bluuebunny/crossref_metadata_2025 huggingface dataset:
Consistency and variation in recognition of text and speech interrupted at variable rates
Authors: Shafiro Valeriy , Fogerty Daniel , Smith Kimberly
Published: June 2017

Recent research indicates that recognition of interrupted text can predict speech intelligibility under adverse listening conditions. However, factors underlying the relationship between perceptual processing of speech and text are not fully understood. We examined contributions of underlying linguistic and perceptual structure by comparing recognition of printed and spoken sentences interrupted at different rates (0.5—64 Hz) in 14 normal-hearing adults. The interruption method approximated deletion and retention of rate-specific linguistic information across the two modalities by substituting white space for silent intervals. Results indicate a remarkably similar U-shaped pattern of cross-rate variation for both modalities, with minima at 2 Hz. Nevertheless, at high and low interruption rates text recognition exceeded speech recognition, while the reverse trend was observed at middle rates. Surprisingly, no significant correlations were obtained in recognition accuracy between text and speech conditions. These findings indicate a high degree of perceptual constancy in recognition of interrupted text and speech, which may rely on retention of rate-specific linguistic and perceptual information retained after the interruptions. On the other hand, results also indicate rate-specific variation in perceptual processing of text and speech, which may potentially affect the degree to which recognition accuracy in one modality is predictive of the other.
Predicting consonant recognition and confusions using a microscopic speech perception model
Authors: Zaar Johannes , Dau Torsten
Published: June 2017

The perception of consonants has been investigated in various studies and shown to critically depend on fine details in the stimuli. The present study proposes a microscopic speech perception model that combines an auditory processing front end with a correlation-based template-matching back end to predict consonant recognition and confusions. The model represents an extension of the auditory signal processing model by Dau et al. [(1997), J. Acoust. Soc. Am. 102, 2892-2905] toward predicting microscopic speech perception data. Model predictions were computed for the extensive consonant perception data set provided by Zaar and Dau [(2015), J. Acoust. Soc. Am. 138, 1253-1267], obtained with consonant-vowels (CVs) in white noise. The predictions were in good agreement with the perceptual data both in terms of consonant recognition and confusions. The model was further evaluated with respect to perceptual artifacts induced by (i) different hearing-aid signal processing strategies and (ii) simulated cochlear-implant processing, based on data from DiNino et al. [(2016), J. Acoust. Soc. Am., 140, 4404-4418]. The model successfully predicted the strong consonant confusions measured in these conditions. Overall, the results suggest that the proposed model may provide a valuable framework for assessing acoustic transmission channels and hearing-instrument signal processing.
Influence of spatial and non-spatial feature continuity on cortical alpha oscillations
Authors: Mehraei Golbarg , Shinn-Cunningham Barbara , Dau Torsten
Published: June 2017

In everyday environments, listeners face the challenge of parsing the sound mixture reaching their ears into individual sources. Perceptual continuity of acoustic features, such as pitch or location, has an obligatory effect on auditory attention even when a feature is not task relevant. Cortical alpha oscillations (8-12 Hz) are thought to functionally inhibit the processing of task-irrelevant information. Here, we hypothesize that discontinuities in a task-irrelevant feature disrupt the attentional modulation of alpha rhythms. Using electroencephalography in humans, we compare physiological measures during a selective auditory attention task where listeners were asked to attend to either talker, based on gender (male or female) or location (left or right). On half of the trials, a discontinuity was introduced in the task-irrelevant acoustic feature. When listeners attended to the talker, there was no evidence of alpha power lateralization, and no effect of a discontinuity in location. In contrast, when listeners attended to location, parieto-occipital alpha power increased ipsilateral to the attended location; moreover, a discontinuity in talker reduced alpha power and disrupted alpha lateralization. Our findings support the importance of parieto-occipital alpha in suppressing sources when listeners focus spatial, but not non-spatial, attention, and show that task-irrelevant discontinuities affect these alpha rhythms.
Sound source localization identification procedures: Accuracy, precision, confusions, and misses
Authors: Pastore M. Torben , Yost William
Published: June 2017

Rakerd and Hartmann (1987) provided a useful set of equations that can describe listener performance in sound source localization identification tasks requiring listeners to identify which loudspeaker presented a sound. The data from such identification tasks can be presented in confusion matrices in which one dimension is the actual sound source locations and the other dimension is the reported/perceived sound source locations. This presentation describes how Rakerd and Hartmann’s measures relate to estimates of sound source localization accuracy, precision, confusions, and misses. We will describe some of the advantages and limitations of these measures of performance in sound source localization identification tasks, especially in conditions involving sound sources located around an entire azimuth circle. [Partially support by a grant from the National Institute on Deafness and Other Communication Disorders, NIDCD.]
The impact of asymmetric rates on interaural time difference lateralization and auditory object formation in bilateral cochlear implant and normal hearing listeners
Authors: Thakkar Tanvi D. , Kan Alan , Litovsky Ruth
Published: June 2017

