bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for activation of sublexical units in auditory lexical decision
Authors: Lyons Emily A. , Luce Paul A.
Published: October 2005

Many words in English (e.g., HEMLOCK) contain component syllables that are themselves words (HEM and LOCK). Some research on spoken word recognition has attempted to determine if these component words are activated when the longer word is heard. If so, what effect does activation of the component words have on the recognition of the longer word? A lexical decision experiment was performed that examined reaction times to bisyllabic spoken words that contained syllables that were themselves either words or nonwords. The results demonstrated that subjects were faster to respond to bisyllabic words in which the first syllable was a word (e.g., KIDNEY) than to bisyllabic words in which the first syllable was a nonword (e.g., CHIMNEY). These findings are consistent with earlier research using cross modal priming techniques that has demonstrated that embedded words can speed responding to a visually presented related word. Additionally, these findings suggest that the activation of component words has a demonstrable effect on recognition time. [Work supported by NIH Grant No. DC-00879-01 to the State University of New York at Buffalo.]
Syntagmatic and paradigmatic states in spoken word recognition
Authors: Auer Edward T. , Luce Paul A.
Published: October 2005

The process of spoken word recognition has frequently been characterized as a mapping of information through a multidimensional space, the dimensions of which correspond to time and acoustic-phonetic similarity. Within this framework, the speed and accuracy of spoken word recognition is a direct function of the ease of traversing a path through the space. The traversal of a path may be affected by at least two states of the space at any point in processing: The first, or syntagmatic, state refers to the history and future of the path. The syntagmatic states of a word correspond to its ‘‘probabilistic’’ phonotactics. The second, or paradigmatic, state refers to the degree of activation within the space at any point (or what has previously been referred to as ‘‘neighborhood activation’’). A connectionist instantiation will be presented of this framework that attempts to predict the speed and accuracy of spoken word recognition as function of syntagmatic and paradigmatic states. Also discussed is a number of empirical tests of the model that provide further insights into the roles of phonotactics and neighborhood structure in spoken word recognition. [Work supported by NIH Grant No. DC-00879-01 to the State University of New York at Buffalo.]
Effects of natural and synthetic adaptors on a synthetic voice continuum
Authors: Mullennix John W. , Baartmans G. , Gorday K. , Webb M.
Published: October 2005

The perception of a synthetic male-female voice continuum was examined using the selective adaptation paradigm. In a series of experiments, voice categorization performance was assessed before and after adaptation with various adaptors. In the first experiment, the results showed that synthetic male and female endpoint adaptors and naturally produced male and female adaptors had similar effects on voice categorization, with voice boundary shifts toward the endpoints. In a second experiment, synthetic adaptors that overlapped with the male endpoint only in F0 or only in formant values were used. Neither of these adaptors had significant perceptual effects. Overall, the results indicate that auditory overlap of the adaptor with the voice continuum endpoint is not necessary or (in the case of isolated acoustic cues related to voice) is not sufficient to produce adaptation. These findings are discussed in terms of the levels of processing and representation used for voice encoding during speech perception.
The transmission of prosodic information via selected spectral regions of speech
Authors: Grant Ken W. , Walden Brian E.
Published: October 2005

In a recent article [K. W. Grant and L. D. Braida, J. Acoust. Soc. Am. 89, 2952–2960 (1991)] it was demonstrated that spectrally different bands of speech with equal articulation index (AI) scores provided approximately equal auditory-visual sentence recognition when combined with speechreading. Given that different parts of the frequency spectrum provide different segmental cues for consonant and vowel recognition, current models of auditory-visual integration [e.g., L. D. Braida, J. Exp. Psychol. 43A, 647–677 (1991)] would predict that some spectral regions of speech are more complementary to speechreading than others. This raises the possibility that the findings of Grant and Braida are attributable, at least in part, to suprasegmental cues that were transmitted equally well by the different spectral bands tested. To test this possibility, the identification of syllable number, syllable stress, sentence intonation, and phrase boundary location was assessed under six approximately equal AI filter conditions similar to those evaluated by Grant and Braida. The results indicate that syllable number and syllable stress are perceived best through high-frequency bands, intonation is perceived best through low-frequency bands, and phrase boundary location is perceived equally well throughout the speech spectrum. These results are discussed in terms of the importance of different spectral regions of speech for the recognition of suprasegmental cues, and how this may relate to overall speech intelligibility. [Work supported by NIH Grant No. DC00792.]
Contributions of voice-source and vocal-tract characteristics to speaker identity
Authors: Eggen J. H. , Nooteboom S. G. , Houtsma A. J. M.
Published: October 2005

