bluuebunny/crossref_metadata_2025 huggingface dataset:
Geoacoustic propagation through random seafloor models
Authors: Dougherty M. E. , Stephen R. A.
Published: October 2005

Finite difference forward models of elastic wave propagation through laterally heterogeneous upper oceanic crust are presented. The finite difference formulation is a two-dimensional solution to the elastic wave equation for heterogeneous media and implicitly calculates P and SV propagation, compressional to shear conversion, interference effects, and interface phenomena. Random velocity perturbations with Gaussian and self-similar autocorrelation functions and different correlation lengths are presented that show different characteristics of secondary scattering. The presence of a water-solid interface in the models allows for the existence of secondary Stoneley waves, which account for much of the seafloor noise seen in the synthetic seismograms for the laterally heterogeneous models. “Random” incoherent secondary scattering increases as the product of wavenumber and correlation distance (ka) approaches 1. Deterministic secondary scattering from larger heterogeneities is the dominant effect in the models as ka increases above 1. Secondary scattering also shows up as incoherence in the primary traces of the seismograms when compared to the laterally homogeneous case. Cross-correlation analysis of thc initial P-diving wave arrival shows that, in general, the correlation between traces decreases as ka approaches 1.
Sound scattering from a randomly rough fluid-solid interface
Authors: Dacol Dalcio K. , Bennan David H.
Published: October 2005

A general formalism for acoustic scattering from a fluid-elastic solid interface is developed. The theory parallels Waterman's work [P. C. Waterman, J. Acoust. Soc. Am. 45, 1417 (1969)], based on the extinction theorem, for acoustic scattering from inpenetrable surfaces. This formalism is then used to study the scattering of sound waves from a randomly rough fluid-solid interface by using perturbation theory to solve the equations for the scattering amplitudes to second order. The Watson-Keller renormalization ansatz [J. G. Watson and J. B. Keller, J. Acoust. Soc. Am. 74, 1887 (1983)] is then used to account for some multiple scattering effects beyond double scattering. A numerical study is presented comparing acoustic scattering in the fluid from a fluid-solid interface with acoustic scattering in the same fluid from a hard, impenetrable surface (Neumann boundary condition). Substantial differences between the two cases are found. Besides the expected acoustic energy loss by transmission into the solid, it was also found that the angular distribution of the remaining acoustic energy that is reflected and scattered by the fluid-solid interface differs greatly from the hard impenetrable surface case, especially near grazing incidence and scattering angles.
Comparison of tissue composition models via the measurement of the nonlinear parameter of mixtures
Authors: Everbach Erich Cart , Apfel Robert E.
Published: October 2005

Recently, several models have been proposed for predicting tissue composition (percent water, protein, and fat) from physical measurements made on the bulk material [Sehgal et al., Ultrasound Med. Biol, 12, 865–874 (1986); and R. E. Apfel, J. Acoust. Soc. Am. 79, 148–152 (1986)]. Each model requires the measurement of several bulk properties such as density, sound velocity, and the acoustic nonlinearity parameter B/A. These models are intended to aid the diagnosis and analysis of tissue pathology. They also share with acoustic absorption and nuclear magnetic resonance (NMR) techniques the prospect of elucidating the characteristics of intermolecular interactions in tissues. As reported at a previous meeting [E. C. Everbach and R. E. Apfel, J. Acoust. Soc. Am. Suppl. 1 80, S4 (1986)], a system to accurately measure the B/A value of liquids and semiliquid substances has been developed. In order to assess the sensitivity of the tissue composition models to differences in molecular structure, B/A has been measured systematically for various proteins and lipids for which acoustic absorption and NMR data are known. To determine the validity of each model, the bulk properties of water-protein-fat mixtures are measured and the model's predictions to the known composition of each mixture are compared. Using the data obtained, the existing models will be compared and suggestions for extending them to more general systems will be offered. [Work supported in part by the U.S. Office of Naval Research and by the National Institutes of Health through Grant 2-R01-GM30419-04.]
Forced radial oscillations of single cavitation bubbles: A comparison of experimental and numerical studies
Authors: Holt G. , Crum L. A.
Published: October 2005

Refinements of an optical scattering technique previously reported [J. Acoust. Soc. Am. Suppl. 1 80, S24 (1986) and Suppl. 1 81, S26 (1987)] have made possible a quantitative comparison of the experimentally obtained radius versus time (R−t) curve with previously obtained numerical R−t results. The response of bubbles with equilibrium radii from 20–80 μ to a 22-kHz acoustic field is presented and compared to the results of previously published numerical models [see, for example, W. Lauterborn, J. Acoust. Soc. Am. 59, 283–293 (1976) and Miksis and Ting, J. Acoust. Soc. Am. 81, 1331–1340 (1987)]. [Work supported by ONR.]
Focal-point shifts for the reversed wave in acoustical phase conjugation experiments: Paraxial analysis and analogy with optical holography
Authors: Marston Philip L.
Published: October 2005

