bluuebunny/crossref_metadata_2025 huggingface dataset:
Waves in inhomogeneous axially symmetric cylindrical shells.
Authors: Wang Zhang , Norris Andrew
Published: October 2005

A first-order ordinary differential equation of a displacement-rotation-stress-moment vector is derived that describes the motions of axially symmetric cylindrical shells. The shell is assumed to be homogeneous in the circumferential direction but is allowed to be inhomogeneous in the axial direction. The vector has eight components, three displacements, one rotation angle, three stresses, and one moment, and is continuous at each axial level. The equation is cast into a form that proves convenient for studying wave propagation in shells that possess inhomogeneities in the axial direction. Moreover, this equation is also equivalent to the Donnell–Yu equation. The dispersion relation and its high- and low-frequency approximations are obtained for uniform cylindrical shells that agree with earlier results. It is shown that the motions in the axial and the circumferential directions can be decoupled from those in the radial direction at high frequencies. These motions correspond to membrane waves and flexural waves, respectively, when frequency goes to infinite. In mathematical terms, the first-order coupled differential equation can be written as two uncoupled first-order ordinary differential equations. The first one describes a four-displacement-stress vector for the axial-circumferential motions and the second one describes a four-displacement-rotation-stress-moment vector for the radial motions. The propagator matrix, the wave propagator, the transmission, and the reflection matrices are derived. [Work supported by ONR.]
Numerical simulation of active structural-acoustic control for a fluid-loaded cylindrical shell.
Authors: Ruckman Chris E. , Fuller Chris R.
Published: October 2005

Recently published studies discuss how vibrational inputs can be used to control the structural-acoustic responses of elementary structures such as beams and plates, a technique known as active structural-acoustic control (ASAC). Most of these studies use analytical models of the dynamic response. However, analytical approaches cannot be used for the practically important case of a three-dimensional structure immersed in a dense fluid, which occurs primarily in marine applications. Such fully coupled problems, in which appreciable fluid–structure interaction takes place, usually require a numerical approach. This paper describes efforts to study ASAC by computing dynamic responses of the structure/fluid system with the computer program nashua. Two separate feed-forward control approaches are developed and compared: a spatial-domain approach based on minimizing the radiated power, and a wave number-domain approach that does not require far-field pressure information. Singular-value decomposition aids in determining an appropriate number of control actuators and their locations. The technique is demonstrated by examining an axisymmetric, finite-length, cylindrical shell. [Work supported by ONR.]
Extension of the surface variational principle to arbitrary motion of bodies of revolution.
Authors: Ginsberg Jerry H. , Wu Kuangcheng
Published: October 2005

Thus far, the surface variational principle (SVP) has been implemented for curved surfaces only in axisymmetric situations. The present work begins the development of the extended principle by using complex Fourier series expansions to describe the azimuthal dependence, while the spatial variation along the shape generator is represented by a set of basis functions that depend on the parameter used in the description of the shape. When these representations are substituted into the variational quantity for SVP, integration over the surface leads to decoupling of the azimuthal harmonics. For each harmonic, the equations for the dependence along the shape generator have the appearance of the analogous axisymmetric problem, but recursion relations substantially reduce the computational effort required to evaluate the coefficients associated with the higher harmonics. The formulation is used to evaluate the surface response and far field generated by rigid body displacement and rotation of an ellipsoid and a capped cylinder. In addition, the modifications required to apply SVP to scattering problems is discussed. [Work supported by ONR, Code 1132-SM.]
Visualization and analysis of acoustic scattering from elastic objects, on the surface and in the far field.
Authors: Schenck Harry A.
Published: October 2005

In typical structural acoustic scattering problems, the surface pressure and normal velocity on the object are determined as well as the far-field pressure or target strength. These functions may be obtained by computation or measurement, and each may be a function of the surface coordinates as well as the direction and time or frequency characteristics of the incident wave. They are typically stored as a multidimensional array of (possibly complex) numbers. Modern visualization techniques greatly aid the analysis and understanding of these large data sets. An efficient architecture and relevant algorithms have been developed for this purpose using commercially available software and a typical workstation. A top-down approach to understanding and analyzing these data sets will be described. This includes spatial, spectral, and statistical processing of the fundamental data. The appropriate use of color, spatial coordinates of the display surface, and time animation will be illustrated with viewgraphs and videotape examples. [Work supported by the Defense Advanced Research Projects Agency (DARPA).]
Negligible reflection coefficient achieved by incorporating a layer.
Authors: Sheiba L. , Maidanik G. , Dickey J.
Published: October 2005

A configuration is modeled as a compliant layer sandwiched between two panels, with a surface impedance of which is mass controlled. The layer is placed on a basic panel that originally faced a semi-infinite fluid atop and vacuum below. The basic panel is specularly reflective with a reflection coefficient the magnitude of which is essentially unity. Can a layer, as defined above, be designed so that, when placed atop the panel, it will cause negligible reflection coefficient at some values of (Θ,ω)? (Here, Θ is the angle of incidence from the normal and ω is the frequency variable.) Consideration of such a design in terms of parameters that describe the properties of the basic panel, the attached layer, and the fluid are illustrated and discussed. The robustness of the design to variations in these parameters is also discussed.
Coupling of in-plane and out-of-plane waves in thick flat plate structure subjected to a transverse load.
Authors: Cuschieri J. M.
Published: October 2005

