bluuebunny/crossref_metadata_2025 huggingface dataset:
Generalized response of a sphere embedded in a viscoelastic medium excited by ultrasound radiation force.
Authors: Urban Matthew W. , Nenadic Ivan , Chen Shigao , Greenleaf James F.
Published: October 2010

Characterization of viscoelastic soft tissues and materials has been a subject of active research for the past two decades. Techniques involving measuring the motion of embedded spheres in viscoelastic media have been employed to measure the viscoelastic material properties of the media surrounding the sphere. The published work using this technique has been restricted to using the Kelvin–Voigt model, which has worked for gelatin-based materials. We report an extension of this method using different viscoelastic rheological models such as the Maxwell, generalized Maxwell, Zener, and Kelvin–Voigt fractional derivative models. We performed experiments using a focused 3-MHz transducer to produce radiation force and a 7.5-MHz pulse-echo transducer to measure the sphere motion. Two phantoms were tested; one made of gelatin and another made of rubber with stainless steel spheres embedded in the materials. The response was fitted with the generalized theoretical model to find the material properties over bandwidths of 25–3000 Hz. The median absolute errors ranged from 0.0036–0.0421 and 0.0365–0.0879 for the gelatin and rubber phantoms, respectively. This generalized method offers added flexibility to characterize different types of viscoelastic materials using the most appropriate rheological model. [Work supported in part by NIH Grant nos. EB002167 and DK082408.]
Measuring the in situ acoustic impedance of a loudspeaker enclosure.
Authors: Leishman Timothy W.
Published: October 2010

The acoustic impedance of a loudspeaker enclosure is usually oversimplified in loudspeaker models. Acoustical methods have been proposed to measure the impedance directly and improve representations of the loading, but they require the driver to be removed from the enclosure. The sound transmission through and around the rear elements of a mounted driver (e.g., the frame, magnet, voice-coil former, spider, pole-piece vent, etc.) can significantly affect the impedance actually seen by the driver diaphragm. This paper introduces and compares measurement techniques to assess the effective acoustic impedance of an enclosure when the driver is in place.
Development of a pair of loudspeaker enclosures.
Authors: Bosch David , Perez Jaime , Algorri Maria Elena
Published: October 2010

This paper presents the design process for a stereophonic loudspeaker system. The enclosures provide a base that is inert to vibration and an effective medium for the uniform formation of acoustic waves. Each enclosure is divided into two parts: the base for the high-frequency transducer (tweeter) and the enclosure for the low-frequency one (woofer). The former consists on a solid marble sphere with a copper heat radiator for the tweeter. This one lies on a rail that allows it to move forward and backward to be synchronized in time and phase. The second enclosure incorporates a rigid and massive quarter wavelength type MDF structure that controls the impedance of the woofer by means of a tube and reduces the amplitude of the sound from the back of the woofer diaphragm while favoring the omnidirectional characteristic and controlling diffraction with the baffle. Simulations in Mathcad from King’s tables for the woofer enclosure and others in Matlab for the filter are presented. This paper shows, as a result, a loudspeaker system of high specifications designed with the use of simple low-cost materials while considering the restrictions of designs of the same type in the industry.
Preliminary studies for the design of electrostatic transducers.
Authors: Harris Martin , Sinnewald Daniel , Gavinowich Daniel , Gomez Pablo
Published: October 2010

This paper compares the properties of a rectangular electrostatic speaker with a circular one. To achieve this, different prototypes were built with the same radiation area (approximately 230 cm2). The radiation diagrams were drawn and distortion measurements were taken so as to establish a correlation between the THD and the different coating resistances of the diaphragm. From the results obtained, the intention is to optimize the design of a large electrostatic transducer.
Three-dimensional polar analysis of a directional endfire microphone array on a measurement manikin due to microphone drift.
Authors: Burns Thomas H.
Published: October 2010

A dual microphone endfire array is a directional system commonly used in hearing aids. The directional performance of such systems are sensitive to sensor mismatch and drift. In this study, a pair of matched omnidirectional microphones in a delay-and-sum configuration are mounted in a hearing aid and their directional response is measured in-situ on KEMAR at 10 resolution in azimuth and elevation. The resulting 3-D polar balloons, directivity indices, and unidirectional indices are computed as a function of frequency. The measured transfer functions are then perturbed with sensor mismatch responses acquired empirically from typical lots of hearing-aid microphones. The resulting polar benchmarks are evaluated and compared to the original benchmarks. A detailed analysis, both visual and numerical, will be presented.
Civil engineering program in audio and acoustics at Universidad Tecnologica de Chile INACAP.
Authors: Muñoz Roberto , Jimenez Cristian
Published: October 2010

