bluuebunny/crossref_metadata_2025 huggingface dataset:
Minimizing plasma damage and in situ sealing of ultralow-k dielectric films by using oxygen free fluorocarbon plasmas
Authors: Mannaert G. , Baklanov M. R. , Le Q. T. , Travaly Y. , Boullart W. , Vanhaelemeersch S. , Jonas A. M.
Published: October 2005

Ultralow-k nanocrystalline silica films with an open porosity of 30–31% and a pore radius of 0.8–0.9 nm have been etched using oxygen free highly polymerizing fluorocarbon plasma. It is shown that such plasma allows minimization of plasma damage in comparison with standard oxygen containing CF4 based plasmas and provides in situ sealing of the pores by deposition of fluorocarbon polymers in the film. We also demonstrate that the resulting surface is well suited for the nucleation and growth of atomic layer deposited WCN films. Characterization of the etched low-k dielectric by various analytical instrumentations demonstrates feasibility of this approach for integration of ultralow-k dielectric films.
Towards a controlled patterning of 10 nm silicon gates in high density plasmas
Authors: Pargon E. , Darnon M. , Joubert O. , Chevolleau T. , Vallier L. , Mollard L. , Lill T.
Published: October 2005

This article demonstrates that a 10 nm isolated silicon pattern on a very thin gate can be achieved if the plasma parameters and chemistry that impact the critical dimension (CD) control are well understood. The parameters investigated are the passivation layers that form on the silicon gate sidewalls which directly impact the CD control, the nature of the mask used during the gate process (resist mask or SiO2 hard mask), the charging effects developed when the plasma lands on a thin gate oxide.
Determination of Mg composition in MgxZn1−xO alloy: Validity of Vegard’s law
Authors: Ashrafi A. B. M. Almamun , Segawa Yusaburo
Published: October 2005

Vegard’s law and inductively coupled plasma atomic emission spectrometry were employed to determine the Mg composition in MgxZn1−xO layers deposited on 6H–SiC substrates. With the increase of Mg composition in MgxZn1−xO layers, the c-axis length decreased by 5.2048−0.072x, while the a-axis length increased to 3.2491+0.047x. The lattice constants estimated by Vegard’s law and a theoretical model exhibited an uncertainty of ∼3% that has been attributed to the ∼2% lattice misfit in the MgO∕ZnO materials system. Localized exciton peaks of MgxZn1−xO alloy in photoluminescence (PL) measurements disappeared completely, while the neutral donor-acceptor pair and 1-longitudinal optical-phonon energies decreased rapidly with the increase of Mg composition. These PL data do not comply with Vegard’s law. The asymmetric behavior in the MgxZn1−xO alloy is the subject of locally disordered Mg potential fluctuations and an artifact of the cMgO and aMgO lengths calculated theoretically.
Physical properties of nanostructures grown by oblique angle deposition
Authors: Singh J. P. , Karabacak T. , Ye D.-X. , Liu D.-L. , Picu C. , Lu T.-M. , Wang G.-C.
Published: October 2005

Isolated three-dimensional nanostructures were grown on templated or flat substrates by oblique angle deposition with or without substrate rotation where the physical shadowing effect dominates and controls the structures. The mechanical and electromechanical properties of Si springs and Co coated Si springs were measured by atomic force microscopy. The electrical property of β-phase W nanorods were measured by scanning tunneling microscopy. Examples of measurements of the elastic property of springs, electromechanical actuation, field emission of electrons, and field ionization of argon gas are presented. Potential applications and improvements of growth of uniform nanostructures are discussed.
Some remarks on propagation characteristics of ridge guides for acoustic surface waves at low frequencies
Authors: Sinha B. K.
Published: October 2005

The plane-stress equations of the theory of elasticity are solved to predict the propagation characteristics of flexural and pseudo-Rayleigh modes of infinitely tall ridge guides for frequencies lower than the lowest thickness-shear frequency of thin plates. The parabolic dispersion characteristic of the former mode shows appreciable departure from the hitherto published results in the above limiting case. The large discrepancy is due to the incompatibility of the flexural type of motion in the ridge and the only Rayleigh type of disturbance that the adjoining free substrate can sustain. This causes undesirable radiation of the surface wave energy into the bulk of the substrate and is responsible for cutoff frequencies obtained by several authors. The consequent implication for the useful operational range of such waveguides is discussed. The nondispersive velocity of the latter mode at dc is found to be 1.5% lower than a microwave network result.
Loss and recovery processes operative at the level of the cochlear microphonic during intermittent stimulation
Authors: Price G. Richard
Published: October 2005

