bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of number theory sequences in architectural acoustics
Authors: D’Antonio Peter , Cox Trevor J.
Published: February 2014

One of the challenges in architectural acoustics is to develop contemporary diffusing surfaces that complement contemporary architecture in the way that statuary, columns, and relief ornamentation complemented classic architecture. Number theory sequences invented by Schroeder [J. Acoust. Soc. Am. 65, 958–963 (1979)] and further developed by D’Antonio et al. [Appl. Acoust. 60, 143–165 (2000)] have been used for two decades to design reflection phase gratings, which provide useful sound diffusion in architectural acoustics. The use of modulation techniques, to enhance performance, and the development of proof-of-performance techniques, to evaluate their performance, will be described. The development of flat and curve optimized binary amplitude gratings will also be presented. The current state-of-the-art utilizing boundary-element multidimensional optimization to design 1- and 2-D diffusors, which incorporate aesthetic constraints, will offer a view of future design possibilities. Photos of installations using these acoustic tools will also be presented to illustrate the usefulness of these devices and their impact on architectural acoustics.
Explaining angels: The effects of nonlinearity on MLS measurements
Authors: Wright Matthew
Published: February 2014

Maximum length sequences are widely used for system identification because their autocorrelation functions are similar to those of white noise. When used to identify systems with weak nonlinearities (in particular those with convergent Volterra series representations) the resulting impulse response estimate can contain spurious echoes, or ‘‘angels’’ in radar terminology. These spurious echoes are shown to be a consequence of the fact that maximum length sequences are indeed of maximum length. It is shown that when the interaction between the nonlinearity and the number of theoretic properties of the sequence in question is understood these artefacts can be used to obtain information about the nonlinearity by calculating the Zech’s logarithm of the sequence. Examples from audiological research are discussed and ways of choosing optimal sequences are examined.
Effects of time variance on MLS measurements
Authors: Svensson U. Peter , Bjerkvik Aslak
Published: February 2014

When a system is measured with the MLS technique, any time variance in the system during the measurement will corrupt the resulting impulse response. The effects will look like extraneous noise and, depending on the type of time variance, the spectrum of the noise might be flat or increasing with frequency. Using an analogy with modulation, these effects are analyzed, and examples from measurements in rooms are presented. It is shown that the noise extracted from the initial time delay of a measured impulse response can be analyzed and compared with the background noise. This way, it is possible to detect the presence of extraneous, time-variance induced noise in an impulse response that is measured without averaging. Both intra- and interperiod time variance will cause similar effects, and a second side of the lowered signal-to-noise ratio is that the system’s impulse response has had some of its energy transformed into noise. Studies of reverberation are especially sensitive to this since the later parts of the impulse response are affected the most in typical room situations.
Error analysis of HRTFs measured with complementary (Golay) codes
Authors: Cheng Corey I. , Wakefield Gregory H.
Published: February 2014

Head-related transfer functions (HRTFs) characterize the spatial filtering properties of the external ear, and can be measured using various system identification techniques. These techniques generally assume that the system under study is time invariant (e.g., motionless). In a recent study, Zahorik presented empirical results concerning the effects of head motion on the accuracy of a popular system identification procedure based on pairs of binary stimulus signals called complementary, or Golay, codes [P. Zahorik, J. Acoust. Soc. Am. 107, 1793–1796 (2000)]. In this paper, we present a simple model for Zahorik’s work which handles not only the effects of head motion, but also measurement noise and dc bias as well. This theoretical formulation confirms the observations made by Zahorik to the extent that head motion can introduce significant errors in both the contour and fine structure of the measured HRTF log magnitude response. Further analysis of this model suggests why another popular system identification procedure based on maximal length sequences (MLSs) does not suffer from these errors. Finally, an unexpected finding is that these errors depend on the spectral shape of the specific Golay pair used during measurement. [Work supported by a grant from ONR.]
Application of pulse coding to low-level atmospheric turbulent scattering
Authors: Bradley Stuart G. , von Hunerbein Sabine
Published: February 2014

A SODAR uses atmospheric turbulence backscatter from several narrow inclined beams to estimate turbulence and wind profiles. Simple averaging-over-range and averaging-over-frequency schemes have been used in some SODAR systems, but generally code techniques are problematic because of the high fractional Doppler shift of 0–0.04. Results are given of detailed simulations, using weather-like targets, of a sequenced comb of frequencies, a chirp, and phase-encoding methods. Three Doppler-adaptive matched filters are described and evaluated against the simulated noisy atmosphere. It is found that the comb of frequencies produce the least variance in estimated Doppler wind speed, and under expected typical turbulence levels, the filter should provide Doppler winds to about 1%. These methods are evaluated in a compact SODAR configuration, with the emphasis on extracting high spatial resolution data over the lowest 20–40 m altitude. This height range has applications in pollutant and agricultural investigations.
Coherence of high-frequency signals with emphasis on environmental effects
Authors: Keranen Joe , Culver Richard L. , Bradley David L. , Reeves Jon , Lutz Steven D.
Published: February 2014

