bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of vocal tract on aerodynamics of hemilarynx
Authors: Alipour Fariborz , Montequin Douglas , Tayama Niro
Published: July 2002

Pressure-flow relationship was examined in the excised canine and human larynges with and without vocal tract. Canine and human larynges were prepared and cut in the midsaggital plane from the top to about 10 mm below the vocal folds. The right half was removed and replaced with a Plexiglas plate with imbedded pressure taps along the medial surface. The thyroid cartilage was glued to the plate and the arytenoid was pressed against the plate with a two-pronged probe for adduction control. The vocal tract was simulated with a 15-cm plastic tube of 25-mm diameter. Simultaneous recordings were made of the glottal pressure, mean subglottal pressure, and average airflow at various levels of adduction. Glottal adduction was controlled mechanically by inserting shims of various sizes. Oscillation was generated by the flow of heated and humidified air through the glottis. Preliminary data indicate that the pressure-flow relationships are similar to those of full larynx and are almost linear. The addition of the vocal tract increased the glottal resistance by moving these pressure-flow lines to the lower flow and higher-pressure region. The human larynx appears to phonate easier on the bench and has lower phonation threshold pressure. [Work supported by NIDCD grant DC03566.]
On estimating length and shape of the vocal tract
Authors: Neuburg Edward P.
Published: July 2002

Automatic vowel recognition is sometimes done by trying to estimate vocal-tract areas, usually derived using linear predictive coding. In the derivation there is a free parameter, namely, the length of the vocal tract; every choice of length leads to a different set of areas. This paper describes a revisit to experiments done in the early 1970s, in which the chosen length is the one that makes the vocal-tract shape most ‘‘human.’’ Using some improved criteria for optimality of shape, involving both smoothness and small variance, it is found that: (a) estimates of vocal-tract length are consistent, or at least highly correlated, with actual length; and (b) the tube shape (area function) derived using the optimal length seems to give a reliable characterization of the vowel, independent of the talker (and, in particular, independent of the talker’s gender). Classification results are about the same as those using the currently popular cepstral coefficients, but areas have the possible advantage that they are physiological features that the talker can actually control.
An interactive atlas of English vowels: Design considerations
Authors: Hagiwara Robert , Hargus Sharon , Wright Richard , Sterling Isaac
Published: July 2002

Discussions of vowel quality differences in dialects of English are often based on imprecise, subjective descriptors (more open, slightly less back) and transcriptions rather than instrumental measurements. Available instrumental data focus on individual dialects rather than a broader picture of dialectal variation. In part to address these concerns, a database of vowel formant frequencies is currently being developed at the University of Washington, beginning with a sampling of static formant frequencies in the American West. The ultimate intent is to produce a web-based, expandable database, or atlas, of reference English vowel formant frequencies and audio examples. It is intended primarily as a pedagogical tool to accurately demonstrate vowel quality variation, and as a ‘‘jumping off point’’ for more intensive studies of acoustic variation. This poster discusses long- and short-term goals of the project, current data, the standardized methodology being used, web tools being developed, and the possibilities for future collaboration in data collection and analysis.
Possible perceptual cues for accent distinction in whispered speech—A case of an aphonic child
Authors: Hirai Sawako , Kobayashi Noriko , Hirose Hajime
Published: July 2002

Japanese word accent is associated with pitch change and F0 change is its major perceptual cue. In whispered speech, however, F0 is absent. We experienced a 10-year-old boy who had been using only whispered speech since birth, although he had no apparent physiological or psychological problems. After voice therapy, he started using voiced speech, but accent distinctions were poorly perceived in his voiced speech, while his whispered speech appeared to have better accent pattern variations. The purpose of this study was to find out the acoustic characteristics and perceptual cues produced by the child to make word accent distinctions in his voiced and whispered speech. The subject produced a vowel sequence /aa/ with different accent patterns. The results showed that accent distinctions were correctly perceived by listeners in both conditions, and that F1 change was significantly larger in whispered utterances than in voiced ones. The present result appeared to support the hypothesis of Higashikawa et al. (1997) that F1 change played a principal role in accent distinction in whispered speech. It was assumed that when the major cue (F0 change) was not available, another possible cut, F1 change, was exaggerated.
The relation between infant speech perception and early communicative development: A longitudinal study
Authors: Liu Huei-Mei , Tsao Feng-Ming , Stevens Erica B. , Kuhl Patricia K.
Published: July 2002

