bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational modeling of accent and intonation in declarative sentences of Spanish
Authors: Fujisaki Hiroya , Nakamura Kei-ichi , Guirao Miguelina , Gurlekian Jorge
Published: October 2005

Although Spanish is commonly known to have stress accent, preliminary study shows that the word accent in Spanish has a clear and consistent manifestation in the voice fundamental frequency contour (henceforth the F0 contour). The present study is aimed at obtaining analytic and quantitative description of the prosodic characteristics of Spanish useful both for basic understanding and for speech synthesis. The speech material consists of a set of 21 declarative sentences of various lengths, designed to examine effects of word accent, syntactic, and discourse structure as well as speaker’s intention. These sentences were read by two native speakers of Castilian Spanish. The F0 contours were extracted by computer and were further analyzed using a quantitative model of the process of F0 contour generation, originally proposed for Japanese [Fujisaki etal., Proc. 7th ICA 3, 133–136 (1971)]. The results indicate that the model applies quite well to F0 contours of Spanish as far as the present material is concerned. An F0 contour can be represented by the sum of phrase components and accent components, the former being correlated to the syntactic structure and the latter to the lexical word accent. Focus is indicated by an increase in the magnitude of the accent component, while speaker’s intention is indicated by the presence of another component occurring toward the end of a phrase or a sentence. These results provide a powerful tool for high-quality text-to-speech synthesis.
Duration of Spanish [s] in three contexts: Citation forms versus fluent reading
Authors: Karn Helen E. , Yeni-Komshian Grace H.
Published: October 2005

Consonants in Spanish rhymes are typically resyllabified to the onset position of the following syllable in all but the most careful speech styles. There is, however, a lack of consensus regarding the temporal characteristics in the production of two identical phones at word boundaries (e.g., lassalas, ‘‘the rooms’’). Malmberg (1971) states that the two segments are reduced to a single sequence, with a slightly longer duration than one phone. According to Navarro Tomás (1968), there is reduction from two segments to one, with no increase in duration. In the present study, adult native Mexican Spanish speakers produced three sets of phrases containing the sequences [s]+vowel, vowel+[s], and [s]+[s] in both citation forms and fluent reading. Preliminary findings support Malmberg’s position regarding the citation form productions and Navarro Tomás’s position in the fluent reading productions. This suggests that Spanish-language speech synthesis systems, in the absence of allophonic variation for a given sequence, can vary the duration of rhyme plus onset sequences at word boundaries to achieve a citation vs. fluent reading speech style.
Resonance effects in axisymmetrically forced bubble oscillations
Authors: Glynn Holt R. , Trinh Eugene H.
Published: October 2005

Large (0.02≤kR≤0.5) bubbles are levitated in a primary acoustic field, trapped slightly above the pressure nodes. A secondary, amplitude-modulated acoustic field is superimposed to directly force the axisymmetric shape modes at a variety of pressures and frequencies. By satisfying the condition for external resonance (when the external modulation frequency fd is nearly equal to one of the mode-number-dependent shape oscillation frequencies fn, n=2,3,4,...) the possibility of coupling energy into the volume mode via internal resonance (when the volume mode frequency f0 is nearly an integral multiple of fn) is investigated. In particular, the viability for such an experiment in 1g at reduced ambient pressures is discussed. Finally, the possibility for performing such an experiment in 0g is discussed. [Work supported by NASA.]
Nonlinear acoustic streaming: Field theory and experiment
Authors: Bradley Charles E. , White Richard M.
Published: October 2005

The theory of nonlinear acoustic streaming is presented with emphasis on physical interpretation and general statements regarding the structure of the flow field. In addition, measurements are shown in which the flow is driven by the evanescent acoustic field near a micromachined thin plate with flexural waves traversing it. A fundamental acoustic field drives dc flow in four ways: (1) via a force field, (2) via an effective mass source distribution in the body of the fluid, (3) via a mass sink distribution at the acoustic projector, and (4), via Stokes pumping. The decomposition of the system of equations into irrotational and solenoidal components results in a number of findings. For instance, it is found that the irrotational flow that arises from the mass sources and sinks exactly cancels the irrotational component of the Stokes flow. Likewise, the solenoidal component of the force source distribution drives purely solenoidal flow while the irrotational component drives a dc pressure field. Several examples are presented to illustrate the findings. The application of the theory in the development of a micropump-on-a-chip is discussed.
A theoretical model for a highly nonlinear bubbly liquid
Authors: Zhu Zhemin , Du Gonghuan , Wu Junru
Published: October 2005

It has been known for some years that the presence of bubbles enhance the nonlinearity of a liquid dramatically. Wu and Zhu [J. Acoust. Soc. Am. 89, 2634–2639 (1991)] measured the nonlinearity parameter B/A of water containing a three-dimensional ensemble of randomly distributed uniform-sized trapped cylindrical bubbles. The measured effective B/A for the system is of the order of 104 to 105, when the bubbles were driven at their resonance frequency. A physical model of a second-order nonlinear wave equation taking account of dissipation as well as the variation of air volume fraction due to bubbles’ pulsation at resonance is developed. The results calculated using this model are in good agreement with the experimental values.
On the shock sound waves in media with oscillators
Authors: Skrynnikov Yu. I.
Published: October 2005

