bluuebunny/crossref_metadata_2025 huggingface dataset:
Musical quality assessment of clarinet reeds using optical holography
Authors: Pinard Fabrice , Laine Benoit , Vach Holger
Published: March 2003

Vibrational modes of 24 clarinet reeds have been observed in both dry and wet conditions using holographic interferometry. Results have been compared with the “musical quality” of the reeds as judged by two professional clarinet players. An excellent correspondence has been demonstrated between specific vibrational behavior and musical quality. The results suggest that the presence and symmetry of a strong first torsional mode are indicative of good or very good musical quality. A second, but less stringent quality criterion is the proximity of frequencies corresponding to the second torsional and the second flexural mode. This proximity leads to the creation of mixed vibrational modes for the very best of the investigated clarinet reeds.
Sound focusing in rooms: The time-reversal approach
Authors: Yon Sylvain , Tanter Mickael , Fink Mathias
Published: March 2003

New perspectives in audible range acoustics, such as virtual sound space creation and active noise control, rely on the ability of the rendering system to recreate precisely a desired sound field. This ability to control sound in a given volume of a room is directly linked to the capacity to focus acoustical energy both in space and time. However, sound focusing in rooms remains a complicated problem, essentially because of the multiple reflections on obstacles and walls occurring during propagation. In this paper, the technique of time-reversal focusing, well known in ultrasound, is experimentally applied to audible range acoustics. Compared to classical focusing techniques such as delay law focusing, time reversal appears to considerably improve quality of both temporal and spatial focusing. This so-called super-resolution phenomenon is due to the ability of time reversal to take into account all of the different sound paths between the emitting antenna and the focal point, thus creating an adaptive spatial and temporal matched filter for the considered propagation medium. Experiments emphasize the strong robustness of time-reversal focusing towards small modifications in the medium, such as people in motion or temperature variations. Sound focusing through walls using the time-reversal approach is also experimentally demonstrated.
An acoustic streaming instability in thermoacoustic devices utilizing jet pumps
Authors: Backhaus S. , Swift G. W.
Published: March 2003

Thermoacoustic-Stirling hybrid engines and feedback pulse tube refrigerators can utilize jet pumps to suppress streaming that would otherwise cause large heat leaks and reduced efficiency. It is desirable to use jet pumps to suppress streaming because they do not introduce moving parts such as bellows or membranes. In most cases, this form of streaming suppression works reliably. However, in some cases, the streaming suppression has been found to be unstable. Using a simple model of the acoustics in the regenerators and jet pumps of these devices, a stability criterion is derived that predicts when jet pumps can reliably suppress streaming.
Comment on “Investigation of sound waves generated by the Hall effect in electrolytes” [J. Acoust. Soc. Am. 111 (5), 2087-2096 (2002)] (L)
Authors: Dobrucki Andrzej B.
Published: March 2003

An improved model of magnetohydrodynamic transducer is presented. According to this model, the equations for direct and inverse transduction effect have the same form and they fulfill the reciprocity principle. The general form of equation for transduction coefficient in magnetohydrodynamic transducers is given
Highly directional acoustic receivers
Authors: Cray Benjamin A. , Evora Victor M. , Nuttall Albert H.
Published: March 2003

The theoretical directivity of a single combined acoustic receiver, a device that can measure many quantities of an acoustic field at a collocated point, is presented here. The formulation is developed using a Taylor series expansion of acoustic pressure about the origin of a Cartesian coordinate system. For example, the quantities measured by a second-order combined receiver, denoted a dyadic sensor, are acoustic pressure, the three orthogonal components of acoustic particle velocity, and the nine spatial gradients of the velocity vector. The power series expansion, which can be of any order, is cast into an expression that defines the directivity of a single receiving element. It is shown that a single highly directional dyadic sensor can have a directivity index of up to 9.5 dB. However, there is a price to pay with highly directive sensors; these sensors can be significantly more sensitive to nonacoustic noise sources.
Study of critical behavior in concrete during curing by application of dynamic linear and nonlinear means
Authors: Lacouture Jean-Christoph , Johnson Paul A. , Cohen-Tenoudji Frederic
Published: March 2003

The monitoring of both linear and nonlinear elastic properties of a high performance concrete during curing is presented by application of compressional and shear waves. To follow the linear elastic behavior, both compressional and shear waves are used in wide band pulse echo mode. Through the value of the complex reflection coefficient between the cell material (Lucite) and the concrete within the cell, the elastic moduli are calculated. Simultaneously, the transmission of a continuous compressional sine wave at progressively increasing drive levels permits us to calculate the nonlinear properties by extracting the harmonics amplitudes of the signal. Information regarding the chemical evolution of the concrete based upon the reaction of hydration of cement is obtained by monitoring the temperature inside the sample. These different types of measurements are linked together to interpret the critical behavior.
Control of voice fundamental frequency in speaking versus singing
Authors: Natke Ulrich , Donath Thomas M. , Kalveram Karl Th.
Published: March 2003

