bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling reflections from rough surfaces in complex spaces
Authors: Siltanen Samuel , Southern Alex , Savioja Lauri
Published: September 2012

Acoustic reflections from rough surfaces occur both in indoor and outdoor environments. Detailed modeling of such reflections is possible with wave-based modeling algorithms. However, their time and resource consumption limits the applicability of such algorithms in practical modeling tasks where the modeled space is large or even unbounded. On the other hand, geometrical acoustics modeling techniques are more efficient in most cases, but they are not able to capture the wave interaction with the rough surface. The presented solution combines a geometric modeling algorithm with a theoretical model of the rough surface. The geometric algorithm is an efficient beam tracer. The theoretical model assumes long wavelength compared to the dimensions of the surface details. The model shows that the effect of the rough surface can be approximated with a exponential decay tail after an impulse in the time domain impulse response. A further approximation is to present multiple such reflections with a decay resembling a gamma distribution. Several complex example cases with a large number of reflections are shown. In addition, comparison of the theoretical model to finite-difference time-domain algorithm modeling results is given. The results support the applicability of the presented approach to practical modeling tasks.
Computational modeling of broadband acoustic fields in enclosures with specular reflection boundaries using a first-principles energy method
Authors: Bliss Donald B. , Michalis Krista A. , Franzoni Linda P.
Published: September 2012

Steady-state sound fields in enclosures with specular reflection boundaries are modeled with a first-principle energy-intensity boundary element method using uncorrelated broadband directional sources. The specular reflection field is represented by a limited set of spherical harmonics, orthogonal on the half-space. For each boundary element, the amplitudes of these harmonics are determined from the incident field from all other elements and sources, and are subject to an energy conservation integral constraint using a Lagrange multiplier method. The computational problem is solved using an iterative relaxation method starting from the 3-D diffuse reflection solution. At each iteration, directivity harmonics are estimated by post-processing and the influence matrix is refined accordingly. For internal sources, simple first reflection images improve accuracy with virtually no penalty on computation time. Convergence occurs in relatively few relaxation steps. Extrapolating to an infinite number of boundary elements and iterations gives very accurate results. Results are compared to exact benchmark solutions obtained from a frequency-by-frequency modal analysis, and to a broadband image method. The method of absorption scaling is verified for 3-D cases, and showing that the spatial variation in rooms is largely determined by source position and the relative distribution of absorption, but not the overall absorption level.
Time-domain simulation of long-range sound propagation in an atmosphere with temperature gradient
Authors: Zheng Z. C. , Ke Guoyi
Published: September 2012

A numerical model for linearized Euler equations using finite difference in time-domain (FDTD) simulation is developed to simulate sound propagation with temperature gradient in the atmosphere. The speed of sound in the air varies with the temperature at different altitude above the ground due to the effect of temperature gradient. For sound propagation at long ranges, an algorithm of moving-frame method is implemented with parallel computation. The numerical results are compared with analytical solutions for sound propagation with downward and upward refraction caused by the speed of sound linearly increasing (downward refraction) or decreasing (upward refraction) with altitude. The 2D normal mode analytical solutions are used to compare the downward refraction results, and the residue series analytical solutions are used to compare the upward refraction results. The comparison show that the numerical simulation results agree very well with the analytical solutions for both downward refraction and upward refraction cases. Several examples of long- and short-range simulation results are then presented.
Wine glass resonance experiment and demonstration
Authors: Thines Benjamin C.
Published: September 2012

Breaking a wine glass with sound is a visually striking achievement and a great way to get potential students interested in Physics. The goal of this project is to not only break the wine glass but to build an apparatus that is portable and easily setup for lecture room demonstrations as well as outreach to area schools. The apparatus should also provide enough visibility for a room full of observers to easily see the process. In order to be able to observe the small deflections of the object a variable frequency strobe will be employed. A strobe has the benefit of being able to see in real time what is going on at a much higher frequency than the human eye would normally perceive. In a larger setting a camera could be used to relay the relatively small image of the wine glass to a projector for better visibility. From a more technical stand point, the project will provide an opportunity to experiment with resonance on a variety of different shapes and compositions of items. In order to prepare for the final demonstration, many different wine glasses will be tested in the test chamber.
Aperiodicity and ground effects on the sonic crystal noise barriers
Authors: Taherzadeh Shahram , Bashir Imran , Attenborough Keith , Chong Alvin Y.
Published: September 2012

