bluuebunny/crossref_metadata_2025 huggingface dataset:
Decision rules of listeners in spectral-shape discrimination with or without signal-frequency uncertainty
Authors: Dai Huanping , Nguyen Quang , Green David M.
Published: October 2005

A correlation technique was used to assess the decision rules of three listeners in two cases of spectral-shape discrimination tasks. In one case the signal frequency was fixed, and in the other it was randomly varied within each block of trials. In order to estimate the decision rule of the listeners, the experimenter superimposed random level perturbations on each frequency component upon each stimulus presentation. Over many trials, correlation coefficients were computed between the random perturbations and the binary responses of the listeners, and were expressed as a function of signal level. For both the fixed- and random-signal cases, the measured correlation functions were in reasonably good agreement with those predicted based on the likelihood-ratio decision rules. Thus the listeners appeared to use information nearly optimally in discriminating spectral shapes. This investigation demonstrated that the correlation technique can be used to reveal the decision rules for cases where the decision statistics are nonlinear functions of the observations.
Identification of multidimensional complex sounds having parallel dimension structure
Authors: Christensen Laurel A. , Humes Larry E.
Published: October 2005

The present series of experiments examined the ability of normal-hearing listeners to make use of cues from multiple, independent stimulus dimensions when classifying multidimensional complex sounds. Ten listeners classified complex sound pulses that differed along three independent dimensions. The stimuli were 100 ms in duration and were synthesized using five simultaneous sinusoids. The three dimensions of the complex stimuli manipulated in this experiment were harmonicity, spectral shape, and amplitude envelope. Each stimulus dimension could take on one of two values, referred to here as target or nontarget. Eight stimuli were synthesized using all possible combinations of the dimension values. Subjects were trained to label two stimuli, the two having either all-target or all-nontarget values, as ‘‘+’’ and ‘‘0,’’ respectively. Following this training, subjects were asked to classify all eight stimuli as either ‘‘+’’ or ‘‘0.’’ Results of this experiment indicated that listeners preferred to classify these stimuli on the basis of one stimulus dimension. However, the preferred dimension was not the same for all of the listeners. In addition, it was demonstrated that it was possible to train an individual to use a dimension other than the one or two initially preferred when classifying the stimuli.
A high-resolution time–frequency representation for musical instrument signals
Authors: Pielemeier William J. , Wakefield Gregory H.
Published: October 2005

Analyzing musical signals to obtain the time-varying magnitudes and frequencies of instruments’ partial frequency components is important for resynthesis, transcription, and instrument physics. Windowing techniques, including Fourier series extensions, short-time Fourier transforms, and constant-Q transforms, generate bias in time and frequency dictated by the uncertainty principle. This is significant to analysis requirements of such properties as attack, which involve changes over millisecond time ranges and require frequency accuracy on the order of cents. Alternatives such as the Wigner distribution avoid the uncertainty principle restriction and associated bias, but nonlinear cross products of magnitude and frequency computations are not smoothed as with windowing methods, increasing those sources of bias. All these techniques belong to Cohen’s class, a framework where this paper develops the modal distribution, exhibiting decreased total bias. Computation of the modal distribution and a constant-Q version are detailed. Comparative examples to windowing methods are provided. Further research on modal distribution magnitude and phase estimation verifies the advantage of this distribution over others.
Acoustic nonlinearity parameter tomography for biological specimens via measurements of the second harmonics
Authors: Zhang Dong , Gong Xiufen , Ye Shigong
Published: October 2005

The acoustic nonlinearity parameter B/A is a new parameter in ultrasound tissue characterization. In this paper, on the basis of a theoretical analysis of finite amplitude ultrasonic wave propagation in fluidlike media, an experimental system for nonlinearity parameter tomography is developed. Using this system, the amplitude of the second harmonic wave cumulated in the propagation path of the primary wave is measured and the finite amplitude insert-substitution method is used in the conventional computer tomography (CT) technique. The filtered convolution algorithm is implemented using the amplitude of the second harmonic as the projection data, then the B/A tomography can be reconstructed. The B/A images for several biological samples are obtained. Besides, the image of porcine pathological liver tissue is studied and is compared with that of porcine normal liver tissue. These results show the potential applications of the nonlinearity parameter B/A in medical diagnosis.
The computation of the scattered pressure field from a cylinder embedded between two half-spaces with different densities
Authors: Fawcett John A.
Published: October 2005

In this Letter a straightforward, efficient method for computing the acoustic field scattered by a cylinder embedded halfway between two half-spaces is presented. These half-spaces have the same velocity but a different density. This method should be useful for benchmarking more general codes.
Computer modeling of the process of the ocean stream velocity remote acoustics sensing in Fram Strait environmental condition.
Authors: Esipov Igor B. , Johannessen Ola M. , Naugolnykh Konstantin A. , Ovchinnikov Oleg B. , Tuzilkin Yury I. , Zosimov Viktor V.
Published: October 2005

