bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of adaptive panels with high transmission loss characteristics
Authors: St. Pierre Richard L. , Koopmann Gary H. , Chen Weicheng
Published: July 2002

This paper presents a design method for minimizing the sound transmitted through panels. This unique method is based on minimizing the volume velocity of individual segments of a vibrating panel using control loudspeakers. In this manner, each of the control segments of the panel can be controlled separately. The basic acoustic equations governing volume velocity control are presented, and it is shown that, at low frequencies, this method will achieve global sound power reductions in the far field. Further analysis shows that this method will achieve significant sound power reductions (10 dB or more) for values of kL of 3.0 or less, where L is the characteristic dimension of each control segment. Tests conducted in a transmission loss chamber verify the efficacy of volume velocity control using a controller based on the filtered-x control algorithm. This controller allows for control over a frequency band, and results show sound power reductions of 9 dB over a 60-Hz bandwidth. These tests are among the first attempts to use the volume velocity control method over a band of frequencies. The experimental results are verified with numerical simulations. The results show promise that this methodology is an effective way to control broadband, low-frequency sound.
A new hybrid model for electrorheological fluid dampers and application to dynamic vibration absorption
Authors: Vavreck Andrew N. , Wang Kon-Well
Published: July 2002

Dampers incorporating electrorheological or magnetorheological fluid (whose damping parameters can be adjusted by altering an imposed electric or magnetic field, respectively) as part of their structure hold great promise as adaptive-passive vibration reduction devices. Extant models of electrorheological dampers are insufficient, because of excessive complexity or the lack of broad experimental validation, to allow the prediction of the response of the damper over a wide range of operating conditions. The subject work proposes a new, simple lumped parameter model for electrorheological dampers, validates the new model against empirical data, and explores the application of an electrorheological damper in a tuned dynamic vibration absorber. The vibration absorption capacity of an electro- or magnetorheological damper in a dynamic vibration absorber is found to depend on the displacement amplitude and frequency of the vibration, but a substantial reduction in vibration is achievable with only adaptive-passive control. [Work supported by U.S. Army Research Office.]
Identifying cross-correlation peaks with autocorrelation functions
Authors: Spiesberger John L.
Published: July 2002

Crosscorrelating the output of two receivers may fail to provide a means to estimate the arrival time difference of the first arriving signals when the crosscorrelation of accompanying multipaths have amplitudes that may be confused with that between the first arrivals. Based on information in two autocorrelation functions, a new method is described for identifying which peak in the cross-correlation function corresponds to the arrival time difference between the first arrivals [J. L. Spiesberger, J. Acoust. Soc. Am. 100, 910–917 (1996)]. The technique relies on (1) a high signal-to-noise ratio following auto and crosscorrelation and (2) time series which have been preprocessed to suppress all signals except those emanating from a single source. The technique works even when (1) the number of multipaths are unknown, (2) the received signal is not visible above the noise, (3) the transmission time is unknown, (4) the transmitted waveform is unknown, and (5) the spatial coordinates of the multipaths are unknown or are impractical to estimate. These techniques may be useful for localizing transient signals.
Chaotic light: A theory of asymmetric resonant cavities
Authors: Stone A. Douglas , Noeckel Jens U.
Published: July 2002

Spherical and cylindrical dielectric cavities support high-Q modes due to total internal reflection of the trapped light. These modes are analogous to the well-known whispering gallery modes of acoustics. When such cavities undergo smooth convex deformations, the ray dynamics corresponding to these modes becomes chaotic in a universal manner determined by the Kolmogorov–Arnold–Moser theory of classical Hamiltonian mechanics. Using concepts from the theory of wave/quantum chaos, it is argued that the corresponding resonances broaden and become highly anisotropic in a universal manner, independent of the wavelength. Comparison with exact numerical results [J. U. Noeckel and A. Douglas Stone, Nature 385, 45 (1997)] shows that the predicted behavior describes the emission anisotropy extremely well, but the resonance lifetime has important corrections which are conjectured to arise due to the dynamical localization of photons and to chaos-assisted tunneling. The theory is able to explain the lasing intensity profile observed in microdroplets and related experiments, and may eventually have applications to microlasers and in fiber-optic communications networks.
Secular behavior of chaotic ray solutions
Authors: Collins Michael D. , Lingevitch Joseph F.
Published: July 2002

Does the topic of this session make sense? The existence of a connection between chaos and predictability in long-range sound propagation is investigated by asymptotically analyzing the ray solution. Along a regular ray, the Laplacian of the phase oscillates about zero so that the solution of the first transport equation [Jensen et al., Computational Ocean Acoustics (American Institute of Physics, New York, 1994), p. 150] does not grow or decay exponentially. Along a chaotic ray, the Laplacian of the phase tends to be positive so that amplitude decays exponentially. The second transport equation (a correction that is not usually implemented) is identical to the first transport equation but with a forcing function that decays exponentially along a chaotic ray. This problem is closely related to the classical secular problem y′+y=exp(−x). Numerical techniques are applied to solve the transport equation and illustrate secularity, which implies that the ray solution is nonuniform and breaks down at long range when chaos exists. [Work supported by ONR.]
A numerical investigation of semiclassical predictability in the presence of chaotic ray motion
Authors: Brown Michael G. , Wolfson Michael A. , Tappert Frederick D.
Published: July 2002

