bluuebunny/crossref_metadata_2025 huggingface dataset:
Audiovisual benefit in the perception of foreign-accented speech by cochlear-implant users
Authors: Waddington Emily , Jaekel Brittany N. , Tinnemore Anna R. , Gordon-Salant Sandra , Goupell Matthew
Published: April 2018

When visual and auditory speech cues are presented together, listeners typically obtain an audiovisual (AV) benefit, or a boost in speech perception accuracy compared to auditory-only (AO) or visual-only (VO) presentations. Visual cues are particularly important for the speech perception of cochlear-implant (CI) users, who show a greater AV benefit than normal-hearing (NH) listeners. However, whether CI users can utilize visual cues for an AV benefit when the speaker has a foreign accent is unknown. Accented speech can alter auditory (primarily temporal) and visual cues, and is significantly more difficult for CI users in AO listening conditions. We investigated the AV benefit in CI users for unaccented and accented speech, presenting IEEE sentences in VO, AO, and AV conditions. The sentences were spoken by one native English speaker and one non-native English speaker who is a native Spanish-speaker from Peru. Preliminary results reveal that CI users show AV benefits in both unaccented and accented conditions, with substantially larger AV benefits for accented speech. Although visual cues alone may be insufficient for speech perception, CI users may necessitate more reliance on visual cues when presented with auditory cues that have been altered in accented speech.
How do differences in voice characteristics affect cochlear implant users’ speech intelligibility in cocktail-party scenarios?
Authors: El Boghdady Nawal , Gaudrain Etienne , Baskent Deniz
Published: April 2018

Speech intelligibility in the presence of multiple competing talkers — the cocktail-party — is quite challenging for cochlear implant (CI) users. Previous literature has indicated abnormalities in CI users’ perception of principal vocal cues (fundamental frequency, F0, and vocal-tract length, VTL), which have been shown to benefit normal hearing (NH) listeners in distinguishing between target and masking speakers in speech-on-speech (SOS) tasks. The hypothesis posited here is that CI users are also expected to benefit from voice differences between target and masking speakers, albeit at a smaller rate compared to NH listeners. Thus, in this study, the benefit in performance in two SOS tasks was measured for both NH (19 participants) and CI users (18 participants) as a function of systematically varying F0 and VTL of the masking talker relative to the target speaker. Results indicate that, contrary to the posited hypothesis and to NH listeners who benefit from differences in F0 and VTL between target and masker, CI users (i) do not benefit from differences in F0, and (ii) demonstrate a slight decrease in performance as the difference in VTL is increased. These data have implications on sound coding strategies that should be developed to address these perceptual deficits in CI users. [Funding: The University Medical Center Groningen (UMCG), Advanced Bionics, Netherlands Organization for Scientific Research (NWO), VICI Grant No. 91817603.]
Developing finer-grained methods for analyzing word recognition performance by individuals with cochlear implants
Authors: Yu Tzu-Ling J. , Rosen Sarah J. , Munson Benjamin , Schlauch Robert S.
Published: April 2018

Cochlear implant (CI) listeners experience overall improvement in speech recognition abilities, but a considerable amount of variability still remains among these individuals. Data from simulated CI listening conditions also show wide variability in monosyllabic word recognition ability. In an adverse simulated condition (2 spectral channels using sinusoidal carriers), the word score can be nearly 0 for some adults with normal hearing. These floor effects pose a challenge for researchers, as they lead to data compression. When analyzing the performance by phonemes, the increase in scores may remove the floor effect. The purpose of this study is to establish the chance performance rate for NU-6 consonant-vowel-consonant (CVC) word lists analyzed by phonemes. To determine this, we randomly paired words from the NU-6 list with CVC words from an on-line corpus of English, the English Lexicon Project, and scored the matches by phonemes using dictionary pronunciations. Thousands of runs of these random pairings were used to generate expected baseline accuracy ranges. These results were compared with individual, behavioral data from people listening to NU-6 words processed using 2-channel sinusoidal vocoders to determine if participants were performing better than chance when scoring by phonemes.
Quality and quantity of infant-directed speech by maternal caregivers predicts later speech-language outcomes in children with cochlear implants
Authors: Dilley Laura , Wieland Elizabeth , Lehet Matthew , Arjmandi Meisam K. , Houston Derek , Bergeson Tonya
Published: April 2018

Caregivers speaking to children often adjust segmental and suprasegmental qualities of their speech relative to adult-directed (AD) speech. The quality and quantity of infant-directed (ID) speech has been shown to support word learning and word segmentation by normal-hearing infants, but the extent to which children with cochlear implants (CIs) benefit linguistically from ID speech is unclear. The present study investigated the extent to which the quantity and quality of ID speech produced in the lab by each of 40 mothers to her child with a CI predicted the child’s speech-language outcome measures at two years post-implantation. Multiple measures of ID and AD speech for each mother were taken, including ID speech quantity in one minute, and several measures of ID speech quality, including fundamental frequency characteristics, speech rate, and the area of the vowel triangle formed by corner vowels in F1-F2 space. Forward stepwise regression showed that both quantity and quality of speech significantly predicted language outcomes measured by the Preschool Language Scales, Peabody Picture Vocabulary Test, and the Reynell Developmental Language Scales. These results support the hypothesis that hearing more ID speech that has acoustic modifications typical of IDS promotes language proficiency in children with CIs.
Robust data-independent object-related transfer function-based beamformer design for remote listening applications
Authors: Barfuss Hendrik , Buerger Michael , Kellermann Walter
Published: April 2018

