bluuebunny/crossref_metadata_2025 huggingface dataset:
Off-resonance contributions to acoustic backscattering from bubble swarms
Authors: Commander Kerry W. , Moritz Elan
Published: October 2005

Recent discrepancies between measurements of bubble populations near the surface in the ocean by optical and acoustical methods have been discussed in detail by MacIntyre [F, MacIntyre, “On reconciling optical and acoustical bubble spectra in the mixed layer,” in Oceanic Whitecaps, edited by E. C. Monohan and G. MacNiocaill (Reidel, New York, 1986), pp. 75–94.] Another possible explanation for the very large number of small bubbles found by acoustic methods is the potential for overestimates of bubble numbers through the use of resonance scattering theory in the bubble population calculations. In this work it is shown that for some bubble distribution of interest, the acoustic backscattering for a particular frequency is actually dominated by scattering contributions from off-resonance bubbles. This effect is more prevalent for high frequencies, causing overestimation of the number of small bubbles, which is precisely where the two methods disagree. The more complete acoustic calculations may not completely reconcile the bubble number estimates obtained from the optical and acoustical bubble spectra; however, they bring them closer together. [Work supported by ONT.]
Efficient, high-frequency, parabolic-equation modeling with surface scattering loss
Authors: Head Martha E. M. , Holmes Eleanor S. , Dozier Lewis B. , Jobst W.
Published: October 2005

Solving the parabolic approximation to the acoustic wave equation by the split-step algorithm is one of the principal methods for estimating the acoustic-pressure field in a range-dependent underwater environment. The algorithm is computationally intensive and is usually practical only at low frequencies. A modification to the split-step algorithm is provided (the calculation-frequency method), which allows rapid calculation of transmission loss at high frequency, includes surface and bottom loss, and provides for the redistribution of surface-scattered energy in wavenumber space.
Ultrasonic absorption properties in excessively fatty rat liver
Authors: Smith Nadine B. , O'Brien W. D. , Erdman J. W.
Published: October 2005

The ultrasonic absorption coefficient was examined in rat liver due to the effects of 1% dietary orotic acid measured using the transient thermoelectric technique @ 1MHz. Dietary orotic acid causes fat concentration to accumulate excessively in rats in a short period of time. Tissue constitutes that are particularly important in absorption are water, protein, collagen, and lipid levels. The concentration of these tissues constitutes in rat liver over a 0-to 10-day period on the orotic acid diet compared to the absorption coefficient suggest that ultrasonic properties can be modeled as a function of constitute concentrations. Using the statistical analysis system, comparisons were made between the tissue constitutes and ultrasonic absorption coefficient where comparisons are significant at the p < 0.05 level. Lipid levels of the fatty liver were shown to be statistically significant to the absorption coefficient. Strong correlations of both collagen and protein with absorption, which have p values of 0.098 and 0.071, respectively, were observed. [Work supported by NIH Grant CA36029.]
Acoustical quantification of thermal injury
Authors: Holmes Anne W. , Forster Fred K. , Olerud John E. , Sharar Sam R.
Published: October 2005

In this study, acoustic imaging was augmented by tissue characterization to more accurately quantify severity of thermal injury. The acoustic attenuation coefficient in normal and burned skin was investigated over the range of 10–30 MHz. Fourteen normal and 21 full-thickness scald burns (1 and 2 min) from goats were analyzed. The results of this study show the importance of choosing sites for attenuation estimates from the image since both normal and burned skin cannot be assumed homogeneous. From regions chosen in the reticular dermis, it was found that the attenuation coefficient was significantly less for the burns. After averaging the results from each group, the integrated attenuation coefficient over the frequency range studied was 8.3 Np/cm for normal skin, and decreased approximately 30% to 5.7 Np/cm for burns. The differences between normal and burned skin were also characterized by the frequency dependence of the attenuation with a power law of the form, afb. Characterized in this manner, the fitting parameters exhibited large changes when comparing values for normal and burned skin. The parameter a increased by more than a factor of 5 and the exponent b decreased by approximately a factor of 2. These quantitative measures appear to be valuable components in an overall acoustic system for burn severity evaluation. [Work supported by NIH.]
Videostroboscopic images associated with glottographic waveforms
Authors: Berke Gerald S. , Gerratt Bruce R. , Hanson David G.
Published: October 2005

Knowledge of vocal fold vibratory morphology in normal and pathologic phonation is important in understanding glottal airflow and acoustics. Although noninvasive measures of phonation such as photoglottography and electroglottography provide some information on vocal fold movement, inferences are required regarding which glottal events correspond to particular points on the glottographic signals. Thus confirmation of the relationship of glottography to the vibratory movements of the vocal folds is desirable and especially important when studying dysphonia. Here a new technique is reported in which sequentially obtained videostroboscopic images are associated with specific vocal fold vibratory events recorded glottographically. The system involves digitizing glottographic signals simultaneous with the horizontal sweep synch of the video signal and a 5-ms synchronization impulse that is also recorded on the audio channel of a video recorder. The advantages of the system include the ability to sample many images and applicability to clinical investigation. Validation of the technique along with the demonstration of the images and waveforms obtained will be presented. [Work supported by a VA Technical Merit Review Grant.]
An esophageal electrode for studying posterior cricoarytenoid muscle activity during speech
Authors: Fujita Mihoko , Ludlow Christy L. , Woodson Gayle E. , Naunton Ralph F.
Published: October 2005

