bluuebunny/crossref_metadata_2025 huggingface dataset:
Histological analysis of biological tissues using high-frequency ultrasound
Authors: Sorensen Kristina M. , Doyle Timothy E. , Borget Brett D. , Cervantes Monica , Chappell J. A. , Curtis Bradley J. , Grover Matthew A. , Roring Joseph E. , Stiles Janeese E. , Thompson Laurel A.
Published: September 2012

High-frequency (20-80 MHz) ultrasonic measurements have the potential to detect cancer and other pathologies within breast tissues in real time, and thus may assist surgeons in obtaining negative or cancer free margins during lumpectomy. To study this approach, ultrasonic tests were performed on 34 lumpectomy margins and other breast tissue specimens from 17 patients to provide pulse-echo and through-transmission waveforms. Time-domain waveform analysis yielded ultrasonic attenuation, while fast Fourier transforms of the waveforms produced first- and second-order ultrasonic spectra. A multivariate analysis of the parameters derived from these data permitted differentiation of normal, adipose, benign, and malignant breast pathologies. The results provide a strong correlation between tissue microstructure and ultrasonic parameters relative to the morphology and stiffness of microscopic features such as ductules, lobules, and fibrous structures. Ultrasonic testing of bovine heart, liver, and kidney tissues supports this correlation, showing that tissues having stiff fiber-like or filled-duct structures, such as myocardium or ductal carcinomas, display greater peak densities in the ultrasonic spectra than tissues with soft, open duct-like structures, such as kidney tissue or normal breast glands. The sensitivity of high-frequency ultrasound to histopathology may assist in eliminating invasive re-excision for lumpectomy patients. [Work supported by NIH R21CA131798.]
The design and fabrication of a linear array for three-dimensional intravascular ultrasound
Authors: Alles Erwin J. , van Dijk Gerrit J. , van der Steen Antonius , Gisolf Andries , van Dongen Koen
Published: September 2012

Current intravascular ultrasound catheters generate high resolution cross-sectional images of arterial walls. However, the elevational resolution, in the direction of the catheter, is limited, introducing image distortion. To overcome this limitation, we designed and fabricated a linear array which can be rotated to image a three-dimensional volume at each pullback position. The array consists of eight rectangular piezo-electric elements of 350 µm by 100 µm operating at a center frequency of 21 MHz with a fractional bandwidth of 80 %, separated by a kerf of 100 µm. The array has been tested on both an ex vivo bovine artery and phantoms and, using the real aperture of the array, axially densely sampled images of the artery are obtained in every position. The array consistently yields significantly higher resolution in longitudinal images and more detail in radial images compared to a conventional catheter.
Parametric imaging of three-dimensional engineered tissue constructs using high-frequency ultrasound
Authors: Mercado Karla P. , Helguera María , Hocking Denise C. , Dalecki Diane
Published: September 2012

The goal of this study was to use high-frequency ultrasound to nondestructively characterize three-dimensional engineered tissues. We hypothesized that backscatter spectral parameters, such as the integrated backscatter coefficient (IBC), can be used to quantify differences in cell concentration in engineered tissues. We chose the IBC parameter since it estimates the backscattering efficiency of scatterers per unit volume. In this study, acoustic fields were generated using single-element, focused transducers (center frequencies of 30 and 40 MHz) operating over a frequency range of 13 to 47 MHz. Three-dimensional engineered tissue constructs were fabricated with mouse embryonic fibroblasts homogenously embedded within agarose. Constructs with cell concentrations ranging from 1x104 to 1x106 cells/mL were investigated. The IBC was computed from the backscatter spectra, and parametric images of spatial variations in the IBC were generated. Results showed that the IBC increased linearly with cell concentration. Further, we demonstrated that parametric images detected spatial variations in cell concentration within engineered tissue constructs. Thus, this technique can be used to quantify changes in cell concentration within engineered tissues and may be considered as an alternative to histology. Furthermore, because this technique is nondestructive, it can be employed for repeated monitoring of engineered tissues throughout the duration of fabrication.
Analysis of electromechanical parameters of thick rings under radial, axial, and circumferential modes of polarization
Authors: sarangapani Sairajan , Bachand Corey L. , Aronov Boris , Brown David A.
Published: September 2012

Piezoceramic short hollow cylinders and annular disks operating in the extensional mode of vibration are typically used where the thickness is small compared to its lateral dimensions. For a thin ring, strain is along the circumferential direction and the mechanical system is considered as one dimensional. But it is not clear as to what extent a ring can be considered as thin. This study calculates the electromechanical parameters of thick rings under different modes of polarization using the energy method. An analytical formulation is presented and expressions for the internal energies and the electromechanical parameters are derived by analyzing the mechanical system of vibration under different polarization. The resonance frequencies, effective coupling coefficient and correction factors for the various electromechanical parameters under different modes of polarization as a function of thickness along the radial direction are presented.
Free in-plane vibrations of annular sector plates with elastic boundary supports
Authors: Shi Xianjie , Li Wen L. , Shi Dongyan
Published: September 2012

