bluuebunny/crossref_metadata_2025 huggingface dataset:
Lessons learned from signal-detection-theory-oriented studies of the processing of auditory patterns
Authors: Watson Charles S.
Published: April 2019

One extension of Fechner’s (1860) methods by which the influence of sensory stimuli on human observers could be quantified in physical units, sometimes termed a "new psychophysics" was Stevens (1938) theory and methodology of perceived magnitude estimation that attempted to bridge the gap between sensation and perception. A more far-reaching second extension began in 1954, when Peterson, Birdsall, and Fox applied statistical decision theory to the recovery of physical signals embedded in background noise and Tanner, Green, and Swets applied those principles to develop a new psychophysical methodology. What became known as “signal detection theory” provided methods of determining the capacity of systems to detect, discriminate, or recognize physical stimuli, a second "new psychophysics." The two alternatives to Fechner represent complimentary approaches to a single set of phenomena, one of which can be characterized as the study of sensory capabilities and the other of response proclivities. The two require entierly different methods of measurement and address fundamentally different questions. Both are of practical and theoretical importance. Levels of stimulus uncertainty and the type and duration of experience with stimuli can have profound influences on measurements of both types. Examples of these effects for complex sounds, both speech and nonspeech, will be presented.
A detection-theoretic approach to cocktail-party listening
Authors: Lutfi Robert , Rodriguez Brianna , Lee Jungmee
Published: April 2019

Cocktail-party listening (CPL) is a key-term referring to difficult listening situations wherein one must "h"" and follow the speech of individual talkers in a crowd. Such situations are commonplace in everyday listening but can be a challenge to study. Important factors affecting performance, such as voice similarity among talkers and uncertainty associated with the dynamic variation of speech, can be difficult to quantify. Spectral and spatial acoustic cues distinguishing talkers are of critical importance but are expressed in different physical units making their relative role difficult to evaluate beyond the particulars of a study. There are also often huge individual differences in listener performance that can complicate the interpretation of results. This paper reviews recent applications of detection theory designed to address these challenges. The distinguishing feature of the approach is that key factors are evaluated in terms of their contribution to the information divergence of talkers, DKL; a single statistic that dictates optimal performance for each task [Lutfi et al., J. Acoust. Soc. Am. 134, 2160–2170 (2013)]. Both published and unpublished studies are reviewed demonstrating the application of the approach to each of the major challenges described above. [Work supported by NIDCD R01-DC001262].
On the theoretical benefit of combining multiple observations: Dependence on the form of the probability distribution of the observations
Authors: Dai Huanping , Buss Emily
Published: April 2019

Auditory research has benefited immensely from the application of the Signal-Detection Theory (SDT; Green and Swets, 1966). The theory has provided a rigorous framework within which the design of experimental studies and the interpretation of experimental results can be carried out in a principled way. A fundamental assumption often made, either explicitly or implicitly, in the application of SDT is that the observations obey Gaussian distributions. Many important results were derived on an equal-variance Gaussian assumption for the "noise" and the "signal"events. One example is the well-known relation between the detectability attainable based on a single observation (d'1) and the detectability that can be achieved when multiple (m > 1) independent and equally informative observations are combined: d'm = √m d'1. As researchers often need to deal with situations where the form of the probability distributions of the observations either is unknown or is known to be non-Gaussian, it is important to understand how the form of the probability distribution can influence the outcome. This presentation will examine different ways by which the interpretation of listeners’ performance with multiple observations would depend on the form of the probability distributions.
Physiological parallels with perception
Authors: Middlebrooks John C.
Published: April 2019

Signal detection theory (SDT) lends itself to comparison among perceptual and physiological results in humans and other animals. In physiological recordings, trial-by-trial distributions of single-unit spike counts or of event-related-potentials typically yield non-normal distributions, calling for non-parametric tests. An empirical receiver operating characteristic (ROC) curve can compare distributions of physiological measures between pairs of stimulus conditions. The area under the ROC curve is a non-parametric measure of sensitivity, yielding the proportion correct and, thence, the sensitivity index, d’. The d’ cumulated over a succession of the increasing values of a stimulus parameter provides a measure of the growth of response over that parameter range. I will present examples from several ongoing projects including: (1) studies of activation of the central auditory pathway by cochlear implants and by a penetrating auditory nerve electrode, with single-unit recordings from the inferior colliculus; (2) comparisons of spatial stream segregation among 2-alternative forced choice in humans, hold-response measures in cats, and cortical single-unit recording in cats; and (3) studies of frequency sensitivity using the auditory change complex and masked onset responses. In general, these techniques derived from SDT yield a satisfying agreement among perceptual measures and their physiological underpinnings.
Magnetorheological elastomer panels with reconfigurable magnetic mass for acoustic wave absorption
Authors: Willey Carson , Chen Vincent W. , Scalzi Ken , Buskohl Philip , Juhl Abigail T.
Published: April 2019

