bluuebunny/crossref_metadata_2025 huggingface dataset:
A kinematic analysis of contrastive stress.
Authors: Goffman Lisa , Smith Anne
Published: October 2005

The present investigation examined the shape and variation of movement patterns associated with specific stress contexts. Movements of the lower lip were recorded using the Optotrak, a noninvasive system in which light emitting diodes are attached to the moving structure. Eight adult subjects produced versions of the utterance ‘‘Buy Bobby a puppy’’ that varied in stress. Initally, this utterance was produced with normal stress patterns. Then, a scenario was presented that elicited a contrastive stressed form (e.g., to stress ‘‘Bobby,’’ the subject responded to the utterances ‘‘Don’t buy Kathy a puppy. Buy Bobby a puppy.’’). A standard technique in the analysis of kinematic data is to measure absolute values of peak velocity, displacement, and duration. Analyses revealed that, as expected, increased duration and amplitude occurred in stressed contexts. A second set of analysis procedures involved the evaluation of underlying movement patterns through time and amplitude normalization (i.e., collapsing absolute differences in duration and amplitude). Pattern recognition techniques were then applied, revealing that underlying patterning differed as a function of contrastive stress. [Work supported by NIDCD.]
Interrogative word is the focus of question in the WH question sentences in Mandarin Chinese?
Authors: Chang Yueh-chin
Published: October 2005

In nontonal languages, intonation is a very important prosodic feature to distinguish sentence meanings. But in tonal languages, such as Mandarin Chinese, declarative and interrogative sentences both have falling intonation. In this case, interrogative sentences differ from the former by having a question particle in the final position of the sentence or a question word. At the prosodic level, what are the prosodic features which distinguish declarative and interrogative sentences, if these two types of sentences have similar intonational contour patterns? Following Lyons (1977) and Li & Thompson (1979), question words are the focus of questions in an interrogative sentence. They should have a phonetic, acoustic realization more important than other words in the sentence. However, in the primary study about the interrogative word ‘‘ji’’ with third tone (how many) in WH-question sentence, ‘‘ji’’ had a short duration, it had not undergone the 3-tone tone sandhi, and was realized as a neutral tone. This study will examine in detail the acoustic phonetic realizations of interrogative words, to find out their prosodic features and to know how listeners react to these features.
Simulations for performance evaluations of a family of fluctuation-based processors.
Authors: George Jacob
Published: October 2005

A family of processors developed at NRL [R. A. Wagstaff, ‘‘The WISPR Filter: A method for exploiting fluctuations to achieve improved sonar signal processor performance,’’ (submitted to J. Acoust. Soc. Am.)] have been shown in data analyses to yield gains in signal-to-noise ratios, and detect weak signals buried in noise. These processors take advantage of the notion that signals from submerged sources (especially those which undergo relatively fewer interactions with the surface) are relatively steady though they may be weak, but ambient noise has greater fluctuations. Simulations using synthetic data have been done to verify the validity of the above premises, and to assess the performance of the family of filters collectively called ‘‘WISPR’’ under several environments. The simulations are also compared with analyses of experimental data. The results of the simulations and the experimental analyses will be discussed. [Work supported by ONR.]
Computer imaging features for classifying semivowels in speech spectrograms.
Authors: Pinkowski Ben , Finnegan-Green Jack
Published: October 2005

Speech spectrograms can be analyzed using computer image processing techniques to yield high recognition rates [B. Pinkowski, Pattern Recognition 26, 1593–1602 (1993)]. In particular, Fourier descriptors (FD’s) have proven useful for characterizing the boundary of segmented isolated words containing the English semivowels (/w/, /y/, /l/, /r/). This study examines the appropriateness of FD’s combined with 17 other general features for classifying spectrogram images. The other features include eigenvalues and eigenvectors, gray-level variance and covariance, run-length and chain encodings, and segment size, shape, and compactness. Principal components (PC’s) are used for feature reduction on a speaker-dependent data set consisting of 80 sounds representing 20 speaker-dependent words containing semivowels. With eight combined features, including four 32-point FD’s and four general features obtained from principal component analysis, a 97.5% recognition rate was obtained using a linear discriminant function. This rate was higher than that observed for any group of features considered separately. [Work supported by NIH.]
Vowel identification from harmonic contours of vowel centers using an automatic algorithm that eliminates windowing error.
Authors: Betancourt Octavio , Antrobus John
Published: October 2005