The question of whether ray-based acoustic wave-field expansions break down under chaotic conditions at a range proportional to the logarithm of the acoustic frequency is investigated numerically. In the assumed idealized environment, the ray equations define an Anosov system; all ray trajectories are chaotic. To address the log breakdown question, full wave simulations are compared to simulations based on the semiclassical Maslov integral representation of the wave-field. Because the Maslov integral remains valid at caustics, one might expect that it remains valid at ranges beyond those at which uncorrected ray theory starts to fail. [Work supported by ONR.]
Hot topics in medical acoustics
Authors: Fowlkes J. Brian
Published: July 2002

Medical acoustics covers a wide variety of applications that are both diagnostic and therapeutic. One of the interesting aspects of acoustics is its capability to be apparently noninvasive (imaging of the fetus with ultrasound) and yet powerful enough to generate biological effects (destruction of kidney stones by shock waves). One new area which seems to be further expanding this capacity is ultrasound contrast agents. Most of the agents under development are very small, stable gas bubbles which can be injected into the bloodstream and still pass through the capillary beds. Some agents provide additional signals in medical imaging for several minutes, and some have the potential for therapeutic applications as well. Contrast agents are one of the fastest growing areas in medical acoustics, as evidenced by the increased research in this area and the number of major pharmaceutical manufacturers becoming involved. Research and development expenditures are expected to increase dramatically as a result and the potential impact on medical acoustics could be significant. Topics for discussion include detection of nonlinear signals, new imaging modes in medical ultrasonics, the ‘‘disappearance’’ or ‘‘reappearance’’ of agents when exposed to an acoustic field, potential bioeffects of agents, and their therapeutic applications such as use in drug delivery.
Discrimination of silent temporal gaps in sinusoidal markers by the budgerigar (Melopsittacus undulatus)
Authors: Amagai Satoshi , Dooling Robert J. , Formby Craig , Forrest Timothy G.
Published: July 2002

The tonal quality and temporal complexity of bird vocalizations have long suggested that birds may excel in auditory spectral or temporal processing. However, most psychophysical studies support the notion that birds have spectral and temporal resolving power roughly comparable to that measured in humans. Rarely have such psychophysical tasks involved both frequency and time cues. An intriguing aspect of gap-detection experiments with sinusoidal markers is the robust dependence on the frequency separation between the markers. In humans, silent gaps become more difficult to discriminate as the frequency difference between the markers increases. This frequency-dependent pattern of thresholds is well fit with a roex-filter model. Here, budgerigars were trained by operant conditioning to discriminate a change in the duration of a silent gap between two tonal markers. Frequency separation between the tonal markers had only a small effect on gap discrimination thresholds in budgerigars, suggesting an unusually broad peripheral auditory filter. This result stands in marked contrast to the results from humans and to estimates of the auditory filter in budgerigars using masking paradigms. Alternate explanations for the apparently broad tuning of the discrimination data will be considered. [Work supported by NIH grants DC-00198 and MH-00982 to RJD.]
Detection of tones in noise by chinchillas using the probe-signal method
Authors: Shofner William P. , Yost William A.
Published: July 2002

The probe-signal method was used to determine whether chinchillas listen selectively for a signal tone in the presence of continuous broadband noise. Animals ran in blocks of 40 trials: 32 trials were tone trials and 8 trials were blank trials. Of the 32 tone trials, the signal tone of 1000 Hz was presented on 24 trials; probe tones of 500 and 2000 Hz were presented on four trials each. The sound levels of the 500-, 1000-, and 2000-Hz tones were adjusted to be equally detectable, as determined from psychometric functions that were generated using the method of constant stimuli. The behavioral sensitivities as estimated by d′ for the signal tone based on the probe-signal method were similar to or larger than the estimated d′ based on the psychometric functions. The sensitivities for the detection of the probe tones were also similar to or larger than the sensitivities measured with the psychometric functions. The results indicate that chinchillas do not listen selectively to a single auditory filter, but rather appear to use a wide-band listening strategy. This apparent wide-band listening strategy may account for the higher detection thresholds observed in animals compared to human listeners. [Work supported by NIDCD.]
Modeling detectability and speech transmission quality of band-specific modulated-noise distortions
Authors: Hansen Martin , Kollmeier Birger
Published: July 2002

