bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibration isolation of buildings for control of ground borne noise
Authors: Wilson George P.
Published: May 2016

Complete vibration isolation has made it possible to locate new buildings on sites with normally unacceptable levels of ground borne noise. The principles are relatively simple but the isolation details are necessarily limited and, to be successful, the isolation bearing pads or springs must have very specific dynamic and structural properties. Since the late 1980s, there have been a number of successful building isolation projects where the intruding ground borne noise from nearby rail facilities and other sources has been reduced to the threshold of hearing or less. The design principles required include massive, high mechanical impedance foundations, very low acoustical impedance isolation bearings, and relatively high stiffness and mass structure for at least two floors above the isolation level. Typical design details and information are presented regarding successful isolation configurations for entire buildings and for box-in-box isolated spaces within the building. Also included are a discussion on isolation bearing materials which have not been successful, as demonstrated by on-site measurements, and a discussion on the mechanical, acoustical, and durability requirements for successful building isolation bearings. An additional item included is a discussion of the differences between building vibration isolation design principles for noise control and building base isolation design for seismic protection.
Design and fabrication of a fission-powered thermoacoustic in-core sensor
Authors: Garrett Steven L. , Smith Robert W. , Smith James A. , Heidrich Brenden J.
Published: May 2016

A standing-wave thermoacoustic engine with dimensions identical to an ordinary fuel rod was designed to be placed in the core of the Breazeale Nuclear Reactor on Penn State’s campus. The heat necessary to produce thermoacoustics oscillations was provided by two 10 mm long by 5 mm diameter, 7.5% enriched, 235U fuel pellets. Those pellets were contained within a stainless-steel finned heat exchanger that was fabricated by additive manufacturing (3-D printing). The (mass-controlled) resonator was suspended in the surrogate fuel rod using two six-armed leaf springs (spiders) that centered the resonator in the “slotted tube” and allowed longitudinal vibrations of the entire resonator that coupled the oscillatory momentum of the gas within the resonator to the surrounding light-water reactor coolant. A 2.0 MPa mixture of 25% argon and 75% helium provided a trade-off between dipole radiation efficiency, resonator length, and low onset temperature differential, to produce a frequency that was high enough to be above the dominant noise produced by coolant and 16N diffusion pumps. These trade-offs were optimized using the Los Alamos DELTAEC software. [Work supported by Idaho National Laboratory and Westinghouse Electric Co. Fabrication and fueling was completed in collaboration with IST-Mirion.]
The hierarchies of phonetic realization of focus in second language speech
Authors: Chen Ying
Published: May 2016

Two experiments were conducted to examine the phonetic realization of focus in L2 Mandarin by L1 American English speakers and in L2 English by L1 Beijing Mandarin speakers. The production data in both experiments indicated an acoustical hierarchy of duration > intensity > F0 at the sentential level. This hierarchy was correlated with another hierarchy in sentence location relative to focus: pre-focus > in-focus > post-focus. In other words, L2 learners tended to produce more nativelike patterns of duration than intensity, and intensity than F0, to code focus. These patterns were more salient in pre-focus condition than in-focus condition, and in in-focus condition than post-focus condition. These findings are consistent with Wu and Chung (2011, ICPhS) and Chen, Xu and Guion-Anderson (2014, Phonetica) that bilingual learners used more duration and intensity than F0 and more in-focus expansion than post-focus compression to code focus in L2 speech. Post-focus compression of F0 was the most difficult acoustic cue in phonetically realizing L2 focus. The nativelikeness of focus realization in L2 speech increased with the increase of L2 experience. [This work was supported by the National Science Foundation of China #61573187 and Fundamental Research Funds for the Central Universities in China NJUSTWGY14001.]
International teaching assistants’ production of focus intonation
Authors: Kao Sophia , Hwang Jiwon , Baek Hyunah , Takahashi Chikako , Broselow Ellen
Published: May 2016

We report on a longitudinal investigation of the realization of English focus by 19 Mandarin-speaking International Teaching Assistants (ITAs). Participants read passages containing contrastive information (e.g., The price of a train ticket is twenty dollars, while the price of a bus ticket is eleven dollars), and then responded to the experimenter’s questions (Is the price of a bus ticket twenty dollars?). ITAs were tested within a month of their arrival in the US, and again at the end of their first semester. Overall, the productions of ITAs at both points in time were judged as less natural by native English listeners than the productions of the native speakers of English, though the naturalness of some ITA productions improved at the second sampling. Acoustic analyses of the ITA productions and comparison with the productions of 18 native English speakers revealed a good deal of interspeaker variability in the ITA productions, with several different patterns associated with the “unnatural” productions: (a) failure to accent the focused element; (b) failure to deaccent the word following the focused element; and (c) failure to align the accent with the stressed syllable of the focused word, with the entire focused word spoken on high pitch.
The perceptual assimilation model for suprasegmentals and cross-language lexical-tone identification
Authors: Alexander Jennifer , Wang Dr. Yue
Published: May 2016

