bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of position of a crack in a concrete block by vibration analysis.
Authors: Abe Masato , Fujii Kiyohito , Sone Toshio
Published: October 2005

This paper describes a method to estimate the position of a crack in a concrete block using many sensors. An array of sensors is attached on the concrete block, and a vibration pulse is forced by using a small hammer. If there is a crack, a reflection wave is generated from the position of the crack. Therefore, conventional methods to estimate the position of the sound source seem to be useful for this purpose. However, since the concrete block is elastic, there are several vibration modes, and the position of a crack cannot be estimated by the conventional methods. Therefore, a new method is proposed to estimate the position of a crack in an elastic block. This is achieved by designing a FIR filter for each sensor output so that the summation signal of the outputs of the FIR filters has zero for useless vibration modes. Some experiments were carried out, and good results were obtained.
Transition duration effects on place perception in hearing-impaired listeners.
Authors: Zakia Reneé A. E. , Carney Arlene E.
Published: October 2005

The purpose of this study was to determine the contribution of transition duration in signaling an alveolar/velar place-of-articulation contrast to listeners with mild-to-moderate sensorineural hearing loss. In the experiments reported here, F1, F2, and F3 transitions were varied between values appropriate for [deh] and [geh]. These were combined with transition durations ranging from 20 to 50 ms in 5-ms steps. In three separate identification tasks, listeners were presented with: (1) all levels of formant pattern varied orthogonally with all transition duration values; (2) all levels of formant pattern combined with an ambiguous duration value; and (3) all levels of transition duration combined with an ambiguous formant pattern. A trend was observed for hearing-impaired listeners to identify stimuli with shorter transition durations as [deh] in the absence of other unequivocal cues for place of articulation. Overall performance of hearing-impaired listeners was more variable than that of normal listeners, predicted in part by the results of Summerfield etal. [Speech Commun. 4, 213–229 (1985)], in which hearing-impaired listeners showed a decreased ability to identify place of articulation from transition information alone. Results of these experiments will be discussed in terms of current views of temporal processing in hearing-impaired listeners. [Work supported by NIH.]
Perception of synthesized vowel pairs by normal and specifically language impaired (SLI) children.
Authors: Stark Rachel E. , Heinz John M.
Published: October 2005

It has been proposed that SLI children have a rapid-rate auditory-processing deficit, and alternatively, that they have special difficulty with signals that are low in information or degraded. In the present study, steady-state vowel pairs, /a/–/i/ and /æ/–/eh/, were presented to 20 normal and 20 SLI children within a series of tasks, namely, discrimination, in which they had to detect change/no-change in a series; identification where they identified stimuli presented one at a time; and sequencing, where they indicated order of presentation of paired stimuli. For both vowel pairs, short (40–5 ms) and long (240–40 ms) series were presented. It was found that the performance of the SLI children was not significantly different from the normals’ in tasks involving /a/–/i/. Both groups of children had greater difficulty with the /æ/–/eh/ than the /a/–/i/ tasks, but the SLI children showed significantly greater decrement in performance than normals for /æ/ vs /eh/. Neither group showed a significant effect of vowel duration. Implications of these findings for child language impairment will be discussed. [Work supported by NIH.]
Studies of ultrasonic velocity, internal friction, and dielectric behavior of aluminum-doped zinc manganese mixed ferrites.
Authors: Ramamurthy Janjanam S. , Veerayya N. , Rao K. V. V. M. Mohana
Published: October 2005

Ultrasonic velocity, Young’s modulus, and internal friction have been studied in aluminum-doped zinc manganese ferrites as a function of aluminum concentration and temperature (300–600 K). The presence of aluminum impurities is found to significantly alter the ultrasonic properties and also the internal friction. In order to ascertain if a similar dependence is reflected in the dielectric behavior as well, the dielectric constant and loss tangent have also been studied in the same ferrites as a function of dopant concentration, temperature, and frequency of measurement. Relaxational behavior is noticed with a remarkable dependence on aluminum impurity concentrations. Results of ultrasonic and dielectric measurements have been explained in the light of cationic exchanges between octahedral and tetrahedral sublattices of the ferrite.
Real lift versus acoustic lift: A unifying spectral representation of the basic force/velocity kernel for the entire linear subsonic regime.
Authors: Martinez R.
Published: October 2005

This paper considers an elemental harmonic force in a uniform freestream U. It uses a wave-number transform to express the basic transfer function linking this differential lift to its induced fluid velocities. The analysis shows that the momentum equation for the convective medium introduces a pole in the computed spectrum, and that this pole in turn generates a shed wake for points downstream of the lifting element. A fundamental benchmark limit for the formulation is the condition of pure acoustic diffraction, obtained from letting U→0: the wake pole then disappears, as it should, and the kernel displays its well-known ‘‘highly singular’’ self-effect of O(x̄−x̄0)−2, where x̄0 and x̄ are source and receiver points. The paper’s main conclusion is that the shed wake predicted for an extended lifting surface has a differential cause, not just a global one, and that standard aerodynamic analyses have apparently hitherto concealed this ‘‘textured’’ feature of the unsteady flow field by prescribing a dynamic ‘‘macro’’ constraint on the bound circulation of the aeroscattering problem.
Frequency selectivity, critical bands, and focused attention.
Authors: Scharf Bertram
Published: October 2005

