bluuebunny/crossref_metadata_2025 huggingface dataset:
Forward scattering from the sea surface: Observations of both subtle and profound effects of bubbles in single-interaction measurements
Authors: Dahl Peter H.
Published: October 2013

For frequencies of O(10) kHz and above, field data show that near-surface bubbles impact forward scattering from the sea surface in three phases. The first occurs under mild conditions (wind speed less than 5–7 m/s); here a pulse forward scattered from the sea surface is extended in time, but only at levels ∼30 dB below the peak level, which itself is not attenuated. The second occurs under more vigorous conditions (wind speed 7–12 m/s); here a significant energy loss is observed, but time and angle spreading (dominated by rough surface scattering) remain relatively unchanged. The third occurs under still more vigorous conditions (wind speed greater than ∼12 m/s). Here, there is near total occlusion of the sea surface, time and angle spreading are manifestly altered, and bubble-mediated energy loss becomes bounded by scattering from bubbles. Examples from ASIAEX East China Sea and other archival data sets will be discussed along with a model for bubble-mediated energy loss in forward scattering from the sea surface. In the case of near total occlusion, an interesting example of the knock-down of horizontal coherence will be discussed along with a model that utilizes the van Cittert-Zernike Theorem. [Research supported by ONR Ocean Acoustics.]
Scintillation index of ocean surface forward scattered HF acoustic signals: Beam pattern and pulse length effects
Authors: Cotté Benjamin , Bradley David , Culver R. Lee
Published: October 2013

The intensity fluctuations of surface bounce path measured during a field test near San Clemente Island in August 2002 have been presented previously. Signals used during this test were 20- and 40-kHz continuous wave (CW) pulses with 0.14- and 1.0-ms durations (‘‘short’’ and ‘‘long’’ pulses, respectively). Experimental results have been compared to predictions of a model by Yang and McDaniel [Waves Random Media, 1, 419–439 (1991); J. Acoust. Soc. Am. 91, 1960–1966 (1992)]. Their initial model assumes CW signals and omni-directional projectors and receivers. We observed a good fit between model and experimental results for the long pulse data when the specular point was in the main lobe of both projector and receiver. The discrepancies observed in the other cases were attributed to beam pattern and pulse length effects. We have extended the model to incorporate these two effects. [Work supported by ONR Code 321US.]
Measurements of mid-frequency bottom backscattering strengths on the Outer Hebrides Platform and the Stanton Banks
Authors: Kunz Edward L. , Gauss Roger C.
Published: October 2013

In July 2002, direct-path, mid-frequency (2–5 kHz) bottom backscattering strength measurements were conducted at 21 sites on the Outer Hebrides Platform and the Stanton Banks (northwest of Scotland) during The Technical Cooperation Program’s T-MAST 02 sea trial. This is a complex area, with bottom grabs indicating the wide presence of stones, pebbles, gravel and rocks throughout most of the region. When stones, etc. were present, bottom backscattering strengths were generally high and flattish in angle (over 10 to 40 deg), with many sites empirically exhibiting a sinθ or flatter angular dependence. The frequency dependence in these cases was mild. When stones, etc. were absent, bottom backscattering strengths were less high and less flat in angle, with strong frequency dependence. These results dramatically illustrate the inadequacies of using Lambert’s Law to model bottom backscattering strengths and suggest that active sonars operating in this environment will encounter strong reverberation. [Work supported by ONR.]
Backscattering from targets residing in caustics resulting from ocean boundary interactions
Authors: Dzikowicz Benjamin R. , Marston Philip L.
Published: October 2013

Detection of targets by backscatter in shallow water can be enhanced by interactions with ocean boundaries. A laboratory experiment is performed where a spherical target passes through an Airy caustic formed by a curved surface. When the target resides in the insonified region of the caustic there are two sets of multi-path rays: two pairs reflecting once off the surface (either to or from the target), and three reflecting twice off the surface (to and from the target). When a target moves across the caustic the singly reflected rays merge, as do the doubly reflected. With a longer tone burst the rays in each set overlap and the backscatter is greatly enhanced as the target moves into the insonified region. For a point target the singly reflected backscatter scales as an Airy function [B. R. Dzikowicz and P. L. Marston, J. Acoust. Soc. Am. 116, 2751–2757 (2004)], and the doubly reflected as the square of an Airy function. For a finite target the doubly reflected backscatter unfolds into a hyperbolic umbilic function. The arguments of the Airy and Hyperbolic Umbilic functions are calculated using the relative echo times of transient pulses. [Work supported by ONR.]
Bayesian inversion of frequency-averaged reflection data
Authors: Dosso Stan E. , Holland Charles W.
Published: October 2013