This study investigated the correlation between speech discrimination in young infants and early communicative development. The MacArthur Communicative Development Inventory, a parent-report measure of words and gestures, was administered to 20 13-month-old infants who had participated in a study of speech discrimination when they were 6 months old. In the earlier study, the conditioned Head-Turn (HT) technique was used to assess infants’ discrimination of the Finnish vowels /i/ and /y/. Infants were required to meet a criterion of seven out of eight correct responses prior to completing a 30-trial test phase. Results showed that the number of trials infants needed to meet the criterion at 6 months of age was significantly negatively correlated at 13 months with the number of phrases understood (−0.662) and words understood (−0.700). In a regression analysis, the number of criterion trials was shown to be moderately predictive of later communicative development, accounting for approximately 40% and 45% of the variance in phrases understood and words understood. The development of these children will be followed with a second administration of The MacArthur Communicative Development Inventory when they are 16 months of age, to further map the relationship between infant speech perception and early communicative development.
Effects of a computer-based voice modification device for a speaker with recurrent nerve paralysis
Authors: Kobayashi Noriko , Hirose Hajime , Matsui Kenji , Hara Noriyo
Published: July 2002

Patients with unilateral recurrent laryngeal nerve (RNL) paralysis may exhibit severe dysphonia depending on the resting position of the affected vocal fold. Major vocal symptoms of these patients are breathy voice, decreased vocal intensity, and physical fatigue due to great effort to approximate the vocal folds and to increase subglottal pressure. In some cases, phonosurgery is not applicable due to other medical problems, while a good prognosis is not expected by voice therapy. Technological assistance may be needed for such a patient. In this study, a real-time formant analysis-synthesis method was used to enhance speech intelligibility of a severely dysphonic patient with unilateral RNL paralysis. The voice source was modified by using inverse-filtered signals extracted from a normal speaker. A special hardware unit was designed to perform an analysis-synthesis process with temporal delay of 40 ms for signal processing. Vowels and sentences produced by the subject both with and without the device were analyzed. An approximately 20 dB increase of overall loudness level and increased harmonic components were observed for the processed speech. Perceptual judgment revealed improved speech intelligibility and less breathy voice quality for the processed speech. The subject reported less fatigue with the device as less effort was required for phonation.
Wavelet domain system/channel characterization
Authors: Young Randy
Published: July 2002

The primary operators in implementing wavelet transforms are the delay, scale, and correlation operators. The physical motion of sources and sensors causes signals to be compressed or dilated (scaled) depending upon their relative direction of motion. For many systems that use a signal modulation with a carrier frequency, this scaling operator leads to a Doppler shift of the carrier. For many acoustic signals (voice, machinery vibrations, structural vibrations, biomedical signals, etc.), they are not carrier-frequency modulated and they possess a large relative bandwidth. Additionally, the relatively slow propagation speeds compared to source/sensor motion leads to much higher compression/dilation ratios than in electromagnetics. Since scaling applies a different Doppler to each frequency, large bandwidth signals experiencing scaling are not well approximated by a single Doppler shift. Thus, the scaling operation, and, therefore, wavelet transforms are more applicable in acoustic analysis/system modeling than electromagnetic analysis. This discussion concentrates on the wavelet transform as an operator utilizing scaling, rather than a signal decomposition technique. Although wavelet transforms as signal decomposition tools have been extensively researched, their contribution as a system/channel analyzer for estimating motion of sources/sensors/environments is less developed. [Nancy Harned, ONR321US, is acknowledged for supporting this work (Contract N00039-97-D-0042).]
Wavelet processing for wideband spreading function estimation
Authors: Weiss Lora G.
Published: July 2002

The statistic used to quantify the amount of environmental spreading a signal undergoes as it traverses through a channel is called a spreading function, and it includes the effects of moving, distributed scattering objects, multipath, boundary effects, etc., on the signal. Traditionally, narrow-band signals have been transmitted, and the spreading functions were estimated by calculating the outputs of narrow-band-matched filters. Now that wideband processing has become more accessible, we need a solid concept of estimating wideband spreading functions. This paper shows that a wideband spreading function can be estimated by computing the wavelet transform of the received signal while using the transmitted signal as the mother wavelet. The paper then computes the second-order statistic, called the wideband scattering function, associated with the wideband spreading function. To assess the total scattering, several scattering functions are convolved to yield an overall representation of the environment. This representation can then be incorporated into a detection processor. The payoff is that if any portion of the scattering environment is known a priori, this information can be exploited in the detector. As knowledge of the scattering process is acquired, it is combined via the cascaded scattering function formulation.
Application of wavelets to scattering for wave-packet synthesis
Authors: Gaumond Charles F. , Drumheller David M.
Published: July 2002

