bluuebunny/crossref_metadata_2025 huggingface dataset:
Scatterer depth estimation using broadband active matched field processing
Authors: Jennison Brian K. , Boyles C. Allan , McCann Kevin J.
Published: July 2002

The reduction of false alarms caused by boundary reverberation is one of the major challenges confronting active acoustic systems used for antisubmarine warfare. Scatterer depth serves as a powerful discriminant for distinguishing false target echoes reflecting from the surface or the bottom from actual targets located within the water column. Active matched field processing provides a technique for estimating the scatterer depth by comparing the measured acoustic data with a series of modeled replicas generated assuming different scatterer depths. This paper considers active matched field processing to estimate the depth of a scatterer (range is assumed known from the delay time of the echo) using a single receive hydrophone. Since matched field processing is sensitive to environmental mismatch, the search space is expanded to include both the scatterer depth and the unknown environmental parameters. Simulated annealing is used to efficiently search the parameter space for the optimal solution. A novel cost function, based solely on multipath arrival times rather than the relative multipath amplitudes, is introduced to make the search robust to uncertainties in scatter characteristics. Simulation results demonstrate the effectiveness of the technique to accurately estimate scatterer depth with limited environmental data.
Structural design for vibration isolation at Benaroya Hall
Authors: Glover Brian H.
Published: July 2002

Vibration and noise isolation criteria, together with an urban site for the Seattle Symphony Hall, created unusual constraints for its structural design. A massive concrete mat foundation bridges and isolates the railroad tunnel running diagonally under the site. Two garage levels and an isolation level further separate the Auditorium from the tunnel, while 30 ft of unexcavated soil remain between the Auditorium and an adjacent underground transit station. Heavy concrete construction is used extensively to add mass for isolation. Concrete topping was added to the Auditorium roof for isolation, and double concrete walls surround the Auditorium. Exterior precast concrete cladding adds further mass and isolation. To speed construction time, the Auditorium balconies, including the inner walls which were cast to odd geometric shapes, are precast concrete. The Auditorium structure is isolated from the surrounding structure by an uninterrupted, 7-in.-wide joint, creating a ‘‘box within a box’’ The only structural connections to the Auditorium inner box are two types of special, natural rubber isolation bearings at its base. One bearing type takes gravity loads. The other type, initially prestressed, takes lateral loads. The need for bearing access under the base of the Auditorium created unusually shaped transfer girders.
Building an acoustic library for categorizing bottom substrate type
Authors: Hedgepeth John , Sullivan Colleen , Sullivan Robert , Schneider Patrick
Published: July 2002

A hypothesis to categorize bottom substrate type is that information about the bottom sediments is encoded in the echo signal. Bottom typing means that to decode this information, however, for data verification, the user of automated typing programs should establish libraries where data acquisition of acoustic data is accompanied by physical core samples of the bottom. Separate verification should be done for different types of bottoms (e.g., %rocks, %sand, %silt, and %clay). Data from 126 observations of sediments in the vicinity of Commencement Bay near Tacoma, WA was used to establish libraries and to test the capability of the Visual Bottom Typer software to categorize correctly. Four different algorithms were used: division of the first bottom echo, ratio of the first and second bottom echo, cumulative intensity of the first bottom echo, and fractal dimension of the first bottom echo. The echo signal parameters depended not only on the type of bottom sampled but also on the equipment parameters. Two different frequencies and two different beam widths were compared. Verification results were valid for particular combinations of equipment parameters.
The multiple scattering interactions of cobbles and pebbles lying on the ocean floor
Authors: Feuillade C. , Meredith R. W.
Published: July 2002

A new model for predicting the sonar target strengths of ensembles of rocks lying on the ocean floor has recently been presented. The model represents rocks by either rigid movable spheres or elastic spheres of variable size, density, and numerical/geometrical configuration. When the rocks are densely packed, and therefore in close proximity to each other, it is important to consider the contribution that multiple scattering interactions make to the collective scattering response. To investigate this question, a T-supermatrix formalism, a self-consistent procedure which includes all orders of multiple scattering [see Lim and Hackman, J. Acoust. Soc. Am. 91, 613–638 (1992)], has been developed to describe the radiatively coupled ensemble. The method allows the coherently summed scattered pressure field in any direction to be determined, as well as the total power scattered by the system. Application to rocks of cobble and pebble size classes indicates that the effect of multiple interactions is dependent upon the acoustic frequency, the rock spacing relative to the radius, and the grazing angle. The results obtained provide a basis for estimating the relative importance of these interactions in determining target strength. [This work was supported by ONR/NRL.]
Gene activation and gene delivery with ultrasound
Authors: Unger Evan C. , McCreery Thomas , Sweitzer Robert , Shen DeKang , Wu GuanLi , Caldwell Veronica
Published: July 2002

