bluuebunny/crossref_metadata_2025 huggingface dataset:
A hybrid model of sound propagation in unconsolidated sediments
Authors: Hefner Brian T. , Williams Kevin L.
Published: October 2013

Efforts to model sound speed and attenuation in sandy sediments have centered on the use of theories for which either the relative motion of the pore fluid is the dominant attenuation mechanism, such as Biot theory, or the dominant loss mechanism is grain-to-grain friction. A recent model which attempts to incorporate grain-to-grain loss mechanisms into a model of sandy sediments was proposed by Buckingham. This model can fit the frequency dependence of the attenuation measured in ocean sediments and laboratory glass bead sediments, but it does not capture the sound speed dispersion as effectively as Biot theory. The relative success of each model suggests that both attenuation mechanisms may play important roles in sediment acoustics. In order to explore this possibility, a hybrid model has been developed which incorporates Buckingham’s grain-to-grain shearing mechanisms into the frame moduli used in Biot theory. In the hybrid model, the grain-to-grain losses dominate at high and very low frequencies while pore fluid attenuation dominates at mid-frequencies where the sound speed dispersion is the most pronounced. As a consequence, the hybrid model is able to describe both the measured sound speed and attenuation in ocean and laboratory sediments. [Work supported by ONR.]
Frequency dependence of the frame bulk moduli of granular marine sediments
Authors: Kimura Masao
Published: October 2013

The frame bulk modulus is important in analyzing the acoustic wave propagation in porous granular marine sediments. As the value of the frame bulk modulus, notable researchers in the community used about 108 Pa (constant value). However, the measured frequency characteristics of the longitudinal wave velocity are not consistent with the calculated characteristics using the constant frame bulk modulus using the Biot-Stoll model. It was reported that the frame bulk moduli in water-saturated glass beads and beach sands are about 109 Pa at the frequency of 500 kHz, and are about ten times greater than that of air-saturated samples. It is also seen that the frame bulk moduli have dependence on the grain size. Moreover, these phenomena can be explained using the gap stiffness model [M. Kimura, J. Acoust. Soc. Am. 116, 2529 (2004)]. The grain size dependence of the frame bulk modulus suggests that there is the frequency dependence of the modulus. In this study, the measured results of the frequency characteristics of the longitudinal wave velocity in water-saturated glass beads and beach sand are compared with the calculated results using the Biot-Stoll model with the frequency dependent frame bulk modulus, derived using the gap stiffness model.
Characteristics of scattered sound from overhead reflector arrays: Measurements at 1:8 and full scale
Authors: Gulsrud Timothy
Published: October 2013

Measurements of sound scattering from reflector arrays have been carried out both at 1:8 scale in a controlled environment and at full scale in a concert hall. The results indicate wave interference between reflections from adjacent panels, resulting in an audible comb filter-like effect. Implications for the appropriate degree of overlap in coverage of adjacent panels will be discussed.
Effect of incidence angle and panel size on the phase of scattered energy from panel arrays
Authors: Rathsam Jonathan , Wang Lily M. , Torres Rendell R.
Published: October 2013

This investigation focuses on factors that influence scattering from different ceiling panel arrays (e.g., incidence angle, and array size and density) by examining the scattered phase. A previous study by the third author [Torres and Vorländer, Acta Acust. (in press)] measured impulse responses using the maximum length sequence method at various receiver positions from scale model panel arrays of different sizes and densities. One interesting conclusion was that for multi-element arrays with panel dimensions and separation on the order of a wavelength, the reflected amplitude decreased, apparently due to destructive interference from inter-panel scattering. Analysis focused on the magnitude of the frequency response but the author noted that the phase curves could also contain information about scattered energy and the hypothesized inter-panel scattering. What the phase curves reveal is the subject of this study. It is expected that noticeable deviations from smoothness observed in the phase curves indicate non-specular scattering from the panels. The frequencies at which these deviations occur are examined to give insight into how the geometrical conditions of the panel array affect scattering.
The Student Council
Authors: Bradley David T.
Published: October 2013

Throughout its history, the Society has been a strong advocate for students exploring the world of acoustics. However, only recently was that support institutionalized and the responsibility placed in the hands of the students themselves. In the spring of 2000, a nascent body was formed to address the needs and concerns of Student Members of the ASA. The Vancouver meeting marks the 5th anniversary of this group, now formally known as the Student Council. The Council has evolved markedly in the past several years. The Council is currently composed of one student representative from each of the 13 technical committees and one Student Chapter Liaison. Recent student focused activities include the creation of a state-of-the-art website, the production of the first in a series of fellowship/grant workshops, and the presentation of a new award honoring the efforts of mentors in the Society. The Councils main focus is disseminating information of concern to students, advocating participation of students in Society activities and meetings, and promoting Society membership benefits to potential student members. Current and future programming and opportunities available to students, and those who work with students, will be presented and discussed.
The ASA Regional Chapters program
Authors: McLaughlin Elizabeth , Arvelo Juan
Published: October 2013

