bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonic stabilization of small lifted flames
Authors: Thiessen David B. , Wei Wei , Marston Philip L.
Published: October 2013

Combustion of a fuel gas (such as methane) flowing at low speeds from a nozzle into air produces a flame commonly described as a ‘‘diffusion’’ flame. As the flow rate of fuel is increased, the flame is known to lift off the nozzle. This premixes fuel with air and improves certain aspects of the combustion. Ordinarily, however, at large flow rates the flame becomes unstable and blows-off. Furthermore, decreasing the rate of flow to a previously lifted flame ordinarily causes the flame to drop-back and reattach to the nozzle. We demonstrate, however, that the stable range of a lifted flame can be enhanced by applying appropriately positioned ultrasonic standing waves. In the simplest case, a transverse standing wave close to the nozzle suppresses reattachment and facilitates improved pre-mixing at low flow rates. In the other case, an ultrasonic standing wave applied to the flame increases the flow rate for blow-off. These results are apparently the consequence of ultrasonic radiation forces on the flame directed, respectively, away from or toward the nozzle. We previously demonstrated the deformation of small diffusion flames within an ultrasonic standing wave [D. B. Thiessen et al., J. Acoust. Soc. Am. 112, 2240 (2002)]. [Work supported in part by NASA.]
Active control of flow-induced noise transmitted through aircraft sidewalls
Authors: Maury Cedric , Gardonio Paolo , Elliott Stephen J.
Published: October 2013

In this paper, the theory and the results are presented of a study concerned with the active control of sound transmitted through aircraft sidewalls when excited by a Turbulent Boundary Layer. The motivation for this study is the control within an aircraft cabin of the flow-induced noise due to wall–pressure fluctuations over the fuselage. First, a theoretical model accounting for the effect of elastic stiffeners is obtained to calculate the boundary layer noise transmitted through tensioned aircraft sidewalls. Parametric studies including comparisons between different models of aircraft fuselage panels valid over different frequency ranges are analyzed. Second, the best possible noise levels reduction that can be achieved are determined using idealized feedback control of the boundary layer noise transmitted through tensioned and stiffened double-panel partitions. It is shown that it is the strategy based on the active suppression of the skin panel structural modes that is the most efficient in terms of the broadband attenuation of the total sound power inwardly radiated. However, it may be more feasible to control the vibration of the trim panel or the pressure in the cavity, and the simulations suggest that the inwardly radiated sound power can still be reduced by a significant amount.
Auditory processing deficits among language-learning disordered children and adults
Authors: Wayland Ratree , Lombardino Linda
Published: October 2013

It has been estimated that approximately 5%–9% of school-aged children in the United States are diagnosed with some kind of learning disorders. Moreover, previous research has established that many of these children exhibited perceptual deficits in response to auditory stimuli, suggesting that an auditory perceptual deficit may underlie their learning disabilities. The goal of this research is to examine the ability to auditorily process speech and nonspeech stimuli among language-learning disabled (LLD) children and adults. The two questions that will be addressed in this study are: (a) Are there subtypes of LLD children/adults based on their auditory processing deficit, and (b) Is there any relationship between types of auditory processing deficits and types of language deficits as measured by a battery of psychoeducational tests.
Perception of relative location of F0 within the speaking range
Authors: Honorof Douglas N. , Whalen D. H.
Published: October 2013

It has been argued that intrinsic fundamental frequency (IF0) is an automatic consequence of vowel production [Whalen et al., J. Phon. 27, 125–142 (1999)], yet speakers do not adjust F0 so as to overcome IF0. It may be that so adjusting F0 would distort information about F0 range–information important to the interpretation of F0. Therefore, a speech production/perception experiment was designed to determine whether listeners can perceive position within a speaker-specific F0 range on the basis of isolated tokens. Ten male and ten female adult native speakers of US English were recorded speaking (not singing) the vowel /a/ on eight different pitches spaced throughout speaker-specific ranges. Recordings were randomized across speakers. Naive listeners made pitch-magnitude estimates of the location of F0 relative to each speaker’s range. Preliminary results show correlations between estimated and actual location within the range. Adjusting F0 to compensate for IF0 differences between vowels would seem to obscure voice quality in such a way as to make it difficult for the listener to recover relative F0, requiring a greater perceptual adjustment than simply normalizing for IF0. [Work supported by NIH Grant No. DC02717.]
Asymmetric kinematic changes in speaking rate explored with FDA
Authors: Lee Sungbok , Narayanan Shrikanth , Byrd Dani
Published: October 2013

