bluuebunny/crossref_metadata_2025 huggingface dataset:
Perfil de niños con déficits en la cognición numérica.
Authors: Arias Rodriguez Indira , Mendes Nascimento Jéssica , Santos Flávia-Heloísa
Published: November 2017

La presente investigación tuvo como objetivo caracterizar el perfil neurocognitivo de niños en relación a las habilidades cuantitativas, intelectuales, de memoria operativa y sus aspectos emocionales. La muestra fue de 42 niños de edad escolar de 8 a 10 años, divididos en dos grupos: con dificultades en aritmética (CDA=21) y sin dificultades en aritmética (SDA=21). Los niños fueron evaluados a través de pruebas cognitivas y escalas de comportamiento, que analizaron variables como: rendimiento escolar, razonamiento abstracto, memoria operativa, cognición numérica, ansiedad y estrés. El perfil de los niños CDA se caracterizó por dificultades en el rendimiento escolar de forma general. Fueron encontrados síntomas de estrés compatibles con fases de alerta y resistencia, baja capacidad de memoria operativa y de cognición numérica, específicamente de procesamiento numérico y cálculo.
Sizing of Photovoltaic-Wind-Battery Hybrid System for a Mediterranean Island Community Based on Estimated and Measured Meteorological Data
Authors: Sajed Sadati S. M. , Jahani Elham , Taylan Onur , Baker Derek K.
Published: November 2017

Deploying renewable energy systems (RES) to supply electricity faces many challenges related to cost and the variability of the renewable resources. One possible solution to these challenges is to hybridize RES with conventional power systems and include energy storage units. In this study, the feasibility analysis of a grid-connected photovoltaic (PV)-wind-battery hybrid system is presented as a microgrid for a university campus-scale community on a Mediterranean island. Models for PV and wind turbine systems are presented to estimate energy production, and net present cost (NPC) and levelized cost of electricity (LCOE) are used as economic metrics. A parametric study is performed with hourly time-steps to determine the sizes of energy generation and storage units to minimize the NPC for a small community as the case study. Two alternate configurations with and without storage are proposed. In both cases, the resulting LCOE is 0.15 USD/kWh while the current electricity tariff for the analyzed location was 0.175 USD/kWh in 2015. This lower unit cost of electricity leads to a lower NPC considering a 25-year lifetime. Different estimated and measured solar irradiance and wind speed data sets are used to evaluate the performance of the designed microgrid. Sensitivity analysis on different available weather data sets shows that the uncertainty in wind resource estimations is much higher than the uncertainty in solar resource estimations. Moreover, the results show that solar and wind resources could be utilized synergistically for the studied location.
Experimental and Analytical Assessment of Cavity Modes in a Gas Turbine Wheelspace
Authors: Berg Rachel A. , Tan C. S. , Ding Zhongman , Laskowski Gregory , Palafox Pepe , Miorini Rinaldo
Published: November 2017

Fast response pressure data acquired in a high-speed 1.5-stage turbine hot gas ingestion rig (HGIR) show the existence of pressure oscillation modes in the rim-seal-wheelspace cavity of a high pressure gas turbine stage with purge flow. The experimental results and observations are complemented by computational assessments of pressure oscillation modes associated with the flow in canonical cavity configurations. The cavity modes identified include shallow cavity modes and Helmholtz resonance. The response of the cavity modes to variation in design and operating parameters are assessed. These parameters include cavity aspect ratio (AR), purge flow ratio, and flow direction defined by the ratio of primary tangential to axial velocity. Scaling the cavity modal response based on computational results and available experimental data in terms of the appropriate reduced frequencies appears to indicate the potential presence of a deep cavity mode as well. While the role of cavity modes on hot gas ingestion cannot be clarified based on the current set of data, the unsteady pressure field associated with turbine rim cavity modal response can be expected to drive ingress/egress.
Thermoacoustic Damping Rate Determination From Combustion Noise Using Bayesian Statistics
Authors: Stadlmair Nicolai V. , Hummel Tobias , Sattelmayer Thomas
Published: November 2017

In this paper, we present a method to determine the quantitative stability level of a lean-premixed combustor from dynamic pressure data. Specifically, we make use of the autocorrelation function of the dynamic pressure signal acquired in a combustor where a turbulent flame acts as a thermoacoustic driver. In the proposed approach, the unfiltered pressure signal including several modes is analyzed by an algorithm based on Bayesian statistics. For this purpose, a Gibbs sampler is used to calculate parameters like damping rates and eigenfrequencies in the form of probability density functions (PDF) by a Markov-chain Monte Carlo (MCMC) method. The method provides a robust solution algorithm for fitting problems without requiring initial values. A further advantage lies in the nature of the statistical approach since the results can be assessed regarding its quality by means of the PDF and its standard deviation for each of the obtained parameters. First, a simulation of a stochastically forced van-der-Pol oscillator with preset input values is carried out to demonstrate accuracy and robustness of the method. In this context, it is shown that, despite a large amount of uncorrelated background noise, the identified damping rates are in a good agreement with the simulated parameters. Second, this technique is applied to measured pressure data. By doing so, the combustor is initially operated under stable conditions before the thermal power is gradually increased by adjusting the fuel mass flow rate until a limit-cycle oscillation is established. It is found that the obtained damping rates are qualitatively in line with the amplitude levels observed during operation of the combustor.
Noise impact modeling in two residential areas from amplified music
Authors: Manley David , Bridgewater Benjamin , Pitney Ted , Patrick Ian , Logsdon Edward
Published: November 2017