It has become increasingly apparent that the ear's behavior in response to intermittent stimulation is complex. In order to study the loss processes operative at the most peripheral level, CM sensitivity at the round window was monitored in a series of acute experiments on 150 cat ears as they were exposed to intermittent or continuous 5.0-kHz pure-tone stimulation. Stimuli were delivered at a SPL either 10 or 30 dB above that intensity necessary to produce a maximum CM output. Stimuli were on a 20% duty cycle with on-times varying from 10 msec to 2 min. Recovery processes taking place between stimuli were also measured. At all but the shortest on-times, loss was bimodally distributed, i.e., ears lost either much more or much less sensitivity than ears exposed to equivalent amounts of continuous stimulation. The shortest on-times, in contrast, tended to produce predominantly large losses. An early recovery process at the level of the CM was explored and found to have the following properties: it proceeded in log-time and the amount of recovery was proportional to the log of the on-time but was unrelated to the amount of residual sensitivity shift. The data were interpreted as showing the possibility that large losses to intermittent stimuli were likely to result when successive stimuli in the intermittent train interrupted the early recovery process before it has run to completion. These data were compared with TTS data from the human ear and parallels noted.
Masking patterns in band-rejected noise
Authors: Richards Alan M.
Published: October 2005

Masking audiograms were determined in the presence of wide-band noise from which a band of frequencies 3/4 octave wide had been rejected. The center of the band-reject gap was adjusted to correspond to 500, 1000, 2000, or 4000 Hz, and two overall noise levels (45 or 65 dB SPL) were used. The results indicated that under all conditions there was a reduction in the SPLs necessary to reach threshold within the gap, while at frequencies outside the gap, the threshold levels were consistent with unfiltered noise of equivalent spectrum levels. For a given gap center frequency, it was found that the higher overall noise level produced masked audiograms which fell off at a faster rate, at both the low- and high-frequency edges of the gap, than the lower noise level. Further, as the frequency of the gap center increased from 500 to 4000 Hz, there was a corresponding increase in the Q of the masked audiograms for both noise levels. Practical, as well as theoretical, considerations of audiograms obtained in band-rejected noise are discussed.
Hydrodynamic solutions at a sonic-boom focus
Authors: Parker L. W. , Zalosh R. G.
Published: October 2005

A numerical shock-following method has been developed and applied to a study of the focusing of sonic-boom N waves. The focusing occurs subsequent to the formation of converging concave shock fronts which can result from refraction by atmospheric inhomogeneities or from aircraft maneuvers. The geometry is two dimensional, or three dimensional with axial symmetry, leading to a line or point focus, respectively. The computer code used in the calculations employs a moving mesh so that weak N wave shocks (relative overpressures of the order of 1/1000) can be followed for large distances without numerical dissipation. In several sample calculations, overpressures at the focus ranging from two to 20 times the nominal overpressure have been computed. The typical length scale of the high-pressure region is the order of a wavelength. It is also found that weak shocks tend to cusp at the axis in accord with the geometric-acoustics description, whereas strong shocks straighten out without cusping.
Ultrasonic holography at the critical angle
Authors: Hildebrand B. P. , Becker F. L.
Published: October 2005

Ultrasonic holography is a recording technique preserving phase and amplitude of a wavefront on a two-dimensional surface. This paper explores the possibility of using this technique to map phase changes occuring on an otherwise featureless surface by illuminating the surface at the Rayleigh critical angle. Since phase response at the critical angle is extremely sensitive to such things as stress concentrations, subsurface defects, or work hardening, it appears that this technique may offer a way to detect and map such distributions. We present preliminary experimental results that substantiate this claim.
Numerical evaluation of Rice's integral representation of the probability density function for Poisson impulsive noise
Authors: Richter W. J. , Smits T. I.
Published: October 2005

Numerical evaluation of Rice's triple integral representation of the probability density function (pdf) for Poisson impulsive noise has been accomplished for the intermediate pulse repetition rate case with several meaningful waveforms. The technique was applied to (1) a case for which a closed form was available, (2) the low-pulse repetition rate case where simplifications are possible, and (3) to several cases for which empirical results were available. In all cases, agreement was excellent. The technique consists of numerically computing the characteristic function, and obtaining from this the pdf by subtracting constant from the characteristic function, and transforming the constant analytically and the remainder numerically. The transformation is carried out separately in different regions, depending on the shape of the curve in a particular region, after which the individual integrals are added. This process overcomes some of the difficulties previously encountered in evaluating Rice's integral.
Bilateral component in speech perception?
Authors: Ades Anthony E.
Published: October 2005

The selective adaptation method was used to investigate the location of speech-related property detectors in the brain. A series of synthetic consonant-vowel syllables, ranging from [b æ] to [d æ], was used for testing the position of the phoneme boundary before and after adaptation. There were three main findings: (1) It was possible to simultaneously fatigue the “B-detectors” in one ear and the “D-detectors” in the other. (2) There was about 55% interaural transfer of adaptation. (3) When components of the adapting stimuli were presented in either binaurally fused or unfused conditions, the adapting effect was greater in the former case. These results are interpreted as showing that some component of speech processing may be performed on both sides of the brain, and that some component is performed after the point of binaural fusion. These two components are not necessarily based on different neural structures. The types of models considered were a two-tiered model postulating relatively peripheral mechanisms driven entirely monaurally, and a one-tiered model assuming that all adaptation takes place beyond the point of binaural fusion in structures which receive input from both ears, but more from one ear than from the other.
Interaural alternation and speech intelligibility
Authors: Speaks Charles , Trooien Terry T.
Published: October 2005