Transfection experiments were performed in vitro in cell culture and in vivo in fish and mice using cationic liposomes with several different reporter genes. The effect of continuous-wave 1-MHz ultrasound on cell viability, cell permeability, and gene expression was assessed. RT-PCR was used to monitor gene expression of cell repair genes in insonated cells. Acoustically active halocarbon-containing liposomes were prepared for gene delivery. Ultrasound increased cell permeability and gene expression following liposomal transfection. RT-PCR showed upregulation of repair of a number of cell repair genes after ultrasound exposure. The acoustically active gene delivery vehicles provided highly efficient transfection both with and without ultrasound in vitro and in vivo. Following IV administration of halocarbon-containing liposomes/gene complexes, preferential gene expression was observed in the insonated tissue. Ultrasound has potentially useful applications for targeting and enhancing gene therapy.
Ultrasound activation of new drugs for killing cancer cells
Authors: Tachibana Katsuro , Uchida Toshiki
Published: July 2002

The study of the destructive action of ultrasound in conjunction with drugs upon cancer has become an exciting area. New substances that are chemically activated by low level ultrasound energy have recently been discovered [Tachibana et al., Lancet 349, 325 (1997)]. Three nontoxic red stains frequently used for cosmetics and food, Rose Bengal, Eosin Y, and Erythrosine B were evaluated if cytotoxic effects can be induced by ultrasound energy in vitro. Gastric and leukemic cancer cell line suspensions were exposed to ultrasound (1 MHz) with or without the drugs. The survival rate of the cells was measured immediately after treatment. The temperature increase was less than 2 °C. Treatment with ultrasound plus drugs resulted in a significant reduction of the survival rate compared to ultrasound alone. Whereas the drug alone showed no change in survival rate. Although the mechanism is unclear, it is postulated that ultrasound energy, possibly cavitation, activated these drugs. Further experiments should be carried out to evaluate its use in the clinical situation. The three stains could be applied as new booster agents for treatment of cancer by ultrasound.
Efficiency and electromechanical resonance in magnetostrictive transducers
Authors: Calkins Frederick , Flatau Alison
Published: July 2002

Analysis of the transduction phenomenon of a Tonpilz Terfenol-D magnetostrictive transducer is presented. Transducer efficiency is discussed from electroacoustic and scalar energy perspectives. Equations are presented for identifying the frequency of most efficient transducer operation based on electroacoustic theory [F. V. Hunt, in Electroacoustics: The Analysis of Transduction, and Its Historical Background (Acoustical Society of America, New York, 1982)]. Experimental results are presented that show this analysis to be accurate. However, two nonintuitive results are observed: most efficient transducer operation occurs at a frequency above mechanical resonance; and changes in operating conditions which result in an increase in transducer efficiency cause the frequency of highest efficiency to increase even further above the frequency of mechanical resonance. This motivated a comparison with a scalar energy analysis for development of a better, or at least more intuitive, understanding of the mechanisms which might explain this result. Energy analysis aids in recognizing the distinction between the transducer’s mechanical and electromechanical resonances and that the magnitude of achievable efficiency will be enhanced by separation of electromechanical and mechanical resonances. Coupling the energy and electroacoustic analyses, one arrives at persuasive arguments for explaining the experimental observations regarding magnetostrictive transducer efficiency.
A study of 1-3 piezocomposites high drive limits
Authors: Howarth Thomas R. , Van Tol David , Allen Charles , Hughes Jack
Published: July 2002

A preliminary study of the electrical drive limits of 1-3 piezocomposites has been completed. Two injection molded 1-3 piezocomposite samples were designed, fabricated, and procured from Material Systems, Inc. of Littleton, MA. Each of the composites had a 25% volume fraction of piezoceramic, a hard epoxylike matrix, a silver epoxy electrode pattern, 6-mm thickness, 100×100-mm total cross-sectional area with an active cross-section of 20×20 mm. One of the samples featured type II (PZT-5H) piezoceramic while the other featured type I (PZT-4). Each of the transducers was fitted with thermocouples to monitor temperature effects. Transducer efficiency, voltage response (TVR), current response (TCR), and power responses (TPR) were measured over the frequency range of 25 Hz–500 kHz in 200-Hz steps where the transducer thickness resonance frequency was approximately 240 kHz. This presentation shall outline the sample fabrication, the tests, and the final results. Photographs will be shown on the units upon failure. A comparison between the 1-3 piezocomposite materials limits shall be made with traditional piezoceramics. [Work supported by Dr. Kam Ng of ONR 334.]
Lamb wave generation in composite plates with a thin linear array of piezoelectric elements
Authors: Demol Thierry , Blanquet Pierrick , Moulin Emmanuel , Delebarre Christophe
Published: July 2002

Since Lamb waves are very efficient in the nondestructive testing of composite plates, new transducers are developed nowadays. They may be movable, stuck onto the surface, or integrated into the plates (‘‘smart structures’’). In order to detect defaults with few transducers, a multi-element linear array transducer has been developed to generate single-mode Lamb waves able to propagate over long distances. Movable prototypes were designed in order to evaluate their ability to generate the appropriate waves. Then, composite plates have been equipped with the same kind of transducers consisting of several thin PZT plates. High response levels have been obtained using a unidirectional composite with propagation along the fiber direction. Results for cross-ply laminates were inferior but still acceptable. The main result obtained during this experimental work was the understanding of the generation process for this kind of transducer. Unlike comb transducers, each element generates a separate wave and suitable time delays or spacing between the elements can improve the global response in accordance with linear rules. Furthermore, the delays are easily determined from the responses of each element. This behavior is very interesting as default detection is possible using the properties of the generation process.
Built-in transducer design for Lamb wave generation in composite structures
Authors: Blanquet Pierrick , Demol Thierry , Moulin Emmanuel , Delebarre Christophe
Published: July 2002