We examine how native lexical-tone experience influences identification of novel tone. Cantonese, Thai, Mandarin, and Yoruba listeners identified CV syllables bearing the six phonemic Cantonese tones. Accuracy scores were submitted to a two-way rANOVA with L1-Group (x4) as the between-subjects factor and Tone (x6) as the within-subjects factor. Tone error patterns were also assessed via rANOVAs with L1-Group (x4) as the between-subjects factor and Response-Pattern (% correct versus % other response) as the within-subjects factor. Consistent with previous reports, native listeners’ confusions reflected effects of ongoing tonal mergers and a crowded tone space. Non-native listeners appeared to assimilate novel tones to L1 tone categories by attending to phonetic cues relevant to the phonological and phonetic properties of their L1s. Overall, results support predictions of the Perceptual Assimilation Model for Suprasegmentals (PAM-S). [Support: NSF grant 0965227 to J.A.A.]
Vowel length and perception of English as a Lingua Franca
Authors: Haslam Mara , Zetterholm Elisabeth
Published: May 2016

English is one of the most widely used languages in the world but, in contrast to many other languages, a majority of users of English are non-native speakers, meaning that many interactions in English fall under the category of English as a Lingua Franca (ELF). Understanding of how non-native speakers’ perception works in English is important for both researchers and English teachers. Jenkins’ (2000) Lingua Franca Core (LFC), a list of pronunciation characteristics which are claimed necessary for accurate ELF perception, has already been adopted as a standard for training English teachers and for students of English. However, the research on which the LFC is based is rather limited. An earlier study by the presenters about the importance of the fortis-lenis distinction on stop consonants for ELF perception indicates that participants’ perception of word-initial stops cannot be explained easily in relation to voice onset time. This study represents a further attempt to investigate the claims of the LFC using more controlled methods, focusing on the claim that length is important for accurate vowel perception. Word tokens from conversations in English between speakers with different L1s are used. Results of vowel-length measurements and their relationship to perceptual results will be presented.
Learning a linear ordered-statistic constant false-alarm rate detector
Authors: Havens Timothy C. , Cummings Ian , Botts Jonathan , Summers Jason E.
Published: May 2016

The linear ordered statistic (LOS) is a parametrized ordered statistic (OS) that is a weighted average of a rank-ordered sample. LOS operators are useful generalizations of aggregation as they can represent any aggregation, from minimum to maximum, including conventional aggregations, such as mean and median. Hence, we propose an LOS-Constant False-Alarm Rate (CFAR) detector that uses an LOS operator to compute the background level. Specifically, we extend ordered weighted average (OWA) learning methods to learn an LOS-CFAR using two regularization methods, L2 and entropy regularization. We demonstrate our learning process for midfrequency active sonar in cluttered shallow-water environments using both synthetic data and physics-based simulated experiments, and present and discuss the performance of the learned CFAR detectors versus the classical OS-CFAR and cell-average (CA)-CFAR. [Work supported by a NAVSEA Phase I SBIR award.]
Seabed property inversion—Sequential and direct approaches
Authors: Michalopoulou Zoi-Heleni , Lin Tao , Aunsri Nattapol
Published: May 2016

The goal of this work is to improve our knowledge of the ocean medium using physics of sound propagation and statistical signal processing. Two of the approaches we discuss are based on global and local optimization combined with sequential filtering. A third one falls under the category of direct (“exact”) methods. The first two approaches are based on the extraction and the association between paths/modes and detected arrivals and also produce posterior probability density functions, characterizing the uncertainty structure of modal/multipath arrivals. These are then propagated backwards through an acoustic model for posterior probability density function calculation of environmental parameters. A third method extends Stickler’s exact inverse approach, employing measurements of a reflection coefficient at low frequencies to obtain the sediment sound speed profile. We develop an approximation based on interpolation and a regularization approach. The former improves on results of a previous method for solving the trace equation using a linear approximation. The latter assists in addressing singularities caused by noise in the data. Several assumptions are initially made in order for the approach to work. We show via a sensitivity analysis that the method is robust with respect to initial assumptions and parameter choices needed for both the interpolation and regularization processes. [Work supported by ONR.]
Maximum entropy estimation of environmental parameter distributions
Authors: Pitre Richard
Published: May 2016

This presentation regards origins and information theoretic foundations of maximum-entropy methods for estimating environmental parameter distributions. Environmental parameter distributions determine uncertainty and confidence levels in transmission loss inputs to mission planning and sonar tactical decision making tools. Given the scale of the oceans and their stochastic-dynamic nature, the sample base for estimation is usually limited relative to the required spatial and temporal resolution. Effective use of estimated environmental distributions for planning and decision making in this context requires well defined and meaningful methods of extrapolative estimation. The principle of maximum-entropy or minimal-presumption provides an important component of such methods. A complete definition of a maximum entropy method requires (1) definition of an application specific information or information base measure that counts the relative number of physically distinct possibilities in measurable subsets of the state space, and (2) a way of imposing minimally informative extrapolation on a combination of data samples, statistical hypotheses, and mathematical presumptions regarding things like smoothness of the underlying distribution. These components of distribution estimation and their interrelationships are discussed.
Representation of depth-dependent gradients in sediment geoacoustics by Bernstein polynomials
Authors: Quijano Jorge E. , Dosso Stan E. , Holland Charles W. , Dettmer Jan
Published: May 2016

