bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors influencing the algebra “reversal error”
Authors: Cohen Elaine , Kanim Stephen E.
Published: October 2005

Given a written problem statement about a proportional relationship between two quantities, many students will place the constant of proportionality on the wrong side of the equals sign. Introductory physics is one of the first courses in which students encounter multiple-step problems that require algebraic (rather than numeric) solutions, and this “reversal error” is relatively common in student solutions to these types of problems. We describe an investigation into three possible influences on students who make this reversal error: variable symbol choice, sentence structure, and context familiarity. Our results, from a calculus-based physics course and an intermediate algebra course, show that sentence structure is the most significant of these three possibilities. However, sentence structure alone does not provide a complete explanation for the reversal error.
Acoustic scattering from viscoelastically coated bodies
Authors: Partridge Chris
Published: October 2005

The deformed cylinder method (DCM) is a very versatile model that can be used on a wide range of acoustic scattering problems. To date, it has been applied to uncoated axisymmetric bodies of circular cross section, whether they be rigid, elastic solids, or shells. In this article, the method is applied to three bodies that are covered to varying degrees by a viscoelastic absorbing layer. These bodies include a coated spheroidal shell, a spheroidal shell partially covered with an axisymmetric coated band, and a cylindrical shell with a lengthwise coated strip. For the coated spheroidal shell, the effects of varying coating thickness and coating loss on the scattering are examined. Results indicate that the coating has little effect below 2 kHz, but above this level, the target strength decreases with increase in either thickness or loss. At the higher frequencies, the analytical solution used in the DCM becomes unstable. To overcome this, a high-frequency solution is obtained by combining the DCM together with the physical optics method and layered plate theory. This high- frequency solution can also be used in situations where the shape of a partial coating is of a form that prohibits the analytical solution from being used. This was the case with the cylindrical shell with the lengthwise strip.
Transient response of lightly damped rooms: A finite element approach
Authors: Easwaran V. , Craggs A.
Published: October 2005

The finite element method is used to calculate the impulse response of an irregular room. Although only a finite number of degrees of freedom are used, there is sufficient information in the model to predict the early reflections from the walls to a source at any location within the room’s interior. The results of calculations, performed for a room with a curved roof, show how absorption material placed at strategic points on the walls can affect the temporal response.
Sound radiation by a cylindrical piezoelastic shell with an asymmetric insertion
Authors: Vovk Igor V. , Oliynik Valery N.
Published: October 2005

An acoustic system, defined as a liquid-filled piezoceramic shell with an asymmetric internal insertion, is considered. The mathematical model is formulated. The problem of sound radiation by such a system is solved using the partial domains method. The acoustic characteristics of the system for a number of insertions with different configurations and acoustic characteristics of surfaces are studied extensively. The analysis of the obtained quantitative data allows the following conclusions. When exciting the piezoceramic shell in the zero (pulse) mode, redistribution of energy among various circumferential modes of vibration of the shell occurs through the asymmetric disposition of the insertions. This fact sets up the conditions for the occurrence of specific low-frequency resonances of the system, absent in the eigenfrequency spectrum of the shell in vacuum.
Sound-production mechanisms of the axisymmetric choked jet impinging on small plates: The production of primary tones
Authors: Henderson Brenda , Powell Alan
Published: October 2005

The present investigation is concerned with the sound-production mechanism of primary small plate tones (S1 tones) generated by the impingement of a choked jet on normal flat plates with a diameter equal to the nozzle exit diameter. The power spectra associated with S1 tones typically contain a fundamental tone and many harmonics. These tones occur when the plate is located in a particular region of the jet. Photographic evidence indicates that S1 tones occur when a Mach disk cuts off a portion of the first conical shock wave leaving a frustum and a standoff shock wave forms in front of the plate. Timed schlieren photographs indicate that sound is generated when the jet boundary near the standoff shock wave contracts suddenly. This occurs as the first shock wave moves downstream and begins to interact with the standoff shock wave. The resulting sound appears to be somewhat impulsive. Reflector tests indicate that the tones may not be part of a feedback loop to the nozzle. Simplified calculations show that once the first shock wave is set into motion, its continued movement downstream is due to an increase in the compression of the upstream fluid.
Kaneohe acoustic thermometer further validated with rays over 3700 km and the demise of the idea of axially trapped energy
Authors: Spiesberger John L. , Tappert Frederick D.
Published: October 2005