Conventional ultrasonic inspection of large composite structures is very time consuming due to the necessity of surface scanning. Because they can propagate over long distances, Lamb waves are an attractive solution to this problem. Two methods are available for the generation of Lamb waves in composite plates. The first method, and the most useful one, consists of using bonded transducers. The second solution is to use a built-in transducer. In both cases, the transducers must be designed to generate efficiently the signal and choose the mode of propagation. In the following, a method to design a built-in transducer will be discussed. First, the case of a unidirectional composite plate is considered. An analytical method is developed, then the results are compared with those obtained using finite element analysis. In the case of a square element transducer embedded in the composite plate, the computed results are compared with experimental data. Then, the method is extended to the case of a multilayered plate. An analysis is performed to determine the optimal design of a built-in multi-element transducer.
Sonofluorescence image in an analogous sonochemical reactor
Authors: Li Huamao , Xie Andong , Zhong Fan , Wan Huijun , Liu Lijun , Feng Ruo
Published: July 2002

According to the sonofluorescence principle of ultrasonic cavitation oxidation suggested by the authors [Huamao Li et al., Acta Acust. 22 (1997)], the cavitation field distribution images in both analogous symmetrical and nonsymmetrical sonochemical reactors filled with aqueous Luminol–KOH alkaline solution have been taken when using an ultrasound with an operating frequency of 1.45 MHz and an ultrasonic electric power of 25 W. The images seem to show that the ultrasonic cavitation field in the analogous symmetrical sonochemical reactor appear symmetrical with uniform distribution, and the ultrasonic cavitation fields in the analogous nonsymmetrical sonochemical reactors appear nonsymmetrical with nonuniform distribution, but the nonsymmetrical cavitation field distribution can be guided along some curved way. The authors think that the sonofluorescence image method can be available for use in a sonochemical reactor designed for getting uniform or positioning cavitation field. [Work supported by the Natural Science Foundation of Jiangxi province and the Science Foundation of Ji’an Teachers’ College.]
Interaction of counterpropagating acoustic waves in materials with nonlinear dissipation and in hysteretic media
Authors: Bailliet Hélène , Gusev Vitalyi , Lotton Pierrick , Bruneau Michel
Published: July 2002

Current interest in the interaction of sound waves traveling in opposite directions is due to progress in thermoacoustics (where the acoustic resonator is a part of the refrigerator) and achievements in diagnostics of solids via the evaluation of standing waves in rods. In the present analysis, the second-order nonlinear processes are described by the equation ∂2V+/ ∂t2 − c20(∂2V+/∂x2) = − (∂/∂t){(∂/∂x)[(ε−1)V−2+V2+] + RV+|V+|−h[V−A+V−sgn (∂V−/∂t)](∂V−/∂x)}. Here V±=υ+(μx,t−x/c0)±υ−(μx,t+x/c0), μ≪1, υ± are particles velocities, and superscript A denotes amplitude of a periodic wave. Elastic nonlinearity [the first group of terms on the right-hand side (rhs)] does not provide effective interaction of ‘‘±’’ waves. Nonlinear dissipation (the term proportional to R on the rhs) is responsible for the additional attenuation of the ‘‘−’’ wave induced by the ‘‘+’’ wave. The chosen form of dissipative nonlinearity is typical of gas-filled porous structures used in thermoacoustics. Hysteretic nonlinearity typical of micro-inhomogeneous materials (the last group of terms on the rhs) leads to amplification of the weak ‘‘−’’ wave in the field of the strong ‘‘+’’ wave. Predicted stimulated backscattering of sound in hysteretic media can influence the operation of parametric underground antennas. [Work supported by DGA.]
A study on natural-sounding Japanese phonetic word synthesis based on the pitch waveform concatenation
Authors: Arai Yasuhiko , Mochizuki Ryo , Honda Takashi
Published: July 2002

A speech output system in which messages are composed by embedding some phonetic words in the prerecorded sentence patterns requires very natural-sounding phonetic words to be embedded. Especially in the case where a very large or an unlimited vocabulary is required, synthesis of very natural-sounding phonetic words would be desired. Therefore, a novel Japanese VCV-concatenation synthesis method based on the pitch waveform concatenation has been studied. The VCV waveforms are extracted from the VCV-balanced spoken word database and pitch waveforms are extracted by means of the excitation synchronous pitch waveform extraction method [Y. Arai et al., ICSLP 96, 1437–1440 (1996)]. The wavelength of each pitch waveform is modified depending on the pitch modification rate, and the global pitch contour of each VCV waveform is modified along with the target pitch pattern, while the micro-prosody and the small perturbation in pitch frequency inherent in that VCV waveform are retained. The auditory tests confirmed the superiority of the novel synthesis method. Finally, the advantage of the spoken word database, which consists of Japanese VCV-balanced word sets uttered forcibly by two pitch accent types (so-called type −0 and type +1 in Japanese) differently from the normal pitch accent, is discussed.
Synthesis of Hindi consonants with natural sounding quality using the PC-based Klatt synthesizer
Authors: Verma Rajesh , Agrawal Shyam S.
Published: July 2002