For nonlinear sound waves in media containing compact oscillators (e.g., liquid with gas bubbles or rubberlike materials with metallic small balls) an evolution equation was obtained taking into account a viscouslike term. With the help of the technique of multiple scales for singular perturbations its solution in the form of the shock wave was found. In contrast to the well-known solution of Burgers equation the front of the obtained shock wave has an unusual form with a horizontal plateau. Owing to this fact the wave energy dissipation may be easily demonstrated to be weak. Actually, the wave energy E release rate due to viscosity is proportional to dE/dt∝−ε, where ε is the dimensionless viscosity. In the limit ε≪1 this rather weak energy dissipation leads only to insignificant distortion of the wave profile involved. So the solution obtained can be considered as a quasi-stationary wave for the rather long time of its propagation in a viscous medium.
Temporal gap detection thresholds in sinusoidal markers simulated with a multi-channel, multi-resolution cochlear model
Authors: Heinz M. G. , Goldstein M. H. , Formby C. , Forrest T. G.
Published: October 2005

Computer simulations were implemented for estimating detection thresholds for silent temporal gaps in sinusoidal markers that differed in frequency. The stimuli were presented in blocks of 50. 2AFC trials in the same adaptive paradigm used to measure human temporal gap detection (TGD) thresholds [Formby etal., companion paper at this meeting]. The stimuli were preprocessed by a multi-channel, multi-resolution cochlear model. The digital simulation of the cochlear model was implemented by a 30-channel basilar membrane filter bank, followed by 30 hair cell/synapse sections [Liu, Ph.D. dissertation, Johns Hopkins Univ. (1992)]. The output for each channel of the cochlear model was lowpass filtered, and a max–min ratio [Forrest and Green, J. Acoust. Soc. Am. 82, 1933–1943 (1987)] was estimated for each of the 30 channels. A majority vote across the 30 max–min ratio values on each trial was used to select the observation interval containing the silent gap. Results from this majority voting scheme were qualitatively similar to, but consistently poorer than, human psychoacoustic TGD thresholds [Formby etal., companion paper at this meeting]. Other decision rules are being investigated and will be presented for simulating human thresholds. [Research supported by NIH.]
Auditory detection of an increment in the rate of a random process
Authors: Brown William S. , Emmerich David S.
Published: October 2005

Recent experiments have presented listeners with complex tonal stimuli consisting of components with values (i.e., intensities or frequencies) randomly sampled from probability distributions [e.g., R. A. Lutfi, J. Acoust. Soc. Am. 86, 934–944 (1989)]. In the present experiment, brief tones were presented at intervals corresponding to the intensity of a random process. Specifically, the intervals between tones were randomly selected from exponential probability functions. Listeners were asked to decide whether tones presented during a defined observation interval represented a ‘‘noise’’ process alone or the ‘‘noise’’ with a ‘‘signal’’ process added to it. The number of tones occurring in any observation interval is a Poisson variable; receiver operating characteristics (ROCs) arising from Poisson processes have been considered by Egan [SignalDetectionTheoryandROCAnalysis (Academic, New York, 1975)]. Several sets of noise and signal intensities and observation interval durations were selected which were expected to yield equivalent performance. Rating ROCs were generated based on subjects’ responses in a single-interval, yes–no task. The performance levels achieved by listeners and the effects of intensity and duration are compared to those predicted for an ideal observer.
Level discrimination in roving-level, notched-noise maskers as a function of masker bandwidth and rove range
Authors: Buus So/ren , Florentine Mary
Published: October 2005

This experiment examines how level discrimination (also called intensity discrimination) of a three-tone complex depends on the bandwidth and rove range of a notched-noise masker. Previous experiments used fixed-level maskers, which may provide profile-discrimination cues. In the present experiment, a roving masker obviated profile cues. Level discrimination thresholds, ΔL’s (=20 log[(p+Δp)/p], where p is pressure), were measured in four listeners. The equality intense signal components at 0.84, 1, and 1.17 kHz were set to 25, 55, or 85 dB SPL. The two masker bands extended 1 or 7 critical bands below 0.77 kHz and above 1.27 kHz. Results show that ΔL’s increase somewhat as the rove range increases from 0 to 20 dB, but for rove ranges less than 10 dB, the increase is small. Contrary to predictions based on profile discrimination, ΔL’s at 60 and, especially, 90 dB SPL tend to be larger with 7-than with 1-Bark-wide masking bands. At 30 dB SPL there is almost no effect of masker bandwidth. These results indicate that profile cues probably did not affect appreciably previous measurements of level discrimination in notched-noise maskers. [Work supported by NIDCD.]
Sample discrimination of intensity differences for mixtures of target and context tones
Authors: Neff Donna L. , Kessler Christina J. , Sullivan Robert E.
Published: October 2005

