bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluctuations of high-frequency acoustic pulses in shallow water
Authors: Wilson Marcia A.
Published: October 2005

High-frequency acoustic propagation and scattering experiments were conducted near Panama City, FL, in August of 1991 and 1993, and in Eckernforde Bay, Germany in May 1993. The Panama City site has a hard sand bottom, but the bottom of Eckernforde Bay is soft mud. Environmental measurements were made in conjunction with acoustic measurements. The water depth at both sites was approximately 30 m. The sources and the receiver arrays were mounted 6 to 8 m from the bottom and were separated by about 90 m. A bottom reflected signal was detected in Panama City, and in some cases, in Germany. The soft mud bottom of Eckernforde Bay, however, absorbed most of the energy directed toward it. Data from pulses 1.0 ms in length, at 1-s intervals, will be shown for frequencies from 20 to 180 kHz. Means, standard deviations, and coefficients of variation of 100 or 150 pulses for each frequency characterize two scales of temporal variability in the data. Data from several of the receiving hydrophones are compared. Spatial variability is shown and related to modeled and measured changes in the sound velocity profile. [Work supported by the Office of Naval Research.]
Three-dimensional acoustic propagation in a waveguide of variable thickness
Authors: Coury Robert A. , Siegmann William L. , Collins Michael D.
Published: October 2005

The parabolic equation (PE) method has proven to be an efficient method for solving range-dependent ocean acoustics problems. Recently an extension has been made to handle two-dimensional waveguides of varying thickness. This type of modeling is necessary when the upper boundary of the waveguide is allowed to change, as for example in propagation up a beach or in an ocean with a gradually undulating surface. The adiabatic mode PE is another extension that has been developed to solve global scale, three-dimensional propagation problems. In this paper, the three-dimensional adiabatic mode PE is extended to handle problems involving a gradual range dependence in the overall thickness of the waveguide. The modified adiabatic PE has several applications. On relatively small scales, it may be applied to solve three-dimensional beach acoustics problems or to model diffraction by an island. It may also be applied to solve global-scale seismoacoustic problems in which topography on the continents plays a significant role. [Work supported by ONR.]
Modeling a directional source in an underwater acoustic waveguide
Authors: Evans Richard B.
Published: October 2005

Techniques for modeling a single frequency directional source in an underwater acoustic waveguide are applied and tested. The techniques are evaluated, with regard to accuracy and efficiency, for use in prediction of source performance. Existing discussions of the topic often focus on one technique. Here, the goal is to consider a larger class of methods. They range from mode matching in the far-field, of the source, to the direct application of a free-space beam pattern at range zero. The techniques are applied to problems that arise due to sparseness of calibration data and the inappropriateness of a free-space beam pattern for waveguide applications. [Work supported by ARA.]
Comparison of theory and experiment of acoustic bottom penetration in a shallow water site
Authors: Chotiros Nicholas P. , Stern Morris , Mautner Adrienne , Kristensen Åge , Michelozzi Enzo
Published: October 2005

Signals from a spark source in water and received by acoustic sensors buried in a sandy sediment in a site off La Spezia, Italy, are compared to theoretical model predictions from a fast field model. The model is a modification of OASES 1.6 that includes Biot’s poroelastic wave propagation model. The received acoustic pulses are compared to determine the transfer function from the in-water source to the buried acoustic sensors. From a theoretical point of view, the sediment is treated as a poroelastic solid governed by Biot’s theory of acoustic propagation. It is predicted to support two acoustic waves. Comparisons are made between theory and experiment. [Work supported by Office of Naval Research, Ocean Acoustics Program, code 321 OA, under the initiative for basic research in the physics of moderate to high frequency acoustics.]
Probabilistic range dependence in a numerical average underwater acoustic propagation method
Authors: Oba Roger M.
Published: October 2005

A computational method for forward propagation of the Helmholtz equation has been developed for numerically computing average complex pressure field in a single pass. It used sound-speed profiles be piecewise probabilistically independent in finite sized range steps to calculate transmission loss and phase for the average solutions in the continuous wave case. This required that the uncertainty is probabilistically modeled within range intervals as ensembles of sound speeds which were independent from one range step to the next. This method can be modified to represent certain cases for which there is statistical dependence in range. This can be achieved by nonlocal averaging over several range steps. The inter-relation of range sound speed and statistical dependence will be considered, and results from numerical experiment will be shown. Similar calculations allow the calculation of growth of standard deviation over range. This modification can also be considered in the limit of small intervals of uncertainty. [Work supported by Naval Research Laboratory and the Office of Naval Research.]
Solution of the acoustic wave equation in underwater environments using an improved finite difference method
Authors: Zingarelli R. A.
Published: October 2005

At the fall meeting, a finite difference solution to the acoustic wave equation for real pressure fields, its implementation, and several applications were presented. An improved differencing scheme developed by Cole etal. has subsequently been incorporated into this numerical model. Using this method runtimes and memory usage for cw problems have been reduced by factors of 10 and 5, respectively, with no loss of accuracy or computational parallelism, making its computational requirements similar to other solution techniques. Because the weightings of various grid elements in this method are based on the source frequency, its usefulness in TD calculations with pulsed sources is limited. Despite this, some low-frequency TD calculations are possible. Applications and limitations of the higher-order method will be presented. [Work supported by ONR.]
A method for computing adiabatic modal wavefronts
Authors: Westwood Evan K.
Published: October 2005

