bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear sound scattering of crossed focused beams in the presence of turbulence—Angular measurements
Authors: Korman Murray S.
Published: October 2005

Experiments are performed involving the interaction of mutually perpendicular crossed, ultrasonic beams overlapping (at a common focal point) and interacting in the presence of turbulence generated by a d = 0.64-cm-diam submerged water jet (Re = 8.5 × 105). Measurements of the radiated sum-frequency intensity, Doppler shift, and-spectral broadening are recorded from the scattered spectra. In the absence of turbulence, no sum frequency can be detected. The two cw primary beams (f1 = 1.9 MHz, f2 = 2.1 MHz) are generated by individual transducer units of 15.2-cm focal length. The receiver (a circular plane array located outside the interaction region) is positioned with its axis perpendicular to the jet at a distance of 30d from the nozzle (the interaction region). Previously, very good theoretical predictions of mean flow and rms turbulent velocity were determined from the Doppler shift and spectral broadening data from a similar crossed-beam scattering experiment [M. S. Korman and R. T. Beyer, J. Acoust. Soc. Am. 84, 339–349 (1988); 85, 611–620 (1989)]. The primary beams were generated by circular plane array elements. Results suggested that the interaction involved an averaging across a large region of flow. The localized crossed-beam interaction region allows turbulent flow properties to be predicted with reasonable spatial resolution. [Work supported by the Naval Academy Research Council.]
Reflection of a plane finite-amplitude pulse from a hard surface: Amplification factor comparison between analytic and simulation
Authors: Sparrow Victor W. , Raspet Richard
Published: October 2005

The amplification factor for a sound wave impinging on a hard wall is the ratio of the acoustic pressure near the wall to the acoustic pressure at the same position with the wall absent. Linear acoustics gives the familiar wall amplification factor of 2, pressure doubling. However, the factor is greater than 2 for finite-amplitude waves. For regular reflection, as opposed to Mach reflection, the factor has been predicted in the ideal gas case analytically. In this presentation the wall amplification factor predicted by a nonlinear acoustics finite-difference simulation will be compared with the analytic result of Pfriem. A short videotape will demonstrate the simulation via animation. [Computations performed at the National Center for Supercomputing Applications, Champaign, IL.]
Acoustic injury of the inner ear: Morphological and physiological perspectives
Authors: Liberman M. Charles
Published: October 2005

Of the many approaches to the study of acoustic injury, one of the most fruitful has been to view the functional changes in the response properties of single auditory-nerve fibers. Since each cochlear afferent contacts only one inner hair cell, single-fiber responses provide a functional window onto a restricted portion of the cochlear duct. Through the use of intracellular labeling, which allows the cochlear origin of selected afferents to be precisely specified, correlations between structural and functional changes have been made on the single-cell level. Correlations so obtained have revealed the functionally important structural changes underlying acoustic injury of the inner ear. Morphological data from both the light- and electron-microscopic levels suggest that most sound-induced permanent threshold shifts can be accounted for quantitatively based on the loss of sensory cells and/or the damage to their stereocilia. Of all the structures in the inner ear, the stereocilia, and especially the “rootlets” that anchor them to the tops of the hair cells, appear to be the most vulnerable to permanent damage from acoustic overstimulation. The structural changes underlying reversible threshold shifts are clearly different from those underlying permanent loss, but exactly which structural changes underly the temporary losses are much less clear. Structure-function correlations in damaged ears have also helped define the contributions of inner versus outer hair cells to the response properties of auditory-nerve fibers. Damage to inner versus outer hair cells results in strikingly different abnormalities in neural tuning, spontaneous activity, and maximal discharge rates. The nature of these differences suggests that auditory perceptual abilities would be very different given threshold shifts of identical severity but differing balance of damage to the two classes of sensory cells.
The use of reciprocity to calibrate a resonant photoacoustic measurement
Authors: Maynard J. D. , Yu Chang
Published: October 2005

While the photoacoustic effect provides a powerful means of measuring very low optical absorptions with pulse lasers, obtaining an accurate calibration has been a problem. However, in a resonant photoacoustic measurement, a reciprocity calibration (which does not require replacing transducers) is readily accomplished. All that is required is that a reversible transducer be present in addition to the photoacoustic (laser) excitation and the usual photoacoustic receiver. By making only electrical measurements using alternately the laser and the reversible transducer for excitation, the absolute acoustic levels in the sample may be determined from the transducer voltage. By also measuring the quality factor (Q) of the resonance from the frequency response, the power deposited by the laser is easily determined. A separate measurement of the incident laser power yields the optical absorption coefficient. [Work supported by the Office of Naval Research.]
Comodulation masking release (CMR) using coherent complex envelopes
Authors: Haggard Mark P. , Fantini Deborah A.
Published: October 2005