We present a seabed parametrization approach for depth-dependent gradients in sediment geoacoustics, a property commonly observed in muds. The method represents continuous functions by a polynomial form, consisting of a finite sum of Bernstein basis weighted by real coefficients which are estimated by Bayesian geoacoustic inversion of seabed reflectivity data. The advantages of the Bernstein representation of continuous gradients are discussed, including efficiency in representing a wide variety of gradients with only a few coefficients, as well as high numerical stability of the polynomial form to perturbation of its coefficients. The performance of the Bernstein parametrization applied to geoacoustic inversion is illustrated with simulated data obtained from a realistic seabed scenario. In addition, the Bernstein approach is applied to experimental data from four mud sites at the Malta Plateau. The estimated geoacoustic profiles are in good agreement to core measurements from the area, and serve to illustrate the ability of the Bernstein-based inversion to represent steep gradients. Comparison to results obtained by discrete (multi-layered) and other continuous gradient representations (line-, sinusoid-, and spline-based) is presented.
On connection between statistical integral equations and statistical inference in ocean acoustics and sonar
Authors: Knobles David P. , Wilson Preston S.
Published: May 2016

Under what circumstances do statistics of source and waveguide parameter values derived from an application of statistical inference, such as Bayesian or Maximum Entropy, reflect the temporal and spatial inhomogeneities of the waveguide? The statistics of the objective function is influenced by model error that reflects the non-deterministic features of the waveguide and the source. This connectivity is explored with a new derivation of statistical equations previously discussed by Dozier and Tappert. The resulting statistical integral equations provide the relationship between the fluctuations in the waveguide to those of the acoustic field. Then, the idea is to infer, from an ensemble of measured acoustic data, marginal probability distributions for the Green’s functions and mode coupling matrix coefficients. This is accomplished by inferring the statistics of the source and the physical properties of an ocean waveguide such as range-dependent sound speed layers in the water column and the seabed, and layer interface roughness parameters. The inferred statistics of the mode coupling operator and Green’s functions, and the noise spatial correlation then become input into the statistical integral equations. In principle these modeled acoustic field statistics can then be compared to the measured field statistics. [Work supported by ONR Code 32 OA.]
Estimation of geoacoustic model parameters from modal amplitude information
Authors: Chapman N. Ross , Duan Rui
Published: May 2016

This paper analyzes an approach for estimating geoacoustic model parameters from information contained in normal modes of a broadband signal. Propagating modes are resolved by time-warping deconvolved signals from light bulb sound sources deployed at short ranges in shallow water. Amplitudes of the resolved modes contain information about sediment sound attenuation through the modal attenuation coefficient. However, the coefficient also depends on the sediment sound speed and density. A sequential inversion approach was developed that enables effective use of modal amplitudes to estimate sound attenuation in sediments. The inversion is based on a sequential Bayesian approach applied to features of resolved modal data that are highly sensitive to specific geoacoustic model parameters. Travel times of modal frequency components are inverted first for sediment sound speed and sediment layer thickness, and these estimates are used in subsequent stages. The effects of errors in estimates from previous stages are analyzed for the impact on estimates of sound attenuation in the final stage. In particular, it is shown that the sediment density is weakly sensitive and does not have significant impact on the estimation of attenuation.
Relative impact of signal-to-noise ratio and propagation effects on the performance of an aural classifier
Authors: Binder Carolyn , Hines Paul C.
Published: May 2016

Passive acoustic monitoring (PAM) is used to study marine mammals in their habitats, which cover diverse underwater environments. The distinct propagation characteristics of different ocean environments alters the time-frequency characteristics of a recorded signal. This may affect the accuracy of PAM systems. To develop a PAM system capable of operating under numerous environmental conditions, one must account for the impact of propagation. An aural classifier developed at Defence R&D Canada (DRDC) has successfully been used for inter-species discrimination of cetaceans. The aural classifier achieves accurate results by using perceptual signal features that model the features employed by the human auditory system. The current work examines the relative impacts of signal-to-noise ratio (SNR) and propagation effects on the performance of the aural classifier. DRDC’s pulse propagation model, Waveform Transmission Through a Channel (WATTCH), was used to simulate signals travelling through the ocean environment over ranges of 0–20 km. Noise was added to both these signals and the original signals, so that performance could be compared for three scenarios expected to decrease classifier performance: decreasing SNR, increasing propagation effects (frequency spreading, multipath, etc.), and combined SNR and propagation effects. In this presentation, the modeled results are compared to experimental data.
Development of a nonlinear model for the pressure dependent attenuation and sound speed in a bubbly liquid and its experimental validation
Authors: Jafari Sojahrood Amin , Li Qian , Burgess Mark , Karshafian Raffi , Porter Tyrone , Kolios Michael C.
Published: May 2016