D.L. Adams Associates has recently worked on two outdoor music venue projects, both in close proximity to residences in which venue owners were concerned about noise impact to the neighboring community. The first project involved the renovation of a city owned garden with the addition of a large stage and audience area. Residences are located within 450 feet of the proposed stage. Modeling was completed to evaluate noise impact, and mitigation recommendations were provided. The second project involved a privately owned sports facility which was leased to provide an Electronic Dance Music (EDM) festival over the course of a weekend. After reading about complaints of many such EDM festivals, the facility Owner wanted to understand the potential noise impact to the neighbors prior to the event. Environmental noise modeling of the facility and anticipated musical acts was completed to predict sound levels in the surrounding neighborhoods and demonstrate to the facility Owner the potential for complaints from the festival.
An analysis of the soundscape of a tidewater glacial fjord environment, LeConte Glacier, Alaska
Authors: Zeh Matthew C. , Pettit Erin C. , Wilson Preston S.
Published: November 2017

Glacierized fjords present a unique set of acoustic environments that are significantly louder than other ice-covered environments, with average sound pressure levels of 120 dB (re 1 μPa) with a broad peak between 1 and 3 kHz [Geophys. Res. Lett. 42, 205 (2015)]. The intensity within this peak is due to the release of bubbles from compressed air-filled pores within melting glacier ice. The glacier-ocean boundary is dynamic, sensitive to fresh- and sea-water balances governed by submarine glacier melt from heat transfer between the glacier face and ocean [J. Phys. Oceanogr. 46 (2016)]. This heat transfer leads to regular calving events (< 200 Hz) contributing significantly to the overall sound level of the environment. Further, as icebergs melt and break apart they may remain in the fjord forming an ice mélange top boundary layer. This talk presents acoustic measurements from and analysis of the soundscape of LeConte Bay, a glacierized fjord in southeastern Alaska, studied from October 2015 to April 2016 using a 6-element vertical hydrophone array. The hydrophones recorded simultaneously at 48 kHz for 2 minutes every hour at depths ranging from 100 to 200 m approximately 1 km from LeConte Glacier. [Work supported by NDSEG Fellowship and ONR.]
Results of subscale model acoustic tests for H3 launch vehicle
Authors: Sarae Wataru , Terashima Keita , Tsutsumi Seiji , Hiraiwa Tetsuo , Kobayashi Hiroaki
Published: November 2017

A subscale acoustic test, the H3-scaled Acoustic Reduction Experiments (HARE), was conducted to predict liftoff acoustic environments of the H3 launch vehicle currently being developed in Japan. The HARE is based on 2.5% scale H3 vehicle models, which is composed with a GOX/GH2 engine and solid rocket motors, Movable Launcher (ML) models with upper deck water injection system and Launch Pad (LP) models with deflector and lower deck water injection systems. Approximately 20 instruments measured far/near field acoustic and pressure data. Preliminary results are presented in this presentation.
Coherence in shallow water reverberation
Authors: Tang Dajun
Published: November 2017

Coherent structure of reverberation intensity versus time and depth is observed during TREX13, and the structure resembles that of sound propagation versus range and depth. The experiment was conducted in shallow water approximately 20 m depth with both source and vertical receiving arrays moored, so the ping-to-ping incoherence in reverberation is believed to be caused by time-dependence of water column properties, especially rough sea surfaces. To understand the observed coherence, simulation of reverberation field is performed, where reverberation pressure, rather intensity, is calculated so phase coherence is included. Possibility of inferring sound propagation information from measured reverberation is discussed. [Work supported by the US Office of Naval Research.]
Time-domain acoustic scattering by elastic objects using finite element analysis
Authors: Simon Blake , Gunderson Aaron M. , Isakson Marcia J.
Published: November 2017

Finite element analysis provides an accurate way of calculating acoustic scattering from underwater objects. The method provides an exact solution to the Helmholtz equation to the order of the discretization. Although commercial finite element software is capable of solving fully 3D scattering problems, it has been previously shown by Zampolli et al. [J. Acoust. Soc. Am. 122, 1472–1485 (2007)] that 3D axisymmetric targets can be solved more efficiently using 2D geometry. This method uses an axial wavenumber decomposition technique, which simulates an incident plane wave from an off-axis direction. In this study, results from this analysis are converted from the frequency domain to the time domain using Fourier synthesis. Elastic spheres and cylinders are considered because the analytical solutions for scattering by these targets are known and can be used to verify the finite element results. The success of this model to simulate time domain scattering will inform the applicability of finite element analysis for more complex targets. [Work supported by ONR, Ocean Acoustics.]
Measurements of methane bubble size distribution from a remotely operated platform in the presence of oil
Authors: Argo Theodore F. , Panetta Paul
Published: November 2017