This paper presents a nonlinear Bayesian inversion of high-resolution seabed reflection data to estimate visco-elastic parameters of the upper sediments. The inversion is applied to data from two sites in the Strait of Sicily. One site is characterized by low-velocity, silty-clay sediments, resulting in data with a well-defined angle of intromission. The second site is characterized by high-velocity clayey sand, resulting in a critical angle. The data were frequency averaged from 500–2000 Hz and inverted for visco-elastic parameters of a half-space seabed model. The likelihood function employed in the inversion is based on the assumption of independent, Gaussian-distributed data errors, with the standard deviation included as a nuisance parameter in the inversion. Statistical tests are applied to the data residuals a posteriori to validate these assumptions. Good results are obtained for sediment compressional-wave velocity, compressional attenuation, and density; shear parameters are less-well determined although low shear-wave velocities are indicated. The Bayesian analysis provides a quantitative comparison of inversion results for the two sites in terms of the resolution of specific geoacoustic parameters, and indicates that the geoacoustic information content is significantly higher for angle-of-intromission data.
Prevalence, nature and risks of voice problems among public school teachers
Authors: Rammage Linda , Hodgson Murray , Naylor Charlie
Published: October 2013

Voice problems among teachers represent a rising cause of teacher absenteeism, use of sick benefits, and stress among teachers and students. In British Columbia, the BC Teachers Federation and Workers Compensation Board are receiving increasing numbers of claims from teachers experiencing occupational voice problems and in the provincial voice clinic, the percentage of teachers in the clinic population is rising. Previous studies of teachers voice problems have typically had low return rates, which can bias the prevalence estimates, and have not incorporated standardized voice inventories, psychological inventories and acoustic measures. A survey study is in progress in B.C. to probe demographic, environmental, voice-use, health, psychological and personality issues that are thought to contribute to development of voice problems among teachers. To ensure validity of prevalence estimates by high return rates, on-site completion of questionnaires is being used in schools. Acoustical measures are also being made of representative classrooms, to determine the degree to which noise and reverberation contribute to voice problems among teachers.
The effects of stimulus parameters on the auditory brainstem response of zebrafish (Danio rerio)
Authors: Margaritis Maria , Higgs Dennis
Published: October 2013

In mammals and birds it is well documented that stimulus parameters have significant effects on auditory processing. However in fish, the effect of different stimulus types remains unclear. Therefore it is difficult to directly compare piscine auditory responses obtained by different investigators, due to variability in testing methods. The current study uses zebrafish (Danio rerio) to evaluate the effects of stimulus type (800 Hz tone bursts versus broadband stimuli from 100–4000 Hz) and stimulus duration (1, 5, 10, or 20 ms) on the auditory brainstem response (ABR). Threshold was significantly lower (p=0.04) for broadband sounds than for tones, but there was no effect on either latency or amplitude. There was a direct and significant effect of duration on threshold (p=0.001), suggesting the response was due to the offset rather than the onset of the stimulus. Duration had no effect on either threshold or amplitude. The stimulus level had no significant effect on latency, however amplitude significantly increased as level increased (p=0.001). Thus, stimulus parameters can significantly affect ABRs. The current findings show the need for a consistent method of testing among investigators in order to reliably compare results. [Work supported by NSERC.]
Geoacoustic inversion of broadband data by matched beam processing
Authors: Chapman N. Ross , Jiang Yongmin
Published: October 2013

This paper describes results of geoacoustic inversion using broadband signals from an experiment carried out at a site near the South Florida Ocean Measurement Centre in the Florida Straits. M-sequence coded pulse trains at different center carrier frequencies from 100 to 3200 Hz were transmitted in the acoustic experiment, and received by a tri-axial array at a distance around 10 km. Geoacoustic inversion was carried out to determine the possibility of inverting the environmental parameters from this long-range propagation experiment. The received signal at 100 Hz consisted of a dominant water column signal and a secondary arrival delayed by 0.4 s. The secondary signal was spatially filtered by beamforming the array data, and the beam data were inverted by matched beam processing combined with an adaptive simplex simulated annealing algorithm. The estimated values of compressional wave speed and density were in good agreement with ground truth values from sediment cores. The inverted shear wave speed appears to be a sensitive parameter and consistent with compressional wave speed. Range and water depth were also included as inversion parameters, and the inversion results were close to the known values within small uncertainties. [Work supported by ONR.]
Validation of high-frequency ultrasound measurements of tissue layer thickness
Authors: Qiu Qiang , Dunmore-Buyze Joy , Boughner Derek R. , Lacefield James C.
Published: October 2013