A study was done on whether a voice-source model, in particular the Liljencrants–Fant model, codes information that is used by listeners to identify speakers by their voices. Automatic analysis/resynthesis techniques were used to generate so-called hybrid vowels for which the voice-source characteristics of one speaker are combined with the vocal-tract characteristics of another speaker. Listeners who were trained to recognize the speakers by their natural utterances, had to indicate which speaker they thought had produced the hybrid stimulus. It was found that there is no general rule that vocal-tract information contributes more to perceived speaker identity than voice-source information. Sometimes vocal-tract information is more important, sometimes voice-source information. The results fit the subjective cues that listeners reported they had been using to perform the speaker identification task quite well. Besides the expected importance of the vocal-tract filter, the spectral balance between high- and low-frequency components of the voice-source spectrum and the flutter of F0 proved to be important perceptual cues for speaker identity.
Auditory spectral cues for the resolution of front–back confusion in humans
Authors: Carlile Simon , Pralong Daniele
Published: October 2005

The interaural level and timing difference cues are ambiguous for sound location and give rise to the so-called cones of confusion. Psychophysical work has demonstrated that spectral cues furnished by the auditory periphery are critical for resolving these front–back ambiguities. The transfer functions were recorded from each auditory canal in human subjects for 365 locations in anechoic space. For anterior locations there are substantial gains around 3–4 kHz and above 13 kHz and a notch in the transfer function that moves up in frequency (8 to 12 kHz) for locations away from the midline. These features remain reasonably consistent over a 60° change in elevation about the interaural horizontal plane (IAP). For posterior sound locations, transmission is relatively flat for locations below the IAP but a sharp notch centered on 9 kHz is evident for locations above the IAP. The changes in the interaural spectral differences are relatively symmetrical for horizontal locations about the interaural axis, although at high frequencies (≳12 kHz) there are some features that might provide front–back information for locations close to the interaural axis. These acoustical data identify several spectral features in the human monaural transfer functions that may provide potent, unambiguous cues to a sounds location. [Work supported by the Beit Foundation, McDonnel Pew Centre for Cognitive Neurosciences, Swiss National Science Foundation, and Foundation for the 450th Birthday of the University of Lausanne.]
The correlation between responses under monaural and binaural conditions
Authors: Gilkey R. H.
Published: October 2005

Gilkey etal. [J. Acoust. Soc. Am. 78, 1207–1219 (1985)] compared ‘‘monaural’’ (NoSo) and ‘‘binaural’’ (NoSπ) performance in a reproducible noise masking task. Despite a large masking level difference, the responses to individual noise samples under the NoSo and NoSπ conditions were highly correlated (p≪0.001). Isabelle and Colburn [J. Acoust. Soc. Am. 89, 352–359 (1991)], on the other hand, found correlations that were weak, and sometimes negative. Gilkey etal. used wideband masking noise, whereas Isabelle and Colburn used narrow-band maskers. On that basis, Isabelle and Colburn argued that the correlation observed by Gilkey etal. might be more appropriately attributed to similarities in across-critical-band processing, rather than to similarities in within-critical-band processing. The present study examined both wideband and narrow-band maskers and found highly significant correlations between monaural and binaural performance for both maskers (p≪0.005). [Work supported by NIH-DC-000786 and AFOSR-91-0289.]
The influence of bottom geoacoustics on the dispersive behavior of Scholte interface waves
Authors: Ali Hassan B. , Bibee L. Dale , Becklehimer Jeffrey L.
Published: October 2005

Scholte seismic interface waves can be an important component of very low-frequency (VLF) acoustic propagation, particularly in shallow-water environments. The propagation characteristics of these seismic waves, including their presence in the water column, are dependent on bottom geoacoustics (particularly shear speeds) and the types of layers overlying the basement level. This work examines the results of recent NRL/Stennis Space Center measurements and compares them with numerical predictions based on the SAFARI model. Scholte waves measured off the Oregon Margin (1991) are shown to have strikingly different characteristics from those obtained off the San Diego coast (April 1992). In particular, the latter results (San Diego) are characterized by strongly dispersed Scholte waves in the 1- to 5-Hz band, whereas those measured off the Oregon Margin contain mostly lower frequencies (1–2 Hz) and display less clearly defined dispersive behavior. The differences in the two data sets are attributed to the significantly diverse bottom/subbottom geoacoustics at the two test sites−in particular, to the different sound-speed gradients in the sediments.
Flextensional transducer modeling using variational principles
Authors: Robinson Harold C. , Richards Roger T. , Blottman John B.
Published: October 2005

The variational principle is an approximation method that allows one to obtain accurate estimates of a quantity using relatively crude trial functions for the physical behavior. This principle is applied to transducer analysis by coupling a variational principle developed for the driving element (including piezoelectric effects) to one for the shell. The motion of the transducer is, in turn, coupled to a variational principle for the pressure in a fluid medium. The modeling of a class V flextensional ring-shell projector will be presented in detail. The in-vacuo resonance frequencies for the piezoelectric ring and spherical shell, as well as the in-vacuo mode shapes for the driver–shell combination will be compared with existing theory and finite element analyses. Results for a free-flooded piezoelectric ring and immersed spherical shell will be presented as tests of the variational fluid loading formulation. Admittance calculations and beam patterns for a single element will be compared with experimental data, equivalent circuit, and finite element analyses. The extension of the variational method to array interaction modeling will also be discussed.
The single European market and its influence on measurement and specification standards for ultrasonics
Authors: Preston Roy C.
Published: October 2005