An esophageal surface electrode was developed for the study of posterior cricoarytenoic (PCA) muscle activity during speech based on an initial design of Woodson and her colleagues. The electrode consists of two multiple strand wires contained in a 5 French pediatric feeding tube. It is passed through one nasal passage into the upper part of the esophagus and picks up PCA activity through the anterior wall of the esophagus. Deep inhalation is a verifying gesture with an absence of activation during sustained modal vowel production. Use was attempted with 19 subjects; 3 normal speakers and 16 patients. The expected activation patterns were obtained in 14 (73.7%) subjects. Problems that interfered with obtaining accurate recordings included a lack of descent into the esophagus and pickup of phonatory vibration. This electrode provides a valuable tool for phonetic and phonatory studies of PCA activation patterns in normal speakers and patients with voice disorders.
Wisconsin x-ray microbeam system: Articulatory pellet tracking specifications
Authors: Nadler Robert D. , Robl Phillip E. , Wahl Daniel J. , Westbury John R. , Fujimura Osamu
Published: October 2005

The x-ray microbeam system for studying tongue movements and other articulatory gestures has been in routine operation for the past year. The precision and accuracy with which the system can track pellets is dependent upon a number of factors. These include the x-ray system operating parameters and characteristics, pellet size, background conditions, and image processing algorithms used for real-time tracking. The results of studies that address these issues, and their importance with respect to interpretation and use of articulatory movement data, will be discussed. Other methodological issues of importance to potential users include head movement correction via the use of reference pellets and empirical specification of anatomical reference planes for expressing the acquired speech movement data. The x-ray dosage incurred by subjects studied to date has also been carefully examined. Even when using peak spatial dose, a conservative estimate, subjects can participate in repeated speech production studies without exceeding the yearly Federal whole body dose limit. The status of the system and planned updates will also be presented. [Support for this facility is provided by NINCDS (NS-16373).]
Labial closing kinematics reconsidered
Authors: Lame Gerald D. , DeWald Richard O.
Published: October 2005

Ladefoged and Maddieson [UCLA Working Papers 64, 1–137 (1986)] have spoken of “the forceful coming together of the tongue or lips in a stop consonant” as “an attempt to throw one part of the vocal tract through another” (p. 3), while Gracco and Abbs [Exp. Brain Res. 65, 156–166 (1986)], in examining closure into the first /p/ for “sapapple,” found peak velocity was attained well before contact. This deceleration into closure, plus “relatively high correlations between the amplitude and peak velocity of individual movements” were taken as evidence that “the labial closure goal was not achieved simply by slamming the lips together” (p. 159). While these descriptions are not necessarily contradictory, they do suggest two different possible movement types. Gracco and Abbs' smooth, centrally peaked velocity profiles resemble those of pointing or reaching. Ladefoged and Maddieson describe, instead, a striking gesture. In order to distinguish these, special care must be taken (1) to ascertain time of contact accurately, (2) not to distort events near impact by excessive low-pass filtering, and (3) to avoid effects of secondary labial articulations. When these precautions are taken, closure into /p/ resembles a blow or tap, with minimal if any deceleration before contact.
Extracting dynamic parameters from articulatory movement
Authors: McGowan Richard S. , Smith Caroline L. , Browman Catherine P. , Kay Bruce A.
Published: October 2005

In order to model the movements of the speech articulators using a dynamical systems approach, it is necessary to specify (1) the specific form of the dynamical equation, (2) the portion of the articulatory trajectory being described/generated by the equation—the “window,” and (3) the values of the coefficients to be used in the equation. In this work, a damped mass-spring dynamical system is assumed, as used in previous task dynamic modeling [Saltzman et al., J. Acoust. Soc. Am. Suppl. 1 82, S15 (1987)]. A program was developed to determine the values of the coefficients for the equations, using various definitions of the articulatory window. The program uses a nonlinear least-squares algorithm to determine the best fit between the observed trajectories and the trajectories generated using a range of values for the coefficients. This program is currently being tested on simulated data with known parameters in order to establish the accuracy and limitations of the procedure. There will be a report on the reliability of the analyses performed using this approach, with an emphasis on numerical considerations. [Work supported by Grant BNS-8520709 from NSF and Grants HD-01994 and NS-13617 from NIH.]
Kinematic characteristics of children's post-vocalic labial stop consonants
Authors: Smith Bruce L. , McLean-Muse Ann
Published: October 2005

