bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting range-frequency interference patterns from broadband sources in a range-dependent, continental shelf environment
Authors: Sell Alexander W. , Culver R. Lee
Published: May 2014

The 2007 CALOPS dataset contains horizontal line array received signals from numerous surface vessels transiting an area off the coast of southeast Florida. Parabolic equation propagation models using measured bathymetric, sound velocity profile, and sediment parameter data suggest that substantial mode coupling should be occurring for several down-slope propagation scenarios in the dataset. However, received acoustical data for these scenarios, in the form of range-frequency interference patterns, are best described by adiabatic propagation. This discrepancy has implications that affect waveguide invariant parameter estimation, which is necessary for invariant-based passive ranging. The causes of the incongruous model output will be discussed, as well as their effects on estimating waveguide invariant distributions for these scenarios. [This research was supported by the Applied Research Laboratory, at the Pennsylvania State University through the Eric Walker Graduate Assistantship Program.]
Fluctuations of arrival time and frequency shifts of a wideband sound signal in the presence of coastal internal Kelvin waves in shallow water
Authors: Katsnelson Boris , Lunkov Andrey
Published: May 2014

Internal Kelvin waves (IKWs) in a near shore area of shallow water with a curvilinear coastal line (gulf, lake, and channel) where the radius of curvature can be about 5–30 km are considered as a reason for the sound field variability. Amplitude of the thermocline vertical displacement due to IKW in such an area changes along the distance from the center of this circle (minimal value, about null) to the coast (maximal value, up to 5 m). Numerical simulations are implemented to study the effect of IKWs on the propagation of acoustic waves generated by a wideband (0.7 to 1 kHz) sound source. The results of the simulations show that the signal propagation time changes up to 1% following the thermocline displacement caused by IKW. Also, considerable shifts (more than 30% of the central frequency) of the interference pattern in the frequency domain are observed. The shifts change with distance from the shore and have opposite directions for positions of a single hydrophone receiver above or below the thermocline. Analytical estimates are obtained; experimental setup and a possible scheme of monitoring IKW are discussed. [Work was supported by RFBR and BSF.]
Speculations on the cause of finite density and sound speed gradients near the interface of muddy sediments
Authors: Pierce Allan D. , Siegmann William L. , Fayton Joseph O.
Published: May 2014

Holland et al. [JASA (2013)] at the previous ASA meeting reported positive density gradients and negative sound speed gradients at the water-mud sediment interface and asked “what processes drive them.” A derivation using the Mallock-Wood relations yields a simple high-porosity approximate relation giving a negative proportionality between sound speed gradient and density gradient independent of depth and porosity. It is also argued that the solid portion of the mud consists of tiny mineral platelets, each of which carries a net negative charge. The presence of dissolved salts causes each platelet to behave as an electrical quadrupole, so that there is, on the average, a small electrical repulsive force between the platelets. With gravity taken into account, the equilibrium separation distance between two parallel vertically aligned platelets is one to two orders of magnitude greater than a typical length scale of the face of a platelet. However, when platelets touch, edge to face, there is an attractive force between platelets, and the net effect is that the platelets tend to be separated at a much shorter distance than the stand-off distance deep within the sediment. Paper reports ongoing efforts to estimate the depth over which the transition occurs.
Is there any acoustical reason that supports non-rectangular concert hall design?
Authors: Lokki Tapio
Published: May 2014

The debate between shoe-box and non-shoe-box concert halls has been around for several decades. From the total concert experience point-of-view, there seems to be pros and cons for both designs. However, when only the acoustics of a hall are considered, the shoe-box design is very often preferred. This presentation discusses the basic differences between these two hall types, and how they affect, e.g., perceived bass, envelopment, clarity, intimacy, and loudness. The presentation is supported by recent data that was gathered in a large listening test during winter 2014. Typical sensory profiles of these two hall types are presented with links to listening test subjects' preferences. Moreover, the presentation will explain why shoe-box halls render larger dynamic range than other halls do. Even though room acoustics, defined with an impulse response, is linear, non-linear dynamic differences exist between halls due to the non-linear excitation (an orchestra) and non-linear human spatial hearing.
Analysis of strongly nonlinear blast waves using the Rankine-Hugoniot relations and the nonlinear ray theory
Authors: Lee Jae-Wan , Ohm Won-Suk , Shim Woosup
Published: May 2014

Blast waves produced by such events as nuclear explosions can be considered as strongly-nonlinear shock waves, the description of which requires a theoretical framework more accurate than the second-order wave equation. In this regard, computational fluid dynamics (CFD) techniques based on the Euler equation are frequently used. However, CFD techniques are very time-consuming for blast waves traveling over great distances. This paper presents a theoretical framework for propagation of strongly nonlinear blast waves, which shines in both speed and accuracy. Local propagation speeds of a blast wave are obtained by applying the Rankine-Hugoniot relations to “infinitesimal shocks” between adjacent phase points comprising the blast wave. By grafting the propagation speed onto the nonlinear ray theory, the evolution of the blast wave can be computed. Phenomena characteristic of strongly-nonlinear blast waves such as the Mach reflection, the Mach stem generation, and the self-refraction are observed from numerical simulations.
Perceptual acuity and production distinctness in child speech: Data from American English /r/
Authors: McAllister Byun Tara , Tiede Mark
Published: May 2014