In this investigation, a generalized Fourier series method is proposed for the in-plane vibration analysis of annular sector plates with elastic restraints along each of its edges. The in-plane displacement fields are universally expressed as a new form of trigonometric series expansions with a drastically improved convergence as compared with the conventional Fourier series. The expansion coefficients are considered as the generalized coordinates, and determined using the Rayleigh-Ritz technique. Several examples are presented to demonstrate the effectiveness and reliability of the current method for predicting the modal characteristics of annular sector plates with various cutout ratios and sector angles under different boundary conditions. It is also shown that annular and circle plates can be readily included as the special cases of the annular sector plates when the sector angle is set equal to 360°.
Comparison of the electromechanical properties of bars vibrating in flexure under transverse, longitudinal, and tangential polarization
Authors: sarangapani Sairajan , Aronov Boris , Brown David A.
Published: September 2012

The calculation of electromechanical properties of stripe-electroded bar vibrating in flexure becomes complicated as it involves nonuniform electric field distributions in the poling and operational mode and nonuniform mechanical strain distributions. This study is an extension of the previous work [J. Acoust. Soc. Am. 130, 2394 (2011)] and involves the calculation of the electromechanical parameters of stripe-electroded bars vibrating in flexure. The contributions due to the prominent longitudinal 33 mode, transverse 31 mode and the shear 15 mode are taken into account and the corresponding expressions for the internal energy (electrical energy, electromechanical energy and mechanical energy) are derived under the assumption that the piezoelement is fully polarized. Results of calculations are presented for effective coupling coefficient as a function of various distances between the electrodes and are compared with single-sided stripe-electroded bar design and the traditional bimorph designs using transverse and longitudinal piezoelectric effect.
Capacitive micromachined ultrasound Doppler velocity sensor using a nickel on glass process
Authors: Shin Minchul , Zhao Zhengxin , DeBitetto Paul , White Robert D.
Published: September 2012

The design, fabrication, modeling and characterization of a small (1 cm2 transducer chip) acoustic Doppler velocity measurement system using a capacitive micromachined nickel on glass ultrasound transducer array technology is described. The acoustic measurement system operates in both transmit and receive mode. The device consists of 168 0.6 mm diameter nickel diaphragms, and operates at approximately 180 kHz. Computational predictions suggest that in transmit mode the system will deliver an 11 degree -3dB beamwidth ultrasound. Characterization of the cMUT sensor with a variety of testing procedures including acoustic testing, Laser Doppler Vibrometry (LDV), beampattern test, reflection test, and velocity testing will be shown. LDV measurements demonstrate that the membrane displacement at center point is 0.1 nm/V2 at 180 kHz. During beampattern testing, the measured response was 0.1 mVrms at the main lobe with 90 kHz drive at 20 Vpp (frequency doubling causes the acoustics to be at 180 kHz). The maximum range of the sensor is 1.7 m. Finally, a velocity sled was constructed and used to demonstrate measureable Doppler shifts at velocities from 0.2 m/s to 0.8m/s. Doppler shifts are clearly seen as the velocity changes.
Acoustic filter design for precise measurement of parametric array in near-field region
Authors: Hwang Yonghwan , Je Yub. , Kim Wonho , Seo Heesun , Moon Wonkyu
Published: September 2012

A parametric array is a nonlinear conversion process that generates a narrow beam of low-frequency sound using a small aperture and that is used in active underwater SONAR and communication systems. A parametric array generates a highly directional difference frequency wave (DFW) by nonlinear interaction of bi-frequency primary waves at higher frequencies. However, it is difficult to measure the parametric array effect in the near distance of the transducer, because the high-pressure level of the primary waves may cause the receiving transducer to provide with pseudo-sound signals of difference frequency by its nonlinearity. The pseudo-sound signals make it difficult to measure the real DFW due to the parametric array process. In this study, we confirmed the existence of pseudo-sound and its effects on measurement of the near-distance DFW by the parametric array using numerical simulations based on the KZK equation. Also, a newly designed acoustic filter was proposed to eliminate pseudo-sound signals. This new acoustic filter uses the resonance of a thickness extensional mode. With the acoustic filter, low frequencies (DFW) were passed and high frequencies (primary frequencies) were effectively reduced. Using this acoustic filter, the precise characteristics of the difference frequencies could be measured. [Work supported by ADD(UD100002KD).]
Neville Fletcher: Scientist, teacher, scholar, author, musician, friend
Authors: Rossing Thomas D.
Published: September 2012

