bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic velocity related distributions
Authors: Budhiantho Matias H. W. , Hixson Elmer L.
Published: October 2005

The acoustic velocity x, y, z components and its resultant amplitudes, the kinetic and total energy density distributions in a reverberation space, were measured using an energy density sensor consisting of four microphones. The space is a 225-m3 with average reverberation time of 6 s at 1 kHz. The room was excited with pure-tone, narrow- or wide-band noise. The result of the measurements showed that the acoustic velocity x, y, z component amplitudes were Gaussian-distributed, its resultant amplitude was Maxwell-distributed. The kinetic and total energy densities were gamma-distributed with three and four degrees of freedom, respectively. In agreement with published literature, the measurement also showed that acoustic pressure was Gaussian and the potential energy density was exponentially distributed, however, the other distributions have not been reported. Theoretical background and measured data will be presented.
Comparison between the 1/10-scale model experiment and the full-scale measurement in a concert hall
Authors: Satoh Fumiaki , Shimada Yasushi , Hidaka Yoshito , Tachibana Hideki
Published: October 2005

In order to examine the accuracy of acoustic scale modeling, the experimental results of a 1/10-scale model study performed for acoustical design of a concert hall and those measured in the full-scale hall after the construction are compared. In the scale model study, the impulse responses were measured by the direct method using a spark discharge source and monaural and binaural microphone systems. For the measurement of the binaural impulse response, a 1/10-scale dummy head system was made on a trial basis. In the real hall, impulse responses were measured by the sweep-pulse method using a dodecahedral omnidirectional loudspeaker and monaural and binaural microphone systems. The monaural impulse responses were measured at the corresponding points in the scale model and the real hall, and such quantities as D50, C80, and Ts were obtained and compared. The binaural impulse responses measured in the model and real hall were convolved with the same sources of a variety of music and presented to the subjects through a transaural reproduction system using two loudspeakers. Through these quantitative and subjected investigations, a fairly good correspondence has been found between the scale model and the real hall.
On counting ocean bubbles acoustically
Authors: Medwin Herman
Published: October 2005

The earliest attempts to determine ocean bubble densities were optical, because everyone knows that ‘‘seeing is believing.’’ Unfortunately, bubbles smaller than 60-μm radius were not always recognized in photographs of the dirty, detritus-contaminated, bubbles. And bubbles greater than 150-μm radius were so infrequently observed that the average values were quite unreliable. Acoustical ‘‘counting’’ by inversion of the linear processes of backscatter, excess attenuation, and dispersion has great advantages over optical measurements. Primarily this is because the acoustic cross sections of a resonating bubble are orders of magnitude greater than optical values for the same radius. The ability to gather data rapidly, the ease of obtaining correlations with other oceanographic variables, and the simple inverse relation between sound frequency and resonant bubble radius have given acoustics great advantages over optical bubble-counting at sea. For 30 years, at several locations, under various ocean conditions, active in-situ pulse echo systems and resonators using broadband transducers have yielded a rich harvest of well-resolved data for bubble radii from 15 to 300 μm. More recently, by passively listening to newly created damped oscillating bubbles, acousticians have provided meteorologists and climatologists with accurate fundamental data of ocean surface gas transfer and hydrosol production due to breaking waves and rainfall. Techniques and results of active and passive linear acoustical monitoring are reviewed. [Research supported by ONR.]
Measuring bubbles, boundary layers, and related processes in the ocean surface layer
Authors: Melville W. Kendall
Published: October 2005

Bubbles entrained by breaking waves are important in the active and passive acoustics of the ocean surface layer, and also play an important role as tracers for acoustic Doppler techniques. Bubbles are not just passive tracers but may also be dynamically significant, thereby affecting the structure of the wave-zone boundary layer. The processes affecting the distribution of entrained air and the distribution of bubble sizes are reviewed in the context of the available measurement techniques, models, and observations of the surface boundary layer. In many respects, the knowledge of the fluid dynamic structure of the surface layer is no better than the knowledge of the acoustics and bubble phenomena, and the talk will emphasize those processes which are important for both fields. These include wave breaking, convection, Langmuir circulations, and turbulent fluxes and dissipation. Indeed, acoustic instrumentation plays an important role in probing the surface layer, and a better understanding of bubble-related phenomena is necessary to better understand the performance of these instruments.
Acoustic techniques for bubble measurements in the ocean
Authors: Yoon S. W. , Choi B. K. , Kim E. J.
Published: October 2005

The bubble size distribution and bubble motion information are critical to understanding underwater sound propagation and acoustic roles of bubbles in the ocean. Some of the conventional linear and nonlinear acoustic bubble sizing techniques are reviewed. For a bubble rising velocity measurement a nonlinear Doppler technique is discussed. For ocean applications, a new semicoherent acoustic bubble sizing technique based on the sound-speed information as well as sound attenuation from the extinction cross section of bubbles instead of direct sound-speed measurement is proposed.
Acoustic observation of a subsurface layer
Authors: Didenkulov Igor N. , Selivanovsky Dmitry A. , Muyakshin Sergey I. , Rodygin Yury L. , Frolov Vladimir V.
Published: October 2005