This paper describes experiments conducted to synthesize Hindi consonants with natural sounding quality using the PC-based Klatt synthesizer. All the most frequently used 29 Hindi consonants have been synthesized in the form of CV and VC syllables. For this purpose, a detailed spectral analysis was carried out to determine minute acoustic differences among the various categories of consonants such as unaspirated/aspirated, voiced/unvoiced, dental/retroflex, liquid/trill, etc.. The synthesis was done using a modified version of the Klatt Synthesizer simulated on a PC. It uses about 60 parameters for the source and vocal tract variations in 5-ms duration. Variations in important parameters were made until a satisfactory quality of consonant was perceived and a clear distinction occurred with its cognate sound. For example, the distinction among dental plosives (t, th, d, dh) and retroflex plosives (t*, th*, d*, dh*) have been achieved by changing formant frequencies at the burst position, intensity of burst, and formant transitions from burst to the target vowel. Similarly the sound /r/ in Hindi takes various forms such as trill or fricative depending upon the context. This is a very special characteristic of /r/ in Hindi. In this same manner the special features of all the 29 consonants are discussed with references to their synthesis in five different vowel contexts.
A review of progress in acoustic telemetry and the challenges of the underwater channel
Authors: Baggeroer Arthur B.
Published: July 2002

High data rate acoustic telemetry in the ocean is limited by both bandwidth and reverberation. Attenuation limits the available bandwidth and most acoustic environments are dominated by reverberation which is spread in both delay and Doppler. The availability of low power VLSI electronics has had an enormous impact upon acoustic telemetry because the algorithms of digital communication systems could be implemented in oceanographic sensors which have severe constraints upon available energy and space. The first demonstration was the DATS (Digital Acoustic Telemetry System) for reverberant acoustic channels. It used MFSK with an (8,4) Hamming code, frequency hopping, and explicit synchronization of time and Doppler. Since then, (i) coherent signaling, (ii) source and channel coding, (iii) adaptive equalizers, and (iv) frequency and spatial diversity and networked configurations all have been used. Bit rates of 5–20 kbs at short ranges and 0.5–1 kbs at long ranges have been demonstrated. Higher rates can probably be obtained with forward error control methods; however, there the relatively slow speed of sound leads to some unique latency issues. Nevertheless, the availability of two-way links leads to acoustic telemetry networks which can be addressed just as any other node on a net. Some other interesting issues in acoustic telemetry concern increasing the data rate within the same bandwidth, low probability of intercept covert communications, methods for high Doppler situations, and network topologies which are robust to node outages. This presentation will provide a brief overview of acoustic telemetry and the evolving research areas, and present some of the challenges of the underwater channel.
Comparative performance of nonbinary Viterbi and sequential decoding in adverse underwater acoustic channels
Authors: Green Dale , Justice Richard , Rice Joseph
Published: July 2002

The application of higher-order alphabets in convolutional forward error correction coding is discussed, specifically the use of Viterbi decoding to obtain maximum likelihood performance with short-constraint-length codes, and the use of Fano sequential decoding with long-constraint-length codes. It is demonstrated that both techniques perform very well even near the respective computational cutoff (Rcomp) region. An 8-ary, constraint-length-3 coder combined with Viterbi decoding provides probability of bit error in a Rayleigh faded channel on the order of 10−4 at Eb/No=11 dB. With an 8-ary, constraint-length-10 coder combined with Fano sequential decoding operating also at Eb/No=11 dB, the probability of undetected error may approach 10−12. The probability of erasure is less than 10−4 with a reasonable amount of computer resources. Viterbi decoding with short-constraint-length codes produces occasional bit errors which may be corrected with the concatenation of a simple block code applied to the input message. Performance comparisons are drawn from a side-by-side analysis of the two using data obtained during telesonar experiments in San Diego Bay. [Work supported by the ONR 321 Sensors, Sources and Systems Program and SSC San Diego Contract No. N66001-96-C-6003.]
Why do traditional opera houses work so well for opera?
Authors: Edwards Nicholas , Kahn David
Published: July 2002