Neville has distinguished himself in many ways. He has received many awards from scientific societies in Australia, America, Europe, and Asia. His hundreds of publications, including seven books, deal with physics, meteorology, biology, acoustics, and even poetry. Today we focus on his contributions to acoustics and especially to the Acoustical Society of America and the Australian Acoustical Society, where he is especially remembered for his work in musical acoustics.
Employing numerical techniques in the analysis and design of musical instruments
Authors: Legge Katherine A. , Petrolito Joe
Published: September 2012

In the simplest of terms, a musical instrument consists of a source of oscillation coupled to a resonating body. The exception to this is an idiophone such as a triangle or gong, where the vibrating source is able to be its own radiator of sound. Whatever the configuration, the radiating structure is generally not a simple shape easily represented by a mathematical formulation, and analytical solutions to the governing equations of even a simplified model are often not obtainable. Working with Neville Fletcher in the 1980’s a personal computer was employed to undertake a time-stepping routine through the equations of a simplified model of a kinked metal bar, to depict nonlinear coupling of its modes of vibration. Similar analysis of a gong modelled by a spherical shell with a kinked edge was well beyond the available computing power. In this paper we illustrate how the development of computers and numerical techniques over the intervening thirty years means that we are now able to describe and analyse complex shapes and are encroaching on the domain of the instrument maker through the use of numerical optimisation for instrument design.
Coupling of violin bridge modes to corpus modes analytical model
Authors: Caldersmith Graham
Published: September 2012

The transmission of string vibration forces to the violin belly by the bridge is modulated by two principal bridge resonances around 3KHz and 6 KHz, frequency bands critical to tone perception by the human hearing system. Much music acoustics research has dealt with these bridge modes (and those of the ‘cello and bass) and their influence on the excitation of the corpus modes at the bridge feet. This analytical treatment of the string to corpus transmission by the bridge is necessarily complex, but reveals factors in the process which explain the action of the different strings through the bridge and the levels of corpus mode excitation amplified by the bridge modes. The theoretical predictions are tested against experimental responses with normal bridges and bridges blocked to eliminate the two important modes.
The didjeridu: Relating acoustical properties to players' reports of performance qualities
Authors: Smith John , Rey Guillaume , Wolfe Joe
Published: September 2012

Relating objective acoustical measurements of an instrument, without a player, to the qualities reported by players is often a difficult goal in music acoustics. The didjeridu offers advantages in such a study because it is inherently ‘blind’—neither player nor researcher knows what is inside—and because there are wide variations in objective parameters. Here, seven experienced players reported several qualities and overall quality of 38 traditionally made didjeridus whose acoustic impedance spectra and overall geometry were measured. The rankings for ‘overtones’, ‘vocals’, ‘resonance’, ‘loudness’ and overall quality were all negatively correlated with the characteristic impedance of the instrument, defined as the geometric mean of the first impedance maximum and minimum. ‘Speed’ was correlated positively with the frequency of the lowest frequency impedance peak, near which the instrument plays. Assessments of geometrically simple PVC pipes yielded similar results. The overall ranking was highest for instruments with a low magnitude impedance, particularly in the 1-2 kHz range. This is the range in which players produce a strong formant in the radiated sound by varying vocal tract resonances with comparable ranges of impedance. This study and the researchers were inspired by the pioneering research in music acoustics by Neville Fletcher.
K-12 acoustics experiments
Authors: Hansen Uwe J.
Published: September 2012

Neville Fletcher has been active in many areas of acoustics, including acoustics education. He chaired a committee charged with revamping the science education curriculum in Australia’s elementary and secondary education programs. Neville believes, as do I, in the old maxim: “You hear - you forget, You see - you remember, You do - you understand”. In keeping with that I will discuss a number of basic acoustics experiments adaptable in the elementary and secondary classroom or hands-on laboratory, including speed of sound, musical intervals, the Doppler effect, beats, resonance, spectral analysis and synthesis, musical instruments (violin, clarinet, etc.), the human voice, and sound level.
The evolution of musical instruments
Authors: Fletcher Neville H.
Published: September 2012

The first musical instruments probably arose by chance because of the observed acoustic properties of materials, tools and weapons. Subsequent human generations have then refined their design to produce the broad array of instruments we know today. Percussion instruments based upon simple wooden slats evolved into marimbas, metal shields evolved into gongs and bells, the taut string of a military bow became a guitar and so on, while in the wind-instrument domain the uniform tubes of bamboo or animal leg bones became flutes, organs, or reed instruments. Hydraulic mechanisms, then electrical motors, developed to power instruments such as pipe organs, while the feed-back oscillations of electric amplifiers gave rise to electronic instruments. It is not possible to cover all aspects of this evolution in a short presentation, but some interesting examples, particularly for wind instruments, will be examined in more detail. It will be seen that this evolution is not a terminated process but is still continuing today under influences very much like those of Darwinian natural selection.
Renovation of an elementary school to meet high performance acoustic prerequisites for a special high school: Design predictions and commissioning results
Authors: Pettyjohn Steve
Published: September 2012

