bluuebunny/crossref_metadata_2025 huggingface dataset:
Design optimization of a piezoelectric microphone with in-plane directivity
Authors: Kuntzman Michael L. , Hewa-Kasakarage Nishshanka N. , Kim Donghwan , Rocha Alex , Hall Neal A.
Published: November 2013

A piezoelectric micromachined microphone with in-plane directivity has been recently introduced [Appl. Phys. Lett. 102, 054109 (2013)]. The work is inspired by a design introduced by Miles et al. [J. Acoust. Soc. Am. 125(4), 2009], which was, in-turn, inspired by the hearing mechanism of a particular type of parasitoid fly. A rocking structure pivots about a rotational hinge in response to in-plane pressure gradients, and the rocking motion is read by springs attached to the end of the rocking ‘teeter-totter’ structure, with the springs themselves employing thin piezoelectric films, which operate in a 3-1 mode. Prototypes have been fabricated that employ rocking structures 1 mm x 2 mm in size and functionality has been verified via directivity measurements performed in an anechoic chamber. This presentation will focus on exploring the design space of this sensor, which is accomplished with a hybrid model based on FEA and network models. Designs which maximize SNR are presented, and anticipated microfabrication challenges of these designs are highlighted.
Experimental and numerical analysis of the effects of depth, diameter, and tension in musical drumhead coupling
Authors: Boe Benjamin , Worland Randy
Published: November 2013

The low frequency vibrations of two-headed musical drums are known to couple. However, little is known regarding the factors that determine the degree of coupling at higher frequencies. In this study, the effects that depth, diameter, and head tension have on the tendency of the drumheads to couple are investigated. Commercial finite element software was used to model a wide range of drums and to identify trends of coupling according to these factors. The numerical results were used to guide which parameters should be tested in the lab. Experimentally, two oppositely facing Electronic Speckle-Pattern Interferometry systems were used to optically view the simultaneous vibrations of both heads of a drum. Several snare and tom tom drums with different diameters, depths, and tensions were observed. To closely analyze the effect of drum depth a tom tom was modified so a range of depths from 1.5’’ to 40’’ could be tested while keeping the diameter and tension constant. The optical and numerical data are used to illustrate trends in the coupling of musical drumheads.
The real world transmission loss chamber: A work in progress
Authors: Bliefnick Jay , Hulva Andrew M. , Chéenne Dominique J.
Published: November 2013

A “real world” transmission loss (RWTL) chamber was recently added to the undergraduate acoustics program at Columbia College Chicago. It aims to demonstrate concepts of transmission loss to students and to provide a “less-than-ideal” environment for construction evaluation prior to certified tests with full-size samples. Each side of the chamber can be used as either “send” or “receive,” and both speaker and microphone placements are infinitely variable. The noise floor can also be adjusted to illustrate potential issues in field tests. Measurements are taken simultaneously from multiple positions, then averaged to yield TL values and an overall isolation rating. Given its construction, the chamber is not expected to produce results as per existing standards as its small size results in modal effects and non-diffuse conditions on both sides of the tested partition. This study’s first goal was to better understand the performance limitations of the RWTL chamber by conducting a thorough evaluation of its maximum TL and modal properties. The second goal was to optimize the chamber’s testing methodology in order to more closely reflect certified laboratory results; this was done by utilizing recently obtained certified data from a door manufacturer who tested reduced-sized samples in the RWTL chamber.
Comparing the time variance of orchestral instrument directivities in Mozart’s symphony in G-minor: First movement
Authors: Hanna Kristin , Wang Lily M.
Published: November 2013

Multiple channel anechoic recordings of the musical instrument parts in Mozart’s Symphony in G-Minor (First Movement) are analyzed to study how the directivity patterns of each instrument varies with time. Static directivity patterns are well-documented for many musical instruments, but studies on how their directional patterns vary with time are not as common. Changing directional patterns in time, however, have been found to impact the realism of room acoustic computer modeling simulations. Previous work at the University of Nebraska has suggested a method for studying the time variance of musical instruments across a number of simultaneously recorded channels in an anechoic chamber. The method involves time-windowing each channel and analyzing how the overall directivity index changes across time and frequency. Comparisons of results from some of the fourteen instruments included in this Mozart symphony are presented. [Work supported by a UNL Undergraduate Creative Activities and Research Experience Grant.]
Assessing the effectiveness of geometrically modified pyramidal diffusers: Scattering coefficient measurements
Authors: Sharma Ariana F. , Bradley David T.
Published: November 2013

A diffuser is a surface with a non-planar geometry used in acoustically sensitive spaces to help mitigate unwanted effects from strong reflections such as echoes and focusing. Although a variety of diffuser surface geometries exist, new designs are constantly being generated for use in specific real-world projects in an effort to expand the aesthetic options available to the architect and acoustical consultant. The effectiveness of these new designs must be determined as part of the responsible acoustical design process. In the current project, the acoustic behavior of surfaces with a pyramidal base pattern has been measured according to standard ISO 17497-1. In particular, the standard outlines the measurement of the scattering coefficient, a quantifier of how much energy has been reflected away from the specular direction. This coefficient gives a general indication of the diffusing effectiveness of the surface and is useful in computational acoustics room modeling. The surface pyramidal base pattern has been varied to create an array of surfaces in an effort to find an optimal combination of geometric input parameters. Certain measurement conditions prescribed in the ISO standard were also varied to determine their effect on measurement accuracy. Results and analysis will be presented.
Area-wide infrasound measurements for two wind turbine facilities
Authors: Carman Richard , Amato Michael
Published: November 2013

