bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite-element simulation of the acoustic guitar
Authors: Derveaux Gregoire P. , Becache Eliane , Joly Patrick , Chaigne Antoine
Published: October 2013

The purpose of this work is a 3-D time-domain numerical modeling of the acoustic guitar. The model involves the transverse displacement of the string excited by a force pulse, the flexural motion of the soundboard, and the sound radiation. A specific spectral method is used for solving the Kirchhoff-Love’s dynamic plate model for a damped, heterogeneous orthotropic material. The airplate interaction is solved with a fictitious domain method, which allows for making a good approximation of the geometry of the instrument while using a regular mesh for the calculation of the 3-D sound radiation. A conservative scheme is used for the time discretization. Frequency analysis is performed on the simulated sound pressure and plate velocity waveforms in order to evaluate quantitatively the transfer of energy through the components of the coupled system. The effects of structural changes in soundboard thickness and cavity volume on the produced sounds are presented. Simulations of the same guitar in three different cases are also performed: ‘‘in vacuo,’’ in air with a perfectly rigid top plate, and in air with an lastic top plate. This allows comparisons between structural, acoustic, and structural acoustic modes of the instrument.
Area oscillations of a bias-flow aperture, with application to phonation
Authors: McGowan Richard S. , Howe Michael S.
Published: October 2013

A thin baffle plate in a mean flow duct partitions the tube into high- and low-pressure regions. The plate spans the whole cross section of the duct and is pierced by a small aperture, through which a nominally steady bias flow is maintained by the mean pressure differential. Sound is generated when the flow is disturbed by imposed, small amplitude cross-sectional area fluctuations of the aperture. For irrotational flow the radiation is determined by the input impedances of the tube on each side of the aperture, and energy flowing into the acoustic field is equal to the work done on the fluid by the suction force at the edge of the aperture. For high Reynolds number flow of a real fluid (modeled by the imposition of a Kutta condition) much of the work goes into the production of vorticity, the unsteady volume flow is greatly reduced, and at low frequencies there can be a substantial oscillating drag force on the plate [M. S. Howe, Proc. R. Soc. London, Ser. A 366, 205–233 (1979)]. The application of these results to phonation indicates that the unsteady drag is most important in the lower harmonics of voice. [Work supported by NIDCD-004688 to UCLA.]
Transient total reflection and transient evanescent wave
Authors: Zhang Hailan
Published: October 2013

The total reflection of a steady plan wave is well known. The transmitted wave is an evanescent wave that propagates along one direction and evanesces along a direction perpendicular to the propagation direction. Evanescent waves also appear in many other acoustic problems, such as the surface wave along a free boundary of a solid medium. In this report, the total reflections with different incident waves are studied, including an incident beam with a limited width, an incident pulse wave with a limited duration, and an incident bulletlike wave package. These incident waves are represented by superposition of plane waves based on the angle spectrum synthesis. Their transmitted wave, therefore, can be synthesized from the transmitted waves of the plane incident wave. Snapshots of the acoustic field are presented that show the procedure of the interaction of the incident wave with the interface of the media. [Work supported by National Natural Science Fundation of China, No. 10534040.]
Metal-polymer-ceramic constrained layer damping system
Authors: Bochkareva Liya , Kireitseu Maksim
Published: October 2013

The focus of this paper is directed toward the investigation into multilayered metal-polymer-ceramic damping coatings and their FEM-based computer modeling that can provide an alternative spacer material in a constrained layer damping configuration so as to enable design of three and more layered damping structures, but with controlled structure and mechanical properties of the gradient damping layers. An advanced measuring system for the analysis of vibrating structures is based on a laser scanning vibration interferometer. The position of a ceramic layer in a constrained layer configuration does matter. The outward position is most favorable for high strength by ceramic layer and damping by constrained aluminum-polymer layer. Modal loss factors obtained in the 60%–80% partial-coverage test cases of cylindrical shell are higher than the maximum modal damping obtained in the case of 100% coverage. The modal damping for the target modes is higher than in the complete-coverage case. An effective damping design involves selecting a proper combination of area coverage, relative thickness and stiffness values of the layers of the damped configuration. [Dr. Bochkareva is currently continuing her research work under 2-year EU INTAS 2005-2007 postdoctoral fellowship Ref. No. 04-83-3067.]
Carbon nanotube-reinforced damping materials: Design and experiments
Authors: Kireitseu Maksim
Published: October 2013