Normal hearing (NH) listeners are able to accurately identify and locate sound sources using auditory object formation (AOF) and interaural time differences (ITDs). Temporal cues can further facilitate AOF and ITD sensitivity: this includes within- and across-ear stimulus’ rate, envelope-, and onset-symmetry. Bilateral cochlear implant (BiCI) listeners are not guaranteed to receive symmetrical or complementing temporal information across ears. Cochlear-Nucleus devices undergo “peak-picking” where stimulation of electrodes could yield asymmetric rates across the ears, interrupting good AOF and ITD sensitivity. We investigated the impact of asymmetric rates and ITDs, on AOF and ITD lateralization. BiCI and NH listeners were presented with diotic and dichotic pulsatile stimulus rates, combined with an ITD. Rate was fixed in one ear, and varied in the contralateral ear. In a single interval, six-alternative forced-choice task, listeners reported where and how many sounds they heard. We hypothesized that with interaural asymmetries in rate, NH listeners would exhibit minimal AOF and poor lateralization, while BiCI listeners may exhibit AOF and lateralization independent of interaural rate asymmetry. The contribution of having matched rates for good AOF and ITD sensitivity helps explain the lack of successful stream segregation in BiCI listeners, whose devices do not deliver temporally-symmetric information.
The effects of diffuse noise and artificial reverberation on listener weighting of interaural cues in sound localization
Authors: Nguyen Tran M. , Macpherson Ewan A.
Published: June 2017

The reliability of interaural time and level difference (ITD, ILD) sound location cues can be degraded by noise or reverberation. In this study, we determined how weighting of ITD and ILD varied with signal-to-noise ratio (SNR) in the presence of interaurally uncorrelated background noise and with direct-to-reverberant ratio (DRR) in the presence of artificial reverberation (generated by convolving the target signal with an interaurally uncorrelated pair of impulse responses created by multiplying Gaussian noise with a decaying exponential, RT60 = 500 ms). Wideband (0.5-16 kHz) 100-ms noise-burst targets were presented over headphones using individual head-related transfer functions. ITD and ILD were manipulated by attenuating or delaying the sound at one ear (by up to 300 μs or 10 dB), and cue weighting was computed by comparing localization response bias to imposed cue bias. Wideband (0.5-16 kHz) and low-pass (0.5-2 kHz) noise and reverberation and SNRs and DRRs from -5 to + 20 dB were used. ITD dominated in quiet, anechoic conditions. ITD was downweighted and ILD upweighted with decreasing SNR for both noises. Only downweighting of ITD and upweighting of ILD were associated with decreasing DRR in wideband and low-pass reverberation, respectively. In general, listeners increased the relative weighting of ILD in more adverse listening conditions.
Effects of masker similarity on the identification and localization of vehicular sounds
Authors: Ericson Mark A. , Weatherless Rachel
Published: June 2017

Several experiments were conducted to determine the effects of masking sound similarity on the identification and localization of airborne and ground vehicle sounds. In some experiments, natural masking sounds were played in the presence of target vehicle sounds. In other experiments, spectral and temporal cues were artificially manipulated to determine their individual effects on identification and localization performance. The Environment for Auditory Research of the Army Research Laboratory was used to create ambient masking sounds. In general, masking sounds that were similar to the vehicle sounds in spectral and envelope shape were more effective than dissimilar sounds in reducing auditory perception abilities of the listener. Although the complexity of most vehicle sounds enabled the listeners to correctly identify and localize the vehicle sounds in many masking conditions. The results of these experiments will be discussed in terms of the aural abilities of human subjects to identify and localize vehicle sounds in various ambient masking conditions.
How accurate dereverberation should be? Effects of underestimating and overestimating binaural room impulse responses
Authors: Srinivasan Nirmal Kumar , Staudenmeier Alexis , Clark Kelli
Published: June 2017

The sound arriving at the listeners' ears is influenced by the binaural room impulse response (BRIR) of the listening environment. Previous research (Srinivasan et al., 2017) has suggested that removing late reflections in BRIR improves speech understanding most when spatial cues are absent. However, in real world listening scenarios, it is difficult to differentiate between the effects of early reflections and late reverberation. Here, we present data from an experiment evaluating the effects of a simple static dereverberation technique on speech understanding for two reverberant environments (T60 = 1 and 2 s). The input speech signal was dereverbered by deconvolving the speech signal under three different conditions: (1) underestimating the effects of reverberation, (2) overestimating the effects of reverberation, and (3) correct estimation of the effects of reverberation. Effects of the three deconvolving techniques on identification thresholds and amount of release from masking will be discussed.
Modelling the frequency dependency of binaural masking level difference and its role for binaural unmasking of speech in normal hearing and hearing impaired listeners
Authors: Hauth Christopher F. , Brand Thomas , Kollmeier Birger
Published: June 2017