We report preliminary results for the effect on tongue movements of varying speaking rate. Speech acoustics and tongue tip and body kinematic data were collected using electromagnetic articulography (EMA) [Perkell et al., J. Acoust. Soc. Am. 92 (1992)]. A subject read each one of 20 sentences three times in a row with a predefined order of combination of three speaking rates (normal, medium, fast). Velocity and acceleration were derived using functional data analysis (FDA) [Ramsay et al., J. Acoust. Soc. Am. 99 (1996)] for smoother estimation of acceleration from the displacement data. Global utterance analyses of phase-space and variability in the displacement-velocity and the velocity-acceleration relations indicate that the fast speech exhibits comparable tongue tip displacements to normal speech but significantly larger accelerations (p<0.00). The difference in the order of combination of speaking rates (e.g., normal changing to fast versus fast to normal) shows significant effects on both voicing effort (expressed as rms energy) and the kinematic parameters. Finally, kinematic variability at some points in the utterance is much more constrained than at other points, irrespective of speaking rate. A possible interpretation of this is that particular portions of the utterance require this stability for linguistic or articulatory reasons. [Work supported by NIH.]
An audiovisual database of English speech sounds
Authors: Frisch Stefan A. , Nikjeh Dee Adams
Published: October 2013

A preliminary audiovisual database of English speech sounds has been developed for teaching purposes. This database contains all Standard English speech sounds produced in isolated words in word initial, word medial, and word final position, unless not allowed by English phonotactics. There is one example of each word spoken by a male and a female talker. The database consists of an audio recording, video of the face from a 45 deg angle off of center, and ultrasound video of the tongue in the mid-saggital plane. The files contained in the database are suitable for examination by the Wavesurfer freeware program in audio or video modes [Sjolander and Beskow, KTH Stockholm]. This database is intended as a multimedia reference for students in phonetics or speech science. A demonstration and plans for further development will be presented.
Simulation of VCV syllables with a parametric area function model of the vocal tract
Authors: Story Brad
Published: October 2013

A model of the vocal tract area function has been developed that consists of three tiers. The first tier is a vowel substrate defined by a system of spatial eigenmodes determined from MRI and/or x-ray microbeam data and a neutral area function. The input parameters to this first tier are coefficient values that, when multiplied by the appropriate eigenmode and added to the neutral area function, construct a desired vowel. The second tier consists of a Gaussian shaping function defined along the length of the vocal tract that modifies the vowel substrate such that a constriction is formed. Input parameters consist of the location, area, and range of the constriction. Location and area roughly correspond to the standard phonetic notions of place and degree of constriction while range defines the amount of vocal tract length over which the constriction will influence the tract shape. The third tier allows length modifications for articulatory maneuvers such as lip rounding/spreading and larynx lowering/raising. All parameters can be specified either as static or time-varying, which allows for multiple levels of coarticulation to be produced. The model will be discussed and then used to simulate several VCV syllables. [Work supported by NIH R01-DC04789.]
Developing a corpus of spoken language variability
Authors: Carmichael Lesley , Wright Richard , Wassink Alicia Beckford
Published: October 2013

We are developing a novel, searchable corpus as a research tool for investigating phonetic and phonological phenomena across various speech styles. Five speech styles have been well studied independently in previous work: reduced (casual), careful (hyperarticulated), citation (reading), Lombard effect (speech in noise), and ‘‘motherese’’ (child-directed speech). Few studies to date have collected a wide range of styles from a single set of speakers, and fewer yet have provided publicly available corpora. The pilot corpus includes recordings of (1) a set of speakers participating in a variety of tasks designed to elicit the five speech styles, and (2) casual peer conversations and wordlists to illustrate regional vowels. The data include high-quality recordings and time-aligned transcriptions linked to text files that can be queried. Initial measures drawn from the database provide comparison across speech styles along the following acoustic dimensions: MLU (changes in unit duration); relative intra-speaker intensity changes (mean and dynamic range); and intra-speaker pitch values (minimum, maximum, mean, range). The corpus design will allow for a variety of analyses requiring control of demographic and style factors, including hyperarticulation variety, disfluencies, intonation, discourse analysis, and detailed spectral measures.
Vowel production, speech-motor control, and phonological encoding in people who are lesbian, bisexual, or gay, and people who are not
Authors: Munson Benjamin , DeBoe Nancy
Published: October 2013

A recent study (Pierrehumbert, Bent, Munson, and Bailey, submitted) found differences in vowel production between people who are lesbian, bisexual, or gay (LBG) and people who are not. The specific differences (more fronted /u/ and /a/ in the non-LB women; an overall more-contracted vowel space in the non-gay men) were not amenable to an interpretation based on simple group differences in vocal-tract geometry. Rather, they suggested that differences were either due to group differences in some other skill, such as motor control or phonological encoding, or learned. This paper expands on this research by examining vowel production, speech-motor control (measured by diadochokinetic rates), and phonological encoding (measured by error rates in a tongue-twister task) in people who are LBG and people who are not. Analyses focus on whether the findings of Pierrehumbert et al. (submitted) are replicable, and whether group differences in vowel production are related to group differences in speech-motor control or phonological encoding. To date, 20 LB women, 20 non-LB women, 7 gay men, and 7 non-gay men have participated. Preliminary analyses suggest that there are no group differences in speech motor control or phonological encoding, suggesting that the earlier findings of Pierrehumbert et al. reflected learned behaviors.
The impact of intended emotion on dynamic changes in talker amplitude
Authors: Wieberg Kimberly , Hall Michael D.
Published: October 2013