A phase-conjugate mirror is one that reverses an outgoing wave front so that it propagates back toward the source. Recent experiments [Kustov et al., Sov. Phys. Acoust. 31, 517–518 (1985)] indicate that wave front reversal can be established through the interaction of a pump wave of frequency f1 with a signal of frequency f2 that diverges from a point source. The nonlinear medium where the interaction occurs is a thin layer of gas bubbles in water. In these experiments, however, the frequency f3 of the reversed wave differed from f2 = 60 kHz since f3 = f1 − f2 = 40 kHz and f1 = 100 kHz. The present research is concerned with the use of a paraxial approximation to predict the location of the focal point of the reversed wave. The normals of the wave fronts of the interacting waves are assumed to be nearly perpendicular to the bubble layer. Let z2 and z3 denote the respective distances of the source and focal points from the layer. If the pump wave is a plane wave propagating perpendicular to the layer, the analysis gives z3 = (f3/f2)z2, so that z3≠z2 when f3≠f2. This result is analogous to the image location in optical holography for cases where the recording and reconstruction process are carried out at different wavelengths [J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, San Francisco, 1968)]. Other applications of this analogy will be noted. [Work supported by ONR.]
The acoustic limit of control of structural dynamics
Authors: von Flotow A. H.
Published: October 2005

The acoustic limit of active control of structural dynamics is investigated; the limit as the control bandwidth includes a very large number of natural modes of the structure. The point is made that, in this limit, modal analysis cannot provide reasonably accurate models of the structural dynamics and that control design with respect to modal models is then of questionable value. Alternative modeling approaches are reviewed. A particular wave propagation formalism, applicable to modeling the acoustic response of networks of slender structural members, is described in some detail. Control options designed with reference to this formalism are reviewed, and speculations as to future developments of such control are offered.
Bending-beam model of vocal-fold vibration
Authors: Bickley Corine , Brown Kevin
Published: October 2005

Recent theoretical developments have shown that a model based on the theory of bending beams is the best predictor of the fundamental frequencies of young children's speech [Bickley, Proc. 11th Int. Congr. Phon. Sci. (1987)]. For children of age 3 years and younger, the values predicted by a spring-mass model are too low, and the values of a vibrating-string model are too high. In the current study, the effect of growth of the vocal-fold structure on fundamental frequency is analyzed. The vocal-fold structure grows nonuniformly; for example, a 1-year-old's vocal folds are approximately one-fifth as long as an adult's folds but only 10% thinner. The bending-beam model is an improvement over other models because it reflects the structure of the vocal folds and the attachments of the vocal-fold tissue to the arytenoid and thyroid cartilages, characteristics previously ignored. The fundamental frequency of the new model depends on both the beamlike characteristics of the vocal folds and the springiness of the structure. Changes in fundamental frequency are predicted from the model as a function of age.
Voicing distinction for fricatives: Acoustic theory and measurements
Authors: Stevens Kenneth N. , Blumstein Sheila E. , Glicksman Laura B.
Published: October 2005

Theoretical analysis suggests that simultaneous generation of vocal-fold vibration and turbulence noise at a supraglottal constriction requires rather precise adjustment of the structures controlling the glottis, the intraoral volume, and the supraglottal constriction. The theory shows that there tends to be a reciprocal relation between voicing amplitude and the amplitude of the turbulence noise. It is not surprising, therefore, that vocal-fold vibration does not always occur throughout the constricted interval when a “voiced” fricative is produced, and that variation in the noise amplitude is often observed. Measurements of the amplitude of voicing (expressed as the spectrum amplitude in the region of the first harmonic) and of frication noise have been made for several fricative consonants spoken by several speakers in a number of phonetic environments, including utterance final and intervocalic position, and in clusters with other voiced and voiceless fricatives. Evidence for voicing can usually be found over some portion of the constricted interval, particularly in the vicinity of fricative onset or release. However, voicing may be weak or absent when the voiced fricative is followed in a cluster by a voiceless fricative. [Work supported in part by Grants NS-04332 and NS-15123 from the National Institutes of Health.]
Respiratory response to loss of velar resistance
Authors: Morr Kathleen E. , Putnam Anne H. B. , Warren Donald W.
Published: October 2005

The hypothesis that speech aerodynamics conforms to the principles of a regulating system was tested in nine normal adult subjects. The velar mechanism was perturbed by having subjects lower the soft palate during a series of words involving plosive consonants. The pressure-flow technique was used to measure oral pressures and velar resistance. Inductive plethysmography was used to measure tidal volumes associated with test consonants. The data indicate that intraoral pressure remained at appropriate levels (> 4.0 cm H2O) after loss of velar resistance. Tidal volume did not change during inspiration but increased during speech expiration. The difference was statistically significant (p < 0.01). These results support previous findings of Warren [Cleft Palate J. 23, 251–260 (1986)] in cleft subjects, Putnam et al. [J. Speech Hear. Res. 29, 37–49 (1986)] in perturbation studies, and Warren et al. [J. Acoust. Soc. Am. 67, 1828–1831 (1980), Folia Phoniatr. 33, 380–393 (1981), Folia Phoniatr. 36, 164–173 (1984)] in bite block studies that intraoral pressures are maintained at appropriate levels in the presence of lowered airway resistance. It is concluded that, under the test conditions, pressure was regulated by controlling respiratory effort. This compensatory response increased airflow rate and volume when resistance fell. [Work supported by NIDR.]
Stress effects on velic gestures
Authors: Krakow Rena Arens
Published: October 2005