An approach has been developed for determining the modal wavefronts that allow normal modes to be propagated adiabatically in smoothly range-dependent ocean waveguides. The method is motivated by the fact that propagation in an isospeed penetrable wedge is accurately modeled by ‘‘adiabatic wedge modes,’’ which are identical to the usual ‘‘vertical modes’’ except that the wavefront curvature induced by the sloping bottom is taken into account. For the wedge, the wavefronts are assumed to be circular arcs centered on the wedge apex. In order to generalize the notion of wedge modes to other types of range dependence, wavefronts are constructed numerically such that the derivative of each mode in the direction normal to its wavefront, ∂φ/∂s, is zero. The result is that the first-order modal coupling coefficients, which involve ∂φ/∂s integrated over depth, are zero, and the adiabatic algorithm can be used. The quantities ∂φ/∂z and ∂φ/∂r versus depth are used to obtain the directions normal to the wavefront. For the isospeed penetrable wedge, wavefronts computed in this manner do indeed correspond closely to the expected circular arcs. [Work supported by the ARL Internal Research and Development Program.]
Reverberant sound in one-, two-, and three-dimensional spaces
Authors: Strong William J. , Copley David C.
Published: October 2005

The method of images was used to calculate impulse responses for a large (30 m×23 m×18 m) three-dimensional space, a large (30 m×23 m) two-dimensional space, and a large (30 m) one-dimensional space. The reverberation time for these spaces was set to approximately 1.5 s and all sound absorption took place at the walls. Similar impulse responses were calculated for small rooms whose dimensions were one-tenth those of the large rooms and whose reverberation times were smaller. A short (10-s) sample of singing was recorded in an anechoic chamber and then convolved with the various impulse responses. The resulting six reverberated samples of singing were recorded binaurally on audio tape. Graphs of the impulse responses and the taped examples will be presented. (Although the taped examples will be presented via loudspeakers, they are best heard via earphones.)
Measuring aircraft noise impact in a low signal-to-noise environment
Authors: Higbie Nathan B.
Published: October 2005

The agreements negotiated for the new Denver Airport present an interesting example of how legal considerations can govern how noise measurements are made. The agreements stipulate certain noise limits on communities surrounding the airport. These limits are expressed in aircraft Leq(24), and are placed at 102 points, some over 15 miles away. There are financial penalties if any values are exceeded for a year. A signal-to-noise measurement problem resulted since modeled values of the aircraft Leq(24) were lower than measured Leq(24) community noise. The problems that needed solving were detection and quantification of aircraft noise in low signal-to-noise, and assignment of each noise event to its source. Arrays and other spatial techniques were proposed, but were too costly and would not meet Type 1 measurement requirements. A floating threshold was implemented so that noise events could be detected for any ambient condition. To date, all airport monitoring systems have used a fixed threshold since signal-to-noise is not a problem. The events are then correlated with the flight track data using a statistical pattern recognition algorithm whose parameters are optimized for each monitor location.
Integrated noise model (INM) 5.0
Authors: Plante Jake A.
Published: October 2005

The ability to accurately assess and predict noise exposure is an increasingly important factor in the design and implementation of airport and airspace improvements. To meet this challenge, the Federal Aviation Administration (FAA) Office of Environment and Energy (AEE) is undertaking a series of operations research initiatives to improve the modeling and other quantitative methods used to evaluate aviation noise impacts. A major effort in recent years has been the redesign of the integrated noise model (INM 5.0) in Windows. While rewritten in a different computer language, the noise calculation algorithms in 5.0 remain essentially the same as V4.11, based on the SAE-AIR-1845 methodology. There are, however, many technical enhancements to the computer code which provide faster run times and more accurate noise predictions. Among the enhancements are (1) a noise calculation module that is between 1.5 and 6 times faster depending on the study case, (2) a new exposure fractioning algorithm for improved accuracy, (3) additions to the aircraft database, (4) new metrics (e.g., Lmax, Leq(n), user-defined), (5) user-defined profile generation for the study of noise abatement landings and approaches, (6) a lateral track dispersion methodology, and (7) GIS analysis with Census, CAD, NFDC, elevation, and ARTS radar data capabilities.
Wide area modeling of en route aircraft noise
Authors: Reddingius Nicolaas , Ebersole Michael
Published: October 2005

Most aircraft noise modeling methods have been so carefully focused on airport-based policies and analyses that they are awkward to use for other purposes. For example, standard noise modeling software is of limited utility for characterizing en route noise exposure or assessing the potential impacts on nonurban populations. The National Park Service has developed alternative methods for modeling aircraft noise and its impacts in outdoor recreational settings. Software created to support Public Law 100-91 analyses permits users to perform observer-based (rather than source-based) aircraft noise analyses; to consider the masking provided by localized sources when modeling noise impacts over areas of tens of thousands of square kilometers; to take terrain relief into consideration; and to present results in the form of map layers for a geographic information system.
Applications of Boston-Logan’s noise monitoring system
Authors: Timmerman Nancy S.
Published: October 2005

