bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic performance of an annular Helmholtz resonator and its application in exhaust system
Authors: Hua Xin , Dholaria Jagdish
Published: June 2017

Helmholtz resonator is a traditional acoustic tuning component, which consists of an enclosed volume and a throat neck. It is tuning and packaging friendly and thus has been widely used in exhaust systems. An annular Helmholtz bottle resonator usually has a straight-through pipe with a certain length of perforation. A larger sleeve is mounted to cover the straight-through pipe with one end open and the other end closed. The annular volume gap between the straight-through pipe and the sleeve becomes the neck of the Helmholtz resonator. In this research, an annular Helmholtz resonator is investigated. Numerical simulation and non-linear least square method are used to propose a correction on empirical equation to estimate the resonator targeting frequency. Afterward, this type of Helmholtz resonator is applied to a two-box exhaust system. Insertion loss is used to investigate the resonator performance in the system.
Proper integration of plane wave models into the design process
Authors: Herrin David , Elnady Tamer
Published: June 2017

Muffler and silencer design is primarily accomplished through cut and try approaches in many industries. Although test mufflers are inexpensive to manufacture and test, better designs can be arrived at rapidly and less expensively using plane wave methodologies. Moreover, engineers develop intuition. The current work is aimed at demonstrating how plane wave models can be integrated into the design process. It is first demonstrated that plane wave models can reliably determine the performance of complicated mufflers below the cutoff frequency. Tips for developing plane wave models are summarized.
Shouting across the chasm
Authors: Wheeler Soren
Published: June 2017

As people are interested in science, we assume science is interesting. But if you want to be an effective science communicator, you must assume the exact opposite. After more than 20 years working on the public understanding of science, the thing that continues to astonish and trouble me is how many people shudder at the word “science,” or at any sniff of the words, cadences, or even attitudes associated with science. And yet those are the people we most desperately need to reach. Thus, to communicate science is to cross a chasm of interest, knowledge, inclination, and language. With a few examples, I will talk about the ways that voice, structure, and emotional experience can help us shout across that chasm, and the ways in which audio storytelling, in particular, can shine a light on how to get people to listen to us when we talk about science.
Talking science with non-scientists
Authors: Heineman Karin
Published: June 2017

Can you explain your research to a non-scientist, or even a 7th grader in 90 seconds or less—and explain it in a way that’s engaging and understandable? Communicating science to an audience of non-scientists requires a very different skill set than giving a successful talk to a conference or exchanging ideas with peers or colleagues. Effective science communication skills are important to have—you’re providing lay audiences with accurate and reliable science information, while protecting the public from misinformation, and also influencing public policy and inspiring a sense of wonder in non-scientists. This talk is targeted for a broad audience of scientists who would like to learn how science communication skills will improve their ability to promote their research and get more media attention. A huge communication tool is video. Don’t be afraid to be on camera—learn what to expect from an on-camera interview; learn tricks to get your message across; learn what impact the right visuals can have in communicating your message and research. Learn the tools and tricks of the trade of communicating science from speech, to tone, to what not to wear— and make a lasting impression on any audience.
Communicating science 101
Authors: Lisle Brad
Published: June 2017

What’s the best way to communicate science to non-scientists? Learn how producer/director Brad Lisle tackles this question through two different science media projects. The first, ZOOM into Engineering, targets engineers who are interested in doing hands-on engineering activities with K-6 students. The second, The Global Soundscapes Project, targets middle school students and the general public and explores the emerging field of soundscape ecology.
Don’t cite it, write it. Raising awareness of acoustics through Wikipedia
Authors: Morata Thais C. , Lum Max , Hare James , Fuks Leonardo
Published: June 2017

Wikipedia is accessed by hundreds of millions around the world and that makes Wikipedia one of the most powerful platforms for the dissemination of science information. While Wikipedia offers high-quality content about certain topics, a large proportion of articles are insufficiently developed. The Wikimedia Foundation has engaged in partnerships with scientific and academic institutions to improve the coverage and communication of science to the public. These efforts are beneficial to professional and academic associations interested in sharing reliable, vetted information about their discipline with the world. The National Institute for Occupational Safety and Health (NIOSH) is one of the agencies engaged in this effort. NIOSH developed and manages the WikiProject Occupational Safety and Health. NIOSH also participated in a classroom program (where students write Wikipedia articles) to expand and improve Wikipedia’s content on acoustics, noise, and hearing loss prevention. Faculty and students from the University of Rio de Janeiro contributed content on basic principles of acoustics. Metrics on these efforts are publicly available so reach can be evaluated by the number of views and quality of entries. Throughout these initiatives, new scientific content related to acoustics was successfully added to Wikipedia, and the quality of the entries were improved.
Modal Analysis of a Bamboo Composite I-Beam—Results of a collaborative interdisciplinary project
Authors: King Eoin A. , Bjarnadottir Sigridur , Castaneda Hernan
Published: June 2017