Area-wide measurements of low frequency wind turbine noise were conducted in residential areas adjacent to two different wind turbine facilities in Southern California. The residential measurement location distances ranged from 615 m to 9 km from wind turbines. Additional measurements were also conducted at distances as close as 125 m from the wind turbines. To obtain the residential measurement data, simultaneous digital recordings were made inside and outside residences using microphones designed to achieve a linear response down to 0.07 Hz. The outdoor measurements were conducted with a ground board and two windscreens. The recorded data at residences were analyzed using a cross-spectral technique to minimize the effects of wind acting on the microphone. The data clearly show the presence of infrasound at the blade passage frequency of the wind turbines as well as at the associated harmonics. The primary range of interest is frequencies between 0 and 10 Hz. The residential data in some instances indicate higher levels of infrasound indoors compared to outdoors, indicating a potential amplification of very low frequency sound energy by the residential structure. Representative infrasound data for both facilities are presented and discussed.
Narrowband low frequency pressure and vibration inside homes in the proximity to wind farms
Authors: Metelka Andy
Published: November 2013

Narrowband fast Fourier transform measurements made outside and inside homes indicate that unlike audible tones, low frequency pressure waves penetrate homes virtually un-attenuated. Simultaneous multi-channel linear weighted pressure measurements were made in various locations as well as seismic floor velocities using various dynamic signal analyzers and sensors. Several areas of concern would include harmonics of blade pass frequencies and also modulation at 20, 30, and 40 Hz (audible). Traditional acoustic models do not predict or measure low frequencies as raw un-weighted pressure. Measurements to be presented indicate pressure levels much higher than the audible tone pressure levels. Similar signatures were measured as seismic ground vibration in the basements of homes at relatively low levels. In order to minimize the effects in the homes and to locate wind turbines properly, it may be important to establish measurement standards for low frequencies before locating wind turbine developments.
Effective Gol’dberg number for diverging waves
Authors: Hamilton Mark F.
Published: November 2013

Interest in characterizing nonlinearity in jet noise has motivated consideration of an effective Gol’dberg number for diverging waves [Baars and Tinney, Bull. Am. Phys. Soc. 57, 17 (2012)]. Fenlon [J. Acoust. Soc. Am. 50, 1299 (1971)] developed expressions for the minimum value of Γ, the Gol’dberg number as defined for plane waves, for which shock formation occurs in diverging spherical and cylindrical waves. The conditions were deduced from a generalized Khokhlov solution and depend on the ratio xsh/r0, where r0 is source radius, and xsh the plane-wave shock formation distance for Γ=∞. Alternatively, by taking the ratio of the nonlinear and thermoviscous terms in Fenlon’s Eq. (2), it is proposed here that effective Gol’dberg numbers may be identified for spherical and cylindrical waves: Λ=Γexp(-πxsh/2r0) and Λ=Γ/(1 + πxsh/4r0), respectively. For a given value of Λ, the diverging waves achieve approximately the same degree of nonlinear distortion as a plane wave for which the value of Γ is the same. Conversely, to achieve the same degree of nonlinear distortion as a plane wave with a given value of Γ, the value of Γ for, e.g., a spherical wave must be larger by a factor of exp(πxsh/2r0). Extensions to other spreading laws are presented.
Preliminary phased-array characterization of near-field military jet aircraft noise
Authors: Harker Blaine M. , Gee Kent L. , Neilsen Tracianne B. , James Michael M.
Published: November 2013

Major developments over the past decade in aeroacoustic beamforming techniques provide more accurate estimates of jet noise source phenomena. In a recent experiment, near and mid-field measurements of an F-22A using linear and planar microphone arrays were taken at various engine conditions about the jet plume. To locate and provide accurate amplitude levels of jet noise sources, conventional beamforming techniques are used with various array shading methods. Equivalent source reconstructions are shown for different engine conditions, observation angles, and frequencies to explore the source region. In addition, different datasets from spatially separated arrays are combined for improved source reconstructions and to account for spatially dependent spectral content. These results are preliminary to further techniques—such as deconvolution methods—to better understand noise source mechanisms within the jet plume. [Work supported by ONR.]
Glass-like phonon scattering from spontaneous nanostructures in silver-antimony-tellurium
Authors: Ma Jie , Delaire Olivier , May Andrew , Carlton Chris , McGuire Michael , VanBebber Lindsay , Abernathy Douglas , Ehlers Georg , Hong Tao , Huq Ashfia , Tian Wei , Keppens Veerle , Yang Shao-Horn , Sales Brian
Published: November 2013