The relationship between the coherence of high-frequency, underwater acoustic signals and the upper ocean acoustic environment has been investigated experimentally. Acoustic and environmental measurements were made under ONR sponsorship (the ARL Program) during October–November 2000 at a site 30 miles off the coast of San Diego in water depths of 200 to 700 m. The transmitted signals consisted of 0.1- to 1.0-ms CW pulses and linear frequency modulated sweeps. Center frequencies of 18, 32 and 46 kHz and bandwidths from 500 Hz to 13 kHz were employed. The projector was suspended from the floating instrument platform (FLIP) at a water depth of 170 m while the receive hydrophones were suspended from a moored buoy at two different ranges of 640 and 2350 m with water depths of 200 and 700 m, respectively. Environmental measurements included water temperature, current speed and direction, directional wave height and wind speed. Temporal and spectral coherence are reported and compared with environmental patterns, theoretical predictions and prior research. [Work supported by ONR Code 321 (ARL Project).]
Comparisons of high-frequency acoustic and shallow-water ocean temperature fluctuations
Authors: Meredith Roger W. , Stanic Steven J. , Goodman Ralph R. , Kennedy Edgar T. , Pace Nickolas G.
Published: February 2014

Dynamic ocean processes produce spatial and temporal fluctuations in the ocean’s index of refraction along the propagation path that cause acoustic propagation fluctuations. This paper reports a second set of measurements designed to determine environmental limits on ping-to-ping amplitude and phase variability of direct path acoustic fluctuations in very shallow water. In September 1997, the Naval Research Laboratory in conjunction with the NATO SACLANT Undersea Research Centre conducted this series of experiments, in shallow water off American Beach, located between Pisa and Livorno, Italy. Established equations for the variance of the acoustic amplitude and phase as a function of the index of refraction variance and the ocean characteristic length scale under conditions of isotropic turbulence are used to predict acoustic fluctuations for comparison with measurements. In these results, measured phase fluctuations are more consistent with sea swell predictions than isotropic turbulence predictions. Phase fluctuations are relatively insensitive to water column stability and anomalous phase fluctuations correlate with wind direction. Amplitude fluctuations are consistent with isotropic turbulence predictions and anomalous amplitude fluctuations correlate with changing stability. [Work supported by ONR.]
Internal wave effects on ocean acoustic propagation in shallow water
Authors: Williams Duncan P. , D’Spain Gerald L. , Kuperman William A.
Published: February 2014

Complementary models are developed to investigate the effect of internal waves on ocean acoustic transmissions in shallow water. An empirical model, based on temperature variations, and a modified Garrett–Munk spectral model of internal wave generated sound speed variations are in turn inserted into an acoustic transmission model. The Garrett–Munk model is itself an empirical model most often used in deep water; in shallow water a different parametric fit is needed to model the complexity found in the environment. The internal wave effects on the acoustic field and, in particular, the patterns of the field extrema, obtained from the numerical modelling are then compared with the results of 2–3 and 5–7 kHz broadband transmissions collected during a shallow water acoustics experiment off the coast of San Diego. The two modelling approaches are used to gain insight into the effects of internal waves on the motion of dislocations; dislocations are places in the sound field where the amplitude goes to zero and so the phase becomes undetermined. [Work supported by ONR.]
Current tomography in coastal regions
Authors: Badiey Mohsen , Mu Yongke , Lenain Luc , Forsythe Stephen E.
Published: February 2014

Reciprocal acoustic transmissions have proved successful for tomography in deep water. However, relatively little effort has been focused on shallow-water environments where sound propagation and scattering takes place often over very short ranges in both the ocean (due to volume and surface) and the seabed. In these regions the effect of depth variations on sound speed is negligible and the salinity and temperature are dominant causes of volume fluctuations. Nevertheless, the methodology can still be utilized to determine the current. In a well-calibrated high-frequency (0.6–18 kHz) acoustic experiment, the range averaged horizontal current in two different directions is determined based on the differential travel times recorded from three reciprocal source–receiver stations. These tripod stations were arranged in a triangular configuration. Data were obtained in nearly isovelocity condition with slight variations in the salinity profile during several tide cycles. The feasibility of obtaining range averaged current profile in very shallow-water regions for long-term measurement is demonstrated. It is also shown that the current can be obtained accurately by utilizing not only the refracted (direct) path, but also the surface reflected arrivals during relatively calm surface conditions. The accuracy of this approach depends on the choice of center frequency and bandwidth of the signal. [Work supported by ONR and Sea Grant.]
Noise generation by breaking waves in the surf zone
Authors: Kolaini Ali R. , Means Steve
Published: February 2014