The CNT-reinforced material damping phenomenon is complex because of the variety of energy dissipation/fracture mechanisms involved, the complex nature of the nanoparticles themselves, etc. that affect damping/dynamics. The focus of this paper is directed toward the experimental validation of the next-generation vibration damping materials, providing a road map to experimental calibration and measurement of these materials. Modified modal strain energy method and FEM-based model created in MSC.visualNastran is employed to support an experiment. SWNT-reinforced polymeric matrix composites are prepared using an extrusion procedure. SWNT particles produced by Dynamic Enterprises, UK (2–5 nm in diameter and 70–90 vol% sample purity) are added in concentrations of 3%–6% by weight along with a surfactant (polyoxyethylene) to aid in dispersion. Resonance frequencies, the mode shape, and damping at each mode were determined by laser vibrometry at standard vibration shaker tests and Bruel & Kjaer vibration system. Data acquisition and control of the electro-dynamic system is based on the computer measurement dystem that is highlighted. Resonance frequency is determined from peaks on a frequency response curve for each of the experimental methods. [Work supported by Marie-Curie Fellowship Ref. No. 021298-Multiscale Damping 2006-2008 at University of Sheffield, UK with Prof. G.R. Tomlinson.]
Syllable structure effects on velum-oral coordination evaluated with real-time MRI
Authors: Tobin Stephen , Byrd Dani , Bresch Erik , Narayanan Shrikanth
Published: October 2013

Seminal work by Krakow (PhD. Diss., Yale University, 1989, Phonetics and Phonology 5, 87–116, 1993) has indicated that intrasegmental coordination of articulatory gestures varies systematically as a function of syllable position. Specifically, onset and coda nasals display different lag times between the velum and oral gestural components. In onset nasals, velum lowering is achieved roughly synchronously with oral constriction, while in codas, velum lowering precedes oral constriction. However, Krakow’s study was limited by its reliance on indirect measures of velum movement. Nor did her work examine nasals other than [m] or syllable organizations other than singleton onsets and codas. Our study employs real-time magnetic resonance imaging [Narayanan et al., J. Acoust. Soc. Am. 115, 1771–1776 (2004); Mathiak et al., Int. J. of Lang. & Comm. Disorders 35, 419–425 (2000)] to acquire direct information about the key vocal tract variables of velum aperture and oral constriction, thereby allowing the calculation of relative gestural timing. We investigate the effects of syllabification on interarticulatory timing in [n], and, in addition to examining codas and onsets, further consider juncture geminates spanning word boundaries. Preliminary real-time MRI results from one of three anticipated subjects do find the predicted timing difference for [n]. Further, we find that the relative timing in juncture geminates mirrors that of coda [n] but presents a velum aperture intermediate between coda and onset [n]. [Work supported by NIH.]
Adaptation of speech production to palatal perturbation: Kinematic analysis using electromagnetometry
Authors: Shiller Douglas M. , Tiede Mark K. , Gracco Vincent L.
Published: October 2013

The extent to which adults are able to flexibly adapt their speech production to altered sensory-motor conditions has considerable implications for oral-motor rehabilitation, yet it remains poorly understood. Previous studies have explored the effects of different physical and perceptual perturbations on speech production, yielding mixed results with respect to the timecourse and extent of adaptation. A major limitation of these studies has been their reliance on acoustical measures as the sole index of motor adaptation. The difficulty with such an approach is the potentially complex relationship between acoustic changes and their underlying articulatory patterns. In the present study, speech adaptation to a palatal perturbation (5-mm thickened alveolar ridge) was investigated by directly measuring articulatory kinematics using electromagnetometry. In contrast to previous claims, subjects were found to produce a significant change in speech-related tongue movement immediately upon insertion and removal of the artificial palate. In addition, subjects gradually fine-tuned their tongue position with continued practice. The observed patterns are consistent with the idea of two independent adaptation processes: a rapid adaptation process that is driven by the mere presence of the false palate and a slower adaptation process driven by the continued presence of the palatal perturbation.
Effect of tone on voice onset time in laryngeal and esophageal speech of Mandarin
Authors: Ng Manwa , Liu Hanjun
Published: October 2013

Defined as the time between the release of burst of a stop and the onset of the following vowel, voice onset time (VOT) directly indicates the interarticulator timing between the voicing source and the articulatory movement in the vocal tract. A number of studies have investigated the VOT characteristics of different languages. Yet, few have studied how VOT is affected by tone level in a tone language, and by the type of phonation. The present study investigated the possible effect of tone level and phonation type on such interarticulator timing characteristics. VOT values were measured from the syllables /pha/, /tha/, and /kha/ produced at four Mandarin tone levels by eight laryngeal (NL) and seven esophageal (SE) speakers who were native speakers of Mandarin. Results indicated that significant differences in VOT were found in the NL speaker group, but not in the SE speaker group. With respect to phonation type, SE speakers showed significantly shorter VOT values than NL speakers. Such differences may be related to the use of pharyngoesophageal (PE) segment as a new sound source. SE speakers appear to take a shorter time to start PE segment vibration as compared to NL speakers.
Computational aeroacoustics of flow through static model of human vocal tract
Authors: Suh Jungsoo , Frankel Steven H. , Mongeau Luc , Plesniak Michael W.
Published: October 2013