The Kaneohe acoustic source transmitted 133-Hz, 60-ms resolution signals over 3709 km from Oahu at 183-m depth to a Naval receiver at 1433-m depth near northern California. Ray theory successfully models the acoustic multipaths whose travel times are unambiguously tracked between 1983–89, despite the fact that the sound bounces one or more times from the Oahu slope before becoming trapped in the sound channel. The eigenrays are inclined at about 15° at the axis of the sound channel. The upper turning depths of the eigenrays are insensitive to realistic perturbations along the section. This supports the finding that the changes in delay of ∼±0.2 s between 1983–89 are due to temperature and not due to changes in the multipaths. Compared with transmission through a smoothed representation of the ocean’s acoustic waveguide, the mesoscale and submesoscale features vertically scatter axially trapped energy about 200 and 800 m, respectively. The submesoscale structure may be associated with internal waves. Scattering from a combination of the meso and submesoscale is not a perturbation since scattering redistributes sound that would be otherwise axially trapped over 1 km; the scale of the acoustic waveguide.
Bayesian modeling of acoustic signals for seafloor identification
Authors: Michalopoulou Zoi-Heleni , Alexandrou Dimitri
Published: October 2005

In this paper the Helmholtz–Kirchhoff approximation for backscattering strength and a Bayesian model of the uncertainty related to acoustic backscatter measurements are integrated into a maximum a posteriori processing scheme for the estimation of seafloor roughness parameters. Two processors are developed based on different levels of uncertainty regarding the angles of incidence for the received acoustic signals and the system calibration. Simulations indicate that the new maximum a posteriori processors are superior to a maximum likelihood estimation scheme that operates under the assumption that the angles of incidence for the backscattered signals are fixed and treats the calibration factor in a deterministic fashion. Specifically, the new processors produce roughness parameter estimates which are very close to the true values of the parameters, which are known in simulations, whereas the fixed angle processors are shown to result in a substantial bias in the estimation procedure.
Adaptation-induced enhancement of vibrotactile amplitude discrimination: The role of adapting frequency
Authors: Delemos Kimberly A. , Hollins Mark
Published: October 2005

Two-interval forced-choice tracking was used to measure amplitude discrimination for 20-Hz vibrotactile test stimuli presented to the thenar eminence of three human observers. For all observers, relative difference threshold could be decreased by adaptation to a 20- or 100-Hz stimulus. Maximal enhancement of discrimination occurred when the amplitude of the adapting stimulus was such that it excited the NP I system to approximately the same degree that the test stimuli did. A signal detection analysis determined that shifts in the observers’ criteria could not consistently account for the enhancement of amplitude discrimination. A more likely explanation, in view of recent physiological discoveries, is that under optimal conditions of adaptation test stimuli differing slightly in amplitude become more distinctive because CNS events underlying the resultant sensory experiences become more refined and stimulus specific.
Masker asynchrony impairs the fundamental-frequency discrimination of unresolved harmonics
Authors: Carlyon Robert P.
Published: October 2005

A series of experiments investigated the finding that the fundamental frequency (F0) discrimination of a group of unresolved harmonics (the ‘‘target’’) is impaired more by a masker which starts before and ends after it than when the masker and target are gated on and off together [Carlyon, J. Acoust. Soc. Am. 99, 517–524 (1996)]. Generally, the masker was a group of unresolved harmonics with an F0 of 210 Hz, the target F0s were geometrically centered on 210 Hz, both the targets and the masker were filtered between 3900 and 5400 Hz, and the target duration was 200 ms. The additional deterioration produced by the portion of the masker occurring before the target (the ‘‘forward fringe’’) was greater than that produced by the portion after the target (‘‘backward fringe’’), but both had some effect. The forward and backward fringes reduced sensitivity even when the portion of the masker synchronous with the targets was absent, although the reduction was greatest when it was present. The deterioration was markedly reduced by filtering the fringes into a frequency region remote from the target and the synchronous portion of the masker, by attenuating the fringes by 10 dB, or by presenting them either contralaterally to the target or diotically. It could not be reduced by allowing the F0 of the fringes and of the synchronous portion of the masker to differ greatly from that of the target, or by adding a low-frequency portion to the fringe, thereby providing an additional cue to the time of transition between fringe and target. Explanations based on peripheral adaptation and on seemingly similar effects previously observed with brief targets [Massaro, J. Acoust. Soc. Am. 58, 1059–1065 (1975); Kelly and Watson, J. Acoust. Soc. Am. 79, 1934–1938 (1986); Divenyi and Hirsh, Percept. Psychophys. 17, 246–252 (1975)] were rejected. The data are discussed in terms of a central mechanism which includes parts of the fringes in its estimate of the pitch of the target/masker mixture.
Detection of frequency changes in transposed sequences of tones
Authors: Kidd Gary R. , Watson Charles S.
Published: October 2005

The ability to detect frequency changes in transposed sequences of tones was examined in a series of seven experiments. Listeners were asked to judge which of two transposed (i.e., frequency-shifted) comparison patterns preserved the sequence of relative frequencies presented in a preceding standard pattern. The task was performed with five-tone and two-tone patterns under conditions of high and minimal pattern uncertainty. Regardless of pattern length or level of uncertainty, frequency discrimination thresholds for a change in the relative frequency of a single tone were considerably higher when patterns were transposed than when they were not. There was a tendency for performance to worsen with increasing degrees of transposition (primarily under high uncertainty) but most of the detrimental effects of transposition occurred within the first two semitones of transposition. Minimal uncertainty testing resulted in large improvements with five-tone patterns (as much as one order of magnitude), but there was no effect of level of uncertainty on performance with two-tone patterns. Thresholds for changes in two-tone patterns were similar to (although slightly higher than) those for five-tone patterns under minimal-uncertainty testing. This pattern of results reveals that the effects of stimulus complexity (sequence length) and pattern familiarity (level of uncertainty) on relative-frequency discrimination are quite similar to the effects of these variables on absolute-frequency discrimination.
A robust sequential test for text-independent speaker verification
Authors: Lund Michael A. , Lee C. C.
Published: October 2005

