bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between head size and biosonar transmit and receive beams in odontocetes
Authors: Au Whitlow
Published: November 2017

The unique shape of a dolphin head, the different specie specific shape and the internal head structure suggest a very complex propagation mechanism for the biosonar signals to travel from the phonic lips into the water. Despite these factors, a circular planar aperture of the appropriate diameter can produce a transmission beam that resembles the corresponding beam of a dolphin. In the similar manner, the reception process is also very complex and not completely understood. Once again, despite the complexity involving the reception of biosonar echoes, a simple circular planar aperture of the right diameter can have a receiving beam that approximate or resemble the receiving beam of odontocetes. For both transmission and reception of broadband biosonar signals, the size of the head compared to the wavelength of the signal will determine the degree of directionality of the beams in odontocetes in a similar manner as a planar transducer. Beam pattern data from Tursiops truncates, Delphinapterus leucas, Pseudorca crassidens, and Phocoena phocoena will be used to demonstrate the relationship between head size and directionality for the transmit signal. Receiving beam pattern data from Tursiops truncates and Phocoena phocoena will be used in a similar manner as for the transmit beam.
Beyond the single-scattering assumption for analysis of diffuse ultrasonic scattering experiments
Authors: Turner Joseph A. , Matz Nathanial
Published: November 2017

Characterization of diffuse ultrasonic scattering is challenging because accurate models require assumptions about the degree of scattering. Most previous research has focused on the single-scattering regime in which rays are assumed to scatter only once before detection. In this presentation, scattering effects beyond single scattering are examined with a focus on polycrystalline materials. The contribution of the second scattering within the response is quantified with respect to measurement parameters and sample properties. The results show that single-scattering models are appropriate for weakly scattering materials, such as aluminum, for a wide range of experiments and grain sizes. However, stronger scattering materials are predicted to have significant components beyond single-scattering for certain measurement parameters even in the Rayleigh regime. Experimental results for a steel alloy are used to verify model predictions. The experimental work shows the domain for which the doubly-scattered response becomes significant as well as the limitation at which the double scattering model is no longer applicable. The results can be used to predict the applicable frequency range for each level of scattering for a given experimental configuration. Finally, the impact of the higher-order scattering is discussed with respect to the detection of defects within a heterogeneous medium.
Nonlinear coda wave interferometry: Characterizing damage in complex solids
Authors: Tournat Vincent
Published: November 2017

In this talk, we report results on the nonlinear interactions of ultrasonic coda waves, in reverberating or multiple scattering mesoscopic solid media. Using the method of coda wave interferometry (CWI), we analyze the effect of mixing a coda wave with an additional lower frequency pump wave. The extracted CWI parameters, known to be highly sensitive to small geometric or elastic modifications of the tested medium, are shown to be pump-amplitude dependent and to capture finely the results of the nonlinear interactions. Although nonlinear self-action effects with coda waves have been reported in unconsolidated granular media, they are difficult to implement in cracked solids or concrete. Instead, the reported nonlinear CWI class of methods (NCWI) shows robustness, a high sensitivity, and has been applied successfully to various complex media and structures. We show through several examples on « model » media (cracked glass plates) and on concrete structures, that NCWI can be useful for the nondestructive evaluation of complex solids that are strongly scattering at usual probing frequencies. Preliminary results and prospects in nonlinear elastic properties imaging and quantitative evaluation with NCWI are discussed.
Propagation of ultrasonic waves in complex media: Investigation of coda wave technique and traditional polar and C-scan imaging
Authors: Declercq Nico F. , Chehami Lynda , Pomarède Pascal , Ez-Zahraouy Othmane , Ahmed Mohammed Esam , Meraghni Fodil
Published: November 2017

A discussion of nondestructive techniques is presented for the investigation of complex media, with a focus on composite samples. Traditionally, one applies ultrasonic C-scans, or polar scans, which are easy to implement and to interpret. However, in many realistic cases, it is important to use more sophisticated approaches as C-scans often do not reveal any useful information. Typically, the early part of received signals is used to extract information, whereas the later part is considered either as noise or as a useless coda wave as in musical acoustics. Nevertheless, it appears that the coda part carries useful information about the medium, and therefore, it is important to explore techniques to extract that information. In addition, it turns out that the coda is very sensitive to material properties and damage as those sound waves interact longer with the material than early arrival waves. First, earlier results will be shown which compare experimental polar scans with numerical simulations, then, for the same samples, coda wave results will be presented to show the effect of damage on the composite samples. The main damage indicator is the change in relative wave velocity which is caused by the damage.
Ultrasound tomography of materials with high sound speed contrast
Authors: Falardeau Timothe , Belanger Pierre
Published: November 2017