Computational aeroacoustics studies of flow through the human vocal tract, here modeled as a planar channel with an orifice, hence referred to as the glottis, were conducted using large-eddy simulation (LES). Comparisons were made between LES predictions and experimental wall pressure measurements and particle-imaging-velocimetry flow fields. Rigid models of both converging and diverging glottal passages, each featuring a 20-deg included angle and a minimal glottal width of 0.04 cm with transglottal pressure of 15 cm H2O, were studied. The compressible Navier-Stokes equations were accurately and efficiently integrated for the low Mach number flow through the use of an additive semi-implicit Runge-Kutta method and high-order compact finite-difference schemes for spatial discretization. Characteristic-based nonreflecting boundary conditions were used together with an exit zone in the context of a multiblock approach. Asymmetry of the flow due to a Coanda effect, and transition to turbulence were observed. An acoustic analogy based on the Ffowcs Williams-Hawkings equation was applied to decompose the near-field acoustic source into its monopole, dipole, and quadrupole contributions to assess glottal geometry effects on far-field sound. The results showed that dipole sources due to the unsteady forces exerted on the duct wall are dominant. [Work funded by NIH Grant RO1 DC03577.]
Acoustic and fiberscopic studies of the voice characteristics of school teachers under vocal abuse conditions with the loud voices of children
Authors: Kobayashi Noriko , Masaki Takashi , Nishiyama Koichiro
Published: October 2013

It has been known that the incidence of vocal pathology was high in school teachers as they had to use a great amount of voice and loud phonation in noisy school settings with the children’s loud voices. A proper vocal hygiene program and voice therapy are effective treatments for these cases. The final goal of the treatment should be to obtain the skills to use effective and healthy phonation even in noisy environments. In our study, three school teachers with vocal nodules, three speech therapists who were trained to produce nonconstricted voice even in noisy environments, and ten college students with no laryngeal pathology (control group) spoke eight sentences with one target word in two environments: a quiet environment and one with meaningful multi-talker babble (MMB). Acoustic analyses and fiberscopic examination revealed higher sound pressure and F0 levels and laryngeal constriction in MMB for the teachers before therapy and the normal talkers, but two speech therapists kept similar F0 levels and laryngeal conditions in both environments. After voice therapy, teachers produced less constricted voice under noise. These results suggested the efficacy of voice therapy with MMB for teachers to obtain effective and healthy voice in their noisy work environments.
Cavitation and acoustic streaming in ultrasonic fields: Applications in bio-, leather-, and chemical processing
Authors: Nagarajan R. , Dhanalakshmi N. P. , Krishnan A. , Sivakumar V. , Swaminathan G. , Goodson M.
Published: October 2013

High-frequency, high-intensity ultrasound influences chemical reactions and transport phenomena via two principal mechanisms, acoustic streaming and cavitation. Bubble implosions associated with acoustic cavitation generate very high temperatures (1000s of Kelvin) and pressures (100s of atmospheres) which can accelerate many biochemical reaction rates by several orders of magnitude; acoustic streaming unidirectional high-velocity flow induced by the pressure gradient can substantially enhance heat-, mass-, and momentum fluxes. These aspects of acoustically driven process intensification are investigated here for three different applications: (1) growth characteristics, enzyme production, and ROS (reactive oxygen species) of Bacillus subtilis under varying conditions of ultrasonic frequency (58–192 KHz) and input power (maximum 500 W, variable between 40% to 100%); (2) dynamics of dye uptake by leather under these conditions; and (3) sono-chemical production of a fluorescent product from the reaction of two nonfluorescing species. Experimental data indicate that a combination of cavitation and acoustic streaming, e.g., by using dual-frequency systems that combine a low frequency (e.g., 58 kHz) with a higher frequency (e.g., 192 kHz), is optimal for accelerating processes that involve simultaneous heat-, mass-, and momentum transfer; purely kinetically limited processes, however, are most sensitively affected by cavitation characteristics of the applied field.
Temporal integration functions of AM detection and AM depth discrimination
Authors: Lee Jungmee , Long Glenis , Jeung Changmo
Published: October 2013

Previous studies (Lee, 1994; Lee and Bacon, 1997) suggested that both AM rate and AM depth discrimination were influenced by the number of AM cycles, instead of by the duration of stimulus. AM detection and AM depth discrimination were measured as a function of the number of AM cycles for the modulation rates of 10, 20, 40, 80, 125, 160, and 320 Hz. The carrier was a broadband noise (10 kHz low pass), and the carrier was either gated with the modulator (gated carrier) or presented 250 ms earlier and 250 ms later than the modulator (continuous carrier). The overall level of each presentation was randomized within 6-dB range from 65 dB SPL. For the lower modulation rates (10, 20, 40, and 80 Hz), there was a significant improvement with the continuous carrier at smaller number of cycles (two and four modulation cycles) as compared to the gated carrier condition. For the higher modulation rates (125, 160, and 320 Hz), however, the thresholds were not affected by carrier type. These results suggest that there might be a different temporal integration process for lower and higher modulation rates. [This work was supported by NIDCD Grant No. R03 DC06605-02.]
Overview of signal processing in uncertain and random environments
Authors: Sibul Leon H.
Published: October 2013