The wavelet transform can be used to analyze the time-scale domain structure of echoes derived from broadband, monostatic, acoustic scattering from ribbed shells. In the time-scale domain, the echoes can be seen to be composed primarily of a few individual components. Each component corresponds to a separate physical scattering mechanism in the shell. Yen has called these separated components wave packets, each having distinctive time-scale dimensions that derive from the physical process that generates it. Because each wave packet has distinctive time-scale domain properties and the wavelet transform is invertible, the wavelet transform can be used to isolate and synthesize a set of wave packets. The resulting wave packets are functions of aspect and time. Greater efficiency of representation can be achieved by representing these wave packets with a bilinear expansion. Wave packets generated with the wavelet transform can be used for matched filter detection. [Work supported by the Office of Naval Research.]
A software package calculating zones of impact on marine mammals around industrial noise sources
Authors: Erbe Christine , Farmer David M.
Published: July 2002

A software package is presented which estimates zones of interference around underwater noise sources affecting marine mammals. An ocean sound propagation model based on ray theory computes the spreading of complex underwater sound such as broadband animal vocalizations and manmade noise. On a grid of receiver locations (representing the affected marine mammal), the received signal and noise sound spectra are compared. Given a species-specific audiogram, the software package plots zones of audibility around the noise source. Given species-specific vocalizations, zones of masking are plotted based on results obtained during an earlier study which measured masked hearing thresholds of a beluga whale. Tools developed during this study (such as an artificial neural network model to predict the amount of masking) can be linked to the software package. Zones of behavioral disturbance are plotted based on received sound levels reported in the literature. Zones of discomfort, injury, and hearing loss could be plotted if thresholds were known or using current estimates. The software package is applicable to a variety of ocean environments requiring location-specific oceanographic input data. The case of icebreakers affecting beluga whales in the Beaufort Sea is demonstrated.
Acoustics of Karen bronze drums
Authors: Nickerson Laura M. , Rossing Thomas D.
Published: July 2002

Bronze drums are important to the culture of the Karen people, who live mainly in Burma and the mountainous region between Burma and Thailand. A Karen bronze drum, which is cast in one piece except for the animal adornments, consists of an overlapping tympanum that may range from 9–30 in. in diameter and a cylinder that is slightly longer than the diameter. Bronze drums have a wide variety of ritual use, both musical and nonmusical. The sound spectrum of a drum shows a dense collection of partials out to about 3 kHz. The corresponding modes of vibration, recorded using electronic TV holography, sometimes show the strongest vibration in the tympanum and sometimes in the cylindrical shell. The sound of the drum and the manner of playing will be illustrated by videotape.
Ultrasound field correction in trans-skull ultrasound surgery using a focused array
Authors: Clement Gregory , Sun Jie , Giesecke Tonia , Hynynen Kullervo
Published: July 2002

Correction of the distortion due to diffraction, reflection, and attenuation in trans-skull ultrasound propagation is investigated. Human skull fragments are positioned between an underwater focused transducer array and a PVDF needle hydrophone. A positioning system is used to scan the hydrophone along a plane normal to the transducer face to provide amplitude and phase delay information as a function of position. The hydrophone measurements are then used to manually correct the driving signal phase of each element in the array. The field is remeasured and the correction evaluated in terms of the obtained focus and the occurrence of grating lobes. The measurements are repeated at different orientations about each skull sample. Finally, skull information is obtained using MRI and CT scans. Variation of the measured ultrasound field as a function of skull thickness, density, and transducer location is examined.
Minimum point search method for improvements in absolute calibration of accelerometers at high frequencies using the fringe-disappearance method
Authors: Wu Lixue
Published: July 2002

The measurement uncertainty in the absolute calibration of accelerometers at high frequencies using the fringe-disappearance method was reduced by a minimum point search method. Outputs of a bandpass filtered photodetector and an accelerometer were simultaneously recorded by two true rms digital voltmeters. Displacement amplitudes were finely controlled by a precision attenuator. Minimum points of the output of the photodetector and the corresponding sensitivities of the accelerometer were found from the recorded data. During data processing, a simple model for the minimum points was proposed and a least mean squares algorithm was used to estimate parameters of the model. Results of calibrations were compared with these obtained using fringe-counting method at lower frequencies. It was found that the minimum point search method could compare with the fringe-counting method in measurement uncertainties. Good measurement reproducibility was also observed that resulted in the reduction of total measurement uncertainty.
Rhythm, expectancy, and time judgments: Some ‘‘surprising’’ results
Authors: McAuley J. Devin
Published: July 2002

A series of time-judgment experiments were performed that manipulated the beginning and ending of a to-be-remembered time interval (the standard) relative to a preceding rhythmic context. Beginning and ending times of the tones marking out the standard were examined for conditions that were on-time, early, and late, relative to the implied beat of the context tones. Consistent with an entrainment model, time judgments about the standard time interval showed a ‘‘shorter’’ perceptual bias in early conditions and a ‘‘longer’’ perceptual bias in late conditions, and an overall expectancy profile, with better performance observed when the standard was on-time than when it was early or late. The most interesting feature of the data was an unexpected interaction between the beginnings and ending manipulations. Interpreted with respect to the entrainment model, the interaction suggests that a tracking oscillator’s phase is more affected by unexpected beginnings, whereas its period is more affected by unexpected endings.
A novel technique for the prediction of the displacement of a line-driven plate with discontinuities
Authors: DiPerna Daniel , Feit David
Published: July 2002