An important part of the general problem of global climate change is the measurement of the heat inflow from the Atlantic ocean to the Arctic basin. An effective tool to measure it is the acoustic methods application. Some aspects of this problem connected with the average water temperature measurements were considered previously [Naugolnykh et al., J. Acoust. Soc. Am. 97, 3264(A) (1995)]. In the present paper the results of computer modeling of the ocean stream velocity remote acoustical sensing with respect to the Fram Strait environment are presented. The computer simulation of the random environment characterized by the 3-D sound-speed field was performed. This process has been done with the assumption of both regular temperature changing in the cross section of the Fram Strait and isotropic random sound-speed variation distribution in the plane in each horizon. Spatial spectra of simulated inhomogeneities can be corrected in the course of modeling. Simulated fields of environmental inhomogeneities were used for the sound signal propagation modeling through the paths directed crosswise and along the water flow to compare Doppler and scintillation methods of stream monitoring.
Multimodal dispersion identification.
Authors: Poplawski James , Birdsall Ted
Published: October 2005

Geometric dispersion in the deep ocean sound channel causes wideband modal arrivals to be spread significantly in time at long ranges. This results in a low modal peak signal-to-noise ratio and interference due to multiple overlapping arrivals. These effects make the identification of individual modal arrivals difficult without the use of a vertical receiving array. The time compression of modal arrivals using phase-only filters is examined as a method for locating and identifying arrivals from a reception at a single depth. A search display, dubbed the dispersion diagnostic display, has proved its worth in computer simulations using a 60 mode range invariant model of SLICE89 propagation. The DD display simultaneously shows a raylike (no dispersion) structure and a patterned modal structure with strongly dispersed early arrivals and lightly dispersed terminal arrivals. [Work supported by ATOC.]
Improved empirical orthogonal functions for ocean acoustic tomography.
Authors: Deffenbaugh Max , Schmidt Henrik
Published: October 2005

The method of empirical orthogonal functions is commonly used in tomography to select a set of basis vectors to represent variations in the sound-speed profile. In this method, historical profiles are used to estimate a profile covariance matrix, and the eigenvectors corresponding to the largest eigenvalues of the covariance matrix are taken for the basis vectors. These basis vectors are the most efficient parametrization of the variations in the profile. They are NOT, however, the parametrization which leads to the most accurate post-measurement estimate of the profile, because, in a tomographic experiment, all profile variations cannot be measured with the same accuracy. In this paper, the set of basis vectors, which will yield the least error in the post-measurement estimate of the profile, are derived taking into account measurement resolution and measurement noise. These improved empirical orthogonal functions are applied to several canonical problems in ocean acoustic tomography, and the resulting enhancement in estimation accuracy is demonstrated. [Work supported by ONR.]
Estimation of stochastic wave-number variations at the Atlantic Generating Station site and comparison with acoustic data.
Authors: Longfritz Michael J. , Badiey Mohsen , Siegmann William L. , Jacobson Melvin J. , Jaya Indra
Published: October 2005

The estimation of horizontal wave-number variations in a stochastic shallow-water environment at the Atlantic Generating Station (AGS) site is constructed. A method using empirical orthogonal functions has been developed [Longfritz et al., J. Acoust. Soc. Am. 97, 3316 (A) (1995)] to relate wave-number fluctuations to environmental variations. First, the AGS site is modeled as a stochastic shallow channel with a range-dependent layered sediment bottom. The layer interface depths and intralayer sound speeds are treated as random variables. Then, the estimation procedure is applied to a particular propagation track, where geoacoustic profiles and acoustics measurements are both available. Environmental profiles along the track are treated as a sample from a stochastic ensemble. Estimates are obtained for both the range variance of the wave numbers and the particular deviations associated with each profile in the sample. Comparisons are made between results from the estimation procedure and simulations from the KRAKEN propagation code. In a separate study, acoustical wave numbers have been generated from experimental data for the track using a method of Thomson. The estimation results are compared to this data.
Acoustic inversion of bottom reflectivity and bottom sound-speed profile in shallow water.
Authors: Yang T. C. , Yates T.
Published: October 2005

This paper presents a full field technique to invert bottom sound profile and bottom reflectivity from acoustic data collected in shallow water. Bottom sound-speed profile and bottom reflectivity have been traditionally estimated using seismic reflection/refraction when acoustic ray paths and travel time can be identified and measured from the data. Due to the shallow depth in shallow water, the many multipaths due to bottom reflection/refraction make such identification and measurement rather difficult. A full field inversion technique is presented which uses a broadband source and an easily deployable array for bottom sound speed and reflectivity inversion. The technique is a modified matched-field inversion technique referred to as matched beam processing. Matched beam processing uses conventional beamforming processing to transform the field data into the beam domain and correlate that with the replica field also in the beam domain. This allows the analysis to track the acoustic field as a function of incidence/reflected angle and minimize contamination or mismatch due to sidelobe leakage. This technique is illustrated with simulated data for a vertical array and can be generalized to other array configurations, such as a towed array.
Shallow-water ambient noise caused by breaking waves in the surf zone.
Authors: Wilson Oscar B. , Stewart Marc S. , Wilson James H. , Bourke Robert H.
Published: October 2005

