bluuebunny/crossref_metadata_2025 huggingface dataset:
Using pronunciation data to study word recognition
Authors: Pitt Mark A. , Johnson Keith
Published: October 2013

Many of the mysteries of spoken word recognition have evolved out of the observation that pronunciation is highly variable yet perception is amazingly stable. Extreme forms of variation can even result in different phonetic percepts, such as consonant assimilation (e.g., ‘‘green ball:’’ ‘‘greem ball’’) and deletion (e.g., ‘‘and:’’ ‘‘an’’), yet listeners still perceive the intended word. The results from two lines of work will be presented in which we are studying the regularity of these production phenomena to evaluate models of how phonological variants are recognized. In one project we examined variation itself. Phonological and acoustic analyses of phonological variation in the Buckeye corpus of conversational speech were carried out in which we asked questions such as the following: How predictable and consistent is regressive assimilation? and How acoustically similar is the assimilated segment to an intended production of that same segment? In a related project, we examined the listener’s sensitivity to the variation found in conversational speech. Results reveal the complexities of these production phenomena, the challenges models must overcome to account for how variants are recognized, and listeners’ sensitivity to stochastic properties of pronunication variation. [Work supported by NIDCD.]
Material discrimination using bispectral signatures
Authors: Nyffenegger Paul A. , Hinich Melvin J.
Published: October 2013

A method is presented for material discrimination and characterization using bispectral signatures acquired from an object actively probed with acoustic pulses. Although bispectral techniques have proven useful in a diverse array of fields including passive acoustic ranging, bispectral processing in active acoustic applications has not been widely explored. The mechanisms responsible for the bispectral signatures revealed using active acoustics have not been well studied and little is known about the relative contributions to the bispectrum originating in the physical properties of the target material itself rather than from target structural acoustics and the propagation media. In a pilot experiment, we determine bispectral signatures for three targets of differing composition but similar dimensions using a submerged ultrasonic apparatus. The experiment is designed to isolate effects due to target properties from those attributable to propagation path, source, or receiver. The source wavelet is a broad-spectrum linear frequency modulated pulse. The normalized bispectrum is calculated using conventional nonparametic methods, and is averaged across many frames. Results indicate that at ultrasonic frequencies this technique provides signatures with the potential of discriminating between classes of materials such as plastic, metal, and rock. [Work supported by Applied Research Laboratories.]
Volume scattering from random porous media
Authors: Ohkawa Keiichi
Published: October 2013

The new volume scattering model, which enables us to treat the scattering of Biot’s slow compressional wave from random porous media, is derived applying the Born approximation to Biot’s equations of motion. Within the framework of the Biot theory it is assumed that the fluid-saturated unconsolidated sediment has low values of frame bulk and shear moduli relative to the other moduli of the medium and the shear wave is negligible. This enables us to treat the Biot theory easier. The equations of motion in inhomogeneous media are then simplified and coupled Helmholtz equations for compressional waves are derived applying the mode’s decoupling method to the simplified equations of motion. The Born approximation is applied to the coupled Helmholtz equations in random media. The derived equations can be treated as extended forms of fluid bottom models. In this model, the 3-D power spectrum is inferred from porosity and permeability fluctuations instead of velocity and density fluctuations generally used. The permeability fluctuation can be estimated from grain-size distribution. In the limit of low frequency or high porosity, the results coincide with the fluid bottom model [T. Yamamoto, J. Acoust. Soc. Am. 99, 866–879 (1996)]. The differences of this new model and others will be discussed.
Estimation of seabed reflection properties from direct blast pulse shape
Authors: Prior Mark K. , Harrison Christopher H.
Published: October 2013

A method is described by which the reflection properties of the seabed can be estimated from the fall-off with time of intensity received on a single hydrophone, tens of water depths away from a broadband source in shallow water. The method is simple and directly applicable to most active sonars. The theoretical basis of the method is described and results presented using experimental data measured in a shallow water region of the Mediterranean Sea. Seabed properties are deduced directly by the method in the form of the rate of change of reflection loss with respect to an angle close to grazing. An extension to the method is proposed whereby seabed sound speed, density and attenuation can be estimated. Good agreement is shown between the results of the method and the results of matched field inversions carried out in the same area using a large-aperture vertical line array. A similar method using target echoes, instead of direct arrivals, is also demonstrated. The features of the method that make it attractive as a candidate for through the sensor probing of the environment are discussed.
Beamforming with collocated microphone arrays
Authors: Lockwood Michael E. , Jones Douglas L. , Su Quang , Miles Ronald N.
Published: October 2013