Relatively little research has been conducted on auditory affect, and less research has focused on quantifying the nature of potential acoustic cues to emotion. A production study was conducted to address the possibility that one dynamic acoustic variable, talker amplitude, may systematically vary as a function of intended affect. Six talkers (three male, three female) were instructed to produce 200 target words with different emotional valences (e.g., joy versus sadness). Target words were phonetically balanced (PB), and each word was produced within a standard carrier phrase. Temporally specific intensity measurements were recorded for each target word. Descriptively and statistically distinct contours were obtained as a function of intended emotion. Furthermore, talkers differed in the way they produced amplitude contours for each emotion. The perceptual relevance of the observed affect-based differences in amplitude then was evaluated. Average contours for joy and sadness were applied to an emotionally neutral set of (CV) stimuli. Listeners discriminated the resulting contours within a two-alternative forced choice task, and sensitivity was evaluated using signal detection analyses. Implications for the potential role of amplitude in the perception of emotion, as well as for the representation of talker information, in words will be discussed.
Intonation contour in synchronous speech
Authors: Wang Bei , Cummins Fred
Published: October 2013

Synchronous Speech (Syn-S), obtained by having pairs of speakers read a prepared text together, has been shown to result in interesting properties in the temporal domain, especially in the reduction of inter-speaker variability in supersegmental timing [F. Cummins, ARLO 3, 7–11 (2002)]. Here we investigate the effect of synchronization among speakers on the intonation contour, with a view to informing models of intonation. Six pairs of speakers (all females) read a short text (176 words) both synchronously and solo. Results show that (1) the pitch accent height above a declining baseline is reduced in Syn-S, compared with solo speech, while the pitch accent location is consistent across speakers in both conditions; (2) in contrast to previous findings on duration matching, there is an asymmetry between speakers, with one speaker exerting a stronger influence on the observed intonation contour than the other; (3) agreement on the boundaries of intonational phrases is greater in Syn-S and intonation contours are well matched from the first syllable of the phrase and throughout.
Validity conditions for the linear statistical assumptions of Kalman filtering
Authors: Zanolin Michele , Makris Nicholas C
Published: October 2013

The fundamental assumption of a Kalman filter is that both the state and evolution equations are linear and that the noise in each of these equations is signal-independent, additive and Gaussian. For many practical problems in Kalman filtering and recursive estimation, however, both the state and evolution equations are actually nonlinear and may involve random variables that are neither additive nor Gaussian. Ad-hoc linearizations with little or no justification are often made to apply a Kalman filter in these cases. Validity conditions for the fundamental linear statistical assumptions of Kalman filtering are derived from the first principles of estimation theory by asymptotic analysis of the likelihood function of the general nonlinear model [E. Naftali and N. Makris, J. Acoust. Soc. Am. 110 (2001)]. An illustrative example involving remote acoustic tracking of a fluctuating target with active sonar is presented.
Detection in shallow water using broadband—DORT
Authors: Fromm David M. , Gaumond Charles F. , Lingevitch Joseph F. , Gauss Roger C. , Menis Richard
Published: October 2013

The decomposition of the time-reversal operator (DORT) [Prada et al., J. Acoust. Soc. Am. 99, 2067–2076 (1996)] has been extended into a coherent, broadband method. Broadband DORT has also been shown to isolate resolvable scatterers at various depths and ranges in a bistatic, active sonar in shallow water. Results are shown from the application of DORT to sea data taken in an area south of Hudson Canyon off the New Jersey coast during Geoclutter II. The vertical source/receiver array with 56 hydrophones spanning the water column was operated between 3.0 and 3.5 kHz. The elements were divided into four groups, with each group acting as a coherent, broadside source. Two methods were used for exciting the separate channels. One method was the use of subsequent LFMs and the other was the use of simultaneous transmission of four pseudorandom-noise signals. The target was a midwater column echo-repeater. Results are compared with modeling based on in situ environmental measurements during the experiment. [The authors acknowledge signal-processing expertise from Dr. Ning Xiang, University of Mississippi, and ENS Alan Meyer, LLNL, support from Dr. Jeff Simmen, ONR, and assistance from Dr. Charles Holland, ARL/PSU. Work supported by ONR.]
Audibility of locomotive horns inside highway vehicles near highway–railroad grade crossings
Authors: Randorff Jack E.
Published: October 2013