Are you involved in a Regional Chapter? The Regional Chapters Program certainly embraces the intent of our Society. ‘‘The ASA was founded... to increase and diffuse the knowledge of acoustics and promote its practical applications. Any person... interested in acoustics is eligible for membership.’’ The history and the activities of each Chapter are unique. There are currently twenty active chapters uniquely positioned to promote acoustics through outreach and involvement with the public. There have been several new developments in the Regional Chapters Program, the most exciting being the incorporation of Student Chapters! Our first, the Nebraska Student Chapter, was approved at the 75th Meeting of the ASA in NYC. Several more are on their way! Existing Chapters are revitalizing! The Washington DC Chapter has recently found new enthusiasm, re-establishing a robust program. A new student scholarship has been organized thanks to the generosity of Larry and Julia Royster. Another recent enhancement is the expansion of the Regional Chapters Website. There one can find useful materials including an updated Chapter Start-up Kit. Involvement in a chapter is a great way to give back to the ASA, to learn, promote acoustics, to socialize, and to involve new persons in our exciting field!
Some recent condensed-matter applications of physical acoustics
Authors: Migliori Albert
Published: October 2013

A non-inclusive sampling of recent advances in the application of physical acoustics to condensed matter physics is presented. Work by Ogi et al. on resonant ultrasound microscopy to map nano-scale variations in elastic moduli provides a new twist to the use of resonances. Laser-ultrasound studies by Wright and Matsuda on photoacoustic effects in ultra-thin metallic and semiconductor films leads to new meso-scale ultrasound studies, while Isaak and Ohno push the symmetry limits and temperature range of resonant ultrasound modulus studies. Migliori and Ledbetter extract the final pieces of an unusually-well-characterized charge-density-wave phase transition and examine very odd elastic behavior in materials with negative thermal expansion, while Pantea demonstrates an all-digital pulse echo system for high pressure work. Souslov probes hidden order with pulse-echo studies in pulsed magnetic fields. [Work supported by the National Science Foundation, the Department of Energy and the State of Florida.]
Speech perception in the presence of other sounds
Authors: Darwin C. J.
Published: October 2013

The human listener’s remarkable ability to recognize speech when it is mixed with other sounds presents a challenge both to models of speech perception and to approaches to speech recognition. This talk will review some of the work on how human listeners can perceive speech in sound mixtures and will try to indicate areas that might be particularly fruitful for future research.
Doubly asymptotic approximations for transient and time-harmonic acoustics
Authors: Geers Thomas L.
Published: October 2013

The development and application of doubly asymptotic approximations (DAAs) in computational structural acoustics are reviewed. Transient radiation/scattering is emphasized, but application to time-harmonic radiation/scattering is also addressed. DAAs formulated for elastodynamic, poroelastic, and electromagnetic scattering are described that illustrate the breadth of application. The advantages and limitations of DAAs are described, and their relation to retarded-potential, similarity-based, and infinite-element methods are discussed.
Numerical study of fluid loading approximations for submerged spherical shells using finite, infinite and boundary element methods
Authors: Botelho Rui M. , Butler Michael J. , Waters John F.
Published: October 2013

Numerical studies were conducted to compare acoustic fluid loading approximations for submerged spherical shells. Rigid and empty elastic shells submerged in a heavy acoustic fluid and subjected to harmonic excitation were considered. Solutions using boundary elements, infinite elements, and analytical approximations were compared, with special attention to modeling the near-field fluid beneath the infinite elements. In this case, the near-field fluid is typically modeled using fluid finite elements with frequency dependent mesh refinement and radial extent. The spherical shell is modeled in the same manner using shell finite elements for both boundary and infinite element solutions in order to provide a direct comparison of the fluid loading approximations. Convergence studies involving the near-field fluid were performed with emphasis on the effects of meshing parameters, including refinement, mesh grading, and polynomial order of the radial basis functions for p-version fluid finite elements. Results of interest include comparisons of the submerged structural response, focusing on the reactive and resistance parts of the fluid impedance.
Frequency dependence of elliptical particle motion of acoustic waves transmitted into the seabed from a point source in water
Authors: Chapman David M. F. , Hines Paul C. , Osler John C.
Published: October 2013

When perpendicular components of the particle velocity of a continuous acoustic wave have unequal amplitude and phase, the displacement traces an elliptical path. This is caused by inhomogeneous waves and/or losses in the medium. For spherical waves radiating from a point source in water and transmitted into the seabed, the orientation of the elliptical orbit varies with receiver location and frequency, and the ellipse major axis is not always parallel to the direction of propagation suggested by Snell’s law. If not accounted for, this could bias estimates of sediment sound speed derived from particle velocity measurements. This presentation describes a simple orbit model based on numerical evaluation of integrals for the transmitted field over the entire wavenumber range. The model provides rapid simulation of results for different experimental geometries and source frequencies. The model is validated using an established full-field model and compared with experimental data. [Work supported in part by ONR Code 32.]
Effect of frequency dependence of complex sound speed on impulse response in littoral seas
Authors: Knobles David
Published: October 2013

