bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculations of intensities for radiation force modeling with the commercial software package FOCUS.
Authors: McGough Robert J. , Vanderlaan Donald J. , Dutch Alexander , Urban Matthew W.
Published: March 2010

Rapid calculations of the intensity are required for models of the radiation force generated by linear ultrasound phased arrays. To determine the computation times and numerical errors produced by two medical ultrasound simulation packages, namely, FIELD II and FOCUS, comparisons of the calculated pressures and intensities are performed using a simulated Vermon L5 phased array probe with 128 active elements. In these simulations, the array generates a fixed focus 25 mm from the array for a 5-MHz excitation, and the pressure field is computed on a 133 × 133 × 261 rectilinear grid that is centered at the focus. Half wavelength sampling is employed in all three directions. In FIELD II, this calculation takes approximately 4 h on a 64-bit laptop running Linux, and in FOCUS, the same calculation takes less than 4 min on the same computer. The numerical errors are also much smaller with FOCUS. Details of the simulation approaches employed for this transducer model will be presented, including selection of FIELD II and FOCUS simulation parameters and calculations of the reference pressure field for error evaluations. The impact of numerical errors on shear wave calculations will also be discussed.
How good is the Roadway Construction Noise Model for predicting highway construction noise impacts?
Authors: Wallace Marc
Published: March 2010

The reconstruction of the I-93/Route 110/Route 113 in Methuen, MA will be conducted over a 4-year period. As part of the project, a new I-93 bridge superstructure will need to be built. This bridge work will consist of constructing the center portion of new superstructure, which will include pile driving. The work will require shifting I-93 traffic lanes several times to accommodate bridge construction over a several months. The design engineers are also considering constructing the superstructure over a weekend by shutting down I-93 and re-routing over local roads to reduce construction impacts. The Federal Highway Administration’s (FHWA) Roadway Construction Noise Model (RCNM) was used to assess potential construction noise impacts on nearby residential neighborhoods. The RCNM is a good screening tool to conservatively assess potential construction noise impacts. There are more sophisticated models, such as the Cadna A comprehensive three-dimensional (ISO 9613-2) model that takes into account topographic and atmospheric conditions. The goals of this paper will be to compare the RCNM and Cadna A model results to assess the accuracy of the RCNM model and to also assess the potential benefits or impacts of constructing the superstructure over a shorter period of time using the Cadna A model.
New York City western rail yard construction noise study.
Authors: Thalheimer Erich
Published: March 2010

This paper will describe the technical approach, regulatory environment, and outcome of a construction noise study performed on behalf of a $2.5 billion private development to be built over the Western Rail Yards in Manhattan. Community noise modeling for the 9 year project was performed in accordance with New York City Environmental Quality Review (CEQR) Manual requirements using the CADNA-A and FHWA TNM models. The on-site noise analysis accounted for the staggered schedule of excavation, foundation laying, erection, and finishing of eight high rise residential and commercial buildings. Construction equipment source emissions used in the CADNA-A model were taken from the FHWA Roadway Construction Noise Model (RCNM) and the NYC DEP Construction Noise Regulations (Local Law 113, Chap. 28). Project-related trucking (mobile) noise was evaluated using the TNM model. Seventeen multi-story noise receptor locations surrounding the development site were evaluated with ambient noise measurements and predictive noise modeling. A construction vibration assessment for the elevated High Line park was also conducted. The results indicated that noise exceedance conditions were expected from pile driving, hoe ramming, and jackhammering operations during daytime, nighttime, and weekend periods, so noise mitigation measures were developed and incorporated into the project’s construction permit.
Report on mitigation of nighttime construction noise.
Authors: Schexnayder Cliff , Shane Jennifer S.
Published: March 2010

Nationally, the amount of road work being done at night appears to be significant. Data taken during the summer of 2001 suggests that one-third of the work zones present on National Highway Systems roadways were active primarily at night. Night work can have impacts on adjacent neighborhoods and businesses that would not be experienced or as disturbing if conducted during the daytime. Construction equipment is a major noise and nuisance generator on nearly all nighttime construction projects. This paper will report on an ongoing Transportation Research Board study that is seeking to identify best practices in terms of source control, path control, and receptor control of noise on transportation projects. Individual DOTs having specific experience and contractors are being queried about their experiences in mitigating nighttime construction nuisances.
Road construction noise inside a radio station.
Authors: Connolly Sean
Published: March 2010

Construction noise limits are typically presented as noise levels not to be exceeded at the exterior of a building or a property line. However, when a building houses noise-sensitive uses, the possible construction noise impacts must be assessed inside the building. In 2004, a contentious legal dispute erupted between a radio station owner and the state highway department over the reconstruction of the highway directly adjacent to the station. The owner claimed that excessive road construction noise would disrupt live broadcasts from his studio. Therefore, the construction noise levels needed to be assessed inside the studio during the entire construction process, but legal maneuvering severely limited access to the station. This paper discusses the criteria and methods used to assess construction noise impacts inside the studio, the relationship between the measured noise levels inside and outside of the studio during various phases of road construction, and of course, if the construction noise interfered with radio broadcasts.
Printer impulsive noise metrics: Sensitivity and repeatability analysis.
Authors: Baird Terry , Ferguson Katy
Published: March 2010