Using the approaches of Mindlin [J. Appl. Mech. 18, 31–38 (1951)] and Kane and Mindlin [J. Appl. Mech. 23, 277–283 (1956)] for, respectively, the in-plane and out-of-plane wave motions in thick flat plates, the equations of motion for the in-plane and out-of-plane waves are unoccupied. That is with these approaches, a transverse load will not induce in-plane motion. This is not the case if one were to use a three-dimensional elasticity solution. Also, from a physical standpoint, if a transverse load is applied on one surface of a thick flat plate structure, apart from the out-of-plane deformation, the plate will also have some in-plane deformation. The reasons behind the decoupling of the in-plane and out-of-plane waves are the simplifying assumptions of the respective approaches, where the solution is based on the midplane of the plate with symmetric or asymmetric deformation about the midplane. If a transverse load is applied on one of the plate surfaces rather than the midplane, this can be represented by two sets of load components. One set consists of two loads pointing in the same direction and represents the excitation of the out-of-plane waves and a second set that represent two ‘‘pinching’’ loads that induce the in-plane wave motion. Using this approach the problem of two coupled plates of different thickness is considered to determine the influence of the thickness discontinuity on the in-plane and out-of-plane waves. [Work sponsored by ONR.]
Air (or water) jet as a vibrating diaphragm in aerial (or underwater) organ pipes.
Authors: Yoshikawa Shigeru
Published: October 2005

The jet works as not only an energygenerator to drive the resonant pipe but also an energycollector to maintain its wavelike vibration over the mouth. The jet may act virtually as a flexible thin diaphragm whether it bears the jet instability or not. Its overall lateral vibration then produces the acoustic mouth current, which must correspond to the feedback current collected by the jet in the jet-drive model [J. Acoust. Soc. Jpn. (E) 1, 175–191 (1980)]. Calculation of the acoustic impedance Z j’ of the jet as a vibrating diaphragm will help one understand how the jet vibration is sustained. Although the energy dissipation that occurred in the jet is much smaller than that in the pipe, the jet as well as the pipe should maintain its own oscillation according to the proper phase relation. In other words, the velocity of the jet diaphragm should be directed out of the mouth when the acoustic pressure is positive at the mouth. The question of whether the organ pipe sounds in water as well as in air was considered theoretically from the above viewpoint and was solved experimentally [J. Acoust. Soc. Jpn. (E) 5, 211–221 (1984)]. In spite of the great difference in fluid dynamical and acoustical properties between water and air, a small underwater organ pipe made of aluminum and driven by the water jet sounded at about 155 dB re: 1 μPa near 1 kHz. Similarities and differences between aerial and underwater organ pipes will also be discussed.
Time domain simulation and jet behavior in the flute.
Authors: Coltman John W.
Published: October 2005

A time domain simulation using parameters closely imitating a Boehm flute gave mode oscillation frequencies varying properly with blowing velocity, terminating tangent to an edge-tone characteristic obtained from the same model. Second harmonic generation was much enhanced by a reflection function representing stretched modes. Stagnation pressure and hot-wire speed measurements yielded profiles for a real jet that broadened greatly under acoustic excitation, with development of a subsidiary peak. Jet swing amplitudes and phases for different frequencies agreed with pressure gradient as the stimulating force, not velocity or negative displacement. A jet blowing a flute embouchure coupled to a nonreflecting, separately excited air column, produced signals that implied an overall jet transfer function consistent with the assumptions of velocity stimulation and injected jet current drive made in the computer simulation.
Jet displacement in edge tone, pipe oscillation, and the precursor.
Authors: Nolle A. W.
Published: October 2005

Hot-wire jet-velocity profiles are obtained at evenly spaced times throughout the steady-state acoustic cycle. Jet displacement due to an imposed acoustic crosswind at the flue exit is studied as well as that in spontaneous oscillation. The parallel-plate geometry of Coltman [J. W. Coltman, J. Acoust. Soc. Am. 60, 725–733 (1976)] is used in the edge-tone observations. Here, and also in pipe configurations, the fundamental-frequency jet displacement near the flue exit has a small phase lead relative to the transverse acoustic velocity. The acoustic radiation due to the external jet flux combines with that due to the acoustic current in the mouth in such a way as to make the external spectrum differ from that to be expected from the internal spectrum corrected for the passive acoustic transmission characteristic of the mouth; e.g., for a wide-scale stopped pipe the second harmonic amplitude is greatly enhanced in the external spectrum, and the third greatly reduced. Results for the precursor, an initial transient signal not sensitive to the pipe length, are considered briefly.
Parametrization of organ sound.
Authors: Chaloupka Vladimir
Published: October 2005