For certain classes of sediments common to littoral ocean environments, there exists theoretical reasons and experimental evidence that the real part of the sound speed is frequency dependent. Further it has been observed for more than 30 years that to model transmission loss data below 1 kHz for such sediments, it is often required that the attenuation possess a non-linear frequency dependence. However, analyses of broadband propagation below 2 kHz in littoral waveguides commonly assume that sound speeds in marine sediments are frequency independent and that the attenuation depends linearly on frequency. It is natural to explore how the neglect of the frequency dependence of the complex sound speed affects the predictability of broadband propagation and under what conditions can inversion methods estimate the functional form of the frequency dependence. In this study simulated impulse responses for typical littoral waveguides over the 10–2000 Hz band are generated assuming a Biot-Stoll formulation. The effects of the frequency dependence of the complex sound speed on the impulse response are examined within the context of how does one form a valid inverse problem that would allow for the frequency dependence of the complex sound speed to be uniquely determined. [Work supported by ONR.]
The need for good acoustic design of schools
Authors: Shield Bridget
Published: October 2013

This paper gives an overview of research into classroom acoustics, highlighting the importance of a good acoustic environment in schools to enhance teaching and learning. The paper is aimed at a general audience of people interested in education and school design. In the past 30 years there has been a great deal of research into the effects of noise and poor acoustics in schools on children and teachers. It has been shown in many studies that children have difficulty hearing and understanding their teachers in noise, and both external environmental noise and noise within a school affect children’s academic performance. Furthermore many teachers suffer from voice and throat problems which may be attributable to a poor acoustic environment in the classroom. The acoustic design of a classroom has a direct influence upon noise levels and the intelligibility of speech. Poor sound insulation and excessive reverberation have the potential to increase noise levels and reduce speech intelligibility. However, despite the introduction in many countries of legislation or guidelines for acoustic design of schools, in general acoustics still has a low priority in school design and many schools, old and new, fail to meet the current standards.
Renovating Teatro alla Scala Milano for the 21st century, Part I
Authors: Arau Higini
Published: October 2013

Teatro alla Scala of Milan, known simply as La Scala throughout the world, is an old but venerable opera house that achieved legendary status in the world of music. A great number of singers of Olympian status have sung there; and major operas, among them Verdi’s Falstaff and Otello and Puccini’s Turandot, premiered there. The 227-year-old theater is beloved with a passion by the Milanese and the Italians, but it has suffered the ravages of time. It needed to be renovated in order to reverse material decay, meet current fire codes and security requirements, incorporate a new HVAC system, and to accommodate badly needed modern stage machinery. This renovation project took 3 years during which the theater was closed, and it included the construction of an elliptical 17-floor fly tower, designed by architect Mario Botta, for housing rehearsal rooms and serving as a scenery changing facility. The renovation proposal originally aroused a strong sense of melodrama among the extremely excitable Italian opera buffs who feared the desecration of their beloved edifice, but the acoustics and the beauty (carried out by Elisabetta Fabbri Architect) of the auditorium were preserved (and even enhanced). In this paper we explain how this project was achieved.
Maintaining the acoustics of Boston Symphony Hall
Authors: Berens Robert , Markham Benjamin , Rosenberg Carl
Published: October 2013

Boston Symphony Hall celebrated its centennial in 2000; one of its biggest birthday presents was a new organ. More correctly, the partially new and partially refurbished organ made its debut in October 2004, for James Levine’s inaugural concert as Music Director of the Boston Symphony Orchestra. Symphony Hall’s original organ was replaced in 1949, but its replacement was never regarded as a great concert instrument. While some wanted the new organ work to include turning the Hall into an organ showcase, the BSO management was adamant that the acoustics of the Hall not be affected. Acentech was asked to provide technical oversight to help minimize any such changes. Tests were conducted to assess the potential impacts that removal and renovation of the organ pipes could have on Symphony Hall’s acoustics. Reverberation times were measured in the organ chamber, on-stage, and in the Hall. Remedial measures were devised for use, if necessary, to counteract the expected changes in the organ chamber acoustics as the pipes were removed. However, such changes showed little effect on the acoustics of the stage or the hall. This paper describes the work done during the organ renovation process to protect the hallowed acoustics of Symphony Hall.
Renovating cultural icons
Authors: Miller Gregory
Published: October 2013

