bluuebunny/crossref_metadata_2025 huggingface dataset:
Free Vibrational Analysis of Sandwich Conical Shells with Free Edges
Authors: Siu Chun Chung , Bert Charles W.
Published: October 2005

An analysis is made of axisymmetric and unsymmetric free vibrational modes of right-circular conical or cylindrical shells with free edges. The shells may be either homogeneous or symmetrical sandwich, with facings and core either isotropic or specially orthotropic. Numerical results for a Rayleigh-Ritz solution are presented and compared with experimental data for conical frustum shells of homogeneous isotropic material and of sandwich construction with specially orthotropic facings and core.
Sensory Function in Multimodal Signal Detection
Authors: Fidell Sanford
Published: October 2005

Five observers detected a sinusoid in noise in a two-interval forced-choice experiment. The signal could occur on an earphone, on an oscilloscope, or on both devices simultaneously. Detection performance was studied as related to (1) mode of occurrence of the signal(s); (2) the external noise correlation in the auditory and visual channels; and (3) the observers' a priori knowledge of the mode of occurrence of the signal. The observed improvement in sensitivity (measured in d′ units) as a function of bimodal signal presentation closely followed the predictions of a statistical summation model and was much lower than predicted by linear and probabilistic addition models. Under conditions of independence of noise in the auditory and visual channels, some improvements in sensitivity were of almost 3 dB. The improvement in sensitivity afforded by a priori knowledge of the mode of occurrence of the signal was less for bimodal signals than for unimodal signals.
Masking-Level Differences Obtained with a Pulsed Tonal Masker
Authors: Hafter Ervin R. , Carrier Samuel C.
Published: October 2005

Masking-Level Differences (MLDs) were obtained for the binaural condition N0Sπ with pulsed tonal signals masked by pulsed tones of the same frequency and duration. MLDs were measured relative to the condition N0S0. Frequencies tested were 250, 500, and 1000 Hz; the duration was 125 msec. Detection was measured with four values of the signal-to-masker phase, which for N0Sπ produced: (a) an interaural difference of time (Δt); (b) an interaural difference of intensity (ΔI); (c) Δt and ΔI both favoring the same ear (consonance); or (d) Δt and ΔI favoring opposite ears (dissonance). The magnitudes of the MLDs were largest for conditions of Δt alone, next largest for consonance, and least for dissonance and ΔI alone. The MLDs were positive in sign, in contrast to the negative MLDs that have previously been reported for similar stimuli. Data were shown to fit a lateralization model in which differential time-intensity trading occurs for consonance and dissonance.
Efficient Monaural Procedure for the Psychoacoustic Calibration of Earphones
Authors: Harris J. Donald
Published: October 2005

A new procedure is examined for psychoacoustic calibration of earphones in which the air-conducted outputs of a standard and an unknown earphone are successively equated for loudness to a reference bone-conducted tone. The problem to the subject is one of monaural loudness discrimination, with arelatively small variance (differential sensitivity, 1.23–1.61 dB), and involves only four sources of variance associated with coupling two earphones to the same ear, and a single loudness discrimination judgment for each phone. The mean test-retest difference in the earphone transfer functions varied by 1.33–5.89 dB at different frequencies (midvalue=3.36 dB). Only a few minutes are required to complete a subject's observations at any frequency. Acceptable group means for transferring audiometric standards to an unknown earphone could be obtained at any frequency by requiring as few as nine subjects to make a single monaural loudness discrimination per earphone by this technique. In contrast, the traditional alternate interaural loudness balancing has a somewhat larger variance associated with the judgment per se (differential sensitivity, 1.50–2.50 dB), and involves the additional variances associated with collecting two absolute thresholds and coupling the two earphones to a second ear when the earphones are reversed on the head. The mean test-retest difference in the earphone transfer functions by the traditional “ear-reversal” method varied by 4.16–7.54 dB at different frequencies (midvalue, 6.30 dB)—nearly twice that of the suggested procedure.
Investigation of the Acoustics of Earmold Vents
Authors: Studebaker Gerald A. , Zachman Thomas A.
Published: October 2005

The influence of three simple earmold vents on the sound levels developed in a 2-cm3 metal cavity and in the human ear canal is studied. Below about 2000 Hz, the vents act in two ways: first, they act as a side branch producing a low-frequency filtering effect of a magnitude that is consistent with calculated values; and second, the vents complete a simple Helmholtz resonator circuit, which produces a reactance resonance superimposed on the power-transmission-loss curve. Above the resonance there is a gradual decrease in level up to the 2000-Hz region, above which complicated resonance patterns are seen. These patterns are probably dimensional resonances. The same over-all effects are seen in the results obtained in the ear canal, except that the resonances are smaller in size because of the higher damping in the real ear as compared to the metal coupler.
Extension of the Neff Neural Model to Situations Demanding Discrimination among Complex Stimuli
Authors: Trahiotis Constantine , Elliott Donald N.
Published: October 2005