Four listeners were presented with multitone complexes (of fixed frequency and number of tones) in a 2AFC task and asked to indicate which interval had the higher mean tone level. Individual levels of the tones were drawn at random from a Gaussian distribution with a standard deviation of 5 dB, and the distributions for the two intervals differed in mean intensity by 5 dB. Across conditions the number of tones presented varied from 1 to 13. Tones were spaced at equilog intervals from 250 to 4000 Hz, beginning with one tone at 1000 Hz and spreading outward with increasing number. Except for one extremely good listener, the results replicated earlier work by Lutfi [J. Acoust. Soc. Am. 86, 934–944 (1989)], despite the use of different frequencies. Conditions were then repeated adding two flanking context tones whose intensities were drawn from the lower (nontarget) distribution. The context tones degraded performance in all conditions by approximately 0.6d′ units. A large increase in the number of context tones reduced performance to chance. Listeners appear unable to apply analytic listening strategies to the task. [Work supported by NIDCD.]
Common stimulus effects on the Weber and loudness growth functions
Authors: Robinson K.
Published: October 2005

The relationship between the Weber function and the loudness growth function is an ongoing and controversial theme in the literature. Although the effect of stimulus differences on the Weber function is well known, no work has exploited these stimulus differences in an effort to demonstrate a relationship between intensity discrimination and loudness scaling. Three listeners performed intensity discrimination using white noise, and using bandlimited tone complexes centered at 0.25 and 3 kHz. An adaptive gated pedestal method was employed. As expected, Weber’s law obtained for intensity discrimination of white noise, whereas the ‘‘near miss’’ obtained for the bandlimited stimuli. The listeners then performed loudness scaling using category rating with the same set of stimuli. Strong linearity was observed in the loudness functions for white noise, whereas nonlinearity was observed in the functions for the bandlimited stimuli. Results are consistent with the multiband excitation model proposed by Florentine etal. [J. Acoust. Soc. Am. 81, 1528–1541 (1988)], which explains the common stimuli effects by differences in excitation patterns. These data therefore show that there is a relationship between the Weber and loudness growth functions.
Masking of a short probe by sinusoidal FM
Authors: Edwards Brent W. , Viemeister Neal F.
Published: October 2005

In experiment I, a 10-ms, 1-kHz probe was detected in the presence of an FM masker centered at 1 kHz and sinusoidally modulated at 16 Hz. The probe was presented when the instantaneous frequency of the masker was 1 kHz. As the modulation index (β) of the masker was increased—increasing the frequency excursion and decreasing the energy of the masker near 1 kHz—the detection threshold of the probe increased by as much as 20 dB. This result is contrary to predictions based on simple energy detection. Since both the sweep rate and frequency excursion of the masker increase as β increases, frequency-clipped FM maskers were used in experiment II to fix either rate or excursion. Thresholds agreed with the data from experiment I for equal excursions but not equal rates. In experiment III, the maskers from the first two experiments were passed through a roex filter centered at 1 kHz and the resulting envelope was used to amplitude-modulate a 1-kHz tone. This AM signal was used as the masker. Probe detection thresholds varied as a function of β, excursion and rate in the same manner as they did with the FM maskers in experiments I and II. [Work supported by NIDCD DC00683.]
Theory and construction of a toroidal waveguide with active walls (the acoustitron)
Authors: Lawrenson Christopher C. , Shields F. Douglas
Published: October 2005

The analytical solution for axisymmetric sound propagation in a viscid fluid-filled infinite tube with rigid walls was first worked out by Kirchhoff and later Lord Rayleigh. This work has been extended to the case of a tube with a controlled surface wave at the fluid boundary. Theoretical calculations show that when the surface wave travels at the intrinsic speed of sound of the fluid, the ratio of the axial to the radial particle velocity amplitude is infinite. A prototype of such a system has been build using a toroidal tube to simulate an infinite propagation path. Theoretical calculations and preliminary results will be presented. [Work supported by ONR.]
Noise attenuation by Venturi tubes
Authors: Selamet A.
Published: October 2005

The reactive silencers installed in the induction and exhaust systems of production vehicles involve a compromise between the noise reduction and the flow efficiency. The present study considers venturi tubes as low flow-loss elements and investigates their acoustic attenuation performance in terms of two approaches: the first one combines the solutions of one-dimensional wave propagation in conical reducers and diffusers, and straight ducts; while the second one approximates the variation in the cross-sectional area by a series of stepwise contractions and expansions. The results from both approaches are shown to agree well for a number of venturis constructed for the experimental validation. Transmission loss predictions are then compared to the data obtained from an extended impedance tube setup. Finally, the acoustic attenuation and the flow performance are presented for one of the constructed venturi tubes against a limit configuration: a contraction chamber with the diameters defined by the duct and throat dimensions of the venturi tube.
An experimental study of fundamental reactive silencers in the induction system of firing spark-ignition engines
Authors: Selamet A. , Novak J. M.
Published: October 2005