The major cause of annoyance from impulsive noise is the impulsive amplitude. Many methods can characterize impulsive amplitude, such as time-averaged measures, peak amplitudes or real-time levels. For example, the “impulsive noise index” described by ISO 11201 or the “impulsive parameter” described in ISO 7779 are time-averaged metrics. Real-time metrics might include peak sound pressure level or peak loudness in the time domain. Impulsive metrics must be evaluated for effectiveness. That is, the metric must agree with the perceived impulsive amplitude. Impulsive metrics must also be practical. They must be insensitive to sample-to-sample variation while still providing the granularity between passing and failing results. This paper focuses on evaluating the sensitivity, measurement repeatability, and result granularity to determine the practicality of various effective impulsive noise metrics.
Constant acoustic fan curves for 92 mm axial fans.
Authors: Beltman Willem
Published: March 2010

The noise emission of fans changes as a function of the operating point. Airflow and acoustic fan plenum experiments can be used to characterize these effects to estimate noise under installed conditions. Recently, the concept of iso-acoustic fan curves was introduced by various authors, and results were presented for small radial blowers and some axial fans. The current paper presents an analysis of the iso-acoustic fan curves for an extensive set of 92 mm axial fans. An analysis is presented of the airflow and acoustic performance of these fans, and expressions for the iso-acoustic fan curves are derived and presented. This allows a direct comparison between the various fans based on operating point conditions.
Vibro-acoustic model of an enclosed electric power generator.
Authors: Copley David C. , Raman Harvind
Published: March 2010

A vibro-acoustic model of an enclosed diesel-powered electric generator was built using commercial vibro-acoustics software (primarily SEA) and empirical methods. The vibro-acoustic sources, including the engine, generator, cooling fan, and exhaust were characterized experimentally for several different operating conditions. The vibro-acoustic performance of the enclosure and sound suppression features were modeled and experimentally validated. Good agreement was achieved between experimental and simulated results.
FAA noise impacts research roadmap.
Authors: Girvin Raquel
Published: March 2010

The Federal Aviation Administration’s (FAA) continuing mission is to provide the safest, most efficient aerospace system in the world. Improving efficiency through airspace redesign, airport capacity expansion, and other initiatives of the FAA Next Generation Air Transportation System (NextGen) may be hampered without an aggressive program to address the environmental consequences of aviation. FAA’s work toward mitigating such environmental consequences includes research to advance the state of knowledge on noise impact analysis. This paper describes the status of FAA’s ongoing research efforts and the comprehensive research roadmap addressing critical noise impacts research needs.
Acoustic repropagation technique and practical source characterization for simulation noise model databases.
Authors: Hobbs Christopher , Page Juliet
Published: March 2010

By utilizing the acoustic repropagation technique in conjunction with an open-source, platform-independent database, a robust noise source can be constructed that is well suited for use in simulation noise models. This paper describes a widely applicable methodology for creating a three dimensional noise source from measurements that can account for source directivity. It will be shown how the resulting data, known as noise spheres, may contain a variety of noise metrics representing the source at a fixed distance for all spherical angles. Such spheres can be combined to represent complex noise sources and depending on their metric content can be used to accurately predict the near and far field environment about the source. A case utilizing narrow band spectra with phase information will be explored. It will be shown how a collection of spheres can be used to represent different operating states of a source and how the use of an independent parameter such as speed or power can be used to interpolate non-exact states in a noise model. By way of example, an approach to incorporating non-linear sound propagation from a high amplitude noise source is explored in conjunction with the advanced acoustic model.
Investigation of the use of lower frequency acoustic data in helicopter environmental noise modeling.
Authors: Boeker Eric , Schulz Noah
Published: March 2010

The current Federal Aviation Administration (FAA) aircraft noise modeling tools, Aviation Environmental Design Tool (AEDT) and Integrated Noise Model (INM), do not consider noise below 50 Hz in their computations. This paper describes a preliminary study to determine the effect of including low-frequency data on the accuracy of AEDT/INM results. Expanded aircraft noise spectra containing one-third octave band data to 12.5 Hz were analyzed using methods adapted from AEDT/INM. Results from expanded spectral data are compared with results from the historical AEDT/INM spectral data (one-third octave band data from 50 Hz to 10 kHz). This comparison showed a range of differences, from increases in overall un-weighted sound pressure levels, to negligible changes in A-weighted and time audible metrics. These changes may be particularly important for helicopters, with dominant low-frequency rotor noise below 50 Hz. Following the comparison, the potential implementation of expanded spectral data in AEDT/INM is discussed.
Examination of the low frequency limit for helicopter noise data in aviation environmental design tool and integrated noise model.
Authors: Boeker Eric , Schulz Noah
Published: March 2010

