bluuebunny/crossref_metadata_2025 huggingface dataset:
Progress in remote sensing of temperature profiles in the atmosphere and oceans
Authors: Brown E. H.
Published: October 2005

Encouraging results have been obtained with a method using three-dimensional interference patterns for the remote sensing of temperature profiles. Measurement of atmospheric wind (or ocean current) profiles are a by-product of the method. Latest experimental results and theoretical analysis of temperature and wind contributions are described. [Work supported by Army Research Office.]
Acoustical observations of oceanic bottom boundary layer particulates
Authors: Proni John R.
Published: October 2005

Studies have been carried out on the oceanic bottom boundary layer using 20 kHz and 3 MHz sound systems. Data will be presented on the generation of a suspended layer of sediment, essentially confined within the bottom boundary layer, by nonlinear internal wave groups on the N.Y. Continental shelf in 120 m of water. Data will also be presented on the existence of a large underwater “cloud” of material found on the continental slope (water depth typically (600-300 m) which has been observed consistently over the last several years and which is highly acoustically reflective. Some data from a high resolution (≃ 1 cm) 3 mHz-acoustical system on particulate concentration estimation will be presented.
Marine acoustics in Australia
Authors: Shaw N. , Marsden M. , Bourne I.
Published: October 2005

A survey was conducted to identify groups, individuals, and institutions using acoustic probes in the marine environment and to ascertain (a) if the group's emphasis was research or industrial application of acoustics and (b) if their general field of interest was in objects and structure within the water column, bottom topography, or subbottom geological structure. Participants specified the acoustic equipment employed and assessed the system's performance, data quality, maintenance requirements, and general capabilities. Specific questions were asked about the group's requirements for remotely sensing physical parameters within the water column and detection of the related distribution of marine organisms. Relevant to this joint JASA acoustic workshop was a call for greater interaction between researchers and those technologies now being developed separately for the atmospheric and aqueous media. For example, estimates of water turbulence and profiles of currents could be remotely sensed by acoustic techniques similar to those already developed for detecting atmospheric turbulence and wind profiles.
An intercomparison of an acoustic remote current sensor and Aanderaa current meters in an estuary
Authors: Scherer W. D. , Sage K. A. , Pryor D. E.
Published: October 2005

An intercomparison experiment of a single-axis bistatic acoustic remote current sensor and Aanderaa current meters was conducted during the fall of 1978 in the Patuxent River near Solomons Island. The acoustic sensors were located on a platform at a mean water depth of 15 m and the acoustic axis pointed essentially downstream. The transmit frequency was set at 270 kHz, and the received signal was cabled to shore and heterodyned to 5 kHz. Up to 128 tone bursts of 10-ms duration were transmitted at 1-s repetition time every 15 min. The back-scattered volume reverberation data were analog recorded, subsequently digitized, and spectrally analyzed. The spectral estimates of the Doppler shift are derived for a number of range intervals and are compared with Aanderaa current speeds projected along the acoustic axis of the remote sensor. The comparison of the time series (15-min intervals) extends over a number of tidal cycles.
A microprocessor-based MODEM for underwater remote sensing
Authors: Prasad S. , Madan B. B. , Kumar Navesh
Published: October 2005

The underwater acoustic channel exhibits large dispersion of the signals in time and frequency domains. The dispersion is characterized by broadening and fading of the signals transmitted through it due to multipath propagation and random motion of particles constituting the medium. Conventional modulation/demodulation techniques, even with forward error correction and ARQ techniques and at moderate data rates, are quite ineffective for data communication over this channel. This paper briefly reviews som signalling schemes which might be suitable for the underwater acoustic channel. A comparative evaluation of them is also presented. The paper also describes a microprocessor-based instrumentation of a versatile MODEM which can implement these schemes under program control with a fixed amount of associated hardware.
Reaction-time measurement of tinnitus
Authors: Goodwin P. E. , Johnson R. M.
Published: October 2005

Reaction times (RTs) were obtained for hearing impaired subjects with tinnitus (experimental group) and normal hearing subjects without tinnitus (control group) to the following sets of frequencies of the tinnitus patients: the tinnitus frequencies (which were associated with abnormal thresholds), nontinnitus frequencies associated with thresholds within normal limits, and nontinnitus frequencies with thresholds similar to the thresholds of the tinnitus frequencies. The only significant difference for RTs for the experimental group versus the control group was to the tinnitus frequencies. There were no significant differences between the two groups for RTs to the two sets of nontinnitus frequencies. There were no significant differences for RTs for the control group among the three sets of frequencies. However, for the experimental group, RTs to each of the three sets of frequencies differed significantly from each other. This study suggests that the measurement of RTs to auditory stimuli provides an objective measure of tinnitus, a means of comparing human and subhuman data, a method for determining recruitment, and a possible technique for mapping areas of tinnitus.
Difference limen for amplitude compression of speech
Authors: Nábělek Igor V. , Koike Kazunari J. M.
Published: October 2005

