bluuebunny/crossref_metadata_2025 huggingface dataset:
Talker-independent information for vowel identity
Authors: Verbrugge Robert R. , Rakerd Brad
Published: October 2005

A male and a female talker each produced a set of /bVb/ syllables (V = /i,I,e,ε,æ,a,ʌ,ɔ,o,ʋ,u/) at metronome-controlled rates. The central 60% of the voiced regions of these syllables was edited out, producing single-talker silent-center syllables [cf. W. Strange, J. J. Jenkins, and T. R. Edman, J. Acoust. Soc. Am. 61, S39 (1977)]. Comparable “hybrid” silent-center syllables were created by appending the final 20% of one talker's syllable to the initial 20% of the other talker's production of the same syllable, again with a 60% silent region intervening. Vowel identification errors were relatively low for both the single-talker (22.4%) and the hybrid (27.0%) silent-center syllables, though errors in each case exceeded those found for the original (unedited) syllables, though errors in each case exceeded those found for the original (unedited) syllables (9.3%). Hybrids were generally heard as coherent syllables from a single source; the error pattern for the hybrids could not be interpreted as a joint function of errors on the initial pieces (55.4% on average) and the final pieces (72.9%). Results indicate that considerable information for vowels is contained in the dynamic regions early and late in a syllable. Moreover, they suggest that this information does not simply subserve computation of an underlying normalized target. The information may specify properties of production dynamics that are invarient for a vowel for all talkers of a dialect. To the extent that such information is available, normalization in perception is unnecessary. [Research supported by NICHD.]
Flux density and caustics for sound multiply reflected or refracted in variable index media
Authors: Burkhard Donald G.
Published: October 2005

A formula is given for the flux density along a ray path when sound or light is propagated in variable index media. The sound may be reflected or refracted by an arbitrary interface between media of different indices of refraction. Results are applicable in the geometrical optics limit, that is, the wavelength must be small relative to other dimensions. The only requirement is that the equation for the geodesics in the media be solvable so that an explicit expression is available for the ray path. Results are applicable to multiple reflection of sound from underwater objects and in assessing the performance of variable index lenses. Equations are also given for the associated caustics.
Effective horizontal sound speeds
Authors: Northrop J.
Published: October 2005

Effective horizontal sound speed, the speed at which most of the energy from shots in the deep ocean sound channel propagates, was computed for several source/receiver geometries in the Atlantic and Pacific Oceans. Results showed values ranging from 1476.8 to 1487.5 m/s, the higher sound speeds being associated with the deeper hydrophones and the lower latitudes and vice versa. These values were compared to measured sound speeds, which varied from 1479.9 m/s in the South Atlantic to 1464.9 m/s in the Northwest Pacific and 1484.6 m/s in the Central Pacific. Computed and measured values for the same travel path agreed within 1.5 m/s, or within 0.1%. Because effective horizontal sound speeds vary for diverse travel paths in the world's oceans, appropriate discrete sound speeds should be used for computation methods employing arrival times. [Work supported by AFTAC Code 1035.]
Path integrals and propagation in surface ducts
Authors: Ryan F. J.
Published: October 2005

Acoustic propagation in an ocean surface duct is computed using Feynmann path integral techniques. The surface duct index of refraction, n = c0/c(z), is modeled by a quartic anharmonic-oscillator potential, n2 = aq2 + bq4, with a pressure release boundary condition at the surface. A closed form expression for the acoustic pressure field is obtained for all values of the coupling parameter b and which implicitly includes all virtual and continuum modes.
What data for the parabolic equation?
Authors: Wood David H. , Papadakis John S.
Published: October 2005

The usual reasoning is that: (a) we seek the sound field, therefore the ideal data are sound fields at a specific range, or (b) we seek the Green's function, therefore the ideal data are delta functions centered on the source. Both of the above arguments are irrelevant if we demand that the solution of the parabolic equation should correspond at long ranges to the solution of the Helmboltz equation—at least when the environment does not change with range. Comparisons using different types of initial data will be presented. We recommend that a mode sum ∑ φn(z)φn(zs)be used for initial data. Three criteria are used to eliminate unnecessary terms from the above sum. First, it is particularly important to eliminate the “non-propagating” modes. These modes are a serious source of error in the solution of the parabolic equation because their relative effects do not decrease with range. Second, it is helpful to eliminate those modes that do not contribute at the depths of interest. Third, why include those modes which are rendered meaningless by phase errors? [Work supported by NUSC.]
Acoustic effects of random currents in an ocean with linear sound speed
Authors: Newhall B. K. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

The effects of random fluctuations in an ocean current on underwater cw sound transmission between a bottomed source and receiver are determined for an ocean channel with a linear, depth-dependent sound speed. A horizontal, depth-dependent current, each of whose components belongs to a random process, is considered. Effects of this model on ray geometry are examined and six basic current-induced ray states are found. Conditions are specified so that only one state occurs. In this case, approximations for travel times, total-field intensity, and their first and second moments are obtained using ocean-current data. Significant changes in these moments can occur, depending on such current properties as correlation length and amplitude variance. For example, at the receiver a 9-dB difference between mean intensity and intensity without current may arise, while the standard deviation of intensity may attain 3 dB. Useful bounds for intensity moments are derived which vary slowly with range except near certain critical ranges. [Work supported by ONR.]
Multipath temporal stability and horizontal arrival angle fluctuations for long-range (800 km) deep-water transmissions
Authors: Clark J. G. , Doubek J. , Zabalgogeazcoa X.
Published: October 2005