Lightweight metamaterials based elastomeric panels are used for sound absorption of low-frequency noise. It is beneficial to tune the resonant frequency of the metamaterial, by varying the stiffness of the panel, to enable use over a broader frequency range. The stiffness of magnetorehological elastomeric (MRE) panels, composed of iron particles embedded in a PDMS matrix, can be tuned by exposure to a magnetic field. This work represents an experimental realization and theoretical understanding of a magnetic mass decorated MRE metamaterial, which allows for tunable stiffness and easy reconfiguration of the masses applied to the panel. The circular panels are clamped at the rim, outfitted with neodymium magnets, and installed in an acoustic impedance tube, where they act as an acoustic barrier between the transmit and receive sides of the tube. There are three competing mechanisms that affect the sound transmission across the panel: (1) the mass increase associated with the magnetic masses, (2) the stiffening of the panel due to the magnetic field of each mass, and (3) the increased reflection from the placed masses. The experimental results demonstrate significant sound absorption by a thin metamaterial panel over a large frequency range through careful placement of magnetic masses.
Non-reciprocal sound propagation using acoustic resonators via space-time modulation
Authors: Li Junfei , Shen Chen , Zhu Xiaohui , Cummer Steven
Published: April 2019

Breaking reciprocity is of fundamental importance in communication and signal processing and is less explored in the field of acoustics. Here, we show that non-reciprocal acoustic transmission can be realized in cascaded resonators that are periodically modulated. In the continuum limit, we also study the sound propagation in a continuously modulated effective medium. Functionalities such as mode conversion, parametric amplification, and phase conjugation are demonstrated. Finite-difference time-domain (FDTD) simulations are carried out to verify the results. An experimental platform is constructed which is composed of a waveguide system with side-loaded resonators. The back walls of the resonators are driven dynamically using speakers so that time modulation can be achieved.
Architected hollow sphere foams for simultaneously tunable noise and vibration control
Authors: Chen Yanyu
Published: April 2019

Architected metamaterials, which are rationally designed multiscale material systems, exhibit novel functionalities and unique properties that cannot be readily achieved in natural bulk solids. In addition to unusual mechanical and physical properties, such as high specific stiffness and strength, negative Poisson’s ratio, negative coefficient of thermal expansion, and negative compressibility, architected metamaterials have been designed and optimized for novel elastodynamic wave phenomena. One example of such architected metamaterials is phononic metamaterial, which consists of periodically topological structures and materials dispersions. These rationally designed structures enable the manipulation of propagating acoustic or elastic waves but not simultaneously. Here, we report a new type of architected hollow sphere foam that can attenuate sound and elastic wave synchronically. Our numerical simulation results suggest that the acoustic wave attenuation is controlled by the drilled area and thickness of the spheres, while the elastic wave propagation can be manipulated by changing the connectivity among the hollow spheres. We printed the architected hollow sphere foams and experimentally demonstrated the existence of omnidirectional acoustic and elastic wave bandgaps. Our findings reported here offer new opportunities to design lightweight architected metamaterials to simultaneously control undesired noise and vibration over a wide range of frequency.
Toddlers' sensitivity to talker age in novel word learning: Children are better teachers
Authors: Wang Yuanyuan , Seidl Amanda
Published: April 2019

From early on, young children are sensitive to talker-specific attributes present in the speech signal. For example, infants attend selectively and learn better from their mother’s voice than another female voice. Since age influences vocal quality, we asked whether toddlers show similar selective attention and learning from talkers of specific ages. We recorded visual and auditory stimuli from 3 adult males and females and 3 boys and girls. In Experiment 1, 24 toddlers viewed two side-by-side video clips of two talkers reciting a nursery rhyme and heard a soundtrack that matched with either the age or gender of one of the two talkers. The results revealed that children were able to match both vocal age and gender attributes to visual attributes. In Experiment 2, 24 toddlers were tested in a novel word learning task with talkers of different ages and genders. The results revealed that toddlers learned novel words from child talkers but failed to learn from adult talkers. These results suggest that young learners are sensitive to talker age information in speech and are biased towards learning words from younger talkers. We discuss the origins of such a bias.
Target strength measurements of spherical and wobbly bubbles
Authors: Padilla Alexandra M. , Weber Thomas C.
Published: April 2019

