bluuebunny/crossref_metadata_2025 huggingface dataset:
Primary Energy Saving Potential of Solar Cooling in Residential Buildings
Authors: Lo´pez Jose´ Uren˜a , Klesse Andreas , Wagner Hermann-J.
Published: March 2012

Cooling in residential buildings becomes more important due to the rising insulation requirements and the increasing human comfort. Therefore, systems that provide heating as well as cooling with a low primary energy consumption will be in future more preferred than conventional single-unit systems. Solar thermal installations can here provide in addition to the domestic hot water and heating demand a significant contribution to the cooling requirement in residential buildings. In this study, low-energy residential buildings with different solar heating and cooling systems are analyzed concerning their primary energy consumption. To cover a large range of different weather conditions, two locations (Madrid and Wu¨rzburg) with different solar energy supply are considered. Further, a conventional solar heating supply system including one or more typical room air-conditioners is as reference system selected. The different systems are modeled by the system simulation platform TRNSYS. In a first step, the question is addressed of whether a solar thermal system with standard dimensioning, taking the domestic hot water and heating demand into account, is sufficient to meet the cooling requirements. To cover the cooling demands, a small-scale thermally driven absorption chiller has been selected. In a next step, the studied systems are compared in terms of primary energy saving as a function of the solar cooling fraction. The simulation results have shown that regions with a high solar energy supply do not take advantage of solar thermal cooling, due to the higher cooling demand. On average, 70% of the cooling demands can be covered by a standard dimensioned solar thermal system. At the same time, a primary energy saving up to 90%, compared to currently installed room air-conditioning units can be achieved.
A Wind Power Forecasting System to Optimize Power Integration
Authors: Haupt Sue Ellen , Wiener Gerry , Liu Yubao , Myers Bill , Sun Juanzhen , Johnson David , Mahoney William
Published: March 2012

The National Center for Atmospheric Research (NCAR) has developed a wind prediction system for Xcel Energy, the power company with the largest wind capacity in the United States. The wind power forecasting system includes advanced modeling capabilities, data assimilation, nowcasting, and statistical post-processing technologies. The system ingests both external model data and observations. NCAR produces a deterministic mesoscale wind forecast of hub height winds on a very fine resolution grid using the Weather Research and Forecasting (WRF) model, run using the Real Time Four Dimensional Data Assimilation (RTFDDA) system. In addition, a 30 member ensemble system is run to both improve forecast accuracy and provide an indication of forecast uncertainty. The deterministic and ensemble model output plus data from various global and regional models are ingested by NCAR’s Dynamic, Integrated, Forecast System (DICast®), a statistical learning algorithm. DICast® produces forecasts of wind speed for each wind turbine. These wind forecasts are then fed into a power conversion algorithm that has been empirically derived for each Xcel power connection node. In addition, a ramp forecasting technology fine-tunes the capability to accurately predict the time, magnitude, and duration of a ramping event. This basic system has consistently improved Xcel’s ability to optimize the economics of incorporating wind energy into their power system.
Optimal Power Generation Unit Sizing for Combined Heating and Power Systems With Uncertain Loads and Fuel/Electricity Prices
Authors: Smith Aaron , Yun Kyungtae , Thomas Robert , Luck Rogelio
Published: March 2012

An optimal sizing method is developed in this work based on an analytical scheme for determining optimal operation decisions. Using the analytic optimal operation scheme allows for a more thorough optimal sizing method because of the minimal computational effort required as compared to mixed integer programming approaches. For example, an optimal sizing method based on this approach can more feasibly consider several years of weather data and the range of likely fuel/electricity costs for the term of operation of the PGU. The optimal sizing method in this work takes advantage of this efficient optimal operation scheme and provides a robust optimal solution with respect to weather and fuel/electricity cost uncertainty. A case study of a medium sized office building is carried out by testing the algorithm for a range of 20 commercially available diesel engine PGUs.
Energy Storage and Waste Heat Recovery: A Synergistic Effect Benefiting Renewable Energy
Authors: Peterson Richard B. , Ingram-Goble Robbie , Harada Kevin J. , Wang Hailei
Published: March 2012

In order for renewable energy to displace 20% or more of the conventional power generating base without depending on significant hot spinning reserves, reliable and cost effective energy storage will be needed at the utility scale. Developing and deploying practical energy storage at this level is a major challenge and no single technology appears to have a dominant position. Storing electrical energy by way of thermal storage at moderate-to-low temperatures has not received much attention in the past. In fact, the conventional thinking is that heat pump/heat engine mediated energy storage is too inefficient (round trip efficiency of 30% or lower) to be practical. However, an innovative and efficient storage approach is proposed in this paper by incorporating sensible heat storage in a Rankine-type heat pump/heat engine cycle to increase the round trip efficiency. Furthermore, by using a source of waste (or otherwise low-grade) heat, round trip efficiencies can be enhanced further. Currently, there appears to be no significant linkage between waste heat recovery and grid-level energy storage, although the market opportunity for each is considerable. Using the thermal approach described here, a system can be created that uses very low-grade heat in the range between 50 to 70 °C. Furthermore, conventional technology can be used to implement the system where no extreme conditions are present anywhere in the cycle. Hence, it is thought to have advantages over other energy storage concepts being developed.
A Correlation Between Thermal Efficiency and Biological Network Cyclicity
Authors: Layton Astrid , Reap John , Bras Bert
Published: March 2012