Previous work has shown that some adult listeners have more sharply defined perceptual categories than others, and listeners who have the most precise auditory targets also tend to produce more robust contrasts (e.g., Newman, 2003; Perkell et al., 2004; Ghosh et al., 2010). While it is likely that this relationship also holds in child/adolescent speakers, the hypothesis has not been directly tested. This study compared perception and production of the English /r-w/ contrast in 20 typically developing children aged 9–14. Two 10-step rake-wake continua were synthesized using rake tokens elicited from two child speakers (8-year-old male, 10-year-old female). Items were presented 8 times each in random order in a forced-choice identification task. Participants also produced rake and wake in a carrier phrase in casual and careful speech. Perceptual sensitivity was evaluated with a logistic function fitted over the number of wake responses at each step in the continuum. Preliminary results show considerable across-participant variation in the slope of the best-fit logistic function, the location of the perceptual boundary, and the acoustic distinctness of /r-w/ in production. We expect to demonstrate a relationship between perceptual acuity and production distinctness similar to that seen in adults. [Work supported by NIH.]
Meeting “green” acoustical requirements in flexible classrooms
Authors: Su Rose Mary , Markham Benjamin
Published: May 2014

Acoustical design in classrooms has evolved significantly since the ANSI S12.60-2002 standard was first established. Since then, institutions such as Leadership in Energy & Environmental Design (LEED) and the Collaborative for High Performance Schools (CHPS) have adopted aspects of the ANSI standard for school projects. Simultaneously, architects are creating increasingly flexible classroom designs. The push for a more flexible learning space sometimes clashes with acoustical design requirements stipulated by LEED and CHPS. This paper will discuss some of the acoustic design challenges of creating flexible, 21st century learning spaces while at the same time meeting the acoustic requirements driven by LEED and CHPS compliance. Discussion will include movable partitions in a learning space that work, sound absorptive finishes implemented beyond the standard suspended acoustical ceiling, and non-conventional mechanical systems in classroom settings. Some case studies will illustrate the discussion.
Consideration of acoustics in leadership in energy and environmental design (LEED) version 4
Authors: LoVerde John J. , Rawlings Samantha , Dong David W.
Published: May 2014

Acoustical criteria have been added to the LEED rating systems with each new revision, beginning with Schools and Healthcare. With the recent Version 4 update, an acoustical credit has been added for the majority of New Construction LEED rating systems. There are weaknesses in the acoustical LEED credits, including imbalance between cost and benefit, mitigation beyond industry standards, and implementation of requirements within non-sensitive areas. This paper reviews the purpose of acoustics within a sustainable design system, identifies areas where the current language hits the mark or should be revised, and adds areas for future consideration of acoustical design within a sustainable design rating system.
Estimates of the bottom reflection coefficient involving vector sensor
Authors: Choi Jee Woong , Dall’Osto David R. , Dahl Peter H.
Published: May 2014

Estimates of the bottom reflection coefficient made in the frequency range of 4–8 kHz, as part of the Targets Reverberation Experiment (TREX) are presented. The TREX experiment took place in the Gulf of Mexico, near Panama City, FL, in waters 20 m deep. At the measurement site the sediments are loosely classified as fine sand. The reflection coefficient R is estimated over the nominal grazing angular range 1 to 20 deg., using measurements made at ranges 50 to 800 m and received on a vertical line array (length 1.6 m). The arrival time and magnitude of the bottom reflection is determined by the matched filtered output of a frequency modulated signal, 4–8 kHz. In addition, the match filter processing technique is applied to the vector sensor data (measured simultaneously and co-located with the line array.) This allows for an extraction of the active intensity contribution associated with the bottom reflection, and provides a vector intensity-based estimate of the bottom reflection coefficient. The estimates of the bottom reflection arrival time are also used to time-gate simultaneously transmitted cw tones (1–4 kHz) to analyze the Lloyd’s mirror pattern associated with seabed reflection. [Research supported by ONR, with partial support from ONRG.]
Modeling the acoustic vector field to simulate glider-based acoustic processing methods
Authors: Dossot Georges , Smith Kevin B. , Sullivan Edmund J.
Published: May 2014

The feasibility of underwater gliders as passive acoustic receiving platforms is explored through simulated data. Over the last decade gliders have proven their worth as operational platforms to the oceanographic community, yet their merits as acoustic sensing platforms remain largely under-explored. Recently, the Office of Naval Research has equipped the Naval Postgraduate School with several gliders, which have now been fitted with acoustic vector sensors. To simulate real-world performance, the intensity vector field is modeled using the three-dimensional Cartesian version of the Monterey-Miami parabolic equation (MMPE) algorithm, which relies upon a split-step Fourier approach. Environmental information representative of the glider’s sawtooth profile is incorporated as a three-dimensional sound speed profile, and incorporated into the PE model. These simulated data serve as the basis for signal processing techniques applicable to glider-based experimentation.
Introduction to “Psychoacoustics in Rooms,” and tutorial on architectural acoustics for psychoacousticians
Authors: Robinson Philip W.
Published: May 2014

