bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of consonant-nucleus-consonant words produced by a female child
Authors: Meredith Morgan
Published: September 2008

The CNC word identification test is part of the speech test battery used to evaluate speech perception by persons fitted with cochlear implants [Luxford et al, Otolaryngology-Head and Neck Surgery, 126–127 (2001)]. This test uses ten lists of 50 relatively common, phonetically balanced English words per list [Peterson and Lehiste, J. Speech. Hear. Disorders, 27:62–70 (1962)]. The version of this test, currently standardized and used across the U.S., contains the words spoken by one male speaker. Research has shown, however, that persons with cochlear implants have more difficulty perceiving speech produced by women and children than speech produced by men [Loizou et al,. J. Acoust. Soc. Am., 103: 1141–1149 (1998)]. The ten CNC word lists were recorded as produced by an eleven-year old girl. Each word was isolated and the word ready spoken by the same girl was added at the beginning of each stimulus sound file. Ten adults with normal hearing identified these words with 98% accuracy. Identification results will be obtained from persons fitted with cochlear implants and compared to the results of the same persons when listening to the original, male voice, CNC word lists. [Work supported by a UW-Madison Hilldale Research Scholarship.]
Why do children attend to global structure in speech signals?
Authors: Lowenstein Joanna H. , Nittrouer Susan
Published: September 2008

Adults can use global structure such as that found in sine wave and vocoded signals for speech perception. Children appear to weight global spectral structure (represented at the syllabic level by formant transitions) even more than adults, prompting the suggestion that children first attend to the relatively slow vocal-tract movements that create global spectral structure rather than to the rapid and discrete gestures more closely associated with individual phonetic segments. But this interpretation hinges on an articulatory account of speech perception, which lacks general support. An alternative explanation is that children attend to formant transitions because they are found in voiced signal portions and so adhere to principles of auditory scene analysis, such as having a common fundamental. This work tested that hypothesis by using stimuli with no fundamental. Adults and children (3, 5, and 7 years) were asked to label fricative-vowel syllables with three kinds of vocalic portions: natural, sine wave, and whispered. Results showed that all listeners attended to formant transitions as much in the sine wave and whispered stimuli as in the natural, leading to rejection of the hypothesis that children prefer formant transitions because they are signal components that adhere to principles of auditory scene analysis. [Work supported by NIDCD Grant No. DC-00633.]
Psychometric functions and psychometric characteristics of Mandarin monosyllables
Authors: Tsai Kuen-Shian , Young Sheunn-Tsong , Tseng Li-Hui , Wu Cheng-Jung
Published: September 2008

The psychometric functions of the 700 most frequently occurring Mandarin monosyllables (whose cumulative usage was 98.38% in 1,125 distinct monosyllables) were evaulated. Twenty normal-hearing subjects were asked to hear and to repeat the 700 monosyllables which were randomly presented at the level from 0 to 55 dB HL in 5-dB step. The psychometric functions for each of the 700 monosyllables were fit with third-degree polynomials. The fitted curves were used to calculate five psychometric characteristics: (1) the threshold at 0% correct; (2) the threshold at 50% correct; (3) the instantaneous slope at 50% correct; (4) the linear slope from 20% to 80% correct; and (5) the intelligibility at the highest presentation level. The mean values of such five psychometric characteristics for 700 monosyllables are 1.1 dBHL, 12.1 dBHL, 4.5 %/dB, 4.1% %/dB, and 93.4%, respectively. With the psychometric characteristics, the 700 monosyllables can be used to create word recognition test lists for different purposes, such as constructing test lists with different homogeneity, different familiarity, or different difficulty; and the recognition performance of test lists will be predictable. Futhermore, the research results also indicated that there is no significant correlation between the psychometric characteristics and the occurring frequences of monosyllables.
Numerical solution of high-frequency acoustic scattering problems by integral equations preconditioned using pseudo-differential impedance operators
Authors: Calvo David , Calamia Paul
Published: September 2008

Exact computations of high-frequency scattering by targets or rough surfaces can be challenging because of the large number of unknowns. A compromise can be obtained, however, using approximate Dirichlet-to-Neumann surface operators that are known in pseudo-differential form and efficiently implemented using rational approximations. These operators can be used as preconditioners to obtain well-conditioned iterative algorithms to solve the Helmholtz integral equation. Using these algorithms, we compute scattering by two- and three-dimensional targets, and rough surfaces with smooth concave or convex parts with incident fields near grazing angles of interest. This case is particularly important for underwater acoustics, where sounds field graze the free surface or bottom in shallow water.
Internal field in an immersed, absorbing fluid sphere excited by a plane acoustic wave
Authors: Foote Kenneth G.
Published: September 2008

