bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation of elastic waves in a fluid-loaded anisotropic functionally graded waveguide: Application to ultrasound characterization
Authors: Baron Cécile , Naili Salah
Published: March 2010

Non-destructive evaluation of heterogeneous materials is of major interest not only in industrial but also in biomedical fields. In this work, the studied structure is a three-layered one: A laterally heterogeneous anisotropic solid layer is sandwiched between two acoustic fluids. An original method is proposed to solve the wave equation in such a structure without using a multilayered model for the plate. This method is based on an analytical solution, the matricant, explicitly expressed under the Peano series expansion form. This approach is validated for the study of a fluid-loaded anisotropic and homogeneous plane waveguide with two different fluids on each side. Then, original results are given on the propagation of elastic waves in an asymmetrically fluid-loaded waveguide with laterally varying properties. This configuration notably corresponds to the axial transmission technique to the ultrasound characterization of cortical bone in vivo.
Analysis of the attenuation of railway squeal noise by preloaded rings inserted in wheels
Authors: Brunel J. F. , Dufrénoy P. , Charley J. , Demilly F.
Published: March 2010

Squeal from railway wheels occurring in short radius curves produces a very intense and highly annoying noise in the range 400–8000 Hz. When the excitation, due to lateral forces acting on the wheel, cannot be avoided, additional systems can be added on the wheel to limit acoustic emission. A very economical approach is the use of metal rings inserted into grooves machined in the wheels. Unfortunately the effectiveness of these so called damping rings varies from one wheel to another and for different rings. Because the mechanisms of attenuation are not well understood, these variations have not to date been explained. The aim of this paper is to clarify the attenuation mechanisms for damping rings especially for the first three axial wheel modes, which are the predominant sound radiated ones in curve passage and for which the effectiveness of the treatment is lower. It has been generally assumed that friction between the ring and the groove has been the mechanism for squeal noise attenuation. Here it is shown that the vibration attenuation is due to modal coupling between the wheel and the ring. The validity of this proposed mechanism is investigated using experimental measurements and theoretical and numerical models. The results presented here will provide an avenue for optimization of the damping ring noise control treatment to obtain significant levels of squeal noise attenuation notably for the first three axial modes.
Learning to perceptually organize speech signals in native fashion
Authors: Nittrouer Susan , Lowenstein Joanna H.
Published: March 2010

The ability to recognize speech involves sensory, perceptual, and cognitive processes. For much of the history of speech perception research, investigators have focused on the first and third of these, asking how much and what kinds of sensory information are used by normal and impaired listeners, as well as how effective amounts of that information are altered by “top-down” cognitive processes. This experiment focused on perceptual processes, asking what accounts for how the sensory information in the speech signal gets organized. Two types of speech signals processed to remove properties that could be considered traditional acoustic cues (amplitude envelopes and sine wave replicas) were presented to 100 listeners in five groups: native English-speaking (L1) adults, 7-, 5-, and 3-year-olds, and native Mandarin-speaking adults who were excellent second-language (L2) users of English. The L2 adults performed more poorly than L1 adults with both kinds of signals. Children performed more poorly than L1 adults but showed disproportionately better performance for the sine waves than for the amplitude envelopes compared to both groups of adults. Sentence context had similar effects across groups, so variability in recognition was attributed to differences in perceptual organization of the sensory information, presumed to arise from native language experience.
Nondiffuse elastic and anelastic passive imaging
Authors: Mulargia Francesco , Castellaro Silvia
Published: March 2010

The property at the basis of passive acoustic imaging is that, taken any two points, one of them can be seen as the source of the waves and the other as the recording station. This property, which was shown to hold also in nondiffuse fields, is here exploited: (1) to allow an undistorted passive imaging through the simple use of the statistical mode to estimate wave velocity, (2) to determine the azimuth of the instantaneous Huygens sources of the noise wavefield, and (3) to measure, provided that the noise bandwidth is wide with respect to that of the local system, the material dissipation constant as a function of frequency. The authors applied this theory to study the seismic noise field in the Ravenna, North-Central Italy, shore area and found it capable to provide velocity dispersion curves matching those of independent surveys, to track the sources of seismic noise to a few major firms in Ravenna port, with the prevailing source switching at the time scale of seconds, and to measure the dissipation quality factor Q at ∼20 independent of frequency in the range 1–30 Hz.
Dispersion of sound in dilute suspensions with nonlinear particle relaxation
Authors: Kandula Max
Published: March 2010

The theory accounting for nonlinear particle relaxation (viscous and thermal) has been applied to the prediction of dispersion of sound in dilute suspensions. The results suggest that significant deviations exist for sound dispersion between the linear and nonlinear theories at large values of ωτd, where ω is the circular frequency and τd is the Stokesian particle relaxation time. It is revealed that the nonlinear effect on the dispersion coefficient due to viscous contribution is larger relative to that of thermal conduction.
Biomechanical modeling of register transitions and the role of vocal tract resonators
Authors: Tokuda Isao T. , Zemke Marco , Kob Malte , Herzel Hanspeter
Published: March 2010