Most computer models of room acoustics assume geometric acoustics (as if sound behaves like light). This has assisted our understanding of how room shape (fan shape versus rectangular, for example) can affect the acoustics of concert halls. When one applies geometric acoustics modeling to the traditional opera house, typically all one finds is a single ceiling reflection. The geometric approach holds little promise for understanding the magic of opera house acoustics. One of the acoustical attributes ignored by the geometric model is edge diffraction of sound. Our research has shown edge diffraction to be essential in predicting the superior acoustics of the traditional opera house. We have developed an alternative to the geometric acoustics model based on edge diffraction. In a two-dimensional representation, the locus of points with equal delay time is an ellipse; in three dimensions, the locus is the volume of revolution of an ellipse. By studying where this ellipsoidal volume intersects with the balcony fronts, we can locate where, at any given time, the edge-diffracted sound is coming from. This model is applied to LaScala, and a ‘‘movie’’ is developed to show how the balcony front edges contribute to the sound that is heard.
Measurement of objective criteria for performers in the ‘‘Teatro di San Carlo’’ opera house
Authors: Ianniello Carmine , Iannace Gino , Maffei Luigi , Romano Rosario
Published: July 2002

In the last two decades some attention has been paid to the acoustics for performers in concert halls. The findings of these studies have shed some light on the structure of the sound field preferred for the ensemble. With respect to a concert hall, the performing condition is quite different in an opera house. Usually, the problems are related to: (a) the balance between singer(s) and the orchestra in the pit; (b) the ease of singing; (c) the ensemble of singers; (d) the ensemble of instrumentalists. To the knowledge of the authors no objective criterion has been suggested yet for (a). Some criteria are reported for the ensemble of instrumentalists (d). Useful information for (b) and (c) is reported in [A. H. Marshall and J. Meyer, Acustica 58, 130–140 (1985)]. Although well aware of the lack of accepted objective criteria, which should be well correlated with subjective criteria for the above-mentioned topics, these authors report the results of measurements carried out in the ‘‘Teatro di San Carlo’’ in the aim of quantifying objectively some of the items (a)–(d). In particular, a criterion is suggested that is related to the comfort of singers on the basis of the study of Marshall and Meyer.
Sound fields in orchestra pits
Authors: Meyer Juergen
Published: July 2002

The main problem for musicians sitting in opera house orchestra pits is the general loudness of the orchestral sound. The sound field occurring at the musicians’ ears is not only affected by direct sound, early reflections, and reverberation, but—particularly for seats under the stage—by standing waves. Whereas direct sound and diffuse reflections appear to come from comparatively large distances, the sound due to standing waves is localized just around the head. Therefore, it is extremely disturbing for the players, impairing the tonal control of their own instruments as well as the ease of ensemble. Disturbing direct sound may be reduced (5–10 dB) by special screens directly behind the musician’s head. Standing waves between the floor and cover of the pit are critical if the musicians’ ears are in the neighborhood of the antinodes; this does not occur with the lowest mode, but for modes having two or three half-wavelengths, assuming the ears at a height of 1.15 m above the floor. Therefore, a distance between floor and cover of 2.0–2.75 m (or below 1.80 m) may be recommended, as in these cases only one disturbing mode occurs which can be damped by well-tuned absorption.
Listening in the pit
Authors: Blair Christopher N.
Published: July 2002

Temporal masking effects are a controlling factor in the ability of performers to hear each other well. Difficulties in ensemble communication and perceived weakness of the acoustic response of the auditorium can be exacerbated by high early energy levels often found in orchestra pits. These problems become particularly acute in orchestra seating positions under stage overhangs. Drawing on experiences as an opera conductor as well as an acoustic designer, the author: (1) provides an overview of the psychoacoustic challenges facing the opera house designer relative to orchestra satisfaction; (2) explores, using architectural examples, the reasons why some pits are highly regarded by orchestras and conductors while others, even those similarly configured, are not; and (3) proposes protoptypical design solutions to improve the listening environment both inside the pit and elsewhere.
Measurements of orchestra acoustics. How reflecting surfaces influence ‘‘Klangfarbe’’ and the possibility of playing in time
Authors: Halmrast Tor
Published: July 2002

When investigating room acoustics, and also stage acoustics, most concern is often based on ‘‘how much energy arrives in the time interval between time x and,’’ and not on how these reflections are distributed within that time interval and how that affects the Klangfarbe and rhythmic conditions. The stage acoustics of the Oslo Concert Hall was measured (MLS) with and without the orchestra on the stage, and with different settings of reflecting surfaces to achieve a better ‘‘ensemble’’ feeling (TOR measurements: Through Orchestra Response). Reflecting surfaces above, behind, and to the side of the orchestra were examined, with a questionnaire for each musician and a number of tonemeisters in the audience area. Similar measurements of the stage acoustics were done also in several European halls on the tour of the Oslo Philharmonic Orchestra/ Mariss Jansons including Gasteig/Munich and Musikverein/Vienna. For further analysis of the ability of playing in time, measurements were done in the Hall for the Norwegian Radio Orchestra, with analysis of both orchestra tutti and multichannel recording situations. The paper analyzes the aspects of playing together in an orchestra, and especially how different placements of reflecting and diffusing elements affect the Klangfarbe and rhythmic conditions, both for the orchestra and the audience.
Sound sources and simulation software in room acoustics
Authors: Semidor Catherine , Couthon Leonie
Published: July 2002