The low-amplitude wave suppression of fundamental reactive silencers in the absence of flow is well established. The present experimental study investigates the performance of these configurations in the presence of both high-amplitude pressure waves and oscillating fluid flow. The silencers are installed in the induction system of a Ford 3.0-liter V6 Vulcan engine in a dynamometer test facility. The experiments with the firing engine have been conducted with speeds ranging from 1000 to 5500 rpm. Measurements including the mean flow rate, the temperatures and the absolute dynamic pressures of the induction air before and after the silencer with fast-response, piezo-resistive transducers facilitate the calculation of acoustic performance of these elements, as well as the flow losses and their influence on the engine performance. The present study describes the experimental aspects of an extensive effort towards employing nonlinear fluid dynamic models in the time-domain for the prediction of the acoustic and power performance of firing internal combustion engines with full vehicle induction and exhaust systems.
Acoustics demonstration experiments, old and new
Authors: Rossing Thomas D.
Published: October 2005

Since the time of Pythagoras, if not before, demonstration experiments have been used by teachers to illustrate acoustic phenomena and important acoustics principles, and to arouse curiosity about the science of acoustics. Sources for ideas about acoustics demonstrations will be discussed, and as many demonstrations as time permits from classic books by Rayleigh, Taylor, Sutton, Meiners, Freier and Anderson, Hilton, Ehrlich, Carpenter and Minnix, the Exploratorium staff, and others will be illustrated.
Efficiency of sound propagation and reflection with balls and liquid in a baking dish
Authors: Apfel Robert E.
Published: October 2005

The efficiency of a vibrating object in converting fluid motion into sound and of an object in reflecting sound depends on whether the fluid in contact with the object has time to get around it during one half an acoustic period. If it does not have adequate time, the fluid is compressed and sound is produced (or reflected). To simulate this invisible process for a classroom of students, a viscous liquid with a large number of small plastic balls is placed in a transparent glass baking dish sitting on a transparency projector. Small, medium, and long paddles sloshing back and forth in the liquid show different behaviors. If the paddle is large and oscillating at a modest or high rate, the particles are seen to be trapped in front of paddle and appear to be compressed. For the small paddle and sufficiently low vibration rates, the particles have enough time to slosh around the paddle. With a minimal amount of analysis, students will quickly learn to appreciate how the efficiency of vibrating surfaces or reflecting objects depends on the relative magnitudes of the object size and the acoustic wavelength.
Degraded synthetic speech for classroom demonstration
Authors: Strong William J.
Published: October 2005

Purposely degraded speech can be useful for demonstrating parameters important in speech perception as well as the effects of common degradations. A four-pole terminal-analog synthesizer whose control parameters could be modified was used to generate natural-sounding and degraded synthetic speech. One category of degradation involved the selective elimination of formants to demonstrate their perceptual role. Another category involved modifying the fundamental frequency contour to change the sense of a sentence or to change its ‘‘expressiveness.’’ Another category involved changing the formant frequencies to produce ‘‘helium speech’’ or ‘‘argon speech.’’ A final category involved degrading the speech waveform via additive noise, bandwidth limitation, peak clipping, and center clipping to demonstrate their effects on speech intelligibility and naturalness. A short demonstration tape will be presented. (This material represents a significant refinement and updating of material originally presented at the 78th Meeting of the Society in November 1969.)
Demonstrations with wind instruments and the spectrum analyzer
Authors: Cottingham James P.
Published: October 2005

The ready availability of the FFT spectrum analyzer has made it possible for such notions as Fourier components and vibration recipes to come alive for students in elementary level courses in musical acoustics. The spectrum analyzer is helpful not only in the laboratory, but also in class demonstrations. Several examples will be shown involving normal modes and overblowing of wind instruments. The instruments are played either mechanically or by human players, and important phenomena can be viewed ‘‘live’’ on the display screen as they are heard.
Considerations in the design of real time electronic musical instruments
Authors: Clark Melville
Published: October 2005

Results of the analysis, synthesis, and perturbation of the sounds of traditional acoustic musical instruments obtained between approximately 1955 and 1972 by several methods will be summarized. The behavior of the sounds produced by various acoustic instruments and the features found to be important and unimportant to the sounds of several percussive and nonpercussive instruments will be reported and a demonstration provided. For example, it has been found important for nonpercussives to provide an attack transient and pseudosteady state, while the decay transient is of much less importance in normally reverberant environments. For percussives, the first part of the sound is of very little auditory significance, but the decay transient is of overwhelming importance. The changes of partials with time during the important epochs is perceptually significant. To prevent tones from cloying, addition of or modulation with pink noise in just the right way and in the right amount is greatly desired. In other situations, inharmonicity of certain partials is vital to the quality of sound. The view is taken that if most people can NOT hear something, that something is NOT important; if most people can hear that something, it is important.
Musical timbre perception: The influence of onset transients
Authors: Iverson Paul
Published: October 2005