Boston’s Logan International Airport has an advanced noise monitoring system consisting of noise, aircraft track, weather, and land use information. The system has been used to support INM 5.0 validation efforts, to improve INM track definitions, to assist in assessing aircraft departure procedures, and to isolate the types of aircraft affecting various communities. Examples of the newer applications pursued will be presented.
Basic model for acoustic reflection and absorption from multilayered underwater, sound-attenuating composites
Authors: Brill Donald , Santiago Armando , Gaunaurd Guillermo
Published: October 2005

To reduce backscattered acoustic echoes from submerged elastic structures, these are routinely covered with viscoelastic (i.e, sound-absorbing) composite multilayers. This old and well-studied area is revisited and a basic, simple, analytical model to predict how these composites behave when tested is presented. The multilayer can have N layers of homogeneous (or inhomogeneous) materials with different elastic/viscoelastic properties, all bonded to each other, and the whole, to a backing (metal) plate. The structure is fluid-loaded and externally excited with plane, monochromatic sound waves. We have developed a ‘‘propagator matrix’’ approach that yields the reflected, transmitted, and absorbed waves from the structure as a product of the N transfer matrices of the layers. The approach is computerized and used to evaluate and plot the reflectivity and/or absorptivity of the structure as a function of frequency for pertinent (often complex) values of the layers’ material parameters and thicknesses. The predictions are experimentally verified for selected test cases (i.e., N=2,3), and the enhancement of the echo-reduction plots at the resonance frequencies of the layers is noted. Additional complexities can be handled in a straightforward fashion. [Work partially supported by the IL-IR Program of the CDNSWC.]
Dynamic mechanical analysis ASTM/ISO
Authors: Peraro James S.
Published: October 2005

Dynamic mechanical analysis (DMA) is used to characterize the behavior of a variety of materials. The development of the methodology for conducting these tests is the responsibility of ASTM D20.10.15 on dynamic mechanical properties. Similar activities are conducted in ISO under the jurisdiction of subcommitte ♯2. The test methods being developed cover a broad range of responses (temperature, frequency, and time) as well as stress states (i.e., tensile, bending, shear, and compression). Instruments have been developed which have greatly simplified the measurement of dynamic mechanical properties. The use of advanced computers and microprocessors and improved computer programs, to properly digest this information, have increased the demand for more sophisticated test results. The ease of developing this test data has resulted in DMA being a requirement in material characterization and specifications. The demand of the global market for this information has increased the interest of both ASTM and ISO members to develop standardized test methods for conducting and reporting DMA test data.
The loss factor of beams with thick constrained layers
Authors: Garrelick Joel
Published: October 2005

A constrained layer beam, consisting of a base beam, viscoelastic layer, and cover plate, is analyzed with each layer modeled using the two-dimensional equations of viscoelasticity. The (three) layers are ‘‘cascaded,’’ enforcing appropriate equations of continuity. A shape factor is invoked to account for the effect of the beam’s finite width on the dilatational wave speed of the constrained layer. Composite loss factors are first defined solely for the freely propagating (modified) flexural wave-number component of the response and then in terms of the overall drive point response of the beam to a mid-span load. At low frequencies results are compared to values obtained from Kerwin’s [1959] classic thin layer model. At the other end, high frequency asymptotic limits are obtained by viewing the constrained layer as being semi-infinite and/or ‘‘fuzzy.’’ Finally, predictions are compared to measurements performed on a steel-Nitrile-steel beam [Junger etal., 1986].
A dynamic absorber and a side-branch resonator for vibration and noise control
Authors: Prasad M. G. , Zanone E. , Abbattista S.
Published: October 2005

This paper presents two demonstrations. The first one deals with control of vibrations of a motor under unbalance excitation. A dynamic absorber is used to reduce vibrations of the motor. The resonance phenomenon and mode shapes in vibrating systems will be shown. The second system is a finite length duct with an acoustic source (speaker) at one end. A Helmholtz resonator as a side-branch device is used to reduce the noise radiating from the open-end of the duct. Audible effects due to acoustic resonances in the duct and side-branch resonator system will be presented.
Demonstrations of acoustic resonant systems
Authors: Sabatier James M. , Raspet Richard , Denardo Bruce
Published: October 2005

The phenomena of ‘‘sonic wind,’’ viscous drag, and high ‘‘Q’’ in resonant acoustic systems is demonstrated. The first two are the well-known Christmas tree balls and rotating cup demonstration. The third is a large heavy tuning fork which rings for a very long time after being struck.
Demonstration of room acoustic parameters using a digital multieffects processor
Authors: Haas Steven M.
Published: October 2005