In order to investigate control of voice fundamental frequency (F0) in speaking and singing, 24 adults had to utter the nonsense word [’ta:tatas] repeatedly, while in selected trials their auditory feedback was frequency-shifted by 100 cents downwards. In the speaking condition the target speech rate and prosodic pattern were indicated by a rhythmic sequence made of white noise. In the singing condition the sequence consisted of piano notes, and subjects were instructed to match the pitch of the notes. In both conditions a response in voice F0 begins with a latency of about 150 ms. As predicted, response magnitude is greater in the singing condition (66 cents) than in the speaking condition (47 cents). Furthermore the singing condition seems to prolong the after-effect which is a continuation of the response in trials after the frequency shift. In the singing condition, response magnitude and the ability to match the target F0 correlate significantly. Results support the view that in speaking voice F0 is monitored mainly supra-segmentally and controlled less tightly than in singing.
Simplified models of flue instruments: Influence of mouth geometry on the sound source
Authors: Dequand S. , Willems J. F. H. , Leroux M. , Vullings R. , van Weert M. , Thieulot C. , Hirschberg A.
Published: March 2003

Flue instruments such as the recorder flute and the transverse flute have different mouth geometries and acoustical response. The effect of the mouth geometry is studied by considering the aeroacoustical response of a simple whistle. The labium of a transverse flute has a large edge angle (60°) compared to that of a recorder flute (15°). Furthermore, the ratio W/h of the mouth width W to the jet thickness h can be varied in the transverse flute (lips of the musician) while it is fixed to a value W/h≈4 in a recorder flute. A systematic experimental study of the steady oscillation behavior has been carried out. Results of acoustical pressure measurements and flow visualization are presented. The sharp edge of the recorder provides a sound source which is rich in harmonics at the cost of stability. The larger angle of the labium of the flute seems to be motivated by a better stability of the oscillations for thick jets but could also be motivated by a reduction of broadband turbulence noise. We propose two simplified sound source models which could be used for sound synthesis: a jet-drive model for W/h>2 and a discrete-vortex model for W/h<2.
Analysis of flexural mode focusing by a semianalytical finite element method
Authors: Hayashi Takahiro , Kawashima Koichiro , Sun Zongqi , Rose Joseph L.
Published: March 2003

Focusing is one of the most promising techniques for the detection of small defects in pipe works, in which guided waves including longitudinal and flexural modes are tuned so that ultrasonic energy can be focused at a target point in a pipe, and analysis of reflected waves gives information on defects such as location and size. In this paper, the focusing technique is discussed by way of a simulation of guided wave propagation in pipe by a semianalytical finite element method (SAFE). Experiments and SAFE calculations were compared for waveforms transmitted by a single transducer and received at different circumferential positions initially, and then the focusing phenomena were experimentally observed using focusing parameters obtained by calculations. Calculation and visualization were conducted to clarify focusing phenomena in pipe in investigating the potential of the focusing technique. These results show that the time-reversal idea helps in understanding focusing and that resolution of focusing is strongly affected by incident waveforms as well as the number of channels available in an experiment.
Oscillatory flow in jet pumps: Nonlinear effects and minor losses
Authors: Petculescu A. , Wilen L. A.
Published: March 2003

A nonresonant, lumped-element technique is used to investigate the behavior of tapered cylindrical flow constrictions (jet pumps) in the nonlinear oscillatory flow regime. The array of samples studied spans a wide range of inlet curvature radii and taper angles. By measuring the rectified steady pressure component developed across a jet pump as well as the acoustic impedance, the minor loss coefficients for flow into and out of the narrow end of the jet pump are determined. These coefficients are found to be relatively insensitive to all but the smallest curvature radii (i.e., sharp edges). For fixed radius of curvature, the inflow minor loss coefficient increases with increasing taper angle while the outflow coefficient remains relatively constant. For all of the samples, the steady flow minor loss coefficients are also measured and compared to their oscillatory flow counterparts. The agreement is good, confirming the so-called Iguchi hypothesis.
Effects of peripheral nonlinearity on psychometric functions for forward-masked tones
Authors: Schairer Kim S. , Nizami Lance , Reimer Jason F. , Jesteadt Walt
Published: March 2003

Psychometric functions (PFs) for forward-masked tones were obtained for conditions in which signal level was varied to estimate threshold at several masker levels (variable-signal condition), and in which masker level was varied to estimate threshold at several signal levels (variable-masker condition). The changes in PF slope across combinations of masker frequency, masker level, and signal delay were explored in three experiments. In experiment 1, a 2-kHz, 10-ms tone was masked by a 50, 70 or 90 dB SPL, 20-ms on-frequency forward masker, with signal delays of 2, 20, or 40 ms, in a variable-signal condition. PF slopes decreased in conditions where signal threshold was high. In experiments 2 and 3, the signal was a 4-kHz, 10-ms tone, and the masker was either a 4- or 2.4-kHz, 200-ms tone. In experiment 2, on-frequency maskers were presented at 30 to 90 dB SPL in 10-dB steps and off-frequency maskers were presented at 60 to 90 dB SPL in 10-dB steps, with signal delays of 0, 10, or 30 ms, in a variable-signal condition. PF slopes decreased as signal level increased, and this trend was similar for on- and off-frequency maskers. In experiment 3, variable-masker conditions with on- and off-frequency maskers and 0-ms signal delay were presented. In general, the results were consistent with the hypothesis that peripheral nonlinearity is reflected in the PF slopes. The data also indicate that masker level plays a role independent of signal level, an effect that could be accounted for by assuming greater internal noise at higher stimulus levels.
Noise sensitivity and reactions to noise and other environmental conditions
Authors: Miedema Henk M. E. , Vos Henk
Published: March 2003