The Audio and Acoustics Engineering program at Universidad Tecnologica de Chile INACAP is quite broad and it has a 12 semester duration. It includes physical acoustics, engineering acoustics, underwater acoustics, electroacustics, noise and vibration control, environmental acoustics, architectural acoustics, sound recording, ultrasound, environmental noise control, digital signal processing, and the design of reinforcement systems. The facilities of the laboratories include an anechoic chamber, electro-acoustic laboratory, and recording studios. Our students gain experience in field measurement techniques, computer calculation, and modeling. Our graduated students are able to work in areas such as recording, production, sound reinforcement, programming, environmental acoustics, and acoustic conditioning for recording studios, media, film production companies, television, and video. Also, they are able to design noise and vibration control systems. The paper will present a comprehensive overview of the program of audio and acoustics at Universidad Tecnologica de Chile INACAP. In part, the paper will contain the following: (1) description of the acoustics and related courses offered; (2) examples of the facilities available at the campus; and (3) listing of graduate thesis, completed and in progress.
Latin American universities’ future.
Authors: Lizana Pablo
Published: October 2010

Latin American universities are at a disadvantage as compared to those of the rich countries. The number of graduates in relation to population, number of research programs in science and technology, budget, etc., reveal their flaws. This paper examines some proposals from the flexible training point of view and also overlooks the organization that usually is based on administration over the academic matters. With few exceptions, the Latin American universities are still pre-modern: the pre-eminence does not generate academic merit, and concern for the infrastructure problems occur instead of the teaching ones, making the results not competitive on the international level. The investigation is insufficient or even nonexistent, and full time researchers are very few and often give opinions that agree with the administration. Some changes are suggested.
A method for comparing sounds of similar instruments.
Authors: Carral Sandra
Published: October 2010

Although the radiated sound of similar musical instruments (e.g., two recorders made by the same maker) can be compared using an artificial excitation apparatus to eliminate a player-induced effect on the sound, this introduces another problem. Even if differences are found, the question remains as to whether these differences are musically significant: Would the musician not be able to compensate for these differences, making them irrelevant? One way of overcoming this problem is to have a musician play the instruments in a manner as close to that of real performance as possible. This paper presents a method for comparing the sounds of similar musical instruments, whereby a musician is asked to play a known piece many times on each instrument. The radiated sounds are recorded and subsequently spectrum-analyzed using the program SNDAN. Later on, time-varying parameters such as the rms amplitude, fundamental frequency, and spectral centroid as well as average and standard deviations of these parameters are calculated for each recorded sample for each instrument. Statistical tests are made in order to establish whether statistically significant differences between the instruments exist. Examples of this method will be presented.
Zero group velocity Lamb modes and edge resonance in a semi-infinite plate.
Authors: Ces Maximin , Clorennec Dominique , Royer Daniel , Prada Claire
Published: October 2010

The local resonances of an elastic plate with a free edge are investigated using laser ultrasonic techniques. It is known that the long wavelength vibrations of a plate can be interpreted in terms of Lamb modes. Low-frequency vibrations can be ascribed to the flexural A0 mode, while high-frequency shear or stretch vibrations occur at the cutoff of higher order Lamb modes. These thickness resonances correspond to an in-phase motion of the whole plate, associated to vanishing Lamb wave number. An elastic plate can also support local vibrations at nonzero values of the wave number for which Lamb mode dispersion curves undergo a minimum. Recently, experiments using laser ultrasonic techniques demonstrated that the local resonance of an infinite elastic plate is entirely governed by these zero group velocity (ZGV) Lamb modes. For a semi-infinite plate, ZGV modes can be observed at a distance as close as two thicknesses from the edge. Coming toward the edge, ZGV resonances slowly vanish, whereas the edge mode resonance appears, whose frequency depends on the thickness and on the bulk velocities of the plate. Using a laser excitation on the edge, the amplitude profile of the normal displacement of the edge was determined.
Cross-language effects for non-speech analogs: A comparison of English /w/-/v/ perception by native speakers of Hindi and English.
Authors: Iverson Paul , Wagner Anita , Pinet Melanie , Rosen Stuart
Published: October 2010

Individuals become specialized through development to perceive native-language speech sounds, but it is not certain whether this specialization occurs solely at the level of phonological categorization or whether pre-categorical auditory processing also becomes specialized. The present study examined this issue using 11 continua based on English /w/-/v/. The stimuli formed a graded set from naturalistic to non-speech by progressively making the source spectrum less natural and removing acoustic cues. The aim was to examine how close a stimulus must be to natural speech in order for cross-language differences to emerge. Native Hindi speakers, who have /w/-/v/ identification difficulties when learning English as a second language, and native English speakers were tested in terms of discrimination and identification. The results demonstrated that there were strong cross-languages differences for naturalistic speech and none for stimuli that were clearly non-speech, suggesting that more basic levels of auditory processing were not affected by language background. However, there were also cross-language effects for a narrow range of stimuli that sounded speech-like but had phonemes that could not be reliably categorized. This suggests that, although these cross-language differences may be speech-specific, they occur at a level prior to phonemic categorization.
The time course of gender influences on fricative identification.
Authors: Solum Renata D. , Munson Benjamin
Published: October 2010