Ambient noise measurements made by Wilson, Wolf, and Ingenito in Monterey Bay, California in 1980 and 1981 were combined with modeled transmission loss (TL) to estimate the spectral source level of surf-generated noise. In the frequency range 20–700 Hz the horizontal directionality of these noise data showed much higher levels from shore than seaward and the overall noise levels decreased with range from shore, strongly suggesting that surf noise was a significant contributor. A Hamilton geoacoustic model of the coastal environment has been derived and used in a finite element parabolic equation propagation loss model to obtain the TL values. These indicate that propagation is significantly dependent on the environment and frequency, particularly near the surf zone. Estimates of wind and local wave noise intensity corrected for the local environment were subtracted from the total measured noise field to determine the contribution due to surf only. Heavy surf breaking on a uniform 12.5-km linear section of beach near Fort Ord was found to be the dominant source of surf-generated noise. The preliminary results provide estimates of the noise source level densities for heavy and light surf at Fort Ord beach. a)Currently at Naval Sea Systems Command, Arlington, VA 22242-5160.
Imaging of passive targets in shallow-water using an ambient noise acoustic imaging system.
Authors: Olivieri Marc P. , Glegg Stewart A. L. , Coulson Robert K.
Published: October 2005

This paper will describe an experiment on the detection of passive targets in shallow water using ambient noise as the sole source of insonification. Glegg and Olivieri [Noise-Con 95, p. 1179] proposed a broadband signal processing technique to achieve this type of passive acoustic detection using a limited number of transducers. An array has been developed to apply this technique in a shallow-water environment. This paper will describe an experiment carried out in Summer 1995 off the Boca Raton inlet in which a target was successfully detected. The size of the target chosen for this test was 1.8×1.2 m and it was placed 40 m from the array. The acoustic field was imaged with and without the target present and both passive and active detection of the target was obtained. The measurements were carried out in low sea states when the primary source of ambient noise was biological and strongly anisotropic. [Work supported by ONR.]
Inference of nonlinear effects from spectral measurements of wind instrument sounds.
Authors: Beauchamp James W.
Published: October 2005

That wind musical instruments in conjunction with their players are highly nonlinear can be inferred from measurements of their output spectra. These show that, for a given performed pitch, bandwidth generally increases with increasing rms amplitude. The cause of this harmonic generation is generally attributed to a nonlinear pressure/flow excitation mechanism which interacts with the instrument’s resonant input impedance characteristic. Since there are no analytical solutions which predict mouthpiece spectra, one must rely on simulations and empirical measurements. Meanwhile, the pipe portion of the wind instrument has long been assumed to be a linear resonant system acting as a high pass filter with resonant minima corresponding to the input impedance maxima. This at least is true at low amplitudes. However, for the trombone large discrepancies in the filter response have been found between measurements made with sine wave input and those made under actual performance conditions, particularly above resonant cutoff. The general effect is that spectral bandwidth (and attendant tonal brightness) increases even more with increasing amplitude than if the system were linear. There is now evidence that this may be due to shock wave formation in the pipe of the instrument.
The measured vocal tract impedance for clarinet performance and its role in sound production.
Authors: Wilson Teresa D.
Published: October 2005

The role of the vocal tract in clarinet performance has been investigated by examining the vocal tract impedance, Zu. Theory predicts that Zu peaks aligned with harmonics of the pitch frequency stabilize the oscillation. The vocal tract impedance was measured directly with a one-microphone technique and indirectly from a calculation using the continuity of flow equation pu/Zu+pd/Zd=0, where pu and pd are the mouth and mouthpiece pressures and Zd is the instrument impedance. The continuity equation was verified for single tones and then used to examine the role of the vocal tract in a variety of musical situations. In orchestral excerpts, the performer tends to align resonances with the first and/or second harmonics, and there is some dependence on the musical context. For multiphonics, the performer creates a resonance that supports an oscillation at a linear combination of the audible pitch frequencies. For tones played with pitchbend, induced by slacking the jaw muscles, the playing frequency is controlled by the frequency of a large-amplitude vocal tract resonance, for which ‖Zu‖≊100–400 CGS ohms. Zu changes only slightly when clarion tones are played without the register key, suggesting that other variables are involved.
Influences of sharp toroidal bends on the tuning of wind instruments.
Authors: Nederveen Cornelis J.
Published: October 2005

A toroidal bend causes tuning changes, which are mode dependent and may amount to 10 cents. This is caused by a change of the inertance in the bend, whereas the compliance is not affected. The inertance change was studied by Nederveen [Acoustical Aspects of Woodwind Instruments (1969)], Rostafinski [J. Acoust. Soc. Am. 52, 1411–1420 (1971)], and Keefe and Benade [J. Acoust. Soc. Am. 74, 320–332 (1983)]. At first sight, the results seem different. However, it can be shown that, at long wavelengths, they are essentially the same: The apparent density equals ρB=ρB2/2[1−(1−B2)1/2], where ρ is the unperturbed air density and B is the ratio of the tube radius and the tore curvature radius. The transition of the torus into the regular cylindrical bore causes a correction which was measured by Keefe and Benade. This was verified by numerical calculations using conformal transformations. The effects of a torus on the tuning can be neutralized by reducing the bore in the torus, for sharp bends of up to some 5%.
Under-seat sound absorption for stadium/arena chairs.
Authors: Coffeen Robert C.
Published: October 2005