Sonic crystal structures consisting of periodically-arranged solid vertical cylinders can act as sound barriers at certain frequencies. Their performance depends on the filling fraction which is determined by the spacing and cylinder radius. To be effective the filling fraction must be high. This means that periodic arrays with relatively low filling fractions such as in trees belts are not effective as traffic noise barriers. The effects of partially perturbing the positions of sonic crystal elements have been investigated by modelling and laboratory measurements and have been shown to improve the insertion loss of the periodic structure. It is argued that partial perturbation of regular tree planting near highways will improve their noise attenuation. Furthermore, much previous research assumes the sonic crystal structure to be in the free field, i.e. no account has been taken of the presence of the ground surface. With a conventional, wall type, barrier the ground effect is reduced by presence of the barrier. Laboratory measurements have been made of periodic and aperiodic arrays of cylinders placed with their axes normal to acoustically hard and soft surfaces. It is found that the ground effects and sonic crystal band gap effects are additive.
Acoustical performance of damped gypsum board in double wood stud wall assemblies
Authors: LoVerde John , Dong David W.
Published: September 2012

A common assembly for demising walls in multifamily residential projects is double wood studs with multiple layers of gypsum board on one or both sides. While improving the acoustical performance, installing multiple layers of gypsum board adds significant cost to the project; complicates scheduling, materials storage, and delivery; and may require additional inspections. On some types of projects, removing these complications has been desired. In these cases, the use of damped gypsum board has been pursued to reduce the number of layers of gypsum board on the demising wall while attempting to achieve equivalent acoustical performance. Acoustical testing was performed to determine if damped gypsum board was a suitable alternative to the standard gypsum board assemblies in typical demising constructions. Laboratory and field tests were performed on double wood stud walls with a variety of gypsum board configurations, and the results are presented.
Effects of boundary conditions on the transmission of impulsive sound at low frequencies through building components into enclosed spaces
Authors: Remillieux Marcel C.
Published: September 2012

The transmission of impulsive sound at low frequencies, through building components, into enclosed spaces is solved numerically. This investigation is directed at what is essentially a transient problem. The shapes of the vibro-acoustic waveforms, in particular peak values, are of principal concern since they relate directly to the auditory response of occupants and possibility to structural damage. The case of an N-wave impinging upon a window panel backed by a rigid rectangular enclosure is considered in this study. At low frequencies, the vibro-acoustic response of a typical building component is dominated by a few modes. Besides, the response is very sensitive to boundary conditions. Therefore, the vibro-acoustic response of the system can be altered by tuning the boundary conditions of the structural components. Three types of boundary conditions are examined: simply-supported, fixed, and visco-elastic. It is demonstrated that the peak amplitudes of the vibro-acoustic waveforms can be reduced significantly by the appropriate choice of boundary conditions.
Predicting structural and acoustic-radiation loss factors using experimental modal analysis
Authors: Shepherd Micah R. , Hambric Stephen A. , Fahnline John B.
Published: September 2012

Standard damping measurements cannot typically distinguish between structural losses and losses due to acoustic radiation. Since the trend in aerospace engineering is to use lighter and stiffer materials, aerospace panels often have their critical frequency at low to mid frequencies making the acoustic losses of comparable or greater value than the structural loss factors. A procedure for measuring acoustic radiation loss factors is presented based on experimental modal analysis. Experimental modal analysis was performed on a composite panel with carbon-fiber facesheets and an aluminum honeycomb core. The loss factors using the standard decay and modal methods are compared to an energy-based method based on the power injection method. The acoustic radiation loss factors were then estimated using boundary element computations of the radiated noise with the modally reconstructed velocity as input. The acoustic radiation damping was then removed from the total damping to predict the losses due to structural damping only.
An approach to increase apparent damping with reduced subordinate oscillator array mass
Authors: Glean Aldo A. , Vignola Joseph F. , Judge John A. , Ryan Teresa J. , O'Malley Patrick F.
Published: September 2012

The case of a lightly damped oscillator (primary mass) adorned with a set of substantially less massive oscillators is known as a subordinate oscillator array (SOA). An SOA can function as an energy sink on the primary, extracting vibration energy from it, thus adding apparent damping to the system. Low apparent Q is achieved by increasing non-dimensional bandwidth, which is the ratio of the bandwidth to the fundamental frequency of the primary. The mass of the subordinate set required to achieve the most rapid energy transfer from the primary is proportional to non-dimensional bandwidth squared. We have shown the limit of apparent damping achievable in these systems is the inverse of non-dimensional bandwidth. In practice, the utility of this result is limited because a great deal of mass (~30% of primary) is required to increase the apparent damping in the system such that Q_apparent→1. This work will focus on an alternative design strategy that produces comparable increase in apparent damping with less added mass. We describe numerical optimizations in which the non-dimensional bandwidth of the isolated natural frequencies of the SOA elements and the distribution of those isolated natural frequencies are used to minimize the total mass of the SOA.
Viscous boundary layer correction on a pressure-field acoustic model
Authors: Li Yizeng , Cheng Lei , Grosh Karl
Published: September 2012