Bubbles in a subsurface ocean layer play a significant role in underwater acoustics and oceanography. Many works have been devoted to different methods of bubble density measurement. Among them, the nonlinear methods of bubble sizing based on combination acoustic scattering have a very high selectivity. These methods were utilized in several types of bubble counters developed in the Institute of Applied Physics for the last decade. In the devices the difference and the sum frequency waves of the incident ones generated by a bubble in the working volume are detected. Another approach to the problem based on the parametric generation of subharmonic of the incident wave frequency was also tested. The results of the measurements of bubble size distribution and density in the subsurface ocean layer and in the wakes of ships are given in the paper. Simulteneous measurements by different linear and nonlinear methods were done to make a comparison between them. The results of linear acoustic echosounding of a subsurface bubble cloud from an underwater research platform are also presented. Possibilities and advantages of linear and nonlinear methods of spectroscopy of structure and movements in a subsurface layer are discussed. [Work supported by RFBR (Grants 94-05-16755, 95-05-15632).]
A comparison of three acoustic techniques for measuring bubble distributions
Authors: Vagle Svein
Published: October 2005

Results of three different approaches to bubble measurement, multifrequency backscatter, pulse propagation, and complex dispersion measurements with an acoustic resonator, are compared. The multifrequency backscatter sonar has the advantage of being a remote sensor and provides high resolution up to the sea surface. However, the limited number of available frequencies and cumulative effects of attenuation due to bubble scatter complicate the inversion. The pulse propagation sonar is an in situ measurement depending on detection of travel time and attenuation for a pulse traveling between two transducers. It has the merit of providing a direct sound-speed and attenuation measurement and may conveniently be operated at quite low frequencies. A resonator that allows simultaneous measurement of sound speed and attenuation spanning the resonant bubble frequency range of interest has been developed. Measurements in three open ocean deployments provide a basis for systematic comparisons between the different bubble detection and different inversion techniques.
High-frequency surface backscattering: A 24-h time series of data showing transition between Bragg and resonant bubble scattering
Authors: Dahl Peter H.
Published: October 2005

Measurements of acoustic backscattering from the sea surface made continually over a 24-h period are discussed. The frequency was 30 kHz and grazing angle coverage was 15–25 deg. The experiment was conducted in 25 m of water near the Dry Tortugus collection of islands off south Florida. During the experiment, the wind speed varied from less than 1 to 6 m/s in three major cycles. Directional wave spectra, and air and sea temperature were also continually measured. For wind speeds ≥ 2.5 m/s, the data are consistent with scattering from resonant-sized bubbles (in this case, ∼100 μm radius) residing near the surface. These data were inverted for bubble concentration and results compared with other field measurements of subsurface bubble concentration. For wind speeds <2.5 m/s, the data are consistent with scattering from wind-generated centimetric waves, or Bragg scattering. The 24-h time series of surface backscattering demonstrates the transition between centimetric Bragg, and resonant bubble scattering modalities in high-frequency surface scattering. [Work supported by ONR Codes 322OM and 3210A.]
A broadband acoustic technique for measuring bubble size distributions
Authors: Terrill Eric J. , Melville W. K.
Published: October 2005

The development of a broadband sound velocimeter allows the simultaneous measurement of sound speed and attenuation over a wide range of frequencies, providing insight into the dispersive characteristics of a bubbly medium. The velocimeter measures the dispersion of a broadband acoustic pulse containing power over frequencies ranging from 2 to 140 kHz across a fixed pathlength. The resulting data are inverted using a simple inversion scheme to arrive at bubble size distributions over a range of radii extending from 20 to 1600 μm. A large wind wave channel located at the Hydraulics Laboratory-S.I.O. provides an ideal location for testing and calibration of the system. Filled with seawater, the channel can generate O(1 m) breaking waves, providing bubble size distributions similar to those found in the field. Results of the lab measurements and comparisons of inverted bubble size distributions with an independent optical bubble sizing technique will be discussed. Preliminary results of a near-shore deployment of the system will be presented, emphasizing results of the data inversions in context of previously reported bubble size distributions. [Work supported by NSF and ONR.]
Light scattering and optical properties of bubbles in water relevant to studies of bubble population and dynamics
Authors: Marston Philip L.
Published: October 2005

Freely rising gas bubbles in seawater illuminated by sunlight exhibit colors [P. L. Marston, Appl. Opt. 30, 3479–3484 (1991)] in the angular region of the transition to total reflection. Light scattering calculations and experiments [D. S. Langley and P. L. Marston, Appl. Opt. 23, 1044–1045 (1984); W. P. Arnott and P. L. Marston, J. Opt. Soc. Am. A 5, 495–506 (1988)] are relevant both to visual properties and to scattering devices to monitor bubble population and single-bubble dynamics. In addition to critical angle scattering, glory-enhanced backscattering and Brewster-angle polarization have been observed. Some shape effects have been studied and some effects of surface coatings have been calculated [Marston et al., Proc. SPIE925 , 308–316 (1988)]. Applications to measuring some of the effects of surfactants on the dynamics of single bubbles [Asakiet al., Phys. Rev. Lett. 75, 2686–2689 (1995); 75, 4336(E) (1995)] will also be discussed. [Work supported by the Office of Naval Research.]
Implementation of holography for identifying and measuring the population of bubbles and particles in water
Authors: Katz Joseph
Published: October 2005