Three case studies of historic renovations are presented where acoustics were a key component of the renovation process. Each hall is an icon of the cultural life in the surrounding community. The first case study is Troy Savings Bank Music Hall, a late nineteenth century musical gem where recent renovations (adding variable acoustic features) required that the unamplified acoustics be unaltered. The second example, the Coronado Theatre in Rockford, Illinois, illustrates the sensitive modification of the acoustics in a historic vaudeville house adapted to modern multi-use requirements. Finally, The Great Hall at The Cooper Union in New York City, where Abraham Lincoln delivered his great ‘‘Right Makes Might’’ speech in 1860, is presented as an example of a renovation that utterly destroyed a historic acoustic environment, and discusses how this can be avoided.
Preserving the acoustics of the Mahaiwe Theater
Authors: Eligator Ronald
Published: October 2013

The Mahaiwe Theater, Great Barrington, Massachusetts, opened in 1905. It has been home to vaudeville, traveling Broadway shows, opera, concerts, and movies. In 2003, the theater began a multi-phase renovation project. The renovation project includes restoration of historic finishes, new seating, installation of air conditioning and heating systems, and installation of sound and projection systems. A stage shell for music performances will also be installed. A key aspect of the renovation is the preservation of what has been widely regarded as excellent acoustics. Some aspects of the original structure contributed to this reputation (e.g., room shaping, finishes), while others undoubtedly were less helpful (e.g., the 1905-era ventilation system). The renovation provides an opportunity to preserve the positive attributes of the room, while correcting the deficiencies. Among the key issues discussed are the design of historically-sensitive finishes that respect the acoustic requirements of the multi-use space, acoustical design of a new quiet air conditioning system, and design of an enclosure for music ensembles.
Preservation of the acoustics of the Salt Lake Tabernacle, Lessons learned from acoustical characterization of the hall
Authors: Rollins Sarah , Leishman Timothy
Published: October 2013

Current and historical properties of the Salt Lake Tabernacle have been investigated to characterize its unique acoustics. This characterization will be used to help maintain the current acoustical conditions after a seismic renovation. This paper discusses computer models developed for this purpose and impulse response measurements taken to quantify the acoustics in their current state. It also explores spatial variation of room acoustic parameters derived from the models and measurements.
Modular autonomous array deployments using passive acoustic time synchronization
Authors: Thode Aaron , Burgess William
Published: October 2013

Multi-element acoustic arrays generally use wired cable to transmit signals to a central recording location. While convenient, hardwiring hydrophones together increases array fragility and field costs while decreasing deployment flexibility. It is thus difficult to integrate acoustic array operations with field activities involving marine mammals in remote environments. Economic trends in the cell-phone and consumer electronics industries, combined with recent trends in tagging technology development, have led to the existence of compact low-power autonomous acoustic recorders that store data to either flash memory or small hard drives. In this presentation it is shown how two or more autonomous recorders can be time-synchronized using passive acoustic measurements of the background ambient noise field, effectively creating coherent array processing systems of varying aperture, spacing, and deployment geometry. Configurations tested to date include short and large-aperture vertical arrays off the coasts of Australia and Alaska, bottom-mounted horizontal arrays in San Ignacio Lagoon, Baja California, and instruments installed inside a glider. [Work sponsored by ONR Acoustic Entry Level Faculty Award.]
3D modeling and animation techniques to elucidate mechanisms of echolocation-based acoustic perception
Authors: Horowitz Seth , Simmons James
Published: October 2013

Current models of echolocation focus on the presence of specular acoustic surface reflections or ‘‘glints’’ as the perceptual cues that provide information about object distance and geometry. Using current material and motion 3D modeling techniques for visual animation, we have developed models of common real-world elements that can be detected by bat biosonar. By mapping acoustic reflectivity data from natural and artificial targets onto luminosity, specularity and reflection coefficients for materials and accurate spatial models of these objects, we have generated visual glint-like reflections from object surfaces that are similar to echolocation data. This allows us to create 3D visual animations of echolocation auditory scenes. Using these animations, human observers can integrate object shapes, sizes and movements based on gestalt grouping, particularly when the target moves or the echolocation source is in moving in relation to the target. These types of modeling tools may help elucidate the perceptual phenomena arising from integration of the individual acoustic glint structures that allow bats and other echolocating animals to create complex umwelts from auditory data.
Structural vibration isolation design for a magnetic resonance imaging (MRI) system
Authors: Himmel Chad
Published: October 2013

This structural vibration control case study presents problems, constraints and design solutions for existing magnetic resonance imaging system (MRI) installation in a medical office facility. Objective: Reduce MRI noise received in adjacent, unrelated spaces. Manufacturer’s data indicated that airborne MRI sound emissions could exceed permissible noise criteria for nearby occupied rooms. Experience with MRI systems indicated possibility of structure borne vibration that could result in radiated noise in other spaces. Structure borne vibration paths needed attenuation or isolation, to prevent excessive or annoying and distracting noise to adjacent office spaces. In addition, containment design was required for loud noises in the magnet room. Measurements revealed transient vibration of building floors, walls, and ceilings coincident with MRI operation. Measurements also revealed transient airborne noise levels consistent with radiated sound produced by vibration acceleration of large surfaces. Spectral analyses of noise and vibration led to design of a retrofit vibration isolation mounting scheme for the MRI on existing building floor. Design parameters included structural resonance of slab, manufacturer’s allowable vibration for MRI, and receiver room permissible criteria. Noise and vibration measurements will show building conditions before and after implementation of retrofit vibration isolation mounts. Plan and section drawings will illustrate design solutions.
Pyschoacoustical comparison of active versus passive noise control techniques
Authors: Mangiante Gerard , Canevet Georges
Published: October 2013