Fluid viscosity plays an important role in many acoustics and structural acoustics problems. For example, using an inviscid approximation to the flow of fluid-loaded micro-electro-mechanical systems and micro-scale biological structures results in large errors in the predicted response. Using a linearized Navier--Stokes solution, however, increases the number of unknowns by at least a factor of three compared to an inviscid approximation where pressure is the only degree of freedom. In this work, an approximate boundary condition is developed to include fluid viscosity for coupled fluid-structure systems. The viscous effect is included as a correction term to the inviscid boundary condition, written in terms of second order in-plane derivatives of pressure. This is the key step enabling the development of a variational formulation that is directly amenable for approximation in a finite element method (FEM) code as only a minor modification to existing structural acoustic code. Hence, this approach retains the great computational advantage over the conventional viscous FEM formulation. We show results demonstrating the accuracy of the approximate boundary condition as compared to the full three dimensional Navier-Stokes solution.
Acoustical design of Calderwood Hall at the Isabella Stewart Gardner Museum
Authors: Beckmann Daniel , Komoda Motoo , Toyota Yasuhisa
Published: September 2012

The Isabella Stewart Gardner Museum opened the expansion to its historic “Fenway Court” Palace in the Back Bay district of Boston, Massachusetts in January, 2012. Renzo Piano Building Workshop was the design architect for the 70,000 square foot addition to the museum. The new Calderwood Hall serves the music programming mission of the museum by creating a 300-seat space where chamber music can equally be enjoyed by all members of the audience. A novel audience configuration is perhaps the most defining element of this highly intimate space for music, where a stage measuring 30 feet square is centered on the bottom level of the space measuring 42 feet square and 45 feet tall. Three stacked balconies, each one row deep, look down on the stage from all four sides. The integrated acoustical and architectural design features are reported.
Acoustical design of Helzberg Hall at the Kauffman Center for the Performing Arts
Authors: Beckmann Daniel , Kallas Kayo , Komoda Motoo , Toyota Yasuhisa
Published: September 2012

Helzberg Hall, the arena-style concert hall in the Kauffman Center for the Performing Arts in Kansas City, Missouri opened in September, 2011. The 1600-seat concert hall was designed by the architect Moshe Safdie, and serves as the principal residence of the Kansas City Symphony. The hall measures 150 feet long, 100 feet wide, and 90 feet tall at the highest point, with an ensemble reflector suspended at 50 feet above the stage to support the stage acoustics. Stage acoustics are also enhanced by motorized risers on the stage, to give the orchestra layout a three-dimensional quality. Motorized draperies concealed in the walls also give flexibility to the acoustics of the space, in order to accommodate amplified events. A 1:10 scale model test of the hall was performed at the end of the design phase to verify the acoustics of the hall. The acoustical design and characteristics of the new space are reported.
Effects of local shape features on the beampatterns of a dynamic biomimetic baffle
Authors: Pannala Mittu , Z. Meymand Sajjad , Mueller Rolf
Published: September 2012

Horseshoe bats have mobile pinnae that can change their shapes as a result of active actuation. A common pattern is an alteration between an upright and a bent-tip geometrical configuration. Numerical predictions of reception beampatterns associated with these different shape geometries have indicated that the upright configurations are associated with beampatterns dominated by a single mainlobe whereas the bent-tip configurations have prominent sidelobes. Using a biomimetic baffle prototype, we have found that this effect can be reproduced qualitatively with just a plain obliquely truncated cone that is fabricated from flexible material (rubber) and bent at the tip. However, local shape features can have a strong impact on the quantitative expression of this effect. The three features studied here were a vertical ridge, an equivalent to the bat's antitragus, and a lateral incision into the baffle rim. The effects of these features on the beampatterns where found to interact with each other and also depend strongly on the deformation stage of the baffle shape. Hence the corresponding biological features may offer bats an opportunity to fine-tune their beampatterns as a function of deformation stage. However, control strategies for biomimetic devices with variable beampatterns have yet to be developed.
Interesting properties of toothed whale buzz clicks
Authors: Gerard Odile , Carthel Craig , Coraluppi Stefano
Published: September 2012

Toothed whales are known to click to find prey. The characteristics and repetition rates of the echolocation clicks vary from one species to another, but clicks are fairly regular during the phase in which the animals are searching for prey. Once they have found prey the repetition rate of the clicks increases; these sequences are called buzzes. Some previous work was done to classify Blainville’s beaked whale buzz clicks. While we did not succeed to classify these clicks individually because of the variation of their characteristics, we found buzz clicks have slowly varying properties from one click to the next. This similarity permits their association as a sequence using multi-hypothesis tracking algorithms. Thus buzz classification follows the automatic tracking of clicks. We also found that buzz clicks from other toothed whales species often have similar properties. In some cases a variant of this property has been found, whereby sub-sequences of clicks also exhibit slowly varying characteristics.
Feature extraction for classification of fish species using the Cepstral analysis
Authors: Matsuo Ikuo , Ito Masanori , Imaizumi Tomohito , Akamatsu Tomonari , Wang Yong , Nishimori Yasushi
Published: September 2012

