with a twelve channel system. Studies included (a) room effects, (b) anechoic listening, (c) localization accuracy, (d) relay loss, (e) use of a single low-frequency source, (f} sound distribution, (g) number and location of sources, (h) comparison with direct listening, and (i) comparison with earphone binaural listening.
Random Efficiency and Back-to-Front Random Ratio of Second-Order Pressure-Gradient Microphone
Authors: Yamamoto Takeo
Published: September 2005

The random efficiency and the back-to-front random ratio of the second-order pressure-gradient directional microphone are computed over a wider parameter range. The minimum random efficiency of 0.111 and the minimum back-to-front random ratio of 0.00395 is obtained.
Air Consumption, per Syllable, in Oral and Whispered Speech
Authors: Schwartz Martin F.
Published: September 2005

A spirometer was used to obtain measures of air consumption, per syllable, in oral and whispered speech. The results, obtained from six adult males, indicated a significantly greater consumption of air for the whispered syllable.
Wave Propagation in Lamellar Composite Materials
Authors: Achenbach J. D.
Published: September 2005

An exact dispersion relation is derived for time harmonic waves propagating in the direction of the layering in a lamellar composite. For high values of the ratio of the shear moduli, the dispersion curves depart at very small dimensionless wavenumbers from the limiting phase velocities for “long waves.”
Special Relationships between the Farfield and the Radiation Impedance of Cylinders
Authors: Sherman Charles H.
Published: September 2005

Relationships have been found between the far sound field in certain directions and the radiation impedance for arbitrary cylindrical vibrators. In special cases these reduce to exact solutions of problems that can otherwise only be solved numerically.
Comments on “Finite Radial Oscillations of a Spinning Thick-Walled Cylinder” [J. L. Nowinski and S. D. Wang, J. Acoust. Soc. Am. 40, 1548–1553 (1966)]
Authors: Huilgol R. R.
Published: September 2005

The exact method based on the theorem on quasiequilibrated motions of incompressible elastic bodies is used to show that the differential equation governing the oscillations of the cylinder obtained in the above paper is correct despite the use of an erroneous approach. Furthermore, the similarity between the oscillations due to a pressure impulse and impulsive angular velocity is pointed out, thereby making it possible to derive most of the results from an earlier paper dealing with pressure impulse.
Sea Lion Echo Ranging?
Authors: Schevill William E.
Published: September 2005

The weakness (even absence) of evidence for echo ranging by sea lions is reviewed. and the justification of Shaver and Poulter's assumption is questioned. Requirements for demonstration of echo ranging (echolocation) are summarized.
Some Relevant Fundamentals
Authors: Fitzpatrick Hugh M.
Published: September 2005

An earlier demonstration of the identity of hertz, “radian per second,” and reciprocal second is correct. Published criticisms are shown to be concatenations of erroneous postulates, invalid logic, and misusage of terminology. All names for this same unit are exact synonyms.
Computer Retrieval of Papers in Acoustics
Authors: Heaps D. M. , Heaps H. S.
Published: September 2005

A program for computer retrieval of papers in acoustics is being used to search titles of all papers that have appeared in four journals over the past 13 years. Title words and author surnames are truncated to five letters. The search may be weighted Boolean, fractional, or for associated words needed to formulate a request.
Brownian Motion in the Cochlear Partition
Authors: Harris Gerard G.
Published: September 2005

Estimates have been made of the Brownian-pressure fluctuations in the air. These are 18 dB below threshold (minimum audible field) for 3000 Hz. It is thus necessary to look into the ear itself to see whether thermal fluctuations limit the sensitivity of the ear. It is assumed that the first stage of amplification of acoustical energy takes place at the hair cell, and that it is the relative shear displacement between the top of the hair cell and the stereocilia that is the relevant parameter. Two estimates of Brownian fluctuation are made. The first estimate assumes a connection rigid enough to provide the greatest flow of acoustical energy to a hair cell—i.e., proper impedance match—and loose enough so that each hair cell has independent thermal displacements. The second assumes a rigid connection between the stereocilia and the tectorial membrane and thus the source of noise is the fluctuation in amplitude of the basilar membrane displacement. The impedances used in making these estimates were based on the in vivo measured impedances at the eardrum and the anatomy of the middle ear. The first estimate gives a singal-to-noise (S/N) ratio of 22 dB at threshold for 3000 Hz. The second estimate gives an (S/N) ratio of −33 dB. This calculation shows that it is necessary to assume that the stereocilia are attached to the tectorial membrane and that the hair-cell bodies are imbedded in the organ of Corti with some degree of rigidity. There is some direct experimental evidence for the assumption of rigid attachment, and there is much indirect evidence from ultrastructural studies. A critical evaluation is made of the assumptions and of the data used in the calculations.
Design of a Concentrator by an Ultrasonic-Ray Technique
Authors: Martner J. G.
Published: September 2005