Bamboo has the potential to be considered a sustainable alternative for conventional construction materials. Traditionally, bamboo culms were used for structural applications (buildings, bridges) in certain parts of the world. The structural behavior of bamboo culms can be unpredictable due to material variations, therefore unsuitable for structural applications in the United States, for example. In recent years, glue laminated bamboo, constructed from bamboo culms that have been crushed and glued together to form boards, has been developed. These boards maintain the excellent mechanical properties of bamboo (high tensile and compressive strength, excellent ductility) while eliminating some material uncertainty. Research into the feasibility of Glue Laminated Bamboo for structural applications, such as I-Beams, is quite novel, and there are many avenues that must be investigated and validated before the standardization of bamboo as a construction material can occur. One key feature that needs to be assessed is how the material properties will influence the dynamic response of an I-Beam during excitation. This paper presents results of a modal analysis of a bamboo composite I-Beam conducted as a collaborative project between undergraduate civil engineering students and acoustical engineering students.
Neuroimaging of the speech network
Authors: Guenther Frank
Published: June 2017

Historically, the study of the neural underpinnings of speech has suffered from the lack of an animal model whose brain activity could be measured using invasive electrophysiological techniques. The development of non-invasive structural and functional neuroimaging techniques in the latter part of the 20th century has led to a dramatic improvement in our understanding of the network of brain regions responsible for speech production. Techniques for measuring regional cerebral blood flow, including positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), have illuminated the neural regions involved in various aspects of speech, including feedforward control mechanisms as well as auditory and somatosensory feedback control circuits. More recently, fMRI studies utilizing repetition suppression have been used to identify the neural representations used in different parts of the speech network, including the identification of a syllable representation in left ventral premotor cortex. Magnetic resonance imaging has also been used to investigate the anatomical structure of the speech network, providing crucial information regarding connectivity within the network as well as identifying anomalies in the sizes of neural regions and/or white matter pathways in speech disorders.
Using electroencephalography as a tool to understand auditory perception: Event-related and time-frequency analyses
Authors: Trainor Laurel
Published: June 2017

Electroencephalography (EEG) largely reflects postsynaptic field potentials summed over many (hundreds of thousands of) neurons that are aligned in time and orientation. These electrical fields propagate in all directions such that determination of the sources of electrical fields measured at the surface of the head is much less accurate than localizations using fMRI. However, EEG can be measured with sub-millisecond timing resolution, offering a great advantage for studies of hearing. EEG can measure activity from various nuclei along the subcortical pathway, from primary and secondary auditory cortex and from cortical regions beyond. EEG can be particularly useful for understanding preconscious processing stages, and auditory processing in infants and others who can not make verbal responses. Traditional methods of analysis relate peaks (“components”) in the EEG time waveform to stages of processing. However, communication between brain circuits is reflected in neural oscillations, which can be measured through time-frequency analyses of EEG recordings. Such approaches reveal, for example, how frequency is encoded in the brainstem, and how predictive timing and predictive coding are accomplished in the cortex. I will illustrate these points with example applications largely from our lab and argue that EEG can greatly enhance our interpretation of psychophysical data.
David Wessel's Inventive Directorship of UC Berkeley's Center for New Music and Audio Technologies (CNMAT)
Authors: Freed Adrian
Published: June 2017

The main professional focus of David Wessel’s final 30 years was the development and nurturing of UC Berkeley’s Center for New Music and Audio Technologies (CNMAT). Jean-Baptiste Barrière succinctly described David Wessel as bringing a scientific consciousness to music and a musical consciousness to science. This was manifest in CNMAT practice by building apparatus/instruments that served musical production AND research-apparatus that was concurrently validated as novel and significant in three communities: music, science and engineering. I present the major achievements of CNMAT and the special transdisciplinary practices that made the center so productive for its modest size in its 3 concurrent spheres: research, music creation, and education. This will include a brief case study of CNMAT’s unique acoustics research apparatus, a 141-driver spherical speaker array. Larger institutions attempted unsuccessfully to create such a high resolution array. David Wessel led CNMAT’s success by attracting strong researchers and support engineers over an extended period, creatively finding funding from a diverse combination of extra-mural, government and industry sources, bringing together experts from multiple institutions internationally and tapping the intellectual capital of the UC Berkeley academic community. I conclude by pointing out recent initiatives of David’s mentees who carry CNMAT practices in their work.
David Wessel: A few stories of an antidisciplinarian
Authors: Loui Psyche
Published: June 2017

Timbre, gesture, Open Sound Control, additive synthesis, parallel computing: These were just a few of David Wessel’s many brainchildren. As a Professor of Music, a founding director of Center for New Music and Audio Technologies (CNMAT), and an Affiliate Professor of Psychology at UC Berkeley, David Wessel was a wise advisor and a wonderful scientist, musician, and friend. I will narrate the exceptional experience of working with the creative force that was David Wessel, both from the perspective of a music perception and cognition scientist, and through the lens of Berkeley's CNMAT, which thrived under his leadership as a synergistic center for performers, researchers, and composers.
Pitching timbre analogies with David Wessel
Authors: Singh Punita G.
Published: June 2017