A robust speaker verification algorithm based on sequential hypothesis testing is presented. In speaker verification, the system performance is severely degraded by deviations from the nominal statistical speaker models caused by insufficient training data, varying microphone and transmission line characteristics, and different levels and types of background noise. Historically, this problem has been addressed by using an empirical method to determine an adequate decision threshold for a desired operating point. The robust detection algorithm presented here is based on a minimax criterion, such that the worst-case performance over a class of distributions is minimized. The sequential test provides further robustness by using additional data if a decision cannot be reached with the desired level of confidence. The sequential detector has been implemented and tested on a realistic database collected specifically for this purpose, and the performance has been shown to be comparable to or better than that of the corresponding heuristic detectors previously described in the literature.
The influence of an applied sound field on bubble coalescence
Authors: Duineveld Paul C.
Published: October 2005

Coalescence of two bubbles of equal size O(1 mm) is inhibited if the bubbles are exposed to a sound field with sufficient amplitude near the resonance frequency of two bubbles. The experiments indicate that coalescence inhibition is caused by a too large approach velocity of the bubble surfaces. The experimental resonance frequency of two bubbles was found to be in good agreement with theory.
Hertzian contact transducers for nondestructive evaluation
Authors: Degertekin F. L. , Khuri-Yakub B. T.
Published: October 2005

Hertzian, dry, pointlike contacts are used to couple ultrasonic energy efficiently to plate wave modes in anisotropic solid plates. A new transducer configuration using a piezoelectric PZT-5H transducer and a quartz buffer rod is realized for this purpose. In particular, the lowest order antisymmetric Lamb wave (A0) mode is excited and detected in anisotropic plates at a frequency of 200 kHz and with signal-to-noise levels exceeding 65 dB. Time delay measurements and FFT techniques are used to obtain dispersion and anisotropy curves of phase velocity in anisotropic plates. The accuracy of the method is limited mainly by the distance measurements. In (001) silicon plates the agreement between theory and experiments is obtained with an accuracy of ±0.08%. Anisotropic phase velocity measurements are also performed for uniaxial graphite/epoxy composite plates and the results are compared with the theoretical model to derive the elastic constants of the composite. Through accurate phase velocity measurements, it is possible to detect delamination defects in composite plates with high resolution operating at 200 kHz. Using the surface impedance approach, a model is also developed to predict the effects of delaminations on phase velocity and the results are verified by experiments.
Vibration damping of large structures induced by attached small resonant structures
Authors: Strasberg M. , Feit D.
Published: October 2005

The paper presents a simple deterministic derivation of the vibration damping induced in a large main structure by a multitude of small substructures attached more-or-less compliantly to the main structure, each dissipating vibratory power at its frequencies of resonance. A simple expression is obtained for the damping induced in the large structure indicating that the damping depends primarily on the total effective mass of substructures resonating within a band centered at the frequency of vibration, and is relatively independent of the damping factors of the individual substructures. The application of this simple expression for induced damping is illustrated by calculating the damping induced by substructures attached to an axially vibrating rod and to a flexurally vibrating beam. For the latter case, the calculated damping factors are compared with measured values.
Measuring the structural intensity and force distribution in plates
Authors: Zhang Yong , Mann J. Adin
Published: October 2005

Identifying the sources of vibration in a structure and the energy exchange between structure elements is an important issue in vibration and noise control. Several formulations for the structural intensity have been presented in the past, but little is said about implementing the formulations using measured data. In this paper, two structural intensity formulas based on different assumptions are compared, and practical issues of implementing the calculations of the structural intensity using k-space analysis are discussed. A force distribution, calculated from Mindlin’s plate motion equations, is shown to be an additional tool to locate vibration sources. Since the calculation of both the structural intensity and the force distribution require the use of fast Fourier transforms (FFT), numerical difficulties arise that are solved by signal processing techniques such as windowing and filtering. The influences of the windowing and the filtering on the calculation of the structural intensity and the force distribution are described. Results show that windowing and filtering are needed to obtain reasonable results of the structural intensity and the force distribution from measurement data; however, they may remove useful information.
Analytical investigation of active control of radiated inlet fan noise
Authors: Risi John D. , Burdisso Ricardo A. , Fuller Chris R.
Published: October 2005