In his cross-language survey of oral and nasal vowel patterns, Schourup [Work. Pap. Linguist. 15, 190–221 (1973)] reported that contextual vowel nasalization is more likely to occur in stressed syllables than in unstressed syllables. This study looks at how spatial and temporal patterns of velic movement are affected by stress and finds articulatory evidence in support of Schourup's claim. Vertical movements of the velum were monitored while the (American English) speaker produced utterances with different stress patterns (mVbVb vs mVbV́b; bV́bVm vs bVbV́m). Velic height measured at the midpoint of the vowels adjacent to the nasal consonants was significantly lower when the vowels were stressed. This pattern, however, primarily reflected temporal differences in the velic gestures due to stress rather than changes in the spatial extent of velic lowering for the nasal consonants. As an example, the velic lowering gestures for the initial /m/ in /mábab/ and /mabáb/ appeared quite similar both in their timing and spatial extent, but velic raising from the low position was initiated considerably later in /mábab/ than /mabáb/. These findings indicate that part of the articulatory distinction between syllables with different levels of stress is the temporal pattern of velic movement. [Work supported by NIH Grants NS-13617 and HD-1994.]
Evaluation of speech under stress and emotional conditions
Authors: Hansen John H. L. , Clements Mark A.
Published: October 2005

This paper presents results from an investigation of how stress and emotion affect speech characteristics with specific application to improving automatic speech recognition. Past studies have been limited in scope, often using only one or two subjects and analyzing only one or two parameters (typically involving pitch). A comprehensive speech under stress database has been established at Georgia Tech for the purposes of stress research. The database is partitioned into five domains, encompassing a wide variety of stresses that include: various talking styles (slow, fast, soft, loud, angry, clear, question, in noise), single and dual tracking workload stress inducing tasks, emotional speech from psychiatric analysis session, and subject motion-fear tasks. A total of 32 speakers was employed to generate in excess of 16 000 utterances. The database evaluation was partitioned into three areas. Analysis was first performed on (i) speech with simulated stress and (ii) speech from stress inducing workload tasks or speech in noise. Statistically significant parameters were established, and an equivalent analysis was carried out over (iii) speech produced under actual stress and emotion. This scheme was chosen since simulated conditions allowed for careful control of vocabulary, task requirements, and background noise characteristics. Evaluation over actual stress or emotional conditions was used to verify results established under simulated conditions. Variables employed in the evaluation include: pitch (mean, variance, higher moments, point process characterization), glottal waveform characteristics, glottal source spectrum (spectral tilt, energy concentration), duration, intensity, formant locations and bandwidths, vocal-tract shaping based on line spectral pair coefficients, and the variability of each of these. Resulting categorizations will be presented, as well as the statistical significance of each set of measurements. [Research supported by U.S. Army Human Engineering Labs.]
The control of voice onset time and vowel duration after paraneoplastic cerebellar degeneration: An acoustic study
Authors: Behrens Susan J. , Anderson Neil , Posner Jerome , Sidtis John J.
Published: October 2005

Speech production was examined in a group of six subjects with paraneoplastic cerebellar degeneration, a neurological disorder that produces severe dysarthria. Subjects were recorded repeating CVC and CVCV syllables that included the stop consonant [p b t d k g] and the vowels [i a u]. Vowel durations preceding voiced and voiceless segments and voice onset time (VOT) were measured. The vowel duration measures assessed the preservation of intrinsic duration properties, and the variation of these properties in conditioning phonological contexts. The VOT measure assessed the coordination of two independent articulatory events. Results indicated that the cerebellar subjects normally differentiated among individual vowels, and altered vowel duration as a function of phonological context. In contrast, they tended to reduce VOT for voiceless segments, and, in the case of the most impaired subject, the voiceless segments were always perceived as being voiced. Although the VOT durations were reduced, there was no overlap between voiced and voiceless VOTs for most cerebellar subjects. These results suggest that the temporal coordination of articulatory maneuvers rather than general timing of segmental duration may specifically involve the cerebellum. [Work supported by NS 17778.]
The control of voice onset time and vowel duration after paraneoplastic cerebellar degeneration: Correlation with regional cerebral glucose metabolism using positron emission tomography
Authors: Sidtis John J. , Behrens Susan J. , Moeller James R. , Strother Stephen C. , Anderson Neil , Posner Jerome , Rottenberg David A.
Published: October 2005

