bluuebunny/crossref_metadata_2025 huggingface dataset:
Fundamental vocal frequency characteristics of hearing-impaired young adult men
Authors: Whitehead Robert L.
Published: October 2005

The purpose of this investigation was to compare perceptual judgments of pitch register with average F0 during oral reading by 156 hearing-impaired young adult men. Judgments of pitch register were made by experienced listeners using a seven-point scale which ranged from “much below optimal level” to “much above optimal level.” Average F0 was calculated for each speaker using a pitch extraction program. A highly significant relationship was obtained between the ratings of pitch register and average speaking F0. In addition, the average F0 data indicated that hearing-impaired young adult males may be expected to demonstrate a range of speaking F0 from below normal to substantially higher than normal. Further, the majority of subjects spoke at an F0/pitch level that was either within a normal range or within a range where therapeutic intervention would be questionable given the probable existence of other, more severe, speech and/or voice problems. [Work supported by US Department of Education.]
Biot model for wave reflection by anisotropic poroelastic media such as an ice sheet
Authors: Yamamoto Tokuo , Badiey Mohsen
Published: October 2005

Wave propagation in anisotropic poroelastic media is modeled by the propagator matrix derived from Biot's theory for transverse isotropic porous media. The complex reflection and transmission coefficients are calculated for a nonhomogeneous case for certain frequencies as a function of the incident angle. It is found that the coupling due to the anisotropy of the media has a significant effect on the reflection and transmission coefficients. This effect is strongly influenced by the incident angle.
Application of Biot's equations to wave propagation in a medium of alternating fluid and solid layers
Authors: Bedford A.
Published: October 2005

Comparison of the Biot theory with experimental results over a broad range of frequencies has proven to be difficult because the coefficients in Biot's equations are functions of frequency whose forms depend upon the microstructure of the medium. In this work, Biot's equations are used to analyze the propagation of plane waves parallel to the layers of a laminated material consisting of alternating layers of an elastic material and a compressible viscous fluid. For this case, all of the coefficients in the theory can be evaluated. In particular, the drag and virtual mass coefficients can be evaluated as functions of frequency using the method of Bedford, Stern, and Costley [J. Acoust. Soc. Am. Suppl. 1 74, S57 (1983)]. Furthermore, the phase velocity and attenuation of plane waves in the layered medium can be determined exactly. Although it is for a special geometry, this comparison provides a definitive test of the ability of the Biot theory to model a two-phase material. It is shown that the Biot theory matches the first two modes of the exact results with great accuracy over a large range of frequency. However, this result is shown to depend upon the use of an appropriate frequency-dependent expression for the virtual mass coefficient.
Scattering by a partially illuminated, doubly periodic, doubly infinite surface
Authors: Lakhtakia A. , Varadan V. K. , Varadan V. V.
Published: October 2005

Using the plane-wave decomposition of the incident field and theT-matrix method, scattering by a partially illuminated, doubly periodic, doubly infinite surface is investigated. The general expressions thus derived are simplified for the case when the illuminated area is large. Numerical examples illustrating the applicability of the procedure are also given.
Hydrodynamic noise on viscoelastic surfaces
Authors: Bakewell Henry P. , Von Winkle William A.
Published: October 2005

The topic of this paper is the determination of whether turbulent wall pressure characteristics can be modified through appropriate selection of wall material characteristics. An early investigation of flow over an elastic layer reported reductions in the turbulent wall pressure spectral levels [W. A. Von Winkle and J. E. Barger, 61st Meeting of the Acoust. Soc. Am., May 1961]. Water tunnel experiments are now being conducted to explore more fully the characteristics of turbulent wall pressure fluctuations on an elastic surface. Small flush mounted hydrophones are being used to measure both cross-spectral and spectral properties of the wall pressure on various surfaces. Initial results on flow over a simple viscoelastic layer will be reported.
Flow-induced sound and the nature of trailing edge flow
Authors: Blake William K.
Published: October 2005

This paper will survey the various mechanisms for flow-induced sound generation at the trailing edges of lifting surfaces. The conditions which favor the onset of tones as well as the methods which may be invoked to control them will also be discussed. The critical features of flow structures which determine the generation of either sound or vibration will be identified in the context of existing theories. For each of the various mechanisms for generating either continuous spectrum sound or flow tones, the controlling flow parameters will be identified and their experimentally determined values will be discussed. Such parameters will include the correlation lengths and spectral distributions of surface pressures as well as the most commonly encountered trailing edge wake characteristics. These descriptions will be made for a range of edge geometries which include sharp, blunt, and slotted.
The influence of the musician on the vibrational behavior of a violin
Authors: Marshall Kenneth D.
Published: October 2005

