bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of spatial resolution and penetration depth using a waveguide in pulsed Doppler ultrasound systems for measurement of blood flow velocity
Authors: Finneran James J. , Hastings Mardi C.
Published: October 2005

Doppler ultrasound is a noninvasive method used to examine anatomy and various physiological functions. A limitation in its use to measure blood-flow velocity is the size and location of the volume within the blood vessel from which the signal is received. The volume is primarily a function of the size of the ultrasonic transducer and signal frequency. In this study, the feasibility of using a waveguide to mechanically adjust the natural focus of the acoustic field is considered. The adjustable focus allows control of spatial resolution and penetration depth of the ultrasonic signal. By controlling these parameters rather than totally relying on digital signal processing of received signals, the Doppler system may be used to examine blood vessels of variable size and shape. Measurements of beam profiles in a wave-guided system are compared with theoretical predictions. Preliminary design of a waveguide for a probe to measure the blood flow velocity at different points through the aorta is presented. [Work supported by NSF.]
Temporal resolution of frequency-modulated signals by hearing-impaired listeners
Authors: Madden John P. , Feth Lawrence L.
Published: October 2005

Hearing-impaired and normally hearing subjects were asked to discriminate between two sinusoidal signals. One signal, the glide, moved from its initial frequency over a linear path to its final frequency. The other, the step signal, was the same except that its trajectory followed a series of discrete steps in frequency. As the number of steps increased, the duration of the individual steps decreased, and the signal more closely resembled the glide. The center frequencies of the signals were 0.5, 1.0, 2.0, and 4.0 kHz. The signals were presented to the two groups at equal SLs and at equal SPLs. The impaired subjects exhibited significantly poorer discrimination than the normally hearing subjects, indicating a reduced ability to temporally resolve the step modulation. A frequency effect was evident in both groups, with much poorer resolution at 4.0 kHz. A level effect was noted in the normal subjects, who exhibited poorer resolution at higher SPLs. The results from the normally hearing subjects were very similar to temporal resolution values obtained in previous studies using amplitude-modulated (gapped) sinusoids. [Work supported by a grant from AFOSR.]
Inaudible stimulus may cause threshold shift
Authors: Young I. M. , Lowry L. D.
Published: October 2005

Interrupted pure-tone threshold measurements were made monaurally by Békésy audiometry with and without presentation of inaudible identical continuous stimulus and white noise on subjects with bilateral normal hearing and unilateral sensorineural hearing loss with and without abnormal auditory threshold adaptation. Thresholds were compared for interrupted stimulus only and both interrupted stimulus and inaudible stimulus presentation. Subjects with normal hearing and sensorineural hearing loss without abnormal adaptation showed no difference with and without presentation of the inaudible continuous stimulus. Subjects with sensorineural hearing loss demonstrating marked abnormal adaptation revealed observable threshold shift for the interrupted stimulus by adding inaudible stimulus. It is assumed that the inaudible stimulus affecting partially damaged nerve fibers produce widespread abnormal adaptation that the threshold for another signal is inaudible until an abnormally high intensity is reached. A stimulus incapable of evoking a response may cause adaptation in such fibers.
Monaural detection with a contralateral cue in normal-hearing and hearing-impaired listeners
Authors: Koehnke J. , Besing J.
Published: October 2005

Monaural detection with and without a contralateral cue (MDCC) in normal-hearing and hearing-impaired listeners is investigated. The signals and cues are 1/3-octave noise bands centered at 500 and 4000 Hz, and the masker is a 4500-Hz low-pass noise. The level of the masker is 77 dB SPL for the normal-hearing listeners and 25 dB SL for the hearing-impaired listeners; when present, the cue is at − 7 dB relative to the masker. Psychometric functions for three normal-hearing subjects and three subjects with moderate-to-severe, bilateral sensorineural hearing losses have been measured. The normal-hearing listeners show a 2–8 dB cued advantage at 503 Hz and a 1–11 dB cued disadvantage at 4000 Hz. Like the normal-hearing listeners, the hearing-impaired subjects have poorer performance at 4000 Hz when the cue is present. At 500 Hz, however, one of the hearing-impaired listeners shows a 5 dB cued advantage, comparable to normal, while the other hearing-impaired subjects have poorer detection when the cue is present. Results of these MDCC measurements will be compared with the performance of these hearing-impaired listeners on other tests of binaural detection and discrimination. [Work supported by DRF.]
Some lexical effects in a generalized phoneme monitoring task
Authors: Lively Scott E. , Pisoni David B.
Published: October 2005