Identification and classification of fish species are essential for acoustic surveys of fisheries. The echo from the fish contains components from multiple reflections, including the swimbladder and other organs. The target strength (TS) and temporal structure, which were measured and analyzed by using the broadband signal, were changed dependent on the incident angles and fish species. The cepstral analysis, which was defined as the inverse Fourier transform, was used to discriminate between the spectral pattern associated with the swim bladder and the interference pattern associated with these reflections. Echoes of Japanese jack mackerel (Trachurus japonicus), chub mackerel (Scomber japonicus), and red sea bream (Pagrus major) were measured and analyzed in the sea and tank. It was clarified that the spectral pattern associated the swim bladder was strongly dependent on both the tilt angle and the fish species. [Supported by the Research and Development Program for New Bio-industry Initiatives, and CREST, JST.]
Observation of sound fluctuations in presence of internal waves: Difference between refractive and adiabatic regimes
Authors: Badiey Mohsen , Katsnelson Boris G.
Published: September 2012

Angular dependence of sound field on the internal solitary wave propagation in shallow water has been previously shown [JASA, vol.122, p747-760, 2007]. In the presence of moving nonlinear internal waves, the interaction between sound field and internal waves can vary from refractive, to adiabatic, and mode coupling regimes. The mechanism is largely dependent on the angle between the direction of an acoustic track and wave front of internal waves. For small angles, refraction of horizontal field (focusing and de-focusing) can occur. However, for larger angles, the characteristics of the interaction between the acoustic field and internal waves is very different. For example for angle of about 15-20 degrees, the variations of the sound field follow variations of the sound speed profile while for the angle of about 5 degrees, focusing is observed. In this paper experimental observations and the corresponding modeling results showing the difference between the sound field for the small and larger angles are presented. This observation has prompted theoretical investigation [shown in an accompanying paper, Katsnelson, Badiey, et al.] showing the analytical aspect of the problem. Good agreement between the model and the experimental data is shown. [Work was supported by ONR.]
Introduction to animal bioacoustics
Authors: Klinck Holger
Published: September 2012

Animal bioacoustics (AB) covers all matters related to the production, transmission, and reception of sound in nature, as well as the investigation and use of natural sound by people and impacts of anthropogenic sounds by on animals. Topics include animal communication; sound production mechanisms; sound reception mechanisms; evolution of sound production and hearing mechanisms; effects of acoustic propagation on natural sounds; sound detection, classification, localization and tracking; estimating populations and population density; impact of human-generated noise on animals; and a variety of other topics. All animals, and indeed all organisms, are considered within the scope of AB, though the most common taxa are marine mammals, birds, primates and other mammals, fishes, frogs and other amphibians, and insects.
Psychological and physiological acoustics: From sound to neurons to perception … to clinical and engineering applications
Authors: Heinz Michael
Published: September 2012

Psychological and physiological acoustics includes a wide range of multidisciplinary approaches and topics, ranging from basic science to clinical and engineering applications. Research in this area of acoustics is concerned with questions such as how sound is processed once it enters the auditory system (both in humans and other species), how sound is used by organisms to help them communicate and navigate their environment, and how experience and pathology can alter the signal processing of sounds through neural plasticity. Topics include the biomechanics of the middle and inner ear; the neuroscience of the auditory nerve, brainstem, and cortex (including both upward and downward connections); and behavioral and cognitive studies of auditory perception. This talk provides a brief overview of several current areas of research, ranging from basic questions about the neural codes that represent various features of sound in the peripheral and central auditory systems, to clinical applications including the development and improvement of cochlear, brainstem, and midbrain implants that bypass the peripheral auditory system to restore hearing to people with profound hearing loss.
The Engineering Acoustics Technical Committee
Authors: Scanlon Michael V.
Published: September 2012

