bluuebunny/crossref_metadata_2025 huggingface dataset:
The Determination of the Relationship Between Isokinetic Leg Strengths and Agility and Speed Performance of Elite Handball Players
Authors: Aktuğ Zait Burak , Dündar Aykut , Murathan Fatih , İri Rüçhan
Published: April 2018

The aim of the study is to examine the relationship between isokinetic hamstring and quadriceps muscle strengths and agility and speed performance of elite male handball players. 15 male handball players participated in the study. The isokinetic leg forces of the handball players participating in the study were determined by isokinetic dynamometer, the agility performances by Ilionis and 505 agility test, and the speed performances by photocell. As a result of the analysis, there was no statistically significant relationship between isokinetic dominant and non-dominant leg hamstring and quadriceps peak torque forces and agility and speed performance at 60°s-1 and 400°s-1 angular speeds (p <0.05). As a result, it can be stated that there is no relation between hamstring and quadriceps muscle strength and speed and agility performances of handball players. This may be related to the requirements and physical characteristics of the handball branch (tall height, high weight, high BMI).
The negotiated equilibrium model of spinal cord function
Authors: Wolpaw Jonathan R.
Published: April 2018

The belief that the spinal cord is hardwired is no longer tenable. Like the rest of the CNS, the spinal cord changes during growth and ageing, when new motor behaviours are acquired, and in response to trauma and disease. This paper describes a new model of spinal cord function that reconciles its recently appreciated plasticity with its long‐recognized reliability as the final common pathway for behaviour. According to this model, the substrate of each motor behaviour comprises brain and spinal plasticity: the plasticity in the brain induces and maintains the plasticity in the spinal cord. Each time a behaviour occurs, the spinal cord provides the brain with performance information that guides changes in the substrate of the behaviour. All the behaviours in the repertoire undergo this process concurrently; each repeatedly induces plasticity to preserve its key features despite the plasticity induced by other behaviours. The aggregate process is a negotiation among the behaviours: they negotiate the properties of the spinal neurons and synapses that they all use. The ongoing negotiation maintains the spinal cord in an equilibrium – a negotiated equilibrium – that serves all the behaviours. This new model of spinal cord function is supported by laboratory and clinical data, makes predictions borne out by experiment, and underlies a new approach to restoring function to people with neuromuscular disorders. Further studies are needed to test its generality, to determine whether it may apply to other CNS areas such as the cerebral cortex, and to develop its therapeutic implications.
Smoke‐induced neuromuscular junction degeneration precedes the fibre type shift and atrophy in chronic obstructive pulmonary disease
Authors: Kapchinsky Sophia , Vuda Madhusudanarao , Miguez Kayla , Elkrief Daren , de Souza Angela R. , Baglole Carolyn J. , Aare Sudhakar , MacMillan Norah J. , Baril Jacinthe , Rozakis Paul , Sonjak Vita , Pion Charlotte , Aubertin‐Leheudre Mylène , Morais Jose A. , Jagoe R. Thomas , Bourbeau Jean , Taivassalo Tanja , Hepple Russell T.
Published: April 2018

Key points

Chronic obstructive pulmonary disease (COPD) is largely caused by smoking, and patient limb muscle exhibits a fast fibre shift and atrophy.

We show that this fast fibre shift is associated with type grouping, suggesting recurring cycles of denervation–reinnervation underlie the type shift.

Compared to patients with normal fat‐free mass index (FFMI), patients with low FFMI exhibited an exacerbated fibre type shift, marked accumulation of very small persistently denervated muscle fibres, and a blunted denervation‐responsive transcript profile, suggesting failed denervation precipitates muscle atrophy in patients with low FFMI.

Sixteen weeks of passive tobacco smoke exposure in mice caused neuromuscular junction degeneration, consistent with a key role for smoke exposure in initiating denervation in COPD.

A neurological basis for the fast fibre shift and atrophy seen in limb muscle of patients with chronic obstructive pulmonary disease (COPD) has not been considered previously. The objective of our study was: (1) to determine if denervation contributes to fast fibre shift and muscle atrophy in COPD; and (2) to assess using a preclinical smoking mouse model whether chronic tobacco smoke (TS) exposure could initiate denervation by causing neuromuscular junction (NMJ) degeneration. Vastus lateralis muscle biopsies were obtained from severe COPD patients [n = 10 with low fat‐free mass index (FFMI), 65 years; n = 15 normal FFMI, 65 years) and healthy age‐ and activity‐matched non‐smoker control subjects (CON; n = 11, 67 years), to evaluate morphological and transcriptional markers of denervation. To evaluate the potential for chronic TS exposure to initiate these changes, we examined NMJ morphology in male adult mice following 16 weeks of passive TS exposure. We observed a high proportion of grouped fast fibres and a denervation transcript profile in COPD patients, suggesting that motor unit remodelling drives the fast fibre type shift in COPD patient limb muscle. A further exacerbation of fast fibre grouping in patients with low FFMI, coupled with blunted reinnervation signals, accumulation of very small non‐specific esterase hyperactive fibres and neural cell adhesion molecule‐positive type I and type II fibres, suggests denervation‐induced exhaustion of reinnervation contributes to muscle atrophy in COPD. Evidence from a smoking mouse model showed significant NMJ degeneration, suggesting that recurring denervation in COPD is probably caused by decades of chronic TS exposure.
Learning Styles of Undergraduate Medical Students
Authors: Cortés Barré Michelle , Gullén Olaya Javier Francisco
Published: April 2018

