bluuebunny/crossref_metadata_2025 huggingface dataset:
A three dimensional investigation into the acoustic performance of dissipative splitter silencers
Authors: Kirby Ray , Williams Paul T. , Hill James
Published: May 2014

Splitter silencers are found in ventilation and gas turbine systems and consist of parallel baffles of porous material placed within a duct so that they split the mean gas flow. Theoretical investigations into dissipative splitter silencers have generally been limited to two dimensions and this limits the analysis to finding the silencer eigenmodes or, for a finite length silencer, to rectangular baffles only. In this article a numerical point collocation approach is used to extend theoretical predictions to three dimensions. This facilitates the analysis of more complex silencer designs such as “bar” silencers and theoretical predictions are validated by comparison with experimental measurements. The insertion loss of different silencer designs is evaluated and the performance of a bar silencer is compared to traditional designs for rectangular and circular ducts. It is shown that a bar silencer with a volume of material identical to an equivalent parallel baffle design delivers a significant improvement in insertion loss at higher frequencies, although this is at the expense of a small reduction in performance at low frequencies. It is also shown that under most circumstances it is possible to get good agreement between prediction and experiment even for relatively large Helmholtz numbers.
Analysis and measurement of the modulation transfer function of harmonic shear wave induced phase encoding imaging
Authors: McAleavey Stephen A.
Published: May 2014

Shear wave induced phase encoding (SWIPE) imaging generates ultrasound backscatter images of tissue-like elastic materials by using traveling shear waves to encode the lateral position of the scatters in the phase of the received echo. In contrast to conventional ultrasound B-scan imaging, SWIPE offers the potential advantages of image formation without beam focusing or steering from a single transducer element, lateral resolution independent of aperture size, and the potential to achieve relatively high lateral resolution with low frequency ultrasound. Here a Fourier series description of the phase modulated echo signal is developed, demonstrating that echo harmonics at multiples of the shear wave frequency reveal target k-space data at identical multiples of the shear wavenumber. Modulation transfer functions of SWIPE imaging systems are calculated for maximum shear wave acceleration and maximum shear constraints, and compared with a conventionally focused aperture. The relative signal-to-noise ratio of the SWIPE method versus a conventionally focused aperture is found through these calculations. Reconstructions of wire targets in a gelatin phantom using 1 and 3.5 MHz ultrasound and a cylindrical shear wave source are presented, generated from the fundamental and second harmonic of the shear wave modulation frequency, demonstrating weak dependence of lateral resolution with ultrasound frequency.
The Jonker-Volgenant algorithm applied to click-train separation
Authors: Baggenstoss Paul M.
Published: May 2014

The problem of click-train separation is cast as a linear assignment problem to obtain a faster solution guaranteed to achieve the global minimum error. It is shown how the problem can be cast in a compact matrix form that is solvable by an off-the-shelf algorithm, the Jonker-Volgenant algorithm.
Acoustic behavior of tuning slots of labial organ pipes
Authors: Rucz Péter , Augusztinovicz Fülöp , Angster Judit , Preukschat Tim , Miklós András
Published: May 2014

The effect of tuning slots on the sound characteristics of labial organ pipes is investigated in this paper by means of laboratory experiments. Besides changing the pitch of the pipe, the tuning slot also plays an important role in forming the timbre. The objectives of this contribution are to document the influence of tuning slots built with different geometries on the pipe sound and to validate the observed tendencies by means of reproducible experiments. It is found that the measured steady state sound spectra show unique characteristics, typical only for tuning slot organ pipes. By separately adjusting the geometrical parameters of the tuning slots on experimental pipes, the impact of each scaling parameter on the steady state spectrum is determined. It is shown that the scaling procedures used currently in organ building practice do not provide sufficient control over the sound characteristics, leaving the capabilities provided by the tuning slot unexploited. Subjective comparison made by organ builders of sound recordings of various setups confirms that the observed sound quality of tuning slot pipes is strongly dependent on the scaling of the slot.
The effect of reverberation on personal audio devices
Authors: Simón-Gálvez Marcos F. , Elliott Stephen J. , Cheer Jordan
Published: May 2014

Personal audio refers to the creation of a listening zone within which a person, or a group of people, hears a given sound program, without being annoyed by other sound programs being reproduced in the same space. Generally, these different sound zones are created by arrays of loudspeakers. Although these devices have the capacity to achieve different sound zones in an anechoic environment, they are ultimately used in normal rooms, which are reverberant environments. At high frequencies, reflections from the room surfaces create a diffuse pressure component which is uniform throughout the room volume and thus decreases the directional characteristics of the device. This paper shows how the reverberant performance of an array can be modeled, knowing the anechoic performance of the radiator and the acoustic characteristics of the room. A formulation is presented whose results are compared to practical measurements in reverberant environments. Due to reflections from the room surfaces, pressure variations are introduced in the transfer responses of the array. This aspect is assessed by means of simulations where random noise is added to create uncertainties, and by performing measurements in a real environment. These results show how the robustness of an array is increased when it is designed for use in a reverberant environment.
Threshold of the precedence effect in noise
Authors: Freyman Richard L. , Griffin Amanda M. , Zurek Patrick M.
Published: May 2014