Subsurface releases of crude oil and methane gas may occur naturally or due to manmade, sometimes catastrophic, events. To determine the quantity of oil and gas being released, measurements can be performed on both the crude oil droplets and methane bubbles to determine their sizes and concentration in the water column. An acoustic backscatter measurement, in the 20–110 kHz range, was developed using transducers mounted on a commercial ROV insonifying an intentional subsurface oil and gas release in a large wave tank. Bubble size distributions for methane mixed in a plume of crude oil were obtained by performing an inversion on acoustic backscattering measurements after accounting for transducer properties and sound transmission through the water column. Due to the rapid nature of the measurements, monitoring of the evolution of the plume in time was also possible. Distributions were consistent with independent measurements using laser scattering techniques.
Observations regarding the noise radiated from full-scale heated, supersonic jets
Authors: Gee Kent L.
Published: November 2017

In this presentation, the characteristics of supersonic jet noise are reviewed. Observations from more than a decade’s worth of measurements of high-performance jet engines and large solid rocket motors are compared against each other and laboratory-scale findings. These include apparent source location and extent, directivity, spectral shape, relative importance of different noise components, and presence of nonlinear propagation effects.
Modeling shock formation and propagation in high-performance jet aircraft noise
Authors: Reichman Brent O. , Gee Kent L. , Neilsen Tracianne B. , Wall Alan T. , Downing Micah , James Michael M.
Published: November 2017

Nonlinear propagation can play an important role in both time and frequency-domain features of far-field supersonic jet noise. Many aspects of nonlinear propagation, such as waveform steepening and greater-than-expected high-frequency spectral levels, have been previously predicted for select angles and engine conditions. This paper builds on previous successes and presents a comparison of nonlinear and linear predictions for the F-35B aircraft. Results are shown over a wide spatial and angular range and over varying engine power conditions, including showing evidence of nonlinear propagation in the forward direction at the highest engine conditions. In addition, specific features, such as individual shocks, are compared between numerically propagated and measured waveforms, highlighting the successes and deficiencies of current propagation models. Weather and multi-path interference effects are also addressed and corrected using an empirical model. [Work supported by USAFRL through ORISE. Distribution A: Approved for public release; distribution unlimited; Cleared 07/10/2017; JSF17-714.]
Acoustic excitation impact on aerodynamic drag measured in aeroacoustic liners
Authors: Jasinski Christopher , Corke Thomas
Published: November 2017

Research interest has steadily grown for understanding the aerodynamic drag produced by acoustic liners for commercial turbofan engines. This is driven by an aim to understand the phenomena fundamentally as well as for application in flight. Stringent government regulations on aircraft noise and next generation aircraft designs that may include liners on more surfaces are key drivers for industry involvement. While the conventional perforate-over-honeycomb liner has proven effective acoustically for decades, liner drag production has not been fully understood. When an acoustic liner sample is excited with sound pressure levels above 140dB re: 20 micropascals, a measurable drag increase is observed at flight velocity. Recent measurements have shown that tonal noise at the same level can produce more than a 50 percent increase in drag coefficient for a liner sample at lower test speeds. By testing liner samples at low speed in the Notre Dame Hessert Laboratory, detailed hotwire probe measurements near the wall have been made and drag coefficient comparisons have been made with the use of a linear air-bearing force balance. The development of the measurement setup, the results produced, and a discussion of implications will be included in this paper.
The importance of tuning curves and two-tone tests in nonlinear acoustic landmine detection
Authors: Nguyen Miahnna , Korman Murray S.
Published: November 2017

During the 1990s through ∼2010, Jim Sabatier’s group (Univ. Mississippi and NCPA) had made significant progress in understanding airborne acoustic landmine detection. In particular, using their development of scanning laser Doppler vibrometry, plastic anti-tank landmines could be detected in soil along roadbeds. Research on the nonlinear acoustic detection of buried landmines by Dimitry Donskoy (Stevens Tech) lead to lumped element models of the target which included a nonlinear spring-like mechanism. Tom Muir studied seismic excitations. Sabatier and Korman suggested that the soil nonlinearity and the soil interaction with the flexural vibration of the top-plate of the landmine or drum-like simulant were both significant factors in nonlinear landmine detection. Nonlinear tuning curves of the soil vibration response vs. frequency (directly over the target) along with rich combination frequency generation in two-tone tests suggested that the vibration was similar to Paul Johnson’s group results on mesoscopic nonlinear elasticity found in geomaterials. Recent airborne acoustic nonlinear landmine detection experiments compare drum-like simulant tuning curves to results using a soil plate oscillator apparatus (two circular flanges sandwiching and clamping a thin circular elastic plate that supports a cylindrical level column of sand above the plate) to help model flexural mesoscopic nonlinear hysteretic behavior.
Experimental study of the impact noise through concrete floor with resilient layers
Authors: Bouttout Abdelouahab
Published: November 2017