Zwicker made evident the ubiquity of the critical band in auditory processing, from the detection of tones in noise to the discrimination of amplitude from frequency modulation. Recently, it has become clear that the critical band defines also the limits of the attention band; listeners who focus on a given frequency detect tones at that frequency and at frequencies in the surrounding critical band but miss tones farther away in frequency. The formation of the attention band in the appropriate frequency region may be effected by efferent signals to the cochlea. Support for this hypothesis is based on preliminary data from patients whose olivary-cochlear bundle had been severed to relieve severe vertigo and who reveal greatly widened attention bands. [Research supported by NIH.]
Temporal resolution within the upper ‘‘accessory excitation’’ region for maskers with fluctuating envelopes.
Authors: Nelson David A.
Published: October 2005

During Zwicker’s numerous investigations of the time structure of masking, he observed that envelope masking period patterns were larger for frequencies above the masker (in the upper ‘‘accessory excitation’’ region) than for frequencies near the masker (in the ‘‘main excitation’’ region). For example, the peak-to-trough ratio of the masking period pattern for a 4-Hz 100% amplitude-modulated masker was only 12 dB when the probe tone was within the main excitation region, at 1000 Hz, while the ratio was as large as 36 dB when the probe tone was within the accessory excitation region, at 3200 Hz [E. Zwicker, Acustica 36, 113–120 (1976)]. In the present research, masking at the peak and within the trough of 500-Hz amplitude-modulated maskers was investigated as a function of test frequency and masker level for modulation frequencies from 4 to 128 Hz in normal-hearing and hearing-impaired ears. Peak and trough masked thresholds were measured using amplitude-modulated signals with phasic and antiphasic envelopes. The results from normal-hearing ears confirm Zwicker’s finding that temporal resolution can be up to three times better in the upper accessory excitation region than in the main excitation region. Masking during envelope peaks remains constant while masking during envelope troughs increases with modulation frequency. This finding, and the slopes of the growth of masking, support Zwicker’s interpretation that masking during the envelope peaks and troughs are associated with simultaneous and nonsimultaneous masking, respectively. Peak-to-trough ratios in the upper accessory region are considerably reduced in hearing-impaired ears, which has important implications for processing speech signals in the presence of maskers with fluctuating envelopes. [Work supported by NIDCD.]
Information-bearing features of complex sounds.
Authors: Terhardt Ernst
Published: October 2005

While Eberhard Zwicker’s psychoacoustic and physiological work was mostly of the fundamental research type, he was extremely concerned about employment of insights and models to human benefit, i.e., hearing diagnostics, hearing aids, cochlear implants, tacticle hearing protheses, aids for the blind, and automatic recognition of speech. These types of application have in common that they are crucially dependent on reduction of complex auditory signals to information-bearing features. In fact, auditory acquisition and processing of information was a prominent guideline of Zwicker’s scientific endeavor, in which the present author through almost three decades had the privilege to participate. As a result, there emerges a picture of auditory information processing that includes significant insights into the perception of complex sounds such as speech and music. While it is apriori evident that auditory information processing is dependent on hierarchically organized, knowledge-based decision mechanisms, the finding is remarkable that pertinent processes are to a considerable extent installed on low levels of the auditory system. Pitch turns out to play a prominent role as a carrier of information on external acoustic objects. These findings throw a new light on early ideas on the significance of auditory frequency analysis in the cochlea, of lateral inhibition, and of interaural pitch formation.
Search for Zwicker’s specific loudness function.
Authors: Hellman Rhona , Florentine Mary
Published: October 2005

A key ingredient of Zwicker’s loudness model is the ‘‘specific loudness’’ function which relates loudness to excitation within a single critical band or Bark. For narrow-band stimuli near 1 kHz this relation is described by a power function with a mid-to-high level slope (exponent) about 20% lower than the overall slope of the loudness function. In normal hearing, a slope reduction can be obtained by partially masking a tone with an adjacent high-frequency band of noise. Implicit in these findings is the assumption that the noise effectively contains the high-frequency excitation evoked by the tone. Recent loudness data obtained by magnitude scaling procedures for 21 listeners with bilateral sloping high-frequency losses provide a validation of this assumption. Measured at a frequency beyond which earphone corrected thresholds increase by more than 50 dB/oct, loudness increases with level at a slower rate than at a lower frequency and in normal hearing. Shallower threshold functions, like high tone-to-noise ratios, have little, if any, effect on the tone’s rate of loudness growth. The overall shape and slope of the loudness functions can be predicted from Zwicker’s model of loudness summation modified to account for noise-induced hearing loss [M. Florentine and E. Zwicker, Hear. Res. 1 (1979)]. [Work supported by the VA Rehab. R&D Service and by NIDCD.]
Subjective and physical evaluation of noise immissions.
Authors: Fastl Hugo
Published: October 2005