In a companion report, an impairment in voice onset time (VOT) control was described for a group of subjects with paraneoplastic cerebellar degeneration who could otherwise produce appropriate segmental duration. The underlying neurophysiological changes were related to regional cerebral metabolic rates for glucose (rCMRGlu) determined by F18-fluorodeoxyglucose/positron emission tomography (PET). Nine cerebellar subjects and 18 normal controls were studied with eyes patched while listening to music and periodic verbal briefings. The rCMRGlu was calculated for each of 28 anatomically defined regions of interest (ROI). The cerebellar subjects could be differentiated from normals by their lower global metabolic rate, and by their rCMRGlu pattern. For those cerebellar subjects who could participate in the acoustic study, cerebellar rCMRGlu was significantly below normal range (p < 0.05) in all but one case. Severity of VOT abnormality appeared to be related not only to cerebellar rCMRGlu, but to abnormally low cortical rCMRGlu as well. The role of the cerebellum in maintaining temporal coordination of articulatory maneuvers appears to involve the coordination of cortical and subcortical brain regions. [Work supported by NS17778 and NS23473.]
Acoustic analysis of hoarse voices in running speech
Authors: Muta Hiroshi , Baer Thomas , Fukuda Hiroyuki
Published: October 2005

A method of pitch-synchronous acoustic analysis of hoarseness requiring a voice sample of only four fundamental periods is presented. This method calculates a noise-to-signal (N/S) ratio, defined from the power spectrum, which indicates the depth of valleys between the harmonic peaks. A discrete Fourier transform based on a continuously variable window spanning exactly four fundamental periods is used to calculate the spectrum. A two-stage procedure is used to determine the exact duration of the four fundamental periods. An initial estimate is obtained using autocorrelation in the time domain. A more precise estimate is obtained in the frequency domain by minimizing the errors between the DFT and the predicted spectrum of a windowed harmonic signal. Analysis of synthesized voices shows that the N/S ratio is sensitive to additive noise, jitter, and shimmer, and is insensitive to slower (8 Hz) modulation in fundamental frequency and amplitude. An analysis of pre- and post-operative running speech of six patients with laryngeal polyps or nodules has consistently indicated the successful therapeutic results for all subjects. [Work supported by NIH Grant NS-13870.]
Fundamental frequency contours produced by normal and dysarthric speakers
Authors: Southwood Helen , Weismer Gary
Published: October 2005

Perceptual descriptions of dysarthric speech often include terms that are meant to index aberrancy in sentence-level fundamental frequency (F0) contours. Whereas there is general agreement that many dysarthric speakers produce “abnormal” F0 contours, two relevant issues that appear to be unanswered are: (1) How should “normal” F0 contours be characterized, and (2) what is the nature of F0 contours produced by dysarthric speakers. In the present paper, a report is made on a category approach to identifying ranges of normal F0 production in young adults and geriatrics, and then F0 contours of speakers with hypokinetic (due to Parkinson's disease) and spastic (congenital) dysarthria are shown. Discussion will focus on the success of the category system, and the motor control implications of the dysarthric F0 contours. [Work supported by NIH.]
Cycle to cycle spectral perturbations in the voices of female speakers
Authors: Yonovitz A. , Yonovitz L.
Published: October 2005

The glottal function was obtained through the use of a reflectionless tube. This tube acted as a pseudoinfinite termination of the vocal tract. Ten female speakers phonated a neutral vowel while target matching to a 210-Hz tone. The glottal waveform was digitized and each cycle was partitioned at zero crossings. This procedure provided an accurate determination of the period and separate timing measures for the positive and negative portions of the glottal pulse. Discrete Fourier analysis on each individual cycle indicated changes in the spectral content. The data showed a systematic change in the spectral parameters related to the open-close ratio for each cycle. Spectral perturbation analysis may be a more inclusive measure of waveshape changes than jitter or shimmer.
Modal contributions of a finite plate to power spectra
Authors: Ko Sung H.
Published: October 2005

The purpose of this work is to compare the modal contribution of a finite elastic plate to the power spectrum and the flexural wave contribution of an infinite elastic plate to the power spectrum. Flexural waves in an infinite plate submerged in a fluid produce pressure waves in the fluid that travel parallel to the plate and decay away from the plate surface in the fluid. These waves may be called evanescent waves and are strongest in a region near the plate where they may represent noise. When a rectangular plate submerged in a fluid is excited, the vibrating plate generates pressure waves that decay away from the plate surface in the fluid and an acoustic wave that radiates into the fluid. The analytical model considered here is a two-sided fluid-loaded rectangular plate simply supported at its boundaries and excited by a forcing function on one side of the plate. Theoretical analyses are discussed and the wavenumber-dependent transfer functions that are used for calculating power spectra are presented. [Work supported by NUSC.]
On a plate/surface wave mode selection criteria for ultrasonic evaluation in layered structures
Authors: Pilarski A. , Rose J. L. , Balasabramaniam K.
Published: October 2005