A long-standing concern in the spoken word recognition literature has been whether use of the lexicon is necessary to complete a phoneme monitoring task. Eimas et al. [J. Mem. Lang. 29(2), 160–180 (1990)], for example, found no lexical effects in a phoneme monitoring task until monitoring responses were accompanied by lexical decisions or noun-verb categorizations. Frauenfelder and Segui [Mem. Cog. 17(2), 134–140 (1989)], in contrast, found facilatory priming effects in a monitoring task when the position of the target phoneme varied randomly from trial to trial. The current study adopts Frauenfelder and Segui's generalized phoneme monitoring paradigm in a speeded phoneme classification task. Subjects participating in a blocked condition demonstrated word frequency and density effects only for blocks of trials in which targets occurred word finally. No lexical effects were observed for responses to word initial targets. Subjects in a mixed condition showed frequency and density effects for word final targets and frequency effects for word initial targets. In terms of Cutler's race model, the data indicate that subjects adopt a postlexical response strategy when targets occur late in the stimulus word or when attention cannot be consistently focused on a particular target position. [Work supported by PHS RO1 DC011-15.]
Listening to the sound of sentences
Authors: Nusbaum Howard C. , Broihier Kevin J. , Goodman Judith C.
Published: October 2005

Although intonation conveys a great deal of information relevant to understanding sentences, it is unknown how listeners actually use this information. How do listeners integrate information in the intonation of a sentence with information derived from a linguistic analysis of the words in the sentence? Syntactic information from the order of words in a sentence may be processed independently from syntactic information perceived from intonation. On the other hand, different sources of syntactic information may be treated as equivalent and integral. Subjects were instructed to judge whether the intonation of a sentence was declarative or interrogative. Statements and questions were produced in two forms; with a declarative intonation and with an interrogative intonation. In one condition, syntactic structure was constant for all trials and intonation varied. In a second condition, syntactic structure varied across trials, as did intonation. The results indicate that listeners are unable to ignore the syntactic structure of a sentence in judging the intonation of the sentence. Listeners treat different types of syntactic information as integral. These results suggest that perception of intonation is a direct and integral part of sentence understanding. [Research supported by NIDCD.]
Some effects of text coherence on the comprehension of natural and synthetic speech
Authors: Ralston James V. , Lively Scott E. , Pisoni David B.
Published: October 2005

Subjects listened to naturally and synthetically produced (Votrax Type-n-Talk) passages of varying levels of difficulty in a sentence-by-sentence listening time task. Listeners controlled the intersentence interval while listening to passages presented in their normal sentence order or in a random sentence order. Subjects listening to Votrax speech had significantly longer intersentence response times in both the normally ordered and the randomly ordered sentence conditions. Furthermore, in a recognition test given after each passage, subjects' performance varied as a function of speech type, passage difficulty, and recognition question type. Subjects listening to synthetic speech responded more accurately to word recognition questions than to proposition recognition questions. Listeners who heard natural speech, in contrast, demonstrated better proposition recognition performance. The results indicate that listeners who heard synthetic speech attended more closely to the acoustic-phonetic input than to the propositions of the passages. The results are discussed in terms of a limited capacity attentional mechanism. [Work supported by NSF IRI 86-17847.]
On the perceptual differentiation of spontaneous and prepared speech
Authors: Remez Robert E. , Berus Stefanie M. , Nutter Jennifer S. , Dang Jessica M. , Davachi Lila , Rubin Philip E.
Published: October 2005

Naive listeners arc readily able to differentiate spontaneously produced speech from speech produced from text. The prior studies have employed lexically, syntactically, and thematically identical pairs of natural sentences extracted from brief fluent monologs (< 40 s in duration), finding relatively high levels of performance in tests of perceptual differentiation. To determine which attributes of the speech signal contribute to the perceptual differentiation of spontaneous and prepared speech, the present study manipulated several likely acoustic parameters employing techniques of speech synthesis. One condition reduced the frequency variation of the synthetic copies of the utterances to a monotone. A second condition removed the segmental attributes (consonants and vowels) from the sentence pairs by low-pass filtering of the synthetic signals, leaving metrical and fundamental frequency variation intact. The final condition neutralized both the segmental and phonatory attributes, leaving only metrical properties available to perceivers by which to differentiate the sentence pairs. Although systematic perceptual effects were anticipated, in fact these acoustic conditions modulated the differentiability of individual sentence pairs in different ways. Evidence of this kind indicates that perceptual analysis of spontaneity takes place at the level of the sentence, and comparisons across the set of conditions prove that no single acoustic emblem of the speech signal conveys spontaneity to the listener.
Further investigation of the semantic and pragmatic effects on speech production
Authors: Charles-Luce Jan , Papadimitriou Basiliki
Published: October 2005

Previous studies have shown that preceding semantic information affects the production of target words, for example blocking phonological rules or modifying duration. In addition, there is evidence that speakers modify their production of words during the speaker/listener exchange, for example in formal versus informal speaking situations. In the present study, two experimental environments were established to address the effects of semantic versus pragmatic contexts directly. In both environments, a subject was visually presented with a prime and then a target. The prime was either semantically related or unrelated to the target. The subject said the prime and target words aloud. In one experimental environment, a second person was present in the room to which the subject was to communicate. In the other environment, a subject performed the task alone. Dependent variables were duration of, fundamental frequency of, and reaction time to onset of pronunciation of the target word. The results will be discussed in the frameworks of interactive activation and pragmatic compensation.
Sound radiation from large raindrops: Dependence on salinity and temperature
Authors: Jacobus Peter W. , Medwin Herman , Nystuen Jeffrey A.
Published: October 2005