In English, vowels tend to be longer preceding voiced versus voiceless obstruents. Although perceptual factors are often thought to be primarily responsible for this effect, part of the difference may also be a result of inherent speech production factors. Adults commonly move their articulators more rapidly when closing into voiceless versus voiced obstruents, which may contribute to shorter vowels preceding voiceless obstruents. Despite several acoustic studies of this general phenomenon in English-learning children, however, little developmental information is available concerning articulatory characteristics of children's post-vocalic consonants. Although children show acoustic vowel duration differences in these contexts, it is not known whether articulatory differences occur in their productions, as they do for adults. One purpose of this study was to obtain kinematic data from children concerning this issue. Articulatory peak velocity data for upper lip, lower lip, and jaw movements were obtained for eight children in each of three age groups and eight adults. A peak velocity difference for [p] vs [b] closing gestures was observed for each of the four age groups. There was also a tendency for the difference between [p] and [b] peak closing velocity to increase with age.
Phonological constructs: Electromyographically obtained speech error evidence
Authors: Mowrey Richard A. , MacKay Ian R. A.
Published: October 2005

In recent years, speech error data have often been cited as evidence for the existence of, or for the psychological reality of, certain phonological constructs, such as the phoneme or the distinctive feature. Further claims have been made concerning the role of these units in the processing of motor control instructions in the production of speech output. This work reports on the collection of phonological speech error data in a controlled laboratory environment using Basmajian electrode EMG in various speech muscles, as well as audio recordings. Both integrated EMG signals and single motor unit analysis are presented. The results lead to the conclusion that published speech error corpora based on field-collected errors are skewed by the combined problems of collection technique, categorical perception, and hearer normalization, and that this skewing leads to circularity in the arguments based on these corpora. This evidence provides support for individual motor instructions as phonological primitives in motor speech control, and does not support higher-order motor control units such as features and segments.
Objective measures of the annoyance due to automobile passenger compartment noise
Authors: Lamancusa John S.
Published: October 2005

The annoyance attributable to complex noises consisting of multiple pure tones (which may or may not be harmonically related) and substantial broadband noise is not easily quantifiable. It has been shown that dBA is a poor indicator of loudness [Hellman and Zwicker, J. Acoust. Soc. Am. 82, 1700–1705 (1987)], and a number of other measures have been proposed. In this study, the results of subjective preference tests of passenger compartment noise are compared to objective measures of loudness and annoyance. Eight synthesized variations of the noise experienced at full throttle acceleration were ranked by 40 subjects according to their desirability. All samples were normalized to 101-dB linear. These results are compared to the objective rating methods: AI (articulation index), ISO 532B (Zwicker method), Stevens Mark VII, CRP (Composite Rating of Preference), and PNL (perceived noise level). The CRP offers the best correlation with subjective results. The results of Mark VII, and ISO 532B are markedly improved by the addition of empirically derived corrections.
Quality assurance in automated monitoring of high-energy impulsive sounds
Authors: Luz George A. , Russell William A. , Lewis Nelson D.
Published: October 2005

U.S. Army policy is to measure noise levels whenever the projections of noise contouring computer programs show a noise environment “unacceptable” for residential use extending beyond the Federal installation's boundary. The threshold for “unacceptable” is an A-weighted day-night level (DNL) of 75 dB for aircraft and a C-weighted DNL of 70 dB for high-energy impulsive sounds. For adequate quality assurance (QA) in monitoring high-energy impulsive sounds, statistical decision criteria are employed including threshold, duration, number of events per unit time, peak-to-SEL differences, and event probability distributions. The strengths and weaknesses of each QA criterion is discussed.
An overview of occupational noise regulations in Canada
Authors: Benwell Deirdre A.
Published: October 2005

In Canada, there are occupational noise regulations at both provincial and federal levels of government. An overview of present Canadian occupational noise legislation is given. In addition, recent Canadian activities concerning occupational noise exposure standards, guidelines, and other important background documents are described. The various methods used to assess compensation for occupational hearing loss are also summarized. Some recommendations are made for future activities in this area.
The critical exposure in acoustic trauma
Authors: Ward W. Dixon
Published: October 2005

As one increases the intensity I of a noise exposure of fixed duration t, the resulting damage grows gradually up to a critical point at which the damage increases precipitously. The intensity at which this occurs, however, is not independent of the duration, so it cannot be called a “critical intensity.” Neither is this point dependent only on the total energy of the exposure It: Less energy is required at shorter durations in order to reach the critical point, so even “critical energy” would be a misnomer. Instead, the implication of an extended series of experiments in which chinchillas were given single exposures of a few minutes to 1.5 days at levels up to 120 dB SPL is that the critical exposure appears to be defined by I2t = C, or equivalently, p4t = k, where k is about 1010 Pa4 s for the chinchilla. This value is in agreement with recent results defining critical exposures to impulse noise in the chinchilla reported by Patterson and Hamernik [J. Acoust. Soc. Am. 81, 1118–1129 (1987)]. The meager data in the literature suggest that for man, k may be around 1010 Pa4 s. [Work supported by NINCDS Grant 12125.]
Influences of temporal spacing of impulse noise on temporary and permanent threshold shifts
Authors: Danielson Richard W. , Henderson Donald , Saunders Samuel S.
Published: October 2005

