bluuebunny/crossref_metadata_2025 huggingface dataset:
High-powered parametric acoustic array in air.
Authors: Haupt Robert W.
Published: October 2013

MIT Lincoln Laboratory has developed a prototype high-powered parametric acoustic array (HPPAA) for standoff acoustic excitation in several applications. Parametric arrays offer a highly directional, narrow beam mechanism to deliver sound in air to desired targets typically within a 100 m range. However, a difficult challenge arises in generating sufficient sound power at difference-frequencies below 1000 Hz at a range which can be critical for many target types. An important objective of the HPPAA design maximizes the difference-frequency pressure amplitude at range by maximizing the end-fire array length established by the PAA. The design optimizes the trade-offs between the three characteristic lengths that control the resultant end-fire array length including the pump or carrier wave attenuation, PAA aperture, and acoustic saturation of air. In field demonstrations, the HPPAA generated a carrier wave pressure power approximately 155 dB re-20-microPa one meter from the PAA face while generating a 300 Hz difference-frequency SPL of 90 dB re-20-microPa 8 meters from the PAA. These sound pressure levels at a few hundred hertz may enable safe standoff excitation and detection of buried landmines and may be useful in standoff nondestructive testing (NDT) damage detection and imaging of structures.
Laboratory applications of truncated parametric arrays.
Authors: Humphrey Victor F.
Published: October 2013

Parametric arrays have characteristics that make them ideally suited for use as versatile sources in the laboratory for performing a range of measurements and acoustic studies. Such measurements can exploit the wideband character of the source to provide detailed acoustic response characteristics of systems as a function of frequency, while the short pulses and narrow beamwidths enable multiple reflections and unwanted echoes to be resolved or minimized. However, the need to make measurements in the nearfield of the array means that truncation of the nonlinear interaction region with an acoustic low-pass filter is advisable in order to generate a region free of secondary-sources and simplify the interpretation of the results. This truncation also avoids the possible influence of hydrophone nonlinearity. The effects of truncation on the array characteristics are illustrated using both model and experimental results. A number of examples of the use of arrays in the laboratory are given, including their use to study acoustic scattering from structures and diffraction from baffles, and measurement of reflection and transmission properties of materials. These demonstrate how the characteristics of parametric arrays can be exploited to make detailed, accurate measurements of relevance to underwater acoustics under laboratory conditions.
Localizing a speech target in a multitalker mixture.
Authors: Kopčo Norbert , Best Virginia , Carlile Simon
Published: October 2013

Despite the importance of spatial hearing in everyday listening, little is known about the accuracy of sound localization in a complex mixture of sounds. Here we measured, for the frontal audio-visual horizon, how accurately listeners could localize a female-voice target amidst four spatially distributed male-voice interferers in a moderately reverberant room. To examine whether listeners can make use of a priori knowledge about the configuration of the scene, we compared performance when the interferer locations were fixed (in one of five known patterns) to when the locations varied from trial to trial. The presence of interferers disrupted target localization, even after accounting for reduced target detectability. Randomizing the interferer locations had a moderate influence, degrading performance in some configurations but improving it in others. All effects were magnified when the target-to-interferer intensity ratio was reduced. The results confirm that spatial perception is disrupted by interfering sounds, and that this disruption is modified to some extent by listeners’ expectations about the spatial arrangement of the scene. [Work supported by HFSP, NIH, VEGA, ARC and a Univ. of Sydney Postdoctoral Fellowship.]
A residual-potential boundary for time-domain problems in computational acoustics.
Authors: Geers Thomas L.
Published: October 2013

For many years, researchers have sought theoretically exact time-domain computational boundaries that are temporally, spatially, and geometrically local. Unfortunately, spatial locality and geometric locality cannot be simultaneously achieved for exact boundaries. Absorbing boundaries offer spatial locality but not geometric locality, whereas impedance boundaries offer the latter but not the former. Following a brief discussion of these topics, a new, theoretically exact impedance boundary is introduced that is based on modal residual potentials for the spherical geometry. The new boundary produces a set of first-order, uncoupled ODEs for nodal boundary responses and a set of low-order, uncoupled stepping formulas for modal boundary responses. The two sets are coupled through nodal-modal transformation based on the orthogonal surface functions for the spherical boundary. Numerical results generated with the boundary are presented for selected benchmark problems. Finally, extension of the method to other separable geometries for the wave equation is discussed.
Experimental validation of vibroacoustic reconstruction of a rectangular plate with different boundary conditions.
Authors: Natarajan Logesh Kumar , Wu Sean
Published: October 2013