In comodulation masking release (CMR), thresholds for a signal masked by a narrow band of noise are improved when a second, flanking, noise band is added which has a similar amplitude envelope to that of the masking band. The parameters of “similarity” are many; this study addresses sharing of frequency components in complex modulations. The following was determined: (a) whether the auditory system may extract components of complex modulation in order to achieve a CMR; (b) whether a “missing fundamental” of a complex modulation matches up with a present modulation component to provide a CMR; and (c) whether the difference or beat frequency of a complex modulation may provide a CMR, for both harmonic and inharmonic complexes. The results indicate a small but significant CMR with complex modulation; the reduction in CMR by comparison with sinusoidal modulation may reflect modulation-modulation masking. Insignificant CMRs were obtained where components would need to be separated to register envelope similarity between differing complex modulations.
The role of envelope information in CMR tasks
Authors: Fantini Deborah A.
Published: October 2005

In comodulation masking release (CMR), thresholds for a signal masked by a narrow-band noise are reduced when additional noise is present, provided that the additional noise has the same amplitude envelope fluctuations over time as the original masking band. Recently, some speculation has appeared in the literature as to the specific source of information which provides the reduction in masked threshold. In the present work, the importance of changes in the envelope of the masker band, due to the addition of the signal at threshold, in providing the CMR, has been investigated. First, CMR thresholds were collected in sinusoidally amplitude-modulated noises which varied either in the phase relationship of their envelopes or in their modulation depth. Then, envelope discrimination (ED) thresholds were collected for changes in envelope phase disparity and for changes in modulation depth per se. The data indicate that the patterns of CMR thresholds with envelope phase disparity and with modulation depth vary differently from that of the ED thresholds. A simulation was then conducted in which the stimulus waveforms were processed through a model that includes an auditory filter [equivalent rectangular bandwidth (ERB) filtering], a square-law nonlinearity, and a sliding temporal window [an equivalent rectangular duration (ERD) filter]. The envelopes were then extracted from the processed waveforms to determine what actual changes in the envelopes were occurring in the signal intervals in both CMR and ED. The results of this waveform analysis indicate that discriminability of envelope changes due to the addition of the signal at threshold in the CMR task are insufficient to explain CMR.
Ultrasonic behavior in an amorphous superionic conductor (AgI)x(AgPO3)1−x
Authors: Hu Jiankai , Zhang Senkui , Zhang Qianlin
Published: October 2005

Amorphous superionic conductor (AgI)x(AgPO3)1−x series samples have been obtained by means of the liquid-nitrogen rapid-quenching technique. In the series of glasses, for AgI with mole concentration of x = 0.45, 0.5, 0.55, and 0.6, the attenuation and velocity of longitudinal waves were measured by an ultrasonic pulse-echo method, in the temperature range 100–300 K at frequencies of 5 and 10.5 MHz. The temperature of the attenuation peak fell with increasing AgI content and decreasing frequency. In addition, the amplitudes of the attenuation peaks increased significantly with increasing AgI content, despite the fact that the total concentration of Ag+ ions is about constant for this series of samples. The sound velocity of the sample x = 0.5, at frequency 5 MHz, decreased monotonously with increasing temperature and had a small anomaly at 204 K. The sound velocity of the glasses decreased slowly as x was increasing at room temperature. The experimental results were fitted well to the unified theory of low-frequency fluctuation, dissipation, and relaxation process, i.e., the infrared divergence response theory proposed by Ngai [K. L. Ngai, Comments Solid Phys. 9, 127 (1979); also, Phys. Rev. B 20, 2475 (1979)]. [Work supported by NSF of China.]
Central processes in the perception of pitch in simultaneous complex tones
Authors: Beerends John G.
Published: October 2005

Pitch identification of two simultaneous complex tones is more difficult than pitch identification of a single complex tone. In this talk, the more central processes that are involved in the perception of simultaneous complex tones will be discussed. Experiments are reported in which subjects had to identify two missing fundamental frequencies. A first set of experiments uses simultaneous two-tone complexes with different distributions of the four partial over the ears. It is shown that subjects can identify the two missing fundamental frequencies and that the identification results only weakly depend on the manner of distributing the four partials over the ears. For some subjects, the identification results showed that the more salient pitch can inhibit to some extent the identification of the less salient one. This “central interference” is most prominent when the partials of the two complex tones are widely separated. In a second set of experiments, the influence of signal duration on the virtual pitch of single and simultaneous complex tones is investigated. The results for single complex tones allow the formulation of a stochastic pitch model in which a central processor derives noisy subharmonics from noisy representation of the partials. For simultaneous complex tones, the behavior is more difficult to model because of the more central processes that are involved.
Lip protrusion in sibilant production
Authors: Faber Alice
Published: October 2005

While anecdotal reports of lip protrusion contributing to sibilant production in a variety of languages exist, little attention has been paid to quantifying its contribution. In the present study, lip position was monitored using a modified SELSPOT optoelectronic tracking system, and location of oral constriction was simultaneously monitored by means of a RION artificial palate. Subjects (speakers of Catalan, English, German, and Italian) produced 50 tokens each of 6 (8) symmetrical VCV utterances, where V ranged over /iau(ü)/ and C over /sš/. As expected, /s/ has a more anterior constriction than /š/, with the constriction for /usu/ being the most anterior; and, there is more lip protrusion for /š/ than for /s/, except for in the /u_u/ context. Across utterance types, the combination of lip protrusion and constriction location is a better predictor of the frequency of a sibilant's centroid than is either parameter alone; within utterance types, lip protrusion and aperture are, in general, better predictors of centroid frequency than is constriction location. [Work supported by NIH Grant NS-07237.]
Interarticulatory relationships in vowel production
Authors: Lindau Mona , Ladefoged Peter
Published: October 2005