Virtual reality offers users to experience remote acoustic scenes which are captured in the original environment by a microphone array carried by, e.g., a third person or a robot. To extract and preserve the spatiotemporal nature of specific sounds of interest in the original acoustic environments, data-independent acoustic beamforming appears to be a suitable technique. In this work, we present recent work on robust data-independent beamformer design which is applicable to unconstrained sensor topologies and allows for an intuitive control of the beamformer’s robustness. Combined with the concept of polynomial beamforming, flexible beam steering in real time is possible. Consequently, the beamformer design is well suited for remote listening applications. If the beamformer design is applied to a microphone array, which is integrated into a scatterer, object-related transfer functions (ORTFs) need to be incorporated into the beamformer design. We briefly discuss selected approaches to obtaining the required ORTFs in this work. Finally, we present exemplary results of our robust beamformer design, carried out for a 12-element microphone array integrated into the head of a humanoid robot.
A hybrid real-time auralization system for binaural reproduction of virtual acoustic environments with simulated room acoustics adapted for hearing aid users
Authors: Pausch Florian , Aspöck Lukas , Vorlaender Michael , Fels Janina
Published: April 2018

A recently developed binaural real-time reproduction system has been extended with an interface to research hearing aids allowing for the conduction of auditory research on subjects with hearing loss. Simulated hearing aid signals based on measurements of generic hearing aid-related transfer functions are additionally processed on a master hearing aid to emulate conventional hearing aid algorithms and played back through the hearing aid receivers. Designed for subjects with mild to moderate hearing loss, the system also facilitates the use of residual hearing capabilities by simulating an external sound field based on generic head-related transfer functions which is reproduced via loudspeakers and acoustic crosstalk cancellation filters. For increased ecological validity, plausible room acoustics are simulated using adjusted simulation models relying on geometrical acoustics. The proposed system was evaluated objectively on different levels by investigating the listening environment and various system components, running a benchmark analysis on the acoustical simulation and auralization, and measuring the combined system latency.
High-resolution room virtualization using first-order source-and-receiver-directional room impulse responses
Authors: Zotter Franz , Zagala Franck , Zaunschirm Markus , Frank Matthias
Published: April 2018

Virtual acoustic environments benefit from involving the source and receiver directivity to become fully interactive. In this contribution we discuss virtualization of a room based on measured source-and-receiver-directional room impulse responses (SRD RIR), captured by first-order-directional source and receiver arrays. Low order arrays may in some ways overcome a directional versus temporal resolution trade off one encounters in directional measurements. This is done by employing the spatial decomposition method of room impulse responses on both the first-order source and receiver side. We discuss the result of these resolution-enhanced and efficiently measured SRD RIR based on a comparative listening experiment involving the variable-directivity icosahedral loudspeaker (IKO), a spherical beamforming loudspeaker array, whose perceptual sculptural effects have been studied in a room. For the virtualization of the IKO, high resolution directivity measurement of the IKO are inserted, and for its rendering, a high-resolution set of head related impulse responses (HRIRs).
Perceived stability and localizability in binaural reproduction with sparse HRTF measurement grids
Authors: Ben-Hur Zamir , Alon David L. , Rafaely Boaz , Mehra Ravish
Published: April 2018

With the increased popularity of virtual reality applications, the need for high fidelity spatial audio has emerged. Reproduction of high quality spatial audio requires high resolution individualized head-related transfer functions (HRTFs). However, these are typically unavailable as they demand a large number of measurements and specialized equipment. Given sparse measurements, it is necessary to spatially interpolate the HRTF before employing it in binaural reproduction. Prior studies suggested the use of spherical-harmonics (SH) representation as the basis for the interpolation. However, interpolation of sparse measurements may lead to errors due to spatial aliasing and SH series truncation. In this study, the effects of these errors on the perceived acoustic scene stability and on the localizability of the virtual sound source are investigated numerically, as well as perceptually. Experimental results indicate a significant effect on both attributes due to truncation error, while the effect of the aliasing error is less dominant.
A customizable artificial auditory fovea
Authors: Casebeer Christopher N. , Snider Ross K.
Published: April 2018