Biomechanical modeling and bifurcation theory are applied to study phonation onset and register transition. A four-mass body-cover model with a smooth geometry is introduced to reproduce characteristic features of chest and falsetto registers. Sub- and supraglottal resonances are modeled using a wave-reflection model. Simulations for increasing and decreasing subglottal pressure reveal that the phonation onset exhibits amplitude jumps and hysteresis referring to a subcritical Hopf bifurcation. The onset pressure is reduced due to vocal tract resonances. Hysteresis is observed also for the voice breaks at the chest-falsetto transition. Varying the length of the subglottal resonator has only minor effects on this register transition. Contrarily, supraglottal resonances have a strong effect on the pitch, at which the chest-falsetto transition is found. Experiment of glissando singing shows that the supraglottis has indeed an influence on the register transition.
US Green Building Council's role as a change agent in the North American construction market.
Authors: Tinianov Brandon D.
Published: March 2010

After observing market reaction to the U.S. Green Building Councils (USGBC) Leadership in Energy and Environmental Design (LEED), one could conclude that it may be the most powerful voluntary market transformation tool encountered in the modern building industry. The LEED voluntary system is not only entering a very diverse array of markets but stimulating changes in product design, professional practices, and educational curricula. It is also prompting debate in various circles another healthy sign of market transformation. This presentation will provide an overview of who USGBC represents, how they view green buildings, and the specifics of how this market transformation takes place.
Acoustics and the Leadership in Energy and Environmental Design (LEED) certification—Why education and healthcare came first.
Authors: Rockstroh Kurt , Sykes David , Cavanaugh William , Tocci Gregory
Published: March 2010

Three decades of Washington neglecting the noise problem in America resulted in general ignorance of and data about human health impacts. This is true with politicians, agency heads, foundations, doctors, educators, architects and builders—whether they “advocate green policies” or not. So when LEED redefined the term “environmental quality” to include acoustics, they focused on “populations at risk”—children (schools), and sick people (healthcare facilities where scientific research on human subjects is routine). Meanwhile, healthcare professionals became attuned to noise and privacy from HIPAA and the patient-centered-care movement. In 2005, the Facility Guidelines Institute, which each re-issues the 60-year-old Guidelines for Design and Construction of Healthcare Facilities every 4 years resolved to address this problem. We commissioned TC-AA.NS.SC to develop comprehensive acoustical guidelines which were completed in 2006 and launched this January. Once drafted, the acoustical guidelines were quickly piloted for LEED by Green Guide for Healthcare, and then the LEED Environmental Quality Technical Advisory Group adopted them as the Reference Standard for LEED HC. From HC it will find broader acceptance in other LEED programs. This process ensures that acoustics re-enters public policy supported by independent, transdisciplinary research on human health impacts and by multiple rounds of peer review in healthcare.
Materials science: A “Green” acoustical wall treatment for controlling room reverberation in healthcare.
Authors: Babineau Francis
Published: March 2010

In healthcare, green criteria must be coupled with a higher standard of stringent infection control requirements. This study was conducted to explore an alternate method for reducing room reverberation in a healthcare setting. Reverberation time (RT) plays an important role in noise levels and speech privacy which are key factors in healthcare. However, RT is difficult to control in healthcare facilities due to strict durability and infection control requirements. In this study of a private patient room in a hospital, instead of improving the ceiling to reduce reverberation, the walls were treated with a new, thin, acoustically absorptive, but paintable, wall material. The wall treatment was a new-to-market acoustical finish with absorption coefficients ranging from 0.05–0.6. To achieve reverberation control, several walls of the room were covered with the treatment. Reverberation times were measured before and after installation, and results were consistent with predicted values. Despite being a small study, results suggest that a thin, paintable, acoustical wall treatment that meets criteria for infection control and durability can be an effective method for controlling reverberation in healthcare facilities, thereby creating a more comfortable environment for patients and staff while giving architects increased design flexibility.
Going green may require new professional relationships and different solution providers.
Authors: Brooks Bennett , Perrone Jason
Published: March 2010

Change is always welcome but often confusing. One way climate change impacts the acoustics profession is through the sudden, government-driven rush to make buildings green by conforming to Energy Star and the U.S. Green Building Council’s LEED rating system (acoustics have only recently become part of the “environmental quality” vocabulary of these systems). Two more ways change impacts acousticians are first the emergence of technologically advanced materials and devices (often from companies you do not know), and second, the emergence of new “solution-providers” with prior contractual relationships with your clients. The presenters represent three entities that have been cooperating to address green-related acoustical issues for large corporate clients in the Northeast USA. The projects described in this presentation have been instructive for all three parties: new materials have been put to use in unexpected ways, independent testing validated the efficacy of novel solutions, and client relationships were managed by a corporation previously unrecognized by most acoustical engineers but that has spent a decade establishing a level of skill in acoustics appreciated by government agencies and leading corporations that have streamlined supply chains and therefore seek to use a limited number of existing supplier relationships to implement change.
Investigations of marine mammal exposure to sound scattered from the sea surface.
Authors: Abawi Ahmad , Porter Michael , Siderius Martin
Published: March 2010