Modal analysis techniques were used to take a “first look” at how the presence of the musician alters the vibrational behavior of a violin. Animated mode shapes of a freely suspended violin will be presented, and compared to the response of the same instrument when held by five different players. The results show that the player imposes a constraint, or boundary condition, to the neck and lower bout of the violin, consisting primarily of a strong viscous damper acting in parallel with a weak spring. The resonant frequencies and mode shapes are only slightly affected, but the amplitude of the response of the violin is significantly lowered. It is concluded: (a) A variety of different violins should be measured for comparison purposes and to establish a decent data base. (b) A violin should always be measured freely suspended. Boundary conditions can always be added later in a mathematical model, but it is extremely difficult to remove a constraint that is present in the test data.
A finite-element model of the guitar top plate
Authors: Richardson B. E. , Roberts G. W.
Published: October 2005

Finite-element analysis provides a viable, if inelegant, method for predicting the normal modes of vibration of strutted anisotropic plates for a variety of boundary conditions. The paper will discuss the problems and successes we have encountered in the formulation of a finite-element model of the guitar top plate. It will deal with the choice of package and elements for the particular problem and will discuss one solution to the problem of modeling asymmetrically mounted anisotropic struts. The paper will conclude by reporting on the current status of the model and out attempts to predict the sound radiation from the plate in response to a typical string force acting at the bridge.
Effects of damping violin interior air modes
Authors: Hutchins Carleen M.
Published: October 2005

The effects of having 65 holes, each 6 mm in diameter, in the ribs of a violin so that they can be left open or plugged with small corks have been discussed and demonstrated. Critical comments suggest that the marked reduction in tonal output when the violin is played with all holes open could be due to the quadrupole effect. To check this, E.A.G. Shaw has provided acoustically tailored tiny soft foam cylinders to plug the holes which are calculated to absorb the interior air modes. The effect of all holes plugged with corks, all holes open, and all holes plugged with soft foam will be discussed and demonstrated.
Discussion of modal and finite element analysis technologies applied to musical instruments
Authors: Hutchins Carleen M.
Published: October 2005

Since research in this area is relatively recent, an informal discussion period is planned for those interested in exploring and sharing experiences in the progress, problems, and potentials of modal and finite-element analysis applied to musical instruments.
Long-range nonlinear geometric acoustic pulse propagation in the atmosphere
Authors: Warshaw Stephen I. , Dubois Paul F.
Published: October 2005

Linear geometric acoustic ray tracing is useful for determining wavefront propagation in inhomogeneous and moving atmospheres. For propagation over many pulse lengths, or for large amplitude pulses, nonlinear advective, dissipative, and diffusive effects need to be accounted for. We have developed a simple, approximate modeling technique for theoretically predicting small amplitude pulse propagation over long distances in the terrestrial atmosphere, which takes these nonlinear effects into account. It consists of extending Blokhintsev's development [D. Blokhintzev, J. Acoust. Soc. Am. 18, 322 (1946)] into the nonlinear regime by applying classical Riemann invariant methods locally to one-dimensional propagation of acoustic pulses along geometric acoustic ray tubes, and including viscosity and heat conductivity effects in an elementary way [S. I. Warshaw, LLNL Rep. UCRL-53055 (1980)]. The advantages and disadvantages of this modeling technique will be briefly discussed. Predictions of the propagation of the pulse and wave front from a surface explosion to ionospheric altitudes based on this approach will be compared with ionospheric radar measurements made during an actual explosion [D. J. Simons et al., EOS Trans. Am. Geophys. Union 62, 979 (1981)]. The agreement between predicted and observed amplitudes, durations, and shapes of the pulse in the ionosphere is good. [Work performed under auspices of U.S. Department of Energy by LLNL under Contract W-7405-Eng-48.]
Second harmonic of a finite amplitude Gaussian beam in a fluid
Authors: Du Gonghuan , Breazeale M. A.
Published: October 2005

The diffraction of a Gaussian ultrasonic beam in absorbing fluids has been shown to produce a Gaussian field distribution in the fundamental component [J. Acoust. Soc. Am. Suppl. 1 76, S23 (1984)]. Now we have derived an analytical expression for the second harmonic and find that it also is a Gaussian function in the quasilinear approximation. Our expressions for the second harmonic also are free of the nearfield oscillations characteristic of the radiation from a piston transducer [cf. S. I. Aanonsen, T. Barkve, J. N. Tjøtta, and S. Tjøtta, J. Acoust. Soc. Am. 75, 749 (1984)]. Calculated results are compared with measurements taken with the Gaussian transducer described previously. Reasonable agreement between theory and experiment are found for both the fundamental and the second harmonic of an initially sinusoidal Gaussian ultrasonic beam in water at 2 MHz. [Research supported in part by the Office of Naval Research.]
Use of the Burgers equation to model the farfield of finite amplitude sound beams
Authors: Hamilton Mark F. , Tjøtta Jacqueline Naze , Tjøtta Sigve
Published: October 2005