Contemporary thinking and research on timbre and its use as a dynamic, structural component in music performance have been profoundly influenced by the insights and insounds of David Wessel. His intrepid and creative approach opened up vistas of timbre spaces navigable through multidimensional trajectories. Wessel’s experiments with timbre streaming [Computer Music J. 3, 4552, (1979)] inspired my own work on perceptual organization of complex-tone sequences [Singh, J. Acoust. Soc. Am. 82, 886-899 (1987)]. The finding of a timbre “interva” akin to a pitch interval as a threshold for streaming reinforced Wessel’s notion of timbral analogies [Ehresman and Wessel, IRCAM Rep 13/78, (1978)]. Later work on measuring timbre differences through FO thresholds for streaming (Singh and Bregman, J. Acoust. Soc. Am. 102(4), 1943-1952, (1997)) also lent support to the idea of intervallic relationship between timbres. More recently, my work relating Auditory Scene Analysis to Hindustani rhythms brought us together again, presenting and drumming in a multicultural percussion session at the ASA meeting in San Francisco in 2013. For a person so into timing and timbre, David’s untimely departure dealt a discordant blow that can be partially assuaged through such tributes that review, extend, and honor his work.
Acoustic renovation for an office courtyard near a busy highway
Authors: Brooks Bennett M. , Flanagin Nathaniel
Published: June 2017

A complex of several office buildings utilizes a common courtyard as an outdoor gathering space. Regularly scheduled events and celebrations occur in this space. These activities can be disrupted by the noise emitted by vehicular traffic on a nearby busy highway. Field tests were conducted to quantify and characterize the background ambient sound due to the road traffic. The office complex, courtyard, and highway were modeled in a computer aided design system, and various renovation concepts to reduce the perception of highway noise at the venue were studied. The auralized results of design studies were used to generate a virtual reality presentation for evaluation by office management. The reduction of highway noise by several treatment options was noticeable. Also, perceived voice clarity (speech intelligibility) in the courtyard improved with reduced noise. The recommended design treatment provided a significant calculated reduction in highway noise level, with an improved acoustic environment (as perceived) for comfort and speech clarity.
Lessons learning from successful projects in Soundscapes of outdoor spaces
Authors: Schulte-Fortkamp Brigitte
Published: June 2017

One oft he most successful projects within Soundscapes is the redevelopment oft he Nauener Platz in Berlin. Integrating the Soundscape approach from the beginning of the project enabled a horizontal, long-term dialog with the people in the area. The project that resulted was effectively guided by many participants, resulting in a unique solution for mitigating noise and creating a much-needed “backyard” for the local residents through an improved soundscape. Evaluation followed up confirms the long-term positive effect of the project. The temptation with this level of success is to apply the strategies from Nauener Platz wholesale to other locations and attempt to replicate its achievements. However, this would be a false promise, even at seemingly very similar sites. An instructive example is the Berlin Wall Memorial, which shares many physical attributes to the Nauener Platz. However, its political and historical layers provide a very different set. The paper will discuss the similarities and differences with regard to the ISO.
Preliminary assessment and extension of an existing Mach cut-off model
Authors: Huang Zhendong , Sparrow Victor
Published: June 2017

Nicholls’ Mach cut-off theory is re-examined for suitability and extensibility. Nicholls’ analytical predictions (from 1971) determined the cut-off Mach numbers based on the local speed of sound, along with wind speed and direction at flight elevation and locations where the acoustic rays bend parallel to the ground’s surface. The current investigation seeks to understand the limitations of the original formulation and to develop modified predictions to account for realistic and continuous atmospheric profiles. In this presentation, several differences between Nicholls’ work and an extended ray tracing model are highlighted. The influence of atmospheric profiles and model assumptions on cut-off Mach numbers is examined. [Work supported by the FAA. The opinions, findings, conclusions, and recommendations expressed in this material are those of the authors and do not necessarily reflect the views of ASCENT FAA Center of Excellence sponsor organizations.]
Sensitivity analysis of supersonic Mach cut-off flight
Authors: Busch Gregory R. , Tai Jimmy , Mavris Dimitri , Duca Ruxandra , Mohan Ratheesvar
Published: June 2017