Most states require that motorists yield the right-of-way to locomotives and their consists at highway–railroad grade crossings. One method of alerting motorists to the proximity of a train is to sound an audible warning using an air horn. In litigation, the effectiveness of a locomotive’s air horn to alert the driver of a vehicle can be a crucial element that allows a jury to determine liability and award financial penalties. Locomotive air horn signal strength, acoustic propagation over distance, excess attenuation, sound isolation of vehicle shells, ambient sound level masking, signal detection ratios, and driver distraction must be considered, measured, and evaluated before the audibility of the air horn can be surmised from the driver’s perspective. The final evaluation must then be presented to a jury through the process of direct and cross examination. Several case examples are discussed relating to this process.
A review of transient detection using higher order correlations
Authors: Pflug Lisa A. , Ioup George E. , Ioup Juliette W.
Published: October 2013

Quieter targets and noisier ocean environments prompted a search for detection improvements in the 1990s. Transient signals were a potential source for detection that had not been exploited. Higher order statistics provided a means to capitalize on one of the unique characteristics of transient signals—nonzero higher order moments. Several years of study led to the conclusion that higher order correlation detectors can in fact perform better than the cross-correlation detector for transient signals. This conclusion is supported by both theory and simulations. Theoretical predictions for unknown and known signals in uncorrelated noise have shown that the gains depend on signal moments, sampling rate, and for the unknown signals, data length as well. Derived upper bounds on the gains in uncorrelated noise show the limitations of these processors. Various mechanisms for further improvement were investigated. One-dimensional prefiltering improved the higher-order correlation detectors due to noise reduction in the higher-dimensional correlation space. Functional inputs of certain narrow-band signals resulted in gains for the higher-order correlation detectors which were not realized with the original signal. Finally, studies indicate that the higher order correlation detectors maintain their advantage over the cross-correlation detector in measured, correlated noise. [Research supported by ONR and NRL.]
Correcting DNL so it works—better
Authors: Schomer Paul
Published: October 2013

The day–night average sound level (DNL), first developed by the U.S. Environmental Protection Agency, is commonly used to quantify and assess environmental noise. A keystone to noise assessment is the dose–response relationship. However, the dose–response relationship is not an absolute; there is great scatter to the data on which it is based. In an attempt to reduce the scatter to the DNL data, the EPA suggested the use of normalized DNL. Normalized DNL is the basic DNL value with a number of adjustments added to account for specific characteristics and factors of the sound. This paper reviews and analyze the concepts inherent in normalized DNL and provide an updated set of normalization factors that can reduce the scatter to dose–response relationships. Several of these normalizations are contained in the new ISO 1996-1:2003.
Audiomotor integration for active sensing in the echolocating bat, Eptesicus fuscus
Authors: Moss Cynthia F. , Sinha Shiva R. , Ghose Kaushik
Published: October 2013

Echolocating bats probe the environment with sonar signals that change as they seek, pursue and intercept insect prey on the wing. Coordinating its sonar vocalizations with flight dynamics in response to changing echo information, the bat exhibits a dazzling display of sensorimotor integration. Our work aims at understanding the mechanisms supporting audiomotor integration for echolocation in the FM-bat, Eptesicus fuscus. Behavioral studies measure adaptive responses of free-flying bats engaged in complex spatial tasks. The directional aim of the bat’s sonar beam and temporal patterning of cries provide explicit data on the motor commands that feed directly back to the auditory system for spatially-guided behavior. Neural studies focus on the superior colliculus (SC), a midbrain structure implicated in species-specific orienting behaviors. A population of SC neurons shows echo-delay tuning, a response property believed to play a role in target range coding. Microstimulation of the SC elicits head and pinna movements, along with sonar vocalizations. SC recordings from tethered, vocalizing bats reveal bursts of neural activity preceding each sonar cry. Collectively, these results suggest that the bat SC plays a functional role in the auditory information processing and orienting behaviors that operate together in echolocation. [Work supported by NSF, NIMH and Whitehall Foundation.]
A dolphin lower jaw is a hydroacoustic antenna of the traveling wave
Authors: Ryabov Vyacheslav A.
Published: October 2013

The purpose of the work is the analysis of a possible function of mental foramens as channels through which the echo passes in the lower jaw fat body and the determination of a role of channels and a skull in formation of the directivity of the dolphin echolocation hearing. Concrete problems were studying of the lower jaw morphology, modeling and calculation of a dolphin, tursiops truncatus p., echolocation hearing beam pattern. The outcomes of the work indicate those morphological structures of the lower jaw; the left and right half represents two hydroacoustic receiving antennas of the traveling wave type, TWA farther. The mental foramens of a dolphin lower jaw represent nonequidistant array of waveguide delay lines, and determine the phase and amplitude distribution of each of the antenna’s array. The beam pattern of the echolocation hearing was calculated with the usage of the TWA model, and the allowance of flat sound wave diffraction. The beam pattern shape is naturally determined by the echolocation hearing functionality. It is equally well adapted both for echolocation and for pulses echo detection. A steepness of the bearing characteristic is estimated; it reaches 0.7 dB per degree.
The temporal and spatial effects of a magnetorheological elastomer in squeeze mode
Authors: Albanese Anne-Marie , Cunefare Kenneth
Published: October 2013