It is postulated that the amount of information carried by speech can be altered by speech modifications which can be perceived aurally. Therefore, amplitude compression might increase intelligibility if a reduction of level differences between strong and weak speech sound is perceivable. Difference limen for attack (TA) and release (TR) times of compression for various compression ratios (CR's) based on a quality change was determined by the adjustment or ABX methods. A 1.7-s-long utterance with approximately constant maximal rms levels of words was submitted to wide-band compression. Masking noise added after compression at −10 dB (re speech) equalized the noise background for various conditions. The smaller the CR or the TA, the shorter the TR had to be to provide a perceptible change in quality; e.g., experienced normally hearing subjects needed TR equal to or smaller than 420 and 250 ms to discriminate a quality change when CR = 5 and TA equal to 10 and 3 ms, respectively, from linear amplification. Naive normally hearing listeners needed a much shorter TR (between 30 and 40 ms for the same conditions). Testing of hearing impaired listeners is presently in progress. [Work supported by NIH NS 12946.]
Prevalence of collapsible ear canals in an elderly clinical population
Authors: Schow Ronald L. , Randolph Loren J.
Published: October 2005

Prevalence of collapsible ear canals was determined for 80 elderly (60–79 yr) subjects drawn for a clinical population. Pure tone air conduction thresholds were established at 500-4000 Hz using standard TDH 39 earphones mounted in (1) an MX-41/AR supra-aural cushion and (2) an Eckstein, model CA circumaural cushion. A correction factor was established to insure equivalency between earphone cushions by testing 20 young adult subjects (20–29 yr). The criterion for a collapsible ear canal was a 15 dB or greater improvement in threshold at any one frequency when circumaural rather than MX cushions were used. None of the younger subjects showed this large a shift in threshold, but 29 elderly subjects (36%) did. These results indicate a higher prevalence for elderly persons than the 4% previously reported on a general clinical population [V. H. Hildyard and M. A. Valentine, Arch. Otlaryngol. 75, 422–423 (1962)]. Based on these data. measurement errors may cause inaccuracies in normative data of about 5 dB. It appears that circumaural cushions or bone conduction testing are needed to avoid errors in hearing tests on the elderly population.
Comparisons between the median hearing threshold levels for an unscreened black nonindustrial noise exposed population (NINEP) and several presbycusis data bases
Authors: Driscoll D. P. , Royster L. H.
Published: October 2005

Hearing threshold level data representing an unscreened black NINEP have been collected. For comparison purposes the median threshold levels of previously established presbycusis data bases have been obtained from the literature. After each data set had been normalized relative to age 18, comparisons were made between the black NINEP and the presbycusis data base median hearing threshold levels for sex and age groupings. The unscreened black NINEP exhibits median hearing levels similar to those of the presbycusis data bases for ages less than approximately 45 years. However, for age groupings greater than 45 years the median hearing levels of the black NINEP are lower than those of the presbycusis data bases. [Work supported by the Rockefeller Foundation.]
Effectiveness of three different types of ear protectors in preventing TTS
Authors: Royster L. H.
Published: October 2005

The effectiveness of the E-A-R, Hear Guard, and Sigma insert hearing protectors in preventing daily temporary threshold shifts in two different industrial environments was investigated. The employees at both plant locations were exposed to an A-weighed Leq of approximately 95.5 dB. The in-the-field protection provided by the E-A-R and Hear Guard ear protectors was investigated at one plant location and at a second plant location the effectiveness of the E-A-R and Sigma ear protectors was evaluated. For the two environments investigated the employees who wore the E-A-R ear protectors did not exhibit a significant TTS; however, the employees who wore the Hear Guard and Sigma style ear protectors did indicate a significant TTS. [Work supported by the Rockefeller Foundation (RF 78001), N.C. Department of Labor and the two industries that participated in the study.]
Some differential effects of infrasound on man
Authors: Nussbaum David
Published: October 2005

In this investigation 63 experimental and 21 control subjects were studied to learn more about realistic effects of infrasound on humans. Experimental subjects received infrasound at a frequency of 8 Hz and an intensity of 130 dB SPL, for a 30-min duration. Control subjects received identical sessions minus the infrasound. Physiological parameters measured included heart rate, respiratory rate, plethysmography, EEG, blood pressure, and audiograms. Performance variables consisted of time estimates and a short term memory task. Subjective response were evaluated via a mood scale as well as by verbal reports. Results indicate that individual differences play a role in the response to infrasound. Some experimental subjects exhibited symptoms consistent with motion sickness and changes in their EEG patterns. Respiratory changes were also noted. A mechanism is suggested which might account for observed subjective response variations in light of physiological differences. These will be discussed in detail in the body of the paper.
Windowing in linear prediction analysis of voiced speech
Authors: Paliwal K. K. , Rao P. V. S.
Published: October 2005