Several experiments dealing with auditory performance of brain-damaged cats have been completed. Subjects with the auditory areas of both cortices ablated are able to discriminate auditory stimuli whose frequency components are present in an ongoing neutral background. Further, it appears that ablated subjects are able to discriminate in situations demanding responses to more than one positive cue over trials, though not within trials. Transfer tasks provided evidence that the basis for the auditory discrimination could not have depended exclusively on the occurrence of a “greater neural event.” The inability of the brain-damaged subjects to perform a Neff pattern discrimination was again demonstrated. However, these same subjects easily performed a frequency discrimination whose frequency components and intensities were identical to those in the pattern task. Both conditions lend credence to the results found in the prior investigations and attest to the adequacy of the ablations performed on the subjects. The results of the main experiment are difficult to interpret in terms of Neff's neural theory [Neff, W. D. (1961). “Neural Mechanisms of Auditory Discrimination” in Sensory Communication, W. Rosenbleth, Ed. (John Wiley & Sons, Inc., New York) pp. 259–278]. Some further research on these problems has been specifically outlined, and some general questions about pattern discriminations have been put forth.
Measurement of Small Changes in Sound Velocity in the UHF Range
Authors: Dooley John W.
Published: October 2005

Several modifications of a pulse-echo technique for measurements of small changes in ultrasonic phase velocities are described. They are of varying complexity and precision. The best methods are accurate to 2 parts per million at 500 MHz; one of these is automatic and has a response time of the order of 1 sec. The methods are applicable as long as the waveform of one echo can be distinguished from noise.
Uniformly Valid Perturbation Series for Wave Propagation in an Inhomogeneous Medium
Authors: Lesser M. B.
Published: October 2005

The one-dimensional wave equation for a medium with small inhomogeneities of arbitrary character is solved by a uniformly valid perturbation technique. The technique does not depend on separation of variables. It is shown that even a small inhomogeneity can cause the common perturbation solution to diverge at large times. As an example, the method is used to obtain the solution to the problem of wave propagation through a medium with a step change in sound speed.
Interaction of a Plane Acoustic Wave with an Elastic Spherical Shell
Authors: Tang Sing-Chih , Yen David H. Y.
Published: October 2005

The interaction of a plane acoustic step wave with an elastic spherical shell is studied. The mathematical model of the shell incorporates the effects of membrane, bending, rotatory inertia, and shear deformation. A Laplace transform with respect to the time coordinate is used in the analysis, and the transformed solution is obtained in the form of a partial-wave expansion. By Watson's transformation, this partial-wave expansion is then converted into a series of integrals, which are evaluated asymptotically. The origins of the reflected and diffracted wave are then identified. Evaluation of the inverse Laplace integral gives the wavefronts and the amplitudes of the shell response and the fluid pressure in the acoustic medium at the wavefronts. A comparison of the results from the membrane and the refined theories of shells is made. Besides, the transient response in a short time after arrival of the incident wave is also computed numerically in the lit region far from the shadow boundary.
Dynamic Response of Elastic Bodies to an Oscillating Point Mass
Authors: Raske Theodore F. , Joung Ki S.
Published: October 2005

An analysis based on linear theory is presented for determining the dynamic response of a simply supported elastic body due to a moving point mass executing longitudinal harmonic motion with small amplitude about the center of the elastic body. The resulting regions of instability are determined in accordance with known procedures for equations which reduce to those of the Mathieu-Hill type.
Refraction Correction in Constant-Gradient Media
Authors: Wood D. H.
Published: October 2005

Let g be the magnitude of the gradient and c0 be the sound speed at the observer. The apparent distance (c0t) and direction (θ0) of a sound source determine the true distance (R) and direction (θ), which are given by R = (2c0/g)[cos2θ0+ (sinθ0+coth12gt)2]−12 and θ = θ0+Tan−1[cosθ0/(sinθ0+coth12gt)]. A compact graph for generating angular correction is based on the fact that θ−θ0 is the argument of the complex number 1+ie−iθ0 tanh12gt. Taking c0/g to be unit distance and g−1 to be unit time, only one ray-wavefront diagram is needed to represent all unbounded constant-gradient media. Scaled distance (Rg/c0) and true direction (θ) can be read directly from this diagram. Intensity (I) in an unbounded constant-gradient medium, measured in decibels, differs from 20 logR by a term that depends only on travel time: −10 logI = 20 logR + 20 log cosh12gt.
Comments on “Calculations of Eigenvalues for Uniform Fluid Waveguides with Complicated Cross Sections” [P. Laura, J. Acoust. Soc. Amer. 42, 21–26 (1967)]
Authors: Hine M. J.
Published: October 2005

The series solution suggested in a paper by Laura [J. Acoust. Soc. Amer. 42, 21–26, (1967)] for a doubly-connected duct, with hard boundaries, is applied to its correct vibration mode as opposed to that implied.
Effects of Electrical Current Applied to Cochlear Partition on Discharges in Individual Auditory-Nerve Fibers. II. Interaction of Electrical Polarization and Acoustic Stimulation
Authors: Teas Donald C. , Konishi Teruzo , Wernick Joel S.
Published: October 2005