Previous research on musical timbre has suggested that onsets are particularly important for the perception of musical timbre; identification is poor if listeners do not hear onsets, and dimensions of MDS solutions tend to correspond to attack length. However, more recent research has demonstrated that the dynamic attributes that influence similarity judgments cannot be localized to onset transients [P. Iverson and C. L. Krumhansl, J. Acoust. Soc. Am. 94, 2595–2603 (1993)]. In separate experiments, subjects rated the similarity of complete tones, the onsets of those tones, and tones with the onsets removed (remainders). Multidimensional scaling solutions revealed that judgments on all three sets of tones were quite similar, demonstrating that the attributes that influence timbre in complete tones are present both at onsets and remainders. Results from acoustic analyses suggested that similarity judgments may rely on global acoustic comparisons rather than on the isolation of specific acoustic attributes. In contrast, identification judgments may rely on specific acoustic attributes present only at the onsets. This research will be reviewed in light of new research on musical timbre perception.
Derivation of a synthesis model from time-variant spectral analysis
Authors: Beauchamp James , Horner Andrew
Published: October 2005

An effective spectrum-based musical instrument synthesis model requires that time-variant spectrum analysis (TVSA) be performed on a large group of tones representing the entire pitch and dynamic range of the instrument. Once enough common properties in the TVSA results are identified, a synthesis model can be devised, implemented, and tested. When the synthesis model is sufficiently complete, it can be employed in music performance or timbral research. It is important that a synthesis model’s physical parameters strongly correlate with perceived timbral features. Our current model employs three time-variant parameters: rms amplitude, spectral centroid, and fundamental frequency, which strongly correlate with loudness, brightness, and pitch. In addition, a centroid-controlled transfer function, preconstructed by averaging TVSA data from the original set of analyzed tones, is used to generate the detailed time-variant spectra. When the three time-variant parameters are matched to those measured in particular instrument tones, global contours and micro-details emerge that contribute to synthesis realism. Small perceptual differences between original and synthetic sounds, which some listeners perceive as ‘‘roughness,’’ may be caused by smoothing of asynchronous spectral fluctuations in the synthesis. Current research is attempting to data-reduce both the time-variant control parameters and the centroid-controlled transfer function without sacrificing quality.
Within-category discrimination of musical chords: Perceptual magnet or anchor?
Authors: Acker Barbara E. , Pastore Richard E. , Hall Michael D.
Published: October 2005

Recent speech research has demonstrated that the presence of prototypes may be reflected in the internal structure of speech categories. Some speech results have found lower discrimination in a vowel P context compared to a NP context, suggesting that a prototype may function as a perceptual magnet, effectively decreasing perceptual distance, and thus, discriminability, between stimuli. The current study examines the function of prototypes in a musical category; another natural, but nonspeech, category. Prototype (P) and nonprototype (NP) sets of major triad stimuli were constructed, with stimuli in the P set being more representative of the category than the NP stimuli. Musically experienced subjects rated the stimuli in each set for goodness as a major triad, with the highest rated stimulus serving as a prototype standard for a subsequent discrimination task. Results from the discrimination task demonstrated better performance in the prototype context. The current nonspeech results appear to follow predictions based on classification and perceptual models (to be discussed), and provide a natural, nonspeech contrast to speech findings. The results will also be addressed in terms of music perception, including aspects such as different temperment systems and the differential importance of chord components.
Does expressive timing remain relationally invariant under global tempo transformations?
Authors: Repp Bruno H.
Published: October 2005

Measurements of tone interonset intervals in pianists’ performances of Schumann’s ‘‘Träumerei’’ at three different tempi [B. H. Repp, Psychol. Res. (in press)] have suggested approximate relational invariance of expressive timing, but with a tendency towards reduced temporal contrast (relative modulation depth) at a faster tempo. In this study a perceptual test was assembled by manipulating global tempo (3 levels) and degree of temporal contrast (5 levels) independently in a single MIDI-recorded performance of ‘‘Träumerei.’’ Skilled pianist subjects rated the resulting 15 performances on a 10-point scale. The question was whether the same degree of temporal contrast would be preferred at all three tempi (suggesting relational invariance), or whether an interaction would emerge, such that smaller degrees of contrast are preferred at faster tempi. The results may speak to the adequacy of simple tempo controls on MIDI instruments or in performance synthesis. [Work supported by NIMH.]
A novel technique for measuring the maximum radius of a sonoluminescing bubble
Authors: Cordry Sean M. , Crum Lawrence A. , Roy Ronald A.
Published: October 2005

Single bubbles are acoustically levitated in a rectangular standing wave resonator filled with clean liquid that has been ‘‘degassed.’’ The acoustic pressure of the sound field induces radial oscillations in the bubble of sufficient magnitude to cause them to sonoluminesce. Measurements of the maximum diameter are then made using a video imaging system composed of a microscope, CCD, and digitizing computer. These diameter measurements are compared to the light emission intensity as measured by a photomultiplier tube (PMT) and single photon counter (SPC). Both measurements of light intensity and diameter are made for pure water and several aqueous solutions. The results of this experiment as well as the accuracy and precision will be discussed. [Work supported by ONR.]
An estimate of the duration of sonoluminescence from an oscillating bubble based upon shock dynamics
Authors: Nadim Ali , Pierce Allan D. , Sandri Guido V. H.
Published: October 2005

