bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaural level differences: Diffraction and localization by human listeners.
Authors: Hartmann William M. , Rakerd Brad
Published: July 2011

Because long-wavelength tones are diffracted around the head, interaural level differences (ILDs) are thought to be too small to provide useful localization cues at low frequency. ILDs are unquestionably useful at high frequency. The boundary between low and high for human listeners has been set as high as 3000 Hz [Stevens, and Newman, Am. J. Psych. 48, 297 (1936)]. In fact, however, the frequency range for useful ILD cues depends on the azimuth of the source. ILDs are physically present at 500 Hz and below but they are sensitive to changes in azimuth only near the forward direction. As the frequency increases to 1000 Hz, ILDs clearly play an essential role in sound localization, but the non-monotonic azimuth dependence caused by an approach to the Poisson/Arago bright spot leads to confusion for azimuths greater than 40 or 50 deg. At 2000–3000 Hz, the non-monotonic bright-spot structure moves out to larger azimuths, and ILDs become a mostly monotonic function of azimuth for an ever larger range of azimuths. Above 3000–4000 Hz, the bright spot affects ILDs only at the largest azimuths, but there can be idiosyncratic structure at smaller azimuths. [Work supported by the NIDCD, Grant No. DC 00181.]
The contribution of intrinsic amplitude modulation to the precedence effect at high frequencies.
Authors: Seeber Bernhard U.
Published: July 2011

The precedence effect (PE) demonstrates our ability to locate sounds correctly at the source despite the presence of interfering sound reflections. It was shown to function with broadband noises of long duration even when lead and lag had simultaneous onsets, i.e., when information was restricted to the ongoing sound part. In a localization dominance task participants indicated the perceived location of lead-lag stimuli played from loudspeakers in an anechoic chamber. Stimuli were harmonic complex tones (HCTs) and Gaussian noise bandlimited to 2500–5500 Hz. Lead dominance existed for all stimuli despite lead and lag overlapping in time and having simultaneous onsets. This demonstrates that information from the ongoing sound part alone can evoke the PE at high frequencies. The amount of intrinsic modulation affected echo thresholds (ETs), which were slightly larger for HCTs with Schroeder positive than negative phase. Localization dominance was weak for the noise; ETs were short and a broad image was frequently reported. This indicates that the fast amplitude modulation inherent in HCTs is crucial for the PE at high frequencies, while the shallow modulation depth of the noise was likely detrimental. The PE should thus be possible for selected sounds with cochlear implants, which encode envelope information.
Stop consonant acoustics in children with fetal alcohol syndrome.
Authors: Bolinger Christopher , Dembowski James
Published: July 2011

Speech of children with fetal alcohol syndrome (FAS) has been little studied compared to language. Becker et al. (1990) found a relationship between prenatal alcohol exposure, oral motor control, and speech articulation. The current presentation is part of a larger study attempting to further examine the relationship between speech and motor control in children with FAS. Behavioral tests suggest deficits in focal oral motor control specific to children with FAS [Bolinger and Dembowski (2010)]. The current project attempts to extend this investigation through acoustic measures. Peak and mean frequencies of stop consonant releases were used to infer control of place of articulation. Voice onset time (VOT) was used to infer articulatory-laryngeal coordination. Preliminary measures on three experimental speakers and two matched neurotypical controls suggest higher stop consonant frequencies in the experimental group, with a poorer distinction between alveolar and velar stops than in the control group. Voiced VOT values were significantly longer for FAS children than for controls. Mean voiceless VOTs were similar across groups, but substantially more variable for the FAS children. Values may be interpreted as acoustic evidence for specific speech motor control deficits in FAS children relative to matched neurotypical children.
Oral receptive and expressive language skills and word recognition in children with cochlear implants.
Authors: Gilbert Rachael , Sladen Douglas , Smiljanic Rajka
Published: July 2011

Compared to children with normal hearing, children with cochlear implants (CIs) have a higher degree of difficulty performing speech recognition in noise [Litovsky et al., (2004); Sc. Thibodeau, (2006)]. The combined contribution of the peripheral-auditory and the cognitive-linguistic skills that underlie this difficulty is not well understood. This study examines the relationship between oral language abilities and the effects of phonetic and semantic enhancements on speech perception in children with and without cochlear implants. Specifically, we compare their performance on the oral and written language scale (OWLS), oral receptive and oral expressive tests, with the results of a sentence-in-noise perception test. The sentence in-noise-test was composed of 120 sentences in which the final words varied in predictability (i.e., high versus low semantic context) and which were produced in conversational and clear speech by one female and one male talker. The relationship between the OWLS scores and word recognition in noise was investigated for ten children with CI and ten children with hearing between the ages of 6 and 13. This research will further our understanding of the lower-level sensory and higher-level cognitive factors that affect speech understanding in children.
Patterns of development in stop-release cues to coda contrasts in American-English-speaking 2-year-olds.
Authors: Song Jae Yung , Shattuck-Hufnagel Stefanie , Demuth Katherine
Published: July 2011