This report describes the temporal patterns of discharges of single nerve fibers recorded by a microelectrode in the modiolus in response to short-term dc (5-sec) and ac stimulation delivered across scala media in the basal turn of the guinea pig's cochlea. These electrical stimuli produce increases or decreases in discharge rates, depending on the polarity of the current, but do not show adaptation effects when the current strength is moderate. Currents with scala vestibuli positive with respect to scala tympani (SV-ST) are usually excitatory, while currents with ST-SV produce reductions in discharge rate. The effect of a given polarity is found to depend on a unit's prestimulation spontaneous rate. When electrical stimulation is added to acoustic stimulation, the intensity function at best frequency is shifted laterally, with the direction of the shift depending on current polarity. When the effects of two sources of stimulation, acoustic and electric, are added, the maximum discharge rate seen for acoustic inputs is not altered; it only occurs at a lower strength of the acoustic signal. The addition of electrical stimulation to acoustic frequencies other than best frequency may show different effects.
Resistance-Capacitance Oscillator for Generating the Frequencies of the Equally Tempered Musical Scale
Authors: Gibbings D. L. H.
Published: October 2005

The frequencies of the equally tempered chromatic scale and the attenuation ratios of a uniform ladder attenuator are both in geometric progression. By modifying a Wien bridge oscillator so that the shunt resistance arm of the bridge is driven from a ladder attenuator, an oscillator has been devised that will generate the frequencies of the scale without requiring awkward component values. Two feedback amplifiers are used: one of them is frequency sensitive, and the other provides the necessary phase reversal and amplitude control. With simple transistor amplifiers, the frequency of oscillation follows the attenuator setting to within about 5 in 104, but ways are described by which the frequency of any semitone within an octave can be made correct to 1 or 2 in 104, without demanding comparable accuracy in the components. The circuit also allows the ratio between semitones to be progressively changed by the small amount required to accommodate the phenomenon of “octave stretching.” The design of an attenuator, using only preferred resistance values, is given, and the question of temperature coefficient and adjustment to standard frequency, A=440 Hz, is considered.
Reduction of Observer Bias in Reading Speech Levels with a VU Meter
Authors: Levitt H. , Bricker P. D.
Published: October 2005

A procedure is described for reading the levels of certain types of speech sources using a VU meter with minor modifications. The method involves random sampling of the waveform, a simple decision about pointer position by the observer, and strict rules for adjusting the range attenuator. The procedure is shown to reduce interobserver variability considerably when a substantial amount of speech is available from a relatively constant source.
The Role of Heat in the Production of Ultrasonic Focal Lesions
Authors: Pond John B.
Published: October 2005

A method was evolved to calculate the temperature cycles at the focus center of an intermittent beam of high-frequency mechanical waves. The computed temperatures were checked in brain tissue, using microthermocouples, for doses just sufficient to damage tissue at the focus center. Similar temperature cycles were produced in brain tissue, in the absence of mechanical wave energy, by applying pulses of electric current to embedded resistance wires in order to find out how far the tissue alteration could be ascribed to heating.
Implications of Speech-Recognition Studies
Authors: Fleming Lawrence
Published: October 2005

Automation has reduced many human tasks to subhuman-skill requirements. In this context, speech-recognition machines appear to be a logical further step.
“Whither Speech Recognition?”—A Rebuttal
Authors: Samuel A. L.
Published: October 2005

There are honest scientific workers in the field of speech recognition who are not blinded by glamor and deceit, who do not behave “like mad inventors or untrustworthy engineers” and who have honest answers to the questions raised by John Pierce [“Whither Speech Recognition?,” J. Acoust. Soc. Amer. 46, 1049–1051(L) (1969)].
Paced Recognition of Words Masked in White Noise
Authors: Holloway C. M.
Published: October 2005

An experiment is reported in which listeners make recognition responses to words mixed with one of five levels of noise and presented at one of five rates of presentation. An interaction is demonstrated between the effects of noise level and rate of presentation, which cannot be attributed to differences in enunciation of the test material at different rates of presentation.
Mechanical Parametric Amplification
Authors: Matzuk Terrance
Published: October 2005

As a possible means of improving signal-to-noise ratios in acoustic systems which must function in hostile environments, direct mechanical parametric amplification schemes have been investigated. Experimental amplifiers have been constructed and are described. A typical single-stage amplifier has a gain of 10 dB over a 450-Hz bandwidth.
Asymptotic Expressions for the Mean and Variance of the Output of Clipped DIMUS Arrays in a Field of Uniform Uncorrelated Gaussian Noise Plus Signal
Authors: Fitelson Michael
Published: October 2005

A new method for determining the mean and variance of the output of large clipped digital multibeam steering (DIMUS) arrays in the signal-noise field of the title is described. Simple asymptotic formulas for the mean and variance are developed under conditions which would otherwise necessitate lengthy computer calculations that would become practically impossible for very large arrays. For the case of an array with 40 hydrophones, the formulas yield results which are no more than 2.5% in error for input signal-to-noise ratio, R⩾1. For a fixed number of hydrophones, N, the accuracy improves as R increases (and vice versa). The formulas are exact in the infinite N limit, for all R>0.
History of Standardization in Mechanical Vibration and Shock
Authors: Muster D.
Published: October 2005