Introduction: According to the experiential learning theory, each person develops a learning style that characterizes his/her preferred way to acquire and transform experiences to create knowledge. The objective of this study was to identify the learning styles of undergraduate medical students. Methods: The Kolb Learning Style Inventory was applied to first-year medical students at the Pontificia Universidad Javeriana (Bogotá, Colombia) during the second period of 2009. Results: 204 students completed the questionnaire (the average age was 18.5 years; 55% were women). Students preferred the abstract styles of learning, including assimilating (47%) and converging (27%) styles. Conclusions: Having information about medical students learning style preferences can help educators to design teaching strategies that promote a more effective learning. Teachers should provide a variety of learning contexts to stimulate the strengthening of their abilities.
Hemimelia del peroné y la tibia, más que un hueso ausente: presentación de casos
Authors: Medina Castiblanco Maria Camila , Vallejo Ángel Juana Maria , Torres Mejía Alejandra , Cogollo Delgado Javier
Published: April 2018

El acortamiento congénito del miembro inferior hace parte de un grupo de trastornos poco frecuentes, entre los que se encuentran la deficiencia femoral focal proximal y la hemimelia de peroné o de la tibia. Pueden presentarse desde una forma leve de hipoplasia hasta ausencia completa del hueso con grados variables de acortamiento, siendo evidente el acortamiento de la extremidad desde el nacimiento. El artículo revisa este tema y presenta los casos de hemimelia de tibia y peroné del Hospital Universitario San Ignacio en los últimos años, se describen los principales hallazgos imaginológicos en radiografía simple y en resonancia magnética.
Broadband acoustic wave propagation and scattering in Delaware Bay Estuary
Authors: Badiey Mohsen
Published: April 2018

Physical oceanography of estuaries is complex due to many factors including fresh water river discharge, oceanic salt water intrusion, variable ebb and flood tides, and surface winds. In these confined environments, high frequency (1–25 kHz) broadband acoustic waves are shown to through large intensity fluctuations with substantial energy scattering due to their interaction with the sea surface, sea bottom, and refraction due to the stratified water column. In this paper, we present results from a series of experiments that were conducted in the Delaware Bay estuary where fixed source-receiver configurations allowed calibrated long-term acoustic and oceanographic measurements to be conducted while atmospheric conditions such as wind speed and direction were carefully measured concurrently. It is shown that intensity fading due to oceanographic features and tide induced sound speed profile refraction in stratified water column occurs regularly and periodically. Wind generated surface gravity water waves in a fetch limited environment also play an important role in modulating and fading surface bounced acoustic energy. Two dimensional Parabolic Equation (PE) model with rough surface is used to simulate the measured broadband signals. Excellent data-model comparison is shown. [Work supported by ONR321OA.]
A propagation experiment in an Arctic glacial fjord
Authors: Deane Grant B. , Glowacki Oskar
Published: April 2018

A propagation experiment was undertaken in the meltwater-modified surface layer in the bay of a marine-terminating Arctic glacier. Broad-band, m-sequence transmissions were made with an International Transducer Corporation 1007 source deployed from a drifting boat tracked using gps, approximately 500 m in front of Hansbreen Glacier in Hornsund Fjord, Southwestern Svalbard in the summer of 2017. Signals were received with a short array of Hitech HTI-96 hydrophones tethered to an autonomous, anchored boat. The distance between the hydrophone array and source was measured every 2 minutes using a laser rangefinder. Propagation effects in this noisy and dynamic environment include waveguide propagation through the meltwater-modified surface layer and occlusion of transmissions by drifting icebergs. Details of the experiment and propagation effects noted during the transmission period will be presented and discussed. [Work funded by ONR, Grant No. N00014-17-1-2633, and by the Polish National Science Centre, Grant No. 2013/11/N/ST10/01729.]
Spatio-temporal patterns in underwater sound within an urban estuarine river
Authors: Marley Sarah A. , Erbe Christine , Salgado Kent Chandra P. , Parsons Miles , Parnum Iain M.
Published: April 2018