A novel technique is presented for obtaining approximate analytic expressions for an inhomogeneous line-driven plate. The equation of motion for the inhomogeneous plate is transformed, and the transform of the total displacement is written as a sum of the solution for a homogeneous line-driven plate plus a term due to the inhomogeneity. This expression may in general be solved numerically. However, by introducing a small parameter into the problem, it may be solved approximately using perturbation techniques. This series may not be convergent, but its convergence may be improved using the Padé approximation. Results are presented for the case of an inhomogeneity concentrated at a single point, and a distribution of points along the line-driven plate. [Work sponsored by the CDSNWC ILIR program and ONR, Code 334.]
Multimedia model for speech transmission through walls
Authors: Su Jiann-Ming , Ginsberg J. H.
Published: July 2002

The paper will describe how an algorithm previously developed to study the distortion of a planar stress wave as it propagates at normal incidence through a multi-layered wall was adapted to study transmission of speech signals. The algorithm is a time domain numerical implementation of the method of characteristics [Ginsberg and Kim, J. Appl. Mech. 11(2), S145–S151 (1992)]. The algorithm is used to produce a digitized waveform of the exiting signal corresponding to an incident signal consisting of a speech fragment. To assess the effects of distortion resulting from internal reflections, a speech pattern is digitized with the aid of standard multimedia tools and used as the input to the transmission algorithm. The transmitted signal is computed and converted to a convenient audio format for playback. To ensure that distortion in the output signal is truly the effect of the medium, the signal is processed again using a noise reduction routine developed by Boll [IEEE Trans. ASSP ASSP-27(2), 113–120 (1979)]. In a blind test, listeners are requested to identify, from both the raw and processed output, the original speech fragment. A demonstration will conclude the presentation.
Acoustic responses of Baleen whales to low-frequency, man-made sounds
Authors: Clark Christopher W. , Tyack Peter L. , Ellison William T.
Published: July 2002

In the last 5 years, two projects were undertaken to evaluate impacts of man-made sounds on whales. Baleen whales were identified as ‘‘at risk’’ because of their use of low-frequency sound for communication, their endangered status, and studies showing responses to continuous noises at exposure levels >120 dB, re: 1 μPa. To evaluate the potential impact of operational ATOC (195-dB source intensity), humpback whales off Kauai were studied during the breeding season. To evaluate the potential impact of U.S. Navy SURTASS LFA sonar, playback experiments were conducted on four species at exposures of 120–155 dB. LFA research was designed to obtain responses during feeding (blue and fin whales, southern California, September–October), migration (gray whales, central California, January) and breeding (humpbacks, Hawaii, March). For the ATOC source, humpbacks showed statistically significant but subtle responses over small time and spatial scales. There were no changes in singing, or larger-scale changes in distribution or relative numbers. For LFA experiments off southern California, whales did not change vocal rates or leave the testing area, and there were no immediately observable responses, even at exposure levels up to 150 dB. Tyack (this session) will discuss results from the gray and humpback whale LFA experiments.
Modeling cetacean ear filters by means of evolutionary computation
Authors: Houser Dorian S. , Helweg David A. , Moore Patrick W. B. , Chellapilla Kumar
Published: July 2002

Modeling cetacean hearing is an important step in advancing models of echolocation and in predicting the potential impact of oceanic noise upon cetaceans. Modeling the response of cetacean ears to acoustic input can be a difficult task and the performance of such models is often sub-optimal. Evolutionary programming was employed as a systematic method of optimizing the response of a bank of pseudo-Gaussian filter shapes to known audiometric functions in order to model the resonant systems of the basilar membrane. The response of the filter banks was tested against normalized audiograms of the bottlenose dolphin (Tursiops truncatus) and the predicted frequency dependent sensitivity of the Humpback whale (Megaptera novaeangliae). Filter banks were created that demonstrated comparable frequency responses to tonal stimuli across the (predicted) range of hearing in both species. The potential for incorporating these ear models into models of echolocation and their use in predicting the sensitivity of baleen whales to manmade noise will be discussed.
Learning to sing a novel piece of music facilitates playing it on the violin but not the other way around: Evidence from performance segmentations
Authors: Drake Carolyn , McAdams Stephen , Berthoz Alain
Published: July 2002