The intelligibility of interaurally alternated speech was measured by two methods: shadowing and subjective estimation. A passage of connected discourse was recorded at two speaking rates, normal (135 wpm) and fast (194 wpm). Shadowing scores and estimations of intelligibility for normal-rate speech were nearly 100% at eight rates of alternation, ranging from 1.0 to 10.0 alternations per second. Estimated intelligibility for fast-rate speech was depressed slightly and shadowing scores approximated 70% for most rates of alternation. In a second experiment a court stenographer transcribed the message, a form of nonvocal shadowing. Although transcription scores varied somewhat with rate of alternation, there was no evidence of a uniquely critical rate at which intelligibility was impaired seriously. The results suggest that (1) interaural alternation does not affect intelligibility appreciably unless the speech is spoken at a very fast rate; (2) no particular alternation rate or region of alternation rates is associated with significantly depressed shadowing scores; (3) estimations of intelligibility made immediately after shadowing are lower than estimations not preceded by shadowing, suggesting that shadowing may interfere with a listener's ability to understand a message.
Comments on “Review of Acoustics—Historical and Philosophical Development, R. B. Lindsay, Ed.” [V. O. Knudsen, J. Acoust. Soc. Am. 55, 685 (1974)]
Authors: Junger M. C.
Published: October 2005

The function of resonators in ancient theatres is discussed with the aim of interpreting Vitruvius's description of their use.
Some preliminary observations on temporal compensation in the speech of children
Authors: Di Simoni Frank G.
Published: October 2005

Temporal compensation was investigated in the speech of three-, six-, and nine-year-old children. In none of the age groups tested was it found to be present.
Helmholtz-equation eigenvalues and eigenmodes for arbitrary domains
Authors: Tai George R. C. , Shaw Richard Paul
Published: October 2005

An integral equation technique is employed to obtain eigenvalues and eigenmodes of the homogeneous Holmholtz equation for a two- or three-dimensional closed region of arbitrary shape with arbitrary first-order homogeneous boundary conditions. The method is described for general (i.e., nonseparable) geometries, with a discussion of the simplification introduced by having a separable geometry given in an Appendix. A numerical example is given for a nonseparable geometry, i.e., a two-dimensional right triangle of arbitrary enclosed angle with Neumann boundary conditions. Results for the special case of an isosceles right triangle agree very well with a known analytical solution.
Emission of higher-order acoustic modes into a moving fluid in a duct
Authors: Ingard Uno , Singhal Vijay K.
Published: October 2005

A study of the influence of fluid motion on the emission of higher-order acoustic modes from a stationary source in a duct is presented. In particular, the ratio between the upstream and downstream higher-order mode amplitudes is calculated. This ratio has been measured for the (1,0) mode in a rectangular duct at flow velocities from zero to 0.25 times the sound speed. The frequency dependence has also been measured at a fixed flow Mach number of 0.1.
Acoustic variability in the ocean
Authors: Burnett Thomas D.
Published: October 2005

The dependency of the magnitude of acoustic variability in the open ocean on parameters characterizing the medium and the acoustic system itself is examined on the basis of in-situ measurements of transmission loss and concurrent environmental and meteorological conditions. The spectrum of conditions considered consists of frequencies of 2.2 kHz, 8 kHz, 16 kHz, and 25 kHz; transmission ranges up to 24 000 yds; source and receiver depths up to 500 ft; and the environmental conditions experiences in the North Atlantic Ocean. Acoustic variability is observed to depend upon frequency in a nonmonotonic manner; to increase with time between transmissions for values of Δt up to approximately 40 min; to be a maximum at a range of approximately 4000 yds; to decrease significantly at sea state 4 and above; to depend upon the path that the energy travels; and to be higher when encountering the thermocline than when transmission is entirely in the mixed layer.
Radiation patterns and radiation impedances of a pulsating cylinder surrounded by a circular cage of parallel cylindrical rods
Authors: Radlinski R. P. , Meyers T. J.
Published: October 2005

Two-dimensional series expansions of cylindrical harmonics are used to study the diffraction of a wave radiated by a pulsating cylindrical transducer at a cage grating that surrounds the transducer. Farfield radiation patterns and radiation impedances, as distorted by the cage grating, are presented as a function of cage radius and number of rods. Decreasing the distance between the cylindrical scatterers and thereby increasing the scattering interaction is shown to increase the frequency range of nearly uniform cylindrical waves emitted from the grating. The shape of the radiation reactance in the frequency intervals where resonant peaks occur in the radiation resistance is explained in terms of Kramers-Kronig relations. Good agreement is shown between the predictions of the two-dimensional analysis and experimental measurements of farfield radiation patterns of a finite-length transducer and cage.
Ultrasonic random-signal flow measurement system
Authors: Bendick P. J. , Newhouse V. L.
Published: October 2005