In this paper, we present an experimental approach to evaluate the sound transmission through floors and building structures. This method is developed in our laboratory at the National Center of Studies and Integrated Research of Building Engineering, CNERIB, Algeria. The method is based on measurement of sound due to impact vibration generated by a standard tapping machine placed on the upper surface of a small concrete floor. This floor has dimensions of 1.2(m)×0.8(m)×0.2(m) and simply supported on four elastic supports with 2 cm of rubber layer. The natural frequency of the floor is measured with an ambient vibration apparatus, and the obtained value is f = 19 Hz. The measurement consists of recording vibration levels in the upper and lower surfaces of the floor, in 1/3 octave frequency bands between 16 Hz and 16 KHz using piezoelectric accelerometer Brüel and Kjær 4508. The sound level meter Brüel and Kjær 2270 has been used to analyze the vibration signal for different cases. The weighted sound reduction index of the floor has 4 dB without any cover. Some samples of cover floor are tested using this procedure. The results show that the weighted sound reduction index of resilient layer can reach 18 dB, 11.6 dB and 6.6 dB for the rubber, Bitumen and PVC material, respectively. The important results obtained in this paper can be used as a platform to correct the impact sound insulation in multi-storey residential building and renovation plans using recycled resilient materials.
Differential pitch analysis for tone and accent languages
Authors: Koffi Ettien N.
Published: November 2017

According to the Critical Band Theory, the auditory perception of F0 data is the same for all human beings. However, when F0 signals are transferred through the auditory cortex to specialized areas of the brain, they are perceived and processed differently depending on whether the language is tonal or accentual. In tone languages, F0 data appears to be processed in Heschl’s gyrus (Schneider 2005), whereas in accent languages, it is processed via the thalamus to inferior frontal regions (Myers 2017). Furthermore, in accent languages, F0 signals are computed on a nominal scale, but in tone languages, an ordinal scale is used (Speaks 2005). These insights support the long-held linguistic view that accent and tone languages are prosodically different. Terms such as strong/weak, stressed/unstressed are used to describe pitch variations in accent languages, whereas in tone languages, the terms used are extra low, low, mid, high, and extra high. Due to these prosodic and processing differences, it is not advisable to apply the same interpretive framework in analyzing pitch variations in tone and accent languages. Examples will be provided from English and Anyi, a West African language, to underscore the pitfalls in doing so.
English focus prosody processing and production by Mandarin speakers
Authors: Takahashi Chikako , Baek Hyunah , Kao Sophia , Yeung Alex. H. L. , Huffman Marie K. , Broselow Ellen , Hwang Jiwon
Published: November 2017

Our study compared the processing and production of English focus prosody by native speakers of English and Mandarin. Twenty-one Mandarin speakers living in the US and 21 English speakers participated in two tasks. In the processing task, participants responded to instructions that contained natural or unnatural contrastive prosody (Click on the purple sweater; Now click on the SCARLET sweater/Now click on the PURPLE jacket.) In the production task, participants guided an experimenter to place colored objects on a white board, with some contexts designed to elicit contrastive focus (Put the yellow arrow over the ORANGE arrow/yellow DIAMOND, please). All adjectives and nouns were bisyllabic trochees. The two groups differed in their realization of focus, with English speakers tending to align the pitch peak with the stressed syllable and Mandarin speakers with the right edge of the focused word. However, comparison of reaction times for the processing task indicated that both groups responded more quickly to instructions with natural than unnatural prosody, although English speakers’ response times were significantly faster in both conditions. We argue that although Mandarin speakers show Mandarin-like realization of focus in their production, they can nonetheless use the English prosodic patterns in their processing.
Live versus art in voice change: The case of Maria Callas
Authors: Eidsheim Nina , Kreiman Jody E.
Published: November 2017

Many commentaries on the voice of singer Maria Callas note that her voice changed markedly over the course of her career, with changes often attributed to “ferocious dieting.” Such claims are particularly troubling in the absence of evidence that weight loss affects voice acoustics, and in the relative absence of acoustic data testing specific hypotheses regarding expected changes in voice with dieting. This paper examines recordings from early and late in Callas’s career, and attempts to determine whether observed changes are more consistent with the acoustic effects of physiological changes associated with extreme and rapid weight loss (changes in hormone levels, respiratory changes, differences in tongue size/vocal tract dimensions, reflux, etc.), with aging (e.g., increasing vocal instability, changes in resonance frequencies, changes in F0), or with artistic choices.
Individual differences in the signaling of prosodic structure by changes in voice quality
Authors: Shattuck-Hufnagel Stefanie
Published: November 2017