Previous research has established that English-speaking listeners identify fricatives ambiguous between /s/ and /∫/ differently depending on whether they believe the fricative to have been produced by a man or a woman. This effect occurs both when the talker’s sex is suggested by presenting speech concurrent with a picture or a man or a woman [E. Strand Journal of Language and Social Psychology (1999)], and when listeners make unprompted inferences about whether an acoustically sex-ambiguous talker is a man or a woman [S. Kemper and B. Munson, Linguistic Society of America (2010)]. This investigation examined the time course of gender influences on fricative identification using a cross-modal interference paradigm. Listeners heard stimuli on a five-step sack to shack continuum created by combining synthetic fricatives with natural rimes produced by a man, a woman, or a talker whose voice had been judged independently to be sex-ambiguous. Pictures of men or women were presented briefly either prior to, concurrent with, or after the stimulus began. Gender influenced fricative identification only when the pictures were presented prior to the speech. This suggests that gender influences on perception occur relatively early in speech processing.
Variation and stability in judgments of talker similarity.
Authors: Munson Benjamin , Marnie Celina C.
Published: October 2010

Listeners judge some pairs of talkers to sound more similar to one another than others. This study examined whether the parameters that listeners attend to when judging talker similarity depend on the type of experience they have listening to the talkers’ voices. We hypothesized that judgments of talker similarity would change over the course of experiment depending on the type of exposure that listeners have to different talkers. Listeners who identify words that talkers produce should attend less to features not relevant for word recognition (i.e., f0 and voice quality), while listeners passively exposed to talkers should not change the parameters that they attended to. Two groups of listeners participated in a three-phase experiment. In the first phase, they judged the similarity of pairs of 16 talkers. In the second, one group conducted a recognition-memory task with the same talkers’ voices. The other listened passively while completing a visual-memory task. In the third, they listened to the same talkers and provided a new set of talker-similarity judgments. Multidimensional scaling was used to analyze the talker-similarity judgments. Preliminary analyzes suggest that the dimensions that characterize talker similarity spaces are similar in the first and third phases for both groups of listeners.
A continuous training procedure to assess infants’ learning of categories from acoustic cue distributions.
Authors: Cristià Alejandrina
Published: October 2010

Many models of infant category learning attribute a crucial role to distributions of acoustic cues. Unfortunately, most of the evidence in favor of this hypothesis is indirect (e.g., infants take longer to learn contrasts with overlapping acoustic cue distributions) and the more direct evidence, from laboratory training studies, is not straightforward. Two published papers show that infants’ perception is affected by different frequency distributions along voice onset time [Maye et al., Dev. Sci. 11, 122–134 (2008); Maye et al. Cognition 82, B101–B111 (2002)] but other studies report either null results [vowel length; Pons et al., ICIS (2006); vowel quality, Pons et al., Cogn. Sci. (2006)] or provide limited support [sibilant place of articulation, Cristià et al., J. Acoust. Soc. Am. 124, 2437(A) (2008)]. Mixed results may still be interpretable if stop voicing categories rely on psychoacoustic VOT discontinuities, whereas category formation is harder when such discontinuities are not available. If so, different contrasts would be learned at diverse rates. To test this hypothesis, a continuous training paradigm was developed to assess the timecourse of infant perceptual learning of categories that depend on very different acoustic correlates (e.g., stop voicing; Mandarin tones T2–T4).
Development of native language preference in the visual modality.
Authors: Ward Nancy , Sundara Megha
Published: October 2010

Infants have been known to be able to discriminate two languages using just the visual cues to speech. [Weikum et al., “Visual language discrimination in infancy,” Science, 316, 1159 (2007)]. There have been no studies that have investigated whether infants can use this ability in their language acquisition. We investigated the importance of visual cues in language acquisition by determining whether infants show a preference for their native language when they just have access to speech in the visual modality. All infants were tested using the visual fixation procedure. Monolingual 4- and 8-month-old infants were presented with side-by-side videos of a bilingual speaker producing English and Spanish sentences. Infants' looking time to each video was calculated and compared statistically. Preliminary data from 4-month-olds show that monolingual English-learning infants look longer to the English stimuli. Results will be discussed in the context of the influence of visual cues in auditory speech perception.
Cross-generational vowel change in Southern American English.
Authors: Fox Robert Allen , Jacewicz Ewa , Salmons Joseph
Published: October 2010

This study focuses on acoustic characteristics of vowels in the regional variety of Southern American English spoken in western North Carolina. It examines the cross-generational pattern of positional vowel changes with special reference to vowel-inherent spectral change. 140 speakers, males and females, ranging in age from 8-year-old children to adults in their early 90s produced 13 vowel categories in isolated hVd words. All participants were born and raised in the area and speak the local dialect. The results show that the reorganization of the vowel system occurs gradually, generation by generation, and there is a correspondence between positional vowel changes and the changes in formant dynamics. In each age group, females represent a more advanced stage of vowel change compared to males. These data clearly document both the systemic nature of vowel change and close interdependent relationships between the nominal monophthongs and diphthongs. The categorical distinction between monophthong and diphthong changes across generations. The oldest speakers produce monophthongal diphthongs and diphthongal monophthongs, whereas younger speakers show increased monophtongization of the former and diphthongization of the latter. [Work supported by NIH.]
Localization of sound sources in rooms using an improved version of steered response power algorithm.
Authors: Lopez Jose J. , Cobos Maximo , Marti Amparo
Published: October 2010