An analytical model has been developed to study the potential of active noise control techniques for reducing radiated tonal inlet noise from turbofan engines. The analytical model consists of multiple control sources placed in the periphery of the engine inlet duct which inject antinoise into the duct to destructively interfere with the tonal sound field generated by the fan. The development of the analytical expressions of the radiated sound fields due to both the disturbance and the control sources is based on duct modal expansion. Attenuation of the radiated sound field is accomplished using a multiple-channel feedforward control approach. Control signals are calculated to minimize the pressure disturbance at desired error sensor locations and are then used to determine the controlled radiated sound field. The model is used to evaluate the performance of the control system for single and multiple circumferential arrays of control sources. The model can be extended for use in design optimization. Sample results are presented to illustrate the predicted sound attenuations.
The distributed column sound system at Holy Cross Cathedral, Boston, the reconciliation of speech and music
Authors: Klepper David L.
Published: October 2005

The question of acoustics for both speech and music in the same space can be addressed by variable acoustics and/or ideal room acoustics for one use and electronic enhancement for the other. A large cathedral can have near-ideal acoustics for liturgical music and satisfactory speech intelligibility by the use of conventional, historically proven architectural design, hard finish surfaces, and a carefully designed, installed, maintained, and operated sound amplification system. Holy Cross Cathedral, Boston, is one such situation. The sound system design, and evaluation of results using the Crown–Techron, L. G. Marshall early-to-late ratio (ELR) testing technique [J. Acoust. Soc. Am. 96, 2251–2261 (1994)] are discussed.
Parametric calibration of electroacoustic transducers
Authors: Zhou Dayu , Peirlinckx Luc , Van Biesen Leo
Published: October 2005

In this paper, an identification approach is introduced for the parametric calibration of electroacoustic transducers. The method is based on the conventional substitution technique for hydrophone calibration and a parametric estimation technique for a linear system. The calibration is carried out in three main steps: (1) measurement of the combined transfer function of an electroacoustic transmitter–hydrophone system; (2) parametric estimation of the measured transfer functions with time delay, and calculation of the zero(s)/pole(s) of the system; (3) common polynomial extraction and reconstruction of the transducer’s characteristics. The calibration approach is illustrated with simulations as well as experiments. This new approach will allow the simultaneous calibration of transmitter and one or more hydrophones, and can be used to calibrate the relative amplitude characteristics as well as the phase characteristics of transducers.
Finite element micromechanical modeling of the cochlea in three dimensions
Authors: Kolston Paul J. , Ashmore Jonathan F.
Published: October 2005

A new cochlear modeling technique has been developed in which the number of assumptions required in model formulation is significantly less than in previous modeling studies. The main new feature of the method is that it allows individual cellular and membrane components of the organ of Corti to be embedded within the model fluid in their true structural positions, with connections to neighboring elements reflecting anatomical geometry. The cochlea is divided into a three-dimensional finite element (3-D FE) network of nodes, connected by branches representing the local mechanical properties. The model system of simultaneous equations, obtained by applying continuity at each node, is solved iteratively using a variant of the conjugate gradient method. Here the formulation and implementation of the 3-D FE method are described. Force generation by outer hair cells is included and results are presented which demonstrate the effect of tectorial membrane and Deiters’ cell mechanical properties on the effectiveness of the cochlear amplifier.
Slopes of distortion-product otoacoustic emission growth curves corrected for noise-floor levels
Authors: Nelson David A. , Zhou Jerry Z.
Published: October 2005

Distortion-product otoacoustic emission (DPE) input/output (I/O) curves were measured at 2f1−f2 frequencies with spectral-averaging and time-averaging procedures from ten normal-hearing ears. Stimuli were equal-level f1 and f2 primary tones with f2/f1 ratios of 1.2 and f2 frequencies at 1200, 2400, and 4800 Hz. Time-averaging procedures lowered noise-floor (NF) levels, compared to spectral averaging, so DPEs could be elicited by stimuli as low as 18 dB SPL in some ears. DPEs were corrected for power summation with NF levels and the resulting DPE I/O curves were fit with sixth-order polynomials. Slopes of fitted I/O curves were specified by the first derivative as a function of the level of the primary tones. Slopes of uncorrected spectrally averaged DPE I/O curves were strongly influenced by the NF level. Slopes of NF-corrected spectrally averaged DPE I/O curves were more representative of the true slope, specified as the slope of the corresponding time-averaged DPE I/O curve well above its NF. True DPE I/O slopes decreased with level from a mean slope near 1.0 dB/dB at 30 dB SPL and below for all three f2 frequencies. Nonmonotonicities in I/O curves were not seen at very low stimulus levels. At moderate stimulus levels and above, nonmonotonicities in individual DPE I/O curves reduced the slopes of individual I/O curves and reduced the average slope across ears.
Preservation of amplitude modulation coding in the presence of background noise by chinchilla auditory-nerve fibers
Authors: Frisina Robert D. , Karcich Kenneth J. , Tracy Todd C. , Sullivan Daniel M. , Walton Joseph P. , Colombo Joseph
Published: October 2005