This paper presents first results of a research project attempting a thorough analysis of pipe-organ sounds. Sound of individual pipes, as well as of combinations of pipes, of representative organs is being systematically acquired. The analysis is performed on a NeXT computer, and includes a variety of software tools such as spectrum analysis, time-domain waveform fitting, and sinusoidal analysis á la McAuley–Quatieri. In the analysis and presentation of the data, the considerable number of numerical results is reduced into a compact ‘‘fingerprint’’ of the whole organ, enabling an easy evaluation of the tuning system, quality of the tuning, and other parameters. Interesting results are obtained on a cross-talk between simultaneously sounding pipes: it is found that under appropriate conditions, two slightly mistuned pipes of different ranks but of the same nominal pitch will lock in a single frequency when sounded simultaneously; sometimes, this common frequency is higher than either of the two original frequencies (e.g., when two pipes sounding at 525.3 and 526.4 Hz lock at 527.7 Hz). [Work supported by the University of Washington Graduate School Research Fund.]
The effect of a temporal notch in a diotic background on the ability to detect an interaural delay of a continuous component.
Authors: Stellmack M. A.
Published: October 2005

The purpose of this study was to examine the processes that produce interference when observers attempt to lateralize a target component in the presence of other components. The present study looks at the effects of a temporal notch in the diotic ‘‘distractor’’ components on a listener’s ability to detect interaural delay of the target component. Threshold IDTs were measured for a 753-Hz tone presented against a diotic background of six additional components. The resulting seven-component complex was centered at 753 Hz with Δf=100 Hz. During each trial, a 753-Hz cue tone 500 ms in duration was followed by a 500-ms test interval. The distractors were gated off briefly 200 ms into the test interval and gated on again for the remainder of the test interval. The duration of the temporal notch in the distractors was 10, 20, 50, 100, or 200 ms. In separate conditions, the target component remained on for the entire test interval or was present only during the distractor notch. Threshold IDTs measured when a temporal notch in the distractors was present were approximately 80% smaller than thresholds measured when no temporal notch was present, and approached thresholds obtained for the target component in isolation. These results show that a very brief ‘‘look’’ at the target component in isolation is sufficient to substantially reduce the interference produced by the distractors. [Work supported by NIH.]
The influence of an interfering band of noise on the lateral position of a target band.
Authors: Heller Lauri M.
Published: October 2005

Observers centered a target sound in the presence of a simultaneously gated distractor. Observers controlled either the interaural time difference (ITD) or interaural level difference (ILD) of a 50-Hz-wide target band of noise that had a center frequency of either 500 or 2000 Hz. The distractor was a 50-Hz wide band of noise with a center frequency of either 250, 500, 1000, 2000, or 4000 Hz. The target and distractor were gated on and off repeatedly within a trial, each presentation having a 150-ms steady-state portion. The ITD (or ILD) of the distractor varied from trial to trial. The effect of the distractor ITD (or ILD) on the lateral position of the target was assessed by the magnitude of the target ITD (or ILD) that was needed to center the target. The distractor ITD influenced the ITD-centered 2000-Hz target to a greater extent than the 500-Hz target, whereas the distractor ILD had an approximately equal effect on the ILD-centered targets at both frequencies. [Work supported by NIH.]
The effects of randomizing interaural phases of components spectrally distant from the target on detection of a dichotic pitch.
Authors: Grange A. N. , Yost W. A.
Published: October 2005

The present study examined the ability of subjects to detect an interaural phase delay of a 20-Hz-wide section of wideband noise. The narrow-band target was centered on 500 Hz and generated a dichotic, Huggins-type pitch. Thresholds for interaural phase delay detection were measured as a function of the width of the surrounding diotic noise, which was also centered on 500 Hz. Interaural phases for frequency components outside of the diotic band were drawn randomly from a rectangular distribution. The spectrum of the entire stimulus ranged from 1–1500 Hz. A two-down, one-up tracking procedure was used to estimate interaural delay thresholds, in which each trial consisted of two 500-ms noise bursts, separated by 250 ms of silence. The two intervals were identical except that the interaural delay of the 20-Hz wide target band was introduced after 250 ms in the target interval. Thresholds were obtained for diotic bandwidths of 900, 700, 500, 300, 200, 150, 125, and 100 Hz. Thresholds decreased systematically as the bandwidth of the diotic surrounding noise was increased from 100 to 500 Hz, and were unchanged as the diotic band was further widened. Comparisons were made with conditions in which the noise outside the diotic band was removed instead of being presented with random interaural phases.
Auditory systems spatial resolving power in the periphery, under serial processing, is more precise than visual spatial processing in the peripheral aspects.
Authors: Costantino Brian L. , Perrott David R. , Cisneros John
Published: October 2005

The relation between minimum audible and minimum visible angle was measured in a sequential localization task and compared. The frontal spatial fields of the visual and auditory systems are superior to their peripheral regions [Wertheim (1894); Mills (1958)]. Localization tasks were related to Vernier’s acuity, except the timing was in a sequential pattern for both the visual and auditory systems. The spatial acuity of the auditory system defined space better at approximately 20-deg azimuth and beyond then the visual system. Four subjects participated, two male and two female, ranging in ages from 23–49. Significant differences were found in the main effects of angles [F(4,3)=30.59, p<0.01] and the interaction between conditions and angle [F(4,3)=3,89, p<0.05]. The implications of these results will be discussed.
Restrictions of computational models of monaural localization.
Authors: Zakarauskas Pierre , Cynader Max S.
Published: October 2005