Raindrops are known to produce bubbles by at least two different mechanisms: type I, the pinch-off of the bottom of the crater, and type II, air entrainment from a turbulent water jet formed as a part of the drop splash. Bubble energy is shown to dominate impact energy for the useful range of type II drops. Previous work [Snyder et al., J. Acoust. Soc. Am. Suppl. 1 88, S2 (1990)] has shown a relationship between drop size and bubble frequency of the type II mechanism. The onset of this mechanism is related to the drop kinetic energy at impact, rather than to velocity. As the drop kinetic energy increases above a threshold of 2 × 10−4 J, the likelihood of bubble entrainment increases to approximately 65%. Further work reveals the effects of temperature, salinity, and surface tension on the sound radiated from large raindrops. The relation between the drop diameter and the spectrum of the underwater acoustic energy is examined for terminal velocity drops. This relation makes possible the remote measurement of both drop size distribution and rainfall rate. [Work supported by ONR.]
Bubble production by capillary waves
Authors: Kolaini Ali , Roy Ronald A. , Crum Lawrence A.
Published: October 2005

Bubble-producing capillary waves can be easily generated in a laboratory tank (8 cm × 22 cm × 150 cm) by blowing air over the water. The lowest wind speed required for the occurrence of this process is measured. The generation of the capillary waves depends solely on the surface tension, which can be changed by adding surfactants and other chemicals to the tank water. The effect of surface tension on the windspeed threshold for bubble production is discussed. Using a coincidence detector, the bubble production rates per unit area can be measured. Lowering the surface tension, surprisingly, increases the rate of bubble production. The dependence of the bubble production rate on wind speed and wind fetch is also discussed. The underwater acoustic emissions from these bubbles are measured. Average power spectrum for several wind speeds are obtained that exhibit a broad range of radiated frequencies (i.e., bubble sizes) and a weak dependence on the wind speed. [Work supported by ONR, ONT, and AEAS.]
The underwater sound produced by the impact of solid objects
Authors: Nicholas Michael , Roy Ronald A. , Crum Lawrence A.
Published: October 2005

There have been many studies that indicate that there is significant underwater sound produced by precipitation [e.g., J. A. Scrimger, Nature 318, 647 (1985)]. It has also been demonstrated that the major contribution to the underwater sound of rainfall is that due to the entrainment of gas bubbles by the impacting drop [Pumphrey et al., J. Acoust. Soc. Am. 31, 1080 (1989)]. In an attempt to understand the underwater sound produced by hail, the impact of solid objects with a plane water surface have been examined. With the aid of a high-speed movie camera and underwater transducers, it has been determined that the air entrained by the impacting object plays a major role in the sound production. The details of this process as well as the implications concerning the underwater sound produced by hail will be presented. [Work supported by ONR.]
Pulse length effects on the transmissivity of bubbly water
Authors: Suiter H. R.
Published: October 2005

The passage of sound through bubbly water is strongly attenuated by scattering and absorption. Such attenuation is most severe around the frequency of resonance of individual bubbles. A bubble takes a finite time to ring up to steady-state conditions and continues to oscillate for a finite time after the driving pressure erases. Low backscatter for short pulse lengths has been observed in near-surface seawater [Akulichev et al., Soc. Phys. Acoust. 32, no. 3]. An experiment is described that looked for a corresponding enhancement in transmission. Comparisons were made between the attenuations of brief waveform bursts and longer bursts. The frequency range of this experiment was 50–200 kHz. The bubbles were made by the electrolysis of fresh water in a small laboratory tank. For bursts of 6–20 wavelengths in duration, no difference in the attenuations was discerned in comparison with a 2.7 wavelength duration burst. [Work supported by ONR.]
Finite element solution to the parabolic wave equation
Authors: Huang Dehua
Published: October 2005

In seeking more ways to predict underwater sound fields, the underwater acoustical parabolic wave equation is solved using the finite element (FE) method. The mathematical theory for the finite element method in an N-medium case is discussed, when the conditions of continuity of pressure and continuity of the normal component of particle velocity are perfectly satisfied at each interface. Several propagation examples for horizontal and irregular interfaces are presented to demonstrate the capability of this effective FE method.
Predictions of internal-wave effects on ocean acoustic coherence, travel-time variance, and intensity moments for very long-range propagation
Authors: Flatté Stanley M. , Stoughton Roland B.
Published: October 2005

Observations of acoustic fluctuation parameters such as phase variance, coherence times, rms wave front tilts, and intensity moments provide measures of the ocean internal-wave spectrum weighted by different combinations of vertical and horizontal wavenumber and frequency. Detailed predictions of the primary acoustic fluctuation quantities for realistic sound-speed profiles over megameter ranges are provided. Improved algorithms for theoretical evaluation of pulse spreading, intensity decorrelation, and scintillation in range-independent environments are also presented.
The Biot–Stoll sediment model: An experimental assessment
Authors: Holland Charles W. , Brunson Burlie A.
Published: October 2005