The Kuznetsov equation has been solved numerically and shown by comparison with experiments to adequately model the nonlinear propagation of directional sound beams in dissipative fluids [S. I. Aanonsen, M. F. Hamilton, J. Naze Tjøtta, and S. Tjøtta, 10th ISNA, Kobe (1984)]. However, such numerical computations are generally quite time consuming, particularly in the farfield where asymptotic formulas are frequently applied. The simplest equation that accounts consistently for nonlinearity and absorption in spherical wave propagation is the Burgers equation. It is shown by way of multiple scale expansion that the Kuznetzov equation is in the farfield asymptotically equivalent to the Burgers equation. Numerical solutions of the Kuznetsov equation show that when an appropriate matching condition is imposed at the Rayleigh distance, the Burgers equation adequately describes the axial field when nonlinearity is not too high. Off axis, however, significant nonlinear effects generated in the nearfield can propagate out to tens of Rayleigh distances. Not until these nearfield effects become insignificant does the Burgers equation correctly predict beam patterns. [Support of MFH was provided by the F. V. Hunt Post-doctoral Research Fellowship.]
Measurement of harmonics generated by finite amplitude sound radiated by a circular piston in water
Authors: Riley Thomas L.
Published: October 2005

A circular piston with diameter selectable as 25, 50, or 76 mm (with values of ka of about 25, 50, and 75) was used to radiate 470-kHz sound in a fresh water lake. Source levels ranged from 195–230 dB re: 1 μPa at 1 m. Beam patterns and axial sound pressure levels at about 7 and 11 m were recorded for the fundamental through fourth harmonic frequencies. The data were used to draw amplitude response curves and curves of beamwidth versus source level. Predictions based on two models of finite amplitude sound radiated by a piston, the equivalent spherical source model [J. A. Shooter, T. G. Muir, and D. T. Blackstock, J. Acoust. Soc. Am. 55, 54–62 (1974)], and the quasilinear approximation model [J. N. Tjøtta and S. Tjøtta, J. Acoust. Soc. Am. 67, 484–490 (1980)], agree well with the data. [Work supported by Office of Naval Research.]
Matched asymptotic expansions for steady second-order effects in acoustics
Authors: McGowan Richard S.
Published: October 2005

Matched asymptotic expansions have been used to solve linear scattering problems for farfield information in the long wavelength limit [D. G. Crighton and F. G. Leppington, Proc. R. Soc. London Ser. A 335, 319–339 (1973)]. They can also supply the necessary nearfield information to solve for the streaming field and the steady radiation pressure. The viscous boundary layer is an important component for streaming. Matched asymptotic expansions can be used here to develop a higher order acoustic boundary-layer theory. This helps to separate forcing terms responsible for streaming and radiation pressure in the boundary-layer region. Examples of application include streaming over a blunt end of a slab, viscous effects on steady pressure, and the effect of wave curvature on radiation pressure. Also, an investigation of the importance of imposed mean field gradients is presented. [Work supported by ONR.]
Derivation of Planck's radiation law and thermodynamic state functions from stochastic nonlinear acoustic fields
Authors: Cantrell John H.
Published: October 2005

The Boltzmann-Ehrenfest adiabatic invariance formalism used to derive the acoustic radiation stress equation for solids [J. H. Cantrell, Jr., Phys. Rev. B 30, 3214 (1984)] is combined with recent developments in stochastic classical dynamics to obtain the internal and Helmholtz free energies in terms of random zero-point nonlinear acoustic modes. The results lead to an expression of the thermal expansion coefficients of crystalline solids in terms of nonlinearity parameters related directly to the acoustic radiation-induced static strains. When the model acoustic non-linearity parameters are set to zero, the internal energy expresion reduces to the Planck radiation law obtained from quantum mechanics. If, in addition, the quasiharmonic assumption is invoked for the model frequencies, the thermal expansion equation reduces to that obtained from Debye-Grüneisen-Einstein statistical model of a system of quantum oscillators.
Higher-order finite amplitude modes in a rectangular waveguide
Authors: Hamilton Mark F. , TenCate James A.
Published: October 2005

Finite amplitude propagation of higher-order modes in a rectangular waveguide is analyzed by decomposing the modes into plane waves. Two types of nonlinear interactions may then be considered. The self interaction of an individual plane wave generates harmonics that propagate in the same direction. Such interactions are unaffected by dispersion because each harmonic propagates at the same speed, although in a different mode. The second type includes noncollinear interactions between plane waves. In this case geometric dispersion prevents efficient transfer of energy between the interacting components. A single transverse mode excited at a frequency not far from cutoff is composed of two plane waves propagating in very different directions. The noncollinear interactions are then so highly dispersive that as a first approximation they may be ignored. The remaining, nondispersive interactions were modeled using a modified Burgers equation that accounts for tube wall absorption of each mode. Theoretical results for this case agree very well with experiment. If the fundamental frequency is well above cutoff, dispersive interactions can no longer be ignored. Experimental waveforms then resemble those observed within finite amplitude sound beams. [Work supported by ONR.]
Responses of human observers and auditory-nerve fibers to reproducible signal and masker combinations
Authors: Langford Ted L. , Salvi Richard J.
Published: October 2005