This paper provides an experimental validation of vibroacoustic responses of a rectangular plate reconstructed using Helmholtz equation least squares (HELS) method. Experimental studies were conducted on baffled rectangular plates of different aspect ratios with free as well as clamped boundary conditions under random excitation. The radiated acoustic pressures were measured using a planar array of microphones at a very close distance to the plate surface and taken as input for the HELS codes. The normal surface velocity distributions were then reconstructed, and the results were compared against the benchmark data obtained using a laser vibrometer. The structural modes of the plate with different boundary conditions were compared with those obtained by experimental modal analysis. Good agreements were obtained for both clamped and free boundary conditions.
Vibro-acoustic coupling of a rectangular cavity backed by a flexible panel with general boundary conditions.
Authors: Du Jingtao , Liu Zhigang , Yang Tiejun , Li Wen
Published: October 2013

Vibro-acoustic coupling system composed of a rectangular cavity and a flexible panel is widely studied in the backgrounds of panel vibration analysis and active noise control in enclosed sound field either by sound or structural actuators, corresponding to ANC and ASAC, respectively. In the most of the current investigation, the boundary conditions of the flexible structure are limited to simple case, namely simply supported and/or clamped. As an important structural parameter, boundary condition has a great effect on the coupling characteristics of such vibro-acoustic system, and a good understanding on this phenomenon will be helpful to the system design as well as active noise control. In this presentation, the analytical model of a rectangular cavity backed by a flexible panel with general boundary conditions is developed. Two sets of improved 2-D and 3-D cosine series with supplementary terms are constructed to respectively describe the displacement and pressure distributions in the boundary structure and 3-D acoustic cavity. The aim of introduction of the supplementary terms is to overcome the potential discontinuity encountered along the structural boundary and the fluid–solid coupling interface respectively for the both fields mentioned above. Numerical calculations are carried out to show the effectiveness of the current method and to study the effect of the structure boundary on the coupling characteristics of the panel-cavity system.
Static and dynamic approaches to understanding vowel perception.
Authors: Hillenbrand James M.
Published: October 2013

The purpose of this paper is to provide a broad overview of work leading up to the current view that vowel inherent spectral change (VISC) plays a significant role in the recognition of vowel identity. Although seldom if ever explicitly stated, the view that implicitly guided vowel perception research for many years assumed that nearly all of the information needed to specify vowel identity was to be found in a cross section of the vowel spectrum sampled at a reasonably steady portion of the vowel. There is now a considerable body of evidence showing that VISC plays an important role in the recognition of vowel identity. Evidence comes from: (1) measurement studies showing that many nominally monophthongal English vowels show significant spectral change throughout the course of the vowel; (2) statistical pattern recognition studies showing that vowel categories are separated with far greater accuracy by models that take spectral change into account; and (3) perceptual experiments showing that vowel steady-states are neither necessary nor sufficient for conveying vowel identity. In spite of this evidence, a static view of vowel identity continues to be implicitly assumed in many studies of vowel quality. [Work supported by NIH.]
Spectral change in the front vowels of North American English.
Authors: Nearey Terrance M.
Published: October 2013

Assmann and Nearey [J. Acoust. Soc. Am. 80, 1297–1308 (1986)] coined the term “vowel-inherent spectral change” (VISC) to refer to change in spectral properties inherent to the phonetic specification of vowels. Although VISC includes the relatively large formant movements associated with acknowledged diphthongs, it was explicitly extended to include reliable (but possibly more subtle) spectral change associated with vowel categories of North American English typically designated as monphthongs. This paper reviews statistical evidence of VISC in the formant patterns in front vowels of /hVd/ syllables in three regional dialects of English: Dallas, TX [Assmann and Katz, J. Acoust. Soc. Am. 108, 1856–1866 (2000)], Western, MI [Hillenbrand et al., J. Acoust. Soc. Am. 97, 3099–3111 (1995)] and Northern, AB (new data). Results suggest that VISC patterns may be useful characteristics for assessing dialect differences. Evidence is presented for the importance of VISC in vowel perception, including recent evidence from our laboratories regarding perception by second language learners. A progress report is provided on research into how VISC is best characterized parametrically and which temporal regions of a vocoid may be most effective in summarizing VISC patterns in varying consonantal contexts.
Developmental study of vowel-inherent spectral change.
Authors: Assmann Peter F. , Nearey Terrance M. , Bharadwaj Sneha V.
Published: October 2013

Children’s speech differs from adult speech in several important ways. First, children have smaller larynges and supra-laryngeal vocal tracts than adults, with the result that their formants and fundamental frequencies are higher. Second, the temporal and spectral properties of children’s speech are inherently more variable, a consequence of developmental changes in motor control. Both of these sources of variability raise interesting questions for theories of talker normalization and vowel specification. In the present study we compare the pattern of time-varying spectral change in vowels from a database of vowel recordings from adults and children ranging in age from 5 through 18 years from the Dallas, Texas region. Preliminary findings indicate systematic age-related differences in the average frequencies of the formants, but the pattern of vowel-inherent spectral change is well preserved across the age span investigated.
Cross-generational differences in dynamic formant patterns in vowels.
Authors: Fox Robert Allen , Jacewicz Ewa
Published: October 2013