A promising approach in the prediction of acoustic wave speeds and attenuations in marine sediments is the use of the Biot theory as implemented by Stoll. The Biot–Stoll physical sediment model is examined here in a field application. Both the geophysical inputs and the geoacoustic outputs were measured at three shallow-water sites in the Mediterranean Sea. This permitted the investigation of the accuracy of the model for a variety of natural marine sediments including silty clay, sand, and gravel. A difficulty in the use of the Biot–Stoll model is the problem of accurately determining the 13 geophysical inputs since many of the inputs cannot be directly measured. Ten of the input properties are derived by empirical means and the other three properties are determined by measurement. Comparisons are made between the Biot–Stoll model predictions of compressional velocity, compressional attenuation, and shear velocity with in situ and laboratory measurements. The model predictions, on the whole, show excellent agreement with the measured data.
Decomposing one-dimensional acoustic pressure response into propagating and standing waves
Authors: Spiekermann Charles E. , Radcliffe Clark J.
Published: October 2005

Few actual sound fields are representative of ideal acoustic pressure responses and ideal boundary conditions, such as those nearly found in anechoic or reverberant rooms. Normally encountered enclosures have complicated responses that are difficult to relate to a boundary condition that is inbetween these two ideal extremes. Yet, the propagating- and standing-wave responses associated with absorptive and reflective boundary conditions seen in the ideal cases are fundamental bases to understand these more complicated problems. An analytical method is developed to decompose a one-dimensional acoustic pressure response associated with a specified partially absorptive boundary condition into an equivalent summation of propagating and standing waves usually associated with absorptive and reflective boundary conditions, respectively. The propagating- and standing-wave responses are scaled and shifted in phase by factors that are dependent on the boundary absorptivity and frequency, but are independent of the spatial location. The complicated mixed response is decomposed into varying amounts of the ideal responses, which can be helpful during a design analysis.
Linear transverse vibration of an axially moving string–particle system
Authors: Wickert J. A. , Mote C. D.
Published: October 2005

A monocable ropeway system is modeled as an axially moving string that transports an attached mass particle. The linear transverse equation of motion is derived, and the response of the string–particle system is represented as d’Alembert waves that are scattered by the point mass. Three solutions of an approximate eigenvalue problem that is valid for small transport speed and particle mass are presented: a closed-form asymptotic solution for vanishing particle mass, roots of a characteristic equation, and solutions obtained from a Galerkin discretization. In general, the spectrum is complex and depends on the axial position of the particle. The discretized equations of motion are numerically integrated, and the free response of the discrete model is compared to that predicted by the approximate eigensolutions.
Analysis of shear horizontal surface waves at the boundary between a piezoelectric crystal and a viscous fluid medium
Authors: Josse Fabien , Shana Zack
Published: October 2005

Surface shear horizontal wave propagation at the boundary of a piezoelectric substrate with a viscous fluid is theoretically analyzed. The analytical solution clearly shows the dependence of the velocity change, the wave propagation loss, and the wave amplitude profile (thus the energy confinement near the surface), in terms of the liquid viscosity and density, the layer thickness, and the wave frequency. It is shown that the viscous fluid loading produces some guidance near the surface but also some damping of the wave. The propagation loss is due only to viscous coupling and not to a mode conversion and viscous coupling as is the case with Rayleigh surface acoustic waves (SAWs). Closed-form expressions are derived for the attenuation coefficient and the fractional velocity change (thus the frequency change) in terms of the piezoelectric crystal and viscous liquid parameters. The theory, applicable to both a Bleustein–Gulyaev (BG) wave and a surface skimming bulk wave (SSBW), indicates that surface shear waves could be used in the implementation of sensitive acoustic wave liquid-phase-based detectors, viscosity sensors, and/or biosensors. These sensors will not experience the high propagation loss associated with Rayleigh SAWs.
Transient pulsations of small gas bubbles in water
Authors: Flynn H. G. , Church Charles C.
Published: October 2005

Transient behavior of small gas bubbles in a liquid set into violent motion by ultrasonic pressure waves is of interest because of widespread use of microsecond pulses in diagnostic ultrasound. Such pulses contain only a few pressure cycles and the transient pulsations of bubbles set in motion by such pulses would determine the bubble–ultrasound interaction. A computer study has been made to obtain a global representation of the pulsation amplitudes R(t) of small gas bubbles (nuclei) in water during the first few cycles of a cw ultrasonic pressure. One objective was to obtain a better understanding of cavitation phenomena where many nuclei with initial radii Rn from 0.1–20 μm are set in motion at pressures ranging from 0.5–5 bars and at frequencies from 0.1–10 MHz. Results allowed construction of surfaces showing the relative bubble amplitude R/Rn as a function of Rn and of the time t/TA, where TA is the acoustic period. One finding is that, in the range of peak pressures found in diagnostic pulses, transient cavities would be generated during the first pressure cycle from nuclei with initial radii as small as a few microns (μm). Nuclei that grow into transient cavities in the first pressure cycle are here called ‘‘prompt’’ nuclei. At a specified pressure, the size range of radii Rn in which they occur decreases with increasing frequency. At 5 bars, the range of Rn for prompt nuclei is 0.166–11.35 μm at 0.5 MHz and vanishes at 10 MHz.
Nonreciprocity of simulated long-range acoustic transmissions
Authors: Mercer J. A.
Published: October 2005