For large audience spaces such as arenas and stadiums, it is often difficult to satisfactorily control the unoccupied reverberation period of the space because of the large volume in relation to the area of surfaces that are available for the practical installation of sound-absorbing material; and when chairs are of the plastic ‘‘stadium chair’’ type, it may be impossible to achieve a suitable stabilization of the reverberation period between unoccupied and occupied conditions. Of course, the use of chairs with sound absorbing upholstery is of major benefit in resolving these problems, but it is frequently found that ‘‘hard’’ chairs are selected for maintenance and cost reasons, and in spite of resulting acoustical conditions. However, this situation can be at least partially remedied by installing sound-absorbing material beneath each chair seat as an integral part of the chair construction. Laboratory sound absorption data, obtained in association with a major chair manufacturer, and field data obtained for a multipurpose arena indicate that this is a useful technique which can be applied when ‘‘hard’’ chairs are to be used for reasons not relating to acoustics.
The resonator system of controlling the reverberation time in an existing hall.
Authors: Hase Shigeo , Kobayashi Yoshihito
Published: October 2005

In this paper, the resonator system of controlling the reverberation time is examined in an existing hall with 500 seats and the room volume of 4160 m3. The cavity of each chair with the volume of 0.012 m3 was utilized as a resonator. Four holes of a 30-mm diameter in the lower board of chairs can be opened or closed by a sliding plate. By use of such a system of chairs, the reverberation time at the low-frequency range in the hall could be controlled as: at 100 Hz: 1.93–1.58 s; at 125 Hz: 1.69–1.44 s; at 160 Hz: 1.54–1.36 s, and at 200 Hz: 1.52–1.45 s.
Examination of a resonator system for sound power absorption by hall chairs in the low-frequency range.
Authors: Kobayashi Yoshihito , Hase Shigeo
Published: October 2005

For the purpose of controlling reverberation time in the low-frequency range in a room, the variable system of sound absorption power by the chairs in the low-frequency range by the experiments in a scale model was examined. As the results of scale model experiments (1/10 scale) in the reverberation room, the absorption power was controlled in the low-frequency range by the opening and closing of holes of the resonator. Because of the achievement of the variable system of sound absorption of the actual chairs, an experiment on sound absorption power characteristics was made in the reverberation room of the chair with resonators given a variable with the quantity and the diameter of holes, a neck’s length, and a cavity volume of the seat. The result was obtained that variable characteristics of the sound absorption power of the chairs with the resonator (four holes, 30 mm diameter of the hole, and neck length 10 mm) is 0.2 m2 each for 125 or 250 Hz by changing the cavity volume of the seat in the experiment. The characteristics under the occupancy condition are nearly equal to it under nonoccupancy conditions.
Sound-pressure simulations on a concentric tube resonator.
Authors: Ciray Mehmet S.
Published: October 2005

A concentric tube resonator was investigated to determine the accuracy of the numerical method used for sound-pressure simulations. The interaction between the tube and the cavity was through a perforated surface, of which the acoustical properties were experimentally determined [J. W. Sullivan, J. Acoust. Soc. Am. 76, 479–484 (1984)]. These properties were imposed as boundary conditions to the finite-element analysis (FEA) code. Predicted and measured transmission losses were compared under no mean flow conditions. The work was then extended to include the effects of mean flow. Empirical equations given in literature were used to modify the acoustical properties of the perforated surface to incorporate the effects of flow [Garrison et al., Pratt and Whitney Aircraft Rep. (1969)]. The mean flow terms in the scalar Helmholtz equation were treated explicitly in order to avoid the additional storage requirements for the FEA code. Special attention had been paid to the design of the FEA code, such that information can be seamlessly exchanged with a computational fluid dynamics (CFD) simulation, for possible future research.
Music for the reed organ.
Authors: Peterson Edward A.
Published: October 2005

Members of the American Guild of Organists and the Reed Organ Society will perform on instruments from the Indianapolis area. Selections will be presented which illustrate the musical range of the reed organ. Commentary on the principles of operation of the instrument and playing techniques will be provided.
‘‘Reed all about it:’’ The giant grass that provides reed cane for musical instruments.
Authors: Eley Marcus
Published: October 2005

Cane reeds for musical instruments are made from the stalks of arundo donax, a giant grass. Although arundo donax grows wild througout the world only certain conditions of soil and climate will produce cane that is suitable for music making. The controlled conditions of plantation growth, as in the plantation system used by Rico International, are proving to be successful in growing cane that is more consistently of high quality. Nurturing and careful harvesting bring the mature stalks to the stage where they can be carefully sun-dried in racks for many months and finally cut, between nodes, into tubes. The cane tubes are then shipped to Sun Valley for the manufacture of musical instrument reeds, a process that involves special tooling and unique manufacturing techniques.
Observed vibration patterns of clarinet reeds.
Authors: Hoekje P. L. , Roberts G. Matthew
Published: October 2005