There is a lack of data in directivity, power, and phase, and most of the time software users have no data at their disposal, so they use an omnidirectional sound source, or they calibrate the simulation with the measurements they operated in situ. But the use of the room is correlated to the kind of source that emits inside of it, so it is fundamental to know the statistical characteristics of emission of real sound sources. In this article, a survey about the way sound sources are taken into account in simulation software is proposed. Then an analysis is presented of a three-dimensional recording of real sound sources (musical instruments), to access to data in power and directivity, which tries to respond to the questions raised. And finally, the results obtained with different simulation software are presented. In conclusion, the need for standardization of sound source data is discussed.
Aggressive region growing filtering for speckle reduction in ultrasound images
Authors: Chen Yan , Yin Ruming , Flynn Patrick , Broschat Shira
Published: July 2002

Speckle noise is present in all conventional ultrasound images, and complicates the process of diagnosis as it can mask small but diagnostically significant features. Speckle reduction techniques can be applied prior to image formation [e.g., Chen et al., J. Ultrasound Imag. 18(2), 122–139 (1996)] or after image formation. Post-formation techniques can be implemented in software, whereas pre-formation techniques generally require hardware modifications. The approach described here is applied after image formation, and consists of two steps. In the first step, small ‘‘seed’’ regions are defined around each pixel in the image, and a homogeneity criterion is used to guide a procedure which identifies the maximal-size homogeneous region containing the pixel of interest. Once determined, this region is smoothed using a truncated arithmetic mean filter. Results on synthetic and real images demonstrate that this method preserves the sharpness of image edges yet reduces speckle noise, and compares well with weighted median filtering [Loupas et al., IEEE Trans. Circuits Syst. 236, 129–135 (1989)] and homogeneous region growing median filtering [Koo and Park, J. Ultrasound Imag. 13, 211–237 (1991)]. [Work supported by NSF and the Carl M. Hansen Foundation.]
Sequential versus iterative methods for recovering acoustical impedance profiles of inhomogeneous media
Authors: Tenenbaum Roberto , Magalhaes Marcelo
Published: July 2002

Optimization methods for identification of nonhomogeneous media are known to be very time consuming. On the other hand, sequential methods (layer stripping methods) are computationally very efficient and rather unstable under noisy data. In this work, some recent optimization techniques are applied to recover the impedance profile from the reflected data. A careful approach has to be used though, since the cost function is highly nonlinear and its evaluation is quite costly in a computational point of view. The optimization method chosen is a secant one, which, instead of using information about the second derivatives of the cost function, generates successive approximations of its Hessian matrix, based on information gathered as the procedure progresses. The sequential method lies in a new algorithm for computing the reflection response of a truly layered media for an arbitrary input, which can easily be inverted. The results of both methods are compared for some synthetic echoes. The behavior of the methods for random and zero-average noise added to the response is studied. The advantage of using each of the methods as a function of the signal-to-noise ratio is then discussed.
Acoustical design of the opera house of the New National Theater, Tokyo, Japan
Authors: Beranek Leo L. , Hidaka Takayuki , Masuda Sadahiro
Published: July 2002

The New National Theater (NNT) project containing three halls started with an open international design competition in 1986 and ended with a grand opening October 10, 1997. The architect is Takahiko Yanagisawa. The opera house, the core of the NNT facility, has a seating capacity of 1810, a volume of 14 500 m3, and a reverberation time with full audience of 1.5 s (stage curtain open). Various model experiments, using a CAD model, 1:10 scale model, and full-sized materials samples, were conducted over a 7-year period. As a result, the main floor has an almost rectangular shape, three-layered balconies have a modest fan shape, and the balcony fronts at each level create a rectangular shape. The overhang of each balcony is minimized to take visibility requirements into consideration. The unique design has a large curved reflector in front of the proscenium and over the orchestra pit and curved reflecting surfaces at the fronts of each of the side balconies to reflect the singer’s voices uniformly from a large portion of the tremendous stage. The balcony fronts, the side walls, and the ceiling also augment the reflections from those surfaces. The unoccupied values are: EDT=1.6 s, C80(3)=2.4 dB, [I−IACCE3]=0.66m and bass ratio=1.1.
Temporal rhythms in the signals of insects
Authors: Forrest T. G.
Published: July 2002

The signals generated by acoustic insects exhibit temporal patterns on several time scales. Annual or seasonal rhythms provide information about temporal changes in insect population size. Knowledge of such changes might be useful in ecological monitoring programs. Circadian or daily rhythms commonly seen in insect signaling are generated by endogenous ‘‘clocks’’ that are reset by environmental cues. Understanding these daily patterns is also important for monitoring insect populations. Within insect populations, the signals of neighbors sometimes show temporal patterns of synchrony or alternation with timing on the order of seconds. The phase relationships among individuals are maintained by acoustic resetting, whereby an individual’s temporal rhythm will change depending on the phase that neighboring signals are received. On still smaller time scales, temporal patterns of insect songs are diverse and generally differ among species. These small-scale patterns are often essential components of mating signals and are used in mate recognition and mate choice.
Estimation of the target strength of juvenile salmonids at any aspect
Authors: Carlson Thomas J.
Published: July 2002