In earlier studies it has been shown that, within a language (English), the jaw and the tongue interact in different ways for different speakers to produce differences between vowels. These studies were, however, limited to front vowels. Using the x-ray microbeam system, articulatory movements were recorded from pellets placed on the lips, mandible, and the tongue, in five speakers saying utterances illustrating all the English vowels. The results show some rather complex relationships. For example, for some speakers tongue height, as measured by the height of the tongue dorsum, does not always distinguish between the high front /i/ and mid front /e/ (e.g., in dee and day); but these vowels are distinguished by the height of the mandible. The height of the dorsum does separate the tense /i/ and the lax /ι/ (e.g., in dee and did) and the back /u/ and /o/ (e.g., in do and doe). The results also show the degree of consistency within individuals in favoring certain trading relationships between the lips, the mandible, and the tongue.
In search of lingual stability
Authors: Vatikiotis-Bateson Eric , Stone Maureen
Published: October 2005

In this study, commensurate data were obtained for tongue motion (coronal and sagittal ultrasound scans), lingual-palatal contact patterns (dynamic palatography), and jaw motion (Selspot). Two subjects repeated /VCVCa/ combinations of /s,∫,l,i,a,o/. To date, the effects of consonant identity on jaw motion and palatal contact patterning have been examined, along with the anticipatory and carryover effects of the three vowels. Initial findings on both jaw height and palatal contact suggest that the tongue-jaw coupling observed for sibilant production was modulated systematically according to adjacent vowel identity. In contrast to /s/ and /∫/, tongue-jaw coupling for /l/ appears to be minimal as shown by the large token-to-token spatiotemporal variability of jaw motion. Instead, there is a very stable, yet highly asymmetrical pattern of lingual contact along the outer edge of the artificial palate. Analogous to the jaw's role in sibilant production, this may serve as a stabilizing brace for the tongue to achieve postures specific to /I/ production, which should be identifiable from analysis of the ultrasound data. These results are consistent with a task dynamic approach to interarticulator coordination [Saltzman (1986)]. [Work supported by NIH.]
Quantitative comparison of articulatory models
Authors: Jackson Michel T. T.
Published: October 2005

Phonological theories invoke a number of different articulatory parametrizations. Traditional phonetic theories and some phonological theories parametrize vowel articulation in terms of tongue height and backness. Particle phonology [S. A. Schane, Phonology Yearbook 1, 129-155 (1984)] parametrizes vowel articulation as blends of particular (extreme) articulations (i,u,a). Harshman, Ladefoged, and Goldstein Acoust. Soc. Am. 62, 693-707 (1977)] parametrize English vowels using front-raising and back-raising factors, each of which generates a family of tongue positions. A multispeaker, cross-linguistic database of x-ray tracings [M.T.T. Jackson, UCLA Working Papers in Phonetics 71, 1–232 (1988)] allows quantitative comparison of these proposals. Each proposal defines a vowel space: The coordinates of vowels in the vowel space can be fixed, and the articulatory correlates of the parameters using multivariate regression can be estimated. Each model can, therefore, be evaluated by standard methods, e.g., χ2 a tests. A number of such articulatory models have been investigated. The results suggest that front-raising and back-raising factors generalize well across languages and fit articulatory data better than height/backness- or particle-based models.
Performance bounds for passive synthetic aperture sonar
Authors: Harvey Richard William
Published: October 2005

The performance bounds for a towed line array are derived and compared with performance achievable using a static array. It is shown that the towed array can provide considerably better performance than the static array when the target is in the nearfield of the synthetic aperture. The theoretical bounds have been validated by computer simulation and the simulation results for a least-squares estimator for various array/target geometries are presented. Methods by which a passive synthetic aperture might be implemented are discussed and the results of a least-squares estimator operating on 120 s of data recorded from a 10-element towed array are presented. [Work supported by SERC and Plessey Naval Systems.]
Farfield projection from sparse nearfield measurement samples
Authors: Borgiotti Giorgio V. , Rosen Eric
Published: October 2005

The nearfield to farfield projection procedure here introduced has the following novel features. (1) The measured nearfield samples do not need to belong to a separable coordinate surface. (2) The number of samples can be as small as the theoretical number of degrees of freedom of the farfield, related to the dimensions of the source in wavelengths. (3) The samples do not need to belong to a regular grid. (4) If the projection is sought only within a limited angular sector, a further reduction of the number of measurement samples is possible. The technique is based on the identification from the measured data of an equivalent monopolar distribution of acoustic sources on a surface completely surrounding the radiator. The farfield is then straightforwardly computed. The identification is based on the pseudoinversion of the matrix representing the mapping of the equivalent sources into nearfield samples, which is obtained by resorting to the singular value decomposition of the matrix.
Impact of sample window choice and location on time delay estimation of transients
Authors: Leybourne Allen E. , Meredith Roger W.
Published: October 2005