A distinctive characteristic of early speech is “exaggerated” release of stop consonants including multiple bursts and heavy post-release noise [Imbrie (2005)]. This study provides an in-depth investigation of changes in the acoustic characteristics of stop coda release from 1;6 to 2;6 years, focusing on their interaction with emerging linguistic contrasts. We examined how various non-spectral coda-release-related cues, such as the presence and duration of post-release noise, varied with coda voicing and place (alveolar versus velar) in spontaneous speech from six American-English-speaking mother-child dyads. Starting as early as 1;6, children produced many of the same types of correlates of voicing and place as adults did, but they exhibited more frequent occurrences and longer durations of these cues compared to mothers; this exaggeration decreased by 2;6. In utterance-medial position, where the decrease was particularly striking, it occurred in a selective, stepwise fashion rather than simultaneously in all contexts. That is, the decrease was larger for voiceless codas than for voiced codas, and for place contrasts, the values decreased first for velars, and only later for alveolars. This observation raises the question of whether such selective fine-tuning is characteristic of phonological development across languages, and if so, what the underlying mechanisms might be. [Work supported by NIH R01HD057606.]
Children’s perception of clear-speech vowels.
Authors: Leone Dorothy , Hsu Sih-Chiao , Baigorri Miriam , Moya-Gale Gemma , Levy Erika
Published: July 2011

Clear speech is an intelligibility-enhancing mode of speech that increases identification accuracy in various listening populations [e.g., Picheny et al. (1986)]. Children identify words more accurately in clear-speech sentences in noise than in conversational-speech sentences in noise [Bradlow et al. (2003)]. At the segmental level, adults identify clear-speech vowels in noise significantly more accurately than conversational vowels in noise, with some vowels benefiting more from clear speech than others [Ferguson and Kewley-Port (2002)]. However, little is known about the clear speech intelligibility benefit for vowels in noise as perceived by children. This study examined children’s identification of clear-speech vowels in noise. Four female adult speakers produced (/i-ε-æ-ʌ/) in carrier phrases in conversational and clear speech. Stimuli were then presented in speech-shaped noise to school-aged children at two signal-to-noise ratios. Children’s repetition of key words were recorded and coded by naive adult listeners. Results revealed children’s poorer vowel identification with decreased signal-to-noise ratio, and a greater clear-speech advantage in the poorer SNR, although listener-variability was evident. These data provide preliminary support for adults’ use of clear speech when communicating with children in adverse listening conditions.
Generalized Bragg scattering for uncertain sea surfaces.
Authors: Oba Roger M.
Published: July 2011

Bragg’s law and related concepts based on acoustic scattering due to surface resonances can provide a framework for computational sea surface scattering. Studies for periodic surfaces [Oba, J. Acoust. Soc. Am. 128, 39 (2010)] demonstrate that variation of acoustic resonance with the surface phase allows Fourier analysis separation of Bragg scattering orders. More generally, consider one-dimensional, undulating, sea surfaces composed of several Fourier components of known wavelengths, but of uncertain amplitude and phasing. A combination of polynomial chaos (PC) and Fourier expansion for the acoustic field consists of sums of products of Laguerre polynomials and complex exponentials, corresponding to parameters for uncertainty in surface amplitude and phase, respectively. Each single PC-Fourier index quantifies the acoustic response to an individual order in Bragg’s law. The Laguerre polynomial terms represent the non-linear acoustic variation with surface amplitude. A particular PC-Fourier expansion coefficient corresponding to several surface wavelength components permits evaluation of cross-component coupling. The PC-Fourier coefficient decay rate indicates the degree of Bragg scattering coupling between components. The robustness of the PC-Fourier coefficients in the presence of a larger set of random rough surface components is explored. [This research is sponsored by the Office of Naval Research.]
Three dimensional analyzes of scattering by pressure release sinusoidal surfaces. I. Theory.
Authors: Welton Patrick J
Published: July 2011

Many previous analyzes of scattering by sinusoidal surfaces are based on the Helmholtz integral equation in two dimensions and assume that the incident energy is a plane wave. Some of these solutions are exact insofar as they do not use the Kirchhoff boundary value approximation. However, all of the analyzes are based on one or more commonly used scattering approximations. Analyses presented here are carried out in three dimensions and are based on an integral equation which is analogous to the Rayleigh integral formula. The scattering is restricted to the plane of incidence, but includes receiver grazing angles ranging from 0 to 180 deg. Both the Fresnel phase approximation and Gaussian source and receiver beam functions are used. One of the objectives of this study is to explore the validity of the Kirchhoff approximation, so shadowing and second order scattering are explicitly included. The surface heights and slopes are not restricted in any way, and the surface slope treatment is exact. The resulting expressions are used in the companion paper to explore various approximations and limiting cases that are often encountered in the scattering literature.
Backscattering from a pressure-release rough surface.
Authors: Joshi Sumedh M. , Isakson Marcia J.
Published: July 2011