High-frequency ultrasound imaging enables nondestructive measurement of layer thickness in tissue specimens. These measurements are valuable for mechanical testing of soft biomaterials. This paper demonstrates a method for assessing the accuracy of high-resolution ultrasonic thickness estimates. Three-dimensional images of six porcine aortic valve cusps were acquired in vitro using a 40 MHz ultrasound system with 40×80×80 μm3 spatial resolution. The cusps were then frozen in liquid nitrogen, sectioned into 10-μm slices, and micrographs of one slice from each specimen were acquired at 4× magnification. The two-dimensional micrographs were registered to the three-dimensional ultrasound images using a cross-correlation method. The boundaries of the fibrosa, spongiosa, and ventricularis layers were segmented in both sets of images using an active contour model. The average thicknesses of the tissue layers in the registered images were estimated and the absolute differences of the optical and ultrasonic estimates were computed. The absolute differences were 55.8±22.6 μm (mean ± standard deviation), 23.5±14.3 μm, and 22.7±17.2 μm for the fibrosa, spongiosa, and ventricularis, respectively. The measurement differences are comparable to the axial resolution of the ultrasound system and are not significant as determined by t-tests (p>0.30 for each layer).
Automated set of test simulations for non-ideal medical ultrasound transducers using Monte-Carlo method
Authors: Lee Hotaik , Smith Nadine B. , Kling Terry A.
Published: October 2013

Using Field II program and Monte-Carlo method, we developed new design tools for medical ultrasound transducers with the automated set of imaging simulations. This simulation environment is used to create and assess the parametric specification of design factors affecting the quality of medical ultrasound imaging. In order to obtain accurate and realistic results, non-ideal transducers whose transfer functions vary either across the transducer or within the transducer are considered. These variations include, but are not limited to: center frequency, bandwidth, sensitivity, ringdown, angular response, time-of-flight, and lateral focus. By applying random numbers within the tolerance range to the variations in input parameters, the automated set of simulations is performed. First, critical input parameters for components of the transfer function are identified by sensitivity analysis. Next, the statistical range of parameter values that yield a transducer model with a certain performance level is determined and the limit of variations in each factor for acceptable degradation of images is set. Finally, the creation of many ‘‘what if’’ cases to predict yield and statistical performance of a transducer and the imaging simulation are performed based on Monte-Carlo method. [Work supported by Sound Technology Inc.]
Engineering applications of limited diffraction beams
Authors: Lu Jian-yu
Published: October 2013

Limited diffraction beams (LDBs) are non-divergence and non-dispersive solutions to isotropic-homogeneous wave equations. These beams have a common characteristic of X-shaped branches and thus are also called X waves. Because of their highly directional propagation property, they have potential applications in medicine, underwater acoustics, and nonlinear optics (Charles Day, Phys. Today, October, 2004, pp. 25–26). In this talk, an overview of the development of LDBs will be given. This includes the conversion of any existing solutions to homogeneous or non-homogeneous wave equations to LDB solutions using Lorentz-related transformation, and a discussion of the orthogonal properties of the X wave transformation pair in representing any physically realizable waves. Experiments on applications of LDBs using our newly developed general-purpose ultrasound system will also be reported. (The system is capable of 128-channel simultaneous ultrasound data acquisitions at 12-bit/40 MHz rate and can hold real-time radio-frequency (RF) data up to 64 GB in one acquisition operation. Arbitrary ultrasound waveforms can be simultaneously produced by 128 12-bit/40 MHz D/A converters and then be linearly amplified to drive 75-Ohm loads or an array transducer at about ±150 V.)
Fiber optic acoustic sensor technology
Authors: Cole James , Kirkendall Clay , Dandridge Anthony
Published: October 2013

Fiber optic sensor technology has been under development for over 25 years, recently a major milestone has been reached- the introduction of the Fiber Optic Wide Aperture Array on the first Virginia class submarine. This paper will review the development of this technology, outlining the principles of operation and the technological developments that led to fiber optic interferometric sensors becoming viable for production in an advanced sonar system. The Fiber Optic Wide Aperture array is a large channel count planar array mounted on the side of the submarine, but fiber sensor technology is also being developed for both towed arrays (as a replacement for the Navy’s thin-line towed arrays) and for bottom mounted acoustic arrays for a number of Navy applications. This paper will describe the development of the fiber optic hydrophones for these applications as well as the optical interrogation techniques. One of the key features of fiber optic sensor technology is the ability to passively multiplex many hydrophone channels per fiber, several multiplexing techniques will also be described. Some of the issues and challenges of this technology, such as coherent noise for large channel count systems will also be briefly discussed.
Development of metrics to identify military impulse noise
Authors: Vipperman Jeffrey S.
Published: October 2013

Urban encroachment of military bases continues to be a serious problem, affecting training exercises and overall military readiness. The military currently performs noise monitoring around bases to ensure that environmental conditions are favorable for tests or exercises. Despite refinements, current monitoring systems still suffer from occasional false positives and rely heavily on human interpretation. The long range goal of this work is to create a more accurate and autonomous noise classifier. The specific aims of the work are to create a library of recorded military impulse noise sources and to develop, test, and refine the noise classifier algorithms. Representative, high quality field measurements of various noise sources (25 mm and larger) will be conducted at a few military bases under varying environmental conditions. Measurements of wind noise and thunder will also be recorded. The software will be developed in MATLAB and will employ several common impulse noise metrics used for hearing conservation, including rise, peak, and fall times, crest factor, A- and B-durations, Lpk and kurtosis, among others. A neural network will be trained to discern between the recorded military noise sources and naturally occuring noise based on these metrics. Preliminary results from the measurements and analysis will be presented. [Work supported by SERDP.]
Low-frequency noise and air vibration generated by a simple cycle gas turbine installation
Authors: Giesbrecht Chris , Hertil Salem
Published: October 2013

