bluuebunny/crossref_metadata_2025 huggingface dataset:
The evaluation of impulse response testing in low signal-to-noise ratio environments
Authors: Knorr Hannah D. , Bleifnick Jay , Hulva Andrew M. , Chéenne Dominique J.
Published: October 2014

Impulse testing is used by industry professionals to test many parameters of room acoustics, including the energy decay, frequency response, time response, etc. Current testing software makes this process as streamlined as possible, but generally must be utilized in quiet environments to yield high signal-to-ratios and more precise results. However, many real world situations cannot conform to the necessary standards needed for reliable data. This study tests various methods of impulse responses in background noise environments in an attempt to find the most reliable procedure for spaces with a high ambient noise levels. Additionally, extreme situations will be evaluated and a method will be derived to correct for the systematic error attributed to high background noise levels.
Comparison of palate impressions and palate casts from three-dimensional laser-scanned digital models
Authors: Tebout Michelle , Lulich Steven M.
Published: October 2014

Palate impressions and their casts in plaster are negatives of each other. While plaster casts are the standard for palate measurements and data preservation, making such casts can be time-consuming and messy. We hypothesized that measurements from 3D laser-scanned palate impressions are negligibly different from equivalent measurements from 3D laser-scanned palate casts. If true, this would allow the step of setting impressions in plaster to be skipped in future research. This poster presents the results of our study.
The analysis of sound wave scattering using a firefighter’s Personal Alert Safety System signal propagating through a localized region of fire
Authors: Broda Andrew L. , Rudisill Chase J. , Smith Nathan D. , Schrader Matthew K. , Korman Murray S.
Published: October 2014

Firefighting is quite clearly a dangerous and risk-filled job. To combat these dangers and risks, firefighters wear a (National Fire Protection Agency, NFPA 2007 edition of the 1982 standard) Personal Alert Safety System (PASS) that will sound a loud alarm if it detects (for example) the lack of movement of a firefighter. However, firefighters have experienced difficulty locating the source of these alarm chirps (95 dBA around 3 kHz) in a burning building. The project goal is to determine the effect of pockets of varying temperatures of air in a burning building on the sound waves produced by a PASS device. Sound scattering experiments performed with a vertical heated air circular jet plume (anechoic chamber) and with a wood fire plume from burning cylindrical containers (Anne Arundel Fire Department’s Training Facility) suggest that from Snell’s Law, sound rays refract around such pockets of warmer air surrounded by less warmer ambient air due to changes in the sound speed with temperature through the medium. Real-time and spectral measurements of 2.7 kHz CW sound scattering (using a microphone) exhibit some attenuation and considerable amplitude and frequency modulation. This research may suggest future experiments and effective modifications of the current PASS system.
Nonlinear scattering of crossed focused ultrasonic beams in the presence of turbulence generated behind a model deep vein thrombosis using an orifice plate set in a thin tube
Authors: Fisher Daniel , Korman Murray S.
Published: October 2014

An orifice plate (modeling a “blockage” in a deep vein thrombosis DVT) creates turbulent flow in a downstream region of a submerged polyethylene tube (1.6 mm thick, diameter 4 cm and overall length 40 cm). In the absence of the orifice plate, the water flow is laminar. The orifice plate is mechanically secured between two 20 cm tube sections connected by a union. The union allows a plate with an orifice to be slid into the union providing a concentric orifice plate that can obstruct the flow causing vorticity and turbulent flow downstream. A set of orifice plates (3 mm thick) are used (one at a time) to conveniently obstruct the tube flow with a different radius compared to the inner wall tube radius. The nonlinear scattering at the sum frequency (f+ = 3.8 MHz), from mutually perpendicular spherical focused beams (f1 = 1.8 MHz and f2 = 2.0 MHz) is used to correlate the Doppler shift, spectral, and intensity as a function of the orifice plate size in an effort to correlate the blockage with the amount of nonlinear scattering. In the absence of turbulence in the overlap region, there is virtually no scattering. Therefore, a slight blockage is detectable.
Effects of sustainable and traditional building systems on indoor environmental quality and occupant perceptions
Authors: Roberts Joshua J. , Ronsse Lauren M.
Published: October 2014

This study examines the effects of both sustainable and traditional building systems on the indoor environmental quality (IEQ) and occupant perceptions in an open-plan office floor of a high-rise building located in Chicago, IL. The office evaluated has sustainable daylighting features as well as a more traditional variable air volume mechanical system. Different measurement locations and techniques are investigated to quantify the indoor environmental conditions (i.e., acoustics, lighting, and thermal conditions) experienced by the building occupants. The occupant perceptions of the indoor environmental conditions are assessed via survey questionnaires administered to the building occupants. The relationships between the IEQ measured in the office and the occupant perceptions are assessed.
Ribbon microphones
Authors: Dooley Wesley L.
Published: October 2014