The current Federal Aviation Administration (FAA) aircraft noise modeling tools, Aviation Environmental Design Tool (AEDT) and Integrated Noise Model (INM), do not consider noise below 50 Hz in their computations. This paper describes a preliminary study to determine the effect of including low-frequency data on the accuracy of AEDT/INM results. Expanded aircraft noise spectra containing one-third octave band data to 12.5 Hz were analyzed using methods adapted from AEDT/INM. Results from expanded spectral data are compared with results from the historical AEDT/INM spectral data (one-third octave band data from 50 Hz to 10 kHz). This comparison showed a range of differences, from increases in overall un-weighted sound pressure levels, to negligible changes in A-weighted and time audible metrics. These changes may be particularly important for helicopters, with dominant low-frequency rotor noise below 50 Hz. Following the comparison, the potential implementation of expanded spectral data in AEDT/INM is discussed.
Flanking noise transmission in condominiums via steel roof deck.
Authors: Borzym Jim X.
Published: March 2010

Noise was found to transmit horizontally via a structure borne path. A lightweight roof consisting of ribbed steel deck spanned two adjacent loft-style condominium residential spaces. This noise transmission path significantly flanked the demising partition wall with known high-transmission loss. Two remedies were attempted to reduce transmission, by adding concrete on top of the roof deck. One remedy was successful.
Shipboard structureborne noise by resonant interactions of two torsional vibration modes.
Authors: Milburn Darrell
Published: March 2010

In recent years several occurrences of a similar engine-firing rate structureborne noise resonance were observed in the passenger areas of different ships. All were 16V four stroke high speed diesel propulsion systems, including engine vibration isolation mountings and remote reduction gears. The engine firing rate noise path came through the reduction gear mounting feet. Interactions of two torsional vibration modes with nearly equal natural frequencies caused the noise: one mode with the maximum amplitude in the engine crank shaft, and the other in the propeller shaft/reduction gear. Over a narrow range of engine speed, the firing rate energy excited both modes. The resonant torsional vibrations were transmitted to the structure through the reduction gear bearing reactions. In the observed cases, the amplitudes of the torsional stresses at resonance were well within the safe limits of the driveline components, raising no concern to vibration analysts assessing only the risk for mechanical failure. This paper outlines the system parameters related to the occurrences of these resonances, permitting noise control engineers to diagnose this problem or to identify “at risk” installations during the design phase. Noise control recommendations are presented as case studies with examples of the achieved noise reduction results.
Sound generation mechanism in low speed axial fans.
Authors: Bianchi Stefano , Corsini Alessandro , Sheard Anthony G.
Published: March 2010

Because of the global civil regulation concerning acoustic emission, the goal of the manufacturers is to substantially decrease the noise radiated by the low-speed fans, without degrading their aerodynamic performance. One of the main goal to accomplish this target is the evaluation of the unsteady aerodynamic sources in the fan rotor responsible for the noise emission. An experimental analysis, based on a cause-effect method, was carried out and the results are presented in this paper. The process focuses on the experimental comparison between the novel prototypes of a family of low-speed fans and enabled the evaluation of the noise sources in the rotor near-field domain. The near-field aerodynamic sources accounted in this work correspond to the zones with high pressure fluctuations amplitude, located in the wake region of the exhaust flow. The sources were measured along the rotor radius and then correlated with the noise emitted by the fan at the far-field domain, using a Fourier based methodology. The analysis was carried out looking at the cross-spectra polar form using the phase shift as revealing tool for aerodynamic noise sources. The results were compared to evaluate the merit of the aero-acoustic performance of each prototype.
Determining the effects of long-range missile noise on wildlife.
Authors: Lavallee Timothy
Published: March 2010

This is presentation on determining the sound levels from missile test and the potential effects on wildlife. The discussion will include an estimate noise from the launch, rocket motor splashdown, sonic boom, and detonation of long-range missiles. An overview of calculations and modeling to determine exposure to wildlife will be incorporated. The discussion will include overview of the ongoing development of noise threshold criteria for marine mammals and terrestrial wildlife, particularly, dolphins, pinnipeds, and avian species. A literature review and detailed review of the effects threshold will be included. A discussion of the benefits and the shortcoming associated with both the noise modeling and the limitations with respect to the existing effects thresholds will be included.
Animal magnetic resonance imaging and acoustic noise.
Authors: Lauer Amanda M. , El-Sharkawy AbdEl-Monem M. , Kraitchman Dara L. , Edelstein William A.
Published: March 2010

