bluuebunny/crossref_metadata_2025 huggingface dataset:
Educational experiments in acoustics, signal processing, and computer data acquisition and calibration
Authors: Swanson David C.
Published: October 2005

The Pennsylvania State University Graduate Program in Acoustics has recently added a Laboratory Course to its curriculum that is required for all full-time degree candidates. The course goals are to teach objective reporting skills, proper calibration of measured data, and the general use of computers and digital recordings for data analysis. Experiments included measurements of propagation changes due to temperature inversions, vibrations, reverberation time measurements, duct acoustics and impedance, source coupling, and directivity. While basic PC software was developed for operation of the A/D boards and signal processing, the experiments involving digital recording and analysis could be reproduced with a variety of commercially available software packages and computer equipment. Traceability is emphasized for all data calibration techniques so that students will understand how to verify good data records that may have been recorded by others. A summary of the particular experiments and results is presented.
The influence of the bow on aperiodicity of violin notes
Authors: Schumacher Robert T.
Published: October 2005

A method has been demonstrated to investigate the aperiodicity in nearly periodic signals [R. T. Schumacher and C. Chafe, ICASSP-90, Paper 6.A1.18, Albuquerque, NM (1990)]. This method, the norm difference method, quantifies the fluctuations in the shapes of waveforms from cycle to cycle. The norm difference method will be explained. As an application, a study of the difference in aperiodicity of a note separately played on a violin by two bows will be presented. In addition, a brief survey of the range of aperiodicities exhibited by other orchestral instruments will be presented in order to compare them with characteristic bowed string aperiodicities.
Dynamic mechanical properties of violin wood
Authors: Fitzgerald Edwin R.
Published: October 2005

Values of complex shear compliance (J* = J′ − iJ″) and modulus (G* = 1/J*) have been measured for spruce and maple over a continuous frequency range from 2–10 000 Hz, and at temperatures from 15 to 40 °C. The wood strip samples of European spruce and Norway maple were supplied by Carleen M. Hutchins in connection with her investigations of the effect of various acoustical parameters of wood on plate tuning and the tone qualities of finished violins. Measurements were made in an automated electromagnetic transducer apparatus [E. R. Fitzgerald and R. E. Fitzgerald, Polymer Bull. 18, 167–174 (1987)] in which samples are sheared while clamped between stainless steel blocks. Values of the shear parameters vary with frequency, but also with the grain orientation, moisture content, and the perpendicular, clamping force on the sample faces while they are vibrated in shear. The mechanical spectra differ, but, in general, several sharp, microstructural compliance modes are superimposed on broad retardation, background spectra [E. R. Fitzgerald, J. Acoust. Soc. Am. 33, 1305–1314 (1961)]. Typical are the results for a spruce sample at 22 °C, sheared cross grain, for which values of elastic compliance (J*) decrease from 2.74 to 0.306×10 9 cm2/dyn (2.74 to 0.306×10−2 MPa−1) as the frequency increases from 10 to 10 000 Hz; the loss compliance (J″) rises to a broad maximum of 1.65×10−9 cm2/dyn (1.65×10−2 MPa−1) at 4000 Hz. Values of the shear sound velocity and attenuation, together with the mechanical loss tangent (J′/J′ = G″/G′), are also calculated for the samples.
The trans-spectral coherence in the solution of the Duffing's equation, undergoing chaos
Authors: Vaidya P. G.
Published: October 2005

An analysis of the time series generated by the Duffing's oscillator, undergoing chaos, has been carried out. The series is inspected for the existence of the trans-spectral coherence, which is the coherence between two different spectral components. (The technique to calculate such coherence has been demonstrated previously by Vaidya and Anderson.) In the case of the Duffing's equation, a significant coherence is seen across the trans-spectrum. This shows the presence of order, co-existing with randomness, in this series. A companion paper at this conference explains the origin of such order.
Existence of a hierarchy of periodic components in the solution of the Duffing's equation, undergoing chaos
Authors: Vaidya P. G. , Athalye Amit
Published: October 2005

Chaos is recognized as a state manifesting the characteristics of both order and randomness. An analysis of the Duffing's oscillator, undergoing chaos, has been carried out. The solution is written as a sum of a periodic solution, representing a limit cycle, and a residue. When the residue is assumed to be small, it is shown to be governed by a linear nonautonomous equation that is unstable. When the residue is allowed to be large, it is governed by an equation whose solution is once again bounded and chaotic. This new solution can, in turn, be represented as the sum of a periodic and a chaotic solution. This process in theory can be carried out indefinitely. The analysis sheds some light on the nature of chaos generated by the Duffing's equation, and it also explains the significant amount of the trans-spectral coherence observed in the time series generated by its solution.
A version of NPE for nonlinear propagation of ultrasonic pulses in focused field
Authors: Too Gee-Pinn James , Ginsberg Jerry H. , Tjøtta Jacqueline Naze
Published: October 2005