Digital multieffects processors is a useful tool to study and demonstrate room acoustic parameters. Live and prerecorded speech and audio program will be processed through a multieffects device and reproduced through a pair of loudspeakers. The listeners will be allowed to hear the effect of varying a number of acoustic parameters that occur in natural spaces. These include: reverberation time, echoes, diffusion of sound, high frequency decay rate, initial time delay gap, spaciousness, and depth. A brief explanation of each parameter will be given before its audible demonstration. The means in which an architectural acoustician designs an acoustic space with these parameters in mind will also be discussed.
Spatial Fourier-transform method for measuring reflection coefficients at oblique incidence. II. Experimental results
Authors: Tamura Masayuki , Allard Jean F. , Lafarge Denis
Published: October 2005

A method using spatial Fourier transforms for measuring the plane-wave reflection coefficient at oblique angles of incidence has been proposed in an earlier paper [M. Tamura, J. Acoust. Soc. Am. 88, 2259–2264 (1990)]. The present paper gives experimental verification of the method. Experimental results are shown for two types of samples: a perfectly absorbing plane (an imaginary plane in the air) and a layer of a polyurethane foam backed by a hard plywood board. The measured results are generally in good agreement with the theoretical value (for the first sample) or with the results calculated from the acoustical parameters of the material (for the second sample). The agreement shows the usefulness of the method for measuring acoustic properties of absorbent materials.
The perceptual evaluation of F excursions in speech as evidenced in liveliness estimations
Authors: Traunmüller Hartmut , Eriksson Anders
Published: October 2005

In order to learn how listeners evaluate F0 excursions, a set of experiments was performed in which subjects had to estimate the liveliness of utterances. The stimuli were obtained by LPC analysis of one natural utterance that was modified by resynthesizing F0, the formant frequencies, and the time scale in order to simulate some of the natural extra- and paralinguistic variations that affect F0 and/or liveliness, namely the speaker’s age, sex, articulation rate, and voice register. In each case, the extent of the F0 excursions was varied in seven steps. The results showed that, as long as the stimuli appeared to have been produced in the modal register (of men, women, and children), listeners judged F0 intervals to be equivalent if they were equal in semitones. When the voice register was shifted without adjustment in articulation, listeners appeared to judge the F0 excursions in relation to the spectral space available below F1. The liveliness ratings were found to be strongly dependent on articulation rate and to be affected by the perceived age of the speaker which, with the manipulated stimuli used here, turned out to be significantly affected by the sex of the listener.
Jovian acoustics and Comet Shoemaker–Levy 9
Authors: Collins Michael D. , McDonald B. Edward , Kuperman W. A. , Siegmann William L.
Published: October 2005

A technique for solving three-dimensional ocean acoustics problems is modified to handle Jovian acoustics problems and applied to model propagation from the impact sites of the fragments of Comet Shoemaker–Levy 9. The adiabatic mode parabolic equation is generalized to media with fluid flow for the case of low Mach number. The vertical dependence of sound speed and density and the latitude dependence of the zonal winds are known from Voyager data. The acoustic model predicts that energy that radiated from the impact sites was vertically concentrated within a sound channel that includes the cloud layers and horizontally concentrated into intense caustics by refraction associated with wind shear. Although nonlinear effects are important near the impact sites, the spatial distribution of energy should be qualitatively represented by the linear acoustics results.
Distortion product otoacoustic emissions created through the interaction of a spontaneous otoacoustic emission and an externally generated tone
Authors: Norrix Linda W. , Glattke Theodore J.
Published: October 2005

An SOAE (f2) and one XT (f1) were used to create 2 f1−f2 DPOAEs. External tones were applied to the ear canal at SOAE/f1 ratios between 1.08 and 1.22 XT/SOAE intensity differences varied from 0 to approximately 50 dB SPL. DPOAE amplitude and SOAE suppression characteristics were variable across subjects. However, the following trends were noted: (1) At larger frequency ratios, DPOAE generation and SOAE suppression were associated with greater XT SPLs; (2) DPOAE growth functions were characterized by slopes <1 dB/dB, a maximum, rollover and disappearance into the noise floor; (3) maximum DPOAEs were observed at frequencies approximately 1/2 oct below the SOAEs; (4) DPOAE maximums were associated with a significant amount of SOAE suppression. The results are consistent with DPOAEs created using two low-level tones [Brown and Gaskill, in MechanicsandBiophysicsofHearing (Springer-Verlag, Berlin, 1990)] and can be interpreted by considering suppression in a nonlinear cochlear model [Zwicker, 163–176 (1986).] [Work supported by NIH-NIDCD grant 1 P60 DC-01409 and Univ. of AZ Graduate Student Development Fund.]
The effect of background noise on the precedence effect
Authors: Chiang Yuan-Chuan , Freyman Richard L.
Published: October 2005

The current experiment examined the influence of noise on the precedence effect, focusing on the importance of noise source location. Listeners seated in an anechoic chamber judged whether the image produced by a lead-lag pair of 4-ms noise bursts (2-ms delay) was to the left or right of midline. The lag loudspeaker was fixed at 45° to the left or right, while the lead loudspeaker was positioned at a variable number of degrees to the opposite side. The angle of the lead loudspeaker producing 50% judgements favoring the lead was used to estimate its perceptual weighting relative to the lag. This weighting, which was quantified using the c metric developed by Shinn-Cunningham etal. [ 2923–2932 (1993)], strongly favored the lead when the sounds were presented in quiet. The value of c was reduced markedly when background broadband noise was introduced from 0° or 180° angles, supporting previous findings of a weakened precedence effect in noise. When the background noise source was off-midline, or lead-lag pairs of noise sources were used, the effects of noise on c were complex and asymmetric. [Work supported by NIH ♯DC01625.]
Active control of acoustic intensity in a duct
Authors: Reichard Karl M. , Swanson David C. , Hirsch Scott M.
Published: October 2005