The renovation of an elementary school to house the MET high school program was done with a goal of meeting High Performance/Green Building (HP/GB) requirements. Two acoustic prerequisites are a part of the HP requirements. If these two requirements are not met, the project can not meet HP criteria no matter the number of points achieved in other areas. Acoustical consulting was brought in at the 90 percent construction document phase with most designs completed for the mechanical system design, wall design and room finishes. An evaluation of the mechanical system, reverberation time and sound transmission loss showed that modifications would be required. The HVAC systems had been ordered and placement was fixed. A room mock-up was done in the school to show that mechanical noise would exceed the 45 dB(A) limit as designed and installed. Early morning tests done on a modified system showed that meeting the prerequisites for background sound would be very difficult without additional modifications. Wall, door and window modifications were implemented as was some of the acoustical treatment. Final sound commissioning tests proved that all of the prerequisites had been met and the low background sound from all sources was a pleasant surprise.
A soundscape study in an open plan classroom in a primary school
Authors: Shin Sang Bong , Siebein Gary W.
Published: September 2012

Advantages and disadvantages on open plan classrooms have been reported since this type of classroom was first constructed in 1970’s all over the world. A new type of open plan classroom combined with small classrooms that accommodate specific learning activities has been developed as the 21st century learning environment to foster creative, interactive learning. In this study, a new school building which has this type of open plan classroom is examined with soundscape approaches in order to investigate the acoustical environments in the building. Acoustical events occurring in the open plan classroom in a primary school were analyzed and categorized. The activities that created specific acoustical events were observed and categorized and then acoustical taxonomies were established for each space. Acoustical measurements were conducted to examine the acoustical characteristics of each acoustic event and the combinations of acoustical events in the learning spaces. In addition, the results of the observations and measurements were compared to determine the differences in the effects of room conditions on the acoustical events in both traditional and open plan classrooms in the same school. The study found that there are differences in the characteristics of the acoustical events as measured in traditional and open plan according classrooms.
Room acoustic effects on speech comprehension by English-as-a-second-language versus native English-speaking listeners
Authors: Peng Zhao , Wang Lily M. , Lau Siu-Kit K.
Published: September 2012

English-as-a-second-language (ESL) listeners are generally more impaired than native English-speaking listeners on speech intelligibility tasks under reverberation and noise; however, more study is needed to ascertain these groups’ performances on speech comprehension tasks, rather than intelligibility. A recent study (Valente et al, 2012) showed that speech comprehension by both native English-speaking adults and children was more negatively affected by adverse acoustic environments than sentence recognition. The current project investigates the speech comprehension of both ESL and native English-speaking adult listeners under combinations of reverberation and noise. Sets of 15-minute long listening comprehension tests based on the format of the Test of English for International Communication (TOEIC) were developed, anechoically recorded, convolved with binaural room impulse responses (BRIRs) to produce five mid-frequency reverberation times (0.4 to 1.1 seconds), and presented over loudspeakers in the Nebraska acoustics chamber. Background noise was also varied at three levels (RC-30, 40 and 50) through an Armstrong i-Ceiling system. In total then, subjects were individually exposed to 15 acoustic combinations of reverberation and background noise. Preliminary results will be presented and compared between ESL and native English listeners. [Work supported by a UNL Durham School Seed Grant and the Paul S. Veneklasen Research Foundation.]
Comparing performance of classrooms with similar reverberation times but varying absorptive material configurations
Authors: Cottrell James R. , Wang Lily M.
Published: September 2012

The ASA/ANSI Standard on Classroom Acoustics S12.60-2010 suggests that the mid-frequency reverberation times of classrooms be less than 0.6 seconds; however, no details are provided on how to place absorptive materials optimally within the classroom. In this investigation, impulse responses from a database measured at Armstrong World Industries have been analyzed to determine the effect of varying absorptive material configurations on resulting acoustic parameters, including reverberation time, clarity index (C50), and speech transmission index (STI). Two different material configurations were analyzed for each of three mid-frequency-averaged reverberation times: 0.6 sec, 0.8 sec, and 0.9 sec. Results show that metrics significantly differ when the material placement varies dramatically, and that configurations with more evenly distributed absorption produce better conditions for speech intelligibility throughout the classroom. [Work supported by a UNL Undergraduate Creative Activities and Research Experience Grant.]
Infrasound propagation in the atmosphere in a presence of a fine-scale wind velocity structure
Authors: Chunchuzov Igor , Kulichkov Sergey , Popov Oleg , Perepelkin Vitaly , Waxler Roger , Assink Jelle
Published: September 2012