The backscattering of an incident Gaussian-tapered acoustic plane wave is modeled using finite elements, the Kirchhoff approximation, and perturbation theory, with the aim of quantifying the validity of the approximate models. von Karman-type power spectra describing the bottom roughness are sampled from the literature with rms roughness from 3–15% of the acoustic wavelength. Realizations of each type of spectrum are made assuming a Gaussian surface height distribution, and an average backscattering cross section is obtained by ensemble averaging. The pressure-release bottom is used instead of a penetrable sediment, as the focus in this study is to quantify the differences between finite elements and the approximate models due to roughness. [Work supported by ONR.]
A study on subcritical penetration into rough seafloor.
Authors: Peng Linhui , Lu Jianhui
Published: July 2011

Bragg scattering from rough interface of seafloor is one of the main causes of subcritical penetration of sound into seafloor. In this paper, the mechanism of subcritical penetration into rough seafloor is analyzed by Bragg scattering from sinusoidal fluctuation surface, and the condition that subcritical penetration can be induced is discussed. Because the refraction angle of minus order Bragg scattering waves is always smaller than refraction angle of Snell’s penetration wave, the subcritical penetration attributes to the minus order Bragg scattering waves which propagate as normal plane wave below the critical grazing angle. So, in order to obtain the subcritical penetration, the minus order Bragg scattering wave should be considered detailed. The first-order perturbation approximation is used for rough surface scattering usually. In this paper the validity of first-order perturbation approximation for rough surface scattering is also checked by comparing the first-order Bragg scattering wave with high-order Bragg scattering waves.
Surface scattering rejection for clear sidescan images.
Authors: Pearce Stephen K. , Bird John S.
Published: July 2011

Surface scattering is a major source of interference for sidescan sonar systems operating in high traffic areas or in choppy water. This surface scattering from wakes, as a result of boat traffic or from the chop of the sea surface, obscures the bottom return. A sonar system with a multi-element array can separate surface signals from bottom signals using beamforming, thereby creating clear images of the seafloor. This multi-element array can have as few as six elements and still effectively remove surface scattering. In this paper, different beamforming techniques are applied and their impact on suppressing surface returns is shown. Comparisons between beamforming methods are made by comparing the relative path levels with and without beamforming applied. The ability of a multi-element array to successfully discriminate between bottom returns and surface returns using beamforming is then shown using both simulated and experimental data. It is concluded that sonar systems employing a multi-element array can produce clear images of the seafloor even in the presence of strong surface interference when beamforming is used to create a beam that has a broad main lobe pointed toward the bottom and low sidelobes pointed toward the surface.
Comparing novel absorptive treatments in operating rooms.
Authors: Hsu Timothy Y. , Ryherd Erica E. , Barnhill Colin , West James , Levit Natalia
Published: July 2011

Hospital noise levels have been rising over the past several decades, and there have been few viable noise control solutions. The hospital environment can have special health requirements due to strict infectious control criteria. In order to meet these requirements, a novel absorbing panel was developed for a previous study in this series and installed in hematological intensive care units at the Johns Hopkins University Hospital Weinberg Building. This current study focuses on the impact of installing the panels in an operating room in the Johns Hopkins University Hospital. The impacts of the addition of sound absorbing materials in these operating rooms were analyzed both acoustically and perceptually. Sound level recordings and reverberation times were measured before and after the installation of the absorbing panels. Comparisons of these acoustic measurements will be presented. Additionally, a before/after questionnaire was administered to the operating room medical staff. Statistically significant differences in the survey results will be presented. These preliminary results in acoustic and survey data illustrate the effectiveness of the use of novel hospital-approved absorbing panels in the operating room.
Isolating above-ground-floor magnetic resonance imaging (MRI) facilities: A case study.
Authors: Noson Dennis , Bruck Daniel , Forrest Dave
Published: July 2011

A successful MRI installation requires careful coordination of design and construction disciplines to produce a noise isolation result satisfying the medical staff and their need for low distraction in the work environment. One of Seattle’s largest medical centers recently constructed a new facility designed to meet stringent requirements for its second floor location, chiefly that sound levels during MRI operation were required to be less than 34 dBA at any adjacent staff area. With separate clinics on the floors above and below the MRI, sound isolation details at perimeter beams, area partitioning, and resilient fastening methods were all important to achieving the noise goal. Design details will be presented, along with measurements of MRI noise reduction spectra collected after completion of the project, and comparison will be made with predicted performance of the architectural assemblies. Vibration isolation was important to the MRI operation. Vibration measurements will also be presented and discussed relative to the MRI manufacturer’s design criteria.
Harmonizing national and worldwide acoustical guidelines for healthcare.
Authors: Sykes David M.
Published: July 2011