The ribbon microphone was invented by Dr. Walter Schottky who described it in German Patent 434855C, issued December 21, 1924 to Siemens & Halske (S&H) in Berlin. An earlier “Electro-Dynamic Loudspeaker” Patent which Schottky had written with Dr. Erwin Gerlach described a compliant, lightweight, and ribbed aluminum membrane whose thinnest dimension was at right angles to a strong magnetic field. Passing an audio frequency current through this membrane causes it to move and create sound vibrations. The December Patent describes how this design functions either as a loudspeaker or a microphone. A 1930 S&H patent for ribbon microphone improvements describes how they use internal resonant and ported chambers to extend frequency response past 4 kHz. RCA dramatically advanced ribbon microphone performance in 1931. They opened the ribbon to free air to create a consistent, air-damped, low-distortion, figure-eight with smooth 30–10,000 Hz response. RCA ribbon microphones became the performance leader for cinema, broadcast, live sound and recording. Their 20–30,000 Hz RCA 44B and BX was manufactured from 1936 to 1955. It is the oldest design still used every day at major studios. Ribbon microphones are increasingly used for contemporary recordings. Come hear why ribbon microphones, like phonograph records, are relevant to quality sound.
Reciprocity calibration of condenser microphones
Authors: Beranek Leo L.
Published: October 2014

The theory of reciprocity began with Lord Rayleigh and was first well stated by S. Ballantine (1929). The first detailed use of the reciprocity theory for the calibration of microphones was by R. K. Cook (1940). At the wartime Electro-Acoustic Laboratory, at Harvard University, the need arose to calibrate a large number of Western Electric 640-AA condenser microphones. A reciprocity apparatus was developed that connected the two microphones with an optimum shaped cavity that included a means for introducing hydrogen or helium to extend the frequency range. The apparatus was published by A. L. Dimattia and F. M. Wiener (1946). A number of things resulted. The Harvard group, in 1941, found that the international standard of sound pressure was off by 1.2 dB—that standard was maintained by the French Telephone Company and the Bell Telephone Laboratories and was based on measurements made with Thermophones. This difference was brought to the attention of those organizations and the reciprocity method of calibration was subsequently adopted by them resulting in the proper standard of sound pressure adopted around 1942. The one-inch condenser microphone has subsequently become the worldwide standard for precision measurement of sound field pressures.
Meucci's telephone transducers
Authors: Campanella Angelo J.
Published: October 2014

Antonio Meucci (1809–1889) developed variable reluctance transducers from 1854 to 1876 and beyond after noticing that he could hear voice sounds from paddle electrodes while he participated in electrotherapy of a migraine patient around 1844 while in Havana, Cuba. He immigrated to Staten Island, NY, in 1850 and continued experimenting to develop a telephone. He found better success from electromagnetics using materials evolved from the telegraph developed by Morse, as well as a non-metal diaphragm with an iron tab, iron bars and a horseshoe shape. Artifacts from his residence on Staten Island are presently on display at the museum of his life on Staten Island from 1850 to his death. Those artifacts, thought until now to be only models, were found to be wired and still operative. Tests were performed in July, 2011. Their electrical resistance is that expected for wire wound variable reluctance transducers. Voice signals were produced without any externally supplied operating current. At least one transducer was found to be also operable as a receiver and was driven to produce voice sounds to the ear. Meucci's life and works will be discussed and these test results will be demonstrated including recordings from voice tests.
The Fessenden Oscillator: The first sonar transducer
Authors: Howarth Thomas R. , Moss Geoffrey R.
Published: October 2014

When the RMS Titanic sunk in 1912, there was a call placed forth by ship owners for inventors to offer solutions for ship collision avoidance methods. Canadian born inventor Reginald A. Fessenden answered this call while working at the former Boston Submarine Signal Company with the invention and development of the first modern transducer used in a sonar. The Fessenden oscillator was an edge clamped circular metal with a radiating head facing the water on one side while the interior side had a copper tube attached that moved in and out of a fixed magnetic coil. The coil consisted of a direct-current (DC) winding to provide a magnetic field polarization and an alternating-current (AC) coil winding to induce the current into the copper tube and thus translate the magnetic field polarization to the radiating plate with vibrations that translated from the radiating head to the water medium. The prototype and early model versions operated at 540 Hz. Later developments included adaptation of this same transducer for use in underwater communications, obstacle avoidance with WW I retrofits onto British submarines for both transmitting and receiving applications including mine detection. This presentation will discuss design details including a modern numerical modelling effort.
Historical review of underwater acoustic cylindrical transducer development in Russia for sonar arrays
Authors: Aronov Boris , Brown David A.
Published: October 2014