Earlier work has shown that speakers of American English often (although not always) produce irregular pitch periods (or other changes in voice quality) at prosodically significant locations, such as the onset of a new intonational phrase or a pitch-accented syllable, when those constituents begin with a [ + voiced] phonemic segment (Pierrehumbert & Talkin 1992). This tendency varied substantially across 5 speakers of FM-Radio-News-style speech (Dilley et al. 1996). Further work with speakers of a west-coast dialect (Garellek 2012) raised questions about the appearance of this cue at phrase onsets, when the phrase begins with a prosodically weak (lexically unstressed) syllable; this suggests that it occurs only for phrasally-strong (pitch accented) syllables, whether they occur in phrase-initial position or not. In contrast, extensive analysis of voice quality changes in a corpus of imitated utterances produced by speakers of a mid-western dialect (Cole & Shattuck-Hufnagel 2011) clearly shows a tendency for voice-quality changes at the onsets of prosodically weak syllables when they occur at the onsets of intonational phrases. This raises the possibility that individual speakers or dialects may differ in the likelihood of using changes in voice-quality to mark different types of prosodic events, such as phrase onsets vs pitch accents.
Estimation of the probability density function of transmission loss in the ocean using area statistics
Authors: Patterson Brandon , Dowling David R.
Published: November 2017

Predictions of acoustic transmission loss (TL) in the ocean and its uncertainty are useful for a variety of ocean and naval engineering applications. Previously, an ad-hoc technique, area statistics (AS), was developed as a computationally efficient method to estimate the probability density function (PDF) of TL in any uncertain ocean environment from a single range-depth TL-field calculation in that environment. Here, the performance of AS is reported for ten ocean environments having uncertain sound speed profile, bathymetry, and seabed properties. In each environment, a parabolic-equation-based prediction of TL from a point source was generated as a function of range and depth at frequencies of 100, 200, and 300 Hz using the most probable values of the uncertain environmental parameters. From these calculations, AS was used to estimate the PDF of TL at more than 3000 locations within the ten environments. These estimated PDFs are then quantitatively compared, via an L1-error norm, to PDFs generated from traditional Monte Carlo techniques for the same locations and frequencies. Current results show that the L1-error of the AS PDF is less than 0.5, indicating 75% or greater overlap between the AS and Monte Carlo PDFs, at 90% of the test locations. [Sponsored by ONR.]
Statistics of bottom-diffracted surface-reflected arrivals in ocean acoustics
Authors: Stephen Ralph A. , Bolmer S. T. , Worcester Peter F. , Dzieciuch Matthew A.
Published: November 2017

Bottom-diffracted surface-reflected (BDSR) arrivals are a ubiquitous feature in long-range ocean acoustic propagation and are not predicted by existing forward models based on available bathymetric and bottom properties data. In a research cruise in the North Pacific in 2013 over 40 distinct bottom diffractor locations were identified within a 25 km radius survey (at least one diffractor location every 50 square kilometers). The BDSRs can be characterized in terms of: (a) grazing angle of the incident field, (b) in-plane or out-of-plane diffractors, (c) frequency (transmissions were made from 77.5 to 310 Hz), (d) receiver type (vertical or horizontal seismometer, hydrophone, etc.), (e) receiver location, (f) signal strength relative to direct and water multiple paths, and (g) location relative to bathymetric features. In this talk, we present the statistics of the BDSRs in terms of these criteria. This information will inform efforts to predict and exploit BDSRs and will be valuable in planning future cruises to identify the geologic features responsible for them. [Work supported by ONR.]
Measurements of the acoustic-field autoproducts
Authors: Lipa Jessica E. , Worthmann Brian M. , Dowling David R.
Published: November 2017

The frequency-difference and frequency-sum autoproducts are quadratic products of acoustic fields at different frequencies extracted from a frequency-domain acoustic field with nonzero bandwidth. In well-ensonified regions of ray-path environments, the autoproducts may—in theory—mimic genuine acoustic fields at frequencies below and above the original field’s bandwidth (Worthmann and Dowling, 2017, JASA 141, 4579-4590). For example, in a Lloyd’s mirror environment, the autoproducts successfully mimic genuine out-of-band acoustic fields except near the surface or the source. In this presentation, results from a water tank experiment are shown that confirm predictions from theory. A 40- to 110-kHz pulse signal was broadcast from a source 20 cm below the surface to a hydrophone positioned at three different ranges between 20 and 50 cm and at depths from 0 to 40 cm. The measured frequency-difference autoproduct fields have cross correlations of greater than 90% with genuine acoustic fields between 0 and 60 kHz. Similarly, the measured frequency-sum autoproduct fields have cross correlations of greater than 90% with genuine acoustic fields between 110 and 190 kHz. Furthermore, the experimentally measured autoproducts correlate well with theoretically predicted autoproducts. Thus, these results serve to confirm the theory. [Sponsored by ONR and NSF.]
A higher-order approximation to a hybrid parabolic equation approach for density discontinuities
Authors: Smith Kevin B.
Published: November 2017