In the absence of leadership from the U.S. Federal Government, the process of developing (and continuously improving) consistent acoustical guidelines for healthcare facilities is like herding cats since many independent authorities compete with each other. Nevertheless, progress continues. 1 year after the release of the FGI 2010 Guidelines—the first code-level, comprehensive U.S. guidelines in sixty years for noise and vibration in healthcare facilities—several groups have agreed to cite the Guidelines as their sole “reference standard”: the Department of Health and Human Services (responsible for HIPAA), the Veterans Administration, the Centers for Disease Control, 38 regional AHJ's (Authorities having Jurisdiction), the U.S. Green Building Council’s LEED for Health Care, the Green Guide for Health Care, 48 State code authorities, and most recently, the International Green Code Council. What is left? The Joint Commission, the Department of Defense, the World Health Organization, and others. Meantime, work on the 2014 edition of the Guidelines is already underway. Since the FGI Guidelines are actively used in 16 countries, it is imperative to involve the global acoustical community in the research and development needed to strengthen them. Can ICBEN help with this task? What is the best way forward?
Practical considerations for helicopter noise control in hospitals.
Authors: Papadimos Chris , Wowk Roman
Published: July 2011

Medical transport helicopters produce very high noise levels including pronounced low-frequency content that has the potential of inducing perceptible vibration. Based on recent experiences helicopter noise and vibration can be very challenging to control inside hospital buildings, especially if the helipad is located on the roof above occupied floors. Although such events may be tolerable in noncritical areas, it should be carefully addressed in patient rooms or any other healing places to prevent harmful effects on patient sleep and recovery. Current standards and guidelines for the design of healthcare facilities do not provide specific criteria for helicopter noise and vibration inside hospitals; however, appropriate limits may be selected based on past sleep disturbance studies and other available information. Appropriate helicopter noise control is particularly challenging with the current trend of exterior curtain wall constructions with a high percentage of glazing, thus requiring early evaluation including proper space planning and budgeting prior to committing to such designs. Helicopter noise studies will be presented to communicate recent experiences for large-scale academic healthcare projects.
Comparison of visual and acoustic detection rates for cetaceans off Washington.
Authors: Calambokidis John , Oleson Erin , Falcone Erin , Schorr Greg , Wiggins Sean , Hildebrand John
Published: July 2011

From 2004–2010, we examined marine mammal occurrence off Washington acoustically and visually. Acoustic monitoring was conducted by Scripps Institution of Oceanography using high-frequency acoustic recording packages (sample rate 80–200 kHz) in Quinault Canyon, part of the Navy’s Northwest Range. Visual surveys were conducted using small 6 m rigid-hull inflatable boats covering out to the location of the HARPs during favorable weather year-round. Visual surveys detected over 500 sighting of 12 species of cetaceans. Humpback whales were the most common baleen whale; harbor and Dall’s porpoise were the most common odontocete detected visually. Species detected acoustically included Pacific white-sided and Risso’s dolphins, and beaked, killer, sperm, humpback, blue, and fin whales. While there were similarities in the detections by both methods there were also some Stark contrasts. Overall, there were more acoustic detections than visual sightings and these included sperm whales, which were detected frequently acoustically but never visually. For humpback whales, acoustic detections were highest in fall and winter (and low in summer), while visual sightings showed highest numbers in summer and early fall. These differences can be explained by the dive and calling behavior of these species and demonstrate how the strengths and weaknesses of these approaches complement each other.
North Atlantic right whale seasonal presence off the coast of New Jersey: Confirmation by passive acoustic monitoring and ship survey data.
Authors: Dudzinski Kathleen M. , Whitt Amy , Laliberte Jennifer
Published: July 2011

North Atlantic right whales (NARW) are one of the most critically endangered marine mammals with abundance estimates for the North Atlantic population at about 438 individuals cataloged in 2008. Data presented here were part of a larger, long-term study to assess presence of marine mammals, sea turtles, and birds along the New Jersey coast in advance of wind farm development. Seasonal presence of NARW off New Jersey was characterized using static passive acoustic monitoring (PAM) and line-transect shipboard surveys. NARW upcalls were detected on 115 days over 21 months of deployment (March 2008 to December 2009) with a significant difference in number of upcalls detected between PAM stations by month (F-ratio = 3.1292, df = 22, p = 0.000). NARW upcalls were detected from March to June and September to December 2008 and from January to March and in June 2009, with the greatest number of calls detected during spring months annually. Presence of NARW was confirmed by sighting data, with sightings all seasons except summer. Four sightings were recorded: three during November, December, and January when right whales are on calving grounds farther south or in the Gulf of Maine and the fourth sighting was a cow-calf pair in May.
A comparison of the song of humpback whales (Megaptera novaeangliae) wintering in the Northwestern and Main Hawaiian Islands.
Authors: Chen Jessica , Lammers Marc O. , Au Whitlow W. L.
Published: July 2011