The presentation includes several examples of application of holography to measurements of the population of particles in space. A reconstructed hologram is a frozen, three-dimensional image of a sample volume that can be scanned at different magnifications. Consequently, it is possible to identify and determine the spatial distribution of particles and droplets in air as well as bubbles, particles, and plankton in water. Multiple-exposure holograms can be used for velocity measurements. Due to these advantages, holography has been used extensively for particle detection. The disadvantages have been the cumbersome optical setup and the tedious analysis procedures, but recent developments in image processing offer some remedies. The presentation includes examples of implementation of holography to measure the bubble and particle populations in water, both in the laboratory, while studying cavitating flows, and in the ocean, including two generations of submersible systems. The minimum particle diameter that can be resolved in liquid is 10 μm using in-line holography and 3 μm using a hybrid, off-axis system. The maximum particle density varies between 1 and 5 per mm3, depending on the optical setup. Recent application to precision, 3-D, high-density (106 vectors per hologram) velocity measurements will be demonstrated.
Acoustic and optical measurements of bubbles in the surf zone
Authors: Deane Grant B.
Published: October 2005

Breakers in the surf zone generate numerous bubbles which are injected into densely packed clouds below the wave. These clouds affect the acoustics of the surf zone by radiating, absorbing, and scattering sound. The motivation for the present surf zone study is to develop a method to invert passive acoustic measurements of breaking waves to recover the bubble size distribution. Some of the physical processes relevant to inversion studies in the surf zone, such as the episodic nature of air entrainment and high void fractions beneath the breakers, will be discussed. Simultaneous surface video and acoustic measurements of breaking waves have been collected in the surf zone from Scripps Pier. Photographic images of bubbles in a 7 cm × 5 cm × 2 cm volume directly beneath breaking waves have also been taken. Preliminary results of acoustic and optical measurements of the bubble size distribution beneath breakers in the surf zone will be presented. [Work supported by ONR.]
Noise generation mechanisms in fresh and salt water bubble plumes
Authors: Orris Gregory J. , Nicholas Michael
Published: October 2005

Continuous plumes of bubbles were entrained by a jet of water impinging on a horizontal surface in both fresh and salt water environments. Several hours of acoustic time series were digitally recorded in both cases. Many of the prominant features of the sound generated in salt water were explained by modeling the plume as a cylindrical resonant cavity at the surface of a shallow-water waveguide. However, for salt water, the extreme low-frequency limit, the dominant mechanism for creating sound, was determined to be hydrodynamic turbulence. In addition to these two mechanisms of noise generation, in the fresh water case there were also large emissions resulting from the growth and break up of bubbly structures around the edges of the main plume—a mechanism that was absent in the salt water environment. Individual bubble oscillations could also occasionally be heard in fresh water at frequencies below 10 kHz. Details of these findings and the theoretical models will be presented, highlighting the important differences between noise emissions from bubble plumes in both fresh and salt water.
Applying root-locus techniques to the analysis of coupled modes in piano strings
Authors: Stilson Timothy S. , Van Duyne Scott A.
Published: October 2005

Previous work in the study of coupled piano string behavior, e.g., by Weinreich and Nakamura, has focused analytically on the interaction of a pair of coupled modes, noting that the rest of the string modes couple similarly. The coupling of three or more modes, as occurs in sets of unison piano strings, is studied. Equivalent circuits (modeling a finite number of modes) of coupled piano strings can be written in state-space form and their eigenvalues analyzed at various levels of detuning and coupling. Alternatively, the transfer functions of the system can often be written in a root-locus analysis form, which lends a control-theory perspective to the analysis. Often, an intuitive understanding of pole movement under variations in a single parameter, such as a single-mode frequency or coupling coefficient, can be developed. Many effects, for example, two-stage decay, can be understood in terms of system pole location. Three-mode coupling is explored and interpreted, as is variation in coupling behavior at different string harmonics.
Two-dimensional motion of a single piano string
Authors: Tanaka Hideyuki , Mizutani Koichi , Nagai Keinosuke
Published: October 2005

