bluuebunny/crossref_metadata_2025 huggingface dataset:
Prototype and feasibility study of a PVDF infant health monitor
Authors: Higgins Joe , Everbach E. Carr
Published: October 2005

Piezoelectric polymer sheets, placed on the floor of a crib, can produce an output voltage that provides information about the heart and breathing rates of an infant in the crib. Such a device could be useful in detecting Sudden Infant Death Syndrome or other infant health problems. A prototype device has been developed with conditioning and detection electronics to isolate the contributions of each signal, and a feasibility study was developed to indicate whether such a device could be made cheaply and reliably enough to be commercially available to a wide population of consumers.
Sound level measurements in background noise
Authors: Staiano Michael A.
Published: October 2005

In many sound measurement situations, a need arises to determine the magnitude of a specific sound source while persistent—although fluctuating—background sound exists due to other sound sources. Usually the specific source can be turned off but no control of the background noise is possible. As a result, measurements can be obtained of the “total” (consisting of the source and background together) and of the background alone. Although “survey methods” for the determination of sound power levels permit background noise “at least 3 dB below the A-weighted sound pressure level with the source operating,” even this requirement may be too stringent for some situations where estimates of band sound levels are required. Mathematically a correction can be derived in any situation where a measurable difference exists between the as-measured total (that is, the source + background) and the background noise levels. Where the difference between the total and the background noise is small, the accuracy is poor. However, if a confidence interval (i.e., a range in which the correct result is likely to occur) can be defined, the estimated result may be of use. This paper explores a scheme for estimating and reporting source sound levels measured in the presence of background noise.
Constrained total least-squares-based extraction of acoustic scattering resonances of elastic targets
Authors: Abatzoglou Theagenis J. , Hackman Roger H.
Published: October 2005

The analysis of the resonance response of elastic targets to an insonifying beam has been a central theme in acoustic scattering investigations in recent years. The motivation for this work is that the resonance structure of such targets is directly related to both the geometry and material properties of the target and this has a bearing on target classification. The development of robust techniques to estimate the resonance frequencies from the transient scattered field in the presence of noise is an important and open problem that is the subject of the current study. In the following, the efficacy of several competing techniques are examined (i.e., the constrained total least squares [T. J. Abatzoglou et al., IEEE Trans. ASSP (May 1991)], the Prony, and a recently developed singular value decomposition based technique), with theoretically calculated scattering data. To simulate scattering data, the spheroidal coordinate based T-matrix formalism is utilized [R. H. Hackman and D. G. Todoroff, J. Acoust. Soc. Am. 78, 1058–1071 (1985)] to compute the impulse response of large aspect ratio, solid elastic cylinders for target aspects ranging from end-on to broadside; additive Gaussian noise is included in the time domain representation. Such scatterers pose realistic challenges in that their target signature varies strongly with frequency and target aspect. Both monostatic and bistatic scattering are considered.
Characterization of white blood cells using inverse acoustic scattering
Authors: Chen Xucai , Apfel Robert E. , Wardlaw Stephen
Published: October 2005

The acoustic scattering functions of human leukocytes (white blood cells) in isotonic saline solution are detected at two angles, along with information on their volume obtained from electrozone sensing. The experimental apparatus has been reported earlier [J. Acoust. Soc. Am. Suppl. 1 84, S163 (1988)]. Different procedures are used to invert the experimental data. Multidimensional histograms are generated and patterns in these histograms are used to recognize white cell subgroups. This technique may be developed into a differential hematology analyzer or combined with currently available analyzers to improve the measurement confidence. [Work supported by the U.S. National Institutes of Health through Grant 5R01CA39374.]
Making complex underwater scattering targets out of polystyrene foam
Authors: Suiter H. R.
Published: October 2005

A method is described of casting polystyrene beads in small quantities for laboratory use as scattering targets. The method is easy and requires no specialized equipment other than a mold. Two such targets are described. One of them is a 4-period shallow wedge grating and the other a 7-period phase grating constructed with acoustically hard aluminum strips imbedded in the acoustically soft foam. Results of a tank experiment on these highly reflective targets will be given. The measured backscattered reflectivities are compared with simple Huygens-Fresnel-Kirchhoff diffraction theory in the high ka regime where the Kirchhoff approximation should work well. Agreement is satisfactory for the wedge gratings. For the phase grating, the facet width must be used as a parameter to reproduce the higher-order behavior. [Work supported by ONR.]
Wave-front fluctuations in the 1000-km SLICE89 experiment
Authors: Flatté S. M. , Duda T. F. , Colosi J. , Hildebrand J. , Hodgkiss W. , Worcester P. F. , Cornuelle B. D. , Howe B. M. , Mercer J. , Spindel R.
Published: October 2005