This special session—“Psychoacoustics in Rooms”—was born from the observation that psychoacoustics and room acoustics are often highly interleaved topics. Those researching the former attempt to determine how the hearing system processes sound, including sound from within specific environmental conditions. Practitioners of the latter aim to produce architectural enclosures catered to the auditory system's needs, to create the best listening experience. However, these two groups do not necessarily utilize a common vocabulary or research approach. This session, a continuation of one with the same name held at Acoustics 2012 Hong Kong, is intended to appeal to both types of researchers and bring them towards a common understanding. As such, the first two presentations are basic surveys of each paradigm. This presentation will focus on common architectural acoustic methods that may be of interest or utility to psychoacousticians.
Model of binaural speech intelligibility in rooms
Authors: Brand Thomas , Warzybok Anna , Rennies Jan , Kollmeier Birger
Published: May 2014

Many models of speech intelligibility in rooms are based on monaural measures. However, the effect of binaural unmasking improves speech intelligibility substantially. The binaural speech intelligibility model (BSIM) uses multi-frequency-band equalization-cancellation (EC), which models human binaural noise reduction, and the Speech-Intelligibility-Index (SII), which calculates the resulting speech intelligibility. The model analyzes the signal-to-noise ratios at the left and the right ear (modeling better-ear-listening) and the interaural cross correlation of target speech and binaural interferer(s). The effect of the hearing threshold is modeled by assuming two uncorrelated threshold simulation noises for both ears. BSIM describes the (binaural) aspects of useful and detrimental room reflections, reverb, and background noise. Especially the interaction of delay time and direction of speech reflections with binaural unmasking in different acoustical situations was modeled successfully. BSIM can use either the binaural room impulse responses of speech and interferers together with their frequency spectra or binaural recordings of speech and noise. A short-term version of BSIM can be applied to modulated maskers and predicts the consequence of dip listening. Aspects of informational masking are not taken into account yet. To model different degrees of informational masking. the SII threshold has to be re-calibrated.
Evaluation of sub-micron, ultrasound-responsive particles as a drug delivery strategy
Authors: Myers Rachel , Graham Susan , Kwan James , Shah Apurva , Mo Steven , Carlisle Robert
Published: May 2014

Substantial portions of tumors are largely inaccessible to drugs due to their irregular vasculature and high intratumoral pressure. The enhanced permeability and retention effect causes drug carriers within the size range of 100–800 nm to passively accumulate within tumors; however, they remain localized close to the vasculature. Failure to penetrate into and throughout the tumor ultimately limits treatment efficacy. Ultrasound-induced cavitation events have been cited as a method of stimulating greater drug penetration. At present, this targeting strategy is limited by the difference in size between the nano-scale drug carriers used and the cavitation nuclei available, i.e., the micron-scale contrast agent SonoVue. In vivo this results in spatial separation of the two agents, limiting the capacity for one to impact upon the other. Our group has successfully formulated two different monodisperse suspensions of nanoparticles that are of a size that will permit better co-localization of cavitation nuclei and therapeutics. A mixture of these nanoparticles and a model drug carrier were passed through a tissue mimicking phantom to provide an in vitro simulation of flow through a tumor. The impact of ultrasound on the penetration of drug carrier from the flow channel was compared between both of our ultrasound-responsive particles and SonoVue.
Spectrum analysis of photoacoustic signals for characterizing lymph nodes
Authors: Chitnis Parag V. , Mamou Jonathan , Feleppa Ernest J.
Published: May 2014

Quantitative-ultrasound (QUS) estimates obtained from spectrum analysis of pulse-echo data are sensitive to tissue microstructure. We investigated the feasibility of obtaining quantitative photoacoustic (QPA) estimates for simultaneously providing sensitivity to microstructure and optical specificity, which could more robustly differentiate among tissue constituents. Experiments were conducted using four, gel-based phantoms (1 × 1 × 2 cm) containing black polyethylene spheres (1E5 particles/ml) that had nominal mean diameters of 23.5, 29.5, 42, or 58 μm. A pulsed, 532-nm laser excited the photoacoustic (PA) response. A 33-MHz transducer was raster scanned over the phantoms to acquire 3D PA data. PA signals were processed using rectangular-cuboidal regions-of-interests to yield three quantitative QPA estimates associated with tissue microstructure: spectral slope (SS), spectral intercept (SI), and effective-absorber size (EAS). SS and SI were computed using a linear-regression approximation to the normalized spectrum. EAS was computed by fitting the normalized spectrum to the multi-sphere analytical solution. The SS decreased and the SI increased with an increase in particle size. While EAS also was correlated with particle size, particle aggregation resulted in EAS estimates that were greater than the nominal particle size. Results indicated that QPA estimates potentially can be used for tissue classification. [Work supported by NIH grant EB015856.]
Parametric assessment of acoustic output from laser-irradiated nanoparticle volumes
Authors: Gray Michael D. , Sengupta Aritra , Prausnitz Mark R.
Published: May 2014