Two-dimensional motion of a piano string has been observed. When the hammer moves to strike the string, the irregularity of the surface causes horizontal as well as vertical vibration of the string. It has been thought that the vertical and the horizontal vibration dominates, respectively, the prompt and after sound of a piano [G. Weinreich, Sci. Am. 240, 118–127 (1979)]. An apparatus was made to observe the two-dimensional motion, assembling two optical fibers and two phototransistors. The wrapped single string E1 was measured with this equipment. The following results were found. (1) The amplitudes of the horizontal and vertical vibrations repeat, increasing and decreasing during the after sound. This means the sound is formed by the coupling of both vibrations, which occurs at the inclined pins of the bridge. (2) When the string is struck by the hammer, it vibrates at first vertically to the soundboard and then, after few seconds, it starts to rotate. The direction of the rotation changes alternately about every 6 s. (3) The first direction of the rotation is not determined. It depends on how one touches the key. This means the touch may change the piano timbre.
Generation of higher harmonics from nonlinear effects in a driven vibrating wire
Authors: Hanson Roger J. , Macomber H. Kent
Published: October 2005

Experimental measurements of various nonlinear effects in a driven vibrating wire have been reported [Hanson et al., J. Acoust. Soc. Am. 96, 1549–1556 (1994)]. Notable effects observed at driving frequencies near a natural resonance included the generation of motion perpendicular to the plane of the driving force, sudden jumps in amplitude and phase, whirling motion, and hysteresis. Reported here are results of amplitude and phase measurements of generated second, third, and fourth harmonics of the driving frequency, both in the plane of the driving force (vertical) and perpendicular to it. These higher harmonics, which are not significant at frequencies far off resonance, become very significant near a resonance. In some regions the amplitude of the horizontal motion exceeds that of the vertical motion of the same harmonic. If a twist (10–130 deg) is introduced before the wire is clamped, significant amplitude changes of the higher harmonics are observed. Under some conditions, when the wire is driven at frequencies near its third natural resonance, a very pronounced subharmonic splitting of order three is observed. Related effects are also observed for a wire vibrating freely after a pluck. Qualitative aspects will be illustrated on video tape.
Vibration analysis of a glass harp by a finite-element method: Minor pitch change due to localized shaving of the bottom part
Authors: Nakanishi Takuji , Nakai Ichiro , Yarai Atsushi
Published: October 2005

The finite-element method (FEM) was applied to analyze the vibration (inherent and the harmonic frequencies) of wine glasses (glass harp) as a musical instrument. FEM analysis for this problem was proven appropriate by confirming the coincidence between the experimental and analyzed inherent frequencies for several glass cups with different shapes. When using wine glasses as musical instruments, minute arrangement of the pitch is necessary. Even today, this is done by filling a certain quantity of water in the wine glasses. This method, however, is very troublesome because each time, just before a performance, a check has to be made to confirm that the correct water quantity had been filled in every vessel. Compounding the problem, the pitch sometimes changes during the performance because of water evaporation. In place of this water-filling method, minute pitch changes have been achieved by locally shaving a bottom part of each vessel. The pitch is found to decrease in proportion to the shaved glass quantity. The relationship between the shaved glass quantity and the changed pitch has been clarified experimentally and analytically through FEM analysis. With this procedure, the desired pitch can be obtained.
Vibrational modes of cymbals and Chladni’s law
Authors: Wilbur Charles , Rossing Thomas D.
Published: October 2005

In 1830, Chladni proposed an empirical law relating the modal frequencies of a flat circular plate to the number of nodal diameters m and the number of nodal circles n. This law leads to a mathematical relationship for the modal frequencies: fm,n=C(m+2n)2, where C is an empirical constant. An earlier analysis showed that a modified Chladni’s law fm,n=Cn(m+2n)Pn could be fitted to modal frequencies in a wide variety of flat and nonflat plates, including cymbals. Using electronic holography, as well as scanning the near-field sound, some 300 modes have been observed in a 16-in.-diam cymbal. These data can be fitted to a modified Chladni’s law fm,n=Cn(m+2n)Pn [T. D. Rossing, Am. J. Phys.50 , 271–274 (1982)] or to a similar equation with three parameters fm,n=C(m+bn)P [Perrinet al., J. Sound Vib. 102, 11–19 (1985)], where b is also an empirical constant. Both modifications of Chladni’s law appear to have some advantages in understanding the acoustics of cymbals.
A pictorial understanding of organ jet physics
Authors: Yoshikawa Shigeru
Published: October 2005

Ab initio transfiguration of the jet disturbance at the sound initiation in organ flue pipes is captured by visualizing a smoked jet with a digital high-speed video camera. The greatest interest centers on the ‘‘two-crest’’ mode of the jet wave disturbance appearing prior to the ‘‘one-crest’’ mode, which corresponds to the steady-state oscillation. This two-crest mode may be sustained by a ‘‘simultaneous double feedback’’: The lowest dominant frequency, which is lower than the first mode of the pipe resonance, is determined by the overall separation–reformation process of the two-crest jet; the second mode of th epipe resonance is simultaneously excited by the rear-crest jet after the two-crest jet is separated and a stagnant vorticity is formed at the mouth. Mode locking is not established between the harmonics until the two-crest mode has been transfigured into the one-crest mode. Moreover, a pictorial analysis of the steaady-state jet wave reveals that these experimental results of the phase speed and the amplification factor show excellent agreement with the theoretical results obtained from a spatial analysis of the jet instability.
The effect of organ reed pipe interior geometry on the vibration spectrum
Authors: Ritchie Jeffrey D. , Plitnik G. R.
Published: October 2005