In a previous contribution [P. Zadarauskas and M. S. Cynader, J. Acoust. Soc. Am. Suppl. 1 87, S65 (1990)], the finite-difference approximation of the first and second partial derivatives of the received spectrum with respect to frequency were investigated for their abilities to provide a sufficient basis for monaural localization. In this paper, a general description of the necessary and sufficient conditions that any transformation of the spectrum must have in order to be used for monaural localization is supplied. Both continuous and discrete transforms are considered. In particular, the Gabor function with a phase of either zero or π/2 is shown to constitute an acceptable basis for monaural localization. a)Also at Department of Ophthalmology, Univ. of British Columbia, 2550 Willow St., Vancouver, British Columbia V5Z 3N9, Canada.
Higher-order theory for fluid-loaded thin elastic plates.
Authors: Manley Martin G.
Published: October 2005

An elastic, infinite plate of finite thickness with fluid loading on one side and vacuum on the other is considered. Appropriate approximations to the dispersion relation based on the full elastodynamic equations will be presented for the range 0<kh<2, where k is the wave number and h is the thickness. [Supported by the PSU Applied Research Laboratory Exploratory and Foundational Research Program. The author acknowledges the advice of A.D. Pierce.]
Vibration of finite-length, fluid-loaded ribbed plates.
Authors: Keltie Richard F.
Published: October 2005

The vibration response of line-forced, finite-length, fluid-loaded flat plates with attached stiffeners has been formulated. The stiffeners may be of arbitrary size and location, but for simplicity were assumed to generate transverse inertial reaction forces only. The solution for harmonic excitation was implemented via an expansion of the in-vacuo plate modes. The resulting formulation required the solution of a set of simultaneous, complex linear algebraic equations for the expansion coefficients. Upon examination of the plate response at several frequencies, it was found that strong local minima in the vibration could occur at certain values of frequency. This behavior was shown to be due to a beating phenomenon between two modes. This beating arose due to the attached rib stiffeners. A quantity called the ‘‘rib function’’ was defined to explain this behavior. This rib function was dependent on the rib sizes, their locations, and on the in-vacuo mode shapes. Discussion is presented on how to use the rib function to synthesize a set of ribs to achieve a desired plate response.
Sound radiation from finite-length, fluid-loaded ribbed plates.
Authors: Keltie Richard F.
Published: October 2005

The acoustic radiation from line-forced, finite-length, fluid-loaded flat plates with attached stiffeners has been formulated. The stiffeners may be of arbitrary size and location, but were assumed to generate transverse inertial reaction forces only. The solution for the plate response due to harmonic excitation was obtained using an expansion of the in-vacuo plate modes. The resulting acoustic radiation was obtained by numerically evaluating Rayleigh’s integral. Calculated sound pressure levels were obtained in both the far field and the near field above the plate at several frequencies. Individual modal contributions to the radiated sound were also calculated. It was found that the presence of the ribs could produce local reductions in the near-field sound level by as much as 20 dB. Explanations for this behavior were found in the presence of beats between various structural modes.
A study on source localization in plates.
Authors: Zhang Yong , Pate Anna L. , Mann J. Adin
Published: October 2005

Structural intensity and a force distribution function are used to localize the sources on a plate based on the knowledge of the plate surface velocity. The plate surface velocity is measured by means of a laser vibrometer which, unlike accelerometer, does not change the plate loading and mass. Two structural intensity formulations are used. The first formulation is based on simple flexural motion that only includes the out-of-plane motion and its special derivations. The second formulation includes all three motion components of the plate displacement. Midlin’s equations of plate vibration, which take into account the rotatory inertia and shear effect on flexural motion, are used to calculate the plate in-plane motions and force distribution function. The in-plane motions are then used to calculate the structural intensity. Some numerical difficulties are overcome by calculating structural intensity in k space. Results show that both structural intensity and the force distribution function can clearly show the source location.
Sensitivity of predicted shallow-water propagation loss to empirical and extrapolated bottom loss values.
Authors: Monti Joseph M. , Sammis Jefferey H. , Herstein Peter D. , Browning David G.
Published: October 2005

The majority of measured bottom loss values were obtained in deep water at grazing angles of 10 deg or greater. An empirical fit to these data, if extended smoothly down to small angles, results in a value greater than 2 dB per bounce at 0 deg. Geophysical models suggest that for hard bottoms a critical angle would be reached in this low-grazing angle region and that the bottom loss would then drop sharply, reaching a zero value at 0 deg. Under downward refracting conditions in shallow water, low-grazing angle paths may provide, in many cases, the dominant propagation mode. Hence, the value of low-grazing angle bottom loss is critical especially under strongly downward refracting conditions. Following the example of Urick, an empirical bottom loss formula developed by Bell has been modified. At low-grazing angles, its regular value at 10 deg down to reach a zero value at 0 deg has been linearly extrapolated. An analysis is conducted for each formula (empirical and extrapolated) for several shallow-water locations and source–receiver configurations.
An overview of theoretical and experimental developments on ultrasonic scattering in tissues.
Authors: Shung K. Kirk
Published: October 2005

