bluuebunny/crossref_metadata_2025 huggingface dataset:
Using passive acoustics to monitor spawning of fishes in the drum family (Sciaenidae)
Authors: Luczkovich Joseph , Sprague Mark
Published: October 2013

The goal of this study was to develop a passive acoustic survey protocol to identify spawning habitats of sciaenid fishes. Based on comparisons of recordings of captive-fish and field recordings of species-specific courtship sounds, spawning areas of red drum, weakfish, spotted sea trout, and silver perch (Family Sciaenidae) have been identified in Pamlico Sound, NC. Sciaenid sounds were recorded using either a portable hydrophone deployed from a boat or timer-operated sonobuoys. Loudness of mating choruses of weakfish and silver perch was strongly correlated with the abundance of pelagic sciaenid-type eggs, suggesting that these areas were used for spawning. Sonobuoy recordings showed that weakfish spawned only in the high-salinity habitats near the inlets, spotted sea trout spawned predominantly in the low-salinity areas near the river mouths, silver perch spawned in both high- and low-salinity areas, and red drum spawned most commonly in low-salinity areas, but only in September. The loudness of mating choruses of silver perch was diminished when vocalizing bottlenose dolphins were present in the area around sonobuoys or when recordings of signature whistles were played back. Such ‘‘acoustical avoidance’’ behavior causes variation in sound pressure levels and could lead to lower estimates of abundance of spawning adults when conducting passive acoustic surveys.
Effect of swimbladder resonance on auditory bandwidth and sensitivity in teleost fishes
Authors: Hastings Mardi C. , Derenburger Corrie J. , Finneran James J.
Published: October 2013

Experimental studies of four teleost species indicate that the response of the swimbladder to sound controls the auditory bandwidth of fish both with and without a direct connection between the swimbladder and the inner ear. Motion of the swimbladder in an acoustic field generated by an underwater loudspeaker was measured in vivo from 200 to 3000 Hz for channel catfish (Ictalurus punctatus), goldfish (Carassius auratus), American shad (Alosa sapidissima), and oscars (Astronotus ocellatus). Data were normalized with local acoustic energy density to obtain swimbladder frequency responses. Channel catfish and goldfish have two swimbladder chambers and Weberian ossicles that connect the anterior chamber to the inner ear, while American shad and oscars have a single swimbladder and no Weberian osscicles. (Shad do have auditory bullas; however, no motion of the bullas was detected.) Swimbladder frequency responses were compared with audiograms reported in the literature. Results indicate that auditory bandwidth correlates directly with the bandwidth of swimbladder resonance in all four species. Auditory threshold, however, does not correlate with amplitude of the swimbladder resonance. The two species with Weberian ossicles have lower auditory thresholds, but swimbladder resonances of approximately the same or somewhat lower amplitude than the other two species.
Small-scale processes and vertical diffusion in the ocean
Authors: Gargett Ann E.
Published: October 2013

A depth profile taken anywhere in the ocean reveals large vertical gradients of oceanic water properties such as temperature, salinity, oxygen concentration, macronutrients such as nitrate and silicate, and micronutrients such as iron. These vertical gradients are formed at the very largest (depth/basin) scales of motion in the sea, and eradicated at the very smallest scales, those associated with three-dimensional turbulence. Turbulent enhancement of vertical diffusion over that associated with molecular motions is central to vital processes within the ocean. Vertical diffusion resupplies nutrients (the ‘‘fertilizer’’ for marine plant life) to the upper sunlit layers of the sea, underpinning marine food webs. The location and strength of turbulent diffusion determines the distribution of manmade pollutants introduced into the ocean, whether by design or by accident. More surprising perhaps is the essential role played by vertical diffusion in determining large-scale oceanic density structure, hence the crucial importance of small-scale turbulent processes to studies of natural and/or anthropogenic climate change. This presentation will review a variety of processes known or believed to generate the smallest scales of velocity and scalar variance in the sea, and describe the tools oceanographers presently use to measure and interprete salient characteristics of these small-scale processes.
Acoustic measurements of global ocean shear
Authors: Pinkel Robert , Rainville Luc , Slater Eric , Green Lloyd , Goldin Mike , Bui Mai
Published: October 2013

The energetics of the ocean can be viewed as a cascade, with energy input at relatively large spatial scales, 1–10000 km, and eventually dissipated by turbulent processes at centimeter–millimeter scales. The turbulence is thought to be triggered by the small-scale shear in the sea. Since the shear field serves as a mediator of ocean mixing, its dynamics are of central relevance to the overall mechanics of the ocean. To gather global shear data, a dual frequency Hydrographic Doppler Sonar System has been developed for the Scripps research vessel Roger Revelle. The System consists of a nested pair of Janus transducers operating at 50 and 140 kHz. The 50 kHz sonar profiles to depths of 700–1000 m with 15 m depth resolution. The 140 kHz sonar achieves ranges of 200–300 m with 3 m depth resolution. Operating since January 2000, the system has detected considerable geographic variability in both shear and acoustic scattering strength. The deep Sea of Japan and the Eastern North Pacific are surprisingly low in shear. Large shears are encountered near the Hawaiian Ridge and in the waters beneath the Kuroshio. With continued operation, the large-scale patterns and underlying governing principles of the shear field will hopefully emerge.
Measured turbulence in ship wakes
Authors: Culver R. Lee , Bradley David
Published: October 2013