The autocorrelation and covariance methods of linear prediction are used for pitch-synchronous and pitch-asynchronous analyses of voiced-speech segments and the effect of weighting the data, prior to its spectral analysis, by a tapered window function is studied. It is shown that for both pitch-synchronous and pitch-asynchronous analyses, the performance of the autocorrelation method improves considerably by the introduction of such a window function. In the case of the covariance method, no such windowing of data is required. Furthermore, it is shown that for pitch-synchronous analysis, the performance of the autocorrelation method is not much worse than that of the covariance method. Hence the use of the autocorrelation method is recommended over the covariance method if stability of the linear prediction filter is to be ensured.
Improved estimate of vocal-tract areas from the speech wave
Authors: Milenkovic Paul , Atal Bishnu S.
Published: October 2005

Areas obtained from linear prediction analysis of the speech wave often differ from actual voice-tract areas. Some of the differences are due to unrealistic assumptions made in the inversion procedure about the losses in the vocal tract, the spectrum of the glottal source, and the high-frequency spectrum of the vocal-tract impulse response. In this paper, we discuss the nature of errors introduced by these assumptions and describe a procedure for avoiding some of the errors. We discuss how lack of high-frequency spectral information creates ambiguities in mapping acoustic information to vocal-tract areas. Ambiguities are also caused by the uncertainity about the source characteristics. We resolve these ambiguities by requiring that the recovered vocal-tract shape be smooth; the smoothness requirement ensures that the dimensionality of the area function is not increased in the process of specifying the missing information. Results obtained from tests on both natural and synthetic speech signals will be presented.
Comparison of glottal pulse shapes derived from linear prediction residual and pole-zero model residual of speech
Authors: Yegnanarayana B.
Published: October 2005

An important problem in voiced speech analysis is the determination of the characteristics of glottal pulses from speech signal. These characteristics can be derived in principle from the residual signal obtained by passing speech signal through the inverse of a model system for the vocal tract. The accuracy of the glottal pulse information thus derived depends on the accuracy of the model representing the vocal tract system. In this study glottal pulse shapes obtained by using an all-pole model and a pole-zero model are compared. The all-pole model is obtained from linear prediction analysis and the pole-zero model from a pole-zero decomposition technique. For most voiced sounds both the methods yield the same glottal pulse shapes. But for nasals and voiced fricatives the pole-zero model provides a more accurate characterization of glottal pulses than the all pole model. The results are explained on the basis of spectral approximation provided by the models.
Application of pitch perturbation measures to the assessment of hoarseness in Parkinson's disease
Authors: Ludlow C. , Coulter D. , Cardano C.
Published: October 2005

To determine whether measures of pitch perturbation relate to the occurrence of hoarseness in a neurological disease, patients with Parkinson's disease (hypokinesia) and normal aging controls were recorded. Pitch period lengths were measured from recordings of extended vowel productions to compute: mean adjacent differences; mean deviations of cycles from predicted values based on adjacent cycles; and jitter ratios. Three trained judges rated hoarseness on a seven-point scale from the same recordings. Mean adjacent differences were linearly related to fundamental frequency in hypokinesia but not in normal speech. Judgements of hoarseness were significantly related to mean adjacent differences, mean deviations and jitter ratios in the hypokinetic speakers. No significant relationships between hoarseness and the perturbation measures were found in the aging controls. Judgements of hoarseness did not accurately discriminate between normal and hypokinetic speakers, while the mean adjacent differences and deviation functions discriminated significantly between the normal and hypokinetic speakers. Mean jitter ratios did not discriminate normalcy from hypokinesia. Thus, adjacent differences and deviation functions are valid measures of hoarseness associated with hypokinetic dysarthria.
Articulation loss of consonants using the English language
Authors: Brey R. H. , Raventos W. , Dick K.
Published: October 2005

Peutz [J. Audio Eng. Soc. 19, 915 (Dec. 1971)] reported a procedure for determining the transmission of auditory information in a room called articulation loss for consonants (Alcons). This procedure was an improvement over the articulation index, primarily because it included variables of room acoustics. Alcons = (200 D2T2)/V + a)%, where T = reverberation time, V = volume of room, D = distance. and a = correction for the type of listener. Reverberation data were measured in constant percentage bandwidth using new microprocessor controlled instrumentation. Stimuli for his research were made up of Dutch consonant verbal consonants (CVC) words. Data will be presented to demonstrate the feasability of using the same formula using English (CVC) words. Subjects were normal hearing individuals who were presented the materials under various reverberation times.
Computer analysis of the effects of valve actions on initial transients in organ flue pipes
Authors: Kinnaugh Norman , Plitnik G. R.
Published: October 2005

Computer measurements have been made of the onset transients of a set of experimental “Principal” organ pipes. The pipes were played individually from a number of valves closely resembling the two most common types of pipe organ valve actions. One action (representative of many electro-pneumatic types) has a small circular valve directly beneath the pipe; the other action (tracker type) consists of a long rectangular valve which admits air into a chamber which feeds the pipe. The analysis was a time-tracking correlation of the fundamental frequency from the time of valve opening through to the steady state. Partials were treated as a quasiharmonic series and analyzed similarly. Steady-state spectra of the same pipe played on different valve actions shows results which are contrary to that reported by some previous researchers. (The pipes and experimental wind chest were donated by the M. P. Moller Co., Hagerstown, MD.)
The effects of mouth adjustments on the acoustic spectra of flue organ pipes
Authors: Nolle A. W.
Published: October 2005