The choice of specific modes while utilizing plate or surface waves, in the ultrasonic evaluation of layered structures, is extremely critical, especially if the purpose is to tune our sensitivity to particular types of imperfections. A direct approach based on the analysis of each individual mode, for particular geometrical configuration and frequency content, is very time consuming. Therefore, it has been proposed [A. Pilarski, Arch. Acoust. 7, 61–70 (1982)] to use an indirect approach by comparing the dispersion curves for different material properties, geometrical constraints, boundary conditions, etc. In this paper, this technique has been applied to a three-layered aluminum-epoxy-aluminum adhesively bonded structure. This was achieved through the numerical solution of the characteristic equation for such a layered structure. The results thus obtained were verified through experimentally generating and studying the behavior of plate/surface waves in specially prepared Al-epoxy-Al bonded specimens with adhesive weaknesses. Both immersion and contact methods are applied in our experimental investigations.
Acoustically generated temperature gradients in plates
Authors: Muzzerall Michael , Atchley Anthony A. , Hofler Thomas J.
Published: October 2005

The results of measurements of thermoacoustically generated temperature gradients in short thin plates located in a resonant tube are reported. The temperature gradient, resulting from a heat flow generated by the acoustic field, is a function of the acoustic pressure amplitude, the Prandtl number of the gas, the configuration of the plates, and the position of the plates in the tube, Measurements were made for pressure amplitudes ranging from approximately 145–162 dB re: 20 μPa, in argon and helium, for single plates and stacks of up to five plates having separations from approximately 4 to 40 thermal penetration depths, and at various positions in the tube. The results are compared to predictions based on a theory by Wheatley and others [J. Wheatley et al., J. Acoust. Soc. Am. 74, 153–170 (1983)]. For pressure amplitudes below 150 dB, the measurements agree well with theory. At higher pressure amplitudes, the agreement diminishes, indicating the presence of effects not addressed by theory. [Work supported by NPS Foundation.]
Evaluations of single-channel and multichannel tactile aids for the hearing impaired
Authors: Weisenberger Janet M.
Published: October 2005

A number of single-channel and multichannel tactile devices for hearing-impaired persons have been evaluated in our laboratory over the last several years. Both commercially available and experimental devices have been tested, including the Tactaid I, II, and V, Minifonator, Minivib, Queen's University tactile vocoder (both laboratory and wearable versions), and Tacticon TC-1600. Normal-hearing and hearing-impaired adults, and hearing-impaired children, have participated in a variety of training tasks, employing both recorded and live-voice stimuli. These tasks include simple detection of sound, environmental sound identification, syllable rhythm and stress categorization, phoneme identification, word identification, phrase and sentence identification, connected discourse tracking, and a question-and-answer “conversation” task. In the present paper, the results from these evaluations are considered as a whole, to permit generalizations about the kinds of information that can be provided by single-channel, dual-channel, and multichannel devices, with and without the addition of lipreading. In addition, results are discussed in terms of the development of “optimal” training procedures for the use of tactile aids. [Work supported by NSF and NIH.]
Speech perception through the sense of touch by profoundly deaf adults and children
Authors: Lynch Michael P. , Eilers Rebecca E. , Oller D. K.
Published: October 2005

Eight congenitally, profoundly deaf children and two deaf adults received unimodal vocabulary recognition training with either a multichannel electrotactile aid or a two-channel vibrotactile aid. The children learned to recognize vocabularies of 15–20 words with 70%–80% accuracy. The adults learned a 50-word list. Following this training, subjects' identification of familiar and novel words was assessed using the tactile devices and aided audition. Vocabulary recognition was tested in each of three conditions: (1) with aided audition, (2) with dual or multichannel aid, and (3) with both tactual and auditory aids. Results indicate that auditory and tactual cues were successfully integrated by both children and adults to yield significantly better performance in combined than in single modality conditions. An additional study of the narrative tracking performance of one of the deaf adults revealed a similar synergistic interplay of taction, audition, and lipreading. [Work supported by Rita and Jerome Cohen, Renata Mahan, and Austin and Marta Weeks.]
Tactile speech reception using augmented Tadoma
Authors: Reed C. M. , Rabinowitz W. M. , Durlach N. I.
Published: October 2005

Results obtained with Tadoma have set a new standard for the tactile communication of speech [Reed et al., J. Acoust. Soc. Am. 77, 247–257 (1985)]. These results, however, are inferior to those obtained in the normal auditory domain: they are roughly comparable to those obtained by normal-hearing subjects listening to speech in signal-to-noise ratios of 0–6 dB. The goal of the current research is to augment Tadoma with supplementary tactile displays to improve the perception of speech segments. Among the supplementary displays investigated were a vibrotactile display of tongue contact with the hard palate and a vibrotactile display of the short-term speech spectrum. The tongue-palate-contact display was effective for improving the discriminability of pairs of consonants difficult to distinguish through Tadoma; however, neither this display nor the multichannel spectral display proved to be effective for augmenting vowel discriminability. A third approach to augmenting Tadoma currently under investigation involves the tactile reception of cued speech. [Work supported by NSF.]
Temporal and spatiotemporal tactile transforms of voice fundamental as an aid to lipreading
Authors: Boothroyal Arthur , Hnath-Chisolm Theresa , Hanin Laurie
Published: October 2005