During the fall of 1997 numerous researchers investigated the physical processes of the surf zone on a barred sandy beach on the coast of North Carolina. The Naval Research Laboratory participated by deploying a 24-phone bottom-mounted hydrophone array. Measurements to characterize the sound generated by breaking waves in the surf zone were made. The sea surface elevations were simultaneously measured with pressure gauges deployed near the array. A video camera was used to capture the breaker images. The spectral analysis of the data demonstrates the presence of a strong acoustic field in the frequency range of 20 Hz to 3 kHz. Features of the spectral shapes and their relationship to the waveheight spectra are discussed. We present convincing data to support the generation of larger bubbles as being the dominant source of the low-frequency sound in the surf zone. In the stormy days the spectral level begins to attenuate at frequencies as low as 400 Hz. This provides evidence of the existence of the large number of bubbles with radii as large as a few centimeters that were kept in the water column by the turbulent structures for an extended period. Finally, the waveguide effect on the propagation of the low-frequency sound is discussed.
High-frequency ocean ambient sound: Estimating wind speed using a 150-kHz ADCP
Authors: Zedel Len
Published: February 2014

Ocean ambient sound is well correlated with wind speed for frequencies between 2 and 50 kHz. At higher frequencies it is conventional wisdom that thermal noise will dominate the wind-generated sound. Data are presented showing that background sound levels recorded by a 150-kHz ADCP demonstrate strong correlation with wind speed and with independent measurements of ambient sound (below 70-kHz frequency). When the ADCP data are calibrated using scaling factors available from the manufacturer, the observed 150-kHz sound levels are consistent with the expected ≂20 dB/decade slope of the high-frequency ambient sound spectrum. Using calibrations based on two independent deep ocean deployments, 150-kHz ADCP background sound levels can be used to estimate ocean wind speeds with an accuracy of 1.5±1.5 ms−1 for wind speeds up to 15 ms−1. [This research was funded by R. D. Instruments.]
Experimental design for geoacoustic parameter inversion
Authors: Tolsma Mischa F. P. , van den Bos Adriaan , Blacquière Gerrit
Published: February 2014

Both model-based and nonparametric classification benefit from a theoretical investigation into the information contained in reflections from the subbottom. Specifically, it is difficult to find out if the properties of a certain bottom type are identifiable with a given acoustical signal due to the complexity of the reflection models used. This problem is approached with the Fisher information matrix of the stochastic model for the measured acoustic response. The problem is unidentifiable when this matrix becomes singular. Its inverse, the Cramér–Rao lower bound, gives the best possible precision of the parameter inversion. This lower bound can be used to design appropriate signals for precise measurement of the subbottom. This has been done for a model of a surface layer with varying density given by Lyons and Orsi [IEEE J. Oceanic Eng. 23, 411–422 (1998)]. It is found that precise measurement of the reported range of model parameters requires a signal with a frequency range of 1–50 kHz. This supports the finding that broadband or multifrequency techniques are needed for the classification of layers with continually varying properties. [Work supported by TNO TPD and Rijkswaterstaat, The Netherlands.]
Modal mapping in range and azimuth for shallow-water waveguides
Authors: Becker Kyle M. , Frisk George V.
Published: February 2014

It is well established that the normal mode solution for sound propagation in shallow water is a function of the local waveguide properties. Much work has been done on the inverse problem where the local modes are measured and used as input data for geoacoustic inversion methods. In the range-dependent case, short sliding-window transform methods based on the Hankel transform have been implemented to extract the corresponding range-varying wave number spectra. A major objective of this work is to extend the range-dependent work to fully three-dimensionally varying environments. Recently, experiments were conducted using cw sources operating in the frequency range 20–475 Hz. The acoustic field was measured on an array of freely drifting hydrophone buoys equipped with GPS navigation. Using the complex pressure measured on these synthetic aperture horizontal arrays, local mode information is extracted as a function of range and azimuth from the source. Emphasis is placed on modal variability for tracks both along and across bathymetric contours at several frequencies. [Work supported by ONR.]
Hot topics in architectural acoustics: New materials
Authors: Tinianov Brandon D. , Shaw Neil A.
Published: February 2014

While both new metrics for measuring sound and analytical software programs for predicting sound performance have proven to be powerful tools of architectural acoustics, new acoustical materials have allowed us to further engineer these sensitive soundscapes. These developments embrace several areas of contemporary acoustical materials. HVAC liners have seen the addition of fiber-free alternatives to traditional linings. New solutions include coated polyimides and melamine foams. In electroacoustics, materials that have improved performance are now replacing some old standbys. PEN materials such as Kaladex are finding more acceptance for use in tweeter domes and microphone elements. Liquid crystal polymer fibers, such as Vectran, which can be used instead of aramid and carbon fibers, offer similar performance improvement for wet lay-up direct radiator transducer cones. Absorptive panels have moved beyond fabric wraps. They are now paintable and can mimic typically reflective treatments. Finally, diffusers have shown advances in both acoustical performance and geometries that better blend with aesthetic goals. These new surfaces consist of a wide range of surface type including modulated reflection phase gratings, binary amplitude gratings, and most recently boundary-element optimized surfaces of constant or variable impedance. Each of these exciting developments are reviewed in this presentation.
Hot topics in structural acoustics: Optical imaging of surface vibrations—Some new developments and applications
Authors: Berthelot Yves H.
Published: February 2014

