bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of results for an analogous acoustical and optical scattering problem: The double sphere
Authors: Dean Cleon E. , Braselton James P.
Published: June 2017

A comparison of results for an analogous scattering problem is made for the interactive scattering of a double sphere in both acoustics and electromagnetic scattering. For initial testing purposes, the problem is simplified to that of two identical spheres with the same size and physical properties. The acoustical scatterer is modeled to match optical characteristics of the already studied optical scattering problem [G. W. Kattawar and C. E. Dean, Opt. Lett. 8, 48-50 (1983).]. Particular study is made of situations that lead to large side scattering responses due to resonance phenomena. The model for the acoustical scattering problem was discussed in a previous Acoustical Society of America meeting [C. E. Dean and J. P. Braselton, J. Acoust. Soc. Am. 139, 1121 (2016)].
The effects of finite amplitude drop shape oscillations on the inference of material properties
Authors: Ansari Hosseinzadeh Vahideh , Holt Ray
Published: June 2017

Acoustic levitation of drops provides a non-contact means of isolation, stable positioning and static and dynamic manipulation. Despite a long history of the use of drop shape oscillations to infer both surface and bulk material properties, and an equally long history of observing behaviors that result in incorrect inference of material properties, researchers continue to employ finite amplitude oscillations for their experimental observations. In this study we use the inference of surface tension and viscosity of known samples of glycerin-water mixtures to illustrate the fact that finite-amplitude oscillations are the dominant mechanism for many reports of ill-behaved drop dynamics, including modal peak-splitting, vorticity, and strong field-coupling. Since this “bad” behavior leads to incorrect inferences of surface tension and viscosity, we show that small amplitude oscillations yields recovery of correct inferences for these properties for known samples. Finally, we show results from experiments with bovine and human blood. [Work supported by NSF grant # 1438569.]
Acoustic frequency splitting in thermoacoustically driven coupled oscillators
Authors: Andersen Bonnie , Wright Jacob H. , Heward Cory J. , Jensen Emily R. , Bridge Justin S.
Published: June 2017

Frequency splitting, or level repulsion, occurs near the point where two resonant modes of coupled oscillators intersect as one parameter is varied such that the resonance of one passes through the resonance of the other. A thermacoustic stack, which provides internal self-sustained oscillations, placed inside the neck of a closed bottle-shaped resonator can set up standing waves of the coupled neck-cavity system. The neck behaves as a quarter-wave resonator because it is closed at the top of the bottle and open at the bottom where it is attached to the cavity. The cavity being closed at the bottom and mostly closed near the neck behaves as a half-wave resonator. A one-dimensional wave equation with appropriately applied boundary conditions is used to generate solutions of the coupled neck-cavity system. These solutions reveal mode splitting near the intersections of the uncoupled neck and cavity modes. Thermoacoustic engines with bottle-shaped resonators were tested while varying one of three geometric parameters: the neck length, the cavity length, and the cavity radius. Graphs of the coupled solutions readily illustrate mode splitting of the coupled oscillator system and in agreement with experimental results.
Seismo-Acoustic numerical simulation of North Korea nuclear tests
Authors: Averbuch Gil , Assink Jelle D. , Smets Pieter S. , Evers Läslo G.
Published: June 2017

A seismo-acoustic event is an event in which seismic energy transfers to acoustic energy in the oceans and/or atmosphere and vice versa. Although measurements confirms the coupling between the mediums, a numerical investigation of these events may provide us with a deeper understanding of the phenomena. In this presentation, a finite element, elasto-acoustic Fast Field Program (FFP) is presented and is applied to the recent 2013 and January 6th, 2016 North Korea underground nuclear tests. The aim of this study is to model the elastic and acoustic wave fields of these events and use this information to estimate the source depths. The modeled depths will be compared to those from seismo-acoustical observations.
Fiber maps from acoustic anisotropy in rodent cardiac tissue
Authors: Milne Michelle L. , Chung Charles S.
Published: June 2017

Previous studies have demonstrated that 3D myocardial fiber maps of excised large mammal hearts can be generated from ultrasonic images by utilizing the acoustic anisotropy of cardiac tissue. The goal of this paper is to demonstrate that detection of acoustic anisotropy and the creation of myocardial fiber maps using ultrasound is also feasible in rodents. Acoustic anisotropy of rat myocardium was confirmed using 2-mm diameter cores taken from the left-ventricular free wall using a 21 MHz probe (VisualSonics Vevo210) in B-mode. The relationship between fiber orientation and ultrasonic backscatter was obtained. These data were confirmed in segments of left ventricular free wall that were scanned and subsequently histologically sectioned serially from the epi- to endo-cardium. Subsequently, a series of long-axis images were taken from intact rat hearts to generate 3D rodent fiber maps. Preliminary data from mouse hearts using a 40 MHz probe produces similar results. We conclude that it is feasible to obtain a cardiac fiber map from ex vivo rodent hearts using echocardiography. Further development of this method may allow for in-vivo fiber direction analysis in live rodents. [Work supported by the American Heart Association (14SDG20100063 to CSC) and a grant from The Patuxent Partnership (MLM).]
Finite element models of crystallized white dwarf cores: A gateway to undergraduate physical acoustics and computational modeling of complex systems
Authors: Pestka II Kenneth A. , Highley Robert C. , Deale Laura K.
Published: June 2017