The mouth height (cutup) of a flue organ pipe and the horizontal position of the upper lip relative to the axis of the jet have a great influence on both transient and steady-state waveforms. Effects of these variables will be shown with data taken on adjustable pipes, open and closed, operating at 40 to 60 mm (water) wind supply pressure. The presentation concerns mainly (a) relative amplitudes of harmonic components in the steady signal, (b) noise components apparently created by the edgetone feedback process, and (c) multiphonic oscillation. The short pipe with highly anharmonic passive resonance frequencies is particularly discussed, because its harmonic content is due to the nonlinearity of the jet-to-pipe excitation described by Fletcher. Radiation from such a pipe may have second harmonic amplitude greater than 10% of fundamental amplitude, with the third harmonic much smaller. Significant characteristics of the jet-to-pipe excitation function are shown by the existence of a minimum of second harmonic content as the horizontal lip position is changed, and changes of the phase of the second harmonic relative to the fundamental.
Some physical mechanisms underlying the pipe voicing art
Authors: Elder S. A.
Published: October 2005

This paper examines underlying mechanisms for changes in the flue pipe spectra caused by selective changes in mouth cutup, pipe length, languid position, etc. The physics of the problem involves the mechanics of jet waves, and the subtleties of their interaction with sound waves. Special interest centers at lower lip, where jet waves originate, and at upper lip, where sound is produced by collision of jet and pipe fluid. The necessities of feedback amplification require jet and sound motions to act in a reciprocal way so that, for example, delay in impulse transmission along the jet is exactly matched by acoustic transmission delay in pipe. Actually, jet waves and their associated sound waves behave in remarkably self-consistent and complimentary ways. Just as sound waves travel up and down pipe to form discrete modes, jet waves also appear in discrete pairs, which travel up and downstream. One of the principal acoustic factors in voicing is the natural “stretching” of pipe mode frequencies, which tends to give pipes voiced to oscillate above resonance a different character from those voiced to oscillate below. An analogous property of jet is thickness Strouhal number, or nondimensional frequency. Since cutoff occurs at a critical Strouhal number, harmonic development on the jet is not possible unless S < 0.05 Sc, High and low Strouhal number jets, therefore, exhibit opposing spectral tendencies. Thus voicing is seen as adjustment toward optimum complimentarity between jet and resonant cavity, consistent with a desired spectral output.
Temperament and tuning in organs with particular reference to accomodation variances applied to electronic divisions
Authors: Mulder George W.
Published: October 2005

Observations on current temperament and tuning practices of organs will be made. New combinations of pipes and electronic divisions in organs require a tuning accommodation in the electronic segment to accommodate temperature variance in the pipes. Through use of variable modulating devices the electronic unit may be readily tuned to accommodate the variance in tuning of the pipes due to temperature differences. Additional reference to pitch variants within differing temperament systems will be discussed.
Transmission loss measurement on a sheet of falling water
Authors: Russell D. R. , Krafft D. F. , Hurst C. J.
Published: October 2005

Transmission loss measurements were made on a sound barrier consisting of a thin sheet of freely falling water. These measurements were undertaken to see if such a sheet of water could be used for noise control where appropriate. The sheet of water was formed across a 2-ft-square duct connecting reverberant rooms. The intensity incident on this sheet of water and the intensity of the sound transmitted through it were measured using a two microphone technique. The transmission loss results thus obtained were checked using conventional reverberant room techniques. The measured transmission losses were lower than predicted, based on assumptions that the sheet of water acted as a point reacting mass wall with negligible fluid velocity. [Work supported by Southeastern Poultry and Egg Association.]
Some comments on the interaction of sound with sound
Authors: Van Buren A. L. , Rogers Peter H. , Piquette Jean
Published: October 2005

The fundamental equations and several derived equations governing the interaction of sound with sound are examined and compared in light of apparent discrepancies among published results for the scattering of sound by sound and the parametric receiver. The discrepancies are only significant for large angles between the interacting waves (such as are involved in the cross-beam experiment and the front-to-back ratio for the parametric receiver) and originate from inaccurate treatment of the problem. It is shown here that an accurate treatment requires that D'Alembertian terms be retained, that boundary condition be taken into account properly, and that the distinction between Lagrangian and Eulerian coordinate frames be maintained.
On the angular spectrum of nonlinearly interacting acoustic waves
Authors: Fenlon F. H.
Published: October 2005

In this paper the radiation field of a propagating finite-amplitude disturbance in an isotropic, homogeneous fluid is derived via spatial Fourier transform theory from the angular spectrum of plane waves in the wavenumber-frequency domain. By invoking the Fresnel approximation this field is shown to be equivalent to that obtained from the ZK equation [E. A. Zabolotskaya and R. V. Khokhlov, Sov. Phys. Acoust. 15, 35–40 (1969)] thus leading to the important conclusion that if preferred one can bypass the latter and instead make use of the angular spectrum to evaluate the nonlinearly generated field. The paper concludes by using this approach to derive the plane wave angular spectrum of a parametric acoustic array and hence the difference-frequency field for the case of weakly interacting Gaussian beams.
Development of generalized nonlinear behavior of elastic waveforms in an arbitrary inhomogeneous, lossy medium
Authors: Akers G. R.
Published: October 2005