The effect of varying the interior geometry of three different styles of reed shallots was studied. Three shallots—American, French, and German—were successively filled with approximately 0.065 g of wax for a total of eight fills. The wax was added to the shallots where the face opening was largest. The spectra for each of the shallots were found after each successive fill. A regulatable air source was adjusted to maintain a constant air pressure of 4 in. of water inside the boot. A reed length in the middle of each shallot’s face opening was kept constant for each shallot to facilitate comparisons. The effect of filling the shallot with wax was that the frequency of vibration initially decreased. Further filling caused the frequency to increase slightly and then level off. In general, the addition of the wax tends to brighten the tone of the spectra by raising the amplitudes of the higher-order harmonics relative to the fundamental.
Measurement of the impulse response of an oboe air column
Authors: Honma Hiroyuki , Mizutani Koichi , Nagai Keinosuke , Kobata Tokihiko , Idogawa Tohru
Published: October 2005

The impulse response of an oboe air column was measured by means of the transfer function method. This will be applied to the construction of the model for synthesizing musical sound and to the trouble-diagnostics of the instrument. Pressures at the two points are simultaneously measured in the cylinder, which is smoothly connected to the tested instrument. A time-stretched pulse is used, with the property of its phase being proportional to the square of its frequency. The generation of the pulse and the acquisition of the signal are synchronously made under computer control. The received signal is then averaged. The advantages of the method are the following. (1) The frequency responses of the measuring system, which is the sum of those of the transducer, microphone, amplifier, and so on, are compensated at once. (2) The time-stretching pulse enables one to impress high power to the test object. (3) The averaging attains a high S/N ratio. Results were obtained, with sufficient accuracy, which allows one to distinguish the shapes of the air column and perceive the differences in the level of the joint.
Hysteretic transitions between vibratory states excited in a cylindrical air column blown by the clarinet mouthpiece
Authors: Tachibana Taka’aki , Onodera Ken’ichi , Takahashi Kin’ya , Idogawa Tohru
Published: October 2005

The sounding mechanism of a simple clarinetlike system has been investigated experimentally and numerically. The system consists of a cylindrical pipe fitted with the clarinet mouthpiece. By artificial blowing, it produced various periodic and quasiperiodic sounds, among which the lowest pitch was C♯3. In particular, hysteresis of the vibratory state transitions was observed when the flowing pressure was increased and decreased under the same lip adjustment. This was also observed for the artificially blown clarinet. The behavior of the simple system is analyzed numerically by using the Schumacher model [Acustica 48, 71–85 (1981)]. The numerical model is characterized as a double-delayed feedback system represented by a simple reflection function consisting of two separated narrow Gaussian peaks. One of the peaks is due to the main reflection from the open end of the cylindrical air column, and the other, which introduces a short delay, originates from the inside discontinuity of the mouthpiece. This numerical model reproduces well nonlinear vibrations of the clarinetlike system, as well as the hysteretic transition between vibratory states.
Compositional style, frequency height, and harmonic influences on melody perception
Authors: Acker Barbara E.
Published: October 2005

The ability of musically trained listeners to detect changes in a learned melody was evaluated in homophonic (H) and polyphonic (P) musical passages. Subjects first learned a 12-note melody in isolation, then listened to three-voice fourth species counterpoints (P context) and three-voice harmonizations (H context) that contained the melody in either the high, middle, or low spectral positions. In a discrimination task, subjects were to respond to changes in the melody only, although changes could also occur in the other two voices. A signal detection analysis found that: (1) performance in the P context was better than the H context for the high and middle melody, but was poorer than the H context for the low melody; and (2) performance for the middle melody was the same as for the high melody location. This second result suggests that the findings of previous work [e.g., Palmer and Holleran, Percept. Psychophys. 56, 301–312 (1994); Acker and Pastore, J. Acoust. Soc. Am. 99, 2482(A) (1996)], where change detection was worst in the middle voice, could be due to this voice never containing the melody. The current results will be discussed in terms of Gestalt principles and Baroque compositional practices. Finally, the differential effects of the chord-related and unrelated changes will be discussed.
Fundamental study of a thermoacoustic refrigerator
Authors: Nohtomi Makoto , Katsuta Masafumi , Ikeda Masami , Maekawa Sachio , Tomikawa Hidetomo
Published: October 2005

Nowadays there are demands on the refrigerator which will be used under maintenance-free condition. In particular, it is hoped that the thermoacoustic refrigerator will be used in artificial satellites, air conditioners, and so forth because of its simplicity and high reliability. This refrigerator has no mechanical parts in its system which cause friction loss and is similar in its refrigeration process to the basic-type pulse tube refrigerator. In this paper, a thermoacoustic refrigerator has been manufactured and its performance is discussed both experimentally and analytically. In experiments investigating the basic performance of this refrigerator, the stacks (which correspond to the regenerator of the pulse tube) of both the stainless-steel parallel plate and the ceramic capillary tube were installed in the resonance tube of quarter-wavelength. The temperature profiles were measured 50 mm apart along the tube. From experimental results, a COP of 0.334 has been obtained. In addition, the theoretical analysis using an advanced enthalpy flow model has been performed. A comparison between predicted and experimental performances was made, a qualitative agreement between them was obtained, and, finally, the effectiveness of the model was confirmed.
Experimental studies on thermoacoustic refrigeration
Authors: Hara Toshitsugu
Published: October 2005