Beginning with the introduction of piezoelectric ceramics in the 1950’s, underwater acoustics transducer development for active sonar arrays proceeded in different directions in Russia (formerly USSR) than in the United States (US). The main sonar arrays in Russia were equipped with cylindrical transducers, whereas in the US, the implementation was most often made with extensional bar transducers of the classic Tonpilz design. The presentation focuses on the underlying objectives and humane factors that shaped the preference towards the widespread application of baffled cylindrical transducers for arrays in Russia, the history of their development, and contributions to theory of the transducers made by the pioneering developers.
Microphone array measurements, high-speed camera recordings, and geometrical finite-differences physical modeling of the grand piano
Authors: Bader Rolf , Pfeifle Florian , Plath Niko
Published: October 2014

Microphone array measurements of a grand piano soundboard show similarities and differences between eigenmodes and forced oscillation patterns when playing notes on the instrument. During transients the driving point of the string shows enhanced energy radiation, still not as prominent as with the harpsichord. Lower frequencies are radiated stronger on the larger side of the soundboard wing shape, while higher frequencies are radiated stronger on the smaller side. A separate region at the larger part of the wing shape, caused by geometrical boundary conditions has a distinctly separate radiation behavior. High-speed camera recordings of the strings show energy transfer between strings of the same note. In physical models including hammer, strings, bridge, and soundboard the hammer movement is crucially necessary to produce a typical piano sound. Different bridge designs and bridge models are compared enhancing inharmonic sound components due to longitudinal-transversal coupling of the strings at the bridge.
Adjusting the soundboard’s modal parameters without mechanical change: A modal active control approach
Authors: Mamou-Mani Adrien
Published: October 2014

How do modes of soundboards affect the playability and the sound of string instruments? This talk will investigate this question experimentally, using modal active control. After identifying modal parameters of a structure, modal active control allows the adjustments of modal frequency and damping thanks to a feedback loop, without any mechanical changes. The potential of this approach for musical acoustics research will be presented for three different instruments: a simplified piano, a guitar, and a cello. The effects of modal active control of soundboards will be illustrated on attack, amplitude of sound partials, sound duration, playability, and “wolf tone” production.
How long are inexperienced-subjects “naive” for ANSI S12.6?
Authors: Gallagher Hilary , McKinley Richard L. , Theis Melissa A.
Published: October 2014

ANSI S12.6-2008 describes the methods for measuring the real-ear attenuation of hearing protectors. Method A, trained-subject fit, was intended to describe the capabilities of the devices fitted by thoroughly trained users while Method B, inexperienced-subject fit, was intended to approximate the protection that can be attained by groups of informed users in workplace hearing conservation programs. Inexperienced subjects are no longer considered “naïve” according to ANSI S12.6 after 12 or more sessions measuring the attenuation of earplugs or semi-insert devices. However, an inexperienced subject that has received high quality video instructions may no longer be considered “naïve” or “inexperienced” even after just one session. AFRL conducted an ANSI S12.6-2008 Method B study to determine what effect, if any, high quality instructions had on the performance of naïve or inexperienced subjects and the number of trials where the subject could still be considered naïve or inexperienced. This experiment used ten subjects who completed three ANSI S12.6 measurements using the A-B-A training order and another 10 subjects completed the study using the B-A-B training order (A = high quality video instructions, B = short “earplug pillow-pack” written instructions). The attenuation results will be discussed and the implications for ANSI S12.6.
Intra-subject fit variability using field microphone-in-real-ear attenuation measurement for foam, pre-molded and custom molded earplugs
Authors: Voix Jeremie , Le Cocq Cecile , Berger Elliott H.
Published: October 2014

In recent years, the arrival of several field attenuation estimation systems (FAES) on the industrial marketplace have enabled better assessment of hearing protection in real-life noise environments. FAES measure the individual attenuation of a given hearing protection device (HPD) as fitted by the end-user, but FAES enable predictions based only on measurements taken over a few minutes and do not account for what may occur later in the field over months or years as the earplug may be fitted slightly differently over time. This paper will use the field microphone-in-real-ear (F-MIRE) measurement technique to study in the laboratory how consistently a subject can fit and refit an HPD. A new metric, the intra-subject fit variability, will be introduced and quantified for three different earplugs (roll-down foam, premolded and custom molded), as fitted by two types of test subjects (experienced and inexperienced). This paper will present the experimental process used and statistical calculations performed to quantify intra-subject fit variability. As well, data collected from two different laboratories will be contrasted and reviewed as to the impact of trained versus untrained test subjects.
Estimation of acoustic loads on a launch vehicle fairing
Authors: Morshed Mir Md M. , Hansen Colin H. , Zander Anthony C.
Published: October 2014