Large surface ships moving at high speed generate extremely turbulent velocity fields containing high concentrations of air bubbles that are distributed in a nonuniform manner. The bubbles are acoustically active, making sonar a useful tool for imaging the ship wake and measuring the spatial and temporal variations of the bubbles. We have employed a 250-kHz multibeam sonar, integrated into an autonomous vehicle (AUV), to image the wakes of two large surface ships from the underside. The AUVs traveled at high speed so that the spatial variation of wake of approximately the same age could be assessed, and ran under different age sections of the wake in order to observe temporal variation. Using an assumed bubble size spectrum for the wake, bubble density has been estimated from the backscattered signals. Variations in bubble density with depth, cross-wake, and along-wake dimension, and with time, are observed. Spatial wave number spectra are used to quantify the scales over which bubbles are distributed, which may be related to the scales of turbulent energy distribution. Comparing measurements of different age wakes indicate how the distribution over spatial scales evolves with time. The multibeam sonar appears to provide quantitative information about the distribution of bubbles, and possibly turbulence, in the ship wake. [Work supported by ONR.]
Dual-mode HIFU phased arrays for noninvasive surgery
Authors: Ebbini Emad
Published: October 2013

Ultrasound phased arrays employing advanced piezocomposite transducer technology are now commonplace in high-power therapeutic applications. When properly designed, these arrays can produce (single or multiple) therapeutic foci suitable for noninvasive surgery for a variety of applications. A properly designed HIFU array has a characteristic therapeutic operating field (ThxOF) around its geometric center. ThxOF defines the volume within which the array is capable of producing therapeutic effects at the intended focal spot(s) without collateral damage at other locations. Recently, we were able to show that HIFU arrays optimized for therapy has a characteristic imaging field of view (IxFOV) around its geometric center. IxFOV defines the volume within which the array is capable of producing images of the target at a specified contrast level. In this talk we outline the optimization procedure for designing dual-mode HIFU arrays suitable for imaging and therapy. In addition, we give illustrative experimental examples of dual-mode operation of HIFU phased arrays. In particular, we emphasize new imaging techniques for visualization of HIFU lesions, both discrete and volumetric. Images of HIFU lesions obtained by the dual-mode HIFU array and a commercial scanner will be compared to demonstrate the superiority of our specialized imaging modes in lesion visualization.
High intensity focused ultrasound for arrest of bleeding
Authors: Vaezy Shahram , Martin Roy , Crum Lawrence
Published: October 2013

High Intensity Focused Ultrasound (HIFU) has been shown to provide an effective method of hemostasis, in animal studies, for both solid organs and blood vessels (acoustic hemostasis). Moderate to profuse bleeding from major blood vessels, liver, and spleen, can be stopped within 1–2 min of HIFU application. The efficacy of acoustic hemostasis has been demonstrated using HIFU frequencies of 1–10 MHz, and acoustic intensities of 1000–5000 W/cm2. Conventional B-mode ultrasound imaging and Doppler appear to provide a effective visualization, targeting, and monitoring methods when extracorporeal application, in case of internal bleeding, is desired. Both thermal and mechanical mechanisms of HIFU appear to be responsible for achieving hemostasis. The thermal mechanism, due to ultrasound absorption, raises the tissue temperature in excess of 70°C in less than a second, leading to shrinkage of the tissue and collapse of small blood vessels. The mechanical mechanism, due to cavitation activity, disrupts the tissue structure, leading to the occlusion of large blood vessels. Both mechanisms result in coagulative necrosis of tissue, and arrest of bleeding. Acoustic hemostasis may provide an effective method in surgery and prehospital settings for treating bleeding in trauma and elective surgery patients.
Wireless telephone design considerations
Authors: Zurek Robert A.
Published: October 2013

As wireless communication devices have shifted from novelty devices to everyday use, the demands on the performance and quality of the device’s audio and acoustic systems has increased. The acoustic portion of wireless phone design can no longer be taken for granted as the size of the devices decrease and the expectations increase. While wireless telephones share many of the design challenges of wired landline systems, they also present additional challenges not normally found in landline systems. The shape and size of today’s phones make past assumptions used in the design of landline systems invalid, such as the assumption that the acoustic load on the receiver is constant. The delay inherent in today’s digital systems coupled with the small size of handsets has led to an increased awareness of acoustic feedback from the receiver to the microphone, which results in an undesirable system echo. In addition to the receiver design and echo concerns is the necessity of designing in an alert or ringer that must produce adequate SPL levels to inform the user of a call, while fitting in a very small space. The aforementioned issues will be discussed along with current design techniques utilized to overcome these challenges.
Scaling issues in a submillimeter MEMS microphone
Authors: Loeppert Peter V.
Published: October 2013