Modeling of sonar interactions with complicated bodies whose characteristic dimensions are of the order of or greater than the acoustic wavelength generally requires use of numerical methods. For validation of associated computer code, a particularly useful example is the internal field excited in an immersed, homogeneous, absorbing sphere by an external plane acoustic wave, since this can be expressed analytically. Here, numerical results are given for a fluid sphere with wave number-radius products spanning the range 1–10 and absorption coefficients spanning the range 0–10 dB per wavelength. The density and sound speed contrasts of the fluid sphere relative to the immersion medium are both varied over the range 0.5–2. [Work supported by NOPP through ONR award no. N000140710992.]
Use of 2-D and 3-D visualization and auralization tools to assess the acoustics of unusual shaped spaces
Authors: Cushner Joshua M. , Biziorek Ryan B.
Published: September 2008

The assessment of room acoustics commonly includes the calculation of relevant metrics by standard empirical equations or computational ray-tracing. These methods are not always sufficient for unusual shaped rooms, and can be supplemented with visualization and auralization techniques that improve our understanding of the behavior of sound in these spaces. Utilizing two- and three-dimensional room models with proprietary developed software, visualization of 360-deg particle emissions from a point source can provide useful information about sound propagation, spatial characteristics, and interactions with room boundaries. Following an iterative visualization process, design verification can be established using auralization techniques in a controlled listening environment. Such techniques facilitate better understanding of the acoustic phenomenon within the room and can help to refine acoustic solutions for room shapes or more efficient use of room surfaces for sound-absorbing finishes. Results from recent project studies show this approach to be useful to enhance communication with the architect and provides the acoustician with another useful analysis tool.
An automated high spatial-resolution scanning system for room-acoustic scale models
Authors: de la Cruz Rolando , Rubin Gordon , Xiang Ning
Published: September 2008

Experimental study of acoustically complex environments is a lengthy and troublesome process, in part due to the great deal of effort in acquiring data. A custom Cartesian scanning system has been developed to perform automated room impulse response measurements in scale models. High spatial-resolution measurements are performed within a planar grid and mapped to observe the spatial distribution of the sound field. Phase relationship across the scanning grid is maintained between measurements using continuous pseudo-random signals. The efficiency and repeatability of the high spatial-resolution scanning system is demonstrated in acquiring a large number of room impulse responses over a predefined Cartesian grid, while maintaining a wide bandwidth in accordance with the spatial Nyquist theorem. This paper discusses some preliminary results obtained in an eighth scale model of a coupled-volume system.
Laser Doppler vibrometer-based acoustical measurement of reflection coefficient up to 20 kHz
Authors: Rubin Gordon , Xiang Ning
Published: September 2008

The well-established two-microphone technique for determining the acoustic reflection of a material in an impedance tube has physical limitations that hinder the measurement of this quantity at high frequencies. Tube geometry, microphone spacing, and perturbation of the sound field by measurement instruments make the determination of normal incidence reflection coefficients above 10 kHz difficult, if not impossible, using microphones and the traditional impedance tube methods. In a recent work, an extended impedance tube technique utilizing a scanning laser doppler vibrometer (SLDV) was presented [Vanlanduit et al., J. Acoust. Soc. Am. 3 (2005)]. In this study, a method using a single point laser Doppler vibrometer (LDV) is used to study the limitations and merits of acousto−optic sensing in impedance tubes. Foams of various thicknesses are measured using the transfer function method in a transparent impedance tube. Results are presented that convey the potential usage of these acousto−optic techniques in the measurement of acoustic reflection properties of materials up to 20 kHz and beyond.
Cavitation microstreaming patterns in single and multiple bubble systems
Authors: Ooi Andrew , Tho Paul , Manasseh Richard
Published: September 2008

Cavitation microstreaming is a well-known phenomenon, yet there are very few flow visualizations or measurements of the velocity fields. In this talk, results from micro-particle image velocimetry measurements and streak photography, illustrating the flow field around a single and multiple oscillating bubbles resting on a solid boundary, will be presented. The different modes of bubble oscillations were also measured in terms of the variation in the radius of the bubble and the movement of the bubbles centroid so that the streaming flow field could be accurately related to the bubble motion. Thus, the resulting flow field can be correlated with the different vibration (volumetric, translating, and orbiting) modes. The flow field resulting from these oscillation modes contains closed streamlines, representing vortical regions in the vicinity of the bubble. Despite some inconsistencies, there is general agreement between these streaming patterns and those found in existing theoretical models. In addition, shape mode oscillations of single bubbles, as well as several different cases of multiple bubbles simultaneously oscillating with the same frequency and phase, were also investigated and show a rich variety of streaming patterns.
Monitoring and simulating stable cavitation during ultrasound-enhanced thrombolysis
Authors: Datta Saurabh , Ammi Azzdine Y. , Coussios Constantin C. , Holland Christy K.
Published: September 2008