Standard noise regulations, measurement techniques, and acoustic treatments can fail to address energy emitted by certain problem gas turbine installations in the form of low-frequency noise and air vibrations. Survey and treatment of the entire acoustic environment is necessary to diagnose and solve these annoyance problems. The presence of ground-borne vibrations, infrasound, and noise in the lower octave bands complicates environmental noise assessment and limits mitigation options. Variability in the perception, effects, and annoyance level of low-frequency noise and air vibrations prevents this relatively common problem from being well understood by industry. Particular attention must be paid to propagation paths when the dynamic range of air-borne and ground-borne vibrations overlaps. This paper is the case study of a 2002 analysis, by ATCO Noise Management, of an installation consisting of 3–120 MW combustion generator turbines causing such low-frequency noise and air vibrations.
Characteristics of infrasound signals from earthquakes
Authors: Mutschlecner Paul , Whitaker Rodney
Published: October 2013

Analysis of infrasound signals is presented for a set of 31 earthquakes located mostly in the western United States and recorded at infrasound arrays operated by the Los Alamos National Laboratory. By normalizing measured amplitudes for the effects of propagation and distance, a pressure-amplitude versus earthquake magnitude relation is derived. Further analysis showed that the observed variance in this relation is likely due to the variation in source ground motion and variation in upper atmospheric winds. Signal durations can be tens of minutes and azimuth deviations have a mean of three degrees (measured from array data compared to great circle azimuths). Other characteristics of the infrasound data will be discussed. Our analysis of the observed data combined with surface ground motion accelerations, led to estimates of the minimum surface accelerations needed to generated infrasound signals measured at distant arrays.
Status report on the establishment of the CTBTO IMS infrasound network
Authors: Hoffmann Thomas L.
Published: October 2013

Steady progress has been made in the establishment of the CTBTO IMS infrasound monitoring network. To date 86% of the site surveys for 60 infrasound stations in the network have been completed, 50% of the stations are transmitting continuous data to Vienna, and 40% of the stations have been certified. While the global distribution pattern of infrasound stations transmitting data to Vienna is still disperse, regional networks begin to form in North and South America as well as in the Australian and South African regions. This presentation will focus on an overview of recent progress made in the establishment of the global infrasound network, and also present some of the challenges and difficulties encountered in this program.
Extension of So/ren Buus’s modeling to loudness growth at high frequencies
Authors: Hellman Rhona P.
Published: October 2013

Loudness matching between tones at different frequencies leads to results that imply that loudness functions, which relate loudness to sound pressure level (SPL) are parallel at frequencies from 1 to 10 kHz but not at higher frequencies [Hellman et al., J. Acoust. Soc. Am. 109, 2349 (2001)]. Within the 12.5 to 16 kHz frequency range, the loudness-matching functions are curvilinear in shape being steeper below 60 phons than at higher loudness levels. The higher the frequency, the greater is the decrease in slope above 60 phons. The slope reduction above 60 phons for frequencies from 12.5 to 16 kHz is ascribed to the tone’s restricted excitation pattern. A computer model by So/ren Buus described in part in Florentine et al. [Modeling Sensorineural Hearing Loss (Erlbaum, 1997), pp. 187–198] provides a good account of the decrease in the mid-to-high level slope of loudness functions derived at high frequencies from the matching data. The agreement between the model predictions and the empirical results further supports the notion that the rate of loudness growth at moderate-to-high SPLs depends on the upward spread of excitation.
Sound radiation of a plate excited by an impact. Physical and perceptual comparisons between numerical and experimental results
Authors: Habault Dominique , Demirdjian Florence , Meunier Sabine , Canevet Georges
Published: October 2013

The study is concerned with the response of a thin elastic baffled plate, immersed in a fluid, and excited by an impact force. An experiment was run, in which a plate was struck by an impact hammer which provides excitations of very short duration. Various shapes of excitation functions were obtained by using different kinds of hammer heads (rubber, plastic, metal). The resulting acceleration on the plate and sound pressure radiated in the fluid were measured, with an emphasis on the very first portion of the signals (initial 30 ms). The recorded signals were then compared, in the time domain, with theoretical predictions based on expansions in resonance modes of the fluid-loaded plate. These predictions provide a quite accurate description of the experimental data. Auditory tests were also run, to compare the signals obtained from the calculations and the recorded sounds. Subjects were asked to evaluate the dissimilarity between test sounds, using an analog scale graduated from 0 (very similar) to 6 (very dissimilar). The tests allowed to identify the perceptual criteria used by the subjects. The aim of the study is to use these criteria to improve the numerical method of prediction of the sound radiation.
A perceptual account of dissimilation
Authors: Brasher Anthony
Published: October 2013