Localization of sound sources inside a room is a challenging problem. The possible applications involving speech-based source localization systems range from teleconferencing to home automation systems. For example, the localization of a speaker inside a conference room can be very useful to place the speaker in a remote room by means of a spatial audio reproduction system. Also, new applications will appear in home automation if accurate source localization systems are available in the future. One of the most robust approaches to source localization is the SRP-PHAT algorithm, which has shown to provide very good localization results inside rooms with moderate reverberation. However, the computational cost is highly dependent on the spatial sampling and the number of microphones, making very difficult the localization of sound events if a coarse spatial sampling is used. In this paper, we propose an improvement of this method where sound events are not missed even if a very coarse grid is used. The improvement is based on a previous calculation of the existent cross-correlation lags between spatially adjacent points in the grid, assuring that the non-sampled space is covered in terms of cross-correlation lags between microphone pairs when running the algorithm. Several experiments conducted in different rooms with complex acoustics confirm the validity and benefits of the proposed method.
An examination of the theory of acoustic virtual mass.
Authors: Hefner Brian T. , Calantoni Joseph
Published: October 2010

A number of researchers have considered what roles rotational and non-orthogonal grain motion play in the elastic response of a granular medium. Recently, Chotiros and Isakson [J. Acoust. Soc. Am. 121, EL70–76 (2007)] proposed that these motions lead to an increase in the inertia, producing a decrease in the sound speed of the elastic waves. They model this increase in inertia as an acoustic virtual mass by considering the coupling of the translational and angular motion at the granular level. Closer examination of the theory for the acoustic virtual mass reveals that it fails to take the macroscopic strain in the medium into account and hence does not actually capture the physics described by the authors. If one argues that the theory can be treated as an approximation for the grain response in the long wavelength limit, an inconsistency in the mathematical development of the model brings the final result into question. This inconsistency can be overcome within the framework of the model, and the new result introduces a frequency dependence to the virtual mass term. [Work supported by the Office of Naval Research.]
Negative velocity dispersion and attenuation in granular marine sediments.
Authors: Kimura Masao
Published: October 2010

The author proposed a gap stiffness model incorporated into the Biot model; that is, the BIMGS model. Reported large velocity dispersion is predicted by this model. However, at higher frequencies, there are some reported data for negative velocity dispersion and attenuation proportional to the first to fourth power of frequency. In this study, the velocities and attenuation in six kinds of water-saturated glass beads and four kinds of water-saturated silica sands with different grain sizes are measured in the frequency range of 80–140 kHz and 300–700 kHz. The measured results are compared with the calculated results by using the BIMGS model plus some acoustic sediment models, such as the BICSQS model plus high-frequency correction, nonlocal model, porosity dynamics model, and multiple scattering model. It is shown that the velocity dispersion and attenuation is predicted by using the BIMGS model in the range of kd ⩽ 0.5 (k is wavenumber in water, d is grain diameter) and by using the BIMGS model plus multiple scattering effects in the range of kd ⩾ 0.5, in which a negative velocity dispersion appears. Finally, the relations between the measured velocity dispersion and attenuation are confirmed by using the twice-subtracted Kramers–Kronig relations.
Comparative measurements of sound-speed and attenuation in the deep seafloor sediments of northern Gulf of Mexico.
Authors: Turgut Altan , Wylie Jeniffer
Published: October 2010

Comparative sediment sound-speed and attenuation measurements were conducted in the northern Gulf of Mexico using three different methods. The first method uses ship noise generated by the attending research vessel, recorded by a hydrophone near the seafloor. The second method uses a deep-towed chirp sonar and estimates sound-speed and attenuation from the reflection data. The third method uses four acoustic probes and measures sound-speed and attenuation at 0.6 m below seafloor. Auto-correlation processing of ship-noise data provided subbottom profiling up to 40 m penetration and the results were in agreement with those of chirp sonar data. The measured sound speed and attenuation are typical to clayey and silty/clayey sediments that agree with the available core data. The frequency dependency of sound speed and attenuation were also estimated within a wide frequency band using the data from co-located ship noise (0.2–5 kHz), chirp-sonar (2–12 kHz), and sediment acoustic-probe (5–120 kHz) measurements. Observed small frequency dependence of sound-speed and linear frequency dependence of attenuation are in agreement with those predicted by the Biot–Stoll model for silty/clayey sediments. [Work supported by ONR.]
Acoustic analysis of the Chavín pututus (Strombus galeatus marine shell trumpets).
Authors: Cook Perry R. , Abel Jonathan S. , Kolar Miriam A. , Huang Patty , Huopaniemi Jyri , Rick John W. , Chafe Chris , Chowning John M.
Published: October 2010