Three effects that show a temporal asymmetry in the influence of interaural cues were studied through the addition of masking noise: (1) The transient precedence effect—the perceptual dominance of a leading transient over a similar lagging transient; (2) the ongoing precedence effect—lead dominance with lead and lag components that extend in time; and (3) the onset capture effect—determination by an onset transient of the lateral position of an otherwise ambiguous extended trailing sound. These three effects were evoked with noise-burst stimuli and were compared in the presence of masking noise. Using a diotic noise masker, detection thresholds for stimuli with lead/lag interaural delays of 0/500 μs were compared to those with 500/0 μs delays. None of the three effects showed a masking difference between those conditions, suggesting that none of the effects is operative at masked threshold. A task requiring the discrimination between stimuli with 500/0 and 0/500 μs interaural delays was used to determine the threshold for each effect in noise. The results showed similar thresholds in noise (10–13 dB SL) for the transient and ongoing precedence effects, but a much higher threshold (33 dB SL) for onset capture of an ambiguous trailing sound.
The interaction of Rayleigh waves with delaminations in composite laminates
Authors: Chakrapani Sunil Kishore , Dayal Vinay
Published: May 2014

In the present work, the interaction of Rayleigh waves with a delamination in a fiber reinforced composite plate was analyzed. Rayleigh waves, upon interacting with delamination mode, convert into Lamb waves in the delamination zone. These guided Lamb modes have the capability to mode convert back into Rayleigh modes when they interact with the edge of the delamination. A unidirectional glass/epoxy laminate with a delamination of known size was fabricated and tested using air-coupled ultrasonics. Finite element models were developed to understand the mode conversions occurring at various sections of the delamination. Particle displacements along with numerical and experimental velocities were considered to identify each mode. Conclusions were drawn based on the velocity analysis.
Properties of Corprene, revisited
Authors: Tressler James F. , Corsaro Robert D.
Published: May 2014

Corprene has long been used in underwater projectors and receivers as an acoustic isolation material. Based on data initially reported by Higgs and Eriksson for type DC-100 Corprene [J. Acoust. Soc. Am. 46, 1254–1258 (1969)], a simple set of empirical relations is formulated that allow its density, sound speed, and acoustic attenuation to be estimated over a wide range of pressures. Laboratory measurements of the compressibility of recently manufactured material are also reported. One of the primary motivations behind this present study is to accurately determine the compressibility of Corprene. This information is needed to ascertain the variable ballast in a submersible as it goes to depth. This newly reported data, which additionally include measurement of hysteresis, agree with the results published by the aforementioned authors, indicating that this common material has remained unchanged over the past four decades.
Measuring the wavenumber of guided modes in waveguides with linearly varying thickness
Authors: Moreau Ludovic , Minonzio Jean-Gabriel , Talmant Maryline , Laugier Pascal
Published: May 2014

Measuring guided waves in cortical bone arouses a growing interest to assess skeletal status. In most studies, a model of waveguide is proposed to assist in the interpretation of the dispersion curves. In all the reported investigations, the bone is mimicked as a waveguide with a constant thickness, which only approximates the irregular geometry of cortical bone. In this study, guided mode propagation in cortical bone-mimicking wedged plates is investigated with the aim to document the influence on measured dispersion curves of a waveguide of varying thickness and to propose a method to overcome the measurement limitations induced by such thickness variations. The singular value decomposition-based signal processing method, previously introduced for the detection of guided modes in plates of constant thickness, is adapted to the case of waveguides of slowly linearly variable thickness. The modification consists in the compensation at each frequency of the wavenumber variations induced by the local variation in thickness. The modified method, tested on bone-mimicking wedged plates, allows an enhanced and more accurate detection of the wavenumbers. Moreover, the propagation in the directions of increasing and decreasing thickness along the waveguide is investigated.
Pseudo-interface Rayleigh wave on a permeable porous medium/vacuum interface
Authors: Gerasik Vladimir , Stastna Marek
Published: May 2014

It is well known that the Rayleigh wave propagating along a permeable plane boundary of a poroelastic half-space may have a high-frequency cutoff beyond which the corresponding Rayleigh pole is absent. The present study investigates the specific features of the surface wave propagation during transition through this cut-off frequency. Using a set of experimentally determined mechanical parameter values for water-saturated sintered glass beads in the framework of Biot's theory, this theoretical investigation indicates the following. The Rayleigh wave upper cut-off frequency may occur within a physical frequency range over which the characteristic wavelength far exceeds typical pore size. Beyond the cut-off frequency, the Rayleigh pole migrates onto the non-principal, in other words, unphysical, Riemann sheet. As a consequence, during this transition, the Rayleigh wave transforms into a pseudo-interface wave and radiates part of its energy into the interior of the half-space in the form of P2-wave motion.
Analysis of scattering from an acoustic cloak in a moving fluid
Authors: Huang Xun , Zhong Siyang , Stalnov Oksana
Published: May 2014