Comparisons of active versus passive noise control techniques can be found in various papers. However, this comparison mainly concerns economic, operational, or technical considerations. The present contribution aims at describing the psychoacoustical effects produced by some of the classical solutions used in passive and active noise control. The models introduced by Zwicker and his coworkers, and by Moore and Glasberg are used to evaluate the auditory efficiency of passive and active noise control techniques. Several types of signals were examined: (i) test signals obtained with a band of noise embedded in a white noise or a pink noise; (ii) actual environmental noises: noise produced by the turbine of an aircraft or by a car engine, and several interior noises (locomotive, helicopter and car). It is shown that the modifications in the spectrum of a signal that can be produced by active control are sometimes disappointing, because they induce a subjective enhancement of the high-frequency portion of the spectrum. What the listener then commonly reports is that overall the signal has become slightly softer, but also more unpleasant. The use of a hybrid noise control technique, combining active and passive control, can greatly reduce this effect.
Wes Nyborg: Scientist, role model, and friend
Authors: Ziskin Marvin C.
Published: October 2013

Wesley L. Nyborg obtained his Ph.D. degree in physics at Pennsylvania State College in 1947. He has held faculty positions at Penn State, Brown University, and since 1960 has been at the University of Vermont where he is presently Emeritus Professor. Dr. Nyborgs entire career has been devoted to biophysical acoustics: low frequencies at first, but since the early 50s ultrasonic frequencies of biomedical interest. He has made significant contributions in many areas of ultrasound biophysics, especially in cavitation and other non-thermal mechanisms relevant to biological effects. He has also derived a number of important relationships that are widely used today in determining temperature elevation in clinical ultrasound examinations. He has been the role model and friend to many colleagues, and has received many awards.
Infrasonic tonal resonances of tropical hurricanes
Authors: Elder Samuel A.
Published: October 2013

In news pictures saturating the media last summer there is contained subtle but compelling evidence that tropical hurricanes emit intense and extremely low-frequency tones, originating in the eye. The excellent symmetry of a well-formed eye predisposes the central cavity of a hurricane to resonate in the normal modes of a low-Q nearly cylindrical chamber, due to the slight mismatch in sound speed at the eye wall. Second order perturbation analysis of interaction between eye-modes and steady wind corkscrewing up through the eye has confirmed that positive feedback is generated, the condition for self-excited oscillation. Dimensions and speed of typical hurricanes require that the tones have frequencies on the order of 1/100 of 1 Hz, which is doubtless the reason why they have escaped previous detection. Visual evidence appears in multiple alternating rain and dry bands that originate around the inner circumference of the eye wall, observable in aerial photos by NOAA. These are most easily explained as due to intense acoustically-driven temperature oscillations about the dew point, inside the eye. For a given hurricane, the actual tonal frequencies can be deduced from the spacing of these startups.
Spherical bubble pulsation between parallel plates
Authors: Cui Jianying , Hamilton Mark F. , Wilson Preston S. , Zabolotskaya Evgenia A.
Published: October 2013

A simple model is proposed for investigating bubble pulsation in a constrained medium. In free space, compressibility of the surrounding medium introduces primarily radiation losses that can often be neglected. In a constrained medium, compressibility plays an essential role. The example we investigate here is linear pulsation of an acoustically driven spherical bubble between two parallel rigid plates. The method of images is used to obtain a bubble dynamic equation that accounts for time delays associated with reflections of pressure waves radiated by the bubble. When the bubble is midway between the plates, the series of terms for the reflections can be expressed in closed form. For narrow plate separations, less than about ten bubble diameters, the bubble resonance frequency is reduced from its value in a free field due to increased effective inertia of the liquid, and radiation damping is increased. For larger plate separations, but less than the acoustic wavelength, the quality factor associated with radiation damping is proportional to plate separation. If effects of compressibility are ignored, the effective inertia becomes infinite, and bubble pulsation is prohibited by the equations of fluid mechanics. [Work supported by NIH Grant EB004047 and ARL IR&D funds.]
Framework for windnoise studies
Authors: Raspet Richard , Webster Jeremy , Dillion Kevin
Published: October 2013