The history of standardization of mechanical vibration in the United States is traced from its inception in 1932 to date, from its beginning in the Z-24 Sectional Committee to the present S2 Standards Committee. In 1964, International Standards Organization Technical Committee 108, “Mechanical Vibration and Shock,” was organized. The current activities and future plans of ISO/TC 108 are discussed in terms of the tasks to which its seven working groups are committed.
Statistics of Combined Sine Waves
Authors: Lyon Richard H.
Published: October 2005

The first-order probability density of sums of sine waves having random phases and amplitudes is approximated using a method developed by H. E. Daniels [Ann. Math. Stat. 25, No. 4, 631–650 (Dec. 1954)]. Three cases are discussed: (1) random phase and equal amplitude, (2) random phase and sine-distributed amplitudes, and (3) random phase and rectangularly distributed amplitudes. Detailed results are presented for the first two cases. It is shown that extremal statistics may be quite poorly estimated by an assumption of normality.
Potential of High-Intensity Noise Testing
Authors: Morrow Charles T.
Published: October 2005

Very nearly all vibration of consequence in missiles and space vehicles is excited by aerodynamic turbulence or noise propagating from turbulence. The presence of noise began to stimulate interest, a decade or more ago, in supplementing the traditional vibration tests of the flight equipment by some form of acoustic noise test. More recently, interest and activity have focused on the application of the technique to major sections of space vehicles. This application is attractive because the noise environment is in principle easier to predict than the vibration environment; the noise test permits simulation of three-dimensional vibration with realistic equipment-to-structure mechanical-impedance relationships, equalization of the excitation signal for armature and fixture resonances is avoided, and the observation of functional interactions between different equipments of the same system during environmental testing becomes possible. Such system environmental testing is made possible by the development of high-intensity noise generators, especially in the form of electropneumatic transducers. The high-intensity noise test has its own peculiar limitations, which must be considered by the shock and vibration engineer if he is to use it to best advantage. As with vibration testing, much of the new technology must be learned while it is being used. For the immediate future, the test will be developed as a means of simulating, by fixed sound-pressure levels and point-to-point correlations, a composite condition of flight. In time, it may become possible to introduce variable time delays in the electrical random noise signals to make the point-to-point correlations of the test sound field correspond more closely to those of successive instants along the trajectory.
Interaction of Acoustic Waves with Moving Media
Authors: Kong J. A.
Published: October 2005

The problem of interaction of a plane incident acoustic wave with n-layer stratified moving media has been solved. The differential equations governing wave behavior in a moving medium are derived by employing first-order Lorentz transformation instead of the Galileian transformation that has been used in previous works. Solutions are facilitated by the introduction of propagation matrices. Reflection and transmission coefficients are then calculated by making use of these matrices.
Lateral Waves on Diffuse Interfaces of Finite Thickness
Authors: Lang R. H. , Shmoys J.
Published: October 2005

An investigation of the lateral wave excited on a transition layer of finite thickness is made. The layer is located between two homogeneous half-spaces of different refractive index. A line source is placed in the medium with the lower refractive index, and an exact integral representation is obtained for the scattered field. This integral representation is asymptotically evaluated for large k0 in two parameter ranges; first, when the layer is thick compared with wavelength; second, when the distance between the source and the observation point is large compared with wavelength. The results of the asymptotic analysis show that for thick layers there exists a close connection between layer continuity and lateral-wave strength.
Free Vibration of the Rectangular Parallelepiped
Authors: Fromme J. A. , Leissa A. W.
Published: October 2005

The “associated-periodicity” extension of Fourier analysis is used to obtain an exact solution of the classical, three-dimensional elasticity problem of free vibration of the rectangular parallelepiped. This problem has been completely stated for more than a century and has been solved for only a very few special cases. The characteristic determinant yielding the eigenvalues is formulated for the completely free, rectangular parallelepiped, although the method of associated periodicity can be straightforwardly applied to arbitrary boundary conditions. Modes are classified into eight mutually exclusive and collectively exhaustive symmetry classes. Numerical results are presented for the frequency spectrum of plane-strain vibrations of completely free rectangles according to two-dimensional elasticity and are compared with classical Bernoulli-Euler beam theory and Timoshenko beam theory (including the effects of shear deformation and rotary inertia).
Finite-Difference Analysis of the Vibrations of Solid Cylinders
Authors: McMahon G. W.
Published: October 2005

A finite-difference analysis has been used to study the free axially symmetric vibrations of solid, isotropic, elastic cylinders. A grid having up to 36 independent lattice points was used with simple central-difference formulas to set up a system of homogeneous equations, whose determinant was solved to yield the resonance frequencies. The results have been compared with Rayleigh-type thickness corrections to the frequency equations for thin disks and slender rods and with experimental observations on solid steel and aluminum cylinders. The results indicate an accuracy within 1% for the first longitudinally symmetric mode and within 4% for the second symmetric and first and second antisymmetric modes over a height-to-radius ratio range of 0.8–3.5 and for Poisson's ratio up to 0.34.
Effect of Clamping and Damping on Piezoelectric Bender Elements
Authors: Kaufman Alvin B.
Published: October 2005