Methane gas bubbles released from the seafloor transport gas upwards through the water column and in some cases even to the atmosphere. Researchers exploit the large acoustic impedance contrast between the gas within the bubble and the surrounding water to acoustically estimate the flux of methane in the ocean. Flux estimation employs the use of analytical acoustic scattering models to convert acoustic backscatter measurements of gas bubbles to size estimates. However, these models assume that bubbles are both spherical and that their radius is much smaller than the acoustic wavelength (ka « 1). Typically, bubbles in the ocean range from 1 to 5 mm in radius are non-spherical in shape and are observed for ka values that are greater than 0.1. A controlled shallow water tank (<6 m) experiment was conducted to assess the uncertainty associated with using analytical models that assume bubbles are spherical and that ka values are much smaller than one. Small, spherical and large, wobbly gas bubbles (radii ranging from 0.7 to 4.5 mm) were ensonified over a broad range of frequencies (10–250 kHz) in order to observe ka values from 0.1 to 5.
Acoustics and AV technology of modern collegiate learning centers
Authors: Woolworth David S. , Roland William
Published: April 2019

Many universities are creating new dedicated spaces for interactive learning that can host all subjects and a more modern and holistic approach to collegiate education. In order to achieve high performance facilities that mix classrooms, testing rooms, collaborative spaces, offices, and counseling all together, acoustical and audio visual requirements must be coordinated early in the project with the end user, with room to adjust to changing programming and technology. This paper presents 3 case studies of repurposed and new collegiate construction and outlines the types of program requirements and the approach to acoustics and audio visual for these projects.
Fast moving biomimetic ears
Authors: Yin Xiaoyan , Müller Rolf
Published: April 2019

Like many other mammals, bats are known to rely on spectral signatures to determine the directions of incoming sounds, especially in elevation. Because of its simple hardware and computational realizations, this principle could also be suitable for small, parsimonious biomimetic sonar systems. However, the biosonar systems of bat species in families such as the rhinolophids and hipposiderids often—but not always—concentrate most of the emitted energy within a narrow frequency band in order to pick up prey-induced Doppler signatures. It remains unclear how the use of such narrow-band biosonar pulses could be reconciled with direction-finding based on spectral signatures. A possible solution to this paradox could be provided by fast pinna motions in these animals that have been shown to produce readily perceivable Doppler-shift signatures in biomimetic reproductions. In the current work, such a biomimetic pinna with fast deformations has been used to map Doppler-shift signatures as a function of direction. For this purpose, the Doppler-shift signatures were clustered based on the similarity of their spectrogram-representations. Mapping the signatures' different cluster associations into direction space resulted in contiguous patches. Hence, it should be possible to obtain stable estimates of target direction based on the received Doppler signatures.    
Biosonar inspiration for radar waveform design
Authors: Coxson Gregory E.
Published: April 2019

Bat biosonar offers a natural source for biomimetic design of radar waveforms with inspirations falling into two categories: (1) biosonar principles similar to ones already employed in radar and (2) principles used by bats that operate in ways not yet understood or not yet embraced yet for radar. This second type offers the possibility for driving radar innovation. Hyperbolic frequency modulation (HFM) waveforms were one of the first aspects of bat biosonar to catch the attention of the radar community. Relative to the popular linear frequency modulation (LFM) waveform, HFM is less vulnerable to Doppler shifts from targets' relative velocities. Another promising possibility for biomimetics is the remarkable ability of some bats to resolve closely-spaced objects using acoustic frequencies on a small platform. Bats' ability to operate in swarms is of interest to radar designers concerned about mutual interference between ships or planes using the same waveforms and frequencies. As bat researchers approach an understanding of the mechanisms behind these, and other, abilities of bats, their results will find a ready audience. This talk will discuss aspects of bat biosonar offering payoffs for radar design, including but not limited to improved resolution, Doppler tolerance and mitigation of inter-system interference.
Left ventricle blood flow patterns in a mouse model of temperature sensitive sodium channelopathy
Authors: Ketterling Jeffrey A. , Aristizabal Orlando , Shekhar Akshay , Yiu Billy Y. , Phoon Colin K. , Fishman Glenn I. , Yu Alfred C. , Silverman Ronald H.
Published: April 2019

Sophisticated methods of visualizing and analyzing the complex blood flow patterns in humans have been available for a number of years on ultrasound machines. To date, these methods have not been applied to healthy mouse models or mice with cardiac defects. Here, a high-speed plane-wave imaging approach was used to study left ventricle blood flow patterns in a model of sodium channelopathy using mice lacking fibroblast growth factor homologous factor 2 (Fhf2KO) and littermate wild-type (WT) controls. FHF2 binds to the cytoplasmic tails of voltage-gated sodium channels in mouse cardiomyocytes and modulates channel inactivation and cellular excitability. Fhf2KO mice have impaired cardiac sodium channel function that when body temperature rises causes a severe reduction in cardiac sodium currents, cardiomyocyte excitation, and conduction failure. The effect is reversible as body temperature returns to normothermia. Fhf2WT and Fhf2KO mice were imaged with a Verasonics Vantage 128 using an 18-MHz linear array with a 30 kHz absolute plane-wave transmission rate. The mice were supine on an imaging platform and a warm-air source was used to raise the body temperature. Surface ECGs were continuously recorded throughout the duration of the experiment. Data were post-processed using a least-squares, multi-angle Doppler analysis approach to obtain vector-flow estimates at all pixel locations. Vortex patterns, flow rates and ECG signals were compared between the Fhf2WT and Fhf2KO mice.
Super-resolution ultrasound imaging beyond the acoustic diffraction limit
Authors: Kim Kang , Chen Qiyang , Yu Jaesok
Published: April 2019