For measurements of noise immissions, presently the equivalent level Leq is used. Leq represents the level of a stationary continuous sound with the same sound energy as produced by a noise immission with time-variant level. Hence, the Leq concept is based merely on a physical magnitude, i.e., sound energy, and lacks a solid psychoacoustic background. Therefore, together with Eberhard Zwicker, a method to evaluate noise immissions subjectively in psychoacoustic experiments was implemented. In short, the perceived loudness of a noise immission is represented by the length of a line displayed on a PC monitor. Examples of the subjective evaluation of noise immission with this method are given for road traffic noise and aircraft noise. In addition, the subjective evaluations are compared to physical measurements by a sound level meter and by Zwicker’s loudness meter. [Work supported by DFG, SFB 204.]
Fault detection in helicopter gearboxes using neural networks.
Authors: Dellomo Michael R.
Published: October 2005

One of the most dangerous problems that can occur in both military and civilian helicopters is the failure of the main gearbox. Currently, the principal method of controlling gearbox failure is to regularly overhaul the complete system. This presentation considers the feasibility of using a neural network to perform fault detection on the accelerometer data. The details and results obtained from studying the neural network approach are presented. Some of the underlying physics will be discussed along with the preprocessing necessary for analysis. Several networks were investigated for detection and classification of the gearbox faults. The performance of each network will be presented. Finally, the network weights will be related back to the underlying physics of the problem.
Sensitivity analysis for acoustic conditioning monitoring of beams.
Authors: Cheng Xiu-Ting , Finch Robert D. , Robin Pierre Y. , Jansen Ben H.
Published: October 2005

Beams have been used to study the sensitivity of the vibration monitoring method of flaw detection. Cracks and other defects can cause shifting and splitting of resonant frequencies, so that these changes can be used to indicate the presence of the defect. The limitation of the vibration monitoring method is that other conditions, such as uncertainties in the geometry of the test object, its surface conditions, and loading, can also affect the vibration response, and it is necessary to distinguish the effects due to harmful conditions from those due to harmless ones. The sensitivity of the method is thus determined by the need to make this distinction. These concepts will be illustrated with experimental results from a test fixture for the case of a slotted beam, assuming that a slot can be used as a model for a crack. The effect of geometrical uncertainties, coatings of damping material, and loading can also be studied experimentally. It is possible to use Thomson’s theory to calculate the amounts of frequency changes due to a slot, so that the experimental results will be discussed in the light of this theory. [Work supported by NSF Grant No. MSS-9024224.]
Parametric ultrasound heating: Experiments.
Authors: Rolt Kenneth D.
Published: October 2005

In companion to the preceding talk, this paper will describe the design and results of two experiments in parametric ultrasound heating. Two focused transducers were operated at 0.9 and 1.5 MHz, respectively, and had coincident foci incident upon a 0.08-mm-diam Chromel–Constantan thermocouple. The thermocouple was embedded in an encapsulate having absorption properties, sound speed, and density on-par with human thigh tissue. For these tests, the results show a temperature nonlinearity factor σheat=1.05, where σheat=Ta+b/(Ta+Tb), Ta+b is the temperature rise for simultaneous operation, and Ta+Tb is superposition of the temperature rise for separate operation. This nominally equates to a 1 °C temperature increase for the same electrical input power when both transducers operate simultaneously than when operated separately.
Experimental study of temperature elevation in a tissue phantom generated by an operating ultrasonic transducer.
Authors: Chase Joseph D. , Wu Junru
Published: October 2005

The temperature elevation in a homogeneous tissue-mimicking material generated by an ultrasonic transducer (focusing or nonfocusing) operating in megahertz frequencies was measured. It was found that in the vicinity of a transducer front face, both transducer surface heating and ultrasound absorption are important sources for tissue heating. As for heating due to ultrasound absorption, the experimental results are compared with theoretical predictions for nonperfused tissue resulting from a Gaussian beam model and from the model used by the NCRP (National Council on Radiation and Measurements).
Nonlinear acoustics of media with complex structure.
Authors: Beljaeva I. Yu. , Nazarov V. E. , Ostrovsky L. A.
Published: October 2005

The paper contains a brief review of a recent investigation of nonlinear properties of media with structural inhomogeneities such as pores, grains, cracks, etc. Such media are shown to possess an anomalously strong acoustical nonlinearity (SAN). As examples, the results of theoretical and experimental research of the following media are presented: (1) Rubberlike media [with μ≪λ (λ,μ are Lamé parameters)] with spherical and cylindrical pores. For such media, the nonlinearity is small. Experiments with a material such as plastizole give a good quantitative agreement with theory. (2) Grainy media (with systems of spherical grains) in which nonlinearity is connected with change of interparticle contact area caused by external pressure. It is established that in this case nonlinear parameters are determined only by the values of initial static deformation. The results of experiments for some samples of crumbly soils give good agreement with theoretical conclusions. The results described seem to be of value in connection with possible new methods of diagnosis in geophysics and seismology.
Finite amplitude wave studies in earth materials.
Authors: Johnson P. A. , Meegan G. D. , McCall K. , Bonner B. P. , Shankland T. J.
Published: October 2005