Ohala [J. J. Ohala, CLS Parasession on Language and Behavior, 178, 203 (1981)] argues that long-distance dissimilation results from hypercorrection; when confronted with words with multiple similar segments, listeners may be confused as to the origin of coarticulated features and attribute cues to one, but not all, segments. The present study evaluates this theory for a sound change involving dissimilation of breathy stops: in sequences of two or more breathy stops, all but the last become modal. If this pattern were reproduced in the laboratory then, when hearing a word with multiple breathy stops, listeners would have trouble assigning the source of the breathy voicing. In this study, Hindi speakers heard two continua of disyllables, where the first syllable varied systematically in the temporal extent of breathy voicing. The continua differed in that the second syllable had a breathy stop in one continuum (dadhak>dhadhak) but a non-breathy stop in the other (dadak>dhadak) (dh=breathy stop). Initial results for Hindi speakers responding in a four-choice identification task support Ohala’s hypothesis. Listeners identified the first syllable reliably when the second syllable is modal, but identified the first syllable inconsistently when the second syllable is breathy.
The influence of stress on some acoustic correlates to the stop voicing distinction in French
Authors: Abdelli-Beruh Nassima , Aravamudhan Radhika
Published: October 2013

This study examined how monolingual French speakers produced the stop voicing distinction in stressed and unstressed syllable-initial stops. Syllables were embedded in sentences. Voicing-related differences in durations of VOT, closure and vowel were calculated and analyzed as a function of stress (stressed on the target syllable, stress on the syllable preceding the target syllable). Percentages of closures with voicing were tallied as function of the voicing category of the stops and the stressed condition. Results from ANOVA showed that the absolute durations were smaller in the unstressed than in the stressed condition. The magnitude of the voicing-conditioned related duration differences in VOT, closure and vowel were also influenced by stress.
The effects of implosives and prenasalized stops on pitch in Shona
Authors: Chavez-Peon Mario E.
Published: October 2013

It is well known that F0 at vowel onset can be influenced by a preceding consonant. That influence varies significantly across languages and consonant types, and may function as a perceptual signal to consonant manner. It has further been suggested that tone languages may behave differently from non-tone languages in this respect, with a shorter duration of consonantal perturbation [Hombert, Studies in African Linguistics, 1977]. Previous studies include a limited range of consonant types, and too few tone languages to test Hombert’s proposal. This study presents the results of an acoustical investigation of the effects of implosives and prenasalized stops on the F0 of a following vowel in Shona, a tone language. It is found that implosives have a similar raising effect on F0 at vowel onset than that of voiceless (aspirated) stops, contrary to expectations based on previous studies [Wright and Shryock, Journal of the Phonetic Association, 1993]. It is also found that prenasalized consonants behave as nasals, having no effect on the F0 of the following vowel, again contrary to expectation [cf. Trithart, Studies in Bantu Tonology, 1976; and Hombert, Studies in Bantu Tonology, 1976]. Finally, duration results do not support Hombert’s position regarding tone languages.
Modeling of forward sector adaptive matched field processing
Authors: Dunne Jeffrey
Published: October 2013

A modeling study was undertaken to examine the potential benefit of adaptive matched field processing (AMFP) to the forward sector capability of single-line, twin-line, and volumetric arrays. Comparisons are made with conventional MFP (CMFP) and plane-wave beamforming (PWB) in order to assess the degree of ownship noise reduction obtainable and any corresponding improvement to the signal-to-noise ratio (SNR). A minimum variance distortionless response beamformer using dominant mode rejection was implemented, applied to both uniform and distorted array shapes. Significant improvement over CMFP and PWB in tracking and SNR was seen for modeled data in both cases, with the distorted array showing, not surprisingly, better left-right rejection capability. A brief investigation of the effects of environmental mismatch was undertaken in order to assess its potential impact on the value-added of AMFP. [Work was supported by the Defense Advanced Research Projects Agency, Advanced Technology Office.]
Subjective evaluation of auralizations created from multi-channel anechoic recordings of a talker in motion
Authors: Vigeant Michelle C. , Wang Lily M.
Published: October 2013

A high degree of speech intelligibility is very important in educational environments. When designing such spaces, like classrooms, auralizations can be used to subjectively assess the degree of speech intelligibility and clarity. Auralizations are most commonly made by convolving the impulse response (IR) of an omni-directional source with a single channel anechoic speech recording. This paper explores the idea of using multi-channel recordings to create the auralizations, using a female talker in motion. An omni-directional source is split into quadrants and the IR is calculated for each section. These IR’s are convolved with the appropriate channel of the anechoic recording and then the four auralizations are mixed to create one final auralization. The auralizations were made using four-channel anechoic recordings of a person walking on a platform while talking. Subjective tests were conducted to determine the ease with which subjects could identify the direction of the movement of the source in rooms with varying amounts of absorption. This method can be used to create more realistic classroom auralizations, as teachers typically move around the room as they teach. [Work supported by the National Science Foundation.]
Classroom auralizations using both speech and intruding noise
Authors: Coffeen Robert C.
Published: October 2013