Pseudorandom transmissions (approximately 20 Hz bandwidth) from a WHOI deep-moored (2000 m) source were acquired at single elements of two continental shelf mounted receivers. The receivers, at a range between 800 and 900 km, were separated by the Gulf Stream. For both receivers a total of 25 transmission samples were acquired, each 90 min in duration. These samples were distributed over a time period of one month. With appropriate averaging procedures applied to each sample, the multipath structure for the transmissions which did not pass through the Guff Stream (first receiver) is shown to be temporally stable over the full month. The multipath structure of the transmission which did pass through the Gulf Stream did not exhibit the same stability. For the first receiver, 18 twelve-hour samples of the carrier of the PRS transmission were also acquired across the full spatial aperture of the receiver. These samples were used to study long-term variability in horizontal arrival angle. The observed spread in horizontal arrival angle is consistent with the hypothesis that the principal spreading mechanism is the mesoscale eddy field.
Deep-ocean sound transmission between moving receivers and sources at intermediate ranges
Authors: Kays J. L. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

Ray theory is used to examine the effects of receiver-source motion on a cw signal transmitted in a deep ocean at ranges of tens to hundreds of kilometers. Numerical results are presented for the amplitude and phase of the received time-varying multipath signal when both the sound source and receiver move on linear paths at the surface. A bilinear sound-speed profile is used, and multipath signals which consist of various combinations of SRBR and RSR arrivals are considered. General analytical expressions, which closely estimate numerical results, are derived and used to study the acoustic total field in terms of range, motion parameters, and multipath composition for particular receiver-source motions. Amplitude displays widely varying patterns which differ in both magnitude and rate of oscillation. The time variation of total field phase is used to show relatively large differences in an approximate Doppler-like frequency shift. A particular frequency shift at the receiver may arise from very different relative receiver-source motions. [Work supported by ONR.]
Multipath statistical model
Authors: Adams S. L.
Published: October 2005

Multipath acoustic propagation models proposed to date fail to account for the fact that the resultant phase spectrum of a cw transmission through a multipath channel contains many of the features of single path phase spectra. Several models of multipath propagation are examined and their first- and second-order statistical properties presented. Of particular interest is a model which considers uncorrelated path length modulations to consist of one part with large mean-squared value and small mean-squared rate accompanied by a second part with small mean-squared value and large mean-square rate. [Work supported of Office of Naval Research.]
Distribution of kinetic energy on a vibrating plate
Authors: Waterhouse R. V.
Published: October 2005

A thin, uniform, rectangular, elastic plate is freely supported in air, and driven so that it vibrates flexurally at a resonance frequency. The modal function, which describes the vibrational displacement over the surface of the plate, is approximated as the product of two cosine functions. The kinetic energy is proportional to the square of this quantity. From this modal function the probability density function (pdf) P(x), for random sampling over the plate surface of the kinetic energy, is calculated to be π−2x1/2 K(1 − x/4), where K is a complete elliptic integral. P(x) has a simple pole at the origin, and declines monotonically as x increases. Using this expression and experimental values sampled randomly over the plate surface, estimates can be made of the mean square vibrational level of the plate. Experimental results are given for a steel plate measuring 4 ft × 3ft × 14 in., resonating at a single frequency. These results are composed with the theoretical cumulative function derived from the pdf given above.
Response of underwater structures to convective component of flow noise
Authors: Chandiramani K. L.
Published: October 2005

Convective component of flow noise (e.g., a turbulent boundary layer) is characterized by length scales of the order of U/f, where U is the vehicle speed and f is the frequency. Nonresonant response of underwater structures to the convective component of flow noise is often of interest. An exact theory of transmission of sound across multiple-layered structures, involving longitudinal and shear waves, is modified so as to apply at convective wavenumbers. Closed form results are presented for a flat plate.
Control ranges and the optimal solutions of the minimal reflectance problem; homogeneous materials, normal incidence, and narrow bandwidths
Authors: Scharnhorst Kurt P. , Hager W. , Wingate J.
Published: October 2005

We study the optimal solutions of the minimal sound reflection problem for planar inhomogeneous sound absorbing layers at normal incidence and narrow bandwidths as a function of their controls. Homogeneous materials are considered. The controls are the real and imaginary parts of the inverse complex longitudinal modulus, K* = K(1 + iη) and the density, ρ. The optimal solutions correspond to multilayered systems, with piecewise constant, extremal control values on the sublayers. The dependence of layer structures, i.e., numbers of sublayers, sublayer thicknesses, and parameter distributions, on the controls can be studied as a function of a certain polyhedron in control space. The shape of the polyhedron, which is determined by the boundary values of the controls, will be correlated with desirable characteristics of the resulting layered structures.
The effect of wall discontinuities on the propagation of flexural waves in cylindrical shells
Authors: Fuller C. R. , Fahy F. J.
Published: October 2005