Contrast enhanced ultrasound (CEU) imaging technologies using microbubbles (MBs) provide superior contrast of vasculatures, effectively suppressing the surrounding tissue signals, but the spatial resolution remains to the acoustic diffraction limit. By localizing the center of each MBs unprecedented high spatial resolution beyond the acoustic diffraction limit can be achieved. However, some methods of localizing each center of the signals from individual MBs that only applies symmetrically distributed signal amplitude require a large number of imaging frames, especially when MBs are densely clumped, therefore result in a long scan time that is not ideal for in vivo scan under physiologic conditions. In this paper, we present an innovative approach using deconvolution technique that will allow for identifying signals from individual MBs from dense population in any forms even grouped together within the full-width-at-half-maximum (FWHM) of the point spread function (PSF) of the US probe. In this way, no collected frame sets require to be excluded for image reconstruction, therefore scan time can be reduced significantly. In vivo application of this new approach in identifying vasa vasorum in rabbit atherosclerotic plaque model will be presented. Some technical limitations including background noise as well as motion artifact will be discussed.
Graduate programs in acoustics at the University at Buffalo, State University of New York
Authors: Kobrina Anastasiya , Burke Kali
Published: April 2019

University at Buffalo is known for its diversity in acoustic and auditory research spanning from signal processing to hearing in humans and animals. These research programs are nested within Anthropology, Biological Sciences, Communicative Disorders and Sciences, Computer Science and Engineering, Linguistics, Psychology, and Music, which leads to a unique variety of collaborations spanning departments and laboratories. The doctoral programs in these departments are aimed at training students for clinical and research-oriented careers. Our graduate programs involve taking extensive coursework and hands on experience in laboratories. In addition, each department holds regular colloquia on various topics in acoustics. University at Buffalo is also home to the Center for Hearing and Deafness. The Center seeks to develop cooperative working relationships with businesses and industries involved in hearing-related activities, such as: hosting the WNY Tinnitus Support Group, testing and evaluating drugs used to treat hearing loss, developing new scientific and clinical instrumentation, and assessing industrial hearing loss and noise regulations. The Center also provides valuable training opportunities for physicians, engineers, and health professionals. In conclusion, the University at Buffalo is an ideal fit for training in acoustics research.
Graduate acoustics research at the University of New Haven
Authors: Dieckman Eric A.
Published: April 2019

The University of New Haven offers graduate study opportunities in acoustics, primarily through a Master of Science in Mechanical Engineering degree. This flexible program allows students to tailor a curriculum toward their interests in preparation for further graduate studies or entry into the workforce. Courses offered include Fundamentals of Acoustics, System Vibrations, Nondestructive Evaluation, and Wave Propagation and Scattering. All classes have a focus on hands-on projects. A one-semester project or two-semester thesis allows students structured time to work on research problems in acoustics.
Effects of age, modulation rate, and modulation depth on sentence recognition in speech-modulated noise
Authors: Fogerty Daniel , Miller Rachel E. , Ahlstrom Jayne B. , Dubno Judy R.
Published: April 2019

Speech is often heard in amplitude modulated backgrounds when speech is glimpsed during momentary masker dips. Increased masker modulation depth provides more improvement in the signal-to-noise ratio of glimpsed speech, but also improves noise modulation detection for potentially greater modulation masking. Mechanisms of modulation masking and glimpsing may also depend on the overlap of the modulation spectra of the speech and noise. This study employed modulation filtering and noise amplitude compression to investigate the combined effects of noise modulation depth and modulation rate on speech recognition. Younger normal-hearing (YNH), older normal-hearing (ONH), and older hearing-impaired (OHI) adults listened to sentences in noise that were spectrally shaped to control for individual hearing thresholds. A second YNH group listened to sentences with the same spectral shaping as OHI listeners. Sentence recognition generally improved with greater noise modulation depth, especially at higher modulation rates. Results suggest that speech recognition for all groups is maximized when speech modulations <8 Hz are preserved, when noise modulation occurs at rates higher than this range, and with greater noise modulation depth. OHI listeners benefit similarly from these conditions, but their poorer overall performance may be due to reduced sensation levels. [Work supported by NIH/NIDCD.]
Talker head orientation discrimination using only auditory cues
Authors: Frazier David L. , Monson Brian B.
Published: April 2019