The behavior of a magnetorheological (MR) elastomer in an adaptive tuned vibration absorber (ATVA) subjected to transient magnetic fields was examined. ATVAs suppress vibration under broadband, variable, and multiple frequency excitations, and are effective because they can rapidly change one or more parameters to retune in very short periods of time. The device examined here features a MR elastomer whose stiffness and static displacement length are both sensitive to magnetic fields; this means that the static displacement transient behavior directly corresponded to the stiffness transient behavior. A magnetic field applied at step intervals was applied to the ATVA, and the static displacement length change and flux density levels through the ATVA were measured as a function of time. For a flux density level change of 0.12 Tesla, a static displacement length change of about 0.4 mm, which amounted to a 4% change in the overall spring length, occurred in 65 milliseconds. The cause of the long transient response is believed to be due to the magnetic–mechanical coupling.
Sonic inspection of concrete bridge decks
Authors: Costley R. Daniel , Boudreaux Gary , Ramsey William Gene
Published: October 2013

One technique for determining the integrity of concrete structures, such as bridge decks, involves dragging a chain across it and listening to the audible response. A distinctive, hollow sound is produced when a chain is dragged over a section of concrete containing a delamination. This technique has been automated by recording the sound produced by a dragging chain with a suitable microphone and processing these signals with a minicomputer to distinguish between ‘‘good’’ and ‘‘bad’’ sections of concrete. The equipment is mounted on a hand-pushed cart with chains attached so that they drag along the surface of the deck. In addition, the microphone is mounted in such a way, using standard noise control techniques, so that external noise is minimized. Traffic noise is filtered electronically. These improvements make the technique operator independent and allow inspections to be made in noisy environments. Another advantage is that this approach produces an objective record of the inspection, available both electronically and in hardcopy. These records can be compared to past and future inspections, allowing the inspectors to monitor the health of the structure. Results from bridge deck inspections will be presented, along with a description of the device and the signal processing techniques.
Influence of semantic similarity on spoken word recognition
Authors: Armbruster Jonna L. , Vitevitch Michael S.
Published: October 2013

Previous research has shown that the number of phonologically similar items influences the processing of spoken words (e.g., Vitevitch, 2002; Vitevitch and Luce, 1998). The present experiment examines the influence of semantic similarity on the speed and accuracy of spoken word recognition using a lexical decision task. Semantic density refers to the number of words that are semantically associated to a given word (Nelson, McEvoy, and Schreiber, 1998). A word that has relatively many semantically associated words has high semantic density and a word that has relatively few semantically associated words has low semantic density. The results showed that words with high semantic density were responded to more quickly and accurately than words with low semantic density, suggesting that semantic information influences spoken word recognition.
Recognition of information-bearing elements in speech
Authors: Hermansky Hynek
Published: October 2013

An acoustic speech signal carries many different kinds of information: the basic linguistic message, many characteristics of the speaker of the message, details of the environment in which the message was produced and transmitted, etc. The human auditory/cognitive system is able to detect, decode, and separate all these information sources. Understanding this ability and emulating it on a machine has been an important but elusive scientific and engineering goal for a long time. This talk critically surveys the situation in the speech recognition field. It puts automatic recognition of speech in perspective with other acoustic signal detection and classification tasks, reviews some historical, contemporary, and evolving techniques for machine recognition of speech, critically compares competing techniques, and gives some examples of applications in speech, speaker, and language recognition and identification. The talk is intended for an audience interested but not directly involved in the processing of speech.
Acoustic classification: An overview of theory and reality
Authors: Greineder Stephen
Published: October 2013

Historically, Bayes’ decision theory has formed the statistical foundation for the development of acoustic classification techniques for problems that contain large numbers of data classes. The successful realization of this approach depends directly on mitigating two important mismatches that are introduced using this classification model. First, the underlying probabilistic structure in the problem is not typically known and therefore must be estimated as part of a classifier training phase. Second, due to the high dimensionality of time series data, a feature extraction stage is added as a preprocessor to most classifiers. Attempting to extract the sufficient information in the problem while limiting the feature set size to a dimension supported by the training data is the ultimate designer’s challenge. This is particularly true in the case of finite data sample sizes. This talk will trace the development evolution of a low false alarm rate multiclass operational algorithm that will provide an overview of the fundamental challenges and resulting mitigation approaches. Examples using real data will be used to demonstrate the points being presented.
The class-specific method for classification
Authors: Baggenstoss Paul M.
Published: October 2013