The highly nonlinear elastic behavior of rock may enable new means of interrogating earth structure, of measuring physical properties, and of modeling the seismic source. Compared to uncracked materials, rocks have a large nonlinear response because they contain numerous microcracks that readily compress under applied stress causing large changes of elastic moduli with pressure. Thus nonlinear effects in rocks can be two orders of magnitude greater than those of the uncracked materials typically studied in nonlinear acoustics. Several areas of nonlinear research are currently being undertaken in these laboratories. First, low-frequency (0.1–100 Hz) attenuation studies using a torsional oscillator show that nonlinear coefficients can be greatly increased by inducing additional microcracks in Sierra White granite. Second, ultrasonic parametric array studies demonstrate that strong difference frequency signal generation can take place inside rock samples. Lastly, energy redistribution of finite amplitude waves may produce progressive changes in observed spectra with distance. If a significant amount of energy is redistributed as a function of distance, then source models (based on assuming linear elastic wave propagation) may be in error. This theoretical and experimental work demonstrates that energy redistribution does indeed take place in rock.
Nonlinear vibration analysis of an ultrasonic cleaning problem.
Authors: Geers Thomas L. , Hasheminejad Mohamad
Published: October 2005

A micron-size spherical particle is bound to an elastic half-space by van der Waals forces. The particle and the surface of the half-space are immersed in an acoustic fluid and excited by harmonic plane waves propagating normally to the surface from either direction. The vibration of the particle is unidirectional and nonlinear about an equilibrium position determined by van der Waals attraction and Hertz contact. In the manner of a previous linear analysis [T. L. Geers and M. Hasheminejad, J. Acoust. Soc. Am. 90, 3238–3247 (1991)], an equation of motion is formulated that incorporates the effects of particle and fluid inertia, radiation and material damping, and surface and particle compliance. Numerical results are presented for a silicon particle adhering to a silicon half-space both in air and in water. Highly resonant primary response is found, the product of long-wavelength scattering in the resonance-frequency region. This result points to ‘‘resonance cleaning’’ as a promising method for efficient particle removal.
Secondary instability of a Stokes boundary layer.
Authors: Thompson Charles , Mehta Vineet , Mulpur Arun
Published: October 2005

Energy exchange in a Stokes boundary layer between primary unstable disturbances and secondary disturbances having subharmonic spanwise character is discussed. Primary disturbances correspond to the least-stable spanwise mode according to linear theory. By virtue of the Reynolds stress, primary and secondary modes are coupled. Hence, the temporal growth rate of the disturbance field is mediated by the energy balance between primary and secondary disturbances. In this presentation, the energy exchange between these modes and their influence on the structure of the velocity field is discussed. These disturbances are found to be chaotic. Both primary and secondary disturbances follow a period doubling route to chaos. However, the transition amplitude of the acoustic modulation for which chaos occurs is a function of the wave-number content of the initial disturbance field. The energy exchange between spanwise modes with respect to the initial wave-number content and the modulation amplitude is discussed. [Work supported by DOE.]
Reverberation imaging.
Authors: Yang T. C.
Published: October 2005

Reverberation imaging is a technique that creates an image of surface and bottom scatterers using low-frequency reverberation data. Reverberation from explosive charges of moderate size are known to last tens of minutes covering a basin-wide ocean. The backscattered signals (reverberations) carry information on the nature and locations of boundary features, thus affording wide-area knowledge from a single measurement location. Because of the multipath propagations, conventional processing of backscattered (reverberation) data cannot separate long-range returns arriving simultaneously from the surface and the bottom, except where there is a dominant feature such as a seamount. Matched field/mode processing could in principle be used to localize the surface and bottom scatterers separately except that these methods assume pointlike sources whereas in reality the scatterers are extended objects. This paper addresses modified matched field/mode processing to create images of surface and bottom scatterers separately.
The SAMSON experiment−Initial results.
Authors: Orcutt John A.
Published: October 2005