In 2001, a group of twenty Strombus galeatus marine shell trumpets were excavated at the 3000-year-old ceremonial center at Chavín de Huántar, Perú, marking the first documented contextual discovery of intact sound producing instruments at this Formative Period site in the Andean highlands. These playable shells are decorated, use-polished, and additionally modified with a V-shaped cut to the outer apical lip. We present an acoustic analysis of the measured response of each instrument, to a variety of excitations, at microphones placed in the mouthpiece, bore, bell, and surrounding near-field. From these measurements we characterize each instrument’s sounding frequency, radiation pattern, and impedance, and estimate its bore area function. Knowledge of the specific acoustic capabilities of these pututus allows us to understand and test their potential as sound sources in the ancient Chav\’{i}n context, whose architectural acoustics are simultaneously studied by our research group.
Do we need two ears to perceive auditory distance in rooms?
Authors: Bidart Arnaud , Lavandier Mathieu
Published: October 2010

In free field, the intensity of a sound source can be used to evaluate its distance, but this evaluation is relative: the listener needs to know a priori the sound level produced by the source, or he/she can only compare different distances assuming a constant source level. In rooms, absolute evaluation of auditory distance is possible. The monaural direct-to-reverberant energy (D/R) ratio has been proposed as the underlying cue for this evaluation [Bronkhorst and Houtgast, 1999]. However, distance perception at fixed D/R ratio depends on the source type and direction [Zahorik, 2002] and on the laterality of room reflections [Bronkhorst, 2002], and it seems to disappear for a source perfectly coherent at the ears [Bronkhorst, 2001]. The source interaural coherence might then be an alternative cue for auditory distance. This question was investigated in a series of experiments, in which perceived distance was measured in virtual rooms, using speech, clicks, and bursts of noise. The tested conditions were chosen so that D/R ratio and coherence varied independently in order to separate the effects of these two potential cues.
Reduction of ultrasound propagation velocity in porcine vertebrae following stereotactic radiosurgery.
Authors: Pollard Julie E. , Steinmann-Hermsen Jessica , Medin Paul M. , Boike Thomas , Richer Edmond
Published: October 2010

Vertebral metastasis occurs in over 100 000 individuals in the United States. Stereotactic radiosurgery (SRS) has helped cancer patients with disabling pain. Over the last 10 years, the use of spinal SRS grew exponentially and typical dosage increased significantly from 10–12 Gy to 16–22 Gy. Yet the tolerance of the vertebrae to high doses of radiation is poorly understood, and the increase in dosage resulted in a correlated rise in vertebral fracture. Yucatan minipigs were radiated with doses 16–18 Gy from third to sixth cervical vertebrae. Radiated volume was parallel to spine and focused on half of the vertebral body, resulting in high dose and low dose irradiated regions. Cubic samples were obtained from the two halves of the irradiated vertebrae 1 year after SRS. Control samples were obtained from nonradiated vertebrae. Ultrasound propagation velocity in bone is an indicator of its mechanical strength. Velocity was measured by correlation with a reference wave, obtaining the phase shift using Hilbert transform. Consistently, high-dose irradiated specimen exhibited a reduction in ultrasound velocity between 1.2% and 15.4%, with an average of 6.9%. Young’s modulus was reduced on average by 15%. This research could provide indicators for safe, effective doses in clinical SRS.
Analysis of mode vibrations of arteries for estimation of elastic properties.
Authors: Urban Matthew W. , Bernal Miguel , Nenadic Ivan , Greenleaf James F.
Published: October 2010

Arterial elasticity has gained importance in the past decades as it has been shown to be an independent predictor of cardiovascular diseases. Ultrasound radiation force has been used to excite propagating waves in arterial vessels in order to measure the wave speeds and characterize the elastic properties of the vessels. Excised pig carotid arteries were excited with impulsive radiation force using 3-MHz tonebursts of length 200, and the propagating waves were measured along the length of the artery over a distance of 2 cm. A 2-D fast Fourier transform was performed on the spatiotemporal data for identification of several propagating modes in the vessel. Multiple propagating modes could be visualized from the spatiotemporal data that varied with the transmural pressure of the artery under investigation over a range of 10–100 mm Hg. The modes present in the data were fitted with a theoretical model to estimate the elasticity of the arteries. The comparison with the model provides insight into characterizing the elastic properties of the artery. [This work was supported in part by NIH Grant no. EB002640.]
Shear-rate dependence of viscosity for improved modeling of cavitation dynamics in visco-elastic media.
Authors: Labouret Stéphane , Coussios C. C.
Published: October 2010