Piezoelectric benders are commonly utilized for transducing elements in phonograph cartridges or reciprocally as emf-force devices. Their behavior in these applications has been well delineated in the literature. When the bender, used as a memory-storage element, is clamped and damped by an encapsulant, it exhibits anomalous behavior, which is not clearly (if at all) described in the literature. The construction, application, and performance of benders encapsulated and used for this application are described. The results of chemical shrinkage, thermal coefficient of expansion (TCE), and dynamic properties of the encapsulant on the piezoelectric-bender performance are delineated.
COMPOUND ACOUSTIC LENS SYSTEM
Authors: DuBois J. L. , Rosenblum W. , Gilmore R.
Published: October 2005

An acoustic compound design fulfilling the aperture and resolution requirements of the quartz-plate Solkolov acoustic image converter is described. Details of the lens construction and images obtained from its operation are presented.
Low-Frequency Auditory Characteristics: Species Dependence
Authors: Dallos Peter
Published: October 2005

The magnitude and phase characteristics of the sound pressure at the eardrum-to-cochlear microphonic potential transfer function were measured at low frequencies for four species: cat, chinchilla, guinea pig, and kangaroo rat. The former two and the latter two demonstrated radically different properties in both magnitude and phase response. It is suggested that, since at low frequencies the middle-ear transfer functions of these four species are similar, the discrepancies are caused by differing acoustic input impedances of the cochleas that are influenced by the physical dimensions of the helicotrema and of the cochlear spiral.
Pitch of Tone Bursts of Changing Frequency
Authors: Nábělek Igor V. , Nábělek Anna K. , Hirsh Ira J.
Published: October 2005

The pitch of tone bursts containing a linear change of frequency, either throughout 100% or for only a portion (5% and 25%) of the total burst duration, was studied. Pitch judgments for the tone bursts with the frequency change throughout the burst duration show that a single pitch can be assigned to the burst as long as the frequency change and duration are not too large. The single-pitch character of such a glide deteriorates as the product of the burst duration and frequency change increases and seems to follow the change of spectra. For the bursts with short transitions, when the frequency change is not too large, the pitch assigned to the burst changes smoothly from the final to the initial frequency according to the delay of the transition onset. For larger frequency changes, bursts can be matched by either initial or final frequency, a case called separation, as distinguished from the more singular fusion. The change from fusion to separation corresponds to the change from spectra with one maximum to those with two maxima, as long as the frequency selectivity of the auditory system permits the formation of corresponding excitation patterns. Results obtained from measurements are compared with those calculated from a model.
Comparison of Violin Response Curves Produced by Hand Bowing, Machine Bowing, and an Electromagnetic Driver
Authors: Bradley J. S. , Stewart T. W. W.
Published: October 2005

Frequency response curves of a violin produced by machine bowing, hand bowing, and moving-coil electromagnetic driver are compared. Hand- and machine-bowed response curves compare favorably, the differences being attributed to the method used to clamp the violin for machine bowing. Machine-bowed and moving-coil driver curves compare less favorably, which fact is attributed to differences in the exciting velocities and rocking motion of the bridge.
Addendum: “Traveling Wave Velocity in the Human Cochlea” [S. Zerlin, J. Acoust. Soc. Amer. 46, 1011–1015 (1969)]
Authors: Zerlin Stanley
Published: October 2005

Some clarifications are offered regarding the acknowledgment in “Traveling Wave Velocity in the Human Cochlea” [S. Zerlin, J. Acoust. Soc. Amer. 46, 1011–1015 (1969)].
Plane Ultrasonic Transducer Diffraction Fields in Highly Anisotropic Crystals
Authors: Kharusi M. S. , Farnell G. W.
Published: October 2005

The diffraction field of a plane aperture or a plane transducer radiating into an anisotropic but homogeneous medium is obtained by means of an angular spectrum of plane waves for which the phase-velocity surface need only be defined numerically. This enables the calculation to be carried out under conditions of very high anisotropy, such as those prevalent for shear acoustic waves in low-symmetry crystals or for arbitrary light propagation directions in optically biaxial crystals. Examples are presented for long narrow, uniform ultrasonic transducers launching longitudinal or shear waves in quartz, the latter to demonstrate internal conical refraction. Reduction of the formulation to accepted angular spectra for isotropy is exact, and agreement is obtained with a published approximation method for longitudinal pure-mode directions.
Local Field of an Acoustic Source in a Submarine Canyon
Authors: Knollman G. C. , Hartog J. J.
Published: October 2005