The NPE (nonlinear progressive wave equation) and associated computer program are a time domain representation that was developed by McDonald and Kuperman to study waveguide problems. The present work extends the earlier studies [Too and Ginsberg (1989–1990)], which developed a modified version of NPE in terms of axisymmetric cylindrical coordinates to describe propagation of finite-amplitude sound beams. In the present studies, a new version of NPE is studied in which axisymmetric spherical coordinates are employed to describe propagation of axisymmetric convergent and divergent waves. The present problem concerns nonlinear pulse propagation in a focused field. In order to initialize the moving window convected by NPE, a linear spherical wave assumption is made adjacent to the transducer; i.e., inside the converging beam, the input field is represented as a linear spherical wave, while outside the beam, the input field is considered to be zero. Temporal waveforms are computed on- and off-axis and are compared to the experimental data by Baker and Humphrey [Frontiers of Nonlinear Acoustics 12th ISNA, pp. 185–190 (1990)]. [Work supported by George W. Woodruff endowment.]
Harmonic generation in focused sound reflected from a curved surface
Authors: Makin Inder Raj S. , Hamilton Mark F.
Published: October 2005

In an earlier presentation [A. Averkiou and M. F. Hamilton, J. Acoust. Soc. Am. Suppl. 1 85, S93 (1989)], as analysis of the linear propagation and reflection of a focused Gaussian beam was reported. The reflecting surface was assumed to be slightly curved and perfectly rigid. Here, second harmonic generation in the incident and reflected beams is investigated, with absorption and finite surface impedance now taken into account. Closed-form solutions for the second harmonic pressure and power are derived from the KZK nonlinear parabolic wave equation. Propagation curves and beam patterns are presented for various target curvatures and impedances. Both before and after reflection, the transverse distribution of the second harmonic pressure is equal to the square of the transverse distribution of the fundamental pressure. Variations in the relative phase between the fundamental and second harmonic components, due to propagation through foci and reflection from the target, significantly influence the process of harmonic generation. Implications for ultrasonic imaging are discussed. [Work supported by NSF, the David and Lucile Packard Foundation, and the Texas Advanced Research Program.]
Nonlinear wave propagation in reacting, viscoelastic fluids
Authors: Marguiles T. , Randall J. , Schwarz W. H.
Published: October 2005

Finite-amplitude wave propagation in a viscoelastic fluid has been investigated with a perturbation approach using multiple time scales. A generalized Burgers' equation (GBE) for planar and nonplanar (i.e., cylindrical and spherical) waves has been developed for a continuum, simple fluid representation of Coleman and Noll. Simultaneous chemical reactions are coupled in the analysis by modifying the pressure perturbations for a reacting system with orthonormalized reaction progress variables. The dissipation in the analysis results from both stress relaxation and chemical relaxation, as well as heat transfer by Fourier conduction. The GBE with an integral stress relaxation functional reduces to the classical Burgers' equation form for the case of a Newtontan viscous, perfect gas without reaction. Other approximations and limitations are discussed, including, for example, approximations of nonconvex equations of state, and derivations of a Korteweg de Vries-Burgers' equation exhibiting both dissipation and dispersion.
Comparison of numerical and analytical treatments of the transient parametric array
Authors: Hogan William , Woodsum Harvey , Westervelt Peter J.
Published: October 2005

Recently, Westervelt [J. Acoust. Soc. Am. Suppl. 1 88, S167 (1990)] has developed an analytical treatment of the transient parametric array that is valid for both far field and near field, for arbitrary taper function and arbitrary modulation of the primary wave. The result was previously shown to be consistent in the far field with results of P. Stepanishen [J. Acoust. Soc. Am. 82 (1987)]. The analysis is based on earlier work in general relativity by Westervelt [Acta Phys. Pol. 27, 831–841 (1965)]. Here, a useful numerical treatment of the same problem is presented. A computer model for this numerical formulation has been implemented, and results have been obtained to compare with Westervelt's analytical results. Comparison is also made between numerical results and relevant experimental data found in the literature.
J. Donald Harris: The humanist and the scientist
Authors: Yonovitz A.
Published: October 2005

J. Donald Harris was born in Brownsburg, Pennsylvania. From an early age, his thoughts and efforts have been devoted to the auditory world and its significance to the human condition. In 1942, he received his Ph.D. in psychology from the University of Rochester. He began conducting research and became head of the Auditory Research Laboratory at the Naval Submarine Medical Research Laboratory in Groton, Connecticut. He continued in that position until his retirement in 1979. He maintained appointments with the Doctoral Program at the City University of New York and the Departments of Speech and Psychology at the University of Connecticut. During his career, he published over 160 articles, including chapters, books, and monographs on subjects ranging from physiological and psychological acoustics to audiology and education. He was the Editor in Chief of the Journal of the American Auditory Society (Ear and Hearing). J. Donald Harris was also the founder and editor of the Journal of Auditory Research. It provided a vehicle for dissemination with a philosophy embracing interdisciplinary acoustics and the advancement of the sciences of hearing. Don provided a modiolus for the student, researcher, and clinician to relate the needs of the human to the research laboratories in hearing. His writing is a gift to those whose efforts are designed to infuse humanitarian sentiments in science. He will be greatly missed.
Acoustic processing as a basis for navigation by divers
Authors: Hollien Harry
Published: October 2005