A collocated microphone array, including three gradient microphones with different orientations and one omnidirectional microphone, was used to acquire data in a sound-treated room and in an outdoor environment. This arrangement of gradient microphones represents an acoustic vector sensor used in air. Beamforming techniques traditionally associated with much larger uniformly spaced arrays of omnidirectional sensors are extended to this compact array (1 cm3) with encouraging results. A frequency–domain minimum-variance beamformer was developed to work with this array. After a calibration of the array, the recovery of sources from any direction is achieved with high fidelity, even in the presence of multiple interferers. SNR gains of 5–12 dB with up to four speech sources were obtained with both indoor and outdoor recordings. This algorithm has been developed for new MEMS-type microphones that further reduce the size of the sensor array.
Overview of shock waves in medicine
Authors: Cleveland Robin O.
Published: October 2013

A brief overview of three applications of shock waves is presented. Shock wave lithotripsy (SWL) has been in clinical use for more than 20 years. In the United States it is used to treat more than 80% of kidney stone cases and has wide acceptance with patients because it is a noninvasive procedure. Despite SWLs enormous success there is no agreement on how shock waves comminute stones. There is also a general acceptance that shock waves lead to trauma to the soft tissue of the kidney. Yet there has been little forward progress in developing lithotripters which provide comminution with less side-effects, indeed the original machine is still considered the gold standard. The last decade has seen the advent of new shock wave devices for treating principally musculoskeletal indications, such as plantar fasciitis, tennis elbow, and bone fractures that do not heal. This is referred to as shock wave therapy (SWT). The mechanisms by which SWT works are even less well understood than SWL and the consequences of bioeffects have also not been studied in detail. Shock waves have also been shown to be effective at enhancing drug delivery into cells and assisting with gene transfection. [Work partially supported by NIH.]
Current state of clinical lithotripsy
Authors: Lingeman James E.
Published: October 2013

Extracorporeal shock wave lithotripsy (ESWL) has revolutionized the treatment of urolithiasis. Because of the clinical success of the original lithotriptor, the Dornier HM3, numerous manufacturers introduced different approaches to lithotripsy based on empiricism rather than an understanding of the fundamental mechanisms of this new technology. Our understanding of shock wave physics and the physiologic effects of shock waves has progressed greatly over the last decade resulting in insights that hopefully will be reflected favorably in future lithotriptor designs and lithotripsy techniques.
Geoacoustic inversion via acoustic-seismic transfer function
Authors: Fokin Vladimir N. , Fokina Margarita S. , Sabatier James M. , Howard Wheeler B.
Published: October 2013

Inversion methods for estimation of geoacoustic model parameters often use the scattered field data for obtaining the properties of viscoelastic layered media. This work presents a method to retrieve ground properties information using the outdoor acoustic–seismic transfer function (admittance). The resonance method developed in A. Nagle, H. Uberall, and K-B. Yoo [Inverse Prob. 1, 99–110 (1985)] is extended and used for a preliminary estimation of a set of parameters for a three-layered ground model. The least squares method is used afterward to choose the model with the best fit to experimental data. Results of the reconstruction show good agreement with the experimental data. A description of the resonant technique and the experimental setup are presented. The effect of a finite size of sound source on the acoustic–seismic transfer function is also discussed. [Work supported by ONR.]
A direct approach to the investigation of quasisteady approximation in phonation
Authors: Park Jong Beom , Mongeau Luc
Published: October 2013

Unsteady pulsating air jets through the human glottis are the main sound source in phonation. The quasisteady approximation has been frequently used for voice modeling. The time-varying air flow in the vocal tract is modeled using a sequence of comparable steady flows with the same wall position and boundary conditions as for the dynamically varying situation. Previous attempts to verify the quasisteady approximation used an indirect method, based on inverse filtering. In the present study, a direct method of comparing the orifice discharge coefficients of both dynamic and static jet flows was investigated. Time varying orifice coefficients of pulsating jets were derived from the measured instantaneous velocity field and orifice area, and then, compared to those of static configurations for the same orifice areas. It was found that dynamic orifice coefficients coincided with the static ones during closing rather than opening. Leading and trailing vortices of the pulsating jets were hypothesized as the main factor causing the dynamic transient effects.
Objective sampling with EAGLE to improve acoustic prediction accuracy
Authors: Rike Erik R. , DelBalzo Donald R.
Published: October 2013

Some Navy operations require extensive acoustic calculations. The standard computational approach is to calculate on a regular grid of points and radials. In complex environmental areas, this implies a dense grid and many radials (i.e., long run times) to achieve acceptable accuracy and detail. However, Navy tactical decision aid calculations must be timely and exhibit adequate accuracy or the results may be too old or too imprecise to be valuable. This dilemma led to a new concept, OGRES (Objective Grid/Radials using Environmentally-sensitive Selection), which produces irregular acoustic grids [Rike and DelBalzo, Proc. IEEE Oceans (2002)]. Its premise is that physical environmental complexity controls the need for dense sampling in space and azimuth, and that transmission loss already computed for nearby coordinates on previous iterations can be used to predict that complexity. Recent work in this area to further increase accuracy and efficiency by using better metrics and interpolation routines has led to the Efficient Acoustic Gridder for Littoral Environments (EAGLE). On each iteration, EAGLE produces an acoustic field for the entire area of interest with ever-increasing resolution and accuracy. An example is presented where approximately an order of magnitude efficiency improvement (over regular grids) is demonstrated. [Work sponsored by ONR.]
Application of the combined higher order time–frequency method to the identification of wave propogation
Authors: Lee Sang-Kwon , Ko Sung-Gyu
Published: October 2013