Using successive nonoverlapping 22.5-ms windows, 16-kHz sampling, no filtering, an automatic algorithm locates five successive windows of minimum spectral velocity, describes a subwindow equal to some multiple of the natural period of F0, and maps the subwindow onto the unit circle, the interval 0, 2π. Consequently, the Fourier analysis is performed on a window where the signal is exactly periodic. Because the spectrum contains no extraneous numerical sidebands it is precise, and consists only of natural harmonics in the acoustic signal. The first 32-integer multiples of F0 are sufficient to describe the spectrum. J. D. Miller’s [J. Acoust. Soc. Am. 85, 2114–2134 (1989)] log F01/3 shift increases recognition of 12 vowels (men, women, and children) in the Hillenbrand et al. [J. Acoust. Soc. Am. 97, 3099–3111 (1995)] data set from 52% to 75% using a Euclidean classifier (EC—with jackknife). Cosine series (12) were used to compare our Betancourt spectrum (EC: 76%) with the Hamming window (EC: 61%). Quadratic discriminant function analysis + log F0 (79%) adds only 3% to our best EC result. With this spectrum and a log F01/3 shift, most vowel information is clearly captured by a simple EC.
Planar acoustic holographic reconstruction by using a moving array.
Authors: Kwon H.-S. , Park S.-H. , Kim Y.-H. , Ko B.-S.
Published: October 2005

Planar acoustic holography has been well acknowledged as a useful tool to predict whole sound fields in space. In practical applications, however, an insufficient number of microphones has trouble measuring whole holograms, therefore limiting the improvement to construct a better picture of sound. This problem conveys the issue to virtually increase the number of microphones so that it can construct a better, realistic sound field. As one of these measuring techniques, the conventional scanning technique requires a reference and holds the array during the measurement of pressures. Instead, the proposed method measures the hologram continuously by a moving array without a reference. Its basic idea is that the pressure signal of a moving microphone is modulated with the carrier frequency which is the frequency of the sound field. Although this is a time signal, it includes the spatial information of pressure distribution; i.e., hologram, due to a constant moving speed. The bandwidth of modulated signal is directly proportional to the Mach number, therefore generally narrow, a hologram can be successfully recovered unless there is a closely located frequency; not closer than the bandwidth. Also this technique can be directly applied to the hologram measurement of a moving source with a fixed array. This method is demonstrated by computer simulations and experiments.
Acoustic scattering by a partially buried three-dimensional elastic object.
Authors: Lim Raymond
Published: October 2005

A formally exact transition-matrix solution for the spectral scattering response of an elastic object that penetrates a plane-stratified fluid host is formulated. The field scattered from the segment in each layer is expanded in a global outgoing basis centered on that segment and these segment fields are superimposed at the field point. A manageable structure for the transition matrix is maintained by using the boundary conditions to couple these segment fields to the interior field of the object via a single exterior surface field expansion centered on the origin of the object. The standard set of regular spherical eigenfunctions of the Helmholtz equation are used to expand the exterior surface field. Numerical tests for an axisymmetric spheroid indicate this choice yields a viable solution but convergence is better for flattened shapes (oblate) than elongated shapes (prolate). Examples are presented to illustrate environmental effects on the backscatter by a bubble and an elastic spheroid that penetrate a water/sediment interface. [Work supported by ONR.]
Backscattering mechanisms for reverberation from deep ocean features using ARSRP data taken at the Mid-Atlantic Ridge.
Authors: Preston J. R.
Published: October 2005

In July 1993 SACLANTCEN participated in an experiment for the acoustic reverberation special research program (ARSRP). The primary objective was to take high-resolution measurements to determine the detailed physical processes dominating the low-frequency scattering from rough topographic features and from deep sediment pond areas. A very detailed set of monostatic and bistatic scattering experiments were conducted (using low frequencies from 200–375 Hz) just west of the Mid-Atlantic Ridge near 26° N and 47° W. This paper presents towed array data recorded by SACLANT Centre’s R/V ALLIANCE for comparison with FEPE two way parabolic equation model estimates of selected ARSRP geometries. The receivers were horizontal arrays of 128 elements spaced at 0.5, 1, and 2 m. Source/receiver depths were ≊130 and 450 m, respectively. Inferences for monostatic bottom scattering mechanisms are discussed based on the FEPE model from Collins to interpret the data. The modeling work isolates different scattering mechanisms to assess their relative contributions to the overall reverberation levels observed in the data.
Bottom backscatter measurements at 100 and 200 kHz with high angular resolution.
Authors: Parkinson Anthony F. , Anstee Stuart D.
Published: October 2005

Measurements of the variation of acoustic bottom backscatter with incident angle have been made at 100 and 200 kHz at sites in Sydney Harbour, Australia, with bottom types varying from sand waves to mud. The measurements were made with transducers mounted on a rotating arm with a radius of approximately 2.4 m. Angular resolution of approximately 0.2° was achieved over a range of nearly 90°. Twin cameras attached to the rotating arm allow the recording of stereo images of the bottom in favorable cases, giving a model of the scattering surface allowing a comparison of measured backscatter with that numerically estimated from surface scattering alone.
High-frequency bistatic scattering from elastic seafloors.
Authors: Ivakin Anatoliy N. , Jackson Darrell R.
Published: October 2005