This article integrates findings from the literature and new results regarding noise sensitivity. The new results are based on analyses of 28 combined datasets (N=23 038), and separate analyses of a large aircraft noise study (N=10 939). Three topics regarding noise sensitivity are discussed, namely, its relationship with noise exposure, its working mechanism, and the scope of its influence. (1) A previous review found that noise sensitivity has no relationship with noise exposure. The current analyses give consistent results, and show that there is at most a very weak positive relationship. (2) It was observed earlier that noise sensitivity alters the effect of noise exposure on noise annoyance, and does not (only) have an additive effect. The current analyses confirm this, and show that the relation of the annoyance score with the noise exposure is relatively flat for nonsensitives while it is steeper for sensitives. (3) Previous studies showed that noise sensitivity also influences reactions other than noise annoyance. The current analyses of the aircraft noise study extend these results, but also indicate that noise sensitivity has relatively little influence on reactions to nonenvironmental conditions.
Informational masking caused by contralateral stimulation
Authors: Kidd Gerald , Mason Christine R. , Arbogast Tanya L. , Brungart Douglas S. , Simpson Brian D.
Published: March 2003

Although informational masking is thought to reflect central mechanisms, the effects are generally much stronger when the target and masker are presented to the same ear than when they are presented to different ears. However, the results of a recent study by Brungart and Simpson [J. Acoust. Soc. Am. 112, 2985–2995 (2002)] indicated that a speech masker that is presented contralateral to a speech signal can produce substantial amounts of informational masking when a second speech masker is played simultaneously in the same ear as the signal. In this study, we conducted a series of experiments that paralleled those of Brungart and Simpson but used a pure-tone signal and multitone informational maskers in a detection task. Both the signal and the maskers were played as sequences of short bursts in each observation interval. The maskers were arranged in two types of spectrotemporal patterns. One type of pattern, called “multiple-bursts same” (MBS), has previously been shown to produce very large amounts of informational masking while the other type of pattern, called “multiple-bursts different” (MBD), has been shown to produce very small amounts of informational masking. Several conditions of ipsilateral, contralateral, and combined presentation of these maskers were tested. The results showed that presentation of the MBS masker in the contralateral ear produced a substantial amount of informational masking when the MBD masker was simultaneously presented to the ipsilateral ear. The results supported the earlier findings of Brungart and Simpson indicating that listeners are unable to selectively focus their attention on a single ear in some complex dichotic listening conditions. These results suggest that this contralateral masking effect is not restricted to speech and may reflect more general limitations on processing capacity. Further, it was concluded that the magnitude of the contralateral masking effect was related both to the informational masking value of the contralateral masker and the complexity of the stimulus and/or task in the ear in which the signal was presented.
Unsteady flow through in-vitro models of the glottis
Authors: Hofmans G. C. J. , Groot G. , Ranucci M. , Graziani G. , Hirschberg A.
Published: March 2003

The unsteady two-dimensional flow through fixed rigid in vitro models of the glottis is studied in some detail to validate a more accurate model based on the prediction of boundary-layer separation. The study is restricted to the flow phenomena occurring within the glottis and does not include effects of vocal-fold movement on the flow. Pressure measurements have been carried out for a transient flow through a rigid scale model of the glottis. The rigid model with a fixed geometry driven by an unsteady pressure is used in order to achieve a high accuracy in the specification of the geometry of the glottis. The experimental study is focused on flow phenomena as they might occur in the glottis, such as the asymmetry of the flow due to the Coanda effect and the transition to turbulent flow. It was found that both effects need a relatively long time to establish themselves and are therefore unlikely to occur during the production of normal voiced speech when the glottis closes completely during part of the oscillation cycle. It is shown that when the flow is still laminar and symmetric the prediction of the boundary-layer model and the measurement of the pressure drop from the throat of the glottis to the exit of the glottis agree within 40%. Results of the boundary-layer model are compared with a two-dimensional vortex-blob method for viscous flow. The difference between the results of the simpiflied boundary-layer model and the experimental results is explained by an additional pressure difference between the separation point and the far field within the jet downstream of the separation point. The influence of the movement of the vocal folds on our conclusions is still unclear.
Beam and phase effects in angle-beam-through-transmission method of ultrasonic velocity measurement
Authors: Wang L. , Lavrentyev A. I. , Rokhlin S. I.
Published: March 2003