Scattering of sound from the rough sea surface results in variations in sound intensity. If the surface height variations are smooth, as they are during a swell, the surface can act as a concave mirror and amplify the sound intensity at its focal region. We have shown both analytically and using numerical modeling that the intensity at the focal region is a function of frequency: for a singly curved surface, the intensity at the focus varies linearly with frequency and for a doubly curved surface, this dependence is quadratic. Scattering of sound waves from a rough surface can also result in a reduction in intensity through dispersion. In this paper, we investigate the possible effects of exposure to sound scattered from the sea surface on marine mammals by computing the scintillation index as a function of range and depth for a variety of ocean environments, including those with surface ducts. We compute the scintillation index using a Monte Carlo technique, where for each surface height realization, we compute the scattered field in the waveguide exactly using the virtual source technique. We compute the Green’s functions needed in the virtual source technique using the Scooter propagation model.
Changes in vocal behavior of individual North Atlantic right whales in increased noise.
Authors: Parks Susan E. , Johnson Mark , Nowacek Douglas , Tyack Peter
Published: March 2010

This study investigates the impacts of anthropogenic noise exposure on the vocal behavior of individual North Atlantic right whales, a baleen whale species found in the urban coastal waters off the east coast of the United States and Canada. A non-invasive acoustic recording tag, the Dtag, was used to record the noise levels received by individual whales and the vocalizations they produced in the Bay of Fundy, Canada. These data were used to assess the variability in the received levels (and therefore source level), duration, and frequency content of calls produced by the tagged whale in varying ambient noise conditions. A single stereotyped call type, the ‘upcall,’ was selected for these measurements. Individual whales producing multiple calls showed increases in received call amplitude and minimum frequency in increasing low-frequency noise conditions. This is one of the first studies to document call intensity changes in baleen whales in response to short-term changes in anthropogenic noise in their environment. This evidence for individual call modification in response to changes in background noise has implications for both descriptive studies of vocal behavior and design for passive acoustic monitoring systems for marine species.
Hearing ability of the lined seahorse (Hippocampus erectus).
Authors: Hastings Susan M. , Kelly Meghan R. , Wu Lisa L. , Hastings Mardi C.
Published: March 2010

The lined seahorse (Hippocampus erectus), a member of the family Syngnathidae (pipefishes and seahorses), occurs in coastal waters of the western Atlantic, Gulf of Mexico, and Caribbean Sea. This harmless species is listed as “vulnerable” on the International Union for the Conservation of Nature (IUCN) List of Threatened Species, meaning that it has a high risk of extinction in the medium-term future primarily due to declines in population from targeted catch, bycatch, and degradation of habitat. However, because little is known about hearing in Syngnathids, it is difficult to assess potential effects of anthropogenic sound on these animals. In this study auditory evoked potentials (AEPs) were measured in four H. erectus specimens to determine hearing thresholds and bandwidth. Thresholds were determined using the staircase method with exposures to tone bursts between 50 Hz and 21.6 kHz. At low frequencies H. erectus had AEP thresholds similar to other bony fishes; however, at frequencies above 2 kHz its auditory sensitivity was similar to that of clupeiform species which detect ultrasound [Mann et al., J. Acoust. Soc. Am. (2001)]. The results of this study provide hearing data that can be used to understand potential effects of human-generated noise on Hippocampus erectus and other seahorse species.
The Arctic underwater acoustic environment.
Authors: Erbe Christine
Published: March 2010

This talk gives an overview of the underwater acoustic environment in the Arctic. Sources of sound will be reviewed, including natural ambient noise (physical + biological) and man-made noise. Sound propagation characteristics will be discussed and examples from field studies will be presented. Features unique to the Arctic will be highlighted. Potential impacts of underwater noise on marine mammals will be summarized. Wild guesses will be made in an attempt to estimate how things might change in the future, particularly relating to climate change.
Target strength spectrum of Atlantic herring over a low-kilohertz frequency band.
Authors: Foote Kenneth G. , Godo/ Olav Rune , Korneliussen Rolf J. , Tenningen Eirik
Published: March 2010