As the position of a vowel changes within the vowel space across generations of speakers, so does its dynamic formant pattern. This study examines variation in the dynamic patterns of vowel formants across two age groups: children (8–12 years) and older adults from their grandparents’ generation (51–65 years). The cross-generational changes in vowels /ɪ, ε, æ/ were examined for each of the three regional variants of American English spoken in Southeastern Wisconsin (affected by the Northern Cities Shift), Western North Carolina (affected by the Southern Vowel Shift) and Central Ohio (not considered to be affected currently by any vowel shift). The following vowels in children’s productions were monophthongized as compared to those of their grandparents’ generation: Wisconsin /ɪ, ε/ (but not /æ/), North Carolina /ε, æ/ (but not /ɪ/), and Ohio /ɪ, ε, æ/. In addition to the reduced formant movement, some of the children’s vowels had a different direction of formant change. These cross-generational changes were assessed in a set of measures including formant trajectory length, spectral rate of change and angle of formant change. The measures were calculated from formant frequencies extracted at points in the vowels corresponding to 20, 35, 50, 65, and 80% of the vowel’s duration. [Work supported by NIH.]
Auditory representation of vowel quality.
Authors: Wallace Andrew B. , Blumstein Sheila E.
Published: October 2013

It is generally assumed that the early stages of speech perception involve the extraction of some kind of generalized auditory patterns or properties from the peripheral input. The auditory representation that results is of considerable interest, since it serves as the input to higher-level, speech specific processes of phonetic perception. The current research examines this auditory representation using a priming paradigm, in which perception of vowel targets is facilitated when the targets are preceded by acoustically matched nonspeech stimuli. By manipulating the acoustic parameters of these nonspeech “prime” tones, it is possible to determine the role of these parameters in the auditory stages of vowel processing. Previous results [Wallace and Blumstein, J. Acoust. Soc. Am. 119, 3245 (2006)] suggest a short window of analysis of no more than 25 ms. In Experiment 1, frequency of nonspeech primes was varied, with results suggesting broad frequency tuning. In Experiment 2, primes matched to both F1 and F2 of the target vowels were found to elicit a greater priming effect than would be predicted by summing the response to separately presented F1 and F2 primes, suggesting that the auditory representation of vowels encodes combinations of formant frequencies.
Cross-dialect differences in vowel identification.
Authors: Neel Amy T. , Ewing Cai S.
Published: October 2013

In this study, identification of vowels produced by Michigan speakers by listeners of two dialects, Michigan (Inland North) and New Mexico (Western) was examined. New Mexico listeners identified sets of ten vowels (i, ɪ, e, ε, æ, ɑ, o, ʌ, U, u) from 30 speakers in the Hillenbrand et al. (1995) database. Their results were compared to the results from the Michigan listeners in the original study. Preliminary results from ten New Mexico listeners show that overall identification rates across the 30 speakers did not differ significantly between dialects. However, NM and MI listeners differed on identification rates for individual speakers and particular vowels. They agreed on the worst speaker but differed by as much as 11 percentage points for others. NM listeners performed worse on /ε/ and /ɑ/ but slightly better on /ʌ/ than MI listeners. To determine the nature of cross-dialect differences in perception, acoustic data such as vowel space area, formant dynamics, and duration characteristics will be examined, and the relation of acoustic data to identification scores will be presented.
Effects of dialect on vowel acoustics and intelligibility.
Authors: Oder Austin L. , Ferguson Sarah Hargus , Clopper Cynthia G.
Published: October 2013

A great deal of recent research has focused on the phonetic variation of American English vowels from different dialects. This body of research continues to grow as vowels periodically and unconsciously undergo formant movements that become characteristic of certain dialects (e.g., the Northern Cities Chain Shift and the Southern Vowel Shift). Two experiments using the Nationwide Speech Corpus [Clopper and Pisoni, Speech Communication, 48, 633–644 (2006)] are exploring whether the Midland dialect is more closely related acoustically and perceptually to the Southern or to the Mid-Atlantic dialect. Experiment 1 consists of acoustic analyses of 11 English vowels from each of the three dialects. In Experiment 2, 11 vowels in /hVd/ format recorded from speakers of the three dialects are being presented to speakers of a Midland dialect for identification. This study will thus further our understanding of acoustic and perceptual differences between the most marked dialects (Mid-Atlantic and Southern) and the least marked dialect (Midland). [Work supported by a University of Kansas Honors Program Undergraduate Research Award.]
Spectral analysis of the vowels of the Peking dialect.
Authors: Lee Wai-Sum
Published: October 2013