The wave propagation in a solid is an interesting topic for mechanical engineering since it often gives an idea for the structure damage. However it is often difficult to measure the wave propagation in beam due to the difference of speed of wave depending on frequency. In order to solve this problem, many time–frequency methods have been developed. Especially Wigner–Ville distribution, wavelet analysis and short time–frequency analysis are recently popular methods in this field. These methods have an advantage and a disadvantage depending on the type of structure. In this paper, the combined higher order time–frequency method is developed and used for the good identification of wave propagation. It can be applied to the damage analysis of the structure in detail. [Work supported by the Nuclear Research Project in Korea.]
Diurnal variability in the anisotropic nature of the ocean’s midfrequency (1–10 kHz) noise field
Authors: D’Spain Gerald L. , Skinner Jeffrey D. , Rovner Galina L. , Batchelor Heidi H.
Published: October 2013

A 131-element, 2-D billboard array with 12-kHz bandwidth per element and interelement spacing equal to half-wavelength at 3.75 kHz was designed and built by the Marine Physical Lab. It recorded data nearly continuously over 8 days in July, 2002. The site was in 175-m water located 2 km from the ‘‘43-Fathom Spot,’’ a popular fishing area in the Southern California Bight. Results from combined conventional beamforming in the vertical and adaptive beamforming in the horizontal commonly display a strong azimuthal dependence of the vertical directionality. A noise notch in the horizontal typically exists at many azimuths during daytime hours, sometimes more than 15 dB lower than higher-angle energy. Numerical modeling illustrates the importance of local (within 20-km range) large-scale bathymetry variations. However, at night, the horizontal noise levels can exceed those at higher angles by more than 10 dB. Horizontal beam spectrograms show two broad peaks centered at 1.5 kHz and around 4.5 kHz that appear shortly after sunset, are strongest at midnight, and disappear at sunrise. This horizontal energy arrives from the direction of the 43-Fathom Spot and probably represents a nighttime chorusing behavior of some species of fish or invertebrate. [Work supported by ONR, Code 321(US).]
Acoustic and cavitation fields produced by shock wave therapy (SWT) devices with different generating principles
Authors: Cleveland Robin O. , Chitnis Parag V.
Published: October 2013

We present measurements from two SWT devices with different generating principles: an electrohydraulic source (EHS) with a focusing reflector (HMT Equitron) and a pneumatic source (PS) with no focusing (EMS Swiss Dolorclast). The acoustic field was measured with a PVDF membrane hydrophone. For the EHS the focal waveform consisted of a shock wave with a short compressive pulse lasting 1 μs (rise time less than 50 ns) and a negative tail of 1.5 μm. The average peak positive pressure at the focus was 20 MPa and showed little variation with energy level. The waveform from the PS had a compressive phase of 2-μm-duration (rise time 1 μs) followed by a complex negative phase of 4-μs duration. The peak positive pressure increased from 2 to 8 MPa with increasing energy setting. A passive cavitation detection (PCD) system was used to monitor the cavitation activity produced by the two devices. The EHS produced measurable cavitation with a life time that varied between 110 to 140 μs. We were unable to detect cavitation from the PS. These data indicate that the two devices studied here have different physical characteristics and this may affect the processes by which they operate clinically.
Evaluation of sound fields in a concert hall involving scattered reflections applying the subjective preference theory
Authors: Suzumura Yukio
Published: October 2013

Convex tilted rear walls in a stage enclosure, an array of circular columns installed in front of walls, and triangular reflectors above the stage were newly adopted as scattering obstacles in an acoustic design of Tsuyama Music Cultural Hall, called “Bell Folêt Tsuyama.” The fundamental shape of the hall was designed using the theory of subjective preference. To calculate the effects of scattered reflections on a sound field in a real concert hall is extremely laborious. For this reason, the evaluation of effects of scattered reflections on the sound field in the hall was made experimentally by use of a 110 acoustical scale. After construction of the hall, therefore, sound fields of the hall, which involves scattered reflections caused by the tilted convex rear, by the array of circular columns, and by the triangular reflectors, were measured using four orthogonal physical factors (LL, Δt1, Tsub, IACC) described in the theory and the acoustical character of these scattering obstacles was clarified. Results clearly showed that these new attempts on scattered reflections substantially improved the quality of the sound field in the hall.