A model is presented which was developed for the prediction of speech transmission quality of (low-bit-rate) speech codecs [Hansen and Kollmeier, ICASSP’97, paper ♯2056 (1997)]. The model is based on a quantitative psychoacoustical preprocessing scheme [Dau et al., J. Acoust. Soc. Am. 99, 3614–3622 (1996)] and was successfully applied to various speech codec test databases. This study presents measurements and modeling results of the detectability of band-specific modulated-noise distortions. Two sentences were used as stimuli. They were telephone-band-filtered and presented to subjects diotically via headphones in a sound-attenuating booth. To mimic band-specific speech codeclike distortions, two types of distortion were applied to the stimuli: modulation with wideband noise (MNRU) followed by critical-band bandpass-filtering, and vice versa. In an adaptive 2I-2AFC experiment, the modulation depth at threshold was measured as a function of the critical-band center-frequency. The measured results were compared with the objective speech quality measure and calculated for the same signals used in the two experiments. At threshold levels of modulation the computed objective quality measure was found to be constant. This indicates a direct monotonic relation between speech transmission quality and the detectability of the distortion.
The effect of completely-in-the-canal hearing aids on localization performance: Normal hearing listeners
Authors: D’Angelo William R. , Morris Linda J. , Mishler Pamela J.
Published: July 2002

The Completely-In-The-Canal (CIC) hearing aid, due to its placement in the ear canal, has acoustic advantages that are not offered by traditional amplification. Among these advantages are increased high-frequency gain, reduction of the occlusion effect, and subjective reports of improved localization ability over other types of aids. Quantitative data are readily available to verify the frequency response and occlusion effect; however, data on localization ability have been primarily anecdotal. A series of experiments has been designed to document the effect of CIC hearing aid use on auditory localization performance. A normal-hearing subject group, fit with low-gain CICs, was used in this phase; later studies will utilize hearing-impaired listeners and a variety of devices. The use of normal hearing subjects allowed an assessment of localization ability independent of the effects of hearing loss. Localization accuracy was measured using the God’s eye localization pointing (GELP) technique [Gilkey et al., Behav. Res. Methods, Instrum. Comput. 27(1), 1–11 (1995)]. Results showed that subjects wearing the CICs were able to localize over the entire spatial presentation range of the stimulus (±180° azimuth, −74° to +90° elevation). Localization accuracy data will be presented.
Recovery of nonhomogeneous media impedance profile from transmitted signal
Authors: Tenenbaum Roberto A. , Magalhes Marcelo B. S.
Published: July 2002

A technique for recovering the acoustic impedance of layered media from its impulse transmission response is presented. A model for evaluation of the reflection response [R. A. Tenenbaum and M. Zindeluk, J. Acoust. Soc. Am. 92, 3364–3370 (1992)] is extended to the transmission problem, leading to an algorithm where the amplitudes of the transmitted signal samples, Hi, are given by polynomials, Pi, of the refection coefficients, Ri, as Hi=Pi(R1,...,RN). For identification purposes, that relation leads to a highly nonlinear system. To solve it, extra information is needed: The inhomogeneity is considered to be inserted in a homogeneous medium, which yields Q(R1,...,RN)=∏k=0N(1+Rk)/(1−Rk)=1. A cost function is then defined as the quadratic difference between the measured transmitted signal and a synthetic one, given by Pi, that is, S=∑i=0N(P2i−H2i)+Q2−1, which is minimized. This is a delicate process, since the Hessian of S is not always positive-definite, requiring the use of smart methods of optimization, such as Levenberg–Marquardt. S may have much local minima, to where minimization methods can converge, leading to the wrong results. This problem is solved by taking successive random initial estimates, and checking to see if the final value of S matches a global minimum criterion.
Computation of impulse response for stage-house geometries with use of edge-diffraction models
Authors: Torres Rendell , Kleiner Mendel , Svensson Peter
Published: July 2002

A mathematical model following diffraction studies by Medwin [J. Acoust. Soc. Am. 72, 1005–1013 (1982)] is developed to calculate the impulse response of a three-dimensional ‘‘stage house’’ geometry in a baffle. The model includes multiple diffraction components in addition to specular reflection, and it forms a more complete approach than current room impulse-response predictors based on geometrical acoustics. Thus it may also be suitable for more accurate auralization, particularly at low frequencies. A comparison is made with results from a ‘‘cone-tracing’’ computer model [B. Dalenbäck, J. Acoust. Soc. Am. 100, 899–909 (1996)] and results from physical scale-model measurements. [Work supported by Axel & Margaret Axson Johnson’s Foundation, Sweden.]
Factors influencing the perception of bass
Authors: Bradley John S. , Soulodre Gilbert A. , Norcross Scott
Published: July 2002

It is commonly assumed that low-frequency reverberation time determines the perception of bass in concert halls. Laboratory experiments were conducted to evaluate whether this and other factors influence subjects’ perceptions of the strength of bass sounds in simulated sound fields. The levels of the early and late arriving low-frequency sounds as well as low-frequency reverberation times were systematically varied. Ten subjects rated the strength of the bass content of the music for each sound field on a five point scale relative to a reference sound field. Both the levels of the early and late arriving low-frequency sound had significant effects on the judgments of the bass content. Low-frequency reverberation time was not significantly related to subjective ratings of bass. The direction of arrival of low-frequency sound had smaller effects on the assessments of the bass content in the sounds. The results suggest that increased low-frequency reverberation time is not important for increasing the sense of bass in concert hall sounds. Further, the low-frequency attenuations caused by the grazing incidence seat dip effect can be compensated for by overhead reflections to increase the sense of bass in concert halls.
Acoustic flow in echo amplitudes and spectra: a viable concept for obstacle avoidance in CF-bats?
Authors: Müller Rolf , Schnitzler Hans-Ulrich
Published: July 2002