Twelve 11- to 14-year-old music students learned to perform a novel piece of music, six on the violin (initial-violinists), six singing (initial-singers), with one recording per week for five weeks. Then, without prior warning, they performed the same piece on the other instrument (sung if they had learned on the violin and visa versa). All performance measures improved over the first five performances: fewer errors, faster, and comprised of fewer, longer, more musically valid segments (as indicated by final-group lengthening). Seven children (five initial-singers, two initial-violinists) demonstrated transfer (performances did not deteriorate after changing instrument), five children (one initial-singer, four initial-violinists) did not (performance deteriorated after changing instrument). The children who transferred successfully performed slower and made more errors than those that did not transfer successfully, but their segmentations demonstrated more hierarchically structured mental representations. Thus, learning mode influenced the creation of the mental representation. Singing, an easy motor task, enables children to concentrate on musical structure and therefore to create musically appropriate mental representations specific to the music rather than the motor task, allowing transfer to other motor tasks. However, playing the violin, a complex motor task, results in task-specific representations, difficult to transfer to other motor tasks.
Physics, phonetics, and physiology of the diatonic harmonica
Authors: Antaki James F. , Bahnson Henry T. , Beery Quinter C.
Published: July 2002

The harmonica is arguably the most widely played instrument in the world, yet there is a surprising scarcity of published studies of its acoustics or physical dynamics. The typical diatonic harmonica and the kinematics of its free reeds are described. The vibration of the reeds, naturally, when producing a bend, and when speaking as an overblow or overdraw is discussed and investigated by simple stopping of the reeds, by videostroboscopic analysis, and by high-fidelity displacement measurements. The reeds of the ten-hole harmonica can be made to vibrate at varying frequencies depending on the size and morphometry of the players vocal tract. Three different modes of speaking from each hole and its pair of reeds are revealed and studied: first, naturally in a closing mode, either blown or drawn; second, as a bend, either blown or drawn, with pitch in the interval between the two notes in the hole; and third, as an overblow or overdraw in an opening mode with a pitch outside the interval between the two natural notes of the hole. This dynamic interaction allows the player to speak with the instrument perhaps as with no other.
On the perception of free reed organ pipes
Authors: Braasch Jonas , Ahrens Christian
Published: July 2002

Sounds of three free reed organ stops were measured throughout the whole frequency range of the stops and compared to the measurements of a striking reed stop and a diapason stop. The steady sound spectra and the attack transients were analyzed and compared. As the results show, free reed pipes differ in a number of parameters. Especially the attack transients show characteristical differences in rise time, amplitude, and initial delays of the partial tones from striking reed pipes and diapason pipes. Interestingly, the rise time of the free reed pipes is comparable to those of the measured diapason pipes, although free reed pipes are often cited to have a sluggish attack transient. A psychoacoustic pair comparison test was conducted to eighteen listeners, using synthesized sounds with mixed acoustical properties of the different organ stops. The results show that the presence of the chiff of the diapason pipes leads to the perception of a shorter attack duration of the diapason pipes compared to the perceptual attack duration of free reed pipes. The importance of the chiff could be stated with, psychoacoustically motivated, rate of change of mag-log amplitude plots. The chiff caused the highest rate of change of the mag-log amplitude that was measured.
Modeling scattering from objects using a Kirchoff/diffraction method
Authors: Fawcett John A.
Published: July 2002

In this paper a facet-model based upon the Kirchoff approximation is derived for high-frequency scattering from rigid objects. In the case of objects with edges, the standard approximation is modified [M. Tran Van Nhieu, J. Acoust. Soc. Am. 99, 79–87 (1996)]. The resulting facet model is used to compute the backscattered time series from spheres and flat-ended cylinders, both smooth and with significant deterministic roughness. Analytical solutions and three-dimensional (azimuthally symmetric) boundary integral equation method solutions are used to benchmark the facet-model time series. Very good agreement between the facet model and the exact solutions are found, even for situations where the validity of the Kirchoff approximation is questionable.
Analytical/numerical description of sound field in irregular waveguides
Authors: Grinchenko Victor T.
Published: July 2002

The problems of the harmonic wave propagation in waveguides with varying cross sections and sound radiation from open ends of ones are considered. The main attention gives to development method of complete analytical description of the sound fields in both cases. This gives a basis to get accurate quantitative and qualitative description of the fields near the junctions of the waveguide cross sections and open ends. Numerical implementation of the general analytical formulas requires special procedures to be adequate the local singularities in vicinities of corner points. The approach is based on the introduction of the idea of the general solution of the acoustical boundary problem. The idea gives a way to construct analytical solutions for the problems under consideration and can be extended to a broad spectrum of radiation and scattering problems. The well known solutions for regular waveguides in the form of normal waves are used as important part of the general solutions. Numerical data for concrete waveguides demonstrate the accuracy and convergence rate of the method. Analysis of the data shows interesting physical properties of propagating waves, flows of energy, and local structure of sound field at the juncture of waveguide parts.
Acoustic signature measurements of a small submersible
Authors: Cuschieri Joseph M. , Vendittis David
Published: July 2002