During the launch of space vehicles, there is a large external excitation generated by acoustic and structural vibration. This is due to acoustic pressure fluctuations on the vehicle fairing caused by the engine exhaust gases. This external excitation drives the fairing structure and produces large acoustic pressure fluctuations inside the fairing cavity. The acoustic pressure fluctuations not only produce high noise levels inside the cavity but also cause damage such as structural fatigue, and damage to, or destruction of, the payload inside the fairing. This is an important problem because one trend of the aerospace industry is to use composite materials for the construction of launch vehicle fairings, resulted in large-scale weight reductions of launch vehicles, but increased the noise transmission inside the fairing. This work investigates the nature of the external acoustic pressure distribution on a representative small launch vehicle fairing during liftoff. The acoustic pressure acting on a representative small launch vehicle fairing was estimated from the complex acoustic field generated by the rocket exhaust during liftoff using a non-unique source allocation technique which considered acoustic sources along the rocket engine exhaust flow. Numerical and analytical results for the acoustic loads on the fairing agree well.
Prediction of acoustic environments from horizontal rocket firings
Authors: Giacomoni Clothilde , Houston Janice
Published: October 2014

In recent years, advances in research and engineering have led to more powerful launch vehicles which yield acoustic environments potentially destructive to the vehicle or surrounding structures. Therefore, it has become increasingly important to be able to predict the acoustic environments created by these vehicles in order to avoid structural and/or component failure. The current industry standard technique for predicting launch-induced acoustic environments was developed by Eldred in the early 1970s. Recent work has shown Eldred’s technique to be inaccurate for current state-of-the-art launch vehicles. Due to the high cost of full-scale and even sub-scale rocket experiments, very little rocket noise data is available. Much of the work thought to be applicable to rocket noise has been done with heated jets. A model to predict the acoustic environment due to a launch vehicle in the far-field was created. This was done using five sets of horizontally fired rocket data, obtained between 2008 and 2012. Through scaling analysis, it is shown that liquid and solid rocket motors exhibit similar spectra at similar amplitudes. This model is accurate for these five data sets within 5 dB of the measured data.
Post-flight acoustic analysis of Epsilon launch vehicle at lift-off
Authors: Tsutsumi Seiji , Ui Kyoichi , Ishii Tatsuya , Tokudome Shinichiro , Wada Kei
Published: October 2014

Acoustic level both inside and outside the fairing is measured at the first Epsilon Launch Vehicle (Epsilon-1). The obtained data shows time-varying fluctuation due to the ascent of the vehicle. Equivalent stationary duration for such non-stationary flight data is determined based on the procedure described in NASA HDBK-7005. The launch pad used by the former M-V launcher is modified for the Epsilon based on the Computational Fluid Dynamics (CFD) and 1/42-scale model tests. Although the launch pad is compact and any water injection system is not installed, 10 dB reduction in overall sound pressure level (OASPL) is achieved due to the modification for the Epsilon, comparing with the M-V. Acoustic level inside the fairing satisfies the design requirement. Acoustic design of the launch pad developed here is revealed to be effective. Prediction of the acoustics level based on the Computational Fluid Dynamics (CFD) and subscale testing is also investigated by comparing with the flight measurement.
Jet noise-based diagnosis of combustion instability in solid rocket motors
Authors: Lee Hunki , Park Taeyoung , Ohm Won-Suk , Lee Dohyung
Published: October 2014

Diagnosis of combustion instability in a solid rocket motor usually involves in-situ measurements of pressure in the combustor, a harsh environment that poses challenges in instrumentation and measurement. This paper explores the possibility of remote diagnosis of combustion instability based on far-field measurements of rocket jet noise. Because of the large pressure oscillations associated with combustion instability, the wave process in the combustor has many characteristic features of nonlinear acoustics such as shocks and limit cycles. Thus the remote detection and characterization of instability can be performed by listening for the tell-tale signs of the combustor nonlinear acoustics, buried in the jet noise. Of particular interest is the choice of nonlinear acoustic measure (e.g., among skewness, bispectra, and Howell-Morfey Q/S) that best brings out the acoustic signature of instability from the jet noise data. Efficacy of each measure is judged against the static test data of two tactical motors (one stable, the other unstable).
Some recent experimental results concerning turbulent coanda wall jets
Authors: Lubert Caroline P.
Published: October 2014

The Coanda effect is the tendency of a stream of fluid to stay attached to a convex surface, rather than follow a straight line in its original direction. As a result, in such jets mixing takes place between the jet and the ambient air as soon as the jet issues from its exit nozzle, causing air to be entrained. This air-jet mixture adheres to the nearby surface. Whilst devices employing the Coanda effect usually offer substantial flow deflection, and enhanced turbulence levels and entrainment compared with conventional jet flows, these prospective advantages are generally accompanied by significant disadvantages including a considerable increase in associated noise levels and jet breakaway. Generally, the reasons for these issues are not well understood and thus the full potential offered by the Coanda effect is yet to be realized. The development of a model for predicting the noise emitted by three-dimensional flows over Coanda surfaces would suggest ways in which the noise could be reduced or attenuated. In this paper, the results of recent experiments on a 3-D turbulent Coanda wall jet are presented. They include the relationship of SPL, shock cell distribution and breakaway to various flow parameters, and predictions of the jet boundary.
On the inversion of sound fields above a locally reacting ground for direct impedance deduction
Authors: Li Kai Ming , Tong Bao N.
Published: October 2014