In binaural tone-in-noise detection experiments humans can achieve substantially lower thresholds if either noise or tone have interaural time or phase differences (ITDs / IPDs) compared to diotic presentation of tone and noise. This effect is named binaural masking level difference (BMLD) and was mainly investigated at 500 Hz. The results obtained in these experiments were used to fit binaural processing errors in the equalization-cancelation (EC) mechanism, which is an effective model of binaural processing. In this study, the frequency dependency of BMLDs is investigated for listeners with normal hearing and high frequency hearing loss. Binaural tone-in-noise detection experiments are conducted for tone frequencies of 250, 500, 750, 1000, 1500, and 2000 Hz, and ITDs of the noise up to 5 times the period of the tested frequency. Furthermore, diotic and dichotic speech reception thresholds for low pass filtered speech in noise are measured with the same listeners. The EC mechanism with processing errors derived at 500 Hz can predict the BMLDs for the remaining frequencies, except for the 250 Hz condition. Moreover, some HI listeners show a reduced BMLD in both tone-in-noise and speech intelligibility experiments, which is not covered by the EC model with normal-hearing processing errors.
Effects of clinical hearing aid settings on sound localization cues
Authors: Diedesch Anna C. , Gallun Frederick J. , Stecker G. Christopher
Published: June 2017

Sound localization cues, particularly interaural level difference (ILD) cues, are known to be affected by hearing aid processing such as wide-dynamic range compression and strong directional microphones. These distorted cues may negatively impact spatial awareness and communication in complex environments, two areas of challenge for new and experienced hearing aid users. Previously, we investigated frequency specific alterations to ILD and interaural time difference (ITD) cues using linear amplification in simulated reverberant rooms and with gaged vent sizes. In reverberation, ITD became erratic and ILD reduced; minimal effects of hearing aid venting were observed (Diedesch and Stecker, Am. Aud. Soc. 2016). Here, we applied that approach to hearing aid settings more typically encountered by clinical patients. Phonak Audeo receiver-in-the-canal (RIC) hearing aids were programmed to typical open-fit hearing impairments using clinically normal settings for compression algorithms and directional microphones. Recordings, collected using an acoustic manikin, were compared across hearing aid coupling (standard open and closed domes) in anechoic and simulated rooms. Frequency-specific ITD and ILD were quantified across coupling, room, and hearing aid settings. [Work supported by the F. V. Hunt Postdoctoral Research Fellowship, NIH R01-DC011548 (GCS), R01-DC011828 (FJG), and the VA RR&D NCRAR.]
Individual differences in cocktail party listening: The relative role of decision weights and internal noise
Authors: Lutfi Robert , Tan Alison , Lee Jungmee
Published: June 2017

A simulated “cocktail-party” listening experiment was conducted to determine the relative role of decision weights and internal noise in accounting for the large individual differences in performance typically observed in these experiments. The listener heard over headphones interleaved sequences of random vowels and were asked to judge on each trial whether the vowels were spoken by the same AAA or different ABA talkers. The A and B vowels had nominally different Fo and spatial position (simulated using Kemar HRTFs), but were randomly perturbed around these values on each presentation. Decision weights for each dimension, internal noise, and efficiency measures were estimated using COSS analysis [Berg (1990). J. Acoust. Soc. Am. 88, 149-158]. Decision weights were nonoptimal and differed across listeners, but weighting efficiency across individuals was quite similar. Individual differences in performance accuracy ranging over 40 percentage points were largely related to differences in internal noise. The results are discussed in terms of their implications for the relative role of sensory and attentional factors affecting individual performance differences in simulated cocktail party listening. [Work supported by NIDCD 5R01DC001262-24.]
The effect of sound intensity on lateralization with interaural time differences
Authors: Alamatsaz Nima , Shapley Robert M. , Ihlefeld Antje
Published: June 2017

Previous studies examining the effect of sound intensity on ITD lateralization disagree on whether ITD lateralization changes with increasing sound level. We tested how sound intensity affects lateralization in three experiments. In all experiments, normal-hearing listeners judged the lateralization of band-limited target noise tokens (300 to 1200 Hz, 1 s duration, 10-ms cos-squared ramp, presented with insert earphones). For each ear and target noise, sensation level (SL) was estimated using two-down one-up adaptive tracking. Each target stimulus contained an ITD of 0, 75, 150, 225, 300, or 375 µs and was presented at 10, 25, or 40 dB SL. In experiment 1, listeners matched the ITD of a variable-ITD pointer (25 dB SL, 300-1200 Hz, 1 s duration, 10-ms cos-squared ramp) to each of the target tokens. In experiment 2, in each two-interval trial of a 2-AFC paradigm, the standard stimulus consisted of the same noise token as in experiment 1 and the signal stimulus had a randomly chosen ITD of + /− 0, 25, 50 or 75 µs relative to the target ITD. Listeners reported whether the sound moved to the left or to the right, and thresholds were estimated at the “50%-right” point. In experiment 3, listeners indicated the perceived laterality by visually pointing on a graphical user interface. Preliminary data suggest that sound level affects lateralization, but that individual differences require testing of a greater number listeners than have historically been assessed.
Influence of source location and temporal structure on spatial auditory saliency
Authors: Podwinska Zuzanna M. , Fazenda Bruno M. , Davies William J.
Published: June 2017

