bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature-scanning ultrasonic measurements in aqueous systems: What is new?
Authors: Kharakoz Dmitri P.
Published: July 2002

Ultrasonic measurements are the only high-precision approach to experimental studies of the mechanical part of free energy in liquids, the part directly related to the volume, pressure, and compressibility. During the last decade, a significant progress has been made in the studies of these parameters in aqueous solutions and dispersions of biomolecular materials. The following aspects are considered in this paper: (1) temperature dependence of volume and compressibility as a means to characterize hydration of solutes in water. Important information on the structure and dynamics of bound water can be obtained. (2) Single-frequency simultaneous measurements of sound velocity and absorption and the investigations of fast kinetics. A first-order phase-transition in lipid vesicles (aqueous dispersion) is considered as a process for which unique and very important kinetic information can be obtained by means of such measurements. (3) Sound velocity, compressibility, and volume as a means to characterize conformational states of macromolecules in aqueous solution. Temperature-induced phase transitions in macromolecules (proteins and other polymers). (4) A puzzle of the intrinsic compressibility and nonlinearity of native protein molecules. (5) The acoustic and calorimetric temperature-scanning measurements: A comparative aspect. [Work was supported in part by Russian Foundation for Basic Research, Grant No. 95-04-12226a.]
Development of human cochlear function
Authors: Abdala Carolina
Published: July 2002

The time course for functional development of the human cochlea is not clear. The advent of otoacoustic emissions (OAE) methodology has made it possible to noninvasively probe cochlear function in humans. Distortion product OAE isosuppression tuning curves indirectly reflect cochlear frequency selectivity. They are generated by presenting a third suppressor tone simultaneously with the stimulating tones f1 and f2 and increasing the level of the suppressor until a criterion amount of suppression is achieved. When the suppressor level required to achieve criterion reduction in DPOAE amplitude is plotted as a function of frequency, a DPOAE suppression tuning curve (STC) can be generated. DPOAE (2f1−f2) STCs have been generated in adults and neonates to investigate development of cochlear tuning in humans [Abdala et al. (1996); Abdala and Sininger (1996)]. Results of these studies suggest that the human cochlea is resolving frequency in an adultlike fashion by term birth. Other findings also support this contention [Bargones and Burns (1988); Eggermont et al. (1996)]. However, results of a recent study conducted with very premature neonates [Abdala (1997)] suggest that STC width and growth of suppression is not adultlike in premature neonates. These results may be indicative of cochelear immaturity just prior to term birth.
Frontiers and backwaters of research on the biological bases of hearing development
Authors: Rubel Edwin W.
Published: July 2002

The goal of this talk will be to summarize recent advances and current challenges in research on the biological bases of hearing development. Three areas will be focused on: functional and structural changes in the cochlea during the early stages of hearing development; the biological bases of critical periods for inner ear and brain development; and the influence of experience on structure and function of central auditory pathways. In each area the dramatic advances in the amount and quality of descriptive information that has emerged over the past decade will be considered. These data provide a firm foundation on which to test hypotheses regarding the mechanisms that govern development. The contributions that the tools of modern cellular and molecular biology can bring toward providing new answers to questions of developmental mechanisms will be discussed.
Interface wave source concepts for a seismic sonar concept
Authors: Gaghan Frederick E. , Baker Steven R. , Muir Thomas G.
Published: July 2002

A seismic sonar concept is being developed which employs guided interface (Rayleigh or Scholte) waves to detect objects buried in sea floor and beach sediments. These waves have the desirable characteristics for this application that (1) they are localized near the interface and (2) the propagation from a compact source is cylindrical. As a result, the wave intensity on targets of interest is enhanced and the reverberation suppressed, compared to a bulk wave. To selectively excite Rayleigh or Scholte waves, a harmonic source employed at the interface must excite elliptical particle motion in the vertical and propagation, or radial, directions. Several such source concepts will be described. Results to date of field tests employing these sources in narrow-band pulse tests will be described. [Work supported by ONR Code 321OA.]
An acoustical appreciation of the extended performance aspects of Eric Dolphy’s musical craft
Authors: Keefe Douglas H.
Published: July 2002

The late 1950s and early 1960s was an era of rapid innovation in jazz in which musicians transformed the compositional and improvisional form of the music. While instrumentalists have incorporated extended performance techniques in a unique manner from the beginning of jazz, an important aspect of the avant garde movement was the breadth of innovation in woodwind instrument performance. Eric Dolphy was a pioneer in this respect, a virtuoso performer of the alto saxophone, bass clarinet, and flute, who helped bring the latter two instruments into prominence within jazz as solo instruments for improvisation. Literal acoustic distortion is present in woodwind multiphonics used by Dolphy and others, produced not merely by using unconventional fingerings and changes in embouchure, but also by alterations in the resonances of the player’s vocal tract [Wilson (1996)]. Aesthetic distortions include the sheer temporal complexity of melodic lines, which cannot be separately resolved by many listeners, and the inclusion of speechlike and bird-song elements within extended musical forms lacking a conventional harmonically related musical structure. Such factors contribute to the overall artistic impact of this music.
Eric Dolphy’s playing style in the Vienna Art Orchestra’s performance
Authors: Hettergott Alexandra
Published: July 2002