Underwater noise environments are increasingly being considered in marine spatial planning and habitat quality assessments, particularly with regard to acoustically specialised fauna. The Swan River in Western Australia flows through the state capital of Perth and consequently experiences a range of anthropogenic activities. However, the river is also extensively used by a resident community of bottlenose dolphins (Tursiops aduncus). This study aimed to describe underwater sound sources within the Swan River, examine spatial and temporal soundscape variability, and determine dolphin responses to noisy environments. Acoustic datasets collected from 2005 to 2015 indicated that the Swan River was comprised of multiple acoustic habitats, each with its own characteristic soundscape and temporal patterns in underwater noise. The anthropogenically “noisiest” site was the Fremantle Inner Harbour (mean broadband noise level: 106 dB re 1 μPa rms [10 Hz–11 kHz]); yet dolphins remained present in this area even at high vessel densities. However, fine-scale analyses indicated significant alterations to dolphin behavior at high vessel densities and to dolphin whistle characteristics in high broadband noise conditions. These results highlight the need to consider spatial and temporal patterns when assessing the composition of underwater soundscapes, and identify potential responses of coastal dolphins to busy, noisy environments.
Measurements and modeling of acoustic propagation in a seagrass meadow
Authors: Ballard Megan S. , Sagers Jason D. , Lee Kevin M. , McNeese Andrew R. , Wilson Preston S. , Rahman Abdullah F. , Dubin Justin T. , Venegas Gabriel R.
Published: April 2018

This talk presents results from an acoustic propagation experiment conducted in the Lower Laguna Madre to characterize the acoustical properties of a seagrass meadow. At the location of the experiment, the water was one meter deep, and the seabed was covered by a dense growth of Thalassia testudinum, a type of seagrass that grows from a long, jointed rhizome buried 5 cm to 10 cm below the seafloor. The biological processes and physical characteristics associated with seagrass are known to affect acoustic propagation due to bubble production, which results in dispersion, absorption, and scattering of sound. During the experiment, a Combustive Sound Source was used to produce broadband signals at ranges of 20 m to 1000 m from the receiver location. Three sensors were positioned at the receiver location: two hydrophones located within and above the seagrass canopy, and a single-axis geophone. The data were analyzed for the purposes of predicting acoustic propagation in seagrass meadows and for estimating environmental parameters in very shallow, biologically active environments. Additionally, seagrasses are a vital part of the global carbon cycle and this work explores the feasibility of using of acoustic signals to estimate carbon stores. [Work sponsored by ARL:UT IR&D and ONR.]
Machine learning for spatial interpolation of noise monitor levels
Authors: Nykaza Edward T. , Blevins Matthew G.
Published: April 2018

Continuously recording noise monitoring stations provide feedback of the noise environment at monitor locations. While this feedback is useful, it only provides information at a few point locations and, in many cases, it is of interest to know the noise level(s) at locations between and beyond noise monitoring locations. In this study, we test several machine learning models (e.g., random forests, support vector machines, and neural networks) for their ability to predict noise levels using a small number of noise monitors. Unlike the hybrid geostatistical-acoustical method proposed by Nykaza [Nykaza, Ph.D. thesis, 2013] which requires knowledge of the source location, the methods proposed in this study can be trained to estimate noise levels without knowledge of the source location. The accuracy of each model is assessed with the root-mean-square-error, and we discuss the practical implications of implementing such approaches in real-time systems.
Verification and validation of a coupled elasto-acoustic-damage system
Authors: Pitt Jonathan S.
Published: April 2018

A novel time-domain method for simulating dynamic damage evolution in a coupled structural-acoustic system is presented. The system is derived via the theory of continuum damage mechanics, and incorporates standard damage evolution models, but is readily extendible to more complex formulations. The overall solution method is staggered, first solving for the dynamic damage evolution with an explicit step, and then using the new values of damage in the coupled computation of the structural-acoustic system. The spatial domain is discretized using a mixed finite element method, and the temporal domain is discretized with a higher-order implicit time discretization scheme. Code and solution verification of the fully coupled solution algorithm are presented, as are validation studies for cases with and without evolving damage. Applications with evolving damage are presented, and present a novel first principles study of changes in the structural acoustic response to dynamically evolving damage in the structure. Special attention is given to brittle fracture. Examples of downstream usage of the evolving structural response are discussed in the conclusion.
The Iterative Nonlinear Contrast Source method: Basics and extensions
Authors: Verweij Martin D. , Selvam Elango
Published: April 2018

There are many applications in which the properties of nonlinear waves play a role. For example, in medical diagnostic imaging, the higher harmonics in nonlinear ultrasound are used to reduce clutter from nearby artifacts and to improve resolution, and in non-destructive testing nonlinear mixing products from crossing ultrasound beams are used to assess the state of materials. Simulation of nonlinear waves is important for optimizing equipment and quantitatively assessing phenomena. Unfortunately, analytical approaches cannot deal with complex realistic situations, while traditional Finite Element and Finite Difference methods require extremely large grids to capture waves with many higher harmonics in large three-dimensional domains. The Iterative Nonlinear Contrast Source method was developed to overcome these issues. It is based on an integral equation involving the analytic Green’s function of the linearized medium and a distributed contrast source representing nonlinearity. The integral equation is solved iteratively, and the computations are based on Fast Fourier Transforms that only require two grid points of the shortest wavelength. In this presentation, the basic principles behind the method will be explained and its extension to lossy and inhomogeneous media will be shown. Moreover, a novel extension will be presented that enables the computation of nonlinear elastic waves.
Efficient, wide-band rigid-body and elastic scattering computations using transient equivalent sources
Authors: Fahnline John B.
Published: April 2018