A frequency-domain implementation of the filtered-x algorithm is used to actively control acoustic intensity in a duct. The frequency-domain filtered-x algorithm uses FFT’s of the necessary signals to compute the transfer function of the optimal control filter. A version of the algorithm has been adapted to use acoustic intensity, computed from the cross spectrum from two pressure microphones, as the error signal. The results of experiments conducted in a duct are presented which demonstrate the effects of measurement error and control source configuration on controller performance.
Large-scale circulation and variability in the northwest Atlantic as determined by long-range reciprocal acoustic transmissions
Authors: Chester David B. , Worcester Peter F. , Cornuelle Bruce D. , Dushaw Brian D.
Published: October 2005

Reciprocal acoustic transmissions are analyzed to determine the general circulation of the region between Bermuda and Puerto Rico. Six tomographic transceivers were moored from March 1991 to March 1992 in the region centered at 25°N, 66°W during the Acoustic Mid-Ocean Dynamics Experiment (AMODE). Large-scale range averages (over 300 to 700 km sections) of temperature and velocity and large-scale areal averages of relative vorticity have been estimated through inversion of tomographic travel time data. The barotropic and first baroclinic mode are well resolved by the acoustic sampling, with poorer resolution of the second baroclinic mode. The 300-day mean circulation of the region indicates a band of westward flow of a few cm/s in the surface and thermocline waters. An active and resolvable mesoscale eddy field is present, with variability typically dominated by motions with spatial scales of 100–200 km, and with a general westward drift of mesoscale eddy features. The tomographic observations have been combined with a quasi-geostrophic numerical ocean model to further investigate eddy kinematics in the region. The model is used both to evaluate the evolution of the barotropic and baroclinic flow field, and to illustrate the utility of tomographic data for constraining a quasi-geostrophic model. [Work supported by ONR.]
The optimization of profiled diffusers
Authors: Cox Trevor J.
Published: October 2005

Methods have been developed to produce profiled diffusers that create a large amount of diffusion. The methods are iterative and required the development of a new parameter to measure diffusion. Achieving scattering independent of angle has been attempted over a wide bandwidth. The methods are also applicable to other diffusion criteria. The diffusers consists of a series of wells of the same width but of different depths similar to Schroeder diffusers. Applications include concert halls, theatres, and studio monitor rooms. The new diffusers have been shown to create better, more uniform diffusion than the previous designs of Schroeder. This is due to the new designs being reliant on accurate boundary element prediction methods rather than more approximate techniques.
The input/output formula: A theoretical approach to the fitting of personal amplification devices
Authors: Cornelisse Leonard E. , Seewald Richard C. , Jamieson Donald G.
Published: October 2005

There is a growing trend for hearing aids to incorporate wide dynamic range compression. The input/output (I/O) hearing aid formula, presented in this report, is a general frequency-specific mathematical approach which describes the relationship between the input level of a signal delivered to a hearing aid and the output level produced by the hearing aid. The I/O formula relates basic psychoacoustic parameters, including hearing threshold level and uncomfortable listening level, to the electroacoustic characteristics of hearing aids. The main design goal of the I/O formula was to fit the acoustic region corresponding to the ‘‘extended’’ normal auditory dynamic range into the hearing-impaired individual’s residual auditory dynamic range. The I/O approach can be used to fit hearing aids utilizing linear gain, linear compression or curvilinear compression to a hearing-impaired individual’s residual auditory area.
Low-frequency propagation modes in a liquid-filled elastic tube waveguide
Authors: Lafleur L. Dwynn , Shields F. Douglas
Published: October 2005

Axisymmetric propagation in a liquid-filled elastic tube waveguide is considered, with emphasis on the two modes existing down to zero frequency. Previous work by Del Grosso is used as the basis of the theoretical description of modal phase velocities and particle displacement profiles in such waveguides. It is shown that certain combinations of material properties can produce a mode which, in the zero frequency limit, has plane-wave motion in the liquid. Two examples of waveguides with very different wall compliance, aluminum/water and PVC/water, are studied numerically and experimentally. Numerical calculations are used to show the frequency dependence of phase velocity in all waveguide modes and the radial dependence of complex particle displacement amplitude in the two low-frequency modes (ET0 and ET1). Contrasting behavior in the two waveguides is seen—approximate plane-wave motion in the liquid occurs in the ET0 mode of the aluminum/water waveguide, but in the ET1 mode of the PVC/water waveguide. Experimental measurements of the frequency dependence of phase velocity in the ET0 and ET1 modes of these waveguides are also presented. Good agreement with numerical predictions is obtained in both cases, although experimental difficulties more severely limit the frequency range of measurement in the PVC/water waveguide.
A limitation of the Biot–Gardner theory of extensional waves in fluid-saturated porous cylinders
Authors: Johnson David Linton , Kostek Sergio
Published: October 2005