This work develops a theoretical framework for acoustic cloak scattering analysis in a low speed non-stationary fluid that is simply described as a potential flow. The equivalent sound source induced by the moving fluid local to the cloak is analytically constructed and is then estimated using Born approximation. The far-field scattering can thereafter be obtained using the associated Green's function of the convected wave equation. The results demonstrate that the proposed analytical approach, which might be helpful in the design and evaluation of cloaking systems, effectively elucidates key characteristics of the relevant physics. In addition, it can be seen that, in a moving fluid, the so-called convected cloaking design achieves better cloaking performance than the classical cloaking design.
Three-dimensional coupled mode analysis of internal-wave acoustic ducts
Authors: Shmelev Alexey A. , Lynch James F. , Lin Ying-Tsong , Schmidt Henrik
Published: May 2014

A fully three-dimensional coupled mode approach is used in this paper to describe the physics of low frequency acoustic signals propagating through a train of internal waves at an arbitrary azimuth. A three layer model of the shallow water waveguide is employed for studying the properties of normal modes and their coupled interaction due to the presence of nonlinear internal waves. Using a robust wave number integration technique for Fourier transform computation and a direct global matrix approach, an accurate three-dimensional coupled mode full field solution is obtained for the tonal signal propagation through straight and parallel internal waves. This approach provides accurate results for arbitrary azimuth and includes the effects of backscattering. This enables one to provide an azimuthal analysis of acoustic propagation and separate the effects of mode coupled transparent resonance, horizontal reflection and refraction, the horizontal Lloyd's mirror, horizontal ducting and anti-ducting, and horizontal tunneling and secondary ducting.
Speech recognition against harmonic and inharmonic complexes: Spectral dips and periodicity
Authors: Deroche Mickael L. D. , Culling John F. , Chatterjee Monita , Limb Charles J.
Published: May 2014

Speech recognition in a complex masker usually benefits from masker harmonicity, but there are several factors at work. The present study focused on two of them, glimpsing spectrally in between masker partials and periodicity within individual frequency channels. Using both a theoretical and an experimental approach, it is demonstrated that when inharmonic complexes are generated by jittering partials from their harmonic positions, there are better opportunities for spectral glimpsing in inharmonic than in harmonic maskers, and this difference is enhanced as fundamental frequency (F0) increases. As a result, measurements of masking level difference between the two maskers can be reduced, particularly at higher F0s. Using inharmonic maskers that offer similar glimpsing opportunity to harmonic maskers, it was found that the masking level difference between the two maskers varied little with F0, was influenced by periodicity of the first four partials, and could occur in low-, mid-, or high-frequency regions. Overall, the present results suggested that both spectral glimpsing and periodicity contribute to speech recognition under masking by harmonic complexes, and these effects seem independent from one another.
Enhanced backscattering in water by partially exposed cylinders at free surfaces associated with an acoustic Franz wave
Authors: Eastland Grant C. , Marston Philip L.
Published: May 2014

When a smooth curved object is lowered into water, the initial specular contribution to high frequency backscattering of sound is weak before the specular point on the object becomes illuminated by incident sound. The associated transition in reflection from a metallic cylinder viewed at grazing incidence was previously studied [Baik and Marston, IEEE J. Ocean. Eng. 33, 386–396 (2008)]. The present research involves analogous measurements of backscattering performed using short tone bursts facilitating improved temporal resolution of distinct mechanisms contributing to the backscattering. The measurements reveal the presence of a delayed contribution to the backscattering that evolves in time in a way consistent with a scattering contribution of an acoustic Franz wave. The wave appears to be partially reflected at the free surface after having been excited on the cylinder by the incident acoustic wave. For slightly exposed cylinders viewed at grazing incidence, the Franz wave mechanism dominated the observed backscattering.
A geospatial model of ambient sound pressure levels in the contiguous United States
Authors: Mennitt Daniel , Sherrill Kirk , Fristrup Kurt
Published: May 2014

This paper presents a model that predicts measured sound pressure levels using geospatial features such as topography, climate, hydrology, and anthropogenic activity. The model utilizes random forest, a tree-based machine learning algorithm, which does not incorporate a priori knowledge of source characteristics or propagation mechanics. The response data encompasses 270 000 h of acoustical measurements from 190 sites located in National Parks across the contiguous United States. The explanatory variables were derived from national geospatial data layers and cross validation procedures were used to evaluate model performance and identify variables with predictive power. Using the model, the effects of individual explanatory variables on sound pressure level were isolated and quantified to reveal systematic trends across environmental gradients. Model performance varies by the acoustical metric of interest; the seasonal L50 can be predicted with a median absolute deviation of approximately 3 dB. The primary application for this model is to generalize point measurements to maps expressing spatial variation in ambient sound levels. An example of this mapping capability is presented for Zion National Park and Cedar Breaks National Monument in southwestern Utah.
Dynamic and acoustic response of a clamped rectangular plate in thermal environments: Experiment and numerical simulation
Authors: Geng Qian , Li Huan , Li Yueming
Published: May 2014