The results of modeling infrasound propagation in the atmosphere from 100-t surface explosion in Israel, and volcano eruptions in Ecuador and Kamchatka are presented. The signal as a function of a range from a source is calculated by parabolic equation method for the vertical profile of wind velocity and temperature obtained from the Ground-to-Space atmospheric model. The effects of fine-scale layered structure of wind velocity and temperature fields on infrasound propagation in the atmosphere have been also taken into account. The one-dimensional (vertical and horizontal) wavenumber spectra of the wind and temperature fluctuations associated with the fine-scale structure are close to the observed spectra in the middle and upper atmosphere. The calculated wave forms, amplitudes and durations of the stratospheric and thermospheric arrivals are compared with those observed in the experiments. It is shown that the scattering of infrasonic signals by anisotropic fluctuations leads to a significant increase in the duration of the stratospheric and thermospheric arrivals in comparison with the case when these fluctuations are absent. The acoustic field scattered from anisotropic nonhomogenerities may be responsible for the arrivals of the acoustic pulses observed in the acoustic shadow zones.
An infrasound calibration system for characterizing the environmental effect on sensor sensitivity and noise floor
Authors: Talmadge Carrick L.
Published: September 2012

An infrasound calibration system has been developed at the National Center for Physical Acoustics. The calibration tank is comprised of a 1" cylindrical shell 40" in diameter, 40" long, with 40" diameter hemispherical end caps. The interior volume of the tank is approximately 1.8 cubic meters. Each hemisphere has a 10" punch-out with sealing gasket that allows either a speaker assembly or an “end cap” to be attached to each end. Normal assess is through an end cap attached to one end, with a speaker assembly attached to the other. The end cap allows rapid switching out of sensors. The speaker assembly consists of a 10" subwoofer with a sealable back volume designed to equalize the static pressure in the interior of the tank to that of the speaker back volume. The subwoofer is able to generate pressures up to 10-Pa in the interior of the chamber, with excellent isolation from external sound. Using 2 subwoofers, by playing a different frequency tone through each speaker and measuring their associated intermodulation distortion in the transduced signal, the linearity of the sensor can be accurately assessed. The measured leak constant of the tank is longer than one week, permitting the characterization the sensor response to ambient pressure to be measured. The large interior volume of the calibration chamber allows the interior be heated or cooled returned slowly to ambient conditions, so that the effects of changing temperature on the sensor can be assessed.
Geomagnetic auroral infrasound wave characteristics and generation
Authors: Oldham Justin J. , Wilson Charles R. , Olson John V. , Nielsen Hans , Szuberla Curt
Published: September 2012

Periods of persistent, high-trace velocity infrasound activity have been routinely observed in the data from the CTBT/IMS I53US infrasound station in Fairbanks, AK. Previous studies of magnetic field disturbances and displays of aurora borealis suggested that these infrasound signals were generated as bow waves by moving auroral electrojets. Recent analysis of the data obtained from the Geophysical Institute Magnetometer Array, the Poker Digital All-Sky Camera, and historic data from the Poker Flat Imaging Riometer have demonstrated the presence of extended periods of infrasound signals during times of enhanced geomagnetic activity along with verification that the observed infrasound is being generated in the lower ionosphere. Further examination of these data sets and the I53US infrasound data provide a basis for comparison with idealized magneto-hydrodynamic models of geomagnetic auroral infrasound wave generation.
Pneumatic infrasound sources
Authors: Muir Thomas , Gorhum Justin , Slack Charles , Barlett Martin , Hawkins Timothy
Published: September 2012

The generation of infrasound from the pulsation of compressed air is examined analytically and experimentally to explore the aerodynamic physics as well as engineering implementations. Several model experiments were developed and utilized to explore the problems associated with this approach. Applications to long range propagation in the atmosphere, including calibration and testing of infrasonic sensor systems are addressed. [Work supported by ARL:UT Austin.]
Application of a blind source separation algorithm for the detection and tracking of tornado-generated infrasound emissions during the severe weather outbreak of 27 April 2011
Authors: Rinehart Hank S. , Clark Chris , Gray Matt , Dillion Kevin
Published: September 2012

April 25-28, 2011 has been identified by many as the most significant and severe single-system outbreak of tornadoes in recorded history. One day in particular, the 27th of April, has been classified by the National Oceanic and Atmospheric Administration (NOAA) as the fourth deadliest tornado outbreak in US history. Severe tornadic activity on this day levied catastrophic damage to life and property across areas of Mississippi, Alabama, Georgia and Tennessee. During this outbreak, multiple Ducommun Miltec-developed infrasound sensors collecting continuous, high resolution data were deployed in two-dimensional array configurations in Northern Alabama. Prior research on the collection and analysis of infrasonic emissions from severe weather phenomenon has provided much insight on the nature of tornado-generated infrasound. Our effort focuses on the application of novel bearing estimation algorithms using closely spaced (4-6 m) array elements. Direction of Arrival (DOA) estimates, derived from Blind Source Separation (BSS) techniques, will be presented for at least two significant tornadoes: the long-track EF5 that impacted Hackleburg and Phil Campbell, AL and the large multi-vortex EF4 that struck Cullman, AL. Correlation of infrasound detection and bearing estimate initiation and termination with NOAA Storm Prediction Center (SPC) Storm Reports will also be reviewed.
Effects of acousto-optic diffraction in the acoustic frequency range on the laser Doppler vibrometry method in air
Authors: Hall Hubert S. , Vignola Joseph F. , Judge John A. , Glean Aldo A. , Ryan Teresa J.
Published: September 2012