Bats are capable of obstacle avoidance based solely on echolocation information. When doing so, species being classified as CF (constant frequency) bats allocate most signal energy to rather long, narrow-band portions of their echolocation pulses. These signal components may subserve obstacle avoidance by means of information conveyed by proportional changes in amplitude (due to geometric attenuation, absorption, compound directivity of emitter and receiver) and frequency content (due to Doppler shifts) of the echoes along a trajectory. It can be demonstrated that a combination of these two putative sensory variables allows, in principal, for a metrical reconstruction of target position relative to the animal’s flight vector within a hemifield. Thus the contained information seemingly suffices for mediating appropriate avoidance maneuvers. CF bats’ unique narrow-band signal design is matched by a likewise peculiar layout of their auditory system. In particular, the existence of an auditory fovea featuring extremely high filter qualities may be hypothesized to aid estimation of proportional changes in frequency. In order to establish the extent to which the informational content of the signal parameters under consideration may be accessible in the auditory system’s primal sketch, the properties of a gammatone filter bank fitted to physiologically determined filter qualities are explored.
Acoustical simulation of active noise control telephone earpiece system
Authors: Baumhauer John C.
Published: July 2002

A lumped-parameter equivalent circuit representation of an active noise control (ANC) feedback system has been developed for telephone handset earpiece application. Since the feedback controller must be stable to avoid ‘‘squealing’’ in the user’s ear, its filter must work with known and robust transducer transfer functions. The earpiece loudspeaker (receiver) is the weak link. As opposed to the feedback electret microphone located between the earpiece and pinna, the moving-coil receiver’s response undergoes a large, negative phase change with increasing frequency owing to multiple, highly coupled degrees-of-freedom. Moreover, the magnitude and phase of the receiver’s transfer function are shown to depend on its electroacoustic parameter tolerances, such as cone stiffness, coil B1, acoustic damping, and handset porting. Another variation is due to the acoustic leak that occurs naturally between the earpiece and the ear. This is not just a function of the earpiece design, but also of the varying handset-to-ear force applied. Not only is low-frequency response in the ear lost with an increased leak, but the high gain feedback magnitude is reduced and the overall phase lag in the receiver becomes greater. Results with simulated ITU-T coupler equivalent circuits demonstrate these effects. A prototype ANC system is discussed.
Vibrational modes of two violins
Authors: Roberts Mark , Rossing Thomas D.
Published: July 2002

Using electronic TV holography, as well as other methods for observing vibrational motion and sound radiation, the normal modes of vibration in two violins have been studied. The principal modes observed in a Hutchins violin showed fairly good agreement with those reported by Marshall [J. Acoust. Soc. Am. 77, 695–709 (1985)] for the same violin. The strongly radiating T1 and C3 modes appear to be doublets, and this phenomenon is discussed. Vibrational modes excited by a force applied to the bridge by internal sound pressure, and by the sound field of a loudspeaker are compared.
Subharmonic generation in cymbals at large amplitude
Authors: Wilbur Charles , Rossing Thomas D.
Published: July 2002

The aftersound in cymbals has been attributed to chaotic behavior at large amplitude, which provides a mechanism for the conversion of low-frequency energy to a rich assortment of modes of much higher frequency [N. H. Fletcher, ‘‘Nonlinear dynamics and chaos in musical instruments,’’ in Complex Systems: from Biology to Computation, edited by D. G. Green and T. Bossomaier (IOS, Amsterdam, 1993)]. When a cymbal is driven sinusoidally at an amplitude slightly lower than that leading to chaotic behavior, the cymbal sound includes harmonics of a fundamental having a fraction (often one-half or one-third) the drive frequency. Nonlinear behavior leading to subharmonic generation as well as chaotic behavior is discussed.
On the dynamic drag coefficient for wave propagation through fluid-saturated highly porous open-cell foams
Authors: Slade Robert E. , Walton Keith , Mead Colin A. , Parsons Alan T. , Pinnington Roger J. , Briscoe Anthony R.
Published: July 2002

This paper considers the damping of waves propagating in high porosity (97%) open-cell foams which are fully saturated by a viscous fluid. The technique of homogenization is applied on two spatial scales to the fluid-foam system. The resulting equations are found to be those of Biot [M. A. Biot, J. Acoust. Soc. Am. 28, 168–178 (1956)] but reduce to the simpler form given by Chase [D. M. Chase, J. Acoust. Soc. Am. 65, 1–8 (1979)] when particular properties of the solid foam matrix are taken into consideration. A number of important material parameters are identified, and of particular significance is the measure of drag between the solid and fluid components. The results of numerical fluid flow experiments are used to obtain estimates of the damping coefficient. Comparisons are made with measurements of the steady state and frequency-dependent damping coefficients, which are determined using specially constructed experimental rigs. [Published with the permission of the Contoller of Her Britannic Majesty’s Stationary Office.]
Estimating pile bearing capacity via acoustic and seismic measurements
Authors: Yang Chung-Ham , Thomas H. Randolph
Published: July 2002