A high-frequency model of bistatic sound scattering is considered assuming an elastic seabed with spatially fluctuating bulk parameters and a slightly rough surface. The first-order perturbation solution is used to obtain an approximate expression for the bistatic scattering strength, different geometric configurations are considered, and the dependence of bistatic scattering strength upon the incident and scattered grazing angles, as well as the ‘‘bistatic,’’ or azimuthal angle, is computed for various seabed types. The parameters of the model include mean values for bulk properties and parameters defining the spectra of fluctuations in bulk properties and seabed relief. The influence of shear elasticity is examined by comparison with the case of a fluid seabed having the same density and compressional wave speed. It is shown that shear effects on both roughness and volume components of scattering are small for sands which consequently can be treated as acoustic fluids for realistic shear velocities (approximately 300 m/s and less). For consolidated sediments and rock, shear effects are dominant, complicated, and very sensitive to bottom parameters. Volume scattering exhibits a strong dependence on correlations between the parameter fluctuations as well as their spectral aspect ratio. [Work supported by ONR.]
Moderate-frequency scattering from layered sediments over an elastic basement.
Authors: Ivakin Anatoliy N.
Published: October 2005

In previous work a high-frequency model for sound scattering by an irregular elastic seabed with volume inhomogeneities and rough water-seabed interface was examined [A. N. Ivakin and D. R. Jackson, J. Acoust. Soc. Am. 98, 2989(A) (1995)]. Scattering from fluid layered sediments with different kinds of irregularities was also considered earlier [A. N. Ivakin, J. Acoust. Soc. Am. 95, 2884(A) (1994)]. But, at many sites, the seabed is of a composite-type consisting of an irregular fluid sediment layer or layers covering an elastic basement. In this case, a fluid scattering model is adequate only for sufficient high frequencies such that absorption renders the influence of the elastic basement negligible. At lower frequencies, sound penetration of the sediment increases, and the effects of scattering from the basement as well as additional channels of scattering from within the sediment due to reflection from the basement become important. These effects are considered and their sensitivity to different model parameters is analyzed. Frequency-angular dependencies of scattering strength are calculated for different types of seabed, and possible applications of predicted interference patterns to remote sensing of the seabed are discussed. [Work supported by ONR.]
Musical instrument directivity in different playing modes, environments, and amplifications.
Authors: Martin Daniel W.
Published: October 2005

Directional effects are reviewed for orchestral trumpet and French horn, for piano, and for organ pipes. The implications for each will be discussed relative to different acoustical environments and instrument amplification systems.
Directivity of a simplified clarinet.
Authors: Strong William J. , Sommerfeldt Scott D.
Published: October 2005

A simplified clarinet was modeled as a closed–open tube of uniform cross section with an open tonehole lattice near its open end. The tube had a length of 50 cm and a diameter of 1.5 cm. The tonehole lattice consisted of five identical toneholes spaced at 2.8-cm intervals. Each tonehole was 0.8 cm in diameter and had an effective length of 1.3 cm. The open end of the tube and each of the toneholes was treated as a simple source, and a corresponding source strength (volume velocity) was calculated at frequencies of interest. The far-field radiated pressure was calculated at a constant radius in a plane that included the tonehole lattice. The pressure was calculated at angular positions from 0 deg (open end) to 180 deg (closed end) for normal mode frequencies. (Circular symmetry about the tube axis was assumed.) Significant directional patterns were seen for frequencies above 2000 Hz. Experiments were performed on a similar structure to measure the directivity and for comparison with the calculations.
Sound radiation from boxes with tone holes.
Authors: Weinreich Gabriel
Published: October 2005

The normal modes of a hollow box with one or more sound holes, such as forms the radiating element of a typical string instrument, are combinations of ‘‘wood modes’’ and ‘‘air modes.’’ Wood modes have an average frequency spacing independent of frequency, whereas the average spacing of air modes is inversely proportional to frequency for frequencies low enough to make the ‘‘thin’’ dimension of the box smaller than half a wavelength, becoming inversely proportional to the square of the frequency for frequencies above that. As a result, the density of modes of, say, a violin, is generally dominated by wood modes at low frequencies and by air modes at high frequencies. The interplay of the two types of modes has radical consequences for the directivity of string instruments, in that the directional pattern can change drastically within very small musical intervals, perhaps accounting for the special ‘‘flashing brilliance’’ that such instruments exhibit. This talk will outline the theory of these effects and support it with experimental observations. [Work supported by NSF.]
The effect of soundpost removal on normal mode radiation efficiency and directivity of a violin.
Authors: Bissinger George
Published: October 2005