An extensive study of the population structure of North Pacific humpback whales (SPLASH) has revealed that many of the whales feeding in the Aleutian Islands and the Bering Sea are not observed in known wintering and breeding areas in the Pacific. Recent findings suggest that the Northwestern Hawaiian Islands (NWHIs) represent a previously undocumented wintering area that may be distinct from the Main Hawaiian Islands’ (MHIs’) wintering ground. To examine this issue further, data from Ecological Acoustic Recorders (EARs) deployed at five locations in the NWHIs and MHIs were analyzed to compare the structure of songs produced by whales in both areas. Previous research suggests that songs from different breeding groups differ from one another, providing a method to evaluate whether whales in the NWHIs are part of the same breeding group as those in the MHIs. Recordings from each site were randomly selected, and song units were classified and counted to compare between sites. Preliminary results indicate that there are differences between the NWHIs and MHIs. These findings suggest that further work using photo ID should be undertaken to confirm whether whales in the NWHIs are indeed those feeding in the Aleutians and the Bering Sea.
Statistical analysis of fin whale vocalizations recorded by a seismic network at the Endeavour Segment of Juan de Fuca Ridge, N. E. Pacific Ocean.
Authors: Soule Dax C. , Wilcock William S. D. , Thompson Richard E.
Published: July 2011

From 2003–2006, an eight-station seafloor seismic network was deployed along the Endeavour Segment of the Juan de Fuca ridge that recorded an extensive data set of 20-Hz fin whale calls. Algorithms have been developed to detect and track vocalizing whales that swim near the seismic network. During the first year of operation, more than 100000 fin calls that include ∼100 whale tracks were identified. Tracks comprise both single whales distinguished by a stereotyped ∼25 s interpulse interval and inferred multiwhale tracks characterized by more complex interpulse intervals. Whale tracks vary from individuals or groups that cross the network in a few hours to those that meander for up to 24 h. The call rates vary seasonally with the highest rates in winter and exhibit an apparent weak diurnal variation. The center frequencies range from 17–34 Hz, with the primary population centered at 20 Hz and a secondary population centered at 25 Hz. Statistical analysis of observed bandwidths and center frequencies, interpulse intervals, seasonality, and diurnal patterns will be presented. Additionally, the ∼100 whale tracks will be used for migration analysis and to quantify the swimming patterns in the network. [Funding from the ONR.]
Integration of real-time odontocete call classification algorithm into PAMGUARD signal processing software.
Authors: Oswald Michael , Oswald Julie N. , Lammers Marc O. , Rankin Shannon , Au Whitlow W. L.
Published: July 2011

Real-time odontocete call classification algorithm (ROCCA) is a tool for real-time acoustic species identification of delphinid whistles. Introduced in 2006 as MATLAB-based software, ROCCA is currently being incorporated into PAMGUARD, a freely-available, open source software package. ROCCA provides automated extraction of whistle contours from a spectrogram. It measures 54 whistle contour features including frequencies, slopes, duration, and variables related to the positions of inflection points and steps. ROCCA currently classifies whistles of seven species and one genus: Globicephala macrorhynchus, Pseudorca crassidens, Steno bredanensis, Stenella attenuata, S. coeruleoalba, S. longirostris, Tursiops truncatus, and Delphinus species. The classifier is a Random Forest trained on 2231 whistles collected over six cruises and 7 years in the eastern tropical Pacific Ocean. The original ROCCA classifier used a combination of discriminant function analysis and CART algorithms on 13 whistle contour features for an overall correct classification score of 35%, which was significantly greater than random (12%). The current Random Forest scheme, trained on 54 whistle contour features, yields an overall correct classification score of 62%. Feedback from at-sea beta testing has been incorporated into the latest version of ROCCA. Additional species, automated detection, and alternate classification schemes are being explored to extend ROCCA into different geographic areas with greater accuracy.
Challenges of using passive acoustic monitoring for marine mammals during anthropogenic activities.
Authors: Guan Shane , Fossati Claudio , Pavan Gianni , Caltavuturo Giovanni
Published: July 2011

Monitoring the presence of marine mammals in the vicinity of an anthropogenic activity using passive sonar can greatly improve detection rates by visual monitoring, and it is the only way to detect marine mammals at large distances during nighttime monitoring. Therefore, passive acoustic monitoring (PAM) is sometimes required by regulatory agencies as a mean to supplement visual monitoring during anthropogenic activities that may potentially adversely affect marine mammals. However, there are many critical aspects that need to be taken into consideration when prescribing PAM to support mitigation measures. These challenges include (1) training for shipboard observers to operate and maintain sophisticated PAM hardware and software; (2) proper design of PAM system that works well during industrial operations (such as seismic vessels); (3) reliable bearing and ranging of calling of animals, thus providing basis for mitigation measures; and (4) the affordability of PAM system to small businesses. This presentation provides a comprehensive analysis on the above aspects that are essential for marine mammal passive acoustic monitoring during anthropogenic activities, and highlights future needs to improve and expands PAM as a standard technique to support mitigation measures to reduce anthropogenic impacts.
Simultaneous high-frequency ultrasound and optoacoustic imaging of in vivo mouse embryos.
Authors: Chitnis Parag V. , Aristizábal Orlando , Mamou Jonathan , Turnbull Daniel H. , Ketterling Jeffrey A.
Published: July 2011