Aiming on the very musical expression intended, ‘‘tone colorist‘‘ Eric Dolphy in his developed avantgarde jazz playing style on alto sax and bass clarinet as well as on flute makes use of several extraordinary playing techniques (e.g., multiphonics). In musically portraying him [Nine immortal non-evergreens for Eric Dolphy, Amadeo 537 096-2], the now 20-year-old Vienna Art Orchestra in a postmodern way renders Dolphy’s compositions in their very performance style, adopts and adorns his melodies typically performed in a highly expressive, noise-inducing way with their own instruments’ rich means of expressions, allowing also for brass instruments. Consequently, the bass clarinet in Hat and Beard is given in solos of trumpet, trombone, and alto sax, the flute in Gazzelloni reflected in both trumpet and f- horn solos, or the alto sax in Straight Up and Down expressed in solos of either trumpet, trombone, and alto sax, respectively. In sound analyses along with sound examples the paper compares several of Dolphy’s playing techniques in his original late recordings (1964) with the recent performances by the Vienna Art Orchestra (1995), focusing on the wind instruments’ (unusual) sounds as part of the personal aesthetics of expression in both model Dolphy and the Vienna Art Orchestra.
Community response to artillery and road-traffic sounds—A new field survey
Authors: Buchta Edmund , Vos Joos
Published: July 2002

With the help of a questionnaire, subjective reactions to artillery sounds (muzzle bangs mainly from 120- and 155-mm caliber weapons, detonating high-explosive shells, and other explosions) were determined for over 400 respondents divided among 17 different residential areas. Also, for the same respondents, the subjective effects of (local) road-traffic sounds were determined, enabling a comprehensive comparison of dose–response relations for the, typically, high-energy impulsive sounds and the road-traffic sounds. For the sake of comparison with other field surveys, the noise dose for the shooting sounds was expressed as the yearly average C-weighted day–night level (LCdn), and that for the road-traffic sounds was expressed as the A-weighted day–night level (LAdn). Similarly, for both sound types the community response in each residential area was expressed as the percentage of respondents being ‘‘highly annoyed.’’ From the comparison of the two dose–response relationships it could be concluded that for numerically equal Ldn values, the artillery sounds were more annoying than the road-traffic sounds. Overall, the difference is equivalent to the change in annoyance produced by a 5-dB shift in either LCdn or LAdn of the sounds.
A further test of the relevance of ASEL and CSEL in the determination of the rating sound level for shooting sounds
Authors: Vos Joos
Published: July 2002

In a previous study on the annoyance caused by shooting sounds [Vos, Proc. Internoise ’96, 5, 2231–2236], it was shown that an almost perfect prediction of the annoyance, as rated indoors with the windows closed, was obtained on the basis of the weighted sum of the outdoor A-weighted and C-weighted sound exposure levels [ASEL (LAE) and CSEL (LCE)] of the impulse sounds. Basically, the annoyance (y) was given by y=c+αLAE+β⋅ΔL⋅LAE, in which ΔL=LCE−LAE. In that study, just one type of facade attenuation (FA) was simulated. In the present study, the annoyance was determined for four FA types that varied from low (windows slightly opened) to very high (20 dB at 16 Hz to 50 dB at 8 kHz). Again, the sounds were produced by firearms ranging in caliber from 7.62 to 155 mm, and were presented at different levels. In all four FA conditions, the annoyance could be very well predicted by the equation given above, multiple r2 varied from 95% to 97%. Relative to the prediction on the basis of ASEL only, the increase in r2 varied from 7% in the slightly opened windows condition to 55% in one of the high FA conditions. It was concluded that for the determination of the rating sound level, the acoustic parameters ASEL and CSEL are very powerful.
Modeling the effects of refraction and diffraction on wave propagation in a 3D, turbulent atmosphere medium
Authors: Gilbert Kenneth E. , Di Xiao
Published: July 2002

In ocean acoustic modeling, it has been established that many nonturbulent, deep-water propagation problems can be treated by the ‘‘N×2-D’’ approximation, where 2-D ‘‘slices’’ are computed along N radials. In the atmosphere, the validity of the N×2-D approximation is questionable because of ever-present, multiscale turbulence. In this paper, a new approach that allows the inclusion of multiscale turbulence in practical calculations is presented. The approximations that are physically motivated by the relative contributions of refraction and diffraction in multiscale turbulence are discussed. It is shown, for example, that for horizontal atmospheric structures larger than 10’s of wavelengths, horizontal diffraction is negligible, and the N×2-D approximation suffices. For smaller turbulence structures, horizontal diffraction is a dominant effect and must be accounted for. The theoretical/numerical method presented allows efficient calculations for both large- and small-scale 3-D atmospheric structure. Numerical examples are given to illustrate the phenomena involved. [Work supported by DARPA and the Pennsylvania State University Applied Research Laboratory.]
The effects of turbulent intermittency on scattering for varying degrees of saturation
Authors: Norris David E. , Wilson D. Keith , Thomson Dennis W.
Published: July 2002