A complex root-finding algorithm is typically used to deduce the acoustic impedance of a locally reacting ground by inverting the measured sound fields. However, there is an issue of uniquely determining the impedance from a measurement of an acoustic transfer function. The boundary loss factor F, which is a complex function, is the source of this ambiguity. It is associated with the spherical wave reflection coefficient Q for the reflected sound field. These two functions are dependent on a complex parameter known as the numerical distance w. The inversion of F leading to the multiple solutions of w can be identified as the root cause of the problem. To resolve this ambiguity, the zeroes and saddle points of F are determined for a given source/receiver geometry and a known acoustic impedance. They are used to establish the basins containing all plausible solutions. The topography of Q is further examined in the complex w-plane. A method for identifying the family of solutions and selecting the physically meaningful branch is proposed. Validation is provided by using numerical simulations as well as the experimentally data. The error and uncertainties in the deduced impedance are quantified.
Wavelet-like models for random media in wave propagation simulations
Authors: Wilson D. Keith , Pettit Chris L. , Vecherin Sergey N.
Published: October 2014

Simulations of wave propagation and scattering in random media are often performed by synthesizing the media from Fourier modes, in which the phases are randomized and the amplitudes tailored to provide a prescribed spectrum. Although this approach is computationally efficient, it cannot capture organization and intermittency in random media, which impacts higher-order statistical properties. As an alternative, we formulate a cascade model involving distributions of wavelet-like objects (quasi-wavelets or QWs). The QW model is constructed in a self-similar fashion, with the sizes, amplitudes, and numbers of offspring objects occurring at a constant ratios between generations. The objects are randomly distributed in space according to a Poisson process. The QW model is formulated in static (time-invariant), steady-state, and non-steady versions. Many diverse natural and man-made environments can be synthesized, including turbulence, porous media, rock distributions, urban buildings, and vegetation. The synthesized media can then be used in simulations of wave propagation and scattering.
Characterization of wind noise by the boundary layer meteorology
Authors: Lyons Gregory W. , Murray Nathan E.
Published: October 2014

The fluctuations in pressure generated by turbulent motions of the atmospheric boundary layer are a principal noise source in outdoor acoustic measurements. The mechanics of wind noise involve not only stagnation pressure fluctuations at the sensor, but also shearing and self-interaction of turbulence throughout the flow, particularly at low frequencies. The contributions of these mechanisms can be described by the boundary-layer meteorology. An experiment was conducted at the National Wind Institute's 200-meter meteorological tower, located outside Lubbock, Texas in the Llano Estacado region. For two days, a 44-element 400-meter diameter array of unscreened NCPA-UMX infrasound sensors recorded wind noise continuously, while the tower and a Doppler SODAR measured vertical profiles of the boundary layer. Analysis of the fluctuating pressure with the meteorological data shows that the statistical structure of wind noise depends on both mean velocity distribution and buoyant stability. The root-mean-square pressure exhibits distinct scalings for stable and unstable stratification. Normalization of the pressure power spectral density depends on the outer scales. In stable conditions, the kurtosis of the wind noise increases with Reynolds number. Measures of noise intermittency are explored with respect to the meteorology.
Statistical moments for wideband acoustic signal propagation through a turbulent atmosphere
Authors: Cain Jericho E. , Collier Sandra L. , Ostashev Vladimir E. , Wilson David K.
Published: October 2014

Developing methods for managing noise propagation, sound localization, sound classification, and for designing novel acoustic remote sensing methods of the atmosphere requires a detailed understanding of the impact that atmospheric turbulence has on acoustic propagation. In particular, knowledge of the statistical moments of the sound field is needed. The first statistical moment corresponds to the coherent part of the sound field and it is need in beamforming applications. The second moment enables analysis of the mean intensity of a pulse in a turbulent atmosphere. Numerical solutions to a set of recently derived closed form equations for the first and second order statistical moments of a wideband acoustic signal propagating in a turbulent atmosphere with spatial fluctuations in the wind and temperature fields are presented for typical regimes of the atmospheric boundary layer.
An investigation of wind-induced and acoustic-induced ground motions
Authors: Naderyan Vahid , Hickey Craig J. , Raspet Richard
Published: October 2014