An integrated optoacoustic (OA) and high-frequency ultrasound (HFU) system that provides detailed images of anatomical structure and molecular contrast in small animals and transgenic embryos is presented. Volumetric imaging was achieved by raster scanning a vertically oriented imaging probe. The imaging probe was a five-element, 40-MHz, PVDF-TrFE-based annular array. A PBS-filled Petri-dish with a center hole was placed on the abdomen of an anesthetized mouse, and a laparotomy was performed to expose an intact uterus. A bifurcated beam from a 532-nm pulsed laser illuminated the embryos from opposing directions normal to the image plane. The central element of the array was excited with a high-voltage impulse synchronized with the light pulse. The resulting ultrasound echo and OA signals from each scan location were digitized from all five array channels and postprocessed. The anatomy of the embryonic head (HFU image) was coregistered with the embryonic vasculature (OA image). Delay-and-sum beamforming was performed and the resulting HFU and OA images exhibited a notable improvement in the depth of field and signal-to-noise ratio in comparison to the images constructed using signals acquired from the central array element alone. The feasibility of real-time, spatially coregistered, dual-modality in vivo imaging of mouse embryos was demonstrated.
Comparison of design methods to achieve wideband operation in tonpilz transducers.
Authors: Wilson Michael B. , Thompson Stephen C. , Gabrielson Thomas B.
Published: July 2011

Wide sonar bandwidth with advanced processing enables improved system capabilities in sensors and arrays. However, transmitting and receiving bandwidth greater than one octave remains an emerging technology. Multiple resonances and high coupling materials are now viable options to increase the bandwidth of a device, but there is no study to date of a multiply resonant device that uses high coupling material. A set of guidelines is presented for the design of elements for wideband sonar arrays having bandwidth greater than one octave using multiple resonances, high coupling materials, or some combination.
Low frequency acoustic sensor or array calibration waveguides of finite length.
Authors: Huang Dehua , Paolero Anthony
Published: July 2011

Calibration acoustic transducers at very low frequencies in confined and well understood environment require special equipment. The Underwater Sound Reference Division has three cylindrical tubes for low frequency calibration. This paper addresses a rectangular cross section of finite length waveguide as calibration environment. The acoustic fields in the new waveguide for standing and traveling waves are both analyzed. The mathematical model and the numerical simulation results will also be presented. [This work is supported by the U.S. Navy.]
Performance of tourmaline hydrophones at low- and midfrequencies.
Authors: Morales Juan , Kale Akash , Hastings Mardi
Published: July 2011

Tourmaline hydrophones are well suited for measurement of underwater blasts and other impulsive type sounds having extremely fast rise times and high peak pressures. The physical characteristics of these small, lightweight sensors, however, make them an attractive choice for other applications. To determine their performance at low- and midfrequencies, substitution calibrations of two tourmaline sensors with a calibrated laboratory hydrophone were completed using a J-ll underwater sound transducer in a 100-gal tank. The calibration signals consisted of tone bursts containing 5–20 cycles at frequencies ranging from 250 to 10 000 Hz and having sound pressure levels from 110 to 180 dB re 1 μa. Results indicate that a tourmaline hydrophone coupled to an in-line charge amplifier and preamplifier to provide fixed voltage gains ranging from 100× to 10 000× has excellent performance over this range of frequencies. [Work supported by the National Oceanographic Partnership Program (NOPP) through ONR Award No. N000140710992.]
Locating multiple incoherent sound sources in three-dimensional space.
Authors: Zhu Na , Wu Sean
Published: July 2011

A new technology for locating incoherent sound sources in three-dimensional space is developed. The underlying principle of this technology is a model based approach that assumes acoustic radiation from a point source in free space, together with triangulations and signal pre-processing to enhance the signal to noise ratio. A prototype developed for this technology consists of six microphones, multi-channel high-accuracy data acquisition module, and a web camera. This device allows for capturing and visualizing target sources in three ways: (1) through the camera viewing angle that shows the actual sources and their Cartesian coordinates directly, (2) through projection of the source positions on a horizontal plane and their traces as they move in space, or (3) automatically switching between the camera and top view displays, depending on whether the target falls inside the viewing angle of the camera or outside. To ensure a real-time display of the results, four microphones are used. The disadvantage of using four microphones is that the accuracy in source localization may be reduced when the input data are contaminated by interfering and background signals. Under this condition, redundancy checks using six microphones can be used to enhance the accuracy and spatial resolution of source localization.
A virtual receiving array using a time-reversal chaotic cavity.
Authors: Lee Jae-Wan , Ohm Won-Suk
Published: July 2011