This paper is an overview of optimum and/or robust signal-processing approaches for detecting signals in random and uncertain propagation and interference environments, a topic that is intertwined with statistical modeling of the medium and signals. The classical approach to processing of signals that have propagated through randomly fluctuating media is based on the concepts of randomly time-varying impulse responses, spreading functions, and scattering functions. This approach uses second-order statistics and gives insight into performance of active sonar. Implementation of maximum likelihood (ML) detectors for signals that have propagated through random environments requires knowledge of the probability density functions (pdf’s) of the random signal and noise parameters. Random signal parameters that are typically affected by medium randomness are amplitude, phase, and arrival time; pulse and Doppler spread; arrival angle bias and spread. Signal pdf’s can be derived from ocean acoustic models using the maximum entropy (ME) principle, which exploits what is known but is maximally noncommittal of what is uncertain. The ME method can be used to generate densities that belong to the exponential class, and for this class, ML detectors can be implemented as an estimator-correlator and estimator-noise canceler structure. [Work supported by The Undersea Signal Processing Program Office of Naval Research.]
‘‘Passing Landscapes.’’
Authors: Moses James
Published: October 2013

This work was created through experimentation with surround recording and manipulation techniques. A variety of coincident and spaced microphone recording techniques are used to create realistic and immersive recordings of everyday environments. Processing and manipulation are then applied to these recordings to create musical material that plays against the recordings and guides us on a contextualized journey through the landscapes many of us pass though everyday.
Tissue-ultrasound interactions: Absorption to imaging artifacts
Authors: Kremkau Frederick
Published: October 2013

Attenuation determines fundamental limitations in sonography. It directly limits the imaging depth (penetration) and indirectly limits the detail, contrast, and temporal resolutions by limiting the frequency. These resolutions improve with increasing frequency but penetration requirements determine the upper limit on frequency in each imaging situation because attenuation (and therefore penetration) is frequency dependent. Attenuation in soft tissue is dominated by absorption (typically about 90%). Absorption occurs primarily at the molecular level. Sonographic artifacts occur when one of the pulse-echo imaging assumptions is violated. These assumptions are that sound travels in straight lines, that echoes originate only from objects located on the beam axis, that the amplitude of returning echoes is related directly to the reflecting or scattering properties of distant objects, and that the distance to these objects is proportional to the round-trip travel time (13 μs/cm of depth). If scattering strength of an object is high but its absorption is low, a hyperechoic presentation will occur with distal enhancement. A more common occurrence is hyperechoic with distal shadow indicating high echogenicity and attenuation, therefore high absorption. Examples of several imaging artifacts will be shown with discussion of the propagation assumptions violated.
Phased arrays for high-intensity focused ultrasound therapy
Authors: Frizzell Leon A.
Published: October 2013

Several groups have examined the design of ultrasound phased array probes for transrectal treatment of the prostate. An effective design must use the entire aperture of the array and maintain relatively low grating lobe intensities, ideally while minimizing the number of elements and associated phasing circuitry. A new approach to the design of a cylindrical array was developed. The cylindrical aperture of the array was divided into six columns of elements oriented along its length. Because of the symmetry when focus formation and scanning are limited to a plane oriented along the length of the array and perpendicular to it, the six columns are really three column pairs such that each column in a pair has the same phasing applied to its elements. The unique feature of this new design is that a different center-to-center spacing (different widths) for the elements was applied to each column pair. This results in a different location for the grating lobes for each of the three column pairs. This leads to much better performance when looking at grating lobe intensity levels compared to the intensity at the focus. [Work supported by NIH and NCSA.]
Thresholds for sound-induced lung hemorrhage for frequencies from 100 Hz to 1 MHz
Authors: Dalecki Diane , Child Sally Z. , Raeman Carol H.
Published: October 2013

Edwin L. Carstensen has made outstanding and wide-ranging contributions to the field of biomedical ultrasound. His many achievements span the areas of bioeffects of ultrasound, acoustic cavitation, lithotripsy, thermal and mechanical mechanisms, and nonlinear acoustics. In 1990, Carstensen first reported that pulsed ultrasound at diagnostic exposure conditions could produce mammalian lung hemorrhage [Child et al., Ultrasound Med. and Biol. 16, 817–825 (1990)]. Recent work from our lab has quantified the thresholds for murine lung hemorrhage over a range of acoustic frequencies from approximately 100 Hz to 1 MHz. Various exposure systems were used to generate acoustic fields over this broad frequency range in the laboratory. Through several different investigations, we have shown that murine lung responds to low-frequency underwater sound as a resonant structure. The resonance frequency of adult murine lung is approximately 325 Hz, and the pressure threshold for lung hemorrhage is lowest at the resonance frequency. The threshold increases for frequencies above lung resonance. The equation Pth=0.01f0.64, where Pth is the threshold pressure in MPa and f is the acoustic exposure frequency in kHz, approximates our experimental lung threshold data, for long pulse durations, over the 2.5–1000-kHz range.
Experimental and calculated frequencies of the Southeast Asian naw
Authors: Dieckman Eric A. , Cottingham James P.
Published: October 2013

