bluuebunny/crossref_metadata_2025 huggingface dataset:
Underwater acoustical testing facilities and capabilities at Applied Research Laboratories, The University of Texas at Austin (ARL:UT)
Authors: Stockton James E.
Published: October 2005

ARL:UT’s first test facility was established in 1952. Facilities and capabilities have expanded since that time to the present day configuration: two rectangular concrete tanks housed inside ARL:UT’s main laboratory building, two cylindrical wooden tanks located outside at the main laboratory, and a lake facility, known as Lake Travis Test Station (LTTS), located approximately 18 road miles from the main laboratory. Underwater acoustic transducers from small probes to units weighing up to 30 tons can be accommodated. Measurement systems currently available are both analog and digital and provide the capability for receive sensitivity, both voltage and current transmit responses, and directivity (beam) patterns over a nominal frequency range of 100 Hz to 2 MHz. Water depths range from 8 to 40 ft in the test tanks and nominally from 80 to 150 ft at LTTS. Test distances up to nominally 60 ft can be achieved in the test tanks and up to several miles at LTTS.
An experimental investigation of masked-threshold and just-notice-level differences of early reflection in a room
Authors: Okano Toshiyuki , Hidaka Takayuki
Published: October 2005

Masked-threshold-level (MTL) and just-notice-level differences (jnld) are two of the most basic and important attributes of early reflection in a room’s sound field because they are deeply related with necessary accuracy of sound field simulation and with subjective efficiency of early reflection. MTL and jnld of reflection were measured using a music source signal. Various types of sound fields that were composed of multiple reflections were tested. MTL of a reflection rises when an additional reflection is added because of the increase of masking by the additional reflection. The rise of MTL is larger than the energy summation low, which is basically the same as the addition of simultaneous masking. The rise of MTL influences jnld of reflection. The jnld becomes larger as the reflection level becomes closer to its MTL, and is expressed as a function of LT, which is the reflection level relative to its MTL.
Pseudo-Stoneley waves predicted by shell theory for the thin spherical shell via proper fluid loading
Authors: Dean Cleon E. , Werby Michael F.
Published: October 2005

By including the effect of fluid loading for the thin spherical shell in a proper manner, so-called shell theories can predict the water-borne pseudo-Stoneley waves described extensively in the literature. Shell theories give reasonably good results for the motion of a bounded elastic shell by using the assumption that various parts of the shell move together in some reasonable manner. Without proper fluid loading, however, shell theories do not predict the pseudo-Stoneley resonances observed in nature and predicted by exact theory. With proper fluid loading, as well as rotary inertia and translational and rotary kinetic energy terms, a shell theory can exactly predict these water-borne resonances. These resonances are predicted by the shell theory and compared with results from exact elastodynamical calculations. [Work supported by ONR/NRL and by ONT Postdoctoral Fellowship Program.]
Toward local effective parameter theories using multiresolution decomposition
Authors: Steinberg B. Z. , McCoy John J.
Published: October 2005

Using the recently developed theory of multiresolution decomposition, a formulation that governs the response of a linear dynamical system with nonstationary microscale heterogeneities is reduced to two coupled formulations, one governing the response smoothed on an arbitrary chosen reference scale with the response fine details as forcing, and one governing the response details with the response smooth as a forcing. By substituting the formal solution of the latter in the former, a new framework, specifically tuned to macroscale variations of the response, in which the effects of the nonstationary microscale heterogeneity are described via a macroscale-effectivematerialoperator, is obtained. Localization of across-scale couplings, as well as the dependence of the response smooth and the effective material operator on the microscale and macroscale geometries, are investigated via general asymptotic considerations and specific numerical examples. The latter concerns the response of a fluid loaded elastic plate with nonstationary microscale mass heterogeneity.
Visualization of 3-D palate shape for an enhanced electropalatography system
Authors: Chiu W. S. C. , Shadle Christine H.
Published: October 2005

Electropalatography (EPG), a system for real-time measurement of tongue–palate contact during speech, uses a stylized 2-D output system which, though useful for speech therapy and research, omits the actual spatial location of the contacts. This paper presents an enhanced EPG (eEPG) system that combines standard EPG data and digitized palate shape data to display the tongue–palate contact pattern in 3D. The palate shape can be obtained using a color-encoded structured light 3-D digitization system [Monks etal., IEEE Coll. on Biomed. Apps. of Dig. Sig. Proc. Dig. No. 1989/144, London (1989)]. The 3-D palate shape is represented by a series of polygons and can be displayed on a graphics workstation as a smoothly shaded, ‘‘lit,’’ colored surface, on which colored EPG contact patterns can be superimposed. Contact patterns can then be related more easily to articulatory features, and parameters derived from the contact pattern can be expressed in terms of absolute distances, making them more useful for sound production models. Examples of cross-subject comparisons will be shown, including cases where the dimensions of the constriction for an /s/ appear identical in EPG but clearly differ with eEPG. [Work supported in part by a Croucher Foundation Scholarship and SERC Grant No. GR/G 2115.]
A fully automated response time test of speech recognition
Authors: Saunders Gabrielle H.
Published: October 2005