Presence of the MBs in the sound field increases the attenuation of the medium and changes the sound speed. A detailed knowledge about the attenuation of the medium is critical for controlling and optimizing the behavior of the MBs in applications. However, existing models of ultrasound attenuation in bubbly mediums are based on linear approximations (low amplitude MB oscillations) and thus are not valid in many regimes used in applications. A model to calculate the nonlinear attenuation and sound speed is developed by deriving the complex and real part of the wave number from the Calfish model. The predictions of the model were validated by measuring the attenuation and sound speed of dilute monodisperse MB solutions (5000 microbubbles/ml) with median diameter of 5.2 and 9.8 µm using acoustic pressure range of 10–130 kPa. The attenuation of the medium was calculated by numerically solving the radial oscillations of the MB and incorporating it in the attenuation model. Predictions of the model were in good agreement with the experimental results. As the acoustic pressure increased, the attenuation and maximum sound speed of the medium increased from 5 dB/cm to 12 dB/cm and 1500 to ~1530 m/s, respectively.
Phantom study on the detectability of micro-tumors in breast tissue using high-frequency ultrasound
Authors: Cowan Nicole , Coffman Zachary A. , Omer Robyn K. , Finch Benjamin F. , Doyle Timothy E.
Published: May 2016

The ability to detect malignant tissue in surgical margins during breast cancer surgery would reduce the risk of local recurrence and the need for subsequent surgeries to remove residual cancer. A surgical study conducted by Utah Valley University with the Huntsman Cancer Institute showed that high-frequency ultrasound (20–80 MHz), and the parameters peak density (number of spectral peaks and valleys from 20 to 80 MHz) and attenuation, are sensitive to breast tissue pathology. Pathology results from this surgical study showed that many margin specimens contained micro-tumors measuring 1 mm in diameter or smaller. The present study’s objective was to determine the sensitivity of high-frequency ultrasound to these micro-tumors using phantoms. Phantoms were created from distilled water, agarose powder, 10X TBE stock solution, and 390–925μm diameter polyethylene microspheres to simulate breast tumors. Microspheres were embedded in phantoms singularly and in clusters of 3–12 microspheres. Pitch-catch measurements were acquired using large (6.35 mm diameter) and small (1.5 mm diameter) 50-MHz transducers, a high-frequency ultrasound system, and glycerol as the coupling agent. Both large and small transducers were sensitive to single microspheres and microsphere clusters across all microsphere diameters. The phantom results confirm the sensitivity of high-frequency ultrasound to breast cancer micro-tumors and validate the surgical study.
The effect of inharmonicity in piano tones
Authors: Anderson Brian E. , Strong William J.
Published: May 2016

This presentation will review research conducted to determine the effect of inharmonic partials on the pitch of piano tones [JASA, 117, 3268–3272 (2005)]. Synthetic piano tones were created based on recordings of an upright piano. One set of tones were made to have inharmonic partials that matched the partial frequencies of the piano tone recording, whereas another set of tones consisted of harmonic partials. Listeners compared a synthetic, inharmonic piano tone to a set of synthetic, harmonic piano tone with varying fundamental frequencies. They were asked to select the harmonic tone whose pitch best matched that of the inharmonic tone. The pitch of the inharmonic tones was perceived to be sharp relative to the harmonic tones (sharp in terms of the comparison of their respective fundamental frequencies).
Disk cavities in soft materials: Their bubble-like resonance and use in thin underwater sound blocking materials
Authors: Calvo David C. , Thangawng Abel L.
Published: May 2016

The acoustics of gas-filled cavities in soft viscoelastic solids, such as rubber and gels, has been a renewed subject of research in recent years owing to usefulness in studies of multiple scattering and importance to sound insulating and anechoic materials. A brief review is followed by a presentation of recent research on disk cavity resonance done at the Naval Research Laboratory [J. Acoust. Soc. Am. 138, 2537–2547]. A lumped parameter analysis of the breathing mode of a disk cavity is presented which yields a natural frequency expression valid for a high-aspect ratio cavity embedded in an elastic medium. A verification approach using finite-element methods is also described which directly computes resonance in the framework of COMSOL Multiphysics. Calculation of scattering cross sections and visualization of the elastic displacement field indicates the importance of shear wave radiation. As an application example, a specially designed single layer array of disk cavities in a thin silicone rubber (PDMS) sheet was modeled that resonantly blocks underwater sound by nearly 20 dB for a favorable wavelength/thickness ratio of 240. Disk cavities are found to provide a wider bandwidth than near-spherical cavities. [Work sponsored by the Office of Naval Research.]
Mind the gap: Electromagnetic articulometer observation of speech articulation in conversational turn-taking
Authors: Tiede Mark , Goldenberg Dolly , Mooshammer Christine
Published: May 2016