Atlantic herring (Clupea harengus) in the stock of Norwegian spring-spawning herring were observed in their wintering area off the northwest coast of Norway in November 2009. The volume backscattering coefficient sV was measured with the Simrad EK60/38-kHz scientific echo sounder, yielding numerical values of fish density ρ through the fundamental equation of echo integration sV = ρσ, where ρ is the mean backscattering cross section of the ensonified fish. Derived values of ρ were used to convert measurements of sV made with the Kongsberg TOPAS PS18 parametric sub-bottom profiling sonar to infer σ, thence its logarithmic measure target strength, over the approximate difference-frequency band 1.5–6 kHz. [Work supported by ONR Award No. N000140910482 and Norwegian Research Council Grant No. 184705.]
Kramers–Kronig relationships applied to shear wave propagation in soft tissues.
Authors: Urban Matthew W. , Chen Shigao , Amador Carolina , Greenleaf James F.
Published: March 2010

Multiple methods have been proposed to characterize the viscoelastic material properties of soft tissues to differentiate normal from pathological tissue. Shearwave dispersion ultrasound vibrometry is a method that uses the dispersion of the shear wave velocity to characterize tissue shear elasticity and viscosity. It has recently been shown [M. W. Urban and J. F. Greenleaf, Phys. Med. Biol. 54, 5919–5933 (2009)] that the Kramers–Kronig relationships can be applied to shear wave measurements in ex vivo skeletal muscle over a frequency bandwidth of 100–600 Hz. We will describe this process where shear wave attenuation is modeled using a power law, and the shear wave velocity dispersion is predicted by applying the Kramers–Kronig relationships. In this study, we apply this method to shear wave propagation measurements made in different soft tissues such as ex vivo porcine skeletal muscle and kidney and in vivo porcine liver. The shear wave velocity predictions using the Kramers–Kronig relationships agree with the velocity measurements. The mean square error for these tissues ranged from 0.0024–0.0625 m2/s2. The Kramers–Kronig relationships can be used in shear wave propagation measurements in different types of soft tissues. [This work was supported in part by NIH Grants Nos. EB002167 and DK082408.]
Visualizing the functional properties of life-threatening atherosclerotic plaques using targeted ultrasound contrast agent and intravascular ultrasound.
Authors: Doyley M. M. , Shekhar H. , Allen J. S. , Rychak J.
Published: March 2010

Acute coronary syndromes may occur when life-threatening atherosclerotic plaques rupture in the later stages of advance cardiovascular disease. Coronary angiography is currently the gold standard for assessing the severity of coronary disease; however, its efficacy is questionable. We have developed a prototype intravascular ultrasound (IVUS) system to assess the functional properties (i.e., inflammation or angiogenesis or both) of atherosclerotic plaques and the arterial wall. In this paper, we report on the results of flow studies that were conducted to assess the nonlinear acoustic behavior of a novel perflourocarbon ultrasound contrast agent, Targestar, at high-transmit frequencies (30 and 40 MHz). Pulsatile flow studies were conducted with vessel phantoms. The subharmonic response of the targeted and non-targeted agents by applying an eight-order band-pass filter to the digitized radio-frequency echo frames. We compared the fundamental and subharmonic signals in absolute and relative terms using paired t-tests. SHI IVUS improves the visualization of the plaque relative to the main vessel, and the subharmonic behavior of the bubbles compared favorable to our theoretical expectations.
Effective scatterer size estimation based on mathematical form factors in a rat fibroadenoma model.
Authors: Wirtzfeld Lauren A. , Hafez Zachary T. , Sen-Gupta Ellora , Battles Andrew P. , Miller Rita J. , Sawarte Sandhya , Oelze Michael L. , Hall Timothy J. , O'Brien William D.
Published: March 2010

Quantitative ultrasound imaging is a model-based approach aimed at lesion detection and classification. In this study, the backscattered rf from rat fibroadenomas was fitted to two mathematical models to yield effective scatterer diameter (ESD). The goal was to aid in understanding potential sources of scattering in live rat tumors. Data were acquired using three single-element transducers with center frequencies of 3.5, 7.5, and 13 MHz. Reference scans were acquired from a Plexiglas plate. Two different theoretical models of scattering were fitted to the data; a fluid filled sphere model, which does not support shear waves, and the spherical Gaussian model for the scatterer. Twenty histologically confirmed fibroadenomas were analyzed. The ESD values obtained spanned the range of typical acini sizes observed in the histology of the fibroadenomas, from approximately 50 μm with the 13-MHz transducer up to 200–300 μm with the 3.5-MHz transducer. The estimates from the Gaussian model were consistently higher than for the fluid filled sphere. The estimates of ESD decreased with increasing frequency, and microstructures corresponding to these different scales were observed in histology. [Work supported by NIH Grant R01CA111289.]
Simulations for investigating contrast mechanism of biological cells with high-frequency scanning acoustic microscopy.
Authors: Juntarapaso Yada , Tutwiler Richard L.
Published: March 2010