The presence of stable cavitation has been shown to be highly correlated with thrombolytic efficacy for recombinant tissue plasminogen activator (rt-PA) mediated thrombolysis. A commercial contrast agent, Definity, was used with 120 kHz pulsed ultrasound to nucleate, promote, and sustain stable cavitation. The effect of stable cavitation on increased penetration of rt-PA into the clots is discussed. Also, the possibility of lowering the rt-PA dose using sustained stable cavitation adjuvant to thrombolytics is presented. To understand the bubble dynamics involved, the bubble response was studied using the Keller-Miksis model and stable and inertial cavitation thresholds were studied as a function of bubble radius. The largest mass loss (26.2%) was observed for clots treated with 120 kHz ultrasound (0.32 MPa peak-to-peak pressure amplitude, 80% duty cycle), rt-PA (96 μg/ml) and stable cavitation nucleated by Definity. A comparable mass loss of 22% was observed at a much lower concentration of 11 μg/ml in the presence of stable cavitation. In addition, the simulation results provide insight into the nuclei sizes relevant for this therapeutic application and possible mechanisms involved.
120 kHz pulsed ultrasound enhanced thrombolysis with tissue plasminogen activator-loaded echogenic liposomes
Authors: Meunier Jason M. , Smith Denise A. B. , Holland Christy K. , Huang Shao-Ling , McPherson David D. , Shaw George J.
Published: September 2008

Echogenic liposomes (ELIP), phospholipid vesicles filled with gas and fluid, can be manufactured to incorporate the thrombolytic drug tissue plasminogen activator (tPA). Real-time thrombolysis of blood clots exposed to tPA-incorporating ELIP (t-ELIP) was monitored using video microscopy with an inverted optical microscope. Human whole blood clots on silk sutures were exposed to tPA alone (3.15 micrograms/ml), t-ELIP alone (3.15 micrograms/ml), t-ELIP and 120 kHz ultrasound (0.18 MPa peak negative pressure, 1.667 kHz pulse repetition frequency, 50% duty cycle), or tPA and ultrasound, for 30 min. The extent of thrombolysis was determined by assessing clot width as a function of time, using a time-lapse microscopic imaging technique. The average percent change in clot width at 30 min for clots treated with t-ELIP alone exceeded tPA alone (22.8% vs. 15.6%, respectively). Thrombolytic efficacy was similar for either tPA or t-ELIP exposed to 120 kHz ultrasound. Thus, the thrombolytic drug could be effectively released by exposure to 120 kHz ultrasound. [This work was supported by The Distinguished Chair for Clinical Research in Emergency Medicine Foundation Award, K02-NS056253, NIH 1RO1 NS047603, and NIH 1R01 HL074002.]
Simulation of diagnostic ultrasound image pulse sequences in cavitation bioeffects research
Authors: Miller Douglas L. , Dou Chunyan , Wiggins Roger C.
Published: September 2008

Research on cavitational bioeffects of diagnostic ultrasound typically involves a diagnostic scanner as the exposure source. However, this can limit the ranges of exposure parameters for experimentation. A single-element laboratory exposure system was used to simulate 1.5 MHz contrast-aided diagnostic ultrasound of rat kidney. Amplitude modulation of pulses (1.7 microsecond duration, 0.43 ms repetition period and 2.3 MPa amplitude) with a Gaussian envelope of 4.6 ms duration reproduced the image pulse sequence (IPS) of 1 s intermittent beam scanning. A 10 microliter/kg/min IV dose of Definity contrast agent was given during 1–5 min exposures. Glomerular capillary hemorrhage was assessed by histology. A fixed beam induced hemorrhage within the exposed area comparable to the diagnostic imager, but the use of 5 exposures at closely spaced positions more faithfully reproduced the effect produced within a scan plane. IPSs consisting of only one or two pulses approximated the effect of the simulated IPS. Use of a 100 ms duration envelope confirmed a previous observation that slow Doppler imaging mitigated the bioeffect. Thus, relatively simple laboratory exposure systems can simulate diagnostic ultrasound scanning in cavitation bioeffects research, allowing exploration of parameter ranges beyond those available on present clinical systems. [Work supported by NIH grant EB00338.]
Effect of leakage in Helmholtz resonators
Authors: Lee Iljae , Selamet Ahmet , Kim H. S. , Huff Norman T.
Published: September 2008

The effect of leakage in Helmholtz resonators has been experimentally and numerically investigated. Transmission loss of a Helmholtz resonator having a gap between the cavity and main duct is measured using an impedance tube setup. The effect of leakage on the transmission loss is examined using different amounts of gap openings. Experimental results are then compared with the predictions from the boundary-element method. The study shows that the leakage increases the resonance frequency substantially and widens the transmission loss. Hence, the leakage needs to be taken into account for accurate predictions of Helmholtz resonators.
Digital reconstruction of sound using array of microspeakers
Authors: Kotsidou Kassiani , Thompson Charles
Published: September 2008

This work examines the digital reconstruction of sound using the method of matched asymptotic expansions. We will study an array of microspeakers and in particular, the role the cut off frequency and the damping ratio have in the successful reconstruction of sound. The transducers are fed by pulses whose duty cycle will be studied and its ramifications will be reported. We will consider how the coupling between the transducers affects the performance of the overall system.
Personal sound system design for mobile phone, monitor, and television set; Feasibility study
Authors: Lee Chan-Hui , Chang Ji-Ho , Park Jin Young , Kim Yang-Hann
Published: September 2008