Four human observers were run in a two-alternative, forced choice procedure to measure the detectability of a 500-Hz tone in the presence of each of 25 digitally generated, 100–3000 Hz maskers. The masker was randomly selected on each trial within blocks of 80 trials. The average percentage of correct responses across all maskers was within the range usually reported. The percentages for the individual maskers varied from chance to near perfect, however. The three maskers which led to the best detection and the three which led to the worst detection were used in the second portion of the study to stimulate low-frequency, auditory-nerve fibers of the chinchilla. Fifty presentations of each signal and masker combination were used to obtain spike rates and phase-locking measures. These results are compared with those obtained from the first portion of the study and with measures of the physical characteristics of the stimuli. [Supported by NIH Grant Nos. NS1928 and NS16396.]
Performance in several binaural-interaction experiments
Authors: Koehnke Janet , Colburn H. Steven , Durlach Nathaniel I.
Published: October 2005

The relationship between interaural correlation discrimination and binaural detection was investigated using common experimental procedures and common subjects. NoSo and NoSπ detection thresholds and interaural correlation jnds were measured at 500 and 4000 Hz using third-octave noise signals for the correlation experiment and pure tone signals and third-octave noise maskers for the detection experiment. Psychometric functions were obtained using a symmetric, two-interval, two-alternative-forced-choice procedure with feedback. The functions for NoSπ detection and correlation discrimination, although variable across subjects and frequency, are largely overlapping, indicating that interaural correlation discrimination and binaural detection are closely related. More specifically, if correlation is expressed as an equivalent signal-to-noise ratio, then correlation thresholds closely aproximate NoSπ thresholds. In order to further explore intersubject differences, interaural-time, interaural-intensity, and monaural-intensity discrimination were measured in a second experiment. As in the first experiment, the results show large intersubject differences for interaural tasks, but not for diotic or monaural tasks. The large intersubject differences for interaural tasks suggest that predictions of interaural correlation discrimination from NoSπ detection (or vice versa) will be considerably more accurate for individual subjects than across subjects. [Work supported by NINCDS.]
Re-starting the binaural auditory system
Authors: Hafter Ervin R. , Buell Thomas N.
Published: October 2005

Detections of interaural differences in amplitude-modulated stimuli rely heavily on information in their onsets. The post-onset declines in effectiveness depend on the rate of modulation, to the point that for high modulation frequencies, there is virtually no interaural sensitivity beyond the initial transient. Since the binaural system seems to go to sleep, one must ask, “What wakes it up; when does it resample?” Previous experiments have shown that temporal gaps [E. R. Hafter and T. N. Buell, J. Acoust. Soc. Am. Suppl. 1 74, S40 (1983)] or bits of noise inserted into the middle of such stimuli improve lateralization, indicative of a retriggering of the binaural process. New tests with a variety of potential triggers lend support to the notion that it is the appearance of energy in previously quiet bands that initiates a new sampling. It is suggested that in nature, such triggering may derive from changes in amplitude and phase produced by head movements. [Work supported by NIH.]
Vibration generation in and sound radiation from squealing chalk
Authors: Kuntz H. L. , Bruce R. D.
Published: October 2005

Chalk squeal is a common phenomenon encountered in the classroom. The sound radiated from a chalk/blackboard system is possible because of two physical characteristics of the system. The first characteristic is that the frictional forces at the board and chalk interface are not constant when (stick-slip phenomenon) steady, normal, and shear forces are exerted on the chalk. The second characteristic is that the resonances of the chalk are excited by the stick-slip forces at the interface. A positive feedback system exists between the two characteristics and the vibrations are reinforced with the result that tonal squeal is generated. The resultant vibrations are called relaxational vibrations. Impedance measurement results are presented and compared to the radiated sound. The influence of the board characteristics are discussed. Methods of reducing chalk squeal are discussed. This work is important to the study of sound radiation from machinery operations, such as the honing of cylinders, which also exhibit relaxational oscillations. [Work supported by Department of Health and Human Services CDC/NIOSH Grant No. 1R43 OH01951-01.]
Lateralization of low-frequency tones and narrow bands of noise
Authors: Schiano Jeffrey , Trahiotis Constantine
Published: October 2005