Materials with very low thermal conductivity are of great interest for both thermoelectric and optical phase-change applications. Synthetic nanostructuring is most promising for suppressing thermal conductivity arising from scattering phonons, but challenges remain in producing bulk samples. In crystalline AgSbTe2, we show that a spontaneously forming nanostructure leads to a suppression of thermal conductivity to a glass-like level. Our mapping of the phonon mean-free-paths provides a novel bottom-up microscopic account of thermal conductivity and also reveals intrinsic anisotropies associated with the nanostructure. Ground-state degeneracy in AgSbTe2 leads to the natural formation of nanoscale domains with different orderings on the cation sublattice, and correlated atomic displacements, which efficiently scatter phonons. This mechanism is general and suggests a new avenue for the nanoscale engineering of materials to achieve low thermal conductivities for efficient thermoelectric converters and phase-change memory devices.
Inelastic scattering and resonance ultrasound spectroscopy for functional materials studies
Authors: Hermann Raphael P.
Published: November 2013

The combined use of inelastic scattering, resonant ultrasound spectroscopy, and other macroscopic thermodynamics characterization techniques will be presented. In particular, inelastic neutron scattering and nuclear inelastic scattering (NIS) by Mössbauer resonant nuclei are two techniques that probe acoustic phonons and provide a microscopic counterpoint to direct speed of sound measurements. Results from new developments for the Sb and Te element specific NIS with sub-meV resolution will be presented for materials with thermoelectric or phase change properties. Specifically the lattice softening in the YbFe4Sb12 skutterudite [Moechel et al., Phys. Rev. B 84, 184306 (2011)] and the systematic softening observed in nanostructured thermoelectric materials [Claudio et al., J. Mater. Sci. 48, 2836 (2013)] with respect to their bulk counterpart will be discussed, as well as lattice softening in magnetocaloric MnFe4Si3. [The European Synchrotron Radiation Facility is acknowledged for provision of the synchrotron radiation facility at beamlines ID18 and ID22N; the Institut Laue Langevin for beamtime at IN6; the Deutsche Forschungsgemeinschaft for funding SPP-1386 ”Nanostructured Thermoelectrics” and SFB-907 ”Nanoswitches"; the BMBF for NanoKoCh 03X3540; and the Helmholtz Gemeinschaft Deutscher Forschungszentren for VH-NG-407 and HRJRG-402.]
A long-sought phase transition in superconducting cuprates observed via resonant ultrasound spectroscopy
Authors: Migliori Albert , Shekhter Arkady , Ramshaw Brad J. , McDonald Ross D.
Published: November 2013

Among the biggest mysteries of high-temperature superconductors is the so-called pseudogap—somewhat similar to the gap in the electronic density of states found in the superconducting phase, but occurring at a different temperature. The pseudogap may represent either the gradual onset of a precursor to superconductivity or an entirely new phase, characterized by the gain or loss of some hidden order. Several experiments in recent years have favored the latter, but the smoking gun, the thermodynamic signature of a pseudogap phase transition, had not been observed. Using resonant ultrasound spectroscopy, we measured the temperature-dependent elastic stiffness of two cuprate superconducting crystals, one underdoped and one overdoped and found a break in slope at a doping-dependent temperature T*. For the underdoped cuprate, T* coincides with the onset of the pseudogap and with earlier neutron-scattering measurements of the appearance of magnetic order (blue squares). Crucially, for the overdoped cuprate, T* < Tc so that extrapolating to higher doping where T* = 0 will yield a quantum critical point, which may be key to understanding the mechanism of high-temperature superconductivity (Nature 498, 75 (2013).
High temperature elastic constants of rare-earth doped Sr0.9X0.1TiO3-δ (X = Pr, Y)
Authors: Gladden Josh R. , Tennakoon Sumudu P. , Adebisi Rasheed , Zhang Qin , Dehkordi A. M. , Bhattacharya S. , Tritt T. M. , Alshareef H. N.
Published: November 2013

Temperature dependence of the elastic constants of polycrystalline rare-earth doped strontium titanate (STO) [ Sr0.9X0.1TiO3-δ (X = Pr, Y)] was investigated in the temperature range of 300 K—750 K using resonant ultrasound spectroscopy. Elastic constants of undoped STO decrease linearly indicating typical softening with increased temperature. Yttrium (Y) doped STO also exhibits a monotonic softening, however, with a pronounced curvature in this high temperature regime. Trends of elastic constants of the praseodymium (Pr) doped STO show a non-monotonic stiffing from room temperature to 475 K, followed by a gradual softening. Changes in attenuation were quantified by the inverse quality factor (1/Q) averaged over measured resonances. Undoped STO showed a monotonic gradual increase of attenuation with increasing temperature while yttrium doped STO showed little variation. In contrast, attenuation of Pr doped STO exhibited a peak around 425 K. These results will be compared to thermal conductivity measurements in the same temperature range and phonon scattering mechanisms will be discussed.
Capacitive micromachined ultrasonic transducers as tunable phononic crystals
Authors: Lani Shane , Rashid M. Wasequr , Sabra Karim G. , Degertekin F. Levent
Published: November 2013