The naw, an Asian free-reed gourd pipe, is constructed of pipes open at both ends with a free reed in the side of each pipe near one end. The pipes of the naw are cylindrical over a significant portion of their length but have a slightly tapered bore near the reed end. The bottom end of the pipe can be covered with the player’s thumb to bend the pitch. Previous research on the khaen, a similar instrument with a cylindrical bore, found that the sounding frequencies of the khaen are well approximated using the simple equation for an open cylindrical pipe. This is not possible for the naw. A method of transmission matrices has been used to calculate the theoretical resonant frequencies of the naw pipes, both open and closed. The calculated values agree well with the resonant frequencies determined experimentally by measuring the input impedance of the pipe. When blown normally, the open pipe sounds near its calculated frequency, while the closed pipe sounds slightly lower than the open pipe frequency. By underblowing the reed, however, the closed pipe can be made to sound near its predicted resonant frequency. [Research supported by NSF REU Grant PHY-0354058.]
Operating room noise at Johns Hopkins Hospital
Authors: Kracht Jonathan , Busch-Vishniac Ilene J. , West James E.
Published: October 2013

Very little reliable information exists on the sound levels present in an operating room environment. In an attempt to remedy this situation, rigorous acoustic testing of the operating rooms in Johns Hopkins Hospital was conducted. Sound levels in each of the operating rooms was recorded for a period of 24 h. The data were analyzed to determine background sound levels, average equivalent sound levels (Leq’s), and frequency distribution. With the assistance of Johns Hopkins Hospital, we were able to match each surgery to the period of noise it produced and to associate sound levels with particular types of surgeries. This data was used to determine the average sound-pressure level for classes of surgery (e.g., orthopedic, neurological, etc.). Averaging over many surgeries, orthopedic surgery was found to have the highest Leq at approximately 66 dB(A). Urology, cardiology, gastrointestinal, and neurosurgery followed closely, ranging from 62 to 65 dB(A).
Sound power emission of a washing-machine cabinet
Authors: Sanchez Beatriz , Llado Juan
Published: October 2013

The noise emitted by a washing machine can be divided into airborne noise produced mainly by the electric motor, and structural-borne noise caused by the cabinet vibration. The aim of this work is to determine the contribution of the structural radiation of the cabinet to the total sound power emitted by a washing machine, and to know which element is the noisiest. The total sound power was measured according to ISO 3744, and in order to know which panel of the cabinet is the noisiest, the standard ISO TR 7849 was applied. This experimental procedure relates the noise radiated by a structure with its vibration velocity, and it was found that the front and lateral left panels were the most relevant. Once the noise transmission paths were characterized, the proposal to reduce noise was focused on reducing the excitation force transmitted by the shock absorbers. As the modification of the force applied by the shock absorber is initially not feasible because it would imply changing the dynamic of the oscillating group, as a first step the panels which support these elements were modified to make them more flexible. A sound power reduction of about 5 dBA was obtained.
Excitation techniques for nonlinear acoustic landmine detection
Authors: Fenneman Douglas , Libbey Brad
Published: October 2013

Nonlinear acoustic landmine detection techniques are currently being investigated. These detection methods employ two tones broadcast in the vicinity of a buried mine. Measurement of the resultant surface velocity yields a spectrum rich in nonlinearly generated combination frequencies. The nonlinear mechanism governing the mine/soil interface is not completely understood. Donskoy et al. have proposed that a discontinuity occurs when the mine/soil system is subjected to acoustic excitation. [Donskay etal, J. Acoust. Soc. Am. 111, 2705–2714 (2002)] In this case, the mine and soil remain in contact during compression, but separate in tension. Concurrently, Korman and Sabatier have documented nonclassical nonlinear effects in conjunction with acoustic mine detection [Korman etal, J. Acoust. Soc. Am. 116, 3354–3369 (2004)]. Specifically, they have observed conditioning, soil dynamics, and hysteresis. These results are consistent with those of geomaterials which exhibit mesoscopic elasticity. It is likely that the nonlinear response above a buried mine is a function of both classical and nonclassical effects. These experiments investigate the amplitude dependence of nonlinear effects above a buried mine as a function of linear velocity. A comparison of the nonlinear amplitude dependence in the presence of a mine versus soil alone is intended to provide insights into the nature of the mine/soil interface.
Scattering of sound by a cylinder above an absorbing boundary
Authors: Li Kai Ming , Lui Wai Keung
Published: October 2013