In this work we present details of several finite element (FE) models of white dwarf stars with cores composed of layered crystalline carbon, oxygen and neon. The FE models, produced by undergraduate physics majors, are constructed using a commercially available software package Femap with NX Nastran. These models can be used to understand the effect of stellar composition and crystallization ratios on white dwarf behavior including vibrational modes, surface velocity and variation in luminosity. While the nature of these ultra-dense stellar remnants can appear quite exotic, the physical acoustic principles required to build and analyze the FE models are directly related to those commonly utilized by research acousticians. This gateway project was designed for undergraduate physics majors in order to illustrate this connection and to encourage interest in applied physical acoustics. The inherent interdisciplinary nature of the project also provides an opportunity for undergraduate physics majors to explore fields that are often considered disparate while improving their computational modeling skills.
Inhibition of Rayleigh-Bénard convection through acceleration modulation for thermoacoustic devices
Authors: Swaminathan Anand , Garrett Steven L. , Smith Robert W.
Published: June 2017

The ability to dynamically stabilize Rayleigh-Bénard convection using acceleration modulation is of interest to groups who design and study thermoacoustic machines, as the introduction of unwanted convection can have deleterious effects on the desired operation and efficiency of the device. These performance issues caused by suspected convective instability have been seen both in traveling wave thermoacoustic refrigerators and in cryogenic pulse tube chillers. This presentation reports the results of an experiment intended to determine the vibratory, fluidic, and geometric conditions under which a small, rectangular container of statically unstable fluid may be stabilized by vertical vibration, evaluating the computational methods of R. M. Carbo [J. Acoust. Soc. Am. 135 654 (2014)]. Measurements are obtained using a long-displacement kinematic shaker of a unique design with the convecting gas characterized using both thermal transport measurements and flow visualization employing tracer particles illuminated by a diode laser light sheet phase-locked to the shaker. [Work supported by the Julian Schwinger Foundation for Physics Research, the Pennsylvania Space Grant Consortium Graduate Research Fellowship, and the Paul S. Veneklasen Research Foundation.]
Lagrangian meshfree particle method for modeling acoustic wave propagation in moving fluid
Authors: Zhang Yong Ou , Hou Qing Zhi , Gong Zhixiong , Zhang Tao , Li Tianyun , Wei Jian Guo , Dang Jian Wu
Published: June 2017

Introducing the Lagrangian approach to acoustic simulation is supposed to reduce the difficulty in solving problems with deformable boundaries, complex topologies, or multiphase media. Specific examples are sound generation in the vocal track and bubble acoustics. As a Lagrangian meshfree particle method, the traditional smoothed particle hydrodynamics (SPH) method has been applied in acoustic computation but in a quiescent medium. This study presents two Lagrangian approaches for modeling sound propagation in moving fluid. In the first approach, which can be regarded as a direct numerical simulation method, both standard SPH and the corrective smoothed particle method (CSPM) are utilized to solve the fluid dynamic equations and obtain pressure change directly. In the second approach, both SPH and CSPM are used to solve the Lagrangian acoustic perturbation equations; the particle motion and the acoustic perturbation are separated and controlled by two sets of governing equations. Subsequently, sound propagation in flows with different Mach numbers is simulated with several boundary conditions including the perfected matched layers. Computational results show clear Doppler effects. The two Lagrangian approaches demonstrate convergence with exact solutions, and the different boundary conditions are validated to be effective.
Diffraction effects of an acoustic beam propagating through a flowing medium
Authors: Frøysa Kjell E.
Published: June 2017

Ultrasonic transit time difference flow meters are today industrially accepted for custody transfer measurements of oil and for natural gas. Such meters are currently planned to be used also subsea, where the calibration possibilities are few. In such subsea applications the velocity of sound measured by these meters will be a powerful input for estimation of density and calorific value of the flowing oil or gas. The ultrasonic transit time measurements in such meters are carried out in a flowing oil or gas, over a range typically between 6 and 40 inches. For precise transit time measurements over such ranges, diffraction corrections may be of high importance. Diffraction effects for an acoustic beam in a flowing medium are therefore studied numerically. The flow direction and the propagation direction of the acoustic beam will be different. The investigation is based on the solution for the acoustic field from a point source in a homogeneous flowing medium. Acoustic beams are modeled using two-dimensional arrays of point sources. The results will be compared to the no-flow case in order to identify effects of flow on the diffraction correction for application of precise transit time measurements in a flowing medium.
Smoothed particle acoustics with variable smoothing length and its application to sound propagation with complex boundary
Authors: Wang Futang , Hou Qing Zhi , Wang Zhe , Zhang Yong Ou , Dang Jianwu
Published: June 2017