This talk describes a new probabilistic method for classification called the ‘‘class-specific method’’ (CSM). CSM is able to avoid the ‘‘curse of dimensionality’’ which plagues most classifiers which attempt to determine the decision boundaries in a high-dimensional feature space. Using CSM, it is possible to build a theoretically optimum classifier without a common feature space. Separate low-dimensional features sets may be defined for each class, while the decision functions are projected back to the common raw data space. CSM effectively extends classical classification theory to handle multiple feature spaces. It is completely general, and requires no simplifying assumption such as Gaussianity or that data lies in linear subspaces. In real-data problems, CSM has shown orders of magnitude reductions in the false-alarm rate. CSM achieves this gain because it is able to make use of partial prior knowledge about the data classes. In contrast, the existing theory can only make use of full knowledge—that is when the parametric forms of the data probability density functions (PDFs) are known.
Performance of a superdirective line array in nonideal environments
Authors: Hines Paul C. , Humphrey Victor F. , Young Victor
Published: October 2013

Superdirective line arrays can provide high gains relative to their dimensions, whenever the inter-element spacing is much less than half a wavelength. However, their performance can be degraded by system noise. System noise can result from limitations in electronic components, inter-element mismatch in gain or phase, or from scatter from array components. Using state-of-the-art electronics and digital signal processing one can drastically reduce the errors due to electronic noise as well as those due to gain and phase mismatch. Thus, acoustic scatter from the array components can determine the performance limit. Since theoretical developments typically assume plane waves incident on idealized point receivers, it is not all that surprising that array performance fails to meet theoretical expectations! This is especially true if the array is merely one component within a much larger system. Nonetheless, impressive gains can still be realized from superdirective arrays even with significant departures from the idealized model. To support this observation, we present results obtained using a 0.8 m long, 5th order superdirective receiver that is part of a much larger system used to study scattering from marine sediments.
Comparison of the performance of vector and sensors using optimum array processing
Authors: Baggeroer Arthur , Cox Henry
Published: October 2013

Vector sensors in sonar are often used for direction finding. With the appropriate processing three component vector sensors are also quite effective at nulling directional interference as well as estimating the ambient acoustic intensity vector. Here we examine optimum array processing (MVDR based) methods for both these applications. We first present the detection performance of a plane wave source operating in directional noise fields as well as noise field based a spheroidial harmonic expansion for modeling diffuse surface, seabed and ducted environments. Next, we use these optimal methods for estimating the intensity vector. Finally, we compare the performance to an array of pressure sensors using the same number of output channels. This indicates that vector sensors are effective against some types of noise fields but not uniformly better than an array of scalar sensors.
Wideband direction finding via shielded gradient beamspace techniques
Authors: Brudner Terry J. , Henderson Terry L.
Published: October 2013

Monopulse techniques have been used for over 50 years in the radar community to estimate the direction of arrival (DOA) of incoming echoes. In recent years, a variant of the monopulse technique has been developed, termed the shielded gradient technique, which allows DOA estimation for signals of arbitrary bandwidth. The technique maps the array-output M-vector into a frequency-invariant B-dimensional beamspace. The work presented here describes the shielded gradient beamspace model in its higher-order form, and develops wideband DOA estimation algorithms analogous to the narrow-band MUSIC, root-MUSIC, and ESPRIT algorithms. The performance of these new algorithms is studied through simulation and application to measured, in-water sonar data. They are also compared via simulation to existing wideband DOA estimation algorithms. [Work supported by the Internal Research and Development Program under Contract No. FEE-800.]
Generalization of the rotated parabolic equation to variable slopes
Authors: Outing Donald A. , Siegmann William L. , Collins Michael D.
Published: October 2013

The parabolic equation method is very efficient for solving range-dependent propagation problems. This approach is also accurate when range dependence is treated properly. This problem was resolved for fluid media by applying energy-conservation [J. Acoust. Soc. Am. 89, 1058–1075 (1991)] and single-scattering [J. Acoust. Soc. Am. 91, 1357–1368 (1992)] corrections. Since these corrections were less successful for problems involving elastic layers, other approaches such as mapping [J. Acoust. Soc. Am. 107, 1937–1942 (2000)] and rotating [J. Acoust. Soc. Am. 87, 1035–1037 (1990)] coordinates were investigated. In this presentation, the rotated parabolic equation solution is generalized to problems involving variable slope. The medium is divided into a series of regions with constant slope. When changes in slope are encountered, the field is propagated beyond the change and then used to interpolate and extrapolate onto a computational grid that is rotated relative to the previous grid. This approach is implemented and tested for the fluid problem. It should also be applicable to the elastic problem, but it will be necessary to apply a change of variables each time the slope changes since the dependent variables are the tangential and normal displacements. [Work supported by ONR.]
The noise quandary of ‘‘green’’ light
Authors: Najolia Dorie A.
Published: October 2013

