bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased resonant frequency of microslit filtered contrast agents
Authors: Rowan Jeffrey S. , McGrath James , Doyley Marvin M.
Published: November 2019

Imaging using ultrasound contrast agents is highly dependent on the resonant frequency of the population. According to the Marmottant model, modern lipid coated agents have three regimes of resonant frequencies corresponding to the three regimes of bubble dynamics, the buckled, elastic, and ruptured states. The transition from buckled to elastic regime corresponds to the largest change in resonant frequency due to the addition of a second term inversely proportional to the bubbles’ radius. For a 1.75 μm bubble, this corresponds to a change from approximately 1.7 MHz, to approximately 5 MHz, leading to higher image resolution, and better separation between the fundamental and subharmonic components. Here we present a novel ultrathin silicon nitride membrane for this purpose. The membrane itself contains thousands of 1.75 × 50 μm slits and is housed in a centrifuge device. While the exact mechanism is unknown, bubbles that are forced across the membrane during centrifugation show a higher resonant frequency than their strictly size isolated counterparts. In addition, the centrifuged agent also had a lower subharmonic threshold compared to native and size isolated agents, independent of concentration. The possibility of tuning the device to precise frequencies for optimized imaging is also examined.
The khaen: Musical traditions and contemporary innovations
Authors: Adler Christopher
Published: November 2019

The khaen is a bamboo free-reed mouth organ prominent among people of Lao ethnicity in Laos and Northeast Thailand. In Thailand, the khaen is considered emblematic of the rural Northeast, but has also enjoyed periods of broader popularity in Thailand, including within the Thai royal courts in the mid-19th century. After a period of modernization during which traditional music was in danger of disappearing, the khaen is once again celebrated as a symbol of Northeast identity, taught in public schools, and figures into regional popular music. The polyphonic music of the khaen is traditionally played solo and to accompany a solo singer, employing improvisation within five different melodic modes. Recent institutionalization has placed a greater emphasis on composition and playing in ensembles with contemporary folk and electrified popular instruments. The author has contributed to the khaen becoming an international concert instrument, by composing, commissioning and recording modern notated works by living composers for the instrument. The paper will survey the changing cultural and musical contexts for the khaen, with demonstrations of traditional and contemporary playing styles and techniques.
Sonic boom prediction and measurement analysis methods for certification of quiet supersonic aircraft
Authors: Loubeau Alexandra , Doebler William , Cowart Robbie , Liu Sandy R. , Naka Yusuke , Page Juliet , Downs Robert S. , Coen Peter , Lemaire Stephane , Wade Lucas , Sparrow Victor
Published: November 2019

New sonic boom noise certification procedures for quiet supersonic aircraft are needed as part of proposed regulations to potentially amend the ban on civil supersonic overland flight worldwide. In preparation for developing these procedures, analyses are performed on an existing N-wave dataset to exercise various methodologies. Six noise metrics (PL, ASEL, BSEL, DSEL, ESEL, and ISBAP) are calculated for the measurements obtained on the ground and aloft above the turbulent boundary layer. Predictions are performed for these same locations under test day conditions and compared to measurements. In addition, predictions are performed under standard day conditions to facilitate assessment without the effects of real-world winds and atmospheric turbulence. Methods for validating prediction tools or correcting for the atmospheric effects are discussed, and limitations of these methods are identified. Ideas on robust methods for implementation in certification procedures are proposed.
Design of experiments: X-59 sonic thump carpets in the eastern United States
Authors: Doebler William , Wilson Sara R. , Loubeau Alexandra , Sparrow Victor
Published: November 2019

NASA is conducting a series of computational experiments to quantify atmospheric effects on low noise sonic booms. In the current study, simulated cruise nearfield pressure data from NASA’s X-59 Quiet Supersonic Technology aircraft were propagated from the aircraft to the ground at four cardinal headings through five years of realistic atmospheric profiles at 30 locations across the eastern USA. Statistical design of experiments was used to select the locations where primary sonic thump carpet widths (CW) and metric levels at the ground were computed. Atmospheric profiles were taken from the Climate Forecast System Reanalysis database, which contains reanalyzed atmospheric profiles four times daily. Decision tree analyses were performed to determine relative importance of predictors for CW and metric levels. Predictors included were latitude, longitude, date, time of day, season, climate, aircraft heading, and ground elevation. Results of this study indicate the propagation resolution needed to adequately characterize the distributions of CW and ground metric data in terms of the necessary separation distance between propagation locations and the total number of atmospheres through which to propagate. This resolution will be used for a follow-on study of simulated X-59 carpets across the entire US mainland.
Leaf ruptures: Acoustic impulse events in wildland fires
Authors: Yedinak Kara M. , Nemens Deborah G. , Anderson Michael J. , Partelli Peltrin Raquel
Published: November 2019