The ONR sources of ambient microseismic ocean noise (SAMSON) experiment was conducted in October–December 1990 to develop a synoptic view of low-frequency (10 mHz–1 Hz) ocean noise excitation and propagation. In order to understand the effects of ocean-atmosphere coupling, the experiment was conducted in coordination with the ONR surface wave dynamics experiment (SWADE) which provided detailed meteorological and wave dynamics data. The participating universities and laboratories included FlowDrill Industries, the University of Miami, Oregon State University, the Scripps Institution of Oceanography, and Washington State University. The field experiment produced continuous recordings from seismic and hydrophone arrays located on the ocean floor and near the deep ocean surface off the North Carolina coast, at the coastline at Duck, North Carolina, and in the Great Dismal Swamp, inland. During the experiment, a hurricane (Lilly) and a strong Nor’Easter passed through the area causing significant weather, sea surface, and noise pattern changes with frequencies ranging from as low as 5 mHz to more than 2 Hz. The correlations between weather and seismo-acoustic noise will be presented as well as patterns of frequency-dependent evolution of primary noise types including single and double frequency microseisms and pressure fluctuations associated with infragravity waves. Globally distributed earthquakes, which occur at frequent intervals, are responsible for a great deal of noise variability in the frequency band 60–100 mHz.
A hundred-day observation of microseism evolution in shallow water using a 6-point shallow buried OBS/P array.
Authors: Yamamoto Tukuo , Nye Thomas
Published: October 2005

A 6-point shallow buried ocean bottom seismometer and pressure gauge (SPOBS/P) array was deployed 2 km offshore of the Army Corps of Engineers’ Field Research Facility at Duck, North Carolina at 15-m water depth as part of the ONR sources of ambient microseismic ocean noise (SAMSON) experiments. An array element consists of three orthogonally mounted accelerometers and a pressure sensor and was buried approximately 1 m below the seafloor. The array aperture was about 1.2 km tuned for shallow-water microseism wavelengths. Although the array aperture is too large for gravity wave directional spectra measurements, the recently developed buried ocean directional spectrometer (BOWDS) method is used to measure the directional spectra of gravity waves simultaneously with the directional spectra of microseisms. The BOWDS method requires only the point measurement of pressure and the two orthogonal components of seabed motion [T. Nye etal., J. Atmos. Ocean Technol. 7, 781–791 (1990)]. Over 100-day continuous recording of real-time data was made starting 15 September 1990. The BOWDS results show good agreement with the linear 9-point array of pressure gauges. From this 100-day observation, a consistent pattern of microseism evolution was identified. Microseisms are suddenly activated right after the sudden shift of wind direction as multidirectional seas start to evolve. Fresh microseisms are generated at high frequency, say at 0.5 Hz at the beginning. As the seas get older, the microseisms at lower frequencies are generated. The evolution of microseisms follows the pattern of newly born seas. [Work supported by ONR.]
The seismo-acoustic response to the nonlinear interaction of ocean gravity waves.
Authors: Kibblewhite A. C. , Wu C. Y.
Published: October 2005

In the absence of shipping, high sea/wind states can produce measurable noise in the sea, various noise mechanisms dominating in different parts of the spectrum. In the band 1–3 to 50 Hz, the noise source is believed to be breaking waves. Between 0.1 to 1–3 Hz, commonly called the microseism band, the high noise levels observed are believed to arise from nonlinear interactions between surface gravity wave trains. At still lower frequencies (0.02–0.1 Hz), noise levels are generally very low and are thought to be controlled by currents and turbulence in the seafloor boundary layer. In the final band from dc to 0.02 Hz the noise again increases. It is felt that the noise in this band originates from very long wavelength swell. This paper examines the generation of ocean and seafloor noise in the microseism band, discusses the question of the source level associated with the wave-interaction process, and examines the dependence of the observed seismo-acoustic noise spectrum on wind speed, on seastate (PM and JONSWAP seas), on water depth, and on the geoacoustical environment. Experimental data from onshore seismic sensors will demonstrate the possibility of using the ULF noise field to measure seastate remotely and to provide insight into the processes controlling the growth and decay of wind-driven seas.
A study of the potential for active control of road noise in automobiles.
Authors: Ferren W. Brent , Bernhard Robert J.
Published: October 2005

Laboratory experiments were conducted on six vehicle suspension systems to determine the extent to which active noise control could be achieved for random excitation of the tire. In each case, a study was conducted to identify a desirable location for an accelerometer controller input sensor. Control at the driver’s head location was achieved using a single-channel commercial, open-loop, digital controller. Broadband noise reductions between 2 and 11 dB were achieved. The results were compared to analytical predictions which accounted for the limitations of coherence and finite size digital filters. The experimental results were comparable to analytical results when similar digital filters were utilized. Various filter alternatives were also studied analytically. In general, recursive filters performed significantly better than transversal filters. Small improvements were achievable using larger filters than currently available commercially. [This investigation was supported by Nissan Motor Co. and Nelson Industries.]
Further results on the duration of infrequent and frequent words.
Authors: Whalen D. H.
Published: October 2005