In recent years, the government has striven to build more sustainable and efficient facilities by introducing the LEED (Leadership in Energy and Environmental Design) rating system and establishing acoustical privacy standards. However, there are some LEED design credits that conflict with the acoustical goals. This paper reviews the issues that arise when architects attempt to accommodate daylighting and acoustical privacy in their designs for government buildings. In achieving LEED certification, points are earned by designs that introduce daylight throughout occupied spaces in a building. Creating a ‘‘line of sight’’ from exterior glazing to interior spaces generally involves using transom, clerestory, side lite windows, or entire glass walls. At the same time, acoustical goals require construction around these spaces to achieve moderate to high levels of sound isolation. Another conflict is that although sound data is available for glass, very little research is available to demonstrate the effect lightweight aluminum framing has on the entire wall system. Incorporating these standards so that they provide the desired lighting and acoustical effects in government buildings needs to be better understood, since achieving both can add cost and complexity to the building design. Alternatively, compromises can be made, if they are understood and planned.
From the bank, through the cafeteria line, and on to council chambers—Do the acoustics right!
Authors: Adams R. Bob
Published: October 2013

A common characteristic of municipal governments is the re-use of existing facilities. When a building’s original use and acoustical design are dissimilar to the new acoustical needs, the project can be a challenge. The City of San Antonio Council Chamber was built as a bank in the 1930’s and is considered an architectural landmark. This case study of the Council Chamber discusses the acoustical problems observed with intelligibility, focusing, and general ambiance from the highly ornate ceiling, internal arches, and an overlooking mezzanine. Primarily used for open City Council meetings, the room is also used as a ‘‘studio’’ for broadcast of other city related issues. The presentation will include photographs identifying the historical aspects of the architecture as well as portions of the EASE model created for the project.
Hair cells in motion: Imaging the organ of Corti
Authors: Mountain David C. , Karavitaki K. Domenica
Published: October 2013

The mammalian cochlea contains two types of sensory cells, inner hair cells (IHCs) and outer hair cells (OHCs). The IHCs provide the vast majority of the synaptic input to the auditory nerve while the OHCs express a unique motor protein, prestin, and appear to participate in an electromechanical feedback loop that amplifies the motion of the organ of Corti (OC). To study this amplification process we have employed stroboscopic video microscopy to quantify the motion of various elements of the OC. Extracellular electrical stimulation was used to excite OHC motility and a computer-controlled high-intensity light-emitting diode (LED) is used to illuminate the organ OC in an excised cochlear preparation. Motion is measured by extracting small regions of interest (ROIs) from the images and cross-correlating the ROIs taken during electrical stimulation with a reference image from the same ROIs taken with no stimulation. The observed motion is quite complex with several vibration modes observed. One of the major findings is that there appears to be oscillatory fluid flow within the tunnel of Corti suggesting that the OHC contractions are pumping fluid longitudinally within the organ. [Work funded by NIDCD.]
Phase conjugation of the second harmonic of a focused ultrasound beam as a method for improving C-scan acoustical imaging in nonlinear inhomogeneous media
Authors: Krutyansky Leonid M. , Brysev Andrew P. , Klopotov Roman V. , Pernod Philippe J. , Preobrazhensky Vladimir L. , Yan Xiang , Hamilton Mark F.
Published: October 2013

Acoustical imaging in complex media (e.g., biological tissue) can be affected by phase aberrations introduced in a wave during propagation. Wave phase conjugation (WPC) of ultrasound is known for its ability to compensate for phase distortions due to inhomogeneity of the propagation medium, and it can be used for improvement of acoustical imaging under these conditions. In a nonlinear medium harmonics are generated during propagation of an intense beam of ultrasound, and this principle is used in tissue harmonic imaging. The parametric method of WPC permits phase conjugation of a selected frequency component of the probe beam. In this way the peculiarities of WPC can be combined with advantages of harmonic imaging. Automated WPC-focusing of the conjugated second-harmonic component of a focused nonlinear probe beam is studied experimentally and theoretically for the case of a homogeneous medium, and experimentally for a medium with pseudo-random inhomogeneities. The generated conjugate wave can also be sufficiently intense to generate higher-order harmonics, which display enhanced focusing. Improvement of a C-scan harmonic imaging system operating in an inhomogeneous medium is provided as an example.
CTA ‘‘L’’ train outdoor noise propagation in Wrigley-ville
Authors: McDuffee Matthew
Published: October 2013