It is well known and universally accepted that people's ability to use ongoing interaural temporal disparities conveyed via pure tones is limited to frequencies below 1600 Hz. We wished to determine if this limitation is the result of the constant amplitude and periodic axis crossings which characterize pure tones. To this end, we employed an acoustic pointing task in which listeners varied the interaural intensitive difference of a 500-Hz narrow-band noise (the pointer) so that it matched the intracranial position of a second, experimenter-controlled, stimulus (the target). Targets were either pure tones or narrow bands of noise (50 or 100 Hz wide). The narrow bands of noise were delayed interaurally in two distinct manners. We delayed either the entire waveform or only the carrier. In the latter case, the envelopes and phase functions were identical. This resulted in a noise which resembles the pure tone case in that the interaural delay is manifested as a constant phase shift and resembles the ordinary noise in that the envelope and phase are random functions of time. Surprisingly, it appears that all three targets were lateralized virtually identically regardless of frequency or bandwidth. Apparently, the dynamically changing envelopes and phases did not effect the listeners' use of interaural temporal disparities in any discernable fashion.
Neural representation of complex spatial patterns in peripheral afferents and somatosensory cortex of the awake monkey
Authors: Phillips John R. , Johnson Kenneth O.
Published: October 2005

The human capacity for tactual, spatial pattern recognition has been investigated by a number of people using embossed letters and Braille characters and the Optacon. The experiments reported here use identical stimuli in neurophysiological experiments to study the neural mechanisms underlying this spatial pattern recognition. The approach is to reconstruct the spatiotemporal patterns of neural activity evoked by these stimuli in the periphery and the cortex. The aim is to determine which pathways convey the critical information underlying pattern recognition and to analyze the transformations as the information proceeds centrally. The results of these experiments are “neural images” which we believe represent the distributed patterns of neural activity as the brain sees them. As expected, these images are mildly distorted replicas of the initial stimuli at the level of the periphery, i.e., the letter A evokes distributed patterns of neural activity in the form of an A. At the level of the cortex the “neural images” reconstructed from a number of neurons are varied in form. Some yield isomorphic imagery while some yield imagery that we have not, as yet, interpreted.
Pacinian corpuscles and polyharmonic vibrations
Authors: Horch Kenneth W.
Published: October 2005

Psychophysical and physiological experiments using low amplitude, high-frequency vibrations which selectively activate Pacinian corpuscle mechano-receptors have been employed to address the question: Can the vibrotactile system distinguish between pure and polyharmonic sinusoidal stimuli applied to the glabrous skin in the presence of concomitant changes in fundamental frequency and amplitude? Human subjects are presented with stimulus pairs in which a pure tone is paired with a tone having a significant second harmonic component. The fundamental frequency and amplitude of each member of the pair are varied independently so they typically differ in peak-to-peak amplitude and frequency composition as well as harmonic content. In addition, different phase relations between the fundamental and harmonic of the diharmonic tone are used. The subjects are asked to identify which member of the pair is diharmonic. Responses of Pacinian corpuscles to the same tone pairs are recorded from afferent fibers in the forelimb of the cat, using both on-center and off-center stimulation. The eventual goal is to collect similar data in primates in order to be able to describe the neural basis for the discrimination ability observed in the psychophysical tests.
The timing of English words by non-native speakers
Authors: Bond Z. S. , Fokes Joann
Published: October 2005

Difficulties with rhythm may be a major cause of lack of intelligibility or naturalness of non-native speakers of English. Inappropriate timing of syllables contributes to the perceived rhythmic deficiencies of non-native English. There is some evidence that non-native speakers do not follow the system of the base work compressions which Lehiste (1972) reports for native English speakers. Preliminary data from Nelson (1982) indicates that native Indian speakers of English do not shorten base words when suffixes are added. The purpose of this study was to investigate the timing of base words and their derivations by non-native speakers of English. The subjects were seven university students from four different language backgrounds, Thai, Malayasian, Japanese, and Yoruba. Subjects were recorded saying four base words in isolation and with three different monosyllabic suffixes and two disyllabic suffixes added. The durations of the base words and their suffixes were measured from duplex oscillograms. For all speakers the base work was longer in isolation than with suffixes although there was considerable variability in their treatment of individual base words. In general, the base word received about the same amount of compression regardless of the number of syllables of the suffix.
Intrinsic time in speech production
Authors: Kelso J. A. S. , Tuller Betty
Published: October 2005

A continuing challenge to our understanding of speech production and perception is the fact that utterances with markedly different acoustic, kinematic, and electromyographic characteristics can nevertheless be perceived as the “same” word. In this paper, we discuss the importance of examining articulation relative to an intrinsic, activity-defined metric. We explore whether relative temporal stabilities previously observed can be achieved without reference to an extrinsic clocking device, but rather in terms of the dynamic topology of the system's behavior. To this end, using a phase plane description of articulatory motion, we show how the temporal analysis originally offered can be redescribed in terms of critical position-velocity states (or, in polar coordinates, phase angles) for interarticulator cooperation. Such coordination, we propose, can be captured in terms of events that are intrinsic to the system's dynamics, not in terms of conventional durational metrics. [Work supported by NINCDS grants NS-13617, NS-17778, and ONR Contract N0014-83-K00.]
The effect of final consonant structure on syllable onset location
Authors: Fox Robert Allen , Lehiste Ilse
Published: October 2005