The problem of acoustic scattering by an impedance infinite cylinder irradiated by a point source is investigated. A theoretical model has been developed to consider the case of the sound scattered by an impedance cylinder above an outdoor ground surface of finite impedance. The formulation is based on the use of the appropriate wave-field expansions, the classical image source method, and the translational addition theorem for cylindrical wave function. The solutions can be expressed in the form of a multiscattering interaction between the cylinder and the image cylinder near a flat boundary. The effect of boundary impedance on the reflected sound fields is incorporated in the numerical model by using the well-known Weyl–van der Pol formula. The numerical results are compared with the published data. The effects of various source and receiver locations around the cylinder above the impedance boundary on the sound field are also studied.
Homogenization of two-dimensional clusters of rigid rods in air
Authors: Torrent Daniel , Håkansson Andreas , Cervera Francisco , Sánchez-Dehesa José
Published: October 2013

The scattering of sound by finite-size clusters consisting of two-dimensional distributions of rigid cylinders in air is studied in the low-frequency limit (homogenization), both theoretically and experimentally. First will be reported analytical expressions for the effective density and sound speed obtained, in the framework of multiple scattering theory, for a circular-shaped cluster. Homogenization is theoretically analyzed as a function of the filling fraction, the type of arrangement of the cylinders in the cluster (hexagonal and square lattice), and the dimension of the cluster. Finally, experiments will be presented for the case of a circular-shaped cluster of 151 wooden cylinders in air. It is demonstrated that, in the long-wavelength limit, this cluster acoustically behaves as a cylinder of argon gas. Moreover, it is shown that homogenization works for frequencies lower than 3 kHz, which corresponds to a wavelength that is four times the parameter of the embedded lattice and is only a quarter of cluster’s diameter.
The error patterns of different nonword repetition tasks in 3-year-old Mandarin-speaking children
Authors: Li Naihsin , Lee Joanna , Fon Janice , Cheung Hintat
Published: October 2013

This study investigates qualitatively and quantitatively 3-year-old Mandarin-speaking children’s error patterns in two nonword repetition tasks which differ in their degrees of wordlikeness, i.e., the nonce word and the gap word sets. Their performances in the two tasks were transcribed and analyzed from two respects: (1) the rate of a specific unit retaining the target structure and (2) the cross comparison between linguistic units and error processes. Results showed that tones and syllable structures of the target forms were easier to retain than the contents. And even though children’s error patterns approximated the adults patterns in gap word repetition task, they had strategic difference in dealing the weight decay in memory: while the children used syllable and rhyme substitutions, the adults used syllable omissions. Our study has implied that children have the same processing mechanism with adults in learning novel words. However, their strategic difference may have an implication for language learning. In addition, the present study also contributes the processing of tone to the linguistically constrained model (Hartley & Houghton, ‘‘A linguistically constrained model of short-term memory for nonwords,’’ J. Mem. Lang. 35, 1–31 1996), so that it can become a more complete model in demonstrating how novel sound sequences are learned and recalled in Mandarin-speaking young children.
Pitch and voice quality in Burmese vowels
Authors: Gruber James F. , Feizollahi Zhaleh
Published: October 2013

Burmese vowels are pronounced with a four-way contrast in laryngeal configuration, described as high, low, creaky, and killed registers [Bradley, Tonation, Pacific Linguistics Series A-62 117–132 (1982)]. However, acoustic descriptions differ as to whether the registers should be defined in terms of pitch or voice quality [Watkins SOAS Working Papers in Linguistics: 10, 139–149 (2000)]. This study investigates whether voice quality or pitch is the more consistent carrier of contrast across the four registers. Four speakers pronounced 20 words (5 vowels ×4 registers) inside a frame sentence surrounded by syllables of low register. Each sentence was repeated five times consecutively. For each syllable, F0 measures were taken at each quartile, as well as peaks and valleys. Voice quality was quantified in terms of spectral slope [Gordon and Ladefoged, J. Phonetics 29, 383–406 (2001)], specifically the difference in dB between the first and second harmonics in an FFT spectrum over a 50-ms window. Results indicate that pitch more reliably indicates register than voice quality. While there was no significant difference in spectral slope between registers, the four registers differed consistently in height and timing of pitch peaks.
Internal and surface wave effects on inverted echo sounder measurements
Authors: Farmer David M. , Duda Timothy F.
Published: October 2013

Inverted echo-sounders operating at 10 kHz, long used to observe mesoscale synoptic variability from the sea-floor through changes in acoustic travel time and pressure, were recently deployed in the South China Sea to explore their potential for detecting nonlinear internal waves. The observations, based on a 6-s transmission rate, reveal both the internal tide and high-frequency nonlinear internal wave packets and are consistent with remotely sensed images and nearby temperature time series. The results motivate exploration of a refinement in instrument operation in which the raw signal is digitized and stored at the full transducer bandwidth, rather than the present scheme of narrow band filtering and threshold detection. If the raw signal is available, it will be related to the surface wave field, leading to the prospect of ocean surface environmental measurements from the sea-floor. An intriguing possibility is that internal wave modulation of the surface wave field, so evident in remotely sensed images, including the consequence of surface wave breaking in convergence zones, might be detectable in this way from the ocean floor, thus linking internal wave observations directly with surface wave modulation. Model calculations of surface scatter are used to gain insight on this approach.
Acoustic impedance of perforations in contact with absorbing material
Authors: Lee Iljae , Selamet Ahmet , Huff Norman
Published: October 2013