A general method of developing the nonlinear wavefield for an arbitrary inhomogeneous medium incorporating energy loss mechanisms is presented. The equations of motion for an inhomogeneous medium with physical constants that are arbitrary functions of position, are modified by the incorporation of a generalized loss function, L. This acts as a sink function by introducing a dissipative force field in the force balance equations that accounts for losses in the medium. A general power series solution is developed and the nonlinear wavefield solution is presented that incorporates the effects of losses and higher order interactions in its functional form. The effect of loss on the dispersion relationship is seen as a frequency shift of the wave and loss effects introduce harmonics which lead to waveform distortion. The classical theory of attenuation is extended by this treatment. [Work supported by Navy Long-term Training Committee.
Studies of the planetary boundary layer using the CRPE triple Doppler sodar
Authors: Klapisz C. , Weill A. , Jaupart C. , Taconet O. , Bouteloup P. , Eymard L.
Published: October 2005

The triple Doppler sodar is now an operational instrument. In convective situations, it allows us to measure the local vertical heat flux, the vertical velocity variance, and the rate of dissipation of the turbulent kinetic energy, as well as local stresses. It also allows the determination of the lowest inversion height. We briefly recall some technical aspects concerning the data treatment. We then discuss the relative importances of the different terms which appear in the turbulent kinetic energy budget and justify the parameterization of several variables introduced. Finally, we review the studies we have undertaken in the homogeneous boundary layer, and present the perspectives offered for the study of the heterogeneous and perturbed boundary layer.
Language learning in deaf children: The critical issues
Authors: Mayberry Rachel I.
Published: October 2005

Research in deaf children's language has centered on three major areas: (1) the effects of educational method, parental communication, and hearing status on deaf children's acquisition of spoken language; (2) the way in which deaf children's spoken language deviates from that of normally hearing children; and (3) the way in which deaf children acquire sign language or develop gesture in its absence. This paper briefly reviews recent research in each of these areas in terms of critical questions germane to deaf children's language and also to first and second language learning.
Multipath analysis of explosive source signals in the ocean
Authors: Bedford N. R. , Mitchell S. K. , Ellis G. E.
Published: October 2005

A computer-based measurement system has been developed for the measurement of acoustic propagation loss in multipath arrivals of signals from explosive sources. The system involves both signal measurement operations and careful theoretical representations of the measured quantities. Initial applications have been for measurement of bottom reflection losses using signals which reflect many times from the bottom. It has been found that the levels of arrival pulses can be strongly affected by predictable surface reflection effects. Measurements demonstrate consistent bottom reflection loss values across homogeneous basin areas. [Work supported by Naval Ocean Systems Center.]
Aircraft noise propagation and reception anomalies at a major airbase
Authors: Dickinson Philip
Published: October 2005

When a U.S. Air Force Air Installation Compatible Use Zoning (AICUZ) study was presented to the local government authorities in the area surrounding one major U.S. airbase, there was some disbelief and much concern about the high noise exposures predicted. So the local government authorities commissioned their own land-use compatibility study to be based on measured noise levels over an 18-month period. The results of the study only exacerbated the worries—noise levels and exposures well in excess of those predicted and large numbers of people exposed to noise more than 20 dB in excess of that generally considered “intolerable.” Yet, complaints are so few as to be almost negligible, and the people seem remarkably healthy. Some of the reasons for the higher noise exposures relate to peculiar temperature effects in the high desert valley in which the base is situated. The low level of complaints is attributed to the scheduling and nature of the flights on the one hand and to the way of life of the local people on the other hand. It is suggested that the OSHA type regulations and EPA/US Air Force recommendations give a false impression of the compatibility of the environment in some circumstances.
The ear's two temporal integrators, operating in series
Authors: Penner M. J.
Published: October 2005

The threshold of a click is traced in the presence of two equivalent noise maskers as a function of the time ΔT between the maskers. Muskets are said to be equivalent if any one of them alone produces the same amount of masking of a click. The time between the offset of the first masker and the click was fixed at 9.25 ms. For very brief ΔT (⩽2 ms) the click threshold is constant, exceeding the single masker threshold by 3 dB. As ΔT increases from 2 to 3 ms, the click threshold rises abruptly. For ΔT > 3 ms the threshold is again constant, exceeding the single masker threshold by about 9 dB. These data are interpreted as support for an early temporal integration system that summates auditory input for 3 ms or less. The output of this early system is modeled as the input to another system that applies a compressive nonlinear transformation and summates auditory input for a considerably longer period of time.
Critical angle diffraction in high frequency scattering by fluid spheres and cylinders
Authors: Marston P. L.
Published: October 2005