A silicon based microphone with a 0.5 mm diam diaphragm has been developed using a combination of surface and bulk micromachining or MicroElectro Mechanical Systems (MEMS) techniques. This device is intended for high volume general purpose markets such as telephony, where cost is a key factor. In batch fabricated MEMS devices, cost is critically determined by the device size. Yet the performance standards for this microphone are set by relatively large electret condenser microphones (ECM) built in competing technologies. This paper will discuss the scaling issues involved in meeting high performance goals in a very small MEMS device. In particular, tradeoffs made to achieve high sensitivity, low noise, and unconditional stability will be discussed.
FEM based simulation of nonlinear effects in armature alerts
Authors: Zurek Robert A. , Koo Simone
Published: October 2013

Although alerts or ringers have been used in wireless phones and pagers since their inception, design of these systems in the past has been limited to estimation of the Helmholtz resonance of the acoustic system followed by trial and error modification until the desired alert level is achieved. With the advent of reasonably fast Vibro-Acoustic Boundary Element and Finite Element solvers, a much more accurate and inclusive method of alert system design is possible. BEM and FEM alert models can take into account the baffling effects of the phone or pager case, losses due to surface absorption and transmission loss, geometrical characteristics of the system’s ports and cavities, and the frequency dependent vibration characteristics of the transducer. These simulation capabilities, combined with Doppler laser vibrometer based alert characterization, provide for an improved alert design cycle. This paper will discuss some of the new alert characterization and simulation techniques used in the Motorola PCS Research Advanced Products Lab. The results of this technique will be compared to measured data and earlier simulation attempts, and future enhancements to the current technique will also be discussed.
New materials for thermal microphone sensors
Authors: Helffrich Jerry , Hanson Heather
Published: October 2013

Existing thermal microphone sensors use MEMS technology to fabricate two beams. These initially heated beams cool with the movement of air in a sound wave. The temperature difference between the two beams due to convective heat transfer can be converted to an air velocity measurement. These microphones have the advantage of an extremely small size and dipole sensing, but suffer from a low signal-to-noise ratio, low-frequency response, and high-power dissipation. We are investigating the use of new, high-temperature coefficient of resistivity (TCR) materials for thermal microphones. This second generation of devices should deliver an improved response than those that are commercially available. Measurements of the response of thermal microphones using new resistive materials will be presented.
Difference method for measuring the vibration sensitivity of microphones
Authors: Brammer Anthony J.
Published: October 2013

In some applications, microphones are subjected to sufficient vibration that their vibration response is of interest (e.g., feedback from earphone to microphone in wireless telephones, and hearing aids). A procedure for measuring this microphone property should take into account the airborne sound produced by the apparatus. In the present method, two microphones of the same type are mounted facing each other with diaphragms parallel, and form the plane, circular ends of a cylindrical enclosure. The dimensions of the air-filled volume between the two microphones are chosen to ensure that both microphones experience the same sound pressure. When the enclosure is vibrated in a direction normal to the plane of the microphone diaphragms (i.e., along the long axis of the cylinder), the vibration responses of the two microphones are essentially out of phase. The difference signal between the two microphone outputs will then provide a measure of the mean vibration response of the microphones from which the common airborne response of the microphones has been subtracted. The extent to which the response to sound within the apparatus interferes with the measurement of the vibration response of individual microphones may then be estimated. Results will be presented for a miniature electrical microphone.
Comparisons of theoretical and experimental transverse motion for a plucked, stiff piano string
Authors: Sánchez José , Irwin James
Published: October 2013

This work is meant to determine whether central or backward difference approximations in computer simulations more closely approximate reality. The stiff piano string motion is experimentally measured by a real-time analog optical technique that was developed to measure the one-dimensional transverse displacement of a plucked string. The optical technique uses a detector that collects laser light not obstructed by the string. The received light is converted to a voltage, which is related to the string displacement perpendicular to the laser beam. The signal is then filtered and conditioned by external circuitry, digitized by a Mona data acquisition system, and are displayed using Cool Edit Pro. These measurements are then compared to two different finite difference computer simulations. One of the computer simulations uses central differences and the other uses backward differences, both with the appropriate boundary conditions and parameters. The comparison of the experimental data and the computer simulations is comprised of informal listening tests, spectral, and time domain comparisons.
Acoustical analysis of an ancient Mexican flute
Authors: Menchaca Rolando , Beristáin Sergio , Velazquez Roberto
Published: October 2013

The acoustical anslysis made on one flute taken from a given class among very old Mexican flutes is discussed. First, some acoustical characteristics of the sounds produced from this musical instrument are presented, such as the acoustic power and the energy spectrum of some of the different sounds generated by the flute. Then an analysis is made on the acoustical details of the construction technology used to build this kind of instrument, like acoustical mass and compliance, turbulence generation, radiation from the tuning holes, and so on. And some discussion on the probable design objectives on the mind of the ancient Mexicans when they developed and built this sound instrumentation, as the possibility that natural sounds were taken as a reference for their art evolution.
Acoustical environments measured in urban and suburban schools
Authors: Erdreich John
Published: October 2013