A 1000-km acoustical transmission experiment has been carried out in the North Pacific in order to quantify long-range acoustic fluctuations at periods of hours to days, and to measure mesoscale and internal-wave sound-speed structure within the source-to-receiver vertical slice. Pseudo-random-sequence pulses were transmitted by a moored broadband sound source (centered at 250 Hz) to a moored 3-km vertical array of 50 receivers. Data are available in the form of approximately 1000 transmisions at 1/h (spanning nine days), with an embedded sequence of another 1000 transmissions at 6/h (spanning 21 h). The multipath arrivals form a clear expected pattern of a single, folded wave front in the earlier part of the received pulses. Each point on the folded wave front represents a specific ray trajectory through the ocean. Several hundred points are available on each of the pulses. Removal of barotropic tides and equipment-motional fluctuations was carried out by averaging techniques, yielding residuals that are dominated by ocean processes such as internal waves. Time-lagged and vertically lagged covariances of residuals show the temporal and spatial scales of variability within the pulse, which can be related to the behavior of ocean processes. Baroclinic tides and internal waves are apparent in the record.
Sounds recorded in the presence of sei whale, Balaenoptera borealis
Authors: Knowlton Amy , Clark Christopher W. , Kraus Scott
Published: October 2005

Opportunistic recordings were made on 12 days during the months of August and September in 1986–1989 between Browns and Baccari Banks on the Nova Scotian shelf. Sei whales, Balaenoptera borealis, were seen in the recording area on 16 of the 32 recording sessions. Subsequent signal analysis revealed that a distinctive sound type was recorded on all of the 16 recording sessions when sei whales were seen and on six sessions when no sei whales were seen. On some recordings two to three different sources (based on sound quality and received levels) are apparent. All these sounds share the same basic characteristics. The signal consists of two phrases, each lasting about 0.5–0.8 s, with an inter-phrase interval of 0.4–1 s, and restricted to the 1.5–3.5 kHz band. Each phrase is composed of a series of 10–20 FM sweeps lasting approximately 30–40 ms/sweep. These signals are similar to the few sei whale sounds reported by Thompson et al. [in Behavior of Marine Animals, Vol. 3, Cetaceans, edited by H. E. Winn and B. L. Olla (1979)]. These sounds are distinctly different from those for all other cetaceans known to frequent these waters.
Articulatory compensation in four-year-olds
Authors: Campbell Melanie M. , McGowan Richard S. , McGarr Nancy S. , Harris Katherine S.
Published: October 2005

The ability of six normal four-year-old children to compensate in their speech production for reduction of two types of feedback was examined. Subjects recorded repetitions of a carrier phrase containing a target word with one of three vowels (/i/, /l/, /æ/) in mixed, randomly selected sequences in four conditions: normal, masking noise, biteblock, biteblock plus masking. The ability of each child to compensate was measured by comparison of the first three vowel formants of each test condition with those of the normal condition. Data from three subjects have been acoustically analyzed using LPC techniques. Preliminary results suggest that while four-year-old children more easily over-come effects of noise, they do not fully compensate for presence of a biteblock. Biteblock effects appear to vary depending upon vowel height of the target. F2 values are lowered in biteblock production of /i/, whereas F1 values are lowered in /æ/. Formant values for midvowel /l/ are less affected. Considerable individual differences are seen in ability to compensate for feedback reduction. [Work supported by NINCDS Grant DC00121-29.]
Perceptual evaluation of infant CV transitions
Authors: Roussel Naneye C. , Daniloff Raymond G.
Published: October 2005

The transition portion of the speech signal has been identified as critical to the perception of both consonants and vowels. Furui [J. Acoust. Soc. Am. 72, 43–50 (1986)] demonstrated that, for adult speakers, a 10-ms segment of the transition centered on the area of maximum spectral movement contained the most critical information for joint consonant and vowel perception and that a period roughly 50 ms long (including the aforementioned 10-ms critical interval) was sufficient for CV syllable perception. An investigation of the perceptual cues contained within consonant-vowel (CV) transitions of infants ages 6–15 months was begun. CV-like syllables were selected from the vocalizations of two infants, a male and a female, and presented to listeners for identification. Truncated versions in which portions of the transition were systematically deleted were also presented for identification and critical intervals for the perception of consonant, vowel, and syllable were calculated and compared with those obtained for adult speakers. Comparisons across age levels were also made.
Developmental and linguistic effects on the coarticulation of fricative-vowel productions
Authors: Siren Kathleen A. , Wilcox Kim A.
Published: October 2005

Previous work (Nittrouer, Studdert-Kennedy, and McGowan, 1989) supports the notion that children attack the acquisition of speech and language in larger-than-segment units, as evidenced by greater coarticulatory interactions in young children's speech that diminish with age. In this study, the experimental design from Nittrouer et al. was expanded to include familiarity versus nonfamiliarity with a stimulus item. The notion of familiarity included two factors, meaningfulness of the stimulus item, and relative amount of motor practice. Results of acoustic measurements of children's (3-, 5-, and 7-year-olds) and adult's productions confirm that children do exhibit a greater effect of a following vowel (/i/ vs /u/) on the preceding fricative (/s/ vs /∫/) when compared to adults. In addition, relative meaningfulness of a stimulus item appears to decrease the degree of coarticulatory interaction between these segments, regardless of age of the individual. These results are discussed with regard to traditional models of coarticulation and traditional theories of speech and language acquisition.
Acoustic typology of infant pre- and post-linguistic protosyllables
Authors: Piroli J. , Daniloff R. , Miller C. J.
Published: October 2005