Chinchillas were exposed to impulse noise conditions with equal acoustic energy and spectra but with three different temporal patterns and two different amplitude levels (135 and 150 dB SPL, counterbalanced by 15-dB trade-offs in number of events). Auditory-evoked responses were used to measure TTS and PTS. Degree of hearing loss and pattern of recovery were not uniform among the groups, contrary to assumptions related to the equal energy hypothesis. Relative to hearing loss after exposure to one impulse/second: (1) less hearing loss was seen after exposures to bursts of 1 impulse/50 ms and (2) greater hearing loss was seen when high-level impulses occurred in salvos (pairs of impulses presented at 1-s intervals, with 50-ms interpulse interval in each pair). Findings will be compared to reports of a possible “period of vulnerability,” during which hearing loss may be more extreme if the ear is exposed to additional impulse noise while the ear is still recovering. [Work supported by NIOSH and the Department of the Army.]
Changes in frequency selectivity in the chinchilla following a noise induced permanent threshold shift
Authors: Davis Robert I. , Ahroon William A. , Hammernik Roger P.
Published: October 2005

Evoked-potential tuning curves (TC) were obtained on 106 chinchillas before and after acoustic overstimulation in order to assess the effects of the magnitude of hearing loss on frequency selectivity. Pre- and postexposure measures of auditory thresholds and masked thresholds (simultaneous tone-on-tone paradigm) were obtained in each animal at 0.5, 1, 2, 4, 8, and 11.2 kHz, using the evoked auditory response recorded from the inferior colliculus. Three TC variables (Q-10 dB, tail-tip difference, and the high-frequency slope) and sensory cell losses were compared to the amount of noise-induced permanent threshold shift (PTS) produced by a variety of noise exposures. Based upon large sample averages, frequencies showing PTS⩾20 dB also showed statistically significant differences between pre- and postexposure measures of all three TC variables. For 10 < PTS < 20 dB only the tail-tip difference showed a statistically significant change, while for PTS ⩽ 10 dB there were no measurable changes in the TC variables. The percentage of outer hair cell loss showed an orderly and systematic increase as PTS increased and as TC variables changed across the entire range of test frequencies. The inner hair cells were essentially unaffected. These results show that there is a systematic change in the TC variables that define the quality of tuning as hearing loss progressively increases and that these changes are clearly related to outer hair cell losses. [Research supported by NIOSH and DOD.]
“Enhanced” evoked response amplitudes in the chinchilla following acoustic trauma
Authors: Salvi R. , Saunders S. , Powers N. , Gratton M. A.
Published: October 2005

The amplitudes of auditory-evoked responses recorded from chronic electrodes in the inferior colliculus of the chinchilla were measured before and after acoustic trauma. Acoustic trauma was induced using a 2-kHz continuous tone that resulted in either 30–40 dB of TTS or PTS between 2–8 kHz. The high-intensity exposures resulted in systematic changes in the input/output functions of the evoked response. The most striking change was an increase in the maximum amplitude (“enhanced”) of the evoked response at frequencies below and at the low-frequency edge of the hearing loss (0.5 and 2 kHz). By contrast, the maximum amplitude seen at frequencies near the middle of the hearing loss or its high-frequency border (4 and 8 kHz) was generally depressed. In addition to the change in maximum amplitude, there were also changes in the slope of the evoked response input/output functions. The results will be related to the pattern of hair cell loss as well as to possible underlying neural mechanisms. [Work supported by NIH R01 NS16761 and NS23894.]
PARQUES: A range-dependent environment propagation loss model
Authors: Grandvuillemin Bruno
Published: October 2005

A proposal to solve the Helmholtz's equation by means of the parabolic approximation in a two-dimensional range-dependent environment will be given. It will make clear the solution for a quadratic development of the propagation operator that allows the consideration of a larger angular aperture of the source. The numerical solution is given by an algorithm of finite difference using the Crank-Nicholson method. The problem of rectilinear horizontal, and oblique interfaces between two fluid media is solved. The problem of a range variable sound velocity profile is treated by conditions of continuity between two media with the given profiles. The regressive wave is also computed. The results of numerical simulations executed on the array processor FPS 164 are presented. Also are shown comparisons between theoretical computation and experimental data for range-independent and range-dependent environment.
Intrinsic modes revisited
Authors: Xiang F. , Cada M. , Felsen L. B.
Published: October 2005