In a study reported at the last meeting of the Society, subjects produced longer durations when reading lists of infrequent words than ones with frequent words. This was in spite of the fact that the words contained exactly the same phonemes by virtue of being homophones (e.g., ‘‘right’’ and ‘‘rite’’). As in that study, subjects in the present experiment read rehearsed lists as quickly as they could, but this time, the two frequency types occurred in each list. Preliminary results show that, as before, the infrequent items were longer in duration, but the magnitude was reduced compared to the earlier results. Since these were the same subjects in the same session, direct comparisons are possible. Several explanations for the difference will be explored. First, the frequency category of the following item might affect duration as well. This effect, found in lexical access studies, may play a role here even though the lists were rehearsed. Second, subjects may simply have spoken more quickly in the later part of the session; the previous results had suggested that the frequency effect did not hold for the fastest talkers. Finally, it may simply be that by the time the subjects had uttered these words ten times, they were all temporarily higher in frequency. Whatever the explanation for the difference, the continued presence of an effect suggests, as before, that a link to the lexicon is maintained throughout production. [Work supported by NIH Grant No. DC-00825.]
Effects of rate and talker variability on the recall of spoken words.
Authors: Nygaard Lynne C. , Sommers Mitchell S. , Pisoni David B.
Published: October 2005

Changes in speaking rate and talker characteristics have profound effects on the acoustic structure of the speech signal. Current models of speech perception hypothesize that listeners must compensate for changes in rate and talker with a normalization process in which phonetic segments are evaluated relative to the prevailing rate of articulation and relative to specific talker characteristics. The present study was conducted to investigate how listeners adjust or normalize for changes in rate of speech and talker characteristics. A serial recall task was used to evaluate the consequences of rate and talker variability on the early encoding and rehearsal of the spoken words. Listeners were asked to recall words from single versus multiple rate lists; from single versus multiple talker lists; and finally, from lists with words produced by multiple talkers at multiple speaking rates. The results showed that words from lists produced at a single articulation rate were recalled more accurately in early serial positions than words from lists produced at multiple articulation rates; words from lists produced by a single talker were recalled more accurately in early serial positions than words from lists produced by multiple talkers; and finally, the combination of variability in talker and rate did not impair recall relative to lists with variation in rate or talker alone. These findings replicate and extend the results of previous research on talker variability [C. S. Martin etal., J. Exp. Psych:Learn. Mem. Cog. 15, 676–684 (1989); S. D. Goldinger etal., J. Exp. Psych:Learn. Mem. Cog. 17, 152–162 (1991)] suggesting that variations in speaking rate and in talker characteristics incur a processing cost that affects the initial encoding and subsequent rehearsal of spoken words. [Research supported by NIH.]
Prominence caused by rising and falling pitch movements with different positions in the syllable.
Authors: Hermes Dik J. , Rump H. H.
Published: October 2005

The object of this study was to investigate whether subjects are able to compare the prominence caused by different types of accent-lending pitch movements, and, if so, whether some pitch movements lend more prominence to a syllable than others. These experiments were carried out with the utterance/mamáma/, with the second syllable accented by either a rise, a fall, or a rise–fall. Subjects adjusted the variable excursion size of a comparison stimulus to the fixed excursion size of a test stimulus in such a way that the accented syllable in test and comparison stimuli had equal prominence. The rise–fall was only presented in standard position, the fall and the rise were tested for five different positions in the syllable. It is concluded that subjects are well able to equate the prominence of syllables accented by various types of pitch movement, viz., a rise–fall in standard position, a rise starting before the vowel onset, and a fall whatever its position in the syllable. Moreover, when lending equal prominence, the early starting rise and the rise–fall have equal excursion sizes. The fall, however, appears to lend more prominence to a syllable than the rise or the rise–fall of equal excursion size, independent of its position in the syllable. This difference increased with increasing declination of the pitch contour.
The small slope approximation for acoustic scattering at a fluid–solid interface.
Authors: Broschat Shira L. , Yang Taiqian
Published: October 2005

Acoustic scattering from the ocean bottom is of much interest to the underwater acoustics community. Recent results for the small slope approximation for one- and two-dimensional randomly rough pressure-release surfaces have been promising. In this paper, work on the small slope approximation is extended to acoustic scattering from a fluid–solid boundary for one-dimensional, randomly rough surfaces with a Gaussian roughness spectrum. Expressions are derived for the scattering strength using both the first- and second-order small slope approximations. Numerical results for the first-order approximation using parameters characteristic of acoustic scattering from a water–granite interface are presented. These results compare well with those obtained by Berman and Dacol [J. Acoust. Soc. Am. 84, 292–302 (1988)] using perturbation theory when it is expected to give accurate results. They contain the same interesting structural features at the critical angles for the transmitted compressional and shear waves. [Work supported by ONR.]
The local parabolic approximation for rough surface scattering.
Authors: Ivanova Kristinka , Broschat Shira L.
Published: October 2005

A method, based on a technique introduced by A. V. Belobrov and I. M. Fuks [Radiophys. Electron. (Izv. VUZ Radiofiz.) 29 (12), 1083–1089 (1986)], is studied for the case of scalar wave scattering from one-dimensional randomly rough surfaces with a Gaussian roughness spectrum. Using a local parabolic approximation of the rough surface, the surface source density is obtained. The small parameter in such an approximation is the inverse of the radius of the surface curvature multiplied by the wave number and the cube of the cosine of the local angle of incidence. The bistatic scattering cross sections per unit length are derived for the Dirichlet and Neumann boundary conditions. The first term for each is that of the Kirchhoff approximation; successive terms account for diffraction effects. Numerical results for both soft and hard surfaces are obtained and compared with other available numerical results. [Work supported by NSF and ONR.]
Renormalization group analysis of rough surface scattering.
Authors: Orris G. J. , Dashen R. F.
Published: October 2005