Lipreading scores of naive subjects rise dramatically when the visible speech movements are supplemented by auditory presentation of voice fundamental frequency (F0). If it can be shown that the tactual transmission of F0 provides similar results, then there is the possibility of developing an effective lipreading aid for deaf subjects. We have tested two vibrotactile transforms of F0. One is temporal. It involves single-channel stimulation with a constant-amplitude square wave, of frequency F0/2, at a fixed locus. The second is spatiotemporal. It uses the same stimulus, but locus varies, displacement being proportional to log(F0). This transform requires a multichannel stimulator. In psychophysical experiments, the temporal display has been found to provide roughly 1/3-oct resolution at the fingertip, but over 1 oct on the forearm. With appropriate scaling, an eight-channel spatiotemporal display provides approximately 1/3-oct resolution on the forearm. With 16 channels, 1/6 of an octave resolution is possible. Experiments with speech stimuli have shown that both displays enhance the visual perception of phonetic contrasts that involve durational cues, but that the multichannel display is a more effective lipreading supplement for contrasts involving intonation contrasts. When sentence material was used with naive subjects, the two displays provided only a small supplement to lipreading. In one experienced lipreader, however, working with the multichannel display over a 13-week period, supplemented performance was significantly better than unsupplemented performance. The addition of the spatiotemporal transform of F0 to the visual signal reduced the number of word recognition errors by 50%. A wearable version of the multichannel display has been developed and is currently in use in field studies. [Work supported by NIH PPG♯17764.]
Evaluation of a multichannel electrotactile device for the hearing impaired—A case study
Authors: Kozma-Spytek Linda , Weisenberger Janet M.
Published: October 2005

A multichannel electrotactile device for the hearing impaired was evaluated as an aid for speech reception and production with a 12-year-old profoundly hearing-impaired child enrolled in an oral school for the deaf. Over an 8-month period the subject received training in speech reception skills in a hierarchy of tasks ranging from discrimination of minimal paired words to connected discourse tracking. Aspects of the subject's speech production skills were evaluated by obtaining ratings from a group of teachers of the hearing impaired, who viewed a videotape of the child during syllable production and connected discourse tracking with and without the device. Results of speech reception testing indicated that the device allowed good discrimination of minimal paired words based on manner contrasts, but poor discrimination based on place contrasts. During tracking, lipreading-pulse-tactile aid conditions were superior to lipreading alone. Results of the speech production evaluation showed that syllable identification was better and ratings on several aspects of speech production were higher under tactile aid conditions. [Work supported by NIH.]
Stress contrast perception by the hearing impaired: Auditory, tactile, auditory-tactile
Authors: Schoepflin Janet Reath , McGarr Nancy S.
Published: October 2005

The perception of stress contrasts in deaf subjects was assessed under three conditions—auditory only, tactile only, and combined auditory-tactile. Test stimuli were three disyllables generated in a two-stage process: multiple repetitions of each disyllable were produced by a normally hearing speaker using normal or exaggerated stress on either the first or second syllable; the averaged acoustic values for peak amplitude, vowel duration, and peak fundamental frequency for each disyllable were then resynthesized and manipulated to create a stimulus set containing none, one, two, and three of the acoustic cues denoting stress. Subjects were asked to indicate whether stress occurred on the first or second syllable for each stimulus item. Performance was above the level of chance in all three conditions. In the exaggerated stress production mode, performance in the tactile condition exceeded performance in the auditory condition for those stimulus items containing a frequency cue. [Work supported by ♯NS-17764.]
The use of tactile aids with deaf-blind children
Authors: Franklin Barbara
Published: October 2005

This paper will present the results of the first year of a 3-year study designed to compare the effects of a 2-channel (Tactaid II) and a 16-channel (Tacticon) aid on expressive and receptive communication skills of deaf-blind children. The Tactaid vibrators are worn on the wrist and the Tacticon is worn as a belt of electrical stimulators on the abdomen. Six children, ranging in age from 22 months to 18 years, from the San Francisco Bay area are participating in the study. A total of three communicative behaviors will be selected for each child (e.g., number of purposeful vocalizations). A single-subject design will be used to compare their communication behaviors in three experimental conditions—no device (control), 2-channel device, and 16-channel device. Only one behavior will be observed at a time, resulting in three separate sub-studies per child. This paper will present the results of Sub-Study ♯1. Despite the tactile defensiveness often exhibited by deaf-blind children, the partipants have been tolerating both devices. [This research is being supported by U.S. Dept. of Educ. Grant ♯G008630416.]
Deviations from a power-function near miss and their relation to loudness functions
Authors: Hellman William S. , Hellman Rhona P.
Published: October 2005