The Single European Market and European Directives will have an enormous impact on all aspects of commercial activities worldwide. In acoustics, Directives dealing with noise at work, machinery noise, and medical devices will have greatest impact. In ultrasonics, the General Medical Device Directive will deal with medical ultrasonic equipment and will lay down comprehensive essential safety requirements that will require manufacturers to comply with standards published by the Comité Européen de Normalisation Electrotechnique (CENELEC), in most cases based on International Electrotechnical Commission (IEC) standards. The initial thrust is to establish ‘‘horizontal’’ standards or ‘‘generic’’ standards that will apply to a wide range of equipment. At the specific product level, ‘‘vertical’’ standards will be required dealing with specific aspects of safety for a product type. For instance, standards will be prepared for diagnostic ultrasonic equipment, therapeutic ultrasonic equipment, and extracorporeal lithotripters. IEC Technical Committee 62: Electrical Equipment in Medical Practice is responsible for the preparation of these standards. These standards will themselves make reference to technical standards dealing with methods of measurement and characterization of ultrasonic fields prepared by Technical Committee 87: Ultrasonics. The current status of standards, either already published or being developed by Technical Committee 87, will be reviewed with particular emphasis on their applicability to the EC Medical Device Directive.
On the propagation of plane waves in dissipative anisotropic media
Authors: Carcione Jose M. , Cavallini Fabio
Published: October 2005

A theory for propagation of time-harmonic fields in dissipative anisotropic media is not a simple extension of the elastic theory. Firstly, one has to decide for an appropriate constitutive equation that reduces to Hooke’s law in the elastic limit. In this work, one relaxation function is assigned to the mean stress and three relaxation functions are assigned to the deviatoric stresses in order to model the quality factors along preferred directions. Secondly, in dissipative media there are two additional variables compared to elastic media: the magnitude of the attenuation vector and its angle with respect to the wave-number vector. When these vectors are colinear (homogeneous waves), phase velocity, slowness, and attenuation surfaces are simply derived from the complex velocity, although even in this case many of the elastic properties are lost. The wave fronts, defined by the energy velocities, are obtained from the energy balance equation. The attenuation factors are directly derived from the complex velocities, but the quality factors require the calculation of the potential and loss energy densities, yet resulting in a simple function of the complex velocities. [Work supported by EEC.]
Interport relations for the infinite elastic plate
Authors: Rudgers Anthony J.
Published: October 2005

For a reciprocal linear system, a set of reciprocity equalities relates dual variables at pairs of system ports. These equalities arise from the symmetry properties that characterize the immittance matrices of reciprocal linear systems. It has been proven previously that the infinite elastic plate, as described by the equations of linear elasticity theory, is a nonreciprocal linear system. Since the plate is a nonreciprocal system, which is characterized by nonsymmetric immittance matrices, reciprocity equalities of the usual kind do not exist for it. There is, however, a set of equations, here termed the ‘‘interport relations,’’ that relates dual variables at pairs of ports in the infinite-plate problem. The plate interport relations, which are the counterpart of the set of the reciprocity equalities that hold for a reciprocal linear system, are described in this paper. [Work supported by ONR.]
Precedence effect with and without interaural differences−Sound localization in three planes
Authors: Rakerd Brad , Hartmann William Morris
Published: October 2005

Separate experiments measured the precedence effect for sound localization in the horizontal, frontal, and sagittal planes. The first two planes involve interaural differences, the third does not. Listeners (N=8) were required to localize trains of clicks, presented by loudspeakers in an anechoic room. A target click originating in a particular plane was followed by a simulated reflection of equal level from a different location within that plane. The delay between target and reflection was the principal independent variable; it varied from 0 to 10 ms. The results of the experiments showed that the precedence effect is more effective in eliminating localization confusion due to reflections when interaural differences are present. However, the functional dependence of target identification upon delay was similar whether interaural differences were present or not. For all three planes there were identical regions of summing localization, of increasing precedence effect, and of confusion caused by echoes. These results show that there is a sagittal plane precedence effect, and, therefore, that the precedence effect does not require interaural differences for its operation. [Work supported by the NIDCD, DC00181.]
Nonlinear resonance and viscous dissipation in an acoustic chamber
Authors: Lee Chun P. , Wang Taylor G.
Published: October 2005