Experiments were performed to investigate the vibration and acoustic response characteristics of a clamped rectangular aluminum plate in thermal environments. Modal tests were carried out to study the influence of thermal environment on natural vibration. With the increment of structural temperature, natural frequencies of the plate decrease obviously. Mode shape interchange was observed for the modes with frequencies very close to each other. The thermally induced softening effect has unequal influences on the plate along the two in-plane directions. Numerical methods were also employed to study the experimental phenomena. Calculated results indicated that the initial deflection has a great influence on the natural vibration of the heated plate. Even a slight curvature can reduce the thermally induced softening effect obviously. Dynamic response tests were carried out under acoustic and mechanical excitations, and the measured results indicate that the variation in damping determines the response amplitudes at resonant peaks in the test.
Robust fundamental frequency estimation in sustained vowels: Detailed algorithmic comparisons and information fusion with adaptive Kalman filtering
Authors: Tsanas Athanasios , Zañartu Matías , Little Max A. , Fox Cynthia , Ramig Lorraine O. , Clifford Gari D.
Published: May 2014

There has been consistent interest among speech signal processing researchers in the accurate estimation of the fundamental frequency (F0) of speech signals. This study examines ten F0 estimation algorithms (some well-established and some proposed more recently) to determine which of these algorithms is, on average, better able to estimate F0 in the sustained vowel /a/. Moreover, a robust method for adaptively weighting the estimates of individual F0 estimation algorithms based on quality and performance measures is proposed, using an adaptive Kalman filter (KF) framework. The accuracy of the algorithms is validated using (a) a database of 117 synthetic realistic phonations obtained using a sophisticated physiological model of speech production and (b) a database of 65 recordings of human phonations where the glottal cycles are calculated from electroglottograph signals. On average, the sawtooth waveform inspired pitch estimator and the nearly defect-free algorithms provided the best individual F0 estimates, and the proposed KF approach resulted in a ∼16% improvement in accuracy over the best single F0 estimation algorithm. These findings may be useful in speech signal processing applications where sustained vowels are used to assess vocal quality, when very accurate F0 estimation is required.
Effects of compression and onset/offset asynchronies on the detection of one tone in the presence of another
Authors: Madsen Sara M. K. , Moore Brian C. J.
Published: May 2014

The weaker of two temporally overlapping complex tones can be easier to hear when the tones are asynchronous than when they are synchronous. This study explored how the use of fast and slow five-channel amplitude compression, as might be used in hearing aids, affected the ability to use onset and offset asynchronies to detect one (signal) complex tone when another (masking) complex tone was presented almost simultaneously. A 2:1 compression ratio was used with normal-hearing subjects, and individual compression ratios and gains recommended by the CAM2 hearing aid fitting method were used for hearing-impaired subjects. When the signal started before the masker, there was a benefit of compression for both normal-hearing and hearing-impaired subjects. When the signal finished after the masker, there was a benefit of fast compression for the normal-hearing subjects but no benefit for most of the hearing-impaired subjects, except when the offset asynchrony was relatively large (100 ms). The benefit of compression probably occurred because the compression improved the effective signal-to-masker ratio, hence reducing backward and forward masking. This apparently outweighed potential deleterious effects of distortions in envelope shape and the introduction of partially correlated envelopes of the signal and masker.
Tracking perception of the sounds of English
Authors: Warner Natasha , McQueen James M. , Cutler Anne
Published: May 2014

Twenty American English listeners identified gated fragments of all 2288 possible English within-word and cross-word diphones, providing a total of 538 560 phoneme categorizations. The results show orderly uptake of acoustic information in the signal and provide a view of where information about segments occurs in time. Information locus depends on each speech sound's identity and phonological features. Affricates and diphthongs have highly localized information so that listeners' perceptual accuracy rises during a confined time range. Stops and sonorants have more distributed and gradually appearing information. The identity and phonological features (e.g., vowel vs consonant) of the neighboring segment also influences when acoustic information about a segment is available. Stressed vowels are perceived significantly more accurately than unstressed vowels, but this effect is greater for lax vowels than for tense vowels or diphthongs. The dataset charts the availability of perceptual cues to segment identity across time for the full phoneme repertoire of English in all attested phonetic contexts.
Acoustic characteristics of Greek fricatives
Authors: Nirgianaki Elina
Published: May 2014

The present study examined the acoustics of Greek fricative consonants in terms of temporal, spectral, and amplitude parameters. The effects of voicing, speaker's gender, place of articulation, and post-fricative vowel on the acoustic parameters were also investigated. The results indicated that first and second spectral moments (i.e., spectral mean and spectral variance), as well as second formant (F2) onset, and normalized amplitude values are the acoustic parameters most correlated with the Greek fricative place of articulation distinction. F2 onset and spectral mean were the parameters that distinguished all five places of articulation, while normalized amplitude differentiated sibilants from non-sibilants. In addition, normalized duration and normalized amplitude are the parameters that distinguish Greek voiced from voiceless fricatives, with high classification accuracy.
Comparison of voice relative fundamental frequency estimates derived from an accelerometer signal and low-pass filtered and unprocessed microphone signals
Authors: Lien Yu-An S. , Stepp Cara E.
Published: May 2014