In a previous paper [W. S. Hellman and R. P. Hellman, J. Acoust. Soc. Am. Suppl. 1 81, S53–S54 (1987)], the neural-count function N(I) was derived from the intensity-jnd function J(I) through the relation N(I)1/2 = (h/2)∫dI/[IJ(I)] + a. Loudness functions were then generated by the prescription L = k[N(I) − N]. Using a power-function near miss for J(I), good agreement between the measured and calculated loudness values for pure tones was obtained. While a power function yields a simple evaluation of the integral for N(I)1/2, the results of many recent jnd studies do not easily conform to a power-function fit. In order to determine how the departures from a power-function near miss affect the form of the loudness function within the model, the integration was performed over the segmented intensity jnd functions observed for gated and continuous tones. The calculated loudness functions and their respective input intensity jnd functions are shown for frequencies of 250 and 1000 Hz. In spite of the segmented, and in some instances, nonmonotonic intensity jnd functions, the results reveal that the smoothing action of the integration over J(I) produces loudness functions consistent with experimental results. [Partially supported by the Rehabilitation Research and Development Service of the VA.]
Overall loudness of tone-noise complexes: Measured and calculated
Authors: Hellman Rhona , Zwicker Eberhard
Published: October 2005

Loudness measured for single-tone-noise complexes [R. P. Hellman, J. Acoust. Soc. Am. 72, 62–73 (1982)] is compared to loudness calculated in accordance with a loudness-calculation program based on ISO 532 B [E. Zwicker, H. Fast, and C. Dallmayr, Acustica 55, 63–67 (1984)]. Data are given for single tones centered within the spectrum of broadband-flat, low-pass, and high-pass noises. The measured and calculated loudness functions exhibit a similar pattern of loudness growth. Both measured and calculated loudness of the tone-noise complexes are nonmonotonic functions of the overall SPL of the complex. Thus two tone-noise combinations at nearly the same overall SPL can produce markedly different loudness values. These results hold over a 30-dB range from about 73–103 dB. The results also show that the magnitude of loudness depends on the spectral shape of the noise and the frequency of the added tone. The close agreement between the measured and calculated loudness-growth patterns means that basic psychoacoustical principles governing loudness and masking can account for the observed effects. [Supported by the Rehabilitation Research and Development Service of the VA and by the Deutsche Forschungsmeinschaft.]
Investigation of a model of loudness
Authors: Chien P. S. , Hall J. L.
Published: October 2005

A model of loudness summation by Schroeder et al. [J. Acoust. Soc. Am. 66, 1647–1652 (1979)], which was used by them to provide an objective quality measure of digital speech coding, is being investigated. (1) Iso-loudness contours generated by the model are compared to iso-loudness contours generated by human subjects. (2) The spreading function used in the model to calculate excitation levels is converted from the critical-band domain to the frequency domain for various center frequencies. The resulting curves are compared to tuning curves measured in the cat. (3) The effect of partial masking on the relative loudness of pairs of pure tones is examined. (4) The model is used to predict the loudness of broad bands of noise from the loudness of narrow bands of noise centered at several frequencies. Studies (1)–(4) have revealed strengths and short-comings of the model.
Loudness adaptation in musicians and nonmusicians
Authors: Baruch C. , Botte M.-C.
Published: October 2005

Measurements of simple and induced loudness adaptation were made on 10–12 musicians and 10–12 nonmusicians by the method of successive magnitude estimations. Simple adaptation (SA) was measured for a 500-, 1000-, or 4000-Hz tone presented monaurally for 3 min at 10 dB SL. Induced adaptation was measured for a continuous 1000-Hz, 60-dB SPL right-ear tone; loudness was judged before, during, and after each occurrence of an intermittent inducer tone set to five frequencies from 500–3260 Hz and presented every 30 s for 10 s to the same ear (ipsilaterally induced adaptation, IIA) or to the left ear (contralaterally induced adaptation, CIA). We also measured CIA with a rapid intermittency of every 1 s for 0.5 s. The level of the inducer was 60 dB for CIA and 75 dB for IIA. Musicians showed less adaptation than nonmusicians whatever the type of adaptation: For the musicians, the maximum loudness decrease was 44% under SA, 30% under CIA, 30% under IIA; for the nonmusicians, this maximum was 70% under SA, 70% under CIA, 41% under IIA, but differences were statistically significant only for SA and for CIA with the rapid intermittency. Moreover, musicians showed significant adaptation over a less extended range of frequencies than nonmusicians.
A pure-tone-induced temporary threshold shift on normal hearing and noise-induced permanent threshold shift
Authors: Young I. M. , Lowry L. D.
Published: October 2005

Temporary threshold shift after an exposure to a pure tone was measured by automatic audiometry on three subjects with normal hearing and three subjects with noise-induced permanent threshold shift. Subjects were exposed to a stimulating pure tone with a frequency 1500 Hz through an earphone at an intensity of 110 dB SPL for a duration of 10 min. Temporary threshold shift was measured beginning at 5 s after the cessation of the stimulation. In normal hearing subjects, the greatest shift was observed at the frequency area of 2000 Hz as demonstrated previously. In subjects with noise-induced permanent threshold shift, temporary threshold shift was demonstrated not only at the frequency region of 2000 Hz, but also at higher frequencies with permanent threshold shift. Post-exposure effects at higher frequencies showed the greater threshold shift for the steady tone resulting in increased separation between normal amplitude pulsed tone tracings and markedly reduced amplitude steady tone tracings. Similar post-exposure findings were observed on a subject with congenital nonprogressive bilateral symmetrical sensorineural loss of high frequencies similar to noise-induced permanent threshold shift. Spread of temporary threshold shift at the higher frequencies was discussed and compared with the greater spread of masking effect at the higher frequencies.
Threshold recovery functions following impulse noise trauma
Authors: Hamernik Roger P. , Ahroon William A. , Patterson James H.
Published: October 2005