Divers traditionally experience substantial difficulty when they attempt to navigate distances underwater. In air, of course, they enjoy good vision plus other sensory cues to accomplish this task. However, when submerged, the diver's visual modality is sharply impaired and, in a sense, he or she is left virtually blind. In many cases, divers attempt to navigate by means of compass settings (dead reckoning), but relevant research has demonstrated that this approach leads to unacceptable errors. Thus it appeared that some other, more efficient, approach needed to be developed. A number of experiments on this topic have been conducted and reported; the overall program was stimulated to a great extent by interface with Donald Harris. The basic approach employed focused on the abilities of divers to navigate by responding to programmed acoustic signals. That is, it had been noted that sound can be made to (perceptually) “move” underwater if it is serially shifted from transducer to transducer. This perception is referred to as the underwater auditory phi phenomenon (UAPP); it greatly aids in sound localization and, ultimately, navigation. Indeed, for diver retrieval, this phenomenon is so powerful that no subject in any of these experiments has ever swum to an area except that from which the source signal emanated. Previously published data will be reviewed briefly; new data on the effects of training and error magnitude will be presented and discussed.
Speech intelligibility for normal and hearing-impaired individuals under “everyday” conditions of acoustic distortion
Authors: Lacroix Paul G.
Published: October 2005

The intelligibility of speech in daily life is often made difficult when acoustic distortions are either produced at the source by the talker, or induced elsewhere in the process of transmission to the listener. Many variables must be defined, ordered, and controlled before the relative and combined contribution of acoustic distortions under “everyday” conditions can be examined. The task of attacking such a multivariate problem is so daunting as to discourage all but the most ambitious researchers, but the benefit of obtaining information so relevant to the handicapping effects of hearing loss in the real world led J. D. Harris to set his formidable intellect to the task with vigor and fervor. This paper explores his views and approach to answering questions such as: What constitutes the domain of “everyday” acoustic distortions? How should speech intelligibility be measured to capture real world validity and utility? What effects are produced by “everyday” acoustic distortions when the listener is hearing impaired? Can a valid sample of “everyday” listening conditions be developed?
Observable-based hybrid ray-mode-resonance system parametrization of acoustic scattering by a finite submerged steel plate
Authors: Felsen L. B. , Kapoor T. K.
Published: October 2005

Numerical finite difference data for pulse scattering by a submerged steel plate of finite width, when processed in the slowness-time domain [J. R. Fricke and A. B. Baggeroer, J. Acoust. Soc. Am. Suppl. 1 88, S51 (1990)], reveals distinct features related to the longitudinal and flexural modes in the plate, their excitation by, and conversion to, edge-diffracted fields in the fluid, and other wave-oriented observables. By an observable-based parametrization (OBP), the problem is phrased here systematically and phenomenologically in terms of ray fields, traveling mode fields, edge coupling matrices, resonances, etc., to build up a self-consistent OBP system format for quantitative prediction. Determination of the elements in the coupling matrices poses a set of canonical problems that can be addressed analytically under highly simplified conditions but must generally be done numerically or by experiment. For the very specialized case of a thin plate under heavy fluid loading, the plate supports only one subsonic wave, and single-edge diffraction has been evaluated analytically [D. C. Crighton and D. Innes, Philos. Trans. R. Soc. London Ser. A 312, 291–341 (1984)]. This solution has been employed in the OBP algorithm to synthesize and compute the far-field acoustic response to on-plate line force excitation of a finite strip. The result is compared with a differently synthesized solution by Crighton. [Work supported by ONR.]
Acoustic radiation from fluid-loaded structures with discontinuities
Authors: Thompson Charles , Mehta Vineet , Sen Rahul
Published: October 2005

The presence of discontinuities, such as joints, in a fluid-loaded structure results in far-field acoustic radiation even when subsonic wave numbers prevail in the main body of the structure. The object of this study is to develop a rational model of this phenomenon using singular perturbation methods. When a flexural wave in a thin structure impinges on a joint, evanescent structural displacement fields are set up in the vicinity of the joint. It is proposed to show that these fields are associated with rotation-dominated modes that are supported by shear-corrected plate theories of the Timoshenko-Mindlin-type flexural mode. The method of matched asymptotic expansions will be used to obtain mode-conversion coefficients, and it will be shown that the spatial wavenumber spectrum of the local field is instrumental in setting up an acoustic far field in the surrounding fluid. An important mathematic issue is the proper description of evanescent fields; this analysis will be based on results obtained previously in connection with acoustic waveguides.
Numerical implementation of ray-acoustic algorithm for sound wave scattering by submerged elastic spherical shells
Authors: Ho J. M. , Gao X. J. , Felsen L. B.
Published: October 2005

The rigorously derived ray-acoustic algorithm for source-excited fluid-loaded thin elastic spherical shells [J. M. Ho and L. B. Felsen, J. Acoust. Soc. Am. 88, 2389–2414 (1990)] is implemented numerically for far-field plane-wave and point-source scattering, and is compared with reference solutions based on exact spherical harmonic expansions. These comparisons permit an assessment of the range of applicability of thin-shell theory, and they indicate when and how [cf. S. P. Kargl and P. L. Marston, J. Acoust. Soc. Am. 85, 1014–1028 (1989)] the algorithm should be modified phenomenologically to accommodate thick shells. The generally good agreement between the observable-based ray-acoustic algorithm and the reference solution provides further confirmation of the utility of the physically incisive ray acoustic parametrization for this canonical problem. Some preliminary results are presented for applying the ray-acoustic scheme to a rigidly baffled hemisphere. [Work supported by ONR and DTRC.]
Finite-element analysis of airfoil vibration using variable thickness plate elements
Authors: Zoccola Paul J. , Hwang Yun-Fan
Published: October 2005