This article investigates a correlation between the thermal efficiency of ideal power cycles and a structural measure of the degree of interactions in networks known as cyclicity. Efficient design of networks that reuse materials and energy motivates the work. Corporate “take-back” plans, multi-company industrial symbioses and public recycling programs recover products, components and materials using partially closed loop networks. As resources become scarcer and more expensive, the prevalence of these networks is likely to increase, and the importance of designing efficient networks grows. Multiple structural and material flow metrics that one might use to aid network design exist. One novel approach to network design involves patterning industrial networks on ecological ones. This latter idea lays at the heart of industrial symbiosis efforts. However, neither the materials metric approach nor the bioinspired ecological patterns approach stands upon a strong theoretical base. As a test of both approaches, this work uses a structural cycling metric, cyclicity, previously used to quantify patterns in ecosystems, to quantify energy flow in ideal thermodynamic cycles. The objective is not to learn about thermodynamic cycles. Rather, the intent of the comparison is to reveal whether trends in network structure as given by cyclicity relate to the fundamental laws of thermodynamics. Familiar ideal power cycles are first redrawn as energy flow networks. Cyclicity values are then calculated for these networks. A comparison shows that thermal efficiency increases with increasing cyclicity for fixed source and sink temperatures within a cycle. This results from the practice of adding cyclical energy paths (i.e. a regenerator) to an ideal power cycle, to increase thermal efficiency. The remainder of the article comments on the potential ramifications of this finding for the design of cycling industrial networks.
A Numerical Model for Thermal Performance of an Unglazed Transpired Solar Collector
Authors: Moaveni Saeed , Tebbe Patrick A. , Schwartzkopf Louis , Dobmeier Joseph , Gehrke Joseph , Simones Matthew
Published: March 2012

In this paper, we will present a numerical model for estimating the thermal performance of unglazed transpired solar collectors located on the Breck School campus in Minneapolis, Minnesota. The solar collectors are installed adjacent to the southeast facing wall of a field house. The collectors preheat the intake air before entering the primary heating unit. The solar collector consists of 8 separate panels (absorber plates). Four fans are connected to the plenum that is created by the absorber plates and the adjoining field house wall. All fresh air for the field house is provided by the solar collectors before being filtered and heated by four, independent two stage natural gas fired heaters. Moreover, the following data were collected onsite using a data acquisition system: indoor field house space temperature, ambient air temperature, wind speed, wind direction, the plenum exit air temperature, the absorber plate temperature, and the air temperatures inside the plenum. The energy balance equations for the collector, the adjacent building wall, and the plenum are formulated. The numerical model is used to predict the air temperature rise inside the plenum, recaptured heat loss from the adjoining building wall, energy savings, and the efficiency of the collectors. The results of the numerical model are then compared to the results obtained from the onsite measurements; which are in good agreement. The model presented in this paper is simple yet accurate enough for architects and engineers to use it with ease to predict the thermal performance of a collector.
Evaluating Supply Chain Energy Use in a Smart Grid Paradigm
Authors: Shah Amip J. , Corrigan Kiara
Published: March 2012

A key paradigm shift resulting from the intersection of the information technology (IT) and utility sectors is the availability of real-time data regarding energy use across different industries. Historically, ascertaining the energy costs across the value chain of a given product or service was a laborious and expensive task, requiring many months of data collection; several proxies or approximations for cases where measured data might not be cost-effectively available; and even then, the resulting energy footprint could have significant uncertainty based on time-of-measurement, geographic diversity of manufacturing sites, etc. As dynamic energy pricing begins to take hold and environmental externalities begin to be priced into existing cost structures, the ability to optimize a given value chain for minimal energy use becomes increasingly attractive. In this paper, we discuss an approach for leveraging dynamically available data alongside historical n-tier supply chain models to avail the ability for such optimization. The approach is illustrated for the case study of a computer manufacturer, where we find that metering electricity use at a small subset of sites can allow for a reasonable estimate of the total energy use across the supply chain.
Smart Grid in California: The Value of Energy Storage and Permanent Load Shifting
Authors: Sreedharan Priya , Miller David
Published: March 2012