Thesis advisor: Yoichi Ando

Copies of this thesis written in English can be obtained from Yukio Suzumura. E-mail address: ysuzu11@lapis.plala.or.jp
Subjective preference evaluation of sound fields by performing singers
Authors: Noson Dennis
Published: October 2013

A model of the auditory process is proposed for performing singers, which incorporates the added signal from bone conduction, as well as the psychological distance for subjective preference of the performer from the acoustic sound field of the stage. The explanatory power of previous scientific studies of vocal stage acoustics has been limited by a lack of an underlying theory of performer preference. Ando’s theory, using the autocorrelation function (ACF) for parametrizing temporal factors, was applied to interpretation of singer sound field preference determined by the pair comparison method. Melisma style singing (no lyrics) was shown to increase the preferred delay time of reflections from a mean of 14 ms with lyrics to 23 ms without (p<0.05). The extent of the shift in preferred time delay was shown to be directly related to minima of the effective duration of the running ACF, (τe)min, calculated from each singer’s voice. Voice matching experiments for singers demonstrated a strong overestimate of the voice outside the head compared with the singer’s own voice (22.4 dB overestimate, p<0.01). Individual singer melisma singing delay preferences were compared for “ah” versus “hum” syllables, and the increased delay preference (41 ms) was shown to be correlated with (τe)min (r2<0.68, p<0.01). When the proposed bone conduction model was applied, using the measured overestimate of sound level of the singer’s own voice for each singer (9.9 dB mean overestimate difference between “ah” and “hum,” p<0.01), the relationship of singer preference to (τe)min was improved (r2=0.97, p<0.01).

Thesis advisor: Yoichi Ando

Copies of this thesis are available from the author by inquiry at BRC Acoustics, 1741 First Avenue South, Seattle, WA 98134 USA. E-mail address: dnoson@brcacoustics.com
Separating volume and roughness components of scattering from the seafloor using spatial coherence filtering
Authors: Ivakin Anatoliy N. , Jackson Darrell R. , Tang Dajun
Published: October 2013

Seabed scattering is usually associated with two mechanisms, interface roughness and volume heterogeneity, which can operate at the same time. In this paper, a method of separately identifying these two mechanisms is presented, involving measurements of spatial coherence of the field with a vertical linear array located near the source. Analytical expressions are derived for the spatial coherence of interface and volume scattering and used to illustrate the potential for their separating and quantifying. It is shown that the correlation scales for the volume and roughness components can be significantly different, and thus spatial filtering can be used for their separating. A Monte Carlo simulation technique based upon the point scatterer model is also developed that makes it possible to generate random time series for the scattered field. An algorithm for data processing is proposed to estimate spatial correlation as an average over realizations (from separate pings) of the measured time series. The simulations illustrate the ability of the algorithm to distinguish and separate volume and surface components of scattering and also verify the analytical expressions for spatial coherence. It is shown that the convergence to the theoretical prediction for both volume and surface components of scattering indeed takes place, but longer pulses require a larger number of measurements (realizations). [Work supported by ONR Code 321OA.]
Correlation of subjective and objective measures of speech intelligibility
Authors: Bowden Erica E. , Wang Lily M. , Palahanska Milena S.
Published: October 2013

Currently there are a number of objective evaluation methods used to quantify the speech intelligibility in a built environment, including the Speech Transmission Index (STI), Rapid Speech Transmission Index (RASTI), Articulation Index (AI), and the Percentage Articulation Loss of Consonants (%ALcons). Many of these have been used for years; however, questions remain about their accuracy in predicting the acoustics of a space. Current widely used software programs can quickly evaluate STI, RASTI, and %ALcons from a measured impulse response. This project compares subjective human performance on modified rhyme and phonetically balanced word tests with objective results calculated from impulse response measurements in four different spaces. The results of these tests aid in understanding performance of various methods of speech intelligibility evaluation. [Work supported by the Univ. of Nebraska Center for Building Integration.] For Speech Communication Best Student Paper Award.
Evaluation of sound field systems in elementary school classrooms
Authors: Vigeant Michelle C. , Kruger Kelly
Published: October 2013

Our primary purpose in this study was to determine the relevant ergonomic issues associated with daily use of sound field systems in elementary school classrooms, in order to develop a purchasing guideline and technical specification. The secondary purpose was to evaluate these systems to identify if one or more acoustical parameters could be used to determine the quality and effectiveness of a system. Six sound field systems, with varying numbers and types of speakers, were chosen as a cross-section of available systems on the market. Six representative classrooms, currently in use, were selected based on a range of reverberation times and background noise levels. All systems were installed for two weeks in each classroom. Student speech intelligibility (SI) tests using phonetically balanced word lists were conducted, as well as teacher interviews. The acoustical parameters measured were clarity ratios C50 and C80, speech transmission indices STI and R(rapid)STI, sound pressure level (SPL) uniformity and frequency response. An improvement in SI was found for all systems. Only SPL uniformity and frequency response were found to be useful distinguishing performance parameters between systems. Ergonomic design aspects of sound field systems had a significant influence on the acceptance and usage in the classroom.
Teaching acoustics online
Authors: Morrison Andrew , Rossing Thomas D.
Published: October 2013