Although many studies focus on human ability to localize a sound source, less is known about human ability to determine the physical orientation of a given sound source. In our study, we assessed listeners’ ability to detect changes in talker head orientation. Participants with normal hearing were asked to detect head orientation changes (relative to 0 deg, i.e., directly facing the listener) for two male and two female talkers. We found listeners are sensitive to changes of approximately 40 deg in talker head orientation using only auditory cues. This is less sensitive than what humans have displayed with only visual cues. These findings indicate that auditory cues are available for head orientation discrimination, which may be of greater utility when visual cues are unavailable.
Low frequency sound absorption by compliant Helmholtz resonators
Authors: Cui Shichao , Harne Ryan L.
Published: April 2019

A traditional Helmholtz resonator is a rigid-walled cavity and an open neck, which result in one acoustic resonance. In this study, a soft-walled cavity with an open neck, a compliant Helmholtz resonator, is investigated for broadband and large absorption of sound at low frequencies. By applying the soft materials, the dynamics of the compliant walls and the material impedance are coupled to the acoustic pressure filed in the cavity. Thus the impedance of the compliant resonator system as seen by an incident acoustic wave is determined by the interaction of the wall dynamics, material properties, and acoustic domain. Compared to a traditional Helmholtz resonator with the same geometric dimensions, the compliant Helmholtz resonator exhibits multiple resonances with large absorption of sound. In addition, strategic design of the structural composition and the material selection leads to resonant behavior at frequencies lower than the conventional Helmholtz resonance. Through exploring an analytical model developed to characterize the resonator, the threshold on material and structural compliance to yield traditional Helmholtz behavior is also illuminated.
Ultra-open acoustic metamaterial silencer
Authors: Ghaffarivardavagh Reza , Nikolajczyk Jacob , Anderson Stephan , Zhang Xin
Published: April 2019

Recently, with advances in acoustic metamaterial science, the possibility of sound attenuation using subwavelength structures, while maintaining permeability to air, has been demonstrated. However, the ongoing challenge addressed herein is the fact that among such air-permeable structures to date, the open areas represents only small fraction of the overall area of the material. In the presented work, in order to address this challenge, we firstly demonstrate that a transversely-placed bilayer medium with large degrees of contrast in the layers' acoustic properties exhibits an asymmetric transmission, similar to the Fano-like interference phenomenon. Next, we utilize this design methodology and propose a deep-subwavelength acoustic metasurface unit cell comprising nearly 60% open area for air passage, while serving as a high-performance selective sound silencer. Finally, the proposed unit cell performance is validated experimentally, demonstrating a reduction in the transmitted acoustic energy of up to 94%. This ultra-open metamaterial (UOM) design, leveraging a Fano-like interference, enables high-performance sound silencing in a design featuring a large degree of open area, which may find utility in applications in which highly efficient, air-permeable sound silencers are required, such as smart sound barriers, fan or engine noise reduction, among others.
Experimental demonstration of an underwater acoustic leaky wave antenna
Authors: Lee Michael , Wiederhold Curtis , Spratt Kyle , Naify Christina J. , Haberman Michael R.
Published: April 2019

Low-power acoustic imaging instrumentation can have a significant impact on underwater exploration and monitoring by enabling longer duration missions. Acoustic leaky wave antennas (LWAs), which consist of a dispersive analogue aperture coupled to a single electro-mechanical transducer, are a promising technological solution to address the demanding requirements of low-power underwater imaging. The dispersive nature of an LWA permits steering an acoustic beam from forward-to-backward directions by simply changing the frequency of the electro-mechanical transducer when used as either an acoustic source or receiver. While acoustic LWAs have been shown to achieve imaging resolution on par with active phased arrays, to date they have only been demonstrated for air-borne acoustic waves. This work presents the first realization of an underwater acoustic LWA using a leaky elastic waveguide consisting of a finite array of locally resonant elastic structures coupled to a single piezoelectric transducer. Finite element analysis was used as a design tool, and preliminary measurements in an underwater testing facility demonstrate forward-to-backward radiated beam scanning of a periodic, heterogeneous aluminum antenna. [Work supported by the Strategic University Research Partnership at NASA-JPL.]
Developmental cascades in reciprocal vocal signaling between infant and caregiver in typical development and autism
Authors: Ramsay Gordon , Ghai Shweta , Kumareswaran Mitra , Edwards Morgan , Bailey Jhonelle
Published: April 2019