An order of magnitude estimate is provided of the duration of the extremely short flashes of light that are emitted at regular intervals when a spherical gas bubble is made to oscillate by ultrasonic excitation—the phenomenon known as sonoluminescence. The estimate is based upon a recently proposed mechanism for this phenomenon [H. P. Greenspan and A. Nadim, Phys. Fluids A 5, 1065–1067 (1993)], which envisions the formation of spherically converging shock waves within the oscillating gas bubble, which itself acts as a spherical ‘‘piston.’’ As the shock wave converges toward the geometric center of the bubble, it gives rise to extremely high temperatures, ionizing the gas and leading to the emission of light. In the present contribution, it is shown that under reasonable assumptions on the distance and strength of the shock from the bubble center when it first occurs, the time during which the gas near the bubble center is hot enough to produce visible light is on the order of tens of picoseconds, in agreement with experimental observations.
The propagation of very-high-frequency sound in a strongly ducted waveguide
Authors: Werby M. F.
Published: October 2005

The method used in the normal mode code SWAMP based on a new mathematical scheme enables one to obtain accurate answers for very high frequencies. To date 1000 modes have been calculated for a strongly ducted waveguide obtained from a Medd. profile with a typical fluid bottom. The water column here is 80 m and calculations have been conducted to 25 kHz. With increasing frequency, strong refraction dominated and the relevant modes are confined by and large in the ducted regions. The higher modes, which produce a phase averaging effect, result in a relatively weak signal where they are dominant and strong bending of waves is rather dramatic with increasing frequency. On the other hand, when a source is placed in the nonducted region, a paradoxical result occurs in which the signal appears trapped in the nonducted region because the modes relevant in the ducted region can not be stimulated from a source outside the ducted region at very high frequency. The fact that the modes contributing in the nonducted region are very high angle–as expected—is evident in the two-dimensional plots presented. Many interesting results will be illustrated graphically over a variation in frequency. [Work sponsored by the Naval Research Laboratory 6.1 Program Element 0601153N.]
On describing pulse signals from explosives in a waveguide
Authors: White Elmer , Werby M. F.
Published: October 2005

SUS charge data are examined in a 300-m waveguide off the straits of Florida. A realistic spectrum was employed for the explosive, and time arrivals and pulse forms were calculated for bandwidths of 200 and 400 Hz centered about 300 and 600 Hz, respectively. The waveguide is strongly downward refracted and data exist for arrivals at 6.7 and and 13.7 nautical miles. It is possible to predict the pulse widths and arrival times as well as the pulse forms correctly. In addition to describing the data, trends for the arrivals as a function of receiver depth are examined. Due to the ducting effect, depth dependence yields interesting information. [Work sponsored by the Naval Research Laboratory 6.1 Program Element 0601153N.]
‘‘Sound in the Ocean:’’ A short video
Authors: Porter Michael B.
Published: October 2005

This video uses several computer models to illustrate the effects of the ocean channel on sound propagation. A Pekeris waveguide shows pulse dispersion and the concepts of group and phase velocity. Data from an experiment [R. H. Ferris, J. Acoust. Soc. Am. 52, 981–988 (1972)] is modeled showing how the channel can separate out individual modes. A simple two-medium problem shows the formation of the head wave and effects on reflected and transmitted waves.
Effective reflection and transmission coefficients for the mean field in a two-layered variable sound-speed waveguide
Authors: Berman David H.
Published: October 2005

This is a continuation of a study of how to incorporate recently developed approximations for rough surface scattering into the description of propagation in a waveguide with rough boundaries and rough interior interfaces. Although reflection and transmission coefficients are not directly useful in variable sound-speed media, it is possible to derive from them an impedance operator that linearly relates pressures on either side of an interface to displacements on either side of the interface. This linear relationship can then be used in a variable sound-speed environment. It will be shown how the Green’s function in a two-layered duct with a rough interior interface can be constructed from solutions for flat-surface Dirichlet and Neumann Green’s functions. The averaged Green’s function can be seen to be the Green’s function for a two-layered duct with effective reflection and transmission coefficients across the mean interface separating the two layers. These effective reflection and transmission coefficients are not simply the mean reflection and transmission coefficients found at an interface separating two half-spaces; they include effects of multiple scattering between the boundaries of the waveguide. This work generalizes that discussed in D. H. Berman [J. Acoust. Soc. Am. 94, 1786(A) (1993)] where only reflection was treated.
Acoustic backscatter analysis from a smooth sand surface
Authors: Chotiros Nicholas P. , Laughlin Julia
Published: October 2005