Engineering Acoustics Technical Committee (EATC) encompasses the theory and practice of creating tools for investigating acoustical phenomena and applying knowledge of acoustics to practical utility. This includes the design and modeling of acoustical and vibrational transducers, arrays, and transduction systems in all media and frequency ranges; instrumentation, metrology, and calibration; measurement and computational techniques as they relate to acoustical phenomena and their utility; and the engineering of materials and devices. EATC’s recently sponsored special sessions attracted members from all areas and is an enabler for overlapping interests: single crystal piezoelectrics, transducer design, vector sensors, materials for high power sonar, micromachined silicon mics, multimedia, 3-D audio, pro-audio, parametric sources, speakers, transduction, projection, materials processing and manufacturing, piezocomposites, sensor fusion, signal processing hardware, data communication, condition-based monitoring of machinery and processes, solid-state sensors and actuators, hearing aids and ear impedance, thermoacoustic refrigerators and engines, wind turbines, energy harvesting, computer modeling methods, acoustic barriers & noise control, array applications, metamaterials, systems for underwater vehicles, mufflers & silencers, borehole acoustics, flow noise mitigation methods, and non-destructive testing with ultrasound & non-contact methods.
Signal processing in acoustics: Why not get involved?
Authors: Culver R. L.
Published: September 2012

The Signal Processing Technical Committee (SPTC) of the ASA provides a forum for discussion of signal processing techniques that transcend any one application. Signal processing research typically presented at ASA meetings includes techniques that show promise in one application - say underwater acoustics - but may also have application to other areas, for example, speech processing or room acoustics. There are two good reasons to get involved in the SP TC. First, since signal processing is an important aspect of many acoustic research areas, you will have the opportunity to better understand new and potentially useful tools. Second, we are a small TC and you can make an immediate contribution.
An introduction to the Physical Acoustics Technical Committee activities
Authors: Garrett Steven L.
Published: September 2012

The primary activity of any ASA Technical Committee is to use collective wisdom of the Committee’s membership to determine which research topics within its specialization area are most active and interesting. Based on that assessment, the Committee organizes special sessions at future meetings that will bring together experts from those areas, not necessarily limited to the Society members, who can share interesting results and provide guidance regarding the directions that will lead to further understanding. In Physical Acoustics, that is a particularly daunting challenge given the scope of topics that fall within its purview: use of sound to probe material properties, sound propagation and attenuation mechanisms on this planet and in other parts of the universe, and physical effects of sound and its interaction with other forms of radiation, all of which could also go well beyond the limitations of a linear acoustical theory. Needless to say, involvement in debates about “what’s hot” is both interesting and educational. Other activities include proposals for Technical Initiatives that allocate ASA resources. Recently, PATC received funding to sponsor a demonstration session at the Physical Acoustics Summer School.
The challenge of orchestrating for the organ and the orchestra
Authors: Raymond Jason L. , Haan Christina , Holland Christy K.
Published: September 2012

Hector Berlioz (1803-1869), though not an organist himself, included descriptions of organ stops, registration, pitch range, and use in orchestral compositions in his Grand Traité d’Instrumentation et d’Orchestration modernes (1855). When discussing the unsuitability of combining the organ with the orchestra, he stated, “…the even and uniform tones of the organ can never fuse completely with the extremely variable sounds of the orchestra….” The objective of our study was to use this statement as a hypothesis to be tested. The relative dissonance of selected organ stops in combination with four orchestral instruments was analyzed using quantitative frequency analysis techniques. Three organs were chosen for study, each built by a different organ company, and each in a different acoustic setting. Four orchestral instruments (violin, flute, oboe, and horn) were chosen for their contrast in timbre and method of sound production. The differences in pitch between the overtones of the organ and instrument were compared in order to quantify the relative dissonance produced by each combination as a function of critical bandwidth of the human ear. In general, the combinations with the oboe and flute resulted in frequency differences less than 2% of the critical band for each overtone, which were perceived as minimally dissonant. In some cases, the violin and horn overtones exceeded 2% and 4% of the critical band, respectively.
Scanning vibrometry studies of reed dynamics in reed organ pipes
Authors: Huber Thomas M. , Seewald Lucas , Hendrickson Charles
Published: September 2012

Unlike most other wind instruments, in reed organ pipes it is not the length of the resonator tube that primarily determines the pitch, but the length of the vibrating reed. The reed, its fluid-structure interaction with the airflow, and feedback from the resonator form a very complicated dynamical system. By utilizing a Polytec PSV-400 scanning laser Doppler vibrometer, it is possible to monitor the operating deflection shapes of a vibrating reed, while using a microphone to monitor the sound production. In the current study, an experienced organ builder made adjustments to the reed/resonator/airflow parameters, both within a musically appropriate range, and for ranges outside of the norm. Results will be presented of the acoustical and vibrational spectral envelope, and the corresponding deflection shapes for each harmonic, for a range of different adjustments to the system. The vibrational results for the reed will be compared to measurements where the non-contact ultrasound radiation force is used to excite the natural resonance frequencies and deflection shapes of the reed in the absence of airflow. In addition to steady-state deflection shapes, results will be presented for the transient dynamics of the system as the airflow into the pipe is initiated.
Categorical sound characteristics of free-reed pipe-organ stops
Authors: Braasch Jonas
Published: September 2012