An exploratory study is presented concerning hydroacoustic signal reception in the locale of a single-frequency CW ultrasonic source situated within an underwater submarine canyon. A first-order laboratory model of a submarine canyon is described together with the hydroacoustic studies that have been made with the simulation setup. For each of several transmitter positions within the canyon, ultrasonic reception has been recorded continuously in (transmitter-to-receiver) range for a variety of orientations and depths of receiver relative to transmitter. Although canyon geometry was arranged to be readily changeable, only canyon width has been varied thus far. Some broad inferences from our study are: (1) a submarine canyon can behave as a waveguide and channel sound almost undiminished for some distance down the canyon, both within and above its confines; (2) the canyon can act as an acoustic horn relative to sound radiation immediately above its confines; and 3) sound reception beyond the locale of the canyon can be appreciably smaller than that realized in the absence of the canyon. Quantitative results depend on the transmitter position within the canyon, canyon geometry and topography, the nature of the sound source, and the relative location of the receiver.
Forced Vibration of a Cantilevered Tube Conveying Fluid
Authors: Chen Shoei-Sheng
Published: October 2005

The problem of the forced vibration of a cantilevered tube conveying fluid is solved for time-dependent loading and under arbitrary initial conditions. The solution is obtained by making use of the properties of the linear operator and its adjoint operator intrinsic to the governing differential equation of motion and boundary conditions.
Application of Holographic Interferometry to Vibrations of the Bodies of String Instruments
Authors: Reinicke W. , Cremer L.
Published: October 2005

Some eigenmodes of both the top and back plates of the bodies of string instruments are known from measurements made with capacitance transducers. But this method is rather tiresome and therefore holographic interferometry is applied. It is not possible to use the “real-time” holographic interferometry because even the short time necessary for the photographic development of the hologram is long enough for the surface of the wooden body to change, perhaps because of small moisture changes. On the other hand, time averaging gives satisfying holographic pictures. Examples of those at low, middle, and high frequencies are given for excitation over the sound post and the bass bar, as well as on the bridge. Although the interference fringes on time-average holograms can be interpreted quantitatively, only qualitative conclusions are made, especially those which seem to be valid not only for this particular specimen but also in general.
Design of a Probe-Tube Adapter for Use with a 1-in. Condenser Microphone
Authors: Copeland Alfred B. , Hill David
Published: October 2005

A probe-tube adapter for use with a 1-in. condenser microphone has been developed. The greater sensitivity of the 1-in. condenser microphone provides a means for measuring the sound-pressure lever of pure tones generated in the human ear canal by application to the cranium of bone-conducted tones. The greater sensitivity is particularly useful in the frequency range below 300 Hz.
Experimental Investigation of the Resolution Capability of Microwave Ultrasonic-Beam Visualization Techniques Using Bragg Diffraction of a Laser Beam
Authors: Tsai C. S. , Hance H. V.
Published: October 2005

The theoretical resolution capability of Bragg-imaging technique for two-dimensional problems has been verified using ultrasonic waves in solids at frequencies in the vhf and L-band range. The resolution was investigated as a function of ultrasonic wavelength and laser-beam convergence angle. With an optical arrangement which utilizes a combination of a diffraction-limited spherical lens and low-grade cylindrical lenses, resolution nearly equal to the theoretical value was obtained. For this investigation it was necessary to devise techniques for generating multiple ultrasonic beams in one- and two-dimensional array configurations with well-defined beam dimensions and separations. It is found that the most reliable method of fabricating such configurations is to deposit a gold-film back electrode with an identical array pattern on a uniform CdS film transducer. The application of Bragg-imaging technique for visualizing the activity pattern of a CdS thin-film transducer is also illustrated.
Observation of Waves Radiated from Circular Cylinders Caused by an Incident Pulse
Authors: Neubauer Werner G. , Dragonette Louis R.
Published: October 2005

Schlieren visualization and hydrophone measurements are used to observe the radiated wavefronts which result when an acoustic pulse is incident on a metal cylinder in water. The range of size parameter ka from 138 to 1419 is considered. The wavefront positions are traced by the refraction, internal reflection, and radiation of shear and compressional waves. In the case of solid cylinders, many wavefronts display an apparent circumferential property derived from the incidence of energy from the normal to the appropriate critical angle. Identification of one of these wavefronts as resulting from previously identified “Rayleigh-type” wave propagation and a single incident angle is denied, although the circumferential property is verified. A previously identified faster circumferential wave is attributed to a composite wavefront resulting from direct compressional transmission and an increasing number of its internal reflections. Other wavefronts depending on mode conversions are also identified. A mechanism is presented to account for the apparent dispersion indicated by an increasing circumferential wave speed determined from previous hydrophone measurements below ka = 200. Simultaneous schlieren and hydrophone receptions that show the wavefront incident on a hydrophone as well as the resultant hydrophone output at ka values of 355 and 138 are presented. For shells, a prominent wave is seen to exist, in the same position, for both air- and water-filled cases. The wave is shown to be a characteristic of thin shells, originating from the transmitted compressional wave and subsequent mode conversion to a shear wave. The radiated wavefronts disclose a circumferential property for the waves that cause them. One such wavefront, believed to be the same described elsewhere as an antisymmetric Lamb wave, is proven in our case to be caused by direct transmission through the interior of a water-filled shell. The wave previously attributed to a Rayleigh-type circumferential propagation is shown to exist in aluminum shells as thin as those with a 0.9 ratio of inner to outer radius.
Sound Propagation in a Channel with Lossy Boundaries
Authors: Bucker Homer P.
Published: October 2005