Measurements of sound levels in numerous classrooms and other instructional spaces in primary educational facilities over the past several years have revealed a lack of acoustical control within public schools. We have found environments in excess of NC-60 more often than we have found NC-30 rooms in unoccupied spaces. Occupied sound levels in instructional spaces may exceed 90 dB(A). Because of poor acoustical design, we have found classrooms on the same floor with background sound levels that vary from NC-60 to NC-25, depending on the distance from the HVAC mechanical room. This paper will present some case studies that demonstrate the need for an acoustical standard for the classroom.
Development of an American National Standard for classroom acoustics
Authors: Lubman David , Sutherland Louis C.
Published: October 2013

A draft ANSI (American National Standards Institute) Standard for classroom acoustics will be submitted for approval this year. It is believed that adopting this Standard will result in a more inclusive and effective education system. Although eliminating acoustical barriers benefits everyone, young children and persons with hearing, language, speech, and learning disabilities are special beneficiaries. Titled ‘‘Acoustical performance criteria, design requirements, and guidelines for schools,’’ the draft, designated ANSI S12.60-200X, limits noise and reverberation in classrooms and imposes minimum values of sound isolation between enclosed classrooms and adjacent spaces. The effort began when many members of the Acoustical Society of America (ASA) became convinced that noise and reverberation in classrooms were serious barriers to learning. The ASA organized a Task Force on classroom acoustics, assembling volunteer scientists and engineers from architectural acoustics, noise, speech, and psychological acoustics. Task Force outreach seminars led to a broad coalition of individuals, and public and private organizations. They determined that a national Standard for classroom acoustics was needed. To develop that Standard, ANSI Working Group 42 on classroom acoustics was established and scoped. Draft 10 was successfully balloted in the S12 Committee in January 2001. In this paper we discuss the development of the Standard.
Numerical study of resonant gas oscillation in a closed tube with varying cross section
Authors: Yano Takeru
Published: October 2013

Nonlinear resonant gas oscillations in closed tubes with varying cross-sections filled with an ideal gas are numerically studied. The resonant gas oscillation concerned is excited by a piston at one end of the tube, which oscillates harmonically with a resonant frequency obtained by solving the quasi-1-D linear wave equation. The system of Navier–Stokes equations for axisymmetric flow is directly solved by a high-resolution upwind TVD finite-difference scheme. The numerical results may be summarized as follows: (i) If the variation of cross-section is small, a quasi-steady oscillation state includes shock waves, as in the tubes of uniform cross-section. (ii) When the variation of cross-section is relatively large, the gas oscillation evolves into a standing wave of large amplitude, but shock waves are not formed. (iii) The (nondimensional) maximum amplitude can attain the order of the cubic root of M, where M is the acoustic Mach number at the sound source. (iv) Such a large amplitude oscillation induces relatively fast acoustic streaming.
Forced response condensations applied to the eigenvalue analysis of damped structures
Authors: Xianfeng Zhao , McDaniel J. Gregory
Published: October 2013

The eigenvalue analysis of nonproportionally damped structures has received much recent attention, as most of the algorithms to solve undamped problems do not directly extend to the damped case. In many cases, one is only interested in finding the eigenvalues that lie in a region of the complex plane. In this presentation, we propose an algorithm that exploits this fact. The algorithm begins by finding the eigenvalues of the undamped problem and tracks the eigenvalues as damping is gradually added. For each increment of damping, new eigenvalue estimates are obtained by forcing the structure at the previous eigenpair and using the forced response vectors to condense the matrices. In this way, one may be assured of finding all of the eigenvalues in a vertical strip of the complex plane. Features of the algorithm will be discussed and initial proof-of-concept results will be presented. [This material is based upon work supported by NSF under Grants Nos. 9978747 and 9984994.]
A new type of vibration damper based on flexural wave propagation in laminated wedges of power-law profile
Authors: Krylov Victor V.
Published: October 2013

Flexural waves propagating towards sharp edges of elastic wedges are slowing down and growing in amplitudes as they approach the edges. Especially interesting phenomena may take place in wedges having cross sections described by a power-law relationship between their local thickness and the distance from the edge, with m being a power-law exponent. In particular, the theory shows that, for m equal or larger than 2—in free wedges, and 5/3—in immersed wedges, the incident flexural waves can become trapped near the edge and never reflect back, i.e., the above structures represent acoustic ‘‘black holes’’ for flexural waves. Because of the deviations of real manufactured wedges from the ideal power-law profiles, first of all because of ever-present edge truncations, the corresponding reflection coefficients are always far from zero. Therefore, in reality such homogeneous wedges can not be used as effective vibration dampers. In the present paper it is demonstrated that the situation can be significantly improved by depositing an absorbing thin layer on the wedge surfaces. In this case the reflection coefficients can be drastically reduced even for wedges with noticeable truncations. Thus, the combination of the power-law profile and a thin absorbing layer can result in a new effective method of damping flexural vibrations.
Phonological and acoustic-phonetic cues in recognizing words ending in nonrelease stop consonants
Authors: Lugo-Marin Janielle , Connine Cynthia M.
Published: October 2013