Estimation of time delays between coherent transient signals is biased by the choice and location of the sampling window. For transients that do not tend to zero within the sampling window (self-windowing), the uniform or boxcar window may not be the best choice due to spectral leakage. This is especially important when processing highly asymmetrical transient signals that are not self-windowing as in the case of acoustic ambient noise. When a sample window is used to suppress spectral leakage, a bias in time delay estimation results from a suboptimal window location. Even though the boxcar window produces the least bias in time delay when the transient is self-windowing, it is shown that sidelobe interference is significant for highly asymmetric signals. This work critically examines these effects and describes an iterative procedure to determine optimal location of the transient within any sample window. [Work supported by the Office of Naval Technology.]
Higher-order correlations and spectra and the detection of narrow-band deterministic transients
Authors: Pflug Lisa A. , Barnes Kenneth H. , Ioup George E. , Ioup Juliette W. , Field Robert L. , Leclere James H. , Rayborn Grayson H.
Published: October 2005

Previous investigators have evaluated higher-order correlations and spectra for detection and time delay estimation of statistical signals. In this study detection of known and unknown deterministic transients, especially those which are narrow band, is considered. Initial results have been reported [G. E. Ioup, J. W. Ioup, K. H. Barnes, R. L. Field, J. H. Leclere, and G. H. Rayborn, IEEE Workshop on Higher-Order Spectral Analysis Proc., 46–55 (1989)]. For narrow-band signals extending from frequency fB to fT, the bispectrum is zero unless 2fθ⩽fT and the trispectrum has zero energy in the first and seventh octants unless 3fB⩽fT, although the remaining octants of the trispectrum are always nonzero. Conditions for adequate sampling for these spectra are presented. Moments and histogram analysis of the ordinate values of the transients are also used in the analysis of the detectors. Performance analysis using ROC curves shows that the simple bicorrelation detector does not do nearly as well as correlation or tricorrelation detectors for transients with 2fB>fT. Other performance analysis results are also discussed. [Work supported by NOARL and Navy/ASEE Summer Faculty Fellowship Program.]
Effect of pressure on sound absorption in seawater at 0°C
Authors: Fisher F. H. , Wright W. M.
Published: October 2005

Earlier measurements of the effect of pressure on sound absorption by magnesium sulfate in seawater by Hsu at 0 °C in the laboratory were limited to pressures of just over 300 bars. The pressure was limited by the strength of the 100-liter titanium sphere, a spare ballast tank from the Woods Hole submarine ALVIN. To obtain data at higher pressures at 0 °C, measurements were recently made in 0.5 M magnesium sulfate solutions in a cylindrical reesonator. Because the magnesium sulfate relaxation frequency is independent of pressure, measurements are necessary at only one frequency. This was done in the 100-kHz region and a sodium sulfate solution was used to correct for wall losses in the cylinder. Mode interference problems as well as a shutdown in the building air circulation system, which gave rise to temperature control problems, degraded the data. Nevertheless, enough data were obtained at higher pressures (600 to 1300 bars) to be useful in assessing the effect of pressure on seawater sound absorption at 0 °C as has been done with earlier work by Fisher at 25 °C on 0.5 molar magnesium sulfate solutions. These results will be incorporated with those of Hsu at lower pressures into an equation for absorption in seawater at 0 °C covering the whole pressure range. Predictions using this equation will be compared with those from the Garrlson-Francois and Fisher-Simmons equations for sound absorption in seawater. [This work was supported by Office of Naval Research.]
Geoacoustic models for bottom loss predictions
Authors: Holland Charles W.
Published: October 2005

A useful theoretical measure of acoustic interaction with the seafloor is the plane wave reflection coefficient (R) which is commonly expressed as bottom loss (20 log |R |)). Predictions modeling the seafloor as a sediment layer over a half-space indicate that bottom loss should be proportional to frequency. Bottom loss measurements (50–1600 Hz) in the deep ocean, however, frequently show a loss that is inversely proportional to frequency. The locations of these anomalous sites are remarkably consistent with the boundaries of the Abyssal Plains which are characterized by turbidite layering. Geoacoustic models including the turbidite layers were constructed based on core data and a ray-based acoustic model was employed to compare the model predictions with measured data in Abyssal Plain areas. The turbidite layering was modeled as a series of pelagic and terrigenous layers in a simple repeating sequence. Model predictions were in accordance with the measured data.
Transition from simultaneous to forward masking III: Phase effects
Authors: Weber Daniel L.
Published: October 2005