Lagrangian smoothed particle hydrodynamics (SPH) method has shown its high potential for solving acoustic wave propagations in complex domain with multi-mediums. Typical applications are sound wave propagation in speech production and multi-phase flow. For these problems, SPH with adaptive particle distribution might be more efficient, with analog to mesh-based methods with adaptive grids. If the fluid flow or moving boundary is taken into account, initially evenly distributed particles will become irregular anyway (dense somewhere and sparse somewhere else). For irregular particle distribution, conventional SPH with constant smoothing length suffers from low accuracy, phase error and instability problems. The main aim of this work is to apply variable smoothing length into SPH and apply it to 2D sound wave propagation in a domain with complex boundary. In addition, the effects of several strategies for variable smoothing length on phase error in smoothed particle acoustics are fully investigated by numerical examples and theoretical analysis. Numerical results indicate that the phase error is reduced by the use of variable smoothing length.
Nat Durlach and the context-coding and trace modes of intensity perception
Authors: Braida Louis D.
Published: June 2017

Nat came to M.I.T. from Lincoln Laboratory and became involved in the teaching of the subject 6.37, Sensory Communication. Nat soon realized that there were certain problems with teaching the subject. Not only were there many different ways to quantify the magnitude of stimuli (detection, discrimination, identification, category and ratio scaling, to name a few), but also the time variable affected comparisons in ways that were not independent of the range of intensities. This bothered Nat as a mathematician. However within two years of effort, Nat assembled a unifying picture that permitted some of the roadblocks to be overcome. All one-interval experiments were assumed to use the context-coding mode exclusively and were described in terms of two experimental parameters. Two-interval experiments were more complicated, using the trace mode that interacted with context-coding mode, and requiring an additional parameter. Nat assumed that an optimal combination of modes was used. Subsequent work extended these models to the cases where Weber’s Law did not hold and to the comparison of loudness of different types of stimuli. As the result of Nat’s efforts, 14 papers appeared in the Journal.
Contributions of Nat Durlach to the field of haptics: Research on tactual communication of speech and manual sensing of mechanical properties
Authors: Reed Charlotte M. , Tan Hong Z.
Published: June 2017

As a sensory scientist, Nat’s earliest contributions were through his theoretical and experimental work in the area of binaural hearing. Early in his career, however, he demonstrated an interest in comparative sensory processing as evidenced by a study to determine if the masking-level difference observed in audition would be found for stimulation on the skin (it was). Nat’s interest in the sense of touch continued through his research concerned with the use of the tactual sense as a substitute for hearing in the communication of speech and language for individuals with profound hearing impairment. This research encompassed studies with experienced deaf-blind users of natural methods of tactual communication (to establish an “existence proof” for the information-bearing capacity of the tactual sense) as well as research on methods for encoding and displaying acoustic signals for presentation through tactile aids. In addition, Nat also spearheaded efforts concerned with the development of haptic displays for use in virtual environment and teleoperator systems. His research in this area was concerned with advancements in knowledge regarding manual sensing and manipulation through a set of basic psychophysical studies. In this talk, we will summarize some of Nat’s important contributions in both of these areas.
Long-range elastic metamaterials
Authors: Carcaterra Antonio , Coppo Francesco , Mezzani Federica , Pensalfini Sara
Published: June 2017

The problem of wave propagation control in one-dimensional systems, including electrical charges and dipole magnetic moments is investigated. The waveguide is characterized by long-range and nonlinear interaction forces of Coulomb and Lorentz nature. Wave propagation properties are derived by a method based on an equivalent partial differential equation that replaces the discrete equation of motion of the chain. The paper shows how the waves propagating in these special systems have characteristics, such as phase and group velocity, that are function of the electrical and magnetic property distribution along the chain. Of interest are also possible wave-stopping phenomena. The paper presents an outline of some basic principles developed by some of the authors in recent theoretical papers and shows also numerical experiments illustrating wave propagation in metamaterials characterized by long-range elastic-electromagnetic interactions.
Bi-anisotropy in acoustic scattering problems
Authors: Quan Li , Alu Andrea
Published: June 2017

Electric and magnetic dipole moments dominate the scattering properties of small nanoparticles in optics. Ordinarily, electric dipole moments are excited by the local electric field, and magnetic dipole moments by the magnetic field. Bi-anisotropy, or magneto-electric coupling, largely enriches the electromagnetic response of materials. Similarly, in acoustics the dominant scattering contributions from objects smaller than the wavelength, monopole and dipole moments, are commonly excited by pressure and velocity, respectively. The recent interest in Willis acoustic materials, for which these responses are coupled, leads us to analyze the opportunities offered by the analogues of bi-anisotropic nanoparticles in acoustics and their relevance in practical applications to tailor sound. We also present an extraction procedure to determine the acoustic polarizability tensor of an arbitrary object and relate its bi-anisotropic response to its geometry and material properties.
On the unique features of mechanical metamaterials with nonlinear local oscillators
Authors: Silva Priscilla B. , Kouznetsova Varvara G. , Geers Marc G.
Published: June 2017