Sound envelope temporal fluctuations are important for effective processing of biologically relevant acoustic information including speech, animal vocalizations, sound-source location, and pitch. Amplitude modulation (AM) of sound envelopes can be encoded in quiet with high fidelity by many auditory neurons including those of the auditory nerve (AN) and cochlear nucleus. From both neurophysiological and clinical perspectives, it is critical to understand the effects of background masking noise on the processing of AM. To further this goal, single-unit recordings were made from AN fibers in anesthetized chinchillas. Units were classified according to spontaneous firing rate (SR) and threshold. Best frequency (BF) pure-tone bursts and AM (10–500 Hz) tone bursts were employed as stimuli at several sound levels, both in quiet and in the presence of a continuous wideband noise. It was found that (1) in quiet, low SR AN fibers show the strongest AM coding, followed in order by medium SR and high SR fibers, respectively. (2) AN units of all three classes generally preserve their AM coding even in the presence of loud (0 or +6 dB S/N) background noise and at high sound levels (over 75 dB SPL). (3) This preservation is usually achieved by lowering the average firing rate proportionately to decreases in the synchronous (fundamental frequency) response. (4) For a few AN fibers, the AM coding increases or is reduced in the presence of the background noise. These findings suggest that AN preservation of AM coding in the presence of a continuous masking noise results from shifts in the operating ranges and firing rates of AN fibers resulting from cochlear nonlinearities and adaptive mechanisms.
The sound absorption of occupied auditorium seating
Authors: Bradley J. S.
Published: October 2005

Measurements of the sound absorption coefficients of blocks of occupied theatre chairs varied approximately linearly with the ratio of sample perimeter-to-area ratio. Extrapolations of such measurements were used to predict the absorption coefficients of occupied chairs in auditoria. Analyses of these and other published data show that the absorption coefficients of occupied chairs also vary with the absorbing properties of the chairs. A more general method for predicting the sound absorption of occupied chairs as a function of sample perimeter-to-area ratio is proposed based on classifying chairs as having low, average, or high absorption characteristics. The new method is simple to apply and is thought to be more accurate than currently accepted methods.
A time domain description for the pitch strength of iterated rippled noise
Authors: Yost William A. , Patterson Roy , Sheft Stanley
Published: October 2005

Two versions of a cascaded add, attenuate, and delay circuit were used to generate iterated rippled noise (IRN) stimuli. IRN stimuli produce a repetition pitch whose strength relative to the noise can be varied by changing the type of circuit, the attenuation, or the number of iterations in the circuit. Listeners were asked to discriminate between various pairs of IRN stimuli which differed in the type of network used to generate the sounds or the number of iterations (n=1, 2, 3, 4, 7, and 9). Performance was determined for IRN stimuli generated with delays of 2, 4, and 8 ms and for four bandpass filter conditions (0–2000, 250–2000, 500–2000, and 750–2000 Hz). Some IRN stimuli were extremely difficult to discriminate despite relatively large spectral differences, while other IRN stimuli produced readily discriminable changes in perception, despite small spectral differences. These contrasting results are inconsistent with simple spectral explanations for the perception of IRN stimuli. An explanation based on the first peak of the autocorrelation function of IRN stimuli is consistent with the results. Simulations of the processing performed by the peripheral auditory system (i.e., interval histograms and correlograms) produce results which are consistent with the involvement of these temporal processes in the perception of IRN stimuli.
The perceptual dimensions of single-electrode and nonsimultaneous dual-electrode stimuli in cochlear implantees
Authors: McKay Colette M. , McDermott Hugh J. , Clark Graeme M.
Published: October 2005

The perceptual dimensions evoked by dual-electrode stimulation were investigated in four cochlear implantees. The dual-electrode stimulation consisted of biphasic current pulse trains, such that two intracochlear electrodes each received one pulse in a 250-Hz cycle. The experiments tested the hypothesis that perceptual qualities would be altered when there was an increased likelihood of interactions occurring between the two electrode places. The parameters of the stimulation which were manipulated to test this hypothesis were the time delay between the pulses on the two electrodes (2 ms and a value between 0.62 and 0.92 ms), the distance between the component electrode rings of each bipolar pair (3.75 mm and either 2.25 or 1.5 mm), and the distance between the two bipolar pairs in the dual-electrode stimuli (from 0.75 to 12.0 mm). Five sets of 15 loudness balanced stimuli were created, each set having different stimulation parameters.