Although pulsed Doppler radar systems are widely used, ultrasonic pulsed Doppler systems which are potentially useful for flow measurement in liquids carrying sound scatterers (such as blood) have been limited in their useful range to a few centimeters due to range-ambiguity problems. An ultrasonic random-signal flow measurement system is described which is shown to have no range ambiguity and to be able to transmit continuously, thus having a low peak to average power ratio. Experimental data from a working random-signal system are: presented demonstrating its advantages over conventional pulsed Doppler systems. The system should be useful for many large-scale flow applications, ranging from measurements in deep-lying blood vessels to wake measurements around ships.
Sound absorption in mixtures of oxygen and water vapor in the temperature range 298–410 K
Authors: Harlow R. G. , Street P. R.
Published: October 2005

Measurements of the absorption of sound in mixtures of oxygen and water vapor were made over the temperature range 298–410 K. The least-squares best fits to the experimental results give: 298 K, f0=9+199h + 115h2; 323 K, f0=12+234h + 117h2; 343 K, f0=14+261h + 1O7h2; 363 K, f0=15+235h + 134h2; 383 K, f0=17+283h + 105h2; 408 K, f0=21+325h + 96h2, where 10 3h is the mole fraction of water vapor, and f0 Hz is the frequency of maximum sound absorption per wavelength at 1 atm pressure. The above results were obtained by combining the present values with earlier data for pure oxygen.
Nonlinear oscillations of gas bubbles in liquids: steady-state solutions
Authors: Prosperetti Andrea
Published: October 2005

The nonlinear oscillations of a spherical gas bubble in an incompressible, viscous liquid subject to the action of a sound field are investigated by means of an asymptotic method. Approximate analytical solutions for the steady-state oscillations are presented for the fundamental mode, for the first and second subharmonics, and for the first and second harmonics to second order in the expansion. These results are compared with some numerical ones and a very good agreement is found.
Control and sampling circuitry for the synchronous detection and measurement of ultrasonic pulse echoes
Authors: Reed Robert W.
Published: October 2005

Synchronous detection of ultrasonic pulse echoes with a lock-in amplifier can be used to obtain improved signal-to-noise ratio in the measurement of ultrasonic attenuation. It is our purpose to present circuitry that can be used for the generation of the necessary timing, trigger, and reference signals. In addition, a high-speed sample and hold circuit, used to convert low-duty-cycle pulse echoes into the square-wave signals needed for operation of a lock-in amplifier, is described. The apparatus described has been used for attenuation measurements over the 10–1400-MHz range in both single- and double-ended sonic sample-transducer configurations.
Effect of ejector spacing on ejector-jet noise characteristics
Authors: Tirumalesa Duvvuri
Published: October 2005

Full-scale engine tests are analyzed as to the effect of ejector spacing on the spectral characteristics and directivity pattern of the noise radiated from ejector jets.
New equation for the speed of sound in natural waters (with comparisons to other equations)
Authors: Del Grosso V. A.
Published: October 2005

A new equation for the speed of sound in sea water has been developed with validity not only for realistic combinations of the parameters salinity, temperature, and pressure, but with extension to pure water as well. This new equation, referred to as NRL II, has a standard deviation of 0.05 m/sec. Tables are presented comparing calculations using this new model to each of eight earlier equations. Graphs are also included indicating approximate corrections that could be applied to existing sound speed profiles, but it is recommended that such profiles be recalculated and new ones obtained according to NRL II.
Variation with temperature of resonant frequencies of anisotropic plates
Authors: Cowdrey D. R. , Willis J. R.
Published: October 2005

This paper presents a new formulation, based on Lagrangian coordinates, for the vibration of plates, both finite and infinite, at varying temperatures. The formulation circumvents a possible difficulty in applying perturbation theory to the usual formulae for infinite plates in a purely mechanical way. Knowledge of the thermal expansion tensor of the material is not required to infer the frequency-temperature behavior for arbitrary orientation of crystal, once experimental results have been established for a few chosen orientations; this contrasts with earlier work. The formulation is also immediately suitable for use in conjuction with the finite element method to obtain the variation of resonant frequency with temperature of finite plates, either with or without mass loading. Results are given for a particular A T-cut quartz resonator.
Noise-induced hearing loss in the chinchilla, as determined by a positive-reinforcement technique
Authors: Clark William W. , Clark Carolyn S. , Moody David B. , Stebbins William C.
Published: October 2005

A positive-reinforcement procedure was used to determine hearing sensitivity and noise-induced hearing loss in the chinchilla. The animals were reinforced with 45-mg pellets (Noyes) for depressing and holding a key for 1–6 sec and either releasing it during a 2-sec tone presentation or not releasing it during a 2-sec catch trial. Using a tracking procedure, thresholds were determined at 9–15 frequencies during each daily 1-h session. Following threshold determinations, two animals were exposed to a 123-dB-SPL band of noise (710–2800 Hz) for 15 min. Threshold shifts were measured daily after the exposure and the animals were sacrificed at 7 and 28 days post-exposure, respectively. Their cochleas were examined under the light microscope and the number of hair cells missing was compared with the hearing loss present. Contrary to previous findings, both animals showed a considerable permanent threshold shift that agreed closely with the degree of change seen in the cochlea. The advantages and disadvantages of the new behavioral procedure are discussed.
Measurement of echolocation signals of the Atlantic bottlenose dolphin, Tursiops truncatus Montagu, in open waters
Authors: Au Whitlow W. L. , Floyd Robert W. , Penner Ralph H. , Murchison A. Earl
Published: October 2005