Atmospheric turbulence is inherently inhomogeneous and intermittent. Periods of high activity are embedded in periods of relative calm. The local spatial and temporal changes in sound speed associated with intermittency increase the likelihood of measuring large values of scattered acoustic signals. Previous work successfully predicted the probability density functions (pdf) of fully saturated, scattered signals measured within an acoustic shadow zone [Wilson et al., J. Acoust. Soc. Am. 99, 3393–3400 (1996)]. The more general case, in which the scattered signal is partially saturated, was considered in this paper. A theory was developed through the use of the Rice–Nagakami pdf. There are two free parameters: one to describe the degree of intermittency, and a second to describe the degree of saturation. For validation purposes, outdoor propagation measurements were made over a flat, hard ground at a range of 283 m, and at frequencies from 90 to 500 Hz. Calculated and measured intensity pdf’s were compared and found to be in excellent agreement. Both the intermittency and saturation increased with frequency, with the scattering at 500 Hz being almost fully saturated.
Scattering by an elastic cylinder buried in a sedimentary fluid media
Authors: Coatanhay Arnaud , Conoir Jean-Marc
Published: July 2002

A new method for predicting the acoustic field scattered by an infinitely long elastic cylinder buried in a sedimentary fluid media is developed. The cylinder is parallel to the interface and the incident wave propagation direction is perpendicular to the cylinder axis. The method describes the interaction between the cylinder and the interface in modal theory. The approach is based on a generalized method of images which is originally restricted to rigid and soft plane interfaces. In this way, the acoustic field in sediment can be expressed as two cylindrical waves series whose emitting centers are symmetric with respect to the interface. The acoustic field transmitted by the plane interface is then calculated with the use of the steepest descent method. The goal is to detect buried objects by analyzing the resonances. At quite a high frequency, a good agreement is observed with regard to experiments.
Bistatic sonar cross sections and time-frequency signatures of simple targets insonified by an acoustic pulse
Authors: Gaunaurd Guillermo C. , Strifors Hans C.
Published: July 2002

The area of acoustics is concurrently trying to develop the concept of impulse sonar. Using a time-frequency approach the very broadband echoes generated by a target when such devices are used can show the time evolution of the resonance features that identify the target. This will enhance the target recognition capability of the traditional sonar cross section (SCS). To this end, the bistatic scattering interaction of acoustic pulses of short duration with targets of simple shapes are studied. The targets are solid spheres and spherical shells. To model the output of an impulse sonar, the waveform incident on the target is a short, ultra-wideband pulse that consists of a few sinusoidal cycles within a Blackman window. For each target the bistatic SCS is displayed as a function of frequency and bistatic angle. Analyzing the scattered waveform when the designed short pulse is incident on each target for a few selected bistatic angles gives information of how and how much scattered pulses are affected by the scattering direction, or the relative location of the transmitter and receiver. The methodology developed by us could be used to assess the performance, including the possibility of target recognition, of any impulse sonar system.
New results for diffraction from an impedance wedge
Authors: Norris Andrew N. , Osipov Andrey V.
Published: July 2002

Acoustic diffraction from the tip of a wedge with impedance boundary conditions is a well covered topic, with extensive work reported in the 1950s. One of the main quantities of interest is the diffraction coefficient, D, for plane-wave incidence. Some new, simple, and useful results for the diffraction coefficient are reported. It will be demonstrated that D factors into the product of three terms: (1) the amplitude at the tip for a unit plane-wave incident from the direction of interest, (2) the same amplitude for a plane wave coming from the observation direction, and (3) an expression involving only trigonometric functions. Furthermore, the magnitudes of the tip, or edge, amplitudes (1) and (2) are very simple if the faces of the wedge are purely reactive (imaginary impedances). The simplicity of the formula for D allows us to answer questions such as: Can the diffraction vanish if the impedances of the wedge faces are properly chosen? The answer is generally in the affirmative, at least for selected incidence and observation directions. These findings will be illustrated by several examples and applications will be discussed.
Physical nature of the first circumferential wave of a Lucite cylinder immersed in water
Authors: Chati Farid , Léon Fernand , Maze Gérard
Published: July 2002