Over the last two decades, metamaterials have attracted a high number of researches motivated by the possibility of designing structures capable of manipulating wave propagation. The basic mechanism underlying the behavior of mechanical metamaterials is their negative effective dynamic parameters (mass and/or stiffness). Within the framework of mechanical metamaterials, most of the developments up to now have considered linear material behavior only. There is a natural need to understand the effect of nonlinear material behavior on the wave propagation through such engineered composites. In this paper, the dynamic behavior of a discrete lattice system composed of a series of nonlinear local resonators is investigated. By making use of the harmonic balance method, approximating dispersion relations are derived. Unlike previous works, super/sub-harmonic generation has been considered and revealed new phenomenon: the possibility of generating multiple transmission dips. The analysis also showed the tunability and multistability features of the system. The semi-analytical predictions were verified with direct numerical simulations.
Anderson localization amongst weakly coupled substructures
Authors: Coleman John P. , Yoritomo John Y. , Weaver Richard
Published: June 2017

It is shown that if vibrational energy is put into one substructure and allowed to diffuse into other weakly coupled substructures (as in the case of statistical energy analysis or reverberant sound diffusing from one room into others through small windows), at infinite time the energy density in the starting room will still be above its equipartition value. We offer a theory to predict the amount of this Anderson localization in such systems of weakly coupled substructures. We compare these predictions with numerical results obtained using random matrix substructures.
A higher order shear deformation model of a periodically sectioned plate
Authors: Hull Andrew J.
Published: June 2017

This talk develops a higher order shear deformation model of a periodically sectioned plate. A parabolic deformation expression is used with periodic analysis methods to calculate the displacement field as a function of plate spatial location. The problem is formulated by writing the transverse displacement field and the in-plane rotations as a series solution of unknown wave propagation coefficients multiplied by an exponential indexed wavenumber term in the direction of varying structural properties multiplied by an exponential constant term in the direction of constant structural properties. These expansions, along with various structural properties written using Fourier summations, are inserted into the governing differential equations that were derived using Hamilton’s principle. The equations are now algebraic expressions that can be orthogonalized and written in a global matrix format whose solution is the wave propagation coefficients, thus yielding the transverse and in-plane displacements of the system. This new model is validated with finite element theory and Kirchhoff plate theory for a thin plate simulation and verified with comparison to experimental results for a 0.0191 m thick sectional plate.
Linguistic masking release in older adults
Authors: Alageel Sarah , Sheft Stanley , Shafiro Valeriy
Published: June 2017

Past studies of speech-on-speech masking in children and young adults (YA) indicate that intelligibility of target speech can improve when target and masker speech are in different languages. We investigated whether such linguistic release from masking is obtained in older adults (OA) with age-typical hearing abilities. All participants were asked to recognize English sentences in the presence of two-talker maskers spoken in either English or Spanish presented at four different Signal-to-Noise ratios (SNR) to each group. Differences in energetic masking between the masker languages were minimized. Overall sentence recognition accuracy was greater for YA participants. However, both groups equally benefited from a linguistic mismatch in the target-masker language with a significant masking release for the Spanish language masker. The magnitude of masking release increased as SNR decreased, ranging across SNR conditions from 1 to 27 percentage points. Age, hearing-in-noise ability and hearing sensitivity of OA listeners did not correlate with masking release. Results confirm previous findings of masking release associated with a linguistic mismatch between target and masker speech, and indicate that in speech-on-speech masking older listeners can improve speech intelligibility by utilizing nonenergetic linguistic differences between the target and masker speech.
Rhythmic characteristics in aging: A study on Zurich German
Authors: Pellegrino Elisa , He Lei , Giroud Natalie , Meyer Martin , Dellwo Volker
Published: June 2017

Age-related changes in speech production influence both speech segmental and suprasegmental characteristics. Previous research focussed on changes in voice quality, vowel formant patterns, f0 and speech rate due to aging but only little attention has been paid on speech rhythm (durational and dynamic). In this study we analyzed the segmental durational variability as well as the syllabic intensity variability between 60 Zurich German speakers ranging in age between 20 and 81 years. Speakers read 90 sentences in Zurich German. Between-speaker durational variability across age was quantified through a variety of different rhythmic variables (%V, ΔCLn, ΔVLn, rPVI-C, nPVI-V, %VO, varcoVO, nPVI-VO, ΔPeak, varcoPeak, and nPVI-Peak). Intensity variability was computed by taking the standard deviations, variation coefficients and PVIs of average syllable intensity and syllable peak intensity values across sentences. Results based on durational measurements show that with aging there is an increase in %V and r-PVI-C. Aged voices also present lower variability in the consonantal and especially in the vocalic intervals (nPVI-V and ΔVLn). We argue that changes in the physical characteristics as well as in the neural control mechanisms of the articulators might play a significant role in age-related rhythmic changes.
Speed of lexical access relates to quality of neural response to sound, not cognitive abilities, in younger and older adults
Authors: Johns Alexis R. , Myers Emily B. , Skoe Erika , Magnuson James S.
Published: June 2017