Previous analyses by the author have shown that transient structural-acoustic problems can be solved using time stepping procedures with the structure and fluid modeled using finite elements and equivalent sources, respectively. Here, the analysis is extended to include scattering problems. Although scattering problems have been discussed extensively in the literature, the current formulation is unique because it approximates the acoustic coupling matrix as sparse. Also, most of the previous analyses have assumed the problem is time harmonic, and there is an advantage to performing the computations in the time domain because only a limited number of time steps are required to obtain wideband frequency resolution. This is especially true if the main emphasis is on the mid- to high-frequencies since the ringing response is typically dominated by the lowest frequency modes. Several examples are solved to validate the computations and to document the computation times and solution accuracy.
Geometric approximation of radiation stress projections for canonical objects
Authors: Marston Philip L. , Daniel Timothy D.
Published: April 2018

Modulated ultrasonic radiation pressure facilitates the selective excitation of modes of objects through modulation of appropriate surface stress projections [P. L. Marston and R. E. Apfel, J. Acoust. Soc. Am. 67, 27–37 (1980)]. For some large objects, it can be impractical to evaluate the needed stress projections using standard analytical or computational methods. For highly reflecting objects geometric approximations may provide useful insight into the relevant stress projections. The simplest projection gives the translational radiation force on the object. In that case, ray analysis of the far-field scattering was shown to recover the radiation force on large perfectly reflecting spheres in plane waves [P. L. Marston, J. Acoust. Soc. Am. 120, 3518–3524 (2006)]. In the present research, the appropriate force limit is also recovered through integrating a geometrically approximated local stress projection on the object’s surface. Appropriate limiting forces for other canonical objects or situations involving illumination by beams are also found to be recovered using geometrical methods. It was helpful to generalize some prior geometrical results [P. L. Marston, J. Acoust. Soc. Am. 121, 753–758 (2007)] for scattering by perfectly reflecting spheres. [Work supported by ONR.]
Time domain simulation of porous surfaces for comparison with the ANSI impedance measurement
Authors: Zhang Junjian , Zheng Z. C.
Published: April 2018

This study is to investigate sound propagation with different porous ground conditions. Sound propagations are simulated using finite difference time domain methods (FDTD). The ground materials are modeled as porous media. Two types of models are used in simulating the porous ground: (1) the original Zwikker-Kosten (ZK) model coupled with the immersed boundary method and (2) a modified ZK impedance model, as proposed by Wilson et al. (2006, 2007), as a time-domain boundary condition (TDBC) derived from the frequency-domain impedance boundary condition. The first method directly calculates the wave propagation inside porous media, while the second method only specifies the ground surface as a porous boundary condition. Both methods are based on the ZK-type models but have different responses in the frequency domain. Sound pressure levels in different frequency ranges are studied and discussed. Simulation results from both of the models are compared with the measurement data in ANSI S1.18 standard.
Electrode length, placement, and frequency allocation distort place coding for bilateral, bimodal, and single-sided deafened cochlear implant users
Authors: Landsberger David M.
Published: April 2018

There is typically a mismatch between the frequency expected at a given cochlear angle and the frequency presented at that angle by a cochlear implant. The frequency mismatch may be particularly important for the population of cochlear implant users who are combining electric hearing across ears or who have electric hearing in one ear and acoustic hearing in the contralateral ear. If the place coding provided by a cochlear implant is misaligned with place coding in the contralateral ear, then the listener may be provided with inconsistent or even conflicting auditory cues. Due to plasticity, the auditory system may be able to compensate for these misalignments. However, data suggest that the ability of some listeners to fully adapt to the distorted or conflicting place maps is limited. The frequency mismatch from a cochlear implant can be adjusted by changing the electrode length, insertion depth, and frequency allocation. Additionally, changing these variables effect the relationship between a change in input frequency and the corresponding change in place pitch.
Measuring spectral asymmetry for cochlear-implant listeners with single-sided deafness
Authors: Bernstein Joshua G. , Stakhovskaya Olga A. , Jensen Kenneth K. , Goupell Matthew
Published: April 2018

Cochlear implants (CI) for individuals with single-sided deafness (SSD) are generally programmed with a standard frequency-allocation table (FAT) to maximize the transmission of speech information through the CI. However, a standard FAT is likely to produce mismatch in interaural place of stimulation, which could limit the spatial-hearing benefits that SSD-CIs provide. This study compared three methods for estimating interaural mismatch for SSD-CI listeners: interaural-time-difference (ITD) discrimination, pitch discrimination, and computed-tomography (CT) scan estimates of electrode intracochlear position. For all three measures, the estimated matched acoustic frequency increased for subsequently more basal electrodes. The ITD-based and CT-based estimates were generally consistent with one another, and were on average about one octave above the standard FAT. The pitch-based estimates were considerably lower, averaging about a half-octave above the standard FAT. These results suggest that pitch-discrimination measurements may be more susceptible to plasticity than ITD-discrimination measurements, and that CT images align with binaural function. The measurements will provide a basis to determine whether reducing mismatch can enhance spatial hearing for SSD-CI listeners. [The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army/Navy/Air Force, Department of Defense, or U.S. Government.]
Results in cochlear implant recipients with substantial contralateral acoustic hearing
Authors: Firszt Jill , Reeder Ruth , Holden Laura , Dwyer Noel
Published: April 2018