Having a personal sound system that does not need to use an earphone or any wire connected microphone would have great interest and potential impact on the associated industries. A device that uses nonlinear characteristics of high intensity ultrasonic sound, such as a parametric array, enables us to localize the sound on any position we want. However, it requires a fairly significant amount of power consumption. Therefore, the mobile phone or note book computer system cannot accept this type of device. Instead, we have attempted to use a line array speaker system to localize the sound in our listening zone. It is known that sound pressure or intensity can be well focused in the zone of interest: For example, see [J.-W. Choi, Y.-H. Kim, J. Acoust. Soc. Am. 111 (2002)]. We applied the method to see the possibility to make a good bright zone around the human head or ears. Depending on the size of the zone and array parameters, for example, array size, speaker spacing, frequency characteristics of the speakers, the quality of the bright zone is changed. The quality means the ratio of sound energy between the bright and dark zone, regarded as acoustic contrast, analogous with what we use for an optical device.
A theoretical dissipative analysis of optimized multimodal resonators coupled to room acoustics
Authors: Antunes José , Inácio Octávio , Axisa François , Debut Vincent
Published: September 2008

Helmholtz resonators are often applied for the sound equalization of control rooms in recording studios, through adequate leveling of the low frequency acoustic modal room responses. The number of controlled acoustic modes depends on the central frequency and damping of resonators, as well as on the modal density of the controlled system within the resonator’s frequency range. In a recent paper, we proposed to improve the efficiency of such devices by, instead of using basic Helmholtz resonators, develop shape optimized multimodal resonators in order to cope with a larger number of intrusive room modes. In spite of the promising results thus obtained, further work is needed to demonstrate the feasibility of such an approach. The present paper is a further step in that direction by analyzing the acoustics of the fully coupled room/resonators system including dissapative effects. More specifically, using an acoustical substructure computational approach, we theoretically derive the coupled modes of rooms fitted with several optimized multimode resonators.
Auditory resolution in auditory virtual environments
Authors: Marentakis Georgios , Peters Nils , McAdams Stephen
Published: September 2008

Minimum audible angles (MAA) were estimated for listeners in the sweet spot of four- and eight-loudspeaker arrays in the studio as a function of angle of incidence (0, 60, 90) and source position within the array (on the loudspeaker, midway between or one-third of the way between loudspeakers). Vector-based amplitude panning (VBAP) was used with a 250-ms broadband stimulus. MAAs increased with angle of incidence in direct comparison to real sources. For frontal incidence, MAA was 7.4, 2.9 for the four- and eight-speaker VBAP system (compared to 1 with real sources). A systematic effect of source position within the speaker array was found with MAAs being smallest for sources halfway between the speakers. The experiment was replicated in a concert hall for listeners at eight positions away from the sweet spot for eight- and 16-loudspeaker arrays and for angle of incidence of 0, 45, and 90 relative to a listener in the sweet spot, facing forward. Participants were able to perceive change in accordance to their relative angle to the stimulus. For frontal incidence, MAA at threshold was 3.24 and 2.0 for VBAP for eight and 16 speakers, respectively. The results are investigated using binaural localization models.
Time series analysis of the Kurdish long necked lute, tanbour
Authors: Alghassi Hedayat , Ferdowsi Sohrab , Alghassi Roozbeh , Khademi Babak
Published: September 2008

There are a variety of long necked, plucked string lutes in the East with the universal name tanbour/tanbur. This research concentrates on the three-stringed fretted tanbour of Yarsan Kurds of Gouran, which is the prevailing derivative of ancient tanbour originated from Persia. Contrary to most of Western stringed instruments, the vibration in tanbour is not limited to soundboard, especially at higher frequencies. This fact, along with string tension modulation, creates a nonlinear vibration of the body and neck. Therefore, the single channel sound pickup and linear modeling is not representing tanbour’s complex sound field. Utilizing an array of four microphones, three spreading in front of soundboard and one in back of body, the system transfer function for tanbour’s main plectrum was derived via suitably optimizing a nonlinear-auto-regressive-exogenous model with the envelope of signals extracted from five tanbours with different known body sizes. Besides neck length and body width, length, and depth, the location of bridge is incorporated in the model, since it has a major role in the vibration, quality, and final setup of tanbour. Employing this model and tanbour’s physical sizes, one can estimate the optimal bridge location on the sound board to achieve finest vibration in any tanbour.
Acoustics of the mridangam: Study of a new design of a South Indian drum
Authors: Krishnamurthy Rohan , Hempe Ian K. , Cottingham James P.
Published: September 2008