Acoustic impedance of perforations in contact with fibrous material is experimentally determined for various hole geometries and filling densities in the absence of mean flow. Two setups are developed to measure the perforation impedance and the acoustic properties of the absorbent, while yielding empirical expressions for both. The experimental results show that both real and imaginary components of the perforation impedance substantially increase as a result of the contact with the fibrous material, whereas they generally decrease with increasing porosity for a given filling density. The empirical expressions developed in this study are implemented in a boundary element method to predict the transmission loss of dissipative silencers, which is then compared with the experimental results.
Visualization of the energy flow for guided waves near the surface of an ensonified fluid-loaded elastic cylindrical shell via the Poynting vector field
Authors: Dean Cleon E. , Braselton James P.
Published: October 2013

The Poynting vector field is used to show the energy flow in the near-surface region of an ensonified fluid-loaded elastic cylindrical shell for both forward and backward propagating waves. The present work uses a method adapted from a simpler technique due to Kaduchak and Marston [Kaduchak & Marston, ‘‘Traveling-wave decomposition of surface displacements associated with scattering by a cylindrical shell: Numerical evaluation displaying guided forward and backward wave properties,’’ J. Acoust. Soc. Am. 98, 3501–3507 (1995)] to isolate unidirectional energy flows.
The effect of concurrent serial digit recall on speech processing in children
Authors: Choi Sangsook , Lewis Dawna , Hoover Brenda , Stelmachowicz Pat
Published: October 2013

Developmental changes in speech perception in a dual task paradigm were investigated in 32 children (7–14 years). Monosyllabic words were presented in noise with or without the concurrent serial recall of visually presented digits (3 or 5). Children were instructed to focus primarily on the listening task, placing secondary effort on digit recall. In both single and dual tasks, word recognition and digit recall improved with age. However, word recognition improved and digit recall decreased in the dual task condition (re: the single task) regardless of age. Greater improvements in word recognition were found for younger children during the dual task in the 3 digit condition. Consequently, the age differences in word recognition observed in the single task diminished during the dual task. Results suggest that the competing digit task might have helped children to optimize attention resulting in improved speech processing. In a follow-up experiment, children will be asked to focus attention on the digit task to determine if the instructions were responsible for observed improvements in word recognition in the first experiment. Results of these studies may have clinical implications for perceptual training methods for children with language delays or hearing loss.
Perception of French stops by French and American English speakers
Authors: Abdelli-Beruh Nassima , Chartan Steve
Published: October 2013

This study examined how native French and native American English speakers perceive edited and unedited word-initial stops produced by two monolingual Parisian speakers. Most words used in this study exist in both languages, yet are produced differently. Listeners were asked to identify the initial stops of French monosyllabic words recorded in isolation. The words were unedited (condition A), edited (condition B), and whispered (condition C). In condition A, words were produced in isolation at modal vocal intensity. In condition B, voicing lead was removed from words beginning with /b, d, g/, and in condition C, words were naturally whispered. Participants were asked to listen to each stimulus and then identify the initial consonant (b, d, g, p, t, k). Statistical analyses show that native French speakers performed significantly better than native American English speakers on identification of the word initial consonant in condition A (unedited words spoken at modal vocal intensity). In condition B (voicing lead removed from words produced at modal vocal intensity), native American English speakers performed significantly better than the native French speakers. Finally, both language groups were equally impaired in condition C (whispered speech). Errors were analyzed as a function of the listener’s language phonetic inventory.
Formant movement and duration in second-language vowel learning
Authors: Iverson Paul , Evans Bronwen G.
Published: October 2013

This study tested native speakers of Norwegian, German, French, and Spanish on their recognition and production of L2 English vowels. A goodness-optimization method was used to construct phonetically detailed perceptual vowel space maps for each listener’s L1 and L2 (English). These maps comprised best exemplar locations in a multidimensional stimulus space that included F1 and F2 target frequencies, F1 and F2 movement, and duration. The maps were then compared to assessments of each individual’s recognition accuracy for naturally spoken English vowels and their degree of accent for spoken English. The results demonstrated that all four language groups used phonetic detail to recognize English vowels; individuals had higher recognition accuracy for natural English vowels when their best exemplars had formant movement and duration contrast that were more like those of L1 English speakers. However, their use of phonetic detail was not entirely predictable by their L1 background. It thus appears that individuals with a range of L1 backgrounds form phonetically detailed category representations during L2 learning, and that their representation of phonetic detail has practical implications for recognizing natural L2 speech.
Training Chinese dialect listeners to perceive English /n/ and /l/
Authors: Li Bin , Wayland Ratree
Published: October 2013