The growth of ultrasonic imaging in the past 2 decades has been phenomenal because of its many advantages. It is noninvasive, capable of providing both anatomical and blood flow information in real-time, less expansive, and portable. It is plausible to see why ultrasonic imaging is now second only to x ray in terms of number of clinical procedures performed. Although it is widely used and much diagnostic information can be retrieved from ultrasonic images, the genesis of ultrasonic texture or speckle exhibited by a tissue in an ultrasonic image is still poorly understood. Since the ultrasonic image is formed from the echoes backscattered from tissues, a systematic and thorough study of ultrasonic scattering in biological tissues is crucial for a better interpretation of ultrasonic images and for the further development of this modality. It is for this reason that ultrasonic scattering in tissues has been under intensive investigation both theoretically and experimentally for many years. In this paper, important experimental approaches that have been developed to measure ultrasonic scattering from tissues and theoretical models developed to analyze these results will be reviewed. [Work supported by NIH Grant No. HL28452.]
Acoustic scattering theories applied to biological tissues.
Authors: Brown David G. , Insana Michael F.
Published: October 2005

Much information of potential diagnostic significance concerning acoustic tissue characteristics can be made available only through sophisticated signal processing. This requires a fundamental understanding of the basic acoustic interactions in tissue. The basic equations of acoustic scattering theory are reviewed as they relate to scattering in soft biological tissues. Using the inhomogeneous continuum model for scattering processes, it is shown how the basic scattering properties are derived for both coherent and incoherent scattering. The treatment begins with scattering from a single inhomogeneity and is then developed to cover scattering from random continua. Backscatter coefficients for isotropic random media are addressed and the extension to anisotropic media considered. An example is given of the analysis of backscatter measurements from the kidney.
Characterization of cardiovascular tissue with ultrasonic backscatter.
Authors: Wickline Samuel A. , Perez Julio E. , Barzilai Benico , Sobel Burton E. , Miller James G.
Published: October 2005

Quantitative characterization of cardiovascular tissue with backscattered ultrasound has evolved from a laboratory tool to a clinical adjunct for conventional echocardiographic imaging. Integrated backscatter imaging was developed by our laboratory to permit analysis of the physical properties of myocardial tissue independent of wall motion or chamber dimension. Initial observations in experimental animals and later in patients revealed that normal myocardium exhibits a cardiac cycle-dependent alteration in the intensity of backscatter that reflects intrinsic myocardial contractile performance. Detection of blunted cyclic variation of backscatter has been used by this laboratory and others to delineate regional contractile dysfunction in patients with infarction, ‘‘stunned’’ myocardium, cardiomyopathy (idiopathic and diabetic), hypertension, and cardiac transplant rejection. Automated ventricular boundary detection is another recent clinical application based on integrated backscatter imaging that allows on-line display and tracking of cavity edges throughout the cardiac cycle in either transthoracic or transesophageal imaging modes to define global ventricular performance.

Another recent clinical innovation, ‘‘lateral gain compensation,’’ permits quantification of and compensation for the ultrasonic anisotropy of scattering exhibited by myocardial tissue, which is attributable to a highly ordered and complex arrangement of myofibers. Promising novel developments for tissue characterization include determination of the frequency dependence of scattering, which may improve the specificity for echocardiographic diagnosis of acute infarction and cardiomyopathy and facilitate quantification of pathologic tissue architectural remodeling. [Work supported by NIH Grant Nos. HL42950, HL40302, HL17646.]
Feature extraction from scattered acoustic fields.
Authors: Chandra Kavitha
Published: October 2005

The scattered pressure field from two-dimensional inhomogeneous biological media is first determined by direct solutions of the integral equation. This work deals with the analysis and interpretation of the scattered pressure measured at the observation locations. Deterministic as well as stochastic isotropic and anisotropic spatial distributions of scatterers are considered. Specific similarity groupings of the variables that allow a global medium characterization from the scattered pressure field are determined. Techniques for estimating the porosity of the scattering volume, the characteristic dimension of the scatterers, and the principal orientation of the distribution are presented. Special attention is paid to cases where the scattering volume is self-similar in the distribution of the radii of the scatterers. The influence of the scattering process on the magnitude of the characteristic fractal dimension of such a distribution is examined.
The effects of being a newborn on otoacoustic emissions.
Authors: Norton Susan J.
Published: October 2005