Acoustic scattering from a Lucite cylinder of infinite length immersed in water and excited by a normal incident plane acoustic wave is investigated at low frequencies. Numerical calculations and experiments are performed for a cylinder with a radius a=0.01 m. The experimental results are obtained with the method MIIR. The resonances of the first circumferential wave are easily isolated in the frequency range 100–300 kHz. A good agreement is obtained between experimental and theoretical results. First, in order to analyze the physical nature of vibration modes associated with this wave, the evolution of the resonance location and that of their corresponding widths are investigated theoretically when the fluid density is perturbated. Contrary to aluminum or steel cylinders, the computed calculus in vacuum are not in good agreement with the experimental results related to the first wave. The detection of this wave depends mainly on the outer fluid. Second, the dispersion curves of the phase velocity for this wave are considered. A noticeable difference of the phase velocity toward the high frequency is observed when the fluid density is modified. The phase velocities toward the high frequency, in the presence and in the absence of water, enable us to characterize this wave.
Algebraic aspects of acoustic scattering
Authors: Fournier Elisabeth , Decanini Yves , Folacci Antoine , Gabrielli Paul
Published: July 2002

Acoustic scattering by an arbitrary number of identical cylinders is studied. The S-matrix associated with such a system is obtained by extending the KKR method developed by Kohn, Korringa, and Rostoker in condensed matter physics. Calculations are carried out for various boundary conditions (soft, rigid, and elastic cylinders). Scattering resonances are the poles of the S-matrix. They are determined in the complex plane of the reduced frequency. Scatterers with discrete symmetries, such as: C2v: two cylinders, C3v: three cylinders located at the vertices of an equilateral triangle, C4v: four cylinders located at the vertices of a square, are more particularly studied. Symmetries are reflected in the S-matrix, which reduces to a block diagonal form where the blocks are labeled by the irreducible representations of the symmetry group. This work is a step toward a complete study of chaos (linked to statistical properties of the S-matrix) in the context of multiple scattering.
Characterization of fault processes in central Arctic ice
Authors: Stamoulis Catherine , Dyer Ira
Published: July 2002

Fault processes in Arctic ice are characterized by particle motion, propagation, and radiation. Estimates of these can be achieved through analysis of individual acoustic events induced by the faults. Thus data from a central Arctic experiment were analyzed. Particle velocity, displacement, and rise time, which characterize particle motion, were estimated through integration of the acoustic signals in the time domain. Particle displacement was in the range O(10−4)–O(10−2) m, significantly lower than that of earthquake-induced faults; particle velocity was 1–67 cm/s, on average 50% lower than that of a displacement discontinuity in rock. Fracture speed, strike angle, and source dimensions, which characterize fault propagation, were estimated in the frequency domain. Fracture speed estimates were in the range 200–1100 m/s. This wide range suggests either multiple fault mechanisms or a single mechanism at different stages in its propagation. Source dimensions were determined from the displacement spectra of the second integral of the signals, with source length 0.7–100 m, and depth 0.4–4 m. Finally, the radiation characteristics were estimated and tensile and shear fracture were identified, both in the low (10–100 Hz) and mid (100–350 Hz) frequency ranges.
A piecewise matched-field tracking algorithm
Authors: Wilmut Michael J. , Ozard John M.
Published: July 2002

Efficient matched-field tracking (MFT) algorithms have been successfully applied to both simulated and measured data. They have been used to track sources moving linearly or on a circular path at constant speed and heading. The input to the tracker is a set of ambiguity surfaces, contiguous in time, generated by matched-field processing. Previously described MFT algorithms assume that the track start and end times are known a priori; this restriction is removed in the piecewise MFT algorithm described here. In a series of simulations it is shown that the statistically significant tracks can be found provided the track signal-to-noise ratio is greater than 10. Their unknown start and end times are in error by one surface or less most of the time. The algorithm is then applied to find track segments for simulated sources moving linearly, or on a circular path. The path segments were of unknown duration and heading.
A modified grid method for matched-field localization
Authors: Xiao Ling , Zhang Renhe , Guo Lianghao
Published: July 2002

A modified grid method (MGM) for matched-field localization is proposed in the paper. It is a practical version of the seed division algorithm (SDA). It adopts the ideal that searches in a coarse grid at first and then regionally fines the grid. The fining process is implemented by SDA. This so-called MGM is tested in the paper by seven two-dimensional global optimization problems. The tests show that MGM is more efficient than the normal grid method. Besides, it is more efficient than some other randomized methods which are currently used today. A numerical test is carried out for matched-field localization in deep ocean. It is based on MGM and WKBZ [Zhang et al., Chin. J. Acoust. 13, 1–12 (1994)]. The result shows that MGM can greatly upgrade the computational velocity and improve the localization’s precision. [Work supported by NSF of China.]
Noninvasive ultrasonic surgery
Authors: ter Haar Gail R.
Published: July 2002