Smart grid has become linked with topics of energy efficiency, renewables integration and climate policy. A smarter grid is one that utilizes communications and information systems to achieve more flexible grid operations. Energy storage and more broadly, load shifting, is one mechanism for achieving flexible grid operations. Unlike demand response, permanent load shifting moves energy on a regular basis, from peak to off-peak. Technologies that can deliver load shifting include thermal storage, electrical and mechanical storage and process shifting. This paper highlights findings from a recent study, mandated by a California Public Utilities Commission order, of permanent load shifting (PLS) opportunities located at customer sites in California. We developed a cost-effectiveness framework to estimate the costs and benefits of PLS technologies, demonstrated the framework with an analysis of PLS systems, and evaluated the market for PLS, including an assessment of challenges to expanding PLS. The cost-effectiveness analysis included a technology-neutral scenario analysis and an evaluation of technology-specific cases. Grid-level benefits of load shifting range from approximately $500–$2500/peak kW. Among the case studies, some approaches, such as refrigerated warehouse precooling, are cost-effective for both the utility and the consumer, while others, such as flow batteries, are not yet cost-effective and can be viewed as emerging technologies. Due to the wide range of technology costs and performance, these results are unsurprising. Still, PLS technologies can be one tool that can help set the stage for integrating large amounts of renewables in the future, a road California is paving.
A Study on the Different Components of Solar Radiation in Order to Calculate the Optimum Solar Angles and the Gain of Solar Energy Using Genetic Algorithm
Authors: Talebizadeh P. , Mehrabian M. A. , Abdolzadeh M.
Published: March 2012

In this paper, the genetic algorithm is applied to calculate the optimum slope and surface azimuth angles for receiving maximum solar radiation in an area of Iran. Different components of solar radiation are employed in order to calculate the solar optimum angles. At first, the optimum angels are calculated in different days, months, seasons and the whole year and the energy gain is calculated. Then, this process is redone with considering different component of solar radiation. These conditions are direct, direct and ground reflect, direct and diffuse, and all together. The results showed that maximum solar energy in different days of a year is received at different slope angels; however, the optimum azimuth angle is zero for receiving maximum solar energy. In addition, adjusting the collector at the daily optimum slope angle can only save energy very little compared with the case at the monthly optimum slope angle. Furthermore, the results of analyzing different components of solar radiation show that the optimum slope angles are mostly related to the direct radiation, however, the gain of energy is considerably different. It is worth mentioning that genetic algorithm is more effective when the independent parameters are numerous and in this case, the optimum angles are easily determined, however, the computation time is reduced.
Behavior and Testing Performance of a Gas Tankless Water Heater
Authors: Grant Peter , Burch Jay , Krarti Moncef
Published: March 2012

Tankless water heaters present an opportunity to dramatically reduce water heating energy use. These impacts are possible because of their dramatic reduction of environmental losses through lower heat transfer areas and not keeping the heat exchanger at operating temperature between draws. The potential for energy savings has caused a lot of interest in the scientific community. However, the scientific community has not yet gained an understanding of these devices and several questions regarding their behavior remain. The areas of uncertainty include the following: 1) how these heaters behave around the minimum flow rate, 2) how well they adapt to changes in water flow rate, 3) how they behave in situations with preheated water (i.e. when used with solar water heaters) and 4) whether or not draw characteristics impact the steady state efficiency. Tests have been performed on a Rinnai R75Lsi to determine the answers to these questions for a specific heater. Tests were performed with 1) gradually changing flow rate to identify the minimum flow rate, 2) rapidly adjusting the flow rate to observe how the heater responded to suddenly changing draws, 3) temperature-flow combinations such that the minimum heat rate exceeded the required heat rate, and 4) draws under steady state conditions with varying flow rates and set temperatures. Minimum flow rate results indicate that the heater will not fire unless the flow rate surpasses 2.8 L/min and will cease firing if the flow rate decreases below 2.15 L/min while the owners manual states that the minimum flow rate is 2.3 L/min. Rapidly changing flow rate results indicate that there can be temperature fluctuations up to 9 °C and unsteady operation for up to 1 minute depending on the magnitude of the flow rate change. Tests with preheated inlet water showed that the heater uses feedback controls to avoid unstable operation at low heat rates. Steady state efficiency tests did not identify any variables which impact efficiency. Future work should include testing additional units to determine how other heaters, particularly those not manufactured by Rinnai, behave in similar situations.
Real-Time Fault Detection for Solar Hot Water Systems Using Adaptive Resonance Theory Neural Networks
Authors: He Hongbo , Menicucci David , Caudell Thomas , Mammoli Andrea
Published: March 2012