Non-destructive evaluation of materials using ultrasounds is frequently used in industry as a way to characterize material properties and to locate defects. Imaging methods based on back propagation of echo signals are limited to reconstruction of low spatial frequency. Ultrasound diffraction tomography is a transmission-based imaging method which gives the possibility of characterizing anisotropic materials. Recent progress in ultrasound tomography using a circular array of transducers enabled velocity mapping of materials with high sound speed contrast relative to the background. In this study, an image of acoustic properties of a titanium rod submerged in water was obtained using bent ray time-of-flight tomography. The experiments were performed on a circular array ultrasonic test bench at 2 MHz frequency on 322 transduction points. A 2D finite element model of wave propagation through water and titanium was developed in order to validate experimental results. Finite element reconstruction matched experimental results within a 10% error for geometry and velocity.
Optical-resolution photoacoustic imaging with speckle illumination
Authors: Bossy Emmanuel
Published: November 2017

Conventional approaches for optical-resolution photoacoustic microscopy generally involves raster scanning a focused spot over the sample. Here, we show that a full-field illumination approach with multiple speckle illumination can also provide diffraction-limited optical-resolution photoacoustic images. Two different proof-of-concepts are demonstrated with micro-structured test samples. The first approach follows the principle of ghost imaging [1], and is based here on solving a linear inverse problem under sparsity assumptions: the object is reconstructed through a pseudo-inverse computation of a reference matrix made of speckle patterns measured during a calibration step. The second approach is a speckle scanning microscopy technique, which adapts the technique proposed in fluorescence microscopy by Bertolotti et al. [2]: in our work, spatially unresolved photoacoustic measurements are performed for various translations of unknown speckle patterns. Because speckle patterns naturally appear in many various situations, including propagation through biological tissue or multi-mode fibers, speckle-illumination-based photoacoustic microscopy provides a powerful framework for the development of novel reconstruction approaches, well-suited to compressed sensing approaches. [1] Katz et al., “Compressive ghost imaging,” Appl. Phys. Lett. 95(13), 2009. [2] Bertolotti et al., “Non-invasive imaging through opaque scattering layers,” Nature 491(7423), 2012.
The fabrication and characterization of nanocarbon foams for their utilization in thermoacoustic device
Authors: Zhang Mei , Wolmarans Paul , Aliev Ali E.
Published: November 2017

Thermo-acoustic (TA) sound generation (thermophone) is a non-resonant technique where electrical energy is converted to sound waves through Joule heating of a resistor (TA heat source) without any mechanical vibration, thus allowing for a wideband operation. It is clear that the material and the structure of the resistor play an important role on the performance of the thermophone. Recently, thermophone transducers fabricated from nanoscale materials hold the promise of a new transducer technology. Transducers made from these nanomaterials operate over a broad frequency range and can be designed to be lighter and thinner than competing technologies. Here, we report the TA heat source using nanocarbon foams. Nanocarbon foams are carbon nanotubes (CNTs) based all carbon porous materials. They have a hierarchically porous structure and the pore size and porosity can be tuned easily during the fabrication process. The foams consist of highly porous conductive CNT networks. They are freestanding, flexible, and mechanically robust in various environments. It is demonstrated that the foams can be used as elastically compressible, flexible TA heat source. The detailed fabrication process, the morphology of the foams, their thermal and electrical properties, and their performance as thermophone transducers will be presented.
An experimentally validated electrical-thermal-acoustic model of non-planar carbon nanotube thermophones
Authors: Asgarisabet Mahsa , Barnard Andrew R. , Prabhu Suraj M.
Published: November 2017

Carbon nanotube (CNT) thin-film thermophones are a solid state, transparent, magnet-free, stretchable, and lightweight transducers that work via the thermoacoustic effect. The rapid change in the temperature of the CNT film with low heat capacity produces a temperature wave accompanied by an acoustic wave in a frequency range of 1 Hz to 100 KHz. The existing lumped parameter models for the planar CNT thermophones are not appropriate for the complex geometries of the CNT film. Using COMSOL multiphysics, an electrical-thermal-acoustic model of the non-planar CNT thermophone has been developed. By applying an alternating electrical current to the CNT film, the temperature variation was obtained and used to simulate the pressure distribution. For different input power levels, the temperature distribution on the CNT film was compared to the experimental data from thermal camera. The experimental sound pressure level at different locations in front of the CNT thermophone were recorded and used to validate the non-planar model.
Music a scientific art: A call for review of Department of Music, University of Nigeria Nsukka’s curriculum and course outline
Authors: Onwubiko Stephen G. , Neilsen Tracianne B.
Published: November 2017

Every academic discipline ranging from the Social Sciences, Engineering, Physical Sciences, Arts, and Humanities is typically categorized as either a Science or Arts discipline. While Music is artistic and creative, there is harm in designating music as solely an Arts discipline. It is literally true that music is art, yet the viral damage of categorizing music as solely an Art discipline cannot be overemphasized. Just like a “wolf in sheep skin,” music is science dressed up like art. Music is an offspring of pure science (physics) expressed as art. Music is made up sound, frequency, pitch, resonance, vibration, echo, and Doppler effect; these topics are pure science with mathematical derived formulas and not just art. For example, the action of a typical upright piano obeys Newton’s third law. This paper condemns the outright definition and categorization of music as strictly an art and recommends the re-evaluation of music education at the university. The music curriculum should be rejuvenated and embedded with elective courses from the department of Physics and Astronomy to enable scholars know more about the science of their instruments, while acquiring the mastery of the art of music.
Assessing temporal compensation of speech due to delayed auditory feedback
Authors: Davis Samantha N. , Brajot Francois-Xavier
Published: November 2017