Many tasks, such as assessment of the state of stocks and observation of migrant behavior, elemental for recovery of Columbia River basin salmonid stocks, are currently performed using active acoustic methods. Detectability models are required to configure acquisition systems, design elements of studies, and process and analyze data. Accurate and precise estimates of juvenile salmonid target strength are necessary input to detectability models. The target strength at 420 kHz of 87 juvenile salmonids was measured within the length range of 45 to 300 mm. The fish were rotated through pitch, roll, and yaw planes. Forty target strength measurements were obtained for each degree of rotation in each plane for each fish. Mean target strengths were computed for 1° and 5° increments of rotation. The mean target strength estimates for each 5° increment of rotation for all fish were fit to the equation σ/λ2=a(L/λ)b. Estimates of mean target strength for regions of the sphere encompassing the fish between the planes of rotation were estimated by interpolation to complete a description of the target strength of juvenile salmon at any aspect.
Perceptual analysis of synthesized struck bars
Authors: Roussarie Vincent , McAdams Stephen , Chaigne Antoine
Published: July 2002

This study is part of a project seeking to understand musical timbre and perceptual phenomena of the sound environment. It concerns the sensitivity of listeners to sounds emitted by simple vibrating structures, such as xylophone bars. Previous studies of timbre have characterized this attribute in terms of a small number of perceptual dimensions of an analytic nature (attack time, spectral centroid, spectral flux). Other studies have suggested a return to the physical characteristics of the sound sources themselves in order to understand their influence on timbre perception. Sounds were synthesized with a computer model of the vibrating bar developed at ENST that allows precise control of physical parameters. Listeners made dissimilarity judgments on all pairs of different sounds. Multidimensional scaling analyses of these data yield a perceptual space with dimensions that correspond strongly to the varied physical parameters (material density and the first term of internal damping) as well as to salient auditory dimensions (pitch for the former and a combination of spectral centroid and decay rate for the latter). These results argue in favor of a privileged processing of source characteristics by the auditory system.
The effect of amplitude and centroid trajectories on the timbre of percussive and nonpercussive orchestral instruments
Authors: Hajda John M.
Published: July 2002

This study explores the salient acoustical attributes of the associative aspects of Western orchestral instrument timbres. Association refers to a subject’s ability to connect or link a stimulus with its intended comparison; this occurs in tasks such as identification, matching, or categorization. Unlike most previous research in instrument association, this study considers both continuant (nonpercussive) and impulse (percussive) classes of instruments. Certain acoustical transformations, such as the partitioning of a signal into attack, steady state, and decay, are not possible for both classes. Findings which have been made regarding the salience of signal segments must be questioned in terms of their application to a more general and inclusive theory of musical timbre. Previous perceptual and timbre synthesis research has demonstrated the importance of global rms amplitude and spectral centroid (the amplitude-weighted mean frequency). Here, both amplitude and centroid are considered in terms of individual trajectories. The evolutions of and relationships between these trajectories are markedly distinct for continuant and impulse classes of instruments. The perceptual significance of these trajectories is measured through the experimental control of their magnitude and direction. A convergence method is employed to ascertain the necessary and sufficient conditions for instrument association.
Computer identification of wind instruments using cepstral coefficients
Authors: Brown Judith C.
Published: July 2002

Earlier results on computer recognition of the oboe and saxophone [J. C. Brown, J. Acoust. Soc. Am. 101, 3167(A) (1997); ‘‘Musical instrument identification using cepstral coefficients as features’’ submitted to J. Acoust. Soc. Am.] have been extended to include the clarinet and the flute. Approximately 30 samples of duration 2–10 s of each of the four instrument types comprise the test set. The training set consists of longer segments of approximately 1 min duration. Eighteen mel-based cepstral coefficients were calculated for each of the sounds. The training data were summarized by a cluster analysis with Gaussian probability density functions formed from the mean and variance for each of the clusters. The probability of belonging to each of the four classes was then calculated for the test sounds, and a Bayes decision rule was invoked to assign them to one of the classes. Results indicate that this is a very promising method for automatic recognition of musical instruments.
Sonically induced growth of gas bubbles by diffusion
Authors: Eller Anthony I.
Published: July 2002

Small gas bubbles that might normally dissolve and disappear may instead grow if set into pulsations of sufficient amplitude by an applied sound field. The mechanism involved is a fundamental asymmetry related to the spherical geometry of the conditions which favors diffusion of gas into the bubble during its expanded state over diffusion out of the bubble during a contracted state. Values of the threshold acoustic pressure for growth were computed by a theory that accounts for spherical bubble dynamics as well as convection terms in the diffusion equation and shows general agreement with measured counterparts. Rates of bubble growth for above-threshold conditions can be unexpectedly high if nonspherically symmetric acoustic streaming occurs. A closely related phenomenon—the onset of nonspherical bubble vibration—occurs within the same general range of acoustic pressures observed for bubble growth and will also be described.
Photoacoustic study of the electron–hole transport in a piezoelectric semiconductor
Authors: Gao Weimin , Gusev Viltali , Glorieux Christ , Van Rostyne Kris , Van Looy Ward , Thoen Jan , Borghs Gustaaf
Published: July 2002