It has been shown that a resonance of the reed contributes significantly to the playing behavior of the single-reed woodwind [S. C. Thompson, J. Acoust. Soc. Am. 66, 1299–1307 (1979)]. As an extended object, the reed is actually expected to possess many resonances, and these have been predicted in FEA calculations [D. Casadonte, J. Acoust. Soc. Am. 94, 1807(A) (1993)] and observed in vibration spectra of isolated reeds [D. H. Keefe and S. Waeffler, J. Acoust. Soc. Am. 94, 1833–1834(A) (1993)]. The current study used holographic interferometry to identify the vibration patterns of a clarinet reed mounted on a mouthpiece, as driven by an acoustic field internal to the mouthpiece. Without a player’s lips to shorten the vibrating section, the lowest frequency and most easily driven resonance is in the region 1500 to 2000 Hz and corresponds to the lowest mode of a rod clamped at one end. The second and third resonances are near 4000 Hz. The second mode displays twisting motion, but with a surprising degree of asymmetry, while the third mode is similar to the second mode of a rod clamped at one end.
Repeatability and reproducibility in hearing protector testing.
Authors: Franks John R. , Murphy William J. , Simon Stephen D.
Published: October 2005

Earlier research [Royster et al., J. Acoust. Soc. Am. 99, 1506–1526 (1996)] has reported on a new laboratory test method to predict the amount of attenuation hearing protectors provide to workers in the real world. The subject fit method (SF) employs the use of subjects who are audiometrically competent but naive with respect to hearing protector use and who must rely only upon the manufacturer’s instructions to fit a protector for testing. One unresolved issue has been the number of subjects and number of repeated tests per subject necessary to achieve the desired levels of repeatability (test–retest within a laboratory) and reproducibility (test–retest between laboratories). Attenuation data from four laboratories collected with the same protocol showed that estimates of variance for the reproducibility across hearing protectors (Bilsom Muff, E-A-R plug, EP100 plug, V-51R plug) for informed user fit (IUF) were greater than estimates of the SF variance. The estimates of variance for the repeatability across protectors and frequency were comparable between the IUF and SF conditions. The average IUF attenuations across protectors and frequency were greater than the average SF attenuations for all of the plugs.
Maximum safe exposure levels for intense reverberant impulses in an enclosure.
Authors: Patterson James H. , Johnson Daniel L. , Yelverton John T.
Published: October 2005

Studies were undertaken to determine the maximum safe-exposure levels in a reverberant wave environment like that produced by firing an antiarmor weapon from a small room. The approach was first, to establish a threshold of injury for organs other than the ear then to determine whether these levels were safe for the ear. Using sheep as an animal model, the threshold of nonauditory injury was found to be approximately 190 dB peak SPL (65 kPa) with a B duration longer than 200 ms for one impulse and approximately 187 dB peak SPL (46 kPa) for three impulses. Two groups of 40 animals were used to establish statistical confidence in the ‘‘no injury levels.’’ The auditory effects were investigated using human volunteers exposed to a progression of levels from 168 to 185 dB at the ear for one impulse and then, to two and three impulses at 183 dB. A temporary threshold shift (TTS), determined 2–4 min post exposure, was used as an indicator of auditory effect. The volunteers wore an earmuff modified to simulate a poor fit, during the exposures. No significant TTS in 59 volunteers was observed, indicating no effects on hearing up to the maximum safe-exposure levels for other organs.
Finite amplitude distortion in derating of ultrasound fields.
Authors: Christopher T. , Carstensen E. L.
Published: October 2005

All ultrasound exposure indices that have been formulated up to the present time assume that the propagation of ultrasound is linear. In fact, under most exposure conditions for which biological effects may be a concern, sound propagation is highly nonlinear. A nonlinear propagation model has been used to evaluate the nature of the effects that occur under realistic exposure conditions encountered in diagnostic procedures. Because of the way that the thermal index is defined, it turns out that ignoring nonlinear propagation leads to underestimates of tissue temperature increments that typically are less than 40%. As currently implemented, the mechanical index may be underestimated by more than a factor of 2 because it ignores the saturation of the sound fields that result from nonlinear propagation. For large propagation distances in soft tissues (e.g., 10 cm at 3 MHz in liver), however, it is physically difficult to exceed tissue pressures corresponding to MI≳2 because of these same saturation phenomena.
Lung hemorrhage from exposure to ultrasound.
Authors: Dalecki Diane , Child Sally Z. , Raeman Carol H. , Penney David P. , Carstensen Edwin L.
Published: October 2005