It has been demonstrated that a virtual transmitting array can be constructed using a small number of transducers glued to a chaotic cavity (or a random reverberator) in conjunction with time reversal acoustics [Montaldo et al., IEEE Trans. Ultrason., Ferroelec., Freq. Contr. 52, 1489–1497 (2005)]. However, a virtual receiving array based on the concept has been neither realized nor reported yet. This paper presents an underwater virtual receiving array using a time-reversal chaotic cavity. The prototype array consists of a single immersion transducer and a chaotic cavity and is made to have a total of 8×8 virtual receiving elements. The performance of the virtual array is compared with a commercial 2-D hydrophone array. [Work supported by the National Research Foundation of Korea Grant funded by the Korean Government (MEST) (NRF-2009- 0077588).]
Analytical comparison of spherical multimicrophone probes.
Authors: Wiederhold Curtis P. , Gee Kent L. , Sommerfeldt Scott D. , Blotter Jonathan D.
Published: July 2011

Probes with microphones flush-mounted in hard spheres have been used to measure energy-based acoustic quantities by estimating the pressure gradient using finite-difference approximations. The number of microphones, their orientation in the sound field, and the frequency content of an incident acoustic wave affect the probe’s accuracy. This study analytically compares errors in measuring acoustic intensity and energy density of plane waves incident on ideal point microphones located on a rigid sphere. The difference between implementing such a probe as a series of three orthogonal 1-D probes or using a least-squares approximation using all microphones is considered. Estimation errors as a function of incidence angle and frequency have been calculated, thereby providing insight into the relative merits of each probe configuration.
Diver monitoring using the Hawaii Experimental Acoustic Range.
Authors: Fedenczuk Tom , Nosal Eva-Marie
Published: July 2011

We will present the preliminary data and results from the first full stage experiment conducted with the newly built Hawaii Experimental Acoustic Range in Oahu, HI. The range is a multipurpose facility that allows for various receiver configurations, hydrophone models, and locations. Data access and control is permitted in three modes: shore/ship, autonomous, or underwater observatory, with a custom designed 16 channel, 24 bit, 192 kHz simultaneous sampling data acquisition system. For this experiment, the receiver configuration included two volumetric arrays of five hydrophones each, and four additional individual hydrophones. The purpose of the experiment was to detect and track divers in a shallow water harbor environment. Two divers were deployed along predefined paths. The divers stopped at control points that were georeferenced by a survey grade total station. A low amplitude transducer was activated at each control point and transmitted a single 20–40kHz sweep to calibrate the tracking algorithms. This talk will present details of the range, experiment, and preliminary results.
Tonpilz type underwater vector sensor with directional sensitivity to acoustic waves.
Authors: Roh Yongrae , Lim Youngsub
Published: July 2011

Typical Tonpilz-type underwater acoustic transducers making use of piezoceramics detect the magnitude of an acoustic pressure, a scalar quantity, and convert this pressure into a proportional output voltage. The scalar sensor has no directional sensitivity. In this paper, a new Tonpilz transducer structure is proposed to measure both the magnitude and the direction of an incoming acoustic wave with a single transducer unit, which is accordingly referred to as a vector sensor. The piezoceramic stack clamped between the head mass and the tail mass of a Tonpilz transducer is divided into four radial segments, each segment polarized alternately to its neighboring one. An acoustic pressure wave coming from outside causes positive or negative signed electric voltage signals in the piezoceramic segments in accordance with their polarization directions as well as a certain amount of time delay between the electric signals. Proper manipulation of the electric signals, i.e., pairing the segments and either adding or subtracting the signals of the paired segments, can provide the relationship between the signals and the magnitude and direction of the acoustic wave. Feasibility of this structure is confirmed through 3-D simulations of the receiving properties of the transducer with the finite element method.
An information-rich learning environment for instruction in acoustics.
Authors: Celmer Robert D.
Published: July 2011

The static written word has always had its limits when it comes to learning about sound. Much of the subject matter is dynamic, multifaceted, and of course, aural. This presentation will describe multimedia materials developed for in-class presentation and self-paced review exercises for acoustics instruction at the University of Hartford. Some of the materials were developed using certain authoring applications, draw and animation programs, sound manipulation software, as well as 3-D-CAD and spectral analysis applets. Audio equipment used in class, as well as acoustic treatments of the classroom/listening environment, will be described. This approach to acoustic pedagogy will be discussed in the context of a student-centered learning environment. Demonstrations of the materials for the instruction of acoustical concepts, as well as case studies, will be presented.
Teaching room modes and diffraction using COMSOL MULTIPHYSICS.
Authors: Muehleisen Ralph T.
Published: July 2011