A NASTRAN finite-element model has been developed for calculating the mode shapes and frequencies of a cantilever beam with airfoil cross section. This model uses QUAD4 elements and takes advantage of the feature allowing a different thickness at each node on the element. This feature is particularly attractive for modeling the trailing edge (wedge) section of the airfoil. Numerical results are compared with those from a model of the same beam using solid (HEXAI) elements and with an experimental modal analysis. For bending modes, the results from the QUAD4 and HEXAI models agreed well with experimental results but the HEXAI model required a much greater number of nodes and much more computer time. For torsional modes, however, a discrepancy exists in the calculated modal frequencies between the QUAD4 and HEXAI models. Reasons for this discrepancy are discussed. The chordwise modal behavior of the airfoil and its influence on the vibroacoustic response are also discussed.
Wave propagation below the ring frequency on fluid-loaded cylindrical shells
Authors: Means Steven L.
Published: October 2005

Williams, Houston, and Bucaro [J. Acoust. Soc. Am. 87, 513–522 (1990)] have published experimental and theoretical helical wave spectra for a point-driven, fluid-loaded shell. A previous attempt (qualitatively successful) by Kouzoupis [J. Acoust. Soc. Am. Suppl. 1 87, S163 (1990)] to explain these spectra in terms of the wave theory of structural acoustics was based on a model that neglected fluid loading in first approximation, but which included it as a correction in a somewhat simple manner. The present paper reexamines the problem with a wave theory of shells that takes fluid loading into account at the outset. The wave theory interprets the helical spectra as a plot within the wavenumber plane (kx vs ky) for fixed angular frequency ω, derived from a dispersion relation F(kx,ky,ω)=0, whose from has nothing to do with the manner of excitation. The more complete analysis produces curves that have shapes that resemble a figure 8, when ω is less than the ring frequency, but a simplified analysis that takes the shell to be arbitrarily thin produces two hyperbolas. The top and the bottom of the eight are sensitive to the shell thickness, and an asymptotic theory is described that shows just how this feature varies with thickness. [Work supported by ONR and by the William E. Leonhard endowment to Penn. State Univ. The author acknowledges the advice of A.D. Pierce.]
Minimal spectral contrast for vowel recognition as a function of spectral slope
Authors: Lea Andrew , Summerfield Quentin
Published: October 2005

Can listeners locate formants not only from peaks in the envelope of the excitation pattern of a vowel, but also from “shoulders”—features giving rise to zero crossings in the third, but not the first, differential of the excitation pattern—as hypothesized by Assmann and Summerfield [J. Acoust. Soc. Am. 85, 327–338 (1989)]? Stimuli were steady-state approximations to the vowels/a, i, ɜ, u/created by summing the first 45 harmonics of 100 Hz. Thirty-nine harmonics had equal amplitudes; the other six formed three pairs that were raised to define three “formants.” An adaptive psychophysical procedure determined the minimal difference in level between the 6 harmonics and the remaining 39 at which the vowels were identifiably different from one another. These thresholds were measured through simulated communication channels giving overall slopes to the excitation patterns of the vowels ranging from −1 dB/erb to +2 dB/erb. Excitation patterns of the threshold stimuli were computed and the locations of formants were estimated from zero crossings in the first and third differentials. With sloping frequency responses, some formants of some vowels were represented as shoulders rather than peaks, confirming Assmann and Summerlield's hypothesis. Implications for models of formant extraction will be discussed.
Evidence for a rhyme and onset model of lexical access in children
Authors: Murphy W. D. , Gerken L. , Cooper R. P. , Aslin R. N.
Published: October 2005

A previous report [Murphy et al., J. Acoust. Soc. Am. Suppl 1 87, S73 (1990)] indicated that 4-year olds do not process spoken words and nonwords in a strict left-to-right manner. Instead, in a matching task they appear to search for the longest uninterrupted sequence of segments or to use a rhyming strategy. This poster reports the results of two subsequent studies designed to determine which of these two strategies was employed. The first follow-up study presented children with comparison items that shared the same number of uninterrupted segments as the target word (“little”). Some comparison items rhymed with the target (“gittle”), and others did not (“litten”). Results did not support the uninterrupted-segment matching model but were consistent with the rhyming model. A second follow-up study used monosyllabic stimuli. Results suggested that (1) children treat words with semivowel second syllable consonants as monosyllabic. and (2) both rhyme and similarity of the onset consonant-vowel sequence play a role in lexical access.
Effect of consonant-vowel intensity ratio on the intelligibility of spectrally degraded speech
Authors: Balakrishnan Uma , Freyman Richard L. , Chuan Chiang Yuan , Nerbonne G. Patrick , Shea Kelly J.
Published: October 2005