When plane waves are reflected from a flat surface between ideal fluids, the reflection is total when the angle of incidence θ exceeds θc = sin−1(c1/c2) where c2 > c1; c1 and c2 are the sound speeds, respectively, of the fluid from which the wave is incident and of the second fluid. For an interface of constant curvature, ray acoustics predicts that the scattered intensity has an unphysically divergent angular derivative as the scattering angle φ approaches the critical scattering angle φc = π − 2θc. This divergence is removed by diffraction which is important in an angular region near φc. The width of this region exceeds (a/λ)1/2, where a is the radius of curvature and λ is the wavelength. A simplified approximation for the diffraction, similar to the optical analog described in “Critical angle scattering by a bubble: physical-optics approximation and observations” [P. L. Marston, J. Opt. Soc. Am. 69, 1205–1211 (1979)], is derived. As φ approaches φc, a ringing and decay of the far-field intensity is predicted which may be observable in scattering by fluid spheres and cylinders.
Creeping wave description of surface wave modes on elastic cylindrical shells
Authors: Dickey J. W. , Nixon D. A. , Breitenbach E. D.
Published: October 2005

Dispersion and attenuation curves are given for identified surface modes in the scattered pressure from elastic cylindrical shells insonified by a normally incident plane wave. The results are derived using two different techniques for air-filled aluminum shells of several different wall thicknesses, b/a (ratio of inner to outer radius). The first series of numerical results are calculated using the Sommerfeld-Watson transformation and determining the roots of a 6 × 6 secular determinant. The second method is used to derive similar results by analysis of the partial wave responses. The second method results, for a thick shell, are favorably compared with previously obtained creeping wave results for a solid elastic cylinder. For low values of b/a, the Rayleigh and Stoneley waves on the shell are shown to approach limiting values for increasing ka which correspond to the Rayleigh and Stoneley wave speeds defined for the infinite half-space, and the Franz and Whispering Gallery modes approach the bulk wave velocities for the external and shell materials respectively. For thin shells (b/a → 1), Whispering Gallery and Rayleigh modes have vanished and the symmetric and antisymmetric Lamb modes are prevalent over limited regions of ka. Calculations are carried out over the range 0.1 ⩽ ka ⩽ 200, the first method valid for higher ka, and the partial wave method valid at lower ranges of ka.
The relation between gap discrimination and auditory stream segregation
Authors: Neff D. L. , Jesteadt W. , Brown E.
Published: October 2005

The relation between gap discrimination and stream segregation [A. S. Bregman and I. Campbell, J. Exp. Psychol. 89, 244–249 (1971)] was examined using sequences of four 200-ms, eight 100-ms, or sixteen 50-ms tones with a total frequency range range from 18 to 212 octaves. A gap of variable duration was inserted between tones of similar or disparate frequency. Gap discrimination, in a 2IFC procedure, became poorer as the difference between the frequencies of the tones bounding the gap increased, but was not influenced by changes in sequence length and rate. Judgments of stream segregation for the same stimuli by the same listeners showed strong individual differences, an influence of sequence length and rate as well as marker-frequency difference, but little relation to gap discrimination. [Work supported by Grant NS-14709 from NINCDS.]
Temporal asynchrony within auditory patterns
Authors: Gilliom J. D. , Brady S. L.
Published: October 2005

Another in a series, the present study explores the effect of temporal asynchrony on the perception of part tones within the context of a musical chord. The basic paradigm requires an observer to perform a monaural yes-no detection task of a tonal signal within Gaussian noise, with signal frequency a random variable. A contralateral frequency cue is provided on each trial prior to the detection interval, enabling an observer to reduce the negative effects on detection performance of such signal frequency uncertainty. The experimental manipulation consists of placing this cue within the context of a three-element musical chord and varying the onset and offset of the cue component relative to the other components of the chord while monitoring the cue's effectiveness in raising detection performance. Shifts in detection performance from such manipulations indicate that the availability of specific spectral pitch information from a part tone within a musical chord is substantially enhanced by making its onset and/or offset asynchronous with that of the remaining components of the musical chord.
Temporal and spectral determinants of informational masking in tonal patterns
Authors: Watson Charles S. , Kelly William J. , Mellen Douglas M.
Published: October 2005

A form of “informational masking” is observed when listeners attempt to detect single target components of word-length tonal patterns [J. Acoust. Soc. Am. Suppl. 1 64, S39 (1978)]. These masking-like effects, sometimes as large as 50–60 dB, occur under conditions of high stimulus uncertainty, when contextual patterns and the temporal and spectral positions of target tones are varied from trial-to-trial, but are absent under conditions of minimal psychophysical uncertainty. Stimulus determinants of informational masking were investigated in three experiments, by (a) varying the duration of the contextual patterns from 0 to 400 ms, (b) varying the duration of the target tones from 20 to 160 ms, and (c) varying the spectral range for the contextual tones from 1 to 2700 Hz. Individual differences in asymptotic detection thresholds, and in training times required to approach those thresholds, are unusually large in these tasks. However, the data are generally characterized by the following rules. Informational masking approaches asymptotic levels for context durations in excess of 160 ms. Little or no masking occurs for target tones longer than 60–80 ms. Similar average amounts of masking were observed for each of the spectral ranges of the context tones. [Work supported by NIH.]
A comparison of localization learning in a monaural aided condition in noise with trained and nontrained listeners
Authors: Bunce J. L. , Brey R. H. , Jones K. O.
Published: October 2005