There is a growing body of data concerning otoacoustic emissions (OAEs) in newborn infants. Because OAEs are a noninvasive, objective measure of cochlear status and can be measured relatively rapidly many investigators are excited about using OAEs as a screening tool for hearing loss in newborns. Preliminary studies indicate that both transiently evoked and distortion product emissions are robust across a broad frequency range in normally hearing newborns. Also, both are absent in newborns later confirmed to have severe to profound sensorineural hearing loss. However, several questions have arisen concerning their relationship between the evoking stimulus parameters and OAE characteristics in infant versus adult ears, the influence of probe, external and middle ear acoustics on newborn responses, and the most appropriate OAE stimulus and response parameters for hearing loss screening. These issues are particularly relevant to identifying mild to moderate hearing loss and to understanding hearing development in humans. [Work supported by NIDCD.]
Technique for measuring low-level otoacoustic emissions.
Authors: Rao Preeti , Bilger Robert , Russell Ann , Meyer Ted
Published: October 2005

To minimize background noise in the measurement of spontaneous otoacoustic emissions (SOEs), which are usually low-level signals, an effective strategy is to narrow the bandwidth of the spectral analysis. The long time required by this strategy makes it impractical in on-line measurement of SOEs, because of the effect of subject-generated noise. A system was configured that allows one to reduce the level of background noise to −13 dB SPL 8-Hz resolution. To achieve these levels, a 60-s sample of sound from a sealed ear canal (16 kHz, 16-bit resolution) was digitized and the conditioned output of a sensitive, low-noise microphone (ER-10) was stored for subsequent off-line spectral analysis. To minimize the subject-generated noise from the ‘‘quiet’’ recording, the resultant waveform is filtered. Digitization and analysis are achieved using an Ariel DSP-32C card. The software package used includes Hypersignal, Ariel Math-32C, and programs written by one of the authors (Rao). Examples will include (a) noise levels for the ER-10 and the ER-10B, (b) comparison of off-line to on-line analyses, (c) fluctuations in the level and frequency of SOEs. (d) SOEs recorded from the ears of identical twins, and (e) SOEs in elderly subjects with sensorineural hearing loss. [Work supported by Grant No. DC 00174.]
Towa tones and stress.
Authors: Bell Alan
Published: October 2005

This paper reports on the phonetics of tones and stress in Towa, a Kiowa-Tanoan language of New Mexico. Towa words have an initial prominent syllable bearing either a high tone or a high falling tone. Long and short vowels also contrast in these initial syllables. Succeeding syllables, which permit only short vowels, may have high (after initial high only), mid, or low tone. (Words appear to have only two underlying tonal melodies, H or HL, with the L falling either on the first or the second syllable.) The basic realizations of initial high and falling tones resemble the Mandarin Chinese first and fourth tones. The contrast is reduced in short monosyllables, and there are notable contextual assimilatory effects. The main issue is whether initial syllable prominence should be attributed to the initial high pitch of words or to stress. On the basis of comparative durations, vowel quality reduction, and the phonetic consequences of prominence loss in compounds, incorporations, and successive initial syllables, it is argued that Towa initial syllables are stressed.
Segment and syllable frequency.
Authors: Maddieson Ian
Published: October 2005

The frequency of individual segments and of each particular syllable has been counted in lists of about 2000 to 5000 lexical entries in a sample of languages drawn from the major areal/genetic groupings. An analysis of a subset of these languages with small segment inventories and simple phonotactics (Maddieson and Precoda, 1992) has shown that the frequency of a particular syllable type can be better predicted from the overall segment frequencies than from the assumption that adjoining articulatory similar segments are preferred, as suggested by Janson (1986). Additional languages are being added to the database to test the generality of this conclusion over a more diverse set of languages. The extended set includes Chinese, Polish, Korean, Comanche, Kwakw’ala, Yupik, !Xóõ, Ngizim, Maninka, Gbaya, Fasu, Turkish, as well as Hawaiian, Pirahã, Rotokas, Shipibo, and Kadazan which were reported on earlier.
Effects of implosives on F0 in SiSwati.
Authors: Wright Richard , Shryock Aaron
Published: October 2005

As is widely known, the fundamental frequency (F0) of the onset of a vowel after voiceless consonants is significantly higher than after voiced consonants. It has been assumed in the literature that implosives (glottalic ingressives) have a raising effect similar to voiceless stops. To investigate this hypothesis, a study was conducted examining the effects of implosives in SiSwati. Four subjects, three males and one female, participated in the study. The wordlist consisted of eight CVX tokens, where C=/ph, inverted open gee, msyllabic em, m/ (voiceless aspirated, implosive, breathy, plain voiced) and where V=/a/ with high or low tone. The tokens were spoken in the frame: ‘‘Tsàní—— fùtsì.’’ (Say——again). The results for /ph/ duplicate the results of earlier studies showing a higher onset F0. The nasals, /msyllabic em,m/, lowered onset F0. However, the results for /inverted open gee/ indicate that implosives have no significant raising or lowering effect on F0.
Focus in insular Spanish.
Authors: Dorta Josefa , Toledo Guillermo
Published: October 2005