We teach an introductory course in musical acoustics using a Blackboard. Students in this course can access audio and video materials as well as printed materials on our course website. All homework is submitted online, as are tests and examinations. The students also have the opportunity to use synchronous and asynchronous chat rooms to discuss the course with each other or with the instructors.
Azimuthal variability of acoustic backscatter from 3 to 8 kHz on the New Jersey continental shelf
Authors: Hines Paul C. , MacDougald Darcy J. , Osler John C.
Published: October 2013

The acoustic backscattering strength of the seabed has been demonstrated to be one of the key inputs required in sonar performance prediction (SPP) models. Extending range independent SPP models to full 3-dimensional—or even the simpler N×2-dimensional—models requires measurements of the azimuthal variability of the backscattering strength. DRDC Atlantic’s Wide Band Sonar (WBS) system, which consists of a parametric transmitter and a superdirective receiver, is ideally suited to make these measurements. In the spring of 2003 the system was used to measure the azimuthal variability of acoustic backscatter at a site referred to as the New Jersey Strataform. Data were collected at 3, 5, and 8 kHz at grazing angles spanning 10–40. Interpretation of the data set is enhanced with swath bathymetry measurements made during the experiment as well as 3-D seismic profiles made by other researchers [C. S. Duncan, J. A. Goff, J. A. Austin, Jr., and C. S. Fulthorpe, Marine Geology 170, 395–421 (2000)]. In this paper the experimental geometry is described and the backscatter measurements are presented.
Statistics of high-resolution seafloor backscatter and the detection of spatial changes
Authors: Caruthers Jerald W. , Goodman Ralph R. , Sidorovskaia Natalia A.
Published: October 2013

The dependence of probability density functions on patch size for high-resolution backscattering, change detection techniques, and implications for scattering models for high-resolution systems are discussed. Data used in these analyses were collected off Panama City using NRL’s dual-angle, multiple-frequency towed sonar array and using USM’s dual-frequency, side-scan sonar (SSS) system. Frequencies used in the NRL system discussed here are 200, 225, 250, and 275 kHz, and aspects of that work are discussed [Caruthers et al., NRL/MR/7184-00-8256 (2000)]. Scattering patch sizes of the NRL system were of the order of a square meter. The SSS operated at the dual frequencies of 150 and 300 kHz, and its patch sizes were nominally a half meter cross-range by a few centimeters downrange. The SSS is capable of digitizing the four signal waveforms at a 1-MHz rate and 12 bits. Each pulse was six cycles long. The characteristics of this unique SSS system are discussed in Caruthers and Fisher [USM/DMS-2003-01]. Techniques are discussed for determining change detection and varying the scattering patch sizes through coherent combinations of the SSS waveforms. The returns for each of these systems appear to be distinctly different from Rayleigh and suggest point-scatter models are appropriate for these high-resolution data. The false alarm probabilities of the observed distributions are discussed and implications addressed. [Work supported by NRL, SPAWAR, and ONR.]
Reverberation measurements in the ocean with a source-receiver array
Authors: Lingevitch Joseph F. , Fromm David M. , Gaumond Charlie F. , Calvo David C. , Perkins John S. , Kunz Edward L. , Kim Y. E.
Published: October 2013

During our time reversal experiment (TREX-03) conducted in May 2003 off the New Jersey coast, a 64 channel midfrequency source-receiver array (SRA) was deployed to measure reverberation and test the focusing capabilities of an SRA in the ocean without explicitly introducing a known probe source. Previous simulations [J. Acoust. Soc. Am. 111, 2609–2614 (2002)] and laboratory experiments [J. Acoust. Soc. Am. 113, 3155–3160 (2003)] have shown that the monostatic reverberation signal due to a rough interface can be decomposed to yield SRA source functions that will focus energy at the interface. The range of the focus is controlled by time windowing the reverberation signal. Additionally, measured environmental data (sound-speed profiles and geo-acoustic parameters) were used to estimate the SRA source weights for focusing at targets that were deployed in the water column and on the bottom. [Work supported by ONR.]
Modeling sound fields in small rooms
Authors: Yoon Sung , Torres Rendell R.
Published: October 2013

In computationally modeling and auralizing acoustics of small rooms, geometrical-acoustics methods do not apply at lower frequencies, and models must account for the wave-nature of sound fields, especially modal effects and scattering in the early impulse response. Common approaches include finite-difference methods, finite-element methods, boundary-element methods, edge-diffraction models, boss models, among others. This investigation describes different time- frequency-domain techniques for computing the sound field in small rooms and introduces new methods as well, including fast algorithms based on cellular automata for calculating scattering from edge discontinuities and other boundary conditions. The latter approach will be described in relation to the pioneering work on the lattice gas time domain (LGTD) approach by Sudo and Sparrow [AIAA J. 33 (1995)] and how it can be applied to modeling the typical timbral and temporal (reverberant) characteristics of small room acoustics. [Work supported by Rensselaer Polytechnic Institute.]
A biological source of bubbles in sandy marine sediments
Authors: Holliday D. V. , Greenlaw Charles F. , Thistle David , Rines Jan E. B.
Published: October 2013