An acoustic field of wavelength much larger than the largest scale of a scattering body is considered. A renormalization group equation has been developed to find an easier way of calculating the ensemble averaged scattered fields, with the renormalized parameter being impedance constant introduced to describe the behavior of the boundary under insonification. The results suggest that rough surface scattering is, in fact, an asymptotic theory, under the limit that the surface structure has no lower cutoff and the scatterer has a power-law surface spectrum. Also, a fundamental difference in the renormalization scheme between the two extreme boundary conditions (von Neumann and Dirichlet) is pointed out. a)Currently at Naval Research Laboratory, Washington, DC 20375-5000.
Operator expansion error estimation by higher-order terms.
Authors: Dubberley John
Published: October 2005

The operator expansion method for quickly solving the Helmholtz boundary value equation was outlined by Milder [J. Acoust. Soc. Am. 89, 529–541 (1991)]. This method was verified by Kaczkowski and Thorsos for impenetrable surface scattering where Kirchhoff and small perturbation theory hold [J. Acoust. Soc. Am. 90, 2258 (A) (1991)]. In this presentation the third-order and higher terms of the symmetric operator expansion will be derived in order to place error bounds on the integral approximation for second-order and higher terms of the expansion. These error bounds can then be used to determine the regions of validity for the next lower-order expansion approximations. Some examples and comparisons to other scattering methods will be shown.
Temporal and spatial variation of bottom backscatter in the STRESS experiment.
Authors: Jackson Darrell R. , Dworski J. George
Published: October 2005

As part of the STRESS (sediment transport events on shelves and slopes) program, bottom backscattering data have been gathered using a circularly scanning sonar operating at 40 kHz. Scans were obtained over a 49-day deployment period at a rate of exactly 10 scans per day. The mechanical and electronic stability of the apparatus made it possible to maintain phase coherence over the entire deployment. As a result, coherent ping–ping correlation can be used to reveal changes in bottom scattering. The results are presented in the form of a false-color movie, which shows that biologically mediated change occurs with several temporal and spatial scales. A point scatterer model has been developed to reduce the measured correlation values to more readily interpreted parameters related to scatterer motion. By fitting the model to data, values for mean-square scatterer displacement between pings are obtained.
Modeling of low-frequency long-range reverberation measured in the CEAREX 89 experiment.
Authors: Yang T. C. , Hayward T. J.
Published: October 2005

In the Arctic ocean, very low-frequency (10–50 Hz) reverberation returns from the ice and bottom both contribute to the total received reverberation and are not easily distinguishable in long-range reverberation data, except where there is a dominant bottom or ice feature. In this paper, a normal-mode scattering model for surface and bottom protuberance is used to model long-range reverberation data collected during the CEAREX 89 experiment in the Norwegian/Greenland Seas. Modeled reverberation spectrum levels at 23 Hz are compared with data to investigate the relative contributions of the ice and bottom to the measured reverberation. It is found that for a source at 91-m depth in the 3000-m-deep basin, the reverberation level for a receiver at 91 m is dominated by scattering from the ice except for reverberation associated with certain identifiable bottom features. For the same environment but a deeper (244-m) source, reverberation levels from the ice and bottom are more comparable. For a strongly range-dependent environment, returns from bottom features are clearly identifiable in the data.
Computational efficiency in a bistatic, range-dependent, normal-mode acoustic reverberation model.
Authors: Fromm David M. , Orchard B. J. , Luther Kenneth H.
Published: October 2005

Acoustic bottom reverberation from a water–sediment interface for bistatic source and receiver configurations in range-dependent, multi-layered, shallow-water environments is calculated with a normal-mode model. The signal field is propagated to and from the scattering regions using adiabatic normal-mode theory. Scattering from the ocean bottom is treated using a three-dimensional Lambert’s-law/facet reflection model. An explicit descripion of the coupling between incident and scattered modes and their contribution to reverberation is obtained. When all possible contributions are considered, the computation time is proportional to the product of the number of incident modes and the number of scattered modes. If the modal contributions to reverberation are weighted and sorted into nonincreasing sequences, then the subsequent summation over all modes may be truncated at a desired level of accuracy. A dramatic increase in computational efficiency may be achieved. Results for a realistic ocean environment are presented which illustrate some of the features of the model. [Work supported by Office of Naval Technology, Code 234.]
On the weakness of using strong syllables as word boundary markers.
Authors: Yerkey Paul N. , Sawusch James R.
Published: October 2005