Capacitive micromachined ultrasonic transducer (CMUT) arrays are made up of microscale (10-100µm wide) membranes with embedded electrodes for electrostatic excitation and detection of acoustic waves. While typically used for far-field imaging, CMUT arrays also support dispersive evanescent surface waves. These surface waves derive their dispersive properties not only from the periodic structure of the array, but also from the membrane resonance. One advantage of CMUTs as a metamaterial is that the dispersive qualities of the array can be tuned by changing the applied bias voltage to the membranes, which in effect changes the membrane stiffness. A second advantage is that the CMUT array elements can be used as receivers to record the acoustic waves with high spatial resolution, which make laser displacement measurement based characterization unnecessary. These properties allow the possibility of CMUTs to exploit these slowly propagating evanescent waves as a means for creating subwavelength resolution fields for high-resolution ultrasound imaging and sensing in the near field by appropriately tuning the physical characteristics of individual membranes. The dispersive behavior of these evanescent surface waves propagating along a CMUT array was quantified using a computationally efficient, boundary element method based model and validated with both finite element analysis and experimental data obtained from a 1 x 16 CMUT array with a membrane resonance tunable between 5 and 6.5 MHz.
Groundborne noise produced by rail transit tunnel construction
Authors: Bergen Thom , Nelson James T. , Watry Derek L.
Published: November 2013

Groundborne noise and vibration produced by rail transit tunnel construction activities was studied recently in Seattle, Washington. Recent and ongoing tunneling is accomplished with tunnel boring machines (TBMs) and associated supply trains. Vibration produced by construction activities in the tunnels 30 to 40 m below the surface propagated efficiently to through the soils in the Seattle area. The local geology consists largely of “overconsolidated glacial till” that is very stiff. The study revealed that the supply trains traveling over rail joints was the dominant source of ground vibration, and the re-radiated groundborne noise in numerous homes above the tunnels was audible. The noise was effectively mitigated by patching and smoothing out the rail joints, and supporting the ties on natural rubber pads.
Nonlinear ultrasonic waves for monitoring thermal stresses in solids
Authors: Nucera Claudio , Lanza di Scalea Francesco
Published: November 2013

It is known that nonlinear ultrasonic waves in solids are sensitive to quasi-static stresses. The stress sensitivity of elastic waves is typically associated to finite strains (e.g., theory of acoustoelasticity). In the case of waveguides, classical nonlinear theories for guided waves are still based on the assumption of finite strains. In the case of constrained solids subjected to thermal excursions, however, there are theoretically no finite strains (for perfectly constrained solids) associated with thermal stresses. A new model is therefore needed to justify the existence of wave nonlinearities in this case of stress without strain. This problem is solved on the basis of the interatomic potential of the solid that indicates a “residual” strain energy, due to the prevented thermal expansion, which is at least cubic as a function of strain. Consequently, a nonlinear wave equation can be derived. The solution to this equation leads to a new nonlinear parameter for double harmonic generation that is directly related to the thermal stresses in the structure. This study finds applications in the monitoring of thermal stresses in buckling-prone structures, such as continuously welded railroad tracks and pipelines. Experimental tests conducted on railroad tracks with realistic support will be also presented.
Younger versus older infants’ use of prosody-like boundaries to locate musical phrases
Authors: Hawthorne Kara E. , Gerken LouAnn
Published: November 2013

In spoken language, particularly of the infant-directed variety, clauses are marked with prosodic cues, such as final lengthening and pitch resets at boundaries (e.g., Soderstrom et al., 2008). Though prosody is specific to language, similar acoustic cues mark phrase boundaries in music, and infants are sensitive to the correlation of these cues at musical boundaries (Jusczyk and Krumhansl, 1993). In the present study, we ask whether younger (4-month-old) and older (16-month-old) infants can use prosody-like boundary cues to facilitate recognition of musical phrases. In a musical extension of Soderstrom et al. (2005), infants were familiarized with one of two brief melodies, then were tested using the head-turn preference procedure on their ability to recognize a phrase versus phrase-straddling excerpt from the familiarization melody when it is embedded in a new musical passage. Preliminary results suggest that younger infants show a familiarity preference for the test melody containing a phrase from the familiarized melody, while older infants do not discriminate between the test item types. This suggests that young infants use prosody-like cues to group acoustic stimuli in a domain-general way, whereas older infants may not.
Stop production in bilingual and second language-learning children
Authors: Lee Sue Ann , Iverson Gregory , Lee Jahyung
Published: November 2013