Normal-hearing subjects' recognition of spectrally degraded speech was evaluated under conditions where the waveform envelope was modified by altering the consonant-vowel intensity (C-V) ratios. Subjects were required to identify 22 consonants presented in the /a-Consonant-a/ format at suprathreshold and near threshold levels of presentation. In both conditions, the stimuli were processed to limit spectral information. In the suprathreshold condition, stimuli were presented at the natural C-V ratio and at six modified C-V ratios. In the near threshold conditions, three C-V ratios were employed—the natural ratio and two altered C-V ratios. The effect of C-V ratio modification on recognition performance varied across consonants. Within groups of consonants, “high” or “low” C-V ratios predisposed listeners to select certain consonants as the response. For example, for high C-V ratios of the stimuli /afa/ and /asa/, listeners selected /asa/ as the response. For low C-V ratios of these consonants, the predominant response was /afa/. Similar C-V ratio-dependent responses were also obtained for the glide and nasal consonant groups. Finally, for some consonants such as the stops, C-V ratio modification did not affect recognition performance. Results from both studies suggest that in the absence of spectral information, listeners depend on the envelope cues available in the speech waveform for speech sound recognition. [Work supported by the Whitaker Foundation.]
Interference for “new” versus “similar” vowels in Korean speakers of English
Authors: Cowie Islay , Jun Sun-Ah
Published: October 2005

Flege (1986, 1987) proposed that although the degree of establishment of a “new” phonetic category in the L2 is proportional to the degree of experience in the L2, equivalence classification prevents adult L2 learners from establishing a phonetic category for “similar” L2 phones. This paper examines the similar English vowels, /i, u, ʌ/, and the new English vowels /ɪ, ᴜ/, in productions by Korean-English bilinguals with different degrees of their experience in English and compares with those of English monolinguals. Also, formant values of the Korean vowels were compared between these Korean-English bilinguals and monolingual Koreans (Seoul dialect) to see whether the L2 acquisition affects their Korean production. Preliminary results partially support Flege's hypothesis. Productions of the new English phones were closer to the English norm than that of the similar phone /ʌ/, but only for highly experienced bilinguals. On the other hand, the monolingual norms for the similar phone /i/ are too close to be called merely similar, whereas those for /ʌ/ seem acoustically too different to be categorized as similar. Thus Hege's notion of similar phone needs to be refined or restricted.
The analysis of F reset in relation to phrase dependency structure
Authors: Sagisaka Yoshinori
Published: October 2005

In Japanese speech, the reset of phrasal F0 downtrends has mainly been analyzed with respect to the number of prosodic units (lg) between the phrase preceding the boundary and the phrase it directly qualifies. This parameter reflects the local structure of the sentence following the boundary and corresponds to the forward limit of local F0 control. In the analysis, an additional parameter (ld) that reflects the left local structure of the sentence is introduced. This parameter is the number of units that modifies the phrase preceding the boundary. To measure the F0 reset, the ratio (F0r) of the averaged F0 values of the phrases preceding and following the boundary is used. Here, F0 reset at right-branching boundaries is expressed as “F0r > 1 when lg > 1.” Using these two parameters lg, ld and the average F0 ratio F0r F0 resetting phenomena were analyzed quantitatively at about 2000 phrase boundaries in 500 sentences. The results show that (1) F0r increases in proportion to lg, (2) at right-branching boundaries (lg>2), F0r increases in proportion to ld, and (3) at left-branching boundaries, there is no strong correlation between F0r, and ld, and F0r, is greater than 1 only at clause boundaries or when a following unit is a headlike one. Moreover, it is also observed that F0r, is larger at coordinate phrase boundaries than at other boundaries. These facts support the usefulness of the new parameter ld and will contribute to the quantitative treatment of F0 control for speech synthesis.
Speaker-independent speech recognition with word models generated from written text
Authors: Bocchieri E. L. , Wilpon J. G.
Published: October 2005

Most current subword-based recognition systems require manual generation of the lexical transcription of vocabulary words. In addition, they generally use application specific data to train the acoustic subword models. Hence, a new database is collected for every task. This study shows that the generation of application specific word models can be completely automated by combining application-independent phonetically based subword models according to a lexicon provided by a text-to-phone transcriber. Continuous-density hidden Markov models of a set of phonetic units have been trained with the segmental K-means parameter estimation algorithm for both the TIMIT and the DARPA Naval Resource Management speech corpora. Each new (application specific) vocabulary word is typed into a text-to-phone converter [M.D. Riley, Proc. ICASSP, 1991 (to appear)] that provides different transcriptions ranked in order of likelihood. The most likely transcription is used to combine phone models into a word model. System evaluation is performed on a 147-item vocabulary {e.g., digits, numerals, words, and two-word phrases) chosen independently from the training data and collected from ten speakers in an office environment {i.e., a different environment than was used to record the training data). The experimental evaluation made use of initial and final silence models, first- and second-order energy and cepstrum derivatives, and state duration models. Currently, the recognition accuracy on the entire vocabulary is 90.0% and 97.8% on a 20-word subset (of 24 syllable words). These accuracies are consistent across the two different training corpora.
Auditory-contrast sensitivity in normal and hearing-impaired listeners
Authors: Hillier David A. , Miller James D.
Published: October 2005