The nonlinear resonance of an air-filled acoustic chamber with rigid endwalls is studied numerically using the fully nonlinear Lagrangian wave equation. The effects of bulk viscous dissipation and external excitation are included. It has been found that at large excitation, the sound amplitude and the quality factor Q of the chamber are independent of viscosity, and are inversely proportional to each other. The highlight of this work is the interpretation of these results in simple physical terms. These results are consistent with those from a previously developed analytical theory, although in the latter they have been overshadowed by algebra and have not been properly interpreted. It has been deduced that the free decay rate of a large-amplitude wave due to bulk dissipation is proportional to its acoustic Mach number, and is also independent of viscosity. Also considered was viscous dissipation on the side walls, but it was found that it is much less important than bulk dissipation at high nonlinearity, considering the typical dimension and boundary layer thickness in this type of system. The wave profiles excited at slightly off-resonance frequencies have also been calculated, and found to be similar to those in a piston-driven resonant tube.
Transient acoustic wave modeling: Higher-order Wentzel–Kramers–Brillouin–Jeffreys asymptotics and symbolic manipulation
Authors: Verweij Martin D.
Published: October 2005

A combination of Wentzel–Kramers–Brillouin–Jeffreys (WKBJ) asymptotics and the Cagniard–De Hoop method is used to determine the space-time domain acoustic wave field in a continuously horizontally layered configuration. First, a Laplace transformation with real and positive transform parameter is applied with respect to the time coordinate, followed by a two-dimensional Fourier transformation with respect to the horizontal coordinates. Using the integral equations of the resulting transform domain problem, a recurrence scheme is derived for the coefficients of the WKBJ asymptotic expansions of the transform domain solutions. This scheme is well-suited for implementation in a symbolical manipulation program. The transformation of the resulting higher-order WKBJ asymptotic representations back to the space-time domain is performed with the aid of the Cagniard–De Hoop method, which is particularly efficient in this case. If both the source and the receiver are located in one homogeneous half-space of the configuration, the Cagniard–De Hoop method allows for an almost completely analytical transformation back to the space-time domain. For various configurations numerical results are presented, which show that the method is valid for instants ranging up to several times the arrival time.
Determination of geoacoustic parameters of the ocean bottom—data requirements
Authors: Rajan Subramaniam D.
Published: October 2005

An important problem in ocean acoustics is the determination of the acoustic parameters of the ocean bottom sediment layers. A variety of inverse methods have been proposed in the literature for obtaining these quantities from measurements of the acoustic field in the water column using either narrow-band or broadband sources. Broadly these algorithms can be classified as direct and perturbative methods. The measured pressure field or quantities derived from it are generally the input data to such inversion algorithms. Here, various quantities that can be used as data in perturbative methods are considered and their ability to yield accurate estimates of the unknown parameters investigated. This is done, separately for shallow water and deep water experiments, by studying various issues like Frechet differentiability, variation of the Frechet derivative from point to point, resolution of estimates, and others. For narrow-band shallow water experiments it is shown that a waveform inversion method that uses the complex pressure field as data is nonlinear, the nonlinearity increasing with frequency and waveguide thickness. Methods that use modal eigenvalues as input data are weakly nonlinear and can successfully yield estimates with acceptable resolution if the experiment is performed over a number of frequencies. In the case of deep water experiments, the experimental configuration can be so arranged as to gate out surface reverberation and this results in making waveform inversion weakly nonlinear. Similar conclusions are arrived at for broadband experiments. In shallow water, methods based on group velocity or phase velocity dispersion data are weakly nonlinear and therefore preferable to waveform inversion that is strongly nonlinear. In the case of deep water broadband experiments, waveform inversion can be used if, by suitable modifications to the experiment, surface reverberations can be gated out.
Effects of modal phase errors on eigenvector and nonlinear methods for source localization in matched-field processing
Authors: Byrne Charles L.
Published: October 2005

Modal phase errors due to rough surface scattering can perturb the algebraic structure of the cross spectral matrix, on which the success of eigenvector and nonlinear methods of source localization depends. By examining the perturbed structure one can determine what source information can be obtained from ambiguity surfaces and what information must be extracted by other means. For significant levels of phase error some type of preprocessing to suppress some sources in favor of others may be necessary, for example, the ‘‘sector-focusing’’ of Byrne and Steele. What information can be obtained from ambiguity surfaces depends on the array geometry. For vertical arrays source range and depth can be determined from the ambiguity surface if there are no modal phase errors, but when phase errors are present other methods may need to be employed. For horizontal arrays bearing, range, and depth of (nonbroadside) sources can be determined from ambiguity surfaces in the case of no modal phase errors; however, if modal phase errors are present it may not be possible to determine anything about the sources from the ambiguity surface.
The effects of notched noise on intensity discrimination under forward masking
Authors: Plack Christopher J. , Viemeister Neal F.
Published: October 2005