Supersonic aircraft designers are pursuing various methods to help facilitate the re-introduction of overland supersonic flight operations. A substantial amount of research has been invested over recent years to demonstrate its feasibility. An alternative method for satisfying the noise standards for supersonic aircraft is more operation-oriented. Under Mach cut-off conditions, the vehicle still generates sonic booms but the acoustic waves refract in such a way that it does not reach the ground. To better understand the propagation of sonic booms during Mach cut-off flight, Georgia Tech (GT) has conducted research under the FAA’s Aviation Sustainability Center (ASCENT). An acoustical model for Mach cut-off flight was developed—GT leveraged this model for sensitivity analysis. The Mach cut-off model allowed GT to vary both atmospheric and flight conditions to study how these dynamic parameters impact sonic boom signatures through the atmosphere. The results of these analyses provide greater insight on how Mach cut-off flight can be achieved and highlights potential technologies to facilitate its re-introduction. [This work was supported by the FAA. The opinions, findings, conclusions, and recommendations expressed in this material are those of the authors and do not necessarily reflect the views of ASCENT FAA Center of Excellence sponsor organizations.]
Infrasound and internal gravity waves generated by atmospheric storms
Authors: Kulichkov Sergey , Chunchuzov Igor , Popov Oleg , Perepelkin Vitaly , Golikova Elena
Published: June 2017

The recordings of infrasound and internal gravity waves (IGWs) obtained during 2015-2016 at infrasound station I43 IMS and a network of microbarographs installed by Obukhov Institute of Atmospheric Physics (OIAP) are presented. The OIAP network of microbarographs is capable of detecting simultaneously an infrasound at frequencies less than 3 Hz and IGWs with periods ranging from 5 min to 3 hr. It is shown that the low-frequency wave processes generated by atmospheric fronts retain high coherence (0.6-0.9) over the areas with horizontal dimensions of a few tens of km. It is found that after the passage of atmospheric front the internal wave trains were observed with the amplitudes considerably exceeding those of IGWs that were detected before the passage of the atmospheric front. The discrete periods of 35 min, 56 min, and 110 min were found in the frequency spectra of the observed wave trains. For these periods, the coherence between atmospheric pressure variations measured at different points reach local maxima, and the sum of the phase differences between selected three points tends to zero. The phase speeds for the observed IGWs are in the range of 10-50 m/c. The wave “precursors” with amplitudes of 10 Pa and periods of 15-20 min were also detected 10 to 15 hr before a passage of the atmospheric front through a network. Along with IGWs, the infrasound associated with atmospheric front was also detected (August 2016) by I43 in the frequency range 0.1-0.4 Hz.
Acoustic characterization of a portable infrasound source
Authors: Barlett Martin , Muir Thomas G. , Slack Charles M. , Hawkins Timothy M.
Published: June 2017

A trailer-able, pneumatic infrasound source is described that can produce tones with frequencies as low as 0.25 Hz. The device is based on compressed gas air flow which is released into the atmosphere from a pair of 500 gallon reservoirs, pressurized to 200 psi (1377 kPa) and modulated by pair of rotating ball valves, with 2 in. (5 cm) diameter ports. Positive air flow is released twice per revolution, so the device is a siren. In addition to the fundamental frequency, the siren also produces a series of harmonics of the fundamental tone, enabling simultaneous measurements to be made at multiple frequencies, up to 20 Hz. This instrument was developed to support in-situ calibrations of infrasound sensors and arrays as well as to provide a controllable source for other infrasound studies, such as signal insertion loss measurements of wind noise suppression structures and characterization of infrasound array azimuthal directivity. The physical attributes of the source are described and results of acoustic measurements of sound pressure levels and azimuthal directivity are presented. The results are also compared to estimates made using improved versions of a previously presented aero-acoustic model (Pneumatic Infrasound Source: Theory and Experiment, POMA 19, 045030 [2013] and papers 4pPA3 and 4pPA4. J. Acoust. Soc. Am. 134 [2013]). [Work supported by the U.S. Army Space and Missile Defense Command/Army Forces Strategic Command (USASMDC/ARSTRAT).]
Reciprocity calibration for infrasound sensors
Authors: Gabrielson Thomas B.
Published: June 2017

Frequency response is a key parameter in understanding the impact of a transducer on a measurement. A single volts-per-pascal value is often cited as an acoustic transducer’s response; however, the magnitude and phase of this ratio over the entire frequency range of interest is required to understand the effects of that transducer on input waveforms. While this ratio can be determined by comparison to a reference transducer, any reference must itself be calibrated in some fashion. The National Center for Physical Acoustics has built two calibration chambers designed for evaluation of infrasound microbarometers. The large interior volume (about 1.5 cubic meters) allows simultaneous testing of several microbarometers and reference transducers. These chambers are also equipped with two drivers—10-in. subwoofers—so that two-tone linearity testing can be done. The incorporation of two drivers opens the possibility for implementing reciprocity calibration, a well-established primary calibration methodology. This paper describes development, evaluation, and uncertainties of a reciprocity-based calibration procedure designed expressly for measuring the complex frequency response of infrasound sensors in the 0.005 to 10 Hz frequency range.
A three-dimensional simulation of vortex formation at the open end of an acoustic waveguide
Authors: Malaga Carlos , Martinez Leon , Zenit Roberto , Rendon Pablo L.
Published: June 2017