Neuroscience shows that auditory neurons extract a variety of specific signal parameters such as frequency, amplitude modulation, frequency modulation, and onsets. Furthermore, biology gives us examples of auditory foveae in bats and owls where there is overrepresentation of behaviorally relevant signal parameters. This shows that biology finds nuances of these parameters to be more important than compact coding considerations such as orthonormal basis functions. In contrast to typical spectrogram approaches where a specific time window is chosen and where the Fast Fourier Transform provides non-overlapping orthogonal rectangular tilings, we start with the smallest tiling possible. The uncertainty principle gives us this tiling as the Gaussian modulated sinusoid. We can rotate this tiling in the time-frequency plane, which gives us a chirplet. We then construct many chirplets (a chirplet set) centered at the same time-frequency point. We then find the chirplet that best matches the signal at this point. Our ability to sample at arbitrary locations in the time-frequency plane with different chirplet sets gives us the ability to create customizable artificial auditory foveae. We use this chirplet front-end for a classification task of identifying Marmoset vocalizations and comparisons to typical spectrogram methods for audio classification are made.
Automatic recognition and immersive representation of environmental soundscapes
Authors: Morgan Mallory M. , Braasch Jonas
Published: April 2018

The goal of this research is to automatically analyze a spatial auditory scene using a 16-channel spherical microphone array and produce an automatic transcript of events that occurred in different directions. The system can be used to establish an automatic protocol for collaborative business meetings or to monitor natural environments. This paper focuses on the automatic data collection of environmental and animal sounds in conjunction with the RPI/IBM Jefferson Project to sensor Lake George, NY. The amount of audio data required for bioacoustics monitoring and other applications is often too large to manually sort the data. Consequently, automatic environmental sound recognition techniques have to be applied to automatically (1) identify and extract relevant acoustic stimuli and (2) classify these stimuli after a training period. Using spatial audio data collected over days in forested areas in Upstate New York, information is automatically extracted and analyzed to find the most relevant parts of these large data sets. The analysis can then be used to create an automated non-linear time-lapse to summarize the events that occurred and meaningfully re-represent them in our immersive virtual environment, CRAIVE-Lab —together with the collected visual material. [Work supported by NSF No. 1631674 and CISL.]
Multiple sound-source localization and identification with a spherical microphone array and lavalier microphone data
Authors: Mathews Jonathan , Braasch Jonas
Published: April 2018

Spherical microphone arrays have attained a considerable amount of interest for their dynamic beamforming and tracking capabilities. Although many robust algorithms have been developed to accurately localize individual sources, multiple source localization, especially for concurrent or colocated sources, has proved to be a challenging topic. This project demonstrates a technique to isolate individual concurrent sources by using lavalier microphone data to determine the relative difference in signal energy between sources. This data is then incorporated into the source-tracking algorithm governing the beamforming spherical array, a particle filter, by allowing the rejection of frames containing concurrent source information. This improves the tracking ability of the system. [Work supported by Rensselaer HASS Fellowship, NSF No. 1631674, and CISL.]
Validating auditory spatial awareness with virtual reality and vice-versa
Authors: Stecker G. Christopher , Carter Steven , Moore Travis M. , Folkerts Monica L.
Published: April 2018

“Immersive” technologies such as virtual (VR) and augmented reality (AR) stand to transform sensory and perceptual science, clinical assessments, and habilitation of spatial awareness. This talk explores some of the general challenges and opportunities for VR- and AR-enabled research, illustrated by specific studies in the area of spatial hearing. In one study, freefield localization and discrimination measures were compared across conditions which used VR to show, hide, or alter the visible locations of loudspeakers from trial to trial. The approach is well suited to understanding potential biases and cuing effects in real-world settings. A second study used headphone presentation to understand contextual effects on the relative weighting of binaural timing and intensity cues. Previous studies have used adjustment and lateralization to “trade” time and level cues in a sound-booth setting, but none have attempted to measure how listeners weight cues in realistic multisensory scenes or in realistic temporal contexts. Finally, a third study used simple VR “games” to measure implicit awareness of reverberation in multi-target scenes. Listeners’ tolerance of reverberant mismatch can be used to assess and habilitate auditory spatial awareness and provides a testbed for future applications of auditory augmented reality.
Designing rehabilitative experiences for virtual, mixed, and augmented reality environments
Authors: Gallun Frederick J. , Seitz Aaron , Vallier Timothy J. , Lewis Dawna
Published: April 2018

It is rapidly becoming possible to conduct nearly all of the diagnostic testing necessary for understanding suprathreshold auditory and visual processing abilities using consumer-grade electronics. It is also the case that all of the psychometric methods used are consistent with a game-based structure, which will encourage engagement and increase reliability of the testing. The obvious next step is to integrate diagnosis and rehabilitation into a single game-based framework, for which virtual, augmented, and mixed reality are an ideal platform. The possibilities include auditory, visual, and memory training and diagnostic games, as well as guided interactions to improve skills in real-life scenarios. Essential to effective design, however, is optimizing interfaces to facilitate universal access. Universal design is essential for rehabilitation because it is necessarily the case that those in need of services cannot be assumed to have optimal auditory, visual, tactile, and balance capabilities. The most exciting challenge for the future will involve designing environments that scale appropriately to engage, challenge, and improve all of the senses and cognitive systems of the participant while being flexible enough to provide engaging experiences for those who can most benefit from the experience.
Use of non-individualized head-related transfer functions to measure spatial release from masking in children with normal hearing
Authors: Peng Z. Ellen , White Ruth , Misurelli Sara , Moua Keng , Kan Alan , Litovsky Ruth
Published: April 2018