The radiative properties of individual mechanical normal modes of vibration of a violin can be calculated from experimental modal analysis results using boundary element radiation programs that integrate the Helmholtz equation over all surface elements. This technique, applied to modal analysis results for a violin with and without a soundpost, helps elucidate the acoustic effects of removal of the soundpost both in terms of the radiation efficiency and directivity of the resultant radiation from each mode and the overall acoustic response. Consonant with the experience of players and luthiers, soundpost removal has a major effect on the predicted acoustic response of the violin. Some violin corpus (sans tailpiece and neck-fingerboard) modes that radiate strongly with the soundpost in place show a substantial change in acoustic response when the soundpost is removed, which is dependent either on the strength of their mechanical excitation and/or their radiation efficiency [G. Bissinger, J. Acoust. Soc. Am. 97, 3154–3164 (1995)]. Particular attention is paid to the predicted acoustic response changes of the first corpus bending modes at 500 Hz.
Reproduction of directivity pattern using multiloudspeaker source.
Authors: Dirogis Philippe , Warusfel Olivier , Caussi Reni
Published: October 2005

A sound source can generally be characterized by three physical properties: timbre, loudness, and directivity. Although loudspeakers give a faithful reproduction of timbre and loudness, their own directivity can conflict with the directivity of the source they aim at reproducing. A general method to optimize the reproduction of any given directivity pattern with a set of independently driven sources is described. At each frequency the synthesized directivity is obtained by looking for the optimal linear combination of the elementary sources, from which the resulting acoustic field can be predicted. This method is applied to a particular source with 12 loudspeakers grouped into a few subsets in order to fit the first spherical harmonics. The comparison between the prediction and the experimental measurements shows excellent agreement. However, the synthesized figures only fit the spherical harmonics in a limited frequency range, which depends strongly on the characteristics of the electroacoustical set (number, position, and directivity of sources). The interest and the limitations of this method are discussed for various types of applications, such as the reproduction of the directivity of instruments, loudspeaker clusters design, and echo cancellation. Finally, an attempt is made to illustrate the perceptual effects of the directivity by analyzing the variations of room acoustics criteria measured with the different synthesized directivity patterns.
Modes of vibration and directivity of guitars.
Authors: Watson Eric T. , Rossing Thomas D.
Published: October 2005

An acoustic guitar radiates sound primarily from the top plate, the back plate, and through the sound hole, leading to a rather interesting sound field [E. T. Watson and T. D. Rossing, J. Acoust. Soc. Am. Suppl. 1 83, S119 (1988)]. The modes of vibration of the guitar body, including the top plate, the back plate, and the enclosed air, and the radiation patterns that result from exciting these modes in an anechoic room, are described.
Acoustic echo cancellation for duplex audio communication.
Authors: Gay Steven L.
Published: October 2005

This paper reviews the problems associated with the application of acoustic echo cancellation to duplex hands-free audio communication. The more popular approaches to the solution of these problems are reviewed as well. In particular, the problems discussed include the effects of communication channels on the human perception of echo, characteristics of the acoustic echo path, double-talk, and stability. The methods which address these obstacles are fast-converging, low-complexity long adaptive filters, double-talk detectors, and suppression and clipping techniques.
Low cost methods for mitigating hands-free acoustics problems.
Authors: Chu Peter L.
Published: October 2005

Key problems in hands-free acoustics for teleconferencing are acoustic echo cancellation, reverberation, noise, varying amplitude, and restricted audio bandwidth. None of these problems can be completely solved via low-cost methods, but their nuisance can be significantly reduced. For acoustic echo cancellation, a sub-band approach has been found to work well, where the speech is divided up into many bands and echo cancellation occurs individually on each band. Reverberation in speech pickup may be significantly reduced via a simple two dipole, automatically steered array which forms a dipole pattern which may be electronically rotated a full 360 deg. Background noise from fans may be suppressed using spectral subtraction techniques. Varying amplitudes of speech may be addressed by means of a voice-activated AGC (automatic gain control), where the voice detector eliminates pumping artifacts usually found in agressive AGC schemes. Finally the use of 7-kHz digital audio compression schemes alleviates the problems of muffled sounding speech due to the 3.4-kHz restricted audio bandwidth found on telephones.
A flexible experimental microphone array.
Authors: Ryan James G.
Published: October 2005

Sound pickup for hands-free communications often requires the microphone to be located at a large distance from the talker. However, in typical environments, the resulting speech signal is corrupted by reverberation and noise which degrade perceived voice quality and impair the operation of automatic speech recognizers. Microphone arrays have been shown to provide substantial improvements in predicted voice quality in computer simulations. To measure microphone array performance in more realistic conditions, a flexible, experimental microphone array has been developed based on digital signal processing technology. This array is flexible enough to permit the implementation of a wide variety of signal processing strategies and array geometries. In this paper the array design will be described and the performance of this array in the variable-acoustics listening room at the National Research Council will be discussed.
Image-derived second-order differential microphone on a finite baffle.
Authors: Elko Gary W.
Published: October 2005