MRI scanner noise can cause discomfort and potential damage to human hearing. MRI is used extensively in animal research and, increasingly, as a diagnostic tool in veterinary medicine, generally with no hearing protection. Effects of noise could be detrimental for research animals that will be used after scanning or for companion animals that will be returned to owners. Though safe exposure standards have not been determined for most animals, it is important to consider that animals exposed to scanner noise may suffer hearing damage. To study potential animal MRI adverse hearing effects, we measured sound levels produced by several animal scanning protocols in a commercial 3T scanner. Using hearing threshold data for research or companion animals, we estimate weighted sound pressure levels and compare these to levels at which damage occurs in humans. SPLs were above 90 dB on many scans and often exceeded 100 dB. Animals may be exposed to these levels intermittently for 1 h or more. Exposure to these sound levels could result in temporary or permanent hearing loss. Thus, it is important to use hearing protection, quieter pulse sequences, or quieter scanners for animal research or companion animal veterinary MRI.
Comparison of impulse noise damage risk criteria using the chinchilla impulse noise exposures.
Authors: Murphy William J. , Khan Amir , Shaw Peter B.
Published: March 2010

The 1968 CHABA recommendations to limit impulsive noise exposure to levels below 140 dB sound pressure level form the basis of current United States occupational and military standards. The U.S. military standard, MIL-STD 1474D, estimates the number of allowable shots to which a person may be exposed using peak level, B-duration, for varying levels of hearing protection usage. The French Weapons Noise Committee has uses the 85 dBA A-weighted equivalent level, LAeq8 hr, as the limit for allowable exposures. The U.S. Army sponsored a series of noise exposures with chinchillas to investigate the effects of level, number of impulses, and interstimulus interval. Several types of impulses were created ranging from acoustic shock tubes to narrow band impacts reproduced by a loudspeaker. The goodness-of-fit and the discrimination of five noise exposure metrics were evaluated in this study: MIL-STD 1474D, AHAAH model, LAeq8 hr, Pfander’s C-duration metric, and Smoorenburg’s D-duration metric. Goodness-of-fit was evaluated with a logistic regression and discrimination was evaluated using the area under the receiver operator characteristic curve. The LAeq8 hr was found to best predict the temporary threshold shifts and the AHAAH model was found to best predict the permanent threshold shifts. [Partial funding provided by US Army Aeromedical Research Laboratories MIPR8J07586218].
Survey of ambient noise in aquariums.
Authors: Jemmott Colin W.
Published: March 2010

Owning and maintaining an aquarium is a common hobby, but the ambient noise in aquariums resulting from pumps, filters, bubblers, and other equipment is not well studied. Elevated ambient noise levels have been shown to adversely affect wild fish and marine invertebrates, and anecdotal evidence suggests that this may be a problem in aquariums as well. Aquariums designed to maintain coral reefs require high water flow and pristine water conditions, which in turn require pumps and protein skimmers that contribute to underwater noise. A survey of ambient noise in both fresh and saltwater aquariums ranging in size from 5 to 550 gal was conducted. The aquariums differed in construction material, number, size and type of pumps, and presence of other equipment. The ambient noise broadband levels, spectrum levels, and time-frequency representations are compared, and general conclusions are drawn about noise characteristics of equipment and aquariums.
A new tranquility rating tool and the role of audio and visual interactions.
Authors: Horoshenkov Kirill , Pheasant Robert , Watts Greg , Whitaker David , Kang Jian
Published: March 2010

Restorative environments which enable individuals to recover the sense of well-being are becoming increasingly important. These environments are characterized by an enhanced level of tranquility. Therefore, obtaining the optimum balance between the landscape and soundscape characteristics and measuring the resultant tranquility of these spaces are essential for their design and maintenance. In order to understand the key factors which affect the tranquillity construct, a large volume of audio and visual data has been collected across a representative range of landscapes in the UK. These data have been analyzed objectively by studying the temporal and spectral characteristics of the recorded sounds and the proportion of the natural and contextual features present in the video clips. The tranquility rating of these landscapes has been obtained from subjective experiments on 44 subjects to whom uni- and bimodal stimuli have been presented in a separate experiment. The results of these experiments make possible to objectively measure the key components of the tranquillity construct and determine their relative importance in the design of a restorative space. On this basis new relations between the tranquility rating, sound pressure level, loudness characteristics, and the visual quality of the scene have been derived.
The effect of anthropogenic noise on the calling behavior of amphibians and birds in urban areas of Puerto Rico.
Authors: Herrera-Montes Maria Isabel , Aide Mitchell
Published: March 2010