The objective of this work is to design and test a real-time solar hot water (SHW) fault detection system that can reliably detect anticipated and unforeseen faults using only those sensors that are normally required to operate a system. The fault detection system includes a data acquisition module and a hierarchical Adaptive Resonance Theory (ART)-based neural network fault detection module. The data acquisition system logs the collector fin temperature and the water tank heat exchanger outlet temperature. The detection module uses a hierarchical ART neural network that can detect faults and classify them by level of severity. The hierarchical ART neural network is trained with information collected from a verified solar hot water system TRNSYS (Transient Systems Simulation program) model. The TRNSYS model uses weather data for Albuquerque, NM, extracted from the National Solar Radiation Data Base (NSRDB), for the 5-year period 2000–2004. The neural network is trained under different weather conditions. The simulation and experimental results show that the trained fault detection system has the capability to detect expected faults including pump faults, impeller degradation, thermosyphon and potential unexpected ones. Simulated and experimental test results are presented.
Thermal Properties of Green Roof Media During Plant Establishment and Growth
Authors: Frey Geoffrey , Qu Ming , Banks Margaret K. , Schwab Arthur , Cherkauer Keith A.
Published: March 2012

In order to ascertain the efficiency benefits of green roofs for buildings, a thermodynamic model must be created for the green roof. This work focuses on the thermal properties (conductivity and specific heat capacity) of several media and how they are affected by root growth within them. The results of this research will be used in creating more accurate thermodynamic green roof models. For this experiment, three repetitions of 16 different planting/media combinations were used to monitor the changing thermal properties of the media with environment changes; a focus being on root growth. This experiment shows that the conductance is probably affected by root propagation.
Synchronization of a Single-Phase Photovoltaic Generator With the Low-Voltage Utility Grid
Authors: Anani Nader A. , Al-Kharji Omar A. , Ponnapalli Prasad V. , Al-Araji Saleh R. , Al-Qutayri Mahmoud A.
Published: March 2012

The increased generation of electrical energy from renewable sources and its integration into the low voltage grid, has necessitated regulations governing the connection of renewable energy generators to the grid. This was deemed necessary to preserve the integrity and the correct operation of the grid. This paper presents a new architecture of a hybrid phase lock loop circuit topology for synchronizing a single-phase inverter fed from a renewable energy source such as a photovoltaic (PV) generator to the low voltage grid. The system uses a digital phase lock loop (DPLL) architecture, which is based on the arctan phase detector, driving a phase lock loop (PLL) to synchronize a PV generator with the grid voltage. The proposed system has been tested by simulation using Simulink/Matlab. The test results demonstrate the ability of the system to synchronize a PV inverter with the grid and to re-establish synchronization following a sudden perturbation in the grid voltage such as a single or a multi-step change in phase.
Developments in Light Vehicle Life Cycle Analysis With Application to Electric Vehicles
Authors: Curtiss Peter S. , Kreider Jan F.
Published: March 2012

An LCA tool first reported on at the ASME ES conference in 2007 has been expanded and improved as follows: • More than 400 production vehicles from all over the world are now in the data base. • Conventional and renewable liquid and gas fuels are included. • Electric vehicles (EVs) and plug in hybrid electric vehicles (PHEVs) are included along with hybrid electric vehicles (HEVs) and conventional internal combustion engine vehicles. • The tool is now web-based. The LCA tool includes both fuel and vehicle life cycle coefficients in its data base. To illustrate the LCA ranking of vehicles using electricity (EVs, PHEVs, and HEVs) vs. conventional vehicles this paper will report on greenhouse gas emissions, total life cycle energy use along with NOx, SOx and mercury emissions. It will be shown, for example, that EVs are not the cleanest solution contrary to claims of various commentators in the popular press and of EV enthusiasts who do not take the entire life cycle into account.
High power impulse magnetron sputtering discharge
Authors: Gudmundsson J. T. , Brenning N. , Lundin D. , Helmersson U.
Published: March 2012

The high power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulses at low duty cycle and low repetition frequency while keeping the average power about 2 orders of magnitude lower than the peak power. This results in a high plasma density, and high ionization fraction of the sputtered vapor, which allows better control of the film growth by controlling the energy and direction of the deposition species. This is a significant advantage over conventional dc magnetron sputtering where the sputtered vapor consists mainly of neutral species. The HiPIMS discharge is now an established ionized physical vapor deposition technique, which is easily scalable and has been successfully introduced into various industrial applications. The authors give an overview of the development of the HiPIMS discharge, and the underlying mechanisms that dictate the discharge properties. First, an introduction to the magnetron sputtering discharge and its various configurations and modifications is given. Then the development and properties of the high power pulsed power supply are discussed, followed by an overview of the measured plasma parameters in the HiPIMS discharge, the electron energy and density, the ion energy, ion flux and plasma composition, and a discussion on the deposition rate. Finally, some of the models that have been developed to gain understanding of the discharge processes are reviewed, including the phenomenological material pathway model, and the ionization region model.
Effect of slice thickness on detectability in breast CT using a prewhitened matched filter and simulated mass lesions
Authors: Packard Nathan J. , Abbey Craig K. , Yang Kai , Boone John M.
Published: March 2012

Purpose:

Dedicated breast CT (bCT) is an emerging technology with the potential to improve the detection of breast cancer in screening and diagnostic capacities. Typically, the 3D volume reconstructed from the scanner is displayed as sectional images. The purpose of this study was to evaluate the effect of section thickness on the detectability of simulated masses using a prewhitened matched filter (PWMF) as a model observer.