Organ pipes with free reeds became very popular in parts of Europe at the end of the 18th century, but vanished about 100 years later following a critical discussion about their characteristic sound qualities. The research reported here is based on the measurement and analysis of 11 free-reed organ stops and 15 striking-reed organ stops, as well as 7 flue-pipe organ stops for comparison purposes. The results show that the sound characteristics between free-reed and striking-reed pipes are perceptually distinguishable. Both types of reed stops have their unique set of characteristics. In general, striking-reed pipes have a higher spectral centroid than free-reed pipes. While the overtone spectra of the latter can be fairly similar to those of flue pipes, their onset characteristics do not match the other two types of pipe organ stops. Their fundamental frequencies gradually increase by a semitone over the duration of approximately 60 ms. The frequency shift can be larger for striking-reed pipes, but the duration of the shift is less than half the value for free reeds. In contrast, flue pipes do not usually show such a characteristic frequency shift.
Aeolian-Skinner Opus 1309 in the Community of Christ Auditorium, Independence, Missouri, USA
Authors: Quimby Michael
Published: September 2012

The 113-rank Auditorium organ located in Independence, Missouri, was built by the Aeolian-Skinner Organ Company of Boston, Mass. Immediately after its installation in 1959, the organ became - and remains - perhaps the most important example of the company's work from the period. The commanding display of exposed Great, Positiv, and Pedal pipework forms the visual centerpiece of the massive conference chamber which seats nearly 5,800 people. The main organ is framed by nineteen acoustical clouds suspended above and in front of it, and by choir seating and the large rostrum beneath it. The entire room is covered by a huge dome, culminating in an oculus rising some 100 feet above the floor. G. Donald Harrison, President and Tonal Director of Aeolian-Skinner and one of the twentieth century's most influential organ builders, was responsible for the organ's initial design and specification in the mid-1950s. Following Mr. Harrison's untimely death in 1956, Joseph Whiteford was appointed Tonal Director and, in collaboration with consultants Catharine Crozier and Harold Gleason, finalized the design and formulated the organ's pipe scales. The organ is a superb example of the “American Classic Organ,” a concept and design developed by Aeolian-Skinner. (Text by Thomas Brown)
Acoustics of the pipe organ
Authors: Kraybill Jan
Published: September 2012

An organist’s perspective on pipe organ acoustics. The range of frequencies produced by a large pipe organ covers 10 Hz to over 10,000 Hz. Three significant pipe organs in the Kansas City metro area will be discussed: the Julia Kauffman Casavant at the Kauffman Center for the Performing Arts in Kansas City (installation completed early 2012) and the two magnificent instruments at Community of Christ Headquarters in Independence, MO (installations in 1993 and 1959). The acoustic qualities of individual pipes, groups of pipes, and the rooms in which these instruments reside affect the approach which these organs’ builders took in designing these one-of-a-kind pipe organs, and the approach each artist takes when making music with them.
Excess attenuation and effective impedance associated with rough hard ground
Authors: Attenborough Keith , Bashir Imran , Taherzadeh Shahram
Published: September 2012

Although ground effect has been studied widely and is an accepted component of outdoor sound prediction schemes exploitation of ground effect has been restricted to the development of porous road surfaces which influence traffic noise generation as well as propagation. Relatively little attention has been paid to the potential for exploiting the effectively finite impedance associated with roughness small compared with the incident wavelengths on an otherwise acoustically-hard ground or to the potential usefulness of the wide variation in soft ground effects that are available. Results of recent laboratory and field measurements on artificially rough hard surfaces including the comparative acoustical performances of randomly- and periodically-spaced roughness are presented. The laboratory data have been used to study the influences of roughness shape and spacing and surface wave formation. Practical outdoor realisations of artificially roughened hard surfaces have utilised low brick wall configurations and their relative merits have been studied through loudspeaker and car pass by measurements and Boundary Element calculations.
Recent advances in sound propagation above a non-locally reacting ground
Authors: Li Kai Ming
Published: September 2012

In the absence of atmospheric effects, the sound fields above a locally reacting ground can be accurately predicted by the Weyl-van der Pol formula. The solution is based on an asymptotic analysis to yield two terms: a direct and a ground reflected wave terms. The reflected wave term can be written as a product of a spherical wave reflection coefficient and the sound reflected from a rigid ground. In the contrary, it is more challenging to derive a similar formula for the sound fields above non-locally reacting grounds. In the past, an approximation in the same form as the Weyl-van der Pol formula has been used which becomes inadequate for layered grounds. In this presentation, a brief review of the asymptotic analysis will be discussed. An overview of the analytical and numerical approaches will be presented for obtaining accurate prediction of sound fields above the non-locally reacting ground. It will be further demonstrated that the reflection coefficient can be split exactly into two terms - a plane wave reflection coefficient and a ground wave term involving the boundary loss factor. The correlation between the numerical distance and the location of the surface wave pole will be examined.
A hybrid computational method for computing urban canyon sound fields exhibiting roughness
Authors: Hart Carl , Lau Siu-Kit
Published: September 2012