Quantifying wildland fires is of interest to both the fires science and land management communities. Remote sensing of these events has exclusively focused on electromagnetic spectra emissions. However, wildland fires also produce sound. Unraveling their acoustic profile will likely reveal new information unrealized through traditional remote sensing techniques. We start with the “crackling” sounds often associated with burning live vegetation. The data in these acoustic impulse events are rich, yielding information about the specific plants involved. In work presented here, acoustic impulse events are used to tease apart the influences of species, age, and plant moisture during combustion of live conifer needles. Needles were collected and burned onsite for six species within the Priest River Experimental Forest. Replicate measurements were carried out in order to reduce the influence of individual branches or trees. Moisture of the needles was ascertained just prior to the experiment through both predawn leaf water potential as well as gravimetric fuel moisture. The burning material was recorded at 50 kHz with a ½ in. measurement microphone. The acoustic impulse events were isolated and analyzed to determine likelihood of unique character traits. We present results of investigating the potential differences in acoustic signature based on species and age.
Architected micro-lattices for wide-band vibration attenuation
Authors: Gerard Nikhil J. , Oudich Mourad , Jing Yun
Published: November 2019

Over the past decade, metamaterials have straddled traditional subject boundaries and emerged as futuristic materials with unconventional functionalities. Architecting material microstructure has been shown to facilitate a myriad of applications for sound and vibration manipulation. The progress of this field has thus been mapped by 3-D printing techniques and the precision that such manufacturing techniques can offer. Recently, large area projection micro-stereolithography, a novel additive manufacturing technique has been shown to be capable of fabricating samples with a high structural complexity and smallest feature sizes ranging from a few microns to over tens of centimeters. From the perspective of mechanical wave propagation, this implies a precise control over micro-structure that can be engineered for a variety of applications. In this work, we develop a unique class of elastic metamaterials that are architected for low frequency, wide-band vibration attenuation. The material is made up of three-dimensional micro-lattices that are shown to possess local resonance band gaps which can be precisely tuned via unit cell geometry and the intrinsic material employed for its fabrication. The working of this material is experimentally verified and the associated functionalities that it can facilitate are discussed.
Measurement and analysis of sound absorption by a metallic composite foam
Authors: Cops Mark J. , McDaniel James G. , Magliula Elizabeth A. , Bamford David J. , Bliefnick Jay
Published: November 2019

A composite foam consisting of polyurethane foam embedded in metallic foam is fabricated and evaluated for sound absorbing properties. The normal incidence sound absorption coefficient is measured in an impedance tube for three different types of foams including the composite foam, a rigid framed metallic foam, and an elastic framed polyurethane foam. A lumped element model is used to predict the energy dissipation mechanisms, which include viscous and thermal losses, structural losses, and coupling losses at the metal and polyurethane interface. The best performing composite foam increased sound absorption by a factor of 6 (from 0.1 to 0.6) in the low frequency test range (around 600 Hz) and by a factor of 2 (from 0.2 to 0.4) over the entire test frequency range (250–4500 Hz). The composite foam maintains the high static stiffness of the metal foam and exhibits acoustic compliance characteristic of the polyurethane foam. Composites such as those presented in this work are advantageous for engineering applications where combined high stiffness and energy absorption are required.
Doubling the efficiency of ocean wave power with doubly coiled-up acoustic metamaterial
Authors: Lee Joonyoung , Park Mincheol , Lee Jong-Rim
Published: November 2019

Ocean wave is a potential renewable energy source with stability and abundance. However, its high initial investment requires high energy harvesting efficiency, limiting its application. In this research, the ocean wave is directly amplified by adopting the structure of the acoustic metamaterial. SHOWPAM—A System of High-efficiency Ocean Wave Power with Acoustic Metamaterial – is designed to achieve this amplification. The mathematical analogy between acoustic wave and water surface wave is found. Also, an effective physical property of the solid obstacle, such as a wall, as a medium of water surface wave is investigated. Coiling-up-space metamaterial structure is simplified to a six-variable system and optimized for maximum water surface wave amplitude using COMSOL Multiphysics. Then, SHOWPAM is constructed based on the simulation result, consisting of a central cavity, energy harvester, and optimized metamaterial on both sides of the cavity. A control model was identical to SHOWPAM but didn’t have metamaterial. Both models are tested in the wave generating pool, and power generation of each model was measured. SHOWPAM showed 225% average power compared to the control model, proving the capability of metamaterial structure to enhance ocean wave power.
A cellular sound-absorbing metasurface with subwavelength thickness
Authors: Crivoi Alexandru , Lisevych Danylo , Fan Zheng
Published: November 2019