Wind noise at low frequency is a problem in seismic surveys, which reduces seismic image clarity. In order to find a solution for this problem, we investigated the driving pressure perturbations on the ground surface associated with wind-induced ground motions. The ground surface pressure and shear stress at the air–ground interface were used to predict the displacement amplitudes of the horizontal and vertical ground motions as a function of depth. The measurements were acquired at a site having a flat terrain and low seismic ambient noise under windy conditions. Multiple triaxial geophones were deployed at different depths to study the induced ground velocity as a function of depth. The measurements show that the wind excites horizontal components more than vertical component on the above ground geophone due to direct interaction with the geophone. For geophones buried flush with the ground surface and at various depths below the ground, the vertical components of the velocity are greater than the horizontal components. There is a very small decrease in velocity with depth. The results are compared to acoustic-ground coupling case. [This work is supported by USDA under award 58-6408-1-608.]
Using an electro-magnetic analog to study acoustic scattering in a forest
Authors: Swearingen Michelle E. , Albert Donald G.
Published: October 2014

Using scale models can be a convenient method for investigating multiple scattering in complex environments, such as a forest. However, the increased attenuation with increasing frequency limits the propagation distances available for such models. An electromagnetic analog is an alternative way to study multiple scattering from rigid objects, such as tree trunks. This analog does not suffer from the intrinsic attenuation and allows for investigation of a larger effective area. In this presentation, the results from a 1:50 scale electromagnetic analog are compared to full-scale data collected in a forest. Further tests investigate propagation along multiple paths through a random configuration of aluminum cylinders representing trees. Special considerations and anticipated range of applicability of this analog method are discussed.
Modeling of sound scattering by an obstacle located below a hardbacked rigid porous medium
Authors: Wang Yiming , Li Kai Ming
Published: October 2014

The boundary integral equation (BIE) formulation takes advantage of the well-known Green’s function for the sound fields above a plane interface. It can then lead to a simplified numerical solution known as the boundary element method (BEM) that enables an accurate computation of sound fields above the plane interface with the presence of obstacles of complex shapes. The current study is motivated by the need to explore the acoustical characteristics of a layer of sound absorption materials embedded with equally spaced rigid inserts. In principle, this problem may be solved by a standard finite element program but it is found more efficient to use the BIE approach by discretizing only the boundary surfaces of the obstacles within the medium. The formulation is facilitated by using accurate Green’s functions for computing the sound fields above and within a layer of rigid porous medium. This paper reports a preliminary study to model the scattering of sound by an obstacle placed within the layered rigid porous medium. The two-dimensional Green’s functions will be derived and used for the development of a BEM model for computing the sound field above and within the rigid porous medium due to the presence of an arbitrarily shaped obstacle.
Analysis of the Green's function for a duct and cavity using geometric image sources
Authors: Bhatta Ambika , Thompson Charles , Chandra Kavitha
Published: October 2014

The presented work investigates the solution for pressure response of a point source in a two dimensional waveguide. The methodology is based on the one dimensional analytical and numerical solution of a finite channel response between two semi-infinite planes. The branch integrals representing the reflection coefficient is implemented to evaluate the pressure amplitude of the boundary effect. The approach addresses the validation of application of geometric image sources for finite boundaries. Consequently, the 3D extension of the problem for a closed cavity is also investigated.
A radical technology for modeling target scattering
Authors: Burnett David
Published: October 2014

NSWC PCD has developed a high-fidelity 3-D finite-element (FE) modeling system that computes acoustic color templates (target strength vs. frequency and aspect angle) of single or multiple realistic objects (e.g., target + clutter) in littoral environments. High-fidelity means that 3-D physics is used in all solids and fluids, including even thin shells, so that solutions include not only all propagating waves but also all evanescent waves, the latter critically affecting the former. Although novel modeling techniques have accelerated the code by several orders of magnitude, NSWC PCD is now implementing a radically different FE technology, e.g., one thin-shell element spanning 90° of a cylindrical shell. It preserves all the 3-D physics but promises to accelerate the code another two to three orders of magnitude. The talk will briefly review the existing system and then describe the new technology.
A comparison of perfectly matched layers and infinite elements for exterior Helmholtz problems
Authors: Bunting Gregory , Prakash Arun , Walsh Timothy
Published: October 2014

Perfectly matched layers and infinite elements are commonly used for finite element simulations of acoustic waves on unbounded domains. Both involve a volumetric discretization around the periphery of an acoustic mesh, which itself surrounds a structure or domain of interest. Infinite elements have been a popular choice for these problems since the 1970s. Perfectly matched layers are a more recent technology that is gaining popularity due to ease of implementation and effectiveness as an absorbing boundary condition. In this study, we present massively parallel implementations of these two techniques, and compare their performance on a set of representative structural–acoustic problems on exterior domains. We examine the conditioning of the linear systems generated by the two techniques by examining the number of Krylov-iterations needed for convergence to a fixed solver tolerance. We also examine the effects of PML parameters, exterior boundary conditions, and quadrature rules on the accuracy of the solution. [Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL850000.]
Improved model for coupled structural–acoustic modes of tires
Authors: Cao Rui , Sakamoto Nicholas , Bolton J. S.
Published: October 2014