Gas in sediments, even in small quantities, will modify the propagation and scattering of sound. Shallow water littoral environments are often sufficiently well lit by sunlight to support healthy populations of benthic and epibenthic marine microalgae. Photosynthesis in marine algae produces oxygen. Oxygen saturation levels as high as 600% have been measured in the pore water of a sandy sediment at 1 mm depth, decreasing to 100% saturation at ca. 4.5 mm. Bioturbation and physical processes routinely mix materials at the surface of the seabed, including algae, to depths of at least a few cm. Mixing times and depths vary with the sediment type and the species and abundance of organisms present, but time scales of minutes to hours are common. While light is rapidly attenuated with depth in sand, measurements show that it can penetrate to depths of a few mm. Physical and biological mechanisms are suggested which could produce gas bubbles in oxygen saturated pore water. Laboratory measurements of sound scattering from marine algae on a sand surface suggest a possible method for in situ bubble detection in shallow marine environments. [Work supported by ONR.]
Forced linear oscillations of microbubbles in blood capillaries
Authors: Sassaroli Elisabetta , Hynynen Kullervo
Published: October 2013

A numerical investigation of the forced oscillations of ultrasound contrast agents in blood capillaries are investigated by means of a simplified model based on the assumption of small amplitude oscillations of the microbubbles acoustically driven. The natural frequencies of oscillations, the thermal and viscous damping coefficients, the amplitude resonances, as well as the average power absorbed by the system, bubble plus vessel, are computed for different kinds of contrast agent bubbles, containing air, octafluropropane, and perflurobutane. It is found that viscous damping is much larger than thermal damping and that the natural frequencies depend much more on the system parameters than the nature of the gas contained in the bubble. Our motivation for this study lies in the possibility of using bubbles as vectors for directed drug delivery and gene transfection into living cells.
Special short wave finite elements for flow acoustics
Authors: Gamallo Pablo , Astley Jeremy
Published: October 2013

Short wave problems of practical interest in acoustics include the modeling of sound attenuation in the ducted regions of turbofan aircraft engines where the convective and diffractive effects of the mean flow are significant. Also, in this case the acoustic wavelength is generally much smaller than the length scale of the scattering geometry and smaller than the characteristic length scale for variations in the mean flow. The Partition of Unity Method (PUM) [J. M. Melenk and I. Babuška, Comput. Methods Appl. Mech. Eng. 139, 289–314 (1996)] is a proved efficient numerical method for solving short wave problems in the absence of flow (Helmholtz equation) [Lagrouche et al., Int. J. Numer. Methods Eng. 54, 1501–1533 (2002)]. The PUM approach is based on the use of a discrete set plane of wave as a local basis for the spatial discretization. When flow is present the wave number of each locally defined plane wave becomes dependent upon the magnitude and direction of the mean flow. The implementation of such scheme for the harmonic acoustic propagation within an irrotational mean flow is proposed in this work. One- and two-dimensional model problems are presented to demonstrate the effectiveness of the approach. [Work supported by EPSRC.]
Infrasonic windscreen
Authors: Shams Qamar A. , Sealey B. Scott , Zuckerwar Allan J. , Bott Laura M.
Published: October 2013

Infrasonic windscreens, designed for service at frequencies below 20 Hz, were fabricated from a variety of materials having a low acoustic impedance, and tested in a small wind tunnel against four specifications: (1) attenuation of wind-generated sound (at a free-stream wind speed of 9.4 m/s), (2) the transmission of low-frequency sound from a known source (Janis subwoofer), (3) spectrum of sound generated from trailing vortices, and (4) water absorption (to determine the suitability for all-weather service). Windscreen materials included three woods (pine, cedar, and balsa), polyurethane foam, and Space Shuttle tile material. The windscreen outside diameter ranged from 0.0254 to 0.1016 m (1 to 4 inches), and wall thickness from 0.003175 to 0.01905 m (1/8 to 3/4 inch). A windscreen made of polyurethane foam revealed a wind noise attenuation of 10–20 dB from 0.7–25 Hz, transmission coefficient near unity from 10–25 Hz, and a spectral peak of 23 Hz due to vortex-generated sound. Data will be presented for a variety of windscreens.
Localized and cumulative nonlinearity in wind instruments
Authors: Gilbert Joel
Published: October 2013

Nonlinearities are very common in wind instruments. A crucial one localized at the input of the wind instrument is responsible for the sound production mechanism. As an illustration, some recent measurements done at clarinet mouthpieces will be shown. Some other localized nonlinear effects take place at the open tube ends. They imply extra losses whose amount depends on the internal geometry of the termination. They control the sound extinction phenomena. It will be shown how the playing range of a clarinet-like instrument is determined by these extra losses. Besides localized nonlinearity, cumulative nonlinearity effects are present as well. The cumulative nonlinear propagation phenomena along the tube of brass instruments can lead to shock waves obtained when the player is playing very loudly with a ‘‘brassy sound.’’
Floor vibration evaluations for medical facilities
Authors: Himmel Chad N.
Published: October 2013