The accuracy of a plane wave approximation for phase velocity measurements in isotropic and anisotropic material using the angle-beam-through-transmission method has been investigated numerically and experimentally. In this method the velocity is measured in different propagation directions as a function of incidence angle. The effect of two factors on the measurement accuracy have been discussed: intrinsic phase shift of the transmitted signal through a fluid–solid interface and beam diffraction due to the finite beam size of receiver and transmitter. It is shown that the interface-induced phase shift can introduce an error in time delay measurements of the shear wave after the first critical angle and that this time delay error can be accurately corrected for. Numerical results obtained by a time-domain beam model show that except at the critical angles, the finite width of the transmitter and receiver only affects the amplitudes of the transmitted signals and has almost no effect on the measured zero-cross time delay; therefore the plane wave approximation for obtaining phase velocity from the measured time delay data by this method and the plane wave interface-induced phase correction are fully applicable.
Auditory spatial discrimination by barn owls in simulated echoic conditions
Authors: Spitzer Matthew W. , Bala Avinash D. S. , Takahashi Terry T.
Published: March 2003

In humans, directional hearing in reverberant conditions is characterized by a “precedence effect,” whereby directional information conveyed by leading sounds dominates perceived location, and listeners are relatively insensitive to directional information conveyed by lagging sounds. Behavioral studies provide evidence of precedence phenomena in a wide range of species. The present study employs a discrimination paradigm, based on habituation and recovery of the pupillary dilation response, to provide quantitative measures of precedence phenomena in the barn owl. As in humans, the owl’s ability to discriminate changes in the location of lagging sources is impaired relative to that for single sources. Spatial discrimination of lead sources is also impaired, but to a lesser extent than discrimination of lagging sources. Results of a control experiment indicate that sensitivity to monaural cues cannot account for discrimination of lag source location. Thus, impairment of discrimination ability in the two-source conditions most likely reflects a reduction in sensitivity to binaural directional information. These results demonstrate a similarity of precedence effect phenomena in barn owls and humans, and provide a basis for quantitative comparison with neuronal data from the same species.
The role of the frozen surface approximation in small wave-height perturbation theory for moving surfaces
Authors: Keiffer Richard S. , Novarini Jorge C. , Scharstein Robert W.
Published: March 2003

In the standard development of the small wave-height approximation (SWHA) perturbation theory for scattering from moving rough surfaces [e.g., E. Y. Harper and F. M. Labianca, J. Acoust. Soc. Am. 58, 349–364 (1975) and F. M. Labianca and E. Y. Harper, J. Acoust. Soc. Am. 62, 1144–1157 (1977)] the necessity for any sort of frozen surface approximation is avoided by the replacement of the rough boundary by a flat (and static) boundary. In this paper, this seemingly fortuitous byproduct of the small wave-height approximation is examined and found to fail to fully agree with an analysis based on the kinematics of the problem. Specifically, the first order correction term from the standard perturbation approach predicts a scattered amplitude that depends of the source wave number, whereas the kinematics point to a scattered amplitude that depends on the scattered wave number. It is shown that a perturbation approach in which an explicit frozen surface approximation is made before the SWHA is invoked predicts (first order) scattered amplitudes that are in agreement with the analysis based on the kinematics.
Noncontact ultrasound stimulated optical vibrometry study of coupled vibration of arterial tubes in fluids
Authors: Zhang X. M. , Fatemi M. , Kinnick R. R. , Greenleaf J. F.
Published: March 2003

Coupled vibration of arterial tubes is analyzed with the wave propagation approach and first-order shear deformation theory. Both the interior and exterior fluids are considered as compressible so that acoustic waves can be generated and propagated in the fluids. Results obtained using the theory have been evaluated against those available in the literature and the agreement has been found to be good. The theory can be used for future research on the vibration and acoustics of arterial walls. Vibration experiments were carried out on a silicone rubber tube in a water tank with a novel ultrasound stimulated optical vibrometry system. This system uses the radiation force of ultrasound to vibrate the tube at low frequency and records the resulting response by a laser vibrometer. Both the excitation and measurement are remote and noncontact. The silicone rubber tube was chosen because it has mechanical properties close to those of arteries. The fundamental frequency is well excited by the radiation force and measured with the laser. The measured fundamental frequency is in good agreement with the present theory.
Imaging in the presence of grain noise using the decomposition of the time reversal operator
Authors: Kerbrat E. , Prada C. , Cassereau D. , Fink M.
Published: March 2003

In this paper, we are interested in detecting and imaging defects in samples of cylindrical geometry with large speckle noise due to the microstructure. The time reversal process is an appropriate technique for detecting flaws in such heterogeneous media as titanium billets. Furthermore, time reversal can be iterated to select the defect with the strongest reflectivity and to reduce the contribution of speckle noise. The DORT (the French acronym for Decomposition of the Time Reversal Operator) method derives from the mathematical analysis of the time reversal process. This detection technique allows the determination of a set of signals to be applied to the transducers in order to focus on each defect separately. In this paper, we compare three immersion techniques on a titanium sample, standard transmit/receive focusing, the time reversal mirror (TRM), and the DORT method. We compare the sensitivity of these three techniques, especially the sensitivity to a poor alignment of the array with the front face of the sample. Then we show how images of the sample can be obtained with the TRM and the DORT method using backpropagation algorithm.
A hybrid SEA/modal technique for modeling structural-acoustic interior noise in rotorcraft
Authors: Jayachandran V. , Bonilha M. W.
Published: March 2003