The environment experienced by a cavitating bubble in visco-elastic media at the micro-scale and in the MHz frequency range remains poorly understood. Comparison of model-based predictions with optical observations of bubble behavior in transparent media suggests that the value of the mechanical properties of the medium can differ from the corresponding static values by two orders of magnitude. Tissue or tissue-mimicking materials have been recently shown to exhibit a sub-micrometer structure which can be assumed equivalent to a pure liquid up to a characteristic length scale, beyond which they can be treated as purely visco-elastic. In order to take this effect into account, a two-scale extension is applied to the cavitation dynamics model recently proposed by Yang and Church [J. Acoust. Soc. Am., (2005)]. Comparison of the extended model predictions with experimental observations of single-bubble dynamics in an agar-based tissue-mimicking material demonstrates that, for a given value of the shear modulus, the values of viscosity required to adequately describe cavitation behavior using the two-scale model are twice those assumed by the single-scale model and depend on the size of the initial cavitation nucleus. The inclusion of shear-dependent viscosity is therefore necessary to adequately describe single-bubble cavitation dynamics in visco-elastic media
Three-dimensional computational modeling of high-frequency ultrasound imaging of murine liver and liver metastases.
Authors: Daoud Mohammad I. , Lacefield James C.
Published: October 2010

High-frequency ultrasound images of preclinical cancer models are sensitive to variations in microanatomy that accompany tumor growth, but the relationships between high-frequency backscattering and tumor microstructure are incompletely understood. To investigate these relationships, a 3-D microanatomical model that incorporates cell number density, sizes of cells and nuclei, and spatial arrangement of cells is used to represent a healthy mouse liver and an experimental liver metastasis. A first-order k-space method is used to synthesize B-mode images by computing linear 3-D propagation of focused 40-MHz pulses through the simulated tissues. Simulated images are compared to corresponding experimental images by constructing gray-level histograms with 13 bins evenly spaced over 256 gray levels. Simulated and experimental speckle distributions for a healthy liver match within one standard deviation in all 13 histogram bins when the sound speed and mass density of the cell nuclei are set to 1503 m/s and 1.43 g/cm3, respectively. Simulated and experimental speckle distributions for the liver metastasis match in 11 of 13 bins when the sound speed and density of the nuclei are set to 1527 m/s and 1.14 g/cm3. These simulations suggest that changes in first-order speckle statistics during tumor development reflect variations in both tissue acoustic and microstructural properties.
Effects of ultrasound on osteoblast proliferation and its mechanisms triggered by calcium transport.
Authors: Katiyar Amit , Sarkar Kausik , Duncan Randall
Published: October 2010

Bone fracture healing is a set of complex sequential physiological processes that involves several cellular activities. FDA has approved the application of low-intensity pulsed ultrasound for accelerated healing of fractures. However, currently the cellular effects of ultrasound and how ultrasound effects healing are not completely understood. We are studying the effects of ultrasound on osteoblast cells in vitro toward this goal. Results of cell proliferation under pulsed ultrasound excitation (0.5–5 MHz, 1–500 mW/cm2, 200 μm, 1 kHz PRF) for a duration of 5–30 min daily will be presented. BrdU and MTS assays were used for the quantification of cell proliferation. We found a significant increase in cell proliferation for the intensity variation of 1–100 mW/cm2. At higher intensities (about 500 mW/cm2) of excitation, cells die. Intracellular calcium storage and its flux through cellular membrane are believed to play a critical role in cell response to mechanical stimuli. We will present results of cell proliferation when calcium transport through the voltage sensitive calcium channels (L-type and T-type) and mechano-sensitive cation-selective channels was blocked. Preliminary data suggest the role of T-type calcium channel toward enhancement of cell proliferation.
Pressure-time profiles of a focused and a radial shockwave device: Measurements in tissue, ex vivo, and in a water bath.
Authors: Kearney Cathal J. , Prevost Thibault , Socrate Simona , Cleveland Robin O. , Spector Myron
Published: October 2010

In the past we have employed shock waves (SW) to stimulate periosteal cell proliferation in both rat and rabbit models. In order to understand the mechanical insult to the cells, single pulse pressure-time profiles were recorded at a periosteal surface using a needle hydrophone for both a ballistic and an electrohydraulic SW source. Three sets of measurements were taken: free field (FF) in a water bath, intramuscularly (IM) by inserting the needle into the leg of a sacrificed rabbit and placing it near the tibial bone corner, and ex vivo using an extracted rabbit tibia bone in a water bath and placing the needle closer to the bone surface. For the ballistic source, the IM and FF measurements of the leading positive peak matched, whereas for the electrohydraulic source, it was attenuated by 57%. The compression was followed by a tensile wave, and for both sources, IM and FF measurements of the pressure and duration were similar. The ex vivo measurements showed additional secondary peaks for the measurements at the bone surface, attributable to surface reflections or creeping waves. These data suggest that periosteal cells subject to SWs are exposed to complex pressure fields that likely stimulate the cell proliferation.
Conventional frequency evaluation of tumor cell death in response to treatment in vivo.
Authors: Papanicolau Naum , Karshafian Raffi , Sadeghian Alireza , Kolios Michael , Czarnota Gregory
Published: October 2010