Hitherto, not many studies have dealt with spatial auditory saliency. Auditory attention studies concerned with spatial aspects generally concentrate on top-down selective or divided attention, e.g., where subjects are asked to attend to one source at a specific location whilst being distracted with sources from different directions. The work presented here reports on experiments in which bottom-up spatial auditory attention, or saliency, has been tested. The tests were run using a fully immersive 3D audio-visual reproduction system, where interactions between auditory and visual modalities have been included. We tested how temporal structure and absolute location of sound sources around the listener influence saliency and attention.
Highly directional source radiation using isotropic transformation acoustics
Authors: Norris Andrew , Su Xiaoshi
Published: June 2017

Recent developments in transformation acoustics (TA) have taken advantage of the isotropic nature of conformal mappings to form gradient index lens devices, such as a two-dimensional monopole-to-quadropole lens. While this TA precisely maintains the wave equation solution within the lens the radiated field is still multi-directional and not fully efficient due to impedance mismatch and non-planar radiation. A three-fold strategy is outlined here to achieve highly directional and impedance matched devices. First, most of the rays leaving the original circular region are mapped to a single face of a polygon. Second, the center of the radiating face is impedance matched by simply scaling the size up or down. Finally, the polygon is replaced by a two-sided crescent moon mapping which optimizes the radiation across the face of higher curvature, allowing near-field focusing and quasi-planar far-field radiation. These ideas are illustrated by example simulations. Practical design methods, including water matrix and solid matrix devices, will be discussed. [Work supported through ONR MURI.]
Redirection and splitting of sound waves by a periodic chain of thin perforated cylindrical shells
Authors: Bozhko Andrii , Sanchez-Dehesa Jose , Krokhin Arkadii
Published: June 2017

A line of perforated cylindrical shells in air is practically transparent for sound since each individual unit is a weak scatterer. However, strong scattering occurs due to the coupling to the acoustic eigenmodes of the chain. Here we develop an analytical theory of sound transmission and scattering at a linear chain of perforated shells and predict strong anomalous effect for oblique incidence. The chain eigenmodes are weakly decaying, with symmetric profile and anomalous dispersion, or with antisymmetric profile and normal dispersion, and their excitation leads to deep minima in the transmission and 90̊-redirection of the external sound. At normal incidence, only the symmetric eigenmode can be excited, otherwise both modes are excited at close frequencies. Moreover, the wave which resonates with the normal-dispersion mode is redirected along the “right” direction, whereas the wave resonating with the anomalous-dispersion mode is redirected in the “wrong” direction. Thus, a periodic chain of perforated shells may serve not only as a 90̊-redirecting antenna but also as a splitter of sound waves with close frequencies. For example, an acoustic signal containing two frequencies around 3 kHz can be split into monochromatic components propagating in opposite directions along the chain, if the beat frequency is ≈500 Hz.
Nonuniform distribution of point defects in ferroelectric phononic crystal
Authors: Chatterjee Chandrima , Ostrovskii Igor
Published: June 2017

The photoluminescence (PL) from point defects in ferroelectric phononic crystal (FPC) is investigated at room temperature. The FPC consists of periodically poled domains 0.45-mm-long each along the x-axis in the 0.5-mm-thick z-cut LiNbO3 wafer. The spectra of PL are excited by 310 nm ultraviolet light and registered in the range of 350 to 900 nm. The PL spectra reveal different point defects including F-center, Ba, Ar, Ne, Cr, K, Fe+, Xe, and others. The electrically active defects such as F-center and Fe+ are expected to be sensitive on a local electric polarization. In a FPC, the ferroelectric neighboring domains are inversely poled and have an opposite electric polarization. The change from polarization “up” to polarization “down” happens across so called interdomain wall. The point defect concentrations along the neighboring domains are researched by PL-scanning, consisting of taking PL-spectra from narrow zones across the domain structure along the x-axis. This scanning reveal a nonuniform distribution of defects along the FPC. The striking result is that some of the defects such as F-center and Fe+ have respectively narrow extrema in PL-intensity right in the interdomain wall location. Engineering application of these findings may be new non-destructive characterization method for ferroelectric phononic crystals.
An improved helical-structured acoustic metamaterial design for broadband applications
Authors: Zhu Jie
Published: June 2017

Helical structured acoustic metamaterial has been proposed to provide non-dispersive sound wave slowdown, which is an interesting topic that not only matters about fundamental explorations of slow wave physics, but also will benefit a lot of applications. Although the effect of delay acoustic signal the sound wave phase modulation is obvious, the helical structured acoustic metamaterial only provides satisfying transmission performance over narrow frequency range. In this presentation, I will introduce an improved design developed based on the original helical structured acoustic metamaterial. Such improved design can slow down acoustic wave propagation through refractive index tuning and wave-front revolution, over a much wide spectra.
Development of a multi-material underwater anisotropic acoustic metamaterial
Authors: Kerrian Peter , Hanford Amanda , Smith Robert W. , Beck Benjamin , Capone Dean
Published: June 2017