A preview study was conducted to look at localization learning in monaural listeners. Eight subjects with hearing ability within normal limits were selected for the study. The subjects were asked to determine which speaker a signal was coming through with one aided and one plugged ear. The eight subjects were divided into two groups of four, an experimental and a control group. Each subject was tested in three 1 h sittings. Testing was accomplished in an anechoic chamber with eight speakers at 45° intervals. The signal was a narrow band noise, 2400–4800 Hz. Two signal-to-noise ratios were selected, −5 and −10. The noise was white noise. Subjects were allowed to move their heads 180°, 90° to either side. The experimental group received immediate feedback as to the actual speaker the signal was coming through and were allowed to take notes of any clues they could acquire. The control group received no feedback. The results indicated that learning takes place with and without training. However, those subjects who received training exhibited significantly better scores.
Effects of musical training on ear advantage for a dichotic rhythm task
Authors: Craig J. D.
Published: October 2005

Four right-handed musicians and six right-handed nonmusicians responded to four-beat dichotic rhythm patterns by using a same/different comparison method. The subjects were tested for laterality in response to the rhythm patterns at five frequencies: 400, 800, 1600, 3200, and 6400 Hz. The results indicated that there was a clear right-ear advantage in the response of nonmusicians to rhythms of 800, 1600, and 3200 Hz, and a slight left-ear advantage for 400- and 6400-Hz patterns. There was virtually no ear advantage in the response of musicians for rhythms of 400 through 3200 Hz, but a definite left-ear advantage was obtained for 6400-Hz patterns. The results support an hypothesis that musical training develops the rhythm areas in the right hemisphere which may be antithetical to the left hemispheric speech structures.
Effects of training and head movements on binaural and monaural localization
Authors: Gatehouse R. W. , Russell P. J.
Published: October 2005

In delineation of localization variables, research has focused primarily on single “main effects.” Therefore, the horizontal and vertical localizing accuracy and bias of 72 normally hearing subjects was investigated under monaural versus binaural, restricted versus nonrestricted head movement, and training with or without feedback listening conditions. A counterbalanced mixed factorial design allowed the parcelling out of the significant interactive effects in a multivariate study that more closely approximates everyday free field localization. The to-be-localized signal was a 2-s burst of pulsed WN (25 dB, SL) which could come from any of 12 azimuths (0, 30°, 60°,…, 330°) at any one of 3 elevations (0° ± 30°). Although some well-documented effects were confirmed, e.g., binaurals localize better in both planes; sources are shifted to unplugged ear side, the results demonstrate that no simple relationships exist between training and head movement conditions. For instance, feedback training benefits monaurals more than binaurals, while head fixation debilitates binaurals more as seen by larger errors and more back-front confusions. The results will be discussed in reference to the “variable weighting” approach of the Searle et al. model [J. Acoust. Soc. Am. 60, 1164–1175 (1976)] of localization.
Perceptual comparisons among a set of vowels similar to /æ/: Some differences between psychophysical distance and phonetic distance
Authors: Klatt Dennis H.
Published: October 2005

A set of 66 vowels acoustically similar to /æ/ were synthesized by adding together sinusoidal harmonics of the appropriate frequencies, amplitudes, and phases [Carlson, Granstrōm, and Klatt, J. Acoust. Soc. Am. Suppl. 1 65, S6 (1979)]. Subjects were asked to estimate either (1) the psychophysical distance, or (2) the phonetic distance between each stimulus and a reference vowel in a 300-trial randomized test. Stimulus manipulations included changes to formant frequencies, formant bandwidths, spectral tilt, phase relations among harmonies, vocal tract length, and filtering passband/stopband. Results indicate that when subjects are making phonetic comparisons among the stimuli, they pay far less attention to changes in phase, filtering passband, spectral tilt, and formant bandwidths than when making psychophysical judgements. An acoustically based distance metric consistent with the phonetic data is being sought. [Work supported by an NIH grant.]
Perception of anticipatory coarticulation
Authors: Martin James G.
Published: October 2005

Articulatory and acoustic studies of speech have shown that anticipatory coarticulation can reach across several segments in an utterance. However, the results of earlier perceptual studies suggest that perceptual effects are limited to adjacent segments only. In the present experiments, the stimuli (e.g., “I say tuzi”) were of the form “I say C V1 z V2” in which C was /p, t, or k/, V1 was (u, æ,/ and V2 was /i, a/ in all 12 combinations, spoken by ten speakers. Reaction time (RT) of practiced listeners was observed to the final vowel target (V2). Sentence pairs differing only in final target vowel were either (a) computer cross-spliced at /z/ onset or (b) left intact (as spoken). In general, RT was slower to crossed targets, suggesting misleading information prior to the cross. These interference effects were dependent on prior phonetic context and differed between and within speakers. Some of the perceptual results were correlated with results from acoustic analyses of the sentence waveforms. It appears that anticipatory coarticulation across several segments provides information which can be used in perception. [Work supported by NINCDS.]
Noise intensity cues of spoken fricatives
Authors: McCasland George P.
Published: October 2005