The bird and amphibian communities of Puerto Rico have high levels of diversity and endemism. Although Puerto Rico has a very high density of roads and high levels of noise pollution, presently 40% of the island is covered in forest. I will address the following questions: Do high levels of anthropogenic noise change species composition of amphibians and birds? Are amphibians and birds modifying the time of calling and/or characteristics of their vocalization in response to anthropogenic noise? I collected sound recordings in two habitats. For recordings I used the automated recording devices developed by our research group. Each recording device was programmed to record for 7 consecutive days; 1 min every 20 min. Previous results showed that noise influences the bird community composition in secondary lowland forest sites, but not in karst forest. Another possibility is that bird and amphibian use other strategies to minimize the effect of noise. This can involve evolutionary changes in signal characteristics, as a long term adaptation or the species may be adjusting signal traits in response to variations in noise levels as a short term adaptation. I will answer these questions when I do analyzing all data.
Would Western noise policies be effective in developing countries?
Authors: Finegold Lawrence , Schwela Dieter
Published: March 2010

This paper examines the question of whether current and evolving Western noise policies would be effective and appropriate for use in developing countries. Differences in noise sources, available finances and noise control technologies, cultural norms, climate, views concerning the role of the government, etc., make it likely that different approaches might be needed in developing countries for their noise policies to be effective. Thus, it recommends that an international consortium of scientists and engineers, government representatives, and key stakeholders be organized to address this important topic. The noise policy needs of developing countries require an awareness of their typical noise problems, along with appropriate, affordable, and technologically feasible solutions, and how these might be incorporated into emerging Global Noise Policy concepts. This paper presents a concept for a Strategic Approach to Environmental Noise Management in Developing Countries, developed by the Swedish Environmental Institute (SEI), to form a foundation for the proposed international consortium. The next step is to now formalize an international consortium to provide additional technical input, to encourage participation by international agencies, professional societies and stakeholders, to organize workshops and special sessions at acoustics congresses, and to promote the evolving SEI concept with the governments of developing countries.
Highlighting the career of Mack Breazeale.
Authors: Miller James G.
Published: March 2010

Mack Breazeale’s creative work was respected and recognized by professional organizations including the Acoustical Society of America, the Institute of Acoustics (Great Britain), and the IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society (UFFC), each of which honored him with the rank of Fellow. Breazeale served as the UFFC Distinguished Lecturer in 1987–1988, during which time he traveled extensively to deliver highly regarded presentations. In recognition of Breazeale’s many contributions to the IEEE UFFC, including his many-year participation in the Technical Program Committee that sets the theme for the Annual IEEE Ultrasonics Symposium, Breazeale was honored with the Achievement Award in 2008, the highest Society-wide award presented to a member in special recognition of outstanding contributions. I had the pleasure of highlighting Breazeale’s many contributions that led to this prestigious honor during the awards ceremony at the 2008 Ultrasonics Symposium in Beijing. When I wrote to Breazeale to express my congratulations on this award and to discuss how I might summarize his many achievements in a career spanning decades, Breazeale responded by saying, “The most important aspect of my career is the fact that I have served as Major Professor to 15 MS candidates and 16 doctoral candidates.”
Theoretical and experimental investigation of the backward beam displacement.
Authors: Declercq Nico F.
Published: March 2010

The discovery of a backward beam displacement of ultrasound interacting with a periodically corrugated surface, dates back from 1976, when Breazeale and Torbett reported it [Appl. Phys. Lett. 29, 456 (1976)]. Since 2002 new investigations have been undertaken partially motivated by Breazeales enthusiasm. An overview is presented of how the phenomenon was first discovered in 1976, how a theoretical explanation was found since 2002 [Declercq et al., Appl. Phys. Lett. 82, 2533 (2003); Declercq et al., J. Appl. Phys. 96, 6869–6877 (2004)] and what further verifications and discoveries have been made since then [Teklu et al., J. Appl. Phys. 97, 084904 1 (2005)]. The report also highlights new research showing the ubiquitous presence of the phenomenon and its importance for nondestructive applications [Herbison et al., J. Acoust. Soc. Am. In press].
Acoustic parametric oscillators: In the footsteps of Mack Breazeale.
Authors: Ostrovsky Lev A.
Published: March 2010

Parametric oscillators have been studied in physics since the 18th century. In acoustics, the effect of transformation of pump energy to a half-frequency subharmonic (or, more generally, to any lower-frequency signals) began to be studied in 1960s by Korpel and Adler and in the laboratory of Breazeale. They observed basic parametric effects such as half-frequency generation and generation of lower-frequency doublets. In early 1970s, our group in Russia began studies of acoustic parametric phenomena in dispersive systems (waveguide resonators), in which most of extra harmonics and subharmonics are suppressed so that generation at the desired frequencies occurs much more efficiently. Indeed, in these experiments the subharmonic mode was generated so intensively that it can even damp the pumping mode in resonance. Also the later experiments with “non-classical,” strongly nonlinear solid materials, such as ferroelectrics and metals, should be mentioned. The more recent works include parametric phenomena in bubbles; moreover, the group of Lauterborn in Germany has demonstrated that the period-doubling scenario of transition to chaos can be realized in cavitation noise. This presentation outlines a brief history of acoustic parametric oscillators and relevant effects in the context of pioneering works of Professor Mack Breazeale.
Close encounters of the distinguished kind.
Authors: Van Den Abeele Koen
Published: March 2010