The transmission of flexural waves through various discontinuities in the walls of cylindrical shells is theoretically investigated. The discontinuities consist of changes in wall thickness or wall material. The solution employs matching boundary conditions with all propagating and evanescent waves provided by the Flügge solution of the cylindrical shell problem. The curves obtained predict high transmission losses at the cut-on frequencies of various axial and torsional waves and at high frequencies approach the flat plate solution. It is also shown that, due to the strong generation of nonflexural waves, the evaluation of transmission losses at a discontinuity by measurement of radial vibrational velocity alone can give a highly misleading result. The attenuation produced by a change in wall material was found to depend more strongly upon the ratios of phase speeds of the materials than their relative stiffnesses, and falls markedly at the ring frequency of the incident pipe due to improved coupling of flexural waves in both materials. The inclusion of damping in the analysis was found to increase the transmission losses. [Work supported by MOD].
Resonance studies in cylinders using stress induced birefringence imaging
Authors: Dardy H. D. , Dragonette L. R. , Flax L. , Hughes R. G.
Published: October 2005

Previous work has considered the effect of free body resonances on the scattering of an incident plane wave by a cylindrical target in water and has related the major features of the theoretical form function resonances to the experimentally obtained farfield reflection patterns. Excitation of these free body resonances is here observed for a glass cylinder in water utilizing a birefringence imaging technique. A fused quartz cylinder is insonified by a long plane propagating pulse and images of the internal stress pattern at resonance frequencies obtained under polarized light. The experimental data are in agreement with a normal mode theoretical computation of the resonance locations and predicted stress distributions for the particular modes.
Propagation of plane, cylindrical, and spherical finite amplitude waves
Authors: Trivett D. H. , Van Buren A. L.
Published: October 2005

A numerical solution to the generalized Burgers' radial wave equation has been developed which allows one to calculate stepwise the harmonic content of a finite amplitude wave in the frequency domain for the case of plane, cylindrical, or spherical geometries. The finite amplitude wave may have any initial harmonic content and the attenuation coefficient of each harmonic is independently adjustable. Remaining in the frequency domain allows much larger steps than conventional programs which alternate between the time and frequency domain. The algorithm is used to verify the farfield behavior of spherical waves as predicted by D. A. Webster [J. Acoust. Soc. Am. 64, S33(A) (1978)] and to investigate the effect of a large second harmonic attenuation coefficient on the generation of a shock wave.
Seismic sensing of shallow water sound
Authors: Urick R. J.
Published: October 2005

It has long been known that in shallow water low-frequency sound below first-mode cutoff travels principally via the bottom. Moreover, a pressure sensitive hydrophone is a poor sensor under these conditions because of the proximity of the pressure-release sea surface. For these reasons one would suspect that under these conditions a more effective sensor for sound generated in the water would be a vibration-sensitive geophone tightly coupled to the sea bottom. That such is the case has been indicated by field work done recently by Northrop off San Diego, by Urick off Ft. Lauderdale, Florida, and on two occasions, by McLeroy off Panama City, Florida. In these experiments a triaxial geophone, having two horizontal and one vertical components, was compared with a nearby hydrophone. In each case, a distant underwater source was received on one or more of the geophone components with a higher signal-to-noise ratio than on the hydrophone. A likely suggestion is that initially water borne sound travels to long ranges in a sedimentary column as deep-going low-loss upward-refracted compressional waves. More theoretical and controlled field work is needed.
Path identification for deep moored-source transmissions to continental shelf receivers
Authors: Weinberg N. L. , Clark J. G.
Published: October 2005

The multipath structure, derived from broadband (PRS) transmission from a WHOI moored source to shelf mounted receivers, has been compared with ray computations in an attempt to identify RR transmission paths. The source was moored at a depth of 2000 m and at a range of approximately 900 km from the receivers. The center frequency of the transmission was 220 Hz and the temporal resolution was approximately 60 ms. Success was achieved in identifying paths with deep turning points; some additional work is needed with early arrivals which can undergo boundary interactions.
Long-range propagation over a mixed-sediment, sloping bottom
Authors: Beebe J. H.
Published: October 2005

Transmission loss is presented in selected one-third octave bands for a deep-to-shallow water propagation path over a mixed-sediment bottom in the Western North Atlantic. The receive hydrophone was 1.5 m above the bottom in water 57 m deep. One-pound charges of TNT were detonated at depths of 37 and 76 m out to a range of 125 km, where the water depth was 265 m. The surficial sediments along the propagation path ranged from gravel to clay. Measured transmission loss is compared with that predicted by model studies using an adiabatic, normal-mode program. The bottom model used in the normal-mode program consists of 18 regions along the transmission path with two to four layers in the model for each region. The bottom models are based on profiling performed with the Huntec deep-tow system, grab samples, and dispersion and seismic refraction analysis. [Work supported by Naval Sea Systems Command.]
Sediment shear-wave velocities derived from Stonely wave observations
Authors: McDaniel S. T.
Published: October 2005