Spatial hearing studies with children have typically been conducted using loudspeakers in laboratories. However, loudspeaker arrays are rare in clinics due to high cost and technical set-up requirements. The use of virtual auditory space (VAS) with non-individualized head-related transfer functions (HRTFs) can increase the feasibility of assessing spatial hearing abilities in clinical settings. A novel paradigm for measuring spatial release from masking (SRM) was developed using non-individualized HRTFs. This paradigm measures the minimum angular separation needed between target and masker to achieve a 20% increase in target speech intelligibility. First, the 50% speech reception threshold (SRT) was measured with target and masker co-located to one side. Then, the masker position was adaptively changed to achieve 70.7% intelligibility while maintaining the signal-to-noise ratio at the level of the co-located SRT. To verify the use of non-individualized HRTFs, normal-hearing children were tested (1) using a loudspeaker array and (2) in headphone-based VAS created using KEMAR HRTFs measured in the same setup as (1). Preliminary results showed that co-located SRTs and target-masker angle separation to achieve a 20% SRM were similar in loudspeaker array and in headphone-based VAS. This suggests that non-individualized HRTFs might be used in an SRM task for clinical testing.
Perceptually plausible room acoustics simulation including diffuse reflections
Authors: Buttler Oliver , Wendt Torben , van de Par Steven , Ewert Stephan D.
Published: April 2018

Immersive and convincing acoustics in virtual reality applications require computationally efficient methods. The fast and perceptually plausible room acoustics simulator [RAZR, see Wendt et al., JAES, 62, 11 (2014)] approaches this demand by drastic simplifications with respect to physical accuracy while still accomplishing perceptual plausibility. RAZR is based on a hybrid approach where early reflections are calculated as image sources for a shoebox-room approximation up to a low order, and the later reverberation is generated by a binaurally extended feedback-delay-network (FDN). Although it was demonstrated that a good perceptual agreement with real non-shoebox rooms is achieved, the shoebox-room simplification might cause limitations for rooms which strongly diverge from this assumption. Here the perception of temporal smearing of early diffuse reflections, effectively simulating effects of scattering and multiple reflections caused by geometric disturbances at walls and by objects in the room, was systematically assessed. A single parameter was introduced to quantify deviations from an empty shoebox room. It was demonstrated that perceptually plausible results can be obtained for auralized natural stimuli and for the binaural impulse responses themselves. It is shown how parameters in RAZR are derived from room geometry and surface materials or from measured BRIRs or frequency-dependent reverberation times.
Shallow water propagation of mid-frequency cross-shelf acoustics on the Chukchi Shelf
Authors: Eickmeier Justin , Badiey Mohsen , Turgut Altan
Published: April 2018

The shallow water Canada Basin Acoustic Propagation Experiment (SW CANAPE) was conducted to study the effects of oceanographic variability on broadband acoustic fields in the Arctic. The physics of the acoustic waveguide on the northeastern edge of the Chukchi Shelf are influenced by dynamic boundary conditions and spatio-temporal fluctuations in the water column temperature and salinity profiles. Several oceanographic and acoustic receiving arrays were deployed across the Chukchi Shelf out to the shelf break region. Linear frequency modulated (LFM) signals were transmitted by two sources on the shelf for a long period of time. The influence of small scale, short-term water column variability, and dynamic upper boundary conditions including open water, marginal, and solid ice zones on shallow water propagation is shown for a 10 km source-receiver separation with well-defined water column properties measured at the source, receiver, and a mid-point along the cross-shelf acoustic path. [Work supported by ONR 321OA.]
Properties of the ambient noise field recorded at the 150 m isobath during the 2016–2017 Canadian Basin Acoustic Propagation Experiment
Authors: Sagers Jason D. , Ballard Megan S.
Published: April 2018

The Applied Research Laboratories at the University of Texas at Austin (ARL:UT) deployed two passive acoustic recording systems along the 150 m isobath of the Chukchi Shelf during the 2016–2017 Canadian Basin Acoustic Propagation Experiment (CANAPE). The first system was a single-hydrophone recorder located on the seafloor, while the Persistent Acoustic Observation System (PECOS) contained a horizontal line array of hydrophones along the seabed and a vertical line array spanning a portion of the water column. The systems were deployed and recovered during open-water conditions, but remained in place during the ice-formation, ice-covered, and ice-melt time periods. This talk presents initial findings of the statistical ambient noise levels during the year-long experiment, presents beam-noise levels recorded by PECOS, and qualitatively discusses the natural, biologic, and anthropogenic sounds present in the acoustic recordings. [Work sponsored by ONR.]
Acoustical characteristics and contributions of bubbles released from melting glacier ice
Authors: Zeh Matthew C. , Wilson Preston S. , Lee Kevin M. , Pettit Erin C.
Published: April 2018