This study examined the behavioral compensation of speech influenced by delayed auditory feedback. It was hypothesized that delayed auditory feedback would yield similar compensation patterns as other auditory perturbations to speech do, in a hypothesis untested by previous experiments. The results of past studies which experimented with pitch, loudness, and formant frequencies look similar to each other, due to somatosensory feedback's role in adaptation. Compensatory responses, when measured against non-altered productions, seem to approach an asymptote, yielding incomplete compensations. Compensatory responses, when measured against the size of the perturbation, resemble a decreasing exponential function, as relative magnitudes get drastically smaller with increasing perturbation size. The data supported the hypothesis as predicted, meaning the compensation to delayed auditory feedback appears to follow the same principles as those observed in other altered auditory feedback paradigms. These results suggest that this compensation technique is consistent for all altered auditory feedback methods, and that it follows a generalized rule for sensorimotor feedback control in speech production.
Implementing electronic speckle pattern interferometry for a variety of activities in a general education acoustics class
Authors: Razo Nicholas J. , Morrison Andrew C.
Published: November 2017

A familiar acoustics laboratory experiment is finding Chladni patterns using flat plates of various geometries. Another method used in musical acoustics to find mode shapes of vibrating objects is electronic speckle-pattern interferometry (ESPI). We introduced students in a general education acoustics class to ESPI in addition to the traditional Chladni plate laboratory activity. A variety of ways to implement ESPI in the class were developed including: comparing traditional Chladni patterns to ESPI, examining traditional musical instruments with ESPI, and an advanced investigation of a well-known acoustics demonstration. A classic acoustics demonstration is rubbing the rim of a wine glass to create a musical tone. A coffee mug, unlike a wine glass, has an asymmetry due to the mug handle. ESPI can be used to study the effects of filling the mug with water in terms of the mug's natural frequency, amplitude, and mode shapes. Results from ESPI showed that the mode shapes do not change with the addition of water. Filling the coffee mug with water lowered the natural frequencies of the lowest modes in a manner similar to that of a wine glass.
Sound speed profile calculations for the Northern Gulf of Mexico
Authors: Sciacca Bradley J. , Ioup Juliette W.
Published: November 2017

Many sound speed calculations for the Gulf of Mexico use an average sound speed over the entire Gulf. In a variety of applications, such as localization or tracking of marine mammals, a more precise sound speed profile is helpful to make more accurate calculations. Using a reasonable approximation to Del Grosso’s equation, the sound speed profile may be computed as a function of temperature, pressure, and salinity. The Littoral Acoustic Demonstration Center—Gulf Ecological Monitoring and Modeling (LADC-GEMM) project collected underwater acoustic data in the northern Gulf of Mexico during the summer of 2015 using Environmental Acoustic Recording Systems (EARS), returning to sites previously surveyed by LADC. Oceanographic data were also collected at those sites and can be used for more accurate sound speed profiles at the specific locations and specific times of the acoustic data recordings, increasing the accuracy of subsequent calculations such as real-time tracking and other applications. Sound speed profiles for sites in the northern Gulf of Mexico will be presented. [This research was made possible by a grant from The Gulf of Mexico Research Initiative. Data are publicly available through the Gulf of Mexico Research Initiative Information & Data Cooperative (GRIIDC) at https://data.gulfresearchinitiative.org.]
Regional dialect perception by British and American listeners
Authors: Bonifield Emma C. , Bent Tessa , Evans Bronwen , Tyrrell Isla , Aguilera Fernanda
Published: November 2017

Speakers’ regions of origin, across and within countries, can substantially impact their native language pronunciation patterns. Previous work suggests that listeners are sensitive to these dialect differences within their home country (Clopper & Pisoni, 2004) and have at least broad representations of dialects outside of their home country (Bush, 1967). The current experiment expands on these findings by investigating dialect perception within and across multiple countries for listeners from two countries: United States and United Kingdom. Fifty-one talkers from the Speech Accent Archive (Weinberger, 2013) representing 6 U.S. regional dialects, 5 U.K. dialects, and 6 dialects from other English-speaking countries produced the same two sentences. Participants ranked these speech samples on their proximity to “Standard American English” or “Standard Southern British English” in two ladder tasks. American and British listeners’ ladder rankings for the American baseline were very highly correlated, with a clear split between North American and non-North American dialects. For the British baseline, American listeners again had a split between the North American and non-North American dialects, while the British listeners showed more gradation across the dialects. The results suggest that listener home dialect and dialect familiarity, possibly through media exposure, shape perceptual representation of regional dialects.
Measurements of the Doppler effect due to a rotating sound source
Authors: McQueney Elizabeth , Landi Maryam , Zhang Likun
Published: November 2017