An acoustical study of linguistic focus in two experiments of production through materials emitted by seven Canary Islands speakers was explored. In one experiment different wh-question contexts triggered read emissions of neutral, broad-focus, and narrow-focus sentences. In a second experiment, speakers produced a read corpus of neutral, single focus at first and last position in the utterance, and dual-focus sentences contextually designed. The experiments have been set up to analyze prominence in focused items encoded through F0, duration, and amplitude features. To that end, intonation contours and digital spectrograms were made for acoustic measurements. Results did not support the findings reported for other cognate languages as Italian and French which indicated a higher degree of prominence in focused words. On the contrary, the statistical data showed no differences among focused and unfocused items, and among neutral and focused sentences. The findings suggested that in this modality of Spanish the prosodic encoding of focus appears to be ruled by the speakers in a contextually independent and unpredictable manner.
Impedance and stability analysis of two thermoacoustic prime movers.
Authors: Belcher James R. , Arnott W. Pat , Bass Henry E. , Raspet Richard
Published: October 2005

Thermoacoustic heat engines can be used to produce sound from heat and to transport heat using sound. The air-filled prime mover studied is a quarter wavelength resonator that produces sound at nominally 116 Hz for a temperature difference of ΔT=176 K. Specific acoustic impedance at the mouth of the prime mover was measured as a function of the temperature difference between the hot and cold heat exchangers. The real part of the impedance changes sign for sufficiently large temperature differences, indicating the possibility of sound production. The theoretical expression for radiation impedance of an open pipe was overlaid on the impedance curves. The operating point was confirmed from the intersection of experimental and theoretical impedance curves. The stability curve was computed for a helium-filled prime mover as a function of the ambient pressure, P0, for the first two modes. The first mode has a minimum ΔT=154.6 K for P0=173 kPa and the second mode for ΔT=455.4 K for P0=200 kPa. The resonant frequencies of these modes are approximately 310 and 610 Hz. The quality factor, which characterizes the exponential decay or initial exponential growth of an initial perturbation, was computed as a function of ΔT at fixed P0=173 kPa for ΔT well in excess of the onset temperature. [Work supported by ONR.]
Shape oscillations of bubbles driven by modulated ultrasonic radiation pressure: The complex frequency response.
Authors: Asaki Thomas J. , Marston Philip L. , Trinh Eugene H.
Published: October 2005

The shape of a bubble in water should change in response to the radiation pressure of an ultrasonic wave. Modulation of the radiation pressure at the resonance frequencies for shape oscillations should facilitate the stable excitation of such modes [P. L. Marston, J. Acoust. Soc. Am. 67, 15–26 (1980)]. Levitation and detection of shape oscillations were previously discussed for bubbles in the size range 1–5 mm diameter [P. L. Marston etal., J. Acoust. Soc. Am. 89, 1885(A) (1991)]. Levitator design improvements have allowed stable trapping and shape oscillation detection for bubbles in the size range 1–12 mm diameter. The quadrupole mode was observed with resonance frequencies in the range 400–15 Hz. Oscillations over a more limited range were studied with a laser light scattering method that allowed the response phase and amplitude to be measured. The phase is referenced to the amplitude modulation of the acoustic field. Further experiments have involved the effects of surfactants, levitation of thin liquid shells, splitting of bubbles, and surface instabilities. [Research supported by ONR and NASA.]
Finite static deformation and translational motion of an acoustically levitated liquid drop in air.
Authors: Tian Yuren , Holt Glynn , Apfel Robert E.
Published: October 2005

Acoustical levitation has been applied in studies of droplet dynamics and interfacial properties. On the ground, when the density difference between droplet and host medium is large, the intensity of the levitation sound field must be strong enough to overcome gravity. As a result, the droplet may significantly deviate from spherical shape. A numerical method to determine the finite deformation and location of an acoustically levitated liquidated liquid drop in air has been developed. Compared with the previous studies [P. L. Marston, J. Acoust. Soc. Am. 67, 15–26 (1980) and H. W. Jackson etal., J. Acoust. Soc. Am. 84, 1845–1862 (1988)], the interactions between droplet and sound field and the nonspherical acoustical scattering are included in our analysis, making the present method valid for droplets with aspect ratio as large as 2. With this method, the droplet shapes and locations as functions of sound pressure, surface tension, and droplet volume in both gravity and nongravity environments have been systematically calculated. The numerical results agree well with these experimental measurements and those of Trinh and Hsu [J. Acoust. Soc. Am. 79, 1335–1338 (1986)]. [Work supported by NASA through JPL, Contract No. 958722.]
Cochlear fluid motion visualized with magnetic resonance imaging.
Authors: Keolian Robert M. , Denk Winfried , Ogawa Seiji , Jelinski Lynn W.
Published: October 2005

With a modification of standard magnetic resonance imaging (MRI) techniques, the oscillatory motion of water and cochlear fluids can be selectively imaged. Displacements of 160 nm could be detected (SNR=3) with 33×66×300 mm3 resolution in the cochlea of an anesthetized rat subjected to 4.6 kHz, 100-dB SPL sound, without averaging. The technique uses oscillating magnetic field gradients that are phase locked to the motion. The hydrogen nuclei of water that moves in synchrony with the oscillating gradient see on average a slightly different magnetic field than the static field, and accumulate an additional magnetic phase shift that can be imaged. This phase-sensitive-detection method, an NMR analog of the lock-in amplifier, permits three-dimensional detection of displacements far smaller than the spatial resolution. The method could be useful for speech research, in which vocalization could be used to drive the gradients, or in materials research, to map the spatial distribution of mechanical relaxations.
Nonlinearities of mechanoelectric transduction in pigeon primary auditory fibers depend on the temporal pattern of their spontaneous activity.
Authors: Temchin Andrei N.
Published: October 2005