Glacierized fjords present a unique acoustic environment that is significantly louder than other ice-covered environments, with average sound pressure levels of 120 dB re 1 μPa with a broad peak between 1 and 3 kHz [Pettit et al., Geophys. Res. Lett. 42, 2309–2316 (2015)]. The energy within this peak is due to the release of bubbles escaping from pressurized air-filled pores within melting glacier ice. These bubbles form during glacier formation via the compression of successive seasonal snow layers. During ice melt, the pressurized air cavities are released, jetting and squirting from the ice and into the surrounding ocean environment [Lee et al., Proc. Meetings Acoust. 20, 070004 (2014)]. In order to more sufficiently characterize this dynamic physical process, acoustic measurements and high-speed video recordings were made using melting glacier ice samples taken from LeConte Glacier in southeastern Alaska. Samples were melted and recorded in a controlled laboratory apparatus as well as at a range of depths at Lake Travis northwest of Austin, TX. Insights gained from these tests are then compared to field recordings taken in LeConte Bay from October 2016 to September 2017. [Work supported by NDSEG Fellowship and ONR.]
Trends in wind, rain, and ships measured from ambient sound in the Bering Sea
Authors: Miksis-Olds Jennifer L. , Nystuen Jeffrey
Published: April 2018

Advances in low-cost passive acoustic technology are providing long term, ambient sound time series from which to better understand the complex interactions between marine life, the environment, and mankind in remote, seasonally ice covered areas such as the Bering Sea. Remotely deployed Passive Acoustic Listeners (PALs) operate according to an adaptive sampling protocol as opposed to recording continuously, thus enabling data collection for a full year at a sampling rate of 100 kHz. Adaptive sub-sampling overcomes hardware and power limitations by reducing the amount of data acquired, while maintaining a high probability of detection and classification of targeted signals. Source contributions to the overall soundscape vary in space and time, and are highly dependent on temporal, geographic, and oceanographic factors. The differences observed in the acoustic record over time and between locations reflect changes in both physical and biological dynamics. This study focused only on the changing patterns of seasonal sea ice dynamics, storm frequency and intensity, and human activity in the acoustic record. As polar conditions continue to change due to reductions in sea ice, warming ocean temperatures, and increases in human use, passive acoustic monitoring will be a valuable tool to identify and track weather dynamics.
The vertical directionality of melt noise from a glacier terminus
Authors: Deane Grant B. , Glowacki Oskar
Published: April 2018

Measurements of the vertical directionality of the sound of bubbles released explosively from a melting glacier terminus are presented. These data are motivated by a desire to infer ice melt rates using the sound generated by bubbles, trapped in the glacier ice at the base of the fern layer and pressurized over time, as they are released by the melting terminus. The free energy available to generate noise is a function of the difference between the bubble internal gas pressure and hydrostatic pressure, both of which can vary with depth beneath the sea surface. Previous studies of bubble gas pressure in glacier ice suggest that the noise generated by bubble release should decrease with increasing depth below the surface. Measurements of noise directionality made with a compact, 4-element hydrophone array approximately 300 m in front of Hansbreen Glacier in Hornsund Fjord, Southwestern Svalbard in the summer of 2017 will be presented and discussed. This study suggests that only the top few 10’s of meters of ice cliff generate the majority of melt noise. This result has important implications for the interpretation of bubble noise in terms of ice melt rate. [Work funded by ONR, Grant No. N00014-17-1-2633 and by the Polish National Science Centre, Grant No. 2013/11/N/ST10/01729.]
Nucleation and stabilization of cavitation nuclei in liquids
Authors: Crum Lawrence A. , Simon Julianna C.
Published: April 2018

The presence of cavitation nuclei are normally required in order to induce cavitation in water-based fluids, as the homogeneous nucleation threshold is beyond the range of most acoustic-pressure generation systems (a notable exception is the “intrinsic threshold” achieved by some histotripsy devices). There are a number of potential models for these nuclei, but one that continues to receive favor is the “crevice model,” in which a pocket of gas is contained in a crack or crevice in a contaminating particle and then stabilized against diffusion by the geometry of the crevice. This presentation will describe this model in some detail, present some (old) data that support the model, and some new data that imply that such activatable nuclei exist in mammalian tissue.
The induction of inertial cavitation from polymeric nanocups—From theory to observation
Authors: Kwan James J. , Lajoinie Guillaume , Stride Eleanor P. , Versluis Michel , Coussios Constantin
Published: April 2018