Previous work has demonstrated a relationship between age-related declines in inhibitory control and difficulties identifying words of low lexical frequency and high neighborhood density (Sommers & Danielson, 1999). We hypothesized that declines in consistency of the auditory brainstem response (ABR; neural response to a repeated sound; Anderson et al., 2012) might also impede lexical access in older adults. We measured audiometric thresholds, ABR consistency, vocabulary, inhibitory control, and working memory in two groups (younger: 18-23yo, n = 41; older: 54-76yo, n = 41). We used mean target fixation proportion from 200 to 750 ms after word onset in a visual world task as a proxy for lexical access speed as listeners identified spoken words (varying on low/high: lexical frequency, neighborhood density, and cohort density; Magnuson et al., 2007). ABR consistency significantly predicted speed of word identification across variations in neighborhood and cohort densities, but contra previous findings, cognitive measures did not improve model fits. Interactions involving age, vocabulary, and lexical frequency suggest age-related linguistic expertise influences lexical access of uncommon words. We conclude that older adults exhibit increases in phonological competition due to declines in auditory encoding, suggesting that a consistent neural response to sounds leads to more efficient speech processing and lexical access.
Velar-vowel coarticulation across the lifespan and in people who stutter: Findings and model
Authors: Frisch Stefan A. , Maxfield Nathan D.
Published: June 2017

The study of anticipatory coarticulation provides insight into the speech production planning process. In the present study, the task involved repeating velar-vowel consonant combinations in a carrier sentence (e.g., for /ke/, “Say a cape again”). Data for velar-vowel coarticulation were analyzed using the Articulate Assistant Advanced software to create tongue traces that were quantified following the procedures for average of the nearest neighbor point-to-point distance between curves (Zharkova & Hewlett 2009, Journal of Phonetics). There were 126 participants total in child (8-12), young adult (18-39), and older adult (55-75) ages and groups of typical speakers (n = 21, 23, 29) and people who stutter (n = 15, 23, 11). Data analysis found a decrease in coarticulatory influence of the vowel on the velar across the lifespan, but no differences in coarticulation for people who stutter. Analysis of variability found greater variability for children and people who stutter. A two allophone model of coarticulation provided the best fit to the data, replicating Frisch & Wodzinski (2016, Journal of Phonetics).
Naturalistic coding for prelinguistic speech at 9 and 12 months of age from two Mandarin-learning children differing in auditory function
Authors: Li Hsin-yu , Chen Li-mei
Published: June 2017

This study investigated the feasibility of Fagan’s (2005) naturalistic coding system for prelinguistic speech of Mandarin-learning children. This system includes 10 categories: single vowel, single consonant, consonant combination, vowel combination, syllable containing glottal sound and vowel, syllable containing supra-glottal consonant and vowel (SGCV), reduplicated vowel, reduplicated consonant, reduplicated CV, and reduplicated “SGCV" (RSGCV). The first 50 clear utterances produced by one normal-hearing (NH) child and one hearing-impaired (HI) child in the audio recordings at 9 and 12 months old were transcribed into 10 categories for comparison. Major findings are (1) compared with NH child, HI child demonstrated no obvious changes in vocalization from 9 to 12 months old; (2) at 12 months old, canonical babbling ratio of HI child was 0, while those of NH child were 0.84 (utterance as unit) and 0.48 (syllable as unit); (3) compared with NH child, HI child did not manipulate supra-glottal sounds and had limited consonant inventory; (4) HI child produced no RSGCV (e.g., /baba/) while NH child was at reduplicated babbling stage at 12 months old. Naturalistic coding system revealed difference in prelinguistic speech between a NH child and a HI child. More participants should be included to verify the findings.
Irregular pitch periods as a feature cue in the developing speech of English-learning children
Authors: Hanson Helen , Shattuck-Hufnagel Stefanie , Pereira John
Published: June 2017