The structural floor design for new medical facilities is often selected early in the design phase and in renovation projects, the floor structure already exists. Because the floor structure can often have an influence on the location of vibration sensitive medical equipment and facilities, it is becoming necessary to identify the best locations for equipment and facilities early in the design process. Even though specific criteria for vibration-sensitive uses and equipment may not always be available early in the design phase, it should be possible to determine compatible floor structures for planned vibration-sensitive uses by comparing conceptual layouts with generic floor vibration criteria. Relatively simple evaluations of planned uses and generic criteria, combined with on-site vibration and noise measurements early in design phase, can significantly reduce future design problems and expense. Concepts of evaluation procedures and analyses will be presented in this paper. Generic floor vibration criteria and appropriate parameters to control resonant floor vibration and noise will be discussed for typical medical facilities and medical research facilities. Physical, economic, and logistical limitations that affect implementation will be discussed through case studies.
The MRI: A noise source of concern in the health care industry
Authors: Standlee Kerrie G. , Begin Joseph C.
Published: October 2013

Two recent trends in the development and use of magnetic resonance imaging (MRI) equipment have created challenges for acoustical engineers: (1) the trend toward more powerful MRI machines with greater magnetic field strengths, and (2) the tendency of health care facilities to locate these machines, which were previously located in basements or on grade, on upper floors adjacent to (and in some cases above) other critical use areas. For newer, 3-T MRI machines, sound levels well over 100 dBA in the examination room are common. Along with these trends, some equipment manufacturers are now providing design recommendations to address the issues of airborne and structure-borne noise within hospitals and clinics. In addition, MRI manufacturers sometimes have strict requirements for acceptable levels of building vibration from other sources, to prevent potential image quality problems. This paper discusses experience gained during the course of addressing MRI-generated noise on several projects. Data for airborne sound levels measured inside MRI rooms and adjacent rooms and vibration levels measured below MRI units will be presented.
Multiple existence of steady state solutions of acoustic streaming in a long two-dimensional rectangular box
Authors: Yano Takeru
Published: October 2013

The large amplitude standing wave excited in a resonator induces acoustic streaming of Rayleigh type outside the acoustic boundary layer on the wall of the resonator. The streaming motion with large Reynolds number is examined numerically in relatively long two-dimensional rectangular boxes. The two-dimensional incompressible Navier–Stokes equations with no external force are used as the governing equations for the streaming velocity. The steady velocity component at the outer edge of the acoustic boundary layer, which induces Rayleigh type streaming, is employed as the boundary condition for the Navier–Stokes equations. By using a finite-difference method, the existence of multiple steady state solutions is demonstrated. Some of the numerically obtained flow patterns bear a resemblance to those obtained experimentally. It may be remarked that all the flow patterns induced by the fifth mode standing wave in a relatively long box can be regarded as combinations of those induced by the second mode standing wave in a short box.
Update on the simulation of streaming in tapered resonators
Authors: Tuttle Brian C. , Sparrow Victor W.
Published: October 2013

In a previous report [J. Acoust. Soc. Am. 110, 2652 (2001)] the authors described a plan to simulate nonlinear acoustic streaming by way of a MacCormack finite-difference scheme running on a cluster-type multiprocessor computer. The object was to investigate how the tapering of a resonator tube affects the acoustic streaming. The experiments of Olson and Swift predict that a temperature-dependent viscosity in conjunction with tube geometry can minimize Rayleigh streaming for a particular taper angle. Recent progress in the present research includes a careful perturbation analysis of the model equations to incorporate additional nonlinear terms that are important to simulate flow near a boundary. A modified computational grid necessary to accommodate the tapered domain as well as the refined boundary layer is discussed. The method of driving the tube and issues arising in the simulation starting conditions are also described. [Work supported in part by ONR.]
Review and comparison of methods using spectral characteristics for the purposes of CASA, Computational Auditory Scene Analysis
Authors: Gregoire Jerry
Published: October 2013

The brain has a remarkable ability to separate signals from a mixture. Although much progress has been made, the goal of replicating this has eluded us. Bregman (90) suggests that the brain divides this analysis into low or primitive, and high or schema processes. Schema processes require memory and subsequent interpretation. Conversely, primitive processes operate only on the innate properties of the incoming mixture and the sources that created it. The major parameters are intra aural time differences, spectrum, onset and offset, phase, and amplitude of each source. In this paper I review and compare previously proposed methods to analyze the frequency spectrum. This includes estimation of the fundamental frequency and partials produced by each source in the mixture.
Coupled volume/double slope subjective listening test
Authors: Ermann Michael , Stuecker Rebecca
Published: October 2013