Scanning acoustic microscopy (SAM) is one of the most powerful techniques for nondestructive evaluation and it is a promising tool to characterize the elastic properties of biological tissues/cells. Exploring a single cell is important since there is a connection between single cell biomechanics and human cancer. SAM provides advantages for investigating cells in the fact that it is non-invasive, provides elastic properties information in sub-cellular details, and no chemical stain on the cells. The first goal of this research is to develop a program for simulating the images and contrast mechanism obtained by high-frequency SAM. We focus on the mechanical and acoustical properties of HeLa cells, which can be analyzed from the V(z) response. Two new algorithms for simulating V(z) responses involve calculation of reflectance function for coupling medium/cell/substrate system, and are constructed based on ray theory and wave theory (angular spectrum). The second goal is to design/optimize transducer arrays for SAM. One-dimensional and two-dimensional (2-D) linear array and phased arrays are simulated using FIELD II program to analyze image resolution and volumetric imaging capabilities. The new 2-D array design will enhance the performance of SAM by electronically scanning and by providing a four-dimensional image of the cells development phase.
High-speed imaging techniques for harpsichord plucking action.
Authors: Brown Marshall J. , Perng C.-Y. Jack , Rossing Thomas D. , Ioup Juliette W.
Published: March 2010

Harpsichords contain vibrating strings whose motion has been studied extensively. The harpsichord sound is produced by a plectrum plucking the string, a behavior not well modeled at present. A high-speed video camera is used to image sequentially the plucking action of a harpsichord plectrum of modern plastic. This action is quite complicated and highly impulsive, too fast for the human eye to register. The tongue holding the plectrum moves backward in the escapement as well as when the plectrum slips by the string as the jack returns to its rest position. The plectrum may contact the string more than once during these events. The high-speed camera is a Casio Exilim Pro EX-F1, capable of 1200 frames/s. To study the plectrum action, monochords and harpsichords were used. One of the major difficulties with high-speed camera images provides sufficient light while maintaining CMOS saturation and keeping image coherence maximized for the fast shutter action. Various solutions to this problem were tested, including using direct sunlight. Further problems encountered (such as CMOS color response) will be described and their solutions discussed. Images show the plucking, the escapement, the plectrum motion, and the string excitation in detail during the plucking action.
Haptic interaction for music with unrestricted freedom of the musician’s motion: Promoting augmented interaction with physical tools.
Authors: Berdahl Edgar , Niemeyer Gunter , Smith Julius O.
Published: March 2010

A haptic musical instrument is an electromechanical musical instrument that provides a musician not only with audio feedback but also with force feedback. Many commercial force feedback devices consist of a tool, such as a thimble or pen, attached to the end of a robotic arm. The musician can grab onto the tool and use it to manipulate a virtual musical instrument. While this configuration provides multiple degrees of freedom, it is suboptimal for many musical interactions. For instance, typically the workspace of the arm is restricted, which can detract from the musician’s enjoyment of the experience. The workspace restriction can be resolved by freeing the tool from the end of the haptic device and having the musician hold the tool, which may be a plectrum, bow, or drumstick, in his or her hand. Further benefits can be reaped if multiple points of haptic interaction are available, enabling the musician to manipulate the points and move freely in between them. A dual voice coil woofer provides a convenient collocated sensor/motor for constructing a single degree-of-freedom point of haptic interaction. We present an example instrument in which a musician employs a conventional plectrum to interact with a virtual digital waveguide string.
A comparison of analytical and optimization inverse techniques for characterizing intrinsic parameters of porous materials.
Authors: Shravage Paresh , Jain Sachin , Karanth Nagesh
Published: March 2010

In recent years, sound absorbing materials are finding many applications in transport industry. In automobiles, they are used as noise control treatments in engine compartment as well as in passenger cabin. To understand and simulate acoustic behavior of these noise control treatments, intrinsic physical parameters are required. The acoustical behavior of poroelastic material is governed by five macroscopic intrinsic parameters, e.g., porosity, flow resistivity, tortuosity, and characteristics lengths as well as three mechanical parameters. Out of these five physical parameters, porosity and flow resistivity can be measured directly by available standardized methods. But measurement of physical parameters such as tortuosity, viscous, and thermal characteristic lengths is very difficult and no accepted procedure is available for their measurement. As an alternative, analytical inverse approach (mid-frequency) and optimization technique Genetic algorithm are well known in the literature. This paper compares the results from both techniques for intrinsic parameters. It also presents the effect of inverted parameters on sound absorption and transmission loss of the porous materials using Johnson–Champoux–Allard model.
Modular room design.
Authors: D’Anna Craig
Published: March 2010

Modular acoustical panels have been used to construct noise control enclosures at least since the early 1950s. This paper presents examples of the early days of modular acoustical enclosures and illustrates the current state of the art where pre-engineered acoustical panels are used to construct acoustical environments for Music Practice, Broadcast Facilities, Recording Rooms, and Sensitive Compartmented Information Facilities in a shorter period of time and at a lower cost than traditional drywall construction. Numerous examples are presented illustrating how, through the use of pre-engineered acoustical panel systems, manufacturers are able to guarantee the acoustical characteristics of a space while maintaining the ability to expand, demount, and relocate the rooms at a later point in time. The benefits of a no-hassle installation and acoustic guarantee, as well as multiple options for fit and finish that will equal the best craftsman’s fine handiwork, are presented.
A novel delayless frequency-domain filtered-x least mean squares algorithm for active noise control.
Authors: Duan Jie , Lim Teik
Published: March 2010