The sound absorbing metasurface efficient in the audible frequency range is proposed. The metasurface has a cellular structure, each cell having a hexagonal shape with a hollow tunnel inside. The wall of the hexagonal cell is sub-divided into six hollow chambers connected to the central tunnel via the six thinner channels of different diameters. The hollow chambers act as Helmholtz resonators providing six different resonant frequencies for each cell. The negative effective bulk modulus property of the metasurface allows full adsorption at the resonant frequencies. By carefully designing the size of the connecting channels we can manipulate the desired sound adsorption frequency range. The thickness of the metasurface is in the range of 0.03–0.1 wavelengths for the sound frequency range between 300 and 1000 Hz. Six absorption peaks are achieved for each unit cell providing broader range of absorption. The hexagonal shape of the unit cell allows full utilization of the metasurface volume by a standard honeycomb tessellation of the cells. By designing a metasurface containing individual cells with different inner channel diameters, the absorption peaks can be multiplied or overlapped and further broaden the frequency range with the absorption coefficient higher than the desired value.
Adaptation to a physical alteration of the vocal apparatus: The effect of visual self-perception on speech motor plasticity
Authors: Barbier Guillaume , Shiller Douglas
Published: November 2019

Adapting speech movements to novel or perturbed conditions relies critically on the processing of self-produced sensory information. In the context of a physical alteration of the vocal apparatus (e.g., palatal prosthesis), talkers have been shown to adapt following 10–15 min of practice to produce improved acoustic output. It is possible that additional information, such as ultrasound imaging of the tongue, may help talkers adapt even more effectively to such perturbations. Providing visual feedback of the tongue surface in real-time has shown promise in the treatment of speech-sound disorders. However, it remains unclear whether the addition of such visual information will influence speech plasticity on the timescale examined in experimental studies of speech adaptation. Here, we examine how neurotypical talkers adapt to a palatal prosthesis, relying on auditory and somatosensory feedback alone (n = 15), or with the addition of ultrasound feedback of the tongue, either in the mid-sagittal (n = 15) or coronal plane (n = 15). Differences in adaptation performance between the three feedback conditions were observed, both in the patterns of speech adaptation and the learning after-effects. The results indicate that talkers will rapidly integrate visual articulatory information into their control of oral speech movements in order to guide productions towards improved acoustic outcomes.
Self-monitoring of speech production in individuals who stutter
Authors: Max Ludo , Kim Kwang S.
Published: November 2019

Self-monitoring plays a critical role in the acquisition and refining of all skilled movements, including speech production. In current theoretical models of the neural control of movement, self-monitoring depends on the acquisition and updating of internal representations of the motor-to-sensory transformations that take place from the generation of motor commands to final movement outcomes (e.g., articulatory movements and speech sound output). During movement planning and execution, these representations are used to predict sensory consequences ahead of time, and actual and predicted feedback can then be compared. For speech, auditory-motor learning (the process through which neural representations are learned and maintained) and auditory-motor integration in general (including bidirectional interactions during the online control of speech) are believed to play an important role in persistent developmental stuttering. This presentation will give a brief overview of recent insights into potentially critical differences between children and adults who stutter vs. individuals with typical speech in terms of: (a) auditory-motor learning in the presence of experimentally perturbed auditory feedback; (b) feedback-driven corrections of ongoing unperturbed speech movements; and (c) the relationship between such learning-based or instantaneous articulatory adjustments and a central modulation of auditory processing that already starts during movement planning prior to speech onset.
Selective active noise cancellation based on directional reference signals
Authors: Xu Buye , Miller Tony
Published: November 2019

Active noise control (ANC) technologies have been successfully applied in headphones to cancel the sound that propagates into one’s ear canal from outside. However, the standard ANC systems would attenuate the sound from all the sound sources blindly ignoring that a listener may prefer to listen to some of them. This paper proposes a feed-forward ANC system for ear-level applications, which is capable of preserving the sound of a source in any given direction relative to a listener while attenuating the sound in other directions. The selective cancellation is achieved based on the creation of appropriate reference signals from the output of a microphone array wore on user’s head. Theoretical analysis and simulation results will be presented to demonstrate the potential benefit and limitations of such a system.
A method for undersea gas bubbles detection from acoustic image
Authors: Zhang Wanyuan , Wang Yajun , Zhou Tian
Published: November 2019

In recent years, there has been an increasing requirement for methods of detecting bubbles released from the seabed into the water column, such as leaks from undersea gas pipelines and seeps from carbon capture and storage facilities. Considering the peculiarity of the layout of submarine gas pipelines and that of the ocean environment around them, we construct an underwater mobile platform equipped with autonomous underwater vehicles carrying multi-beam sonars and various types of other sensors. Analogous to optical flow, this paper describes a scale-invariant feature transform (SIFT) flow algorithm, which includes both the detection of key points and the computation of local descriptors. This SIFT flow algorithm estimates the motion characteristics of gas leaks and quantifies the flux of gas. Finally, the validity of this method is verified in pool and sea experimental research.
Extensive underwater radiated noise analysis of a research vessel in compliance with DNV SILENT notation
Authors: Wei Ruey-Chang , Wang Chi-Chun , Chiu Pai-Ho , Huang Bo-Jhih
Published: November 2019