The acoustical properties of the ancient Carnatic drum, the mridangam, have been studied, including instruments of traditional design as well as instruments with a newly designed mounting method for the drumheads. The mridangam is comprised of three primary parts: The tonal head (valanthalai), the bass head (thoppi), and the central shell (katta), to which the two heads are traditionally fastened by leather rope. The new design is proposed as a convenient and practical way to mount and tune the drumheads. Measurements were made on drums with the drumheads mounted in the traditional way, and then repeated with the heads remounted using the new design. For measurements of the modes and mode frequencies of the drumheads, the modes were excited by a mechanical vibrator and vibration of the drumhead was measured using a laser vibrometer system. The frequencies of the first few modes of the tonal head were found, as expected, to be tuned to be approximately harmonic. Measurements of drumhead vibration and sound spectra were also made when the drumhead was excited by a skilled player using standard strokes. Some effects of coupling between the two drumheads were studied. [Work supported by the Kalamazoo College HHMI Undergraduate Research Program.]
The design of experimental studies of noise impacts on wildlife: Issues and outcomes
Authors: Bowles Ann E. , Hunsaker Donald , Denes Samuel L. , Kull Robert , Dunk Jeffrey R. , Hayward Lisa , Wasser Samuel L.
Published: September 2008

Historically, most studies exposing terrestrial wildlife to anthropogenic noise experimentally have failed to prove biologically-significant impact. These counter-intuitive outcomes have given rise to political debate, fueled by marginal effects or weak trends in some studies that might have proved to be significant with better sampling procedures or controls. A number of recent studies have attempted to address these weaknesses by developing adequate sampling designs and balancing exposures with respect to important environmental factors (e.g., habitat type). Examples include studies of: (1) Effects of low-flying NATO aircraft on Mexican spotted owl territory occupancy and reproduction; (2) effects of U.S. Marine Corps. helicopters on passerine reproductive success; (3) effects of operations on a U.S. Air Force bombing range on small mammal abundance; (4) impact of off-highway vehicles on reproduction of northern goshawks in the Plumas National Forest; and (5) impact of Enduro motorcycle races on northern spotted owl physiology in the Mendocino National Forest. To date, preliminary outcomes of the studies suggest that more sophisticated models of effect should be developed, and additional research should focus on long-term cumulative impact.
Response of gopher tortoises to military training operations: Preliminary data
Authors: Delaney David , Pater Larry , Radzio Tom , Hackler Joseph , Walde Andrew , Hinderliter Matthew
Published: September 2008

The Department of Defense (DOD) needs defensible data to understand how gopher tortoises utilize military lands to address the question of potential military effects on tortoise populations, while also maintaining its ability to continue to train to standard. The objective of the research is to examine if there are differences in tortoise activity and behavior due to variation in military training activity. Automated radio-telemetry equipment is being used to monitor the activity patterns of gopher tortoises on Camp Shelby, MS. The automated radio-telemetry equipment enables one person to monitor the activity of many transmittered tortoises continuously over an extended time, regardless of weather, light level or terrain. Video surveillance and sound recording equipment are also being used to monitor tortoise behavior in proximity to burrows and quantify and characterize potential anthropogenic disturbances within study locations. The goal of this study is to benefit the recovery and management of gopher tortoise populations on DoD and non-DoD lands by providing natural resource managers detailed temporal and spatial data on gopher tortoise activity, behavior, and movement patterns under varying conditions. Funding was provided by the Engineering Research and Development Center. Preliminary examples of field data and database tables will be presented.
Effects of the sounds from an artificial oil production island on bowhead whale calling behavior
Authors: Blackwell Susanna B. , Greene Charles R. , McDonald Trent L. , Nielson Ryan M. , Nations Christopher S. , Richardson W. John , Streever Bill
Published: September 2008

The westward migration of bowhead whales (Balaena mysticetus) was studied during autumn 2001–2004 to examine the effects of sounds from an artificial oil production island (Northstar) on whale calling behavior. Whale calls were recorded by an array of directional autonomous seafloor acoustic recorders (DASARs) located 6.4–21.5 km northeast of Northstar in the Beaufort Sea. Simultaneously, a continuous record of sounds produced by Northstar was obtained ∼450 m north of the island. More than 130,000 bowhead calls were detected, and were classified as to their type, including five types of simple calls and one complex call category. In addition, the directional capability of DASARs allowed triangulation of an estimated whale position for a majority of the calls. The primary objectives of the study were to assess any effects of Northstar sounds and environmental-physical covariates on the duration, midfrequency, frequency range, type of call, and call detection rates. The analyses showed that an increase in transient sounds from Northstar (i.e., boats) resulted in significantly shorter calls. In addition, call detection rates were significantly higher for whales upstream of the array, and the use of complex calls increased significantly as the whales swam westward past Northstar. [Study funded by BP Exploration, Alaska.]
Acoustic to seismic signatures of layered near-surface soil
Authors: Howard Wheeler , Hickey Craig J.
Published: September 2008