The peak-to-valley ratio (depth of modulation in dB) of sinusoidal spectral envelopes necessary to distinguish such modulated spectra from flat spectra was investigated in several experiments. In addition, several adaptation experiments were performed to test the hypothesis of envelope frequency channels in the auditory system similar to spatial frequency channels in the visual system. Factors in hearing impairment that lead to contrast enhancement (recruitment) and contrast reduction (loudness saturation and loss of spectral resolving power) are discussed. Finally, auditory contrast sensitivity functions for two hearing-impaired subjects are presented.
Auditory processing of complex signals using the multichannel EWAIF
Authors: Anantharaman Jayanth , Feth Lawrence L. , Krishnamurthy Ashok K.
Published: October 2005

The envelope weighted average instantaneous frequency (EWAIF) has been used to model listener performance in complex signal discrimination [L. L. Feth, J. Acoust. Soc. Am. Suppl. 1 88, S48 (1990)]. Previous work with EWAIF has involved narrow-band signals that are confined entirely to a single critical band; consequently, it is sufficient to compute a single EWAIF value from the signal. Here, the application of EWAIF to wideband signals is extended. The signal is first passed through the gamma-tone filter bank of the Patterson-Holdsworth auditory sensation processing model [R. Patterson, J. Acoust. Soc. Am. Suppl. 1 88, S26 (1990)] and an EWAIF is computed from the output of each channel. This leads to a vector of EWAIF values, which are used in two ways: (1) the EWAIF values from the different channels are combined back into a composite EWAIF value, which is then used to model listener performance in complex sound perception such as profile analysis, comodulation masking release, and modulation masking; and (2) the vector of EWAIF values is used as a feature vector in a vowel recognition task. Preliminary results will be presented and further modifications to the model discussed. [Work supported by a grant from AFOSR.]
A new technique for measuring spectral shape discrimination
Authors: Kidd Gerald , Mason Christine R.
Published: October 2005

A new technique for measuring the ability of listeners to discriminate between sounds on the basis of spectral shape—called “auditory profile analysis”—is described. In this technique, the signal is a series of intensity increments and decrements to an equal-level multitone reference spectrum. For any stimulus trial, the signal is either an intensity increment to the odd-numbered tones and an intensity decrement to the even-numbered tones, or vice-versa. The advantage of the technique is that it reduces, by one-half (in a two-down, one-up adaptive procedure), the range of the random, within-trial rove in overall level needed to limit the usefulness of level cues. Using this technique, discrimination performance was measured for a group of normally hearing listeners for broadband, low-pass, and high-pass filtered conditions, and for individual hearing-impaired listeners. The results indicated that the new technique appears to be well suited for studying auditory profile analysis in hearing-impaired listeners where the range of sound intensities that may be presented is often quite limited. [Work supported by NIH/NIDCD.]
Gap thresholds obtained with auditory steady-state responses
Authors: Champlin Craig A.
Published: October 2005

Human gap thresholds were obtained electrophysiologically using auditory steady-state responses (ASRs). Three types of stimuli-bandpass, low-pass, and high-pass noise—were presented at three sensation levels (30, 50, and 70 dB SL). The cutoff frequency for the latter two noises was 1000 Hz. The otherwise-continuous stimuli were interrupted 40 times/s, thus creating a repetitive sequence of gaps. The duration of the gap was 0, 2, 4, 6, 8, 10, 15, 20, or 24 ms. The magnitude and phase of the time-averaged ASRs were obtained for each stimulus condition. Gap thresholds obtained with the bandpass and high-pass noises were similar, while thresholds obtained with the low-pass noise were larger. These results are consistent with existing psychophysical data.
Effects of temporal-envelope correlation on the strength of vertical fusion of noise-band pairs
Authors: Rappold P. W. , Mendoza L. L. , Collins M. J.
Published: October 2005

Vertical fusion is the perceptual grouping of co-occurring auditory signals into a single acoustic event. In contrast, horizontal streaming is the perceptual grouping of auditory signals occurring in a temporal sequence. In the present experiment, “strength” of fusion was inferred from the interstimulus interval (ISI) necessary to evoke a predominant percept of horizontal streaming rather than vertical fusion. Perceptual grouping heuristics suggest “strength” of fusion is greater for AM noise bands with correlated temporal envelopes than for AM noise bands with uncorrelated temporal envelopes. It was therefore predicted that a shorter ISI would be necessary to shift the percept from vertical fusion to horizontal streaming when noise-band envelopes were correlated than when they were uncorrelated. This prediction proved accurate for two of four subjects. The remaining two subjects, however, showed no significant difference between the ISIs needed to shift the percept from fusion to streaming. The results will be discussed in reference to implications for the bases of the comodulation masking release phenomenon.
Gender classification based upon statistics of the spectral distributions: Walking perception
Authors: Li Xiao-Feng , Pastore Richard E. , Logan Robert J.
Published: October 2005