Joe Perkell pioneered the use of electromagnetic articulometry (EMA) for the observation and quantification of the kinematics of speech articulator movements. In the spirit of his research, we have extended these methods to EMA observation of two facing speakers interacting in conversation. The gaps or pauses between turns in speaking are known from acoustic measurement to be relatively short in duration, about 200 ms or the length of a syllable on average, and this gap duration has been shown to be consistent across widely diverse languages and cultures (Stivers et al., 2009). However, because the cognitive latencies for producing a response are much longer than this interval its planning must occur during the incoming turn. Here we provide evidence for this planning from articulator movements that anticipate speech. Movements of sensors attached to the tongue, jaw and lips have been tracked for each of 12 speaker pairs. Gaps are measured as the difference between the acoustic end of one speaker's turn to the onset of aggregated articulator movement above a 20% peak velocity threshold for the respondent. Results show that the speech articulators typically assume an appropriate posture for initiation of a speaking turn well before the onset of speech.
Acoustic and kinematic estimates of laryngeal stiffness
Authors: McKenna Victoria S. , Heller Murray Elizabeth S. , Lien Yu-An S. , Stepp Cara E.
Published: May 2016

Vocal fold movements differ between individuals with typical voices and those with voice disorders associated with increased laryngeal stiffness. Modeling suggests that changes in vocal fold kinematics correspond to changes in laryngeal muscle stiffness. In this study, 12 healthy adults produced repetitions of /ifi/ while varying their self-perceived vocal effort during simultaneous acoustic and nasal-endoscopic recordings, in order to compare a kinematic estimate of laryngeal stiffness to an acoustic measure. The acoustic measure, relative fundamental frequency (RFF), was determined from the last ten voicing cycles before the voiceless obstruent (offset) and the first ten voicing cycles of the following vowel (onset). A kinematic stiffness ratio was calculated by normalizing the maximum angular velocity by the maximum value of the glottic angle during vocal fold adductory gestures. A linear mixed-effect model found that RFF accounted for 52% of the variance in the kinematic data. Examined within-subject, 83% of participants exhibited at least a moderate negative linear relationship (r = −0.5 to −0.91) between the offset cycle 10 RFF and the kinematic stiffness ratio. Overall, the relationship between the acoustic and kinematic measures was strong and both measures showed consistent changes during self-modulated changes in vocal effort.
Objective assessment of vocal hyperfunction
Authors: Hillman Robert E. , Mehta Daryush , Stepp Cara , Van Stan Jarrad , Zanartu Matias
Published: May 2016

Vocal hyperfunction (VH) is associated with the most frequently occurring types of voice disorders including benign vocal fold lesions (e.g., nodules) and dysphonia that occurs in the absence of concurrent pathology (e.g., muscle tension dysphonia). In 1989, Hillman et al. (J. Speech Hear. Res. 32, 373–392, 1989) proposed and initially validated the first experimental framework for hyperfunctional voice disorders that was based on using objective measures of vocal function to test basic concepts about VH. This initial work set the stage for a program of research aimed at improving the prevention, diagnosis, and treatment of hyperfunctional voice disorders by attaining a better understanding of the etiological and pathophysiological mechanisms that underlie specific disorders within the broad range of those associated with VH. An update on the progress of this ongoing work will be provided including new insights gained through the use of ambulatory voice monitoring, machine learning, and computer modeling of phonatory mechanisms. [Work supported by NIH-NIDCD R33 DC011588 and the Voice Health Institute.]
Detection of an object bottoming at seabed through modeling consecutive reflected signals
Authors: Kim Sunho , Im Sungbin , Shim Taebo , Kargl Steve G.
Published: May 2016

In various fields, it is very important to detect an object bottoming at seabed. In this paper, a scheme is proposed for detecting an object bottoming at seabed in the shallow water. In this work, a monostatic active sonar system is considered to use a linear frequency modulated signal as a transmitted signal, and to send consecutive pings in the shallow water. An object is assumed to be randomly located within 1000 m from the transmitter. A reflected signal received at the receiver can be modeled using a previously received reflected signal with Wiener filtering, to produce a FIR filter with estimated coefficients. This filter can be applied to predict the next received signal with the current received signal as input. The energy can be computed from the error signal between the predicted and received signals. In the case when the object is not located in the search area, the reflected signal is very similar to each other, and thus the energies of the error signals are very small. However, in the case when the object is placed and the reflected signal is scattered from the object, the energy of the error signal may be increased because the coherence between the predicted and received signals is low. The advantage of this approach is not to require a prior information on the characteristics of the sediment with the assumption that the seabed is consisting of an uniform sediment. The verification of the proposed scheme is investigated in terms of detection probability and detection range through computer simulation.
Guided wave reconstruction in complex geometries with a dictionary learning framework
Authors: Alguri K. Supreet , Harley Joel B.
Published: May 2016