The effect of acousto-optic diffraction on the transmitted laser signal light path in the laser Doppler vibrometry (LDV) method has been a known concern to measurement accuracy. To further understand and quantify the LDV accuracy implications, for the in-air case, an experimental study was performed in a high-intensity sound field within the acoustic frequency range (less than 20 kHz). Results of the study showed that acousto-optic diffraction has minimal impact on the accuracy of LDV measurements for the in-air case in sound-fields less than 20 kHz. Follow-on work investigating the effect of measurements in water is proposed. It is hypothesized that the higher refractive index of water will exacerbate the impact of the acousto-optic effect on the accuracy of LDV measurements. Previous work in the field in the megahertz frequency region has shown this. However, within the acoustic frequency range, the accuracy implications remain unknown.
References per coherence length: A figure of merit for multireference acoustical holography
Authors: Wall Alan T. , Gardner Michael D. , Gee Kent L. , Neilsen Tracianne B.
Published: September 2012

Multireference partial field decomposition (PFD) can be used to generate coherent holograms for scan-based near-field acoustical holography measurements. PFD is successful when the reference array completely senses all independent subsources, but meeting this requirement is not straightforward when the number of subsources and their locations are ambiguous (such as in aeroacoustic sources). A figure of merit based on spatial coherence lengths, called references per coherence length (RPLc), is a useful metric to guide inter-reference spacing in the array design so that the source is spanned. Coherence length is defined as the axial distance over which the ordinary coherence drops from unity to some desired value. Numerical experiments involving an extended, partially correlated source show that sufficiency of the reference array for different source conditions may be simply expressed in terms of RPLc. For sources of varying spatial coherence and over a large range of frequencies, one reference per coherence length is equivalent to sensing all independent subsources.
Experimental investigation on reconstruction of sound field based on spherical near-field acoustic holography
Authors: Qiu Xinguo , Li Minzong , Lu Huancai , Jiang Wei
Published: September 2012

This paper presents the results of an experimental study on the methodology of spherical near-field acoustic holography (spherical NAH) to reconstruct interior sound field. The experiment was carried out in a full anechoic chamber, in which the sound filed was generated with different combination of speakers at different positions, a rigid spherical array was used to collect the field acoustic pressures as input to the reconstruction calculation. There are three cases which were investigated. Case 1, a source was set near to the microphone array. Case 2, two sources were eccentrically set opposite to each other around the microphone array. And Case 3, two sources were placed on one side of microphone array on the same orbit, while they were positioned apart at a small angle. The accuracy of the reconstruction of sound field was examined and analyzed compared to the benchmarks and the results of the numerical simulations. The reconstructed results show that the methodology of Spherical NAH is capable to locate sources and reconstruct sound field within certain accuracy.
Confusability of Bengali consonants and its relation to phonological dissimilarity
Authors: Khan Sameer ud Dowla
Published: September 2012

Language-specific consonant similarity can be measured indirectly by looking at the phoneme inventory, the lexicon (e.g. cooccurrence restrictions), or the phonology (e.g. processes that take the notion of similarity of dissimilarity into account). A more direct approach involves the use of the confusion matrix. For Bengali, thus far, consonant similarity has only been measured indirectly, through the lexicon and phonology. Previous studies (Khan 2006, 2012) claim that Bengali speakers judge the similarity of consonants in echo reduplication (similar to English doctor-schmoctor), where the initial consonant of the base is systematically replaced with a phonologically dissimilar consonant in the reduplicant. This measurement of similarity assumes a set of features assigned language-specific weights; for example, [voice] is weighted more heavily that [spread glottis], to explain why speakers treat the pair [t, th] as more similar than the pair [t, d]. But does the measurement of similarity inherent in the echo reduplicative construction correspond to the relative perceptibility of different consonant contrasts? The current study compares the relative confusability of Bengali consonants produced in noise with the claims of phonological notions of similarity associated with echo reduplication.
Effects of age, hearing loss, and phonological neighborhood density on children's perceptual confusions
Authors: Vandam Mark , Silbert Noah H. , Moeller Mary Pat
Published: September 2012