Three hundred quasisyllabic utterances were excerpted from the vocalizations of three infants at monthly intervals in the 4- to 14th-month epoch of development. Samples were recorded while at play with the mother in a toy-filled, sound-treated chamber. F1, F2, f0, and I0, trajectories for the entire quasisyllable were extracted from digital FFT/waveform displays. Syllable, consonant, vowel and transition durations, formant and I0 envelope velocities, and jitter ad shimmer measurement were made. Natural-class transcriptions and articulatory “well-formedness” evaluations were made for each utterance. A behavioral analysis checklist was available for each utterance. Analysis revealed that even perceptually labelable seemingly unexceptional tokens displayed combinations of nonadult-like acoustic parameters. Tokens were sorted by clusters of variables into a typology of emergent syllabic forms based upon adult and nonadult-like values of the classificatory acoustic-perceptual variables. The syllable well-formedness related complexly to the infant's attributed intent to communicate. The prelinguistic utterances were considerably more “juvenile” acoustically than perception would lead one to believe.
Perceptual limits of octave harmony
Authors: Demany Laurent , Semal Catherine , Carlyon Robert P.
Published: October 2005

Three subjects were monaurally presented with dyads of frequency-modulated pure tones approximately 1 octave apart. The tones, with carrier frequencies FL and FH, were heard in a background of pink noise and at a low sensation level, so that they were completely resolvable by the subjects' peripheral auditory filters. In experiments 1 and 2, subjects judged on each trial which of two dyads was inharmonic (FH≠2.FL); the relative mistuning of the inharmonic dyad [(FH − 2.FL)/2.FL] was varied independently of FL and could be either positive or negative; FL was fixed within trials in one experiment, and varied within trials (from about 8%–20%) in the other experiment. In both experiments, performance monotonically worsened when FL was increased from 300–2000 Hz; in addition, negative mistunings were better identified as inharmonicities than positive mistunings. In a third experiment, a 4I-2AFC procedure was used to assess the detectability of changes in FH irrespective of their effect on the perception of harmonicity. Performances were not the same function of FL as in the other two experiments, and were much better for high FL values. Thus it is concluded that detection of inharmonicity (experiments 1 and 2) was limited by factors other than those responsible for fine pitch discriminations. These results also have implications with respect to the origin of human listeners' melodic octave templates.
Key-distance effects in melody recognition reexamined
Authors: Takeuchi Annie H. , Hulse Stewart H.
Published: October 2005

Key distance is a theoretical measure of the relatedness of two musical keys. Key-distance effects in melody recognition denote that perception of a transposed melody depends on the key distance between the keys of the original and transposed melodies. Key-distance effects in melody recognition are often cited in the psychology of music literature. However, reexamination of a classic study of key-distance effects [J. C. Bartlett and W. J. Dowling, J. Exp. Psychol.: Hum. Percept. Perfect. 6, 501–515 (1980)] suggests the effects are not robust, and may be an artifact of their experimental design. Three new experiments failed to find the effect Bartlett and Dowling reported, better discrimination of transpositions from nontranspositions in distantly related keys than in closely related keys, even when contextual conditions were designed to enhance the effect. A reversed key-distance effect, better discrimination in closely related keys than in distantly related keys, was found in some conditions. However, the effect was not robust. Different contextual conditions produced different results, suggesting that perception of melodies is influenced by tonal context. [Work supported by NSF.]
Methods for forecasting impulse noise propagation through the atmosphere
Authors: White Michael J.
Published: October 2005

Predicting the sound levels outdoors at long distances from a given noise source is a challenging and important problem. The propagation depends strongly on several environmental factors, such as the terrain and the wind and temperature profiles. These factors are often beyond our ability to control or measure adequately in a large experiment. In principle, a precise forecast would demand a dense sampling of the environment over time and throughout the media. However, if one were able to obtain a sufficiently dense sampling of the environment, it is likely that the large volume of information gathered would make it of little practical use! In this paper, several models are compared for predicting the sound field at large distances from an acoustic source. Particular attention is given to blast waves in the linear acoustics regime. A new model is proposed for rapid prediction of the mean noise levels. Some discussion is presented on the distributions of measured levels about their mean values and the importance of these distributions in noise prediction and control.
Normal mode solution for a downward refracting atmosphere above a complex impedance plane
Authors: Raspet Richard , Baird Gordon
Published: October 2005