The inability for therapeutics to distribute throughout the entirety of the tumor is a major challenge in cancer therapy. Acoustic cavitation from microbubbles promotes drug distribution and improves therapeutic efficacy. Yet microbubbles are too large to navigate the microvasculature of the tumor, and are destroyed by the ultrasound wave. Thus, there is a need for submicron cavitation nucleation agents. Recently, we have developed a submicron polymeric nanocup capable of trapping a nanobubble within the surface crevice. Using a modified Rayleigh-Plesset model that accounts for the size and shape of the crevice on the surface of the nanocup, we predicted that the cavity trapped bubble expands and contracts yet remains in the cavity. With a sufficient peak negative pressure amplitude, the model indicated that the surface bubble extends beyond and detaches from the crevice before inertial collapse. To verify our predictions, we exposed nanocups to high intensity focused ultrasound at different driving frequencies and observed bubble nucleation from nanocups using the Brandaris ultra high-speed camera. Acoustic emissions were recorded using a passive cavitation detector. These direct observations of the induction of inertial cavitation from nanocups verified the predictions made by the modified Rayleigh-Plesset crevice model.
Laser nucleation of single bubbles and clouds in an acoustic resonator via pressure-dependent dielectric breakdown
Authors: Holt R. G. , Sukovich Jonathan R. , Anderson Phillip , Sampathkumar Ashwinkumar , Murray Todd W. , Gaitan D. F.
Published: April 2018

Obtaining bubbles on demand at precise times and locations in a non-contact fashion can be useful in a variety of applications. Of special importance is the combination of laser nucleation with acoustics, so that bubbles are only just nucleated by the optics but grown to macroscopic size solely by the acoustics. We present theory and experiment for the non-thermal laser nucleation of bubbles in an acoustic field in the absence of significant absorbing/scattering particles. First we present theory and experiment for the threshold for dielectric breakdown in water, resolving the distinct minimum at 20 bar. Then, we present a method and results for nucleating single and multiple bubbles with temporal uncertainty of 5 ns, and spatial uncertainty of 1 mm. Results for bubble number and first cycle expansion are reported as functions of the timing of the nucleating laser pulse with respect to the acoustic field. [Work supported by Impulse Devices, Inc.]
Micro-cavitation on demand via the nanoparticle mediated interaction of light and sound
Authors: Roy Ronald , Farny Caleb H. , Wu Tianming , Holt R. G. , Murray Todd W.
Published: April 2018

The safe utilization of controlled cavitation for HIFU therapy and ultrasound assisted drug delivery requires nucleation sites for bubble formation. We consider the potential for nucleating transient vapor cavities using laser-illuminated gold nanoparticles combined with high-intensity focused ultrasound. An transparent polyacrylamide gel phantom was seeded with 82-nm diameter gold particles and exposed to 20 ns pulses from a 532 nm Nd:Yag laser. Laser firing was synchronized with the arrival of a burst of 1.1 MHz focused ultrasound. Acoustic emissions from ensuing inertial cavitation were detected passively using a 15 MHz focused transducer. At a laser energy of 0.10 mJ/pulse, the resulting inertial cavitation nucleation threshold pressure (peak-negative focal pressure) was as low as 0.92 MPa. In comparison, a peak-negative focal pressure of 4.50 MPa was required to nucleate detectable cavitation without laser illumination (nano-particles were present in both cases). Experimental results agree well with a simple model for transient heating and cavity formation. Since the particles are durable, one can re-activate them as needed, essentially yielding cavitation nuclei “on demand.” [Work supported by the Dept. of the Army (Award No. DAMD17-02-2-0014) and the Center for Subsurface Sensing and Imaging Systems (NSF ERC Award No. EEC-9986821).]
Use of interactive simulations in pre-class learning activities
Authors: Neilsen Tracianne B.
Published: April 2018

To facilitate an effective in-class discussion, students must engage with the material prior to class. Assigned textbook reading is the traditional way students are asked to prepare, with possibly a reading quiz due before class. While carefully designed reading quizzes can be effective, a different approach is to use unscripted pre-class learning activities that provide hands-on interaction with the material. I created pre-class learning activities for the “Descriptive Acoustics” class at Brigham young University that use interactive simulations available on the internet. Provided with basic instructions, the students explore the simulation and write a description of their experience using terminology from the corresponding textbook chapter. Exploration followed by writing, even if incorrect, has increased the level of student understanding and provides a natural way to have students participate in class as they describe their experiences. The pre-class exposure to the interactive simulations also increases the efficacy of using the simulations during class, as each student is familiar with the interface and thus can better follow the in-class demonstration. Interactive simulations are a powerful active-learning tool for the current generation of students but only if they have had personal experience with the simulation prior to seeing it in class.
Using interactive simulations to build understanding and promote scientific inquiry
Authors: Piacsek Andrew A.
Published: April 2018