In a piezoelectric semiconductor acoustic waves can be excited via the inverse piezoelectric effect. This excitation process is the result of a screening of the applied electric field by the expanding space distribution of electrons and holes which are generated by pulsed laser radiation. The time and space characteristics of the electron–hole transport in this process are contained in the corresponding acoustic signals. The piezoelectric direct-gap semiconductors cadmium sulfur selenide and gallium arsenide are investigated experimentally at room temperature. A pulsed nanosecond UV excimer laser is used to excite electrons and holes on these samples. The generated longitudinal acoustic waves are detected by a laser interferometer. The obtained acoustic pulses of cadmium sulfur selenide show that both the expansion of the screened region in space and the electron–hole plasma expansion are supersonic at the time scale of laser action. The observations in this optoacoustic experiment indicate that the fast carrier transport is governed by photon recycling, i.e., the reabsorption of photons released by radiative recombination of electron–hole pairs. Experiments for gallium arsenide are in progress and will also be reported.
Nonlinear reflection of acoustic waves at the dissipative isotropic solid–solid interfaces
Authors: Jiang W. H. , Chen J. J. , Shui Y. A.
Published: July 2002

The nonlinear reflection at the solid–solid interfaces is investigated under the condition that a SV wave is incident from a nondissipative solid medium to a dissipative solid medium. The amplitude of the freely propagating reflected second harmonic SV wave is calculated. Comparing with previous calculation without consideration of dissipation, it is observed that the peaks of the reflected second harmonic SV wave in the vicinity of critical angles for refractive P and SV waves become smooth and the influence of nonlinear properties of the refractive medium on the amplitude of the reflected second harmonic wave is more notable. A experiment is carried out for glass–copper or rock interface. The SV wave of 8 MHz is incident from glass in which the attenuation of the acoustic wave is negligible upon glass–copper or rock interface. The reflected second harmonic SV wave is detected by a transducer with the working frequency of 16 MHz. The amplitudes of the second harmonic wave at the different incident angles are measured. The resultant angular dependence is in basic agreement with the calculation. [Work supported by NSF of China.]
Particle interactions in coupled phase theory for sound propagation in concentrated emulsions
Authors: Evans J. M. , Attenborough K.
Published: July 2002

Theoretical studies of the acoustically induced interphase heat transfer in concentrated emulsions are reviewed. Interactions between the thermal fields around the particles influence the heat transfer and hence the complex wave number of propagating sound. Two modeling approaches are discussed: a hydrodynamic treatment and thermal wave scattering. These methods are used to calculate the interphase heat transfer at high concentrations. Modified heat transfer terms including the effect of particle interactions are obtained, which may be used in coupled phase theory. Predictions of the complex wave number using a revised coupled phase model [J. M. Evans and K. Attenborough, J. Acoust. Soc. Am. 102, 278–282 (1997)] are compared with experimental data on ultrasound propagation in oil in water emulsions. The comparisons show the nondimensional frequency and volume fraction regions where interactions have a significant effect on the wave number.
Approach to characterize the sound field of pulse-excited ultrasonic sensors using a Laser-Doppler vibrometer
Authors: Henning Bernd , Prange Stefan , Schuart Mark , Dierks Karsten
Published: July 2002

A new efficient approach to make visible sound fields in front of acoustic sensors in liquids will be presented. The goal is to investigate the sound field characteristic of real manufactured acoustic transmitters particularly by discontinuous excitation like pulse, burst, and other. Another point is the analysis of the influence of materials and sensor design on the final acoustic behavior. In comparison to the Schlieren technique it is possible to use moderate excitation of transmitters (only a few volts) and more variable signal shapes too. The experimental setup consists of a Laser Doppler vibrometer and a high-resolution three-dimensional positioning system. The control of the positioning system as well as the data acquisition and processing will be fully automatic realized by a personal computer. A software tool archives the data and calculates the complex sound field characteristic in dependence on time or place. The result is an interesting animation representing the real sound field characteristic of acoustic sensors. The advantages and limits of the approach and developed experimental setup will be described. Some examples will show the sound fields in front of cylindrical focusing transmitters. The influence of different excitation signal shapes on the final sound field will be discussed.
Resonators attached to a structure—a SEA canon
Authors: Lyon R. H.
Published: July 2002

One of the earliest problems analyzed using SEA ideas was a plate structure connected to a single resonator. Then structure-to-structure problems replaced the single resonator with a multiplicity of resonators as a model for the second structure. Because of the desire to relate the problem to those involving real structural connections—to beams, plates, and sound fields—the resonators became models for the natural modes of the structure and the resonators lost their identity. Fuzzy structure models have emphasized the resonators themselves, with passing attention to actual structural arrangements that they apply to. Of particular interest to SEA, however, is the relationship between modal density and ‘‘mass density,’’ and the relative strengths of internal and coupling damping, particularly as they relate to the transient response of the system. This presentation will discuss these matters.