Existing theories describing backscattering behavior from smooth water-filled sands were reviewed. Currently only single-scatter theories have been employed to describe the grazing angle and frequency dependence of backscattering on smooth surfaces. A comparison of the existing backscattering models to experimental results was then conducted. Of particular interest was the dependence of backscattering strength on grazing angle and frequency. Due to the simplistic nature of single-scattering theory, analysis of theoretical versus experimental data led to many discrepancies. In an effort to more accurately describe backscatter behavior in water-filled sands, alternative scattering theories were explored. [Work supported by ONR.]
Sensitivity and predictability of intensity statistics for shallow-water propagation with a sediment scattering layer
Authors: Howell K. J. , Jacobson M. J. , Siegmann W. L. , Carey W. M.
Published: October 2005

It is well known that uncertainties in bottom properties are a significant factor in limiting accuracy of shallow-water acoustic predictions. In this paper, a scattering layer is introduced at a horizontal water–bottom interface to model effects of attenuation due to interface and sediment scattering. Using a wide-angle PE, formulas for intensity statistics are found for a geoacoustic model consisting of three isospeed layers. The sensitivity of these statistics to parameters such as frequency and scattering layer thickness and correlation length are then investigated analytically and numerically. Comparisons are made between intensity statistics of the three-layer model and of other isospeed and depth-dependent sediment profile models. Additional comparisons are made between three-layer model statistics and data from a recent New Jersey Shelf experiment. Results from the inclusion of a scattering layer for the prediction of relative intensity statistics are evaluated over a wide range of acoustic frequencies. Sensitivities to parameter variations are also investigated. [Work supported by ONR.]
A shallow water acoustic/geoacoustic experiment at the New Jersey Atlantic Generating Station Site
Authors: Badiey Mohsen , Jaya Indra , Pulaski Mark , Cheng Alex
Published: October 2005

Shallow water acoustic experiments were conducted at the Atlantic Generating Station (AGS) Site on the New Jersey Continental Shelf as a part of a long-term study of the shallow water physics in this region. A vertical hydrophone array was used to assess the dispersion characteristics of a broadband acoustic field. A geoacoustic data set and bottom impedance profiles were constructed based on previous measurements of geological parameters from sediment core data. Experimental results show that the acoustic wave field dispersion is dependent on the azimuth. This dependency may be attributed to several factors relating to topography and range and depth features. Empirical orthogonal functions (EOF) were used to decompose the acoustic normal modes. A preliminary discussion of simulation results and the sediment layering effects on the features of the acoustic normal modes and the corresponding group and phase velocities associated with each mode will be given in connection with the experiment. a)Present address: Office of Naval Research, Ocean Acoustics program Code 324OA, 800 North Quincy St., Arlington, VA 22217-5000.
A high-order time-domain paraxial equation for weakly nonlinear acoustic propagation
Authors: Kulkarni R. S. , Siegmann W. L.
Published: October 2005

A time-domain paraxial equation for acoustic propagation has been developed that possesses capabilities for shallow-water propagation. The equation incorporates effects of nonlinear wave steepening, wide propagation angles, dissipation, and spatial variability in both ambient density and sound speed. Dissipative mechanisms due to viscosity and heat conduction are included, with extensions possible to incorporate relaxation effects. The derivation procedure is a hybrid approach combining operator formalism with the method of multiple scales. The operator formalism is used to factor the two-way equation and to introduce a high-order Padé approximation to the square-root operator, while multiscaling permits simplifying estimates of terms in the equation. Comparisons have been made with other time-domain paraxial models. A computational strategy, based on splitting the equation into components representing distinct physical processes, will be discussed. Numerical results for particular cases will be presented and compared with those from other paraxial models. Effects of weak nonlinearity and dissipation will be described. [Work supported by ONR.]
Empirical orthogonal function representations of stochastic sound-speed ensembles
Authors: Longfritz M. J. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

The representation of stochastic ensembles of sound-speed profiles by convenient and efficient means is examined. The procedure is based on using discrete empirical orthogonal functions (EOFs) with random coefficients. The eventual objective is to use the EOF representations in random wave propagation models, for which their efficiency is expected to reduce significantly the computational expense. To illustrate the procedure, two specific model ensembles are considered. The first consists of deep-water (Munk) sound-speed profiles, and the second has shallow-water profiles obtained from temperature profiles generated by a portion of the generalized digital environmental model (GDEM). After a statistical distribution of stochastic environmental input parameters is assumed, EOFs are calculated for ensembles of up to 10 000 profile samples. Relations between the statistics of the input parameters and the sound speed profiles that are obtained from EOF representations are investigated. In each case examined, the number of EOFs needed to account for virtually all of the sample variance is at most four. Additional cases are considered using Continental Shelf data by assuming measured profiles represent ensemble samples. [Work supported by ONR.]
Revisions to an empirical surface loss model using a correction for pH-dependent attenuation
Authors: Christian Raymond J. , Browning David G. , Williams David G.
Published: October 2005