Changes in phonation patterns have long been studied as correlates of various linguistic elements, such as the occurrence of irregular pitch periods (IPPs) at significant locations in prosodic structure (in phrase-initial, phrase-final, and pitch accented contexts) and word-final voiceless stops, especially /t/. But less is known about the development of this phonation pattern in children [cf. Song et al., JASA, 131, 3036-50, 2012], particularly in toddlers between the ages of 2;6 and 3;6. The study of its course of acquisition may shed light on the mechanisms involved, since child vocal folds are very different physiologically from those of adults, and change strikingly during development. Monosyllabic target words from the Imbrie Corpus of speech from 10 toddlers 2 1/2 to 3 1/2 years old, ending in /t, d/ were examined for evidence of IPPs. Preliminary results based on three adult/child pairs suggest that both adults and children produce IPPs preceding coda /t/ about 50% of the time. But children produce fewer IPPs before coda /d/ than adults do (38% v 8%), suggesting (like earlier reports) that children are not simply imitating the cues produced by the adults around them. Data from additional adult/child pairs will be presented.
Development of acoustic speech discrimination abilities in school-aged children
Authors: Trudeau-Fisette Pamela , Maysounave Melinda , Vidou Camille , Menard Lucie
Published: June 2017

The acquisition of speech perception skills is challenging for children. Although some studies have shown that categorical perception boundaries become steeper during childhood and are sometimes shifted in children compared to adults, very few experiments on discrimination abilities in children have been conducted. To investigate this, we conducted a perceptual discrimination task in school-aged children. Sixty-seven 6- to 12-year-old native Quebec French-speaking children were asked to complete a speech perception task that used an AXB scheme. The children were asked to discriminate synthesized 5-formant vowels belonging to three continuums: /i-e/ and /e-ø/ (in which stimuli were equally stepped along F1) and /e-ø/ (in which stimuli were equally stepped along F2). There was a significant effect of age on peak discrimination scores, with older children having higher peak scores than younger children. There was no effect of age on the location of the categorical boundary on the three tested continuums. These findings support the hypothesis that speech development and learning experience play significant roles in the establishment of strong phonological targets.
Do mothers enhance the tonal contrasts in their monosyllabic Cantonese tones directed to their infants?
Authors: Wong Puisan , Ng Hoi Yee
Published: June 2017

Introduction Some studies reported that adults enhanced acoustic differences of phonemes when speaking to young children. We examined whether mothers improved the contrasts among the lexical tones when speaking to infants. Methods Nineteen native Cantonese-speaking mothers produced the six Cantonese tones in 45 monosyllabic words to an adult and their 7- to 12-month-old infants. The 1709 words were low-pass filtered to preserve the pitch contours but eliminate lexical information. Five judges categorized the tones of the filtered words. Acoustic analysis was performed. Results Infant-directed tones had higher fundamental frequency (F0) and longer duration, but were identified with lower, though not significantly different, accuracy. Larger mean F0 differences were found in four pair of tones in infant-directed speech. However, these increased acoustic contrasts did not lead to higher perceptual accuracy of these tone pairs. Despite substantial perceptual confusion between T2 (HR) and T5 (LR) has been reported in previous tone studies, the difference in the slopes of the two tones was not enhanced in infant-directed speech. Conclusion Mothers acoustically modified their tones when speaking to infants. However, little evidence supported that mothers enhanced the phonetic contrasts of the tones in infant-directed speech. [Work supported by Research Grants Council of Hong Kong.]
Modelling and estimation of the spatial impulse response in reverberant conditions
Authors: Tashev Ivan J. , Gamper Hannes , Corbin Lyle
Published: June 2017

Modern audio signal processing and speech enhancement relies more and more on machine learning approaches, which require vast amount of data for training. One of the ways to create a dataset for training is by convolving measured impulse response between the sound source and the device with clean speech and adding noise. This approach is limited to the pair of used sound source and microphone, as it incorporates not only the reverberation of the room, but also the radiation pattern of the sound source (typically mouth simulator or head and torso simulator) and the directivity patterns of the microphones in the device under test. In this paper we propose using a spherical loudspeaker array as a transmitter and a spherical microphone array as a receiver to create a sound source and receiver independent impulse response. During the dataset synthesis this spatial impulse response is modified to model the impulse response between transmitter and receiver with given directivity patterns.
Liquid filled encapsulation for thermoacoustic sonar projectors
Authors: Mayo Nathanael K. , Blottman John B.
Published: June 2017

Thermoacoustic projectors produce sound by rapidly heating and cooling a material with low heat capacity. These “thermophones” were originally demonstrated in 1917 using thin platinum filaments [Arnold, H., I.B Crandall, (1917) Phys. Rev. 10(1):22-38], but were very limited in their efficiencies and bandwidth until the much more recent discovery of new nanomaterials. The first underwater thermophones were made by Aliev et al. in 2010 [Aliev, A. E et al, (2010) Nano letters 10 (7), 2374-80] which utilized a carbon nanotube (CNT) sheet submerged in deionized water. These devices worked well for demonstrational purposes, but the CNT sheet would become damaged when retracted from the water, which made characterization difficult. More recently, new methods for enhancing the robustness of freestanding sheets have been developed which allow few layer CNT sheets to be repeatedly dipped and withdrawn from a water bath without damage. Such methods have enabled revisiting the study of submerged thermoacoustic projectors. Our studies of CNT thermophones in various liquid baths give evidence to the mechanism for acoustic wave generation in these systems. The potential to improve the impedance matching between the thermoacoustic source and surrounding fluid media suggest enhanced designs for compact sonar transducers.
Four dimensional sound speed environments in ocean acoustic simulations
Authors: Bhatt EeShan C. , Schmidt Henrik
Published: June 2017