The current study continued the previous research using as stimuli the sounds of humans walking on a hard surface [Li et al., J. Acoust. Soc. Am. Suppl. 1 87, S24 (1990)] to investigate the acoustic properties that delineated categories of ecologically valid auditory source events. Various statistics of the walking spectra were computed, and subjected to a factor analysis in order to identify the spectral properties that differentiated between actual gender class of source events (male and female walkers). Two classes of information were identified as important in distinguishing between the male and female spectra: (1) central tendency and (2) slopes of spectral attack and decay. A multiple regression analysis indicated the importance of these classes of information in determining the perception of the walker gender. A follow-up experiment then manipulated these statistical properties to verify their contributions in the perceptual classification of walker gender. [Work supported by NSF.]
Short-range surface and bottom backscattering strength measurements from the CEAREX 89 arctic experiment
Authors: Hayward Thomas J. , Yang T. C.
Published: October 2005

Short-range SUS reverberation data collected during the CEAREX 89 experiment in the Norwegian/Greenland Sea are analyzed to extract under-ice and bottom backscattering strengths from direct-path measurements. Because of the mildly bistatic experimental geometry, propagation paths with different grazing angles contribute to the reverberation at the same time; therefore, a least-squares method is used to recover the angular dependence of backscattering strength. Ice backscattering strengths are compared with the results of Milne, while bottom backscattering strengths are compared with results for similar ocean bottoms. [Work supported by ONR arctic sciences program.]
The effects on long-range ocean acoustic propagation of step-periodic roughness along the interface of a shear-supporting basement
Authors: Chin-Bing Stanley A. , Murphy Joseph E.
Published: October 2005

It has been observed [Evans and Gilbert, J. Acoust. Soc. Am. 77, 983–988 (1985)] that one of the effects of ocean subbottom roughness is to slightly decrease the acoustic propagation in the ocean waveguide. While this transmission loss is small, it is cumulative and the net effect over a long range can be a significant decrease in the received acoustic signal. To demonstrate this cumulative loss, Evans and Gilbert used a full-wave range-dependent coupled mode model (COUPLE) to account for backscatter from a periodic-step subbottom. COUPLE represented a significant advancement in ocean acoustic propagation modeling since it could correctly include the coupled backscattered acoustic field due to range variations in the ocean boundaries. Their roughness simulation has been duplicated using our full-wave range-dependent finite-element ocean acoustic models (FOAM, FFRAME, and PE-FFRAME) and also included the effects of ocean subbottom compression-shear conversion using this full-wave range-dependent finite-element ocean seismoacoustic model (SAFE). Using a cw full-field backscatter method, it has been possible to isolate the various effects due to the shear and roughness to give insight into the complicated processes that account for cumulative losses over long ranges. [Work supported by ONR/NOARL.]
Scattered field calculations for three-dimensional fluid-elastic interfaces
Authors: LePage Kevin , Schmidt Henrik
Published: October 2005

The calculation of the three-dimensional scattered field caused by the insonification of two-dimensionally rough interfaces in horizontally stratified elastic media is discussed. In general, the scattered field may be calculated either deterministically for a realization of surface roughness, or stochastically as scattered covariances for a surface with a specified roughness power spectra. The perturbation method of Kuperman and Schmidt [J. Acoust. Soc. Am. 86, 1511–1522 (1989)] is used in the full three-dimensional formulation to model an isotropically rough elastic ice plate floating over a fluid half-space. Scattered field realizations are calculated for the point source configuration, exhibiting the antiplane shear (SH) coupling unique to the 3-D model. The ability of explosive sources in the water column to generate SH waves in ice has been observed experimentally and it is argued that rough surface scattering is the likely mechanism that facilitates this mode conversion. [Work supported by ONR.]
Estimation of boundary layer transition noise from velocity measurements
Authors: Krane Michael H. , Pauley Wayne R.
Published: October 2005

Velocity measurements of artificially generated flow structures in the transition region of an incompressible boundary layer with zero pressure gradient are described. These measurements made in a laminar flow water channel allow calculation of the velocity normal to the wall in a turbulent spot. This velocity specifies the linearized boundary condition for the acoustic equation at the wall. The approach relates the radiated noise to fluctuations in the normal velocity at the plate through fluctuations in the displacement thickness. Although this approach has been previously proposed [H. W. Liepmann, unpublished (1954), J. Laufer, J. E. Ffowcs-Williams, and S. Childress, AGARDograph 90, 39–42 (1964), G. C. Lauchle, J. Acoust. Soc. Am. 69, 665–671 (1981), G. C. Lauchle, ASME NCA 5, 31–38 (1989)] it has never been applied. The results of these experiments will be compared to concurrent experiments run in an anechoic wind tunnel. Ultimately this work will be extended to naturally occurring structures in the transition region. [Work supported by ONR under Grant ♯N00014-90-J-1365.]
Choked-jet edge-tone experiments
Authors: Powell Alan , Lin Dan
Published: October 2005