The present study evaluated longitudinal performance outcomes in adult cochlear implant recipients with substantial hearing in the contralateral ear (mean better-ear PTA of 23.7 dB HL; range 0–40 dB HL). Of the 19 participants, 10 used a better-ear (BE) hearing aid both pre- and post-implant. Test intervals included pre-implant, 6 and 12 months post-implant. Participants’ everyday listening condition was primarily a single hearing ear pre-implant and bimodal (CI + BE) post-implant. Results indicated significant improvement over time in the everyday listening condition for sentences at a soft presentation level, sentences in noise (either surrounding or toward the BE), and localization. Self-reported communication ability also improved significantly over time. Group mean CNC word scores for the implanted ear alone improved significantly pre- to post-implant. Ear conditions were compared at the 6-month post-implant test interval. The same measures that demonstrated improvement over time in the everyday listening condition demonstrated significant bimodal improvement compared to the BE alone at the 6-month test interval. Bimodal benefit for these participants varied in degree and by measure compared to adult CI recipients with greater HL in the contralateral ear. Cochlear implantation was an effective treatment for individuals relying on a single hearing ear pre-implant.
Dichotic listening performance and listening effort for asymmetrical inputs
Authors: Milvae Kristina D. , Kuchinsky Stefanie E. , Stakhovskaya Olga A. , Goupell Matthew
Published: April 2018

Binaural hearing typically improves speech understanding in difficult listening situations. Cochlear-implant (CI) recipients seek to gain binaural hearing benefits through bilateral implantation. However, the standard of care is currently sequential implantation, possibly with a long difference in the duration of deafness between the ears. Sequential implantation may cause interaural asymmetry in the quality of the signal, which could limit binaural benefits. A range of bilateral CI listeners, from those who experience binaural benefits to those who demonstrate interference, were recruited for this experiment. Listeners attended to one ear and reported digits heard in monotic and dichotic conditions. Perceptual performance and listening effort (via pupillometry) were measured. A control group of normal-hearing listeners were tested and were presented unprocessed, four-, and eight-channel vocoded digits, and the processing was independent across ears. It was hypothesized that attending to a poorer-quality signal in the presence of a better-quality signal would lead to poorer performance than in the monotic condition. Pupillometry was hypothesized to reflect the listener’s ability to perceive the poorer-quality signal in the presence of a better-quality signal. Results will inform strategies to maximize binaural hearing in bilateral CI listeners.
Propagation effects on acoustic particle velocity sensing
Authors: Collier Sandra L. , Denis Max , Ligon David , Solomon Latasha , Erikson Madeline M. , Noble John , Alberts W. C. Kirkpatrick , Sim Leng , Reiff Christian G. , James Deryck D.
Published: April 2018

The effects of atmospheric turbulence on the acoustic particle velocity are examined for both narrow-band and wide-band sources. The statistical distributions of the acoustic particle velocity and pressure fields are analyzed for a series of field tests. Applications to signal processing with particle velocity sensors are considered.
Obtaining acoustic intensity from multisource statistically optimized near-field acoustical holography
Authors: Stout Trevor A. , Wall Alan T. , Gee Kent L. , Neilsen Tracianne B.
Published: April 2018

Multisource statistically optimized near-field acoustical holography (M-SONAH) improves the field reconstruction process by directly incorporating into the pressure propagator types of wavefunctions that correspond most closely to the source geometries of interest [A. T. Wall et al., J. Acoust. Soc. Am. 137, 963–975 (2015)]. The M-SONAH method has previously been used to localize acoustic sources in a full-scale jet engine plume above a rigid reflecting plane by adding a second set of cylindrical wavefunctions corresponding to the image source [A. T. Wall et al. J. Acoust. Soc. Am. 139, 1938–1950 (2016)]. Here, M-SONAH theory is extended to obtain the vector particle velocity and, by extension, the acoustic intensity. Discussed are two examples that relate to the full-scale jet noise-with-image-plane reconstruction problem: (1) a Gaussian line source with image and (2) a jet-like wavepacket and image, with hologram geometry identical to that of the full-scale experiment. The results from both examples reveal intensity errors less than 3 dB and 10 degrees within the top 20 dB of the reconstruction region. The results also suggest that intensity reconstruction magnitudes less than those obtained at the measurement aperture edges should be discarded. [Work supported by ONR.]
The blended dominant mode rejection adaptive beamformer
Authors: Buck John R. , Singer Andrew , Wage Kathleen E.
Published: April 2018