These stimuli consisted of five single-electrode stimuli (a 250-Hz pulse train on each of five electrodes) and the ten dual-electrode stimuli formed by the combinations of those five electrodes. Two perceptual dissimilarity matrices were obtained for each subject and each set, and were analyzed using repeated nonmetric multidimensional scaling techniques. The resultant ‘‘stimulus spaces’’ were then examined to see how many perceptual dimensions the stimuli were best described by, and to what perceptual or stimulus qualities the dimensions might correspond. The results showed that the percept evoked by dual-electrode stimulation contained two main dimensions. Increasing the width of the current path to create substantially overlapping stimulation areas, or altering the temporal delay between the two electrodes, had very little effect on this percept. The position of the stimuli in the two-dimensional space was related to the distances of the two component electrodes along the electrode array. These results are relevant to speech processing strategies and electrode design for cochlear implants, as they imply that the creation of discrete, nonoverlapping areas of stimulation may not cause the percepts to be more distinct, and therefore may not necessarily lead to better speech perception.
Gap detection for pairs of noise bands: Effects of stimulus level and frequency separation
Authors: Hall Joseph W. , Grose John H. , Joy Saju
Published: October 2005

Temporal gap detection was determined for single 20-Hz-wide noise bands having various center frequencies, and for simultaneously presented pairs of noise bands where the spectral separation between center frequencies was varied. In most conditions, each noise band was presented 30 dB above its detection threshold, but in some conditions, each noise band was presented 15 dB above its detection threshold. The results for single noise bands indicated that the gap threshold did not vary significantly across center frequency. Gap detection was significantly better for pairs of noise bands than for single noise bands. The improvement in gap detection when two noise bands were presented instead of one was greater at the 15-dB presentation level than at the 30-dB level. In the case where pairs of bands were presented, there was no effect of the spectral separation between bands, even though the spectral separation was varied over a range of 5 oct. Spectral integration for gap detection may be limited only by the audibility curve.
Children’s processing of prosodic cues for phrasal interpretation
Authors: Beach Cheryl M. , Katz William F. , Skowronski Aire
Published: October 2005

Using synthetic speech, word duration and fundamental frequency (F0) contours were parametrically manipulated to examine processes of phrasal interpretation by adult and child (5 and 7 years old) listeners. From an adult male voice, versions of the phrase ‘‘pink and green and white’’ were resynthesized to produce stimuli suggesting two possible interpretations: [(pink and green) and white] and [pink and (green and white)]. For each stimulus, listeners pointed to a picture to indicate which interpretation was intended. All subjects used duration and (to a lesser extent) intonation as perceptually salient cues for phrasal interpretation. The manner in which subjects processed this information was evaluated by comparing subjects’ performance with the predictions of three different information processing models: a nonindependent cue-evaluation model, and two independent cue-evaluation models (an additive model, and the multiplicative, fuzzy logical model). Performance was best described by the fuzzy logical model, which assumes independent cue evaluation and generates a classification function characterized by cue trading relations. The results suggest that, similar to adults, children as young as 5 years of age rely on acoustic-prosodic information for syntactic phrase interpretation, and they process this information in an adultlike manner.
Frequency ratios of spectral components of musical sounds
Authors: Brown Judith C.
Published: October 2005

A recently developed high resolution frequency tracker [J. C. Brown and M. S. Puckette, ‘‘A high resolution fundamental frequency determination based on phase changes of the fourier transform,’’ J. Acoust. Soc. Am. 94, 662–667 (1993)] has made it possible to measure the ratios of the frequencies of the upper harmonics of a sound with respect to its fundamental frequency with high accuracy. Calculations were carried out on digitized sounds produced by a clarinet, alto flute, voice, piano, violin, viola, and cello. The sounds produced by the stringed instruments included examples played pizzicato and bowed both with and without vibrato. Measured ratios were exactly equal to integers for all instruments except the piano and strings played pizzicato. Anomalous behavior was observed for the fundamental frequency for vibrato sounds played by stringed instruments with the frequency deviation exceeding the extrema of the other harmonics divided by their harmonic number by about 1% on average. Piano inharmonicity was proportional to harmonic number squared in agreement with Fletcher [J. Acoust. Soc. Am. 36, 203–209 (1964)]. The major limitation on this calculation was found to be instrumental fluctuations.
Feasibility of a mechanical waveguide to control the ultrasonic field of a pulsed planar piston transducer
Authors: Finneran James J. , Hastings Mardi C.
Published: October 2005

An important consideration in the use of ultrasound in biomedical applications is controlling the range and spatial resolution. In this study, the feasibility of using a mechanical waveguide to control the axial range of a flat disk transducer is considered. The waveguide is a water-filled, circular glass cone fixed to the transducer. Experimental beam measurements are compared to theoretical predictions for transducers with and without waveguides. The results confirm that mechanical waveguides may be used to control the axial location of the natural focus and reduce the beamwidth at the focus and beyond. They provide a relatively inexpensive alternative to phased arrays and more flexibility than single-element transducers, as different sized waveguides would allow a single transducer to operate at a variety of axial ranges and spatial resolutions.
Vibrational relaxation and sound absorption and dispersion in binary mixtures of gases
Authors: Townsend Lawrence W. , Meador Willard E.
Published: October 2005