Current dynamic methods estimate pile bearing capacity through the measurements of in-pile stress waves. Typically, accelerometers and strain gauges are mounted to the pile shaft. This on-pile instrumentation is expensive and interrupts the driving operation. The high cost and interruptive nature of the on-pile instrumentation imposes practical limits on the number of piles that can be tested. The limited amount of tested piles cannot reliably represent the remaining piles that might be driven through a variety of subsurface conditions. This research is aimed at developing a method for estimating pile bearing capacity through the acoustic and seismic measurements. The pile–soil system is modeled as a single-degree-freedom mass-spring-slider-dashpot system. Based on principles of vibration, the pile bearing capacity is analytically derived as a function of the vibrating mass, damped natural frequency, damping ratio, and soil quake. The damped natural frequency and the damping ratio are determined from ground waves and air pressure waves,a nd the vibrating mass and soil quake are estimated based upon in-situ soil properties. The measurement of ground waves needs no on-pile instrumentation and does not interrupt the driving operation. This enables every pile at a site to be tested.
Factors in the detection of environmental sounds
Authors: Gygi Brian , Watson Charles S. , Kidd Gary R.
Published: July 2002

In separate experiments, detection and identification thresholds were obtained for a set of 25 common environmental sounds (e.g., dog barking, car starting). In the detection task, threshold values of the event-to-noise ratio (Ev/N) were established using an adaptive tracking procedure. The identification experiment was part of a larger individual differences study reported earlier [Watson et al., J. Acoust. Soc. Am. 99, 2516(A) (1996)]. A 3AFC identification task was used, with sounds presented at eight levels of Ev/N. Thresholds were estimated from the psychometric functions derived from the data. The correlation between thresholds in the two tasks indicates that the identifiability of these sounds is only weakly related to their detectability. Several models were evaluated to identify the properties that determine the detectability of environmental sounds. Leaky integrator and cross-correlation models were used to predict detection data; identification data were evaluated using a multidimensional scaling algorithm.
Auditory attention beyond the ear: Precues and postcues
Authors: McKeown Denis
Published: July 2002

In a ‘‘precueing’’ experiment listeners may come to pay attention to a narrow cued frequency band and fail to monitor other frequencies. In the experiments a cueing tone was presented at some short delay before or after a target signal. In experiment 1, one of two cues at different frequencies was presented shortly before the single interval of a yes/no signal trial. Signal and cue were at the same frequency on 50% of the trials, so the cue was not informative as to signal frequency. Performance was analyzed separately for trials in which the signal occurred at the same frequency as the cue (valid trials) and when it was at a different frequency (invalid trials); the cue to signal delay varied. At short delays performance was enhanced on valid relative-to-invalid trials, but not at longer delays. In experiment 2, the cue was presented following the signal. In this post-cueing experiment subjects responded following the cue; the delay from signal to cue was varied. Performance was below chance performance on invalid trials but above chance on valid trials. These findings suggest that attended listening may modulate the processing of detected signals rather than modulate detection itself.
Change in envelope beats as a possible cue in comodulation masking release (CMR)
Authors: Buss Emily , Hall Joseph , Grose John
Published: July 2002

The detection advantage associated with masker envelope coherence across frequency has typically been described in terms of comparisons across auditory channels. More recently it has been suggested that analysis of the output of a wider initial filter, similar to that suggested for the TMTF, can account for the data [Berg, J. Acoust. Soc. Am. 100, 1013–1023 (1996)]. In particular, a change in envelope beats was proposed as the cue to the addition of a pure-tone signal. Data are presented for the detection of a tone added to multiple maskers with coherent envelopes. In one condition a change in envelope beats is an accurate potential cue, and in others it is a much less reliable or unreliable indicator of the presence of the signal. All conditions employing maskers with coherent envelopes produce very similar thresholds, and all showing improved sensitivity over the case of detecting a signal added to a single masker centered on the signal frequency. Results are interpreted as evidence that a change in envelope beats does not form the basis of detection in CMR. One version of the cued-listening hypothesis, an across-channel model, is reconsidered in light of these results. [Work supported by NIH-NIDCD.]
Backscattering of sound from ribbed plates and cylinders with oscillators attached to the ribs
Authors: Pierce Allan D.
Published: July 2002

A sequence of simple models is discussed to identify and quantify key theoretical issues pertaining to how such oscillators can affect sound scattering. The first such model consists of a sound wave incident obliquely on a plate with a single rib which has a continuous smear of oscillators along it. The presence of the rib alters the apparent natural frequency of the oscillators and causes the backscattered sound to be anomalously high when the incident sound has the same frequency as the apparent natural frequency. The width of the spectral line in the plot of backscattered cross section versus frequency for the fixed angle of incidence is controlled both by the radiation of flexural waves away from the rib and by the overall loss of energy through radiated sound. Other models considered are an infinitely long cylinder with a single rib, smeared oscillators along the rib, an infinitely long cylinder with a single oscillator attached to a rib, a plate with a periodic array of ribs with attached oscillators, and an infinitely long cylinder with a similar hierarchy of configurations.
Temporal processing and phonotactic probability in spoken word recognition
Authors: Vitevitch Michael S. , Luce Paul A. , Charles-Luce Jan
Published: July 2002