The paper presents the spectral characteristics of the dorsal and apical vowels in open syllables of the Peking dialect. Results show that (i) of the dorsal category the high and low vowels are monophthongs, whereas the mid-back vowels and rhotacized ə are diphthongal; (ii) the two apical vowels are similar in F1 and F2, but differ considerably in F3, with a lower F3 for the retroflexed than the plain one; (iii) the extensive overlaps between the vowel ellipses for the unrounded mid-back vowel and plain apical vowel in the F1F2 plane and between those for the rhotacized ə and retroflexed apical vowel indicate that the difference in perceptual quality between the paired vowels may be attributed to the dynamic property of the formant frequencies; (iv) as expected, the average F-values for the vowels are higher for females than males, however, the patterns of positions of the vowel ellipses in the F1F2 plane between the two genders are similar; and (v) the scaling between female and male F-values is nonuniform across vowel categories and across formant frequencies. The formant data will also be discussed in connection with the quality descriptions of the vowels in the past studies of the Peking dialect.
A duration-dependent account of coarticulation for hyper- and hypoarticulation.
Authors: Sussman Harvey M. , Lindblom Bjorn , Agwuele Augustine
Published: October 2013

Hyperarticulated and hypoarticulated speech are accompanied by spectral expansion and spectral reduction of vowel nuclei, respectively. These shifts in F1/F2 vowel space directly affect degree of anticipatory coarticulation in consonant + vowel sequences apart from traditional vowel context effects. Examining the opposite conditions of emphatic stress [Lindblom et al., J. Acoust. Soc. Am. 121, 3802–3813 (2007)] and faster speaking rates (Agwuele et al., Phonetica, in press) it was shown that coarticulatory effects could be documented independently of the expected vowel expansion/reduction effects. A modified locus equation regression metric was used in both studies to isolate alterations in F2 transition onsets due to prosodic and speech rate conditions apart from vowel space shifts per se. The current study provides a unified empirical and theoretical account for the opposite coarticulatory effects by providing duration data as the common variable tying both studies together. Articulatory and acoustic simulations of deeper (emphasis) and shallower (increased tempo) closures are provided to explain the shifts of observed F2 onsets relative to predicted F2 onsets due simply to expanded/reduced vowel space.
Variability of vowel productions within and between days.
Authors: Heald Shannon L. M. , Nusbaum Howard C.
Published: October 2013

Theories of speech production and speech perception assume that phonetic categories can be characterized by stable properties. For example, the notion of stable vowel targets is used to organize articulation, and such targets could serve as the acoustic basis for recognizing vowel categories. However, there is substantial variation in the acoustic patterns of phonetic categories. The lack of invariance between acoustic properties and the phonetic categories of speech has posed a theoretical problem for understanding human speech perception. Although most theories vary in how acoustic-phonetic variability is approached, theories treat such variability as inherent in speech production or statistically regular or noise. In order to begin to understand acoustic-phonetic variability, we examined the naturally occurring variability in speech production over time. Participants’ productions of seven different vowels ([IH], [EE], [EH], [AW], [AH], [AE], [UW]) were recorded in nine sessions: at three specific times in the course of each testing day (9 a.m., 3 p.m., 9 p.m.), every other day, over the course of 5 days. Formant frequencies and variability of formant frequencies were analyzed to assess how vowel categories change over time. We will discuss the results and consider the theoretical implications of these results.
Relative contribution of jaw and tongue to the vowel height dimension in American English.
Authors: Whalen D. H. , Noiray Aude , Iskarous Khalil , Bolanos Leandro
Published: October 2013

Vowels are typically described according to three articulatory dimensions: height, frontness, and rounding. Other researchers propose a role for the jaw in the height dimension. In the present study, we measured the relative contribution of the tongue and jaw for vocalic height distinction in American English vowels. Tongue and jaw motions were collected in six adult speakers for six vowels from all portions of the vowel space, embedded in [hVd] sequences. Tongue shape was captured via HOCUS (Haskins Optically Corrected Ultrasound System) which combines digital ultrasound imaging at 127 Hz with optical three-dimensional tracking of infrared emitting diodes (IREDs) positioned on the speaker’s head and probe for subsequent decoupling of tongue motion from the jaw motion. Results showed a consistent role of the tongue in creating the vocalic constriction for the six subjects investigated, though with some idiosyncratic strategies. Jaw contribution was more sizable for vowel pairs traditionally contrasted by height than for tense/lax pairs, confirming previous findings from x-ray studies. One new result is the dominance of tongue contribution over the jaw’s, even for vowels distinguished by height. [Work supported by NIH grant DC-02717.]
Entropy estimation using pattern matching in bioacoustic signals.
Authors: Buck John R. , Suzuki Ryuji
Published: October 2013