It is demonstrated that the Gardner theory of attenuation of extensional modes in porous fluid-saturated cylinders is not the low frequency limit of the Biot theory in that geometry. The calculated attenuation within the Gardner approximation is much less than that predicted by the full Biot theory unless the permeability is less than a specific crossover value which depends on the size of the rod: κxc=(ηφaVE/√8Kf). Typically κxc≊1 Darcy for water-saturated porous media of radius a=1 cm having extensional speeds VE on the order of 1 km/s. For permeabilities larger than κxc the attenuation predicted by the full Biot theory can be orders of magnitude larger than that predicted by the Gardner approximation, even in the limit as the frequency tends to zero.
Distortion product otoacoustic emission delay measurement in human ears
Authors: O Mahoney Cliodna F. , Kemp David T.
Published: October 2005

The measurement of distortion product otoacoustic emission (DPOAE) delay using the phase gradient method is discussed. A short f2 sweep paradigm is described. Its merits are discussed and comparisons made with other methods. Using sweeps of less than 4%, consistent and reliable measurements were obtained from 12 normal ears, except for a few isolated measurements. Investigation of these apparent anomalies indicated that the short f2 sweep method was sensitive to the localized effects of narrow distortion product intensity notches and spontaneous emissions. It is possible that middle ear pressure instability or some local change in the cochlea sometimes compounded the situation. The intersubject range (63% of the mean) of DPOAE delay values was greater than the range of values observed due to measurement variability (5.6% of the mean) or intrasubject variability (8.5% of the mean) demonstrating that the method can detect real differences between ears. However, comparison with previous work shows that caution is needed in interpreting these data, as all DPOAE phase methods provide only partial latency values. The physical interpretation depends on both the stimulus sweep used and the origin of DPOAES. Our data shows that f1 sweep derived latency is lower than f2 sweep data by more than 20%. Caution also needs to be exercised when comparing cochlear traveling wave delay, as inferred from electrophysiological data, with that obtained from DPOAE delay measurements.
Borehole wave propagation in three dimensions
Authors: Cheng Ningya , Cheng C. H. , Toksöz M. N.
Published: October 2005

In this paper the three-dimensional finite difference method is used to simulate borehole wave propagations in an isotropic as well as an anisotropic formation. The finite difference results agree excellently with the analytic solutions of a point force source in the transversely isotropic medium. The finite difference synthetics are also in very good agreement with the discrete wave-number solutions for fluid-filled borehole wave propagation. The finite difference synthetics are compared with ultrasonic lab measurements in a scaled borehole model. The borehole is drilled along the X axis in an orthorhombic phenolite solid. Both monopole and dipole logs agree well. The observations of the shear wave splitting in the dipole logs are confirmed by the finite difference simulations. The 3-D finite difference method is applied to the fluid-filled borehole wave propagation in the tilted isotropic formation and in the orthorhombic phenolite formation. In a borehole drilled along the Z axis in a phenolite formation, the monopole log shows the P wave traveling with velocity vzz. There are no shear-pseudo-Rayleigh wave arrivals. The dipole log is dominated by the single slow flexural mode. In a borehole drilled along the Y axis in a phenolite formation, the monopole log shows the P wave traveling with velocity vyy. There are shear-pseudo-Rayleigh wave arrivals shown on the monopole seismograms between P and Stoneley waves due to the shear wave anisotropy. The anisotropy also causes the shear wave splitting in the dipole log. The two shear wave arrivals correspond to the fast and the slow flexural modes.
Individual differences in the glottalization of vowel-initial syllables
Authors: Dilley Laura , Shattuck-Hufnagel Stefanie
Published: October 2005

Speakers of American English often glottalize the onset of a vowel-initial syllable, and recent work has shown that this is particularly likely to occur when the syllable is located at prosodically significant locations, such as the beginning of an intonational phrase, or at a pitch accent [Pierrehumbert and Talkin Labphon II, 1992; Dilley etal., 2978 (A) (1994)]. Analysis of speech read by 4 different professional radio news announcers and 4 nonprofessional speakers shows (a) the importance of prosodic structure in determining the occurrence of glottalization holds across speakers, (b) speakers are differentially likely to glottalize overall, and (c) speakers are differentially likely to glottalize in different prosodic contexts. For example, the 4 FM radio newscasters showed overall glottalization rates of 41%, 38%, 22%, and 7%, and some speakers were more likely to glottalize reduced vowels than others were. The implications of these patterns of variation for speech recognition and synthesis, as well as for models of speech production planning, will be discussed. [Supported in part by a grant from NIDCD.]
Numerical simulation of gas cavity response to shock waves
Authors: Ding Zhong , Gracewski S. M.
Published: October 2005