The near-surface soil structure, which strongly influences agricultural productivity and soil erosion, is amenable to study by acoustic to seismic techniques. These techniques utilize the coupling between airborne sound and seismic vibrations of the soil to investigate the distribution of soil’s mechanical properties. Two field sites were chosen over which the acoustic to seismic coupling signature of the ground, was measured. A predictive model, assuming acoustic plane waves incident on a vertically stratified ground was developed to predict the acoustic to seismic response. In this presentation, the acoustic to seismic signatures from these sites are compared to model results using the ground truth from seismic refraction and cone penetrometer surveys as input to the model.
The influence of water potential, moisture, and temperature on sound speed and the hysteretic nonlinearity parameter of granular materials
Authors: Lu Zhiqu
Published: September 2008

In the 153rd ASA meeting (Salt Lake City, Utah), the results of a long-term survey of a field soil by using both linear and nonlinear acoustic techniques were reported. The study showed that soil water potential is the predominant factor governing the sound speed and the hysteretic nonlinearity parameter while moisture plays a minor role. It was also found that, unlike sound speed that is insensitive to temperature, the nonlinear parameter shows strong temperature-dependent behavior. The question remains: Is this temperature effect an intrinsic property of the hysteretic nonlinearity parameter, or is it caused by the degradation of the transducers since the measurement has been running for two years? To answer this question, the influence of water potential, moisture, and temperature on sound speed and the hysteretic nonlinearity parameter of granular materials (unconsolidated sands) has been studied in the lab with temperature-controlled conditions.
Varied amplitude nonlinear acoustic method of landmine detection
Authors: Fillinger Laurent , Libbey Brad , Sutin Alexander , Sarvazyan Armen
Published: September 2008

Acoustic methods of land mine detection are being developed for nonmetal mines where conventional electromagnetic methods fail. Nonlinear acoustic methods have shown higher sensitivity than linear methods. In previous studies, the nonlinear methods, based on interaction of two frequency waves and phase inversion of two pulses, were investigated. We propose an alternative nonlinear method based on the use of wide-frequency pulses with different amplitude and subtraction of the normalized received signals. This method evaluates the nonlinear effects in a wide-frequency band similar to the phase inversion method and it detects nonlinear components that are lost in the phase inversion method. In our tests, the suggested method was combined with time reversal acoustic focusing to concentrate seismic wave energy in proximity to the mine, which increased nonlinear effects. Experiments with various types of mines were conducted at Fort Belvoir using six loudspeakers in a box for excitation in the frequency band 50–500 Hz. The nonlinear mine response measured by the varied amplitude method provides the highest mine/no mine contrast among all the experiments performed using linear and nonlinear techniques. [Work was supported by the U.S. Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate.]
Evaluation of parametric acoustic array technology in application to the acoustic landmine and improvised explosive device (IED) detection problems
Authors: Korman Murray S. , Sarkady Antal A. , Sabatier James M.
Published: September 2008

There has been recent interest in using the parametric acoustic array for obtaining highly directional low frequency sources in acoustic landmine and IED detection. Experiments (using a commercial parametric array (0.5 m diam) located 1.5 m directly over the target and driven by a swept sine audio modulated 60 kHz tone) were performed to compare the ‘‘on’’ to ‘‘off’’ target soil surface particle velocity of an inert VS 1.6 (plastic) anti-tank landmine buried 2.5 cm deep in masonry sand in a concrete box located in the anechoic chamber facility. The laser Doppler vibrometer response (normalized to the microphone) was measured from 100–1,100 Hz using a spectrum analyzer. A SPL of 40 dB re 20 μrmPa at 150 Hz was insufficient, where the mine was known to have its largest resonance. Resonances between 300–600 Hz also went undetected, but amplitude contrast ratios of 20 and 3 were measured at 850 and 1,050 Hz, respectively, upon signal averaging. Limitations in carrier SPL, auditory damage, saturation effects, distortion, and low efficiency need to be addressed to achieve the required 60–80 dB SPL needed near 100 Hz. Mines or IEDs buried at 15 cm require more SPL. [Work supported by ARL.]
Seismic excitation using a high power CO2 laser
Authors: Libbey Brad , Krissoff Jamie , Perea James , Newsome Gwen
Published: September 2008

Lasers provide one method of remotely exciting propagating waves in soil. The absorption of optical energy results in plasma formation, a dynamic change near the soil surface, and excitation of propagating waves. Experiments were performed using a high power CO2 pulsed laser to determine the pressure waveforms generated in desert sand and caliche clay. The laser energy ranged from 400–750 J with a pulse duration of 35 μs. The resulting pressure pulse was observed for duration of at least 400 μs and had a peak pressure of 100 kPa. The duration increased at greater depths, while the peak pressure and energy in a pulse decreased rapidly at these depths. Surface velocity reached a peak of 35 mm/s as acquired on geophones placed in proximity to the laser plasma event. This system, in combination with a laser Doppler vibrometer, has the potential to be a useful component of non-invasive mine detection equipment.
Seismic refraction tomography of a small earth dam
Authors: Hickey Craig J. , Duddu Lakshmikanth
Published: September 2008