Parabolic equation models based on the highly efficient and stable split-step Fourier (SSF) algorithm have been known to suffer from accumulating phase errors in range when bottom interactions are prevalent. The primary cause has been identified as due to the treatment of the density discontinuity at the water/sediment interface, whereby a smoothing function is introduced to model the step function. The scale of this smoothing function is proportional to wavelength, and can distort the environmental representation at low frequencies. Yevick and Thomson (1997) introduced a hybrid approach to the problem whereby the density terms were treated separately from the SSF approach via a finite-difference approximation. While this approach was shown to significantly reduce the aforementioned phase errors, the solutions were found to be highly sensitive to the choice of depth mesh size, making general usage of this approach less optimal. The finite difference approach of Yevick and Thomson was based on a 2nd order approximation of the differential operators. In this work, higher order approximations are applied in an attempt to stabilize the finite difference approximations. Solutions are presented for a simple shallow water waveguide utilizing the various approaches previously investigated as well as the higher order approximations. The results are compared with respect to both solution accuracy as well as numerical stability.
Analysis of sound propagation from the transitional area to deep water
Authors: Qin Jixing , Zhang Renhe , Li Zhenglin
Published: November 2017

Underwater acoustic propagation over the continental shelf and slope is complicated and is also an important issue. Motivated by a phenomenon in an experiment conducted in the South China Sea indicating that the energy of the received signal around the sound channel axis is significantly stronger than that at shallower depths, we study sound propagation from the transitional area to deep water. Numerical simulations with different source depths are first performed, from which we reach the following conclusions. When the source is placed near the sea surface, acoustic wave will be strongly attenuated by bottom losses in a range-independent deep-water environment, whereas it can propagate to a very long distance because of the continental slope. When the source is mounted on the slope bottom in shallow-water area, acoustic energy will be trapped near the sound channel axis, and it converges more evidently than the case where the source is located near the surface. Then, simulations with different source ranges are performed. By comparing the relative energy level in the vertical direction between the numerical and experimental results, the range of the unknown air-gun source is roughly determined. [Work supported by the National Natural Science Foundation of China under Grant Nos. 11434012 and 41561144006.]
Taming reverberation in an outdoor amphitheatre—The Ford
Authors: Hoover K. Anthony
Published: November 2017

The historic Ford Amphitheatre in Hollywood, CA, recently completed an overall renovation and expansion. The centerpiece is the 1,200-seat outdoor amphitheater, which features a dramatic arroyo backdrop. The side walls, rear wall, towers, and house flooring were built of concrete in 1931 after a brush fire destroyed the original 1920 wood structure. Several sound-absorptive treatments had been applied to the walls over the years previous to our involvement, but excessive reverberation and some anomalous reflections remained. The new design features an expanded “sound wall” that helps to mitigate highway noise while providing optimal lighting and control positions, and offering an opportunity to improve the acoustical treatment scheme. The result is a unique installation of decorative perforated-metal panels that tame the reverberation, especially in the low frequencies. Assorted design challenges, apparent arroyo hillside contributions, and the resultant reverberation will be discussed.
George Ioup’s contribution to the Gulf of Mexico acoustic research: paving the path into the future
Authors: Sidorovskaia Natalia , Ioup Juliette W.
Published: November 2017

By the end of the 1990s, researchers and regulators recognized the need for understanding how anthropogenic activities impact cetacean’s populations in the Gulf of Mexico. In 2000, George Ioup was one of the founders of the Littoral Acoustic Demonstration Center (LADC), a consortium of Gulf Coast scientists, with the long-term goal of studying the anthropogenic soundscapes of the Gulf of Mexico and their impact on marine mammals. In 2001, LADC was the first team to collect long-term acoustic data rich in sperm whale phonations from bottom-moored autonomous buoys, technology developed by NAVOCEANO and adapted for LADC needs. The first step in establishing a baseline database was taken. At the same time, George sparked the interest of bioacousticians with ideas on how to employ the differences in sperm whale phonations to identify individuals similar to how humans recognize voices. LADC endeavors continued through designing acoustic surveys to characterize the soundscapes of seismic exploration arrays and being the first team to record beaked whales in the Gulf of Mexico in 2007. Recent advances in understanding marine mammal habitats, studying the oil spill impact on these animals, and introducing new acoustic technologies would not be possible without the seminal work of George Ioup.
Modeling as a complementary tool to acoustic data for understanding the impact of environmental disasters on marine mammals
Authors: Ackleh Azmy S. , Chiquet Ross , Tang Tingting , Veprauskas Amy , Cawell Hal , Sidorovskaia Natalia , Ma Baoling
Published: November 2017