The development of the fast field and parabolic equation solutions to the wave equation has made it possible to solve for the combined effects of refraction in a layered atmosphere and the interaction of sound with a complex impedance ground surface. In many respects the numerical methods have advanced beyond an understanding of the basic phenomena. In an earlier study [J. Acoust. Soc. Am. 89, 107–114 (1991)], the residue series solution for upward refraction was investigated and provided insight into the nature of the interaction of refraction and ground reflection. In this paper, results of a similar normal mode solution are presented for downward refraction by a bilinear sound velocity profile above a complex impedance ground surface. This model is used to investigate when the surface wave is excited for downward refraction conditions and to develop criteria for the maximum range of cylindrical decay as a function of ground impedance phase and magnitude and the magnitude of the sound velocity gradient. [Work supported by NASA Langley Research Center.]
Correlation between excess attenuation and geometric or meteorological parameters
Authors: Moritz Charles T. , Lamancusa John S.
Published: October 2005

Extensive experimental measurements of sound propagation and vertical sound-speed profiles over level agricultural terrain are presented. A high-power speaker generating pure tones at approximately one-third octave band center frequencies from 160–4000 Hz was used as the noise source. Sound levels were measured and recorded at ranges of 2, 125, 250, and 500 m from the source during various time periods of interest from 3–7 July 1990. Simultaneously, meteorological conditions were measured using a variety of tower mounted anemometers and temperature sensors. A total of 50 sets of 10-min averaged data at each of 12 frequencies and 4 ranges was obtained. Temperature and velocity profiles were reconstructed using Monin-Obukhov scaling theory. A statistical regression analysis to determine the correlation between excess attenuation and measurable geometric and meteorological parameters was completed. Sample measurements are presented and comparisons are made to the Daigle model [J. Acoust. Soc. Am. 65, 45–49 (1979)].
Scattering of a plane wave at a plane boundary presenting an impedance discontinuity
Authors: Tjøtta Jacqueline Naze
Published: October 2005

The scattering of a sound wave by a boundary presenting an impedance discontinuity has been the object of many theoretical investigations based on the Wiener-Hopf method. Although the method provides an exact solution, the expressions obtained are involved and not very useful in the vicinity of the boundary. The present work addresses the simple case of a plane wave incident on a plane boundary that is made up of two half-planes. One of the half-planes is perfectly rigid, the other is pressure release. The boundary between the two half-planes is a straight line, and the medium over the boundary is a lossless fluid. It is shown that a simple analytical solution can be obtained by taking advantage of the symmetry properties of the problem. The solution is expressed in terms of one-dimensional integrals that can be evaluated numerically. Numerical results for the sound pressure and velocity are presented. The case where the incident plane wave is replaced by a sound beam is briefly discussed. [Work supported by ONR and The Norwegian Research Council for Science and Humanities (NAVF).]
Signatures from pulse signals scattered at oblique incidence from elongated elastic solids at carrier frequencies in the region of bending resonances
Authors: Werby M. F. , George Jacob
Published: October 2005

It has been determined that time-domain signals can manifest characteristic signals when the midpulse frequency is in some resonance region. This will be discussed in an upcoming book on resonance scattering theory by Überall. This work is a further extension of that study to illustrate unique signals characteristic of pulse scattering at frequencies associated with bending or flexural resonances. In the earlier work, beat patterns and damped sinusoidal patterns (as a function of time) were associated with single or specific clusters of resonances. Here, alternating damped sinusoidal patterns are associated with intervals of interference patterns that are shown to be associated with bending modes excited at oblique incident angles.
Resonances of Scholte-Stoneley waves propagating on cylindrical shells at oblique incidence
Authors: Remert P. , Lenoir O. , Izbicki J. L. , Ripoche J.
Published: October 2005

This paper deals with the oblique scattering of an incident monochromatic plane wave by a circular cylindrical shell immersed in water. The propagation direction of the incident wave makes an angle α with a normal to the longitudinal axis of the shell. Experiments are carried out over the broad reduced frequency range 0 < ka > 35, involving the method of isolation of resonances, for two targets: (1) an air-filled aluminum shell with b/a = 0.94 (b = inner radius of the shell: a = outer radius of the shell) whose length is infinite with regard to the incident acoustic beam cross section; and (2) the same shell of the finite length: In this case, the incident beam insonifies the entire target. With α varying from 0° to 35°, the backscattered spectra—obtained from the signals scattered by both targets—exhibit wide minima which are due to the reemission of Scholte-Stoneley waves. Resonance peaks are located at the same frequencies on the corresponding resonance spectra. The frequency position of these peaks slowly increases with the increasing values of α. Follow-up of these frequencies is easy, especially beyond the shear critical angle, which confirms that these resonances are related to external waves. These new experimental results are similar to theoretical ones obtained for an infinite pipe by Kaplunov et al.
Variational scattering calculations for a prolate spheroid
Authors: Freund D. E. , Farrel R. A.
Published: October 2005