A photoacoustic technique is being investigated for application to intracellular drug delivery. Previous work [Chakravarty et al., Nat. Nanotechnol. 5, 607–611 (2010)] has shown that cells immersed in nanoparticle-laden fluid underwent transient permeabilization when exposed to pulsed laser light. It was hypothesized that the stresses leading to cell membrane permeabilization were generated by impulsive pressures resulting from rapid nanoparticle thermal expansion. To assist in the study of the drug delivery technique, for which high uptake and viability rates have been demonstrated, an experimental method was developed for parametric assessment of photoacoustic output in the absence of field-perturbing elastic boundaries. This paper presents calibrated acoustic pressures from laser-irradiated streams, showing the impact of parameters including particle type, host liquid, and spatial distribution of laser energy.
Acoustical level measuring device
Authors: Cameron Robert H.
Published: May 2014

This abstract is for a poster session to describe a patent application made to the patent office in November 2012. The patent describes a system and method for determining the level of a substance in a container, based on measurement of resonance from an acoustic circuit that includes unfilled space within the container that changes size as substance is added or removed from the container. In particular, one application of this device is to measure the unfilled space in the fuel tanks of vehicles such as cars and trucks. For over 100 years, this measurement has been done by a simple float mechanism but, because of the development of tank design for vehicles that involve irregular shapes this method is increasingly less accurate. The proposed device will overcome these limitations and should provide a much more accurate reading of the unfilled space, and therefore, the amount of fuel in the tank since the total volume of the tank is known.
The cyber-physical system approach for automatic music accompaniment in Antescofo
Authors: Cont Arshia , Echeveste José , Giavitto Jean-Louis
Published: May 2014

A system capable of undertaking automatic musical accompaniment with human musicians should be minimally able to undertake real-time listening of incoming music signals from human musicians, and synchronize its own actions in real-time with that of musicians according to a music score. To this, one must also add the following requirements to assure correctness: Fault-tolerance to human or machine listening errors, and best-effort (in contrast to optimal) strategies for synchronizing heterogeneous flows of information. Our approach in Antescofo consists of a tight coupling of real-time Machine Listening and Reactive and Timed-Synchronous systems. The machine listening in Antescofo is in charge of encoding the dynamics of the outside environment (i.e., musicians) in terms of incoming events, tempo and other parameters from incoming polyphonic audio signal; whereas the synchronous timed and reactive component is in charge of assuring correctness of generated accompaniment. The novelty in Antescofo approach lies in its focus on Time as a semantic property tied to correctness rather than a performance metric. Creating automatic accompaniment out of symbolic (MIDI) or audio data follows the same procedure, with explicit attributes for synchronization and fault-tolerance strategies in the language that might vary between different styles of music. In this sense, Antescofo is a cyber-physical system featuring a tight integration of, and coordination between heterogeneous systems including human musicians in the loop of computing.
Interactive conducting systems overview and assessment
Authors: Nakra Teresa M.
Published: May 2014

“Interactive Conducting” might be defined as the accompaniment of free gestures with sound—frequently, but not necessarily, the sounds of an orchestra. Such systems have been in development for many decades now, beginning with Max Mathews’ “Daton” interface and “Conductor” program, evolving to more recent video games and amusement park experiences. The author will review historical developments in this area and present several of her own recent interactive conducting projects, including museum exhibits, simulation/training systems for music students, and data collection/analysis methods for the study of professional musical behavior and response. A framework for assessing and evaluating effective characteristics of these systems will be proposed, focusing on the reactions and experiences of users/subjects and audiences.
Reverberation time in ordinary rooms of typical residences in Southern Brazil
Authors: Klein Michael Ã. , Panosso Andriele da Silva , Paul Stephan
Published: May 2014

In order to develop a subjective evaluation to assess the annoyance related to impact noise, it is necessary to record samples of sounds in an impact chamber that is acoustically representative for ordinary rooms, especially with respect to reverberation time. To define the target reverberation time measurements were carried out in 30 typical residences in Southern Brazil. This study presents the characteristic reverberation times of 30 furnished living rooms and 30 furnished bedrooms in buildings and houses with an average age of 34 years, 40% of them with wooden floor coverings, not as usual in modern constructions. The median T30 at 1 kHz for living rooms with an average volume of 63.60m³ (std dev: 18.27m³) was 0.68 s (std dev: 0.14 s), thus higher than the reference TR = 0.5 s according to EN ISO 140 parts 4, 5, and 7. The median T30 at 1 kHz for bedrooms with average volume of 33.76m³ (std dev: 8.38m³ ) was 0.49 s (std dev: 0.13 s), nearly exact the reference TR according to EN ISO 140 parts 4, 5, and 7. Data will also be compared to studies from other countries.
Response of a channel in a semi-infinite stratified medium
Authors: Bhatta Ambika , Zhou Hui , Nagdewate Nita , Thompson Charles , Chandra Kavitha
Published: May 2014