As part of a series of acoustic measurements conducted off the coast of Jacksonville, Florida in 1976, experiments were performed to determine sediment shear-wave velocities. Explosive charges were used to excite Stonely waves which were detected by an ocean-bottom seismograph at ranges of 0.5 to 1.5 km. The shear velocity as a function of depth in the sediment was derived from the frequency dependence of the Stonely wave group velocity. Near surface shear velocities of 670 m/s were obtained at one site. Computations using a normal-mode model are presented which show the effect of sediment rigidity on low-frequency propagation. [Work supported by Naval Sea Systems Command.]
A comparison of long range water-borne and seismic arrivals from large explosive charges
Authors: Cobb A. D. , Stafford W. , Browning D. G.
Published: October 2005

During Project LADLE a series of large explosive charges were detonated in the ocean near the Puerto Rico trench. Signals were received on hydrophones and a seismograph at a range of approximately 1500 km. An analysis is made of travel times and sound intensities. The results show the relative importance of water-borne, water-borne/seismic, and seismic transmission paths.
Session M. Architectural Acoustics I: Symposium on Traceable Calibration of Acoustical Test Instruments
Authors: Guernsey Richard M.
Published: October 2005

Recently Committee E-33 of the American Society for Testing and Materials (ASTM) proposed a new standard, Guidelines for the Preparation of the Accreditation Section of Acoustical Test Standards. The Guidelines recommend that a section on laboratory accreditation be included in every acoustical test standard to inform accrediting authorities what requirements should be satisfied by the facilities, instruments, procedures, and quality assurance program of an accredited laboratory. The accuracy required for test instrument should be specified, and accredited laboratorie should be required to demonstrate that test instruments satisfy the specifications. Both the accreditor and the accredited laboratory—in fact anyone who uses acoustical instruments—should understand what constitutes traceable calibration of test instruments. A panel will discuss the problems and requirements of traceable calibration. The panel will include representatives of:

• the National Bureau of Standards,

• the National Research Council of Canada,

• instrument manufacturers,

• laboratory managers,

• acoustical consultants.

The audience will be invited to participate in the discussion.
Fiber-optic microbending acoustic sensor
Authors: Lagakos N.
Published: October 2005

A new mechanism for fiber-optic acoustic sensing is proposed: displacement induced microbending. The microbending is introduced to the fiber by a set of two corrugated plates, the deformer. When pressure is applied on the diaphragm attached to one of the plates a relative displacement of the plates will be introduced, which will cause light coupling from core modes to clad modes. Thus, pressure applied on the deformer could be detected by monitoring the light intensity in the clad modes. The proposed sensor could be also utilized to detect displacement, temperature, stress, etc. Such a sensor was tested and displacements less than 1 A or pressure 50–60 dB (re 1 μPa) could be detected. The dynamic range of the sensor was found to be 110 dB or better with linearity of ≃ 1%.
Wave propagation in filled silicone rubber materials
Authors: Corsaro R. D. , Jarzynski J.
Published: October 2005

The propagation of ultrasonic waves in rubbers with microscopic fillers is studied experimentally and theoretically. The longitudinal wave speed and attenuation are measured at frequencies from 0.5 to 7 MHz in silicone rubber samples with varying amounts of different fillers. The fillers used include glass and bakelite microballoons, and ferric oxide particles. The experimental data is compared with theoretical predictions from a mixture theory using expressions for effective elastic moduli derived by Kerner [E. H. Kerner, Proc. Phys. Sec. B69, 808–813 (1956)], and with predictions from scattering theory where multiple scattering effects are taken into account by following the method of Waterman and Fruell [P. C. Waterman and R. Fruell, J. Math. Phys. 2, 512–537 (1961)].
Acceleration canceling pressure gradient hydrophone
Authors: Mahler John I. , Douglas George R. , Geil Fred G.
Published: October 2005

An acceleration canceling pressure gradient hydrophone is described. The unique difference between the conventional pressure gradient hydrophone and the current phone is a plumbing and counterweight arrangement whereby acceleration induced forces from the enclosed fluid are balanced by counterweight forces. Cancelation ratios of 35 dB flat from 10 Hz up are reported from tank measurements. One axis decoupling techniques are described to enhance this ratio at 12 dB/octave from decoupler resonance. The effects of some hydrophone outer housings on the decoupler are shown. Three field tests are described: two using a new radial arm device in a quiet lake, and one using a bottom mounted cable in a tidal estuary. The first radial arm test indicated a cross-over between structure borne and turbulent boundary layer noise as flow rates rise above about 12knot. The tidal estuary test showed large enhancements of gradient acoustic output near irregular boundaries. This is attributed to the excess pressure gradients in curved wavefronts. Tests of a cardioid version of the hydrophone are included. [Work supported by NAVELEXSYSCOM.]
Real-time wave vector analys's with a charge coupled device
Authors: Cascio Carl A. , Clark Joseph A.
Published: October 2005