An analysis of the pure-tone threshold recovery functions obtained from 118 chinchillas exposed to high-level impulse noise showed that there are at least three distinctly different types of threshold recovery functions. Type I: the classical recovery function that declines monotonically with increasing postexposure time; type II: a delayed recovery, i.e., for a period as long as 6 h following removal from noise, the pure-tone threshold remains elevated and stable before a monotonically declining recovery process sets in; and type III: the growth function, i.e., over a period of at least 6 h following removal from the noise, pure-tone thresholds continue to get worse before a stable monotonically declining recovery process begins. Frequencies characterized by a type III recovery process show more PTS and sensory cell loss than do those characterized by the type I recovery process. The existence of three distinctly different audiometric recovery functions implies the existence of different mechanisms of cochlear trauma.
Flow/acoustic interaction in duct inflow
Authors: Quinn Margaret C.
Published: October 2005

Sound generation in the convection of turbulence into a flow intake duct is discussed by examination of an idealized problem. Ideal fluid is in motion with uniform low, subsonic velocity above and parallel to a plane rigid wall. A thin, rigid, semi-infinite plate is parallel to the wall and the fluid flows past its leading edge. The radiated sound is calculated for a turbulent eddy modeled by a weak line vortex that is allowed to convect passively past the leading edge of the plate. Account is taken of the contribution to the radiated sound from the disturbance produced by the convecting vortex in the boundary layers on each side of the plate by means of Howe's (1981) theory of displacement thickness fluctuations (Proc. R. Soc. London Ser. A 374, 543–568), the strength of such disturbances being fixed by a leading edge Kutta condition. It is concluded that the predicted level of the radiated sound is substantially reduced by these boundary layer disturbances relative to when they are neglected. The case of the convection of a frozen two-dimensional gust is also considered. Examination of the analogous problem of plane-wave radiation from the duct shows that the presence of displacement. waves enhanced both the far-field intensity in the ambient fluid and the reflected field within the duct. [Work supported by ARE Teddington, UK.]
Resonance conditions in branching structures
Authors: Raphael David T. , Epstein M. A. F.
Published: October 2005

In complex branching structures, recursive algorithms are often employed to calculate impedances at successive nodes. For a rigid symmetric Nth-order branching network terminating in 2N closed branches, a technique is presented whereby the open-ended input impedance, and its corresponding resonance condition, can be explicitly formulated in terms of the branch lengths and cross-sectional areas, the angular frequency, and the integral harmonic number. In the low-frequency range, the resonance condition can be modified so as to facilitate volume estimation of the branching structures. Experimental studies with rigid second-order symmetric and asymmetric branching structures are discussed. [Work supported by the University of Connecticut Research Foundation.]
Surface roughness effects on flow noise
Authors: Christoph George H.
Published: October 2005

The Corcos wall pressure model was modified to incorporate surface roughness effects. The longitudinal cross-spectral density part of the Corcos model was modeled from rough wall data taken from the literature. The wall pressure frequency spectrum was nondimensionalized by the wall shear stress and boundary layer displacement thickness and shown to fit both smooth and rough wall data. The boundary layer parameters were obtained from a finite-difference boundary layer code developed by the author to account for surface roughness effects by the discrete roughness approach [G. H. Christoph and R. H. Pletcher, AIAA J. 21, 509–515 (1983)]. The blockage of the roughness height, shape and spacing is explicitly accounted for in this approach. Flow noise was calculated for a variety of roughness element heights and spacings in air and in water. The calculations clearly show that element spacing as well as height is important and that the viscous sublayer height, not the boundary layer thickness, determines the influence of roughness on flow noise. Thus roughness is typically more important in water than in air because of the thinner viscous sublayer. Also, the effect of transducer size and viscoelastic layer thickness are shown for rough surfaces.
Helicopter rotor speed effects on farfield acoustic levels
Authors: Mueller Arnold W. , Childress Otis S. , Hardesty Mark
Published: October 2005

The design of a helicopter is based on an understanding of many parameters and their interactions. For example, in the design stage of a helicopter, the weight, engine, and rotor speed must be considered along with the rotor geometry when considering helicopter operations. However, the relationship between the noise radiated from the helicopter and these parameters is not well understood, with only a limited set of model and full-scale field test data to study. In general, these data have shown that reduced rotor speeds result in reduced farfield noise levels. This paper will review the status of a recent helicopter noise research project designed to provide flight experimental data to be used for further understanding of helicopter rotor speed effects on farfield acoustic levels. Preliminary results will be presented relative to tests conducted with a McDonnell Douglas Helicopter Company model 500E helicopter operating with the rotor speed as the control variable over the range from 103% N2 to 75% N2 and the forward speed maintained at a constant value of 80 knots.