Mack Breazeale entered my life at the very start of my research career in Kortrijk, Belgium. At the 20th anniversary of the university campus, he was co-organizer together with Oswald Leroy of the Physical Acoustics Meeting. I had the honor to edit and compile the book containing all contributed papers. Since that moment we have met each other regularly in Kortrijk or at an international meeting. Later he was a member of the jury at the defense of my doctoral thesis, and the same evening he managed to persuade my wife and me to come to NCPA for a year as a post-doc. We will always remember Ole-Miss and the parties at the gentle Breazeale family. Upon returning to Belgium I immediately got an email from Paul Johnson, triggered by Mack Braezeale, asking me to apply for a post-doc at Lanl. Thanks to Mack (and Paul), we had an unforgettable experience there. I consider it the birth of nonlinear acoustics and ultrasonics in Belgium. Oh, and by the way, we have performed some great science together in acousto-optics and nonlinear acoustics.
Frequency dependence of the ultrasonic parametric threshold amplitude for a fluid-filled cavity.
Authors: Teklu Alem A. , McPherson Michael A. , Breazeale Mack A. , Declercq Nico F.
Published: March 2010

The excitation of fractional harmonics in a liquid-filled cavity by ultrasonic waves was described previously as a parametric phenomenon [L. Adler and M. A. Breazeale, J. Acoust. Soc. Am. 48, 1077–1083 (1970)]. That is, by driving a transducer at one end of a fluid-filled cavity parallel to a rigid plane reflector at the other end, standing ultrasonic waves can be generated. Variations in the cavity length resulting from transducer motion lead to the generation of resonant frequencies lower than the drive frequency (known as fractional harmonics). The system was modeled by using a modified Mathieus equation whose solution resulted in the prediction of critical threshold drive amplitude for the excitation of parametric oscillation. The apparatus used by Adler and Breazeale was recently refined for accurate measurements of the threshold amplitude for parametric excitation at frequencies ranging from 2 to 7 MHz. The measurements showed that in this range the threshold amplitude increases with increasing drive frequency in apparent discrepancy with the results of Adler and Breazeale. Analysis of the theory indicates, however, that both past and current results lie in two different stability zones, and each is in agreement with the existing theory.
Optical Bragg imaging of acoustic fields after reflection.
Authors: McPherson Michael S. , Breazeale M. A. , Declercq Nico F. , Teklu Alem
Published: March 2010

If visible light is incident at the Bragg angle on an acoustic wave of the appropriate frequency, the light will undergo Bragg diffraction from the acoustic wavefronts in a manner analogous to the Bragg diffraction of x-rays in a crystalline lattice. If the acoustic beam has previously passed through an object before having light diffracted from it, the structure of that object will be imaged in the optical diffraction orders. In traditional Bragg imaging applications, the sound is first transmitted through the object. In this presentation a new reflection-based method of Bragg imaging (where light is reflected from rather than transmitted through the object) will be discussed. This technique is capable of imaging structures at or near the surface of the object and may have potential industrial and biomedical NDT applications.
Ultrasonic imaging and characterization of objects submerged in highly attenuating fluids.
Authors: Raeymaekers Bart , Pantea Cristian , Osterhoudt Curtis F. , Sinha Dipen N.
Published: March 2010

An ultrasonic scanning tool to image objects with high-spatial resolution submerged in highly attenuating fluids is described. The attenuation coefficient of the fluids used range over two orders of magnitude. For deeper penetration into the attenuating fluids, a parametric array with a difference frequency between 200 and 500 kHz was used. The primary frequencies that generated this difference frequency varied between 2 and 8 MHz. This parametric array provides a collimated beam for imaging. Both simple tone burst and frequency chirp signals were used for the measurement. Using this apparatus, the quality and accuracy of the image as a function of frequency, fluid attenuation coefficient, and fluid type (clear and suspensions) were investigated. It was found that imaging was possible over a wide range of attenuating coefficients and fluid types.
Multipole expansion for nonlinear acoustic scattering at the difference-frequency.
Authors: Silva Glauber T.
Published: March 2010