Dialects and Mandarin subdialects in certain areas of southern China do not distinguish between /n/ and /l/. Native speakers of these dialects usually have difficulty distinguishing these two sounds when learning English, even after years of experience with the language. The goal of the present research is to develop a set of procedures that would be effective in training these speakers to learn this non-native speech contrast in English. Forty listeners were recruited from 3 dialect areas (6 Gan, 11 Jianghuai, and 23 Xinan). Listeners were instructed to identify the initial consonant in an English word spoken by 3 native speakers of American English. A pre- and a post-test design were used to assess the effect of a 4-day training. A generalization test containing the same stimuli spoken by 2 new talkers was also carried out on the same day of the post-test. Overall, subjects’ performance improved significantly from the pre-test to the post-test and there was no significant group difference. Additionally, there was no significant difference between their performance of /n/ and /l/ either before or after training. Vowel contexts and syllable structures are also found to have affected listeners’ perception in the post-test.
Amplitude statistics for high-frequency underwater acoustic communications
Authors: Yang Wen-Bin , Yang T. C.
Published: October 2013

Amplitude statistics is one major channel characteristic of a communication system, particularly when an energy detector is used as an incoherent receiver. The amplitude statistics is usually modeled as a Rayleigh or a Rician distribution for an rf channel. From our recent study, the amplitude statistics of high-frequency underwater acoustic communications channel is found to be a K-distribution based on M-sequence data collected during the TREX04 experiment. The TREX04 experiment was conducted in shallow water (∼70-m depth) off the coast of New Jersey. The source and receivers were located about 35 m deep. The M-sequence signal was operated at 17 kHz with a 5-kHz bandwidth. The K-distribution is one of non-Rayleigh family and may be approximated by a combination of a long-term fading and a short-term fading statistics. The long-term and short-term fading statistics are close to a lognormal distribution and a Rayleigh distribution, respectively. [Work supported by the Office of Naval Research.]
A low-complexity fading simulator for underwater acoustic communication channels
Authors: Zheng Y. Rosa
Published: October 2013

Shallow water is an extremely complicated place for communications, and realistic channel models can provide an effective tool for system design. This paper proposes a low-complexity simulator that generates channel impulse responses for broadband frequency-selective acoustic channels. It uses a sum-of-sinusoids (SoS) method to generate Doppler fading impulse responses for wide-sense stationary correlated scattering (WSSCS) Ricean fading channels. The line-of-sight component is obtained by G0(t,τ0)=A0exp[2π(1+ε0)ftcosα0+φ0δ(τ−τ0 ) and the scatterers by Gs(t,τ)=∑n=1NAnexp{j[2πft∑m= 1M(1+εm)cosαm,n+ψnδ(τ−τn), where the random parameters An, αm,n, ψn, and τn are, respectively, the attenuation coefficients, impinging angles, initial phases, and path delays. The Doppler scaling is (1+εm)f, where f is the carrier frequency and εm depends on the speed of sound propagation in water and the velocities of the transmitter, receiver, and wind. Nonuniform probability density functions are selected for impinging angles αm,n to account for the nonisotropic waveguide effect in shallow-water channels. The proposed simulator is a general stochastic model that does not require site-specific information. It only uses 6N+4 random variables and requires O(N) multiplications and additions, where N is on the order of several tens. This low-complexity simulator can be easily implemented by real-time digital signal processors.
Simulations of head-related transfer functions in wideband acoustics
Authors: Seppälä Eira T. , Kirkeby Ole , Kärkkäinen Asta , Kärkkäinen Leo , Huttunen Tomi
Published: October 2013

Head-related transfer functions (HRTFs) have been simulated in three dimensions for a head-and-torso model for the entire audio frequency range, from 20 Hz to 20 kHz. As opposed to data acquired through measurements, the results derived from computer simulations are free from the effects of noise and imperfections in the electro-acoustic chain. In addition, the spatial resolution can easily be made better than in any practical experiment. The simulations have been performed using an ultraweak variational formulation method for solving Helmholtz equation. The numerical method with its parallel computing capability is efficient, enabling numerical calculations of large physical systems, e.g., of size 0.4×0.5×0.8 m, at high frequencies. The method uses plane-wave basis functions instead of polynomial basis as in standard finite-element methods (FEM), resulting in the need of much sparser volume mesh than in FEM. For HRTF calculations, a so-called perfectly matched layer has been utilized and the solutions are derived in the far field. Thus, exterior problems often solved using boundary-element method are dealt with. The specific HRTF simulations have been performed using fully reflecting, sound hard, boundaries on the head and torso, and also with complex impedance boundaries on the torso such as clothing.