Methods:

A breast CT scanner has been designed and fabricated in the authors' laboratory with more than 200 women imaged in IRB‐approved phase I and phase II trials to date. Of these, 151 bilateral data sets were selected on the basis of low artifact content, sufficient breast coverage, and excluding cases with breast implants. BIRADS breast density ratings were available for 144 of these patients. Spherical mass lesions of diameter 1, 2, 3, 5, 11, and 15 mm were mathematically generated and embedded at random locations within the parenchymal region of each bCT volume. Microcalcifications were not simulated in this study. For each viewing plane (sagittal, axial, and coronal) and section thickness (ranging from 0.3 to 44 mm), section images of the breast parenchyma containing the lesion were generated from the reconstructed bCT data sets by averaging voxels over the length of the section. Using signal known exactly (SKE) model observer methodology, receiver operating characteristic (ROC) curve analysis was performed on each generated projected image using a PWMF based model observer. ROC curves were generated for each breast data set, and the area under the ROC curve (AUC) was evaluated as well as the sensitivity at 95% specificity.

Results:

For all lesion sizes, performance rises modestly to a peak before falling off substantially as section thickness increases over the range of the study. We find that the optimal section thickness tracks the size of the lesion to be detected linearly with a small positive offset and slopes ranging from 0.27 to 0.44. No significant differences were observed between left and right breasts. Performance measures are negatively correlated with measures of breast density, with an average correlation coefficient of −0.48 for the BIRADS breast density score and −0.81 for the proportion of glandular tissue in the breast interior.

Conclusions:

This study shows quantitatively how PWMF detection performance of a known lesion size is influenced by section thickness in dedicated breast CT. While the optimal section thickness is tuned to the size of the lesion being detected, overall performance is more robust for thin section images compared to thicker images.
Green’s functions for a volume source in an elastic half-space
Authors: Zabolotskaya Evgenia A. , Ilinskii Yurii A. , Hay Todd A. , Hamilton Mark F.
Published: March 2012

Green’s functions are derived for elastic waves generated by a volume source in a homogeneous isotropic half-space. The context is sources at shallow burial depths, for which surface (Rayleigh) and bulk waves, both longitudinal and transverse, can be generated with comparable magnitudes. Two approaches are followed. First, the Green’s function is expanded with respect to eigenmodes that correspond to Rayleigh waves. While bulk waves are thus ignored, this approximation is valid on the surface far from the source, where the Rayleigh wave modes dominate. The second approach employs an angular spectrum that accounts for the bulk waves and yields a solution that may be separated into two terms. One is associated with bulk waves, the other with Rayleigh waves. The latter is proved to be identical to the Green’s function obtained following the first approach. The Green’s function obtained via angular spectrum decomposition is analyzed numerically in the time domain for different burial depths and distances to the receiver, and for parameters relevant to seismo-acoustic detection of land mines and other buried objects.
Analysis of unidirectional broadband piezoelectric spherical shell transducers for underwater acoustics
Authors: Aronov Boris , Brown David A. , Bachand Corey L. , Yan Xiang
Published: March 2012

This paper presents an analytical investigation and experimental verification of the properties of unidirectional broadband piezoelectric acoustic transducers utilizing axisymmetric vibrations of both complete and incomplete spherical piezoelectric shells and is a continuation of a previous paper that presented the electromechanical modal analysis part of the problem [J. Acoust. Soc. Am. 130(2), 753–763 (2011)]. The analysis covers the treatment of the acoustic radiation and reception problem by including analysis of the acoustic impedances and diffraction coefficients as a function of geometry and modal excitation as well as providing specific design examples including multimode spherical acoustic transducers with conformal baffles, and transducers made of incomplete shells (e.g., hemispheres and caps) with free circumferential boundary conditions. The energy method is used to obtain equivalent parameters for a multi-contour electromechanical circuit representation of the transducer and to calculate the transducer performance characteristic as sound projectors and as receivers. Experimental results are obtained on representative piezoceramic transducer prototypes and are in good agreement with the analytical results.
Demonstration comparing sound wave attenuation inside pipes containing bubbly water and water droplet fog
Authors: Leighton Timothy G. , Jiang Jian , Baik Kyungmin
Published: March 2012

This paper describes a demonstration and explanation of sound absorption in water due to bubbles, and in air due to a fog of water droplets. It is suitable for 10–12 year olds, but the paper indicates where further exploration of the simplifications in the explanations provided for that age range would allow the demonstration to be used for undergraduate and Masters-level teaching. Applications to submarines, the space shuttle, and neutron generators are described. The demonstration is designed for transportation in a family-sized car.
Creating an active-learning environment in an introductory acoustics course
Authors: Neilsen Tracianne B. , Strong William J. , Anderson Brian E. , Gee Kent L. , Sommerfeldt Scott D. , Leishman Timothy W.
Published: March 2012