The Doppler effect is a common principle in all types of waves when sources and receivers have a relative motion. In acoustics, there are scenarios where sound sources rotate and produce the Doppler effect. These scenarios include sound produced by a speaker with a rotating horn and by the rotational motion of helicopter blades and airplane propellers. In this study, we experimentally measure the frequency shift due to a rotating sound source. A buzzer (2.8 KHz) is set to rotate at a fixed radius (75 cm) with the rotational velocity (60 rpm) controlled by a stepper motor. The radiated sound signals are recorded by a microphone at different locations. Spectrograms of the recorded signals display a shift from the buzzer’s original frequency. The shift oscillates with the period of the source rotation. We characterize the dependence of the shift on the position of the microphone. A formula for the shift is derived and is used to compare with the measurements. Our measurements and analyses gain insight into the Doppler effect due to a rotating source.
Comparisons of measured sound power levels across octave bands gathered from different methods and labs
Authors: Underwood Samuel H. , Wang Lily M.
Published: November 2017

This poster presents results to date from an interlaboratory study, aimed at quantifying the bias and reproducibility of three different sound power measurement methods used in the heating, ventilation, and air-conditioning industry: free field method, diffuse field method, and sound intensity method. The sound power of a certain loudspeaker sound source has been measured in at least 15 testing facilities using the methods generally applied in those facilities. Two test signals are used in the measurements: a broadband signal whose slope decreases −5 dB per octave band, and the same signal with four discrete frequency tones at 58, 120, 300, and 600 Hz. Comparisons of the measured sound power level data, gathered to date, are presented across one-third octave bands. The project continues to collect data from other test facilities so that rigorous findings on the repeatability, reproducibility, laboratory bias, and measurement method biases may be determined, according to ISO 5725. [Work supported by the Air-conditioning, Heating and Refrigeration Institute.]
Detailed experimental modal analysis of a trumpet: An application of laser Doppler vibrometry
Authors: Cockrill Martin , Chowanietz Maximilian
Published: November 2017

Much work has been conducted on the physics of musical instruments and the trumpet has been included in numerous studies. However, the majority of the work is directed at understanding the air column physics since that is the dominant mechanism of a brass instrument. While this is the largest contribution to understanding the sound, it fails to explain the minute differences between instruments from both the player’s point of view and the audience. We have looked to add to the global body of work by conducting a full experimental modal analysis of an entire trumpet. By utilizing a 3D scanning laser Doppler vibrometer, we have been able to measure the dynamic response both in and out-of-plane over the entire trumpet. We have been able to do this at around 500 locations providing detailed geometric resolution and resolving higher order modes. We have then solved the resulting dynamic model to provide natural frequencies and mode shapes. It is hoped that the results of this work can be combined with the virtual modelling of other researchers to refine the state of the art in terms of understanding the properties and mechanisms inherent in trumpets and the quality of the sound they produce.
Experimental techniques for the visualization of the acoustic fields radiating from brass musical instruments
Authors: López-Carromero Amaya , Campbell D. Murray , Kemp Jonathan A.
Published: November 2017

Radiation from brass instrument bells under artificial excitation can be visualized using a number of experimental techniques. In this work, we present two different approaches: Schlieren optical imaging using a high speed camera and acoustic 2D scanning using a linear microphone array. The potentials and limitations of both methods, as well as their methodological requirements, are discussed. Examples of measurements on several instruments are presented. Schlieren optical imaging is applicable for the detection of large amplitude wavefronts formed by nonlinear wave steepening and is this is particularly sensitive to the high frequencies that form within these waves. The 2D scanning linear microphone array on the other hand can, in principle, measure all frequencies and the use of the exponential sine sweep method allows any nonlinear behaviour (in the loudspeaker and microphone or in the air) to be removed to get an accurate measurement of the linear radiation field for any frequency of choice within the measurement bandwidth.
Investigating vocal tract effects during note transitions on the saxophone
Authors: Pàmies-Vilà Montserrat , Scavone Gary , Hofmann Alex , Chatziioannou Vasileios
Published: November 2017

The resonances of the vocal tract are used by single-reed woodwind players for tuning purposes, timbre modification, and other musical effects. Using pressure or impedance measurements, the influence of the vocal tract on saxophone playing has been previously studied for steady tones. This study considers note transitions in which the players might perform vocal tract modifications (e.g., wide intervals) and combines pressure and reed bending measurements to analyze the effect of the vocal tract as well as its dependence on the articulation technique. The measurement setup consists on recording the acoustic pressure in the players' mouth and in the mouthpiece of the instrument. A strain gauge attached to the reed surface captures both the reed oscillations and the tongue-reed interaction due to articulation. Complementary details about the playing technique are obtained by recording the upper teeth force on the mouthpiece and the open-closed configuration of two selected keys. Preliminary results show that saxophonists are able to drive the vibrations of the reed by modifying the vocal tract configuration, while adapting the blowing pressure and tongue-reed interaction to the articulation technique.
Preliminary measurements of vibrations and resonances of a Kundum xylophone
Authors: Onwubiko Stephen G. , Neilsen Tracianne B.
Published: November 2017