The relative phase of a sinusoidal masker and signal necessarily has a large effect upon the signal power required for a simultaneous-masked threshold but has no effect on the forward-masked threshold. Threshold for a 20-ms (20-ms raised cosine ramps with no steady state produced a signal 20 ms long measured at the half-voltage points on the envelope), 1-kHz sinusoid, masked by a 300-ms (no ramps), 1-kHz sinusoid, was measured as a function of the signal's temporal position to examine how the phase effect disappeared in the transition from simultaneous to forward-masking conditions. Although listeners differ, the phase effect remains unchanged at least until 10% of the signal energy is subject to forward masking and is substantially reduced, if not eliminated, when 50% of the signal is subject to forward masking. These results are interpreted to indicate that forward masking tends to be the more sensitive detection process when a signal is subject to both simultaneous and forward masking.
Dependence of the acoustic to seismic coupling ratio on the angle of incidence and geophone depth
Authors: Arnott W. Pat , Sabatier James M. , Messer John O.
Published: October 2005

An atmospheric sound wave can couple with the poroelastic ground, resulting in ground (or seismic) motion. This is the phenomenon of acoustic to seismic coupling. Microphones are used to measure the sound pressure level at the surface and geophones are used to measure the resulting seismic motion at or below the surface. The seismic:acoustic transfer function (SATF) characterizes a particular site. SATF measurements are reported as a function of the angle of incidence of the sound wave for frequencies 15 Hz to 1 kHz. The angle of incidence varied from 50° to 80°, and normal incidence. Surface vertical and radial-horizontal geophones were used. In addition six vertical geophones at depth intervals of 10 cm, starting at 10 cm, were used. A seismic p-wave survey indicated a first layer depth of 44 cm having a wave velocity of 159 m/s overlying a layer of velocity 379 m/s. This gives a critical angle of incidence of 65°. It was anticipated and confirmed that the SATF would increase in magnitude for certain frequency bands as the angle of incidence approached and passed over the critical angle. Comparisons of experimental results and multilayered elastic and poroelastic media theory will be addressed as time permits. [Work supported by ONR.]
Low-frequency, long-range sound propagation modeling over a locally reacting boundary with the parabolic approximation
Authors: Robertson J. S. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

There is substantial interest in the analytical and numerical modeling of low-frequency, long-range atmospheric acoustic propagation. Ray-based models, because of their frequency limitations, do not always give an adequate prediction of quantities such as sound pressure or intensity levels. However, the parabolic approximation method, widely used in ocean acoustics, and often more accurate than ray models for frequencies of interest, can be applied to acoustic propagation in the atmosphere. Modifications of an existing implicit finite-difference implementation for computing solutions to the parabolic approximation are discussed. A locally reacting boundary is used together with a one-parameter (the flow resistivity) ground impedance model. Intensity calculations are performed for a number of flow resistivity values in both quiescent and windy atmospheric sound channels. Variations in the value of this parameter are shown to have substantial effects on the spatial variation of the acoustic signal. [Work supported by NASA.]
Weighting functions in a multiple tone task
Authors: Berg Bruce G.
Published: October 2005

An analytical technique is used to assess the relative weight given to each observation in a multiple tone task. After listening to a sample of seven tones presented sequentially, observers try to discriminate if the tones were sampled from a “high” or “low” distribution. The frequency of each tone is determined by sampling from one of two Gaussian distributions with means of 1000 and 1100 Hz. Reliability of each tone is manipulated by changing the standard deviation of the distributions as a function of temporal position. In experiment 1, the three central tones have either equal, greater, or less reliability than the remaining tones. Observers adjust their weights appropriately. In experiment 2, sequentially presented tones alternate between high and low reliability, and intensity cues their reliability. Observers adjust their weights appropriately when highly reliable tones have greater intensity, but not when highly reliable tones are cued by low intensities. Finally, in a two-tone experiment, only the first tone of fixed intensity is reliable. Unexpectedly, discrimination accuracy decreases as the intensity of the second, uninformative, tone is increased. [Work supported by AFOSR.]
Effect of multiple presentations on detection and recognition of pure tones and tonal patterns
Authors: McKinley Robert C. , Weber Daniel L.
Published: October 2005

This study examines the effect of multiple observations on detection performance, and on the ability to recognize one signal from a set of possible signals, for three different sets of four signals. One set is four pure tones (100-ms sinusoids, frequencies of 707, 1000, 1414, and 2000 Hz). Two sets contain tonal patterns each made of seven 100-ms sinusoidal components. The first set of four patterns used different frequencies from different one-fourth octave bands (centered at 707, 1000, 1414, and 2000 Hz) to produce a single pattern of relative frequencies in different frequency regions. The second set had different sequences of a single set of frequencies. All stimuli were adjusted to equal sensation level in the presence of a continuous white noise (spectrum level 20 dB SPL). Each trial had multiple presentations (n = 1, 2, 4, 8, or 16) of a given signal plus noise (probability of a signal trial was 0.5) or noise alone. Detection performance for the pure tones and the first set of tonal patterns was well described by a square root of n improvement; detection for the second set of patterns was not. Recognition performance was generally poorer than that predicted by the detection/recognition theorem [S. J. Starr, C. E. Metz, L. B. Lusted, and D. J. Goodenough, Radiology 116, 533–538 (1975)] and was not affected by multiple presentations other than as predicted by the increase in detection performance. [Research supported by AFOSR through AAMRL/BBA, Wright-Patterson AFB.]
Fatigue effects of a pure tone and pure tones
Authors: Young I. M. , Lowry L. D.
Published: October 2005