In this work, the scattering at the difference-frequency (DF) of two finite-amplitude plane waves by a rigid sphere in a fluid is studied. The DF-scattering is present in some acoustic imaging methods such as vibro-acoustography. This has motivated us to perform this study. We obtain for the first time the multipole expansion for the DF-scattered pressure in the farfield. Theory is based on the successive approximation and the Green’s function methods. From the multipole expansion, we derive some quantities such as scattering cross-section and the total DF-scattered power. Furthermore, we show that the DF-scattered pressure increases with the observation distance r like r ln r, while it varies almost linearly with the difference-frequency. Despite the amplification, we demonstrate that the DF-scattered pressure does not grow indefinitely because of absorption in the fluid. The theory is applied to the scattering in the Rayleigh limit (scatterer much smaller than the incident wavelengths). Only monopole and dipole moments are relevant in this limit. In conclusion, we believe that this theory can help to understand better the nonlinear scattering in acoustics.
A new form of Gaussian beam function as the base function for generic wave field analysis.
Authors: Wen J. J.
Published: March 2010

Wave propagations are best described by three major approaches: the spherical wave approach represented by Rayleigh integral, the planar wave approach represented by spatial Fourier analysis, and the Gaussian beam approach. Spherical and planar wave approaches, both in form of double integrals, are analytically inconvenient and computationally expensive. In contrast, the Gaussian beam approach, with huge advantages in analytical operability and computational efficiency, has been quietly but firmly winning popularity. Dr. Breazeale’s article: A diffraction beam field expressed as the superposition of Gaussian beams, co-authored with Wen, is not only a most representative work for Gaussian beam approach but also a most cited academic work in sound field analysis and computation. As a memory of Dr. Breazeale’s pioneer role in the raise of Gaussian beam method, this article presents a new enhancement to the existing Gaussian beam method. A modified form of Gaussian beam function introduced as the base function set for wave field analysis greatly reduces the error rooted from the parabolic approximation, the number of Gaussian beams needed, and the run-time computation burden. The process for calculating the beam coefficients and beam parameters is also greatly simplified.
Modeling of the auditory periphery for hearing aid evaluation and design.
Authors: Bruce Ian C.
Published: March 2010

Amplification schemes and gain prescriptions for hearing aids have thus far been developed and evaluated based on perceptual criteria such as speech intelligibility, sound comfort, and loudness equalization. Finding amplification strategies that simultaneously optimize all of these perceptual metrics has proven difficult, despite decades of research. Furthermore, novel amplification schemes based on rough conceptual models of the normal and impaired auditory physiology have often proven to be unsuccessful. In this talk, I will describe studies directly employing physiologically accurate computational models to evaluate more rigorously what hearing aids are likely doing to the neural representation of speech. The results of these investigations indicate that (i) a physiologically accurate auditory-nerve (AN) model can predict optimal linear and nonlinear amplification gains, (ii) optimal gains are dependent on both the spike-timing and mean-rate representations of speech in the AN, (iii) the proportion of outer hair cell and inner hair cell dysfunction in an impaired ear can affect optimal gains, and (iv) slow wide dynamic range compression (WDRC) or automatic gain control better restores the neural representation of speech than does fast WDRC.
Auditory models of suprathreshold distortion in persons with sensorineural hearing loss.
Authors: Grant Ken W. , Summers Van , Bernstein Joshua G. W. , Phatak Sandeep A. , Makashay Matthew J. , Grassi Elena , Mehraei Golbarg
Published: March 2010

Hearing technology has advanced to where it is now reasonable to ask whether signal processing algorithms can be developed to compensate for an individual’s hearing loss, thus allowing them to hear functionally in a manner similar to persons with normal hearing. Clinically, the pure-tone audiogram is the primary tool used to represent the patient’s hearing status. However, it has been well established, experimentally and theoretically, that the audiogram cannot reflect fully all aspects of the hearing loss, most notably that part which pertains to suprathreshold distortion. Much has been written about the distortion component of sensorineural hearing loss, yet there is little agreement on estimating its importance to speech recognition, nor much consensus on which hearing factors (e.g., spectral and/or temporal resolution) most accurately represent the distortion. Recent attempts to use biologically inspired models of auditory processing to represent a patient’s internal auditory experiences have shown promise as a way to understand the role that suprathreshold distortions might play in speech recognition. This talk reviews recent work to develop auditory models of {\it individual} hearing-impaired listeners to predict differences in the perception of speech and non-speech signals not readily explained by audiometric thresholds. [Work supported by the Oticon Foundation.]
Real-world application of auditory models to hearing instrument design.
Authors: Launer Stefan
Published: March 2010

Auditory models provide a powerful tool for designing and developing signal processing algorithms of modern digital hearing instruments and can even be integrated directly into these algorithms. Models for loudness perception have been applied directly in hearing instrument algorithms with two applications: to control the gain of a hearing instrument and to limit the maximum output power of a hearing instrument as a “loudness limiter.” Another example is the application of a very simple model in a hearing instrument to help resolve localization problems due to the microphone position in BTE hearing instruments, resulting in reduced front/back confusions. Examples of the application of models to the development and analysis of hearing instrument performance in real-life environments include the use of auditory scene analysis models to better understand human sound source classification and to improve the performance of automatic control systems in hearing instruments. A last example is the application of models describing human localization performance under realistic acoustic environments to understand the impact that hearing instrument signal processing has on the ability of hearing impaired people to localize sounds with hearing instruments. This talk will explore and discuss the potential of these different approaches for hearing instrument technology.
Prediction of binaural speech intelligibility when using non-linear hearing aids.
Authors: Ellaham Nicolas N. , Giguère Christian , Gueaieb Wail
Published: March 2010