An understanding of cavitation phenomena including the response of a gas cavity in liquid to a time-dependent pressure wave is important in a large range of situations. In the paper, the response of a gas cavity in water to shock waves is analyzed using the arbitrary Lagrangian–Eulerian technique. An axisymmetric model is used in the numerical simulation of a gas cavity response to both weak shocks (p/p0≤300, with p0=0.1 MPa) and strong shocks (p/p0 ranges from 5000 to 20 000). An artificial viscosity to capture the shock was developed. A simple, stable, and adaptive mesh generation technique was designed to generate finer meshes at higher pressure gradients. The shock propagation, rarefaction, and transmission were analyzed over the entire computational domain. When impacted by a weak shock, a gas cavity will collapse almost spherically creating a large pressure within the gas and the surrounding liquid due to the rapid compression of the gas. When impacted by a strong shock, a gas cavity will collapse with a jet penetrating the opposite side of the interface with a speed as high as 2000 m/s.
Acoustical ecological risk
Authors: Margulies Timothy S.
Published: October 2005

Risk-based prioritization and decision making has been implemented by the U. S. EPA in several areas to assure quality and consistency of risk and environmental assessment and to identify areas to reduce uncertainty. This talk will review the elements of risk assessment and risk management and will compare the paradigms for considering primarily ionizing radiation and mechanical radiation to assess existing and projected risks to human health and the environment. Treatment of uncertainty propagation in model parameters, such as latin hypercube Monte Carlo sampling and by adjoint methods, as well as decision-making approaches including statistical hypothesis testing will be discussed for comparing alternatives to control unwanted sounds.
The influence of bubble clouds on surface scattering strengths
Authors: Nicholas Michael , Odgen Peter M. , Erskine Fred T.
Published: October 2005

One of the most comprehensive sets of surface scattering strength measurements was made during the CST experiments between August 1988 and May 1993, covering a frequency range from ∼70 to ∼1500 Hz. An extensive set of environmental measurements (including bubble cloud measurements) collected on several of these experiments make this a unique data set for examining the effect of sub-surface bubble clouds on surface backscattering strength. Analysis of these data have shown that wind speed, while the most important environmental descriptor, cannot by itself explain some important differences in the surface scattering strengths measured for the different CST experiments. These differences appear to be linked to the sub-surface bubble clouds which, in turn, are influenced by the dynamics of the upper layers of the ocean. Latest results from the continuing analysis of the surface scattering and bubble cloud data will be presented which illustrate the influence of the bubble clouds and indicate how the stability of the upper layers of the ocean play a role in distributing those bubble clouds. [Work supported by ONR.]
Scattering of sound by sound within the interaction zone: Approximate solutions
Authors: Westervelt Peter J.
Published: October 2005

The exact second-order transient solution to the interaction of an arbitrary wave with a plane wave is given by Westervelt [P. J. Westervelt, 3320 (1994)]. Let the arbitrary wave be χ(x0−m̂⋅r), a plane wave traveling in the m̂ direction. In this case σ=(1−n̂⋅m̂)−1χ and the solution to Eckart’s equation becomes ρsc20=E12 +(1−n̂⋅m̂)−1(Λ+2n̂⋅m̂)=cos θ ∇2ψ2, which is identical to Eq. (10) of Westervelt [P. J. Westervelt, 934 (1957)] provided the substitutions ψ2=1/2(w1w2)−1W12 and n̂⋅m̂=cos θ are made. It is asserted that this exact solution serves as an approximate solution to the far-field interaction of arbitrary sources. This is done by allowing m̂ and n̂ to be space dependent. As an example, the exact solution for the cardioid wave χ=(4πr)−1[n̂⋅m̂(G,0+Gr−1)−G,0] interactions with a plane wave is obtained from σ=−(4πr)−1G,0, where G=G(x0−r) and m̂=rr−1. In the far field of the cardioid source, σ=(1−n̂⋅m̂)−1χ, as in the plane wave–plane wave interaction, thus demonstrating the assertion.
Acoustical design criteria for the guitar
Authors: Richardson Bernard E.
Published: October 2005

The acoustical function of the guitar is now reasonably well understood. The various modes of the vibrating string couple to structural and air-cavity modes of the body. These in turn interact with the surrounding air thus enhancing the radiation of energy from the string to the listener. The modal properties of the instrument are thus of central importance in determining its sound quality. It is of great interest to the maker to know how these modal properties might be adjusted to produce instruments of pre-determined sound quality. This paper will give a resume of experimental and theoretical work undertaken at Cardiff to determine formal relationships between physical properties of the instrument (construction and materials) and psychoacoustical evaluation of guitar tones. The aim of this work is not to define parameters of an idealized ‘‘perfect’’ instrument—that would be a futile goal. Instead, the aim is to identify those features of construction which have a perceptible effect on the guitar’s sound and to define acceptable limits for modal properties. The latter will be discussed theoretically, but taped demonstrations will be presented to emphasize the points being made.
The relationship between aided articulation indices, performance, and subjective satisfaction with programmable and conventional hearing aids
Authors: Saunders Gabrielle H. , Cienkowski Kathleen M.
Published: October 2005