Subjects with normal hearing were exposed to moderate intensity of a pure tone and pure tones. Exposure frequency consisted of: a single tone, 1500 Hz; two tones, 1500 and 2000 Hz; and three tones, 1500, 2000, and 3000 Hz. Fatigue effect measurements were made by automatic audiometry immediately after exposure. The greatest fatigue at frequencies 1/2–1 oct above an exposure frequency of 1500 Hz was shown by a single tone, the least effect by three tones, and the intermediate effect by two tones. The fatigue effects at the remote high frequencies were in the reverse order. These findings may be explained on the basis of harmonics and combination tones arising in the ear on stimulation with tones.
Frequency resolution for broadband-noise masked normal listeners
Authors: Dubno Judy R. , Schaefer Amy B.
Published: October 2005

When evaluating frequency resolution of hearing-impaired listeners, it is often difficult to determine if changes observed in auditory analysis with increasing auditory threshold reflect abnormal cochlear function or represent normal auditory processing at high stimulus levels. This experiment was designed to investigate the dependence of frequency-resolution measures on threshold and signal level. Auditory-filter characteristics, critical ratios, psychophysical tuning curves, and masking patterns were obtained from normal-hearing listeners in quiet and in the presence of broadband noise at five levels (30 to 70 dB SPL). These findings were then compared to previously obtained frequency-resolution results for subjects with sensorineural hearing loss whose auditory thresholds in quiet were comparable to the normal-hearing listener's masked thresholds. These comparisons, while limited to individuals with moderate hearing loss and broadband-noise masked normal listeners, suggest that frequency resolution observed in hearing-impaired listeners is similar to that seen in the normal auditory system at high stimulus sound-pressure levels. [Work supported by NIH NS 18015.]
Gap detection and discrimination in complex speechlike signals
Authors: Nelson Peggy B. , Norton Susan J.
Published: October 2005

Speechlike stimuli consisting of /s/-like noise and F 1-like frequency sweeps were used for gap detection and discrimination experiments. Five normal-hearing subjects participated in the tasks: (1) detection of gaps in /s/-like noise, (2) discrimination between gaps in noise, (3) detection of gaps between noise and glide, and (4) gap discrimination between noise and glide. Stimuli for the latter two experiments were patterned after synthesized “say” and “stay” speech signals. These stimuli consisted of 120 ms of high-pass-filter digital white noise (simulating the /s/ phoneme), followed by a silent gap varying from 0–120 ms in duration, and a 50-ms linear frequency sweep from 230–611 Hz (simulating the F 1 transition). The same high-pass-filtered white noise was used for all experiments. An adaptive psychophysical procedure was used in the first two experiments; a method of constant stimuli procedure was used for the complex stimuli tasks because of the shallow-sloping psychometric functions. Subjects required extensive training to reach asymptotic performance levels on the latter two experimental tasks. Results indicated significantly longer durations are required for the complex stimulus tasks.
Gap detection in narrow bands of noise as a function of the number and proximity of the bands
Authors: Grose J. H. , Hall J. W.
Published: October 2005

The minimum detectable gap in a noise decreases both as the bandwidth of the noise increases and as the number of independent noise bands carrying the gap increases. The present study attempted to relate these two observations by differentiating between the parameters of bandwidth and number of active channels. The stimuli consisted of either one band or five independent bands of noise, each 20 Hz wide. In all conditions, one of the bands was centered on 1000 Hz. The multiple bands were either juxtaposed to give a single band of noise centered on 1000 Hz or were spaced in various configurations, resulting in a set of conditions ranging from all bands passing through a single auditory channel to each band passing through an independent channel. The stimuli were presented at a spectrum level equal to that of a 15-dB SL, 20-Hz-wide band of noise centered on 1000 Hz. The gap was imposed with a 10-ms rise-fall time. Gap thresholds improved with an increased cumulative bandwidth, but more so for the spaced bands than for the juxtaposed bands. [Research supported by AFOSR.]
Statistical analysis with fundamental frequencies of 12 Korean monophthongs
Authors: Shin H. J. , Yoon S. W.
Published: October 2005

The 12 Korean monophthongs pronounced by five male vocal musicians, each at five fundamental frequencies, are studied by a method of statistical analysis with the fundamental frequencies (SAFF) based on the format analysis. In this study, the SAFF method shows more reasonable results of the format frequencies in the Korean monophthongs. It is also observed that the first and second formants are characterized by the resonance of the cavities of the pharynx and mouth, respectively. The lip-rounding effect decreases the second-formant frequency.
Effects of Consonant context and lexical stress on vowel formant frequencies in continuous speech
Authors: Huang Caroline B.
Published: October 2005