Adults habitually adopt a special vocal register when talking to children. Current evidence suggests that the acoustic properties characterizing infant-directed speech change over development, in response to changes in infant vocal behavior, but the factors driving these changes remain largely unknown. The goal of this study is to elucidate developmental progressions in the acoustic structure of infant-directed speech over the first two years of life, and to determine the origin of these changes in infant vocal response. Samples of adult- and infant-directed speech and infant vocalizations were extracted from audio recordings of 10 typically developing infants and 10 infants later diagnosed with autism and their mothers, collected from 0 to 24 months using LENA technology. Multitaper analysis was used to determine the time-varying harmonic structure of each utterance, deriving indices summarizing differences in source and filter properties between infant- and adult-directed speech. In typical development, transitions were found towards the end of the first year of life from baby talk, emphasizing prosodic properties, towards mature child-directed register, emphasizing resonance dynamics. In autism, caregivers persisted in baby talk or shifted into adult-directed register, concurrent with disruptions of vocal contingency, which may be stimulating the transition.
Glazer music performance center at Nazareth College
Authors: Kahn David
Published: April 2019

The new Glazer Music Performance Center at Nazareth College opened to rave reviews in Fall 2018. This project had several unique challenges including budget, schedule and a goal for simultaneous use of a warm-up room that sits within the footprint of the upper volume of the concert hall. The concert hall, while only seating 700, has a performance platform sized for a full symphony orchestra and choir. In order to acoustically accommodate these large ensembles, the room volume was set to 625 000 cubic feet. Since this would have required an unusually and impractically tall space, additional volume was captured above some of the hall’s circulation areas, backstage, and above a few acoustically sensitive warm-up, teaching and practice spaces located behind the backstage area. Substantial sound isolation construction was developed to allow for simultaneous use. A second and related challenge was the project budget of $14M, translating to an average construction cost of $580/SF and included no low-cost spaces. A third challenge was an extremely aggressive project schedule requiring the facility to open in time for their 50th anniversary celebrations. All challenges were overcome thanks to an integrated design process carried out by talented and dedicated design and construction professionals.
The evolution of bat robots
Authors: Müller Rolf , Kuc Roman B. , Sutlive Joseph
Published: April 2019

The extraordinary skills of bats in supporting dexterous mobility in complex environments based on just two pulsed trains of one-dimensional biosonar echoes has attracted attention from engineers for several decades already. To explore whether it is possible to reproduce at least certain of these capabilities, a diverse set of “bat robot” prototypes have been built. The earliest, most basic of these systems were limited to estimating the distance of sonar targets based on the acoustic time-of-flight. From there, systems improved to take advantage of more echo waveform features, e.g., for target recognition. Two (or more) receivers were introduced to exploit binaural differences, e.g., for target tracking. Rigid ear rotations served to enhance the signal-to-noise ratio be focusing on a target or to determine target direction from the echo amplitudes received across a scan. Biomimetic emission and reception baffle shapes, i.e., “noseleaves” and “pinna,” were added to narrow the sonar beams and create direction-depended spectral signatures. Deformations of flexible baffle structures that mimic the muscular actuation of the noseleaf and pinna shapes seen in bats have been added to these systems. Mobility of the entire systems has been provided by mounting them on pan-tilt units, robot arms, mobile robots, and drones.
Acoustic emission system for a bat robot
Authors: Cox Nathan , Sutlive Joseph , Müller Rolf
Published: April 2019

One of the more difficult challenges in producing a biomimetic bat robot is replicating the bats' biosonar emission capabilities. For mimicking horseshoe bats (Rhinolophidae), this means creating a high-power acoustic source that can also properly illuminate the noseleaf structure over a bandwidth of approximately 20 kHz. Computer tomography (CT) scans were used to inform an accurate noseleaf model which was then abstracted from life using three-dimensional mesh software. A waveguide was designed to direct sound from two electrostatic transducers into a small nozzle, creating a point source. Numerical acoustic simulations were used to optimize these waveguide shapes to obtain a good compromise between point source behavior, high output amplitudes, and minimal internal reverberation. Physical geometries were procedurally generated to create a three-dimensional design space with parameters eccentricity, length and convexity. Data from each waveguide were analyzed for volume, multidirectionality, and echoing. A second round of simulations was executed to determine the effect of nozzle width on the output. Findings indicated that waveguide convexity and eccentricity played primarily into echoing and increased length reduced output volume. As nozzle diameter increased, the output volume increased, but sound became unidirectional. Future research may include development of alternative emission systems without a need for waveguides.
Bat-board: An integrated electronic system for a robotic bat
Authors: Mun Lucas , Sutlive Joseph , Müller Rolf
Published: April 2019

The biosonar of horseshoe bats combines the standard elements of any sonar system, i.e., pulse generation and echo processing, with a peripheral dynamics provided by deforming baffle shapes for ultrasonic emission ("noseleaves") and reception (ears). Realizing a “bat robot” to reproduce this biological system requires the implementation of three main electronic functionalities: power distribution, analog signal conditioning, and robot control. To meet the size constraints of the bat robot, the work presented here has designed/implemented a “Bat Board” that integrates all three of these functionalities within a single circuit board. The power distribution component of the Bat Board supplies the high voltage amplifier, the air compressors/valves for the pneumatic actuators in the noseleaf/the ears of the sonar head, and the data acquisition systems. The high voltage signal amplification component was designed to power the electrostatic transducers that were selected for their broad-band output. To combat interferences originating from the power distribution and the digital control signals, different PCB layout paradigms were implemented in the design process such as separating ground planes and the extensive use of bypass capacitors. The result of this efforts has been a single PCB implementation with a very compact footprint and the potential for further miniaturization.
Integrating a brain into a bat robot
Authors: Khyam Mohammad Omar , Alexandre David , Bhardwaj Ananya , Müller Rolf
Published: April 2019