The relative fundamental frequency (RFF) surrounding the production of a voiceless consonant has previously been estimated using unprocessed and low-pass filtered microphone signals, but it can also be estimated using a neck-placed accelerometer signal that is less affected by vocal tract formants. Determining the effects of signal type on RFF will allow for comparisons across studies and aid in establishing a standard protocol with minimal within-speaker variability. Here RFF was estimated in 12 speakers with healthy voices using unprocessed microphone, low-pass filtered microphone, and unprocessed accelerometer signals. Unprocessed microphone and accelerometer signals were recorded simultaneously using a microphone and neck-placed accelerometer. The unprocessed microphone signal was filtered at 350 Hz to construct the low-pass filtered microphone signal. Analyses of variance showed that signal type and the interaction of vocal cycle × signal type had significant effects on both RFF means and standard deviations, but with small effect sizes. The overall RFF trend was preserved regardless of signal type and the intra-speaker variability of RFF was similar among the signal types. Thus, RFF can be estimated using either a microphone or an accelerometer signal in individuals with healthy voices. Future work extending these findings to individuals with disordered voices is warranted.
Experimental evidence for the basal generation place of the short-latency transient-evoked otoacoustic emissions
Authors: Moleti A. , Sisto R. , Lucertini M.
Published: May 2014

Time-frequency analysis of the transient-evoked otoacoustic emission response was performed on a population of subjects affected by sensory-neural hearing loss characterized by a sharp audiometric profile, caused by firearm noise exposure (42 ears), and on a control population of normal-hearing subjects (84 ears). Time-frequency filtering permitted a careful evaluation of the relation between the audiometric profile and the spectral shape of the long- and short-latency otoacoustic components. Both filtered spectra closely follow the shape of the audiometric profile, with a frequency shift between them. The typical frequency shift was evaluated by averaging the otoacoustic spectra and the audiograms among groups of ears with the same cutoff frequency. Assuming that the otoacoustic emission source function depends on the local effectiveness of the cochlear amplifier, this experimental evidence suggests that the short-latency response is generated at a cochlear place displaced towards the base by about 0.5–1 mm with respect to the generation place of the long-latency component. The analysis of the control group demonstrates that, below 4 kHz, the observed effect is not dependent on the data acquisition and analysis procedure. These results confirm previous theoretical estimates and independent experimental evidence based on the measured latency difference between the two components.
Discrimination of foreign language speech contrasts by English monolinguals and French/English bilinguals
Authors: McKelvie-Sebileau Pippa , Davis Chris
Published: May 2014

The primary aim of this study was to determine whether late French/English bilinguals are able to utilize knowledge of bilabial stop contrasts that exist in each of their separate languages to discriminate bilabial stop contrasts from a new language (Thai). Secondary aims were to determine associations between bilabial stop consonant production in the L1 and the L2, between language learning factors and production and discrimination, and to compare English bilinguals' and monolinguals' discrimination. Three Thai bilabial stop consonant pairs differentiated by Voice Onset Time (VOT) (combinations of [b], [p], and [ph]) were presented to 28 French-English bilinguals, 25 English-French bilinguals, and 43 English monolinguals in an AX discrimination task. It was hypothesized that L2 experience would facilitate discrimination of contrasts that were phonemic in the L2 but not in the L1 for bilinguals. Only limited support for this hypothesis was found. However, results indicate that high production proficiency bilinguals had higher discrimination of the phonemic L2 contrasts (non-phonemic in L1). Discrimination patterns indicate lasting L1 influence, with similarity between unknown foreign language contrasts and L1 contrasts influencing discrimination rates. Production results show evidence for L2 influence in the L1. Results are discussed in the context of current speech perception models.
The influence of alcoholic intoxication on the short-time energy function of speech
Authors: Heinrich Christian , Schiel Florian
Published: May 2014

This study investigates rhythmic features based on the short-time energy function of speech signals with the aim of finding robust, speaker-independent features that indicate speaker intoxication. Data from the German Alcohol Language Corpus, which comprises read, spontaneous, and command&control speech uttered by 162 speakers of both genders and various age groups when sober and intoxicated, were analyzed. Energy contours are compared directly (Root Mean Squared Error, statistical correlation, or the Euclidean distance in the spectral space of the contour) and by parameterization of the contour using the Discrete Cosine Transform (DCT) and the first and second moments of the lower DCT spectrum. Contours are also analyzed by Principal Components Analysis aiming at fundamental “eigen contour” changes that might encode intoxication. Energy contours differ significantly with intoxication in terms of distance measures, the second and fourth DCT coefficients, and the first and second moments of the lower DCT spectrum. Principal Components Analysis did not yield interpretable “eigen contours” that could be used in distinguishing intoxicated from sober contours.
Sound energy decay in coupled spaces using a parametric analytical solution of a diffusion equation
Authors: Luizard Paul , Polack Jean-Dominique , Katz Brian F. G.
Published: May 2014