The kundum xylophone is unique among bar instruments because it has bull horn resonators. The kundum is made and played primarily by the Birom ethnic group found in Vom in the Plateau state of Nigeria, which is in the central and northern part of the Nigeria. It complements both the Western and African musical genres but is played mostly in traditional folk music. The unique tone quality of the kundum is far more superior and richer than other xylophone types found in traditional Nigerian societies. The handmade kundum consists of a row of wooden slabs that are struck with a hammer. The vibrations of the wooden slabs are amplified by closed-tip bull horns placed beneath the slabs. The bull horns are sized to produce a high-pitched note; the kundum uses overtones of the open-closed bull horns. This paper examines preliminary measurements of the vibrations of the wooden slabs, as well as natural resonances of closed-pipe bull horns. Comparisons are made with the resonances of ideal cylindrical and conical open-closed tubes to see if the effect of the curved tip of the bull horns warrants further study.
Grain size distribution measurement of Ti-6Al-4V plate using laser-ultrasonics
Authors: Dong Feng , Yang Quan , Krishnaswamy Sridhar
Published: November 2017

As the most widely used titanium alloy, Ti-6Al-4V, has wide range of applications in aerospace industry and medical prostheses. Grain size is a significant parameter that should be controlled during material processing for the reason that it can affect the strength and toughness directly. Laser-ultrasonics is an appropriate method for in-situ measurement of the grain size and distribution during heat treatment of Ti-6Al-4V as it is a nondestructive and non-contact technique. In this study, a laser-ultrasonic system was established combining an 8 ns width pulsed laser for ultrasound generation and a two-wave mixing (TWM) interferometer for detection. Several Ti-6Al-4V samples were heat treated variously to get different grain sizes but with the same phase ratios. Attenuation rates of ultrasonic waves in the different specimens were precisely calculated using exponential fitting for various frequencies. The true values of grain size and distribution were observed via scanning electron microscopy and electron backscatter diffraction (SEM-EBSD). The frequency dependent attenuation of ultrasonic waves was obtained for various grain sizes of Ti-6Al-4V. A statistical correlation between the grain size distribution and the frequency-dependent ultrasonic attenuation was established.
Study of temperature and pressure dependent elastic properties of porous ceramics
Authors: Karunarathne Ashoka , Gladden Josh R. , Priyadarshan Gautam
Published: November 2017

Resonant Ultrasound Spectroscopy (RUS) is a widely used experimental approach to investigate the elastic properties of solid materials at different temperature and pressure. In RUS, experimentally obtained vibrational resonance spectrum of a sample is used to calculate the full elastic tensor of the material. We report here a series of RUS measurements of novel porous ceramics material designed by LG which has applications in high temperature fuel cells. The elasticity and the acoustic damping of a porous material are influenced by its porosity and its saturation fluid. The time dependent elasticity obtained from RUS measurements exhibits a two-step process of stiffening with two distinct time constants. The stiffening-softening behavior during the heating-cooling cycles and the reduction of acoustic damping in the low-pressure conditions were observed depending on the synthesis history of the material.
Acoustic monitoring of aluminum-alloy sensitization
Authors: Kharal Shankar , Jones Nicholas , Petculescu Gabriela
Published: November 2017

Segregation of atomic species in metastable solid-solution alloys results in a gradual change of the alloy’s properties, sometimes rendering the materials ineffective for the particular task they were designed for. An example of such a case is the sensitization of strong and lightweight Mg-rich aluminum alloys used in marine applications. The ASTM standard is an acid-corrosion test (G67), a destructive and lengthy procedure that requires large specimens analyzed off-site. Ultrasound is a well-known tool for nondestructive material characterization and it can offer a solution for on-site testing. To this end, the sensitivity of ultrasonic parameters to the degree of material degradation through sensitization has been identified. Velocity and attenuation for shear and longitudinal waves were measured as a function of sensitization for 5083 and 5456 aluminum alloys with two different methods: Resonant Ultrasound Spectroscopy (RUS) and Pulse Echo (PE). The longitudinal and shear velocities change by 0.5% and 1.5%, respectively, while the attenuation coefficient of longitudinal waves changes by of 20% (all represent saturation values). The JMAK equation for phase kinetics is used to understand the observed evolution of the acoustic parameters vs. sensitization.
An acoustic approach to assess natural gas quality in real time
Authors: Petculescu Andi
Published: November 2017