An experimental study is made of the design parameters and the construction of a power ultrasonic concentrator. The technique is that of generating “rays” at the surface of a ferroelectric short cylinder vibrating in its lowest-frequency mode. A plot is made of the surface motion components of the cylinder, and it is found that the predominant components are radial rather than axial. The disseminator shape is determined by the internal ultrasonic-ray configuration that involves direction, reflection, and impingement upon the surface of a processing cavity. The resulting body is, essentially, a truncated ellipsoid of revolution whose outer surface is made of conic segments to facilitate construction. A ferroelectric disk is bonded at the center of the truncated flat surface and is driven by an oscillator and a power amplifier. In operation, a strong sonic field was observed within the cavity whose center is that of one focal point of the ellipsoid of revolution. The other focus determines the normal truncating plane that contains the driving transducer. Two devices are constructed where the number of reflecting planes is varied, and their feasibility as particulate-aerosol generators is disclosed. A simplified version of the device, where three reflecting surfaces are used, is able to form an aerosol cloud made from 0.5 gm of 100-μ aluminum platelets within 3 sec after initiation. The frequency of the devices tested is 46.6 kHz, which coincides with that of a BaTiO3 disk 5.1 cm in diam by 3.8 cm thick, coupled to a large piece of aluminum. A photographic study of the disseminator environment disclosed the formation of unexplained concentric rings about this vibrating device and visible on the surface containing said device.
Recognition Performance as a Function of Detection Criterion in a Simultaneous Detection-Recognition Task
Authors: Lindner William A.
Published: September 2005

On each trial, one of three stimulus events occurred: Presentation of (1) a 500-cps signal added to a sample of white noise; (2) an 1100-cps signal added to the noise; or (3) no signal added to the noise. In the detection-recognition condition, each listener reported whether a signal occurred (detection) and which of the two signals it was (recognition). The listeners' criteria for a YES response were manipulated through instructions. The functions of primary concern were those relating the proportion of correct recognition responses to the proportion of YES responses on signal-plus-noise trials, p(YES|S). The ability of listeners to detect the signals when they were not required to make the recognition response was measured in the detection condition. The proportion of correct recognition responses on trials on which the detection response was NO, p(C|NO), was above chance at all detection criteria. The data contradict the predictions made by a threshold model adapted to the detection-recognition situation. The proportion of correct recognition responses on all signal trials, whether the detection response was YES or NO, p(C), was unaffected by changes in criterion.
Adaptive Optimum Detection: Synchronous-Recurrent Transients
Authors: Nolte L. W.
Published: September 2005

Adaptive optimum-detection theory is applied to the problem of detecting a recurrence phenomenon in noise. This phenomenon consists of one of a finite number of possible transient waveforms whose temporal uncertainty is synchronous Poisson. The optimum (likelihood ratio) receiver is designed from the viewpoint of obtaining a receiver implementation with a practical memory size while at the same time maintaining optimum-detection performance. The optimum detector for the synchronous-Poisson case recirculates and averages a nonlinear function of the input data in contrast to the optimum detector for the periodic case that recirculates and averages the input data itself. The detection performance is evaluated, and the receiver operating characteristics (ROC) are presented as a function of average duty factor ν, number of synchronous intervals k, transient waveform energy Ec ,and the noise power per unit bandwidth N0. At low transient signal-to-noise ratios and low average duty factors, the detectability d is given approximately by ν2k (2Ec/N0). The effect of transient uncertainty on detectability is also presented on the ROC.