Computer simulations of physical phenomena, with graphical output, have long been used to enable visualizations of processes that are inherently invisible, such as sound wave propagation, or that operate on time scales that make direct observation difficult. For students struggling to make sense of an abstract physical concept, such as the relationship between the propagation of a mechanical wave and the associated motion of the medium, an animated simulation of wave motion can accelerate the “aha!” moment of understanding. But to solidify and build on that understanding, students need to be able to formulate and test predictions. This can be accomplished with an interactive simulation, in which the user can adjust certain parameters of the model and view the response in the solution immediately. In this way, students can conduct virtual experiments. This presentation will use three examples of interactive simulations to demonstrate how interactive simulations can be used in a structured way to support specific learning objectives related to acoustics, and how they can be used to foster independent learning and scientific inquiry. Two examples come from a general education course in musical acoustics; the third example has been used in an advanced undergraduate/first-year graduate course in acoustics.
Simulations in acoustics and vibration education: What is the appropriate ratio of “learning to make” and “learning to use” for undergraduate students?
Authors: Wilson Preston S.
Published: April 2018

Within most undergraduate engineering curricula in the US, there is room for perhaps one or two acoustics and vibrations-related courses, which are generally offered as technical electives rather than as required classes. Numerical computation is also taught in one or two (typically required) courses. Yet, in the current environment, very powerful commercial simulation packages are available that can be used to solve complex real-world problems. Since there is no room in the current curriculum to teach both aspects fully, this begs the question, “What is the most appropriate mix of teaching?” Should one focus on the fundamentals, such that students learn the basics of various solution methods, but suffer limited exposure to the solution of real-world applications, or should one focus on the use of specific software packages that can solve real-world problems? These issues are explored and various examples are presented in hopes to further discussion of this topic in the community.
Using animations to better understand acoustic impedance
Authors: Anderson Brian E.
Published: April 2018

It is very common for students to struggle to grasp a conceptual understanding of acoustic radiation impedance and input impedance. Often graduate students need exposure to impedance concepts in more than one course before they start to understand its importance and meaning. Instructors commonly suggest that impedance can be thought of as a resistance, ignoring the imaginary part of the impedance (the reactance), and the word “sloshing” is sometimes used to describe what the radiation reactance represents. This presentation will show some animations that have been developed in MATLAB to help students visualize the motion of the air particles near a vibrating surface. These animations utilize the relevant physical equations to observe the ratio of the pressure to the particle velocity. While these animations are not directly interactive, the user can change things like the frequency, source size, and excitation amplitude and recreate a new animation. Thinking of the impedance as the ratio of a potential quantity to a flow quantity can often be helpful, with this ratio having an in phase component and a component where the two quantities are 90 degree phase shifted.
Numerical simulation and use of the PICUP framework for use in an undergraduate acoustics course
Authors: Morrison Andrew C.
Published: April 2018

The use of numerical simulations in an undergraduate course introductory acoustics course can be a way to provide students with a method of exploring concepts that are difficult or costly to replicate in a classroom. For a course taught that serves a diverse group of students studying a large variety of majors, the importance of having multiple ways to present and revisit concepts should not be underestimated. Several simulations have been developed using Glowscript for use in a general education acoustics course. Additionally, the PICUP framework for development of exercise sets has been used to structure classroom activities in a way that encourages scaffolding of concepts from the most basic ideas to more complex applications. Examples of the Glowscript simulations and the development of PICUP exercises will be demonstrated.
Combining interactive simulation with scaffolded visualization in ESAIL to teach fundamental concepts of acoustical oceanography
Authors: Summers Jason E. , Ross Mark A. , Walker Zachary , Longerbeam Paul , Redmond Daniel
Published: April 2018

To understand and interpret active-sonar returns and effectively employ active sonar systems for purposes such as antisubmarine warfare (ASW), operators must understand fundamental concepts of acoustical oceanography that govern how sonar interacts with the environment. Experts achieve high levels of performance in analysis and employment not by solving acoustic-propagation equations, but rather by employing simplified mental models that characterize the functional relationships governing how the environment affects acoustic propagation. Thus, a key goal in educating operators is helping them to develop and use such mental models. Here, we describe the development and employment of ESAIL, the Environment for Surface ASW Interactive Learning, a learning platform that combines interactive simulation with scaffolded visualization to facilitate instructors and students in conducting and assessing the outcome of “what if…?” experiments. In ESAIL, users are scaffolded in performing “what if…?” experimentation by tools that automatically classify user-modified acoustical environments as well as predictive acoustical models. This capability for direct exploration of cause-and-effect relationships with scaffolding to help develop expectations facilitates operators actively learning the mental models and mental-simulation capabilities experts use to interpret displays and reason about the underlying tactical scenario to achieve more optimal employment. [Work supported by the Naval Sea Systems Command.]
The relation between choir size and choir dynamics
Authors: Titze Ingo R. , Maxfield Lynn M.
Published: April 2018