Sound field behavior in performance spaces is a complex phenomenon. Issues regarding coupled spaces present additional concerns due to sound energy exchanges. Coupled volume concert halls have been of increasing interest in recent decades because this architectural principle offers the possibility to modify the hall's acoustical environment in a passive way by modifying the coupling area. Under specific conditions, the use of coupled reverberation chambers can provide non-exponential sound energy decay in the main room, resulting in both high clarity and long reverberation which are antagonistic parameters in a single volume room. Previous studies have proposed various sound energy decay models based on statistical acoustics and diffusion theory. Statistical acoustics assumes a perfectly uniform sound field within a given room whereas measurements show an attenuation of energy with increasing source-receiver distance. While previously proposed models based on diffusion theory use numerical solvers, the present study proposes a heuristic model of sound energy behavior based on an analytical solution of the commonly used diffusion equation and physically justified approximations. This model is validated by means of comparisons to scale model measurements and numerical geometrical acoustics simulations, both applied to the same simple concert hall geometry.
On the modeling of sound transmission through a mixed separation of flexible structure with an aperture
Authors: Yu Xiang , Cheng Li , Guyader Jean-Louis
Published: May 2014

Modeling sound transmission among acoustic media through mixed separations, consisting of both rigid/flexible structures with apertures, is a challenging task. The coexistence of both structural and acoustic transmission paths through the same coupling surface adds system complexities, hampering the use of existing sub-structuring modeling techniques when the system configuration becomes complex. In the present work, a virtual panel treatment is proposed to model thin apertures involved in such complex vibroacoustic systems. The proposed virtual panel considers an aperture as an equivalent structural component, which can be integrated with the solid/flexible structure to form a unified compound interface. This allows handling the entire compound interface as a pure structural element, thus providing an efficient and versatile tool to tackle system complexities when using sub-structuring techniques. The accuracy and convergence of the method are investigated and validated, and the effective thickness range allowing for the virtual panel treatments is determined. The capability and the flexibility of the proposed formulation are demonstrated through several numerical examples, with underlying physics being explored.
Towards a sub 15-dBA optical micromachined microphone
Authors: Kim Donghwan , Hall Neal A.
Published: May 2014

Micromachined microphones with grating-based optical-interferometric readout have been demonstrated previously. These microphones are similar in construction to bottom-inlet capacitive microelectromechanical-system (MEMS) microphones, with the exception that optoelectronic emitters and detectors are placed inside the microphone's front or back cavity. A potential advantage of optical microphones in designing for low noise level is the use of highly-perforated microphone backplates to enable low-damping and low thermal-mechanical noise levels. This work presents an experimental study of a microphone diaphragm and backplate designed for optical readout and low thermal-mechanical noise. The backplate is 1 mm × 1 mm and is fabricated in a 2-μm-thick epitaxial silicon layer of a silicon-on-insulator wafer and contains a diffraction grating with 4-μm pitch etched at the center. The presented system has a measured thermal-mechanical noise level equal to 22.6 dBA. Through measurement of the electrostatic frequency response and measured noise spectra, a device model for the microphone system is verified. The model is in-turn used to identify design paths towards MEMS microphones with sub 15-dBA noise floors.
Multiple scattering in porous media: Comparison with water saturated double porosity media
Authors: Franklin H. , Luppé F. , Conoir J. M.
Published: May 2014

Multiple scattering in a poroelastic medium obeying Biot's theory is studied; the scatterers are parallel identical cylindrical holes pierced at random in the medium. The paper focuses first on the influence, on the effective wavenumbers, of the mode conversions that occur at each scattering event. The effect of the holes on the dispersion curves is then examined for two different values of the ratio of their radius to the pores mean radius. Depending on the latter, the dispersion curves of the pierced material are compared, for the fast and shear waves, with those of either a more porous medium or a double porosity medium.
Comment on “Wave model of the cat tympanic membrane” [J. Acoust. Soc. Am. 122(2), 918–931 (2007)]
Authors: Serwy Roger D.
Published: May 2014

The tympanic membrane model as developed by Parent and Allen [(2007). J. Acoust. Soc. Am. 122(2), 918–931] is shown to have active, lossy, and non-reciprocal properties despite being described as lossless. These properties are traced back to its scattering junction formulations. Some impedance parameters are shown to have ambiguous values which complicate interpreting the physics of the model's internal wave propagation. Certain model parameters omitted from the original paper have been derived from the original computer simulation source code used by Parent and Allen.
Assessment of a hybrid finite element-transfer matrix model for flat structures with homogeneous acoustic treatments
Authors: Alimonti Luca , Atalla Noureddine , Berry Alain , Sgard Franck
Published: May 2014