Guided waves are an attractive tool for structural health monitoring (SHM) due to their ability to interrogate large areas of a structure. Yet, guided waves are characterized by multi-modal and frequency dispersive behavior and quickly grow in complexity with the structure. For example, guided wave reflections from plate edges, fasteners, or joints will lead to complex, difficult to analyze data. Most SHM algorithms try to remove or ignore these reflections. Yet, knowledge about the reflections and their acoustic behavior can significantly improve detection and localization algorithms. Hence, accurate knowledge about guided waves reflections is of a significant interest in SHM. In this paper, we reconstruct and predict guided wave measurements from geometric environments with reflections. We leverage dictionary learning and sparse recovery algorithms to achieve this goal. Dictionary learning is used to learn the building blocks of guided waves from simulation data. Sparse recovery algorithms are used to create predictive models of wave propagation based on experimental data. From simulation results, we show that our framework can successfully predict wave propagation, including reflections, across an aluminum plate with an accuracy of more than 95% from just 20 measurements. We demonstrate similar results with experimental data.
Numerical analysis of underwater sound propagation over the Chukchi Sea shelfbreak
Authors: Lin Ying-Tsong , Badiey Mohsen , Duda Timothy F. , Muenchow Andreas , Kemp John , Eickmeier Justin , Dzieciuch Matthew , Worcester Peter
Published: May 2016

During the 2015 Canada Basin Acoustic Propagation Experiment (CANAPE) expedition on the southern edge of Canada basin (northern Chukchi Sea shelfbreak), shipboard suspended underwater sound sources were deployed to transmit acoustic signals to hydrophone arrays moored on the deep basin as well as the shallow shelf. In this paper, numerical simulations utilizing the Parabolic Equation method are conducted to provide physical insights into the variability of signals propagating over the shelfbreak and slope and recorded on a vertical array on the Chukchi Sea shelf. The numerical models simulate sound propagating over the slope via the Pacific Halocline duct, which is a water-borne vertical sound duct formed between the layers of Pacific summer water and Atlantic water. The source to receiver distance is about 130 km, and realistic variability is introduced in the numerical models. The previous studies reported in the literature have concluded that the shelfbreak circulation, specifically upwelling, and the sub-mesoscale eddies spun off the shelfbreak jet are the two major causes of the temporal and spatial variability of the Pacific Summer Water Layer over the slope in the region. The numerical simulation study also emphasize on the scattering and attenuation effects caused by ice cover and roughness. A preliminary data-model comparison is made and discussed in this paper. [Work supported by the Office of Naval Research.]
Investigation of coprime scattering arrays as sparse sound diffusers
Authors: Melsert Kevin A. , Bush Dane , Xiang Ning
Published: May 2016

Number-theoretic coprime sparse samplers have recently sparked research activities in the fields of signal processing and acoustics. The concept of coprime sparse sensing has been successfully implemented and experimentally tested in form of acoustic sparse microphone arrays, as shown in the publication [D. Bush and N. Xiang, J. Acoust. Soc. Am. 138, 447-456 (2015)]. The current study investigates how coprime theory can be applied to scattering incident sound. It also investigates how coprime array concepts can be applied to volumetric diffusers using solid cylinders as sparse array elements. These are arranged in pairs of subarrays whose number of cylinders are two mutually prime (coprime) integers in a sparse arrangement. Coprime scatter arrays are tested experimentally as sparse sound diffusers using one-fifth scale modeling and an acoustic goniometer to investigate coprime sparse diffuser effectiveness in real world applications.
A physical model of a highly nonlinear string and its use in the music composition Quartet for Strings
Authors: Berdahl Edgar , Beck Stephen D. , Pfalz Andrew
Published: May 2016

A real-time virtual string model is created that supports two modes of haptic force-feedback interaction. Using one haptic controller, the string can be plucked, and using a second haptic controller, the virtual string's pitch can be continuously varied by applying pressure to the string. Via both controllers, the vibrations of the virtual string can be felt while it is played. These functionalities are achieved by modeling the string as a finite sequence of interleaved masses and stiffening springs. For artistic purposes, a nonlinear spring force characteristic function is selected that limits the effective stiffness of each spring to a range between k and (k + ks). This function is F(x) = kx + (ksx3)/(β2+x> + x2), where x is the displacement of the nonlinear spring and β approximately adjusts the displacement at which the stiffness becomes significantly nonlinear. For small displacements, the string's undamped fundamental frequency is tuned by k, and for sufficiently large displacements, the string's undamped fundamental frequency is approximately tuned by (k + ks). The composition Quartet for Strings features the model tuned to four different scales (treble 1, treble 2, alto, and bass), each of which is played by a human performer according to the score of Quartet for Strings. For this composition, (k + ks) is set so that when the string is vibrated at sufficiently large displacements, the pitch increases by approximately an octave but not precisely an octave, in order to provide for a more complex pitch space.
Aircraft carrier noise measurements of a high-performance fighter jet
Authors: Wall Alan T. , McKinley Richard L. , Sedillo Michael R. , Swayne Billy J. , Smith Michael J. , Aubert Allan C. , Nantz Robert E. , Imhof Gregory J.
Published: May 2016

The on-deck measurement of F-35C noise levels occurred during the DT-II sea trials aboard the USS Dwight D. Eisenhower in October 2015. The existence of aircraft carrier flight deck fighter noise data is extremely rare, with this data set being only the second of its kind in terms of its scope. Custom acoustic recording instrumentation was designed to obtain quality broadband noise measurements of high-amplitude signals, protected from extraneous noise due to high wind speeds, and shielded from intense electromagnetic interference from the multiple on-board radar systems. The data collected allow for the estimation of noise exposures at all pertinent flight deck locations where crewmembers are positioned. [Work supported by USAFRL through ORISE and F-35 JPO.]
Development of a direct aerodynamic drag measurement system for acoustic liners
Authors: Jasinski Christopher
Published: May 2016