Continuing work with computer auralizations for education spaces—Can realistic speech auralizations be obtained for classrooms and similar spaces with disturbing ambient noise as produced by HVAC systems, noise from adjacent spaces, aircraft flyovers, and other common noise sources? Several auralizations will be presented relating to these situations.
Classroom sound quality—a comparison of recordings to virtual auralization
Authors: Roy Kenneth P. , Browne Sean D.
Published: October 2013

Sound quality in classrooms is an important consequence of the architectural and mechanical systems design. And it is the primary factor in determining the potential for speech intelligibility, which of course is also dependent on individual listening characteristic and capabilities. So the question is ‘‘how do we assess the potential for good sound quality within the design phase of school construction?’’ An obvious solution is to use architectural modeling and auralization ... but the question here is ‘‘how good are these virtual techniques?’’ as with the use of EASE software. We will present 1st a sample of the modeling and auralization process showing the capabilities via the generated sound files. Next we will listen to recordings made in an occupied classroom both before and after architectural interventions. Then we will listen to a series of auralized classroom settings. And finally, we will compare recordings to auralizations for the same classroom. One important aspect of ‘‘real room’’ sound quality is occupant generated noise (non-speech), which is not an easy aspect to include in virtual models.
Minimum audible angles for aerial pure tones in a northern elephant seal (Mirounga angustirostris)
Authors: Holt Marla M. , Schusterman Ronald J. , Southall Brandon L. , Kastak David
Published: October 2013

Recent work has shown that several pinniped species localize aerial broadband signals as accurately as some terrestrial carnivores. Additionally, both harbor seals and California sea lions can better localize both the lower and higher frequencies of their hearing range compared to performance at intermediate frequencies. These results are congruent with the duplex theory of sound localization which states that low frequencies are localized by interaural time differences while high frequencies are localized by interaural intensity differences. Northern elephant seals are land breeding pinnipeds whose range of best hearing sensitivity is shifted toward lower frequencies compared to other pinnipeds tested thus far. In this study, we tested a female northern elephant seal in a hemi-anechoic chamber at six frequencies ranging between 0.8 and 16 kHz that were presented at levels approximately 25 dB above threshold. A left/right behavioral procedure was used to measure minimum audible angles (MAAs) at 75 percent correct discrimination. MAAs ranged from approximately three to fifteen degrees. Best performance occurred at the lower frequencies while worse performance occurred at the two highest test frequencies. Unlike sea lions and harbor seals, this subject showed a decreased ability to utilize interaural intensity differences above 4 kHz.
Long-term variability in hydrothermal vent flow and temperature fluctuations by acoustic scintillation
Authors: Di Iorio Daniela
Published: October 2013

An acoustical scintillation instrument is described that has been used to measure flow and temperature fluctuations at a hydrothermal vent plume. The vertical buoyancy driven flow together with the root-mean-square temperature fluctuations are obtained for vent structure 8F of the Main Endeavour vent field on the Endeavour segment of the Juan de Fuca Ridge. Long term (71 days) measurements are obtained and an estimate of the heat flux density which is of the order 0.06 MWm−2 is calculated. Measurements also show oscillations in the log-amplitude variance that result from either plume advection or increased entrainment of ambient fluids by the ambient tidal currents, thus demonstrating the need for a long time series measurement of simultaneous horizontal and vertical flow. Future measurements in the Main Endeavour vent field, with possible integration into the NEPTUNE seafloor observatory, will be over extended periods of time so that comparisons of these processes can be made with independent seismic data collected by NOAA/PMEL SOSUS array.
Development of interactive digital scientific acoustic systems for monitoring and assessment of physical and biological variables from ocean observatory platforms
Authors: McClure Robert , Acker Tim , Dawson James , Ebrahim Assad E. K.
Published: October 2013

Scientific echosounders are in regular use for measurement of fish and plankton distribution and abundance, fish behavior, submersed aquatic vegetation, bottom sediment classification and water mass interface characteristics. Both fixed-aspect and mobile acoustic data are commonly collected from surface-deployed echosounders. Advancements in digital scientific echosounder technology and integration of other technologies has moved the capabilities of advanced echosounder systems into the realm of new applications and deployment possibilities. These advancements make possible the deployment of a new generation of integrated and interactive sensors which can provide high resolution, continuous, extended duration, recording, intelligent processing, and reliable monitoring and assessment of both biological and physical parameters of the ocean environment. Deployments from cabled observatories, moored and drifting buoys, manned and unmanned mobile platforms, and fully autonomous installations are all now reality. The deployment of these quality scientific instrument suites hold unlimited potential for research, resource management, and education. Existing and planned implementation of advanced digital scientific echosounder applications on observatories as well as considerations in design, deployment, and integration with other observatory and oceanic acoustic activities are discussed.
Passive acoustic detection of fish sound production: The promise of ocean observatories
Authors: Mann David
Published: October 2013