Over the past 50 years there were nearly 11,000 flood control dams constructed by the United States Department of Agriculture (USDA) nationwide in 2,000 watersheds (USBR, 1987). The failure of these earth dams is associated with erosion, seepage, piping, slope failures, and slides. Precursory evidence for certain failures can be identified by visual inspection; however, others are not so easily detected. Seismic imaging may provide unique and valuable information about the subsurface to assist in the evaluation of the integrity of an earth dam. In this presentation, results from a field study carried out on Drewery Lake Dam in the Upper Yocona River watershed to determine the feasibility of using seismic refraction tomography for imaging earthen dams is discussed. Attributes in the refraction tomograms are correlated with the location of the drainage pipe and the excavated surface given in the as-built plans indicating that seismic refraction tomography does have sensitivity to the internal structure of a dam. This study also suggests that the construction practices for earthen dams result in seismically uniform structures. A uniform background is very advantageous if seismic tomography is to be used to detect zones of internal weakness.
Independence in the perception of complex non-speech sounds
Authors: Silbert Noah , Townsend James , Lentz Jennifer
Published: September 2008

Little, if any, work has explicitly addressed independence in the perception of complex sounds. General recognition theory provides a powerful framework in which to address such issues. Two experiments were carried out to test within-stimulus, between-stimulus, and decision-related notions of independence in each of two stimulus sets. One set consisted of broadband noise stimuli varying in frequency and duration, the other set consisted of harmonic tone complexes varying in fundamental frequency and spectral shape. Model fitting analyses indicate that decision-related independence (decisional separability) holds for all participants with the noise stimuli and the majority of participants with the harmonic stimuli, that within-stimulus independence (perceptual independence) holds for all participants with the noise stimuli and between-stimuli independence (perceptual separability) holds for all but two participants with the noise stimuli, whereas considerable individual differences are exhibited in a variety of failures of either perceptual independence or perceptual separability or, occasionally, both, for participants with the harmonic stimuli. The noise stimulus results are consistent with expectations based on models of frequency and duration encoding, whereas the harmonic stimulus results present a challenge to a number of models of pitch and timbre encoding. [This work was supported by NIH Grant No. T32 MH019879-13.]
Preliminary evaluation of the speech perception assessment and training system (SPATS) with hearing-aid and cochlear-implant users
Authors: Miller James D. , Watson Charles S. , Kistler Doris J. , Wightman Frederic L. , Preminger Jill E.
Published: September 2008

SPATS is evaluated as a testing and training system for hearing-aid (HA) users and cochlear-implant (CI) users. Criterion measures include the HINT, CNC tests, W22 tests, and Coxs CDT, parts of Gatehouses SSQ and a special SPATS inventory. SPATS measures include the identification of syllable constituents (onsets, nuclei, and codas) and measures of top-down and combined top-down and bottom-up recognizing spoken sentences. Control subjects were measured on criterion and SPATS tests, and then retested after a pause of several weeks. Trained subjects took all of the same tests, but in the time between first and second testing underwent either 12 or 24 hours of systematic training using special SPATS algorithms that focus training on items of intermediate difficulty in quiet and noise. Trained subjects show gains on speech-perception measures in quiet and noise, and in look-and-listen tasks, even though there was no training of visual speech perception. Subjects report that SPATS training and testing gave them a much clearer understanding of the severity of their hearing impairments and led to improved speech perception in everyday life through greater attention to detail, and to differences between talkers. [Supported by Grant No. R44DC006338 from NIH/NIDCD.]
The absolute threshold of hearing changes by perceiving a previous sound in the contralateral, ipsilateral, and both ears
Authors: Hasegawa Hiroshi , Yoshida Junji , Kasuga Masao , Watanabe Yu
Published: September 2008

This study investigated the effects of a previous sound on loudness at the absolute threshold of hearing. Change of the absolute threshold of hearing was measured when a pure tone preceded the test tone in the measurement of the threshold. The previous sound at 60 dB SPL was presented first in one ear, and then the test sound was presented in either the contralateral or ipsilateral ear at an interval of 0.5 s. When the previous sound was presented first in both ears, the test sound was presented second in one ear (left or right ear). Both the previous and test sounds had the same frequency of 500 Hz, and the same duration of 3 s. The threshold change was obtained from the difference between the thresholds with and without the previous sound. The threshold was found to be decreased by 3.1 dB when the previous sound was presented in the contralateral ear and increased by 0.9 dB in the ipsilateral ear. On the other hand, the threshold was decreased 2.3 dB when the previous sound was presented in both ears.
Intelligibility differences between male and female bone conducted speech when presented in high noise environments
Authors: McBride Maranda , Hodges Meghan , French Jon
Published: September 2008