In this study, we investigate for the first time the potential to quantify tumor responses to therapy in vivo, using spectral and signal envelope statistics analysis of conventional frequency ultrasound data. Tumors were grown in SCID mice using a human prostate cell line (PC-3) and treated in three groups consisting of combinations of ultrasonically stimulated micro-bubble anti-angiogenic treatment and 8 Gy doses of single fraction 100 kVp X-ray radiation. Data collection consisted of tumor images in addition to radiofrequency data prior to treatment administration and at 24 h following. Analysis of the normalized power spectra of 10-MHz data yielded an increase in mid-band fit of approximately 3.8±0.7, 4.6±0.8, and 5.8±0.7 dBr compared to data acquired before treatment. Spectral slopes were relatively invariant. However, the 0-MHz intercept followed the trend of the mid-band fit. Signal envelope changes were compatible with observations made from spectral data and linked to correlative increases in cell death. The aim of this research is to investigate the potential of conventional frequency ultrasound to noninvasively quantify response to cancer treatments, laying the groundwork for future investigation into the viability of 10-MHz ultrasound to be employed in a clinical setting.
Some important considerations about the use of new materials in sound barriers.
Authors: Arenas Jorge P. , Alba Jesus , del Rey Romina
Published: October 2010

Several alternatives to mitigate road traffic noise impact have been reported, although constructing a noise barrier is probably the most important mitigation measure when the construction of a highway is planned. A noise barrier impedes the transmission of traffic noise, resulting in low noise levels at the receiving point. Earth-mounds, fences, or walls are common ways to implement a noise barrier. Due to environmental concern and economic costs of sound barriers, the use of new materials in building sound barriers has received a large amount of attention in recent years. However, a sound barrier is a solid structure that has to meet several standards in order to assure its proper use. In this work, the use of new materials in sound barriers is discussed from a practical point of view. Engineering concerns about visual impact, effects on ecosystems, safety for drivers, effects on residents, and public acceptance are discussed. Although the use of new low-cost and environmentally friendly materials is becoming very important in recent years, its practical application in sound barriers presents several challenges to meet technical specifications.
Main features of the materials used in and the type of sound barriers built in Chile.
Authors: Surez E. , Arenas J. P.
Published: October 2010

Since the 1990s sound barriers have been designed as usual solutions to control environmental noise in Chile. These solutions have been used to control noise in industrial activities and, particularly, in highways. Since 2003 about 20 km of sound barriers have been implemented in urban highways and more than 19 km have been implemented in intercity projects. Sound barriers built in Chile have been made from different materials: transparent, metal/transparent, concrete/transparent, concrete or masonry blocks, metal, metal/concrete, and metal/transparent. At this time, more than 10 highway projects that consider the use of sound barriers are under execution. On the other hand, 27 other projects are under evaluation for 2010 and 2011, where the pertinence of using sound barriers is analyzed according to the directives of the Department of Public Infrastructure (MOP) of the Chilean government. The main reasons to implement these barriers in sensitive areas (residences and educational, health, and worship facilities) have been the national legislation for stationary noise sources (industries and workshops activities), the requirements of the environmental impact evaluations, and the decision of MOP to implement infrastructure projects of high standards.
An inverse method to characterize fibrous sound absorbing materials.
Authors: Ramis Jaime , Alba Jesus , Del Rey Romina
Published: October 2010

Characterization of sound absorbing materials is needed to predict its behavior. The most commonly used models to do so consider the flow resistivity, porosity, and average fiber diameter as parameters to determine the acoustic impedance and sound absorbing coefficient. Besides direct experimental techniques, numerical approaches appear to be an alternative to estimate the material’s parameters. In this work an inverse numerical method to obtain the porosity, the fiber density, and the fiber average diameter of a fibrous material is described. Using normal incidence measurements of the sound absorption coefficient and then using the model proposed by Voronina, subsequent application of basic optimization techniques allows one to characterize a sound absorbing material. The numerical results agree fairly well with the experimental data.
Shape optimization of reactive-dissipative mufflers.
Authors: Kuskinen Cristóbal , Riveros Alejandro , Floody Sergio
Published: October 2010

The optimization problems based on genetic algorithms and the use of finite element method to represent physical models have been used as a design tool in different areas of acoustics. This study utilizes the interaction of these methods to build a software that allows adjusting the user requirements by optimizing the acoustic performance of a muffler under space constraints and also considering a backpressure to be inserted into the exhaust system of an internal combustion engine. The research focuses on developing a programming code and user interface, taking into account that the user of the software has relevant knowledge on the subject. Theoretical results are presented for three types of silencers: simple, double, and triple expansion chambers, incorporating sound absorbing material in the different chambers. At the end of the investigation, results of the measurements made to a few mufflers are presented and compared with the theoretical results.
The influence of moisture and recycled porous medium on the acoustical properties of soil substratum used on green noise barriers and absorbing building facades.
Authors: Horoshenkov Kirill , Khan Amir , Benkreira Hadj , Mandon Agnès
Published: October 2010