Adaptive beamformers balance competing demands of enhancing desired signals, suppressing discrete interferers and attenuating background noise. This requires an accurate estimate of the spatial covariance matrix that is challenging to obtain in nonstationary environments. The dominant mode rejection (DMR) beamformer [Abraham & Owsley, Oceans, 1990] addresses this challenge by replacing the sample covariance matrix (SCM) eigenvalues of the noise subspace with the average of these eigenvalues to improve its conditioning. The DMR beamformer requires an estimate of the interferer subspace dimension, and the DMR beamformer's performance degrades when this estimated dimension is inaccurate. We propose the Blended DMR beamformer, whose array weights are formed as a mixture of fixed-dimension DMR beamformer array weights across a range of interferer dimensions. The contribution of each fixed-dimension DMR beamformer is a function of its recent performance in suppressing interferers and attenuating noise. The performance of this blended DMR beamformer approaches that of the best fixed-dimension DMR beamformer in stationary environments, and can outperform any fixed DMR beamformer in many nonstationary environments. [Work supported by ONR Code 321US.]
Frequency-difference beamforming with multiple realizations in an inhomogeneous environment
Authors: Douglass Alexander S. , Dowling David R.
Published: April 2018

Frequency-difference beamforming is a sparse-array signal processing method that shifts the signal analysis to lower, out-of-band (difference) frequencies, provided that the difference frequency does not exceed the signal bandwidth. In an inhomogeneous environment with discrete scatterers, low-frequency fields may not be significantly affected, provided the scatterers are small relative to the signal wavelength. However, when the scatterer sizes are comparable to the signal wavelength, scattering effects are likely to be more significant. Previously, it was shown that frequency-difference beamforming can overcome some of the performance degradation from the high frequency scattering by shifting the processing to lower, out-of-band frequencies. In this case, the frequency-difference output was comparable to the output using a lower-frequency signal in the same environment. In this talk, theoretical fields that include scattering at the in-band frequencies are considered to predict the performance of the frequency-difference method. Furthermore, simulations and experiments in a 1.07-m-diameter water tank with a sparse array are used to determine the performance and robustness of the method in the presence of discrete high-contrast scatterers. Multiple realizations of randomly placed scatterers are combined to quantify performance statistics. [Sponsored by NAVSEA through the NEEC, and by ONR.]
Field testing of in-room impact noise
Authors: LoVerde John , Dong David W.
Published: April 2018

The sound generated by footfall within the source space, sometimes called in-room impact noise, affects the noise level due to movement within a room and also the occupants’ perception of quality. Initial studies are based on the standard tapping machine as the source. While no ASTM standard yet exists for measuring the source room sound level, source room measurements with the tapping machine have been performed on several recent laboratory testing programs. The authors have measured source room power levels in the field using the same flooring products that were measured in the laboratory. The data are analyzed to evaluate the correlation between the laboratory data and the resultant noise level realized in the field. The usefulness and applicability of future laboratory and field in-room impact noise standards is discussed.
Drop Tower Testing—The next step in heavy weight impact testing
Authors: Golden Matthew V.
Published: April 2018

Over the last few years, research into heavy hard impacts from fitness activities has become an active field of investigation and product development. In order in facilitate our efforts, Pliteq has built a custom drop tower capable of repeatability dropping up to 150 kg from well over 2 m height. During the impact, the force, displacement, velocity, and acceleration can be obtained. This paper will give an overview of this apparatus, the type of data that it can collect, how this data can be used to make better products and how the data can be used to predict field performance.
The problem of finding passageways in foliage with biomimetic sonar
Authors: Wang Ruihao , Jin Xin , Wang Haosen , Müller Rolf
Published: April 2018

Bats living in densely vegetated habitats must have the ability to find passageways in foliage. To explore the sensing problem posed by this navigation task, a sonar head that mimicked a bat's biosonar periphery and emitted a bat-like chirp was placed on a linear track to scan artificial foliages (plastic leaves resembling broad-leaf foliage) interrupted by gaps of controllable width. The first approach to detecting the gaps tested has been based on comparing echo energy levels received when facing a gap as opposed to a closed foliage. The ability to detect a gap in this way depends on the employed beamwidth and the distance to the foliage, i.e., the narrower the beam and closer the sonar head, the narrower a gap can be detected. However, narrower beams were also found to increase the variability in the energy of the returned echoes which could impact the ability to reliably distinguish the different levels of echo energy associated with closed foliage and gaps. Since bats tend to have wide beams due to their limited size relative to the employed wavelengths, it may be hypothesized that the animals have evolved alternative approaches to improve the ability of detecting narrow passageways at a distance.
Assessing continuous sensory information encoding by a biomimetic dynamic sonar emitter
Authors: Yang Luhui , Müller Rolf
Published: April 2018