The Articulation Index (AI) was developed as a method for predicting speech recognition performance from objective measurements. It should therefore be an efficient method for predicting and comparing potential user benefit from different hearing aids. In this study subjects wore six different hearing aid fittings for 3 months each. Performance on a number of speech tests was measured at the start and end of each 3-month period and self-rated satisfaction with each hearing aid was assessed. AIs for each hearing aid fitting were calculated from real ear aided gains. The relationship between the AIs, performance, and satisfaction will be presented and the efficacy of using the AI as a predictor of performance and satisfaction will be discussed.
Preliminary values of clarity and intelligibility for small auditoria, meeting, and teleconference rooms
Authors: Campanella Angelo J.
Published: October 2005

Clarity (C80) and intelligibility (D50), normally measured for large auditoria, provide an alternative to reverberation time (RT60) to evaluate the acoustical performance of many critical smaller rooms. A Larson Davis 2900 real time analyzer and sound level meter was used to record a rapid sequence of octave band spectra from impulsive sound. A PC program was written to extract this data from the LD2900 and process it into C80, D50, and TCT values. Experimental values were obtained in ten different rooms including auditorium, church, theater, lab, chapel, gym, music, rehearsal, teleconference, and living rooms. Room qualities varied from good through those in need of correction for the intended room use. Measured quantities were compared with opinions on existing room performance to provide preliminary desirable ranges of C80, D50, and TCT according to room use.
Collinear ultrasonic four-wave mixing mediated by a suspension
Authors: Kwiatkowski Christopher S. , Marston Philip L.
Published: October 2005

In previous work, ultrasonic four-wave mixing mediated by a suspension was observed by oblique Bragg reflection of a high-frequency probe wave from a periodic grating [H. J. Simpson and P. L. Marston, 2244(A) (1991)]. The grating in the number density of suspended polymer microspheres was induced by the radiation pressure of a standing pump wave. In the present investigation, a different geometry is examined which has potential advantages for the investigation of this class of mediated interactions of sound with sound. The new geometry uses a high-frequency probe beam that is collinear with the axis of the pump standing wave. The Bragg signal for this geometry is amenable to analysis with transfer matrices. The interaction investigated has potential applications to the acoustical probing of suspensions. [Work supported by the Office of Naval Research.]
Detection of decrements and increments in sinusoids at high overall levels
Authors: Moore Brian C. J. , Peters Robert W. , Glasberg Brian R.
Published: October 2005

Thresholds for the detection of decrements in level of sinusoidal signals were measured as a function of duration (2, 4, 6, 10, and 14 ms), level (70, 80, and 90 dB SPL) and frequency (250, 500, 1000, 2000, and 4000 Hz). Seven normally hearing listeners were tested at each frequency. Thresholds for detecting a 10-ms increment in level were also measured. The sinusoids were presented in a background noise intended to mask spectral splatter associated with the decrement or increment. Performance improved with increasing frequency for all decrement and increment durations. Performance also tended to improve with increasing level at 2000 and 4000 Hz. The results were analyzed using a four-stage model consisting of an auditory filter, a nonlinearity, a sliding temporal integrator, and a decision mechanism. The analysis indicated that the improved performance with increasing frequency and increasing level can be attributed mainly to changes in the detection process following the temporal integrator rather than changes in the equivalent rectangular duration (ERD) of the temporal integrator. The ERD varied little with changes in frequency and level. At higher frequencies and levels a smaller change is required at the output of the integrator for threshold to be reached.
Effects of military aircraft noise on residential property sale prices near Langley Air Force Base
Authors: Fidell Sanford , Tabachnick Barbara , Silvati Laura , Cook Brenda
Published: October 2005

An empirical, market-based method was developed to assess whether military aircraft noise exposure has affected residential property values in the vicinity of Langley Air Force Base over the last two decades. Multiple regression models that accounted for the bulk of the variance in property sale prices were developed and validated for independent samples drawn from areas of Hampton, VA exposed to levels of military aircraft noise lower than DNL=60 dB. The predictive performance of these models was indistinguishable in areas of Hampton exposed to military aircraft noise in excess of DNL=65 dB. Maps constructed by geo-coding property sale locations permitted spatial comparisons of property values with aircraft noise exposure contours. These maps confirmed the independence of the spatial distributions of property values and aircraft noise contours in the vicinity of Langley Air Force Base.
Pressure effects on the dynamic and static properties of perforated elastomers used in underwater acoustics
Authors: Beretti Stephane , Audoly Christian , Guillaussier Philippe
Published: October 2005

The microinhomogeneous materials made with air-filled cavities in viscoelastic matrices, have many possible uses in underwater acoustics including anechoic coatings, acoustic decoupling, or reflectors for arrays. Theoretical models are necessary to predict the acoustic properties of these materials by evaluating the properties of the equivalent homogeneous material, as a function of frequency, pressure, and temperature. During recent works an abnormal effect of the applied pressure on these materials was noted: The plot of the longitudinal sound speed and of the bulk modulus, versus static pressure, had the lowest value for 10 to 20 bars of applied pressure, instead of a regular increasing plot predicted by the models [G. Gaunaurd etal., 173–177 (1984)]. Different results, including test panel measurement in a tank, or measurement of the static and dynamic bulk modulus agree with this consideration. Theoretical models to predict the static and dynamic effective material properties as a function of the pressure were compared with these results.