This study examined stops produced by 7 year-old Korean-English bilingual (KEB) children and age-equivalent Korean children who had learned English as a second language (L2) in order to investigate how duration of exposure affects the PHONETIC systems of their two languages. A total of 60 children participated (15 per group; monolingual English, monolingual Korean, KEB and L2 children). Word-initial VOT and f0 values in the following vowel were measured in both languages. Comparison of English and Korean stops produced by monolingual children showed that the two English (voiced and voiceless) and three Korean (fortis, lenis, & aspirated) stop types were fully distinguished. Like the monolinguals, KEB children produced English and Korean stops distinctively, indicating that they possess two separate stop systems. But while L2-learning children distinguished English voiced from Korean fortis, and English voiceless from Korean lenis, they produced English voiceless and Korean aspirated stops similarly. Compared to adult Korean L2 learners who did not distinguish English voiced from Korean fortis (Kang and Guion, 2006), the results here suggest that young L2 children express more sophisticated phonetic categories than do adult L2 learners. [Funded by NICHD (RHD061527A).]
Difficulty in the acquisition of Mandarin high level and high falling tones by Cantonese learners
Authors: Wu Xianghua , Saito Kazuya
Published: November 2013

Native speakers of tone languages commonly have difficulty discriminating tones with the same phonological function (Huang, 2001), such as Cantonese high level and high falling tones; however, acquisition of such tones with distinctive phonological status in a second language (L2) remains unclear. This study tested 34 Cantonese learners before and after training on Mandarin high level, mid-rising, and high falling tones. Perception was evaluated using a forced-choice identification task, and nine native speakers of Mandarin judged productions from repetition and narrative tasks. Despite improvement in post-tests, perception of high level and high falling tones was found to be more difficult than mid-rising tone in both pre- and post- tests. Misidentification patterns also showed more confusion between high level and high falling tones than other tone pairings, but no effect of training was observed. Compared to the perception results, high falling tone was produced more frequently as high level tone, particularly in the narrative task before and after the training. The results suggest that L2 tone acquisition is complicated by the complex phonological correspondence between L1 and L2 tones. [Research supported by Language Learning Research Grant.]
Non-native vowel production accuracy and variability in relation to overall intelligibility
Authors: Dimov Svetlin , Bradlow Ann
Published: November 2013

Previous research suggests that accuracy (i.e., distance to the average location of native productions) has less effect on adaption to non-native speech than category variability [e.g., Wade et al., Phonetica 64, 122-144 (2007)]. Here we investigate the relationship between overall intelligibility of Mandarin-accented English for native English listeners and (a) vowel production accuracy, and (b) vowel production consistency. Intelligibility estimates were based on sentence-in-noise recognition accuracy scores. Vowel accuracy and consistency estimates were based on formant measurements of point vowels (/i/, /u/, /ae/, and /a/) extracted from words in the sentence materials that were presented to listeners for intelligibility testing (8-20 samples/vowel/talker). If listeners have expectations about a vowel category location based on accumulated exemplar storage, then greater accuracy (smaller Euclidean distance to native category mean) should be positively related to intelligibility. If listeners are sensitive to vowel category distributions, then greater consistency (smaller standard deviation of f1 or f2 within categories) should be beneficial to intelligibility. A mixed effects linear model revealed that only consistency was a significant predictor of intelligibility. Accuracy was not a significant predictor. This result suggests that intra-speaker variability is detrimental to L2 intelligibility, regardless of distance to native categories.
Information-theoretic quantification of underwater acoustic source localization performance
Authors: Hayward Thomas J.
Published: November 2013

Metrics that historically have been applied to quantify the performance of signal processing for source localization are algorithm-dependent. For example, performance of conventional beamforming or matched-field processing is usually quantified by main-peak width and secondary-peak levels of the beam response or spatial ambiguity function, while performance of Bayesian localization may be quantified by measures of the statistical dispersion of the a posteriori pdf of source location. While algorithm-dependent performance metrics permit comparisons within a given class of signal processing algorithms, they do not provide comparability across algorithm classes. The present work identifies fundamental information-theoretic quantities that can be used as metrics to quantify the source localization performance of diverse signal processing algorithms and thus provide for performance comparisons across signal-processor classes. These quantities include conditional entropy of source location given processor output, mutual information of source location and processor output, and cross-entropy of actual and posterior source-location probability distributions. Applications of these information-theoretic metrics are illustrated in examples of Bayesian localization, conventional beamforming, and matched-field processing of a time-harmonic source in a range-independent shallow-water acoustic waveguide. The results are interpreted in the light of the data processing inequality of information theory. [Work supported by ONR.]
Position estimation of rotating sound source using Kalman filtering based on time difference of arrival measurements
Authors: Lee Jaehyung , Go Young-Ju , Choi Jong-Soo
Published: November 2013

In this work, we are interested in tracking a rotating sound source using a Kalman filtering technique based on a set of non-linear time difference of arrival (TDOA) measurements. Array of microphones measure acoustic signal emitted from a rotating source and the TDOA estimates are calculated followed by a solution for hyperbolic position fix. The position estimation of sound source based on TDOA is a popular technique in source localization. The method involves calculation of a set of nonlinear equations and poor accuracy of TDOA estimates often results in inaccuracy in location. In this work, the range difference is expressed by a model movement on which a recursive extended Kalman Filter has been developed. The TDOA measurements optimize the estimated values which are reduced as observation in extended Kalman filtering algorithm. Location estimation is updated from TDOA measurements along with the time history data. The Cramer-Rao Lower Bound (CRLB) is derived and simulations are compared. [Work supported by National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2010-0014978).]
Prototype development of underwater noise impact alert region prediction system
Authors: Cheng Yu-Chen , Chang Andrea Yuan-Ying , Chen Chi-Fang , Lin Sheng-Fong
Published: November 2013