Bat species in the rhinolophid and hipposiderid families can deform the shapes of their noseleaves and pinnae when emitting/receiving ultrasound. Prior work has shown that these deformations enhance the encoding of sensory information. So far, quantifications of the impact on sensory information encoding have been based on small numbers of discrete shapes and clustering of head-related transfer functions into discrete alphabets. In the current work, an improved estimator for mutual information that is based on entropy estimates from k-nearest neighbor distances (Kraskov et al., 2004) was used to overcome these limitations. With this approach, mutual information was estimated based on individual head-related transfer functions along the entire duration of biosonar pulses that were represented by high sampling rates suitable for ultrasonic signals. Testing was carried out with a data set from a dynamic sonar emitter inspired by the noseleaf of Pratt's roundleaf bat (Hipposideros pratti). The results were found to be in good agreement with the cluster-based approach. The high temporal resolution employed showed that mutual information between beampatterns decreased very quickly within the pulse duration demonstrating that the noseleaf dynamics can provide the bats with the equivalent of several nearly independent views of the environment within a single pulse.
A decade of marine mammal acoustical presence and habitat preference in the Bering Sea
Authors: Seger Kerri , Miksis-Olds Jennifer L.
Published: April 2018

As Arctic seas rapidly change with increased ocean temperatures and decreased sea ice extent, traditional marine mammal distributions may be altered, and non-traditional Arctic species may shift poleward. Extant and seasonal continental shelf odontocete species in the Arctic Ocean include sperm whales, killer whales, beluga whales, delphinids, harbour porpoises, and Dall’s porpoises. Until recently, recording constraints limited higher sampling rates, preventing detection of many of these high frequency-producing species in the Arctic seas. Using one of the first long-term data sets to record clicks, buzzes, and whistles, multiple species have been detected and classified to explore shifting distributions in the Arctic Corridor. The data were then paired with environmental variables for generalized linear and additive modeling. Pacific white-sided dolphins were detected for a few years during minimal ice coverage. Dall’s porpoises and Risso’s dolphins may have been acoustically detected in areas farther north than previously documented in acoustical records. Of all the species, beluga whales are the most highly coupled to the ice edge. Adjusted habitat distributions, suggestions for newly present species to be aware of during visual surveys, and environmental model results will be reviewed in this presentation. [This work was funded by the Office of Naval Research.]
Binaural AEP audiograms in seven Beluga whales (Delphinapterus leucas) from the Okhotsk Sea population
Authors: Sysueva Evgeniya , Nechaev Dmitry , Popov Vladimir , Tarakanov Mikhail , Supin Alexander
Published: April 2018

Hearing thresholds were measured and audiograms were obtained in seven belugas, three males and four females, provisionally 2 to 7 years old. The measurements were performed using a transducer located 1 m in front of the head. The stimuli were tone pip trains of carrier frequencies ranging from 11.2 to 128 kHz with a pip rate of 1 kHz. Auditory evoked potentials (the rate following responses) were recorded from the head vertex. In majority of the subjects, audiograms were similar to the typical odontocete audiograms with the lowest thresholds (from 53.7 to 56.4 dB re 1 μPa) at mid-frequency range (from 32 to 64 kHz) and a sharp thresholds rise (up to 79.5 dB re 1 μPa) at high frequencies (90–128 kHz). One beluga (female, 6–7 years old) featured an asymmetric hearing loss within a frequency range from 22.5 to 54 kHz. The reason for the loss is the subject for not defined. The evoked potential audiograms should be included into base screening of odontocete subjects involved in any kind of hearing research. Work supported by the Russian Science Foundation (project # 17-74-20107), the Russian Foundation for Basic Research and The Russian Geographic Society.]
High-frequency acoustic observations of a tidal cycle in the Connecticut River
Authors: Kidwell Autumn N. , Isakson Marcia J. , Story Mark , Reiter Andrew J.
Published: April 2018

Rivers and estuaries can be highly energetic and present a challenging environment for sonar deployment and observation. To better understand this environment, a high-frequency, wide-sector forward-looking bathymetric sonar was used to observe tidal phenomena in the lower Connecticut River in June 2017. The stationary sonar system provided Eulerian measurements of the lower estuary for a complete tidal cycle, covering a large portion of the main channel. The system was able to map the observed region and differentiate between bathymetry and non-stationary phenomena in the water column. The data highlight the difference in acoustic propagation for the different phases of the tidal cycle. Doppler processing of the data shows the motion of various subsurface features in the river. These data are compared with other observations, including simultaneous in situ point measurements of salinity, temperature and turbidity from a REMUS 100 AUV. The data from this experiment can be used to improve the understanding of acoustic propagation in riverine and estuarine environments. [Work sponsored by the Office of Naval Research.]
Introduction to the Technical Committee on Physical Acoustics
Authors: Keppens Veerle M.
Published: April 2018