Current ocean acoustic simulation environments often rely on a single depth-varying sound speed profile. This work introduces a robust and configurable Octave/C + + implementation of a four-dimensional sound speed environment (4D SSP) for use with Bellhop in the MIT/LAMSS software package for acoustic simulations. This tool shows considerable advances in that the 4D SSP environment can be created from MIT GCM model output, CTD data, or manually varied from existing historical profiles. By considering the fluctuations in sound speed in longitude, latitude, depth, and time, output pressure data better approximates experimental data. Two experiments in the Arctic and the Santa Barbara Channel (SBC) are simulated in 1-D and 4-D to compare to experimental data taken. A framework for acoustic data assimilation using this new simulated data environment in tandem with experimental data is shown to derive the true sound speed field. [Work supported by ONR under the Information in Ambient Noise MURI.]
Acoustical Society of America R. Bruce Lindsay Award: Bradley E. Treeby
Authors: McDannold Nathan J.
Published: June 2017

The R. Bruce Lindsay Award (formerly the Biennial Award) is presented in the Spring to a member of the Society who is under 35 years of age on 1 January of the year of the Award and who, during a period of two or more years immediately preceding the award, has been active in the affairs of the Society and has contributed substantially, through published papers, to the advancement of theoretical or applied acoustics, or both. The award was presented biennially until 1986. It is now an annual award.
Helmholtz-Rayleigh Interdisciplinary Silver Medal in Psychological and Physiological Acoustics, Speech Communication, and Signal Processing in Acoustics: Blake S. Wilson
Authors: Dorman Michael , Zeng Fan Gang , Hansen John
Published: June 2017

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.
Acoustical Society of America Gold Medal: William M. Hartmann
Authors: Moore Brian C. J. , Colburn H. Steven
Published: June 2017

The Gold Medal is presented in the spring to a member of the Society, without age limitation, for contributions to acoustics. The first Gold Medal was presented in 1954 on the occasion of the Society’s Twenty-Fifth Anniversary Celebration and biennially until 1981. It is now an annual award.
Materials properties of resilient materials used for remodeling of aged apartment
Authors: Song Gukgon , Kim Yonghee , Lee Won-Hak , Yoon Yongjin , Kim Myung-Jun
Published: June 2017

In Korea, resilient materials such as EPS and EVA are used to reduce the floor impact sound between adjacent houses in apartment. With the revision of the Ministry of Land, Infrastructure, and Transport (MOTT) Notice, new apartment buildings are required to construct concrete slabs of 210 mm or more and to ensure floor construction with impact insulation performance within 4th grades. However, most of the apartment buildings approved by the government prior to the enactment of the related laws in 2004 are usually constructed with a slab thickness of 120--150 mm, causing disputes and complaints over floor impact sound. This study investigated the mechanical properties like as dynamic stiffness, loss factor, compressibility, dimensional stability, etc., of resilient materials for remodeling of aged apartments. About 200 kinds of resilient materials and structures applied in commonly in recently 3 years were selected and investigated. Because of notification revision including compressibility and dimensional stability, dynamic stiffness of resilient materials was increased and lots of composite layer resilient structures were developed. In addition, it is necessary to develop a resilient materials or structures that can reduce the total thickness of floor structure because the aged apartment has low indoor height. [This research was financially supported by the Seoul R&BD Program (No. PS150001) through the Research and Development for Regional Industry.]
Development of an automated system for American society for testing and materials test method E1007
Authors: Scinto Jennifer M.
Published: June 2017

The use of a tapping machine in four specific configurations is required in the determination of the field impact insulation class rating of a floor-ceiling assembly as prescribed in the American Society for Testing and Materials Test Method E1007. When performed with presently available equipment, the procedure requires either two acousticians be present—one taking measurements in the room below while the other moves the machine into the four required positions in the room above or one acoustician who must repeatedly return to the machine to change its position after taking each measurement. Either case results in a waste of man-hours, which could be more effectively utilized. The objective of this work is to design a proportional-integral-derivative-controlled automated testing system using National Instruments MyRIO robotics components to be retrofitted to an existing tapping machine. This allows for the wireless remote control of the position of the tapping machine from the floor below, allowing a single acoustician to perform the test more quickly and accurately.
Experimental methods for determining the cross-over frequency above which phaseless geometrical methods for room acoustics computer simulation is suitable
Authors: Avelar Marcio , Bonifacio Paulo , Azikri de Deus Hilbeth , Bertoti Elvis , Brandao Eric , Fonseca William D. , Sarda Alexandre , Prestes Pedro
Published: June 2017