In an effort to characterize the acoustic signature of a small autonomous submersible, the FAU Ocean Explorer (OEX) class AUV (autonomous underwater vehicle), measurements of the acoustic source level were performed in a reverberant tank, with the submersible held stationary, with and without the propeller. For comparison, source level measurements were also performed off-shore at the South Florida Test Facility (NSWC-CD), in Ft. Lauderdale, FL and at the Acoustic Research Detachment (NSWC-CD), Lake Pend Oreille in Bayview, ID. The results of these measurements show that because of the relatively slow rotational speed of the propeller, the acoustic signature is low, although distinct features in the signature are discrete tones, which seem to be coming from the propeller. In fact measurements of the acoustic signature under power were difficult to obtain even in low background noise environments. For this reason, the reverberant tank measurements present a very effective approach provided broadband information is sufficient and directivity information is not necessary. Results from these three sets of measurements will be presented, together with an analysis of what are potentially the significant sources contributing to the acoustic signature. [Work supported by ONR.]
Visualization of acoustic pressure fields radiated from a complex vibrating structure
Authors: Rayess Nassif , Wu Sean F.
Published: July 2002

This paper presents visualization of acoustic pressures radiated from a complex vibrating structure using the Helmholtz equation least-squares (HELS) method [Z. Wang and S. F. Wu, J. Acoust. Soc. Am. 102, 2020–2032 (1997); 104, 2054–2060, (1998)]. The structure under consideration has the same shape and dimension as those of a full-size vehicle front end. Random noises are generated by an engine noise simulator that consists of many loudspeakers of different sizes. The radiated acoustic pressures are measured a certain distance away from the vehicle surface, which are then taken as the input to a computer model based on HELS formulations. Experiments are conducted in a 12 ft by 12 ft by 6.5 ft fully anechoic chamber at the Acoustics, Vibration, and Noise Control Laboratory of Wayne State University. The reconstructed acoustic pressures on vehicle surfaces and in the field are compared with the measured data. Also shown are comparisons of the reconstructed and measured acoustic pressure spectra at various locations on the vehicle back surface. Results show that good agreement can be obtained with relatively few expansion terms over the low- to midfrequency range. The accuracy of reconstruction, however, decreases with the increase of frequency as expected. [Work supported by NSF.]
Acoustic propagation in strong surface ocean ducts. Scattering from elastic shells that excite the lowest-order symmetric Lamb mode and amplitude-modulated signals
Authors: Werby M. F.
Published: July 2002

The concept of group velocity is routinely used in terms of a mathematical construct but frequently confused with the actual physical process of energy transport. The origin comes either from using the stationary phase method in constructing the time domain from the frequency domain, from calculating sound signals at differing frequencies and identifying the arrivals with an envelop function, or by using wave-packet theory (usually in quantum mechanics) with something like Gaussian pulses centered about some carrier frequency. In many cases this definition of the derivative of angular frequency with respect to wave number is adequate and does characterize the arrival times of energy packets. There are cases for which such a definition is meaningless and occurs when the stationary phase method to first order breaks down. Usually when this happens the related pulse signal is amplitude modulated. Two examples are demonstrated. One has to do with wave propagation in which there is strong ducting at the ocean surface. The other occurs when scattering from an elastic shell, the first symmetric Lamb mode, is excited. In each case the results are atypical, surprising, and delightful. [Work sponsored by the Office of Naval Research and the Naval Research Laboratory.]
The size and generality of units in speech perception
Authors: Nearey Terrance M.
Published: July 2002

In English, the perception of syllables can be largely predicted from the perception of phonemes. Experiments reviewed by Allen [IEEE Trans. Speech and Aud. Proc. 2, 567–577] have consistently shown that the correct identification of nonsense CVC syllables in noise is extremely well predicted from the marginal identification rates of their constituent phonemes. Simulations suggest that this result can be easily achieved when syllable patterns can be ’factored’ into phoneme parts. Representations allowing even slightly idiosyncratic relationships between stimuli and syllables apparently cannot produce such results. Evidence for phoneme factorability is also provided by the results of certain parametric speech perception experiments. In such experiments, listeners hear synthetic syllables that span two or more categories of two or more segments (e.g., ‘‘bad,’’ ‘‘bet,’’ ‘‘bat,’’ ‘‘bet’’). Analysis of several such experiments shows that syllable identification can be accurately modeled using independent phoneme-sized units that are sensitive to stimulus properties, plus certain highly constrained influences of higher level symbolic elements (e.g., words). These higher level influences are limited to bias effects that do not interact with stimulus properties. These results suggest that small, highly general elements play the key role in the transduction of signals to symbol in speech. [Work supported by SSHRC.]
An acoustic interferometer for measuring sound-speed variations in a turbulent fluid
Authors: Daley Michael J. , Gilbert Kenneth E. , Goodman Ralph R.
Published: July 2002