Laser Doppler vibrometry is routinely used for a vast range of applications to measure surface vibrations in the nanometer range. Some new developments include the use of laser vibrometers with continuous tracking on moving targets, the detection of the vector displacement of a surface (either with multiple beam interferometry or with a photo-emf probe), and the direct measurement of torsional vibrations on rotating shafts. Electronic speckle pattern interferometry (ESPI) is a full-field optical technique that is also commonly used to image surface vibrations. An interesting development of ESPI is electronic shearography. Some applications of these optical techniques will be discussed. These include calibrations of transducers and MEMS devices, imaging of rotating parts, mapping of structural intensity, characterization of the dynamic response of viscoelastic materials, as well as some more exotic applications such as damage assessment of frescoes and painting, three-dimensional vibration imaging of the ossicular chain in cats, and dynamic characterization of human teeth.
Physically informed stochastic modal sound synthesis
Authors: Cook Perry R.
Published: February 2014

A general and flexible sound synthesis method is described, which is based on controlled random excitations and parameter modifications of resonant filters. Parameters can be derived from simulations of particle/friction systems, from data extracted from physical experiments, from signal analysis (a developing yet still open topic of research), or from simple experimentation and ‘‘tweaking.’’ The algorithm has proven convincing and useful for modeling the sounds of many common objects and interactions in music and everyday life. Particle system examples include maracas, windchimes, coins in a pocket, ice cubes in a glass, shoveling gravel, breaking glass, etc. Friction systems include coins rolling along a table, squeaking floor panels and hinges, etc. Aside from being flexible and realistic, the algorithm is extremely efficient by nearly any standard of computation or memory use. Most exciting is the ability to drive and modify the parameters in real time, resulting in virtual objects and systems which are ‘‘playable’’ in musical performance, or easily useable for sound effects in games and virtual reality.
Scat singing generation using a versatile speech manipulation system, STRAIGHT
Authors: Kawahara Hideki , Katayose Haruhiro
Published: February 2014

A set of procedures to generate scat singing by manipulating a small set of seed voices using a speech manipulation system called STRAIGHT [Kawahara et al., Speech Commun. 27, 187–207 (1999)] is proposed. F0 adaptive spectral smoothing based on a second-order cardinal spline combined with an F0 extractor based on a fixed-point analysis from filter center frequencies to the output instantaneous frequency enables the STRAIGHT system to generate a highly natural manipulated singing sound. Group delay manipulation for generating the excitation source signal introduces new control flexibility in source characteristics. F0 trajectories are generated using a dynamical model based on F0 feed-forward control regulated by auditorily mediated feedback [Kawahara et al., Vocal Fold Physiology, edited by H. Fletcher and P. Davis, pp. 263–278 (1996)]. Effects of the spectral interpolation function and interactions between F0 and the spectral envelope are also discussed and demonstrations of a scat chorus are presented. [Work supported by CREST and MEXT, Japan.]
Enhanced digital music glove
Authors: Chong Uipil , Lee Changwon
Published: February 2014

Most of electronic music works are created off line using studio editing techniques and hand-crafted computed-generated or sequence control streams [M. Goldstein, Systems, Man, and Cybernetics, 1998 IEEE International Conference, Vol. 2, pp. 1076–1079]. In this paper a digital music glove (DMG) system playing musical scores in real time is implemented. Furthermore, the present commercial product, TouchGlove, connected to an I-CubeX Digitizer [http://www.infusionsystems.com/products] becomes a finger tip controller for drum machines, but this DMG, by selecting any instrument in the sound card through the interface with the player can be used for many other instruments including the drums. Additionally, this new system controls the pitch, duration, chorus, reverberation, and velocity of sound by updating the pitch wheel change message, polyphonic aftertouch, and channel pressure according to the MIDI file generation. The computer, according to the status of the fingers and foot switches, generates the sound signals and sends them to the speaker systems through the application C++ program and MIDI message. [Work supported by Korean Ministry of Communication and Information.]
On the structural acoustic modeling of cetacean mammals by the finite element method
Authors: Marcus Martin H. , Gaumond Charles F.
Published: February 2014

Requirements for the computational modeling of a mammal are presented. In general, meticulous attention to details of its anatomy is needed. The extent of detail must go beyond size and shape to include an inventory of each organ and bone. Also, some components are unique to a species, such as the melon in dolphins. The elastic properties of several biological materials must be determined. A few of these materials are bone, connective tissue, and fat. The compressional sound speeds of the above materials in humans are easily available. Transverse sound speeds and anisotropic information are somewhat less abundant. The compressional and transverse sound speeds are sufficient to model isotropic materials, such as fat, but anisotropic information is necessary for materials that have a grain, such as connective tissue. The modeling of bone may require an understanding of the separate layers of bone, which are quite different from each other. A simple FEM model of a dolphin is presented. The model is run over a range of frequencies to examine the nature of resonances that can be found in such a structure. It is found that the bone structure plays a significant role in the resonance behavior. [Work supported by ONR.]
Effects of ultrasound on the heart
Authors: Dalecki Diane
Published: February 2014