The most used computer codes for simulating the sound propagation in closed spaces are based on geometrical acoustics. Such an approach is known to be suitable when sound waves interference does not play a major role. For estimating a cross-over frequency above which this condition is met, acousticians use a simple formula for the so called “Schroeder frequency,” which in turn is related to modal overlap. In this work, two methods for observing experimentally the cross-over frequency above which wave interference may be disconsidered are presented. One of them is related to the statistical independence of room impulse responses (in space), while the other one is based on the analysis of impulse responses' phase information within a frequency band. Preliminary results for a shoebox room, based on analytically generated impulse responses, and measurements performed in an auditorium are shown, and indicate similar frequency values, also comparable to the estimated Schroeder frequencies.
Modification of the head-related transfer functions for auditory proximity in rooms
Authors: Pätynen Jukka
Published: June 2017

The human hearing uses two signals entering the ears to interpret surrounding spaces and sound sources, and certain acoustic impressions are often regarded favorably by the listeners. At times, music consumers may consider auditory proximity and intimacy as a desired sensation. In some scenarios, the acoustic reflections, often arriving from lateral angles, succeed in enhancing the perceived proximity, even though all acoustic events occur at far distances. In contrast, natural sounds emanating from a very close proximity are instinctively perceived as intimate. The perception of spatial sound is based on the binaural cues, which can be modeled with head-related transfer functions (HRTF). Earlier research has demonstrated that the interaural level difference for lateral incidence is the foremost difference between near and far-distance HRTFs. In the context of room acoustics, only lateral reflections arrive from angles which at high frequencies create traces of interaural level difference otherwise characteristic to near-field HRTF. This paper explores altering the auditory proximity of auralizations by introducing near-field-type interaural level differences to widely available far-field HRTFs. Analysis of the application of these modified HRTF to reflected sound provides more insight into the sources of auditory proximity.
Binaural reproduction of self-generated sound in virtual acoustic environments
Authors: Arend Johannes M. , Stade Philipp , Pörschmann Christoph
Published: June 2017

Virtual acoustics aims to immerse the user in a virtual acoustic environment (VAE). However, most VAE systems do not feed self-generated sound back into the virtual room, even though there is evidence that adequate reproduction of self-generated sound affects the user’s perception and might even enhance immersion. Thus, if at all possible, sonic interaction between the user and the virtual room is very limited in most current systems. This work presents a VAE system that is able to capture and reproduce self-generated sound in real time. Hence, the VAE is complemented with a reactive component providing the acoustic response to the actions of the user. The major difference compared to the few reactive VAEs introduced so far is that the system presented here considers the varying directivity of the user or the sound source, and that it generally works with any arbitrary source. The study includes a first technical evaluation of the system as well as an example application of a virtual concert hall. The reactive VAE can be used as a virtual practice room for musicians, or as a tool for psychoacoustic experiments investigating the influence of self-generated sound on human perceptual processes.
Measured and simulated room acoustic characteristics in three concert halls with unique architectural geometry using beamforming techniques
Authors: Navvab Mojtaba , Heilmann Gunnar
Published: June 2017

Sound reflections and time delay between direct and reflected sounds are key variables that shape and contribute to the acoustic quality and listening experience within concert halls. To demonstrate these architectural space characteristics from a designer’s standpoint, three internationally well-known halls are simulated and selectively measured for their acoustic characteristics utilizing beamforming techniques. The results are analyzed given recommended procedures within ISO3382 standards. Realistic computer reconstructions of these concert halls provides the opportunity to examine the sound quality of each and the differences in their performance using the latest sound quality measures. Known indicators such as reverberation time, sound strength, center time, echo, clarity-definition for speech and music, speech transmission index and articulation loss are used to show important acoustical features of these halls. The simulated and measured results provide supportive data toward the recognition of key architectural elements in each hall and show how the space geometry contributes to the high quality of sound experienced by an audience. Final results are offered as quantitative and qualitative indicators that identify the significant geometry and space volumes that shape listener experience in each hall. This research direction is significant for the future architecture design of concert halls and may contribute to understanding of the acoustical effects of architectural elements and improve upon current standards.
Assistive listening systems in assembly spaces
Authors: Badrak James S.
Published: June 2017

This paper will show the perspective from the facility owner and the challenges encountered trying to offer premium assisted listening experiences. The recent opening of the Dr. Phillips Center for the Performing Arts in Orlando, FL, has brought to light many of these challenges. Our experiences this past year included having to determine the viability of different systems and what type of system works best in our spaces. The ultimate choice of system was different than what was originally installed and resulted from a process of working with a local audiologist, patrons of the arts center, assistive listening manufacturers, and our house staff. This paper presents that process along with our suggestions for further research and advancement of this technology.