Many theoretical methods for computing the scattering amplitude, T, employ an initial approximation (trial field) to the exact fields within, or on the surface of, the scatterers. Variational principles are unique in that they possess the important feature known as quadratic convergence. That is, first-order errors in the trial fields manifest themselves as only second- and higher-order errors in the desired quantity T. Results that were remarkably accurate at all wavelengths were achieved previously [D. E. Freund and R. A. Farrell, J. Acoust. Soc. Am. 87, 1847–1860 (1990)] by using the Schwinger variational principle in conjunction with simple, physically motivated, trial fields for the case of scattering from a soft sphere. Here, the efficacy of these simple trial fields is investigated further by applying them to the more severe test of scattering from an acoustically soft prolate spheroid with a plane wave axially incident. Accurate forward- and backscattering results are found for spheroids with aspect ratios ranging from 2:1 to 100:1. [Work supported by the U. S. Navy under Contract N00039-89-C-0001.]
Opening rate of the transverse cusp diffraction catastrophe in scattering from oblate penetrable spheroids
Authors: Dean Cleon E. , Marston Philip L.
Published: October 2005

Sound scattered by an oblate penetrable spheroid should produce a transverse cusp caustic in the region associated with the rainbow in optics (for relative speed of sound cscatt/c < 1). The principal curvatures of the generic local wave front that produces the far-field transverse cusp are examined. This wave front is shown to generate a caustic curve (U − Uc)3 = d∝ V3, where U and V are horizontal and vertical scattering angles, and Uc is the cusp point direction. The far-field opening rate d∝ is calculated for the transverse cusp. It is shown that d∝ has a simple dependence on the parameters of the generic wave front. Define the aspect ratio q = D/H, where H is the height and D is the equatorial width of the penetrable spheroid. Generalized ray tracing is used to relate q to principal curvatures and shape parameters of the outgoing wave front and hence to d∝. Measurements of d∝ in the optically analogous problem appear to support the calculation. As q goes to q14 ≈ 1.31, the critical value for the generation of a hyperbolic umbilic focal section, the predicted d∝ goes to infinity. The nature of the divergence was numerically investigated as was the rate at which d∝ vanishes as q approaches other critical values. The analysis suggests benchmarks for testing numerical scattering codes. [Work supported by ONR.]
Effects of age on auditory spatial resolution in the horizontal plane
Authors: Chandler David W. , Grantham D. Wesley
Published: October 2005

The purpose of this research was to determine if auditory spatial resolution in the horizontal plane changes with age. Spatial resolution was measured in static conditions, represented by the minimum audible angle (MAA), and in dynamic conditions, represented by the minimum audible movement angle (MAMA). MAAs and MAMAs were measured for adult subjects 60 to 80 years of age with normal (or near normal) hearing thresholds. All measurements were obtained in a darkened anechoic chamber. Thresholds were measured as a function of stimulus bandwidth, center frequency, and listening azimuth, for both MAA and MAMA. Additionally, MAMAs were measured as a function of the velocity of the moving stimulus source. MAAs and MAMAs of the elderly will be compared with previous measurements for young normal adults that were obtained under the same stimulus conditions [D. W. Chandler and D. W. Grantham, J. Acoust. Soc. Am. Suppl. 1 87, S64 (1990)]. It is hypothesized that auditory spatial resolution in the horizontal plane diminishes with age because of generalized deficits of central nervous system processing. This diminished resolution should be reflected by poorer MAAs and poorer MAMAs among the elderly subjects than among the young, normal-hearing subjects. [Work supported by NIH.]
Different discrimination strategies for vowels and consonants
Authors: Schouten Bert , Hessen Arjan van
Published: October 2005

In speech perception research, one is often interested in the relationship between phoneme identification and discrimination of stimuli drawn from the same stimulus continuum. If discrimination performance is completely predictable from identification, perception is often said to be completely categorical: In both tasks, subjects (can) only use phoneme labels. How should one compare a one-interval identification task with a two-interval forced-choice discrimination task in which subjects have to determine the order of the stimuli? Using standard SDT assumptions about optimal processing [D. M. Green and J. A. Swets, Signal Detection Theory and Psychophysics (New York, 1974)], it was found that identification and discrimination of natural vowels were nearly equivalent, but with natural stop consonants identification d′ was, paradoxically, twice as high as discrimination d′. It was concluded that subjects probably use a different strategy for the discrimination of natural stops: They do not subtract the traces of the two stimuli, but the estimated distances between the stimuli and the phoneme prototypes. Such an assumption yields d′ values that are twice as high as the standard values.
The role of multiple acoustic properties in specifying the internal structure of phonetic categories
Authors: Hodgson Philip , Miller Joanne L.
Published: October 2005