Many bioacoustic signals consist of a sequence of discrete stereotyped sounds occurring in repeated patterns. A natural question to ask is how best to characterize the underlying structure of the source producing the sequence of sounds. The structure of the source manifests itself as constraints on the patterns observed in the sequence of sounds. These constraints determine how predictable the order of the sounds is. The information entropy of a discrete symbol sequence is a quantitative measure of how unpredictable the sequence is. A straightforward but biased technique for estimating the entropy of an unknown source is to substitute observed symbol frequencies into parametric models such as Markov models. More general nonparametric entropy estimators exploit the relationship between the entropy and the average length of matching patterns within the sequence. This nonparametric entropy estimate forms an upper bound on the amount of information conveyed by the sequence of sounds. Additionally, comparing entropy estimates from the parametric and nonparametric models provides a hypothesis test determining whether the parametric model sufficiently captures the constraints of the source. These techniques are illustrated in analyses of humpback whale songs and leopard seal calling bouts.
Classification of audio signals using generalized spatial fuzzy clustering.
Authors: Luong Huynh V. , Kim Cheol Hong , Kim Jong-Myon
Published: October 2013

With the increasing use of multimedia data, the need for automatic classification and retrieval of certain kinds of audio data has become an important issue. In this paper, we propose an efficient method of audio signal segmentation and classification from audiovisual database. While conventional methods apply thresholding to audio features such as energy and zero-crossing rate to detect the boundaries, causing misclassification for audio signals which contain certain audio effects such as fade-in, fade-out, and cross-fade, the proposed algorithm, called general spatial fuzzy c-means algorithm (GSFCM), solves the problem by taking into account the local spatial information which is weighted correspondingly to neighbor elements based on their distance attributes. GSFCM detects the boundaries between two different audio signals, classifies segments, and then extracts unique feature vectors. This results in the accurate detection and classification. Experiment results for the audio signal from TV news program at 44.1 kHz with 30-min long confirm that the proposed method outperforms conventional methods in terms of accuracy of the audio signal classification. These results demonstrate that the proposed method is a suitable candidate for audio-video indexing which is compressed by MPEG. [Work supported by the MKE, Korea, under the ITRC supervised by IITA (IITA-2008-(C1090-0801-0039)).]
Detection and classification of defects in underground pipes using reflection coeffecients.
Authors: Bin Ali Muhammad Tareq
Published: October 2013

Detection and classification of defects developed in underground pipes have been an important issue for a long time. A novel sensor has been developed to find defects (i.e., blockage, deformation, crack, etc.) in buried pipes. Theoretical analysis has been supported by the experimental results. The sensor consists of a speaker and four microphones. The location of the defect is determined by the reflected signal recorded in the microphones. The reflected signal from a particular defect is sent through filter banks to identify the signal properties, which are related to the property of the defect. Different types of defects have been simulated in the lab and in the field. The sensor has been found to locate and classify the defect considerably well.
Detecting and localizing pipe changes via matched field processing.
Authors: Tolstoy A. , Horoshenkov K. , Bin-Ali M. T. , Tait S. J.
Published: October 2013

In this work we shall demonstrate that the presence of some pipe changes, e.g., blockages can be detected via matched field processing given an array of two or more microphones. In particular, the location of such transient irregularities can also be determined using this technique. We shall show data processed with this technique for a variety of blockages in a variety of locations for a variety of pipes (concrete, PVC, and clay). There is no acoustic modeling of the fields required, and only the simple linear processor is applied. The method can be used to determine the location of change and its severity.
Boundary effects on elastic signatures of proud tilted aluminum cylinders.
Authors: La Follett Jon , Marston Philip L.
Published: October 2013

Synthetic aperture sonar (SAS) and frequency response as a function of tilt (acoustic color) are two methods used to study target backscattering. Close proximity to a boundary can affect both the SAS and spectral signatures of a target. To improve understanding of these effects, scaled tank experiments were carried out on solid aluminum cylinders having flat ends and length to diam ratios of 2:1 and 5:1. To partially simulate the mechanisms present when an object is resting on the ocean bottom and illuminated at shallow grazing incidence, the cylinders were suspended through the air-water interface of a tank. Monostatic measurements were obtained as the source/receiver was scanned along a line parallel to the interface to produce SAS images. Backscattering measurements were also made as the target was rotated in a plane parallel to the interface, with the source/receiver stationary, to give the spectrum (color) as a function of tilt. Some of the elastic features in the SAS images and the acoustic color diagrams could be interpreted using a previously developed ray-based theory of generalized Rayleigh waves [K. Gipson and P.L. Marston, J. Acoust. Soc. Am. 106, 1673–1689 (1999);, 107, 112–117 (2000)]. [Research supported by ONR.]
Monostatic and bistatic measurements of targets resting on or buried under the seafloor.
Authors: Lopes Joseph , Williams Kevin , Kargl Steve , Hefner Todd , Thorsos Eric , Marston Philip , Paustian Iris , Lim Raymond
Published: October 2013