The sound field of a CW point source in a duct with lossy boundaries is written as a normal-mode sum. It is assumed that the boundaries are parallel and that the sound velocity varies only with depth in the duct. As an illustrative example, calculations are made for a shallow water duct and compared to field data.
Derivation of the Stochastic Helmholtz Equation for Sound Propagation in a Turbulent Fluid
Authors: Neubert Jerome A. , Lumley John L.
Published: October 2005

The basic stochastic wave equation for sound propagation through a turbulent field is derived from first principles as represented by the continuity equation, the Navier-Stokes equations, and an appropriate equation of state. It is shown that, for very low turbulent Mach numbers and monochromatic transmissions sound propagation in a turbulent field can be adequately represented by the stochastic Helmholtz equation, ∇2p+k02μ2p = 0, if the acoustic wavelength does not exceed the Taylor microscale λg divided by [(σκ)12(u/c)]12, where σκ is the Prandtl number and u/c is the turbulent Mach number. In addition, the comparison of similar turbulent flows in air and in water, with respect to estimating their acoustic frequency limitations, is illustrated by contrasting: (1) the Baerg and Schwartz experiments with the Stone and Mintzer experiments, and (2) the turbulent lower atmosphere with the turbulent upper ocean.
Sound-Speed Dispersion in Liquid Cylinders
Authors: Del Grosso Vincent A. , McGill Richard E.
Published: October 2005

An inversion of the ordinate in the usual plot of the dispersion curves for axial acoustic propagation in liquid cylinders permits tracking the modes from their evanescent region for proper ordering and greater confidence in their use for acoustic waveguide mode analysis.
The Noisiness of Impulsive Sounds
Authors: Fidell Sanford , Pearsons Karl S. , Grignetti Mario , Green David M.
Published: October 2005

Four experiments were performed in an anechoic chamber to investigate the effects of duration, intersignal interval, repetition, and frequency on the perceived noisiness of impulsive signals. All data were collected by an adaptive psychophysical procedure called Parameter Estimation by Sequential Testing (PEST). The major conclusions were that (1) the phase spectrum of an impulsive signal is irrelevant to its perceived noisiness, and (2) the ear's sensitivity to noisiness of impulsive signals resembles an energy summation process; i.e., it appears to integrate total acoustic power of noise events to at least 100 sec.
Sampling and Interpolation of Bandlimited Signals by Quadrature Methods
Authors: Grace O. D. , Pitt S. P.
Published: October 2005

Methods of developing real and complex interpolatory representations of a bandlimited signal in which the quadrature components of the signal are explicitly exhibited are presented. Applied to the case of a bandpass signal, the real formulation is a new interpolatory result that has useful computational properties. Exact and approximate envelope and phase calculations are used to demonstrate some of these properties. In a similar application, the complex formulation gives the well-known result of Goldman and Woodward.
Earmold Alteration Effects as Measured in the Human Auditory Meatus
Authors: McDonald F. Douglas , Studebaker Gerald A.
Published: October 2005

Human ears were utilized to examine the effects of change in earmold form upon sound-pressure levels in the ear canal at selected discrete frequencies from 0.1 to 4 kHz. Four earmolds were fabricated for each of eight subjects. One retained an unaltered form for the purpose of comparison, while the other three were modified, respectively, to a shortened canal form, a shortened canal form which was vented, and an open form. Measurements were made utilizing a probe-tube microphone assembly. Relative to the unaltered earmold form, the shortened canal modification caused a slight reduction for all frequencies except 3 and 4 kHz, while the vented and open forms produced marked reductions in low-frequency response accompanied by large resonances. Certain relevant measurements made using a standard 2-cm3 a coupler and a special 2-cm3 coupler are also presented.
Classification of Spherical Targets Using Likelihood Ratios and Quadrature Components
Authors: Hoffman J. F.
Published: October 2005

The ability of a likelihood ratio processor to classify similar spherical underwater targets using quadrature components of their acoustic echoes was measured under highly controlled conditions. The five targets used were 7-in.-diam, 5-in.-diam, and 3-in.-diam solid aluminum spheres; a 5-n.-diam styrofoam sphere; and a 5-in.-diam hollow aluminum sphere. A pulsed sinusoid and a linear FM signal were transmitted, both with the same bandwidth. The performance of the likelihood ratio processor for a specified signal-to-noise (S/N) ratio (peak amplitude of echo to rms of noise amplitude) was portrayed with a Receiver Operating Characteristic (ROC) curve. For the pulsed sinusoid with known epoch, the performance was satisfactory for a majority of the target pairs when the S/N ratio was 0 dB or larger. For the pulsed sinusoid, it was found that the S/N ratio was a sensitive parameter that affected performance, and that an uncertainty in epoch over a cycle of the carrier resulted in the same degradation in performance as a 6-dB decrease in the S/N ratio. The performances obtained with the likelihood ratio processor for the linear FM transmission when the S/N ratio was −6 dB were of the same order as, but better than, that obtained for the sinusoidal pulse when the S/N ratio was 0 dB. Equivalent performances were obtained for both transmissions when the signal energies to mean-square-of-noise amplitudes of the messages for both transmissions were equal.
The Acoustic Position Reference System Used by the GLOMAR CHALLENGER on the Deep Deep Sea Drilling Program
Authors: Schneider William P.
Published: October 2005