A single first-order dipole microphone placed close to a reflecting plane results in a unidirectional second-order differential microphone. In practice an infinite reflecting plane is not attainable and it is therefore of interest to examine the effects of using a finite reflecting surface on second-order image-derived microphones. This talk will present results obtained in the investigation of a finite reflecting surface size by using the solution to the wave equation for scattering and diffraction from an oblate spheroid. The particular solution that is investigated is for the case of an infinitesimally thin oblate spheroid, the disk. Results show that the response of a first-order bidirectional sensor over the disk is sensitive to sensor location as well as to disk size relative to the acoustic wavelength. For a centrally located image-derived second-order microphone, the differential sensor response approaches a second-order response at a frequency where the reflecting baffle size is at least one-half the acoustic wavelength. Experimental results for both circular and rectangular baffle geometries will also be shown.
Practical applications of first- and second-order differential microphones in personal computer (PC) multimedia products.
Authors: McAteer Jeffrey P.
Published: October 2005

Directional microphones are used in PC voice and telephony applications to reduce the pickup of noise and reverberation, as well as reduce loudspeaker-to-microphone acoustic coupling. Differential-type directional microphones are popular because of their small size and relatively low cost. This talk focuses on how differential microphone technology has been used in new products and solutions developed by AT&T intelligent acoustic systems for the PC multimedia industry.
Predictability of acoustical effects of microphone ports in the telecommunications equipment.
Authors: Yeager David M.
Published: October 2005

Low-cost electret microphones are ubiquitous in telecommunications equipment. They are capable of providing nearly ideal response, while often employed as point receivers. However, uniform response is not always optimal, especially for digital applications or microphone arrays, nor is it easily achievable given mechanical packaging constraints. It is therefore essential for a given design to incorporate frequency-dependent effects of the microphone housing. Frequency shaping is typically done electrically, but acoustical filters can be realized by appropriate selection of series or parallel cavities at the microphone. Damping must be accounted for by estimating thermal-viscous effects of the cavity openings, or by introducing flow-resistive materials for which acoustical parameters are known or can be measured. The frequency effects of microphone housing geometries can be modeled using any one of several techniques, the choice dictated by the desired accuracy, complexity of the physical realization, and available resources. In this paper, two prediction methods will be discussed. First, classical lumped- and distributed-element models will be described along with analyses obtained using MATLAB. Second, some preliminary results of numerical models using boundary or finite element methods will be presented.
Acoustic echo cancellation by short-time Fourier transform and cross-spectrum processing.
Authors: Okuno Takatoshi , Nakajima Hirofumi , Tohyama Mikio , Yanagawa Hirofumi
Published: October 2005

Acoustic echo cancellers have problems in estimating room transfer functions (TFs) for acoustic echo paths when the conditions are noisy in the acoustic space. In this article, the possibility of estimating the room TFs is investigated by taking a time-frame-averaged cross spectrum(CS) between the input signals and error signals, which are composed of echo signals through the echo path and the surrounding noise. First, the short-time Fourier transforms (STFTs) and cross spectrum for both the input and error signals are taken. The TFs can be estimated from the ratio of the CS to the power spectrum of the input signal, since it can be expected that the time-frame-averaged CS components between the input signal and the surrounding noise will be zero. It was reconfirmed by computer simulation that the echo signals can be suppressed as the averaging process goes on, even in noisy conditions. The room TFs could be estimated as long as the S/N ratio was about 10 dB. This STFT-CS method requires more calculations than a time domain method, such as the RLS method; however, it can be implemented using general purpose FFT boards. Adaptation for rapid TF changes is going to be investigated in the near future.
Simulation and cancellation of echoes in a reverberant room.
Authors: Mehta Vineet , Lai Ming-Yi , Thompson Charles
Published: October 2005

The evolution of voice communications technology promises high-fidelity teleconferencing systems without encumbering the user with hand-held devices. The freedom of movement provided by hands-free devices yields dynamic acoustic environments and allows for greater separation between source and receiver. Furthermore, these teleconferencing environments may feature communication over multiple audio channels. The sound quality in such environments is typically degraded due to acoustic reflections from nearby walls, people, and objects. These undesired echoes must be removed if one is to maintain a high sound quality. In this work the problem of acoustic echo cancellation is examined. The technique for acoustic echo cancellation is based on sub-band decomposition. For a reverberant room, the source to receiver impulse response is computed by an image- based method. The influence of scattering from objects with high acoustical contrast is computed by a Padé approximants based method. A model for the impulse response resulting from nonideal images, frequency-dependent wall impedance and acoustic scattering is presented. Results compare single and multiple scattering effects. The variations in scattering amplitude due to scatterer motion are examined. The impact of these features on echo-canceller performance is evaluated.
Sound velocity measurements in mixtures of air bubbles in castor oil.
Authors: Day Colin P. , Korman Murray S.
Published: October 2005

Experimental measurements of the phase speed are performed in a medium of air bubbles in castor oil. Castor oil has been chosen as the host liquid due to both its density and sound speed being closely matched to that of water. The viscosity of castor oil is about 1000 times greater than water which allows bubbles to rise relatively slowly in a cylindrical container. The phase speed will be measured in an apparatus similar to the standing wave tube setup reported by E. Silberman [J. Acoust. Soc. Am. 29, 925–933 (1957)]. We are interested in comparing our results with the phase speed theory that was reported by K. W. Commander and A. Prosperetti [J. Acoust. Soc. Am. 85, 732–746 (1989)]. The volume void fraction β (of air volume to total mixture volume) is estimated by electronic measurements which involve measuring the capacitance of a cylindrical coaxial capacitor in air, in oil, and in bubbly oil.
A transmission-line model of the vocal tract during fricative production.
Authors: Ibarra Jesse
Published: October 2005