This study examines the effects which final consonants have upon the location of vocalic onsets in rhythmically produced speech. Three talkers produced 296 sequences of seven monosyllabic tokens of the form/da (C) (C) (C)/. These token sequences were either homogeneous (identical component tokens) or alternating (consisting of a token produced in alternation with /da/). Talkers produced the stimuli both in a metronome (i.e., in time with a rhythmically recurring 100-ms tone burst) and nonmetronome condition. Preliminary results suggest that syllable-final manipulations have a significant effect on the location of vowel onset relative to the recurring tone burst. Increasing the number of consonants at the end of a syllable results in increased anticipation of the timing pulse. In addition, syllabic onsets of tokens produced in the nonmetronome condition deviate from isochrony in a fashion similar to that observed when initial consonant structure is varied. These data support the hypothesis that P centers (or stress centers) of monosyllabic words are determined on the basis of the acoustic/phonetic structure of the entire syllable. [Work supported by NINCDS Grant 1-R01-NS21121-01.]
Analysis of phoneme and pause durations in conversational and clear speech
Authors: Uchanski R. M. , Reed C. M. , Durlach N. I. , Braida L. D.
Published: October 2005

When speech is spoken “clearly” the durations of segments and words increase relative to “conversational” speech, and there is a corresponding drop in average speaking rate. [Picheny, Durlach, and Braida, J. Acoust. Soc. Am. Suppl. 1 67, S38(1980)]. We report new measurements of pause durations (silence gaps exceeding 10 ms between words) and phoneme durations for content words in 50 nonsense sentences as a function of speaking mode. Separate statistical analyses were made for conversational durations, clear durations, and the percentage increase of durations. Results show that the percentage increase is strongly phoneme dependent: It varies from 15% for voiced plosives to 95% for semivowels. Analysis with respect to factors such as stress, serial position, and environment suggests that different production rules are used in the two speaking modes. [Work supported by NIH.]
Composite model for under-ice scattering
Authors: Mellen R. H. , Nuttall A. H. , Deavenport R. L. , Di Napoli F. R.
Published: October 2005

Long-range propagation in the Arctic is characterized by a refractive surface duct with a rough boundary. Below 100 Hz, experimental attenuation values are more than a factor of 2 greater than estimates based on scatter theory for statistically homogeneous surfaces and small roughness parameter. The more realistic composite model consisting of random patches having one of two different degrees of roughness does not appear to account for the discrepancy per se. As a step to investigate the apparent inadequacy of the theory, we examine the properties of a model realization—a simulated surface composed of random overlapping ellipsoidal bosses. [Work supported by NUSC.]
High-frequency acoustic reflection from the Arctic ice layer
Authors: Branch G. H. , Posey J. W.
Published: October 2005

High-frequency plane-wave reflection from an elastic solid bounded by two fluid half-spaces is investigated using the Haskell matrix model [N. A. Haskell, Bull. Seismol. Soc. Am. 43, 17–34 (1953)]. A similar study by D. F. McCammon and S. T. McDaniel [J. Acoust. Soc. Am. Suppl. 1 75, S31 (1984)] investigated plane-wave reflection at lower frequencies. The matrix model is shown to be useful for predicting reflection effects due to shear and compressional mechanisms in the arctic ice layer. A standard model for the sound speed profile in 3 m of ice was obtained from data reported by Bogorodskii [Sov. Phys. Acoust. 19, 305–322 (1973)]. Reflection coefficients are calculated for various ice thicknesses and numbers of layers. The effect on the reflection coefficient of a slush layer at the ice-water interface is also studied. The inclusion of a snow layer at the upper boundary is shown to have no effect on the acoustic attenuation at high frequencies. The Haskell matrix model is inefficient for handling sound profiles with sharp gradients such as the inclusion of a 10-cm slush layer and an alternative approach using the ray model approximation is discussed. The ray model can also be used to study surface relief and ice inhomogeneities in Monte Carlo simulations. [Work supported by NAV-SEA.]
An experimental study on siren efficiency
Authors: Pia Frederic G. , Reethof Gerhard
Published: October 2005

A flexible two stator ports research siren has been carefully designed to investigate and improve its sound generation mechanism. The acoustic components consist of a pipe connected to a nozzle (inlet chamber) forcing the air through the rotor ports into an exponential diffuser connected to an anechoically terminated test section. The novelty lies in the design of the inlet chamber. As opposed to the plenum-type inlet used in the past, the nozzle inlet decreases the energy lost through turbulence and drag forces on the rotor. In addition, the length of the inlet chamber can be changed by moving the end plunger, allowing the siren to be tuned for maximum efficiency. Test results are presented for various flow rates and frequencies. The effectiveness of the tuned inlet is obtained by comparing test data with results obtained with a shortened and much enlarged inlet chamber, typical of the previous plenum chamber design.
Absolute force gauge response characterization using a lift test method
Authors: Carroll G. P. , Clark J. A.
Published: October 2005