The Technical Committee on Physical Acoustics (TCPA) of the Acoustical Society of America (ASA) is home to scientists and engineers with an interest in the underlying physics of acoustical phenomena and/or use acoustic waves to study the physical properties of matter. It is one of the broader communities within the Acoustical Society, as the research areas and methods cover the entire frequency range from infrasound to ultrasound, while studying the interaction of these sound waves in all three states of matter: liquids, solids, and gasses. TCPA currently has about 575 members with a primary interest in physical acoustics with 75–125 typically attending open TCPA meetings.
An introduction to the acoustical oceanography technical committee
Authors: Colosi John A.
Published: April 2018

As is evidenced by the complex acoustic physiology and sophisticated auditory processing capability of marine organisms, it is clear that acoustics is a critical modality for interpreting the ocean environment. The acoustical oceanography (AO) technical committee (TC) seeks to foster a broad range of work in pure and applied acoustics with an aim towards gaining new fundamental understanding of physical, biological, geophysical, and chemical processes in the ocean and at its boundaries. With this focus, the AO TC is necessarily strongly interdisciplinary having close ties to other TCs such as animal bioacoustics, physical acoustics, signal processing, and underwater acoustics. This talk will describe many of the break-through discoveries that have been made in our field and point to inspiring present and future work.
Introduction to the Technical Committee on Noise
Authors: Murphy William J.
Published: April 2018

Noise presents both a health hazard and a societal hazard. Health hazards due to noise have been around since the development of metal forging and forming. As modern society has developed, community noise has affected where and how we interact with the soundscapes where we live. The United States Environmental Protection Agency, Office of Noise Abatement and Control was responsible for noise regulations that rate the production and reduction of noise until it was defunded. Federal agencies such as the National Institute for Occupational Safety and Health, the Occupational Safety and Health Administration, and the Mine Safety and Health Administration have conducted research to develop regulations for occupational noise exposures. Recent community noise issues have focused on windfarms and the low-frequency noise that nearby residents might experience. This presentation will cover a wide range of noise-related topics and highlight efforts in standards for noise assessment and noise control.
Psychological and physiological acoustics: Responses to sounds in biological systems
Authors: Gallun Frederick J.
Published: April 2018

The Technical Committee on Psychological and Physiological (P&P) acoustics is organized around the investigation and dissemination of information about responses to sound in humans and other species. Areas of interest include, but are not limited to the following topics: (1) perception and perceptual organization of simple and complex sounds, including speech; (2) anatomy and function of the auditory pathways, including all physical and biological responses to auditory stimulation; (3) hearing disorders, hearing loss, and auditory prostheses; (4) vibrotactile and vestibular sensation, and the interaction of hearing with other sensory modalities; (5) developmental, aging, learning, and plasticity effects in auditory function; and (5) theories and models of auditory processes. Examples will be given of hot topics in these areas as well as areas of overlap with other TCs in the ASA.
An open source noise dosimeter for evaluating exposure metrics
Authors: Smalt Christopher J. , Thul Lawrence , Davis Shakti K. , Calamia Paul
Published: April 2018

Noise dosimeters can be effective tools for measuring individual risk to sound exposure, especially in free-moving environments where sound pressure levels can vary significantly as a function of location and time. Commercial noise dosimeters typically compute noise exposure as an average A-weighted energy over an 8-hour work day (LAeq8hr), and health guidelines suggest a maximum exposure of 85 dB or 90 dB to limit noise-induced hearing injuries. However, recent studies have suggested that conventional noise exposure metrics may not be satisfactory and may not predict susceptibility to synaptic damage in the cochlea nor protect suprathreshold hearing. There is also evidence to suggest that the LAeq may under-predict health risk in complex noise environments, where there is both continuous and impulse noise, and over-predict health risk for long-duration impulse noise. This suggests a need for improved dosimeters with the ability to incorporate new noise metrics. Here we utilize a low-cost open source audio platform to implement standard and experimental noise exposure metrics in an open-source microcontroller programming language. A Bluetooth connection also enables real-time reporting of noise exposures to a smartphone. This system has a significant advantage over using persistent acoustic recordings which have privacy issues and may capture conversations. We envision that this system will be used to further noise exposure research and help evaluate new metrics of auditory health risk. [Work supported by ONR.]
Recent developments in the NASA auralization framework
Authors: Tuttle Brian C. , Aumann Aric R. , Rizzi Stephen A.
Published: April 2018

The NASA Auralization Framework (NAF) is an open software architecture that facilitates the conversion of numerical noise data, specifically aircraft flyover noise, into an audible pressure-time history that may be further analyzed or used as stimuli in psychoacoustic studies. The framework provides a set of libraries for management of the auditory scene and propagation paths, synthesis of simple sources, and a basic environment including a uniform standard atmosphere and hard flat ground. Advanced capabilities may be added in the form of dynamic-link library plugins either developed by the user or provided by NASA as pre-compiled binaries. Recent additions to the NASA collection of advanced plugins include synthesis of periodic noise sources, enhanced ground reflection and impedance models, an atmospheric turbulence model, a post-processing module for computing sound quality metrics, and an interface with the Aircraft NOise Prediction Program 2 (ANOPP2). This presentation highlights these advanced capabilities as they relate to current NASA research into noise from existing and proposed aircraft designs.