The presented work focuses in the exact response of two globally reacting surfaces separating a semi-infinite channel from two mediums to a point source when the speed of sound of the host medium is greater than that of the other two mediums. Analytical and numerical image based response will also be discussed in detail for different medium profiles. The modal solution of the 2-D semi-infinite channel of the stratified mediums will be obtained. The Green’s function evaluated from the image based reflection coefficient will numerically be compared with the modal solution. The solution approach will be extended for three-dimensional channel. The 3-D response will be discussed in relation with the case of locally reacting surfaces of the channel.
Shelter from the Glutamate storm: Loss of olivocochlear efferents increases cochlear nerve degeneration during aging
Authors: Liberman M. Charles , Maison Stephane F.
Published: May 2014

The olivocochlear (OC) feedback pathways include one population, the medial (M)OC projections to outer hair cells, which forms a sound-evoked inhibitory reflex that can reduce sound-induced cochlear vibrations, and a second population, the lateral (L)OC projections to the synaptic zone underneath the inner hair cells, that can modulate the excitability of the cochlear nerve terminals. Although there is ample evidence of OC-mediated protective effects from both of these systems when the ear is exposed to intense noise, the functional significance of this protection is questionable in a pre-industrial environment where intense noise was not so commonplace. We have re-evaluated the phenomenon of OC-mediated protection in light of recent work showing that acoustic exposure destroys cochlear neurons at sound pressure levels previously considered atraumatic, because they cause no permanent hair cell loss or threshold shift. We have shown that loss of OC innervation at a young age causes the cochlea to age a greatly accelerated rate, even without purposeful noise exposure, when aging is measured by the loss of synaptic connections between cochlear nerve fibers and hair cells. Possible relevance to hearing-in-noise problems of the elderly will be discussed.
Prosodic variability in the speech of children who stutter
Authors: Arbisi-Kelm Timothy , Hollister Julia , Zebrowski Patricia , Gupta Julia
Published: May 2014

Developmental stuttering is a heterogeneous language disorder characterized by persistent speech disruptions, which are generally realized as repetitions, blocks, or prolongations of sounds and syllables (DSM-IV-R, 1994). While previous studies have uncovered ample evidence of deficits in both “higher-level” linguistic planning and “lower-level” motor plan assembly, identifying the relative contribution of the specific factors underlying these deficits has proved difficult. Phrasal prosody represents a point of intersection between linguistic and motoric planning, and therefore a promising direction for stuttering research. In the present study, 12 children who stutter (CWS) and 12 age-matched controls (CWNS) produced sentences varying in length and syntactic complexity. Quantitative measures (F0, duration, and intensity) were calculated for each word, juncture, and utterance. Overall, CWS produced a narrower F0 range across utterance types than did CWNS, while utterance duration did not differ significantly between groups. Within utterances, CWS (but not CWNS) produced a greater degree of pre-boundary lengthening preceding relative clauses in syntactically complex sentences, as well as higher F0 variability at these juncture points. Such differences suggest that for CWS utterance planning is sensitive to syntactic complexity, possibly reflecting either a deficit in syntactic processing or the relative effects of syntactic processing on a strained processing system.
VocaliD: Personal voices for augmented communicators
Authors: Bunnell H Timothy , Patel Rupal
Published: May 2014

The goal of the VocaliD project (for vocal identity) is to develop personalized synthetic voices for children and adults who rely on speech generating devices (SGDs) for verbal communication. Our approach extracts acoustic properties related to source, vocal tract, or both from a target talker’s disordered speech (whatever sounds they can still produce) and applies these features to a synthetic voice that was created from a surrogate voice donor who (ideally) is similar in age, size, gender, etc. The result is a synthetic voice that contains as much of the vocal identity of the target talker as possible yet the speech clarity of the surrogate talker’s synthetic voice. To date, we have deployed several synthetic voices using this technology. Three case studies will be presented to illustrate the methods used in voice generation and the results from three pediatric SGD users. We will also describe plans to greatly extend our database of surrogate voice donor speech, allowing us to better match regional/dialectical features to the needs of the target SGD users.
Wind turbine blade health monitoring using acoustic beamforming techniques
Authors: Niezrecki Christopher , Poozesh Peyman , Aizawa Kai , Heilmann Gunnar
Published: May 2014

Wind turbines operate autonomously and can possess reliability issues attributed to manufacturing defects, fatigue failure, or extreme weather events. In particular, wind turbine blades can suffer from leading and trailing edge splits, holes, or cracks that can lead to blade failure and loss of energy revenue generation. In order to help identify damage, several approaches have been used to detect cracks in wind turbine blades; however, most of these methods require transducers to be mounted on the turbine blades, are not effective, or require visual inspection. This paper will propose a new methodology of the wind turbine non-contact health monitoring using the acoustic beamforming techniques. By mounting an audio speaker inside of the wind turbine blade, it may be possible to detect cracks or damage within the structure by observing the sound radiated from the blade. Within this work, a phased array beamforming technique is used to process acoustic data for the purpose of damage detection. Several algorithms are evaluated including the CLEAN-based Subtraction of Point spread function from a Reference (CLSPR) on a composite panel and a section of a wind turbine blade in the laboratory.
Compressive beamforming with co-prime arrays
Authors: Rogers Jeffrey S. , Edelmann Geoffrey F. , Gaumnd Charles F.
Published: May 2014