A transient gravimetric method is described by which force gauge response characteristics are determined by measuring the response of the force gauge to a unit step force input which is created by suddenly lifting a known mass from the gauge. Absolute estimates of gauge sensitivity and frequency response can be obtained directly from the time history by measuring the response step height and time decay parameters or by taking the time derivative of Fourier transform of the time history. Magnitude and phase errors associated with the basic technique and the processing options will be examined and compared to currently accepted approaches. Of particular concern in this study are phase errors of the order of three degrees or less which have been shown by the authors to yield significant inaccuracies in power flow measurements [J. Acoust. Soc. Am. Suppl. 1 76, S66 (1984)]. Results of an investigation of cable motion induced case strain on force gauge response performed using a lift test in conjunction with a vibration shaker test will be described. [Research supported by David Taylor Naval Ship Research and Development Center, Washington. DC.]
Stability analysis of an acoustic wave in a waveguide carrying a mean flow
Authors: Kuo Shyang-Lin
Published: October 2005

The nonlinear interaction of the mean flow and disturbance in the Stokes boundary layer inside a 2-D waveguide having a slowly varying height will be investigated. Time scales and other nondimensionalized variables associated with this modulated flow will be discussed. It is shown that the dynamic behavior of the enclosed fluid is governed by the values of four parameters, ε = 1/R, 1/S, and RS, where ε is the wall slope, 1/R is the square of the ratio of the oscillatory boundary thickness lv to the typical duct height, H0, 1/S is the ratio of the oscillatory particle displacement u0/ω to H0, and Re is the Reynolds number Ū0L/v. The results of this analysis will be compared to that given by Thompson [J. Acoust. Soc. Am. Suppl. 1 75, S77 (1984)] who investigated the stability of the Stokes layer without mean flow.
Ultrasonic wave propagation in thick filament wound graphite-epoxy composite
Authors: Kishoni Doron , Heyman Joseph S.
Published: October 2005

Ultrasonic waves were transmitted through a thick cross layered filament wound graphite-epoxy composite sample, in the plane of the fibers. The through-transmitted waveform was monitored at different relative orientations with respect to the structure. Results show that the propagation pattern is highly influenced by the structure of the anisotropic material, and any application of NDE should take into consideration the changes in velocity at different orientations, as well as the curved propagation path of the waves. Propagation versus ply angle curves will be presented to demonstrate the complex interaction of the fiber/matrix system. [Work supported by NRC.]
A CAMAC based ultrasonic data acquisition workstation
Authors: Barna B. A. , Beller L. S. , Johnson J. A. , Shull C. R. , Taylor S. C. , Walter J. B.
Published: October 2005

Computer Automated Measurement and Control (CAMAC) is an instrumentation and interface standard that provides both hardware and software flexibility. Using standard CAMAC modules and a few custom designed routing and clock circuits we have developed a computer-controlled system for general purpose ultrasonic scanning and data acquisition. The CAMAC system provides a relatively easy way of interfacing to the motor controllers and a transient recorder for complete computer control. The main advantage is that the interface software can be written in a high-level language such as FORTRAN to send commands to individual modules in the system to move motors or to activate a transient or to readout the transient recorder data. The system has the capability of performing sequences of commands repeatedly so processes like signal averaging can be easily implemented. New, custom applications can easily be accommodated by changing modules and writing new interface routines in FORTRAN. For example, we have modified the basic system by replacing the transient recorder with a time-to-digital converter and we now have the capability to record time-of-flight ultrasonic data. Another example is the ease with which new scanning devices can be added to the system. The stepper-motor controllers can be reprogrammed to accommodate the characteristics of the new device, again using a high-level language such as FORTRAN.
Acoustic intensity by intuition
Authors: White J. E.
Published: October 2005

For a plane sinusoidal acoustic wave, we know that average intensity is directed perpendicular to the wave front and uniform in magnitude. For two identical plane waves at right angles, intensity must be directed at 45° and be increased by √. Wrong! For a standing wave, we realize that average intensity is zero. For two standing waves at right angles, the average intensity must surely be zero. Wrong again! Measurements in a 4-ft by 8-ft enclosure confirmed the circulating flow of energy which can exist. In an elastic solid, average intensity is perpendicular to the wave front for both compressional and shear plane waves. When a plane shear wave and a plane compressional wave at the same frequency travel in the same direction, one would expect the direction of average energy flow to be perpendicular to the wave fronts. Actually, the direction of average intensity as a function of distance oscillates about the perpendicular. It is clear that intuition based on linear theory may lead one astray when applied to a nonlinear phenomenon like intensity.
Numerical calculations for resonance scattering by an elastic sphere in an elastic medium
Authors: Brill D. , Gaunaurd G. C.
Published: October 2005