Input–output functions (IOFs) were investigated in pigeons’ auditory fibers with random and quasiperiodic spontaneous activity (SA) [A. N. Temchin, J. Comp. Physiol. A 163, 99–115 (1988)]. The first group showed regular sigmoidal IOF shape at the characteristic frequency (CF) and the slopes were virtually frequency-independent for each fiber. The second group had nearly linear IOFs only around CF and showed single-tone suppression of SA. At any suppressive frequency the IOF slopes were negative threshold and level at which total suppression occurred (15–20 dB). Positive slope of IOFs increased as the difference between CF and frequency of stimuli increased. Transition from total suppression of SA to saturation occasionally took place within as little as 10 dB. The minimal thresholds of suppression were often 7–8 dB less than thresholds at CF. The results cannot be explained by nonlinearities of basilar membrane and presumably indicate that active electrical properties of avian hair cells are involved in mechanoelectric transduction. [Work supported by Callier-UTD Excellence in Education and M. F. Jonsson Funds.]
Influence of signal rise time on the amount of forward masking.
Authors: Turner Christopher W. , Relkin Evan M.
Published: October 2005

Previously, a discrepancy between the amount of forward masking in the auditory nerve and published behavioral data was reported by these laboratories [E. M. Relkin and C. W. Turner, J. Acoust. Soc. Am. 84, 584–591 (1988)]; in that physiological experiment, however, a 2-ms signal rise time was employed, while the previous behavioral data used longer rise times. In the present behavioral study, both 2-ms and 10-ms signal rise-fall times were employed. The results show that for 10-ms ramps, the maximum amount of masking is large (at least 30 dB), in agreement with previous data. In contrast, for 2-ms ramps, the maximum amount of masking is smaller (15 dB). This is similar to the amount of masking in the auditory nerve reported in Relkin and Turner (1988), and indicates little or no discrepancy between behavioral and auditory nerve forward masking. This difference is observed for wide- and narrow-band maskers, suggesting that the results are not simply explained by the short-term spectra of the ramps. [Work supported by NINCDS.]
The effect of click rate on ABR stability measured with the REPs/ABR protocol.
Authors: Lauter Judith L. , Hawkins Lyman K. , Venema Theodore H.
Published: October 2005

Previous studies reported to this Society regarding our repeated evoked potentials (REPs) protocol for auditory brainstem responses (ABRs) have used a click rate of approximately 11 per s. Revisions in the REPs/ABR protocol requiring collection of as many as 16 waveforms in a single session encourage test streamlining, such as increasing click rate. The ABR literature suggests that while click rates of 30/s and above may affect 11/s-based absolute ABR parameters such as peak latency and peak amplitude, fewer changes will be seen with rates lower than 30/s. There are no data on the effect of click rate on ABR peak stability, the dependent variable targeted by the REPs procedure. Eight young adults with normal hearing (four women and four men) were tested in a within-subjects five-session design. Each session involved collection of 4 left ear, 4 right ear, and 8 binaural ABR waveforms; in sessions 1 and 5 a click rate of 11.1 per s was used; for sessions 2, 3, and 4, responses were evoked at click rates of 22.2, 33.3, and 44.4 per s, respectively. Results indicate that click rates faster than 30/s do create the most changes in 11/s-based peak latency and amplitude, though the effects for all increases are differentially distributed by peak, ear condition, and individual subject. Changes in click rate also have marked effects on ABR stability, both latency and amplitude, with details highly specific to individuals. In general, however, changes in stability as a function of click rate occur in the context of replication of the overall shape of the ‘‘stability profile’’ for each subject, providing further evidence of the ‘‘fingerprint’’ nature of this means of characterizing individual auditory brainstems.
Efficacy of long latency auditory evoked/event-related potentials (AEP) in phonetic perception tasks.
Authors: Molt Lawrence F. , Saul Richard S.
Published: October 2005

Latency functions for the auditory evoked potentials N100, P200, and the auditory event-related potential P300 were explored to determine their efficacy as indicators of neurologic processing time for the recognition of differences in three divergent levels of acoustic phonetic patterns. Stimuli consisted of digitally reproduced and altered pairs of spoken numbers with either acoustically identical (four, five with identical /f/), acoustically similar (four, five with natural /f/), or acoustically dissimilar initial phonemes (eight, two). Each stimuli pair was presented in a traditional 80%/20% AEP ‘‘oddball’’ paradigm. For the experimental group of 20 normal-hearing adult subjects, no statistically significant differences were observed in N100 or P200 waveform latency among the three levels of acoustic divergence. P300 latency exhibited significantly greater intersubject variability as phonetic acoustic divergence increased. Suggestions of possible brainstem or subcortical processing aspects, as well as subject-variable alternative processing strategies, are presented.