The results of compressive beamforming using arrays formed by Nyquist, co-prime samplers, Wichmann rulers, and Golomb rulers are shown along with forms of array gain, resolution and latency as measures of performance. Results will be shown for the idea case of few sources with Gaussian amplitudes in spatially white Gaussian white noise. Results will also be shown for data taken on the Five Octave Research Array (FORA). [This work was supported by ONR.]
How round is the human head?
Authors: Xu Buye , Merks Ivo , Zhang Tao
Published: May 2014

Binaural microphone arrays are becoming more popular for hearing aids due to their potential to improve speech understanding in noise for hearing impaired listeners. However, such algorithms are often developed using three-dimensional head-related transfer function measurements which are expensive and often limited to a manikin head such as KEMAR. As a result, it is highly desired to use a parametric model for binaural microphone array design on a human head. Human heads have been often modeled using a rigid sphere when diffraction of sound needs to be considered. Although the spherical model may be a reasonable model for first order binaural microphone arrays, recent study has shown that it may not be accurate enough for designing high order binaural microphone arrays for hearing aids on a KEMAR (Merks et al., 2014). In this study, main sources of these errors are further investigated based on numerical simulations as well as three-dimensional measurement data on KEMAR. The implications for further improvement will be discussed.
Frequency-difference matched field processing in the presence of random scatterers
Authors: Worthmann Brian , Dowling David R.
Published: May 2014

Matched field processing (MFP) is an established technique for locating remote acoustic sources in known environments. Unfortunately, unknown random scattering and environment-to-propagation model mismatch prevents successful application of MFP in many circumstances, especially those involving high frequency signals. Recently a novel nonlinear array-signal-processing technique, frequency difference beamforming, was found to be successful in combating the detrimental effects of random scattering for 10 kHz to 20 kHz underwater signals that propagated 2.2 km in a shallow ocean sound channel and were recorded by a 16-element vertical array. This presentation covers the extension of the frequency-difference concept to MFP using sound propagation simulations in a nominally range-independent shallow ocean sound channel that includes point scatterers. Here again, 10 kHz to 20 kHz signals are broadcast to a vertical 16-element array, but the frequency difference approach allows Bartlett and adaptive MFP ambiguity surfaces to be calculated at frequencies that are an order of magnitude (or more) below the signal bandwidth where the detrimental effects of environmental mismatch and random scattering are much reduced. Comparison of these results with equivalent simulations of conventional Bartlett and adaptive MFP for different of source-array ranges are provided. [Sponsored by the Office of Naval Research.]
Development of a uniaxial pressure-acceleration probe for diagnostic measurements performed on a spherical sound projector
Authors: McConnell James A.
Published: May 2014

Historically speaking, underwater acoustic vector sensors have seen widespread use in direction finding applications. However, given that this class of sensor typically measures both the acoustic pressure and at least one component of the particle velocity at a single point in space, they can be used effectively to measure the acoustic intensity and/or the acoustic impedance. These metrics can be useful in understanding the acoustic field associated with simple and complex sound radiators. The focus of this paper concerns the development of a uniaxial pressure-acceleration (p-a) probe to measure the specific acoustic impedance of a spherical sound projector (i.e., International Transducers Corporation ITC1001 transducer) over the frequency range from 2.5 to 10 kHz. The design, fabrication, and calibration of the probe are covered along with the results of the aforementioned experiment. Results show that reasonable agreement was obtained between the measured data and an analytical prediction, which models the sound projector as a point source positioned in a free-field.
An adaptive beamformer algorithm using a quadratic norm of the Poynting vector for vector sensor arrays
Authors: Baggeroer Arthur B.
Published: May 2014

An adaptive beamformer for vector sensor arrays (VSA's), which uses a quadratic norm of the acoustic Poynting vector (PV) and linear constraint on the PV itself, is introduced. The paradigm follows minimum variance distortionless response (MVDR) but now the metric to be minimized is a quartic function of the filter weights and the constraint is quadratic. This leads to numerical approaches for the optimization instead of a matrix inversion for MVDR. This exploration is motivated by the observation that many nonlinear processing methods lead to “better” performance when a signal is above some threshold SNR. Examples of these include split beam arrays, DIFAR's and monopulse systems. This presentation discusses the optimization method and compares the results for ABF with linear processing for VSA's. The use of linear and quadratic refer to the clairvoyant processing where the ABF uses ensemble covariances and leaves open the problem of sample covariance estimation. [Work supported by ONR Code 321, Undersea Signal Processing.]
Detection and tracking of quiet signals in noisy environments with vector sensors
Authors: DelBalzo Donald , Leclere James , Lindwall Dennis , Yoerger Edward , Charalampidis Dimitrios , Ioup George
Published: May 2014