Reaction kinetics is used in concert with the usual gas species continuity and momentum equations to derive a pure wave equation for a single parameter (pressure or density). Solutions are obtained for sound absorption and dispersion in a binary mixture of gases which are equivalent to those derived from the phenomenological theory of irreversible thermodynamics. The methods are illustrated by comparison with acoustic measurements of vibrational relaxation in nitrogen–water vapor mixtures near room temperature.
General study of axisymmetric waves in layered anisotropic fibers and their composites
Authors: Nayfeh Adnan H. , Nagy Peter B.
Published: October 2005

A unified general treatment of the propagation of longitudinal waves in coaxial anisotropic assembly of fiber systems is presented. The fiber system consists of an arbitrary number of coaxial layers, each possessing transversely isotropic symmetry properties, that are either perfectly attached at their interfaces or bonded via imperfect interface zones. The single fiber system is either embedded in an infinitely extended solid or fluid host or kept free. As a natural extension of the single fiber case, uniformly distributed fiber systems in a matrix material, which model unidirectional fiber-reinforced composites, are also studied. All solutions are derived in the form of dispersion relations using the transfer matrix technique. Imperfect interface zones are modeled by degenerate transfer matrices reflecting jumps in the field variables of the neighboring layers. The results are numerically illustrated for a wide range of applications.
Dosimetry measurements using a probe tube microphone in the ear canal
Authors: Shotland Lawrence I.
Published: October 2005

Federal and international standards recommend use of microphone placement either on or in the vicinity of the shoulder for dosimetry to minimize deviations from the undisturbed sound field. Probe microphone measurements from the ear canal were compared to shoulder and chest measures in order to investigate the validity of current dosimetry methodologies. Six subjects were monitored in an industrial setting. As expected, ear-canal levels exceeded other measures for all subjects. Shoulder and chest measures showed very low intersubject variability whereas ear-canal measures resulted in large intersubject variability. The ear-canal methodology has the potential to identify individuals whose external ear gain exceed the mean, putting them at increased risk of noise-induced permanent threshold shift (NIPTS). It is proposed that overall external ear pressure gain be used as an index to adjust exposure levels when predicting NIPTS using ISO 1999. A normative database of external ear pressure gain was constructed from 30 ears for this purpose.
Latency and multiple sources of distortion product otoacoustic emissions
Authors: Stover Lisa J. , Neely Stephen T. , Gorga Michael P.
Published: October 2005

A novel analysis approach has been developed to examine the latency of distortion product otoacoustic emissions (DPOAEs). DPOAEs were measured in ten normal-hearing adults in a paradigm in which f2 was held constant and f1 was varied. This paradigm was used with a wide range of primary levels. Latency was estimated in two ways. In the first, a phase-slope delay measurement was used which showed a significant response latency increase as stimulus intensity was decreased. In the second approach, an inverse-FFT procedure was used to provide a temporal analysis of the data. Results of this analysis reveal a complex latency structure with multiple peaks in the envelope of the time waveform. The latencies of individual peaks remain constant across level, however short latency peaks have the greatest amplitudes at higher levels, and longer latency peaks are largest at low levels. These results would be consistent with the idea that there are multiple intracochlear sources for distortion product generation; however, a simple model, in which generation is assigned to the f2 and the 2 f1−f2 place, does not adequately explain the number of envelope peaks that were present in many ears.
Mechanical and ‘‘temporal’’ filtering as codeterminants of the response by cat primary fibers to amplitude-modulated signals
Authors: Greenwood Donald D. , Joris Philip X.
Published: October 2005

From previous studies it appears that at least two factors limit the upper frequency at which auditory-nerve (AN) fibers can entrain to the envelope of a sinusoidally amplitude-modulated (AM) tone. Cochlear mechanical filtering insures that, in the local motion driving a fiber tuned to the carrier, sidetone amplitudes decrease as sidetone displacement envelopes separate with modulation frequency (fm). Only if at least one sidetone’s amplitude is large enough, relative to carrier’s, will there be modulation of basilar motion at the point tuned to the carrier. In addition, processes within haircell and fiber limit the upper frequency at which they follow variations in amplitude. To assess change, along the cochlea, in the two factors’ relative importance, AN modulation transfer functions (MTFs) [Joris and Yin, J. Acoust. Soc. Am. 91, 215–232 (1992)] were replotted versus distance in mm between sidetones and carrier, using an empirical frequency-place function [Greenwood, J. Acoust. Soc. Am. 87, 2592–2605 (1990)]. MTF bandwidths, converted to mm, changed little over the apical 40% of cochlea but decreased basally. Expressed in Hz, they increased from apex to base and reached an upper limit at a characteristic frequency (CF) of 20 kHz. This is consistent with the idea that at high CFs phase-locking constraints limit envelope-following before mechanical filtering does, while in apical regions spatial filtering reduces envelope amplitude variation, hence envelope following, before limits on phase locking do. Consistently, MTF bandwidths parallel tuning curve bandwidths in the apical cochlea, but are smaller near the base, where tuning curve bandwidths and spatial filtering appear constant.
Spectral weights for overall level discrimination in listeners with sensorineural hearing loss
Authors: Doherty Karen A. , Lutfi Robert A.
Published: October 2005