The objective of this paper is to establish the validity of a measurement apparatus for determining aerodynamic drag caused by acoustic liners. Conventional acoustic liners for ducted turbofan engine nacelles have been proven to reliably reduce engine noise in commercial aircraft for a narrow frequency range. Traditional acoustic liners consist of a porous facesheet, honeycomb core, and solid backing. As technology has developed, new liner designs, including variable-depth cores, show promise of reducing noise in a broad frequency range. Additionally, the next generation of aircraft design may allow for additional aircraft surface area to be covered by acoustic liners, further reducing aircraft noise perceived on the ground. Before these advanced acoustic technologies can make their way onto commercial aircraft fleets, the aerodynamic drag caused by the liners must be understood. Using the Mach 0.6 Wind Tunnel at the University of Notre Dame, a direct drag measurement system has been developed utilizing a linear force balance. In combination with indirect drag measurements taken at NASA Langley’s Curved Duct Test Rig, measurement confidence has been established. This paper will detail the capabilities of the direct drag measurement system at Notre Dame and explore its intended future use in developing new liner technologies.
Acoustic hysteresis of varying cavity length of a bottle-shaped thermoacoustic prime mover with a neck to cavity ratio of 1:10
Authors: Jensen Emily , Andersen Bonnie
Published: May 2016

A previous study showed hysteresis in transition regions to overtones of bottle-shaped thermoacoustic prime movers with a neck to cavity diameter ratio of 1:2.4 while varying the cavity length. Hysteresis regions were studied with a neck to cavity diameter ratio of 1:10. The device consisted of a neck (5.15 cm long, 0.75" ID) with a heating element around it and a cavity (ID 3.75") with a sliding piston, allowing the cavity length to be varied up to 38 cm long. Copper mesh was used for the heat exchangers and were located about 30{\%} away from the top of the neck and 16 mg of steel wool served as the stack. A pressure sensor was connected to the center of the piston to measure acoustic pressure at the bottom of the cavity. Acoustic pressure, frequency, and hot and cold temperatures were recorded while both increasing and decreasing the cavity length from about 2 to 38 cm in increments of 0.2 cm over time intervals of 20 s with an input power of 10.5 W. Three transitions to overtones occurred at 6.8, 15.2, and 27.4 cm while pulling the piston out and at about 25.2, 15.6, and 6.0 cm while pushing the piston in. Frequencies and transition regions agreed with expected values. Both hot temperature and acoustic pressure increased during transition regions. This could be caused from multiple acoustic waves being produced.
Entrainment of two thermoacoustic engines
Authors: Symko Orest G. , Flitcroft Myra , Gillman Brenna , Rodriguez Ivan , Wilson Cedric C.
Published: May 2016

In order to build more powerful sources of sound for energy conversion, the synchronization of two thermoacoustic heat engines has been studied. Experiments were performed on engines in the acoustic frequency range of 2.6 kHz and also on very small engines in the ultrasonic range of 24 kHz. In both cases, the engines were mounted on a cylindrical cavity, and they were coupled mainly by the acoustic field in the surrounding air at one atmosphere. They were driven by heaters of resistance wire in contact with the hot heat exchanger. At a specific coupling between the 2.6 kHz, engines' synchronization occurred, and also for the 24 kHz devices; frequency pulling in each pair of engines led to a common frequency in each set, i.e., in-phase synchronization. The strength of the synchronization was determined as a function of detuning of engines. Mutual entrainment was observed at the onset of oscillations and this is attributed to drive by fluctuations. Moreover, as a result of synchronization, the critical temperature gradient for onset of oscillations was reduced from that of the individual values. Delays between two oscillators in the start up led to quenching of the generated sound output ( oscillation “death” of Rayleigh).
Irregular reflection of weak acoustic shock pulses on rigid boundaries
Authors: Cyril Desjouy , Ollivier Sébastien , Marsden Olivier , Dragna Didier , Karzova Maria , Blanc-Benon Philippe
Published: May 2016

The reflection of weak shockwaves on rigid boundaries at grazing angles was studied in different geometrical configurations. It was shown that even in the case of weak shocks, irregular reflection of N-waves can lead to the formation of a three shocks pattern with a Mach stem, a triple point above the rigid surface and an angle reflection which differs from the incident one. Experiments were done using spark generated spherical shock waves with peak pressure lower than 10 kPa. Reflection patterns of shocks were obtained using a Schlieren visualization setup. Both regular and irregular regimes of reflection were observed. Numerical simulations of the nonlinear propagation were also performed. They were based on the high-order finite difference solution of the two dimensional Navier-Stokes equations. Optical measurements were compared with the results of simulations. Both experimental and numerical results showed the growth of the Mach stem with the distance of propagation. In the case of a randomly or periodically rough surface, the Mach stem is shorter, and nonlinear interactions between reflected waves occurs. [This work was supported by the Labex Centre Lyonnais d’Acoustique of Université de Lyon, operated by the French National Research Agency (ANR-10-LABX-0060/ANR-11-IDEX-0007).]
Quadspectral nonlinearity analysis of military jet aircraft noise waveforms
Authors: Miller Kyle G. , Gee Kent L. , Reichman Brent O. , Neilsen Tracianne B. , James Michael M.
Published: May 2016