The natural gas industry needs fast and robust techniques to monitor the quality of the natural gas, if possible during the flow measurement process. A potential technique relies on extrapolating the dynamic specific heat of the gaseous mixture via measurements at a few frequencies (Petculescu and Lueptow, Phys. Rev. Lett. 94, 238301 (2005); Sensors and Actuators B: Chemical 169, 121–127 (2012)). At the core of this approach lies a first-principles model for sound absorption and dispersion in polyatomic gases. We will show and discuss the applicability and limitations of this potential technique to predicting the content of nitrogen, oxygen, carbon dioxide, and water in natural gas.
Ultrasonic investigation of fatigue, tensile damage, and impact damage in woven glass-fiber fabric reinforced composites with comparison to X-ray tomography
Authors: Declercq Nico F. , Pomarède Pascal , Ez-Zahraouy Othmane , Miqoi Nada , Chehami Lynda , Meraghni Fodil , Peltier Laurent
Published: November 2017

This work was done on woven glass-fiber fabric reinforced composite samples. Those materials exhibit a complex anisotropic evolution of defects induced by several damage mechanisms. In order to non-destructively evaluate the damage accumulation within this material, a methodology based on the measurement of the complete stiffness tensor is considered. After validation of the detectability of increasing damage state with this method, a new damage indicator is proposed to thoroughly quantify it. Samples were damaged by tensile tests (quasi-static and fatigue) at increasing stress levels along and out-of fibers axis. Afterwards, drop-weight impact is performed to consider several damage situations. Finally, an X-ray tomography is conducted to identify the damage mechanisms as well as the evolution of the void volume fraction. It is shown that this evolution has the same tendency with the ultrasonic damage indicator.
Design and measurement of an acoustic bi-anisotropic metasurface for scattering-free manipulation of the refracted wavefront
Authors: Li Junfei , Shen Chen , Díaz-Rubio Ana , Tretyakov Sergei , Cummer Steven
Published: November 2017

Relying on the generalized Snell's law which defines a phase gradient to the surface, extraordinary control of the reflected and transmitted wavefronts can be achieved by metasurfaces with subwavelength thickness. However, a fundamental limitation for such metasurfaces is their power transmission efficiency, especially at large deflection angles. Building on the theoretical requirements for the boundary conditions at an ideal metasurface, we designed and fabricated the necessary bi-anisotropic cells for a wave-front transformation acoustic metasurface that overcomes the fundamental limits of conventional designs, allowing us to steer the energy flow in an arbitrary manner without parasitic scattering. The design with a discretized structure is verified both numerically and experimentally and an energy conversion efficiency of 93% is observed for the transmitted wave into the desired direction of 60 degrees, higher than the corresponding theoretical upper limit in generalized Snell’s law based designs (89%). Our experimental demonstration confirms the theoretical results and opens a new way of designing practical and highly efficient metasurfaces for different functionalities, allowing nearly ideal control over the energy flow through metasurfaces.
Passive acoustic metasurfaces for high-efficiency wavefront transformations
Authors: Quan Li , Alu Andrea
Published: November 2017

Metasurfaces have offered new degrees of freedom to control the propagation properties of acoustic waves. Gradient metasurfaces, first proposed in optics, and recently extended to acoustics, add an extra transverse momentum to the incident plane wave so that reflected and refracted waves can be rerouted without having to rely on conventional Snell’s Law. However, recent studies have shown that gradient metasurfaces cannot transfer all incident energy into the desired direction without causing unwanted parasitic diffraction and limiting the overall transformation efficiency. More sophisticated metasurface designs have considered impedance matching to address this issue, but this inherently requires the use of active and lossy materials for extreme wave transformations. In this talk, we present our recent efforts in designing passive acoustic metasurfaces with unitary efficiency in beam steering, even when considering extreme steering angles. We consider nonlocal surface impedance profiles and the use of bianisotropic inclusions, which are both effective routes to realize efficient metasurfaces without relying on gain elements. Our work opens new design approaches for metasurfaces, and it can improve the operational efficiency of metasurfaces.
Thermoviscous effect on sound propagation in acoustic metastructures
Authors: Zhang Likun , Fan Xudong , Jiang Xue , Li Yong
Published: November 2017

Thermoviscous dissipation plays an important role in sound propagation through acoustic metastructures for a variety of applications. The thermoviscous effects rely on the resonances in the structures of subwavelength features. Our analyses and numerical simulations reveal that thermoviscous dissipation can significantly reduce the transmission of sound waves through acoustic metastructures of hybrid resonances in certain scenarios even when the thickness of the viscous boundary layer is much smaller than the width of the slit in the structure [Jiang et al., J. Acous. Soc. Am. (2017)]. To further explore how the resonances affect the significance of the losses, we analyze and simulate sound propagation in acoustic metamaterials of various configurations, including a slit connected to one or multiple resonators at the side of the slit or at the end of the slit. We take into account both wall friction and thermoviscous diffusivity in both the slits and the resonators. The results are compared with that without the resonators to gain insight into the role of the resonances. Optimal designs for both minimal dissipation and maximal absorption are addressed.
Acoustics of locally bilinear periodic metamaterials
Authors: Titovich Alexey S.
Published: November 2017