Thermoacoustic refrigeration phenomena in a resonance tube were studied experimentally. A horizontal brass tube of 400 mm in length and 40 mm in diameter was closed at one end and attached to the acoustic driver (audio speaker) at the other end. Atmospheric air was enclosed in the tube as a working fluid. Stacks which were made of a bundle of ceramic tubes, a rolled abrasive paper with garnet, or a rolled copper metal netting, were set in the tube. Driven acoustic frequency was varied from 100 to 300 Hz, and electric power to the driver was varied from 0 to 7.8 W. Pressure and temperature distributions in the tube were measured by an axially movable pressure transducer and a Copper–Constantan thermocouple. The relation of refrigeration capacity and refrigeration temperature was also measured. It was found that the maximum cooling temperature was obtained when the stack was located near the closed end equivalent to the pressure antinode. Maximum refrigeration capacity was found to be made by the ceramic tubes stack composed of a bundle of ceramic tubes 0.8 mm in hydraulic diameter. A maximum temperature difference of 12 °C was achieved in this experiment.
The transport properties of helium–xenon mixtures from acoustic measurements
Authors: Gillis Keith A. , Moldover Michael R. , Mehl James B.
Published: October 2005

Helium–xenon and helium–argon mixtures have been proposed as good choices for working fluids in thermoacoustic refrigerators, because the Prandtl number of the mixture is lower than that of a pure noble gas. Accurate measurements of the viscosity and the Prandtl number, obtained with acoustic resonance techniques, will be presented for three mixtures: He(25%)/Xe(75%), He(50%)/Xe(50%), and He(75%)/Xe(25%). The measurements span temperatures from −20 to 30 °C and pressures up to 2 MPa. The viscosity measurements are performed in a calibrated Greenspan acoustic viscometer [K. A. Gillis, J. B. Mehl, and M. R. Moldover, Rev. Sci. Instrum. 67, 1850–1857 (1996)]. The Prandtl number measurements are performed in a cylindrical resonator that was modified to have a large surface area near the center [K. A. Gillis and M. R. Moldover, J. Acoust. Soc. Am. 97, 3376(A) (1995)]. In this modified cylindrical resonator, damping of the odd-numbered longitudinal modes is primarily due to viscous boundary effects, whereas the even-numbered modes are damped primarily by thermal boundary effects. With the interaction parameters deduced from these measurements, the transport properties of any helium–xenon mixture may be determined. [Work supported by the Office of Naval Research.]
Measurements of oscillating temperature fields in the stack region of a thermoacoustic refrigerator model
Authors: Wetzel M. , Herman C.
Published: October 2005

In previous meetings of the Acoustical Society of America a thermo- acoustic refrigerator model was introduced. The goal of the design was not efficiency but the possibility to apply visualization techniques such as smoke injection, thermochromatic liquid crystals, and holographic interferometry. Particularly, holographic interferometry combined with high-speed cinematography is a unique measurement technique to visualize the oscillating temperature fields in the stack region and its neighborhood of the thermoacoustic refrigerator model. Holographic measurements with a high-speed camera were taken at a frame rate of 5000 picture frames per second. Thus, for one period of oscillation (3 ms), about 16 holographic images were obtained. Applying digital image processing to the holographic images, the oscillating temperature fields can be quantified. Once these temperature fields are determined, heat fluxes and heat transfer coefficients can be calculated. Results of these experiments will be presented at the meeting. [Work supported by ONR; Martin Wetzel is also supported by a scholarship from DAAD.]
Measurements of the evolution of the temperature profile in a parallel plate stack
Authors: Hebert David D. , Atchley Anthony A.
Published: October 2005

Results of preliminary measurements on the evolution of the temperature profile in a parallel plate stack were previously reported [Atchley et al., J. Acoust. Soc. Am. 99, 2559(A) (1996)]. Those measurements were made on a 6.89-cm-long, five plate stainless-steel stack, with a 2.46-mm plate separation and located at kx=3.46 within a 2.75-m-long standing resonator. The resonator was at atmospheric pressure and driven at a frequency of approximately 93 Hz. Those measurements showed that the steady-state temperature gradient was approximately linear along the plate for drive ratios below approximately 2%. For higher drive ratios, the gradient was no longer linear. More complete measurements are reported using various gases at different mean pressures. In particular, the plate is instrumented with several thermocouples within an acoustic displacement amplitude of the edges of the plate. In addition, thermocouples are placed in the gap between the plates. The purpose of this work is to investigate transient effects in thermoacoustic devices and to provide data to test nonlinear, time-dependent models of thermoacoustics. [Work supported by the Office of Naval Research.]
Investigation of a toroidal thermoacoustic prime mover
Authors: Lin Hsiao-Tseng , Atchley Anthony A.
Published: October 2005