The effects of consonant context and lexical stress for vowels and vowels in continuous speech have been investigated in previous acoustic studies [e.g., K. Stevens and A. House, J. Speech Hear. Res. 6, 111–128 (1963); P. Delattre, Final Rep., University of California (1969); F. Koopmans-van Beinum, Ph.D. thesis, University of Amsterdam (1980)]. However, the studies of consonant context and lexical stress involved only isolated words or words in a carrier phrase, and the studies of continuous speech did not consider each consonant context separately. In the present study, formant frequencies are measured in vowels taken from a read story that is well controlled with respect to consonant context and lexical stress. The vowels studied are /iy/, /ey/, /ɪ/, /ɛ/, and /ʌ/. The consonant contexts are /b/, /d/, /g/, /w/, /r/, and /l/. The vowels carry primary or secondary lexical stress. The same vowels and contexts are elicited in a retold story and in nonsense words spoken in a carrier phrase. Preliminary results from one speaker indicate that consonant context and lexical stress do affect vowels in continuous speech, as expected. Furthermore, results so far show no gross differences in the effects of these factors on vowels in continuous speech and in the isolated words studied previously. [Work supported in part by NIH.]
Specification of vowel height using F 1 trajectories
Authors: Gopal H. S. , Manzella Joyce
Published: October 2005

Recently, the claim has been made that both acoustic and perceptual ambiguities between high and low vowels can be reduced when F 1 time/frequency variations, rather than F 1 “target” values, are considered [Di Beneditto, J. Acoust. Soc. Am. 86, 55–66 (1989)]. The current study investigates the efficacy of the F 1 time/frequency variation (the F 1 trajectory) as an acoustic measure of vowel height using an extended set of vowels. Additionally, the effect of speaking rate on these trajectories as it relates to vowel height is investigated. Four high-low vowel pairs in /pVC/ target syllables containing voiced and voiceless stops and fricatives are included. These syllables were produced at various rates in sentence context by four American English speakers, two males and two females. F 1 trajectory versus F 1 maximum measures are discussed in terms of their relative efficacy in classifying vowels into high and low groups.
Acoustic comparison of unvoiced fricatives in telephone speech versus typical speech
Authors: Petr David W. , Ellenberger Todd G. , Frost Victor S.
Published: October 2005

The results of a pilot study designed to compare the acoustic properties of unvoiced fricatives in telephone speech versus speech typically used for acoustic-phonetic analyses are reported. Two new characterizing parameters for the unvoiced fricatives are introduced: the half-power bandwidth (resonance width) and a three-point energy versus time contour. It is found that the average fricative power normalized by the average adjacent vowel power is considerably larger in the telephone speech for all speakers, fricatives, and fricative positions studied. Also, half-power bandwidths tend to be larger for [f] and [θ] in telephone speech, but smaller for [s] and [∫]. The study yields a preliminary understanding of these acoustic differences in terms of the differences in vocal effort, microphone placement, and frequency response and bandwidth of the recording equipment. Finally, possible distinguishing perceptual cues for the different recording environments in terms of the acoustic differences are hypothesized. In particular, the energy-time contour of [θ] exhibits a peculiar high-low-high pattern that is most pronounced in the telephone recordings. [Work supported by AT&T, NSF, and the University of Kansas.]
Perceptual judgments of modified deaf speech
Authors: Yeni-Komshian Grace H. , Bunnell H. Timothy , Mahshie James J.
Published: October 2005

The perceptual effects of modifying speech produced by deaf talkers were investigated to examine, in part, the changes necessary for disordered speech to be judged normal. Recordings of the rainbow passage produced by a number of deaf male speakers were studied and three passages judged to be moderately disordered were selected. The word “beautiful” was extracted from these passages and from a similar passage recorded by a hearing talker. Each of the deaf talkers' productions was paired with the normal production to make two types of continua. One type was based on a time warping of the disordered speech to fit the temporal structure of the normal speech, while the other was based on a time warping of the normal speech to the temporal structure of the disordered speech. Each continuum contained ten steps, ranging from disordered to normal spectral properties. Graduate students in the fields of speech and hearing judged whether the stimuli sounded normal or disordered. Continua based on the normal talker's timing provided ordered responses showing an increasing proportion of “normal” responses for steps approaching normal spectra. For continua based on the deaf talkers' timing, however, responses were generally not ordered across the spectral continuum. The relative merits of temporal and spectral modifications will be discussed.
Binaural detection with reproducible short-duration narrow-band maskers
Authors: Colburn E. , Colburn H. Steven
Published: October 2005

Hit and false alarm rates were measured for detection of a 500-Hz tone target in each often samples of 1/3-oct noise centered at 500 Hz with a duration of 10 ms, for both NoSπ and NoSo conditions. Two target waveforms were used, differing only in their phase relative to the masker. Three subjects are being tested, but extensive data is available from only one subject so far. Also, the NoSo experiment has been done for only one target phase. The NoSo hit rates correlate very well with the energies in the waveforms. For NoSπ, the effect of target phase on hit rate is substantial, with almost no correlation between the rates for the two target phases. This is very different from earlier results with long duration waveforms [e,g., Gilkey et al., J. Acoust. Soc. Am. 78, 1207–1219 (1985)]. Neither models based on lateral position nor models based on the sum of the squares of the interaural differences correlate well with the data. Since subjects report multiple images and the interaural differences sometimes change substantially over the 10-ms duration, models that process the first and second halves of the waveforms are analyzed separately. [Work suported by NINCDS.]
Some acoustic properties of layered-composite plates
Authors: Hwang Y. F. , Zoccola P. J.
Published: October 2005