This paper reports laboratory measurements of the effect of thermal fluctuations on sonar ping returns from two discrete scatterers. It is the first part of an ongoing investigation of acoustic backscatter from targets and surfaces immersed in a turbulent fluid containing thermal inhomogeneities. A simple theory was developed to relate sound-speed variations and the echo level from a pair of discrete targets. The theory treats the return level from the targets as an interferometer, sensitive to the spatially averaged sound speed between the targets. Measurements were made of 200-kHz echoes from a pair of targets for various temperature conditions. As an initial calibration test, the water column was heated as a unit and allowed to cool over time. In a second set of measurements, Kolmogorov thermal turbulence was created in the water column, and the fluctuating echo level was measured. Using the amplitude of the echo, the average sound speed between the two targets was calculated for each ping. The acoustically determined sound-speed variations were compared to those inferred from thermal fluctuations and found to be in approximate agreement. Sources of error and approaches for improving the measurements will be discussed briefly. [Work supported by ONR and the Applied Research Laboratory, Pennsylvania State University.]
The transient conical wave field emitted by a supersonic source in a two media configuration
Authors: Kooij Bert Jan , Kooij Cornelis
Published: July 2002

The acoustic conical wave field due to a supersonic motion of a rigid object over a half-space is investigated. The research presented here is of great importance for the modeling of the transmitted and reflected conical waves that are excited by supersonic airplanes that fly over sea or land. The media involved are acoustically modeled as homogeneous, isotropic fluids and the moving object is represented as an acoustic source of the dipole type. The linearized acoustic field equations are applied to obtain representations for the fields in a combined Laplace–Fourier transform domain. To these representations, which are mapped into the proper form, we apply the Cagniard–de Hoop technique in order to find closed-form time-domain solutions for the reflected and transmitted acoustic fields. In the Cagniard–de Hoop technique we use a new transformation in order to get separate expressions for the reflected and transmitted conical waves as well as the conical headwave that can occur under certain circumstances. These special wave phenomena come forward from the procedure with precursive fronts and clearly defined trailing edges. Numerical results for the reflected as well as the transmitted conical wave are presented in a configuration where conical headwaves can occur.
Field of acoustic parametric array generated by a point source in a cylindrical waveguide with rough boundaries
Authors: Georgi Michael
Published: July 2002

Consider the possibility of using obtained theoretical solving for the diagnostics and checking a structure of the nonlinear acoustic parametric array (APA) field in inwardly closed or half-closed volumes of diagnosing structures via the determination of field structure over distinctive parameters: pressures, displacing, oscillatory velocities, etc., with allowance for a physical nonlinearity of the media, hydrodynamic, boundary and other conditions of ultrasonic field forming. A theoretically designed method of solving an interior problem on the finding of ultrasonic field in a cylindrical waveguide with rough surface at irregularity description functions h(a,z), where the method of consequent approximations is used for obtaining and representing boundary conditions under small magnitudes of irregularities, commensurable with magnitudes of acoustic field wavelengths. Herewith roughness (irregularities) is considered to be, for example, a border-reflecting surface, beside which is a geometric with a small change in the scale of working wavelength, in our case, field of primary pumping waves (PPW). The physical problem model represents itself as consideration of an acoustic field of the monochromatic point source of an inwardly circular cylinder with radius a, the physical characteristics of which are assumed as ideal reflecting, and the irregularity (roughness) of its surface is given in general type by the function of roughness’ description h(a,z).
Renovating a landmark: London’s Royal Festival Hall
Authors: Giegold Carl P. , Calamia Paul T.
Published: July 2002

Since its opening in 1951, London’s Royal Festival Hall has been plagued with a number of acoustic shortcomings. Specifically, the hall suffers from a short reverberation time despite its size, a relatively weak bass response, a sense of acoustic ‘‘detachment’’ for listeners in the under- balcony, and difficult playing conditions on stage. Plans for a major renovation of the hall are currently being prepared for submission to the National Lottery. The authors will discuss the potential remedies for the issues noted above, with particular attention paid to implementation and measurement in a 1:20 scale model.
Experimental evaluation of the performance of coherent digital communications algorithm in littoral ocean
Authors: Al-Kurd Azmi A. , Yang T. C.
Published: July 2002