Offshore wind farms are the main project in western Taiwan. Since the underwater noise generated by piling poses a threat to the marine mammals, the issue of detrimental impact of noise on Sousa Chinensis is proposed. To avoid causing behavioral disturbance and injury from pile driving noise, Underwater Noise Impact Alert Region Prediction System (UNIARPS) was established to estimate the acoustic field at any depth and distance from piling source. The system can be illustrated as four components, environment databases, acoustic propagation model, source modeling, and noise level prediction. The ocean numerical model (TCONFS) generates time spatial dependent temperature profiles for water column variability, and geo-acoustic and bathymetry databases are imported as environmental inputs. Adiabatic mode theory is used to simulate the piling noise propagating in shallow water and the impulsive noise emanating from source is evaluated via finite element method. While the auditory threshold of cetacean set as criterion level, the system can demonstrate the modeling outputs and predict noise impact region, and these results are useful to prior planning on how to station the guarding boats in preventing dolphins entering the noise impact region. [The financial support provided by Bureau of Energy (Grant No.102-D0105) is gratefully acknowledged.]
Depth-tracking of a near-surface target from the deep ocean
Authors: Danesh Sheida , Schmidt Henrik
Published: November 2013

Determining the depth of an acoustic source in a deep ocean environment can be approached using a variety of existing methods, each with inherent limitations. A method for determining the depth of a moving near-surface acoustic target from a fixed vertical array below the deep ocean critical depth is presented using the characteristics of the Lloyd mirror pattern of a near-surface acoustic signal and a library of calculated patterns. Depth estimates of the moving target are made in real-time and incorporated into a confidence metric for tracking the target motion. Results indicate that this method is robust, performing well in conditions involving environmental mismatch and a moderate amount of surface noise.
Evaluation of complex broadband biomimetic waveforms for active sonar
Authors: Dobbins Peter
Published: November 2013

There is an expanding requirement to reduce the impact of man-made sound, including active sonar transmissions, on marine mammals in the defence, offshore, and other sectors. One way this might be achieved in sonar applications is to use signals derived from natural sounds such as the vocalizations of the animals themselves. It might be expected that such sounds would appear more familiar, thus reducing possible abnormal behavioral impacts. This paper reviews the use of such waveforms and presents the results from a trial designed to compare the detection capabilities of a variety of broadband signals, both conventional and ‘novel’, with a medium frequency active sonar. Two biomimetic signals were tested, one based on sperm whale echolocation clicks and the other on pilot whale whistles. Preliminary analysis suggests the detection performance of these signals using conventional matched filters is comparable with linear FM chirps with a similar bandwidth, but may be improved with detection techniques commonly used for marine mammal vocalizations, such as spectrogram correlation. The paper will conclude with an assessment of the potential impacts of such signals on marine life.
Interpulse noise assessment during shallow water seismic survey using airgun excitations
Authors: Guan Shane , Vignola Joseph F. , Ryan Teresa J.
Published: November 2013

Offshore energy exploration and geophysical research activities using seismic airgun arrays are known to generate intense underwater sound. Such seismic imaging has the potential to impact marine mammals through hearing impairment and behavioral modification. Few studies have investigated multipath propagation and reverberation from these airgun impulses. These phenomena could increase the duty cycle within the sound field sufficiently to impact long distance communication or result in detrimental acoustic masking for marine mammals. We report initial findings on the elevation of the sound level between airgun impulses during a shallow, open-water seismic survey. This work uses continuous recordings collected from three bottom-mounted hydrophones deployed in the Beaufort Sea in summer 2012. A quantitative method is used to examine the root-mean-squared noise levels between seismic impulses and the noise level dependence on source range. Preliminary results show that ambient noise increases above non-impulsive harassment levels defined by the National Marine Fisheries Service (120 dB re: 1 microPa) for a portion of the time between seismic impulses at intermediate ranges from the source. In addition, the duration of reverberation is related to the source range, with significantly longer decay times measured on hydrophones at greater distances from the source.
Effects of wideband source types on accuracy of wideband path-loss prediction based on finite-difference time-domain scheme
Authors: Kim Yongjune , Koh Il-Suek , Lee Yongshik
Published: November 2013