This study investigates the effects of probabilistic likelihood and of certain acoustic–phonetic cues in the recognition of word-final nonrelease stop consonant stimuli. Recognition of the word was examined by assessing the activation of an embedded word (inconsistent with a release) relative to the activation of the whole word. The missing release was presented in contexts that predict a higher (a following consonant) or lower (a following vowel) likelihood of a release. The contribution of acoustic–phonetic cues was examined by including word-final stop consonants that were voiced (do not require release for recognition) or voiceless (release required for recognition). Four experiments were designed to examine the effects of the probabilistic likelihood for the release and of acoustic–phonetic cues in the activation of a canonical version of a word, when the final stop-consonant release is not present. Priming of the embedded word was greater for the voiceless relative to the voiced stimuli, and also for the following consonant context relative to vowel context. In the absence of the following context, the embedded word was primed for the voiceless but not for the voiced stimuli, and the whole word was primed to a greater extent for the voiced relative to the voiceless stimuli.
Transconsonantal coarticulatory patterns in VCV utterances: Effects of a bite block
Authors: Yunusova Yana , Weismer Gary
Published: October 2013

The concept of coordinative structures, or articulatory synergies, envisions a collection of articulators organized to achieve a specific articulatorly or acoustic goal. The mandible figures prominently in concepts of articulatory synergies because of its potential interaction with labial and lingual shaping of the vocal tract. What happens to these hypothesized synergies when one component is taken out of the collective? Bite block articulation is a common experimental approach to eliminating the jaw from its synergistic role in articulation, and studies have shown that the speech mechanism is able to reorganize its target configurations almost immediately when speaking with a fixed jaw. In the current study we examine vowel-to-vowel, transconsonantal effects with and without a bite block. Although there is one study [Sussman, Fruchter, and Cable, J. Acoust. Soc. Am. (1995)] showing stability of coarticulatory effects in biteblock conditions, that conclusion was based primarily on locus equations. In the current study, we hypothesize that more traditional acoustic measures of right-to-left and left-to-right coarticulation will show that reducing an articulatory synergy by holding one of its components constant will result in different-from-typical coarticulatory behaviors. [Work supported by NIDCD Award No. DC 000319.]
Phase transitions in a repetitive speech task as gestural recomposition
Authors: de Jong Kenneth J. , Lim Byung-jin , Nagao Kyoko
Published: October 2013

Tuller and Kelso (JSHR, 1991) show the relative timing of peak glottal opening and oral closure in repetitive /ip/ production differs between /ip/ and /pi/ productions. Also, as repetition rate increases, the timing in /ip/ merges with that in /pi/. The authors interpret this to indicate two stable regions in glottal-to-oral phasing, one for codas and one for onsets. The current paper examines a similar corpus of glottal transillumination traces of repeated syllables, which includes both labial and lingual stops. Preliminary examination of peak glottal timing with respect to acoustic landmarks indicating closure shows the same pattern of timing differences at slow rates and neutralization at fast rates. However, peaks in the transillumination traces often do not indicate glottal abduction for the consonant, but rather indicate a relatively open glottis for vocalic voicing, happening in the context of glottal stoppage at the onset of the vowel. In addition, coronal codas exhibit cycle-to-cycle variation from glottalized to abducted voiceless forms. Thus while rate does induce stepwise changes in glottal activity, phasing, in the sense of relative timing, does not account for many of the rate effects. Rather, rate appears to be inducing a recomposition of the gestures which comprise the speech.
Effects of synthesis fidelity on vowel identification: Role of spectral change and voicing source
Authors: Assmann Peter F. , Katz William F.
Published: October 2013

Recent studies have shown that synthesized versions of American English vowels are more accurately identified when natural time-varying changes in the formant frequencies are preserved rather than flattened. A limitation of these experiments is that vowels generated with cascade formant synthesis are generally less accurately identified than natural vowels. To overcome this limitation, a high-quality analysis–synthesis system was used to reexamine the effects of spectral change. Using this new technique, synthesized versions of 12 American English vowels spoken by adults and children were identified as accurately as natural vowels. Two experiments confirmed the beneficial effects of preserving the time-varying changes in the formants, both in vowels synthesized with pulsed excitation (as in voiced speech) and noise excitation (as in whispered speech), and verified that identification accuracy does not decline when the fundamental frequency is held constant. However, in contrast to earlier findings, (i) whispered vowels were identified as accurately as the voiced versions, and (ii) the benefits of time-varying spectral change were greater than previously found with cascade formant synthesis. The findings are consistent with recent studies showing that the measured effects of spectral and temporal manipulations in vowels can vary as a function of synthesis fidelity.
Intelligibility of narrow-band speech is enhanced by unmodulated flanking noise: Restoring intelligibility by masking of silence
Authors: Lenz Peter W. , Bashford James A. , Warren Richard M.
Published: October 2013