Many fishes make species-specific sounds during courtship and spawning. These sounds can be recorded and quantified to study the temporal and spatial dynamics of spawning. Fish sounds typically range in frequency from 20–1500 Hz, and are usually inversely related to fish size. Time series of fish sound production recorded with autonomous recorders from Tampa Bay, Florida, and the mid-Atlantic bight, New Jersey illustrate how passive acoustics can be used to determine diel and seasonal timing of spawning. The great promise of ocean observatories is that they will not only provide unprecedented data on fish sound production, but that these data will be coupled with physical data on the same time and space scales. Ocean observatories will be powerful tools in studying the role of physical factors in driving variability in spawning and recruitment of fishes.
Basin Acoustic Seamount Scattering Experiment (BASSEX ’04) III. Array performance
Authors: Becker Kyle M. , Baggeroer Arthur B. , Heaney Kevin D. , Scheer Edward K. , von der Heydt Keith
Published: October 2013

The ONR Five-Octave Research Array (FORA) was employed as the acoustic receiving system during the Basin Acoustic Seamount Scattering Experiment (BASSEX04). The array was primarily used in a towed configuration with receptions recorded for source/receiver separation distances ranging from 500–3200 km. Measurements made in proximity to the 75 Hz source moored near Kauai used a vertical array configuration. This paper presents array capabilities and performance during this first deep-water application of the FORA. Both acoustic and non-acoustic array performance during the BASSEX will be examined. In particular, array attitude and stability will be reviewed for different tow conditions, and for the array vertically deployed. Flow noise over the array will be examined for different tow speeds. Own-ship noise contamination will be presented for the array deployed vertically. Acoustic data will be presented as both individual channel measurements and beamformed output for a variety of source/receiver geometries and propagation conditions. Data quality will be assessed as it pertains to the stated objectives of a particular measurement. Based on both acoustic and non-acoustic performance characteristics the advantages and/or deficiencies of the FORA will be discussed for its use in future low-frequency long-range acoustic propagation research. [Work supported by ONR Ocean Acoustics Program.]
Effect of critical-band smoothing of musical instrument spectral data
Authors: Beauchamp James W. , Horner Andrew B.
Published: October 2013

It has been found that second-order harmonic smoothing of musical instrument spectral data can have a significant effect on timbral perception, depending on the instrument tested [McAdams et al., J. Acoust. Soc. Am. 102, 882–897 (1999)]. With critical-band smoothing, the lower harmonics, since they are in different critical bands, retain their individual amplitudes and temporal envelopes. Thus, it is hypothesized that critical-band smoothing has a lesser perceptual effect on most instrument tones than harmonic smoothing. On the other hand, upper critical bands consist of groups of harmonics. It is hypothesized that it is difficult to hear out individual harmonics within critical bands. Thus, for each band the independent harmonic temporal envelopes can be replaced by a composite rms-amplitude envelope. Spectra within bands can be replaced by time-averaged spectra. Alternatively, time-dependent amplitude versus Bark-frequency spectral envelopes can be smoothed for each individual analysis frame. Further, amplitudes can be averaged in dB or linear units. Results for various processing combinations and various musical instrument sounds will be given and demonstrated.
An alternative solution for positioning sound sources in loudspeaker-based virtual environments
Authors: Braasch Jonas
Published: October 2013

In auditory virtual environments it is often required to position an anechoic point source in three-dimensional space. When sources in such applications are to be displayed using multichannel loudspeaker reproduction systems, the processing is typically based upon simple amplitude-panning laws. This paper describes an alternative approach based on an array of virtual microphones. The aim of the system architecture design was to comply with the expectations of audio engineers and to create sound imagery similar to those associated with standard sound recording practice. In the newly designed environment, the microphones, with adjustable directivity patterns and axis orientations, can be spatially placed as desired. This way, time-delay panning can be included by simulating a non-coincident microphone array. By the use of omnidirectional microphones the panning is almost solely based on time-delay panning and thus performance can take advantage of the precedence effect. Also, the proposed architecture is flexible enough to include classic amplitude panning laws by translating the requested panning law into physically non-existing microphone directivity patterns. Moreover, the virtual directivity patterns do not have to be rotationally symmetrical. [Work supported by VRQ.]
Scattering by truncated targets with and without boundary interactions
Authors: Marston Philip L. , Baik Kyungmin , Espana Aubrey , Osterhoudt Curtis F. , Morse Scot F. , Hefner Brian T. , Blonigen Florian J.
Published: October 2013