A typical thermoacoustic prime mover has a well-defined acoustic impedance in at least one place. For instance, many prime movers have a rigid end which forces the acoustic velocity to be zero at that point. Such ‘‘built-in’’ boundary conditions serve as convenient starting points for computational analysis of the performance of a device. They also serve to place the stack in a thermoacoustically effective position relative to the acoustic field. A toroidal prime mover poses some interesting questions. A toroidal prime mover has the cold end connected to the hot end via a duct that does not impose any obvious dominating boundary conditions that would force a node or antinode at any particular point. Indeed, if the stack and heat exchangers were not there and the toroid had a uniform cross section, a standing wave would have no preferential orientation. In this work, a toroidal thermoacoustic prime mover has been built and an experimental study is presented. A model based on acoustic propagation in infinite periodic waveguides is proposed to simulate the experimental results. [Work supported by the Office of Naval Research.]
Thermal boundary layer effects in an annular acoustic Stirling engine
Authors: Smith Eric
Published: October 2005

A stability and transport analysis is performed for a simplified model of a strongly coupled thermoacoustic prime mover stack in an annular resonator. The result demonstrates that, even in the limit that other flow impedances of the resonator and stack can be ignored, there is a thermal impedance mismatch created in the boundary region at the ends of the stack. This can cause the gain predicted for the wave traversing the interior of the stack to differ significantly from the gain that drives sound in the resonator. The analysis is used to derive scaling relations between the heat and mass transport around the annulus, and to show how different scaling regimes relate to the maximum sound intensity that the stack can induce in the absence of other losses.
Cost-effective electrodynamic drivers with improved efficiency for thermoacoustic refrigerators
Authors: Ward William C.
Published: October 2005

Commercial loudspeakers were made practical for laboratory thermoacoustics by placing one in the cold end of the resonator [S. R. Murrell and G. Mozurkewich, J. Acoust. Soc. Am. 94, 1772(A) (1993)], but the efficiency of such devices suffers from the opposed directions of traveling wave/standing wave heat pumping effects and from additional thermal loads at the cold heat exchanger. Efficient designs using drivers at the higher temperature end typically require special materials and fabrication. In the proposed compliant configuration, a driver with mechanical resonance below the operating frequency (which is typical of available loudspeakers) is placed close to the ambient heat exchanger and the volume backing the driver is tuned to achieve resonance and a high electrical efficiency. Numerical results show that the current ×BL product can be as little as 25% of the required driver effort. This bypasses requirement for the expensive, high flux-density magnets needed in successful efficient designs with high effort, low-impedance drivers [Garrett et al., J. Acoust. Soc. Am. 94, 1773(A) (1993)]. Predictive models of a compliant design using a slightly modified loudspeaker and the best current supermagnet designs indicate comparable efficiencies. [Work supported by DOE.]
Issues in modeling of timing for text-to-speech synthesis
Authors: van Santen Jan P. H.
Published: October 2005

Text-to-speech synthesizers commonly have three components: text analysis, prosodic modules (timing, intonation), and synthesis. Here the focus is on research underlying the approach the Bell Labs text-to-speech system uses for the prosodic modules, in particular the timing module. In this approach, greedy algorithms select to-be-recorded text with maximal coverage of a prosodic feature space; segmental durations are measured in the recorded speech; exploratory data analysis and robust statistical estimation are applied to find the best-fitting models in a class of multiple regression-like models (‘‘sums-of-products models’’) and to estimate their parameters. This approach raises several issues. (1) Why not use syllabic (or other larger-unit) durations? (2) Why not use general-purpose learning engines such as classification and regression trees, requiring no human intervention? (3) Should one model subsegmental timing, and how can this be done? (4) How can this approach be used for intonation modeling?
Automatic detection of accentual phrase boundaries using prosodic features and phoneme boundaries
Authors: Hirai Toshio , Ostendorf Mari , Higuchi Norio , Sagisaka Yoshinori
Published: October 2005

There are two approaches for constructing an appropriate fundamental frequency (F0) control method for speech synthesis: statistical and rule-based. The statistical approach has the advantage of automatic training, but it requires a large corpora of speech that is annotated with prosodic boundaries. Recently, a method is proposed for high-accuracy detection of these boundaries [Ostendorf and Ross (1996)], given a set of prosodic boundary candidates in which almost all the correct boundaries are included. This paper proposes a detection method to generate these boundary candidates, specifically for accentual phrases which represent one of the smallest prosodic units. The detection algorithm uses local maximums and minimums of the F0 contour and low-energy regions of the speech waveform for finding candidate regions that correspond to accentual phrases and pauses in speech. The candidate phrase boundaries are then aligned to the nearest phoneme boundaries, which are detected automatically using forced alignment with a speaker-independent speech recognition system given a phoneme transcription. This method was applied to 250 read Japanese sentences. High-detection accuracy (97%) was obtained, with almost all the missed detections having valid candidates within ±3 phonemes. The insertion error rate was less than double the number of correct boundaries.
The use of prosody in automatic speech recognition
Authors: Ljolje Andrej
Published: October 2005