Intrinsic modes [J. M. Arnold and L. B. Felsen, J. Acoust. Soc. Am. 76, 850–860 (1984)] are wave objects that propagate without coupling upslope or downslope in a homogeneous ocean wedge above a penetrable bottom. They have been observed experimentally and have been referred to as wedge modes in that context [F. B. Jensen and C. T. Tindle, J. Acoust. Soc. Am. 82, 211–216 (1987)]. The exact analytic form of the intrinsic modes (IM) involves a spectral integral which, for small slopes, can be reduced asymptotically to a simpler integral expression that leads to the conventional adiabatic modes where these apply but is valid also through the upslope cutoff transition. Except for small slopes, this simplified form upslope or downslope is flawed by energy balance defects beyond upslope cutoff and by inaccuracies of the field leaked into the bottom. The exact form of the IM has now been reexamined and restructured so as to be computable directly. In fact, the convergence of this restructured form, which tracks multiple reflected plane wave spectra, improves with slope angle, thereby making it complementary to the small slope approximated algorithm. Calculation of the complete IM removes the defects noted above and thereby establishes the IM firmly as the analytical wave object that describes the experimentally observed wedge modes. Numerical comparisons of the IM with wedge solutions obtained by the parabolic equation and coupled mode codes confirm this conclusion. [Work supported by ONR Ocean Acoustics.]
A space-time split-step algorithm for pulse propagation in refracting media
Authors: Codona Johanan L.
Published: October 2005

A simple, time-domain split-step algorithm for pulse propagation in a refracting medium is derived from the time-dependent wave equation (TDWE). The derivation is similar in form and spirit to the factored Helmholtz equation methods used in finding generalized parabolic equations. Like the Helmholtz equation analyses, the factored TDWE involves nonlocal pseudodifferential operators and a commutator term. Making use of causality, and considering media in which the index-of-refraction changes only slowly over a typical acoustic wavelength, the commutator term can be neglected and the TDWE reduces to a Schrodinger-like equation in space-time. From here, a variety of methods (for example, phase-space path integrals) can be employed to generate marching algorithms for computing the evolution of an acoustic pulse in a refracting medium. A fast split-step algorithm (of the form FFT/multiply/FFT/multiply/etc.) only results if the operator playing the role of the Hamiltonian in the pulse Schrodinger equation is separable, which is only a good approximation for narrow-band, forward propagation. However, a somewhat slower phase-space algorithm based directly on the phase-space path integral does not suffer any of these limitations. The time-domain split-step algorithm will be compared with other pulse-propagation methods (such as direct Fourier synthesis) and the resulting accuracy and numerical efficiencies discussed.
Computing ocean pulse propagation using parabolic equations and numerical phase correction
Authors: Gilbert Robert P. , Wood David H.
Published: October 2005

When one uses a parabolic equation instead of the Helmholtz equation to synthesize a pulse propagating in the ocean, the so-called “phase errors” in solutions of the parabolic equation lead to errors in the shape and arrival time of the pulse. Of course, different kinds of parabolic equations are known to have different types and sizes of phase errors. A transmutation approach is used, that is, the kernel of an integral transformation is sought that maps solutions of the parabolic equation into solutions of the Helmholtz equation. Naturally, different types of parabolic equations require different transmutation kernels. Using the appropriate transmutation kernel, the effects of parabolic phase errors can be numerically corrected for. In an ocean with slow horizontal variation, it is possible to periodically update the transmutation kernel as the solution is tracked horizontally. Numerical examples will be presented.
Computing ideal starting fields for parabolic equations: Approach and examples
Authors: Robinson E. Richard , Wood David H.
Published: October 2005

A parabolic equation model requires a starting field, that is, the values of the field must be given as a function of depth at a fixed range. The ideal starting field is a weighted combination of propagating normal modes. Since it is time consuming to compute normal modes, the usual practice is to use a more easily computed result such as a Gaussian, filtered Gaussian, sinc, or uniform ocean starting field. However, in our approach, less effort is required because the individual normal modes are not computed but only the desired combination of normal modes that gives the ideal starting field. Two example normal mode starting fields are computed and are compared to other starting fields. The effects of the various starting fields on the propagation loss predicted by a parabolic equation model are shown.
The effects of dispersion, attenuation, range, and other factors on the duration of transients
Authors: Del Balzo Donald R. , Field Robert L. , Collins Michael D.
Published: October 2005

In this paper, the results of a theoretical investigation into the effects of various factors including dispersion, attenuation, and range on the duration of transients in shallow water ocean environments are presented. An acoustic source with the time history s(t;ω) = 0 for t < 0 and sin (ωt) for t > 0 is placed in the ocean several kilometers from a receiver. The duration of the transient is the amount of time between the first arrival and the achievement of a time harmonic state at the receiver. Using. a range-dependent time domain model developed at NORDA, the Klein-Gordon equation is solved to obtain the received signal P(t;v) due to the Gaussian source S(t;v) = exp[ − (vt)2]. Then, P(t;v) is convolved to obtain the reponse p(t;ω) due to s(t;ω). Qualitatively, one would expect transient duration to increase with dispersion and range and to decrease with attenuation. A presentation of quantitative results to illustrate these relationships and discuss the possibility of the use of transient duration to solve inverse problems will be given. [Work supported by ONR and NORDA.]
Transient acoustic wave propagation in a fluid layer with stepwise range dependent perfectly reflecting boundaries
Authors: Brooke Gary H. , Glover Roderick E. , Chamuel Jacques R.
Published: October 2005