Clear and intelligible verbal communication is essential in many organizations. When designing verbal communication devices, developers must not only consider the electrical and mechanical components of the devices themselves, but also various parameters of both the listening environment and vocal signals being transmitted. Bone conduction communication devices have recently been introduced into several tactical organizations; however, the effectiveness of these devices in transmitting vocal signals has not yet been comprehensively explored. This paper describes a study investigating the impact of voice type (male and female), vibrator location (condyle of the jaw and mastoid process), and background noise level (0, 83, 93, and 103 dB(A) SPL) on the intelligibility of bone conducted verbal communication. The fundamental frequencies of the male and female voices were approximately 100 and 185 Hz, respectively. The background noise used in the study was pink noise. Six male and six female students from Embry-Riddle Aeronautical University participated in the study. The results of the study indicate significantly higher speech intelligibility scores for the male voice than for the female voice, and the condyle was significantly more effective than the mastoid in transmitting intelligible speech in each of the high noise environments tested.
Using multichannel communication systems to observe selective and divided attention
Authors: Gripper Misty , Letowski Tomasz , Mermagen Tim
Published: September 2008

The objectives of this study are to compare the effectiveness of bone- and air-conduction radio communication while listening to natural auditory signals through air conduction and to assess the feasibility of using a mixed bone- and air-conduction system for multichannel radio communication. There are many benefits to both air-conducted and bone-conducted systems, but little research on combining the two into one radio system. The goal of the study is to explore this possibility. The SATASK test developed at the U.S. Army Research Laboratory is used to observe human capabilities to distribute attention across multiple channel communication systems. This test consists of sentences structured as follows: NAME write the number NUMBER on the COLOR OBJECT. Five different multichannel communication systems (three three-channel and two four-channel systems) consisting of various combinations of air-conducted earphones, bone-conducted vibrators, and an array of loudspeakers are used for data collection. Each channel presents different sentences in different voices. Listeners are given a target name and they are to record the corresponding information associated with that name (selective attention) or they are to record information from all channels (divided attention). The results of the study will be discussed at the meeting.
Auditory detection of amplitude modulation in psychophysical notched noise task and electroencephalography
Authors: Shim Allison I. , Berg Bruce G. , Srinivasan Ramesh
Published: September 2008

Notched tone-in-noise detection tasks have commonly been utilized to investigate the properties of auditory filters. A similar design is used to study filters for auditory temporal processes; amplitude modulated (AM) noise is used as the signal component rather than tone. The signal is composed of a 200 Hz wide noise-band with a 40 Hz modulation rate and centered at 1,000 Hz. Notched-noise maskers composed of 200 Hz unmodulated noise bands located an equal distance logarithmically on either side of the stimulus create the notch. Psychophysical thresholds were measured using a 2IFC adaptive staircase procedure. A common assumption is that thresholds for signal detection are unaffected until the masker impedes upon the edge of a filter. Data were fit using a leaky integrator model with three forms of the bandpass filter. Results support the existence of wide filters necessary for temporal processing. In an effort to integrate psychophysical and brain imaging methods, a similar study was conducted using electroencephalography. Cortical evoked responses at the gamma frequency (40 Hz) also appear to be affected by narrowing notch widths. [Work supported by the Center for Hearing Research, University of California, Irvine.]
Audio visual interaction in an auditory streaming task involving vowels
Authors: Gaudrain Etienne , Grimault Nicolas , Berthommier Fredric , Healy Eric , Bra Jean-Christophe
Published: September 2008

Previous studies suggest that sequential segregation mechanisms might be primary in concurrent speech segregation tasks for hearing-impaired listeners. Other studies involving speech materials indicate that timbre cues and pitch cues primarily modulate sequential segregation. Finally, concurrent speech segregation has been reported to be enhanced by visual cues associated with speech reading. In this study, sequences of vowels having alternating fundamental frequencies (low and high) were presented to normal-hearing listeners who were asked to report the presentation order of the vowels. Lower performance in such a task has been related to increased sequential segregation. By directing listeners to the perception of a single stream, this task leads to an estimation of the pitch-based obligatory streaming evoked by the sequence. Simultaneous with the presentation of each high-frequency vowel, visual cues simulating lip movements were provided. Lip movements were either steady (control condition), open-closed (rhythm condition), or congruent with each particular vowel (congruent condition). As such, lip movements were used in this study as a potential distracter. The lower performance (increased streaming) in the congruent condition relative to control conditions suggest that visual cues may interact with sequential obligatory streaming mechanisms at a sensory level.
Coupled cross-modal activity in the human auditory and visual cortices
Authors: Winter William
Published: September 2008

From the perspective of systems analysis, the reactions of the brain to a steady state stimulus (steady state evoked fields) represent the brain’s system response. In a linear system, these responses are expected to occur only at the stimulus frequency. However, in a nonlinear system, power can disperse to other frequencies, usually at integer combinations of the stimulus frequencies. By stimulating different components of a nonlinear system at various frequencies, it is possible to evaluate the strength of coupling between components. In this study, steady state auditory and visual stimuli are presented at various frequencies to human subjects to evaluate the nonlinear coupling between the auditory and visual systems. Subjects in whom strong responses are found will be further evaluated with simultaneous electroencephalography/functional magnetic resonance imaging and diffusion tensor imaging to attempt to determine the extent to which the cross-modal activity is due to field versus fiber propagation.