The intelligibility of notch-filtered sentences may improve by 10% or more when a large spectral gap is filled with noise rather than silence [Warren et al., P&P 59, 275–283 (1997)]. The present study shows that a comparable ‘‘spectral completion’’ (SC) effect occurs when a narrow band of speech is surrounded by complementary noise. In Experiment 1, intelligibility of 2/3-octave everyday sentences, centered at 1.5 kHz [2000-order FIR filtering, slopes greater than 1000 dB/octave], was 65% without noise, 72% with complementary low-pass or high-pass noise, and 76% with both noise bands present (noise spectrum level at 20 dB relative to the speech). Experiment 2 found a comparable SC effect with partially masked speech: The 2/3-octave sentences were about 40% intelligible when masked by narrow-band noise having the same spectral limits (relative spectrum level again 20 dB), but were 50% intelligible when the noise was broadband. Hence, out-of-band noise enables listeners to make better use of information within narrow-band speech, perhaps by masking an otherwise misleading absence of energy in normally coactive regions of the spectrum. Under partial masking conditions, this SC effect can produce an apparent release from masking in the absence of comodulation. [Work supported by NIH.]
Acoustic wave diffraction tomography
Authors: Devaney Anthony J.
Published: October 2013

The classical theory of Diffraction Tomography (DT) is formulated within the context of the acoustic and elastic wave equations. A number of applications for the generalized theory are reviewed including ultrasound tomography in variable density and elastic wave media and cross-well geophysical tomography and offset vertical seismic profiling (VSP). The general theory of DT is compared and contrasted with classical focus-on-transmit and focus-on-receive confocal acoustic imaging as well as with various standard ad-hoc imaging methods often employed in applications. The use of slant stacking for converting point source to plane wave insonification is reviewed as is the theory of acoustic tomography in known layered background media. A number of computer simulations and results from experimental data are presented.
Geoacoustic inversion techniques workshop: Test cases 4 and 5
Authors: Fulford James K. , King David B. , Chin-Bing Stanley A.
Published: October 2013

Acoustic transmission loss and reverberation data from two exercises were selected as inversion test cases for the Geoacoustic Inversion Techniques workshop, May 2001. The data was collected using air deployed sonobuoys with standard 0.82 kg SUS charges as sources. The acoustic data was presented in octave bands for frequencies from 25 to 800 Hz, and a 1/3 octave band for 3.5 and 6.5 kHz center frequencies. Environmental data consisted of bathymetry, and sound speeds gathered by AXBT’s. Background geophysical information was not given to the participants. Inversion results were encouraging. Selected examples will be shown. [Work supported by ONR/NRL and SPAWAR.]
Extraction of modal backscattering matrix from reverberation data in shallow-water waveguide. Part I. Theory
Authors: Shang E. C. , Gao T. F. , Tang D. J.
Published: October 2013

Extracting the bottom backscattering information from reverberation data in shallow-water waveguide is an attractive but difficult issue. In previous works, some a priori assumption (for instance, the Lambert’s Law, or the separability of the backscattering matrix) has been made in order to solve this problem. In this paper, new approaches are proposed. The modal backscattering matrix can be extracted directly from reverberation data without any a priori assumption on scattering coefficient. The backscattering information inversion is based on the following three components: (1) mode-filtering at the receiving vertical array, (2) changing the point source depth to obtain different incident mode excitation, and (3) using mode stripping in the waveguide as an additional mode filter. For lower frequency the linear inversion is presented, and for higher frequency the sequential inversion with angle interval smoothing is proposed. [Work supported by ONR.]
Comparison of bistatic scatter modeling with experimental tank data at 250 kHz
Authors: Brothers Richard J. , Heald Gary J. , McCloghrie Paul , Blondel Philippe , Pace Nicholas G.
Published: October 2013

Experimental data gathered in the laboratory at the University of Bath have been compared to bistatic scattering models. The data were gathered at 250 kHz over different controlled sediment types (sand/gravel/cobble), and at a range of scattering angles using a directional source and omni-directional receiver. Stringent system calibration was undertaken, along with extensive pre-experimental analysis, in order to guarantee high-fidelity scattering data within the confines of a tank environment. Having established the validity of the scattering models, they have been incorporated into a bistatic sonar model. This is achieved by integrating a function that includes the scattering cross-section at each point on the sediment surface, as well as spreading and absorption losses. This model is designed to investigate optimum sonar parameters for the bistatic detection of objects on and in the seabed.
Directivity of human talkers
Authors: Chu Wing T. , Warnock Alf , Guy Jean-Charles
Published: October 2013