A three-dimensional ray-tracing code is used to simulate a reciprocal tomography experiment over 2000-km paths. The modeled enviroment includes relatively large sound-speed and current perturbations due to four mesoscale eddies and a western boundary jet. Errors in the estimates of ray-averaged currents, owing to nonreciprocity of forward and reverse eigenrays, are found to be approximately 30%–40%. The error is proportional to the number of eddy perturbations and decreases linearly with decreasing current magnitude. The displacements between forward and reverse eigenrays are relatively small, especially in depth, but the accumulated effect of passing through different sound-speed and current-velocity fields results in significant nonreciprocal travel-time differences. Restricting the propagation to the range-depth plane, i.e., only two dimensions, gave basically the same results as the full three-dimensional solution.
Vibrating circular plates with stepped thickness over a concentric circular region: A general, approximate solution
Authors: Avalos D. , Laura Patricio A. A. , Larrondo Hilda A.
Published: October 2005

Natural frequencies corresponding to axi- and antisymmetric modes of vibration of the structural elements described in the title are studied using the optimized Rayleigh–Ritz approach. It is assumed that the plates are elastically restrained against translation and rotation. The plate amplitude is approximated in terms of polynomial coordinate functions that satisfy the boundary conditions, each one containing an undetermined exponential parameter that allows for the minimization of the eigenvalues under investigation.
Ultrasonic microprobe hydrophones
Authors: Moffett Mark B. , Powers James M. , Clay William L.
Published: October 2005

Ultrasonic microprobe hydrophones, with element dimensions less than 1 mm, have been constructed in several volume-expander configurations using various piezoelectric materials. The best type, consisting of a single 30×30×15-mil (0.8×0.8×0.4-mm) slab of lead titanate supported by 3-mil (0.08-mm) wires and potted in a ρc polyurethane, was omnidirectional (±1 dB) to 500 kHz and had a sensitivity of −234 dB∥1 V/μPa (±1.5 dB) at the output of a 19.5-dB preamplifier located approximately 1 m from the microprobe. The noise equivalent pressure was approximately 89 dB//1μPa2/Hz at 100 kHz.
Resolution for speech sounds: Basic sensitivity and context memory on vowel and consonant continua
Authors: Macmillan Neil A. , Goldberg Rina F. , Braida Louis D.
Published: October 2005

Discrimination and identification experiments were performed for a vowel continuum (/i/– /i/–/q/) and two consonant continua (/ba/–/pa/ and /ba/–/da/–/ga/). The results were interpreted in terms of a generalization of a theory of intensity resolution [N. I. Durlach and L. D. Braida, J. Acoust. Soc. Am. 46, 372–383 (1969)] that makes precise the distinction between basic sensitivity (sensory-based resolution) and context coding (labeling processes). On the vowel continuum, basic sensitivity increased gradually across the range, whereas, for both consonant continua, sensitivity peaked between phonetic categories. All speech continua were found to have small ranges (measured in jnd’s); context memory was good, and better for consonants than for vowels. The stimuli that could be labeled most reliably were near the category boundaries on the vowel continuum, but near good phonetic exemplars for consonants. Introduction of a standard in identification primarily altered response bias, not sensitivity.
Spectro-temporal analysis in normal-hearing and cochlear-impaired listeners
Authors: Hall Joseph W. , Davis Adrian C. , Haggard Mark P. , Pillsbury Harold C.
Published: October 2005

Detection thresholds for a 1.0-kHz pure tone were determined in unmodulated noise and in noise modulated by a 15-Hz square wave. Comodulation masking release (CMR) was calculated as the difference in threshold between the modulated and unmodulated conditions. The noise bandwidth varied between 100 and 1000 Hz. Frequency selectivity was also examined using an abbreviated notched-noise masking method. The subjects in the main experiment consisted of 12 normal-hearing and 12 hearing-impaired subjects with hearing loss of cochlear origin. The most discriminating conditions were repeated on 16 additional hearing-impaired subjects. The CMR of the hearing-impaired group was reduced for the 1000-Hz noise bandwidth. The reduced CMR at this bandwidth correlated significantly with reduced frequency selectivity, consistent with the hypothesis that the across-frequency difference cue used in CMR is diminished by poor frequency selectivity. The results indicated that good frequency selectivity is a prerequisite, but not a guarantee, of large CMR.
Remarks on Riemann’s method of characteristics
Authors: Paynter Henry M. , Busch-Vishniac Ilene J.
Published: October 2005