The delayless frequency-domain implementation of least mean squares (LMS) algorithm is attractive because it can eliminate undesired block delay in the signal path while still remain the advantages of the frequency-domain LMS algorithm. However, the conventional delayless frequency-domain LMS experiences difficulties in slow convergence when it is applied to harmonic signal control at some frequencies. In this study, an overlap-save implementation of the delayless frequency-domain LMS algorithm is proposed to overcome the convergence problem mentioned above. Simulations show that the proposed implementation has better performance than the original one either in the pure tone application or in the vehicle powertrain noise application.
Active noise control of magnetic resonance imaging scanner using inverse modeling technique.
Authors: Li Mingfeng , Rudd Brent , Lee Jing-Huei
Published: March 2010

In active noise control applications, internal model control (IMC) is a strategy to convert from feedback to feedforward control. In this configuration, the optimal solution of the controller will be the inverse model of the secondary path. However, the inverse model of the secondary path may not always exist. In fact, for the non-minimal phase system, the inverse model is unstable. In this case, the non-causal or delayed version of the inverse model will be employed. In general, this approach is not suitable for active noise control if the objective is to treat broadband noise. However, for harmonic signal control, this is not an issue. Magnetic resonance imaging (MRI), a procedure for medical diagnosis and biomedical research, generates undesirable levels of acoustic noise emission. The noise is normally dominated by clusters of harmonics throughout the audio spectrum. Due to its tonal nature, MRI noise control is a candidate for IMC. In this paper, an active noise control scheme using the inverse modeling technique is proposed and studied for pre-recorded MRI noises obtained during operation of a 4T whole-body MRI scanner. The recorded MRI noise is played back through a stereo system in a sound quality room and controlled using a headset equipped with the proposed active controller. The results demonstrate almost 20 dB reduction can be achieved.
Acoustical considerations in future building design processes.
Authors: Hunter Tyrone
Published: March 2010

“Sustainability” is the major buzzword in the building design and construction arena today. The context often talks about products that will result in a smaller initial and ongoing carbon footprint. This paper will look at the idea of sustainability as a process, covering the end-to-end design and construction process as well as the process of generating and managing building data during its life cycle. The advent of lean construction and building information modeling is an opportunity to make acoustics more inherent to the conceptual design and prevent it from being a casualty of the “value engineering”. Significant questions do arise, however, with regard to the acoustical information needed for such processes. These questions include, but are not limited to, what information is needed, who will need it, and how will it be exchanged. The answers to these questions differ when considering the above-mentioned processes and efforts to be holistically efficient and sustainable. The answers to these questions will be integrated into how building design is taught with regard to acoustics other specialties.
Acoustics of technology enabled collaborative learning environments.
Authors: Coudriet Gregory A. , Babich Jeffery E.
Published: March 2010

Collaborative classrooms and workstations are increasingly common in higher education buildings. These spaces present unique acoustical challenges that force designers to rethink traditional concepts and solutions. In student-centered classrooms, the lecturer is removed as the visual and acoustical center of attention. Instead, students are seated in groups around technology enabled workstations, often facing away from the lecturer and other students. Acoustical conditions must support small-group interaction, classroom discussion, and learning via multimedia content. Outside the classroom, collaborative workstations vary greatly, but typically facilitate small-group interaction around a multimedia display and/or work surface. To promote impromptu use by students, these spaces are often open to highly public areas of learning commons, classroom buildings, and digital libraries. Traditional noise control solutions fail to isolate these spaces without compromising their spontaneous feel and function. Despite obvious acoustical challenges, both space types will continue to proliferate and new acoustical solutions must be developed.
The influence of openings in a partition on its of tonal sound transmission loss and some applications.
Authors: Rosenhouse Giora
Published: March 2010

Kirchhoff’s integral developed for optics [Born and Wolf 1970] and its approximations by Fraunhofer and Fresnel constitute a useful tool in acoustics, in general, as well as in building acoustics. They help in estimation of the changes in the sound level at the control point due to arbitrarily shaped solid barriers and openings in such barriers or partitions. While noise analysis justifies energetic approach, tonal sound is sensitive to frequency, phase, and interference effects. This dependence yields the mapping of positive and negative Fresnel zones over the barrier or the aperture. Those zones depend also on the location of the source and the control point. Since sound waves under regular conditions are linear and we assume locally reacting surfaces, then a small barrier or an aperture, which is located over a single Fresnel zone, causes a stronger acoustic effect at the control point than exactly the same elements if they cover parts of Fresnel zones of different signs. This situation allows, according to the need, acoustic design for minimization or maximization of the effect of apertures and barriers on the sound level at the control point. Applications involve arbitrarily shaped sound barriers, arbitrarily shaped openings in partitions and barriers, acoustic tiles, and transmission loss of non-uniform partition.
Sound isolation provided by shading screens applied in facades.
Authors: Matos Jorge , Carvalho Antonio
Published: March 2010