Thresholds for lung hemorrhage from exposure to pulsed ultrasound have been determined in neonatal mice (24–36 h), juvenile mice (14 days), and adult mice (8–10 weeks), and neonatal (24–36 h) and young (10 days) swine. The threshold at 2 MHz is approximately 1 MPa and the threshold increases gradually with frequency in the range from 0.1 to 4 MHz. Positive and negative pressure pulses are equally damaging. Following exposure, suprathreshold lesions are not progressive with time and are repaired by usual physiological mechanisms. Although the unique sensitivity of lung tissue to ultrasound is associated with the presence of air in the alveolae, this does not necessarily implicate acoustic cavitation as the responsible mechanism. Thin sections of murine lung are more sensitive than thicker regions probably because of reduced reflection at the surface of the lung tissue.
Experimental study of the Scholte wave interaction with a square section defect.
Authors: Tinel Alain , Duflo Hugues , Duclos Jean
Published: October 2005

In this work, an experimental study of surface wave diffraction on a substrate immersed in water is presented. The Scholte wave was generated by bulk wave conversion at the extremity of the substrate. The sample was a plane plate of duralumin 10 mm thick and 200 mm long which had a defect (a tenon or a mortise) with square section dimensions close to the wavelength of the wave in the fluid. Only one obstacle perpendicular to the direction of propagation of the incident wave was investigated. The acoustic pressure at 300 mm around the diffraction zone was recorded. Phenomena of mode conversions were observed. They were the same as in the Scholte wave diffraction by a dihedral: the generation of the transmitted and reflected Scholte waves, and the generalized Rayleigh waves. The study was extended to the A wave diffraction on a thin plane plate. The dimensions of the square section of the defect were half of the plate thickness. In this case, the waves generated were generalized Lamb waves.
Experimental study of A wave propagation along a plane or curved plate in contact with two different liquids.
Authors: Martinez Loïc , Duclos Jean , Tinel Alain , Veksler Naum
Published: October 2005

The A wave propagation was first studied on 200-mm-long plane plates made of brass. The plates were 0.2 or 0.1 mm thick. The external fluid was always distilled water, and air, water, propanol, or glycol was used as internal fluids. With propanol or glycol, a second wave was observed, called A*, similar to the A wave but having a strong attenuation in the direction of propagation. Using time frequency techniques, group dispersion curves were shown to be a function of the frequency thickness product in the range 0.1–1 MHz mm. When possible, the phase velocity was derived from experimental results using the phase of the signal spectrum. Experimental results presented a very good agreement with theoretical values. The A and A* wave propagations were then investigated using cylindrical brass boxes. The thickness was also 0.2 or 0.1 mm and the radius was 60 mm. The box was filled with air, distilled water, propanol, or glycol. The experimental dispersion curves were comparable to those in the case of plane plates. If propanol or glycol were used, A* or A waves (respectively) were detected tangentially. Their attenuation was also measured.
Elastic interfacial waves in orthotropic interlayers.
Authors: Sotiropoulos Dimitrios A.
Published: October 2005

Elastic interfacial waves propagating along one of the planar boundaries separating an orthotropic interlayer of arbitrary uniform thickness from an orthotropic infinite surrounding solid are studied. The axes of material symmetry of the two materials are aligned with one of the axes coinciding with the propagation direction and another being perpendicular to the interfaces. The dispersion equation is derived in explicit form yielding the interfacial phase or group speed in terms of frequency, nondimensionalized with respect to the interlayer thickness, and the elastic constants and mass densities of the interlayer and the surrounding solid. Limiting cases of the dispersion equation give the secular equation for interfacial (Stoneley) waves in two semi-infinite orthotropic materials and the frequency equation for an orthotropic plate. Analysis of the dispersion equation reveals several features. Under parameter conditions which are defined propagation at low frequencies cannot occur. Also material parameter combinations are found for which interfacial waves of arbitrary wavelength as compared to the interlayer thickness cannot propagate. Finally, the existence of standing waves as solutions of the bifurcation equation, a special case of the dispersion equation, is defined with respect to the parameters of the interlayer and the host material.
The Kirchhoff–Helmholtz integral theorem and related identities for waves in an inhomogeneous moving fluid.
Authors: Godin Oleg A.
Published: October 2005

The Kirchhoff–Helmholtz integral theorem (KHT), which expresses the wave field in a volume inside (or outside) a given surface in terms of the field’s value on the surface, is well known and widely used in acoustics of motionless media. In this paper, an extension of the theorem to acoustic-gravity waves in an arbitrary inhomogeneous moving fluid is obtained as a corollary of the reciprocity-type relations constituting the recently established flow reversal theorem (FRT) [O. A. Godin, J. Acoust. Soc. Am. 97, 3396(A) (1995); 98, 2866(A) (1995)]. The KHT takes a concise form when stated in terms of acoustic pressure and oscillatory displacement of fluid particles. The KHT is applied to study uniqueness of solutions to acoustic boundary value problems in moving media and to establish unitarity and other general properties of the scattering matrix for surface and volume scattering as well as in an irregular (range-dependent) waveguide with flow. Relation of the scattering matrix properties to the FRT and to wave-action conservation is discussed. [Work supported by NSERC.]
Giant sonic stop bands in 3-D periodic array of liquid balloons.
Authors: Kushwaha Manvir S. , Singh Rama N.
Published: October 2005