The millimeter and submillimeter wavelengths of megahertz ultrasound in tissue mean that this form of energy can be brought to a tight focus in the body at a distance from the acoustic source. If the energy carried by the ultrasonic beam is sufficiently high, then it is possible to destroy tissue lying within the focal region, while sparing adjacent and overlying tissues. Typical peak intensities at the focus for ablation of tissues using 1–2 s exposure times are 1 kW/cm2. For a focused bowl transducer with focal length 15 cm, 8 cm in diameter, operating at 1.7 MHz, the focal region is ellipsoidal in form, with axial length 15 cm and diameter 1.5 mm. A number of different exposure methods may be used to ablate clinically useful tissue volumes. Focused ultrasound is capable of selectively destroying tissue at depth without the need to expose the site of interest surgically. The mode of tissue destruction is primarily thermal in origin, temperatures in excess of 60 °C being induced very rapidly. This type of cellular damage is capable of destroying both normal and malignant cells, and of occluding selected blood vessels. Potential applications for this technique lie, among others, in urology, oncology, and fetal medicine.
Boxes and sound quality in an Italian opera house
Authors: Cocchi Alessandro , Garai Massimo , Tavernelli Carla
Published: July 2002

The sound field in the boxes of an 18th century Italian opera house was studied by means of binaural measurements and computer simulations. The differences in listening between the boxes and the stall is best described by the values of ITDG, clarity, and spatial criteria resulting from the measurements. The periodic variation of the ITDG along the boxes depends also on the reflections coming from the ceiling. The best boxes for clarity and spatial impression are found in very different positions. Computer simulation supports these conclusions and helps in understanding the two different mechanisms by which the boxes influence the sound field in the hall: the equivalent sound absorption of the boxes and the periodic structure of the box-covered walls. A validated computer model allows one to forecast how the sound field in the historical theater could be if some interior lining were added to the boxes, trying to restore the velvet lining which was supposed to exist in ancient times.
Therapeutic ultrasound
Authors: Crum Lawrence A. , Bailey Michael , Beach Kirk , Caps Michael , Carter Stephen , Chandler Wayne , Cleveland Robin , Helton Scott , Kaczkowski Peter , Keilman George , Martin Roy , Mourad Pierre , Roy Ronald , Schmiedl Udo , Stewart Brent , Vaezy Shahram
Published: July 2002

Although diagnostic ultrasound is now a multibillion dollar a year industry, the therapeutic applications of ultrasound were initially thought to have more promise. Indeed, the Fry brothers were performing brain surgery on human patients in the early 1950s, and with considerable success. However, therapeutic ultrasound has still not yet gained its promising potential. Recently, there has been an enormous resurgence of interest in this topic, and several major projects are underway at various facilities around the world. Our own substantial efforts in this area at the University of Washington are reviewed, with brief discussions of topics in lithotripsy, ultrasound-enhanced drug delivery, HIFU surgery, and acoustic hemostasis. [Work supported in part by DARPA and the NIH under Grants DK-43881 and R43HL57739.]
Absolute amplitude measurements using a capacitive receiver
Authors: Breazeale M. A.
Published: July 2002

Absolute acoustical amplitudes can be measured in solids with a capacitive receiver. Amplitudes as small as 10−4 Å=10−14 M have been measured. A system is described with dimensions used for frequencies between 5 and 60 MHz. Two special innovations are described: low-temperature measurements which require adjustment of the spacing of the capacitor and high-sensitivity measurements (amplitudes smaller than 10−14 M) which are accomplished by using a dielectric to prevent electrical breakdown.
Automatic creation of CV templates for formant type speech synthesis based on HMM-based segmentation and syllable boundary detection
Authors: Ohtsuka Takahiro , Yang Chang-Sheng , Kasuya Hideki
Published: July 2002

A formant type speech synthesis method has an enormous advantage in that it allows one to generate speech with various voice quality variations and talker individualities. But it has suffered from unnatural speech quality, not because of theoretical limitations but because of an incomplete set of rules for the synthesis. Any insufficient approximation to the acoustics causes degradation of the perceived quality of synthetic speech. A novel formant type speech synthesizer in Japanese based on concatenation of CV (consonant-vowel) formant-source templates obtained from natural utterances has been investigated, in which multiple sets of formant and voice source parameter values are used for each of the CV syllables. This paper describes an automatic method to create the CV formant-source templates from speech corpus. The ARX (autoregressive with exogenous input) analysis method is first used to automatically extract formant and voice source parameters and then an HMM based segmentation is performed to locate the CV segments. The segments are further analyzed to detect a starting point of the syllable. A distance measure is used to decide the number of templates needed for each of the syllables. The method is proved to be useful in creating CV templates by experiments performed on 503 Japanese sentences.
The Hablarte text-to-speech system
Authors: Karn Helen E.
Published: July 2002

This paper presents an overview of the architecture of Hablarte, an unrestricted text-to-speech system for Spanish which runs on DOS-based personal computers. The input to Hablarte is an ASCII text with conventional Spanish orthography and punctuation. The front-end text processing routines convert the input text’s graphemes to phonemes, determine phonological phrases, syllable structure, and the location of primary stress, and assign prosodic values to the phonetic representation [H. E. Karn, ‘‘Aspects of phonetics and phonology in a text-to-speech system for Spanish,’’ Doctoral dissertation, Georgetown University, 1996]. The acoustic signal is generated by Mbrola v2.02, using the Spanish male diphone database and utilities of the MBROLA project [http://tcts.fpms.ac.be/synthesis/mbrola.html]. Evaluations of Hablarte’s text processing components and sample audio output are given.
Pitch-controlled variable bitrate CELP speech coding
Authors: Oberhofer Robert , Owens Frank
Published: July 2002