Experimental measurements of tire tread band vibration have provided direct evidence that higher order structural-acoustic modes exist in tires, not just the well-know fundamental mode. These modes display both circumferential and radial pressure variations. The theory governing these modes has thus been investigated. A brief recapitulation of the previously-presented coupled tire-acoustical model based on a tensioned membrane approach will be given, and then an improved tire-acoustical model with a ring-like shape will be introduced. In the latter model, the effects of flexural and circumferential stiffness are considered, as is the role of curvature in coupling the various wave types. This improved model accounts for propagating in-plane vibration in addition to the essentially structure-borne flexural wave and the essentially airborne longitudinal wave accounted for in the previous model. The longitudinal structure-borne wave “cuts on” at the tire’s circumferential ring frequency. Explicit solutions for the structural and acoustical modes will be given in the form of dispersion relations. The latter results will be compared with measured dispersion relations, and the features associated primarily with the higher order acoustic modes will be highlighted. Finally, the effect of tire rotational speed on the natural frequencies of these various modes types will also be discussed.
Simulating sound absorption in porous material with the lattice Boltzmann method
Authors: da Silva Andrey R. , Mareze Paulo , Brandão Eric
Published: October 2014

The development of porous materials that are able to absorb sound in specific frequency bands has been an important challenge in the acoustic research. Thus, the development new numerical techniques that allow one to correctly capture the mechanisms of sound absorption can be seen as an important step to developing new materials. In this work, the lattice Boltzmann method is used to predict the sound absorption coefficient in porous material with straight porous structure. Six configurations of porous material were investigated, involving different thickness and porosity values. A very good agreement was found between the numerical results and those obtained by the analytical model provided in the literature. The results suggest that the lattice Boltzmann model can be a powerful alternative to simulating viscous sound absorption, particularly due to its reduced computational effort when compared to traditional numerical methods.
Extending interior near-field acoustic holography to visualize three-dimensional objective parameters of sound quality
Authors: Lu Huancai
Published: October 2014

It is essential to understand that the ultimate goal of interior noise control is to improve the sound quality inside the vehicle, rather than to suppress the sound pressure level. Therefore, the vehicle interior sound source localization and identification should be based on the contributions of sound sources to the subjective and/or objective parameters of sound quality at targeted points, such as driver’s ear positions. This talk introduces the visualization of three-dimensional objective parameters of sound quality based on interior near-field acoustic holography (NAH). The methodology of mapping three-dimensional sound pressure distribution, which is reconstructed based on interior NAH, to three-dimensional loudness is presented. The mathematical model of loudness developed by ANSI standard is discussed. The numerical interior sound field, which is generated by vibrating enclosure with known boundary conditions, is employed to validate the methodology. In addition, the accuracy of reconstruction of loudness distribution is examined with ANSI standard and digital head. It is shown that the results of sound source localization based on three-dimensional loudness distribution are different from the ones based on interior NAH.
A comparative analysis of the Chicago Transit Authority's Red Line railcars
Authors: Nottoli Chris S.
Published: October 2014

A noise study was conducted on Chicago Transit Authority’s Red Line railcars to assess the differences in interior sound pressure level between the 5000 series railcars and its predecessor, the 2400 series. The study took into account potential variability associated with a rider’s location in the railcars, above ground, and subway segments (between stations), and surveyed the opinion of everyday Red Line riders as pertaining to perceived noise. The test data demonstrated a 3–6 dB noise reduction in ongoing CTA renovations between new rapid transit cars and their predecessors. Location on the train influenced Leq(A) measurements as reflections from adjacent railcars induced higher noise levels. The new railcars also proved effective in noise reduction throughout the subway segments as the averaged Leq(A) deviated 1 dB from above ground rail stations. Additionally, this study included an online survey that revealed a possible disconnect between traditional methods of objective noise measurement and subjective noise ratings.
Tongue motion characteristics during vowel production in older children and adults
Authors: Vick Jennell , Foye Michelle , Schreiber Nolan , Lee Greg , Mental Rebecca
Published: October 2014

This study examined tongue movements in consonant-vowel-consonant sequences drawn from real words in phrases as produced by 36 older children (three male and three female talkers at each age from 10 to 15 years) and 36 adults. Movements of four points on the tongue were tracked at 400 Hz using the Wave Electromagnetic Speech Research System (NDI, Waterloo, ON, CA). The four points were tongue tip (TT; 1 cm from tip on midline), tongue body (TB; 3 cm from tip on midline), tongue right (TR; 2 cm from tip on right lateral edge), and tongue left (TR; 2 cm from tip on left lateral edge). The phrases produced included the vowels /i/, /I/, /ae/, and /u/ in words (i.e., “see,” sit,” cat,” and “zoo”). Movement measures included 3D distance, peak and average speed, and duration of vowel opening and closing strokes. The horizontal curvature of the tongue was calculated at the trajectory speed minimum associated with the vowel production using a least-squares quadratic fit of the TR, TB, and TL positional coordinates. Symmetry of TR and TL vertical position was also calculated. Within-group comparisons were made between vowels and between-group comparisons were made between children and adults.
Experimental evaluation of the constant tongue volume hypothesis
Authors: Skordilis Zisis Iason , Ramanarayanan Vikram , Goldstein Louis , Narayanan Shrikanth S.
Published: October 2014