Research in wind noise reduction in outdoor measurement microphones has been limited largely to comparisons between bare and screened microphones. Morgan and Raspet [J. Acoust. Soc. Am. 92, 1180–1183 (1992)] used simultaneous wind velocity and noise measurements to show that the source of wind noise is incident wind fluctuations. In this paper, two methods for predicting the upper limits of wind noise pressure spectra from velocity spectra in the inertial range are developed. A lower limit on wind noise is estimated from two theories of the intrinsic turbulent pressure fluctuations. Empirical results for the self-noise windscreens in substantially non-turbulent flows are also presented. Measurements of the wind velocity spectra and wind noise spectra from a variety of windscreens are described and compared to the theoretical predictions. All of the wind noise data lies between the upper and lower limits. The theoretical framework allows windscreens to be evaluated in terms of the best and worst-case scenarios and establishes practical lower limits on wind noise reduction for varying wind conditions. [Work supported by the Collaborative Technology Alliance sponsored by the US Army Research Laboratory.]
Nighttime traffic noise in an urban environment
Authors: Gilbert Kenneth E. , Waxler Roger , Talmadge Carrick L. , Chambers James P.
Published: October 2013

Traffic noise ducted near the ground at night and in the early morning can be represented simply in terms of normal modes. The effects of surface loss and atmospheric absorption, as well as meteorology, are contained in the mode attenuation coefficients. For a long (5–10 km) road section, the average noise levels are a function of the product of the mode attenuation coefficients and the perpendicular distance from the roadway. This paper considers a two-dimensional model for computing the effective mode attenuation coefficients in an urban environment. Modal attenuation is estimated by propagating modes over an irregular surface that approximates typical urban structures. The mode attenuation due to scattering from the urban structures is compared to the attenuation from atmospheric absorption and from a finite ground impedance. Predicted noise levels are compared to available data and the implications for nighttime urban traffic noise are discussed.
The stability of the nocturnal quiet height
Authors: Waxler Roger , Gilbert Kenneth E. , Talmadge Carrick
Published: October 2013

It has recently been demonstrated that for narrow band signals propagating in the nocturnal boundary layer there is a height, a few meters off the ground, at which the sound pressure is significantly reduced. In this presentation the stability of the quiet height against fluctuations of the sound speed will be discussed. It is demonstrated theoretically, and verified by experiment, that, in the first few meters of the atmosphere, the dependence of the sound pressure level on altitude, relative to the sound pressure level at any fixed altitude, is insensitive to sound speed fluctuations.
Wind noise at a flush microphone in a flat plate
Authors: Dillion Kevin , Raspet Richard , Webster Jeremy
Published: October 2013

Elliot [Boundary Layer Meteorology 2, 476–495 (1972)] states that a flush-mounted microphone can measure the turbulent pressure fluctuations in outdoor flows without self-noise problems. This suggests that flush mounted microphones can be used to minimize wind noise. Wind velocity spectra from a hot wire anemometer and wind noise spectra from a flush- mounted microphone in a flat plate at ground level have been measured outdoors. The velocity power spectral densities and average velocities as a function of height are determined from the data. The measured pressure power spectral densities are compared to theoretical values calculated from fluid dynamic and meteorological turbulence theory. In particular we investigate the contributions of predicted turbulence-turbulence and turbulence-mean shear contributions to the pressure spectrum measured at the surface of the plate. [Prepared in part through collaborative participation in the Collaborative Technology Alliance for Advanced Sensors sponsored by the US Army research Laboratory under Cooperative Agreement DAAD19-01-0008.]
The banjo in the time-domain
Authors: Dickey Joseph
Published: October 2013

The banjo is under-represented in the musical acoustics literature. This is the case even though it is basically a vibrating and radiating membrane driven by a plucked string, and thereby lends itself naturally to modeling and analysis. A recent frequency domain model, [Dickey, J. Acoust. Soc. Am. 114, 2958–2966 (2003)] will be reviewed. The work reported here is a time domain analysis. First, the response of an isolated, plucked, lossy and dispersive string is presented. The string is then connected through a bridge to the center of a circular membrane. The string and head are treated as two fully connected dynamic systems and the response of the head is calculated. The isolated head is then driven off-center with an harmonic drive and the temporal response is determined by ray-tracing and summing amplitudes over a grid. Resonance frequencies and modal patterns agree well with experiment thereby validating the technique. Finally, the resonant string is considered as an external, transient, off-center and spatially distributed drive and the temporal response of the head is derived using the ray tracing technique. These modal patterns evolve in time and eventually stabilize to patterns that are in qualitative agreement with experiment.
Effects of subglottal acoustics on phonation onset
Authors: Neubauer Juergen , Zhang Zhaoyan , Berry David
Published: October 2013