As well as the level of speech, the directivity of the sound field surrounding the human head is important when estimating speech privacy in open offices. Information on this subject was found to be sparse so the sound field surrounding human talkers was recorded by two sets of eight microphones fixed on two orthogonal meridian arcs in an anechoic chamber. Talkers were positioned at the center of the two arcs of the microphone arrays and rotated through six positions at 15° increments to survey the whole sound field. Twenty male and twenty female subjects were used. No significant differences in directivity were detected between male and female talkers although the mean spectra were different. There was good agreement between the field and laboratory measurements of the male voice spectra though some differences were found for the female voice spectra. No significant differences in directivity or frequency content were detected between English and French talkers. Similar directivities were obtained for the average human talker and the Bruel and Kjaer Head and Torso Simulator. Agreement with other published information is fairly good. This work was done as part of a project for Public Works and Government Services Canada.
The felid purr: A healing mechanism?
Authors: von Muggenthaler Elizabeth
Published: October 2013

A current hypothesis suggests the purr indicates contentment, however, cats purr when they are severely injured or frightened. Forty-four felids were recorded including cheetahs, ocelots, pumas, domestic cats, and servals. A Sony TCD-D8 Digital Audio Recorder (DAT) and Statham Radio microphones recorded the purrs. FFTs and spectrographs were performed using National Instrument’s Polynesia. An accelerometer was also used to measure domestic cat purrs. Every felid in the study generated strong frequencies between 25 and 150 Hz. Purr frequencies correspond to vibrational/electrical frequencies used in treatment for bone growth/fractures, pain, edema, muscle growth/strain, joint flexibility, dyspnea, and wounds. Domestic cats, servals, ocelots, and pumas produce fundamental, dominant, or strong frequencies at exactly 25 Hz and 50 Hz, the two low frequencies that best promote bone growth/fracture healing [Chen et al., Zhong. Wai Ke Za Zhi. 32, 217–219 (1994)]. These four species have a strong harmonic exactly at, or within 2 Hz of 100 Hz, a frequency used therapeutically for pain, edema, wounds, and dyspnea. An internal healing mechanism would be advantageous, increasing recovery time and keeping muscles and bone strong when sedentary. [Published with permission from the New Zealand Veterinary Journal; work supported by Endevco.]
Dynamics of bottom boundary layers in the coastal ocean
Authors: Trowbridge John
Published: October 2013

The bottom boundary layer is the region adjacent to the sea floor, with a thickness typically on the order of meters to tens of meters, where turbulence generated by bottom drag produces vertical mixing of mass, heat, and momentum. Oceanic boundary layers are influenced not only by turbulent mixing, but also by planetary rotation, stratification, topography, surface waves, internal waves, and interaction with the erodible sea floor. Historically, understanding of the oceanic bottom boundary layer has been based on classical results in engineering and meteorology. However, recent theory and measurements have revealed unique features of oceanic boundary layers. Outstanding problems include measuring the interaction of the flow with the erodible sea floor; measuring the spatial scales of turbulent motions that accomplish vertical transport of mass, heat, and momentum; and understanding the processes that control the intensity and scale of boundary layer turbulence, particularly in stable stratification.
Laboratory and field measurements of breaking-induced turbulence: Implications for ocean acoustics
Authors: Melville W. Kendall
Published: October 2013

The entrainment of air by breaking surface waves, its breakup into bubbles, and their transport in the surface layers by breaking-induced turbulence and Langmuir circulations have important consequences for active and passive acoustical oceanography. Recent laboratory and field work related to these issues will be presented. The description of breaking-induced turbulence and air entrainment by just field experiments is very difficult and there are some advantages to separating the issues into those that must be addressed in the field and those that are better studied in the laboratory. For example, the statistics of breaking cannot be resolved by laboratory measurements, whereas the detailed structure of the turbulence is probably better studied in the laboratory. New results from airborne measurements of breaking statistics, and laboratory (and field) measurements of breaking-induced turbulence will be presented and their implications for upper ocean acoustics will be discussed. Similarities between breaking-induced turbulence and Langmuir circulations will be discussed. [Work supported by ONR and NSF.]
Doppler measurement of velocity structure beneath surface gravity waves
Authors: Farmer David , Gemmrich Johannes , Vagle Svein
Published: October 2013

The acoustic Doppler method has proved particularly useful for the investigation of small scale velocity structure associated with wave motions, shear instability, and turbulence. The incoherent bistatic approach permits measurement of the velocity field at meter scales within the crests of large and steep waves, allowing direct comparison with predictions in the region where theory is most likely to break down. At the other end of the scale, coherent Doppler measurement at megahertz frequencies can be used to identify and estimate the magnitude of turbulence beneath breaking waves. We contrast these different approaches using observations with a bistatic incoherent Doppler sonar placed on the floor of the North Sea and an array of monostatic coherent sonars deployed on the ocean surface off the California coast. The observations illustrate the power of Doppler techniques in resolving various aspects of wave dynamics which have been inaccessible using traditional methods.
Coherent Doppler profiler measurements of near-bed suspended sediment fluxes
Authors: Smyth Carolyn E. , Hay Alex E.
Published: October 2013