Ultrasound and lithotripter fields can affect the function of the heart. A single, pulse of ultrasound can produce two qualitatively different effects on the heart. When the pulse is delivered during systole, it can cause a reduction in the developed aortic pressure. Evidence suggests that this effect arises from an action of radiation force on the cardiac tissues. A premature cardiac contraction results when the ultrasound pulse is delivered during diastole. The threshold for producing a premature contraction with a 5-ms pulse at 1.2 MHz is on the order of 5 MPa. The presence of ultrasound contrast agents in the vasculature significantly enhances the effect. When Albunex is present, the pressure threshold for the production of a premature cardiac contraction is reduced by nearly an order of magnitude. In addition, when contrast agents are present, premature contractions can be produced with diagnostically relevant pulse durations and pressure amplitudes. Other researchers have observed premature contractions in humans using clinical imaging devices.
Bubble and cavitation-assisted hyperthermia (BACH)
Authors: Holt R. Glynn , Edson Patrick A. , Yang Xinmai , Roy Ronald A.
Published: February 2014

Rapid hyperthermia resulting in tissue necrosis has proven to be a useful therapeutic modality for clinical application of high-intensity focused ultrasound. At therapeutic intensities, the hyperthermia is often accompanied by bubble activity. In vitro and in vivo experiments alike have shown that under certain conditions bubble activity can give rise to a doubling of the heating rate. With a view toward harnessing the energy-concentrating effects of bubbles to do useful clinical work, we report the results of experiments and modeling for the dynamic and thermal behavior of bubbles subjected to 1-MHz ultrasound at megapascal pressures. The dominant heating mechanism depends on bubble size, medium shear viscosity number, and frequency-dependent acoustic attenuation. The bubble size distribution, in turn, depends on insonation control parameters (acoustic pressure, pulse duration), medium properties (notably dissolved gas concentration), and bubble-destroying shape instabilities. The evidence obtained so far points to a range of control parameters for which bubble-enhanced heating can be assured. [Work supported by DARPA.]
Cardiopulmonary function in rats with lung hemorrhage induced by exposure to superthreshold pulsed ultrasound
Authors: Kramer Jeffery M. , Waldrop Tony G. , Frizzell Leon A. , Zachary James F. , O’Brien William D.
Published: February 2014

The study’s objective was to assess cardiopulmonary function in rats exposed to superthreshold ultrasound known to produce lung hemorrhage. In nine rats, five ultrasound-induced lesions were produced in the left lung, and in six rats, five ultrasound-induced lesions were produced on each lung. Lesions were induced using superthreshold conditions (3.1-MHz, 1.7-kHz PRF, 1.3-μs pulse duration, 60-s exposure duration, 17-MPa in situ peak rarefactional pressure, MI of 5.8). Lesions volumes were measured and approximately 3.4% and 7.9% of the lung was damaged in one-sided and two-sided exposures, respectively. Cardiopulmonary data were quantified before and 30 min after the last exposure: measurements included pulsatile arterial pressure, heart rate, end-tidal carbon dioxide, respiratory rate, and blood gases. In one-sided exposures, there were no statistically significant differences in cardiopulmonary function, pre- and post-exposure. In two-sided exposures, statistically significant differences were detected for arterial pressure and arterial pO2. We concluded that damage of one lung does not affect peripheral indicators of lung function because of functional respiratory capacity retained in unexposed lung. However, when two lungs were damaged, the functional respiratory reserve was decreased to the point where rats were unable to maintain resting levels of arterial pO2. [Work supported by NIH Grant No. HL58218.]
Repair of lung lesions following exposure to pulsed ultrasound
Authors: Zachary James F. , Frizzell Leon A. , O’Brien William D.
Published: February 2014

This is the first study to examine the long-term effects of ultrasound-induced hemorrhage in lung. The reparative responses were characterized in a rat lung following exposure to pulsed ultrasound. Forty five adult rats were exposed at two sites, the left sixth and ninth intercostal spaces [3.1 MHz, in situ (at the pleural surface) peak rarefactional and compressional pressures of 17.0 MPa and 39.7 MPa, respectively, 1.7-kHz PRF, 1.2-μs pulse duration, and MI of 5.7]. Lung lesions were evaluated macroscopically and microscopically at 0, 1, 3, 5, 7, 10, 13, 16, 19, 23, 27, 30, 34, 37, and 44 days post exposure. Macroscopic lesions progressed between 0 and 44 days post exposure from large bright red ellipses of hemorrhage to small areas of light yellow–brown discoloration. Microscopic lesions progressed between 0 and 44 days post exposure from areas of acute alveolar hemorrhage, to areas of intense cellular proliferation, to areas with small quantities of hemosiderin pigment and septal fibrosis. Alveoli returned to near normal morphology and functional diameter by 44 days post exposure. Under our exposure conditions, lesions induced by ultrasound do not appear to have long term residual effects in lung. [Work supported by NIH Grant No. HL58218.]
Evaluation of the acoustic boundary conditions at the pleural surface that causes ultrasound-induced lung hemorrhage
Authors: O’Brien William D. , Miller Rita J. , Kramer Jeffery M. , Waldrop Tony G. , Frizzell Leon A. , Zachary James F.
Published: February 2014