Most research in efficient speech coding concentrated for many years on algorithms which produced a fixed bit rate. Fixed bit rates are, however, not a requirement for modern packet-based telecommunications and computer networks as well as voice storage applications. This makes the implementation of speech coders feasible, which adapt to the changing properties of speech for improved efficiency or quality. Variable bit-rate coding has therefore become the focus of considerable research activity in recent years [A. Gersho and E. Paksoy, ‘‘Variable Bit Rate Coding,’’ Signal Processing VII, Theories and Applications, EUSIPCO 1994, pp. 1169–1173; L. Zhang et al., ‘‘A CELP Variable Rate Speech Codec with Low Average Rate,’’ ICASSP 1997, pp. 735–738; B. C. Xydeas, ‘‘Source Driven Variable Bit Rate Prototype Interpolation Coding,’’ ICASSP 1996, p. 220; B. Shen et al., ‘‘A Robust Variable-Rate Speech Coder,’’ ICASSP 1995, p. 249]. While all of these coders focus on classification procedures for efficient bit allocation, the analysis frame size remains mainly static. The coder featured in this paper adapts the analysis frame size and bit allocation according to the pitch of the signal. A pitch frame extractor and classifier at the front end feeds the detected frame into the speech coding back end, which uses traditional CELP-based techniques [B. S. Schroeder et al., ‘‘CodeExcited Linear Prediction (CELP): High Quality Speech at Very Low Bit Rates,’’ ICASSP 1985, pp. 937–940]. This approach allows the reduction of the bit rate from a constant 4800 bps (bits per second) with original CELP to typically 3200–4000 bps, depending on the speech situation. This figure is even reduced to typically 2600–3200 with the inclusion of Voice Activity Detection. The speech quality equals the quality of the original CELP coder.
Assessment of the intelligibility and perceived quality of speech produced by text-to-speech engines
Authors: Hall Michael D. , Stevens Erica B. , Eyraud Richard , Padden Denise M. , Kuhl Patricia K.
Published: July 2002

The intelligibility and quality of speech produced by current text-to-speech (TTS) engines was assessed using well-established tests of speech intelligibility. TTS engines included Microsoft’s Whistler, AT&T’s Watson, and Elan Informatique’s ProVerbe. The speech intelligibility tests varied in complexity and in the degree to which syntax and lexical knowledge could aid perception. Stimuli included CVC words, semantically meaningful sentences, semantically anomalous sentences, and paragraphs representing different styles of discourse. Intelligibility was evaluated using transcription accuracy for isolated word and sentence items, as well as ratings of the clarity of articulation for word and paragraph items. Perceptual errors on word items also were analyzed by phoneme and word position (initial, medial, or final). Additional ratings were used to determine the perceived ‘‘naturalness’’ of meaningful sentences and paragraph items. Across levels of speech complexity, clear and consistent differences between TTS engines were obtained in terms of both intelligibility and naturalness. Possible explanations of the results will be discussed, as will potential areas where text-to-speech synthesis can generally be improved.
Simulation of the effects of thermal turbulence on beamforming and time reversal techniques using Gaussian beam summation and Fourier modes superposition techniques
Authors: Lhuillier Christian , Fiorina David , Berton Jean-Luc , Juve Daniel
Published: July 2002

In-service inspection of Fast Breeder Reactors will require submerged ultrasonic imaging devices. For this purpose, the CEA (French atomic commission) is developing an orthogonal imaging system, based on beamforming applied to two linear arrays. In order to evaluate the performance of this technique for realistic physical conditions, one must take into account the possible effects of weak thermal turbulence on the propagation and focusing of ultrasound. To achieve this study, a numerical model has been implemented. It is based on the Fourier modes superposition method to generate independent realizations of turbulent fields and on the Gaussian beam summation method to calculate the associated acoustic pressure fields induced by point sources. First, the model has been used to show the aberrations that are created in the focusing of a multielement transducer. Second, the model has been used to verify the efficiency of the time reversal technique for the correction of these aberrations, in the case of slow temporal evolutions of the turbulence.
Advanced system identification techniques for acoustics enhancement
Authors: Cao Yuchang , Poletti Mark
Published: July 2002