The scope of traditional metamaterials is expanded by analyzing bilinear discontinuities in an otherwise continuous medium. This amplitude independent nonlinearity is sought for its practicality and utility. Wave propagation has to be solved for in the time domain due to the difference in energy transfer from compression to rarefaction across an interface. Various sizes, orientations and shapes of the discontinuities are analyzed on a unit cell level. Periodic chains with the same type of material discontinuity have recently been shown to exhibit a rich dispersion behavior, such as negatively sloped dispersion branches [Titovich (2017), J. Acoust. Soc. Am. 141(5), 3698]. These waves are now investigated in a continuum, where the discontinuity is modelled as displacement-dependent complex impedance relating the interface tractions. The onset of chaotic behavior as well as its effect on absorption is discussed. Also, the ability of such periodic discontinuities to produce nonlinear non-reciprocity is investigated.
Speaker and production characteristics of posterior nasal fricatives
Authors: Zajac David J.
Published: November 2017

Posterior nasal fricatives (PNF) are unusual articulations produced by children both with and without velopharyngeal (VP) anomalies to replace oral fricatives. PNFs are produced by occluding the oral cavity and forcing airflow through a partially closed VP port to create turbulent noise. Often, extra noises occur due to displacement of mucous and/or tissue flutter. The headset of the nasometer was used to record the separate oral and nasal acoustic signals from 18 children who produced PNFs. They ranged in age from 4 to 15 years, 11 were males, and 11 had some form of cleft palate. Examination of the oral acoustic waveforms revealed that all children produced a stop gesture during intended fricative targets—typically a lingual-alveolar or palatal articulation. Sixteen of the children produced a clear flutter (raspberry-like) noise as evidenced by quasi-periodic components in the nasal spectra. All children used PNFs to replace /s/, 13 (72%) to replace /z/, 12 (67%) to replace /tʃ/, and 6 (33%) to replace /ʃ/ and /dʒ/. Most of the children had known histories of conductive hearing loss. Most of the children with cleft palate had adequate VP closure during stop consonant production. Possible causes of PNFs are discussed.
Articulatory insights on the evolution of nasal vowels in Slavic
Authors: Shosted Ryan
Published: November 2017

The complex articulatory-acoustic mapping of the vocal tract suggests that the acoustic effects of nasalization are tied to other articulatory mechanisms besides velopharyngeal opening; this has been borne out in many recent studies. But do these findings settle on any consensus regarding the articulatory mechanisms (besides velopharyngeal opening) that differentiate nasal and oral vowels and cause shifts in vowel inventories across time? Do articulatory results mirror or contradict the relatively larger corpus of findings regarding the acoustics of nasalization? Are these results idiosyncratic reflections of language differences or do they represent universal properties of phonological development? To approach these questions, results of a series of magnetic resonance and electromagnetic articulography studies of French, Portuguese, and Hindi are compared to historical sound changes in Slavic, a language family where most nasal vowels are now lost. Nasal vowels have been implicated in a number of diachronic Slavic vowel shifts, particularly the lowering of nasal /i/ and nasal /e/ and the raising of nasal /a/ in the development of Late Middle Slavic. Height-related phenomena are well-attested in the articulatory studies and seem predictive of Slavic changes; however, frontness changes, also attested in the articulatory studies, do not find clear Slavic counterparts.
Achieving the transparent ocean
Authors: Stein Peter J.
Published: November 2017

Our common impression is that radar systems monitor the vast majority of the airspace above the earth’s surface. Safe travel is nearly taken for granted, and for the purposes of national security there is a constant close eye on the comings and goings through our airspace. The same cannot be said for under the ocean’s surface, from way out at sea, to near our coast, and within our harbors and waterways. The need for the long-coveted “Transparent Ocean” is evident, and in this paper we explore the visionary aspects of achieving this goal. This includes reviewing concepts and a framework around which state-of-the-art often stove-piped techniques in underwater acoustics, signal processing, and acoustical oceanography, along with non-acoustic modalities including radar and EOIR, are combined into an integrated system.
Littoral Acoustic Demonstration Center passive acoustic localization and tracking of marine mammals in the Northern Gulf of Mexico
Authors: Ioup Juliette W.
Published: November 2017

The Littoral Acoustic Demonstration Center (LADC) consortium, founded in 2000, has collected underwater acoustic data in the northern Gulf of Mexico since 2001 using Environmental Acoustic Recording Systems (EARS) buoys. These hydrophone systems were developed by the U.S. Navy, and originally LADC could record underwater signals only up to 11.7 kHz. Since then the EARS have been upgraded several times and currently record up to 192 kHz, thus allowing recordings of not only sperm whale clicks and codas, but also signals of beaked whales and dolphins. One goal of LADC is to develop an acoustic method for identification of individual animals, with the goal of an “acoustic catalog” similar to the existing photographic catalog of individual whale flukes. Localization and tracking is an important component for acoustic identification. Some localization and tracking techniques and procedures developed and used by LADC will be presented and discussed.
Detection localization and tracking of aircraft using Sparse distributed passive acoustic system
Authors: Sedunov Alexander , Salloum Hady , Sutin Alexander , Sedunov Nikolay , Masters David
Published: November 2017