Modeling complex vibroacoustic systems including poroelastic materials using finite element based methods can be unfeasible for practical applications. For this reason, analytical approaches such as the transfer matrix method are often preferred to obtain a quick estimation of the vibroacoustic parameters. However, the strong assumptions inherent within the transfer matrix method lead to a lack of accuracy in the description of the geometry of the system. As a result, the transfer matrix method is inherently limited to the high frequency range. Nowadays, hybrid substructuring procedures have become quite popular. Indeed, different modeling techniques are typically sought to describe complex vibroacoustic systems over the widest possible frequency range. As a result, the flexibility and accuracy of the finite element method and the efficiency of the transfer matrix method could be coupled in a hybrid technique to obtain a reduction of the computational burden. In this work, a hybrid methodology is proposed. The performances of the method in predicting the vibroacoutic indicators of flat structures with attached homogeneous acoustic treatments are assessed. The results prove that, under certain conditions, the hybrid model allows for a reduction of the computational effort while preserving enough accuracy with respect to the full finite element solution.
Effect of broadband and narrowband contralateral noise on psychophysical tuning curves and otoacoustic emissions
Authors: Wicher Andrzej , Moore Brian C. J.
Published: May 2014

The relative effectiveness of narrowband and broadband noises in activating the efferent system was assessed by comparing the effect of contralateral stimulation (CS) with such sounds on psychophysical tuning curves (PTCs) determined in simultaneous masking, using signal frequencies of 1000 or 2000 Hz. To check that the CS stimuli used did activate the efferent system, distortion product otoacoustic emissions (DPOAEs) were also measured in the absence and presence of narrowband and broadband CS. The CS had no consistent effect on the masker level at the tips of the PTCs. A broadband pink noise CS consistently reduced the masker level required for threshold on both the low- and high-frequency sides of the PTCs for the 2000-Hz signal frequency. However, there were no consistent effects of the CS for any other case. The broadband pink noise CS had a greater effect in reducing DPOAE levels than the narrowband CS. The results provide psychophysical evidence supporting the idea that the efferent system is activated more effectively by a broadband than by a narrowband CS, at least for a signal frequency of 2000 Hz.
Temporal control and compensation for perturbed voicing feedback
Authors: Mitsuya Takashi , MacDonald Ewen N. , Munhall Kevin G.
Published: May 2014

Previous research employing a real-time auditory perturbation paradigm has shown that talkers monitor their own speech attributes such as fundamental frequency, vowel intensity, vowel formants, and fricative noise as part of speech motor control. In the case of vowel formants or fricative noise, what was manipulated is spectral information about the filter function of the vocal tract. However, segments can be contrasted by parameters other than spectral configuration. It is possible that the feedback system monitors phonation timing in the way it does spectral information. This study examined whether talkers exhibit a compensatory behavior when manipulating information about voicing. When talkers received feedback of the cognate of the intended voicing category (saying “tipper” while hearing “dipper” or vice versa), they changed the voice onset time and in some cases the following vowel.
The acoustic properties of panels with rectangular apertures
Authors: Vigran T. E.
Published: May 2014

A model for the acoustic properties of a plate perforated with slots of rectangular shape is proposed. The model is based on known expressions for the complex density and compressibility of a pore of rectangular shape together with the radiation impedance of a rectangular shaped piston in a baffle. For the so-called end correction of a rectangular aperture in a plate, an approximate solution is shown to fit an exact solution for the imaginary part of the radiation impedance, the latter solution based on the work of Lindemann [J. Acoust. Soc. Am, 55, 708–717 (1974)]. Two different procedures are tested to calculate the mutual influence of the apertures on the end correction, the one calculating the mutual impedance of neighboring pistons in the plate, the other by calculating the end correction of a piston placed in the end of an infinitely long tube. The model is used calculating the input impedance and absorption coefficient of a Helmholtz resonator with such a plate, comparing with measurement results. The fit between predicted and measured results, using plates with narrow slits, is good, but it is believed that the model also cover a wider range of dimensions for such a slotted plate.
Racial Tasking and the College Quarterback: Redefining the Stacking Phenomenon
Authors: Bopp Trevor , Sagas Michael
Published: May 2014

The purpose of this study was to ascertain if positional segregation continues at the quarterback position in college football. To determine its existence, we examined differences in run and pass plays executed by African American and White quarterbacks over four different seasons in the NCAA DI-FBS (N = 548). Results revealed significant differences such that African American quarterbacks rushed the ball more and averaged fewer pass attempts than their White counterparts. Likewise, the percentage of rush attempts made by African Americans nearly doubled that of Whites, while White quarterbacks passed the ball 12% more often than their African American counterparts. We argue that these findings support that a new form of discrimination and positional segregation, one we define as racial tasking, may exist.
Effect of Long-Term Starvation on the Survival, Recovery, and Carbon Utilization Profiles of a Bovine Escherichia coli O157:H7 Isolate from New Zealand
Authors: Xavier Ron N. , Morgan Hugh W. , McDonald Ian R. , Withers Helen
Published: May 2014