Studies have shown that underwater-radiated noise from ships may have both short and long-term negative consequences on marine life, especially marine mammals. An international community of researchers, environmental groups, government agencies, and sectors of the shipping industry has recognized shipping noise as an important marine conservation issue. In 2010, Det Norske Veritas (DNV, the Norwegian Classification Society) made the first attempt to fix the radiated noise limits for commercial ships, in which vessels fulfilling the requirements will be given an optional class notation SILENT. In this study, underwater noise measurements were performed on a new research vessel in shallow water in compliance with DNV SILENT notation. More speeds were tested than required by DNV, to understand the characteristics of related noises. Results show the new ship satisfies the allowable noise level curve for type R (Research); however, the measured noise levels do not increase as speed accordingly. Moreover, level differences can be significant between starboard and port side tracks especially at low frequencies. Commonly observed coastal currents play an import role on ship maneuverings and test conditions and therefore unexpected results. Practical considerations and suggestions about performing measurements and analyzing the data will be discussed and summarized.
Overhead stage canopies in a coupled volume theatre: Effects on the sound energy distribution and on the secondary reverberation
Authors: D'Orazio Dario , Fratoni Giulia , Garai Massimo
Published: November 2019

Nowadays, opera houses are often used for symphonic music, even though the intrinsic characteristics of these theatres are not suited for this purpose, due to their coupled volumes and high absorption of the fly tower. When symphonic music is performed in these halls an overhead stage canopy is often used to enhance the orchestral performance. In the present work, the effects of a canopy array in a coupled volume theatre were studied. The array canopy was designed and installed based on Geometric Acoustic (GA) simulations calibrated with in-situ measurements. Results showed peculiar effects on the sound energy distribution through space: the sound strength values depends on the “effective” volume of the theatre, varying with the sound source position. Moreover, when the stage is covered by the canopy array, the sound strength depends on the distance from the aperture instead of the distance from the sound source position. In other words, the decay curve is “tilt” by “effective volume” and “shifted” by the canopy array. Furthermore, the changes in sound behaviour due to the canopy array may be considered as a switch-off of the secondary reverberation effect.
Prediction of sound fields after propagation through sound barriers by CNN and DCNN algorithms
Authors: Kim Jonghwan , Jung Gwanghoon , Park Junhong
Published: November 2019

Sound fields are affected by the size of the space and the surrounding environments. The ray tracing method analyze the sound propagation through geometric constraints. For prediction of sound fields in a real-time to investigate the influence of surrounding environments, an effective calculation method is required. During the prediction, it is necessary to calculate the sound field distribution according to the layout of equipment or sound reflecting devices to minimize noise in working spaces. This procedure is required for an optimal arrangement of barriers according to noise sources. To improve this repetitive work, it is devised to develop a machine learning model that predicts the change in the sound field according to the position of sound barrier through CNN and DCNN algorithms. Training data were generated by using a commercial tool. The proposed approach recognizes the characteristics of sound fields at spaces after acoustic barriers.
Behavioral and environmental context of Antarctic minke whale vocalizations
Authors: Weindorf Sarah , Cade Dave , Casey Caroline B. , Friedlaender Ari , Goldbogen Jeremy , Levy Emma , Linsky Jacob , Nowacek Douglas
Published: November 2019

Acoustic signaling is the predominant form of communication between cetaceans, and understanding the behavioral state of calling individuals can provide insights into their function. We used multi-sensor tags equipped with concurrent video and acoustic recorders to characterize the vocal repertoire and associated behavior of Antarctic minke whales around the Antarctic Peninsula. Whale vocalizations were sorted into distinct call types based on several known acoustic parameters including 90% call duration, frequency bandwidth, and frequency quartiles. Call types were then compared to concurrent video and sensor data to determine the behavioral state and environmental conditions surrounding vocalizing individuals. We found several distinct sound types ranging in frequency from 180–560 Hz, consisting of pulse trains, down-sweeps, growls, and other sound types not previously described. These sounds are produced during distinct behavioral states including foraging, traveling, socializing, and resting and are emitted both in solitary and in groups of up to five animals. Additionally, vocalizations were emitted in both open water and sea ice conditions. By combining acoustic recordings with animal-borne video, our results represent a significant advancement in our understanding of Antarctic minke whale behavior and improve our capacity to acoustically monitor this species in a rapidly changing Antarctic region.
Reliable lower bound for number of calling marine mammals in Chukchi Sea
Authors: Spiesberger John , Berchok Catherine L. , Woodrich Daniel , Iyer Pranav G. , Schoeny Alexander , Sivakumar Krishna
Published: November 2019