In spoken fricative-vowel syllables /fi, fa, fu, θi, θa, θu, si, sa, su, ∫i, ∫a, ∫u/, the fricative noise was replaced by segments of both /f/ and /θ/ sustained noise the intensity of which had been amplified to −6 dB relative to vowel level; 24 modified syllables in all. Siblilant /s/ percepts were heard in nearly 100% of the originally /s/ and /∫/ syllables and in the majority of the originally /f/ and /θ/ syllables; nonsibilant /f/and /θ/percepts in the remainder. It was previously shown (Harris, 1958) that when /f/ and /θ/ noise at the natural, low intensity level relative to the vowel replaced the fricative noise in originally /s/ and /∫/ syllables, /θ/ percepts resulted. In the present experiment, relatively high intensity /f/ and /θ/ noise served as a cue for /s/ percepts, typically overrode conflicting formant transition cues and might be considered strident in distinctive feature terminology. Noise spectrum is implicated only in the lack of sibilant /∫/ percepts. This investigation extends work previously reported by the author [J. Acoust. Soc. Am. Suppl. 1 63, S21(A) (1978) and 65, 578(A) (1979)].
Psychoacoustic parameters of the /r/-/l/ perceptual distinction
Authors: Syrdal-Lasky A. K.
Published: October 2005

The possibility that the psychoacoustic distinction between rising and steady-state F3 transitions may underlie the categorical perception of /r/ and /l/ was raised in a study of perception of the /ra/-/la/ continuum [Miyawaki, Strange, Verbrugge, Liberman, Jenkins, and Fujimura, Percept. Psychophys. 18, 331–340 (1975)], but later rejected because the perceptual distinction between /ri/ and /li/ was made between two stimuli with raising F3 transitions rather than between rising and steady-state F3 stimuli [McGovern and Strange, Percept. Psychophys. 21, 162–170 (1977)]. The possibility that the perceived distinction between rising and steady-state F3 occurred further from the physical steady-state value because of masking by the spectrally proximal F2 in /ri/-/li/ syllables was examined and confirmed using five synthetic stimulus conditions: /ri/-/li/ syllables identical to McGovern and Strange's, /ri/-/li/ syllables composed of F2 and F3 only, /ri/-/li/ syllables with F3 amplitude raised and F2 amplitude lowered, a /ri/-/li/ duplex condition, and isolated F3 stimuli. The perceptual distinction between /ri/ and /li/ was made closer to the physical distinction between rising and steady-state F3 as masking by F2 was reduced. [Work supported by NSF.]
Distinctive features of sibilants: A closer look
Authors: Catford J. C. , Krieg L. J.
Published: October 2005

Perkell, Boyce, and Stevens [Speech Communication Papers Presented at the 97th Meeting of the Acoustical Society of America, 109–113 (1979)] emphasized the quantal role of the sublingual cavity in differentiating the noise spectrum of the sibilants [s ∫] in English. Other languages, however, differentiate more than two primary articulatory postures for sibilants. For example, there are three in such languages as Polish, Marathi, and Basque. The greatest number of primary contrastive postures for sibilants appears to be four, as in three Northwest Caucasian languages (Adygbe, Ubykh, and Bzyb). Previously published radiographic tracings for these languages, together with our spectral analyses suggest the need for either a multivalued sublingual cavity feature (nil, small, medium, or large, together with associated frequency characteristics) or additional articulatory distinctions (such as alveolar versus postalveolar and apical versus laminal).
The contribution of synthetic low-frequency speech information to speechreaders
Authors: Ardell LeeAnn H. , Kuhl Patricia , Sparks David W.
Published: October 2005

The contribution of frequency and amplitude information carried in the fundamental frequency (f0) of speech to the speechreading performance of normal-hearing subjects was measured using a connected-discourse tracking procedure [C. L. DeFilippo and B. L. Scott, J. Acoust. Soc. Am. 63, 1186–1192 (1978)]. Tracking performance was measured under five receiving conditions: (1) speechreading alone, (2) speechreading in combination with lowpass-filtered (below 300 Hz) speech (LPF), (3) speechreading in combination with the f0 extracted from the speaker's voice and presented at a constant amplitude (FM alone). (4) speechreading in combination with a 225-Hz pure tone (the mean f0 for this speaker), amplitude-modulated by the intensity variations occurring in the lowpass-filtered version of the speech waveform (AM alone), and, (5) speechreading in combination with the extracted and amplitude-modulated f0 (AM + FM). Performance was highest for LPF and AM + FM and lowest for speechreading alone with AM alone and FM alone performance in between. The implications of these results for the development of auditory and tactile prostheses for the profoundly hearing impaired will be discussed. [Work supported by NIH.]