The method of Riemann characteristics has been used for more than a century to describe linear and nonlinear waves propagating in a medium. In this paper, the history of the method of characteristics is reviewed and examples of its use are provided. The useful properties of the method of characteristics are discussed, namely: that it may be applied to both linear and nonlinear systems; that it may be applied equally well to solids, liquids, and gases; and that it provides a clear picture of the causal relations governing system behavior. One-dimensional wave propagation in uniform and nonuniform ducts and pipes is discussed in terms of the characteristics, and the importance of impedance scaling is shown. The use of characteristics when there is heat transfer is also discussed for a uniform duct.
The timbre of sung vowels
Authors: Bloothooft Gerrit , Plomp Reinier
Published: October 2005

The perception of timbre differences in a vowel sung by eight male and seven female singers has been investigated by means of two types of listening experiments: (1) using the paradigm of the comparison of similarity, and (2) using judgments on 21 semantic bipolar scales. Using INDSCAL analysis for the similarity-comparison data and MDPREF analysis for the semantic-scale judgments, vowel configurations in a multidimensional perceptual space were derived, as well as a space that showed the weighting of perceptual dimensions by individual listeners (INDSCAL). The interpretation of semantic scales was represented by directions in the perceptual space (MDPREF). The perceptual vowel configurations, either based on timbre similarities or semantic scales judgments, were comparable. Broadly, semantic scales clustered into the categories vocal technique, general evaluation, vibrato, clarity, and sharpness. These five clusters were not independent and could be described in two dimensions. Timbre differences could be predicted on the basis of differences in (1)/(3) -oct spectra of the vowels. It showed up that only sharpness had a constant interpretation for the various stimulus sets and was roughly related to the slope of the spectrum. One experiment, using a song phrase, extended the results to a more general domain.
On the measurement of glottal flow
Authors: Cranen Bert , Boves Louis
Published: October 2005

For developing a comprehensive description of voiced speech sounds in terms of a phonation and an articulation component, it is necessary to know to what extent the volume flow modulations at the entrance of the vocal tract are due to vocal fold motions and to what extent they are due to variations in the transglottal pressure. In order to be able to study this problem, it is important that the flow at the glottis can be measured during normal speech production in a reliable fashion. In this article, a flow measurement technique is described that differs from the more usual inverse filtering approach to the extent that the flow is not measured at the mouth, but much closer to the glottis. The technique is based on the measurement of pressure gradient. It is shown that the proposed method also leads to an inverse filtering problem, but that, since this problem is much simpler, the gradient method yields more reliable estimates of the shape of the glottal flow waveform, though without the zero flow level (dc component) and without a magnitude scale. By means of theoretical considerations about velocity profiles in pulsatile flow in cylindrical tubes, it is shown that the method for measuring flow during phonation proposed in this article may be expected to yield reasonable flow waveform estimates in a frequency region from any normal fundamental frequency to an upper frequency determined by the transducer sensitivity and separation and vocal tract geometry. In this case, the frequency limitation was estimated to be 1000 Hz. The merits of the newly developed method are evaluated by means of a modeling study and by carrying out some cross-checks on real measurement data.
Estimation of scatterer concentration from randomly scattered signals
Authors: Yu Guo Yao , Newhouse V. L. , Satrapa J.
Published: October 2005

An experiment has been carefully designed and performed to test the method suggested by Newhouse and Amir [V. L. Newhouse and I. Amir, Ultrason. Imag. 7, 161 (1985)] for estimating the volume concentration of scatterers that are too small and close together to be resolved near a surface. The experimental result has confirmed that the method is valid under conditions where the Born approximation holds. The method uses the fact that, when a scatterer containing the object is illuminated with an acoustic wave, the ratio of the coherent to incoherent reflected power depends on the concentration of the scatterers, multiplied by a known function of the transmitted signal and of the transducer and device geometry. Furthermore, based on this method, a theoretical quantitative analysis is presented for estimating the scatterer concentrations and concentration gradient near a surface which separates two regions with a sharp scatterer density gradient.
Using an equivalence of response for the mechanical oscillator to estimate damping
Authors: O’Hara George J. , Cunniff Patrick F.
Published: October 2005

This letter examines the behavior characteristics of the mechanical oscillator composed of a mass, spring, and dashpot. An equivalence of response is observed between an undamped oscillator subjected to a decaying sinusoidal forcing function and a damped oscillator subjected to a sinusoidal forcing function. This equivalency of response has potential use for estimating the presence of modal damping in shock excited structural systems as demonstrated by means of an example problem.
Duration discrimination of speech and tonal complex stimuli by normally hearing and hearing-impaired listeners
Authors: Bochner Joseph H. , Snell Karen B. , MacKenzie Douglas J.
Published: October 2005