Predicting the three-dimensional sound field within an urban canyon is essential for urban noise assessment. Several analytical and computational methods exist to predict the canyon sound field. Generally building facades can be characterized as both geometrically reflecting and dispersive. The image source method is well suited to scenarios where surfaces are geometrically reflecting. Given dispersive surfaces the radiosity method predicts the sound field well. On the other hand a canyon exhibiting geometric and dispersive facades requires a computationally intensive technique such as the finite-element method (FEM) or the boundary-element method (BEM). Due to computational limitations neither the FEM nor BEM are well suited for computing large, unbounded, three-dimensional, urban canyon domains. A prediction method which synthesizes adaptive beam tracing and a secondary model for edge diffraction serves as an alternative technique for analyzing urban canyon acoustics, which contain façades exhibiting both geometric and dispersive surfaces. Advantages of the hybrid method include the ability to model unbounded domains simply, no requirement for discretizing geometric boundaries, and the ability to model sound propagation in the time domain. The magnitude of acoustic dispersion from a surface is related to surface roughness. The effect of surface roughness on the canyon sound field is investigated.
Investigations of measured temperature and wind effects on outdoor sound propagation
Authors: Ronsse Lauren M. , Valente Dan , Nykaza Edward T. , White Michael J.
Published: September 2012

Temperature and wind effects on outdoor sound propagation have been well-studied in numerous theoretical investigations, leading to a number of commonly held beliefs about how weather affects outdoor propagation. For example, louder sound levels are expected when downwind propagation and temperature inversions are present, whereas lower levels are expected when upwind propagation and temperature lapses exist. However, the validity of such relationships has not been rigorously tested in the field for various terrains at long distances from an outdoor source. One is justified in questioning the validity of these relationships due to the difficulty of adequately modeling the dynamic atmosphere along the entire propagation path. This study examines some commonly held notions of outdoor sound propagation by experimentally investigating the effects of temperature gradients and wind speed/direction on sound propagation at long distances from a typical impulsive source. Temperature and wind conditions measured near the source and along the line of sound propagation are correlated with the received sound pressure levels recorded at distances up to 15 km from the source. The variability of peak sound pressure levels occurring under similar wind and temperature conditions is assessed, demonstrating that much complexity underlies these common aphorisms.
A modified saddle point method for predicting sound penetration into a rigid-porous ground
Authors: Tao Hongdan , Li Kai M.
Published: September 2012

An approximate analytical formula has been derived for the prediction of sound penetration into a semi-infinite rigid porous ground due to a monopole source. The sound fields can be expressed in an integral form that is amenable to analytical and numerical analyses. A modified saddle point method is applied to evaluate the integral asymptotically that leads to a closed form expression. The validity of the asymptotic formula is confirmed by comparing with the numerical results computed by the fast field formulation and the direct evaluation of the integral. It has been demonstrated that the present analytical formula is sufficiently accurate to predict the penetration of sound into the semi-infinite rigid porous ground. Furthermore, the sound fields predicted by modified saddle point are compared with that computed by the double saddle point method. It is found that these two asymptotic schemes give precise solutions at far fields but the modified saddle method is more accurate at the near field especially when both the source and receiver are close to the air/ground interface. [Research is partially funded by the China Research Scholarship Council.]
Measurements of acoustic transmission loss over a rough water surface
Authors: Tollefsen Cristina , Pecknold Sean
Published: September 2012

Recent interest in understanding acoustic propagation over rough water surfaces has been driven largely by the increasing presence of offshore wind turbines and concerns about the potential for community noise disturbance. In addition, there has been interest in evaluating directional acoustic hailing devices for use at sea, in determining potential environmental impact of naval gunfire exercises, and in understanding the in-air acoustic footprint of maritime-based military assets. Measurements of acoustic transmission loss over a rough water surface were made during the period of 3 Oct and 7 Dec 2011 near Halifax, Nova Scotia, Canada. The acoustic source was a propane cannon, firing four consecutive shots once per hour during daylight hours. A receiver was positioned at ranges of 2 km to 7.5 km from the source, with a clear line-of-sight across the water, for periods ranging from 5-21 days at each location. Temperature, wind velocity, relative humidity, and ocean surface wave height were acquired from a variety of sources, including point measurements, radiosonde profiles, and output from an atmospheric forecasting model (Environment Canada’s Global Environmental Multiscale [GEM] model). The measured values of transmission loss are compared to results obtained with a parabolic equation-based atmospheric acoustic propagation model.
Effects of inclusion shapes within rigid porous materials on acoustic performance
Authors: Hong Hyun , Lau Siu-Kit
Published: September 2012