A reliable lower bound is derived for the number of vocalizing bowhead whales and walruses in the Chukchi Sea from ten acoustic receivers deployed during NOAA's CHAOZ experiment in 2011. The lower bound is derived from extremely reliable 100% confidence intervals (CI) of the sound's locations. CI are derived from measurements of the Time Differences of Arrival (TDOA) of sound between receivers. Sequential Bound Estimation (SBE) is used to estimate the CI by assimilating the TDOA. SBE was successfully and independently evaluated by the U.S. Navy. It is a nonlinear non-Bayesian technique capable of explicitly accounting for all errors affecting uncertainty while being computationally efficient. To date, its CI always contain the true location of the source. The CI are affected by uncertainty of sound speed, TDOA, receiver location, and clock time. For two-dimensional models of location, i.e., longitude/latitude, it appears necessary to utilize isodiachrons instead of hyperbolas to obtain reliable CI because of the extreme non-homogeneity of sound speed needed to obtain correct location. [Supported by the North Pacific Research Board and Microsoft.]
Reconstruction of shear wave speed in layered media using time-harmonic excitation and pulse-echo imaging
Authors: Dayavansha E. G. Sunethra , Grimm Peter D. , Rubinstein Jack , Mast T. Douglas
Published: November 2019

Recent advances in high-frequency ultrasound imaging have opened new possibilities for quantitative characterization of skin properties. Noninvasive, accurate measurements of elasticity for multiple layers (e.g., stratum corneum, epidermis, dermis) are potentially beneficial for development and validation of new skin treatments. Here, pulse-echo ultrasound imaging using linear arrays is used to measure time-harmonic tissue displacements induced by a mechanical shaker. It is shown that reconstruction of time-harmonic displacement amplitude and phase in induced elastic waves is feasible for frame rates exceeding the Nyquist frequency and for echoes acquired using multiple transmits per frame. Measured wavefields are inverted using spatial Fourier analysis, numerical solution of the Helmholtz equation by finite difference methods, and direct observation of shear wavelengths. These approaches are validated using a 5 MHz diagnostic imaging array with a clinical scanner (Zonare z.one, L8-1 array) and multlilayered phantoms with varying elastic properties and echogenicity. Further verification of these methods is performed by comparing with finite-element simulations employing a linear elasticity model. Feasibility for measurement of skin layer elastic properties using high-frequency ultrasonic imaging is demonstrated using a 50 MHz linear array and a small-animal scanner (Vevo 2100, MS700 array) for measurements on porcine skin.
Blood viscosity could explain shear wave dispersion in the liver
Authors: Aichele Johannes , Catheline Stefan
Published: November 2019

We recently showed that the observed shear wave dispersion in a soft, porous, water-saturated tissue can be explained by Biot’s theory of poroelasticity. The theory explains the shear wave velocity increase with frequency due to a relative movement between the solid and the viscous fluid. We propose that fluid-solid interaction explains the observed shear wave dispersion in the liver, a naturally saturated organ. The liver is drawn through by a network of blood vessels and exposes a total porosity of about 14% [1]. Blood viscosity changes from patient to patient and depends on different factors such as hydration and fitness. We included the blood viscosity for a 14% porosity liver into the elasticity estimation from shear wave speed measurements for a given shear wave elastography dataset [2]. For 11 out of 50 patients, the fibrosis classification would change if blood viscosity is included. [1] C. Debbaut et al., “Perfusion characteristics of the human hepatic microcirculation based on three-dimensional reconstructions and computational fluid dynamic analysis,” J. Biomech. Eng. 134(1), 011003 (2012). [2] Jang et al., “Hemorheological alteration in patients clinically diagnosed with chronic liver diseases,” J. Korean Med. Sci. 31(12), 1943–1948 (2016).
What is the correct ear-canal boundary condition for simulating HRTFs for open-ear listening?
Authors: Khaleghi-Meybodi Morteza , Hoffmann Pablo , Miller Tony
Published: November 2019

Emerging open-ear binaural reproduction methods for virtual and augmented reality are an opportunity to rethink how we pose the simulation problem for head related transfer functions (HRTFs). Historically, researchers have experimentally measured HRTFs using a simplifying blocked meatus condition, then used those HRTFs to reproduce spatial audio using low-latency head tracking, an HRTF convolution engine, and carefully calibrated free-air-equivalent coupling over-the-ear headphones. This blocked meatus boundary condition was then carried over as researchers have moved toward numerical simulation of HRTFs, allowing for direct comparison of simulation and experiment. Now that the industry is trending toward numerically-simulated HRTFs and open-ear playback methods, a more realistic ear-canal input impedance needs to be further investigated. In this paper, we report changes in the sound pressure at the entrance to the ear-canal from open to blocked meatus conditions, using a Multiphysics Finite Element model. The blocked meatus boundary is replaced with a nominal frequency-dependent ear-canal input impedance and the pressure-division ratio of open to blocked condition is evaluated. These modeling results suggest that it may not be necessary to perform detailed geometry capture of the ear-canal and that a simplified input impedance is sufficient to simulate the open ear effect.
On listeners preferences in subjective assessment tests of multichannel audio on mobile phones
Authors: Toosy Fesal , Ehsan Muhammad S.
Published: November 2019