Age, hearing loss, and phonological neighborhood density have been shown to substantially affect the accuracy of productions in a word imitation task [VanDam, et al., 161st ASA Meeting]. Older children (7 years of age) are more accurate than younger children (4 years of age), normal hearing children are more accurate than children with mild- to severe hearing loss, and words from sparse phonological neighborhoods are produced more accurately than are words from dense neighborhoods. In an ongoing series of analyses, we extend these findings by analyzing how patterns of perceptual confusion vary as a function of age, hearing status (normal hearing versus hearing loss), and phonological neighborhood structure. Multilevel cognitive models fit to confusion data provide detailed quantitative descriptions of perceptual space and response bias and enable analysis of between- and within-group variability. Results shed light on the organization of the lexicon in young children with both normal hearing and hearing loss, and add to our understanding of the relationship between speech production and speech perception in children.
Phonological neighborhood clustering coefficient influences word learning
Authors: Goldstein Rutherford , Vitevitch Michael S.
Published: September 2012

Network science is one approach used to analyze complex systems, and has been applied to a complex cognitive system, namely the phonological lexicon (Vitevitch, 2008). One of the measures provided by network science, termed the clustering coefficient or C, influences lexical processes such as speech production (Chan & Vitevitch, 2010) and speech perception (Chan & Vitevitch, 2009). The current study presents evidence of C influencing the process of learning new words. Participants were trained and tested on nonword-nonobject pairs over three lab sessions at one week intervals. Testing occurred immediately after training and after a one week interval. Participants were tested on a picture naming task, a two-alternative-forced-choice task, and a lexical decision task. Results show an advantage for learning new words with a high clustering coefficient. A spreading activation account is used to explain the findings.
Optimized speech sound category training bootstraps foreign word learning
Authors: Yi Han-Gyol , Chandrasekaran Bharath , Maddox W. Todd
Published: September 2012

The COmpetition between Verbal and Implicit Systems (COVIS) model posits multiple cognitive learning systems that are functionally distinct and compete with each other throughout learning. COVIS indicates two cognitive systems: a hypothesis-testing system mediated predominantly by the frontal cortex and a procedural-based system mediated by the striatum. Initial learning is dominated by the hypothesis-testing system, but with increased practice, control is passed to the procedural system. Importantly, each learning system can be optimized differentially to maximize performance. In this study, the COVIS model was applied to optimize Mandarin tone learning by adult native English speakers. The optimized category training (OCT) was designed to boost the hypothesis-testing system initially, then the procedural-based system subsequently. We then examined the extent to which OCT enhanced performance in a word learning task which required the participants to use their attained categories for Mandarin tones to disambiguate words. OCT was found to significantly enhance word learning relative to a control condition in which the learning systems were not optimized. These results demonstrate that a multiple systems approach can be used to develop optimized training protocols to maximally boost category learning.
The young and the meaningless: Novel-word learning without meaning or sleep
Authors: Kapnoula Efthymia C. , Packard Stephanie , Apfelbaum Keith S. , McMurray Bob , Gupta Prahlad
Published: September 2012

Existing work suggests that sleep-based consolidation (Gaskell & Dumay, 2003) is required for newly learned words to interact with other words and phonology. Some studies report that meaning may also be needed (Leach and Samuel, 2007), making it unclear whether meaningful representations are required for such interactions. We addressed these issues by examining lexical competition between novel and known words during online word recognition. After a brief training on novel word-forms (without referents), we evaluated whether the newly learned items could compete with known words. During testing, participants heard word stimuli that were made by cross-splicing novel with known word-forms (NEP+NET=NEpT) and the activation of the target-word was quantified using the visual world paradigm. Results showed that the freshly learned word-forms engaged in competition with known words with only 15 minutes of training. These results are important for two reasons: First, lexical integration is initiated very early in learning and does not require associations with semantic representations or sleep-based consolidation. Second, given studies showing that lexical competition plays a critical role in resolving acoustic ambiguity (McMurray, Tanenhaus & Aslin, 2008; McMurray et al, 2009), our results imply that this competition does not have to be between semantically integrated lexical units.
Recognition memory in noise for speech of varying intelligibility
Authors: Gilbert Rachael C. , Chandrasekaran Bharath , Smiljanic Rajka
Published: September 2012

Speech intelligibility is greatly affected by the presence of noise. However, there has been little research investigating the effects of noise on recognition memory. Per the effortfulness hypothesis (McCoy et al., 2005), we expect that processing speech in challenging listening environments requires additional processing resources that might otherwise be available for encoding speech in memory. This resource reallocation may be offset by speaker adaptations to the environment and to the listener. Here we compare recognition memory for conversational and clear speech sentences recorded in quiet (QS) and for sentences produced in response to the actual environment noise, i.e. noise adapted speech (NAS). Listeners heard 40 unique conversational and clear QS or NAS sentences mixed with 6-talker babble at SNRs of 0 or +3 dB. Following the exposure, listeners identified 80 sentences in quiet as old or new. Results showed that 1) increased intelligibility through conversational-to-clear speech modifications leads to improved recognition memory and 2) NAS presents a more naturalistic speech adaptation than QS, leading to better sentence recall for listeners. This experiment suggests that acoustic-phonetic modifications implemented in listener-oriented speech lead to improved speech recognition in challenging listening conditions and, crucially, to a substantial enhancement in recognition memory for sentences.
The intelligibility of clear and conversational allophones of coda consonants
Authors: Makashay Matthew J. , Solomon Nancy P. , Summers Van
Published: September 2012