The coupled mode solution technique JR. B. Evans, J. Acoust. Soc. Am. 74, 188–195 (1983)] is adapted to the problem of transient acoustic wave propagation in a single fluid layer with perfectly reflecting boundaries. Properties of one of the boundaries are allowed to vary in a stepwise range dependent manner. The transient response due to an impulsive line source is synthesized from solutions to a global matrix formulation of the coupled mode problem for two-dimensional waveguides. Several numerical examples are presented that model: (i) waveguide scattering behavior of both single and multiple scatterers placed near the boundary of the fluid layer and (ii) propagation in a waveguide with a variable impedance boundary comprised of alternate free and rigid strips. The numerical results are compared with experimental observations taken from measurements performed at ultrasonic frequencies using an air-suspended waveguide [J. R. Chamuel and G. H. Brooke, J. Acoust. Soc. Am. Suppl. 1 77, S13 (1985)].
Dependence of vibrational modes of a handbell on thickness and added mass
Authors: Sathoff H. John , Zhiqing Jiang , Rossing Thomas D.
Published: October 2005

The vibrational modes of a large tuned handbell (G2) are compared with those of an untuned bell casting having the same shape but with twice the thickness. Doubling the wall thickness is found to raise the frequencies of the various modes by factors ranging from 1.4 to 2.4 (flat plate theory predicts a factor of 2 for all modes). Unlike the tuned G2 handbell, whose pitch coincides with the frequency of the fundamental mode of vibration, the thick bell has two prominent strike notes, depending upon where it is struck. These subjective tones appear to be created by groups of three nearly harmonic partials radiated by the (m,l) and (m,l♯) families of modes, respectively. The acoustical effects of attacking up to twelve 35-g brass cylinders have also been observed, both in a symmetrical pattern and in clusters similar to the clusters of mei found on ancient Chinese bells [Rossing et al., J. Acoust. Soc. Am. Suppl. 1 77, S102 (1985)]. The additional masses lower the frequencies of certain modes but have relatively little effect on modal decay rates.
The architectural space: A comparison of acoustical criteria used to assess aircraft noise in rooms and aircraft interiors
Authors: Hougland Dana S.
Published: October 2005

The aircraft as a sound source is viewed in different ways depending upon the location of the receiver of concern. Although, often, the same source is dealt with, there are definite differences between the impact on a building occupant near an airport and the crew or passengers within the actual aircraft. Studies of both receivers use similar primary criteria such as speech intelligibility, fatigue, annoyance, and hearing loss. The criteria differ in relative importance, length of exposure, and perception of value. The application of secondary criteria used in noise control studies to quantitatively express attenuation through the exterior shell, acceptable background levels, and room effect, vary between the two fields of study. The comparison of similarities and differences in existing, commonly used criteria for these two fields of study is explored. Suggestions for areas of further study and correlation between the two fields of study are investigated.
Aircraft interior noise research at the NASA Langley Research Center
Authors: Powell Clemans A. , Silcox Richard J.
Published: October 2005

The Structural Acoustics Branch at the NASA Langley Research Center has been a major contributor to the field of aircraft interior noise research for the past 15 years. In addition to contributions from its in-house program, the branch has supported many contributions from other organizations through an active grant and contract research program. Although the current emphasis of the program is on advanced turboprop airplanes and helicopters, the goal has always been to develop and improve interior noise prediction methodology. This allows for the incorporation of appropriate control measures in new aircraft at the design stage rather than through the use of add-on acoustical treatments with potentially large weight penalties and reduced effectiveness. The proposed presentation will concentrate on some of the more recent basic research activities concerned with the transmission of noise into aircraft interiors through both airborne and structureborne paths. These include modeling of the structural response, the interior acoustic response, energy flow techniques, and acoustical-structural coupling. In addition, some results of recent activities in active noise control will be presented. Although the emphasis of the presentation will be on research conducted in-house, some research conducted under contracts and grants that is closely connected to in-house activities will also be discussed.
Interior noise characteristics of rotorcraft
Authors: Cox Charles R.
Published: October 2005

The major noise sources and weight-efficient means for noise control in different size, single-rotor helicopters were determined by numerous measurements. Noise inside helicopters is characterized by numerous high-frequency tones during all flight modes and by broadband wind noise at cruise airspeeds. The tones, emanating primarily from the main transmission, the engine gearbox, and accessories, are the most objectionable and are present in the cabin of a helicopter at much higher levels than in the cabins of fixed-wing aircraft. Because of this characteristic, certain criteria used to determine acceptability, particularly speech intelligibility, are found inappropriate when applied to helicopter interior noise. Noise control is realized by design changes, e.g., source reduction and sound transmission path interruption, and by tailored soundproofing treatments. While some of these design changes are generic, most are unique to a particular helicopter model. This reflects the multiple structural designs concepts, the variety of drive system mounting configurations, and extensive use of composite materials. Emerging challenges involve the noise control of all composite rotorcraft airframes and of the new tilt rotor aircraft.
Wind instrument transfer responses
Authors: Beauchamp James W.
Published: October 2005