In a previous study [J. Acoust. Soc. Am. 108, 1290 (2000)], the acoustic impedance difference between intercostal tissue and lung was evaluated as a possible explanation for the enhanced lung damage with increased hydrostatic pressure, but the hydrostatic-pressure-dependent impedance difference alone could not explain the enhanced occurrence of hemorrhage. A hypothesis was suggested that the animal’s breathing pattern might be altered as a function of hydrostatic pressure, which in turn might affect the volume of air inspired and expired. The acoustic impedance difference between intercostal tissue and lung would be affected with altered lung inflation, thus altering the acoustic boundary conditions. In this study, the rat’s respiratory system was inhibited, a ventilator was used to control lung volume, and superthreshold ultrasound exposures of the lungs were conducted (3.14-MHz, 1000-Hz PRF, 1.3-μm pulse duration, 10-s exposure duration, 16.9-MPa in situ peak rarefactional pressure, MI of 5.8). Deflated lung was more easily damaged than inflated lung. The acoustic impedance difference between intercostal tissue and lung is much less for the deflated lung condition, suggesting that the extent of lung damage is related to the amount of acoustic energy that is propagated across the pleural surface boundary. [Work supported by NIH Grant No. HL58218.]
Potential new transducer materials: Ferromagnetic shape memory alloys showing 6% field-induced strain
Authors: O’Handley Robert C. , Henry Christopher P. , Feuchtwanger Jorge , Marioni Miguel , Tello Pablo G. , Bono David , Allen Samuel M.
Published: February 2014

Very large field-induced strains (e=6%) have been reported for Ni–Mn–Ga single-crystal ferromagnetic shape memory alloys (FSMAs) at room temperature. While these materials show the conventional thermoelastic shape memory effect upon transformation to the high-temperature phase, the magnetic field-induced strain occurs fully within the low-temperature, martensitic phase by twin-boundary motion. Fields of 320–400 kA/m (4–5 kOe) are sufficient to produce the maximum strain under opposing stresses of order 1 MPa. The blocking stress observed here is approximately 2 MPa but can be up to 10 MPa. An ac test system is described that applies an axial load to the sample via a spring. A magnetic field applied transverse to the load causes axial extension. Result indicate that the effective magnetostrictivity, d31 (output strain per unit field), is little changed over the actuation-frequency range accessible with our present power supplies, namely 320 Hz. The hysteresis in the strain-versus-field curves can be as large as 100 kA/m but in some samples is much less. The field dependence and stress dependence of the strain are well accounted for by the simple thermodynamic model. All parameters for the model can be measured from stress-versus-strain curves and magnetization-versus-field curves.
A quantitative theory of magnetization and magnetostrictive hysteresis in Terfenol-D
Authors: Armstrong William D.
Published: February 2014

New theory presented successfully reproduces and explains the experimental magnetoelastic hysteresis behavior of Terfenol-D. It is assumed that a very large number of individual domain wall translation events combine to produce each measurable domain transformation in a macroscopic sized sample. Each individual domain wall may be expected to suffer some level of domain wall translation inhibition; however, the severity of the inhibition will spatially vary. It is therefore assumed that the presence of defects in the material increases the directional magnetization potential of subsequent domain states within a process, and distributes nontrivial probabilities of the occupation of 〈111〉 type domain states in a parameter selected, inverse exponential form familiar from the study of statistical thermodynamics. The increased magnetization potential of subsequent high magnetostriction and high magnetization states retards their occupation until higher intensity applied magnetic fields are produced, thus shifting the increasing applied magnetic field curve in a positive field direction and shifting the decreasing applied magnetic field curve in a negative field direction in a form consistent with experiment.
Noise ordinances: The good, the bad, and the ugly; An overview of more than 200 existing noise ordinances
Authors: Les Blomberg
Published: February 2014

The Noise Pollution Clearinghouse (NPC) has collected more than 200 community noise ordinances and state noise regulations and is in the process of putting them in the NPC Online Law Library. This paper provides an overview of existing noise ordinances, examining what’s covered and what’s missing, as well as what’s enforceable and what’s unenforceable. In addition, the paper will include a summary of how communities are handling various noise problems such as impulsive noise, boom cars, lawn equipment, air conditioners, etc. Finally, new and emerging issues in community noise control and enforcement are discussed.
Progress on a Model Community Noise Ordinance Standard
Authors: Brooks Bennett M. , Finegold Lawrence S.
Published: February 2014