Measurements were conducted to investigate monostatic and bistatic scattering of targets resting on or buried under a seafloor. The measurements were performed in NSWC-PCD’s Facility 383, which is a 13.7 m deep, 110 m long, 80 m wide test pool with a 1.5 m layer of sand on the bottom. Two synthetic aperture sonar (SAS) rail systems were utilized in the measurements, and they were placed perpendicular to each other and oriented so as to look at the same region of the bottom. This strategy allowed a particular target and environment configuration to be set up and studied for both monostatic and bistatic geometries. Targets included a 0.61 m diam stainless steel shell and two 0.3 m diam solid aluminum cylinders with lengths of 0.61 and 1.52 m. This paper summarized the measurement setup and instrumentation. A sample of the results of these measurements will be presented. Subsequent papers will provide detailed analysis and comparisons with predictions of models. [Work supported by the Office of Naval Research and the Strategic Environmental Research and Development Program.]
Three-dimensional structural-acoustics modeling and its validation for free-field and littoral environments.
Authors: Dey Saikat , Sarkissian Angie , Mestreau Eris S. , Houston Brian H. , Kraus Larry
Published: October 2013

Accurate numerical modeling of structural acoustics scattering in littoral environments, in mid-to-high frequency regimes, presents several challenges, including the ability to model the truncation of the nonhomogeneous exterior domain with free surfaces. Additionally, the frequency-dependent nature of the problem introduces significant dispersion errors with increasing frequency. This makes low-order three-dimensional discretization prohibitively expensive for high accuracy computations. We present a modeling framework for three-dimensional acoustic scattering in littoral environments treated as two half-spaces defined as the fluid and the sediment, respectively. The fluid portion may terminate at a free-surface boundary. The sediment may be a damped fluid or poroviscoelastic solid. The model admits rigid or viscoelastic scatterer with complex three-dimensional shapes including internal structural details and fillings. Exterior domain truncation uses perfectly matched-layer (PML) approximations. An hp-finite-element approximation scheme is utilized to control dispersion errors providing high-accuracy solutions in mid-to-high frequency regimes. Large-scale three-dimensional problems consisting of millions of unknowns solved scalably using a combination of efficient multifrontal solvers and domain-decomposition (FETI-DP) techniques. Numerical results validating applications in free field as well as littoral environment against experimental data will be presented. [Work supported by HPCMP and ONR.]
An overview of the waveguide invariant and some of its applications to signal processing.
Authors: Kuperman W. A. , D’Spain G. L. , Gerstoft Peter , Hodgkiss W. S. , Song H. C. , Thode A. M.
Published: October 2013

While the waveguide invariant is a compact descriptor of certain aspects of acoustic propagation in the ocean, it also has a broad range of applications from describing acoustic fluctuations to assisting in various types of signal processing. After presenting a brief theoretical and experimental overview of the invariant in terms of both normal modes and rays, some applications to signal and array processing are discussed.
Waveguide invariance for active sonar.
Authors: Quijano Jorge E. , Zurk Lisa M.
Published: October 2013

Active sonar signal processing in shallow water has proven to be a challenging problem due to the strong interaction of sound with the boundaries of the channel and the dependence on typically unknown environmental parameters. This has motivated research on properties of acoustic propagation that are not sensitive to those factors, such as the waveguide invariance. The invariance principle has found application in passive sonar signal processing by relating the frequency content of a broadband source to the range between source and receiver. More recently, experimental evidence has suggested that a similar structure exists for active sonar. This structure provides additional information about the location of a target, and information can be exploited in sonar processing algorithms such as target tracking. Data from several sea experiments have been analyzed to determine the behavior of the active invariance, and tank experiments have been designed to confirm the presence of the range-frequency structure in signals reflected by a moving target. This presentation provides an overview of the active invariance phenomena and describes the performance of a target tracking formulation that incorporates invariance structure into the state space representation for improved performance.
Environmentally invariant features for classification of active sonar signals.
Authors: Loughlin Patrick , Okopal Greg
Published: October 2013

Dispersion and damping (frequency-dependent spreading and attenuation) can be significant in shallow water sound propagation. These propagation-induced effects can be detrimental to classification of active sonar returns because the observed backscatter depends not only on the target, but also on the propagation environment and how far the wave has traveled, resulting in increased variability in the received signals. We address this problem by extracting propagation-invariant features from the wave that can be used in an automatic classifier. In this talk, we review various moment-like features we have developed that are invariant per mode to dispersion and damping. Simulations of the backscatter from different steel shells propagating in a channel with dispersion and damping are presented to demonstrate the classification utility of the various invariant features. [Work supported by ONR Grant N00014-06-1-0009.]
Full spectrum acoustic wave propagation prediction.
Authors: Clark Cathy Ann , Smith Kevin B.
Published: October 2013