Stevens Institute of Technology has conducted extensive long-term testing of acoustic systems designed to track low-flying small aircraft in remote location and recorded over 2 years of data. The system consisted of 4 nodes placed in difficult remote terrain with separation ranging 1–4 km, each node comprising a pyramid-shaped volumetric cluster of 5 microphones an embedded computer, and a pan-tilt-zoom camera steered to detected targets in real time. and communication device. Each nodes' computer performed direction of arrival finding communicated to a central computer collected that data and processed it to generate tracks and classify targets. The duration and the scale of the deployment allowed to identify and solve many problems, including the effects of propagation delays between station and on cooperative localization and tracking, the seasonal changes in environmental noise, persistent and transient noise sources, and the diversity of targets of opportunity and their signatures. The propagation delay effects led to development of separate trackers for review of target trajectories and for immediate action such as steering the camera. An overview of the algorithms is presented along with the long-term observations. [This work was funded by DHS’s S&T Directorate.]
An overview of the Seabed Characterization Experiment 2017
Authors: Wilson Preston S. , Knobles David P.
Published: November 2017

A multi-institutional, multi-disciplinary ocean acoustics experiment, Seabed Characterization Experiment 2017 (SCE2017), was conducted 95 km south of Martha’s Vineyard, MA, USA, in March and April of 2017. Three research vessels and more than a dozen principle investigators conducted several types of experiments to improve our understanding of the acoustics of fine grained sediments, forward modeling of sound propagation in shallow water over fine grained sediments, and inverse and statistical inference processes used to characterize the seabed in such environments. The measurements included impulsive and tonal source tows received on vertical and horizontal line arrays, direct measurement of sediment bulk acoustic waves and interface waves, and supporting oceanographic observations. The 2017 experiment was preceded by survey cruises in 2016 and 2015 in which more than 200 sediment cores were obtained and detailed sub-bottom profiling was conducted. Here, an overview of the 2017 experiment is presented. [Work supported by ONR.]
Vector sensor observations of the 2 + mode pattern on the New England Mud Patch at 57 Hz
Authors: Dall'Osto David R. , Dahl Peter H.
Published: November 2017

We present recordings made by an Intensity Vector Autonomous Recorder (IVAR) deployed on the seafloor during the Sediment Characterization Experiment (SCE17) conducted on the New England Mud Patch [40°28’ N, 70°35’ W] in March of 2017. IVAR continuously and coherently records four channels of acoustic data, three from a tri-axial accelerometer embedded in a neutrally buoyant sphere and one from an omnidirectional hydrophone positioned 10 cm above the centroid of the sphere 1.2 m above the seafloor. Here we focus on IVAR recordings of a 57 Hz continuous wave tone generated by a low-frequency acoustic source (J-15) that was towed at 30 m depth by the R/V Endeavor along transects roughly parallel and perpendicular to bathymetric contours. Over the entire tow track deep signal fades occur in 1000 m intervals, suspected to be caused interference between two modes trapped by the sediment basement. A signature in the vector data identifies an additional interference structure superimposed on this pattern (a 2 + mode pattern at 200 m intervals) which fades when the source moves to the northeast of IVAR, where sediment surveys indicate thinning of the overlaying mud layer. Comparison with a mode based model provides an estimate of the sediment properties.
The Intensity Vector Autonomous Recorder (IVAR) as deployed in the Sediment Characterization Experiment
Authors: Dahl Peter H. , Dall'Osto David R.
Published: November 2017

The IVAR system (Intensity Vector Autonomous Recorder) is a bottom deployed system developed for first-use in the Sediment Characterization Experiment (SCE17), conducted on the New England Mud Patch [40°28’ N, 70°35’ W] in spring 2017. IVAR continuously and coherently records four channels of acoustic data, three from a tri-axial accelerometer embedded in a neutrally buoyant sphere (diameter 10 cm) and one from an omnidirectional hydrophone positioned 10 cm above the centroid of the sphere positioned 1.2 m above the seafloor. Despite operations being significantly impacted by two Gale-force storms, IVAR obtained 72 h of data over 2 deployments that included low frequency signals from a towed source (J-15) deployed from the R/V Endeavor and broad band SUS charges deployed from R/V Neil Armstrong. Interesting features of the intensity (Umov) vector field emerge in both bandwidth regimes, but here we focus on measurements of the 100 + SUS charges. The measured Umov vector for each SUS charge is first compared with the known source bearing, and is followed by an analysis of precursor arrivals and dispersive water-borne arrivals in the context of the received vector field. The source locations provide complementary information on range and azimuth dependence of the sediment properties.