The effect of subglottal acoustic loading on the vocal fold vibration was investigated using a self-oscillating mechanical model of the folds. Although the influence of the supraglottal tract on vocal fold vibration has received more attention than the subglottal system, the influence of the subglottal system on vocal fold vibration is also potentially significant, and merits investigation. In this study, the subglottal system consisted of a uniform tube connected to an expansion chamber on the flow supply end (e.g., a pseudo-lung). The length of the subglottal tube was varied systematically over a relatively large range in order to investigate the influence of subglottal acoustics on vocal fold vibration. Phonation onset and offset pressures were measured in the subglottal tube as a function of tube length. Over the range of investigation, the fundamental frequency of phonation was found to be negatively correlated with the subglottal tube length. However, both phonation onset and offset pressure were positively correlated with subglottal tube length, with the onset pressure increasing faster than the offset pressure. This hysteresis effect vanished and the two pressures merged at a small value of the subglottal tube length, indicating a change in the onset behavior from a subcritical Hopf bifurcation to a supercritical Hopf bifurcation (a codimension-2 bifurcation point). In addition, phonation did not exist below a critical subglottal tube length.
Variation in acoustic activity of North Atlantic right whales in three critical habitat areas in 2004
Authors: Parks Susan E. , Clark Christopher W.
Published: October 2013

The North Atlantic right whale is a critically endangered species. Five major habitat areas have been defined based on the presence of groups of right whales during different seasons of the year. Autonomous seafloor acoustic recorders, ‘‘pop-ups,’’ have been used over the past five years to identify the presence/absence of right whales in Cape Cod Bay, Massachusetts by detection of right whale contact calls. These recordings have shown the effectiveness of using acoustics to monitor right whale behavior. In 2004, multi-unit arrays of pop-ups were deployed in three critical habitat areas; Cape Cod Bay (January–April), Great South Channel (May), and the Bay of Fundy (August). The presence/absence of right whale calls within range of the array, estimates of the minimum number of individuals calling, the types of calls recorded, and the diurnal patterns of sound production were measured to compare the acoustic repertoire use of right whales in these three habitats. These data were compared to visual survey data in the Bay of Fundy. These results can be used to compare diurnal and nocturnal behavioral patterns of the whales and provide information on behavioral differences between these three critical habitat areas.
The influence of surface diffusivity on reverberation time prediction
Authors: Zhang Yan , Augenbroe Godfried
Published: October 2013

It has been reported in the literature that the reverberation time tends to be overestimated if the ray-tracing simulation does not consider surface scattering effects. However no simple, quantitative method is available to estimate the effect of surface diffusivity on reverberation time. This article provides such a model to establish the relation between reverberation time and a surface diffusivity factor. It has also been observed that the influence of scattering reflections increases when the material is less uniformly distributed. Therefore the authors studied the current prediction method with non-uniformly distributed material and observed the following: Kutruff equation based on the diffusive surface assumptions yields shorter reverberation times than Eyrings formula, while another equation containing reflective assumptions yields longer RT than Eyrings formula. It is demonstrated that the difference can reach up to 50%. Therefore the authors propose a linear combination of these two equations, with the proportion to each end determined by the surface diffusivity, assessed against Hann and Fricks method. A comparison between Boston Symphony Hall and New York Avery Fisher Hall is performed to demonstrate the significance of the surface diffusivity, and a Monte-Carlo simulation is included to support the result even under parameter uncertainties.
Biomass assessment in commercial catfish ponds
Authors: Chambers James , Minchew C. Douglas , Beecham Rachel
Published: October 2013

With increasing seafood demand aquaculture is poised to become a major growth industry in the United States in the 21st century. In particular channel catfish represent an approximately $260 million industry in Mississippi with strong growth potential. A major portion of the costs associated with raising channel catfish are related to the cost of feed and aeration which are directly related to the total number of fish being raised in each pond. Crop insurance and bank loans are also contingent upon accurate population estimates. A high frequency, horizontally scanning, active pulse echo sonar system, the Aquascanner, has been developed to estimate pond populations. Commercial catfish ponds are typically 2 to 10 acres and, unlike many offshore fisheries, have fairly shallow depths of 1 to 2 m. The system components and its use will be presented along with results from field tests. [Work supported by US Dept. of Agriculture.]
Twenty years of barrel-stave flextensional transducer technology in Canada
Authors: Jones Dennis F.
Published: October 2013

The barrel-stave flextensional transducer, a compact underwater sound source, was conceived at DRDC Atlantic in 1986 [G. W. McMahon and D. F. Jones, U.S. Patent No. 4,922,470 (1 May 1990); Canadian Patent No. 1,285,646 (2 July 1991)]. Over the years, five barrel-stave designs belonging to three flextensional classes were built and tested at DRDC Atlantic. Three Class I transducers with operating frequencies ranging from 800 to 1600 Hz were integrated into submarine communications buoys, low frequency active horizontal projector arrays, and a broadband sonar towbody. A high-power Class II and broadband (1–7 kHz) Class III transducer were deployed under the ice in the Lincoln Sea for research related to rapidly deployable surveillance systems. These barrel-stave flextensional transducers have also supported a variety of marine mammal studies including vocal mimicry in long-finned pilot whales, coda dialects in sperm whales, and the R&D of acoustic detection and tracking systems for endangered northern right whales. In August 2004 a barrel-stave transducer was used to lure a trapped juvenile humpback whale to the sluice gates of a tidal generating station on the Annapolis River in Nova Scotia by transmitting humpback whale calls underwater. The acoustic performance parameters for all 5 transducers will be presented.
The acoustic environment of the southern resident killer whales in Haro Strait: Propagation modeling and analysis of field measurements
Authors: Jones Christopher , Wolfson Michael
Published: October 2013