This paper describes a hybrid technique that combines Statistical Energy Analysis (SEA) predictions for structural vibration with acoustic modal summation techniques to predict interior noise levels in rotorcraft. The method was applied for predicting the sound field inside a mock-up of the interior panel system of the Sikorsky S-92 helicopter. The vibration amplitudes of the frame and panel systems were predicted using a detailed SEA model and these were used as inputs to the model of the interior acoustic space. The spatial distribution of the vibration field on individual panels, and their coupling to the acoustic space were modeled using stochastic techniques. Leakage and nonresonant transmission components were accounted for using space-averaged values obtained from a SEA model of the complete structural-acoustic system. Since the cabin geometry was quite simple, the modeling of the interior acoustic space was performed using a standard modal summation technique. Sound pressure levels predicted by this approach at specific microphone locations were compared with measured data. Agreement within 3 dB in one-third octave bands above 40 Hz was observed. A large discrepancy in the one-third octave band in which the first acoustic mode is resonant (31.5 Hz) was observed. Reasons for such a discrepancy are discussed in the paper. The developed technique provides a method for modeling helicopter cabin interior noise in the frequency mid-range where neither FEA nor SEA is individually effective or accurate.
On the significance of reflection coefficients produced by active surfaces bounding one-dimensional sound fields
Authors: Leishman Timothy W. , Tichy Jiri
Published: March 2003

Active boundary surfaces intended to control reverberation or other characteristics of enclosed sound fields have often been investigated using plane wave tubes. This paper presents an analysis of actively terminated semi-infinite and finite-length plane wave tubes to provide needed clarification of the effects of these surfaces. By considering relationships between complex pressure-amplitude reflection coefficients and acoustic energy quantities, the investigation reveals that increases in reflection coefficient moduli at terminations do not always produce corresponding increases in total energy or energy flux in adjacent fields. These relationships are shown to depend upon physical properties of the acoustic spaces, sources, and source positions. The investigation also demonstrates how the impact of reflection coefficients with moduli exceeding unity may be easily misinterpreted.
Characterization of an optical multilayer hydrophone with constant frequency response in the range from 1 to 75 MHz
Authors: Wilkens Volker
Published: March 2003

The performance of an optical multilayer hydrophone for ultrasound measurements is investigated both in theoretical terms and experimentally. The optical measurement system comprises a thin high-finesse dielectric interference filter structure that is deposited onto a plane glass plate. An incident acoustic pressure wave deforms the layer system, and the induced variation of the optical reflectance is determined. Applying the concept of an optical off-axis detection scheme offers good sensitivity and a simple and low-cost setup. A primary interferometric calibration technique is applied to experimentally determine the pressure–voltage transfer function in the range from 1 to 75 MHz. Within the measurement uncertainty a constant transfer factor is obtained for the whole frequency range. Measurements of broadband ultrasound pulses are influenced neither by acoustic resonances of the very thin sensing element nor by diffraction phenomena that are known to cause waveform distortions in small probe hydrophone measurements. High temporal and spatial resolution is combined with high durability of the probe, which is why the optical multilayer hydrophone is well suited for use as a reference for secondary hydrophone calibration.
The effects of hearing loss on the contribution of high- and low-frequency speech information to speech understanding
Authors: Hornsby Benjamin W. Y. , Ricketts Todd A.
Published: March 2003

The speech understanding of persons with “flat” hearing loss (HI) was compared to a normal-hearing (NH) control group to examine how hearing loss affects the contribution of speech information in various frequency regions. Speech understanding in noise was assessed at multiple low- and high-pass filter cutoff frequencies. Noise levels were chosen to ensure that the noise, rather than quiet thresholds, determined audibility. The performance of HI subjects was compared to a NH group listening at the same signal-to-noise ratio and a comparable presentation level. Although absolute speech scores for the HI group were reduced, performance improvements as the speech and noise bandwidth increased were comparable between groups. These data suggest that the presence of hearing loss results in a uniform, rather than frequency-specific, deficit in the contribution of speech information. Measures of auditory thresholds in noise and speech intelligibility index (SII) calculations were also performed. These data suggest that differences in performance between the HI and NH groups are due primarily to audibility differences between groups. Measures of auditory thresholds in noise showed the “effective masking spectrum” of the noise was greater for the HI than the NH subjects.
Theoretical calculation and experimental study on the third-order nonlinearity parameter C/A for organic liquids and biological fluids
Authors: Xu Xiao-chen , Mao Feng , Gong Xiu-fen , Zhang Dong
Published: March 2003