Can experienced listeners of music discern a double-sloped decay from a Sabine decay? Do they prefer the double slope? Concert hall designers use coupled-volumes and their signature double-slope sound decay in an effort to reconcile the inversely related qualities of reverberance and clarity. A simulated space, based on an actual built coupled-volume hall, was conceived in the room acoustics software CATT-Acoustic. Variations in the aperture sizes that sonically expose the main hall to the coupled volume generated both classic Sabine decays and double-sloped decays. The impulse responses generated were convolved with the same anechoic musical recording, grouped in pairs, and played for an opportunity-sample of 21 volunteers from the Architectural Acoustics section of the 145th meeting of the Acoustical Society of America in Nashville. Participants listened to the 11 recorded pairs over headphones and were asked to determine (1) if the two recordings sounded different, (2) which recording was more likely to have a double slope or had a more dramatic double slope, and (3) which of the two recordings they prefer.
Representational specificity of within-category phonetic variation in the mental lexicon
Authors: Ju Min , Luce Paul A.
Published: October 2013

This study examines (1) whether within-category phonetic variation in voice onset time (VOT) is encoded in long-term memory and has consequences for subsequent word recognition and, if so, (2) whether such effects are greater in words with voiced counterparts (pat/bat) than those without (cow/*gow), given that VOT information is more critical for lexical discrimination in the former. Two long-term repetition priming experiments were conducted using words containing word-initial voiceless stops varying in VOT. Reaction times to a lexical decision were compared between the same and different VOT conditions in words with or without voiced counterparts. If veridical representations of each episode are preserved in memory, variation in VOT should have demonstrable effects on the magnitude of priming. However, if within-category variation is discarded and form-based representations are abstract, the variation in VOT should not mediate priming. The implications of these results for the specificity and abstractness of phonetic representations in long-term memory will be discussed.
Do listeners perceive coarticulatory differences for normal talkers and neurologically impaired talkers?
Authors: Tjaden Kris , Sussman Joan , Yu Ya-ju
Published: October 2013

Speech production studies suggest that the extent of coarticulation varies across talkers. The extent of coarticulation may even vary for repetitions of the same utterance produced by a single talker. Thus, an utterance or talker could be characterized by an average degree of coarticulation, a high degree of coarticulation, or a low degree of coarticulation. The perceptual consequences, if any, of this coarticulatory variability are not well understood, particularly for individuals with speech motor control disorders. The current study examined whether the listeners’ speed and accuracy of vowel identification for naturally-produced CV sequences varied depending on the extent of anticipatory vowel coarticulation. Speakers and speech tokens included those characterized by an average degree of anticipatory coarticulation, a high degree of coarticulation, and a low degree of coarticulation. Healthy talkers, speakers with multiple sclerosis, and speakers with Parkinson’s disease produced the stimuli. Consonants in CV syllables beginning with /s/, /k/, or /t/ followed by the vowels /i/ or /u/ were excised and presented to listeners for identification of the following vowel. While identification accuracy may be high across speakers and stimuli, the speed of response should vary with extent of coarticulation, if listeners are sensitive to coarticulatory cues in the acoustic speech stream.
Beamforming for aircraft noise measurements
Authors: Dougherty Robert P.
Published: October 2013

Phased array beamforming for aircraft noise source location has a long history, including early work on jet noise, wind tunnel measurements, and flyover testing. In the last 10 years, advancements in sparse 2-D and 3-D arrays, wind tunnel test techniques, and computer power have made phased array measurements almost common. Large aerospace companies and national research institutes have an advantage in access to major facilities and hundreds of measurement microphones, but universities and even consulting companies can perform tests with electret microphones and PC data acquisition systems. The type of testing remains a blend of science and art. A complex noise source is approximated by a mathematical model, and the microphones are deployed to evaluate the parameters of the model. For example, the simplest, but often the best, approach is to assume a distribution of mutually incoherent monopoles. This leads to an imaging process analogous to photography. Other models include coherent distributions of multipoles or duct modes. It is sometimes important to simulate the results that would have been obtained from single microphone measurements of part of the airplane in an ideal environment, had such measurements been feasible.
Near-field acoustical holography in enclosed spaces
Authors: Burroughs Courtney
Published: October 2013

In enclosed spaces, the locations of surfaces from which most of the noise radiation occurs can be difficult to determine in the presence of reverberation and contributions from other sources. By using microphones configured in an array that confirms to the surface of interest, it should be possible to map the acoustic field inside the enclosed space produced by the surface under the array using nearfield acoustical holography processing on the unsteady pressures measured by the microphones in the conformal array. Such an acoustic mapping could therefore be used to isolate contributions to the interior noise make by different surfaces. Because enclosed spaces rarely have simple geometries, it is often necessary to measure the propagation function (i.e., the Green’s function) for the enclosed space. To explore the sensitivity of mappings to measurement and physical parameters, a mathematical model of the acoustic field inside a capped cylindrical shell was developed. Measurements at locations on a conformal array are simulated, maps of the interior acoustic fields developed by applying numerical nearfield acoustical holography algorithms on the simulated measurements and resulting acoustic mappings compared to acoustic fields predicted directly from known surface vibration distributions.