A new objective measurement system is proposed to predict speech intelligibility in binaural listening conditions for use with hearing aids. Digital processing inside a hearing aid often involves non-linear operations such as clipping, compression, and noise reduction algorithms. Standard objective measures such as the articulation index, the speech intelligibility index (SII), and the speech transmission index have been developed for monaural listening. Binaural extensions of these measures have been proposed in the literature, essentially consisting of a binaural pre-processing stage followed by monaural intelligibility prediction using the better ear or the binaurally enhanced signal. In this work, a three-stage non-linear extension of the binaural SII approach is introduced consisting of (1) a stage to deal with non-linear processing based on a simple signal separation scheme to recover estimates of speech and noise signals at the output of hearing aids [Hagerman and Olofsson, Acust. Acta Acust. 90, 356 (2004)], (2) a binaural processing stage using the equalization-cancellation model [Beutelmann and Brand, J. Acoust. Soc. Am. 120, 331 (2006)], and (3) a stage for intelligibility prediction using the monaural SII [ANSI-S3.5, 1997 (R2007)]. Details of the new procedure will be discussed. [Research supported by NSERC (Canada).]
Predict the intelligibility of individual consonants in noise for hearing-impaired listeners.
Authors: Li Feipeng , Han Woojae , Allen Jont
Published: March 2010

The performance of hearing-impaired (HI) listeners to understand speech often deteriorates drastically in cocktail-party environments. To understand why a particular HI listener can hear certain sounds and not the others, it is critical that we take the prior knowledge about speech cues into consideration and investigate the effect of different types of cochlear hearing loss on speech perception. In the last 2 years we have tested over 50 hearing-impaired ears on consonant identification in noise. To evaluate the impact of shift of hearing threshold on the intelligibility of individual consonants in masking noise, a consonant intelligibility index (CII) is developed to predict the perceptual scores of individual consonants. Results of preliminary study indicate that CII makes an accurate prediction for flat mild-to-moderate hearing loss, but fails for the cases of cochlear dead region and extremely unbalanced (e.g., severe high-frequency) loss, suggesting that audibility alone does not fully account for the hard of speech perception in noise for many HI listeners.
Evaluating hearing aid processing with an auditory model of modulation sensitivity.
Authors: Gallun Frederick J. , Souza Pamela E. , Hoover Eric
Published: March 2010

Amplitude modulation is one of the fundamental aspects of sound to which humans are sensitive. A number of auditory models based on this sensitivity have been successful at explaining other aspects of human behavior, both in the domains of psychoacoustics and speech perception. A constrained-parameter model of perceptual similarity based on modulation sensitivity (the spectral correlation index) has recently been developed for use in the prediction of perceptual confusions at the phonemic level [Gallun and Souza (2008)]. The relatively small parameter set of the model allows for efficient adaptation of the basic architecture to novel problems. With a single change in the range of one parameter, this model can be used for the evaluation of hearing aid processing by predicting the confusions that will accompany various choices of amplification parameters. This approach demonstrates the value of evaluating signal processing strategies in hearing aids through changes in perceptual similarity as predicted by auditory models. [Work supported by NIH NIDCD R01 DC0060014 and VA RRD CDA-2 C4963W.]
Derivation of a Ritz series modeling technique for acoustic cavity-structural systems based on a constrained Hamilton’s principle.
Authors: Ginsberg Jerry H.
Published: March 2010

Hamilton’s principle for dynamic systems is adapted to describe the fully coupled interaction of a confined acoustical domain and a bounding elastic system in cases of imposed velocity or pressure fluctuations on the surface or forced excitation of the structure. A key part of the modified principle is the treatment of the surface traction as a Lagrange multiplier function that enforces continuity conditions at the fluid-solid interface. The structural displacement, fluid velocity potential, and traction are represented by Ritz series, where the usage of the velocity potential as the state variable for the fluid assures that the flow is irrotational. Designation of the coefficients of the potential function series as generalized velocities leads to corresponding series representations of the particle velocity, displacement, and pressure in the fluid, which in turn leads to descriptions of the mechanical energies and virtual work. Application of the calculus of variations to Hamilton’s principle yields linear differential-algebraic equations whose form is identical to those governing mechanical systems that are subject to nonholonomic kinematic constraints. Criteria for selection of basis functions for the various Ritz series are illustrated with an example of a rectangular cavity bounded on one side by an elastic plate and conditions that change discontinuously on other sides.