This study is focused on how environmental disasters, such as the Deepwater Horizon oil rig explosion in 2010, affect the dynamics of marine mammal populations, particularly sperm whales and beaked whales, in the Northern Gulf of Mexico. We briefly describe how modeling techniques are used to estimate densities of marine mammals using passive acoustic data. We then develop a matrix model to examine the possible long-term effects of a disaster. We consider cases in which the effects of a disturbance result in reductions in either survival (lethal impacts) or fecundity (sublethal impacts). This model, combined with demographic stochasticity, allows us to study the long-term recovery process following an environmental disaster. In particular, recovery probabilities and recovery times of the population are computed, and formulas are derived to compute the sensitivity of the recovery time to changes in properties of the population or the environmental disturbance. We then extend the modeling methodology to consider how marine mammals may be affected by the response of their prey population to a disturbance. Our analysis highlights the difficulty of projecting impacts and recovery in the absence of detailed demographic data, and the value of population models in exploring scenarios and identifying important processes and general relationships. [This research was made possible in part by a grant from The Gulf of Mexico Research Initiative.]
Parity-time synthetic phononic media
Authors: Christensen Johan
Published: November 2017

Classical systems containing cleverly devised combinations of loss and gain elements constitute extremely rich building units that can mimic non-Hermitian properties, which conventionally are attainable in quantum mechanics only. Parity-time (PT) symmetric media, also referred to as synthetic media, have been devised in many optical systems with the ground breaking potential to create nonreciprocal structures and one-way cloaks of invisibility. Here, we demonstrate a feasible approach for the case of elasticity where the most important ingredients within synthetic materials, loss and gain, are achieved through electrically biased piezoelectric semiconductors [1]. We study first how wave attenuation and amplification can be tuned, and when combined, can give rise to a mechanical PT synthetic media with unidirectional suppressed reflectance, a feature directly applicable to evading sonar detection [2]. [1] J. Christensen, M. Willatzen, V. R. Velasco, and M.-H. Lu, Phys. Rev. Lett. 116, 207601 (2016). [2] S. A. Cummer, J. Christensen, and A. Alu, Nature Rev. Mater. 1, Article number: 16001 (2016).
Thermoacoustic sound projector: Beyond the fundamental efficiency of carbon nanotubes
Authors: Aliev Ali E.
Published: November 2017

Advances in thermophone transduction from the perspective of novel nanostructured materials, device design, and signal processing will be presented. The comparison of studied 2D and 3D networks of nanostructured materials with aerogel structures will be given. The energy conversion efficiency of encapsulated thermoacoustic devices excited by short pulses with varying duty cycle, shape of pulse, and carrier signal frequency will be analyzed for a variety of fabricated devices. I will provide an extensive experimental study of pulse excitation in different thermodynamic regimes for freestanding carbon nanotube sheets with varying thermal inertias (single-wall, multi-wall with varying diameters, and number of superimposed sheets) in vacuum and in air. The experimental observations are rationalized within a basic theoretical framework. The acoustical and geometrical parameters providing further increase in efficiency and transduction performance for open and closed resonant systems will be discussed. [Research supported by ONR, Grant No.: N00014-17-1-2521.]
Evaluating the validity and efficiency of tablet audiometry in school-age children
Authors: Supinski Jenna , Pereira Olivia M. , Hammond Mackenzie , Scharf Samantha , Morlet Thierry , Nagao Kyoko
Published: November 2017

Tablet-based automated audiometry offers a portable alternative to traditional audiometry. The limited research available (e.g., Rourke et al., 2016) supports the clinical use of automated audiometry for pediatric hearing screenings, but its accuracy in children and efficiency outside of clinical environments is undetermined. This study’s objective is to evaluate the validity and efficiency of automated audiometry in school-age children. This initial phase aimed to establish its validity in a clinical setting. Hearing thresholds for 0.5, 1, 2, 4, 6, and 8 kHz were collected in children ages 6–12 years old using standard audiometry and an iPad app automated audiometry in a sound-proof booth. Tympanometry, acoustic reflex thresholds, and distortion product otoacoustic emissions were administered to examine peripheral hearing function. Preliminary results of 16 children show no significant difference between the two test durations. Automated audiometry thresholds were within 5 dB of the standard audiometry thresholds for each tested frequency, except at 6 kHz where they were within 7dB. There was no test preference among the participants. Our preliminary results support the use of automated audiometry in children. Current testing is evaluating its validity and reliability under less ideal testing environments. [Work supported by NIH COBRE Grant P30GM114736 and the Nemours Foundation.]
Noise levels during recreational flight of a Cessna 172 Skyhawk
Authors: Jones Drew , Lewis James D. , Hedrick Mark
Published: November 2017