Zeng et al. [Hear. Res. 55, 223–230 (1991)] reported that at moderate levels there is an increase in the intensity jnd for 25-ms sinusoidal pedestals presented 100 ms after an intense narrow-band noise. They suggested that this effect is related to the finding that low spontaneous rate (SR) auditory-nerve neurons take a considerable time to recover from adaptation [E. M. Relkin and J. R. Doucet, Hear. Res. 55, 215–222 (1991)]: 100 ms after the noise, the low-SR neurons still have elevated thresholds. Therefore, the intensity of a pedestal falling between the saturation level of the high-SR neurons and the elevated threshold of the low-SR neurons will be poorly represented in neutral firing rates, and the jnd will be high. A problem with this interpretation is that subjects may listen ‘‘off frequency.’’ Theoretically, it should always be possible to choose a frequency channel for which the pedestal level is within the dynamic range of the high-SR neurons. In the present study, the experiment of Zeng et al. was replicated but with the pedestal presented in the temporal center of a notched noise to prevent off-frequency listening. Surprisingly, the notched noise substantially decreased the jnd at mid levels, removing or severely reducing the mid-level jnd elevation. This was true for pedestal frequencies of 1 and 6 kHz. It was also found that even if the notched noise was terminated before pedestal onset the jnd elevation was reduced. This suggests that the effect of the notched noise is not due to suppression. Finally, it was found that gating the notched noise with the pedestal was also sufficient to reduce the jnd elevation. This argues against an explanation for the effect of the notched noise in terms of adaptation. The effect of the notched noise on intensity discrimination is hard to explain on the basis of events occurring at the level of the auditory nerve. Because the notched noise obviously does more than limit off-frequency listening, the role of this latter process in the original Zeng et al. experiment is still unclear.
External ear transfer function modeling: A beamforming approach
Authors: Chen Jiashu , Van Veen Barry D. , Hecox Kurt E.
Published: October 2005

In this article, a beamformer is proposed as a functional model for the spatial and temporal filtering characteristics of the external ear. The output of a beamformer is a weighted combination of the data received at an array of spatially distributed sensors. The beamformer weights and array geometry determine its spatial and temporal filtering characteristics. A procedure is described for choosing the weights to minimize the mean-squared error between the beamformer response and the measured response of the external ear. The effectiveness of the model is demonstrated by designing a beamformer of several hundred weights that duplicates and interpolates the measured external ear response of a cat over broad ranges of frequency and direction. A limited investigation of modeling performance as a function of array geometry is reported.
An alternative algorithm based on subspace rotation invariance techniques for directions-of-arrival estimation using the compressed data pencil
Authors: Chen Yuan-Hwang , Chen Chao-Hung
Published: October 2005

In this paper, an alternative algorithm based on subspace rotation invariance techniques is presented for estimating the directions-of-arrival (DOAs) of uncorrelated narrow-band plane waves in noise using the data pencil compressed by the Karhunen–Loève transform (KLT). It is shown that the compressed data pencil preserves the rotation invariance property, and therefore it can be employed by subspace rotation invariance algorithms, e.g., the original ESPRIT, the TLS-ESPRIT, and PRO-ESPRIT, to estimate the DOAs. Due to the reduced-dimension compressed data pencil, the proposed algorithm has a much faster speed in computation than the above ESPRIT algorithms. In addition, computer simulations illustrate that the proposed algorithm exhibits better statistical characteristics than the original ESPRIT and comparable to the PRO-ESPRIT and the TLS-ESPRIT, respectively.
Optimum array detection of weak signals in spatially correlated non-Gaussian noise
Authors: Izzo Luciano , Paura Luigi , Tanda Mario
Published: October 2005

The structure of the locally optimum array detector for a random signal embedded in non-Gaussian noise is derived. In this observation model the noise samples are assumed to be temporally independent at each array sensor, but correlated across the array at each time instant. Since the synthesis of the detector involves multivariate densities of the noise spatial samples, the transformation noise model, which is characterized only by the univariate probability density function and the covariance matrix, is considered. The performance is assessed via computer simulations by assuming for the first-order statistical properties of the noise the two-parameter generalized Gaussian family of distributions. A comparison with the performance of the locally optimum array detector synthesized for spatially independent noise is stated.
Active structural acoustic control of broadband disturbances
Authors: Baumann William T. , Ho Fu-Sheng , Robertshaw Harry H.
Published: October 2005

A control design technique is developed to actively suppress the acoustic power radiated from a structure, with negligible fluid loading, that is persistently excited by narrow-band or broadband disturbances. The problem is constrained by the assumption that the far-field pressure cannot be measured directly. A method for estimating the total radiated power from measurements on the structure is developed. Using this estimate as a cost function and assuming knowledge of the spectrum of the disturbance, a controller is designed using the linear-quadratic-Gaussian (LQG) theory to minimize the cost. Computer simulations of a clamped–clamped beam show that there is a significant difference in the total radiated power between a system with a vibration-suppression controller and a system with an acoustic controller that accounts for the coupling of these vibrations to the surrounding fluid. In some cases, the acoustic controller increases the system vibration in order to minimize the radiated power.
Bubble oscillations in the nearly adiabatic limit
Authors: Kamath V. , Og̃uz H. N. , Prosperetti A.
Published: October 2005