Some experimental results for a choked jet from a 4.8∂:∂ rectangular orifice impinging on a long 8° (w)edge are presented. For nozzle-edge distance h> three cell lengths, < 15∂ and in the pressure ratio range 2.09 to 3.31, violent edge-tone oscillations occur that may be above, approximately equal to and merge with, or below the frequency of the simultaneous single screech mode of the free jet. The pressure field (≈evanescent waves) of the growing sinuous jet instability are clearly visible in Schlieren photographs, as is the associated periodic asymmetrical sound field. Preliminary estimates indicate consistency with the proposed feedback formula for the fundamental acoustic wavelength λ [Powell, Acoustica 3, 233–243 (1953)], h′/λ = (N + p) × (Mcon)/(1 + Mcon) with: instability convection Mach number Mcon≈0.5–0.7; nozzle to acoustic source distance h′ ≈ h + 14 × (sinuous instability wavelength); integral number of cycles in the feedback loop N = 4, 5, or 6 with p≈0.4±0.2. Normal hysteretic jumps appear negligible, but other hysteretic effects are suspected. [Partial support from the Texas Advanced Research Program.]
Screech: Edge-tone-like behavior induced by a small plate
Authors: Powell Alan , Umeda Y. , Ishii R.
Published: October 2005

The dominant screech frequency of round choked jets falls steadily with increasing pressure ratio, interrupted by jumps as the jet instability mode—A1 and A2 (toroidal), B (sinuous), C (helical), and D (sinuous again≈B)—changes. A small normal plate (diam/nozzle diam = 0.35) on the axis radically changes the behavior. Preliminary results indicate that oscillations in the screech frequency range take place only in four “preferred” frequency bands, three being narrow of constant frequency, separated by prominent “dead” bands of no activity. With variable nozzle-plate distance, the composite plot for all pressure ratios shows each composite band to be reminiscent of classical sawtooth edge tones, with the number of cycles N in the apparent feedback loops from 2 to at least 8, with continuity of each N from band to band. But each band may contain more than one screech-like mode: Just toroidal for the band of highest frequency, then sinuous and helical, then sinuous, helical and sinuous again and finally just sinuous for the lowest frequency band. [Partial support from the Texas Advanced Research Program.]
Reflection coefficient of a fluid-loaded anisotropic plate
Authors: Chimenti D. E. , Rokhlin S. I.
Published: October 2005

The acoustic reflection and guided wave behavior of an orthotropic plate immersed in an ideal fluid is examined as a function of fluid loading. Coincidence of zeros and real parts of reflection coefficient poles occurs only in the limit of vanishing or infinite fluid density. The modification of the pole and zero plate spectra in the presence of a variable fluid density will be discussed in the context of Lamb wave measurements on low density solid plates, such as graphite-reinforced plastics (GRP). Numerical results are presented showing functional dependence of pole and zero branches on fluid density and plate elastic properties at constant phase velocity or constant frequency-thickness product. It will be shown that propagating and evanescent wave modes exchange portions of their branches, and that reflection coefficient zeros also undergo extensive, but differing, transformations. Even very low fluid density (< 0.1 g/cm3) values can cause significant changes in the wave behavior of the fluid-loaded GRP plate. Fluid loading transforms the wave spectrum from Lamb waves in a traction-free plate to “constrained-slip” waves in a plate satisfying mixed boundary conditions.
Measurement of unsteady pressure and shear stress using surface acoustic wave devices
Authors: Macrorie Michael , Varadan Vasundara V. , Pauley Wayne R.
Published: October 2005

A new technique is being investigated for the direct measurement of surface stresses (both pressure and shear) in Steady and unsteady wall bounded flows. The technique utilizes surface acoustic wave (SAW) devices. A first generation sensor has been used to measure mean wall shear stress beneath a turbulent boundary layer at speeds from 10 to 20 m/s in air. Good agreement with a standard technique was found. To demonstrate the dynamic response, an artificially generated vortex structure was propagated over the SAW sensor. The time dependent pressure and shear stress oscillations due to the passage of the unsteady vortex were measured by the SAW sensor and compared with the response of a hot wire probe. Further reduction in the size of the sensors, multiple sensing elements, and refinement of the calibration technique will produce sensors capable of resolving the full stress vector due to near wall flow structures in transitional and turbulent boundary layers. [Work supported by ONR under Grant No. N00014-89-J-3102.]
Slowly varying method for high-frequency scalar scattering problems
Authors: Zhu Han
Published: October 2005

A new formulation called the slowly varying method (SVM) is proposed to asymptotically solve high-frequency scalar scattering problems. It is known that, excited by a plane harmonic incident wave U0(x) impinging on a scatterer, the scattered field U(x) for Neumann B.C. or ∂U(x)/∂n for Dirichlet B.C. shows strong oscillation on scatterer when ka ≫ 1. Here k is wave number and a is typical scatterer dimension. The paper shows that the function V(x) = U0*(x)U(x) for Neumann B.C. or Vn(x) = U0*(x)∂U(x)/∂n for Dirichlet B.C. exhibits much slow variation on scatterer for the same ka for some cases. Here U0*(x) is the complex conjugate of U0(x). The relations among V(x), Vn(x) and the acoustic energy densities have been analyzed. A new boundary integral equation in terms of unknown V(x) has been derived and either solved by BEM or simplified by asymptotical approximations. For the former case, the requirement that the boundary element dimension be proportional to 1/(ka) may be waived for obtaining satisfactory numerical results. For the latter case, a nonelement numerical solution of V(x) has been obtained by an algebraic arithmetic. Some numerical results have been presented in the paper.