ITU standard listening tests like the ITU-R BS.1534-3 (MUSHRA) emphasize on the use of expert listeners especially for rating global attributes like Basic Audio Quality. The ratings of expert listeners are more reliable but naïve listeners are often used for such tests, especially when attributes like Quality of Experience are being measured. Moreover, the results from naïve listeners are actually considered more reflective of average consumer preference. This paper presents further statistical analysis of the results of two such previously conducted tests for assessing multichannel audio versus stereo and mono on mobile phones using headphones. The procedure and materials used in the tests were compliant with the MUSHRA requirements and the test material consisted of audio excerpts with 6 or 8 channels. The multichannel excerpts were object coded and served as the reference which in turn was further down-mixed to different versions of stereo and mono to serve as the medium and low anchors. The media player used had custom HRTF's and rendered the multichannel excepts for a binaural playback on headphones. The analysis involved measure of rank correlations on the results in order to study the listener ratings in more detail. The results showed that for the ratings in both tests, the preference for multichannel, stereo and mono had little correlation with age and gender but a regression model for predicting ratings of one test from the ratings of the other was possible.
Silk purse? Brass-instrument research with limited resources
Authors: Pyle Robert W.
Published: November 2019

Can we make a silk purse from the proverbial sow's ear? That is, can we do meaningful experiments with inexpensive equipment? It is certainly much easier than it used to be. The advent of digital audio and cheap computing power has revolutionized musical acoustics research. In this paper the author looks at several projects on brass instruments, most of which he funded out of his own pocket. Some yielded better results than others, but all pointed toward interesting work yet to be done.
Musical instrument directivity measurements
Authors: Leishman Timothy W. , Bellows Samuel D.
Published: November 2019

Over the past several decades, researchers have developed various techniques to measure directional radiation patterns of musical instruments. After summarizing and categorizing several of them, this presentation will focus on recent developments made by the authors to measure directivities with high angular resolution. The frequency-dependent patterns of 16 played musical instruments were acquired using 2522 unique microphone positions over a sphere in an anechoic chamber. This led to associated frequency-dependent spherical-harmonic expansions with readily shareable coefficients. Several steps were implemented to improve and validate the measurements, and make their costs manageable. The presentation will discuss key results and future directions.
Simple solutions, happy clients
Authors: Hoover K. Anthony
Published: November 2019

Various problems involving outdoor entertainment noise were resolved with simple solutions, which were especially gratifying when clients had presumed expensive and complicated solutions. This paper will review some examples, including a lakeside amusement park ride largely intended to generate group screams at regular intervals, an outdoor town center featuring evening movies and weekend performances, an NFL stadium that hosts several rock concerts every year, and Mumbai “firecracker” bands impacting Bollywood soundstages.
Optimization of quasi-periodically ribbed structures to improve stealth and discreteness of underwater vehicles
Authors: Dubus Bertrand , Croënne Charles , Deleplanque Samuel , Hladky-Hennion Anne-Christine
Published: November 2019

Acoustic stealth and discreteness of underwater vehicles are important issues in underwater acoustics. These vehicles are constituted of shells which are periodically reinforced by ribs. Acoustic fields radiated or scattered by such structures are strongly affected by phenomena related to this periodicity such as Bragg diffraction and Bloch-Floquet waves. The introduction of a slight modification of each rib is considered here to reduce this signature for radiation problem, scattering problem or both radiation and scattering problems. Geometrical and material parameter variations used to obtain these new solutions may also be constrained by technological limitations. In a classical process, the design would be realized by experts using tools and methodologies that have been developed over the years. Another approach of the problem consists in using optimization algorithms (genetic, greedy, etc.) which have to be coupled to simulation models of the acoustic radiation and scattering problems. This approach is considered here in the case of a plate periodically reinforced by ribs. Simulation results are reported and the impact of the choice of the objective function, the parameter to be varied, the simulation model and the optimization algorithm on the final performance are also discussed.
Inverse design method for acoustic metamaterials
Authors: Gao He , Zhu Jie
Published: November 2019

When designing acoustic metamaterials for complex environments, it is very challenging to derive the acoustic field distribution analytically and obtain the desired devices with the conventional method. Here, we propose to optimize some acoustic devices with inversely design method, which can actively find the optimized structure parameters with prescribed property. This inverse design method avoids the complex analytical calculation and can obtain some performances that are not attainable with the conventional method. This inverse design method takes a significant step towards realizing practical devices and would open up new possibilities for manipulating sound wavefront with optimized performances.
Modeling the spatial variations of the intracochlear fluid pressure based on in vivo mechanical measurements
Authors: Rouleau Michael , Meaud Julien
Published: November 2019