Acoustic measurement in the wavenumber domain can contribute significantly to the understanding of turbulent boundary layer processes. Unfortunately, the complexity of the required instrumenration generally prohibits field measurements. Similar problems occur in the real-time analysis of wave propagation in dispersive media. Previous work [G. Maidanik and D. W. Jorgensen, J. Acoust. Sec. Am. 42, 494–501 (1967)] has been limited to a narrow wavenumber range. In the present study, a charge coupled device (CCD) was adapted to allow spatial steering over an extended range of wavenumbers (25 to 125 m−1). A 16-stage parallel input-serial output CCD chip was selected to sample and then delay signals from an eight-element accelerometer array. Variation of a master clock steered the wave vector analyzer over the spatial domain. Simulated beam patterns for equal, binomial, and Dolph-Chebyshev amplitude shading were obtained. The method was illustrated by measuring the directionality of dispersive flexural waves in a 14-in. aluminum plate. The simplicity and compactness of the CCD chip offer distinct advantages over previous methods.
Effects of nonlinear attenuation in parametric acoustic arrays
Authors: Tjötta Jacqueline Naze , Tjötta Sigve
Published: October 2005

The nonlinear interaction of two sound beams propagating in the same direction (parametric acoustic array) is considered. Model equations are derived which consistently account for nonlinearity, diffraction, and absorption. In the case of strong nonlinearity, a simple asymptotic formula (Fay-type solution) is obtained for the difference frequency sound in the farfield region. On the basis of Burgers' equation we first calculate the nonlinear attenuation of the carrier waves and its effect on the generated difference frequency sound. This is done by seeking an expansion in terms of a double power series in the acoustic Reynolds numbers of the two carrier waves. The result is then inserted in the nonlinear source term of the governing equation for the parametric acoustic array. Comparison is made with results of previous models which use finite amplitude taper functions. The range of validity of solutions based on the governing equations of Westervelt [J. Acoust. Soc. Am. 35, 535–537 (1963)], Zabolotskaya and Khokhlov [Sov. Phys. Acoust. 15, 35–40 (1969)], and Bartram [J. Acoust. Soc. Am. 52, 1042–1044 (1972)] is examined. [Work supported by the office of Naval Research.]
Designing community surveys to provide a basis for noise policy
Authors: Fields James M.
Published: October 2005

Social surveys of human response to noise will make a greater contribution to noise abatement policy if the surveys give special attention to selected aspects of three types of study variables: physical noise characteristics, subjective human responses, and nonacoustical neighborhood characteristics. A re-analysis of several surveys shows that better estimates of the effects of noise characteristics (time of day, ambient levels, noise, and number tradeoff) require that (1) the precision of the noise measurements is specified. (2) sufficient independence of the study variables is insured by the sample design, and (3) the precision of the social survey estimates is increased by better sample and data collection designs. Surveys can provide better information about human response if questionnaires (1) share core annoyance questions between surveys, (2) include more meaningful indicators of human impact, and (3) ascertain public opinion about alternative noise control policies. An analysis of the effect of nonacoustical neighborhood characteristics shows that such local variables provide useful information for public policy when they are based on the reports of trained observers rather than on the subjective impressions of the social survey's respondents.
Validation of annoyance scales for social surveys of community reaction to noise exposure
Authors: Fidell S. , Teffeteller S.
Published: October 2005

Judgments of the degree to which each of a set of terms describes annoyance due to exposure to community noise sources were analyzed to produce a five interval, closed response category scale. This scale, useful for questionnaire items dealing with annoyance in social surveys of community response to noise exposure, was then used by a group of people to rate the annoyance of a set of commonly heard noise sources. Mean absolute differences in sound levels associated with each response category were determined as an aid to interpretation of the scale. Research sponsored by the Office of Noise Abatement and Control of the Environmental Protection Agency.
Variation of annoyance to aircraft noise
Authors: Dempsey Thomas K.
Published: October 2005

A two-part investigation was conducted as part of a continuing program at Langley Research Center to account for the variability in response of people to aircraft noise. Earlier studies within this program indicated a systematic and substantial increase in the annoyance of people to aircraft noise during a day of testing. Logically, this increase could be attributed to either a time-of-day effect, i.e., a circadian rhythm effect, or simply to increases in the number of aircraft noise exposures during the test period. In order to investigate the time factor, thresholds of annoyance to noise were obtained from 72 subjects at home as they went about their daily activities. These thresholds were obtained with cassette tape recorders/headsets every 2 h over a 24-h period. The effect of number of aircraft noise exposures was investigated using the same subjects, but within the laboratory situation. In these tests, thresholds of annoyance to noise were obtained from subjects after exposure to varying numbers of aircraft exposures. The threshold of annoyance data over 24 h indicated subjects showed only a small increase of sensitivity to noise between 10 p.m. and 6 a.m. Consequently, these data cannot explain response variation to tests conducted during the daytime. However, the number of aircraft exposures in a laboratory influences subject sensitivity and accounts for this type of test period variation.
Forward masking as a function of masker duration
Authors: Jesteadt W. , Lehman J.
Published: October 2005