Mouthpiece and output pressure signals from several instruments (e.g., trombone, clarinet, saxophone) have been recorded, harmonic spectra have been computed, and transfer responses have been estimated by taking ratios of corresponding harmonic amplitudes. Each transfer response appears to be a series of points on a smooth high pass filter function, even though it actually corresponds to points on (tending toward the minima of) a multiresonant response curve. According to simplified assumptions the measured responses would be independent of amplitude and fundamental frequency. However, there is, in fact, a considerable degree of variation. Results will be presented and reasons for the variations will be discussed.
On the bore-to-driver feedback in double-reed conical woodwinds
Authors: Agulló J. , Barjau A. , Martínez J. , Cardona S.
Published: October 2005

The nonlinear behavior of double-reed drivers makes advisable the use of time domain to study bore-to-driver feedback. The characteristic trends of the impulse response of a conical woodwind are revised. The low intensity of the reflection coming from the first open hole shows the essential role that Bernoulli pressure plays in the reed self-sustained oscillation (also proved by the reed squeaks that players produce to check reed readiness). Time-domain study of these instruments leads to the convolution product relating pressure and velocity at the bore input section. The use of the impulse response h(t), the plane-wave and the spherical-wave reflection functions, Rp(t) and Rs(t) respectively, as kernel functions in this product is revised. The sharp fluctuations of Bernoulli pressure may impair the use of Rp(t) while R s(t) is unsuitable due to the usual taper discontinuity in the staple-main body junction of these instruments. Computed and experimental initial transients are given for the case of a “tenora” (Catalan tenor shawm).
The role of tambura spectra in drone tunings of North Indian ragas
Authors: Carterette Edward C. , Jairazbhoy Nazir , Vaughn Kathryn
Published: October 2005

As part of a program on the role of drone interactions with North Indian ragas played on the sitar, the waveforms of the tambura for the most common drone tuning of the four strings [pa, sa1, sa2, sa′ (low sa)] were analyzed. Each of the strings was played with and without juari threads that have the effect of separating the string slightly from the bridge. The resulting sound is referred to by Indian musicians as a buzz. Without juari the pitch heard is very close to the string fundamental and the partials fall linearly in decibels. With juari the pitch is heard at one or even two octaves above the base pitch and the partials have great power as far as the 20th partial. With juari the 4th, 7th, 11th, or 12th, and the 17th partials have more amplitude than the fundamental. Total harmonic distortion is on the order of 1 to 19 dB without juari but ranges from 12 to 44 dB with juari. The upward spread of energy into higher partials imparts richness to tambura tones, and underlies the use of different drone tunings for different ragas. The pitch and timbre changes with tambura are discussed in terms of the psychoacoustics of complex tones.
An adaptation model for source displacement in multiple-source environments
Authors: Wakefield Gregory H.
Published: October 2005

In general, the acoustic field at the two ears is not sufficient to support source localization for more than one source. Experiments on localization indicate that the co-occurrence of two sources can lead to substantial source localization error that reflects either the ambiguity present in the acoustic field or some form of bias in the binaural processing of that acoustic field. It is shown that displacement of the perceived lateral position of a narrow-band noise away from the lateral position of a narrowband interferer [G. H. Wakefield and N. F. Viemeister, J. Acoust. Soc. Am. Suppl. 1 76, S91 (1984)] does not lie on the surface of possible source positions supported by the acoustic field. Therefore, it does not appear that anomalous localization can be explained entirely with respect to ambiguities in the acoustic field. Instead, a modification of Stern's position variable is proposed to account for source displacement by introducing a frequency-dependent form of spatial adaptation. Much, but not all, of our displacement data are consistent with an additive form of adaptation with a time constant of 25 ms in which the level of adaptation at a given position does not depend on excitation at other positions. The manner in which the model fails to predict displacement for long-duration sources suggests the presence of a weaker adaptation across position.
Detection of interaural phase shifts and level differences in portions of broadband noise
Authors: Yost William A.
Published: October 2005

Versions of Cramer-Huggins pitch stimuli were generated such that a narrow band (bandwidths ranged from 1–100 Hz) of a wideband, diotic noise (low-passed filtered at 8000 Hz) was presented dichotically with an interaural phase shift or an interaural level difference. The threshold value for detecting a phase shift or a level difference in the dichotic, narrowband portion of the broadband noise was determined as a function of the center frequency of the dichotic, narrow band of noise and as a function of the bandwidth of the dichotic, narrow band of noise. A single-interval procedure without feedback was used to estimate three point psychometric functions relating d′ to interaural phase or d′ to interauralevel difference. A random variation in the interaural level difference of the entire noise waveform was also used to force the listeners to use pitch as the cue for detection rather than some aspect of lateral position. The data will be discussed in terms of models of binaural processing and binaural pitch. [Work supported by NINCDS.]
Using reciprocity to predict aircraft interior noise due to multiple correlated input forces
Authors: Ver Istvan L. , Mayes William H. , McGary Michael C.
Published: October 2005