Previous work in the open literature has described three potential ways to create an acoustic metamaterial with anisotropic mass density and isotropic bulk modulus: (1) alternating layers of homogeneous isotropic materials, (2) perforated plates, and (3) solid inclusions. The primary focus of this work will be to experimentally demonstrate the anisotropic behavior of a metamaterial comprised of a multi-solid inclusion unit cell in water. The two material design of the unit cell consists of one material more dense and one less dense than the background fluid, which results in an effective mass density tensor for the unit cell where one component is more dense and one component is less dense than the background fluid. Successful demonstration of an anisotropic metamaterial with these effective parameters is an important step in the development of structures based on transformational acoustics.
Acoustic wave phenomena in Willis metamaterials
Authors: Goldsberry Benjamin M. , Haberman Michael R.
Published: June 2017

The design of acoustic metamaterials requires accurate modeling of the dynamics present at all relevant time and length scales. Recent work has shown that the effective dynamic properties of inhomogeneous elastic materials can result in constitutive relations that couple strain to momentum and velocity to stress, which is often referred to as Willis coupling [Willis, Wave Motion, 3(1), 1-11, (1981)]. The current work will examine macroscale acoustic propagation for waves on different time scales in a material by solving the coupled first-order equations of motion with the constitutive relations that account for Willis coupling. Specifically, second-order perturbation theory will be used to examine the classic problem of a high-frequency, low-amplitude “signal” wave superposed on a low-frequency, high-amplitude “pump” wave. Of particular interest is the slowly changing momentum bias generated by the pump wave and implications on dynamic control of signal wave propagation. Analysis and discussion will be restricted to one-dimensional wave motion.
Acoustic valley states and acoustic valley transport in sonic crystals
Authors: Lu Jiuyang
Published: June 2017

We report the discovery of acoustic valley states in sonic crystals and the observation of the valley transport in the domain walls. The concept of valley pseudospin, labeling quantum states of energy extrema in momentum space, is attracting attention for its potential as a new type of information carrier. Inspired by the recent valley related phenomenon in election systems, the acoustic version of valley states in sonic crystals is studied and the vortex nature of such states is revealed. The extraordinary chirality of valley vortex states may provide new possibilities in sound manipulations and will be appealing to scalar acoustics since the absence of spin degree of freedom here. We further experimentally observe the topological valley transport of sound in sonic crystals. The acoustic valley transport is confined in the domain walls of the sonic crystals and behaves negligible reflection to the interface corners. The acoustic valley transport of sound, strikingly different from that in traditional sound waveguides, may serve as the basis for designing devices with unconventional functions.
Evidence of multimodal vibration damping using a single piezoelectric patch with a negative capacitance shunt
Authors: Romero-García Vicente , Bricault Charlie , Pézerat Charles , Collet Manuel , Pyskir Adrien , Perrard Patrick , Matten Gaël
Published: June 2017

In this work, a piezoelectric patch shunted with a negative capacitance circuit has been used to simultaneously damp several modes of a square aluminum plate at low frequencies. The active nature of such electromechanical system leads to regions of instabilities in which the highest vibration attenuation performance appears in the softening region. Once the geometry is fixed, the system has two degrees of freedom, dominated by the electrical parameters of the circuit: the resistance and the negative capacitance. We tune both the value of the negative capacitance, in order to place the structure close to the instability in the softening region, and the resistance of the circuit in such that control the losses of the system. This work shows an optimal design to simultaneously damp several modes with non-zero electromechanical coupling factors using a single shunted patch at low frequencies. The problem is solved numerically and tested experimentally with good agreement. The results show the possibility of controlling the modal response of the system, opening prospects to improve the acoustic comfort with systems using piezoelectric shunted damping circuits with small additional mass with a high tunability by only adjusting the properties of the shunt.
Design and assessment of a distributed active acoustic liner concept for application to aircraft engine noise reduction
Authors: Lissek Herve , Boulandet Romain , Karkar Sami , Matten Gaël , Collet Manuel , Ouisse Morvan
Published: June 2017

Acoustic liners are a widespread solution to reduce turbofan noise in aircraft nacelles, due to lightweight and relatively small dimensions for integration within nacelles. Although conventional liners might be designed so as to target multiple tonal frequencies, their passive principle prevents the adaptation to varying engine speeds and therefore lowers their performance during flight, especially in the take-off and landing phases. This paper presents a novel concept of active acoustic liner based on an engineered design of microphones and loudspeakers, aiming at absorbing noise over a broad frequency bandwidth. Integration issues have been taken into account so as to fit to the targeted application to aircraft engines, yielding thickness minimization, with a view to challenging existing passive, narrow-band, liners. The sound absorption performance of the proposed active lining concept is evaluated, through commercially available finite-element software, in a configuration mimicking an aeronautical insertion-loss measurement setup, and then tested in the corresponding experimental facility in the presence of flow. The results show that such a concept is readily surpassing conventional passive liners, both in terms of insertion loss value and frequency bandwidth.
Vibration damping using a spiral acoustic black hole
Authors: Jeon Wonju , Lee Jae Yeon
Published: June 2017