The human tongue is considered to be a muscular hydrostat (Kier and Smith, 1985). As such, it is considered to be incompressible. This constant volume hypothesis has been incorporated in various mathematical models of the tongue, which attempt to provide insights into its dynamics (e.g., Levine et al., 2005). However, to the best of our knowledge, this hypothesis has not been experimentally validated for the human tongue during actual speech production. In this work, we attempt an experimental evaluation of the constant tongue volume hypothesis. To this end, volumetric structural Magnetic Resonance Imaging (MRI) was used. A database consisting of 3D MRI images of subjects articulating continuants was considered. The subjects sustained contextualized vowels and fricatives (e.g., IY in “beet,” F in “afa”) for 8 seconds in order for the 3D geometry to be collected. To segment the tongue and estimate its volume, we explored watershed (Meyer and Beucher, 1990) and region growing (Adams and Bischof, 1994) techniques. Tongue volume was estimated for each lingual posture for each subject. Intra-subject tongue volume variation was examined to determine if there is sufficient statistical evidence for the validity of the constant volume hypothesis. [Work supported by NIH and a USC Viterbi Graduate School Ph.D. fellowship.]
Ultrasound study of diaphragm motion during tidal breathing and speaking
Authors: Lulich Steven M. , Bonadies Marguerite , Lulich Meredith D. , Withnell Robert H.
Published: October 2014

Studies of speech breathing by Ladefoged and colleagues (in the 1950s and 1960s), and by Hixon and colleagues (in the 1970s, 1980s, and 1990s) have substantially contributed to our understanding of respiratory mechanics during speech. Even so, speech breathing is not well understood when contrasted with phonation, articulation, and acoustics. In particular, diaphragm involvement in speech breathing has previously been inferred from inductive plethysmography and EMG, but it has never been directly investigated. In this case study, we investigated diaphragm motion in a healthy adult male during tidal breathing and conversational speech using real-time 3D ultrasound. Calibrated inductive plethysmographic data were recorded simultaneously for comparison with previous studies and in order to relate lung volumes directly to diaphragm motion.
A gestural account of Mandarin tone sandhi
Authors: Yi Hao , Tilsen Sam
Published: October 2014

Recently tones have been analyzed as articulatory gestures, which may be coordinated with segmental gestures. Our data from electromagnetic articulometry (EMA) show that purported neutralized phonological contrast can nonetheless exhibit coordinative difference. We develop a model based on gestural coupling to account for observed patterns. Mandarin Third Tone Sandhi (e.g., Tone3 → T3S /_ Tone3) is perceptually neutralizing in that the sandhi output (T3S) shares great similarity with Tone2. Despite both tones having rising pitch contours, there exist subtle acoustic differences. However, the difference in underlying representation between T3S and Tone2 remains unclear. By presenting evidence from the alignment pattern between tones and segments, we show that the acoustic differences between Tone2 and T3S arises out of the difference in gestural organizations. The temporal lag between the initiation of the Vowel gesture and that of Tone gesture in T3S is shorter than that in Tone2. We further argue that underlying Tone3 is the source of incomplete neutralization between the Tone2 and T3S. That is, despite the surface similarity, T3S is stored in the mental lexicon as Tone3.
A real-time MRI investigation of anticipatory posturing in prepared responses
Authors: Tilsen Sam , Spincemaille Pascal , Xu Bo , Doerschuk Peter , Luh Wenming , Karlin Robin , Yi Hao , Wang Yi
Published: October 2014

Speakers can anticipatorily configure their vocal tracts in order to facilitate the production of an upcoming vocal response. We find that this anticipatory articulation results in decoherence of articulatory movements that are otherwise coordinated; moreover, speakers differ in the strategies they employ for response anticipation. Real-time MRI images were acquired from eight native English speakers performing a consonant-vowel response task; the task was embedded in a 2 × 2 design, which manipulated preparation (whether speakers were informed of the target response prior to a go-signal) and postural constraint (whether the response was preceded by a prolonged vowel). Analyses of pre-response articulatory postures show that all speakers exhibited anticipatory posturing of the tongue root in unconstrained responses. Some exhibited interactions between preparation and constraint, such that anticipatory posturing was more extensive in prepared- vs. unprepared-unconstrained responses. Cross-speaker variation was also observed in anticipatory posturing of the velum: some speakers raised the velum in anticipation of non-nasal responses, while others failed to do so. The results show that models of speech production must be flexible enough to allow for gestures to be executed individually, and that speakers differ in the strategies they employ for response initiation.