The acoustic correlates of prosody, energy, duration, and fundamental frequency are easy to extract from the speech signal. Yet, prosody has virtually been ignored in large vocabulary speech recognition. Many systems use energy and its time derivatives in addition to spectral information, and some systems use phoneme duration models. However, those cannot truly be referred to as prosodic models. There are many reasons why it has been difficult to successfully use models of prosody in speech recognition: (a) Speech recognition models are based on phoneme-sized acoustic units, while prosodic information spans several levels, ranging from subphonetic, to phrase level; (b) speech recognition assumes quasistationarity and primarily deals in terms of absolute values, while prosodic models are susceptible to such effects as speaking rate and the speakers F0 range, requiring analysis in terms of relative values, which can cause problems in one-pass real-time systems; (c) the benefits of prosodic modeling in speech recognition are moderate (for English), and the computational cost can be huge. However, there are potential solutions for most of these problems, and as the speech recognition problem gradually becomes a speech understanding problem, more aspects of prosodic modeling will find their way into the speech recognition and understanding systems.
Evaluation of a phase-spotting method incorporated with prosodic information in spontaneous speech
Authors: Hanazawa Toshiyuki , Yoshiharu Abe , Nakajima Kunio
Published: October 2005

Spotting phrases from continuous speech is a difficult task especially from spontaneous speech. To cope with the problem, a phrase-spotting method has been proposed containing prosodic information. In this paper, evaluation results of the method are described when applying it to spontaneous speech. In this method, the prosodic likelihood of the phrase boundaries is statistically calculated based on a pitch pattern HMM network, and integrated to the spotting source of the phrase. The pitch pattern HMM network models the pitch contour of sentences by connecting pitch pattern HMMs which model pitch contour of phrases. It is thought that the use of prosodic likelihood has an effect to reduce the false alarms. The method was evaluated using the ATR spontaneous speech database. As for the pitch pattern HMMs, two types of HMMs were used with different lengths for long- and short-duration phrases and filled pauses. To construct an accurate pitch pattern HMM network, a bigram model was applied to transition the probability between the pitch pattern HMMs. Using the prosodic likelihood improved the phrase detection rate from 53% to 62%. Thus it was confirmed that the method is effective for spontaneous speech.
Speech disfluencies and their modeling: Speech errors and stuttering in English and Japanese
Authors: Kubozono Haruo
Published: October 2005

This paper examines the linguistic patterns of speech disfluencies in Japanese and their relationship with the phonological structure assumed in theoretical linguistics. The investigation focuses on spontaneous speech errors and stuttering produced by native speakers of Japanese in comparison with those produced by English speakers. One striking feature of Japanese speech errors and stuttering concerns the point where words are split as a result of speech disfluency. The loan word paasento ‘‘percent,’’ for example, yields pansento in speech errors. In this instance the second half of the long vowel, paa, has been replaced by the coda nasal of the following syllable, sen. This segmentation pattern is crucially different from what happens in English speech errors, where words are split between the consonant(s) and the vowel in the word-initial position: e.g., J_om and Jerry for T_om andJ _erry. Essentially the same interlanguage difference in segmentation is found in stuttering: i.e., [se se se sentaa] for sentaa ‘‘center’’ in Japanese versus [s s s sent■] for center in English. This paper attempts to interpret this kind of behavioral difference between Japanese and English in light of the syllable models proposed in the linguistic literature, notably the mora model and the onset-rhyme model. [Work supported by STPF.]
Posterior use of prosodic features to aid speech recognition
Authors: Hirose Keikichi , Iwano Kouji , Sakurai Atsuhiro
Published: October 2005

A method was proposed for posterior use of prosodic features to ensure correct recognition and to detect recognition errors. Fundamental frequency contours (F0 contours) are generated for recognition hypotheses using the prosodic rules developed for speech synthesis and are compared with the observed contour. Partial analysis-by-synthesis absorbs unexpected variations in the observed contour. This method can detect recognition errors accompanied by accent type changes and/or syntactic boundary shifts. While syntactic boundaries are useful for speech recognition, detecting them based on prior use of F0 contours is sometimes rather hard since they are less marked in the F0 contours. Therefore, the method was evaluated to determine how well it can detect syntactic boundaries using pitch information. Preliminary results given by K. Hirose and A. Sakurai [Proc. ICASSP-96, 809–812 (1996)] were further validated on the ATR continuous speech conference registration database, which includes 37 major syntactic boundaries (not preceded by long pauses but) accompanied by F0 rises reflecting to phrase components. The method identifies these boundaries with 92% accuracy within 2-mora position error, and, within 1-mora position error, with 86% accuracy. Discussion will extend to augmenting this method using statistical techniques such as HMMs.