The finite-difference time-domain (FDTD) scheme is a well-known numerical algorithm that can solve a wideband response of a wave equation in time domain. When the FDTD scheme is applied to the problem of the underwater path-loss, however, the wideband source excitation may generate various problems at low frequency band. For instance, when a source is implemented with a large magnitude near the zero frequency, a spurious response can be generated in the FDTD simulation due to the DC component that cannot propagate. On the other hand, when a source is implemented with very small magnitude at low frequencies, the numerical accuracy cannot be guaranteed. In this work, implementation of a new wideband source for FDTD scheme is proposed that is suitable for response over a wide bandwidth, including very low frequencies. The Tukey window is applied to a wideband Gaussian pulse in the frequency domain, which eliminates the DC component effectively. By utilizing the steep slope of a Tukey window, higher accuracy is achieved in the low frequencies. To verify the proposed wideband source, the path-loss results based on the FDTD scheme are compared with the famous normal mode solution, KRAKEN, as well as the ray solution, BELLHOP.
Sensitivity of the underwater sound field in submarine canyons to water column variability
Authors: Lin Ying-Tsong , Zhang Weifeng Gordon , Duda Timothy F.
Published: November 2013

The ocean dynamics in the geologically and morphologically complex submarine canyons can have strong spatial and temporal variability due to the presence of internal tides/waves and upwelling currents. Our fundamental research question is what the acoustic effects of these oceanographic processes are in such environments where the sound propagation is also strongly influenced by the seafloor complexity. A simple example showing the joint effects is the bottom reflection of sound that has complicated patterns depending on the shape of canyon seafloor, seabed properties, and acoustic incident angles. Among these factors, the incident angle is the link connecting the acoustic effects of marine geology and physical oceanography. Specifically, the ocean dynamics changes the water column stratification and thus the incident angle of sound onto the seafloor, which explicitly determines the reflection of sound from the complex canyon seafloor. More involved examples using integrated regional ocean and full-field sound propagation models will be shown in the talk, and sensitivity analysis of underwater sound propagation along and across canyons will be performed. [Work supported by the Office of Naval Research.]
Scattering objects imaging using an autonomous underwater vehicle towing a source and an horizontal array
Authors: Pinson Samuel , Holland Charles W.
Published: November 2013

Recently, seabed sound-speed profile measurement by the image source method had been performed using an Autonomous Underwater Vehicle (AUV) towing a broadband source (frequency band from 1600 to 3500 Hz) and a linear array of hydrophones. This method provides an automatic process by the use of the semblance function. In that communication, the semblance ability to detect coherent reflections is used to image scattering objects such as mud volcanoes by integrating the results of successive measurement along the AUV track. Due to the horizontal array configuration, there is an ambiguity on the scatterers localization that could be solved by the use of hydrophone triplets.
Some results from the very shallow water TREX13 reverberation experiments using the Five Octave Research Array triplet module
Authors: Preston John R.
Published: November 2013

A large experimental effort called TREX13 was conducted in April-May 2013 off Panama City, Florida. As part of this effort, reverberation and clutter measurements were taken in a fixed-fixed configuration in very shallow water (~20 m) over a 22 day period. Results are presented characterizing reverberation, clutter, and noise in the 1800-5000 Hz band. The received data are taken from the triplet sub-aperture of the Five Octave Research Array (FORA). The array was fixed 2 m off the sea floor and data were passed to a nearby moored ship (the R/V Sharp). An ITC 2015 source transducer was fixed 1.1 m off the seafloor nearby. Pulses comprised of gated CWs and LFMs were used in this study. Matched filtered polar plots of the reverberation and clutter are presented using the FORA triplet beamformer. There are clear indications of biologic scattering. Some of the nearby shipwrecks are clearly visible in the clutter, as are reflections from a DRDC air-filled hose. The noise data show a surprising amount of time-dependent anisotropy. Some model-data comparisons are made using the author's normal mode based reverberation model. Help from the Applied Physics Laboratory at the University of Washington was crucial to this effort. [Work supported by ONR code 322OA.]
Multistatic sound speed profile estimation
Authors: Shiba Hisashi
Published: November 2013

Sonar is an indispensable component of harbor security systems. Sound propagation is one of the big problems for coverage estimations, since sound speed profiles are complicated under the complex environment like harbors. A new approach for sound speed profile estimation had been proposed using surface scattering by single sonar for frequent measurements which are required in the operation planning phase of high accuracy coverage evaluations. Although the configuration is simple, it consumes much time for higher accuracy estimations, because multiple angle transmissions need multiple waiting time and averaging considering surface fluctuations also need lots of time. This requirement is not favorable for quick sonar operations. One of the ideas reducing estimation time is using multiple sonars under multi-static configurations. This new concept uses multiple sonars, and it is suitable for harbor protections, since all sonars on the bottom do not become obstacles for ship navigations unlike tethered arrays used in acoustical tomography. And it can be said that multiple sonars should be deployed for covering wide and complex harbor areas with networks. Under this situation, a multi-static operation is a natural conclusion for harbor security. This new approach reduces the total estimation time. The rest problem is accelerating computing time of solving nonlinear simultaneous equations. A new acoustical structure model is under evaluation. The trial results are reported, if it is found to work well.
Measurements of the peak pressure and sound exposure level from underwater explosions
Authors: Soloway Alexander G. , Dahl Peter H.
Published: November 2013