Periodic binary systems can create complete acoustic bandgaps (i.e., stop bands) within which sound and vibrations are forbidden. This is of interest for applications such as acoustic filters, noise control, and improvements in transducers; as well as for pure physics concerned with the Anderson localization of sound and vibrations. The band structures for 3-D periodic arrays of water balloons surrrounded by mercury have been computed. Complete, multiple stop bands are found for fcc, bcc, and sc lattices. It is stressed that such a simple 3-D inhomogeneous system exhibits the widest stop bands ever reported for elastic as well as for dielectric composites. The gap/mid-gap ratios are found to be as high as ∼1. For mercury balloons surrounded by water the gaps are found to be comparatively much smaller. Physical importance and applications of such gaps will be discussed.
On the reflection of elastic waves in monoclinic incompressible materials.
Authors: Sotiropoulos Dimitrios A. , Nair Sudhakar
Published: October 2005

The reflection of plane elastic waves from a free surface of monoclinic incompressible materials is examined under plane strain conditions in a plane of material symmetry. The propagation condition is derived which together with the law of reflection yields an inequality that defines the range of existence of the two (one homogeneous and the other homogeneous or inhomogeneous) reflected waves in terms of the angle of incidence of a homogeneous wave, the orientation of the free-surface with respect to a material axis of symmetry, and the elastic constants of the monoclinic material. The critical orientation beyond which there exist two homogeneous reflected waves is derived in explicit form in terms of the elastic constants. One of these reflected waves has an angle of reflection equal to the angle of incidence only for specific orientations which are found. In the range of existence of the two reflected waves, exclusion points are defined for which there exists only one reflected (homogeneous) wave with nonzero amplitude.
Individual differences in human sound localization behavior.
Authors: Wightman Frederic L. , Kistler Doris J.
Published: October 2005

Results from studies of the apparent positions of virtual and real sound sources conducted over the past 5 years reveal large individual differences. To characterize these differences in global terms such as accuracy or variance does not tell the whole story. Listeners differ in the extent to which they make front–back or back–front confusions, the extent to which they report apparent positions above or below the horizontal plane, the resistance of their judgments of apparent position to interaural level imbalance, and other factors. It seems clear that some of these differences might be traced to differences in outer-ear acoustics. Since pinna shapes vary tremendously from person to person, there are large individual differences in the resulting head-related transfer functions (HRTFs). The cues provided by the direction-dependency of HRTFs are known to be important, especially for determining apparent source elevation. HRTFs lacking in detail provide ineffective cues and thus listeners must adopt differing strategies for combining HRTF cues with other cues to determine source position. Unfortunately detailed analyses of both HRTF differences and differences in localization behavior does not reveal a simple relationship. [Work supported by NASA and NIDCD.]
Time for a new form of temporal integration.
Authors: Patterson Roy D.
Published: October 2005

Dave Green has repeatedly emphasized the paradox in the leaky integrator model of temporal processing and stressed the need for new approaches. Recent experiments at APU on envelope asymmetry, period jitter, and fine-structure regularity reinforce the paradox. When ‘‘damped’’ noise with a repeating exponential envelope is time reversed (‘‘ramped’’ noise), it alters the envelope and carrier percepts, supporting damped/ramped discrimination for envelope periods from 8–125 ms. The Weber fraction for jitter on the period of a click train peaks around 60 ms; perfectly regular click trains sound irregular in this region reducing jitter detection relative to longer and shorter periods. These experiments suggest a long time constant for the leaky integrator. When iterated rippled noise masks random noise, it is 15 dB less effective than the equivalent random noise; low-level random noise disrupts the fine-structure regularity of iterated noise. This suggests a short time constant, since values over 8 ms remove the fine-structure that appears to underly the timbre discrimination. ‘‘Strobed temporal integration’’ offers a potential solution to the primary paradox; the fine-structure of periodic sounds is preserved in an ‘‘auditory image’’ which decays relatively slowly thereafter. [Research performed at APU in collaboration with Drs. Akeroyd, Allerhand, Datta, Handel, Irino, Lorenzi, Tsuzaki, and Yost.]
Temporal cues in monaural and binaural detection and discrimination.
Authors: Eddins David A.
Published: October 2005

The auditory system can extract temporal information from complex stimuli to perform a variety of detection and discrimination tasks. At low stimulus frequencies, the auditory system may encode stimulus fine structure and temporal envelope. At higher frequencies, the coding of fine structure diminishes as phase locking deteriorates, while the coding of the temporal envelope remains. The present study investigated the relative contributions of interaural differences in stimulus envelope and fine structure to the masking level difference (MLD). NoSo and NoS thresholds were measured at stimulus frequencies of 500 and 4000 Hz using two types of narrow-band (50 Hz) noise: Gaussian and low-noise noise. Gaussian noise maskers yielded MLDs of 15 at 500 Hz and 9 dB at 4000 Hz, the reduction reflecting minimal fine structure cues at 4000 Hz. Low-noise noise yielded lower NoSo and higher NoS thresholds than Gaussian noise. MLDs of 8 at 500 Hz and 0 dB at 4000 Hz reflected minimal masker envelope cues in both conditions and reduced fine structure cues at 4000 Hz. While the pattern of results was consistent, threshold differences among the six listeners were substantial. Additional MLD conditions and data from CMR and noise discrimination tasks employing low-noise noise will be discussed.
Iceberg revisited.
Authors: Fujimura Osamu
Published: October 2005