Recreational and private pilots are regularly exposed to potentially hazardous noise levels during flight training sessions and recreational flying. For the first part of this study, light airplane noise was recorded during recurrent 1.5-hour flight training sessions. Measurements were made at the level of the pilot’s left and right shoulders (using dosimeters). Data demonstrated that changing inflight operations and power adjustments were associated with specific acoustic patterns. Noise levels (Leq) ranged from 76 dBA to 96 dBA during flight. The second part of this study examined the effect of the noise on subjective and objective measures of the pilot’s auditory function. Measurements were made before and immediately after flight training sessions. Pure-tone audiometric thresholds, middle-ear absorbance and click-evoked otoacoustic emissions did not show significant changes from pre- to post-flight. Although inflight noise levels are potentially hazardous, the use of an aviation headset acted to mitigate the risk of hazardous exposure. Future research directions include measurements in diverse aircraft and across longer flight durations.
Humidity influences on natural Timpani heads
Authors: Nagl Wolfgang , Mayer Alexander
Published: November 2017

Varying air moisture is an issue timpanists using natural skins have to deal with. Moisture, which in concert halls is often created by the audience or by the musicians on the stage, causes natural skin to loose its tension and therefore flattens the pitch of the instrument. The present paper deals with the effects of moisture on the pitch of timpani with natural skin presenting an experiment for measuring the relationship between air moisture and skin tension resp. pitch variation. An experimental setup has been created where the natural skin head was mounted on a copper shell containing an ultrasonic humidifier. The humidification process was computer controlled in order to establish exact humidity levels. The resulting change of the kettledrum skin parameters was measured using an impulse hammer and force transducers at all mounting points of the tensioning hoop. Stretching parameters have been captured by a special video-system. Measurements have been made in a relative humidity range of up to 91%. The results may also guide musicians and help them to cope with humidity variations during their concerts.
Sound fields forever: Mapping 3D sound fields using position-aware smartphone technology
Authors: Hawley Scott H. , Alegre Sebastian , Yonker Brynn
Published: November 2017

Google Project Tango is a suite of built-in sensors and libraries allowing certain mobile devices to track their motion and orientation in three dimensions, without the need for any external hardware. Our new Android app, “Sound Fields Forever,“ combines position information with sound intensity data for multiple frequency bands obtained from a comoving external microphone plugged into the phone's analog audio jack, and filtered digitally. These data are sent wirelessly via a WebSockets connection to a visualization server running in a web browser. This system is intended for multiple roles: (1) education, providing visual representations of introductory acoustics laboratory phenomena such as interference patterns and room modes; (2) live sound reinforcement, providing front-of-house engineers real-time maps of a loudspeaker system's effects throughout the venue; (3) architectural acoustics, aiding builders and designers in evaluating acoustical properties of halls. The relatively low cost of our approach (∼$400 for the smartphone) compared to more sophisticated 3D acoustical mapping systems could make it an accessible option for such applications. We present visualizations of various sound field measurements and intend to demonstrate how the bandpass filters make it suitable for use even in the presence of nontrivial ambient noise.
Investigating the effects of formulation and processing conditions on the mechanical properties of wheat flour noodle dough
Authors: Guillermic Reine-Marie , Kerhervé Sébastien O. , Wang Huiqin , Strybulevych Anatoliy , Hatcher Dave W. , Scanlon Martin G. , Page John H.
Published: November 2017

Characterization of the mechanical properties of soft food materials is crucial in the food industry, both for process design and for quality enhancement purposes. The goal of this project is to develop a non-contact on-line quality control technique for use in processing of sheeted products such as Asian noodles. In the case of the Asian noodle industry, composition and work input during the sheeting process are important parameters that influence the mechanical properties of the dough, and as a consequence, final product quality. An accurate and fast determination of noodle properties and how they are influenced by formulation and processing parameters will certainly improve quality control during production. To address this need, we are conducting a full study of noodle dough with ultrasonic techniques. A non-contact ultrasonic technique in transmission is used to assess the mechanical properties of noodle dough sheets and has been evaluated in pilot-plant trials, showing its feasibility for real-time quality control. Additionally, for a better understanding of the material properties, including how both bubbles and the dough matrix are affected by sheeting, contact longitudinal experiments over a wide range of frequencies (0.5 to 12 MHz), along with ultrasonic shear experiments, have been performed.
On time-dependence of mechanical metamaterials properties
Authors: Ruzzene Massimo , Trainiti Giuseppe
Published: November 2017

The study focuses on wave propagation in time-periodic mechanical matamaterials, such as beams with time-modulated elastic modulus. The time-dependence of the elastic modulus results in a system with a frequency-periodic dispersion diagram. Flat bands originate at the intersections of the dispersion branches, signaling zero group velocity modes. Through an analytic approach, we obtain approximate expressions for the range of wavenumbers associated to flat bands, as well as their dependence on the modulation parameters. It is shown that the flat bands lead to unbounded growth of the displacement field, which is due to the interaction between the structure’s dynamics and the energy provided to it by means of the elastic modulus variation. If such phenomenon is properly confined over a limited time window, it provides a way to filter wave propagation over a ultra-wide frequency range by property choosing the modulation parameters. Numerical simulations, obtained by implementing a FDTD scheme, verify the theoretical findings. Finally, an experimental validation of the results is discussed, which employs piezoelectric patches and time-dependent negative capacitance shunted circuits.