The amount of forward masking was determined for maskers that varied from 10 to 320 ms in duration. All maskers and signals were 1000-Hz sinusoids with 5-ms cosine-squared ramps. A 10-ms signal followed the masker by 4, 8, 16, and 32 ms. Four levels of the masker were used for each combination of masker duration and masker-signal inverval (Δt). Because forward masking increases linearly with the level of the masker in all conditions, it is possible to estimate the amount of masking that would be obtained for any level within the range used. Comparisons for equal-energy maskers are of particular interest. Longer duration maskers produce more masking than shorter duration maskers of equal energy, despite the fact that the energy in the longer duration maskers is separated by a longer period of time from the signal. This result is in agreement with data recently reported by Penner [J. Acoust. Soc. Am. 66, 1719–1724 0979)] for noise maskers and click signals. The effect is greater for smaller values of Δt and higher masker levels. [Work supported by NIH.]
Forward masking of clicks with diotic and dichotic maskers
Authors: Hanna Thomas E. , Robinson Donald E. , Shiffrin Richard M.
Published: October 2005

Thresholds for diotic clicks in a forward masking paradigm with broadband noise maskers were obtained as a function of noise level, temporal parameters of the masker, number of maskers and interaural phase of the masker (0° to 180°). Comparison of MLD's at two different masking intervals with masker intensities equated for amount of diotic masking, showed larger MLD's when the time between masker and signal was short. When two nonoverlapping maskers were combined, additional masking above that predicted by an intensity sum was obtained. The amount of additional masking in the dichotic condition was approximately equal to that in a diotic condition when the amount of masking produced by a single masker was equated in the diotic and dichotic conditions. Differences from previous studies that show additivity for the dichotic condition [K. Berg and W. A. Yost, J. Acoust. Soc. Am. 60, 173–177 (1976)] will be discussed. Within the context of an intensity coding model [M. J. Penner and R. M. Shiffrin, J. Acoust. Soc. Am. 67, 617 (1980)], the additional masking can be explained by an early compressive intensity transformation. [Work supported by NSF.]
Forward masking in chinchillas
Authors: Giraudi D. M. , Salvi R. J. , Henderson D.
Published: October 2005

The forward masking paradigm has been used extensively to investigate temporal processes in the human auditory system. There is, however, a paucity of such studies in species which differ, to varying degrees, anatomically or physiologically from man. This study examined the time course of forward masking in four monaural chinchillas with stimulus parameters similar to those employed in human studies [Elliott, J. Acoust. Soc. Am. 34, 1108 (1962)]. A 50-ms burst of white noise served as the masker and the probe signal was a 10-ms tone burst with a frequency of 1 kHz. The masker was presented at 70 and 90 dB SPL. The animals were trained using a shock avoidance conditioning procedure. Masked and unmasked thresholds were measured with a modified tracking procedure. The results indicate that as the temporal separation between masker and probe increased, probe threshold decreased monotonically to approximately 100 ms. The relationship between the magnitude of threshold shift (in decibels) and log ΔT was approximated by a straight line. As masker level increased, the slope of the function increased; however, both functions intersected at roughly 100 ms. Comparison of the present findings with those obtained from humans shows that at short ΔT's the chinchilla exhibits greater threshold shift than man at equivalent masker levels. The time course of forward masking, however, is similar for the chinchilla and man.
Phase effects in forward and simultaneous masking: Diotic and dichotic conditions
Authors: Yost W. A. , Grantham D. W.
Published: October 2005

The phase angle of addition α between the brief (20–30 ms) tonal signal and a 500-ms, 60 dB SPL tonal masker was varied from 0° to 135° in both forward and simultaneous masking. Both diotic (MoSo) and dichotic (MoSπ and MoSm) listening conditions were investigated. In all conditions the frequency of the signal and masker was 500 Hz. In simultaneous masking, thresholds varied as a function of α in both diotic and dichotic conditions. However, thresholds in the diotic conditions were consistently different from those in the dichotic conditions—i.e., there were masking-level differences (MLD) at each value of α tested. In forward masking, thresholds were independent of α in both diotic and dichotic conditions. However, dichotic thresholds remained below the diotic thresholds, yielding MLD's of 3 to 6 dB. Thus, in forward masking, there is a clear effect of interaural phase on signal detectability, while the phase relation between signal and masker in one ear does not appear to influence signal detectability. These results will be discussed in relation to assumptions concerning those aspects of the masker which are preserved in the nervous system in a forward masking condition. [Work supported by NSF.]
A durational and spectral analysis of simple French words
Authors: O'Shaughnessy D.
Published: October 2005