The sophisticated biosonar systems of horseshoe bats have enabled these animals to navigate and pursue prey in complex environments. A conspicuous peripheral dynamics in which the animals' noseleaves and pinnae change during biosonar behaviors could play an important role in enabling these capabilities. It may be hypothesized that for the integration between peripheral dynamics and neural signal processing/estimation to be maximally effective, the periphery should be controlled by feedback from the output of the subsequent neural echo processing. In the way, the specifics of sensory information encoding in the periphery could be controlled based on the needs of the neural signal processing. As a first step towards such an integration in a biomimetic sonar head, a computational model for the inner ear and the auditory nerve's spike code has been integrated with a dynamic periphery that—like the computational models—mimics horseshoe bats. For each model stage, alternative versions with different levels of complexity have been implemented to test how module complexity and the values of the associated parameters affect the capacity of the echo representation to encode sensory information. These effects have been tested based on a large dataset of 220 000 echoes collected in natural forest environments.
Bat biosonar study using spatial audio techniques
Authors: Lee Hyeon , Ming Chen , Roan Michael J. , Simmons James A.
Published: April 2019

Bats have highly specialized hearing adaptations that give them target detection, localization, and interception abilities that far surpass any man-made SONAR. There is a large body of research that has studied and attempted to mimic this remarkable natural sonar system using various methodologies. In many studies, multiple microphones and time difference of arrival were used for bat ultrasonic wave measurements. In this work, a new method using spatial audio techniques is introduced for bat biosonar measurements and analyses. A custom-built tetrahedral soundfield microphone that captures high-frequency sound up to 80 kHz from all directions was developed to acquire bat ultrasonic echoes in Ambisonic B-format. The recorded sound was processed using the HARPEx (High Angular Resolution Planewave Expansion) technique that decodes the 1st order spherical harmonics of the soundfield at the microphone into two plane waves in each time-frequency bin. The use of the soundfield microphone and associated processing provides new tools for analysis of bat echoes from the perspective of the bat. This talk will present details of the hardware and software development along with experimental validation results.
Biomimetic sonar and the problem of finding deterministic targets in foliage
Authors: Sutlive Joseph , Müller Rolf
Published: April 2019

The ability of (bio)sonars to find targets-of-interest is often hampered by a cluttered environment. For example, naval sonars encounter difficulties finding mines partially or fully buried within sand. Such situations pose target identification challenges are much harder than target detection and resolution problems. There are many bat species which navigate and hunt in dense vegetation and thus must be able to identify targets-of-interest within clutter. Evolutionary adaptation of the bat biosonar system is likely to have resulted in the “discovery” of features that support making distinctions between clutter and echoes of interest. The most well-established case is given by cf-fm bats that use Doppler shifts caused by the wingbeat of a flying insect prey to identify the prey in foliage. Other bat species have been shown to use a passive sonar approach that is based on unique prey-generated acoustic signals. Some of the most interesting cases can be found in bat species that are successful in finding preys that apparently does not emit any distinguishing sounds themselves and would hence limit the bats to an active-sonar approach. Such bat species could provide model species for new ways in which the target-identification problem in clutter can be solved with active sonar.
On the phenomenon of natural-frequency splitting of a guitar string caused by a magnetic field
Authors: Feinberg Jack , Yang Bingen
Published: April 2019

A magnet can affect the vibration of the metal strings in a musical instrument. We show that the magnetic field from a magnetic pickup can cause a frequency splitting of a metal guitar string’s normally degenerate transverse vibration modes, leading to a beat note in the resulting sound. The amount of frequency splitting induced by the magnet depends on the product of the induced magnetization in the ferromagnetic string, and the magnet’s spatial gradient at the position of the string, and is on the order of a few Hz. We apply free vibration theory to the string to obtain an eigenvalue problem, which we solve using a distributed-transfer function method. This method accurately predicts the natural frequencies of the vibrating guitar string in a non-uniform magnetic field. Videos of a high-E string vibrating with and without a nearby magnet will be shown.
Differences and similarities of peripheral auditory systems
Authors: Long Glenis R.
Published: April 2019