This study starts with a simple question: can we efficiently reduce the vibration of plates or beams using a lightweight structure that occupies a small space? As an efficient technique to damp vibration, we adopted the concept of an Acoustic Black Hole (ABH) with a simple modification of the geometry. The original shape of an ABH has a straight wedge-type profile with power-law thickness, with the reduction of vibration in beams or plates increasing as the length of the ABH increases. However, in real-world applications, there exists an upper bound of the length of an ABH due to space limitations. Therefore, in this study, the authors propose a curvilinear shaped ABH using the simple mathematical geometry of an Archimedean spiral, which allows a uniform gap distance between adjacent baselines of the spiral. In numerical simulations, the damping performance increases as the arc length of the Archimedean spiral increases regardless of the curvature of the spiral in the mid- and high-frequency ranges. Adding the damping material to an ABH can also strongly enhance the damping performance while not significantly increasing the weight. In addition, the radiated sound power of a spiral ABH is similar to that of a standard ABH.
Vibroacoustics behavior of self-similarly loaded sandwich structures
Authors: Derré Jérémie , Simon Frank
Published: June 2017

The reduction of structural vibrations and acoustic radiation is increasingly challenging due to lightweight material use driven by mass reduction, particularly in the aerospace industry. Trim panels are well-known materials with high acoustic transmission and radiation. This study combines semi-analytical modeling, numerical simulations and experiments on the vibroacoustic behavior of sandwich constructions locally overloaded by a pre-fractal mass distribution. The research originality lies in the overload distribution (a self-similar pattern inspired by the Cantor set) which is directly slotted within the honeycomb core, so that the structure load-bearing capability is not altered. As the mass effect spatially localizes the vibrations, the pre-fractal pattern focuses the effect of localization on some specific frequency band gaps, which reduces the total vibrational energy and thus the acoustic radiation. Before the extension to composite plates, simulations of a homogenized beam model have been computed to form a numerical modal database. Experiments have been conducted to compare and tune the mechanical model parameters. Satisfying agreement has been obtained between simulations and experiments. Finally, acoustic radiation simulations of self-similarly loaded structures have been conducted and radiation coefficients are expected to be weaker than for classical bending beams.
Three dimensional MRI analyses of tongue muscle behavior
Authors: Stone Maureen , Zhuo Jiachen , ElSaid Nahla , Woo Jonghye , Xing Fangxu , Prince Jerry
Published: June 2017

3D and 4D MRI provides unique, high dimensional data for use in clinical applications and scientific models. Our group is currently using diffusion tensor MRI (DTI) and tagged-cine MRI (tMRI) to explore the fiber direction of muscles in the tongue and the shortening patterns of those fibers during speech. tMRI uses “magnetic tags” to mark and track tissue points, so that when the tissue deforms, the tags reflect these deformations. Soft tissue motion patterns, such as those within the tongue during speech, provide a link between muscle activation and tongue surface shape. Tissue points also demark the endpoints and internal points of muscles, and can identify tongue muscle position and shortening during speech. Tracking tongue muscle motion is unique to tMRI because their interdigitated fibers make them fairly opaque to EMG. Disambiguating muscles and identifying their shortening pattern is a first step to relating muscle action to tongue deformation. The second tool, DTI, identifies the location and orientation of “muscle fibers” within a muscle volume. We will use these tools to track shortening of several tongue muscles during speech.
Discovering functional units of the human tongue during speech from cine- and tagged-MRI
Authors: Woo Jonghye , Stone Maureen , Xing Fangxu , Green Jordan , Gomez Arnold , Wedeen Van , Prince Jerry L. , El Fakhri Georges
Published: June 2017

Tongue motion during speech or other lingual behaviors involves synergies of locally deforming regions, or functional units. Determining functional units will provide an insight into the mechanisms of normal and pathological muscle coordination, leading to improvement in understanding of speech production and treatment or rehabilitation procedures. In this work, we present an approach to determining functional units using cine- and tagged-MRI. Functional units are estimated using a sparse non-negative matrix factorization (NMF) framework, learning latent building blocks and the weighting map from motion features from displacements and strain. Current models of gesture production suggest that, during speech planning, talkers select temporal frames prior to specifying the appropriate spatially fixed clusters. Our analysis is intended to parallel this process by using NMF to first identify temporal frames in the data based on change points in motion features, and then to identify the spatially fixed clusters for all the input quantities in each time frame. A spectral clustering is performed on the weighting map of each time interval to define the coherent sub-motions, revealing temporally varying tongue synergies. Synthetic and human tongue data including both controls and patients with glossectomy and amyotrophic lateral sclerosis are used to define subject/task-specific functional units of the tongue in localized regions.
Computer simulation of the vocal tract in speech production
Authors: Stavness Ian , Widing Erik , Roewer-Despres Francois , Gick Bryan
Published: June 2017