This study examined the influence of phonotactic information on spoken language recognition in adults. Subjects performed a lexical decision task on 120 phonotactically legal bisyllablic CVCCVC nonsense words that varied in their phonotactic probability and primary stress placement. Subjects responded faster to nonsense words containing low probability initial syllables and slower to nonsense words containing high-probability initial syllables. On the other hand, subjects responded faster to nonsense words containing high probability final syllables and slower to nonsense words containing low-probability final syllables. Our results suggest that two phonotactically based processes may be used during word recognition. The first process is a winnowing of candidate words based on their phonotactic probability. The second process is a confirmatory process in which the lexical status of the sole candidate is confirmed based on the phonotactic probability of the item. [Work supported by NIH-NIDCD.]
Ability to detect changes in musical pieces is a function of musical training and musical context
Authors: Crawley Edward J. , Acker Barbara E. , Pastore Richard E.
Published: July 2002

The ability of musicians and nonmusicians to detect a one-note change from a fixed three-voiced musical piece (the standard) was evaluated. Following previous studies, which had tested only musicians, several potentially important variables were manipulated. Musical context (polyphonic or homophonic) was manipulated between subjects. Melody location (high, middle, or low voice), and thus the standard, was varied for each subject across sessions. Within a session, changes varied in harmonic relatedness (related or unrelated), and voice location (high, middle, or low). Subjects performed a same-different task and indicated their confidence as to whether or not a change had been present. Furthermore, a signal detection analysis of the subjects’ pattern of responses was performed to directly measure sensitivity to the presence of changes. As expected, musicians were more confident in their responses and revealed a higher sensitivity to changes than nonmusicians. Interestingly, the effects of musical training on sensitivity to changes did not interact with any variable except musical context. The results will be discussed in terms of general and music-specific aspects of perception and training. [Work supported by AFOSR.]
Use of note partials’ energy to improve the identification of polyphonic piano signals
Authors: Rossi Lucile , Girolami Gerard
Published: July 2002

The identification of the fundamental frequency of musical sounds is a difficult task which has been studied for more than 20 years. Methods using spectral approaches are used to identify polyphonic sounds. A novel approach for identifying monophonic and polyphonic piano sound signals has been developed by the authors [L. Rossi and G. Girolami, J. Acoust. Soc. Am. 100, 2842(A) (1996)]. The identification is carried out by comparing the incoming spectrum with a database (automatically built previously) containing the frequential distribution of the partials of each piano note. The rate of correct identification is in the 90% range for polyphonic sounds. One kind of error is due to the artificial construction of a note by the combination of partials belonging to other notes; another one results from the difficulty of separating the case of one note played a long time with the case of this same note played two successive times with an overlap. The aim of this paper is to show how the evolution of the partials’ energy associated with the search for information about the time of the note attacks can be used to reduce the false identification.
Temperature-dependent ultrasonic properties of aluminosilicates glass ceramics
Authors: So J. H. , Green D. H. , Yun S. S.
Published: July 2002

The longitudinal wave velocity and attenuation and shear wave velocity for machinable aluminosilicate glass-ceramic (MACOR) samples were measured as functions of frequency and temperature with the pulse-echo method. Frequencies of 5–30 MHz were used in the temperature range of 100–300 K. The velocity differences between 100 and 300 K were about 1% for longitudinal waves and 3% for shear waves. The monotonic decrease in the longitudinal attenuation coefficient between 100 and 300 K was approximately 50%. The longitudinal wave attenuation coefficient increases linearly with frequency and nonlinearly with decreasing temperature. This contrasts with the longitudinal and shear wave velocities, both of which decrease with increasing temperature. These data were used to calculate the elastic moduli, Poisson’s ratio, and Lamé parameters for the material. These results are interpreted in terms of thermal stress cracking and microstructure-related absorption.
Some intrinsic differences between atmospheric and ocean acoustic parabolic equation models
Authors: Gilbert Kenneth E. , Di Xiao
Published: July 2002