We analyze the utility of vector sensors to detect and track underwater acoustic signals in noisy environments. High ambient noise levels below 300 Hz are often dominated by a few loud discrete ships that produce a complicated and dynamic noise covariance structure. Horizontal arrays of omni-directional hydrophones improve detection by forming (planewave) beams that “listen” between loud azimuthal directions with little regard to changing noise fields. The inherent 3-D directionality of vector sensors offers the opportunity to exploit detailed noise covariance structure at the element level. We present simulation performance results for vector sensors in simple and realistic environments using particle filters that can adapt to changing acoustic field structures. We demonstrate the ability of vector sensors to characterize and mitigate the deleterious effects of noise sources. We also demonstrate the relative value of vector vs. omni-directional sensing (and processing) for single sensors and compact arrays.
Very low frequency acoustic vector sensor calibration
Authors: Donskoy Dimitri
Published: May 2014

In-water calibration of Acoustic Vector Sensors (AVS) operating at very low frequencies (fraction of Hz to hundreds of Hz) presents a set of unique challenges as the acoustic wavelengths are much longer than any existing laboratory calibration facilities. The developed calibration approach utilizes existing Naval Undersea Warfare Center’s pressurized horizontal calibrating steel tube equipped with two independently controlled sound sources located at the opposite ends of the tube. Controlling the phase and amplitude of these sources allows for creating of pressure or velocity fields inside the tube. Respective pressure and particle velocity complex amplitudes are measured and calculated, respectively, with two reference hydrophones. Experimental results of this calibration approach is presented for a newly developed very low frequency AVS comprising of pressure and non-inertial velocity sensors built into an acoustic velocity horn.
Meeting the classroom acoustics standard on a historical room
Authors: Jaramillo Ana M. , Olson Bruce C.
Published: May 2014

The Department of Speech-Language-Hearing Sciences at University of Minnesota occupies Shevlin Hall built in 1906. We were called in 2013 to help with the acoustic and sound system redesign of room 110 to be used as a classroom, as the room had very poor speech intelligibility due to the very high ceiling and hard walls, resulting in a very reverberant environment. Our goal was to meet the current classroom acoustics standard ANSI S12.60. Reverberation time and noise measurements were performed, and the room was modeled using EASE for the prediction of results. The model was compared with measurements, and several alternatives were explored. After the changes were implemented, measurements confirmed the improvement to the room's intelligibility was acquired and the historic character of the room was preserved.
Detection and identification of helicopter noise in beach environments
Authors: Summers Jason E.
Published: May 2014

Noise generation by helicopters has been studied extensively as has auditory perception of helicopter noise—both in terms of detection and identification and in terms of annoyance. Recent work [Hoglund et al., J. Acoust. Soc. Am. 128, 164–171 (2010)] has identified the importance of accounting for the specific soundscape when modeling detection performance, suggesting that empirically derived signal-specific detection thresholds must be further adapted to account for differences between real-world ambient environments. Beaches and other coastal environments are an interesting case study for evaluating real-world performance of detection and identification models. In addition to a presenting an unusual and highly dynamic propagation environment for helicopter noise, the natural soundscape resulting from wind and breaking waves has unique spectral and temporal properties that influence how it masks the acoustic signature of helicopters. Here, measurements of a helicopter operating in a beach environment are compared with theoretical and empirical models including models of airborne noise from breaking waves [Bolin and Åbom, J. Acoust. Soc. Am. 127, 2771–2779 (2010)]. Detection and identification performance are compared with predictions of models for rotorcraft noise—developed in other ambient environments—and models for wind-turbine noise—developed for similar coastal environments.
Trillium: A thermoacoustic-Stirling refrigerator implementation using an inline topology
Authors: Poese Matthew E. , Keolian Robert M. , Smith Robert W. , Mitchell Eric C. , Roberts Cory M. , Garrett Steven L.
Published: May 2014

To meet a small but growing demand for low global-warming potential refrigeration technologies, a thermoacoustic-Stirling refrigerator has been developed that uses helium as the working gas. Using a new multi-stage topology [Backhaus and Keolian, “In-line stirling energy system,” US patent 7,908,856 B2 (2011)], Trillium employs a collinear stack of three linear motors driven by voltage signals phased 120 degrees apart from one another. Above each motor is a thermal core that is comprised of a pair of novel aluminum microchannel heat exchangers on either side of a rolled Kapton® regenerator. The heat exchangers have an equivalent pore size of about a thermal boundary layer thicknesses that allows high effectiveness. The linear motors drive an acoustic wave that travels along the length of the machine. Taken in isolation, each thermal core and the motor-driven piston above and below (sealed using novel plastic flexure seals) forms a single alpha-Stirling machine; taken together Trillium is three Stirling machines working together with, in principle, zero vibration due to a stationary center-of-mass as a result of the motor phasing. The talk will explain the design and present performance measurements. [Work generously sponsored the Advanced Research Project Agency—Energy (ARPA-E) under their BEETIT program.]
Gedeon streaming suppression in a small scale thermoacoustic-Stirling engine-generator
Authors: Wilcox D. , Spoor P.
Published: May 2014