The extent to which a phonetic segment may be specified by more than one acoustic property was investigated using the trading relation between vowel duration and closure duration, two properties known to play a role in specifying the voicing contrast for intervocalic bilabial stops. Specifically asked was whether a change in preceding vowel duration results in a comprehensive remapping between closure duration and phonetic category, or whether trading effects are confined to the category boundary. Two series of disyllables were created ranging from /aba/ through /apa/ to * /apa/ (an exaggerated /p/) having initial vowel durations of 153 and 250 ms, respectively. Closure duration in each series varied from 20 to 400 ms. A preliminary experiment revealed a standard trading relation, in that the /b/-/p/category boundary was located at a longer closure duration for the stimuli with a long, compared to a short, preceding vowel. In the main experiment, listeners were asked to judge each disyllable in each series for the goodness of its consonant as a member of the /p/ category. For both series the /p/ category was perceived as having internal structure, with a limited range of stimuli being judged as the best exemplars. Furthermore, the range of best exemplars for the long vowel series was displaced relative to that for the short vowel series toward longer values of closure duration. These findings indicate that the acoustic properties in question trade against each other not only at the phonetic category boundary but also within the category. This results in a comprehensive remapping of phonetic category structure similar to that observed in earlier research for changes in speaking rate. [Work supported by NIH.]
Independence of scene analys's and the speech module
Authors: Whalen D. H. , Liberman Alvin M.
Published: October 2005

Even the first example of the duplex effect [Rand, J. Acoust. Soc. Am. 55, 678–680 (1974)] gives evidence that speech perception can bring together portions of the speech signal that scene analysis says are separate: Although a formant transition on one ear sounds like a nonspeech “chirp,” its speech information is used by the syllable on the other ear. The present work explores the competition between these two organizations of the signal by extending previous work [Whalen and Liberman, Science 237, 169–171 (1987)] in which F3 formant sinusoids provided speech information both below and above the intensity level at which the nonspeech aspect of the tone was just perceptible. As an extension, alternative “scenes” were made plausible for the transitional tones by (1) extending them 50 ms before the syllable; (2) extending them 50 ms after the syllable; (3) creating two harmonies based on the tone; and (4) creating four harmonics based on half the frequency of the tone. Identification of the speech sounds was always above chance, indicating the success of the speech module. However, the harmonic series (below the detection level) and the precursor tone (below and above the detection level) reduced the accuracy of the speech judgments, suggesting competition with scene analysis. Scene analysis and speech perception, though independent, are often in competition for the same signal, and speech takes precedence in a wide array of circumstances. [Work supported by NIH Grant HD-01994.]
Channel-adaptive matched filter processing of large time-bandwidth product signals: Preliminary results
Authors: Hermand Jean-Pierre , Roderick William I.
Published: October 2005

Techniques that incorporate propagation channel modeling into conventional matched filter processing can improve detection and localization performance of low-frequency active sonar systems. In January 1989, an acoustic transmission experiment under known oceanographic conditions was conducted by SACLANTCEN in a deep water (2800-m) area west of Sardinia. Large time-bandwidth product signals were transmitted by a broadband projector and were received at a 30-km range in the broadside beam of a horizontal line array of 64 hydrophones. Source and receiver were towed near the channel axis at depths of 100 and 150 m, respectively. The transmitted signals consisted of linear FM pulses with time-bandwidth products that ranged from 400 to 4000. Environmental parameters, calculated from measured and archival data, were introduced in the GENERIC sonar model to compute the eigenrays at discrete frequencies closely spaced over the transmission bandwidth. The (band-limited) impulse response of the channel was obtained by complex summation of the eigenrays in both time and frequency domains. For each bandwidth, the transmitted signal, convolved with the modeled channel response, was correlated against its replica. The predicted matched filter outputs were compared with those obtained from the observations. The results will be discussed in the context of channel-adaptive matched filtering.
Evaluation of interference effect in the estimation of underwater target abundance by the echo-integration method
Authors: Sun Zhigang , Gimenez Gérard
Published: October 2005

The estimation of fish abundance by the echo-integration method is based on the assumption that the total integrated echo intensity returned from randomly distributed targets is proportional to their quantities. In the case where the multiple scattering between targets is negligible, the precision of this estimation can be affected by the interference between individual echos from every single target. In this work, an evaluation function to determine the eventual divergence of the estimated result from the linearity is proposed. As a function of different parameters, such as the total number and the dimension of targets, the transmitted signal frequency, distance from transducer to the network plan and the transducer beamwidth, the importance of interference effect is analyzed for a network of spheres with various spatial distributions. [Work supported by [FREMER.]
Expansions and modifications of the four-channel model for touch
Authors: Bolanowski S. J.
Published: October 2005

The model proposing that there are four distinct channels mediating the mechanical aspects of touch [Bolanowski et al., J. Acoust. Soc. Am. 84, 1680–1694 (1988)] was based on psychophysical and physiological experiments conducted on the glabrous skin of humans and required assumptions regarding the neural code used by each channel. Continuing psychophysical experiments have expanded the model to include hairy skin which, in the least, operates using three separate channels: a low-frequency (0.4–3 Hz) one that is temperature insensitive, and middle- (3–50 Hz) and high- (50–500 Hz) frequency ones that are both sensitive to temperature. The sensitivity of all of these channels is greater for larger stimulus areas. Furthermore, physiological experiments directed at testing some of the assumptions used in the model to establish the psychophysical-physiological link show that it must be modified. In particular, activity arising from a single Pacinian corpuscle cannot account for the increases in sensitivity that occur for increases in stimulus duration required by the phenomenon of temporal summation known to exist in the P channel. Therefore, it is likely that the neural code for threshold in the P channel requires the activation of more than one Pacinian corpuscle. This finding may have implications regarding the neural code used by other channels possessing temporal summation (e.g., NP II).
Cortical representations of learned vibrotactile stimuli
Authors: Merzenich M. M.
Published: October 2005