The purpose of this study is to examine the articulatory-to-acoustic mapping of the fricatives /s,sh,z,f,v,th/. The study utilizes MRI-derived vocal-tract area functions for two subjects [Narayanan et al., J. Acoust. Soc. Am. 98, 1325–1347 (1995)] and an articulatory synthesizer that is based on the analog circuit simulator HSPICE. The synthesizer [Rael et al., J. Acoust. Soc. Am. 97, 3430(A) (1995)] uses a transmission-line analog model of the vocal tract with the specification of the type and location of dependent or independent sources (voltage or current). Modeling involved placing noise sources in the vicinity of the maximum constriction and at other locations in the vocal tract. A voicing source (KLGLOTT88) was used for the voiced fricatives. Synthesized spectra matched naturally spoken spectra of /s,sh,v,z/ by placing two or three voltage sources near the constriction and near the lips for /s,z,v/, and at 1.2 cm away from the lips for /sh/. The current (monopole) source was not useful in synthesizing these fricatives. Results for /v,z/ were satisfactory using both voicing and noise sources even though /v/ was spectrally flat above 1.5 kHz. The model did not successfully synthesize /f,th/; this may be attributed to the seemingly more complex radiative and turbulent behavior for these sounds. [Work supported by NSF.]
Undergraduate research projects in noise and vibration control courses.
Authors: Mongeau L. , Jones J. D.
Published: October 2005

The integration of projects in undergraduate noise and vibration control courses allows the students to creatively apply the course material to practical problems. The projects also provide the opportunity to investigate some technologies and concepts that are beyond the scope of the lecture material. For a number of years, interdisciplinary projects have been realized in the context of the noise and vibration control courses offered by the School of Mechanical Engineering at Purdue University. Juniors and seniors in mechanical, electrical, and industrial engineering work in teams of three to five students. The objectives of each team are defined in collaboration with selected faculty members and practicing engineers from the local industry, designated as ‘‘customers.’’ The projects culminate during the last week of class with oral presentations from each team. In this poster session, the results of selected student research projects realized during the last few years will be presented.
Modern noise and vibration design of internal combustion engines.
Authors: Albright Michael F.
Published: October 2005

In recent years, new engine design for the transportation industry has occurred in an atmosphere of strict compliance with aggressive noise and vibration performance targets. The inevitable result is a growing arsenal of tools, methodologies, and experience in the design of quiet, smooth, high-performance engines. In this discussion, some of the key issues facing engine designers responsible for noise and vibration performance will be introduced. The discussion will focus on the application of some of the newest experimental and analytical tools which are applied to such complex issues as combustion noise, crankshaft to block interaction, valvetrain, and piston to cylinder contact forces. A particular emphasis will be placed on recent developments in combustion noise control and the future of the wholly analytical engine noise and vibration signature simulation model.
A survey of automobile wind noise.
Authors: George Albert R. , Callister John R.
Published: October 2005

The study of automobile aerodynamic noise is a field that has grown rapidly in the past decade. Automobile manufacturers and independent researchers now have a better understanding of the mechanisms of automobile aerodynamic noise. Methods of making wind noise measurements have been improved. Some fundamental wind noise reduction measures have been developed. In this paper, the basic mechanisms of automobile aerodynamic noise generation are explained. Current wind noise measurement instrumentation and techniques are reviewed. Some wind noise reduction measures found on today’s automobiles are discussed. Finally, a prediction method for an idealized case of automobile aerodynamic noise is shown. Knowledge of these advances will help automobile manufacturers to design quieter vehicles.
Vehicle interior noise. I. Noise paths: Structure-borne and airborne.
Authors: Parrett Alan V. , DeJong Richard G.
Published: October 2005

This paper gives an overview of vehicle interior noise, its characteristics, and control methods. There is a wide variety of noise problems encountered in automobiles due to the sources involved and the range of operating conditions. Depending on these operating conditions, either airborne or structure-borne noise can be dominant. The complexities of automotive structures mean that a variety of analysis techniques needs to be applied to the problems, from the early design stage through to vehicle hardware development. These include both analytical and empirical methods. Examples are given of automotive airborne and structure-borne noise problems in a source, path, receiver framework. Source characteristics (tonal or broadband), problem frequencies, available analysis techniques, and practical solution methods are discussed. Solutions include quieting the source, using isolation at mounting points, and damping and trim materials in the vehicle interior. In practical terms, noise control solutions need to be balanced to comply with overall vehicle cost, mass, and other performance constraints.
The acoustic characteristics of automotive body seals.
Authors: Danforth Robert , Mongeau Luc
Published: October 2005