We will discuss the complicated shallow water acoustic environments of the southern resident killer whales in the Haro Strait of the Puget Sound through combined analysis of field measurements and acoustic propagation modeling in the frequency range of 1 to 20 kHz. Haro Strait is a highly variable acoustic environment with active commercial shipping, whale watching, and Naval activity. Southern resident killer whales are of unique public concern in this area because of potentially high impact by anthropogenic sound sources, either by auditory masking that may interfere with foraging strategies or annoyance and disorientation due to complicated reverberation. Predictive acoustic modeling in combination with field measurements can aid in understanding the mechanisms of impact and better inform assessment of the risk, providing a critical step towards the quantitative evaluation of impact in the context of complicated environments, changing background sound levels, and emerging management issues. Preliminary results of modeling and analysis of data collected in the summer of 2004 will be presented.
Reliable but weak voice-formant cues to body size in men but not women
Authors: Rendall Drew , Vokey John R. , Nemeth Christie , Ney Christina
Published: October 2013

Whether voice formants provide reliable cues to adult body size has been contested recently for some animals and humans and the outcome bears critically on theories of social competition and mate choice, language origins, and speaker normalization. We report two experiments to test listeners’ ability to assess speaker body size. In Experiment 1, listeners heard paired comparisons of the same short phrase spoken by two adults of the same sex paired randomly with respect to height and indicated which was larger. Both sexes (M=20; F=22) showed an equal but modest ability to identify the larger male (mean correct=58.5%; T=31.5, P<0.001) that correlated with the magnitude of their height difference but could not pick the larger female (mean correct=52.0%; T=1.05, P=0.305) regardless of the height difference. Experiment 2 used single word comparisons, focused only on male voices, and controlled F0 while manipulating F1−F4 between speakers. When F0 was equal but F1−F4 predicted the height difference between speakers, both sexes (M=12; F=18) correctly chose the taller male (80%). When F1−F4 values of the shorter male were reduced below those of the taller male (or vice versa), subjects shifted to pick the shorter male as being larger.
Testing marine mammal hearing with a vocal response paradigm and the method of free response
Authors: Finneran James J. , Carder Donald A. , Schlundt Carolyn E. , Ridgway Sam H.
Published: October 2013

Behavioral hearing tests with marine mammals often use single interval experiments with a go/no-go paradigm, where the subject pushes a response paddle or similar device to indicate the presence of a hearing test tone. This approach is widely accepted, but the time required for the subject to physically move and/or interact with the response device and the requirement of one trial per reinforcement interval limit the speed at which data can be collected (typically 20–30 minutes for a threshold). An alternative to the single interval/paddle press approach is the use of a vocal response technique and the method of free response, where multiple trials are presented within a single reinforcement interval. An acoustic or vocal response eliminates the need for the subjects to physically move, allowing for faster responses and shorter inter-trial intervals. The method of free response allows multiple tone presentations between reinforcement periods, dramatically increasing the rate at which data may be collected, especially from diving marine mammals. This talk describes the application of these techniques to hearing tests of bottlenose dolphins, white whales, and California sea lions and the advantages and disadvantages compared to the single interval experiment. [Work supported by ONR.]
Thinking Before We Act
Authors: Voight Benjamin F.
Published: October 2013

Analysis of coding variation highlights the challenges of addressing actionable, incidental findings from clinical genomics testing.
TESTING TIMES FOR SUPERSYMMETRY: LOOKING UNDER THE LAMP POST
Authors: DIGHE AMOL , GHOSH DIPTIMOY , PATEL KETAN M. , RAYCHAUDHURI SREERUP
Published: October 2013

We make a critical study of two highly-constrained models of supersymmetry — the constrained minimal supersymmetric standard model (cMSSM), and the nonuniversal Higgs mass (NUHM) model — in the light of the 125–126 GeV Higgs boson, the first observation of Bs→μμ at the LHCb, and the updated B → τν branching ratio at BELLE. It turns out that these models are still allowed by the experimental data, even if we demand that there be a light stop with mass less than 1.5 TeV. The only significant effects of all these constraints are to push the mass of the light stop above ~500 GeV, and to prefer the universal trilinear coupling A0to be large and negative. We calculate the Higgs boson branching ratios to WW, ZZ, ττ and γγ in these models and show that improved experimental limits on these could put them to the most stringent experimental tests yet.