Recent electrophysiological studies have shown that cortical somatosensory representations are shaped by tactual experiences. These adaptive neuronal processes underlying cortical contributions to tactual learning and nondeclarative memory have been studied by: (a) distorting the factual experiences of monkeys and rats over a limited time epoch; (b) determining the consequences of special skin and peripheral nerve manipulations that test hypotheses about the neural network origins and cortical plasticity; (c) evaluating the consequences, for cortical representation and cortical network organization, of the perturbation of the network by microstimulation; and (d) training monkeys to make distinctions about tactile stimuli while tracking training-induced changes in their cortical representations. These studies bear significance for understanding the neural origins of tactile perception, and provide a basis for understanding how idiosyncratic tactual perceptual abilities emerge from tactile experience. [Work supported by NIH Grant NS-10414, the Coleman Fund, and Hearing Research, Inc.]
Altering tactile spatial sensitivity
Authors: Craig James C.
Published: October 2005

Recent animal studies have demonstrated that extended tactile experience can alter cortical organization [Jenkins et al., J. Neurophysiol. 63, 82–104 (1990)]. The present study examined the effect of extended tactile stimulation on spatial sensitivity in human subjects. Four subjects received repetitive, tactile stimulation presented on the volar surface of the forearm. The tactile stimuli, taps, were delivered periodically through small vibrators worn by the subjects for up to 18 h per day. After a period of 5 to 8 weeks of wearing the vibrators, three of the four subjects reported anomalous sensations when attempting to localize tactile stimuli. Subjects had difficulty in localizing stimuli and reported sensations of pressure and diffuseness. Single stimuli applied to the forearm would sometimes evoke double and triple sensations separated by as much as 20 cm. After removing the vibrators, subjects continued to report anomalous sensations for up to 15 weeks. These results suggest that the neural organization of human subjects may be altered by extended tactile experience.
Neural mechanisms of tactual roughness perception
Authors: Johnson Kenneth O. , Connor Charles E. , Hsiao Steven S.
Published: October 2005

The neural mechanisms underlying tactual roughness were investigated in a combined psychophysical and neurophysiological study. Stimuli consisted of surfaces embossed with dot arrays of varying dot diameter and spacing. Human subjects scanned the surfaces tactually and responded with numerical magnitudes proportional to their sense of roughness magnitude. The same surfaces were scanned across the receptive fields of cutaneous mechanoreceptive afferents in monkeys while recording the evoked action potentials. Hypothetical neural codes for roughness magnitude were computed from the neural response patterns and tested for their ability to account for the psychophysical data. Four types of neural coding mechanisms were considered: (1) mean firing rate; (2) general variation in firing rate; (3) short-term temporal variation in firing rate; and (4) local spatial variation in firing rate. Mean firing rate failed to explain the psychophysical results: Surfaces that evoked the same firing rate evoked very different roughness judgments. In contrast, neural codes based on spatial firing rate variation, especially in slowly adapting afferents, account for the psychophysical results [Connors et al., J. Neurosci. 10, 3823–3826 (1990)]. [Work supported by NIH.]
Identifying the direction of simulated movement on the skin: The effects of an irrelevant stimulus
Authors: Evans Paul M. , Craig James C.
Published: October 2005

Movement was simulated on the index and middle fingerpads by activating, in rapid succession, adjacent columns (or rows) of the tactile display of the Optacon. The stimuli either moved from left to right (or vice versa), or from the top of the display to the bottom (or vice versa). Subjects were trained to respond “1” for two of the stimuli and “2” for the remaining stimuli. The subject's task was to focus attention on the index fingerpad (the target location), to identify the stimulus that was presented to that site, and to ignore the stimulation on the middle fingerpad (the nontarget location.) There were three trial types: (1) the stimuli were physically identical (moved in the same direction; (2) the stimuli were physically different but assigned the same response; and (3) the stimuli were different and assigned different responses. The results showed that when the nontarget and target had the same response (regardless of whether they were physically identical or not), accuracy was higher and reaction times were faster than when the non-target and target had different responses. The results suggest that subjects are unable to restrict processing to a single site on the hand. Moreover, a tactile stimulus at a nontarget location appears to be processed to the level of response activation. [Work supported by NIH.]
The glass harp: “The sound of heaven.”
Authors: Turner Jamey
Published: October 2005