In an earlier paper [J. Acoust. Soc. Am. Suppl. 1 76, S9 (1984)] we developed the complete RST formulation for an elastic sphere in an elastic medium under shear and compressional wave incidences. We also showed how that work contained a variety of simpler cases that we have studied in the past, such as, a fluid-filled cavity in an elastic matrix, an elastic sphere in water, a gas bubble in a liquid, etc, … as particular cases. We now develop the entire computational machinery of the RST and show the many useful plots that it can produce. These numerical displays include: (a) The SEM-type poles with their relation to the various types of surface waves that they generate. The Franz-zeros also fall under this category. (b) The graphs of the five types of scattering amplitudes (i.e., fpp, fps, fsp, fss, ftt) that are pertinent to this elastic problem. (c) Their decomposition into partial waves or normal modes, (d) The decomposition of the partial waves into backgrounds and resonances, (e) The informative three-dimensional plots of the response surface of all the scattering amplitudes, in the mode-order and frequency domains, and, (f) The dispersion plots for the phase velocities of the various surface waves. All this is done for two material combinations (i.e., epoxy sphere in steel and steel sphere in epoxy) for which two different types of backgrounds are required to isolate the modal resonances. All displays are constructed in wide nondimensional frequency bands that include the resonance region for which λ≈a. Physical interpretations of all plots are given.
Structure of the auditory nervous system in vertebrates
Authors: Parks Thomas N.
Published: October 2005

Anatomical and physiological studies of the central auditory system have illuminated both the neural mechanisms of hearing and some more general issues in neurobiology. This theme will be developed by discussion of three topics: (1) The basic plan of the auditory system; (2) Specializations of the central auditory system; and (3) Development of the central auditory pathway. The classically known centers and ascending tracts will be identified. The additional complexity of connections revealed by the newer tract methods will be mentioned, but the main emphasis will be placed on three major features of auditory system organization: Multiple parallel ascending pathways, multiple decussations, and descending pathways. Finally, auditory projections outside the main ascending pathway (in particular, those to the cerebellum and superior colliculus) will be mentioned. The size and complexity of certain central auditory structures appear to be positively correlated with the level of certain auditory abilities. As an example, the evidence for separable neural systems that are adapted to analyzing interaural time or intensity cues for sound localization in birds and mammals will be mentioned. Evidence from studies in barn owls that these two pathways converge in the colliculus to create a map of auditory space will also be presented. Three developmental influences will be reviewed. The adjustments in cell number and axonal branching necessary to match up the cochlear nerve afferents with their target neurons in the cochlear nucleus; the developmental mechanisms which allow individual cochlear nerve fibers to form multiple representations of the cochlea and numerous ending types in the cochlear nucleus; and, the body of evidence that early acoustic experience or destruction of the inner ear can profoundly influence the structure of auditory pathway will be summarized.
An efficient computational scheme for evaluating the Helmholtz integral
Authors: Brod K. , Koopmann G. H.
Published: October 2005

Numerical solutions to the Helmholtz integral provide a means of computing the surface pressure on an arbitrarily shaped body with a prescribed surface velocity. When using the “exterior” form of the integral, i.e., restricting the source and field coordinates of the Green's function to the surface of the body, singularities within the Green's functions are encountered along with uniqueness problems for the solutions at certain eigenfrequencies of the interior space. In this study, we show that both of these problems can be circumvented by using the “interior” form of the integral, i.e., locating all of the field points in the interior space where a zero pressure condition is prescribed. Criteria for choosing the optimum set of interior field points are described along with a general discussion of the accuracy of the method. Comparisons of numerical and closed form solutions are presented for the monopole and dipole radiators. The method has been developed for use on a personal computer. [Work supported by NSF.]
Accuracy of infinite elements in structural acoustics modeling
Authors: Allik Henno , Haberman Robert C.
Published: October 2005

Infinite elements are used in conjunction with finite elements to solve a number of structural-acoustics problems. When finite elements alone are used to model an infinite fluid domain, a truncation of the model is necessary at a “sufficiently large” distance from the area of interest. In addition, steady state problems require the imposition of a boundary condition to absorb outgoing waves. A common practice in fluid-structure interaction problems is to model approximately one-and-a-half acoustic wavelengths of external fluid and to impose a plane-wave absorbing boundary condition. Although workable, this approach can result in very large models that are costly to solve. An alternate way to treat the infinite domain and significantly reduce the number of equations is by using infinite elements [e.g., P. Bettess, Int. J. Numer. Methods, Eng. 11, 53–64 (1977)] alone, or in conjunction with finite elements. This is possible because infinite element shape functions contain terms that describe an outward traveling and exponentially decaying wave. The derivation of the element is reviewed and its accuracy in problems involving infinite cyclinders is presented. Results from two-dimensional scattering off rigid and elastic cylinders are compared to theoretical and previously published results. The fluid impedance for waves on a cylindrical boundary is also calculated and compared with closed form solutions. In all instances considered, accurate answers were obtained with the use of no more than two layers of finite elements, plus a layer of infinite elements. In many instances, the infinite elements alone produced excellent results.