Neuro-musculoskeletal function can be well characterized for most human movements, such as walking, through a combination of experimental measurements, including motion capture, electromyography, and force sensing. Movements of the vocal tract, however, pose a considerable challenge in terms of holistically measuring and visualizing the neuro-musculoskeletal processes underlying speech production. This is due to the inaccessibility of the vocal tract, the large number of small, deep muscles involved, the fast speed of movements, and the inherent three-dimensional nature of vocal tract shape during speech production. An array of measurement and imaging modalities have been tailored to vocal tract measurement, such as MRI, EMA, EPG, and ultrasound, each providing valuable, but incomplete information regarding vocal tract movements. Computer simulation of the vocal tract can play an important role in complementing these sparse experimental measurements by aiding in the fusion of multiple imaging modalities, helping to describe and visualize the 3D structures of interest, filling in the gaps in experimental measurements (both spatial and temporal), and extrapolating from the small sample sizes commonly found in speech production studies. We will discuss two types of computer simulations that are emerging as important complementary forms of speech production investigation: forward biomechanical simulation of the vocal tract articulators and probabilistic simulation of neuro-musculoskeletal parameters.
Directive and focused acoustic wave radiation by tessellated transducers with folded curvatures
Authors: Harne Ryan L. , Lynd Danielle T. , Zou Chengzhe , Crump Joseph
Published: June 2017

Guiding radiated acoustic energy from transducer arrays to arbitrary points in space requires fine control over contributions of sound provided to the point from each transducer constituent. Recent research has revealed advantages of mechanically reconfiguring array constituents along the folding patterns of an origami-inspired tessellation, in comparison to digitally processing signals sent to each element in a fixed configuration. To date, this concept of acoustic beamfolding has exemplified that far field wave radiation may be adapted by orders of magnitude to a point according to the folding of a Miura-ori tessellated array when the array constituents are driven by the same signal. This research investigates a new level of adaptive acoustic energy delivery from foldable arrays through study of tessellated transducers that adopt folded curvatures, thus introducing opportunity for near field energy focusing alongside far field directionality. The outcomes of these computational and experimental efforts plainly reveal that foldable, tessellated transducers that curve upon folding empower straightforward means for the fine, real-time control needed to beam and focus sound to points in space. Discussions are provided on the potentials and limitations of the current tessellations considered, and means for future studies to build upon the new understanding.
Cramer-Rao bound for direction finding at a tri-axial velocity-sensor of an acoustic event having an AR(1) temporal auto-correlation
Authors: Kitavi Dominic M. , Wong Kainam T. , YEH Lina , Lin Tsair-Chuan
Published: June 2017

Various acoustical events have an order-1 autoregressive temporal autocorrelation model. This investigation derives the Cramer-Rao bound (CRB) for direction finding of such an AR(1) acoustical event, if the data is collected by a tri-axial velocity-sensor.
An array of two biaxial velocity-sensors of non-identical orientation— Their “spatial matched filter” beam-pattern's pointing error
Authors: Nnonyelu Chibuzo J. , Lee Charles H. , Wong Kainam T.
Published: June 2017

A biaxial velocity-sensor (a.k.a. a v-v probe) measures two Cartesian components of an incident acoustical wavefield's particle velocity vector. Such biaxial velocity-sensors are sometimes used as elements in an array. If these elements are not identically oriented, what would happen to the array's “spatial matched filter” beam-pattern? This paper investigates such a beam-pattern's pointing error, for a pair of non-identically oriented biaxial velocity-sensor. This pointing error is investigated here in terms of (i) the biaxial velocity-sensor's misorientation skew angle, (ii) the biaxial velocity-sensor's spatial separation, (iii) the incident signal's wavelength, and (iv) the beamformer's nominal look direction.
Ira Dyer and the BBN Applied Research Division
Authors: Barger James
Published: June 2017

Ira Dyer was one of the first hires by Leo Beranek for the fledgling company Bolt, Beranek and Newman (BBN). Ira in turn hired many of the now recognized pioneers in ocean, structural; and ocean acoustics and formed the BBN Applied Research Division. Members investigated all aspects of sound and vibration in ships, submarines, aircraft, and spacecraft. An example includes during the mid-1950s, Ira helped design the US Navy X-1 Submarine, a small four-man quiet diesel-electric submarine for ADM Rickover. BBN designed an innovative engine mounting system that quieted the vehicle and led the way for ultra-quiet submarines in the future Navy. This submarine is now on display at the Navy Submarine Museum at Groton, CT. Other contributions by members include SEA (statistical energy analysis) and criteria for modeling flow-excitation forcing functions to structural radiation. Ira created a golden era for acoustics at BBN.
The role of fluctuations in the interpretation of sonar detection performance
Authors: Abbot Philip , Premus Vincent E. , Helfrick Mark N. , Gedney Charles J. , Emerson Chris J.
Published: June 2017