For many hearing-impaired (HI) listeners, hearing-aid amplification provides near-normal speech recognition in quiet. Nonetheless, many of these same listeners show large speech deficits, relative to normal-hearing (NH) listeners, that are not effectively addressed via amplification in noisy listening conditions. One compensating strategy HI listeners use is to ask talkers to speak clearly. However, as one of the features of clear speech is a shift to higher frequencies, HI listeners may not benefit as much as NH listeners if the new frequencies are outside their audible range. This study examined the intelligibility of conversationally- and clearly-spoken coda consonants in nonsense syllables. These free-variant allophones of 21 American English consonants were produced in three phonological environments: syllable (utterance) final; syllable final followed by schwa; and syllable final followed by palatal approximant and schwa. The stimuli were presented in broadband noise and in quiet to NH and HI listeners. Consonant confusions were investigated to determine whether NH and HI listeners receive similar clear-speech advantages. [The views expressed in this abstract are those of the authors and do not necessarily reflect the official policy or position of the Departments of the Navy, Army, or Air Force, the Department of Defense, or the US Government.]
Variability in speech understanding in noise by listeners with hearing loss
Authors: Nelson Peggy B. , Nie Yingjiu , Svec Adam , Koerner Tess , Katare Bhagyashree , Gregan Melanie
Published: September 2012

Listeners with sensorineural hearing loss (SNHL) report significant difficulties when listening to speech in the presence of background noise and are highly variable in their tolerance to such noise. In our studies of speech perception, audibility predicts understanding of speech in quiet for most young listeners with SNHL. In background noise, however, the speech recognition performance of some young listeners with SNHL deviates significantly from audibility predictions. We hypothesize that vulnerability to background noise may be related to listeners’ broader auditory filters, to a loss of discrimination ability for rapid spectral changes, or to a disruption of the speech temporal envelopes by the addition of noise. Measures of spectral resolution, spectral change detection, and envelope confusion will be presented for listeners with SNHL. Relationships between those estimates and speech recognition in noise will be described. Results may suggest a range of custom strategies for improving tolerance for background noise. Work supported by NIDCD R018306 to the first author.
Relationships among word familiarity, volume unit level, root-mean-square power, and word difficulty
Authors: Goshorn Edward L.
Published: September 2012

Due to time constraints, 10-25 item NU-6 word lists that are rank-ordered by word difficulty (W-D) are often used for audiological speech intelligibility testing rather than full 50-item lists (Hurley and Sell, 2003). The factors contributing to W-D are not well delineated. Although word familiarity is well established as an important contributor to W-D (Savin, 1963), the contributions of acoustical factors such as peak VU level (VU) and root-mean-square (RMS) power are less known. A better understanding of relationships among factors associated with W-D may prove useful in compiling word lists. This study investigated the relationships among word familiarity, VU, RMS power, and W-D for four 50-item NU-6 word lists. VU and RMS measures for each word were obtained with SoundForge. The standard frequency index (SFI) provided a measure of word familiarity (Carroll et al, 1971). An unexpected positive significant (p<.05) correlation was found between W-D and VU level for one list and weak positive correlations for three lists. Positive correlations are in the opposite direction hypothesized for this variable. No significant correlations were found between W-D and RMS power. Significant negative correlations were found between W-D and SFI for three NU-6 lists. Expected and unexpected findings will be addressed.
Modeling talker intelligibility variation in a dialect-controlled corpus
Authors: McCloy Daniel , Wright Richard , McGrath August
Published: September 2012

In a newly created corpus of 3600 read sentences (20 talkers x 180 sentences), considerable variability in talker intelligibility has been found. This variability occurs despite rigorous attempts to ensure uniformity, including strict dialectal criteria in subject selection, speech style guidance with feedback during recording, and head-mounted microphones to ensure consistent signal-to-noise ratio. Nonetheless, we observe dramatic differences in talker intelligibility when the sentences are presented to dialect-matched listeners in noise. We fit a series of linear mixed-effects models using several acoustic characteristics as fixed-effect predictors, with random effects terms controlling for both talker & listener variability. Results indicate that between-talker variability is captured by speech rate, vowel space expansion, and phonemic crowding. These three dimensions account for virtually all of the talker-related variance, obviating the need for a random effect for talker in the model. Vowel space expansion is found to be best captured by polygonal area (contra Bradlow et al 1996), and phonemic overlap is best captured by repulsive force (cf. Liljencrants & Lindblom 1972, Wright 2004). Results are discussed in relation to prior studies of intelligibility.