Vertical profiles of vertical turbulence intensity and vertical sediment fluxes were collected by an acoustic Coherent Doppler Profiler during two experiments: at Queensland Beach, NS and SandyDuck97. Measurements are investigated as a function of bedstate from low energy vortex ripples to high energy flat bed. Ensemble-average vertical turbulence intensity profiles exhibit a peak within the wave boundary layer at heights of O (1 cm) above bottom for all bedstates. Peak average turbulence intensities are relatively independent of bedstate, varying by no more than 50% despite a factor of 7–10 variation in average wave energy. This otherwise remarkable observation can be understood from the corresponding decrease in the physical roughness of the bed, associated with the different observed bedstates. Estimated wave friction factors are highest for low energy rippled beds and smallest for flat bed conditions. Estimates of the vertical suspended sediment flux partitioned into mean, wave, and turbulent components, show that in general, there is a balance between upward fluxes and downward settling; except immediately above the bed, and except for the case of a stationary ripple field. The suspended sediment flux coherence indicates enhancement at incident wave frequencies, with the largest coherence for flat bed conditions very near the bed.
Technology development for directional acoustic arrays
Authors: Arnold David P. , Nishida Toshikazu , Cattafesta Louis N. , Sheplak Mark
Published: October 2013

The need for noise source localization and characterization has driven the development of advanced sound field measurement techniques using microphone arrays; however, the cost and complexity of these systems limit their widespread use. One common application is the study of aircraft noise in wind tunnels. The arrays typically consist of moderate numbers (<40) of conventional condenser microphones and range in size from several inches to several feet. Arrays consisting of more microphones and/or the use of multiple arrays may be needed to analyze complex multipole noise sources. However, the feasibility of scaling the current technology to multiple arrays with large numbers of microphones is limited by the cost per channel, array mobility, and data handling efficiency. A reduced cost, mobile, high speed 16-channel array has been constructed to demonstrate key technologies to address these scaling issues. The system is based on a hybrid package that combines a silicon piezoresistive microphone and amplification circuitry. Each package is socketed into a printed circuit board, providing electrical connections and structural support. High speed data acquisition and signal processing hardware is used to generate the array response in near real time. The results of the initial array calibrations are presented.
Effects of temperature and humidity on the bending stiffness of a sheet of paper measured by laser ultrasonics
Authors: Cornwell Matthew A. , Berthelot Yves H.
Published: October 2013

Laser ultrasonics has great potential for monitoring the bending stiffness of paper during on-line operations. The temperature and humidity conditions at the paper have a significant effect on the bending stiffness, and there is a need to quantify this dependence before an on-line system can be deployed. A laser pulsed source illuminates a point on a paper sample placed inside a controlled environmental chamber and generates ultrasound that is detected by a fiberoptic interferometer. The waveform is analyzed to extract the frequency dependence of the group velocity of the A0 lamb mode, and the corresponding bending stiffness. Three different methods of signal analysis are compared: the complex wavelet transform, the short-time Fourier transform, and the phase-unwrapping method, which requires measurements at two locations. The error bars associated with the bending stiffness are estimated both for the intrinsic experimental errors and for the point to point variablity in the paper itself. Results are presented for temperature ranging from 25°C to 93°C, and for relative humidity ranging from 2% to 75%. [Work supported by the Department of Energy and the Institute of Paper Science and Technology.]
A physically attractive alternative to Lighthill’s quadrupole aerodynamic sound source
Authors: Powell Alan
Published: October 2013

Now an impressed force/unit vol. fi acting alone on an acoustic medium results either directly in the formal mathematical monopole distribution ∂fi/∂yi but which is physically unrealistic, not appearing in the continuity equation, or the given dipole distribution fi by the divergence theorem. These both yield point dipoles, Iyk∂fi/∂yi by Taylor expansion or the expected Ifi, where I=‘‘of strength proportional to the instantaneous volume integral of.’’ Aerodynamic sound generation based on Lighthill’s inhomogeneous wave equation yieds directly a source distribution of the form (a) monopole ∂2Tij/∂yi∂yj, ≊∂2ρuiuj/∂yi∂yj=∂/∂yi⋅∂ρu iuj/∂yj. By the divergence theorem alternative integrally equal distributions are (b) dipole ∂ρuiuj/∂yj and (c) Lighthill’s quadrupole ρuiuj. All yield point quadrupoles for (a) Iykyl∂2ρuiuj/∂yi∂yj and (b) Iyk∂ρuiuj/∂yi by Taylor expansions, (c) Iρuiuj. Distribution (a) is unrealistic physically just like ∂fi/∂yi; (b) appears directly in the momentum equation, like fi, and is equivalent to an applied force/unit volume resulting in sound-generating fluid acceleration, while (c) appears in it only in derivative form. Hence (b) is an attractive alternative to the customary (c) because of that basic relationship which has simple physical appeal.