The drilling vessel GLOMAR CHALLENGER has the requirement of maintaining a relatively fixed position in the deep ocean for periods as long as two weeks. The vessel's position is maintained by a dynamic positioning system that uses a sea-floor acoustic beacon for the position reference. This beacon, which is free falling and nonrecoverable, provides an acoustic signal consisting of a 4-msec pulse of energy at a frequency of 16 kHz every 2 sec; the beacon is battery operated and can be used in water depths up to 20 000 ft. This acoustic reference system has been used in drilling operations for over 2 yr with very satisfactory performance.
Ensemble and Time Averages of Reverberation from a Sea Surface: A Computer Study
Authors: Bourianoff G. I. , Horton C. W.
Published: October 2005

A realistic computer simulation of reverberation from a moving sea surface has been used to compare time and ensemble averages. The experiment simulated has a directional source and an omnidirectional receiving hydrophone located at a depth of 350 yd (320 m). The surface is insonified in a strip of constant width independent of range. The reverberation is calculated in three “windows” of width 0.1 sec located at 0.5, 1.0, and 1.5 sec for a fully developed sea resulting from wind velocities of 10 and 20 kt (5.1 and 10.3 m/sec). The pulse waveform is two cycles of a 1-kHz sinusoid. The sea surface is generated by using random phases in a Fourier polynomial of 100 terms. It is shown that, when the reverberation is reduced in the manner suggested by Ol'shevskii, the derived process is not stationary, but behaves like a narrow-band noise of constant amplitude and random phase. The lack of stationarity arises because the statistical properties of the phase change with time. The backscattering strengths of the sea surface, computed for six combinations of grazing angle and sea state, agree only moderately well with experimental measurements at sea.
Effect of a Random Bottom on Acoustic Propagation in a Two-Dimensional Ocean
Authors: Seifer Arnold D. , Jacobson Melvin J.
Published: October 2005

The effect of a stochastic ocean bottom on underwater acoustic propagation is examined in two previous papers by the authors [J. Acoust. Soc. Amer 43, 1395–1403 (1968); 44, 1103–1114 (1968)]. In those investigations, the first and second moments of the random acoustic intensity are determined for various source and receiving-point geometries. In a more recent study by the authors [J. Stat. Phys. 2, 279–289 (1970)], the amplitude and decibel amplitude, as well as the intensity, of a random acoustic field are examined. There, each of the three measures of acoustic strength is shown to differ from the others in the analytic properties of its mean value and standard deviation. Therefore, in the present paper, the random-bottom problem of the two earlier studies is reexamined. In particular, the first and second moments of the total-field amplitude and decibel amplitude are studied under certain restrictions and are compared with those of the intensity. Furthermore, the first and second moments of the total-field phase are treated.
Sound Attenuation between 200 Hz and 10 kHz
Authors: Skretting Audun , Leroy Claude C.
Published: October 2005

Trials have been conducted in the Western Mediterranean to confirm the excess attenuation of sound at frequencies between 200 Hz and 10 kHz. As sound propagation along the deep refracted path in the isothermal deep water of the Mediterranean is affected only by geometrical spreading and attenuation, it is possible to measure the attenuation separately for each frequency. The trials used explosive sound sources at different depths and at accurately determined ranges between 200 m and 30 km. Special care has been taken to separate the effects of finite amplitude from the attenuation and it is shown that the former are not responsible for the excess attenuation found at low frequencies. The authors have reported the analysis more thoroughly in SACLANTCEN Technical Report No. 156, “Sound Attenuation Between 200 Hz and 10 kHz.”
An Approach to Computing Time-Dependent Interaction Forces and Mutual Radiation Impedances between Pistons in a Rigid Planar Baffle
Authors: Stepanishen P. R.
Published: October 2005

An approach is presented to computing the time-dependent force acting on a piston as a result of the velocity of an adjacent piston which may be any specified time-dependent function. The method is based on a Green's function solution to the time-dependent boundary-value problem for an impulsive piston velocity motion. An asymptotic expression for the mutual radiation impedance between square pistons has been obtained using the method. A numerical approach is also presented to obtain the mutual radiation impedance coefficients from the time-dependent solution of the boundary-value problem. Numerical results obtained from the asymptotic expression are shown to agree with previously published numerical results and the results obtained using the numerical approach indicated in the paper. Numerical results for time-dependent interaction forces resulting from sinusoidal piston velocities are also presented and discussed.