It is often assumed that propagation models developed for ocean acoustics can be applied with minimum modification to atmospheric sound propagation. Experience shows that one often finds subtle but significant problems that can lead to serious numerical (prediction) errors, even in cases where the atmospheric environmental inputs seem similar to those in ocean acoustics. In this paper three sources of error and methods for reducing the errors to acceptable levels are discussed. The first error was recently discovered by Erik Salomons [E. M. Salomons, ‘‘Improved Green’s function parabolic equation (GFPE) method for atmospheric sound propagation,’’ J. Acoust. Soc. Am. (submitted)] and concerns the failure of standard FFT algorithms when applied to atmospheric split-step parabolic equation calculations for propagation over hard ground surfaces. The second problem concerns accurate numerical treatment of the surface wave that is excited by a point source over a locally reacting ground surface. The last issue discussed is the need for improved approaches to implementing an outgoing-wave boundary condition in calculations of long-range outdoor sound propagation. Numerical examples are presented showing the effect of the errors on the predicted signal. [Work supported by the Army Research Laboratory and the Pennsylvania State University Applied Research Laboratory.]
Modeling the acoustics of American English /r/
Authors: Espy-Wilson Carol Y. , Shrikanth Narayanan , Alwan Abeer , Boyce Suzanne E.
Published: July 2002

It is often assumed that speakers use idiosyncratic combinations of constrictions at the lips, pharynx, and along the hard palate to achieve the low F3’s—typically between 1300 and 1800 Hz—characteristic of American English /r/. This account was tested in a modeling study using attested vocal tract dimensions derived from three-dimensional magnetic resonance imaging data from four speakers [Alwan et al., J. Acoust. Soc. Am. (to be published) (1997)]. These dimensions were used as input to the Maeda computer model. It was determined that (1) a constriction in the post-alveolar region of the palate and at least one other constriction are needed to bring F3 into the 1300- to 1800-Hz range, (2) the maximum effect of the lip constriction was around 100 Hz, while that of the pharyngeal constriction was around 200 Hz, and (3) the effects of changing constrictions were not additive. Over all manipulations, the lowest F3 achieved was 1495 Hz, which is high compared to many /r/ productions. Using ‘‘retro- flex’’ dimensions, the lowest F3 achieved was 2224 Hz. It may be that additional acoustic mechanisms are required to account for the full range of acoustic profiles seen for /r/. [Work supported by NSF and NIH.]
Do children with phonological disorders use more ballistic articulatory movements?
Authors: Fourakis Marios , Beckman Mary E. , Edwards Jan
Published: July 2002

This examination of speech motor control in phonologically disordered children adapted a paradigm that has been used in the dysarthria literature [Weismer et al., J. Acoust. Soc. Am. 91, 1085–1098 (1992)]. Six preschool-aged children with phonological disorders, six age controls, and six adults repeated the phrases ‘‘baby dog’’ and ‘‘good baby’’ at normal and fast rates. F2 tracks of the fast rate tokens were processed using an in-house algorithm to calculate the transition slope in Hz/ms. For the alveolar and velar stops (but not for the labial stops) the F2 slope distributions for the typically developing children were quite similar to those of the adults, and both differed from the children with phonological disorders in showing smaller slope values. The phonologically disordered children had faster movements than either their age controls or adults, but only in the sequences where the tongue–jaw complex was harnessed for the consonant as well as for the contiguous vowel. This pattern suggests that the phonologically disordered children are using a faster, more ballistic gesture for lowering the tongue–jaw complex for all three stop places of articulation, while the typically developing children and adults use this strategy only after a labial closure.
Disordered phonology: An acoustic description of the acquisition of the anterior distinction among coronal fricatives
Authors: Miccio Adele W. , Forrest Karen
Published: July 2002

This paper reports on a longitudinal analysis of the acoustic properties of speech samples of a child, age 5 years and 7 months, with disordered phonology. The child, who produced [s] for both alveolar and postalveolar fricatives, was enrolled in a remediation program that focused on the correct production of the voiceless postalveolar fricative [■] ‘‘esh.’’ Training involved imitation of [■] in isolation and spontaneous production of [s] and [■] in minimally paired words. Acoustic measurements were taken prior to treatment, immediately following the 2-week treatment program, and again 2 months following termination of treatment. Temporal and spectral measurements were conducted. Results indicated no significant differences between [s] produced for the target alveolar fricative /s/ vs [s] produced for the target postalveolar fricative /■/ prior to treatment. Following treatment, the child produced the anterior–nonanterior distinction among coronal fricatives. Acoustic measurements showed that she did not simply add a postalveolar fricative to her repertoire of speech sounds but also changed her productions of target-appropriate /s/. [Work supported in part by NIH-DC 00260.]
Variability in /s/ and /S−P174n/ productions within and across talkers
Authors: Newman Rochelle S.
Published: July 2002

A primary issue in speech perception research is the apparent ‘‘lack of invariance’’ between the acoustic information in a signal and the listener’s phonemic perception. The same intended phoneme can be produced with a wide range of acoustic values, and different intended phonemes may be produced with the same values. Although the existence of this variability is not in question, the degree to which listeners have to account for it is unclear. Some studies have attempted to measure the extent of this variability, but few have done so for fricatives, making it difficult to determine the degree to which individuals need to normalize fricative input for the individual talker. The current experiment attempts to rectify this hole in the literature by examining the fricative centroids for over 100 utterances beginning with /s/ and /■/ from each of 20 different speakers. Although there was variability in the centroid values, the categories showed virtually no overlap within a talker. However, there was substantial overlap across talkers. This suggests that if listeners use centroids to cue the /s/–/■/ distinction, they would first need to normalize the signal for the individual talker’s frequency range. [Work supported by NIDCD Grant No. R01 DC00219 to SUNY at Buffalo.]
A 3-kHz class VII flextensional transducer
Authors: Butler Stephen C. , Lindberg Jan F.
Published: July 2002