This paper discusses a method of calculating the modes of wave propagation in a composite plate. A composite plate consists of layers of different elastic and/or viscoelastic materials. A novel three-layer sandwich plate, which utilizes a light weight soft core sandwiched between stiffer septums (to increase flexural rigidity without severe weight or cost penalty), will be closely examined in terms of its antisymmetrical (flexural or bending) and symmetrical (longitudinal or bulge) modes of wave propagation. The dispersion relationship and the coincidence frequency of the flexural wave will be discussed. Effects of fluid loading and some other acoustic properties of the composite plate, such as the transmissibility and reflectivity of sound, will also be discussed.
The damping of beam vibrations by viscoelastic layers bearing pellets: Theory and experiment
Authors: Martinez Rudolph
Published: October 2005

A number of powerful solutions for the scattering action of spherical inclusions in extended elastic media are available in the literature. These analyses are relatively general and thus are usually too complex to provide direct insight into the relations between their many design variables. Rather, they often require parametric studies based on numerical results. The present development takes instead a simpler view that focuses on the two only possible types of motion of a single underformable pellet in an incident field containing dilatational and shear waves: a translational response for the dilatational case and both pellet translation and rotation for the shear wave field. The analysis emphasizes the fact that each type of motion has an associated broad resonance and antiresonance pair about which energy dissipation is maximized. These frequencies depend on pellet mass and moment of inertia, and may therefore be controlled to increase damping within given bands of interest. Our study of flexural vibrations applies the single-pellet theory to predict the effective loss factor of beams having constrained and unconstrained layers bearing undeformable inclusions, and compares the model's results to measurements.
Transient propagation of a one-dimensional wave in a harmonically inhomogeneous medium
Authors: Kim Hyun Sil , Ginsberg Jerry H.
Published: October 2005

This paper considers the transient propagation of a one-dimensional dilatational wave in a spatially harmonic inhomogeneous medium of semi-infinite extent. A regular perturbation analysis of the response, suitable when the amplitude of the inhomogeneous deviation is small, reveals that inhomogeneity causes backscattering in the second-order term. A temporally harmonic excitation generating a signal whose wavelength is twice the periodicity of the inhomogeneity is shown to lead to a second-order standing wave behind the wave front whose amplitude growth ultimately invalidates the solution. The frequency at which this situation occurs matches the frequency at which Floquet theory predicts instability in the steady-state response. A finite-difference analysis based on the method of characteristics confirms the early-time validity of the perturbation solution. It also reveals that the late-time signal is essentially a standing wave in the region extending outward from the transducer to within several wavelengths of the wave front, whereas it most closely resembles a nondispersive propagating wave in the region of the wave front. [Work supported by NSF.]
Embedded fiber-optic acoustic transducer and sensor arrays for acousto-ultrasonic evaluation of materials
Authors: Thompson Chris , Claus Richard O.
Published: October 2005

A novel technique for generating acoustic pulses inside a material and then sensing the signal again within the material is proposed. A hollow core fiber-optic waveguide is constructed with periodic solid “plugs” fused in place. The optical fiber is embedded in a solid material, and laser light is sent down the hollow core fiber. The laser energy is absorbed and attenuated at the plug locations, causing localized heating that will then act as a source of ultrasonic waves due to the thermoelastic mechanism. Fiber-optic sensors are also embedded to receive the acoustic wave fronts. Any material disturbances in the path of the acoustic waves will effect the velocity and attenuation of the wave, which can be quantified using the stress wave factor (Vary et al.). The fiber-optic transducer/receiving pairs can be located anywhere within or upon a material or structure and can be used to detect damage in situ. This technique is particularly valuable in assessing damage in composite materials.
Analysis by variational principles of the vibration and acoustic radiation of a vibrating elastic plate with circumferential stiffeners
Authors: Ginsberg Jerry H. , McDaniel James
Published: October 2005

This study concerns the effects of circumferential ring stiffeners on the vibration and acoustic radiation of a submerged circular elastic plate. The disk, which is excited by an arbitrary axisymmetric harmonic force, may be supported by either a rigid annulus or by an infinite baffle. The analysis employs variational principles [J. H. Ginsberg and P. T. Chen, J. Acoust. Soc. Am. Suppl. 1 82, S1 (1987)], in which surface pressure and velocity are represented by assumed model functions. The presence of stiffeners alters the kinetic and potential energies of the plate, but it does not affect the formulation of the fluid-structure interaction. Two structural formulations are addressed, differing by whether the connection between the plate and the stiffeners is implicitly or explicitly enforced. The results for surface response are used in conjunction with the Kirchhoff-Helmholtz integral theorem to evaluate near- and farfield pressures. Results include radiation patterns showing the influence of stiffener size and location. (Work supported by ONR.)