This work investigates the acoustical and related non-acoustical properties of soil substratum that is used on vegetative noise barriers and green walls. The following effects are studied in the laboratory: (i) soil moisture content, (ii) soil blending with porous recycled materials, and (iii) multi-layering of soil with porous recycled materials. The acoustic absorption and surface impedance measurements are carried out using a standard 100-mm impedance tube. The flow resistivity measurements are carried out using a calibrated flow resistivity apparatus having the diameter of 100 mm. Samples of soil substratum are prepared in a specially designed sample holder that enables accurate control of the moisture content, porosity, material compaction, and soil density. The observed experimental data are used to validate the theoretical predictions which are based on a model that requires the knowledge of the flow resistivity, porosity, tortuosity, and pore size distribution of soil and recycled porous media.
Pre-Colombian and traditional Mexican wind instruments.
Authors: Zenker Miguel
Published: October 2010

Wind instruments such as flutes were known in ancient Mexico 3000 years ago. When the Spaniards arrived, pre-Colombian cultures used many kinds of ceramic peak flutes of one, two, and three tubes, made by the musicians themselves, who played them and break them down at the rituals. Other wind instruments were so-called ocarinas as well as all kinds of whistles with the most exotic sounds, like the death-whistle. They also knew some kind of lip-vibrated instruments, made from seashells or wood and other materials. Seashell trumpets were also copied in clay and made them to be blown in the same way as the original instrument. The Spaniards destroyed as much as they could of the native culture and introduced their own, mainly through religion: music was an essential part of Catholic service. Pipe & tabor and shawms were widely used. Those instruments became part of the cultural heritage of the natives and we can hear them play today. This presentation will show pre-Colombian wind instruments, with sound examples, diagrams, and acoustical analysis made by different scholars, as well as traditional and ethnographic wind instruments made with natural materials used at present times.
Mexican resonators with mirliton.
Authors: Velazquez Roberto
Published: October 2010

In ancient Mexico, resonators with mirliton were used and similar instruments could be used in other zones, but there are very few papers on them. Many misidentified ancient tubes with a hole for the membrane were found in museums and publications, but were lost due to their biological perishable materials. Their models can be played as the flutes or may be excited with vocalizations and can produce nasal or buzzing musical notes, as well as complex and variable sounds like those of some animals, callers or gamitaderas. Flutes with membrane are still used in Asia and in the Pame town of Santa Maria Acapulco, San Luis Potosi, Mexico, which are made of local natural materials: carrizo (cane for the resonating tube with four finger holes), shaft of a turkey feather (wind way for the blowing), propoleo (bees wax to attach the parts), leaf of maize (to support the membrane vibration), and a thin sheet of an egg-sac of spider silk (mirliton). Historical, organological, and acoustical characteristics and possible uses of some flutes and their models with membrane are discussed. Available recordings were used to analyze the Pame flute sounds.
Construction and operation of the Southeast Asian free reed mouth organs.
Authors: Cottingham James P.
Published: October 2010

Among the most significant indigenous musical instruments of Southeast Asia are the free reed pipes and mouth organs. Details of the origin and development of these instruments are connected with the history and prehistory of a multitude of ethnic groups. There are several types of these instruments. Results of acoustical studies as well as descriptions of techniques and materials of construction are summarized for three of these types: the free reed pipe with finger holes, the gourd windchest mouth organ, and the Lao raft mouth organ (khaen). The khaen and the gourd pipe employ free reeds mounted in the sides of pipes open at both ends, although in the gourd pipe the player has the option of altering the pitch by closing the bottom of the pipe. The pipe with finger holes may be either side-blown or end-blown. These instruments have traditionally been constructed with very simple tools using natural materials, primarily bamboo and wood. Bamboo is often still used for the reeds as well as the pipes, although metal reeds have been common for some time. Traditionally, a black substance resembling beeswax is used as a sealer.
Soundscape versus long-term average methods of noise mapping.
Authors: Bettcher Adam D. , Siebein Gary W.
Published: October 2010

A babbling brook at 65 dB is a sound of a much different nature than a car horn at 65 dB. Similarly, a resident in a house may value these sounds differently than a cyclist on a lone highway listening for passing cars. Existing methods of community sound planning compress this information into a single-number rating or spectrum, perhaps mapped across a geographic area. The result is the loss of much information about the nature of the sound, and with it the potential for much more highly informed acoustical design decisions. This presentation examines a method of community noise planning that includes elements of soundscape analysis to produce “sound maps” that contain information on the composition of the sounds that are being measured. The results of the soundscape-mapping method are then comparatively analyzed against results produced by a more traditional method of averaged, long-term acoustical measurements to determine potential differences in suitability for target uses over geographic areas.