An overview of a normal mode solution to the Helmholtz wave equation to describe the underwater sound field for a fixed point source in a plane multilayered medium which utilizes Bessel functions of order 1/3 is presented. The mode functions are continuous across turning points of the separated depth-dependent differential equation due to careful selection of the representations to be used for Bessel function arguments in various regions of the complex plane. A quotient involving vertical wave number and phase is seen to behave as a constant through turning points, enabling the mode amplitude functions to remain analytic, changing from oscillatory to exponential on traversing the turning point, thus enabling smooth incorporation of the continuous spectrum. The method also provides vertical directionality at all field points without post-processing the complex acoustic field. Comparisons of model results to a limited number of measured data sets and benchmark propagation codes are presented. Derivation and verification of the solution for bottom-interacting modes, including shear and compressional reflection and transmission for a layered bottom, as well as an extension into horizontally varying, shallow water environments are also discussed. Portions of this work have been published in the IEEE Journal of Oceanic Engineering.
Passive ranging using the waveguide invariant.
Authors: Cockrell Kevin L. , Schmidt Henrik
Published: October 2013

A range versus frequency spectrogram of an acoustic field due to a fixed source in a waveguide will exhibit striations whose slopes depend on the range to the acoustic source and the value of the waveguide invariant. While many authors have pointed out that the range to an acoustic source can be estimated from the slopes of the striations in the spectrogram, few have presented an explicit algorithm to do so. An algorithm for estimating the range is presented and tested on experimental data collected in a shallow water waveguide during GLINT08, an exercise performed off of Pianosa Island, Italy. The experimental data consist of a fixed broadband acoustic source emitting energy at frequencies from 300 to 800 Hz, with a hydrophone measuring the acoustic field along a 1.75-km track directly away from the acoustic source.
Evaluation and control of the acoustical environment in a long-term-care facility.
Authors: Hodgson Murray , Steininger Gavin
Published: October 2013

This paper discusses the acoustical evaluation of the Minoru Residence long-term-care facility, to respond to concerns by its staff regarding the acoustical conditions. A review of existing acoustical standards with an analysis of their applicability to health-care facilities was conducted for the problems observed in the Minoru Residence. Measurements were made of the acoustical characteristics: unoccupied and occupied noise levels, reverberation times, Speech Intelligibility Index, and noise isolation. They showed that background noise levels in several key areas including the Rehabilitation Office and the Patient Lounges exceeded acceptable values. Reverberation times were excessive in the entrance lobby and patient common areas. The Speech Intelligibility values in the Nurse Stations and Rehabilitation Offices were below acceptable values. The noise isolation was inadequate between the entrance lobby and office areas. Recommendations were made for the improvement of the acoustical conditions. These recommendations include the reinforcement of the Front Office façade, and the application of acoustical ceiling tiles to the Rehabilitation Office and the entrance lobby.
Achieving green design acoustical standards in healthcare facilities.
Authors: Holst Peter , Salter Ethan
Published: October 2013

With the advent of the green guide for healthcare, and the introduction of LEED health care, which both include acoustical design credits, the benefits of good acoustical design have been recognized for improving patient recovery rates as well as staff health and efficiency. The acoustical issues in designing health care facilities cross the spectrum of acoustical design: sound isolation/speech privacy, room acoustics, sound masking, mechanical noise/vibration, environmental noise, and project-specific features, such as MRI and helipads. It is the responsibility of the acoustical consultant to address each item with the design team to develop cost-effective solutions to meet the criteria established by the green standards. This paper will provide background information on the acoustical design challenges for healthcare facilities and will discuss general approaches that achieve the goals of green acoustical design. Specific examples from projects will also be included, drawing from experience in design of hundreds of health-care facilities, as well as documentation of credits achieved for numerous medical centers that plan to submit for LEED healthcare. This paper will be a valuable resource for acoustical consultants in the design of all types of healthcare facilities, such as hospitals, central plants, medical office buildings, and nursing facilities.
Canadian hospital acoustical evaluation.
Authors: Sbihi Hind , Hodgson Murray
Published: October 2013

The aim of this study was to evaluate the acoustic conditions of two wards in a research/teaching hospital in British Columbia, Canada. The selection of the wards was based on managerial staff needs and perceptions of issues related to the acoustical working environment with respect to privacy and also aggressive behaviors. The two selected units were an adult emergency department and a long-term care facility where the patients population was a mix of elderly with different mental and physical health conditions. The methods will include long-term noise measurements, building acoustical measurements and interviews with nursing staff. In particular, measurements will be made of the following acoustical parameters in the facilities: unoccupied and occupied noise levels; reverberation time; Speech Intelligibility Index; noise isolation. Results will be evaluated by comparing them with acceptability criteria. Identification of nonoptimal aspects of the facilities acoustical environments will result from the consideration and analysis of staff responses and comparison with published guidelines.
Proposed components of an “ideal” indoor noise criteria rating system.
Authors: Wang Lily M.
Published: October 2013

A number of studies have been conducted at the University of Nebraska on correlating human performance and perception to indoor noise criteria systems. Task performance and subjective perception data were gathered from subjects exposed to background noise conditions commonly due to mechanical systems, including some with tonal components and some with time-varying fluctuations. Results show that perceptions of annoyance and distraction are highly correlated to the character of the noise, but the current indoor noise criteria systems (such as noise criteria and room criteria) do not accurately reflect that relationship. This paper presents a proposal for what an indoor noise criteria rating system should ideally include, to quantify acceptable building mechanical system noise in commercial buildings. [Work supported by the American Society of Heating, Refrigeration and Air-Conditioning Engineers.]
A case history comparing noise criteria.
Authors: Lilly Jerry G.
Published: October 2013