The ability to discriminate changes in the length of vowels and tonal complexes (filled intervals) and in the duration of closure in stop consonants and gaps in tonal complexes (unfilled intervals) was studied in three normally hearing and seven severely hearing-impaired listeners. The speech stimuli consisted of the vowels /i, I, u, u, a, v/ and the consonants /p, t, k/, and the tonal complexes consisted of digitally generated sinusoids at 0.5, 1, and 2 kHz. The signals were presented at conversational levels for each listener group, and a 3IFC adaptive procedure was used to estimate difference limens (DLs). The DLs for speech were similar to those for tonal complex stimuli in both the filled and unfilled conditions. Both normally and impaired-hearing listeners demonstrated greater acuity for changes in the duration of filled than unfilled intervals. Mean thresholds for filled intervals obtained from normally hearing listeners were smaller than those obtained from hearing-impaired listeners. For unfilled intervals, however, the difference between listener groups was not significant. A few hearing-impaired listeners demonstrated temporal acuity comparable to that of normally hearing listeners for several listening conditions. Implications of these results are discussed with regard to speech perception in normally and impaired-hearing individuals.
Auditory/phonetic categorization with the Symbion multichannel cochlear implant
Authors: Dorman Michael F. , Hannley Maureen T. , McCandless Geary A. , Smith Luke M.
Published: October 2005

The phonetic identification ability of an individual (SS) who exhibits the best, or equal to the best, speech understanding of patients using the Symbion four-channel cochlear implant is described. It has been found that SS: (1) can use aspects of signal duration to form categories that are isomorphic with the phonetic categories established by listeners with normal auditory function; (2) can combine temporal and spectral cues in a normal fashion to form categories; (3) can use aspects of fricative noises to form categories that correspond to normal phonetic categories; (4) uses information from both F1 and higher formants in vowel identification; and (5) appears to identify stop consonant place of articulation on the basis of information provided by the center frequency of the burst and by the abruptness of frequency change following signal onset. SS has difficulty identifying stop consonants from the information provided by formant transitions and cannot differentially identify signals that have identical F1’s and relatively low-frequency F2’s. SS’s performance suggests that simple speech processing strategies (filtering of the signal into four bands) and monopolar electrode design are viable options in the design of cochlear prostheses.
Clutter interference along the target range axis in the echolocating bat, E
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Authors: Simmons James A. , Kick Shelley A. , Moffat Anne J. M. , Masters W. Mitch , Kon David
Published: October 2005

The sensitivity of the echolocating bat, Eptesicus fuscus, for detection of a sonar target is impaired by the presence of additional targets located at similar distances. At a range of 54 cm, sensitivity to one target declines if the range separation to other targets is smaller than 8–9 cm. This loss of sensitivity is an example of clutter interference along the range axis, created by simultaneous masking of one set of echoes by another. Echoes that fall within an experimentally defined critical range band may sum together to contribute collectively to detection in that band. Echoes falling into separate bands may be detected independently. Acoustic glints within a band appear to be grouped together to be perceived as a single range-extended target of complex structure. Range bands may thus define what a ‘‘target’’ is by specifying within-target and between-target differences in range. The width of critical range bands appears to depend upon target range, with wider bands at greater ranges.
Perception of the missing fundamental in nonhuman primates
Authors: Tomlinson R. W. Ward , Schwarz Dietrich W. F.
Published: October 2005

In preparation for neurophysiological experiments aimed at mechanisms of pitch perception, four rhesus monkeys were trained to press a button when the fundamental frequencies (missing or present) of two complex tones in a tone pair matched. Both tones were based on a five-component harmonic series. Zero to three of the lowest components could be missing in the first tone, while the second (comparison) tone contained all five harmonics. The range of fundamentals tested varied from 200 to 600 Hz. Three monkeys learned to match tones missing their fundamentals to comparison harmonic complexes with the same pitch, whereas the fourth monkey required the physical presence of the fundamental. Consideration of several cues available to the monkeys suggests that the animals could perceive the missing fundamental.
Passive synthetic arrays
Authors: Autrey Samuel W.
Published: October 2005

This article develops the concept of the passive synthetic array, including its design and implementation, its response to signal and noise, and its overall performance. The only case considered is the ideal case of a constant velocity receiver, a constant bearing narrow-band source, stationary signal and noise statistics, and single-path propagation in the plane of the source and receiving synthetic array. It is shown that, in this ideal case, the passive synthetic array is identical to the narrow-band spectrum analyzer in both implementation and performance, with the total gain determined to a close approximation by the bandwidth of the signal. Considering the processor to be a synthetic array beamformer, however, yields additional information about a detected narrow-band source because the bearing of the source can be determined if a course or speed change is made by the sensor.
Fundamental limitation of resolution enhancement by wave-field extrapolation
Authors: Lee Hua , Sullivan Douglas P.
Published: October 2005