Ray methods have been applied to the scattering of various truncated targets having wavenumber-radius products as small as 10 [F. J. Blonigen and P. L. Marston, J. Acoust. Soc. Am. 107, 689–698 (2000); S. F. Morse and P. L. Marston, ibid. 112, 1318–1326 (2002); B. T. Hefner and P. L. Marston, ARLO 2, 55–60 (2001)]. Recent work emphasizes the exploration of scattering enhancements for other situations including plastic cylinders having curved ends, truncated plastic cones, partially exposed cylinders, and objects in simulated conditions for burial in a seabed. Enhanced scattering is often associated with a locally flat outgoing wavefront. For plastic targets it has been helpful to examine the time dependence of the backscattered envelope as a function of target tilt for targets illuminated by short tone bursts. For partially exposed objects it is helpful to examine the backscattering as a function of the target exposure. For simulated buried targets, it has been helpful to excite target resonances. [Work supported by the Office of Naval Research.]
Production of evanescent acoustic waves and their scattering by resonant targets
Authors: Osterhoudt Curtis F. , Dudley Christopher , Thiessen David B. , Marston Philip L. , Morse Scot F.
Published: October 2013

An environmentally-friendly liquid mixture, denser than water and immiscible with it, and with a sound speed slower than water’s, has been produced and incorporated into a scattering facility. This liquid mixture is submerged in a volume of water. In this way, the water above the denser fluid simulates a sandy ocean bottom, with the dense fluid simulating the ocean water column. When insonified by an acoustic beam from within the denser liquid, evanescent wave fields are produced in the water volume. Various targets and detectors are scanned in the water (the simulated sandy bottom) or in the mixture (the simulated ocean water column), and coupling of the evanescent waves to low-frequency resonances of cylindrical targets has been observed. Such coupling may reveal important structural characteristics of scatterers. Additionally, the complicated soundfield structure in the simulated bottom has been mapped. The structure is associated with the production of evanescent acoustic waves by a beam of sound. A model for this structure was developed using numerical wavenumber integration. [Work supported by the Office of Naval Research.]
How does the mammalian brain code for binaural information?
Authors: Marquardt Torsten , McAlpine David
Published: October 2013

We will summarize new physiological results which contradict established models of binaural hearing, namely (1) the A-limited range of encoded interaural time difference, ITD, (2) a correlation between ipsilateral inhibition and best ITD, and (3) a frequency dependent non-linear mapping of ITD which reflects distribution of naturally occurring ITDs. Furthermore, we will outline a new concept for binaural models which incorporates these new results, and will propose a new illustrative format in which to present the triplet of binaural parameters: interaural phase difference, interaural intensity difference, and interaural coherence (redefined).
Elastoacoustic response of laminated plates
Authors: Kolar Ramesh
Published: October 2013

The application of composite materials in the aerospace and naval structures has increased enormously due to high specific strength and specific stiffness afforded by these materials. In this paper a formulation is developed based on Hamilton’s Principle and laminated composite plate theory to study the elasto-acoustical response of composite plates under heavy fluid loadings. The formulation starts by using Hamilton’s principle in conjunction with shear deformable theory of laminated composite plates. The acoustic pressure described by wave equation is computed similar to Sandman and Nelisse. Using the Rayleigh Ritz method and symbolic mathematics for evaluation of integrals, the formulation provides efficient approach for the problem defined. Typical results include radiation impedance as a function of driving frequency, vibroacoustic indicators such as radiated sound power and mean square velocity for a model problem. Such results are very important in studying constrained layer damping when viscolastic dampers are used in structural components.
Prediction of radiation from finite-length fluid-loaded periodic structures subject to broadband excitation using local-global homogenization
Authors: Danilov Pavel V. , Bliss Donald B.
Published: October 2013

Local-Global Homogenization (LGH) is a method to predict directly the smooth global response of periodic fluid-loaded structures in a self-contained manner. Many fluid-loaded structures, such as fuselages and hulls, have periodically spaced braces, ribs, or attachments. Structural motion, acoustic radiation, and the interior sound field are of interest. Calculating the motion of such fluid-loaded structures is difficult because of their complexity and the disparity of length scales. Periodic discontinuities cause the structural response to occur in a broad spectrum of spatial wavenumbers, and to exhibit stop-band and pass-band behavior. The broad spatial wavenumber spectrum contains both radiating and non-radiating components. The global low-wavenumber part of the response is most efficiently coupled to the acoustic field, since low wavenumbers correspond to supersonic phase speeds. In the LGH reformulation, an infinite order operator that embodies both the structural modes and the evanescent component of the fluid loading governs the equivalent smooth global problem. Numerical implementation is demonstrated for the structural response and acoustic radiation from a finite-length fluid-loaded plate with periodic impedance discontinuities subject to broadband excitation. Calculations show good agreement with the exact solution and substantially improved computational efficiency. Radiation characteristics are discussed for single frequency and broadband structural motions.