Previous research has shown that a strong–weak syllable distinction may play an important role in word segmentation. Cutler and Norris [JEP:HPP 14, 113–121 (1988)] asked subjects to identify words at the beginnings of two syllable nonwords. Subjects were faster to identify a word when the second syllable was weak than when it was strong. The present study included lax vowels in addition to the tense and neutral vowels previously used to form the second syllables. The lax vowel produces a strong syllable of short duration; something not previously present. By comparing word identification for items in which the second syllable is strong with either a tense or lax vowel to the weak syllables, the relative roles of strong versus weak syllables and vowel duration can be explored. To the extent that tense and lax vowel syllables produce equivalent effects, strong syllables act as a cue to word boundaries in English. [Work supported by NIDCD Grant No. DC00219 to SUNY at Buffalo.]
Novel findings concerning intelligibility of bandpass speech.
Authors: Riener Keri R. , Warren Richard M. , Bashford James A.
Published: October 2005

Very high intelligibility was found for a number of narrow-band filtering conditions. Four hundred listeners (20 groups of 20 subjects) were presented with bandpass filtered CTD sentences (‘‘everyday speech’’) and monosyllabic words. Separate groups received center frequencies of 370, 530, 750, 1100, 1500, 2100, 3000, 4200, or 6000 Hz at 70 dBA SPL. In experiment 1, intelligibility of single 1/3-octave bands with steep filter slopes (96 dB/oct) averaged more than 95% for sentences centered at 1100, 1500, and 2100 Hz, and more than 50% for monosyllabic words centered at 1500 and 2100 Hz. Experiment 2 used the same center frequencies with extremely narrow bands (slopes of 115 dB/oct intersecting at the center frequency)−intelligibility remained relatively high for most bands, with greatest intelligibility at 1500 Hz (77% for sentences, 18% for words). In experiment 3, 1/3-octave bands (96 dB/oct) centered at 370 and 6000 Hz were presented simultaneously either diotically or dichotically (when presented separately in experiment 1, intelligibility of these bands did not differ significantly, and averaged 23% for sentences and 3% for monosyllabic words). When the bands were combined, diotic and dichotic presentations were equivalent. Intelligibility rose to an average of 77% for sentences and 34% for words. [Work supported by NIH Grant No. DC00208.]
Perceptual segregation of tones embedded in modulated noise maskers.
Authors: Singh Punita G. , Bregman Albert S.
Published: October 2005

Maskers comprising four noise bands derived from same or different noise sources, and multiplied by same or different modulators, were compared for their efficacy in enabling perceptual segregation of a tone embedded in one of the bands. A two-interval paradigm was used, with a 1-kHz target tone followed by two noise bursts. The target tone was either absent, or present in the first, second, or both noise intervals at a fixed intensity level. The noise bands were centered at 0.5, 1, 1.5, and 2 kHz. A five-category labeling task was used. Labels ‘‘1,’’ ‘‘2,’’ and ‘‘3’’ enabled subjects to report if the target tone was audible as a distinct perceptual entity in the first, second, or both noise intervals, respectively. Label ‘‘4’’ allowed reports of timbre change for cases where the cue tone was not perceived as a distinct entity, but the noises seemed different. Label ‘‘5’’ implied that the noise bursts seemed identical with no tones or timbre change perceived. Data for ten normally hearing listeners indicate that maskers with coherence of modulator envelopes across the four bands enabled better perceptual segregation of the tone, in accordance with predictions based on results from CMR experiments. The envelope-coherence cue oveshadowed other variables such as masker bandwidth or sameness or difference of noise source. However, an interesting perceptual consequence was noted for the narrowest bandwidth (12.5-Hz) maskers. These tonal noises were more likely to be labeled as containing the target, despite its physical absence in the stimuli. While successful perceptual segregation of the target tone can be attributed to factors related to auditory grouping such as similarity of envelopes within the masker, it seems that other factors pertinent to grouping, such as similarity of features of the target and masker also play a role. [Work supported by NSERC.]
The subtractive nature of illusory continuity: Reciprocal changes in alternating sounds.
Authors: Warren Richard M. , Bashford James A. , Healy Eric W.
Published: October 2005

When portions of one sound are replaced by a louder sound, the missing segments may be restored if the louder inducing sound is a potential masker. This phenomenon has been examined extensively using pulsation threshold, auditory induction, and phonemic restoration paradigms to measure the conditions required for perceptual synthesis of the fainter sound. These studies have generally neglected to examine changes produced in the inducing sound. Decreases have been measured in apparent level of the inducer using inducer/inducee pairs consisting of tone/tone, noise/noise, and noise/speech. Interestingly, changes in the inducer occurred even when the inducee was above the pulsation threshold. Under some conditions loudness reduction was coupled with a marked alteration in timbre: Especially profound changes in the quality of the inducer occurred when the alternating sounds differed only in intensity (e.g., two levels of a 1000-Hz sinusoidal tone)−apparently, a residue with anomalous neural representation remains following subtraction of components corresponding to the inducee. These observations involving the inducer require modification of current theories concerning the apparent continuity and restoration of absent sounds. [Work supported by NIH Grant No. DC00208.]