The ability to maintain a dual lifestyle of colonizing the ruminant gut and surviving in nonhost environments once shed is key to the success of
Escherichia coli
O157:H7 as a zoonotic pathogen. Both physical and biological conditions encountered by the bacteria are likely to change during the transition between host and nonhost environments. In this study, carbon starvation at suboptimal temperatures in nonhost environments was simulated by starving a New Zealand bovine
E. coli
O157:H7 isolate in phosphate-buffered saline at 4 and 15°C for 84 days. Recovery of starved cells on media with different nutrient availabilities was monitored under aerobic and anaerobic conditions. We found that the New Zealand bovine
E. coli
O157:H7 isolate was able to maintain membrane integrity and viability over 84 days and that the level of recovery depended on the nutrient level of the recovery medium as well as the starvation temperature. In addition, a significant difference in carbon utilization was observed between starved and nonstarved cells.
Investigating Microbial Eukaryotic Diversity from a Global Census: Insights from a Comparison of Pyrotag and Full-Length Sequences of 18S rRNA Genes
Authors: Lie Alle A. Y. , Liu Zhenfeng , Hu Sarah K. , Jones Adriane C. , Kim Diane Y. , Countway Peter D. , Amaral-Zettler Linda A. , Cary S. Craig , Sherr Evelyn B. , Sherr Barry F. , Gast Rebecca J. , Caron David A.
Published: May 2014

Next-generation DNA sequencing (NGS) approaches are rapidly surpassing Sanger sequencing for characterizing the diversity of natural microbial communities. Despite this rapid transition, few comparisons exist between Sanger sequences and the generally much shorter reads of NGS. Operational taxonomic units (OTUs) derived from full-length (Sanger sequencing) and pyrotag (454 sequencing of the V9 hypervariable region) sequences of 18S rRNA genes from 10 global samples were analyzed in order to compare the resulting protistan community structures and species richness. Pyrotag OTUs called at 98% sequence similarity yielded numbers of OTUs that were similar overall to those for full-length sequences when the latter were called at 97% similarity. Singleton OTUs strongly influenced estimates of species richness but not the higher-level taxonomic composition of the community. The pyrotag and full-length sequence data sets had slightly different taxonomic compositions of rhizarians, stramenopiles, cryptophytes, and haptophytes, but the two data sets had similarly high compositions of alveolates. Pyrotag-based OTUs were often derived from sequences that mapped to multiple full-length OTUs at 100% similarity. Thus, pyrotags sequenced from a single hypervariable region might not be appropriate for establishing protistan species-level OTUs. However, nonmetric multidimensional scaling plots constructed with the two data sets yielded similar clusters, indicating that beta diversity analysis results were similar for the Sanger and NGS sequences. Short pyrotag sequences can provide holistic assessments of protistan communities, although care must be taken in interpreting the results. The longer reads (>500 bp) that are now becoming available through NGS should provide powerful tools for assessing the diversity of microbial eukaryotic assemblages.
Analysis of Multiple Tsetse Fly Populations in Uganda Reveals Limited Diversity and Species-Specific Gut Microbiota
Authors: Aksoy Emre , Telleria Erich L. , Echodu Richard , Wu Yineng , Okedi Loyce M. , Weiss Brian L. , Aksoy Serap , Caccone Adalgisa
Published: May 2014

The invertebrate microbiome contributes to multiple aspects of host physiology, including nutrient supplementation and immune maturation processes. We identified and compared gut microbial abundance and diversity in natural tsetse flies from Uganda using five genetically distinct populations of
Glossina fuscipes fuscipes
and multiple tsetse species (
Glossina morsitans morsitans
,
G. f. fuscipes
, and
Glossina pallidipes
) that occur in sympatry in one location. We used multiple approaches, including deep sequencing of the V4 hypervariable region of the 16S rRNA gene, 16S rRNA gene clone libraries, and bacterium-specific quantitative PCR (qPCR), to investigate the levels and patterns of gut microbial diversity from a total of 151 individuals. Our results show extremely limited diversity in field flies of different tsetse species. The obligate endosymbiont
Wigglesworthia
dominated all samples (>99%), but we also observed wide prevalence of low-density
Sodalis
(tsetse's commensal endosymbiont) infections (<0.05%). There were also several individuals (22%) with high
Sodalis
density, which also carried coinfections with
Serratia
. Albeit in low density, we noted differences in microbiota composition among the genetically distinct
G. f. fuscipes
flies and between different sympatric species. Interestingly,
Wigglesworthia
density varied in different species (10
4
to 10
6
normalized genomes), with
G. f. fuscipes
having the highest levels. We describe the factors that may be responsible for the reduced diversity of tsetse's gut microbiota compared to those of other insects. Additionally, we discuss the implications of
Wigglesworthia
and
Sodalis
density variations as they relate to trypanosome transmission dynamics and vector competence variations associated with different tsetse species.