The present study investigates the influence of various shapes of inclusions having same volume embedded in a porous rigid material. Previous studies showed improvement of the broadband sound absorption with particular shapes of inclusions. However, different volumes of the inclusions have been considered; therefore, the bulk densities are not the same for comparison. The present study extends the investigations of inclusions in porous materials with same volume (or bulk density) to eliminate the influence by the change of bulk density. The effects of shape will be discussed. Finite element modeling will be used for this study. Total four different shapes: circle, square, ellipse, and triangle, have been studied at various orientations. It has been found that specific configurations can be able to improve the broadband sound absorption compared with reference (no inclusion). It is being expected that a better control of sound absorption of porous materials at desired frequency range can be achieved with the results of the present study.
Wesley Nyborg and bioacoustics at the University of Vermont
Authors: Wu Junru
Published: September 2012

Wesley Nyborg, Physics Professor Emeritus at the University of Vermont, passed away on September 24, 2011 after a full and wonderful life of 94 years. Wes came to the University of Vermont in 1960 where he did his most pioneering research in microstreaming, acoustic radiation pressure and bioeffects of ultrasound. He was considered as one of most influential pioneers by the international biomedical ultrasound community. Wesley Nyborg has developed an active bioacoustics and biomedical ultrasound research in the university. His research was continuously supported over 20 years by NIH. In this presentation, his research and life with the university will be reviewed.
Gauging the likelihood of stable cavitation from ultrasound contrast agents
Authors: Bader Kenneth B. , Holland Christy K.
Published: September 2012

Clinical ultrasound scanners use the Mechanical Index (MI) to gauge the potential for bioeffects due to inertial cavitation. However, the advent of ultrasound contrast agents (UCA) introduces nucleation mechanisms for bubble activity far different than that assumed in the development of the MI. Such exogenous agents promote bubble activity at substantially lower acoustic pressures than those required for inertial cavitation. The onset of this type of gentle bubble activity is within a stable cavitation regime. The minimum thresholds of both stable cavitation (as indicated by the onset of subharmonic oscillations) and the rupture of UCA were numerically calculated as a function of frequency. Both of these thresholds were found to depend linearly on frequency, and a “cavitation index” will be introduced. This index will be compared to the MI and compared to bioeffects studies in the literature. This cavitation index is not intended to replace the MI. Rather, it may be used to gauge the destruction of UCA, or promote bubble activity to induce beneficial bioeffects mediated by stable cavitation. This work was supported by the National Institutes of Health, grant numbers NIH RO1 NS047603, NIH RO1 HL059586, and NIH RO1 HL74002.
Recent advances concerning acoustic radiation forces and torques and Wes Nyborg's helpful discussion of acoustic streaming
Authors: Marston Philip L. , Zhang L. K. , Thiessen David B.
Published: September 2012

Recent theoretical advances concerning the geometrical interpretation of acoustic radiation forces [L. K. Zhang and P. L. Marston, Phys. Rev. E 84, 035601R (2011); L. K. Zhang and P. L. Marston, J. Acoust. Soc. Am. 131, EL329-EL335 (2012)] and the scaling of acoustic radiation torques for symmetric objects in beams and in standing waves with increasing helicity [L. K. Zhang and P. L. Marston, Phys. Rev. E 84, 065601R (2011)] will be summarized. For spheres in beams it has been possible to find situations giving transversely stable radiation forces using finite elements. The predicted scaling properties of acoustic torques have been verified in an investigation by an independent group [C. E. M. Demore et al., Phys. Rev. Lett. 108, 194301 (2012); A. G. Smart, Physics Today 65 (6), 18-20 (2012)]. This work will be examined in the context of broader discussions with, and/or a few of the interests of, Wes Nyborg and his practical analysis of acoustic streaming [W. L. Nyborg, in Nonlinear Acoustics, edited by M. F. Hamilton and D. T. Blackstock (Academic Press, San Diego, CA, 1998)] pp. 207-231. [Marston and Thiessen were supported in part by ONR. Zhang was supported in part by NASA.]
Acoustic streaming in therapeutic ultrasound
Authors: Crum Lawrence A.
Published: September 2012

Wesley Nyborg’s contributions to a theoretical description of acoustic streaming were pioneering, rigorous, and so thorough that little additional work has been published. Acoustic streaming has had many applications in acoustics, especially medical acoustics, in which it is difficult to avoid. In many cases, it can be used to enhance or accelerate a particular therapeutic effect. This presentation will provide a few examples of the role of acoustic streaming in therapeutic ultrasound as well as share a few warm memories of this kind and generous man. [Work supported in part by the NIH and NSBRI.]