In the present paper we deal with calculating and measuring the third-order nonlinearity parameter C/A for organic liquids and biological fluids. For the organic liquids, the second-order derivative of sound speed with respect to pressure at constant entropy is discussed in terms of thermodynamic parameters, and a formula for calculating C/A is established. Calculated results of C/A for various organic liquids demonstrate that omitting the second-order derivative of sound speed with respect to sound pressure in an isentropic process, could overestimate the value of C/A about 20%–30%. For measuring C/A, the finite-amplitude insert substitution technique is employed. A theoretical description of the sound pressure amplitude for the third-order harmonics is obtained using the perturbation method, in which the sound pressure amplitude of the third-order harmonics is shown approximately as a parabolic function of the propagation distance in the medium. By measuring and comparing the sound pressure amplitudes of the third-order harmonics when inserting a test sample, the reference liquid, and a comparative liquid, respectively, the value of C/A for the sample liquid is determined with reference to known C/A values of reference and comparative liquids. An experimental setup is developed, and the measured values of C/A for the organic liquids agree with the predicted ones calculated by the thermodynamic methods. Furthermore, the finite-amplitude method is extended to measure the C/A parameter for biological fluids, and the measured values of C/A for several biological fluids are also presented.
Spectral shape discrimination by hearing-impaired and normal-hearing listeners
Authors: Lentz Jennifer J. , Leek Marjorie R.
Published: March 2003

The ability to discriminate between sounds with different spectral shapes was evaluated for normal-hearing and hearing-impaired listeners. Listeners discriminated between a standard stimulus and a signal stimulus in which half of the standard components were decreased in level and half were increased in level. In one condition, the standard stimulus was the sum of six equal-amplitude tones (equal-SPL), and in another the standard stimulus was the sum of six tones at equal sensation levels re: audiometric thresholds for individual subjects (equal-SL). Spectral weights were estimated in conditions where the amplitudes of the individual tones were perturbed slightly on every presentation. Sensitivity was similar in all conditions for normal-hearing and hearing-impaired listeners. The presence of perturbation and equal-SL components increased thresholds for both groups, but only small differences in weighting strategy were measured between the groups depending on whether the equal-SPL or equal-SL condition was tested. The average data suggest that normal-hearing listeners may rely more on the central components of the spectrum whereas hearing-impaired listeners may have been more likely to use the edges. However, individual weighting functions were quite variable, especially for the HI listeners, perhaps reflecting difficulty in processing changes in spectral shape due to hearing loss. Differences in weighting strategy without changes in sensitivity suggest that factors other than spectral weights, such as internal noise or difficulty encoding a reference stimulus, also may dominate performance.
Predicting the vibroacoustic response of satellite equipment panels
Authors: Conlon S. C. , Hambric S. A.
Published: March 2003

Modern satellites are constructed of large, lightweight equipment panels that are strongly excited by acoustic pressures during launch. During design, performing vibroacoustic analyses to evaluate and ensure the integrity of the complex electronics mounted on the panels is critical. In this study the attached equipment is explicitly addressed and how its properties affect the panel responses is characterized. FEA and BEA methods are used to derive realistic parameters to input to a SEA hybrid model of a panel with multiple attachments. Specifically, conductance/modal density and radiation efficiency for nonhomogeneous panel structures with and without mass loading are computed. The validity of using the spatially averaged conductance of panels with irregular features for deriving the structure modal density is demonstrated. Maidanik’s proposed method of modifying the traditional SEA input power is implemented, illustrating the importance of accounting for system internal couplings when calculating the external input power. The predictions using the SEA hybrid model agree with the measured data trends, and are found to be most sensitive to the assumed dynamic mass ratio (attachments/structure) and the attachment internal loss factor. Additional experimental and analytical investigations are recommended to better characterize dynamic masses, modal densities and loss factors.
The scattering of guided waves in partly embedded cylindrical structures
Authors: Vogt T. , Lowe M. , Cawley P.
Published: March 2003

The scattering of ultrasonic guided waves at a point where a free cylindrical waveguide enters an embedding material is investigated. A modal solution that is valid when the guided waves are incident from the free section of the waveguide is developed. It is shown that in this case it is valid to consider only the modal fields over the cross section of the waveguide, neglecting the fields in the embedding material. As an application, the scattering of the lowest-order longitudinal mode in a cylindrical waveguide, L(0,1), is examined in detail. As well as considering epoxy resin as an embedding material, the case where the embedding material is replaced by a perfectly rigid boundary is discussed. The latter gives some insight into the role of nonpropagating and inhomogeneous waveguide modes in the scattering process. The results from the modal solution are validated using Finite Element modeling, very good agreement being obtained.
The role of contrasting temporal amplitude patterns in the perception of speech
Authors: Healy Eric W. , Warren Richard M.
Published: March 2003