This paper proposes a novel scheme of adaptive system identification for acoustics enhancement applications. The proposed scheme incorporates a variable exponentially weighted-step-size LMS algorithm, called the VES algorithm, the time-average, and the group measurement methods. A key contribution of this study is the development of the VES algorithm based on the statistics of the overall varying characteristics of the estimate of room impulse responses. The modeling error of the VES algorithm can be reduced to −20 dB after only 2N iterations (N is the length of adaptive filter), about 4 times faster than the normalized LMS algorithm under the test conditions. The increase of the computation load of the VES algorithm is small. When the algorithm is employed in a multichannel system identification, the increase of the computation load is only about 10%. Since the identification scheme has to operate under strong interference in most cases, the time average and group measurement approaches have also been investigated and are suggested to be employed in the scheme to further improve the identification accuracy. The proposed techniques can be used to eliminate undesired feedback, equalize the frequency response, and allow the design of more advanced multichannel assisted reverberation systems, which can provide larger loudness and reverberant gains than conventional systems.
Experimental performance of concatenated coding in shallow-water channels
Authors: Kilfoyle Daniel
Published: July 2002

In a series of phase coherent underwater acoustic communication experiments near the New England continental shelfbreak, the coding gain realized by a concatenated outer block code and trellis coded modulation (TCM) inner code was measured and compared to ideal asymptotic limits. Viterbi decoding of the inner code was fully integrated into the adaptive decision feedback equalizer structure. Coding gain is typically not realized until after decision delays of several code constraint lengths. Delayed decisions for the tap update algorithm, however, degrades equalization performance. Two specific techniques were employed to mitigate this conflict, including linear extrapolation of the carrier phase correction and a unique evolution of the tap weights for each state of the Viterbi trellis. Coding gains were realized for both eight-level phase shift keyed (8 coding states) and 16 quadrature amplitude shift keyed (128 coding states) waveforms. Bit error rate as a function of output signal-to-noise ratio was computed to demonstrate practical, as opposed to asymptotic, coding gains. The extent to which coding increased the system performance envelope will then be discussed.
Adaptive array processing for acoustic communications through time-varying ocean channels
Authors: Preisig James C.
Published: July 2002

In many underwater environments, the acoustic communications channel is reasonably modeled using a micro/macro multipath model. While this model was developed by Flatte [S. M. Flatte, Sound Transmission Through a Fluctuating Ocean (Cambridge U.P., Cambridge, 1979)] and others to describe the effect which random channel fluctuations caused by linear internal waves have on propagating narrow-band acoustic signals, it provides a useful paradigm for modeling the effects of a wider range of environmental fluctuations on wideband communications signals. With this paradigm as a starting point, an analytic two-level model for the effect of random channel fluctuations is presented and compared with experimental data. Using the two-level model, a two-stage adaptive array processing algorithm is developed for processing acoustic communications signals. The algorithm exploits the space/time correlation structure of the received signals which is implied by the channel fluctuation model. The performance of this algorithm in terms of both bit error rate and computational efficiency is analyzed and compared with that of other multi-channel communications algorithms. [Work supported by the Office of Naval Research under Grant No. N00014-95-1-1316.]
Acoustical studies of the upper ocean boundary layer
Authors: Farmer David
Published: July 2002

Ocean surface processes control the vertical transfer of heat, mass, and momentum, affecting water properties and influencing climate. At higher sea states the upper ocean can be one of the most energetic environments on the surface of the planet, presenting special observational challenges to the oceanographer. Acoustical methods provide new approaches to upper ocean measurement and have already deepened our understanding of wave breaking, Langmuir circulation, and bubble distributions. High-frequency sonar images of bubble clouds delineate the patterns of near surface circulation while acoustic Doppler reveals the corresponding flow field; high-resolution coherent Doppler can resolve the microscale turbulent velocity fluctuations. Interpretation of ambient noise allows us to sense wave breaking and presents an intriguing inverse problem requiring separation of sound generation and propagation effects. In situ acoustical sensors can now provide reliable determinations of bubble size distributions. Our experience with many of these techniques is limited, but significant advances can be expected through the combined application of diverse approaches to the study of this climatically sensitive boundary.
Study on experimental equations for on-stage acoustics design
Authors: Nakamura Shun-ichi
Published: July 2002

The relationship between the configuration of an orchestra shell and the acoustics inside have been studied based on the results obtained from the impulse response analysis using scale models of a series of 27 different conditions. Three points on a time profile curve were chosen as the acoustic factors in order to represent the onset process, the stationary state, and the decay process of the reflecting sound field, respectively. The averaged values adopted for discussion have been calculated using the data of three 1/1 octave bands around 1 kHz measured at three different positions in the main part of a stage floor. A remarkable difference in acoustics is found in the onset process between the cases with and without sound diffusers on the inner surface of a stage enclosure, and in the decay process as well. A faster rising in the onset process introduced by sound diffusers is followed by a faster decaying. They have a close connection. Finally, it is found to be possible to derive the experimental equations which relate these factors to the size and the shape of an orchestra shell, considering also the effect of reflections from the audience side of a hall.
Evaluation of the flanking transmission in a scale model of two adjoining rooms
Authors: Cocchi Alessandro , Semprini Giovanni , Secchi Simone
Published: July 2002