Miksis and Ting [J. Acoust. Soc. Am. 81, 1331 (1987)] reported examples of a marked increase of the radius of an oscillating gas bubble as predicted by their nearly adiabatic model. They attributed this phenomenon to a process of rectified heat transfer into the bubble. By comparison with a more complete model which contains the nearly adiabatic one as an approximation, it is shown that the real cause of this result is instead the error inherent in the approximation. This error arises primarily from the failure of the approximation to capture the complex behavior of the gas temperature and manifests itself in a spurious growth of the mass of gas contained in the bubble. In addition to being more accurate, the more complete model is also found to be less computationally demanding than the approximate one.
The existence of generalized eigenfunctions and multiple eigenvalues in underwater acoustics
Authors: Evans Richard B.
Published: October 2005

An example is given of a horizontally stratified acoustic waveguide that supports generalized eigenfunctions in addition to the usual eigenfunctions or normal modes. Generalized eigenfunctions occur when the characteristic equation has a zero with multiplicity greater than one. Both eigenfunctions and generalized eigenfunctions are required to provide a complete representation of a wide class of functions. The separation of variables solution for a point source in a waveguide, based only on the usual eigenfunctions or normal modes, is not valid for the example presented here. The correct solution, based on a combination of eigenfunctions and generalized eigenfunctions, contains modes that are simultaneously exponentially damped and algebraically amplified in the direction of propagation.
A model of the phonatory response time of stutterers and fluent speakers to frequency-modulated tones
Authors: Nudelman Harvey B. , Herbrich Katherine E. , Hess Kenneth R. , Hoyt Bradley D. , Rosenfield David B.
Published: October 2005

Stutterers and fluent speakers tracked frequency-modulated tones by humming. The response time (RT) to the first corrective change in fundamental frequency in response to linear ramps of increasing and decreasing frequency was measured. The results demonstrate that RT is a function of the stimulus ramp velocity. A model of this dependency is provided which consists of parameters of threshold frequency and a fixed time delay. The estimated threshold frequency for the fluent speakers is 2.029 Hz with 95% confidence interval: (1.70 Hz, 2.35 Hz) whereas that of the stutterers is 3.937 Hz (3.28 Hz, 4.60 Hz). These threshold frequencies are significantly different (p<0.0001). This implies that stutterers are slower to respond to changes in frequency than are fluent speakers. The fixed time delays for the two groups are not significantly different. This means that it is possible for the stutterers to respond as fast as the fluent speakers (i.e., their basic ‘‘reflexes’’ are the same); however, they spend more time in the detection of the change in a tracking signal. This supports the model of the stuttered event as being triggered by an instability in a multiloop speech motor control system.
A new technique for controlling noise transmission into a cavity using acoustic pressure feedback
Authors: Koshigoe Shozo , Gillis James T. , Falangas E. T.
Published: October 2005

A new technique for controlling noise transmission into a cavity using piezoelectric actuators on an elastic plate is discussed. This study involves construction of a fully coupled acoustics/plate interaction model. This model is used to guide development of a new active noise control method. Implementation of this approach does not require adaptive signal processing such as the least-mean squares to minimize the acoustic energy in the cavity for control [Pan etal., J. Acoust. Soc. Am. 87, 2098–2108 (1990)]. It is similar in concept to plate velocity feedback control. However, the plate velocity feedback control is only effective for the plate controlled modes, whereas the new method is effective for both the plate and cavity controlled modes. A comparison of the simulations using velocity feedback and the least-mean-squares method with the new technique will be discussed.
The Southeast Alaska acoustic measurement facility (SEAFAC)
Authors: Chwaszczewski Richard S.
Published: October 2005

US Navy submarines must operate undetected. A rigorous silencing program maintains their acoustic superiority. SEAFAC is the program’s new West Coast measurement site in Behm Canal, near Ketchikan, AK. SEAFAC has three major elements. (1) At the Underway Site, signatures of a submerged submarine are measured as it travels back and forth between sensor arrays. (2) The Static Site is the nation’s most unique measurement tool. Here, signatures are measured while the submarine is stationary and submerged. Suspension barges lower the submarine on cables and position it between sensor arrays. (3) The complex on Back Island is a self-sufficient acoustic laboratory and support facility that is capable of continuous 24-h operations with berthing and messing for several dozen people. An ideal location, state-of-the-art data analysis and signal processing systems, and a solid support structure make SEAFAC the Navy’s premier acoustic measurement facility.
Experimental results of the differential Doppler compensated cross correlator and its application in target motion analysis
Authors: Sauvet-Carof Marie T.
Published: October 2005