This paper reports on how to utilize reciprocity to predict aircraft cabin noise due to multiple correlated point forces, such as those acting on engine mounting points. The transfer functions are determined by a reciprocal experiment by measuring, at the force excitation points, the magnitude and phase of the vibration response due to the operation of a point sound source located in the cabin. The experiments reported were carried out on the fuselage of a light aircraft. The methodology, the experimental apparatus, the software, and the test results will be presented and the advantages of the reciprocity method discussed. [Work supported by NASA Langley Research Center.]
Hand-held auditory screener
Authors: Alvord Lynn S.
Published: October 2005

A new hand-held auditory screener is presented that utilizes filtered square waves as test signals. Circuit design has resulted in a total size of 212 × 4 × 212in., including earphone and cushion. High-frequency filtering of the square wave signal results in acceptably low levels of harmonic distortion according to ANSI specifications for audiometers [ANSI S3.6-1970]. Low current drain design provides for a “battery-low” and “signal-on” indicator. Individual intensity pots allow for periodic calibration or modification of presentation levels between 20 and 40 dB HL. Initial clinical trials with 50 patients show good agreement with conventional, pure-tone audiometric screening. Rationale for increased use of hearing screening by health care practitioners is presented.
Using MIDI, the standard Musical Instrument Digital Interface, for psychoacoustic experiments
Authors: Williams H. E. F. , Gibian G. L. , Harnden E. N. , Evans A.
Published: October 2005

MIDI, the music industry's standard Musical Instrument Digital Interface, allows control of commercially available music synthesizers by personal computers, as well as measurement and reproduction of musical performance parameters. The resolution in frequency, amplitude, timbre, and time of the system is adequate for various psychoacoustic experiments. A Yamaha DX7 synthesizer controlled by an IBM PC was used to measure subjects' judgments of the similarity of synthesized tones differing in timbre [G. L. Gibian et al., J. Acoust. Soc. Am. Suppl. 1 82, S68 (1987); G. L. Gibian et al., Audio Engineering Society Preprint ♯2488 (1987)].
A programmable subject response box for psychophysical experimentation
Authors: Ling Robert , Burns Edward M.
Published: October 2005

Software that utilizes a commercially available touch pad (“Koala Pad”) as an all-purpose subject response box will be demonstrated. [Work supported by NINCDS.]
Transducer and transducer measurement system for the PC
Authors: Allen J. B.
Published: October 2005

The measurement of several acoustic transducers using a measurement system that is implemented on the PC will be shown. This system uses the ARIEL DSP-16 and a PC-6300. The software developed for this purpose, which is called SYSid, was developed first about 8 years ago, and in the past few years was ported to the PC. SYSid will measure the frequency response of a transducer in less than 100 ms with an accuracy that is determined by either the nonlinearities or the noise in the system. Typically, this noise and distortion is more than 80 dB down, giving results that are accurate to 1 part in 104. SYSid also will measure the phase, group delay, impulse response, and the distortion as a function of frequency and level. In the demonstration, an attempt will be made to measure the acoustic impedance of a section of tube, and a rho-c screen.
Techniques for free-field testing of spatial attributes of acoustic signals
Authors: Gatehouse R. Wayne
Published: October 2005

For a number of years Gatehouse and his coauthors have reported on studies of various aspects of spatial acoustics (localization, depth perception, masking) done under free-field conditions of signal presentations. Basically, the paradigms have involved comparisons of the responses of normally hearing, artificially degraded (monaural or binaural occlusion by ear muffs and plugs), and real hearing impaired subjects of various types and degrees of loss, under conditions that presumably mirror the more normal hearing environment, i.e., reverberant or semireverberant rooms, all types of signals (noises, tones, speech), from positions that vary in both azimuth and elevation and from all around the subjects. In this session, some of these techniques and conditions will be displayed in a more detailed manner than is usually available in verbal presentations of the methodologies. [Work has been supported under various NSERC and MRC grants.]
Positron emission tomography (PET) as a technique for studying patterns of regional cerebral function associated with auditory perception and speech production
Authors: Sidtis John J. , Dhawan Vijay , Moeller James R. , Strother Stephen C. , Eidelberg David , Rottenberg David A.
Published: October 2005

PET is an in vivo technique for the measurement of patterns of regional cerebral blood flow (rCBF), metabolic rate for glucose (rCMRGlu), and the uptake of neurotransmitters such as dopamine. Scanning times range from 1 min for rCBF, to 2 h for dopamine, with rCMRGlu scans requiring 1 h. Studies of rCMRGlu in patients with movement disorders and dysarthria have demonstrated correlations between voice onset time abnormalities and rCMRGlu in the basal ganglia; similar studies with dopamine are currently in progress. Because of the shorter scan time, rCBF studies are better suited for perceptual studies. Using a steady-state C0150 inhalation technique, 14 1-min scans can be obtained back-to-back. The C0150/PET has been used to study rCBF patterns in within-subject studies that include both stimulated and unstimulated periods, with stimuli such as broadband white noise, music, and complex tones in a pitch discrimination task. Results to date demonstrate that both regional and global changes are associated with stimulation states. PET provides a unique technique for studying human cerebral physiology associated with auditory perception and speech production. [Work supported by NIH.]