The mammalian cochlea is a complex system consisting of two fluid-filled ducts separated by a structure known as the organ of Corti. Fluid pressure in the cochlear ducts interact with the organ of Corti to stimulate the mechanoelectrical receptors responsible for hearing. Because, until recently, in vivo dynamic measurements were limited to the basilar membrane, most cochlear models consider only basilar membrane—fluid interactions. Recent measurements of tectorial membrane and reticular lamina motions using optical coherence tomography motivate us to develop cochlear models that takes into account separately coupling of the fluid with all these components of the organ of Corti. In this work, finite element models are used to simulate an apical slice of a mouse cochlea. Using experimentally measured motion of the stapes, reticular lamina, basilar membrane, and tectorial membrane [Lee et al., J. Neurosci. (2016)] as input, spatial variations of pressure in the cochlea are explored. This study investigates fluid dynamics in the cochlear ducts and explores the relationship between the motion of the organ of Corti and spatial pressure variations while providing a basis for future computational models to consider cochlear fluid dynamics in the entire cochlea.
Ripple spectrum resolution by prelingual and postlingual cochlear implant users
Authors: Nechaev Dmitry , Goykhburg Marina , Supin Alexander , Bakhshinyan Vigen , Tavartkiladze George
Published: November 2019

The correlation between ripple spectrum resolution and speech recognition was investigated for prelingual and postlingual cochlear implant users. The test signal had a band limited rippled spectrum (spectrum with alternated maxima and minima of spectral power) with equivalent rectangular bandwidth of 1 oct. The central frequency of the spectrum was 1, 2, or 4 kHz. The principle of rippled-spectrum test was to find the maximum ripple density (ripples/octave) at which listeners could detect the phase reversion of the spectrum. A balanced test set of Russian worlds by Greenberg-Zinder was used for estimation of speech recognition. The average ripple discrimination thresholds were approximately 2 ripples/octave in both pre- and postlingual patients. The thresholds did not depend from central frequency. The best correlation between speech recognition and rippled spectrum resolution was found in prelingual patients with perimodiolar electrode array compared with straight array (r = 0.85). In postlingual patients, correlation was markedly lower (r = 0.44 and r = 0.13 for rippled-spectrum tests centered at 1 or 2 kHz, respectively). [Work supported by the Russian Science Foundation, Grant No. 16-15-10046.]
Structural vibration of an elastically supported plate due to excitation of a turbulent boundary layer
Authors: Vlahopoulos Nickolas , Diaz Jonmarcos , Maki Kevin
Published: November 2019

High-Reynolds number turbulent boundary layers are an important source for inducing structural vibration. Small geometric features of a structure can generate significant turbulence that result in structural vibration. In this work, we develop a new method to couple a high-fidelity fluid solver with a dynamic hybrid finite element formulation for the structure. The plate where the flow excitation is applied is considered as part of a larger structure. A hybrid approach based on the Component Mode Synthesis (CMS) is used for developing the new hybrid formulation. The dynamic behavior of the plate which is excited by the flow is modeled using finite elements. However, the rest of the surrounding structure is modeled using finite elements for the static modes and an analytical solution for the dynamic modes of the CMS decomposition. The two main elements of the new work, the hybrid structural formulation and the process of applying the fluid load on the structural dynamic model are discussed. Validation of the new methodology is done by using test data from the literature for the vibration of plates excited by air flow, and through comparisons between the new methodology and traditional finite element based solutions.
Lexically guided perceptual learning in Cantonese-English bilinguals: A web replication study
Authors: Chan Leighanne , Johnson Khia A. , Babel Molly E.
Published: November 2019

Speech is incredibly variable, yet listeners have little difficulty adapting to new talkers. One proposed mechanism for how listeners rapidly map novel variants to established categories is perceptual learning. This study is a web replication of our previous work, which implements a version of perceptual learning that leverages lexical knowledge to retune phonetic categories [Norris et al., Cogn. Psychol. 47, 2014 (2003)]—here, Cantonese [f]. Embedded in a lexical decision task, Cantonese-English bilingual participants heard words where [f] was expected (e.g., 豆腐 dau6fu6 “tofu”), but replaced with an ambiguous [f]-[s] sound. Participants then categorized tokens from ambiguous nonword-nonword continua. Lab participants in the experimental condition successfully retuned Cantonese [f], compared to controls. Replicating this finding online demonstrates the viability of the paradigm outside the lab for this population, and provides precedent for future work. By recruiting from the same population as our lab study, we can more directly compare lab and web results than previous studies with Amazon’s Mechanical Turk. This provides a clearer picture of how the participants’ environments drive variability in online speech perception research.
The effect of clear speech and masking noise on listening effort in native and non-native listeners
Authors: Meemann Kirsten , Smiljanic Rajka
Published: November 2019