This presentation will consist of three parts: (1) A musical performance on the glass harp will demonstrate the incredible beauty of this instrument, which the author has played on all the national television networks and with many symphony orchestras. Music written for several kinds of glass instruments played by rubbing will be performed, including some by Mozart and Beethoven. Glasses will be distributed for audience participation on one selection. (2) A short historical discussion will be given of the rich legacy of glass instruments and music spanning three centuries, with roots that go back over 2000 years to glass instruments tapped rather than rubbed. (The author was privileged to examine the original glass harmonica invented by Ben Franklin.) (3) The making of the glass harp will be discussed, with emphasis on selecting the glasses, the water, the table, and other elements that are important to the quality of the sound.
The Benjamin Franklin glass harmonica
Authors: Allen Kathleen J.
Published: October 2005

The instrument described is from a design by Benjamin Franklin, of modern manufacture by Gerhard Finkenbeiner of Waltham, Mass., played by Vera Meyer of Cambridge, Mass., and encompasses three octaves. Two notes from each octave were investigated at varying amplitudes of excitation and different speeds of rotation. Data will be presented to show that harmonic richness is a function of octave, and is relatively unaffected by amplitude of excitation; also that the rotation of the disks splits the degeneracy of the normal modes. An analysis will be presented of the splitting by decomposition into traveling waves around the circumference of the disk, which relates rotation speed and the shear velocity of sound in the glass medium.
Large amplitude wall pressure events beneath turbulent boundary layers
Authors: Karangelen Carolyn
Published: October 2005

Examination of the fluctuating wall pressures can yield much information on the turbulent structures within a flow. The wall pressure signal may be considered a footprint of these structures. The pressure fluctuations measured at the wall are produced from velocity fluctuations within the flow that are propagated through the flow medium. The sporadic large amplitude wall pressure events are thought to be footprints of turbulent bursting events in the near wall layer. Large amplitude events were captured using conditional sampling techniques and analyzed for their statistical, temporal, and spectral characteristics. The results of this analysis will be presented. [Funded by ONR and IBM.]
Excitation of resonators by blood flow in arteries
Authors: Mast T. Douglas
Published: October 2005

Resonators are known to exist in human arteries. These include aneurysms and weakened sections of the arterial wall. The present paper gives a quantitative theory of how such resonators are excited under physiological conditions. Considered mechanisms of excitation include turbulence and flutter. The pulsatile nature of blood flow is taken into account, as are the flexible walls of arteries. The time-varying frequency, bandwidth, and amplitude of such resonances are related to parameters that characterize the cardiovascular system. [Work supported by the William E. Leonhard endowment to Penn State Univ. The author acknowledges the advice of A. D. Pierce.]
Spherical cavity resonator: Singular boundary-shape perturbation?
Authors: Mehl James B.
Published: October 2005

A nearly spherical cavity resonator has been investigated using boundary-shape perturbation theory. The cavity parts consist of two perfect hemispheres of radii a and b = a(1 − ε), aligned along their common axes and connected by a plane surface at θ = π/2. The lowest-frequency nonradial modes with acoustic pressure proportional to Φz = jt(kr)cos θ and Φx = jt(kr)sin θ cos φ have been investigated. These modes have fairly uniform velocity fields oscillating along the z and x axes, respectively. Boundary-shape perturbation theory has been applied to develop an expression for the eigenfrequency perturbation in powers of the small parameter ε. The first-order perturbations of the eigenfrequencies vanish for both modes. The second-order perturbation series for the Φx mode converges; the results agree with numerical calculations based on a boundary-integral-equation (BIE) technique. The second-order perturbation series for the Φz case diverges. The BIE numerical results suggest the presence of a nonsingular term proportional to ε2 log ε2.
A simple circuit model for the thermodynamics of thermoacoustic devices
Authors: Ceperley Peter H.
Published: October 2005

A simple circuit model of the thermodynamics of thermoacoustic devices will be presented. This model allows the simple calculation of thermoacoustic gain, efficiency, and thermal current. More importantly, it allows a simpler, more intuitive approach to optimizing the parameters of a thermoacoustic device. Results calculated using this model will be compared with the exact results calculated for a parallel plate (or slit) geometry for a range of slit widths and phasings. [Work supported by ONR.]
Complex eigenfrequency analysis of thermoacoustic heat engines
Authors: Arnott W. Pat , Raspet Richard , Bass Henry E.
Published: October 2005

Gas in a straight tube, open at the cool end and closed at the hot end, can be made unstable with respect to acoustic oscillation by placing a sufficiently large temperature gradient along the tube. The possibility of spontaneous oscillation exists when the externally applied temperature gradient is larger than the temperature gradient associated with a standing acoustic wave in the tube. Energy for oscillation in this non-equilibrium system is supplied by the heat input necessary to maintain the temperature gradient. Rott and his students [Rott, Adv. Appl. Mech. 20, 135–175 (1980)] have investigated this instability for a variety of conditions. The instability analysis is given in this paper for a thermoacoustic prime mover known as a Hoffler tube. The complex eigenfrequency (CEF) of a recently constructed Hoffler tube is computed as a function of temperature. The frequency of oscillation and the quality factor, or Q, are determined from the real and imaginary parts of the CEF. Spontaneous oscillation can occur in the limit 1/Q→0. Application of the CEF to thermoacoustic refrigerators is discussed. [Work supported by ONR.]