Underwater acoustic communications data using phase modulated signals were collected during the Littoral Warfare Advanced Development 98-1 experiment, conducted in the Gulf of Mexico in Nov. 1998. CW pulse and quadrature phase shifted keying (QPSK) signals were projected from a towed source. Data of three baud rates were collected to study the temporal and spatial variation of the acoustic impulse response of the ocean and to evaluate the performance of a phase coherent digital communication algorithm. Post-experiment analysis examined the Doppler shift, signal amplitude fluctuation, signal-to-noise ratio of the received signal, channel impulse response, temporal correlation function of the received signals, and signal fluctuation statistics during several segments of the experiment. The objective is to determine the characteristics of signal propagation in littoral environment, and to determine whether and how these characteristics affect the bit-error-rate of a coherent acoustic communication algorithm. The analysis results serve as guidance in the design of a reliable coherent digital communication system. [This work is supported by the Office of Naval Research.]
Main difficulties in the midfrequency range and reduced matrix models for structural-acoustic problems
Authors: Soize Christian
Published: July 2002

In the MF range, the modal density of 3-D structures increases with respect to the LF range, but is not yet high enough to be able to apply SEA, which is adapted to the HF range. This means that finite-element models have to be used to model the master system constituted of the master structure coupled with the internal and external acoustic fluids. The main difficulties in the MF range are due to the mechanical model and the solving methods. Concerning the mechanical model, the difficulties are induced by the structural complexity for which the fuzzy structure theory can be used; we present recent results concerning the validation of the fuzzy structure theory for continuous junctions between the master structure and the fuzzy substructures whose structural complexity is due to local modes of continuous structures on which are attached many discrete dynamical subsystems. Concerning analysis and solving methods in the MF range, finite-element models of master systems have a large number of DOF and modal analysis is not efficient for constructing a reduced model. We then present recent developments and applications concerning a reduced model adapted to structural-acoustic systems in the MF range.
A comparison between an indirect Trefftz method and the finite-element method for solving coupled vibro-acoustic problems
Authors: Desmet Wim , Sas Paul , Vandepitte Dirk
Published: July 2002

The finite-element (FE) method is most commonly used for solving time-harmonic structural acoustic problems in bounded domains. Since the dynamic variables within the element domains are expanded in terms of simple, approximating shape functions, a large amount of elements is required to get a reasonable prediction accuracy and this amount increases with frequency. This results in large, computationally expensive models, so that the use of FE models is practically restricted to low-frequency applications. In a newly developed, indirect Trefftz method, the dynamic field variables are expanded in terms of wavefunctions, which exactly satisfy the governing dynamic equations. The wavefunction contributions to these expansions result from a weighted residual formulation of the boundary conditions. Since an approximation is only involved with the boundary conditions, the resulting models are substantially smaller than FE models. However, the small wave models are fully populated, complex, and frequency dependent. The performances of the indirect Trefftz method and the FE method are compared for some validation examples. It is illustrated that the new method provides a high prediction accuracy with substantially smaller computational efforts. In this way, the indirect Trefftz method can be applied up to much higher frequencies.
Structural acoustic noise modeling of a supercavitating high-speed vehicle using statistical energy analysis
Authors: Koch Robert M.
Published: July 2002

The simulation of propagation of structureborne vibratory and acoustic energy within a supercavitating high-speed underwater vehicle is studied herein. The supercavitating vehicle is rocket propelled and rides entirely within a cavity in order to reduce drag and allow for higher underwater speeds. A ventilation system exists within the vehicle to ensure the cavity completely encloses the vehicle. With the exception of isolated control surfaces, the only wetted portion of the vehicle is the cavitating sonar array at the vehicle nose. This paper focuses on the use of statistical energy analysis (SEA) to quantify and parametrize the high-frequency transmission of vibro-acoustic energy within the complex, multiply connected marine vehicle, as well as including contributions from the reverberant cavity and seawater acoustic paths. Additionally, an examination of the many potential noise sources is made, including a discussion on handling the effects of surface backscattering and volume reverberation within an SEA framework. Numerical case studies are performed to exercise the model in order to predict the effects of specific design modifications such as structural design variations, isolation mounting scenarios, etc.
Energy flow modeling in the mid-frequency range
Authors: Shorter Philip J. , Mace Brian R.
Published: July 2002

This paper describes how uncertainties in the properties of a structure may be included in energy flow models derived from finite element analysis. Current approaches to stochastic dynamics either adopt a detailed probabilistic approach, as in the stochastic finite element method, or a broad brush approach as in statistical energy analysis (SEA). In the former, detailed information about the joint probability density function of a large number of physical properties is required in order to define an ensemble. In the latter, the ensemble is defined implicitly by assuming some distribution of the local dynamic properties of a structure (typically one that is uniform in some dynamic sense). In the mid-frequency range neither approach is entirely satisfactory. This paper presents an alternative definition of the ensemble, defined in terms of the statistics of the local natural frequencies of a structure. A numerical technique, which combines component mode synthesis with a Taylor series expansion and a Monte Carlo simulation, is then described and used to obtain a stochastic energy flow model of a structure.