Thermoacoustic-Stirling engines, or traveling wave engines, have been shown to convert heat to acoustic power very efficiently (over 30% first-law) in the laboratory. The laboratory prototypes are generally heated from the inside by an embedded electric heater, have a long, bulky resonator, and deliver their work to an acoustic load rather than as electricity, leaving significant challenges required for commercialization unaddressed. The authors are part of a team developing a compact acoustic Stirling engine that is externally heated and is coupled to a pair of linear alternators, dubbed the Thermoacoustic-Stirling Engine-Generator (TaSEG). An important part of this work has been developing a commercially viable means of suppressing Gedeon streaming, a steady flow that circulates in an acoustic engine's toroidal geometry. In the laboratory, this streaming is typically suppressed by either a latex barrier or a “jet pump,'' a special flow element with asymmetric flow resistance, adjusted from the outside of the engine via a rod that passes through the pressure vessel. This work describes the design and testing of a simple, compact, and inexpensive element with multiple jet-pump orifices (the “jet plate''), which can replace the laboratory versions in a commercial engine.
Bayesian-based model selection and physical parameter estimation of the acoustical properties of rigid-frame porous media
Authors: Fackler Cameron J. , Xiang Ning , Horoshenkov Kirill V. , Khan Amir
Published: May 2014

This paper studies an application of Bayesian inference to determine the most appropriate model for the acoustical properties of rigid-frame porous media. The Bayesian framework encompasses two levels of inference: model selection and parameter estimation. Both are based on the posterior probability distribution, which is unique to each combination of acoustic model and material sample. The posterior distribution provides statistically informed guidance on selecting an appropriate acoustic model for a material sample as well as determining the physical parameters of the porous microstructure. Using the nested sampling algorithm, the posterior distribution for each material sample and acoustic model is explored and integrated numerically. This process computes the Bayesian evidence for each model, which is used to select a suitable model for the acoustical properties of the material. The process also provides estimates of the physical parameters, which are used with the selected model for accurate prediction of the acoustical properties of the material.
Convergence behavior and steady state response of a rib-stiffened, layered plate structure subjected to high frequency acoustic loading
Authors: Cipolla Jeffrey , Murray Patrick , Teferra Kirubel
Published: May 2014

An existing analytical, frequency domain solution for wave propagation in coated, ribbed, three-dimensional elastic layered plates excited by acoustic plane waves provides fast solutions for high frequency excitations. The solution methodology, which is found to be numerically unstable under certain conditions, contains an Ansatz for a particular wave number expansion in the direction of periodicity. Evidence is presented to show that the numerical instability is due to the specific choice of the wave number basis. In order to provide a remedy while retaining the positive aspects of the solution methodology, we determine the set of admissible propagating (and attenuating) waves via an eigenvalue analysis. Several approaches exist to determine the admissible waves of structures with periodicity. The Wave Guide Finite Element (WFE) method leads to a two parameter, nonlinear eigenvalue problem, which is difficult to solve. The Scale Independent Element (SIE) formulation results in a two-parameter quadratic eigenvalue problem and overcomes the numerical issues of the WFE method. This study examines available methods in determining the admissible waves and compares them with those established using the dispersion relation. The computed admissible waves are then compared with the aforementioned Ansatz.
Neurometric amplitude-modulation detection threshold measured in the chinchilla ventral cochlear nucleus following sensorineural hearing loss
Authors: Sayles Mark , Hickox Ann E. , Heinz Michael G.
Published: May 2014

Amplitude modulation is a common feature of natural sounds and an important cue in audition. Modulation supports perceptual segregation of “objects” in complex acoustic scenes, and provides information for speech understanding and pitch perception. Previous work in our laboratory showed increased modulation gain without change in temporal modulation transfer function (tMTF) bandwidth in auditory-nerve fiber responses to sinusoidal amplitude-modulated (SAM) tones measured in chinchillas with noise-induced hearing loss (HL), compared to normal-hearing (NH) controls. The ventral cochlear nucleus (VCN) provides significant input-output transformations with respect to amplitude-modulation representation, with enhanced spike synchrony to the amplitude envelope in several distinct cell types. We recorded spike times in response to SAM tones with modulation depths between 3% and 100% from all major VCN unit types in anesthetized NH and HL chinchillas. HL animals were previously exposed to 116 dBSPL 500 Hz-centered octave-band Gaussian noise. Spike times were analyzed in terms of synchrony to the amplitude envelope, tMTFs were calculated, and a signal-detection theoretic analysis was used to compute modulation-detection and discrimination thresholds. Results will be related to human perceptual studies, which have shown better modulation-detection thresholds in HL. [Work supported by an Action on Hearing Loss Fulbright Commission scholarship (M.S.), and NIH grant R01-DC009838.]