A 3-kHz class VII flextensional transducer was developed at NUWC. The class VII flextensional is a modified class IV shape having concave radiating surfaces rather than convex. This transducer is commonly referred to as a ‘‘dogbone‘‘ flextensional because of its similar shape. This design, originally described by Merchant in U.S. Patent 3,258,738 (28 June 1966), has the advantages that all the surfaces of the shell radiate in-phase and a positive compressive stress is maintained on the ceramic driver as the operation depth increases. The shell can support thinner walls, since hydrostatic pressures do not have to be overcome in order to keep the piezoelectric ceramic driver under compression, as in a conventional class IV transducer. The transducer was designed using two different modeling approaches: finite element modeling (using ATILA) and an equivalent circuit model based on plane-wave and lumped parameters. Based on the modeled results, a transducer was fabricated and then tested in August 1996. The transducer volume is 5 in. (12.7 cm) high, 5 in. (12.7 cm) long, and 2.5 in. (6.35 cm) wide, the shell material is stainless steel, and the ceramic stack is composed of 30 0.1-in. (2.54-mm)-thick PZT-8 plates, two of which are unpoled and used for insulators. The in-air weight is 10 lbs. The transducer performed exceptionally, matching the modeled data while producing an SL of 202 dB at 10 kV/in., a resonance frequency of 3050 Hz, a mechanical Q of 5, an in-water effective coupling coefficient of 30% (typical of class IV transducers), and an electro-acoustic efficiency of 80%. [Work supported by ONR.]
Finite-element study and experimental verification on irregular composite transducer design
Authors: Qi Wenkang , Cao Wenwu
Published: July 2002

In this paper 2-2 composite transducers with both regular and irregular kerfs have been studied by using FEM and experimental methods. Undesirable lateral modes are shown in the electrical impedance curves of periodic 2-2 composites. These lateral modes are well suppressed in a 2-2 composite with irregular kerfs when the ceramic volume percentage is low. However, the beam pattern shows some degree of distortion. In order to restore the beam pattern, mirror symmetry is introduced into a 2-2 composite with irregular kerfs, and the beam pattern of these 2-2 composites has been experimentally measured and calculated using FEM. Excellent agreement has been achieved. As expected, when the system is more disordered, the lateral modes are well suppressed, but the beam pattern is poorly focused. On the other hand, when the system is more ordered, the lateral modes are poorly suppressed, but the beam pattern is more focused. A trade-off is a sequence of 3; in this case the lateral modes can be effectively suppressed, and the beam pattern is also well focused.
Use of automatic modeler and small array receiver for acoustic source location
Authors: Lu Xiaorong , Sachse Wolfgang , Grabec Igor
Published: July 2002

A statistical, nonparametric regression analysis utilizing a conditional average and a smoothed empirical probability distribution forms the basis of an automatic modeler that resembles the operation of a neural-like network. Coupled with a small receiver array, the modeler can determine both the distance and direction to a source of acoustic emission. The use of such a small receiver array to locate sources of emission on a thick plate is demonstrated. The characteristic property of such a system is its capability for predicting the locations of various sources in a structure from the emitted waveforms. Using the modeler involves two steps. First, the modeler is trained with the computed Green’s functions for the structure. In the examples shown, these correspond to a normal force and the corresponding displacement signal for a broad range of source/receiver separations. The database of these responses forms the basis of the modeler memory. After training, the modeler can be used to locate sources of emission on the plate. The operation of the system is demonstrated with both synthetic as well as measured waveforms corresponding to impact and step-loading forces on a thick plate. [Work supported by AFOSR.]
Just-noticeable differences in vertical vibration for seated subjects
Authors: Pielemeier William J. , Otto Norman C. , Meier Raymond C. , Jeyabalan Vadivelu
Published: July 2002

Just-noticeable differences in bandlimited vertical vibration were studied for subjects sitting on automotive seats. Stimuli consisted of octave band frozen Gaussian noise centered at 4, 8, and 16 Hz. Two-interval forced-choice paired comparisons were used, with a reference level of 8 mg. The level of the alternative stimulus in the pairs varied from 8.25 to 10 mg. Stimulus intensity was measured with a seat pad accelerometer. Stimulus durations of 4 s plus 1/2-s tapers were used for all frequency bands, with 1/2 s between stimuli. Sets of trials with 2-s durations at 16 Hz were done as a test of duration effects. Three subjects were trained with feedback until performance stabilized. Then 200–250 trials were performed in blocks of 25 or 50 for each of four alternatives at each frequency and each subject. Thresholds determined from the psychometric functions ranged from 0.6 to 1.8 mg, with most between 0.6 and 1.2. Little frequency dependence was evidenced over all frequency bands, and little duration effect was seen between 2- and 4-s stimuli at 16 Hz.