Flanking transmission is the sound propagation through the lateral structures of two adjoining rooms. Evaluation of this transmission is possible with a statistical model of two rooms that considers mainly the reduction in vibration transmission between the partition and the lateral structures. With this model, which is the object of a project of international standard (Pr EN 12354), it is possible to evaluate the transmission through each path, considered independent of each other. The research carried out at the Acoustics Laboratory of the University of Bologna has validated the CEN model by measuring the vibration reduction index and the sound transmission in a scale model. The vibration transmission index has been measured both with transient and steady excitation of the structures, the first by means of a hammer and the second of an electromagnetic shaker. The sound reduction index of each path of transmission has been calculated measuring the mean pressure level in the source room and the mean vibration level of each structure in the receiving room. The paper presents the validation of the model with a comparison of the different kinds of measurement techniques.
Loss factor at the boundary of a single-leaf wall under a vibrational field of diffused bending waves
Authors: Kuroki Soichiro , Yasuoka Masahito
Published: July 2002

The internal loss factor (etaint) is an important parameter in the case of calculating the transmission loss of a panel by using SEA (statistical energy analysis). Though energy loss at the edge is fairly large in practical walls, etaint have been ordinarily treated including the edge loss. So it must be necessary to treat quantitatively the energy loss at the boundary of the wall. In this paper, assuming that a panel in excitation is a two-dimensional vibration field of diffused bending waves, a formula of the decay time of a panel is deduced. The subject for experimental study is an aluminum panel mounted in the opening between transmission suite. The panel is excited by a piezoelectric ceramic diaphragm. Vibrational decay time is measured by the impulse response method. The calculation method of the energy absorption coefficient and loss factor at perimeter is indicated by using measured values of decay time and sound radiation.
A study of the reverberant field in rooms with various absorptions, including prediction of spatial variation
Authors: Franzoni Linda P.
Published: July 2002

The sound fields of two rectangular rooms of different size and proportion have been studied using a computer simulation. Point sound sources and absorbing walls are mathematically modeled and the wave equation is solved, the direct-field is removed, and the result is an exact calculation of the reverberant field in the room at any spatial location. Both the overall volume-averaged sound-pressure level and the spatially varying cross-sectional averaged levels are computed and compared to theoretical results. A new theoretical result for the spatial variation is developed using an energy balance applied to cross-sectional slices of the room. Good agreement is shown between this result and the calculated values. The same theory gives overall levels by integrating cross-sectional averages, this is compared to classical results (Sabine, etc.) and to the computer generated data. An improvement can be made to the classical theory by reducing the source power to account for first reflections. Some experimental results will also be presented for comparison. [Work sponsored by NSF.]
Basin-scale internal-wave tomography using a large-aperture vertical array
Authors: Colosi John A. , Cornuelle Bruce D. , Dzieciuch Matthew A. , Munk Walter H. , Worcester Peter F.
Published: July 2002

Basin-scale acoustic transmissions which are received at a large-aperture vertical line array (VLA), like those deployed for the Acoustic Thermometry of Ocean Climate (ATOC) program, provide several acoustic fluctuation observables that can be used for internal-wave tomography. A single receiver provides observations of wavefront travel-time variance, pulse time spread, and temporal signal coherence. A VLA adds the observations of vertical wavefront coherence and modal time spread and time coherence. The combination of wavefront and modal observations provides tomographic vertical resolution of average internal-wave energies as a function of depth. In addition, vertical and temporal wavefront coherences are complementary observations, since spatial and temporal internal-wave variabilities are related through the dispersion relation. Also, vertical and temporal coherences help test the assumption of a separable internal-wave spectrum in terms of frequency and vertical wave number. First efforts to combine several of these acoustic fluctuation observations from the ATOC North Pacific VLAs in an internal-wave tomographic analysis will be presented. Directions for future research will be discussed.
Monitoring temperature variability along the California coast using acoustic tomography
Authors: Morvillez Thierry , Chiu Ching-Sang , Collins Curtis A.
Published: July 2002

The electronic emissions of a low-frequency sound source placed by the Acoustic Thermometry of Ocean Climate (ATOC) project on Pioneer Seamount were monitored by a bottom-lying receiver on Sur Ridge from April 1996 to February 1997. The processed signals show a stable arrival pattern that was repeated in all the transmissions during the 11 months. Using the processed data, a tomographic analysis to study the coastal ocean variability along this California transmission path was conducted. Systematically, the analysis involved forward acoustic modeling of the arrival structure using ray theory, associating the observed arrivals with the modeled arrivals, extracting the travel times of the arrivals, inverting the travel times for temporal and spatial temperature changes, and interpreting the observed temperature variations. In particular, the tomographic estimate was compared to the temperature and wind measurements from an in situ mooring deployed by the Monterey Bay Aquarium Research Institution (MBARI). The comparison shows that the tomographic estimate is of high quality and that the observed temperature variations were linked to coastal upwelling and downwelling events. The data, methods, and results, demonstrating fully the feasibility of using tomography to study coastal temperature variability in central California on a long-term basis, are presented.