Discrete bandlimited wave-field extrapolation is a resolution enhancement technique equivalent to extending the aperture by analytic continuation of the wave field. This converts the knowledge of the frequency passband of the wave field and the measurement constraints into the form of aperture expansion. This article describes the formulation and structure of the extrapolation algorithm in terms of orthogonal decomposition and recombination. It is also pointed out that the resolution enhancement by wave-field extrapolation is, in general, signal dependent, and the enhancement capability is governed by the effective subspace associated with the singular-value distribution.
Energy relations in concert auditoriums. I
Authors: Barron M. , Lee L-J.
Published: October 2005

Extensive objective acoustic measurements have been made in 15 unoccupied concert halls and two multipurpose halls used for music in Britain. Only monophonic objective measures at midfrequencies are considered here, in particular, the early decay time, the early-to-late sound index, and the total sound level. The measured results have been compared with traditional predicted values. The widest divergence was found in the observation that the total reflected sound level decreases with increasing distance from the source. A revised theory of sound decay in concert spaces is proposed. This assumes that the total sound is composed of a direct sound component and a linearly decaying reflected component which starts when the direct sound arrives. On average, the measured results are found to be well described by the revised theory. However, certain divergences from average behavior are found; these have been associated with various design characteristics such as the diffusivity of the ceiling, wide fan shapes in plan and absorbent in the stage area. The results help place in context the significance of reverberation time and hall size for concert auditoriums.
Random vibration of laminated plates modeled within a high-order shear deformation theory
Authors: Cederbaum Gabriel , Librescu Liviu , Elishakoff Isaac
Published: October 2005

This article deals with the dynamic response of simply supported, symmetric cross-ply laminates to stationary random load. The theory of laminated plates used here takes into account transverse shear flexibility, transverse normal stress, and rotary inertia effects for orthotropic and transversely isotropic laminates. Two cases of random pressure fields are considered in this analysis. In the first case, the random pressure field is modeled as a point load, random in time, with constant spectral density (ideal white noise), while in the second case, it is modeled as a turbulent boundary layer pressure fluctuation. The analysis presented herein, as well as the obtained response characteristics expressed in terms of mean squares, may be useful in the reliability computation of composite structures subjected to random pressure fields.
Source level estimation of a monopole source at rest in the presence of multipath
Authors: Chotiros N. P.
Published: October 2005

The problem of estimating the source level of a broadband cw monopole source in coastal waters using a vertical array of hydrophones was investigated. The statistics of the sound field in a particular coastal region were modeled. The medium was idealized as a wedge-shaped volume bounded by a pressure release surface and a lossy inclined plane. The transfer function between source and receiver positions was treated as a random process. The signals from the hydrophone array were processed to give an estimate of the source level of the sound source. The efficiencies of a number of estimators were analyzed including beamforming, focusing, and linear and log power averaging. The bias and standard deviation of each estimator were measured as a function of the number of elements in the array. A numerical model implemented on a computer and a sea test provided the data samples on which the statistics were based.
Intonation precision of choir singers
Authors: Ternström Sten , Sundberg Johan
Published: October 2005

Results from two experimental investigations on the acoustics of choirs are reported. The first concerns sound-pressure levels (SPL) inside choirs, and the balance of loudness between a singer’s own voice and the ‘‘reference’’ sound from the rest of the choir. Long-term SPL averages during rehearsals typically gave 80–100 dB, with little variation between choirs or with position in the choir. The fundamental frequency precision of choir singers was found to deteriorate abruptly when the reference was too loud. The influence of room acoustics and of the spacing between singers is discussed. The second investigation concerns the effect of spectral variations in the reference sound. Experiments were made primarily with individual singers under laboratory conditions. Changes in vowel quality, and absence/presence of certain partials and of vibrato, were all found to affect somewhat the degree of fundamental frequency agreement between singers. Standard deviation in fundamental frequency between section colleagues in live rehearsal was found to be between 0.10 and 0.15 semitones, or 0.6% and 0.9%. Reference vowels with common partials reinforced by formants were found to increase fundamental frequency precision.
Trading relations in the perception of /r/–/l/ by Japanese learners of English
Authors: Underbakke Melva , Polka Linda , Gottfried Terry L. , Strange Winifred
Published: October 2005

The role of language-specific factors in phonetically based trading relations was examined by assessing the ability of 20 native Japanese speakers to identify and discriminate stimuli of two synthetic /r/–/l/ series that varied temporal and spectral parameters independently. Results of forced-choice identification and oddity discrimination tasks showed that the nine Japanese subjects who were able to identify /r/ and /l/ reliably demonstrated a trading relation similar to that of Americans. Discrimination results reflected the perceptual equivalence of temporal and spectral parameters. Discrimination by the 11 Japanese subjects who were unable to identify the /r/–/l/ series differed significantly from the skilled Japanese subjects and native English speakers. However, their performance could not be predicted on the basis of acoustic dissimilarity alone. These results provide evidence that the trading relation between temporal and spectral cues for the /r/–/l/ contrast is not solely attributable to general auditory or language-universal phonetic processing constraints, but rather is also a function of phonemic processes that can be modified in the course of learning a second language.