A case history of an indoor HVAC noise problem in a new residential building will be presented. Noise measurements collected in the living room and in the bedroom of the impacted living unit will be examined using several of the available noise criteria methods including, NC, RC, NCB, and RNC (ANSI S12.2). Although the architect and the building owner believed that the HVAC noise was unacceptable, the measured noise levels met the NC, NCB, and RNC noise criteria. Only the RC method was able to accurately detect the problem.
Acoustic analyses of two undocumented sound patterns in the Drosophila suzukii and D. takahashii species subgroups.
Authors: Lai Yuwen , Yeh Shu-Dan , Gleason Jennifer , True John
Published: October 2013

Acoustic analyses of the courtship songs of the suzukii and takahashii subgroups in the Drosophila melanogaster species group were conducted. The primary and secondary pulse phases that are common in the melanogaster subgroup were not observed in these two subgroups. However, two undocumented sound patterns were discovered. D. biarmipes and D. pulchrella (suzukii subgroup) produce high amplitude, nonrhythmic “toot” sounds, which range from 82–158 ms in duration. The toot sound in D. biarmipes has a consistent dynamic frequency profile. It starts with an onset of 479 Hz and gradually falls to 422 Hz and then rises to 477 Hz. The toot sound in D. pulchrella has a significantly lower frequency when compared to D. biarmipes. Its frequency profile falls gradually from 352–259 Hz. In addition, a “turbo” sound was recorded in D. prostipennis (takahashii subgroup). It is composed of short, high frequency pulses (520 Hz) with 4 ms interpulse intervals. In the melanogaster subgroup, the parameters of pulses have been proposed to play an important role in female preference. The results of the present study suggest that there might be other parameters at play in the species investigated in the current study.
Delivery of targeted echogenic liposomes in an ex vivo mouse aorta model.
Authors: Hitchcock Kathryn E. , Sutton Jonathan T. , Caudell Danielle N. , Pyne-Geithman Gail J. , Klegerman Melvin E. , Huang Shaoling L. , Vela Deborah , McPherson David D. , Holland Christy K.
Published: October 2013

Optimal ultrasound parameters to enhance delivery of therapeutic-loaded echogenic immunoliposomes (ELIP) into the arterial wall are being developed for the treatment of atherosclerosis. The aim of this work was to determine whether anti-ICAM-targeted, rhodamine-labeled ELIP (Rh-ELIP) would adhere to and penetrate the vascular endothelium in atheromatous murine arterial segments with intravascular flow treated with 1-MHz continuous wave ultrasound (CW US). A broadband focused hydrophone, confocally aligned with the artery and 1-MHz transducer field was used as a passive cavitation detector (PCD). Arteries were insonified with 1-MHz CW US (0.49 MPa peak-to-peak pressure), and the PCD was used to verify the duration of the resulting stable cavitation. Perivascular saline was collected and analyzed spectrofluorometrically for the presence of Rh-ELIP. Arteries were prepared for histological analysis by a pathologist blinded to the exposure conditions. Arteries exposed to Rh-labeled ELIP and 1-MHz US exhibited greater adherence of Rh-ELIP to the vascular endothelium and greater passage of Rh-ELIP across the vessel wall. No damage was detected in any of the arteries on histology. These studies will aid in the development of a strategy for improving atheroma treatment without causing ultrasound-related tissue damage.
Electrocardiogram-gated imaging of a mouse heart using a high-frequency annular array.
Authors: Ketterling Jeffrey A. , Mamou Jonathan , Aristizábal Orlando
Published: October 2013

Gated imaging is a technique in which M-mode data, referenced to a feature of an ECG signal, are acquired at a series of lateral positions and then reassembled into B-mode images to achieve high effective frame rates. It is only effective for imaging objects with periodic motion. Annular arrays and synthetic focusing allow for an improved depth of field (DOF) and resolution versus single-element transducers. Here, a five-element, 35-MHz annular array was utilized in combination with ECG and respiratory gating to image adult mouse hearts. An experimental system was assembled to permit appropriate triggering conditions and to collect all 25 transmit-to-receive echo data sets from the annular array at a series of lateral positions. The system was initially tested with a hexagon-shaped target that rotated at 10 revs/s and generated a trigger each rotation. After system testing, data were acquired from an adult mouse heart using a trigger in phase with the R-wave of the ECG signal. The synthetically-focused B-mode images showed several cardiac cycles over a 1200 ms duration captured at 100 fps over a 1-cm depth and a 6-mm width. Data from the mouse heart were acquired with conventional monocycle excitation and also with coded excitation.