Despite a lack of traditional speech features, novel sentences restricted to a narrow spectral slit can retain nearly perfect intelligibility [R. M. Warren et al., Percept. Psychophys. 57, 175–182 (1995)]. The current study employed 514 listeners to elucidate the cues allowing this high intelligibility, and to examine generally the use of narrow-band temporal speech patterns. When 13-octave sentences were processed to preserve the overall temporal pattern of amplitude fluctuation, but eliminate contrasting amplitude patterns within the band, sentence intelligibility dropped from values near 100% to values near zero (experiment 1). However, when a 13-octave speech band was partitioned to create a contrasting pair of independently amplitude-modulated 16-octave patterns, some intelligibility was restored (experiment 2). An additional experiment (3) showed that temporal patterns can also be integrated across wide frequency separations, or across the two ears. Despite the linguistic content of single temporal patterns, open-set intelligibility does not occur. Instead, a contrast between at least two temporal patterns is required for the comprehension of novel sentences and their component words. These contrasting patterns can reside together within a narrow range of frequencies, or they can be integrated across frequencies or ears. This view of speech perception, in which across-frequency changes in energy are seen as systematic changes in the temporal fluctuation patterns at two or more fixed loci, is more in line with the physiological encoding of complex signals.
Analysis of nonlinear behavior of loudspeakers using the instantaneous frequency
Authors: Huang Hai , Jacobsen Finn
Published: March 2003

It is well know that the weakest link in a sound reproduction chain is the loudspeaker. The most significant effect on the sound quality is nonlinear distortion of loudspeakers. Many methods are applied to analyze the nonlinear distortion of loudspeakers. Almost all of the methods are based on the Fourier transform. In this work, a new method using the instantaneous frequency is introduced for describing and characterizing loudspeaker nonlinearities. First, numerical integration is applied to simulate the nonlinearities of loudspeakers caused by two nonlinear parameters, force factor and stiffness, separately. Then, a practical loudspeaker is used in an experiment and its nonlinear characteristics are analyzed with the instantaneous frequency. The results provide a clear physical interpretation of the nonlinearities of loudspeakers and will be useful for understanding the nonlinear behavior of loudspeakers. It will also be helpful for compensating for the nonlinearities and for improving the quality of sound reproduction. [Work supported by Sino-Danish International Co-operative Project, No. AM13: 66 and DANIDA (Denmark).]
Measurements of bottom reflection loss in the East China Sea
Authors: Choi Jee Woong , Dahl Peter H.
Published: March 2003

Measurements of bottom reflection loss were conducted in 105 m of water in the East China Sea (ECS) at location 29 39N, 126 49E as part of the Asian Seas International Acoustic Experiment (ASIAEX), in the spring of 2001. Sources in the frequency range 2–20 kHz were located at depths 25 m and 50 m, and receivers were deployed at a range of 500 m and at of depths 26 m and 52 m. Bottom reflection loss measurements are obtained as a function of frequency and, to a limited extent, grazing angle. Experimental values are compared with model calculations based on independently measured geoacoustic and bottom roughness parameters. The frequency dependence of sediment attenuation, influence of bottom roughness, and role of the critical angle will be discussed in the context of these measurements. [Work supported by ONR, ASIAEX program.]
Acoustic detection of pneumothorax
Authors: Mansy Hansen A. , Royston Thomas J. , Balk Robert A. , Sandler Richard H.
Published: March 2003

This study aims at investigating the feasibility of using low-frequency (<2000 Hz) acoustic methods for medical diagnosis. Several candidate methods of pneumothorax detection were tested in dogs. In the first approach, broadband acoustic signals were introduced into the trachea during end-expiration and transmitted waves were measured at the chest surface. Pneumothorax was found to consistently decrease pulmonary acoustic transmission in the 200–1200-Hz frequency band, while less change was observed at lower frequencies (p<0.0001). The ratio of acoustic energy between low (<220 Hz) and mid (550–770 Hz) frequency bands was significantly different in the control (healthy) and pneumothorax states (p<0.0001). The second approach measured breath sounds in the absence of an external acoustic input. Pneumothorax was found to be associated with a preferential reduction of sound amplitude in the 200- to 700-Hz range, and a decrease of sound amplitude variation (in the 300 to 600-Hz band) during the respiration cycle (p<0.01 for each). Finally, chest percussion was implemented. Pneumothorax changed the frequency and decay rate of percussive sounds. These results imply that certain medical conditions may be reliably detected using appropriate acoustic measurements and analysis. [Work supported by NIH/NHLBI ♯R44HL61108.]
Standardized Medium-Size Basis Sets for Calculations of Molecular Electric Properties: Group IIIA
Authors: Černušák Ivan , Kellö Vladimir , Sadlej Andrzej J.
Published: March 2003

The idea of what is called the basis set polarization method is reviewed and the available polarized basis sets are surveyed. Following the basis set polarization approach and certain empirical rules developed earlier, the first-order polarized basis sets for the Group IIIA elements are generated. These basis sets have been developed for both nonrelativistic and spin-averaged Douglas-Kroll relativistic calculations. Their performance is tested in calculations of atomic dipole polarizabilities and in high-level-correlated calculations of the dipole moments of GaF, InF, and TlF. The relativistic effects have been found to significantly affect the calculated molecular dipole moments of the studied fluorides. The results are in satisfactory agreement with reference data. The present study completes the library of the first-order polarized basis sets for all atoms of the main groups of the Periodic Table.
Application of MP2 Results in Comparative Studies of Semiempirical Ground-State Energies of Large Atoms
Authors: Flores Jesus R. , Jankowski Karol , Słupski Romuald
Published: March 2003