The concepts of room modes and diffraction are fairly easy to explain in a qualitative way but the math involved to develop the physics of both can be difficult. When explaining the concept of room modes in more detail, many educators start with the idea of a rectangular room with rigid boundaries to get analytic solutions. However, convincing students that room modes exist in rooms of other shapes is not always easy since analytic solutions cannot be found. Similarly, diffraction is easy to explain as a concept but the functions involved in mathematically explaining diffraction are advanced and difficult to understand. In order to get meaningful solutions to both room mode and diffraction, some researchers and educators turn to finite element software. In this paper, the use of Comsol Multiphysics, a general purpose finite element program, in teaching room modes and diffraction, is shown. COMSOL can be used to draw rooms of an arbitrary shape and generate resonance frequencies and room modes in a matter of minutes. COMSOL can also be used to generate animations of sound waves diffracting around objects. Examples of both uses will be shown.
A first laboratory course for teaching advanced acoustics.
Authors: Garrett Steven L.
Published: July 2011

The overwhelming majority of “structured” instructional activity in graduate schools offering advanced degrees in acoustics is spent in classes that require solution of problems sets and exams and might also include some relevant literature searches and reports. Most potential employers of these advanced degree recipients assume that their education included exposure to some hands-on measurement of sounds and vibrations followed by analysis and presentation of those measurements in an appropriate (typically graphical) format. At the very least, measurements using sound level meters, hydrophones, and accelerometers should be included along with their calibration as well as experience with transducers that includes comparison of measurements with theory. Nine laboratory exercises will be described that are required for an MS degree. These currently include characterization of electrodynamic loudspeaker parameters, Helmholtz resonators, coupled acousto-mechanical systems, sound propagation in a water-filled waveguide, shock wave development and wave-wave interactions in one dimension, determination of elastic moduli by measurement of bar resonances, reciprocity calibration, and accelerometer calibration. Instrumentation utilized in the course includes multi-channel spectrum analysis (swept-sine and FFT), lock-in amplifiers (phase-sensitive detection), function generators, and waveform capture using a digital storage oscilloscope. The importance of completing a “preliminary exercise” prior to each laboratory will be stressed.
A pedagogical demonstration of weak-shock propagation from a gas-filled balloon explosion.
Authors: Muhlestein Michael B. , Gee Kent L. , Macedone Jeff H.
Published: July 2011

A classroom demonstration of weak-shock propagation theory has been developed and studied. A balloon filled with a stoichiometric mix of acetylene and oxygen is ignited, causing a near-spherical explosion. Because peak sound pressure levels at 1 m exceed 180 dB, nonlinear theory is clearly required for a proper analysis of the acoustic propagation. Weak-shock theory is first reviewed and then applied to the propagation of a simplified explosion model consisting of a shock with an exponentially decaying tail. A comparison between the model and an experiment using 3.18 mm condenser microphones reveals good agreement between theory and measurement for the nonlinear spatiotemporal wave evolution. Potential pedagogical uses for this demonstration are discussed.
The Verasonics ultrasound system as a pedagogic tool in teaching wave propagation, scattering, beamforming, and signal processing concepts in physics and engineering.
Authors: Kaczkowski Peter J. , Daigle Ronald E.
Published: July 2011

The Verasonics ultrasound system is a highly programmable data acquisition and processing platform designed to facilitate development of new medical ultrasound imaging methods. In contrast to conventional commercial ultrasound systems, individual element digitized rf data are available to the developer. All beamforming and postprocessing are done in software, and both the hardware data acquisition sequence and the host computer processing flow are programmable by the user using a MATLAB interface. Because the system is designed to be highly flexible, it can also be useful as a practical tool in teaching acoustic wave physics, transducer and array design, and data processing concepts, using benchtop scale homemade acoustic and elastic media, including flow models. For script evaluation and testing, the Verasonics system includes a hardware simulator that uses a simple point scatterer numerical model to compute rf backscatter data. rf data can also be recorded during a hardware acquisition, and then reprocessed using different user-developed algorithms for comparative study. Because the system is easy to learn, many fundamental concepts can be explored in a laboratory setting, using scattering media or custom transducers fabricated as part of the student experimental plan. The system enables sophisticated hands-on experience with acoustics beyond the numerical world.
Energy flux streamlines versus the alternatives for the visualization of energy flow in acoustical scattering problems: Simple examples.
Authors: Dean Cleon E. , Braselton James P.
Published: July 2011

Energy flux streamlines yield certain advantages for the visualization of acoustical scattering processes. They give information about scattering angles, interaction with surfaces and scatterers, and can even show the relative intensity of the sound at a given location. However, the use of energy flux streamlines presents certain difficulties as well. Beyond the difficulty in calculating them, the use of the energy flux field presumes a complete solution of the sound scattering problem. Thus energy flux streamlines are usually descriptive rather than predictive. And while the set of streamlines can be chosen so as to show the relative intensities of the sound field, what works in one geometry will not necessarily work in another. Examples will be adduced illustrating these points and more.