For high enough levels of acoustic pressure inside a tube, a nonlinear mechanism is responsible for the formation of annular vortices at the open end of the tube, which results in energy loss. Higher sound pressure levels in the tube lead in turn to larger values of the acoustic velocity at the exit, and thus to higher Reynolds numbers. It has been observed [Buick et al., 2011] that two regimes are possible depending on whether the acoustic velocity is low, in which case vorticity appears in the immediate vicinity of the tube, or high, in which case vortices are formed at the open end of the tube and are advected outwards. We use a Lattice Boltzmann Method (LBM) to simulate the velocity field at the exit of the tube in 3D, for both cases. We plan to compare these numerical results with experimental results obtained through particle image velocimetry (PIV). The effect of varying both the geometry of the tube and the shape of the termination on the magnitude of the nonlinear losses at the exit is also examined.
Three-dimensional model for acoustic field created by a piezoelectric plate in a resonator
Authors: Ghoshal Goutam , Ross-Johnsrud Benjamin P. , Chitale Kedar C. , Ilinskii Yurii A. , Zabolotskaya Evgenia A. , Lipkens Bart
Published: June 2017

A three-dimensional model is developed to describe an acoustic field excited by a piezoelectric plate of finite size in a fluid filled resonator. First, the eigenfunctions (modes) of a bare plate are derived using general piezoelectric equations considering the elastic and electric properties of the plate. Then, the piezoelectric plate is placed into a fluid media such that only one plate side is in fluid and an acoustic field generated by the plate in the fluid is estimated. Finally, a reflector is placed to be parallel to the piezoelectric plate and acoustic field in a resonator is evaluated. The solution for a piezoelectric plate of finite size is obtained using Singular Value Decomposition (SVD) method. Equations for acoustic and electric variables are presented. Radiation force on spherical particles in the standing wave field is derived and discussed. Numerical results are presented to show the three-dimensional modal displacement and electrical characteristics of the plate at various frequencies and aspect ratio. Finally, the analytical results are compared with two-dimensional and three-dimensional finite element results using COMSOL Multiphysics commercial software.
Directed self-assembly of three-dimensional user-specified patterns of particles using ultrasound
Authors: Prisbrey Milo , Greenhall John , Guevara Vasquez Fernando , Raeymaekers Bart
Published: June 2017

Particles dispersed in a fluid medium are organized into three-dimensional (3D) user-specified patterns using ultrasound directed self-assembly. The technique employs standing ultrasound wave fields created by ultrasound transducers that line the boundary of a fluid reservoir. The acoustic radiation force associated with the standing ultrasound wave field drives the particles into organized patterns, assuming that the particles are much smaller than the wavelength, and do not interact with each other. A direct solution method is theoretically derived to compute the ultrasound transducer operating parameters required to assemble a user-specified pattern of particles in any 3D simple, closed reservoir geometry with any arrangement of ultrasound transducers. This method relates the ultrasound wave field and its associated radiation force to the ultrasound transducer operating parameters by solving a constrained optimization problem that reduces to eigendecomposition. Experimental validation of the method is accomplished by assembling 3D patterns of carbon nanoparticles in a cubic water reservoir lined with four ultrasound transducers. Additionally, the versatility of the method is demonstrated by simulating ultrasound directed self-assembly of complex 3D patterns of particles in cubic and noncubic reservoir geometries lined with many ultrasound transducers. This method enables employing ultrasound directed self-assembly in a variety of engineering applications, including biomedical and materials fabrication processes.
Microsecond interaural time differences of acoustic transients are decoded by inhibitory-excitatory interactions in neurons of the lateral superior olive
Authors: Franken Tom P. , Smith Philip H. , Joris Philip X.
Published: June 2017

The lateral superior olive (LSO) in the auditory brainstem generates sensitivity to interaural level differences (ILD), an important cue for sound localization, by comparing excitatory (E) input from the ipsilateral ear with inhibitory (I) input from the contralateral ear. Large axosomatic synapses (e.g., calyx of Held) point to the importance of precise temporal processing, but that is not easily reconciled with ILD detection. We propose that the IE interaction allows detection of interaural time differences (ITD) of acoustic transients, to which humans are exquisitely sensitive. We obtained in vivo whole cell recordings of LSO and MSO neurons in the gerbil, while presenting monaural and binaural clicks. We found that ITD functions to clicks in the LSO are surprisingly steep, in contrast to MSO neurons, which are considered the main ITD detectors. Intracellular LSO recordings show EPSPs generated by the ipsilateral click and IPSPs by the contralateral click, where IPSPs often arrive earlier. Binaural spiking is maximally suppressed when the EPSP coincides with the falling slope rather than the peak of the IPSP. We conclude that LSO neurons are more sensitive to ITDs of transients than MSO neurons. This clarifies the importance of timing specializations in the LSO circuit.
Selecting an acoustic correlate for automated measurement of /r/ production in children
Authors: Campbell Heather M. , Harel Daphna , McAllister Byun Tara
Published: June 2017