Research in physics education has indicated that the traditional lecture-style class is not the most efficient way to teach introductory physical science courses at the university level. Current best teaching practices focus on creating an active-learning environment and emphasize the students’ role in the learning process. Several of the recommended techniques have recently been applied to Brigham Young University’s introductory acoustics course, which has been taught for more than 40 years. Adjustments have been built on a foundation of establishing student-based learning outcomes and attempting to align these objectives with assessments and course activities. Improvements have been made to nearly every aspect of the course including use of class time, assessment materials, and time the students spend out of the classroom. A description of the progress made in improving the course offers suggestions for those seeking to modernize or create a similar course at their institution. In addition, many of the principles can be similarly applied to acoustics education at other academic levels.
The song of the singing rod
Authors: Anderson Brian E. , Peterson Wayne D.
Published: March 2012

This paper discusses basic and advanced aspects of the sound radiated by the singing rod demonstration commonly used in physics courses to depict an example of longitudinal waves. Various methods of exciting these rods are discussed along with the issues associated with each method. Analysis of the sound radiated by various rods with small-signal and large-signal excitations is presented for four different rods. The small-signal sound radiation consists of a fundamental frequency and odd harmonics (each corresponding to a longitudinal mode) when the rod is held at its midpoint. Large-signal sound radiation is highly dependent on the rod’s geometry. The large-signal sound can possess strong even harmonics and/or beating tones resulting from modal coupling of transverse bending modes and either subharmonic longitudinal modes or torsional modes. A detailed analysis of the sound radiation from a singing rod can provide excellent laboratory exercises or classroom demonstrations for advanced undergraduate or graduate level acoustics courses whose scope includes resonances of a bar.
Auditory brainstem responses to chirps delivered by different insert earphones
Authors: Elberling Claus , Kristensen Sinnet G. B. , Don Manuel
Published: March 2012

The frequency response and sensitivity of the ER-3A and ER-2 insert earphones are measured in the occluded-ear simulator using three ear canal extensions. Compared to the other two extensions, the DB 0370 (Brüel & Kjær), which is recommended by the international standards, introduces a significant resonance peak around 4500 Hz. The ER-3A has an amplitude response like a band-pass filter (1400 Hz, 6 dB/octave – 4000 Hz, −36 dB/octave), and a group delay with “ripples” of up to ±0.5 ms, while the ER-2 has an amplitude response, and a group delay which are flat and smooth up to above 10000 Hz. Both earphones are used to record auditory brainstem responses, ABRs, from 22 normal-hearing ears in response to two chirps and a click at levels from 20 to 80 dB nHL. While the click-ABRs are slightly larger for ER-2 than for ER-3A, the chirp-ABRs are much larger for ER-2 than for ER-3A at levels below 60 dB nHL. With a simulated amplitude response of the ER-3A and the smooth group delay of the ER-2 it is shown that the increased chirp-ABR amplitude with the ER-2 is caused by its broader amplitude response and not by its smoother group delay.
The use of extra-terrestrial oceans to test ocean acoustics students
Authors: Leighton T. G.
Published: March 2012

The existence of extra-terrestrial oceans offers the opportunities to set examination questions for which students in underwater acoustics do not already know the answers. The limited set of scenarios in Earth’s oceans that can be presented to students as tractable examination questions means that, rather than properly assessing the individual scenario, students can rely on knowledge from previous examples in assessing, for example, which terms in equations are large and small, and what numerical values the answers are likely to take. The habit of adapting previous solutions with which the student is comfortable, to new scenarios, is not a safe approach to learn, as it ill equips the future scientist or engineer to identify and tackle problems which contain serious departures from their experience.
Pitch strength of normal and dysphonic voices
Authors: Shrivastav Rahul , Eddins David A. , Anand Supraja
Published: March 2012

Two sounds with the same pitch may vary from each other based on saliency of their pitch sensation. This perceptual attribute is called “pitch strength.” The study of voice pitch strength may be important in quantifying of normal and pathological qualities. The present study investigated how pitch strength varies across normal and dysphonic voices. A set of voices (vowel /a/) selected from the Kay Elemetrics Disordered Voice Database served as the stimuli. These stimuli demonstrated a wide range of voice quality. Ten listeners judged the pitch strength of these stimuli in an anchored magnitude estimation task. On a given trial, listeners heard three different stimuli. The first stimulus represented very low pitch strength (wide-band noise), the second stimulus consisted of the target voice and the third stimulus represented very high pitch strength (pure tone). Listeners estimated pitch strength of the target voice by positioning a continuous slider labeled with values between 0 and 1, reflecting the two anchor stimuli. Results revealed that listeners can judge pitch strength reliably in dysphonic voices. Moderate to high correlations with perceptual judgments of voice quality suggest that pitch strength may contribute to voice quality judgments.
Cross-language differences in fundamental frequency range: A comparison of English and German
Authors: Mennen Ineke , Schaeffler Felix , Docherty Gerard
Published: March 2012