Iceberg patterns refer to a particular part of the flesh-point coordinate time function of a crucial articulator for an obstruent gesture [O. Fujimura and W. Spencer, J. Acoust. Soc. Am. Suppl. 1 76, S59 (1983)]. They were found stable for a given demisyllable in different prosodic contexts, when a microbeam pellet height value, around which the time function was excised for comparison, was optimally selected. The time for crossing such a selected threshold height was found useful for studying phonetic phrasing patterns. The C/D model [O. Fujimura, J. Acoust. Soc. Jpn. (E) 13, 39–48 (1992); O. Fujimura, Proc. ICPhS 3, 10–17 (1995)] proposes that the articulatory control function is composed of impulse response functions (IRFs) for elemental gestures, which are magnified according to the syllable strength. Therefore, the movement velocity at a given time relative to the syllable pulse (i.e., in a given phase of transition) will vary according to the syllable magnitude. The two approximation principles will be shown to be mutually consistent when the saturation effects of the physical articulatory system is considered along with general properties of the IRFs for obstruent gestures. [Work supported in part by research and education funds provided by ATR/ITL and ATR/HIP.]
Across session variability in lip–jaw synergies for bilabial closure.
Authors: Alfonso Peter J.
Published: October 2005

Movements of the tongue, lips, and jaw were transduced by electromagnetic midsagittal articulography. A single session included 20 repetitions of
Variation of subglottal pressure during sentence production: Effect on glottal source amplitude and spectrum.
Authors: Hanson Helen M.
Published: October 2005

With the goal of synthesizing natural-sounding speech based on higher-level parameters, variations in subglottal pressure for sentences having different stress patterns have been studied. A Rothenberg mask was used to collect oral pressure and airflow signals from several subjects producing reiterant speech. Acoustic sound pressure was also recorded, and sound pressure levels (SPLs) for both reiterant and natural utterances were compared to verify the suitability of reiterant speech for the task. Subglottal pressure Ps was inferred from oral pressure measured during stop consonant closure of reiterant speech, average glottal flow Ug was estimated from the low-pass-filtered airflow signals, and average glottal area Ag was calculated using Ps and Ug. Glottal source amplitude and spectral tilt were estimated from the speech waveform. Preliminary analysis shows that accented syllables are marked by an increase in Ps of about 50% relative to the weakest unaccented syllables, an increase in SPL of 10 to 15 dB, and some increase in Ag. A model for estimating glottal parameters during these utterances has been developed. Attempts to synthesize sentences based on this model, by including Ag and Ps as control parameters, are described. [Work supported by NIH grants DC00075 and MH52358.]
The effect of lexical complexity on segmental intelligibility.
Authors: Nusbaum Howard C. , Francis Alexander L.
Published: October 2005

Most intelligibility tests are based on the use of monosyllabic test stimuli. This constraint eliminates the ability to measure the effects of lexical stress patterns, complex phonotactic organizations, and morphological complexity on segmental intelligibility. Since these aspects of lexical structure affect speech production (e.g., changing syllable duration), it is likely that they affect the structure of acoustic-phonetic patterns. It also seems plausible that listeners make use of this knowledge during segmental perception. Thus, to the extent that text-to-speech systems fail to modify acoustic-phonetic patterns appropriately in polysyllabic words, intelligibility may suffer. This means that while most standard intelligibility tests may accurately estimate segmental intelligibility in monosyllabic words, this estimate may not generalize prediction of segmental intelligibility with more complex lexical forms. The present study was carried out to measure segmental intelligibility in stimuli varying in lexical complexity. Monosyllabic, bisyllabic, and polysyllabic words were used varying in morphological complexity (monomorphemic or polymorphemic). Listeners transcribed these stimuli spoken by two human talkers and two text-to-speech systems varying in speech quality. The results indicate that lexical complexity does affect the measured segmental intelligibility of synthetic speech.
Modeling the effects of shear conversion on low grazing angle bottom penetration.
Authors: Chin-Bing Stanley A. , Murphy Joseph E.
Published: October 2005

Modeling shear conversion with finite-element/finite-difference codes at a kilohertz and above is difficult due to the number of computational elements needed for such small wavelengths. Typically six to ten nodes per wavelength are required to attain good accuracy. Thus, a typical shallow-water two-dimensional scenario can require hundreds of thousands of computational elements. In this model study, a brute-force hybrid approach is applied. The computational resources of supercomputers with large memories are combined with hybrid modeling techniques to produce simulations of compressional/shear-wave conversions at low grazing angles over range-dependent bathymetry. Examples will be presented that illustrate the effects of these conversions in both horizontally stratified and inhomogeneous anelastic ocean bottoms. [Work supported by ONR/NRL and by High Performance Computing grants.]