The acoustic characteristics of rubber primary bulb weather seals, used around road vehicle doors to isolate the passenger compartment from water infiltration and air leaks, were investigated experimentally. Short seal samples were mounted within the test section floor of a small, quiet, low-speed wind tunnel adjacent to a soundproof anechoic enclosure. The geometry of the fixture hosting the samples approximated that of a typical vehicle door gap. The results demonstrated the importance of small air leaks and that of the flow-induced Helmholtz resonance of the door cavity on the acoustic performance of the seal assembly. The noise reduction of perfectly sealed systems appeared to be slightly higher with a flow excitation than that measured with a random acoustic excitation using a reverberation room method. The experimental results were compared to the predictions from a two-dimensional lumped-element analytical model based on the assumption that the seal behaves like two limp membranes separated by a closed cavity. The influence of seal compression, rubber properties, and cavity geometry were investigated. [Work supported by Cooper Tire and Rubber Company.]
A model for predicting roughness of powertrain sound.
Authors: Feng B. John , Wakefield Gregory H. , Otto Norman C.
Published: October 2005

The semantic dimension of rough/smooth can be an important factor in customer preference of automotive powertrain sound. With this in mind, a new model is proposed for predicting roughness of powertrain sound. The model performs a signal decomposition into critical bandwidth channels, specific roughness prediction for each channel, and a combination of specific roughness across frequency to yield an overall roughness measure. Signal decomposition is performed with a bank of overlapped, critical bandwidth, bandpass filters. Because the signal in each channel is well represented by a small number of harmonically related, narrow-band components, it is assumed that specific roughness can be determined from the peaks in the magnitude spectrum of the envelope signal. A masked threshold estimate from the input signal is used to predict audibility of envelope fluctuation in each filterbank channel. Channels whose envelope fluctuation falls below threshold are assumed not to contribute to overall roughness, and are therefore discarded. Specific roughness values of the remaining channels are combined with a power-law model, yielding an overall roughness measure [E. Terhardt, Acustica 30, 201–213 (1974)]. Results of subjective tests of powertrain sounds are presented which validate the performance of the model. [Work supported by Ford Motor Company.]
Magnetic resonance imaging guided and monitored ultrasound surgery.
Authors: Hynynen Kullervo
Published: October 2005

During the past few years there has been an interest in using magnetic resonance imaging (MRI) to guide focused ultrasound beams during noninvasive surgery. MRI offers good soft tissue contrast, allowing the beam to be accurately aimed. Temperature sensitive MRI sequences can be used during low power test pulses to visualize the temperature elevation in the focal zone at temperature levels that do not cause tissue damage. This allows the beam to be aimed, eliminating all potential image or ultrasound propagation distortions. It may even be possible to calibrate the MRI signal to give the temperature elevation and use it as a feedback to modify the power output to assure adequate thermal exposure during every therapy sonication. Finally, MRI allows tissue changes induced by the sonication to be detected. This may be useful after the treatment to establish the boundaries of the thermal damage and is also very useful when experiments are conducted. All of these aspects of MRI guided ultrasound surgery have been investigated using in vivo experiments and the results will be reviewed here. The future technical developments and potential clinical applications will be discussed. [Work supported by NIH and General Electric Medical Systems.]
Renal injury induced by clinical doses of shock waves.
Authors: Evan Andrew P. , Willis Lynn R. , Connors Bret A. , Trout Anne , Lingeman James E.
Published: October 2005

Both clinical and experimental reports clearly show that shock wave lithotripsy (SWL) causes acute renal effects in a majority, if not all, treated kidneys. SWL-induced acute renal damage results in injury to the nephron, microvasculature, and surrounding interstitium. What has not been established is a set of objectively determined criteria for the safe clinical use of SWL. To accomplish this goal, animal experimentation has been conducted so that the time course and severity of acute alterations could be followed in a model that closely mimics human kidney. We chose the pig to determine the effect (or risk) of the size of the kidney and/or the number of treatments during the same session on the severity of the change in renal hemodynamics. Our data shows the greatest degree of change was induced in the kidney with the least mass and receiving multiple treatments. [Work supported by NIH.]
Damage to tissue-like structure by wrinkled focused shock waves.
Authors: Howard Danny D. , Sturtevant Bradford
Published: October 2005