A current need in the field of speech pathology is the development of reliable and efficient techniques for the purpose of evaluating changes in speech production over the course of treatment. The industry standard for scoring speech is time consuming and expensive, as it involves aggregating perceptual ratings across expert listeners. As techniques for automated measurement of speech improve, acoustic measures have the potential to play an expanded role in the clinical management of speech disorders. The current study asks which of several acoustic measures of children’s productions of English /r/ corresponds most closely with ratings given by trained listeners. This study fits a series of ordinal mixed effects regression models to a large sample of children’s /r/ productions that had previously been rated by three trained listeners (speech-language pathologists). Controlling for age, sex, and allophonic contextual differences, the acoustic measure that accounted for the most variance in speech rating was F3-F2 distance, normalized relative to a sample of age- and gender-matched speakers. Therefore, this acoustic measure is recommended for use in future automated scoring of children’s production of rhotic targets.
On the use of hypothesis-driven reduced models in auditory neuroscience
Authors: Goodman Dan F.
Published: June 2017

There are a number of detailed models of auditory neurons that are able to reproduce a wide range of phenomena. However, using these models to test hypotheses can be challenging, as they have many parameters and complex interacting subsystems. This makes it difficult to investigate the function of a mechanism by varying just one parameter in isolation, or to assess the robustness of a model by systematically varying many parameters. In some cases, by limiting the scope of a model to testing a specific hypothesis using a particular set of stimuli, it is possible to create a reduced mathematical model with relatively few, independent parameters. This has considerable advantages with respect to the problems above. In particular, if a certain behavior is robust and does not depend on finely tuned parameters, then different implementations are more likely to produce the same results—a key property for reproducible research. In addition, the code for these models is typically simpler and therefore more readable, and can often run faster, enabling us to carry out systematic parameter exploration. I will illustrate these points with a reduced model of chopper cells in the ventral cochlear nucleus.
Anomalous refraction and asymmetric transmission of SV-waves through elastic metasurfaces
Authors: Su Xiaoshi , Norris Andrew
Published: June 2017

Recent advances in acoustic metasurface design make it possible to manipulate sound waves in an almost arbitrary way. Here, we present several elastic metasurfaces comprised of an array of subwavelength plates for controlling SV-wave in solids. The underlying physics are the coupling between the SV-wave in the elastic body and the flexural wave in plates, and the coupling between the P-wave in the elastic body and the longitudinal wave in plates. By varying the thicknesses of the plates, a wide range of phase delay for flexural waves can be obtained, while keeping constant the phase delay for longitudinal waves. The anomalous refraction of SV-waves is achieved by selecting the thickness of each plate to engineer the phase change according to the generalized Snell’s law. This metasurface has another feature that it redirects SV-waves only, which enables it to be used to split SV- and P-wavefronts into different directions. In addition, this metasurface can be paired with a uniform metasurface to break spatial symmetry and achieve asymmetric transmission for normally incident SV-waves. Other potential applications, such as focusing and negative refraction, will also be discussed. [Work supported through ONR MURI.]
Design of broadband acoustic metamaterials for low-frequency noise insulation
Authors: Liu Zibo , Feng Leping , Rumpler Romain
Published: June 2017

An innovative configuration of an acoustic sandwich structure is proposed in this paper, which uses the locally resonant structures to generate stopbands in desired frequency regions and hence to increase the sound transmission loss of the panel. Effects of different types of resonators, including the mounting techniques, are investigated. The methods to broaden the effective stopbands are discussed. The acoustic properties of the sandwich panel with non-flat laminates are also studied. Numerical analyses show that good results can be obtained when combining the laminate modification with the locally resonant structure, especially when the stopbands are designed to compensate the corresponding coincidence effects of the sandwich panel. The analysis is based on the Finite Element models constructed in COMSOL. Bloch wave vectors are derived at first Brillouin zone by using wave expansion method. Dispersion relation of the structure is discussed. Experimental validation is planned, and the results will be shown in the conference.
Low frequency bandgaps in lightweight metamaterial panels using rotation inertia multiplication
Authors: Delpero Tommaso , Hannema Gwenael , Schoenwald Stefan , Zemp Armin , Bergamini Andrea , Van Damme Bart
Published: June 2017

Of all possible features of structural metamaterials, the formation of bandgaps is the most studied one due to its direct application for sound and vibration isolation. While achieving low frequency values for the position of the first bandgap is, in general terms, not an unsurmountable challenge, the combination of material properties such as high stiffness, low density, and reduced size of the unit cell, with low (in absolute terms) frequency bandgaps, may well require some careful consideration. In previous work, we designed panels with a 3D network of resonators, clearly improving the vibration isolation compared to a homogeneous panel with the same weight. Recently, we have devised a novel implementation of inertia amplification, based on coupling the energy of longitudinal waves into the rotational oscillation of inertia elements within the unit cell. In this contribution, we present examples of phononic crystals based on this approach, and we discuss the interaction of acoustic waves with the discussed lattices.
Optimal sound-absorbing structures
Authors: Sheng Ping
Published: June 2017