Empirically derived surface loss values are not obtained directly but are derived from propagation loss measurements that include at least two other components. Surface loss is determined by making assumptions with regard to spreading loss, volume attenuation (and bottom loss, if appropriate). Marsh and Schulkin [AVCO Marine Electronics Office Tech. Rep. (1962)] analyzed an extensive set of transmission loss data from surface duct propagation to obtain surface loss values. They assumed that attenuation was entirely due to magnesium sulfate and used the early Marsh–Schulkin [J. Brit. IRE 25, N6 (1963)] attenuation formula (Thorp, Mellen etal., and Francois Garrison attenuation formulas were not known at the time). Corrections to the Marsh–Schulkin surface loss data have been computed that account for the differences between the Marsh–Schulkin and Mellen etal. [NUSC TR 7293 (1983)] attenuation formulae. The revised values show less loss for all frequency-wave-height (F-H) products. The Kuo [J. Acoust. Soc. Am. 36 (1964)] perturbation theory estimates of surface loss are shown to be in good agreement with the revised data at low F-H products.
Architectural acoustics
Authors: Siebein Gary W.
Published: October 2005

This tutorial will familiarize people with basic concepts in architectural acoustics. Many slides of actual buildings and a brief audio tape will be used to illustrate connections between the visual appearance of buildings and the qualities of their sonic environment. The presentation will provide examples and explanations of common acoustic experiences in buildings with the under-lying reasons for their occurrence. Architectural acoustics can be characterized as an evolving, empirical exploration of basic principles from many areas of acoustics through creative testing in the design and subsequent evaluation of buildings. A historical review of applied acoustical principles translated into the medium of architecture will be presented in four primary areas: (1) subjective impressions, including qualities of music, speech intelligibility, and annoyance, which are the basis for current design criteria; (2) room acoustics design with an emphasis on auditoria, schools, restaurants, and other public buildings; (3) providing privacy from unwanted sounds and vibrations through discussion of standard measurement techniques such as sound transmission class (STC); and (4) management of noise from HVAC systems and other equipment and processes in buildings. Interesting case studies will demonstrate how complex the practical application of even relatively simple acoustical principles can be in many buildings. In recent years a significant community of laboratory and applied researchers dedicated to this field has emerged to question and quantify the empirical knowledge base that has been accumulated over time. Recent topics of interest such as new measurement, modeling and simulation techniques will be briefly introduced.
Low-frequency impedance measuring device for underwater acoustic materials
Authors: Cole John E. , Martini Kyle
Published: October 2005

A laboratory testing device for measuring the direct and transfer impedances of acoustic materials below 1 kHz has been developed. The 3-ft-long test chamber accommodates 4-in.-diam material samples. Excitation of the sample is by means of an impedance head consisting of a piezoelectric tonpilz driver and force gage. Responses of the excitation and of the sample backing plate are sensed by accelerometers. The material can be hydrostatically pressurized up to 500 psia. A unique feature of the device is a water layer that couples the impedance head to the material sample. This layer permits materials to be tested after deformation under hydrostatic loading. Design features and performance characteristics of the testing device are described. Results of calibration tests and measurements on an air-rubber material are presented. [Work supported by the Office of Naval Research.]
Ultrasonic measurements in air or water saturated porous media
Authors: Castagnède B. , Melon M. , Brown N. R. , Allard J.-F.
Published: October 2005

Low-frequency (20 kHz–180 kHz) ultrasonic measurements have been performed in numerous air-saturated acoustic materials, i.e., various foams and felts. By using a standard pulse-echo technique, very precise wave-speed measurements were achieved with either a cross-correlation procedure or by using the Hilbert transform of the transfer function between a reference signal (with no sample) and the signal transmitted through the sample. The amplitude measurements were done in the Fourier domain via the cross power. The signal processing routines were implemented in the LabVIEW 2.0 environment. Some significant physical properties (e.g., tortuosity) related to the propagation of acoustic waves in porous media [e.g., J.-F. Allard, PropagationofSoundinPorousMedia (Elsevier, New York, (1993)] were obtained. Preliminary results made at 500 kHz, with the aim of measuring the viscous as well as thermal characteristic lengths, on water-saturated sandstone specimens will also be reported.
Pressurized dynamic analyzer: A device for measuring dynamic properties of materials over pressure and temperature
Authors: Africk Steven A. , Caplan Mark D. , Hoefler Jeffrey J.
Published: October 2005

Many acoustic materials used in underwater applications have properties and hence performance which varies with depth pressure and temperature. A device has been built in which both the static deformation of a sample and its dynamic modulus and loss factor can be routinely measured up to 1000-psi pressure. This consists of a shake-table apparatus within a dedicated temperature-controlled pressure vessel. Pressurization is by air to avoid mechanical shorting paths. Transfer impedance measurements are made and the complex effective modulus of the sample—that which it would have if it were homogeneous—is inferred. Data are taken using a dual-channel analyzer under PC control, and analyzed by specially written Matlab software. Sample deformation is measured by an LVDT probe. Temperature control supports extrapolation of data in frequency by WLF scaling. Measured modulus and loss factor of two acoustic materials as a function of pressure show slightly different behavior. [Work supported by ONR.]