A conditional-on-a-single-stimulus (COSS) analysis procedure [B. G. Berg, J. Acoust. Soc. Am. 86, 1743–1746 (1989)] was used to measure the weight or relative reliance that normal-hearing and hearing-impaired listeners give to different frequencies in the discrimination of the overall level of a multitone complex. On each trial, two multitone-tone complexes comprised of six octave frequencies from 250 to 8000 Hz were presented to subjects. The levels of the frequencies for each complex were randomly varied. The listeners task was to identify the complex with the higher overall intensity level. Normal-hearing listeners used a variety of listening strategies to perform the task, showing no general preference to weight one component over another. Hearing-impaired listeners, however, showed a general tendency to give greatest weight to the spectral information in the region of their hearing loss. Thirteen of the 14 hearing-impaired listeners, all of whom had a high-frequency sensorineural hearing loss, weighted one or more of the high-frequency components in the complex the greatest.
Deoxyribonucleic acid concentration using acoustic radiation force
Authors: Yasuda Kenji , Kiyama Masaharu , Umemura Shin-ichiro , Takeda Kazuo
Published: October 2005

A deoxyribonucleic acid (DNA) concentration method using acoustic radiation force is proposed. Ethanol was added to an aqueous DNA sample in order to initiate clustering of the DNA molecules of 2686 bps. The change in the distribution of the DNA clusters induced by a standing wave ultrasound irradiation was observed with an optical microscope. The observable DNA clusters gathered on the pressure node in the ultrasonic standing wave field and formed larger clusters that did not break apart after the irradiation was stopped. Without ultrasound irradiation, no significant change in the cluster distribution was observed. This method may have a potential use for concentrating and collecting biomaterials such as nucleic acids and proteins.
A new fast field program for a multiple-source system
Authors: Li Y. L. , White Michael J.
Published: October 2005

A new fast field program (FFP) has been developed for numerical computation of sound pressure from a phased multiple-source or multiple-receiver system in a layered atmosphere. The new FFP is based on a far-field approximation for which a criterion of validity is given. Using the stationary phase method, the twofold integral for sound pressure is reduced to a onefold integral representing the far-field approximation of sound pressure. The onefold integral makes the new FFP very efficient.
The time course of effects on intensity discrimination following monaural fitting of hearing aids
Authors: Robinson Ken , Gatehouse Stuart
Published: October 2005

Systematic effects on intensity discrimination occur in listeners who have experienced long-term unilateral amplification [Robinson and Gatehouse, J. Acoust. Soc. Am. 97, 1183–1190 (1995)]. For a bandlimited tone complex centered at 3 kHz, the normally aided ear showed better discrimination performance than the unaided ear at sound-pressure levels greater than 85 dB, yet was worse than the unaided ear at lower levels. No effects were found at 0.25 kHz. In the present study, intensity discrimination was investigated prospectively for five listeners with bilateral, sensorineural, hearing impairment following provision of unilateral amplification. The stimuli were the same as those used previously. Weber functions for both ears were similar at both frequencies prior to fitting the aid, and 4 to 12 weeks postfitting. From 15 weeks, the normally aided ear showed better discrimination performance than the unaided ear at 3 kHz for a sound-pressure level of 95 dB. No effects were observed at 0.25 kHz, or for the unaided ear. Hence, changes in intensity discrimination occur in the normally aided ear following long-term exposure to the frequency-gain characteristics of unilateral amplification. Further research should examine the generality of these results to other listeners, and show whether it extends beyond intensity discrimination to other psychoacoustic capabilities.
Structural and acoustic response of mass-spring loaded cylindrical shells: Spectral formulation and ray synthesis
Authors: Ho Jin-Meng
Published: October 2005

Ray techniques resolve individual physical mechanisms in describing wave radiation and scattering, and have been successfully applied to reparametrize the sound field of source excited elastic shells immersed in fluid but without internal load. Motivated on the same grounds, this paper reexamines, in ray acoustic terms, a submerged thin cylindrical shell mounted with an interior mass-spring oscillator. The formulation is facilitated by spectral theory, just as for the empty shell case. As is well known now, internal loading is equivalent to inducing forces, and moments in more general situations, at the internal-shell joints that act on the shell as external forces. However, the strengths of such forces are determined by the dynamical balance of the composite system at those joints, and may be ultimately expressed in terms of the empty shell displacements excited (by unit-amplitude forces) and observed at the joints. Both flexural and membrane waves contribute to the latter, and hence their distinctive characteristics evince in the overall response via radiation of the coupling forces. With the modified ray acoustic algorithm developed recently for near-field scattering, all the ray fields are represented uniformly over the entire azimuthal domain, and they yield accurate numerical results compared to the normal mode series in the frequency range 1≤ka≤25 considered here.