To study the usefulness of second-order Møller-Plesset (MP2) correlation energies for ground states of closed-shell atoms (referred to as MP2/CA energies) in estimations of the total correlation energies of larger closed-shell atoms, we have considered atoms and ions containing from 10 to 86 electrons. First, it is demonstrated that for N-electron systems, 10 ≤ N ≤ 18, the MP2/CA energies provide very good approximations to the very accurate estimates of atomic correlation energies by Chakravorty and Davidson. Next, for systems with 10 ≤ N ≤ 54, comparisons are made with the semiempirical energies obtained when using the models by Chakravorty and Clementi as well as by Clementi and Corongiu. Finally, for atoms with 10 ≤ N ≤ 86, the MP2/CA energies are employed for comparison with DFT energies recently obtained by Andrae et al. (Int. J. Quantum Chem. 2001, 82, 227). The MP2/CA results proved to provide reasonable estimates to the total correlation energies in all the cases considered.
Magnetic Linear Birefringence in Rare Earth Systems. Second-Order Approach
Authors: Smentek Lidia
Published: March 2003

An analysis defines the improved version of the theoretical model of magnetic linear birefringence in rare earth doped materials developed and applied in several papers of Kolmakova et al. The approach presented here is formulated in the language of tensor operators instead of equivalent Stevens objects, and in addition the radial terms of the effective operators contributing to the polarizability tensor are all defined for the complete radial basis sets of one-electron functions. The approach is based on perturbation theory. The effective operators represent the perturbing influence of singly excited configurations 4fN-1n' l' for l' = d, g and all n'. The model is defined within the single configuration approximation, and it addresses especially the problem of evaluation of the radial integrals. The discussion of the tensorial form of the effective operators is completed by the numerical values of appropriate radial integrals evaluated for the ions across the lanthanide series to be used in future theoretical analysis.
The Ground State Potential for the Chromium Dimer Revisited
Authors: Roos Björn O.
Published: March 2003

Results are presented from a new theoretical study of the ground state potential curve of the chromium dimer using multiconfiguration second-order perturbation theory. A new basis set of the atomic natural orbital type is used where the construction includes correlation of the semi-core 3p orbitals and scalar relativistic effects are added using the Douglas-Kroll Hamiltonian. The active space used in the CASSCF/CASPT2 calculations comprised 16 orbitals with 12 active electrons. The resulting ground state potential is in agreement with experiment. Computed spectroscopic constants are (with experimental values within parentheses): Re = 1.66 (1.68) Å, D0 = 1.65 (1.53 ± 0.06) eV, ∆G1/2 = 413 (452) cm-1. Higher vibrational frequencies are also well reproduced.
Dirac-Coulomb Hamiltonian in N-Electron Model Spaces
Authors: Pestka Grzegorz , Karwowski Jacek
Published: March 2003

Relations between matrices representing non-relativistic and relativistic N-electron Hamiltonians in N-electron model spaces are analyzed. The model spaces are defined as the antisymmetric parts of products of the N-th Kronecker power of either a two-dimensional (the non-relativistic case) or four-dimensional (the relativistic case) spinor space and of an orbital (or configurational) space. The explicit relation between the matrices corresponding to the relativistic and non-relativistic cases is derived and its practical implications are briefly discussed.
New Version of the Rayleigh-Schrödinger Perturbation Theory
Authors: Kalhous Miloš , Skála Lubomír , Zamastil Jaroslav , Čížek Jiří
Published: March 2003

New version of the Rayleigh-Schrödinger perturbation theory based on the linear dependence of the perturbation wavefunctions on the perturbation energies is summarized. It is shown that this method is suitable also for multidimensional problems and the linear dependence can be used at an arbitrary point inside the integration region. The resulting perturbation theory is simple and can be used at large orders. As an example, the method is applied to the Barbanis hamiltonian.
A Nonorthogonal Coordinate Approach to Atom-Diatom Parallel Reactive Scattering Calculations
Authors: Laganà Antonio , Crocchianti Stefano , Faginas Lago Noelia , Pacifici Leonardo , Ferraro Gianni
Published: March 2003

Computational approaches to the evaluation of the reactive scattering properties of atom- diatom reactions are revisited. The aim is to exploit both the use of nonorthogonal coordinates in reactive scattering and the restructuring of related computer codes for concurrent computing. To this end, bond length, bond-order and hyperspherical bond order coordinate formalisms are examined for the collinear case. At the same time, the evolution of parallel models from coarse to fine granularity and the development of parallelization supports from directive libraries to programming environments are discussed. The scalability of related codes is tested by measuring the performances of restructured codes. The suitability of the use of nonorthogonal coordinates for scattering purposes is tested by performing collinear calculations for the H + H2 reaction.