The echlocation signals of two Atlantic bottlenose dolphins, Tursiops truncatus, were measured while the animals were involved in a target-detection experiment conducted in open waters. The time intervals between successive pulses in a pulse train were found to be highly variable, although the intervals were longer than the time needed for an acoustic signal to travel from the animals to the target and back. Sound pressure levels of the echoranging signals were measured for target ranges of 60, 70, 75, and 80 yds. The peak-to-peak click-source level at 1 yd showed little variation with the target range; the average level was 120.4 dB re 1 μbar for one animal and 122.3 dB for the other. These open-water sound pressure levels are at least 30 dB higher than any click-source levels reported in the literature. Oscilloscope photographs and their Fourier transforms of these high-amplitude clicks are presented. The typical clicks had average durations of 40 μsec, with peak energies between 120 and 130 kHz, much higher than the previously reported energy peaks centered at 35 to 60 kHz.
Scattering from a periodic corrugated surface: finite-depth alternately filled plates
Authors: DeSanto John A.
Published: October 2005

In a previous paper [J. Acoust. Soc. Am. 53, 719 (1973)] we discussed the calculation of the scattered field for scalar plane-wave incidence on a type of filled periodic corrugated surface. The surface consisted of parallel half planes, alternate adjacent pairs of which were filled with a material having different density, and supporting waves of different velocity structure from those in the surrounding medium. This paper considers a related problem with plates of finite rather than semi-infinite depth. Both soft- (Dirichlet) and hard- (Neumann) boundary conditions are considered. Limiting cases of the problems considered here correspond to the results of Deryugin. The most characteristic effects observed are the Brewster-angle and resonance anomalies.
Time-harmonic wave scattering by obstacles in an infinite inhomogeneous medium
Authors: Shaw Richard Paul
Published: October 2005

The scattering of time-harmonic waves by an obstacle in a locally inhomogeneous infinite medium—i.e., a medium which becomes essentially homogeneous at some distance from the obstacle—is treated. An artificial outer boundary is drawn within the homogeneous region and an outer-boundary integral equation (OBIE) is used to relate the dependent variable and its normal derivative at this boundary. This in turn is used to complete another set of equations obtained by standard techniques—e.g., finite differences—for the inhomogeneous interior region. Numerical examples are given for water wave scattering by a circular island surrounded by various locally variable depth topographies.
Fitting velocity profiles with two-dimensional cubic splines
Authors: Solomon L. P. , Barnes A. , Port S.
Published: October 2005

Many underwater-acoustics propagation problems are solved using geometrical acoustics. This approach uses an approximate formulation of the wave equation which is exact in the limit of infinite frequency. The computation of the ray paths and the associated intensities involve the use of four first-order nonlinear ordinary differential equations. In order to have smooth, continuous solutions, the velocity field (i.e., the speed of sound field) and its derivatives, which appear in the coefficients of the set of differential equations, must be twice continuously differentiable (C2) throughout the region. The use of splines—cubic polynomials which are continuous through the second derivative—insures compliance to these requirements. This paper gives a technique for calculating a spline field in two dimensions, given data points which are available at specific ranges, but at different depths. The technique is easily extendable to include arbitrary location of data points. This use of splines, in order to provide a smooth function for use in differential equation-solvers found so often in computer algorithms, should be of utility in various fields.
Possible source mechanisms for a frequently occurring infrasonic signal
Authors: Thomas Joe E. , Kuckertz Thomas H. , Logan James D. , Law Tak K. , Craine Lloyd B.
Published: October 2005

Commonly occurring infrasonic waves recorded during the winter months are believed to originate by means of aerodynamic source mechanisms. Acoustic power spectra of these commonly observed signals are compared to the power spectra one would observe from theoretical source mechanisms. From this comparison, the theoretical source mechanism believed responsible for production of the observed signals is thought to be isotropic turbulence in the lee of mountain peaks. Experimentally recorded signals and their power spectra are shown. Source regions of three signals are identified.
Experimental studies of the covariance function of the envelope of narrow-band reverberation processes
Authors: Plemons Terry D.
Published: October 2005

Experimental investigations were made of the covariance structures of the envelope functions of several nonstationary reverberation processes. It is shown that, when the process is stationary, the covariance of the envelope is approximately equal to the square of the envelope of the covariance of the narrow-band process. However, when the nonstationarity of the reverberation process becomes noticeable, then this simple relationship is no longer valid.
Acoustic-internal wave interaction at long ranges in the ocean
Authors: Porter R. P. , Spindel R. C. , Jaffee R. J.
Published: October 2005

Fluctuations in the amplitude and phase of low-frequency sound propagated to long range in the ocean are predicted. Phase fluctuations are attributed to the passage of acoustic radiation through the internal gravity-wave field; predictions are based on measured and modeled internal wave spectra. Ray theory is used to determine phase and amplitude variations as a function of time, space, and acoustic frequency. It is shown and experimentally verified that mean-square phase fluctuations are depth dependent.
Interpretation of time records and power spectra of scattered ultrasonic pulses in solids
Authors: Pao Yih-Hsing , Sachse Wolfgang
Published: October 2005