The American National Standards Institute (ANSI) Accredited Standards Committee S12, Noise, has charged its Working Group (WG) 41 to develop a model community noise ordinance standard. This ordinance, or group of ordinances, should be suitable for various urban, suburban, and rural communities. This new standard will include, at a minimum, metrics, criteria, and an enforcement methodology. The model ordinance(s) could be used by local authorities around the United States as a basis for their own ordinances or zoning performance regulations. To date, WG 41 has developed a draft ordinance with three sets of criteria. The first set includes familiar A-weighted sound pressure level (SPL) limits for noise emissions at a receiver’s property line. The other criteria sets include additional limits on low frequency noise emitters, such as industrial plants, musical entertainment at night clubs, and noise from automobiles. One criteria set uses C-weighted SPL noise limits. The other places limits on the allowable noise levels in specific octave bands, including the low frequency (bass) octave bands. The relative advantages of each criteria set are discussed and guidance is provided to assist local government officials in selecting the most appropriate approach for their community.
An experiment below the wave diffraction limits with an acoustic sink: the ideal time reversal experiment
Authors: de Rosny J. , Fink M.
Published: February 2014

Time reversal has successfully demonstrated the ability to focus acoustic waves in the laboratory for several years. However, the minimal focal spot dimension is always larger than half the wavelength, which is in agreement with diffraction limit. We will show that this behavior is related to the presence of a diverging wave that is always created after the convergent wave collapse at the focus. In a time reversal experiment, by replacing the initial source by its time reversed image, we may eliminate this diverging wave. Such a process allows to create an acoustic sink which absorbs the converging wave. Thus, with the elimination of the diverging wave, the focal spot can become much smaller than the one predicted by the diffraction limit. In this paper, we present the first experimental demonstration of an acoustic sink and we observe focal spot smaller than 1/14 the wavelength.
Numerical investigation of sound diffraction by arbitrarily-shaped thin obstacles
Authors: Suh S. , Mongeau L. , Bolton J. S.
Published: February 2014

The sound diffracted by rigid, thin, arbitrarily-shaped obstacles was investigated using a commercially available boundary element code. The numerical procedures were validated by computing the sound field in the shadow region of a rigid circular disk. The results were compared with predictions from available analytical expressions and with experimental data. Excellent agreement was obtained between the predicted and the measured insertion loss values. Scattering from objects having various random shapes, previously suggested by other researchers [Menounou, Bailey, and Blackstock, J. Acoust. Soc. Am. 107, 103–111 (2000)], was then investigated. The performance of these objects as sound barriers was compared to that of regularly shaped obstacles. Potential application to linear sound barriers will be discussed. [Work supported by INDOT, JTRP, FHWA, and SQDH.]
Giant acoustic band gaps in a two-dimensional periodic system of fluids
Authors: Kushwaha M. S. , Djafari-Rouhani B.
Published: February 2014

Periodic binary systems can give rise to genuine acoustic stop bands within which sound and vibrations remain forbidden. Extensive band structures for two-dimensional (2D) periodic arrays of air cylinders in water have been computed. Complete, multiple, huge stop bands are found for both square and hexagonal arrangements. The lowest stop bands are largest for a range of filling fraction 10%≤f≤55%, with a gap/midgap ratio of 1.8. The most interesting finding of the present investigation is that the low-frequency, flat passbands for a perfectly periodic system correspond to the discrete modes of a single airy cylinder. This is attributed to the low filling fraction and huge density contrast in air and water. It is stressed that such a simple inhomogeneous system as made up of air and water exhibits the largest stop bands ever reported for 2D and/or 3D elastic as well as dielectric composites.
Rayleigh wave propagation in a curved elastic waveguide
Authors: Harris John
Published: February 2014

A JWKB asymptotic expansion describing in-plane elastic waves is used to approximate a Rayleigh-like wave guided within an elastic waveguide whose curvature is small and changes slowly over a wavelength. The two lowest eigenmodes in a curved guide, taken together, constitute the Rayleigh-like wave. It is shown that this wave lies in the shadows of four closely spaced, virtual caustics. If the curvature becomes too large, the virtual caustic closest to the outer surface enters the guide, after which Rayleigh-like propagation ceases. This wave is dispersive: The dispersion arises both from the confinement within the guide and from the curvature. Propagation in both a thin and a thick guide are examined. Propagation into an environment of increasing curvature is studied, for both waveguides, to exhibit the influence of nearby caustics.
A coherent method for the measurement of the dispersive curves of elastic waveguides
Authors: Zhang Hailan , Dai Shuwu , Zhang Chengyu
Published: February 2014