The predictive probability of detection (PPD) is a metric that accounts for uncertainty in sonar detection performance due to random fluctuations in transmission loss, noise level, and source level [P. Abbot and I. Dyer, Impact of Littoral Environmental Variability on Acoustic Predictions and Sonar Performance, 2002]. It is well known that a significant portion of Ira’s career was dedicated to understanding the role fluctuations play in interpreting acoustic measurements. Building on this foundation, we now embrace the notion that a useful statement of sonar system performance is one linked with a probabilistic description of the acoustic environment’s intrinsic variability. In this paper, we discuss the impact of fluctuations on passive sonar performance, including how PPD facilitates the interpretation of sonar system recognition differential. Data from a recent field test conducted in August, 2011, on the New Jersey continental shelf, will be used to illustrate the methodology and interpret measured detection performance in the presence of a cold pool duct and variable ambient noise conditions.
Acoustic intensity fluctuation studies in shallow water over the past quarter century
Authors: Lynch James , Colosi John A. , Duda Timothy F. , Lin Ying-Tsong , Newhall Arthur
Published: June 2017

One of Ira Dyer’s seminal contributions to underwater acoustics was in the understanding of acoustic intensity fluctuations. In particular, the 5.6 dB intensity fluctuation of a large number of interfering narrowband multipaths, which is often informally referred to as “the Dyer number”, is a robust and well know effect. In shallow water, a number of physical effects can modify this basic number. These effects have been measured in various experiments over the years, and we will show a subset of these results. The physics of the effects, the measurement techniques, and the implications of this work for sonar processing will all be discussed. Work supported by ONR.
Analysis of marginal ice zone noise events: Revisited
Authors: Chen Chi-Fang
Published: June 2017

Acoustic transients observed in a noise time series, called noise events, are believed to be the major contributor to Arctic Ocean ambient noise. Underwater ambient noise data from the Marginal Ice Zone Experiment 1984 (MIZEX84), at frequencies between 20 and 2000 Hz, are studied. Results show that temporal and spatial distribution of events are characterized by clustering and seem to depend on environmental conditions such as swells and ice concentration. Event densities increase as f at frequencies below 200 Hz, decrease as f −1 at frequencies above 300 Hz, and reach a maximum at frequencies between 200 and 300 Hz. The change in trend may indicate a transition in the source mechanism for frequencies below 200 Hz and above 300 Hz. The noise source can be modeled as octo-pole which is the best fit from the noise data. [Work supported by Office of Naval Research, and completed under Prof. Ira Dyer's supervision in Massachusetts Institute of Technology in 1990.]
The vision of Ira Dyer
Authors: Makris Nicholas C.
Published: June 2017

We will describe how Ira Dyer's scientific ideas and vision have been passed on to us and survive as strong as ever influencing the future.
Changing Arctic ambient noise
Authors: Poulsen Andrew J. , Schmidt Henrik
Published: June 2017

The Arctic Ocean is undergoing dramatic changes, with the most apparent being the rapidly reducing extent and thickness of the summer ice cover. Furthermore, a persistent inflow of a shallow tongue of warm Pacific water has recently been discovered in the Beaufort Sea region of the Arctic, often called the Beaufort Lens, which creates a strong acoustic duct between approximately 100 and 200 m depth. These changes have had a significant effect on underwater acoustic propagation and noise properties. In spring 1994, acoustic data was collected in the Beaufort Sea region of the Arctic using a suspended vertical array; in spring 2016, similar data was collected in the same region. The 1994 data features meandering narrow-band features due to ice ridge friction, while the 2016 data in the new Arctic is largely dominated by ice mechanical events at discrete ranges and bearings. Supported by acoustic noise modeling, we illustrate these and other noise properties measured more than two decades apart in a region of rapid and significant change. [Work supported by ONR and DARPA.]
Ira Dyer and MIT Arctic acoustics research
Authors: Duckworth Gregory L.
Published: June 2017

Ira Dyer and his colleague Art Baggeroer began MIT’s Arctic Acoustics research efforts in the latter half of the 1970s. In this pre-GPS and newly digital era, Ira helped define an ambitious program for the Office of Naval Research that brought large-aperture high-quality acoustic array data acquisition to bear on the problems of Arctic acoustic science. Supporting a generation of graduate students, this work explored ambient noise generation mechanisms in the ice, Arctic basin reverberation, seismic reflection and refraction studies to understand the underlying crustal structure, and long-range propagation that is now exploited for acoustic thermometry to study global climate change. Advanced signal processing, combined with fundamental physical understanding and modeling of the ice, water column, and underlying crust vastly increased our understanding of these phenomena in the Arctic. I will show some of the results of this work, and how it has been extended for use in active sonars and measurements of sea-ice dynamics over large areas of the Arctic.
Three-dimensional model benchmarking for cross-slope wedge propagation
Authors: Rodríguez Orlando C. , Sturm Frédéric , Petrov Pavel S. , Porter Michael
Published: June 2017

Cross-slope wedge propagation is considered for the three-dimensional benchmarking of three underwater acoustic models, one based on normal mode theory and the other two based on ray tracing. To this end, the benchmarking relies on analytic solutions for adiabatic and non-adiabatic propagation, as well as on experimental data from a scale tank experiment (a previous benchmarking with a parabolic equation model is known to provide extremely accurate predictions in all cases). The benchmarking allows to identify the advantages, accuracy and limitations of the considered models.