This article presents the study and implementation on real signals of a delay and Doppler differential estimator: ‘‘The differential Doppler compensated cross correlator’’ (DDCC), with application on target motion analysis (TMA). After a brief review of degradation caused by a differential Doppler on the conventional cross correlator output signal, the DDCC performance improvement is demonstrated in detection (signal to noise ratio) and estimation (measurement accuracy) compared to the conventional cross correlator with finally the test of a DDCC implementation on simulated and real signals. Analysis of theoretical, simulated, and real performance of this system demonstrates that it reaches the Cramer–Rao bounds. The measurement accuracy obtained enables the use of this system within a modern method of TMA where the state vector estimation is realized by batch processing of measurement sets with a maximum-likelihood method. The final and most important part of this paper corresponds to various experimental results, fully demonstrating the excellent behavior of this system in real conditions.
Measuring and predicting the effect of an audience
Authors: Bradley J. S.
Published: October 2005

Previous research has shown that the sound absorption of arrays of occupied and unoccupied theater chairs is related to the ratio of perimeter-to-area of a sample of chairs [J. Acoust. Soc. Am. 91, 1514–1524 (1992)]. This work has been extended by using sound absorption measurements of various sized samples of occupied and unoccupied chairs to predict the absorptive effect of audiences in auditoria. In the auditoria, a full range of modern room acoustics quantities were measured both with and without the audience present. This was accomplished using a maximum length sequence signal and fast Hadamard transform technique to obtain impulse responses without significantly disturbing the audience. The influence of the audience was measured in terms of changes to: reverberation times, early decay times, sound levels, early-to-late sound ratios, and lateral energy fractions. The effect of the audience on reverberation times was compared to the changes in the other quantities. The changes in reverberation times and the added absorption due to the audience is predictable from the reverberation time measurements.
Instrument modeling using sampled sound
Authors: Mauchly Bill
Published: October 2005

The modern electronic keyboard instrument is asked to imitate all the familiar musical instruments. Virtually all rely on digital sampling. Compared to older synthesis techniques, sampling at first seemed to present startling realism. But the exact reproduction of a single recording of a single note does not fool the ear. Every musical instrument has a set of cues which, when absent, expose the imposter. This talk examines a number of techniques that are used to create more realistic simulations of acoustic instruments in Ensoniq’s latest sampling keyboards. The problems addressed include temporal variations in loudness, pitch, and brightness; formants; legato connections between notes; sympathetic resonances, restrike of a vibrating string, and nonlinearities. Expressive nuance in performance poses additional questions. How can a performer, squeezed through the pipe of digital information, create expression in a sampled sound? The answer must include ergonomic physical controllers linked to perceptually important sound parameters. Since samples are inherently static, special tricks are needed to give the illusion of a dynamic process.
Measuring the acoustic reflectivity of panels at low frequencies and high oblique angles
Authors: Dlubac J. J. , Deigan R. J.
Published: October 2005

Conventional short-pulse techniques for measuring the reflectivity of acoustic panels requires that the reflected and incident waves be separated in time so that their ratio can be established. This technique is limited to high frequencies and low oblique angles, since under these extremes the direct and reflected waves overlap. An interference method is investigated as a way of making reflectivity measurements at low frequencies and high oblique angles. The total field (incident and reflected) in the vicinity of the panel is measured relative to the incident field without the panel. The total field, which depends on frequency and angle of incidence as well as the panel material, is then examined and manipulated to extract information on the reflected wave. The technique is demonstrated with data reduced on steel plates of various thicknesses.
Use of vector Bragg wave-number scattering condition in bistatic scattering experiments
Authors: Oeschger John , Goodman Louis , Szargowicz Diane , Hebda Peter
Published: October 2005

Applying the Born approximation to a buoyant plume yields the Bragg scattering condition that determines along with knowledge of the scattering potential, the scattered wave at any given scattering angle. The Bragg scattering condition allows for information obtained from the same Bragg direction albeit different scattering angles to be pieced together to form an entire Bragg wave-number spectrum of the scatterer. Data are taken in a multiple bistatic configuration whose geometry is predetermined via knowledge of the bandwidth of the transducers and the desired overlap of the resulting Bragg phase space. Results are given for a buoyant axisymmetric laminar plume. As an aside of the Bragg scattering condition an empirical formula derived from the far-field expressions for the Green’s function solution to the Hemholtz equation given the scattering dimensionality of the plume, which is acoustically measured and shown to give expected results.
Recollections of Acoustical Society founders and early decades
Authors: Martin Daniel W.
Published: October 2005

Memories of the founders, and the stories they told, will be recounted along with first-hand accounts of interesting happenings later in their lives, especially at Acoustical Society meetings.
Bringing noise reduction to product design
Authors: Lyon Richard H.
Published: October 2005