In most European countries, legislation exists about airborne sound insulation in dwellings, including facades. Mainly in southern European countries, the glazed windows of building facades normally have shading systems to minimize the excessive heating of interior rooms due to the solar rays’ incidence and to provide for darkening of the room. The effect regarding sound isolation of those shading systems is usually not analyzed in the buildings’ acoustic project. This study presents laboratory measured values of weighted sound isolation index (Rw) provided by several shading system types (outside and interior screens of different materials) and presents a simple model to predict their sound isolation index.
Acoustics of energy efficient elevator systems.
Authors: Joshi Darshit
Published: March 2010

Traditional systems for vertical transportation require both machinery and space to operate. New, high performance, elevators eliminate these requirements, and in doing so significantly decrease the noise and vibration impacts associated with the traditional system architecture. Furthermore, machine roomless elevator systems offer superior electrical efficiency, a reduction in shaft wall requirements, centralized structural loading, and eliminate the need for pits, sumps, and the possibility for water contamination from spilled hydraulic oil. Also, interior environmental considerations are impacted by a number of innovations that result in a reduction in hydraulic pump, pump room and plumbing noise, motor and cab vibrations, and other significant improvements. Finally, the cost associated with ongoing maintenance and support such as lubrication of steel ropes is greatly reduced through the use of systems and technologies specifically engineered to reduce the need for many routine services that conventional systems require.
Design and characterization of a tuned vibration absorber for exhaust components.
Authors: Ptak Keith
Published: March 2010

Truck exhaust components must withstand vibration inputs from the diesel engine as well as from road inputs. Cumulative damage from the significant mileage these vehicles are exposed to can be severe; however, customers have an expectation that the components will last the life of the vehicle. Tuned vibration absorbers (TVAs) are an effective way to mitigate vibrations resulting from excitation of resonances due to random vibration exposure. A pipe section was tested to verify its expected mode shapes to aid in proper TVA placement. Subsequent tests were performed not only with TVAs but also with an equivalent mass in order to determine the true improvement due to the TVA effect. This paper covers a case study demonstrating the use of a TVA to achieve a 60% reduction in vibration.
Perspective on launch noise: Measurement, prediction, and characterization.
Authors: McInerny Sally Anne
Published: March 2010

The noise generated by launch vehicles is examined in terms of the key source, radiation, instrumentation, and estimation issues. Basic source and acoustic radiation characteristics of un-deflected rocket exhausts are compared and contrasted with those of supersonic jets. Next, the instrumentation demands of, and unique characterization methods applied to, rocket noise sound pressure measurements are discussed. Finally, on vehicle sound pressure measurements during the launch from a covered pad are presented. Contradictions between these loads and those predicted using traditional lift-off loads methods are highlighted. This paper concludes with a brief outline of research and instrumentation needed to improve agreement between the physics of the prediction model and the actual measured lift-off loads.
Acoustic design of launch pad for advanced solid rocket.
Authors: Tsutsumi Seiji , Fukuda Kota , Takaki Ryoji , Ishii Tatsuya , Ui Kyoichi
Published: March 2010

In the mission of the Advanced Solid Rocket studied in JAXA, the launch-pad is required to improve the operation performance as well as to reduce the cost. While, exhaust plume from the solid booster generates severe acoutic wave so that decrease in the acoustic level at lift-off is also an important design issue. Preliminary trade-off analysis is peformend by using computational fluid dynamics. Major noise sources such as the Mach wave and the impingement noise and their correlation with the vehicle’s altitude are revealed. The knowledge of the acoustic characteristics gives us idea how to decrease the acoustic level within the mission requirements. Based on the configuration found in the numerical study, subscale test using 1/43 scale mock-up is planned to ensure the acoustic level around the vehicle.
Multichannel soundscape recording techniques.
Authors: Case Alex U.
Published: March 2010

Several goals motivate the recording a soundscape: measurement, archiving, mitigation, preservation, design, modeling, education, marketing, and entertainment. Salient properties of a soundscape are similarly broad: levels versus frequency and time, their averages and associated statistics, discrete sound source identities, distance, localization, size, spaciousness, envelopment, and additional subjective sound qualities, sometimes subtle. While traditional noise metrics are based on single microphone measurements, a soundscape is better captured, quantified, and studied using multi-microphone techniques. Multichannel recording techniques for large-scale soundscapes, borrowed from the multitrack recording practices of concert halls and recording studios, are defined and compared. The resulting data and audio files are evaluated for their ability to satisfy the needs of owners, designers, and end-users of a soundscape.
Behavioral consequences of weakened medial olivocochlear efferent noise-control mechanisms in mice.
Authors: Lauer Amanda M. , May Bradford J.
Published: March 2010