If six distinct levels of choir dynamics ( pp p mp mf f ff ) are to be achieved over two octaves of fundamental frequency in a choir section, how distinct are these levels? The just noticeable difference for sound level in a free field environment is 1-2 dB, while a doubling of loudness requires a 10 phon increase (10 dB SL increase at 1000 Hz). Most singers cannot double their vocal loudness 5 times. Generally the dynamic levels are 3–6 dB apart, depending on the individual voice range profiles of the singers. Overall choir size has no effect on dynamic range, unless the size is varied dynamically by not all singers singing all the time. A few loud voices dominate ff if everyone sings. To achieve an effective choir pp, only a few voices who can sustain very soft notes should sing. The dynamic range can be significantly limited when choral blend for loudness is imposed on a non-homogeneous group of singers.
Choir spacing vs choir formation: Long-term average spectra comparisons
Authors: Daugherty James F.
Published: April 2018

Choral methods books have long advised that repositioning choir singers solely according to voice part sung (i.e., choir formation) alters choral sound quality. To date, acoustical studies of choir formation have found no significant mean differences in long-term average spectra (LTAS) attributable to this strategy. Other investigations have indicated that changing the spatial distance between choir singers (i.e., choir spacing) yields significant LTAS differences. As yet, however, no study has compared the LTAS of choir spacing and choir formation conditions using the same choir. This paper reports experiments comparing LTAS of performances acquired from two microphone positions (conductor position, audience position) by three choirs of varied voicing (TTBB, SSAA, and SATB) singing in contrasting inter-singer spacing conditions (close, lateral, circumambient, and uneven) and voice-part formations (block sectional, mixed). Although recording venues and sung literature varied, each of the three choirs exhibited a pattern of significant mean timbral differences according to singer spacing conditions, but not according to formation conditions. Results were discussed in terms of the logics informing the spacing and formation approaches to modifying choir sound and implications for choral practice.
The barbershop sound: The characteristic timbre of the male barbershop quartet
Authors: Drown Colin , Cottingham James P.
Published: April 2018

A feature of the homophonic barbershop style is an emphasis on major and dominant seventh chords which are sung with little vibrato and with pitches adjusted to achieve tuned chords in just intonation. A principal resource for the investigation reported here was the library of online recordings of the 2016 and 2017 international competitions sponsored by the Barbershop Harmony Society. These recordings provide a wealth of examples of the barbershop sound. They include hundreds of quartet samples performed in a context that features a uniform expectation of what constitutes good sound, along with uniform recording conditions and ranking by judges who serve as expert listeners. A large number of spectra were obtained for a loud, sustained major chord on an open vowel. Tuning of these chords was investigated, and for each sample a spectral contour was constructed with amplitudes normalized to simplify comparisons. From the consistency of these spectral contours it is possible to obtain a picture of the timbral features that distinguish the barbershop sound. In addition, patterns of relatively small differences in spectral envelope among the samples are strongly correlated with the ranking of the quartets by the competition judges.
Acoustic vortex beam created with a continuous phase ramp lens and resulting radiation torque response of a sphere
Authors: Fortuner Auberry R. , Daniel Timothy D. , Marston Philip L.
Published: April 2018

An acoustic vortex beam was created in water using a lens with a phase ramp placed in front of a focused transducer. The lens was made from a polystyrene disk and CAD machine milled to have a continuous ramp in height about the center axis, with the ramp step height corresponding to a 2π phase difference between waves propagating in water and polystyrene at 500 kHz. This causes the transmitted beam through the lens to exit as a vortex beam with an angular phase ramp. It has been predicted [L. Zhang and P. L. Marston, J. Acoust. Soc. Am. 136, 2917–2921 (2014)] that the torque exerted by a vortex beam on an impenetrable sphere in a viscous fluid is proportional to the incident intensity due to dissipation of angular momentum in the viscous boundary layer near the sphere. This should result in steady rotation of the sphere with viscous drag proportional to angular velocity. Our upward-directed vortex beam was used to trap and spin a Styrofoam (closed foam) ball floating at the water surface. The spin rate was approximately proportional to the square of the source voltage as expected. [Work supported by ONR.]
Qualitative analysis of mode transitions in bottle-shaped resonators with waterfall plots
Authors: Andersen Bonnie , Eldred David , Dimond Josh
Published: April 2018

A closed bottle-shaped resonator consists of the coupled neck and cavity. Such a system yields avoided crossings where the resonance of the neck matches that of the cavity when one bottle dimension is varied. Self-sustained oscillations within the bottle are generated thermoacoustically. Mode transitions were previously observed to occur at the same position within a few millimeters when a piston controlled with a translation stage was moved with a manual control to adjust the cavity length. The dominant mode was recorded using a power spectrum of the signal measured with a pressure sensor. In this study, the piston motion is automated and eight neck/cavity combinations were tested at three different piston speeds and at various input powers. The input powers were adjusted to just above thermoacoustic onset and not to exceed thermal limits of the materials used. Waterfall plots allow the visualization of the time evolution of the power spectrum where intensity is plotted both as a function of time and frequency. Qualitatively, the transitions occur at the same place within the cavity after a threshold input power is reached. Interestingly, overtones appear in most cases to be harmonics of the fundamental with either all or only odd harmonics present.