Creating products that sound good means that product design engineers must have the skills to extract those features that relate to favorable or objectionable sounds from the acoustical signal generated by the product. They must also have the ability to associate those features with specific events in the operation of the product. Some engineering groups, particularly those in the automotive industry, have begun to develop these skills, but there is an increasing need throughout industry for more capability in these areas. Educational materials of various forms, courses, and new ways of delivering the information are being developed for people in industry. In some ways, this continuing education process is moving faster than are programs for university students. Some suggestions for university teaching of acoustics in design are offered.
New initiatives in noise control reflecting on lessons from Arden House
Authors: Eldred Kenneth McK.
Published: October 2005

In June 1972, the Acoustical Society held a conference on Acoustics and Societal Problems (CASP) at Arden House in Harriman, New York. Over 50 members participated in the 3-day conference, organized in seven task teams under the able general chairmanship of John C. Johnson. The 89-page report of this conference contains detailed assessments of needs and recommended actions in five scientific and technical areas of societal concern and two other areas related to communication of information and ideas. These seven areas were: (1) noise and man; (2) outdoor sound propagation and sources; (3) motor vehicle noise; (4) biomedical acoustics; (5) acoustic applications; (6) interorganizational activities and relationships; and (7) diffusion of knowledge. This paper draws upon the 20-yr-old repository of knowledge to find needs and ideas in the area of noise control that are as relevant today as they were 20 yr ago. The items found in this unfinished agenda provide a partial basis for the development of new initiatives for noise control and insight into the difficulties of their implementation. Hopefully, these ideas and insights can lead to effective execution of new initiatives in the future.
Scattering from infinite coated cylindrical shells by a new shell theory
Authors: McDaniel J. Gregory , Ginsberg Jerry H.
Published: October 2005

Acoustic coatings have very low sound speeds in comparison to the underlying shell, and therefore tend to respond in higher-order thickness modes not contained in most shell theories. Previously, a variationally based, arbitrary order shell theory has been formulated in order to describe vibration of viscoelastically coated cylindrical shells. In this approach the dependence of all displacement components on the thickness coordinate are represented by a series of Legendre polynomials. Coated shells are modeled by independent expansions in the shell and coating, with displacement compatibility conditions between the shell and coating enforced explicitly. The formulation is extended in the present work to model plane wave scattering from an infinite cylindrical shell with a coating attached to its exterior surface. Numerical results include the backscattered form function, which is compared to published results, and detailed plots of displacement variations through the thickness. A focus of the present work is to assess the effect of higher-order thickness variations on the vibroacoustic response. [Work supported by ONR.]
Acoustic harmonic scattering from cylinders using a new internal source density method
Authors: Stephanishen Peter R. , Ramakrishna Sudheer
Published: October 2005

Two-dimensional acoustic harmonic scattering from rigid cylinders, which are symmetric about an axis, is addressed using a new internal source density approach. A least-mean-square error method is used to determine the internal monopole and dipole source density line distributions along the axis of symmetry of the cylinder by utilizing the rigid boundary condition at the cylindrical surface. The surface and exterior scattered pressure fields are then readily obtained from the source distributions. Numerical results are presented to illustrate the method for the case of plane wave scattering from circular and elliptical cylinders. Typical numerical results for the total surface and far-field scattered pressures are presented for plane wave scattering by a circular cylinder and compared with closed form solutions to illustrate the accuracy of the method. Finally plane wave scattering from elliptical cylinders are presented and discussed to illustrate the effects of aspect ratio, frequency, and angle of incidence.
A fast perturbation approach for calculating pulses in a waveguide with applications
Authors: Werby M. F. , Broadhead M. K.
Published: October 2005

A fast normal mode code based on a full perturbation method and a fast Fourier transform method has been developed. This enabled one to perform broadband pulse calculations to high frequencies. Further the pulse returns can be decomposed into their constituent modes. Studies are preformed on pulse returns for realistic shallow water waveguides for signals out to 25 km, the various dispersion effects are illustrated, and model arrivals are separated with increasing distance from the source. Particular emphasis is placed on strong channeling.
Fricatives: Sound sources and modification
Authors: Rekart Deborah , Andrews Cathy
Published: October 2005

Formulas in current texts describing sound sources and their modification for fricatives do not help students with little mathematical background. In lab sessions, waveform-editing software and a digital filter are used by pairs of students to show high- and low-frequency components in the fricative–vowel syllable [∫i], input with the low-pass filter set to 6300 Hz. In this ‘‘normal’’ condition, the high frequencies of the fricative and the low frequencies of the vowel are visible in the waveform. A low-pass filter setting of 1250 Hz blocks high frequencies and the fricative disappears; the signal sounds ‘‘muffled.’’ A high-pass filter setting of 1250 Hz blocks low frequencies and the vowel disappears; the signal sounds ‘‘whispered,’’ [z̢] is similarly analyzed. Wideband and cross-sectional spectrograms are made of [s:∫:] to examine how place of constriction determines the frequency range of the friction noise. Cut-off frequencies and peaks of greatest intensity are visibly higher in frequency for (:s) with a more anterior constriction. Variations in /s/ production are evident with greatest intensity ranging from approximately 4000 to 14 000 Hz.