Shock waves are focused in extracorporeal shock wave lithotripsy (ESWL) machines to strengths sufficient to fracture kidney stones. Substantial side effects—most of them acute—have resulted from this procedure, including injury to soft tissue. The focusing of shock waves through various layers of tissue is a complex process which stimulates many bio-mechano-chemical responses. This paper presents preliminary results of an in vitro study of the initial mechanical stimulus. Planar nitrocellulose membranes of order 10 μm thick were used as models of thin tissue structures. Scattering media were used to simulate the effects of acoustic nonuniformity of tissue and to alter the structure of focusing shock waves. Hollow glass spheres of 65 μm diameter were added to ethylene glycol, glycerin, and castor oil to vary the properties of the scattering media. Multiple layer samples of various types of phantom tissue were tested in degassed castor oil to gage the validity of the scattering media. The scattering media and tissue samples wrinkled the shock structure in a similar fashion. Membranes were damaged by shear stress induced by the altered structure: after about 20 shocks immersed in the scattering media and after about 100 shocks behind the tissue samples. The mode of failure was in shear with multiple tears about 0.1 cm to about 3 cm depending on the number of shocks and membrane thickness. [Work supported by NIH Grant P01 DK43881-01A3.]
Application of geometrical shock dynamics to weak shock focusing in extracorporeal shock wave lithotripsy.
Authors: Cates Joseph E. , Sturtevant B.
Published: October 2005

In extracorporeal shock wave lithotripsy (ESWL), weak converging shock waves are focused to shatter kidney stones. Accurate knowledge of the flow field in the focal region is required to understand the source of tissue damage and the primary mechanisms of stone fragmentation. A finite-difference numerical method for geometrical shock dynamics has been developed and used to evaluate the accuracy of this approximate theory for the complex nonlinear processes which occur in shock focusing. The shock dynamics results duplicate the strong, moderate, and weak shock behaviors seen in experiments [B. Sturtevant and V.A. Kulkarny, JFM, 73, 651–671], with good agreement for focal pressures and triple-point path. Similar behavior is observed for the ESWL problem of axisymmetric shock focusing in water. The primary source of error is the fact that shock dynamics always yields Mach reflection at the centerline, so regular reflection in the theory is impossible. Adequate resolution of the focal region is necessary to assess the accuracy of the shock dynamics theory, or of any other theory. The shock dynamics theory and numerical method have also been extended to the more general case of shock propagation into a nonuniform media with free-stream velocity.
Robert T. Beyer from his students’ perspective.
Authors: Moffett Mark B. , Letcher Stephen V.
Published: October 2005

Professor Robert T. Beyer guided 20 Ph.D. students and 9 Sc.M. students during his career at Brown University. He did a masterful job of preparing his students for successful careers in teaching and research. His genial, outgoing personality ensured good communication with even the introverts among them and his relaxed style (and the close quarters during the Wilson Hall days) encouraged interactions among the students; they often learned the tricks of the ultrasonics trade from each other. He kept a close watch, however, and when he determined that a student was ready to present his first paper at an Acoustical Society meeting (often before the student considered himself ready), he strongly encouraged it and instilled the confidence needed for the task. He personally introduced his students to many of the Society’s members, resulting in lifelong friendships and collaborations. Although none of Bob Beyer’s students ever succeeded in emulating his ability to tell a story or a joke, they all have benefited greatly from their association with him.
Robert T. Beyer’s contributions in ultrasonics.
Authors: Letcher Stephen V.
Published: October 2005

Robert T. Beyer was a major contributor to our understanding of ultrasonic relaxation processes in liquids and solids during the heyday of that field. One could argue that this period ran roughly from the time of his major review article in 1951 [J. J. Markham, R. T. Beyer, and R. B. Lindsay, Rev. Mod. Phys. 23, 353–411 (1951)] until his monograph in 1969 [R. T. Beyer and S. V. Letcher, Physical Ultrasonics (Academic, New York, 1969)]. He adopted and extended new measurement techniques of ultrasonic attenuation and used them to advance our understanding of relaxation processes in liquified gases, in water and aqueous solutions, in organic liquids and organic single crystals, and in liquid metals.
R. T. Beyer’s contributions to nonlinear acoustics.
Authors: Blackstock David T.
Published: October 2005

Except for a review article on radiation pressure [Am. J. Phys. (1950)], Robert T. Beyer’s earliest research in nonlinear acoustics was on the increase of absorption with intensity for water and other liquids [J. Acoust. Soc. Am. (1956) (1957), and Sov. Phys.–Acoustics (1958)]. New directions soon followed: the experimental work on the parametric array [Belli et al., J. Acoust. Soc. Am. (1960) (A)], the Keck–Beyer perturbation solution for finite-amplitude waves in a viscous liquid [Phys. Fluids (1960)], and calculation of the parameter of nonlinearity B/A [J. Acoust. Soc. Am. (1960)]. Continuation and expansion of the latter work made Bob the foremost authority on B/A. Later interests include nonlinear effects in the field of a piston radiator [Ryan et al., J. Acoust. Soc. Am. (1962)], finite-amplitude propagation in a relaxing fluid, self-demodulation of a pulse [Moffett et al., J. Acoust. Soc. Am. (1970, 1971)], and various aspects of the crossed beams problem [J. Acoust. Soc. Am. (1970–1982)]. To these specific contributions must be added Beyer’s book Nonlinear Acoustics and several review articles in handbooks and journals.
Beyer on Beyer.
Authors: Beyer Robert T.
Published: October 2005

Reflections.