Experiments were conducted to investigate the scattering of a wide bandwidth pulse by a fluid-filled cylindrical cavity in an elastic solid. The pulse amplitude-time record and the corresponding Fourier power spectra of the scattered pulses are analyzed. The sequence of pulses received by a transducer is identified by applying the theory of geometric acoustics and the pulse arrival times are related to the cavity diameter and the wave speed in the fluid. The power spectrum is interpreted in terms of the resonance of the fluid inclusion, the natural frequencies of which also depend on the size and property of the inclusion. Investigations show that both pulse-time record and power spectrum can be utilized to detect the size and the wave speed of a fluid inclusion in a solid.
Response patterns of cochlear nucleus neurons to excerpts from sustained vowels
Authors: Moore Thomas J. , Cashin John L.
Published: October 2005

Excerpts from sustained vowels as well as pure-tone bursts were used as input signals to the guinea pig's auditory nervous system. Single unit responses to these signals were recorded from the cochlear nucleus. The results indicated that a neuron's response pattern to a particular vowel was determined by the ratio of the vowel's spectral energy that fell within the excitatory and inhibitory areas of the neuron. Addition of energy in a neuron's inhibitory region resulted in major modifications in the response of the neuron to both vowels and sinusoidal inputs. Generally, the addition of inhibitory energy resulted in a “temporal sharpening” of the response pattern.
Diffraction of waves and stress intensity factors in a cracked layered composite
Authors: Keer L. M. , Luong W. C.
Published: October 2005

Elastodynamic stress intensity factors are computed for diffraction of antiplane shear waves by a crack in a layered composite. The crack is normal to and bisected by the midplane of the layer. Both cases of a partially broken layer and a completely broken layer are studied. Integral transform techniques are used to formulate the problem as a singular integral equation. The propagation of symmetric modes (Love waves) is studied numerically, and stress intensity factors are obtained for several values of frequency, geometrical parameters, and material constants. The amplitude ratios of the incident waves to incident plus scattered waves at a large distance from the crack are also calculated.
Investigation of the aerodynamic noise generating region of a jet engine by means of the simple source fluid dilatation model
Authors: Hurdle Patrick M. , Meecham W. C. , Hodder Brent K.
Published: October 2005

An experiment was conducted on a full-scale jet engine to investigate the aerodynamic noise generating regions in the free jet. Cross-correlation measurements were made between the static pressure fluctuations and the farfield radiated sound. These measurements were made for two different static pressure probe positions and a large number of farfield positions (at various angles). In addition, each test geometry was run for four different jet exit velocities. The measured, normalized cross-correlation functions varied between 0.004 and 0.155. A new Q-function, based on the above normalized cross correlation is defined and plotted. This function represents the source strength per unit volume within the jet region. This Q-function shows dependence on the probe position, the angular position of the farfield microphone, and the jet exit Mach number. Third-octave analyses of both the probe signal and the farfield radiated sound were made. The results show that cross-correlation techniques are a valuable tool in the investigation of the aerodynamic noise generating regions of an actual jet engine.
Rectified diffusion in the presence of, and absence of, acoustic streaming
Authors: Gould Robert K.
Published: October 2005

Individual air bubbles held in the central interior of a water-filled chamber by a 20-kHz pressure-gradient force, were observed dissolving in undersaturated water and growing by rectified diffusion in saturated water. When bubbles grew or dissolved in the absence of nearby acoustic streaming, present theories for normal diffusion and for rectified diffusion in the absence of streaming gave reasonable agreement with experiment. When crispations appeared on a bubble, acoustic streaming accompanied the surface activity and the rate of dissolution or growth of the bubble was intensified up to twentyfold. Measurements of threshold sonic pressures for onset of crispation revealed that, in general, the larger the bubble the lower the pressure required. Present theories for diffusion in the presence of acoustic streaming imply, in contrast to experiment, that streaming should inhibit rectified diffusion in saturated and undersaturated liquids. For gas bubbles dissolving in undersaturated liquids, the effects of sound on mass transfer can be made negligible, and experimental measurements of the diffusion coefficient of the gas in the liquid can be obtained.
Studies in reverberation. I. Scattering of sound by a plane vortex sheet
Authors: Pekeris C. L.
Published: October 2005

A plane wave is incident obliquely at a boundary between two liquid half spaces, of which the lower one moves with velocity U parallel to the interface relative to the upper one. It is found that the reflection coefficient depends only on the component of U parallel to the direction of the incident wave. Total reflection occurs when the wave has a component of propagation in the direction of U, but not in the reverse case. It is shown that in the case when U is any function of depth z below the interface, the reflection coefficient vanishes for normal incidence. For U of the order of c/1000, the reflection coefficient is appreciable only near grazing incidence.
Ultrasonic bounded beam reflection effects at a liquid-anisotropic-solid interface
Authors: Plona Thomas J. , Behravesh Mohamad , Mayer Walter G.
Published: October 2005