This paper presents a systematic comparison of various measures of f0 range in female speakers of English and German. F0 range was analyzed along two dimensions, level (i.e., overall f0 height) and span (extent of f0 modulation within a given speech sample). These were examined using two types of measures, one based on “long-term distributional” (LTD) methods, and the other based on specific landmarks in speech that are linguistic in nature (“linguistic” measures). The various methods were used to identify whether and on what basis or bases speakers of these two languages differ in f0 range. Findings yielded significant cross-language differences in both dimensions of f0 range, but effect sizes were found to be larger for span than for level, and for linguistic than for LTD measures. The linguistic measures also uncovered some differences between the two languages in how f0 range varies through an intonation contour. This helps shed light on the relation between intonational structure and f0 range.
Estimating concentration of ultrasound contrast agents with backscatter coefficients: Experimental and theoretical aspects
Authors: Leithem Scott M. , Lavarello Roberto J. , O’Brien William D. , Oelze Michael L.
Published: March 2012

Ultrasound contrast agents (UCAs) have been explored as a means to enhance therapeutic techniques. Because the effectiveness of these techniques relies on the UCA concentration at a target site, it would be beneficial to estimate UCA concentration noninvasively. In this study, a noninvasive method for estimating UCA concentration was developed in vitro. Backscatter coefficients (BSCs) estimated from measurements of Definity® UCAs were fitted to a theoretical scattering model in the 15–25 MHz range using a Levenberg-Marquardt regression technique. The model was defined by the UCA size distribution and concentration, and therefore concentration estimates were extracted directly from the fit. Calculation of the BSC was accomplished using planar reference measurements from the back wall of a Plexiglas® chamber and an average of 500 snapshots of ultrasonic backscatter from UCAs flowing through the chamber. In order to verify the ultrasonically derived UCA concentration estimates, a sample of the UCAs was extracted from the flow path and the concentration was estimated with a hemacytometer. UCA concentrations of 1, 2, and 5 times the dose recommended by the manufacturer were used in experiments. All BSC-based estimates were within one standard deviation of hemacytometer based estimates for peak rarefactional pressures of 100–400 kPa.
Propagation of guided waves through weak penetrable scatterers
Authors: Maurel Agnès , Mercier Jean-François
Published: March 2012

The scattering of a scalar wave propagating in a waveguide containing weak penetrable scatterers is inspected in the Born approximation. The scatterers are of arbitrary shape and present a contrast both in density and in wavespeed (or bulk modulus), a situation that can be translated in the context of SH waves, water waves, or transverse electric/transverse magnetic polarized electromagnetic waves. For small size inclusions compared to the waveguide height, analytical expressions of the transmission and reflection coefficients are derived, and compared to results of direct numerical simulations. The cases of periodically and randomly distributed inclusions are considered in more detail, and compared with unbounded propagation through inclusions. Comparisons with previous results valid in the low frequency regime are proposed.
Adaptive beamforming for array signal processing in aeroacoustic measurements
Authors: Huang Xun , Bai Long , Vinogradov Igor , Peers Edward
Published: March 2012

Phased microphone arrays have become an important tool in the localization of noise sources for aeroacoustic applications. In most practical aerospace cases the conventional beamforming algorithm of the delay-and-sum type has been adopted. Conventional beamforming cannot take advantage of knowledge of the noise field, and thus has poorer resolution in the presence of noise and interference. Adaptive beamforming has been used for more than three decades to address these issues and has already achieved various degrees of success in areas of communication and sonar. In this work an adaptive beamforming algorithm designed specifically for aeroacoustic applications is discussed and applied to practical experimental data. It shows that the adaptive beamforming method could save significant amounts of post-processing time for a deconvolution method. For example, the adaptive beamforming method is able to reduce the DAMAS computation time by at least 60% for the practical case considered in this work. Therefore, adaptive beamforming can be considered as a promising signal processing method for aeroacoustic measurements.
Assessing the Deepwater Horizon oil spill impact on marine mammal population through acoustics: Endangered sperm whales
Authors: Ackleh Azmy S. , Ioup George E. , Ioup Juliette W. , Ma Baoling , Newcomb Joal J. , Pal Nabendu , Sidorovskaia Natalia A. , Tiemann Christopher
Published: March 2012