The mammalian medial olivocochlear (MOC) efferent feedback system protects the ear from intense noise exposure, aids in cochlear gain control, and improves responses to signals in noise. Unequivocal behavioral effects of eliminating MOC feedback have been difficult to demonstrate. We used an acoustic startle reflex (ASR) modification paradigm to reveal behavioral effects of eliminating MOC feedback in mice. Mice lacking the alpha9 nicotinic acetylcholine receptor subunit showed increased facilitation of the ASR reflex in the presence of background noise, abnormal responses to brief fluctuations in background noise, and abnormal inhibition of the ASR by changes in the location of noise in azimuth and elevation. Abnormal behavioral responses occurred in the absence of cochlear hearing loss. The behavioral effects of weakened MOC feedback may reflect both direct and indirect effects of abnormal cochlear gain control in the presence of noise. The results provide further evidence for a role of MOC efferent feedback in hearing in noise and demonstrate that noise-related hearing deficits can occur when hearing thresholds are normal.
Detection of a resonant target in shallow water using iterative, single-channel time reversal at low frequencies (2–23 kHz).
Authors: Waters Zachary J. , Simpson Harry J. , Dzikowicz Benjamin R. , Houston Brian H. , Berdoz Alain R. , Kraus Larry A.
Published: March 2010

Iterative time reversal with a single-channel transducer has been shown to enhance echoes from resonant targets both in scaled high-frequency (0.5–2-MHz) laboratory experiments [Waters et al., IEEE UFFC 56, 1429 (2009)] and in mid-frequency (20–200-kHz) pond experiments [Dzikowicz et al., J. Acoust. Soc. Am. 123, 3755 (2008)]. These techniques are applied to study scattered returns from a proud, spherical target at low frequencies, 2–23 kHz, in a littoral environment. Monostatic scattering experiments are conducted in the Gulf of Mexico near Panama City, FL in 14-m-deep water. The target, a 60-cm-diameter stainless steel spherical shell (1.5 cm thick), rests on a sandy bottom at a range of 35 m from a rail-mounted source-receiver pair positioned at a height of 2.3 m from the bottom. Through iterative retransmission of windowed and time reversed scattering returns, enhancement of target echoes with respect to background noise and reverberation is explored. Frequencies to which the time reversal process converges are compared with analytical predictions and pristine laboratory measurements of the free-field scattering response. [Work supported by ONR.]
Scattering of linear frequency modulated chirps by resonators: Effect on pulse compression.
Authors: La Follett Jon , Marston Philip L.
Published: March 2010

Pulse compression is a common technique used to improve the signal to noise ratio and time resolution of a sonar system. A linear frequency modulated (LFM) chirp is one type of excitation used in conjunction with matched filtering to produce pulse compressed time domain data. This approach uses a correlation between the transmitted and received signals. Scattering by a target having a narrow resonance within the bandwidth of the LFM chirp may contain a superposition of specular scattering and scattering features associated with the transient response of the resonator. If the frequency sweep rate is not sufficiently slow relative to the ring-down time of the resonator, the transient response may result in artificial features and decreased time resolution in the pulse compressed signal due to decreased correlation with the transmitted signal. To explore this effect, water tank experiments were carried using a water filled cylindrical shell as the resonant target. Experiments demonstrate that for sufficiently rapid chirp rates, the target response envelope has an oscillatory modulation that affects the pulse compressed signal. [Research supported by ONR.]
Absorption, scattering, and diffusion coefficients: Overview.
Authors: D’Antonio Peter
Published: March 2010

Acoustical design and computer modeling rely on the availability, accuracy, and use of coefficients which characterize how boundary surfaces affect incident sound. At this time three coefficients have been developed to characterize how incident sound is modified by absorptive and scattering surfaces. The random incidence absorption coefficient, which is a measure of the proportion of incident sound that is absorbed, is measured according to ISO 354/ASTM C423. It is well known that coefficients measured according to this standard suffer from several systematic errors which will be reviewed. Measurement of the random incidence scattering coefficient, which is the proportion of incident energy scattered in non-specular directions and used in computer modeling programs, is experimentally determined by ISO 17497-1. The limitations of this standard and applications will be discussed. Measurement of the diffusion coefficient, which is a measure of the uniformity of scattered sound and used to evaluate potential surfaces and in optimization programs, is described in AES-4id-2001 and ISO 17497-2 (pending). As with all standards it too has limitations which will be discussed. Detailed information on all three coefficients is given in Cox, T. J., and DAntonio, P. (2009). Acoustic Absorbers and Diffusers (Taylor & Francis, London).