Understanding the impact of jet noise can be improved by quantifying the nonlinearity in a signal with a single-microphone measurement. Based on the quadspectral Morfey-Howell indicator, a nonlinearity gain factor called νN has been derived from an ensemble-averaged, frequency-domain version of the generalized Burgers equation [Miller et al., AIP Conf. Proc. 1685, 090003 (2015)]. This gain factor gives a quantitative expression for the change in sound pressure level spectrum over distance. Past results show that νN accurately characterizes nonlinear evolution of waves in simulation and model-scale jet data. Here, noise waveforms from a high-performance military jet aircraft are characterized using the νN indicator; results are compared with those from other indicators that have been used previously (e.g., derivative skewness, time-waveform steepening factor, etc.). Far field results show that the nonlinear gains at high frequencies (>1 kHz) tend to balance the absorption losses, thus establishing the characteristic 1/f2 spectral slope. Additionally, trends over angle, distance, and engine condition are explored. [Work supported by the AFRL SBIR program.]
Dynamics of cavitating layer on a surface of quasi-empty cavity in a real heterogeneous liquid
Authors: Kedrinskiy Valeriy , Bolshakova Ekaterina S.
Published: May 2016

The state dynamics of a heterogeneous medium surrounding the spherical cavity is considered, using the multi-phase mathematical model with an incompressible liquid component. The heterogeneous medium contains 1.5-micron bubbles with a density of 106 cm−3. At t = 0, the pressure in the cavity is sharply decreased up to p (0) values forming instantly the dynamically changing decompression wave in the surrounding medium. Numerical analysis allowed to find the significant influence of p (0) values on the dynamics of the cavitating layer on the cavity surface. When p (0) = 10−2 MPa, approximately 20 pulsations of bubble radii and their internal pressure are observed during the collapse time of 1 cm cavity (T is 0.9 ms). Most of them reach only its initial state with a pressure about 0.1 MPa. But at approaching to the time moment close to T value, a few pressure pulsations demonstrate the cumulative effect of over-compression up to the pressures of 0.6, 1.8, and 3 (in log-scale). The letter means that cavitating boundary layer accumulates the energy of high density. When the p (0) = 10−4 MPa, only one pulsation synchronous with the cavity collapse as well as the over-compression effect are observed. [Work supported by RFBR, grant 15-05-03336.]
Yeast flocculation using acoustic agglomeration
Authors: Holdhusen Mark H.
Published: May 2016

A major cause of haziness in beer is due to yeast suspended in the liquid. The most common methods used to flocculate the yeast and have it settle out of the liquid solution are to use various chemicals, cold temperatures, and/or extended time. This research considers using acoustic agglomeration to cause the yeast to flocculate as a means to clarify beer. Acoustic agglomeration uses high intensity acoustic standing waves to clump fine particles together in order for them to become large enough to settle out of the fluid. In this work, an ultrasonic acoustic transducer will be implemented to achieve standing waves in the beer. In theory, these standing waves will cause the yeast particles to clump together and settle. The results from this approach will be compared to the traditional methods of yeast flocculation. This approach may lead to an increase in efficiency in clarifying beer without the use of undesirable chemicals. The preliminary work considered here is a proof of concept and will use visual inspection as a means of clarity comparison. Future work will use more in-depth laboratory analysis as a means of comparison of clarity.
Discrimination and streaming of speech sounds based on differences in lateralization in the horizontal and median planes
Authors: David Marion , Oxenham Andrew
Published: May 2016

Understanding speech in complex backgrounds relies on our ability to perceptually organize competing voices into streams. Differences in fundamental frequency (F0) between voiced sounds are known to enhance stream segregation; less is known about the perceptual organization of unvoiced sounds such as fricative consonants. We showed previously that natural consonant-vowel (CV) pairs can be segregated based on F0 differences, despite lacking F0 cues in the fricative part. This study also used CVs, filtered by head-related impulse responses (HRIR) to simulate different positions in the horizontal and median planes. In the median plane, cues are limited to high frequencies, and so should affect fricatives more than vowels. Both discrimination, using a three-interval forced-choice task, and streaming, using a within- or across-stream repetition-detection task, were tested. The CV pairs were either held constant during a trial, or varied randomly. In the constant condition, any difference in spectrum would indicate a change in location along the median plane; in the variable condition, such differences would require listeners to extract spectral regularities from across widely varying spectra of the speech stimuli. Preliminary results suggest that discrimination and streaming are more challenging in the median than in the horizontal plane. [Work supported by NIH grant R01DC012262.]