Long-term monitoring of endangered species abundance based on acoustic recordings has not yet been pursued. This paper reports the first attempt to use multi-year passive acoustic data to study the impact of the Deepwater Horizon oil spill on the population of endangered sperm whales. Prior to the spill the Littoral Acoustic Demonstration Center (LADC) collected acoustic recordings near the spill site in 2007. These baseline data now provide a unique opportunity to better understand how the oil spill affected marine mammals in the Gulf of Mexico. In September 2010, LADC redeployed recording buoys at previously used locations 9, 25, and 50 miles away from the incident site. A statistical methodology that provides point and interval estimates of the abundance of the sperm whale population at the two nearest sites is presented. A comparison of the 2007 and the 2010 recordings shows a decrease in acoustic activity and abundance of sperm whales at the 9-mile site by a factor of 2, whereas acoustic activity and abundance at the 25-mile site has clearly increased. This indicates that some sperm whales may have relocated farther away from the spill. Follow-up experiments will be important for understanding long-term impact.
Time–frequency analysis of linear and nonlinear otoacoustic emissions and removal of a short-latency stimulus artifact
Authors: Jedrzejczak W. Wiktor , Bell Andrew , Skarzynski Piotr H. , Kochanek Krzysztof , Skarzynski Henryk
Published: March 2012

Click-evoked otoacoustic emissions (CEOAEs) are commonly recorded as average responses to a repetitive click stimulus. If the click train has constant polarity, a linear average results; if it contains a sequence of clicks of differing polarity and amplitude, a nonlinear average can be calculated. The purpose of this study was to record both protocols from the same set of ears and characterize the differences between them. The major features of CEOAEs were similar under both protocols with the exception of a region spanning 0–5 ms in time and 0–2.2 kHz in frequency. It was assumed that the signal derived from the linear protocol was contaminated by stimulus artifact, and so a simple procedure was used---involving high-pass filtering and time-windowing---to remove components of this artifact. This procedure preserved the short-latency, high-frequency responses; it also produced a marked similarity in the time–frequency plots of recordings made under the two protocols. This result means it is possible to take advantage of the better signal-to-noise ratio of the linear data compared to its nonlinear counterpart. Additionally, it was shown that CEOAEs recorded under the linear protocol appear to be less dependent on the presence of spontaneous otoacoustic emissions (SOAEs).
Coherence and interference in diffuse noise: On the information and statistics associated with spatial wave correlations in directional noise fields
Authors: Walker S. C.
Published: March 2012

Broadband noise correlation methods for the passive extraction of information about the propagation of waves between distant sensor locations have received considerable attention in the literature. For the case of an isotropic ambient field distribution, there is a well-defined relationship between the expectation value of the wave coherence over the sensors and point-to-point wave propagation. Experimental applications, however, must contend with ambient field anisotropy as well as the performance limitations associated with stochastic fluctuations. This paper explores the influence of ambient field directionality on both (1) the connection between the measured wave coherence and sensor-to-sensor propagation and on (2) the rate at which measurements stochastically converge to the expectation value of the underlying wave coherence. Due to diffraction, the relationship between the measured wave coherence and sensor-to-sensor propagation is shown to be robust to even highly directional ambient field features. While the fluctuations of a stochastic system are generally known to depend on bandwidth and measurement duration, the rate of stochastic convergence depends additionally on the cross-spectral power density (coherent power) relative to the power-spectral density (total incident power). Practical experimental implications of these results are discussed.
The pulsed to tonal strength parameter and its importance in characterizing and classifying Beluga whale sounds
Authors: Miralles Ramón , Lara Guillermo , Antonio Esteban Jose , Rodriguez Alberto
Published: March 2012

A large number of the vocalization studies on mammals are based on time–frequency analysis of the produced sounds. The patterns, which are extracted from the time–frequency representations, determine the classification in the different sound categories. However, there are situations where this pattern related recognition does not allow a precise characterization of the vocalization to be obtained. In these situations, a feasible alternative, which can help by giving the dominant component of the sound, is to measure the strength of the tonal and pulsed constituent units. In this work, the use of a ratio of pulsed to tonal strength is proposed to objectively measure the distribution of energy between these two components. This pulsed to tonal ratio (PTR) can be computed with the aid of the discrete cosine transform. It is demonstrated that the PTR can be obtained with a relatively simple expression without having to go through the time– frequency representation. This work presents examples that show how the PTR can be used to distinguish between two very similar Beluga whale sounds and how to dynamically track the power distribution between the pulsed and tonal components in non-stationary signals.
The diffuse sound field in energetic analysis
Authors: Del Galdo Giovanni , Taseska Maja , Thiergart Oliver , Ahonen Jukka , Pulkki Ville
Published: March 2012

Measuring the degree of diffuseness of a sound field is crucial in many modern parametric spatial audio techniques. In these applications, intensity-based diffuseness estimators are particularly convenient, as the sound intensity can also be used to obtain, e.g., the direction of arrival of the sound. This contribution reviews different diffuseness estimators comparing them under the conditions found in practice, i.e., with arrays of noisy microphones and with the expectation operators substituted by finite temporal averages. The estimators show a similar performance, however, each with specific advantages and disadvantages depending on the scenario. Furthermore, the paper derives an estimator and highlights the possibility of using spatial averaging to improve the temporal resolution of the estimates.