There is an interest by the Navy to determine the sound field produced by underwater explosions to minimize the impact on marine life during training exercises. This work presents measurements of underwater explosions collected 7 km off the coast of Virginia in shallow water (depth 14 m) with sound speed conditions considered approximately iso-speed. Explosive charges with TNT equivalent weight 0.1 to 6.0 kg (W) were deployed at approximately mid-water and bottom depths. Acoustic data were recorded using a 9 element vertical line array at range 430 m and single-element autonomous systems at ranges 170, 430, and 950 m. The peak pressures and sound exposure levels (SEL) are calculated from the data; at 430 m peak pressures as high as 220 dB re 1 μPa and SEL as high as 190 dB re 1 μPa2 s were measured. The peak pressures are compared to semi-empirical equations that are functions of range and W to the one-third power, such as Arons [J. Acoust. Soc. Am. 26, 343-346 (1954)], and both the peak pressures and SEL are compared to simulations obtained using the parabolic wave equation. [Research supported by Naval Facilities Engineering Command.]
Analysis of ambient noise in the habitat of Indo-Pacific humpback dolphin (Sousa chinensis) in the West Coast of Taiwan
Authors: Wei Ruey-Chang , Kuo Lian-Han , Wu Jeff Chih-Hao , Chen Chi-Fang
Published: November 2013

The west coast of Taiwan is one of the major habitats of Indo-Pacific humpback dolphin (Sousa chinensis). Ambient noise, changes with natural environment and human activities, is possible to affect the behaviors of marine mammals. Thus, it is necessary to conduct a long-term and systematic investigation of ambient noise in this area. This study deployed two underwater acoustic recorders (SM2M) in New Huwei River of the Yun-Lin coastal area (site YL) and Waisanding sandbar (site WS). 68- and 45-day acoustic data were collected in site YL and site WS. Results show that the low-frequency noise in site WS is lower than site YL due to the contributions of shipping or mechanical noises. In site YL, ambient noise of 1 to 2 kHz contains periodic changes because of the behaviors of croakers. Croakers usually appears before midnight in site YL, but no similar phenomenon is found in site WS. The frequency overlap between hearing range of marine mammal and high-level ambient noise is possible to cause the masking effect, even hearing loss. [Sponsored by the Forestry Bureau, Council of Agriculture, Taiwan under project “Population Ecology of Chinese White Dolphins and Ambient Noise Monitoring in its Habitat” No. 101-08-SB-14).]
A model for peripheral auditory mechanics in the oyster toadfish, Opsanus tau
Authors: Rozin Rachel , Edds-Walton Peggy L. , Hastings Mardi C.
Published: November 2013

Frequency response of the peripheral auditory system in the oyster toadfish was analyzed using a biomechanical model based on morphometric data obtained from a CT scan of a mature female, 21-cm long. Tissue properties for system equations were estimated from those found in the literature. The saccule is considered to have a single degree-of-freedom corresponding to the primary directional orientation of the hair cells. The model determines relative displacement between the sensory epithelium and otolith due to response of the saccule to motion from the sound source (direct path) and swim bladder (indirect path). Largest relative displacements correlate with highest auditory sensitivity (lowest thresholds). Results indicate a flat response at low frequencies with high sensitivity near 100 Hz, and are in good agreement with best stimulus frequencies measured physiologically in the auditory medulla and midbrain, and with the toadfish behavioral audiogram. Moreover, results confirm that the indirect path has little, if any, influence on auditory thresholds. Detection of the phase difference between direct and indirect signals, however, may contribute to the ability of oyster toadfish to localize sound sources.
Soundscape ecology: A review of a new synthesis area of acoustics of landscapes
Authors: Pijanowski Bryan C. , Villanueva-Rivera Luis
Published: November 2013

Soundscape ecology is an emergent area of acoustics that attempts to synthesize the concepts of landscape ecology, bioacoustics, noise, music, ethics, and biogeography. By focusing on the interplay of three main sources of sound: biological, geophysical, and anthropogenic, we hope to understand how humans impact ecosystems at a variety of spatial and temporal scales. Another focus of our work is the identification of special ecological places that possess unique and highly valued soundscapes. I will review the current state of the science and efforts to move this field forward using the expertise across these varied disciplines along with the work that we are conducting in the temperate forest, tropical, and desert ecosystems of North America.
Radiated ship noise level estimates from measurements in a fjord
Authors: Coward Stian , Tollefsen Dag , Dong Hefeng
Published: November 2013

This paper presents estimates of radiated ship noise levels (20 Hz—1 kHz) due to commercial shipping in the Oslofjord (Norway). Data were recorded at two Networked Intelligent Underwater Sensors (NILUS) units, each equipped with an omni-directional hydrophone placed near the seabed, at water depths of 45 and 110 m, respectively. Received noise levels due to traffic in two nearby shipping lanes (ranges, 0.4–3.0 km) were for these non-ideal test site conditions processed and corrected to monopole source levels by use of the RAM propagation model with range estimates from auxiliary data, environmental input from a prior survey of the area, and a vertically distributed source model [Trevorrow et al., J. Acoust. Soc. Am. 124(2), 767–778] to model uncertain source depth. Estimates of source spectra and of broadband source levels of cargo ships are presented and compared with deep-water measurements from the literature.