A coherent technique is presented to measure the dispersive curves of elastic waveguides. Waveforms received at several positions along the propagation path are transformed into the frequency domain by FFT. The phase thus obtained has been truncated into the range of the principle value. The true phase difference between the nearest and the farthest waveforms is restored from the truncated phases by summing all phase differences between the contiguous waveforms which are picked up at the positions close enough that the phase differences between contiguous waveforms are less than 4. The restored phase is then used to calculate the phase velocity at different frequencies. The use of the phase information makes the measurement more precise and stable than traditional noncoherent methods. The method is applied to measure the dispersive curves of an aluminum plate with rough surfaces and the result is compared with that of the smooth plate. It is found that the effect of the roughness is the attenuation of the amplitude and slight reduction of the phase velocity. These results agree with the prediction of a theoretical model based on the perturbation method. [Work supported by Nature Science Foundation of China, No. 19774062.]
Numerical study on 3D acoustic field in borehole generated by eccentric sources
Authors: Zhang Hailan , Shen Jianguo
Published: February 2014

Two new tools for well logging, circumferential acoustic device (CAD) and sector bond test (SBT), are used in oil fields in which the transmitting transducers are either pressed onto or located close to the borehole wall and the acoustic field thus generated is three-dimensional. We calculated the acoustic field along a fluid-filled cylindrical borehole in an elastic medium generated by a point source in the hole and close to the wall. The method called real axis integral is used. The spectrum of the acoustic field in the domain of the frequency and axial wave number is expressed as an infinite series of Bessel functions. Its truncation is analyzed which is dependent on the frequency and radius of the borehole. In the calculation Bessel functions up to the 60th order are used. The spectrum is first calculated and then transformed to the time-space domain. The waveforms at some receiving positions and some snapshots are given in the paper. It is shown that the field consists of the direct wave, reflected waves, and interface longitudinal and transverse waves. [Work supported by Nature Science Foundation of China, No. 19974059.]
Effect of harmonic structure of environmental noises on vowel perception
Authors: Ishizuka Kentaro , Aikawa Kiyoaki
Published: February 2014

This work reports new findings on the effect of the harmonic structure of environmental noises on vowel perception. An experiment was conducted to examine how listeners perceive natural vowels under noisy environmental conditions at around −2 dB in SNR. Vowels were presented at 60-dB SPL. Eight types of noise were used: white noise and seven types of harmonic structured noises each having the same flat spectral envelope and energy. The fundamental frequency of the vowels was about 260 Hz. A pure tone of 260 Hz and its harmonics (A), a pure tone of 520 Hz and its harmonics (B), and a pure tone of 260 Hz and its odd harmonics (C) were used as noises. Mean identification scores for the white noise and noises (A), (B), and (C) were 33.73%, 59.93%, 66.80%, and 60.27%, respectively. The spectral envelope has been widely used for automatic speech recognition as the feature parameter. However, experimental results demonstrated that perceptual identification scores are significantly different depending on the detailed spectral shape of the noise. The difference between noises (B) and (C) suggests that the even harmonic components of the vowel make less of a contribution to noisy vowel perception than the odd harmonic components.
The effect of spectral contrast enhancement on speech perception in hearing-impaired listeners
Authors: Müsch Hannes , Pavlovic Chaslav
Published: February 2014

The effect of enhancing the spectral contrast of clean and noisy speech on intelligibility and listening comfort in hearing-impaired listeners is explored. Spectral contrast refers to the difference between the amplitude of spectral peaks and valleys in a short temporal window. A method of enhancing spectral contrast similar to that suggested by Bunnell [H. T. Bunnell, J. Acoust. Soc. Am. 88, 2546–2556 (1990)] was implemented in a simulated hearing aid with fast acting multiband wide-dynamic-range compression. The aid’s frequency response was adjusted to accommodate the individual listeners’ hearing losses. The effect of several degrees of spectral contrast enhancement on phoneme identification in quiet and in the presence of speech-spectrum-shaped noise was measured. In addition, listeners’ preferences for several degrees of spectral contrast enhancement were assessed in an A/B comparison of spectrally enhanced connected speech in quiet and in the presence of cafeteria noise. The experimental results will be reported and their implications for the use of spectral contrast enhancements in hearing aids will be discussed.
A model for predicting speech intelligibility
Authors: Müsch Hannes , Buus So/ren
Published: February 2014

A statistical-decision theory based model for predicting speech intelligibility is introduced. This model, which we call the speech-recognition sensitivity (SRS) model, aims at predicting speech-recognition performance from the long-term average speech spectrum, the masking excitation in the listener’s ear, the linguistic entropy of the speech material, and the number of response alternatives available to the listener. Unlike articulation-index (AI) models, the SRS model can account for synergetic and redundant interactions among spectral bands of speech. It also accounts for effects of linguistic entropy and number of response alternatives on intelligibility scores without resorting to the empirically determined ad hoctransformations employed by AI models. The effects of linguistic entropy are modeled by an entropy-dependent central noise, which modifies the listener’s identification sensitivity to the speech. The effect of the number of response alternatives on the test score is a direct consequence of using statistical decision theory. The SRS model also appears to predict how the effect of linguistic entropy varies with the filter condition and how linguistic entropy and language proficiency interact with the signal-to-noise ratio. Fits of the SRS model to data from the literature and consonant-discrimination data collected in our laboratory will be presented. [Work supported by NIH and SigmaXi.] a)Current affiliation: GN ReSound Corporation.