The properties of the ears of the wide range of species processing auditory signals can vary greatly depending on both important environmental sounds, and the sounds generated by individual members of the species (which are shaped by the sound processing and sound generation systems). Unfortunately, most anatomical and physiological research is conducted on a small subset of mammals and there are many pressures on auditory researchers to limit their research to species that are easy to work with in laboratories which are motivated to explain normal and impaired hearing in humans. Psychoacoustics has played a major role in our understanding of auditory processing in humans, but is difficult and time consuming in nonhuman species. Much of the investigation in nonhuman species is invasive and not appropriate for use with humans. Otoacoustic Emissions (sounds generated by the inner ear and measured in the outer or middle ears) can be used in most species, but we are still investigating the extent to which OAE obtained from different species reflect similar underlying processes. The combination of OAE measurement and computer modelling of the data has made us aware of the importance of evaluation of cross-species and individual differences in auditory processing.
Critical examination of critical bands
Authors: Carney Laurel H.
Published: April 2019

The concept of the critical band has driven the design and interpretation of psychophysical experiments for decades. The critical band was initially proposed by Fletcher [Rev. Mod. Phys. 12, 47 (1940)] to describe results of masking experiments, and it is generally interpreted as evidence for a filter that limits the signal-to-noise ratio in stimulus representations that are provided to the central nervous system. This filter-based interpretation of masked-detection thresholds has been extended and applied to numerous tasks, including many without masking. The concept of a bank of critical-band filters also forms the basis for signal-processing strategies used for hearing aids and cochlear implants. This talk will review both psychophysical and physiological results that challenge the concept of the critical-band filter. For example, the minimal effect of roving-level paradigms on masked-detection thresholds directly refutes the critical-band based power-spectrum model. Furthermore, most auditory neurons have receptive fields that are much broader than critical bands at the moderate to high sound levels used in most psychophysical tasks, with or without masking. Alternative concepts that are robust across a wide range of levels and in roving-level paradigms, such as fluctuation profiles, explain the original masked-detection results and related experiments, such as psychophysical tuning curves.
Accounting for task switching when measuring listening effort: A cautionary tale for the dual-task paradigm
Authors: Lee Adrian K. C.
Published: April 2019

Listening in everyday environments inevitably involves task switching. For example, one might be typing up an abstract while listening to children singing in the background or one might be listening to a radio news program while finding a parking space on a crowded street. While there is an extensive body of research that examines how cognitive control processes support the ability to adjust behavior dynamically, how task-switching impacts listening is less explored. In this talk, different kinds of costs associated with task switching will be reviewed. Specifically, how these well-studied switch costs could impact our interpretations of dual-task paradigm findings—an experimental framework that is often used to interrogate listening effort—will also be discussed. [Work supported by NIH R01 DC013260].
Surface acoustic waves over bianisotropic metasurfaces
Authors: Quan Li , Alù Andrea
Published: April 2019

Metasurfaces are the two-dimensional planarized analogues of metamaterials, yielding unique sound manipulation along a surface. Our group recently proposed the concept of bianisotropic metasurfaces achieved by exploiting the strong nonlocal coupling between neighboring vibrating units, yielding anisotropic impedance in airborne acoustics, and we have applied this property to realize acoustic hyperbolic metasurfaces, which require extreme impedance anisotropy. In this talk, we investigate the wave propagation properties of bianisotropic metasurfaces and report all-angle backward-wave propagation on the surface. By carefully designing the coupling between unit cells, both negative phase index and energy index for surface acoustic waves are observed above the metasurface for all propagation directions, hence realizing converging waves for a radiating point source. Since in bianisotropic metasurfaces the energy can be transmitted not only through surface waves, but also through the coupling units, negative energy index for surface waves does not violate energy conservation laws, as it can be sustained by a positive energy flow within the connected unit cells composing the metasurface.
Acoustic pressure enhancing metamaterials through impedance contrast
Authors: Kwon Hyung-Suk , Popa Bogdan Ioan
Published: April 2019

Acoustic pressure enhancing devices are widely used to extend the range of sensors used for detecting weak and distant sounds. However, conventional sound enhancing devices such as acoustic horns and parabolic reflectors require bulky structures and thus limit miniaturization of sensing systems. To overcome this limitation, metamaterial techniques have been employed and promising results have been reported. However, acoustic pressure enhancing metamaterials reported so far rely on frequency dependent mechanisms to increase acoustic pressure such as resonances or wave compression methods. Therefore, in these approaches, waves are distorted during the enhancement process and this limits their applications considerably. In this presentation, we will show that metamaterials can significantly enhance acoustic waves without wave distortion while keeping the size of the metamaterial subwavelength. Our metamaterial is based on the property of the acoustic waves to increase their acoustic pressure while propagating without insertion loss from a medium of low impedance into a medium of higher impedance. The pressure gain is constant regardless of the frequency, allowing the wave to maintain its shape during enhancement. Here, we will provide the physics of the phenomenon along with numerical and experimental results which were in good agreement with the theoretical prediction.