Schlieren techniques are used to show that a bounded ultrasonic beam impinging on a liquid-single-crystal-copper interface, and generating generalized surface and pseudo surface waves, can produce reradiation fields which result in changes in the reflected beam similar to effects observed at liquid-isotropic-solid interfaces when Rayleigh waves are generated. The existence of these reflected beam effects at water-single-crystal-copper interfaces is attributed to the component of the particle displacement ellipse of the generated surface wave which is perpendicular to the crystal surface. A parameter β, characteristic of this perpendicular particle motion, is introduced and its value calculated from existing surface-wave particle-motion data. Observed reflected beam effects are described in terms of the parameter β.
Urban noise model
Authors: Malchaire Jacques B. , Horstman Sanford W.
Published: October 2005

A model has been developed for predicting median levels of traffic noise in a variety of local conditions. Sound sources are grouped into two categories: major thoroughfares with average daily traffic volume greater than 5000 vehicles are considered individually as line sources with uniform distribution of traffic and all other streets are grouped into a set of square areas. The model makes use of readily available traffic and census tract data. It takes into account interruptions in the traffic stream. Noise levels predicted by the model are in agreement with levels observed during a noise study in Cincinnati, Ohio. The correlation coefficient was 0.90, and 64% of the predicted levels fell within ±2.5 dB of the observed levels. Both sections of the model, involving line and area sources, performed equally well and no systematic bias was observed. This simple model is proposed as a practical working tool to predict noise levels under any existing or proposed set of conditions.
Hypothesis on the function of the crossed olivocochlear bundle
Authors: Geisler C. Daniel
Published: October 2005

It is suggested that a function of the crossed olivocochlear bundle is to shift to a higher level the range of intensities to which auditory-nerve neurons are rate sensitive. Some available behavioral data seems consistent with this hypothesis.
Model of crossed olivocochlear bundle effects
Authors: Geisler C. Daniel
Published: October 2005

A modification of the familiar variable-resistance electrical circuit is presented as a model of the crossed olivocochlear bundle's effects mediated by efferent synapses on the outer hair cells. The model's field potentials and neural discharges are compared with experimental findings.
Acoustic Velocity with Relation to Chemical Constitution in Alcohols
Authors: Marks Graham W.
Published: October 2005

The results of this investigation extend and confirm conclusions given in the literature deduced from sound velocity and auxiliary data concerning alcohols. Acoustic velocities at 500 kcps were measured in a large number of alcohols and in three series of alcoholic binary solutions with a precision ultrasonic interferometer within the temperature range of 0°–80°C. Viscosities were determined at 25°C and densities within the range 14°–37°C. At fixed temperature, increase in sound velocity with increase in number of carbon atoms in primary alcohols follows a simple exponential law. The square root of the viscosity varies inversely as the molecular sound velocity. Secondary alcohols have lower sound velocities than the corresponding primary isomers because of lower densities. The increment in van der Waals' b per CH2 group is about 20 cm3 per mol. This holds true for all the homologous series studied. Fluorinated alcohols have much lower sound velocities than the alcohols from which they were derived. Rao's constant (molecular sound velocity) drifts somewhat with temperature, which is to be expected for associated liquids. The three series of binary solutions studied were n-propanol and isopropanol, n-propanol and n-octadecanol, and aqueous solutions of a propane diol derivative. Apparent molal adiabatic compressibilities for the component taken to be the solute vary as the square root of the molality at fixed temperatures.
Reflection of Wave Trains in Semi-Infinite Plates
Authors: Torvik Peter J.
Published: October 2005

A method for using the well known modes of vibration for the infinite plate as elements of an expansion applicable to semi-infinite plates is given. The method is employed to study the reflection of an infinite train of waves from the free edge of an elastic plate. The incident train of waves induces other, nonpropagating, modes. As has previously been discovered, a resonance may occur in such a mode that will increase the portion of the plate for which the evanescent modes affect the stress distribution. Above a critical frequency, a transfer of energy from one propagating mode to another occurs during the reflection. Generally, energy brought to a free edge by waves of one wavelength will depart in wave trains of several different wavelengths. The presence of a mode which, for a limited range of frequency, carries energy in a direction opposite to the motion of the waves is confirmed. Some observations are made about necessary restrictions in an extension of St. Venant's principle to dynamic loadings.
Effects of Vibrator Types and Their Placement on Bone-Conduction Threshold Measurements
Authors: Weston Peter B. , Gengel Roy W. , Hirsh Ira J.
Published: October 2005

Monarual bone-conduction thresholds in the quiet were obtained for 10 normally hearing young adults at both forehead and mastoid positions with two hearing-aid-type vibrators of different manufacture. Physical calibration data for the vibrators were obtained by other laboratories with two different Beltone artificial mastoids. Bone-conduction force thresholds (in root-mean-square dynes) are reported, along with identification of sources of variability.
Middle-Ear Characteristics of Anesthetized Cats
Authors: Guinan J. J. , Peake W. T.
Published: October 2005