Causal nature of the acoustic response dictates an inequality that relates the absorption spectrum of the sample to its thickness. We use the causal constraint to delineate what is ultimately possible for sound absorbing structures, and denote those which can attain near-equality for the causal constraint to be “optimal.” By using acoustic metamaterial as backing to conventional porous absorbers, a design strategy is presented for realizing structures with target-set absorption spectra and a sample thickness close to the minimum value as dictated by causality. By using this approach, we have realized a 12 cm-thick structure that exhibits broadband, near-perfect flat absorption spectrum starting at around 400 Hz, while the minimum sample thickness as calculated from the causal constraint is 11.5 cm. To illustrate the versatility of the approach, two additional optimal structures with different target absorption spectra are presented. This “absorption by design” strategy enables the tailoring of customized solutions to difficult room acoustic and noise remediation problems. [Work done in collaboration with Min Yang, Shuyu Chen, and Caixing Fu.]
Simulation of coupled structural-acoustic response with dynamic damage evolution
Authors: Pitt Jonathan
Published: June 2017

A novel time-domain method for simulating dynamic damage evolution in a coupled structural-acoustic system is presented. The system is derived via the theory of continuum damage mechanics, and incorporates standard damage evolution models, but is readily extendible to more exotic formulations. The overall solution method is staggered, solving for the dynamic damage evolution first with an explicit step, and then using the new values in the coupled computation of the structural-acoustic system. The spatial domain is discretized using a mixed finite element method, and the temporal domain is discretized with a higher-order implicit time discretization scheme. Efforts toward fully coupled verification of the solution algorithm are presented, as are validation studies for cases without evolving damage. Applications with evolving damage are presented, and present a novel first principles study of changes in the structural acoustic response to dynamically evolving damage in the structure. Special attention is given to brittle fracture. Examples of downstream usage of the evolving structural response are discussed in the concluding remarks.
Rhoticity in Cajun French
Authors: Blake Katherine M. , Berkson Kelly
Published: June 2017

Previous studies of Cajun French (CF) report a shift in pre-rhotic vowel quality (Conwell & Juilland 1963, Blainey 2015, Dubois & Noetzel 2005, Salmon 2007, Lyche, Meisenburg & Gess 2012). This is unsurprising, in that such behavior is reported for numerous Francophone varieties, but prior work on rhotics in CF has been largely impressionistic. As such, the current study presents acoustic analysis of pre-rhotic vowels in CF. Formant measurements were taken from data collected from three native speakers. The question of whether rhotic deletion is present in CF is also addressed: /r/-dropping is widely attested cross-linguistically, and has been reported in the closely related Francophone variety of Acadian French (Cichocki 2012, 2006). Given the previous literature on /r/-dropping and rhoticity in CF and other Francophone varieties, it was expected that these data would show variable /r/ production, compensatory lengthening of vowels preceding a dropped /r/, and a general trend of /r/-induced vowel lowering. Results of this study confirm the presence of highly variable rhotic deletion, a lack of compensatory lengthening triggered by this deletion, a centralization effect of the rhotic on the quality of preceding vowels, and variable lowering of the third formant.
Acoustic properties of Mexico City Spanish vowel weakening
Authors: Dabkowski Meghan F.
Published: June 2017

Mexico City Spanish exhibits weakened vowels that have been described as reduced, relaxed, unstable, obscured, abbreviated, devoiced, and “lost,” indicating likely reduction in duration, voicing, and/or quality. The objective of this study is to precisely identify the acoustic nature of this vowel weakening. To this end, recorded spontaneous speech was collected from 20 speakers native to Mexico City. 3000 tokens, i.e., monophthongs, were analyzed acoustically in Praat (Boersma & Weenink 2016), and measurements were taken for F1, F2, vowel duration, and voicing duration. Findings show that vowel weakening in this variety consists primarily of shortening and weakened voicing, but not raising or centralization. Instead of simple presence or absence of voicing, many tokens show weak voicing, characterized by a lower intensity in the waveform and a lighter voice bar, or partial voicing that does not endure throughout the entire vowel. The presence of frication distinguishes devoicing from weak voicing when other aspects of the acoustic signal are not clear indicators. Many tokens exhibited full voicing, but only consisted of 2-3 wave cycles, resulting in a severely shortened vowel. Uncovering the acoustic properties of these weakened vowels is crucial to understanding how this variety fits with cross-linguistic vowel weakening trends.
Phonetic variability in Moroccan Arabic rhotics
Authors: Freeman Aaron
Published: June 2017