It is well known to those who reside in Chicago that the elevated mass transit trains, known as the L, are the largest culprit of outdoor noise pollution in most neighborhoods throughout the city. Many potential residents and buyers will make their choice of where to live in the city simply based upon the building’s relationship to the L. For those who live directly next to the tracks vibration becomes a major issue. The study focused on the environmental noise impact of the CTA red line train traveling through Chicago’s north side in the Wrigley-ville neighborhood. Approximately 1.5 miles of elevated track stretch between the Addison station (near Wrigley field) and the bridge that crosses Montrose Avenue. Eight locations were chosen throughout an area covering 17 city blocks surrounding the red line tracks to perform field measurements. The field measurements, taken in Leq, were correlated against a computer model designed using Cadna/A outdoor noise propagation software. The models polygons (representing buildings) were created using ESRI Arc View mapping software to view digitized aerial photographs of the north side of Chicago. The models predictions correlated to within plus or minus 1 dB on 6 out of 8 field measurements.
Design features for free-field qualification of a new semi-anechoic room, and qualification performance
Authors: Cunefare Kenneth A. , Biesel Van , Holdhusen Mark , Shoemaker Austin
Published: October 2013

Precision qualification of a semi-anechoic room requires careful attention to the sound source and traversing method. Prior work, with test sources mounted above the reflecting floor of such a room, has indicated the potential for image source problems in the resulting field. To address such shortcomings, the new Georgia Tech semi-anechoic room was constructed with a recessed enclosure in the center of the floor. This enclosure permits the implementation of test sources coincident with the reflecting plane of the floor. In addition, prior work in an anechoic room has indicated the inadequacy of qualification traverses implemented at large spacings. To address this issue, hard-points were designed and implemented within the room to permit installation of traverse cables extending radially from the in-floor source enclosure out to the walls and corners. These traverse cables are an integral component of a custom continuous traverse system. The design features of the chamber which facilitate chamber qualification will be presented, along with the broadband and pure tone results of the qualification performed on the chamber.
3D finite-difference simulation of acoustic waves in turbulent moving media
Authors: Symons Neill , Aldridge David , Wilson D. Keith , Marlin David , Ostashev Vladimir
Published: October 2013

A finite-difference algorithm appropriate for modeling acoustic waves in a fully heterogeneous moving 3D media has been developed. The model is characterized by: acoustic velocity, density, and the three components of the background media velocity. The approach solves a set of coupled 1st order velocity-pressure differential equations appropriate for an adiabatic divergence-free background velocity. The equations are staggered in time and space and the algorithm uses second order temporal and fourth order spatial finite-differences. Since approximations are not adopted in the solution of the equations all arrivals are modeled with fidelity providing the spatial and temporal grids are chosen appropriately. The algorithm can include either a pressure or velocity free surface on the bottom boundary and absorbing boundaries on other model flanks. Designed to run on large scale parallel computational platforms, the algorithm has been validated for four machine architectures. Comparisons are presented to an analytic solution for a constant wind model and fast-field program results for a vertically stratified wind model. Data resulting from simulations through a kinematic turbulence wind profile developed with the quasi-wavelet method are also presented. Sandia National Laboratories is operated by Sandia Corporation, a Lockheed Martin Company, for the USDOE under Contract No. 94-AL85000.
Sound propagation in an urban environment. II: Preliminary FDTD model
Authors: Liu Lanbo , Albert Donald G.
Published: October 2013

A 2-dimensional finite difference time domain (FDTD) method was used to simulate a data set recorded by a microphone array in an urban terrain. The FDTD model uses a coupled system of first-order differential equations for excess pressure and particle velocity. The perfectly matched layer method was used to truncate the model domain. This technique is much more efficient in diminishing unwanted reflections from the domain boundaries than any other absorptive boundary technique. The numerical integration was carried out with a staggered grid system. This algorithm has been validated with comparison with analytical solutions for cases with uniform physical parameters and simple geometries. For the predicted sound levels, although they are in general agreement with the measured values at 13 sensor locations, there is a significant discrepancy occurred at one particular sensor location (microphone location 9) behind one building (Building A). The observed sound level is about an order of magnitude greater than the predicted level, suggesting that much sound energy has propagated through this building. In contrast, a general consistency, or comparable level, can be reached between the measured and the modeled sound levels within 2-fold for the remaining 13 stations. [Work funded by the US Army.]
Analysis and comparison of three energy density probe designs
Authors: Locey Lance L. , Sommerfeldt Scott D.
Published: October 2013

Previous research has demonstrated the utility of acoustic energy density measurements as a means to gain a greater understanding of acoustic fields. Three energy density probes are under development. The first probe has three orthogonal pairs of microphones embedded on the surface of a sphere. The second design is a similarly sized sphere with four surface mounted microphones, equidistant from the center of the sphere. The four microphones are arranged to correspond with the origin and unit vectors of a Cartesian coordinate system, where the origin and the tips of the three unit vectors are on the surface of the sphere. As a result, all four microphones lie on the surface of the top hemisphere. The third design consists of a similarly sized sphere with four surface microphones arranged in a tetrahedron configuration. The author will discuss some of the errors and limitations associated with the four microphone designs as compared to the six microphone design. [Work supported by NASA.]