Ossicular motion was measured visually with stroboscopic illumination. Tonal stimulation ranged from 30 to 10 000 Hz. Up to 130 dB SPL (sound-pressure level), the motion of the stapes is predominantly piston-like, and its displacement amplitude is linearly related to sound pressure. At frequencies under 3000 Hz, the ossicles move as one rigid body; at higher frequencies, the stapes and incus displacements lag behind the malleus displacement, which suggests that the incudo-malleolar joint flexes. From measurements of stapes displacement at known sound pressures, we calculate a transfer characteristic for the middle ear with the tympanic cavities open. The effects of closing the tympanic cavities on the transfer characteristic were determined from measurements in which the electric response recorded from the round window was used as an indicator of middle-ear output. By combining these data, we obtain a transfer characteristic for the middle ear with the tympanic cavities intact. An attempt is made to compare middle-ear characteristics of cat and man.
Syllable Duration in Oral and Whispered Reading
Authors: Schwartz Martin F.
Published: October 2005

The average duration of the syllable in oral and whispered reading is studied. The results, obtained from 12 male speakers, indicate a significantly greater duration for the whispered syllable.
Specular Scattering of Underwater Sound from a Wind-Driven Surface
Authors: Medwin Herman
Published: October 2005

A wind-driven water surface possessing the gross characteristics of a simple sea (near-Gaussian distribution of slopes and a 1.53 ratio of the upwind-downwind slope to the cross slope) has been studied acoustically by analyzing the specular scattering of a broad range of frequencies at normal incidence surface roughness √g = 4πσ cosθ/λ ranging from 0.56 to 5.1). Theory, based on the Helmholtz integral and the Kirchhoff approximation, modified for beam diffraction, is used to provide values of the root-mean-square surface height from specular scatter at small roughness and of the root mean square slope from the asymptotic results at large roughness. The predicted exponential decrease of intensity with increasing but low value of roughness is corroborated even for wavelengths as large as the surface correlation distance, that is, far beyond the restrictions of the Kirchhoff assumption. The acoustically determined value of the root-mean-square slope is 17% less than the optically measured value. The form of the distribution of specularly scattered pressure is found to vary from near Gaussian distribution for the relatively smooth surface to near-Rayleigh distribution for the rough surface. At any instant, the relative specularly scattered intensity decreases monotonically with increasing frequency to a minimum value at √g≃2.3 from which it is possible to get a second estimate of the root mean square height: above √g∼2.3 the instantaneous scattered intensity is a nonstationary oscillating function of frequency, varying about the asymptotic value.
Quality of Violin Vibrato Tones
Authors: Fletcher Harvey , Sanders Larry C.
Published: October 2005

Typical violin tones with vibrato were recorded on magnetic tape. From a special analysis, synthetic tones were constructed that were very difficult to distinguish from real tones. The analysis showed that not only the frequency was varying up and down about sit times per second, but there were three other important characteristics varying at this same rate. All of the harmonics had the same variation of the frequency level, in cents, from the note being played. There was also an intensity-level variation of the harmonics at the same vibrato rate, but the intensity-level variation was greatly different for different harmonics. Also, the intensity of some of the harmonics would be rising while that of others would be falling during the vibrato period. Thus, a curve showing the relative intensity level of the harmonics at any instant changed back and forth during the vibrato cycle. The intensities of the sympathetic tone coming from the open strings also varied either at the vibrato rate or twice the vibrato rate, while the frequencies of these tones remain constant and correspond to the natural frequencies of the fundamental and harmonics of the open strings. The after-ring is due principally to these transient tones. This effect is negligible when the frequencies of the fundamental and its harmonics are not close to those of the open string.
Acoustics of Powell Symphony Hall, St. Louis
Authors: Harris Cyril M.
Published: October 2005

The new home of the St. Louis Symphony Orchestra was inaugurated on 24 January 1968. This concert hall was reconstructed from a large motion picture theater first opened in 1925. This paper describes the major problems encountered in the reconstruction of the house, the changes that were made, the design of the stage enclosure, the finishes and furnishings, and the resulting reverberation-time characteristics of the Hall.
Driving-Point Impedances of Cantilever Beams—Comparison of Measurement and Theory
Authors: Kerlin R. L. , Snowdon J. C.
Published: October 2005

The driving-point impedances and natural frequencies of small, rigidly terminated, metal cantilever beams in bending vibration have been measured at low strain amplitudes. The results show excellent agreement with the predictions of the Timoshenko theory, which has been extended to account for the internal damping of the beams in addition to the effects of rotary inertia and shear displacement. Values of impedance measured at the free end of a magnesium alloy beam have a maximum dynamic range of 6×106; the lowest measured value of impedance was 4.1×10−5 lb-sec/in. Attempts to avoid the excitation of the third beam mode by driving the beam at a nodal point near its midpoint have proved both successful and straight-forward. Driving-point impedance has also been measured at the ends of a manganese-copper alloy beam and an aluminum beam coated with an unconstrained layer of damping compound. The driving-point impedance of this damped beam has been closely matched theoretically by the impedance of an equivalent, internally damped, homogeneous beam.