Listening effort increases when perceiving speech masked by noise and when listeners are non-native speakers of the target language (Zekveld and Kramer, 2014; Borghini and Hazan, 2018). Listener-oriented clear speech (CS) improves word recognition in noise and recognition memory (Keerstock and Smiljanić, 2018). It is unclear, however, whether the CS benefit can be explained by reduced listening effort during processing of easier-to-understand speech. The goal of this study was to examine the effect of CS on listening effort associated with degraded listening conditions differing in the source of difficulty and underlying cognitive mechanism: energetic masking, informational masking, and non-native listening. Native and non-native English listeners performed a word recognition in noise task and a visual response task, i.e., pressing keys to indicate the orientation of an arrow on the screen, first separately and then simultaneously. In the word recognition task, listeners repeated back sentences produced in CS and conversational speech and mixed with speech-shaped noise and 2-talker babble. The presentation will discuss analyses aimed at uncovering how hyper-articulated CS and masker type influence listening effort for native and non-native listeners as measured by objective and subjective dual-task cost.
Unsupervised machine learning for acoustic tomography and event detection
Authors: Bianco Michael J. , Gerstoft Peter
Published: November 2019

We present acoustic tomography and event detection approaches based on unsupervised machine learning (ML). ML describes a set of techniques for automatically detecting and utilizing patterns in data. These techniques can roughly be categorized as either supervised or unsupervised learning. In supervised learning, an ML system (e.g., neural network (NN)) is trained to produce a desired output based on labeled training examples. In unsupervised learning, no labels are given and the task is to discover interesting or useful structure within the data. In acoustic and geophysical signal processing, often large training datasets are available, but have few labeled examples. We discuss how unsupervised ML can leverage training data without explicit labels to improve acoustic models. We first give an overview of the relevant ML theory. Next, we describe an approach to array tomography, called locally-sparse travel time tomography (LST). LST regularizes the inversion of travel time measurements for geophysical structure using dictionary learning (unsupervised). Dictionary learning is here used to obtain a dictionary of small-scale geophysical features that best represent the measurements. Finally, we discuss an approach to automated event detection in acoustic time series based on autoencoder NNs, which learn salient features from NN inputs with unsupervised learning.
A learning-based classification of indoor noise type/position in an apartment building
Authors: Yang Haesang , Choi Hwiyong , Lee Seungjun , Seong Woojae
Published: November 2019

This study presents a learning-based method as an indoor noise source type/position classification technique closely related to the interfloor noise problem causing serious conflict between South Korean neighbors. For this study, an indoor noise dataset recorded by a single mobile phone was collected on three floors of an apartment building. Using a convolutional neural networks based classifier, the data containing five source type labels and four position labels is trained and evaluated. In addition, unlabeled data that is not used in the model development is tested for robustness evaluation of our classification system.
Prediction-error filters for signal and noise separation within ultrasound recordings
Authors: Jennings Joseph , Jakovljevic Marko , Biondi Ettore , Dahl Jeremy J. , Biondi Biondo
Published: November 2019

Ultrasonic image quality can be compromised by several mechanisms such as reverberation, off-axis scattering, and sound-speed inhomogeneities. These mechanisms can cause a loss of coherence of signals across the aperture and clutter in a B-mode image potentially leading to inadequate visualization and misdiagnosis. We develop a processing technique based on prediction-error filters (PEFs) for isolating tissue signal and several types of noise in the individual channel data of ultrasound scans. We first estimate a set of PEFs that allows for prediction of the 2-D spectra of signal and noise in the channel data domain and then use these filters to separate the signal and noise components within the recorded echoes. We use the Van Cittert-Zernike theorem as a priori knowledge of the signal spectrum to develop the signal-PEF, while the noise-PEFs are estimated directly from the channel data. We apply our PEFs to channel data from fullwave simulations of abdominal scans and to data acquired on a lesion phantom through a layer of bovine tissue. The proposed technique successfully separates signal from noise and improves lag-one coherence of the speckle signal from 0.47 to 0.97.
Multiyear variability of very-low-frequency ambient noise
Authors: Eller Anthony I. , Bradley David L. , Heaney Kevin D.
Published: November 2019

Several years of continuous low-frequency underwater ambient noise data have been made available for examination by the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). The data provide ambient noise in the spectral range from 1 to 120 Hz, and studies of the data are in progress at several organizations. Results presented here address the frequency band from 1 to 10 Hz, with special emphasis on discovering evidence of long-term changes in the environment and on quantifying by means of the variance spectrum the contributions of separate noise sources. Long range horizontally refracting propagation and noise source models are used to estimate the contribution of distant events to the observed noise level.