Moroccan Arabic /r/ and its pharyngealized counterpart exhibit a wide range of variability in their pronunciation, with reported articulations ranging from apical trills to uvular fricatives. Using an phonetic dataset elicited from speakers of the dialect of Fès (reported to traditionally have a uvular variant), I assess the distribution and acoustic properties of rhotic variants, including coarticulatory effects. The data present three distinct rhotic articulations: (1) an apical trill or tap, (2) an apical continuant produced together with high-frequency sibilant noise, and (3) a dorsal sonorant or rhotacized vowel similar to English “burred /r/.” Despite claims in the literature, no uvular fricative was observed in the data, and the dorsal sonorant was identified by speakers as the idiosyncratic local pronunciation. Variants (1) and (2) further exhibit devoiced positional variants. Lowered F2 of adjacent vowels and of sonorant portions of the rhotic signal differentiate the pharyngealized phoneme /rʕ/ from its plain counterpart /r/. However, both phonemes were found to exhibit the same range of variation in their primary articulation. Two acoustic properties common to all variants were (a) depression and attenuation of upper formants and (b) the presence of some aperiodic noise above 5 kHz.
Exploring the acoustic characteristics of individual variation
Authors: Tucker Benjamin V. , Brenner Daniel
Published: June 2017

Studies of the acoustic properties of words often analyze a small subset of words across a large population of speakers. Much of the previous research has not investigated the individual variation produced by a single speaker in large sets of words. The present study analyzes the individual variation produced by a male Western Canadian English speaker, who produced 26,800 English words and 9,600 pseudo-words. All pseudo-words were phonotactically licit and were generated using the software package Wuggy (Keuleers & Brysbaert, 2010). Each word has been force-aligned using the Penn Forced Aligner (Yuan & Liberman, 2008) and then hand corrected by trained phoneticians. We investigate the formant space, word pitch contours, segmental duration, and other acoustic characteristics relevant to classes of segments (such as center of gravity for fricatives). An acoustic comparison is performed between the words and pseudo-words. We explore the acoustic variation of the individual segments produced by this speaker and investigate his individual speech patterns. Finally, we consider the value of delving deeply into productions of a single speaker rather than relying on averaged summaries across a sample a large sample.
Uncertainty of glottal airflow estimation during continuous speech using impedance-based inverse filtering of the neck-surface acceleration signal
Authors: Espinoza Victor M. , Mehta Daryush , Van Stan Jarrad , Hillman Robert E. , Zañartu Matías
Published: June 2017

The aim of this work is to determine the uncertainty of non-invasive glottal aerodynamic measures that are obtained using subglottal impedance-based inverse filtering (IBIF) of the signal from a neck-placed accelerometer during continuous speech. Currently, we are studying the vocal behavior of individuals with typical voices and voice disorders by analyzing weeklong recordings using a smartphone-based ambulatory voice monitor. We extend on previously reported analyses of sustained vowel production using subglottal IBIF and move toward continuous speech applications where IBIF parameters are estimated in a frame-based approach. Selected voiced frames of both oral-airflow (baseline) and acceleration signal from the Rainbow Passage are used to build a probabilistic model of IBIF parameters to run multiple random realizations of the inverse-filtered neck-surface acceleration signal. Confidence intervals are estimated for both the glottal waveform and derived features. The probabilistic model is tested using data from patients with vocal hyperfunction and matched-control subjects with normal voices at a comfortable pitch and loudness in an acoustically treated sound booth. Results show that model parameters follow approximately normal distributions, and the confidence intervals for the estimates of glottal aerodynamic measures were <10%, which is in close agreement with previously reported IBIF performance using sustained vowels.
Aeroacoustic consequences of tongue troughs in labiodentals
Authors: Shadle Christine H. , Nam Hosung , Katsika A. , Tiede Mark , Whalen D. H.
Published: June 2017

It has long been accepted that the main constriction for fricatives /f, v/ is formed by the lower lip pressing against the upper teeth, thus allowing the tongue to freely coarticulate with preceding and following segments. Here, electromagnetic articulometry data were obtained from 5 subjects in a study of tongue troughs, defined as a discontinuity in anticipatory coarticulation, such as when the tongue drops during a bilabial consonant in /ii/ context. The corpus included /f/ and /v/ in VC(C)V contexts, where V = /i/ for C= /v/, and V = {/i a u/} for C= /f/. The tongue moved down and back for /f/ in all vowel contexts; in /iC(C)i/ context, the troughs were deeper for long (VCCV) than short labial consonants, as predicted, and deeper for /f/ than for /p, b, v, m/, which was unexpected. There seems to be a secondary gesture specifying that the tongue be down during labiodental fricatives. Our hypothesis is that lowering the tongue for /f/ ensures that the airflow resistance will be due only to the labiodental constriction, thus providing an aeroacoustic advantage for the onset of turbulence. This is supported by comparison of asymmetric vowel contexts (e.g., /uffi/-/iffu/ tokens); tongue dorsum and blade sensors show the tongue moving quickly away from /i/ to /f/ position, in contrast to movement from /u/ to /f/. Aerodynamic considerations thus appear to be actively incorporated into the speech motor plan. [Work supported by NIH grant DC-002717.]