Intelligible and natural-sounding synthetic speech requires accurate specification of phoneme durations and spectra. Toward a goal of French synthetic speech-by-rule using a formant synthesizer, a set of 285 words was read in frame sentences by a French Canadian and analyzed via wide-band spectrograms for durations, formants, and bandwidths. Phoneme durations were found to vary widely with primary dependence on the following factors: for vowels—height, nasality, and voicing and manner of articulation of ensuing consonants; for consonants—voicing, manner of articulation, and voicing and manner of articulation of adjacent consonants (in consonant clusters); for both vowels and consonants—position of syllable within the word and number of syllables in the word. A generative model of French phoneme durations in stressed words will be presented, along with a model for time trajectories of formants and bandwidths in terms of targets and smoothing rules.
Speaking clearly: Acoustic characteristics and intelligibility of stop consonants
Authors: Chen F. R. , Zue V. W. , Picheny M. A. , Durlach N. I. , Braida L. D.
Published: October 2005

A current study [M. A. Picheny et al., J. Acoust. Soc. Am. Suppl. 1 67, S38 (1980)] has indicated that “clear speech,” defined as the speech spoken with specific instructions to enunciate clearly, may be substantially more intelligible when presented to hard of hearing listeners than “conversational speech.” The purpose of this study is to determine segmental differences in the acoustic properties of stop consonants enunciated “clearly” and “conversationally” and to correlate these differences with differences in intelligibility. The corpus consisted of 18 CV syllables (six stop consonants and three vowels) embedded in a carrier phrase spoken several times by three male speakers under the two conditions, yielding 540 tokens. The CV's were excised from the carrier phrase and presented to listeners with simulated hearing loss for the purpose of intelligibility testing. In addition, acoustic parameters, such as formant frequencies, burst intensity, CV ratios, and formant transition rates were measured. Preliminary results of acoustical analysis of the speech waveforms and of intelligibility tests will be presented.
Speaking clearly: Intelligibility and acoustic characteristics of sentences
Authors: Picheny M. A. , Durlach N. I. , Braida L. D.
Published: October 2005

In a recent study [M. A. Picheny and N. I. Durlach, J. Acoust. Soc. Am. Suppl. 1 65, S135(A) (Spring 1979)], the intelligibility of speech spoken in a conversational manner versus speech spoken while consciously attempting to increase one's clarity was examined. Four hearing-impaired listeners were tested on groups of 50 Harvard PB sentences enunciated by a single speaker and presented at listener-selected levels. For all four listeners, the intelligibility of the clear speech was substantially higher than that for the conversational speech (average of 18 percentage points). This report will present preliminary results on the intelligibility of syntactically normal but semantically ambiguous sentences [P. W. Nye and J. H. Gaitenby, Haskins Laboratory Status Report on Speech Research SR-37/38 (1974)] spoken clearly and conversationally to hearing-impaired listeners and normal-hearing listeners with simulated losses. In addition, preliminary acoustical analyses of the two types of speech materials will be presented.
A reaction-time study of the production of [s] and [š]
Authors: Isenberg David
Published: October 2005

Talkers produced steady-state vowels until they heard an auditory go-signal when they initiated articulation of [s] or [š] as rapidly as possible. Talkers knew the target fricative in advance. The reaction-time, measured from the go-signal to the cessation of glottal pulsing, was faster for [s] than for [š] by 11.5 ms following the vowels [i, a, u, ʌ]. This result can be interpreted as supporting the claim that [š] demands more precise control of the tongue tip than [s] [J. S. Perkell, S. E. Boyce, and K. N. Stevens, J. Acoust. Soc. Am. Suppl. 1 65, S24 (1979)]. Preliminary data suggest that [s] is not faster than [š] following the vowel [ɝ]-since both [š] and [ɝ] are thought to involve similar types of anterior tongue movement, this observation is a further indication that tongue tip control is the crucial factor that slows [š] articulation following [i, a, u, ʌ]. Measures of spectral change were applied to these utterances to examine in detail the time course of events between the go-signal and the fricative steady state. [Research supported by a grant from NINCDS.]
Imitation of /s/ duration in VCV's
Authors: Karno E. , Porter R. J.
Published: October 2005

V1CV2 syllables were created by editing naturally produced segments: V1 was always a 412-ms /a/; V2 was a 300-ms /ε/, a 315-ms /i/, or a 390-ms /u/; C was an (unfounded) steady-state /s/ segment with one of seven durations, from 116 to 416 ms, in 50-ms steps. All V2 and /s/-duration combinations were presented six times, randomly, to subjects who were instructed to listen carefully to each stimulus and then to imitate it, taking care to produce the same segment durations, vowel qualities, etc., as in the stimulus. Acoustic segments' durations in the responses were measured using oscillographic displays. EMG activity for the obicularis oris were also obtained to address the question of when (in time) coarticulatory activity began relative to acoustic onset of /u/. Subjects were remarkably sensitive to stimulus variation but showed some tendency to undershoot target durations. EMG onset varied with subjects and /s/ duration, suggesting variation in response strategies as a function of these variables. Results will be discussed in terms of their implications for the interrelation of perceptual and productive mechanisms. [Work supported in part by NIH BRSG RRO7196-03 and The Kresge Foundation.]
Analytical synthesis of brachistochrones is an arbitrary velocity field
Authors: Adams W. M. , Lewis C. H.
Published: October 2005

Consider the problem of finding the brachistochrone between two points on the boundary of an area of interest having a spatially varying velocity field. The arbitrary velocity field can be synthesized from a set of simpler functions, for example, by a Fourier representation or a power-series expansion. Now consider the analogous brachistochrone problem, using the same endpoints, for each of the simpler functions. Each of these problems is often solvable analytically. The solution to the original brachistochrone problem can be expressed in terms of the solutions to the set of brachistochrone problems on the simpler surfaces. The theory and an application will be presented. [Work supported by NSF and NOAA.]
Multiple scattering of waves from two cylindrical shells in fluid
Authors: Radlinski Ronald P.
Published: October 2005

The impedance formulation developed by Junger [J. Acoust. Soc. Am. 24, 366–373 (1952)] to describe a thin elastic shell is used for an eigenfunction expansion solution to the plane wave scattering from two elastic cylindrical shells in fluid. The two-dimensional approach employs the addition theorem as first reported by Twersky [J. Acoust. Soc. Am. 24, 42–46 (1952)]. The effects of the resonances of the shell are shown by comparison with the cases of scattering from two acoustically soft or two acoustically rigid cylinders. The interaction between the cylindrical shells is discussed. Finally, the method of images is used to investigate the scattering of a plane wave from a cylindrical shell near an infinite plane.
Scattering of acoustic waves by finite elastic cylinders immersed in water
Authors: Numrich S. K. , Varadan Vasundara V.
Published: October 2005

Backscattering measurements using short acoustic pulses were made for finite elastic cylinders immersed in water. These solid aluminum cylinders were terminated with solid hemispherical caps. The overall length of the cylinders is four times the radius. For frequency scaling the factor 12kl (or 2ak) was used. Measurements were made perpendicular to the cylinder axis, end on, and at 45°. Results ranging from less than 4.0 to greater than 5.0 in 12kl were compared with the theoretical predictions using a T-matrix formulation made by Varadan, Varadan, and Flax [V. V. Varadan, V. K. Varadan, and L. Flax, J. Acoust. Soc. Am. 60, S81 (1979)].
Calculation of schlieren patterns of ultrasonic transducers with laws
Authors: Cook Bill D.
Published: October 2005

From first principles it is possible to calculate schlieren patterns from given transducer velocity profiles. By use of the Fourier projection theorem, the sound field need not be calculated as the integrated optical effect for light passing through the sound field is found directly. By applying the principles of optical spatial filtering, schlieren patterns similar to those observed can be calculated. These patterns depend on sound level, transducer configuration, and type of spatial filtering. The effect of these patterns of a flaw, i.e., a region of no motion on the transducer, will be presented.
Control of jet engine noise
Authors: Schiff M. I.
Published: October 2005

A review covering the more than two decades of Industrial Acoustics Company's experience in the design and manufacture of jet engine noise suppression equipment. The development of this equipment for aircraft and test stand applications is traced. Some of the more significant noise control sytems are illustrated. Examples of how the interaction of acoustics, aerodynamics, and mechanical performance impacts the operation and service life of jet engine noise suppression equipment are included.
Test cell and hush house noise suppression developments
Authors: Lepor M.
Published: October 2005

The Navy has a number of technical approaches under development to diminish the noise impact of ground run-up testing. Since resources are scarce, it is important that all reasonable designs for satisfying noise abatement objectives be considered to ensure proper committments to these resources. The initial thrust of the development effort where the engine is in the aircraft (e.g., “in-frame”) is the acoustical enclosure or hush house program. A series of these facilities have been designed for a variety of air station requirements. An alternate air-cooled noise suppression system under consideration for out-of-frame testing is the design of a test cell exhaust section based on the application of the Coanda/Refraction concept. Current methods for design of water-cooled jet engine test cells for out-of-frame testing are largely empirical. By developing working internal thermo/aerodynamic models prior to preliminary design, the design of new test cells and/or required modifications of existing water-cooled facilities would be greatly enhanced. The need for the development of models and for advances in material technology for optimization of test cell and hush house designs are discussed.
Velocities of seismic waves in composite, multi-phase media
Authors: Toksöz M. Nafi , Cheng C. H.
Published: October 2005

The elastic moduli and seismic wave velocities in two-phase media can be calculated theoretically using a scattering approach. With the long wavelength approximation, the scattered displacement fields from individual inclusions are equated to those from an equivalent sphere having the effective properties of the composite material. By equating coefficients, effective properties are found. This result can be further refined using an iterative process. Theoretical predictions are compared to laboratory data of solid spheres suspended in liquid and empty spherical cavities in glass. The agreements in both cases are excellent, and better than the “self-consistent” approximation. The second-order terms in the scattering theory can also be included in formulation and these show the dispersive characteristics of the seismic waves. The shapes of inclusions are found to play a very important role in determining the seismic velocities in the multi-phase media. The inclusions are modeled as oblate ellipsoids of varying aspect ratios (thickness-to-length ratio). Thin inclusions have a larger effect than an equivalent volume of spheres. An inverse method of formulating shapes of inclusions from compressional and shear waves and their dependence on pressure is formulated. Examples are chosen to show effects on seismic velocities of pores in rocks, solid suspensions in water, and gas bubbles in liquids.