A fully automated computer-controlled word recognition test was developed to investigate both speech recognition and central processing capacity (ability to focus versus divide attention appropriately). The test consists of word lists that can be presented either diotically in the presence of a noise masker−for investigation of peripheral function; or dichotically−for investigation of central auditory function. Subjects monitor the word lists for words in prespecified categories. The percentage of correctly identified words is noted and the time taken to respond is measured and stored automatically on computer for later analysis. Three advantages of this test over conventional measures are: (1) its flexibility for use as a peripheral and/or a central test; (2) the measurement of response time, which appears to be more sensitive than the percent correct measure; and (3) the need for the subject to understand as well as to hear the test stimuli. [Work supported by a grant from the Veterans Administration.]
Attention and hearing impairment: Nonspeech auditory task performance
Authors: Seitz Philip F. , Rakerd Brad
Published: October 2005

Previous research has demonstrated that speech listening demands significantly more attention from subjects with moderate-to-severe sensorineural hearing impairments than it does from normal-hearing subjects. The present experiment is one of a series intended to trace the components of this attentional demand. At issue was whether vigilent listening to auditory input in general requires more attention from hearing-impaired listeners. At MCL, hearing-impaired and normal-hearing subjects monitored for bursts of speech-noise presented at random intervals, in memory-loaded and nonloaded conditions. Normal-hearing subjects also performed auditory monitoring in a condition where the signals were presented slightly above threshold. To compare their perceptual abilities in an unimpaired modality, all subjects also performed visual monitoring tasks. Results show comparable performance between the two subjects groups. This indicates that exceptional attentional demands of speech listening for the hearing impaired are due not to the maintenance of auditory vigilence per se, but rather to phonetic and linguistic processing requirements. [Work supported by NIH-NIDCD and Gallaudet Research Institute.]
The effect of intensity on gap detection in hearing-impaired listeners
Authors: Dwyer Susan , Nelson Peggy B.
Published: October 2005

Previous investigations of gap detection by hearing-impaired listeners have yielded results that are inconsistent across listeners and studies. The full effect of stimulus intensity and audibility on hearing-impaired listeners’ performance has not been described. This study investigated the effect of intensity on gap detection abilities of normal-hearing listeners and listeners with similar mild to moderate high-frequency hearing impairments. Listeners were required to detect a gap in a high-frequency narrow-band noise over a wide range of intensities above threshold, and to judge the loudness of the signal. Results indicated that at low intensities all listeners showed reduced gap detection ability. As intensity increased, the listeners’ performance improved and stabilized at high sensation levels. At these higher intensities, the performance of hearing-impaired listeners was similar to, but still significantly different from that of normals (mean group difference=1 ms). This difference in listeners’ performance was found when results were compared in sensation level, sound-pressure level, and loudness. Consistent results across eight hearing-impaired listeners suggested that ensuring full audibility of the stimulus yields more consistent performance. These results suggest that temporal resolution ability is affected by both hearing impairment and by stimulus intensity.
Forward and backward projection of axisymmetric pressure fields from shells of revolution using an internal source density method
Authors: Stepanishen Peter R. , Hillenbrand Janet
Published: October 2005

The forward and backward projection of measured harmonic pressure fields from complex vibrators is a subject of considerable interest in the areas of transducer calibration and structural acoustics. A general methodology for addressing such projection problems for surfaces of revolution using internal line source density distributions along the axis of the body is presented. The focus of the present paper is however on the rotationally symmetric problem. A least-mean-square error method is used to determine an internal line monopole source density distribution along the axis of symmetry of the measurement surface by matching the measured pressure in the field to the pressure field of the source distribution at the surface. The resultant source density distribution can then be used to determine the pressure and velocity fields exterior to the body of revolution; hence, the measured pressure field can be forward and backward projected. Numerical results are presented to illustrate the accuracy of the projection method for the case of spherical, spheroidal, and finite cylindrical vibrators with rotationally symmetric velocities.
Computer identification of musical instruments
Authors: Narasimhan Sudha Rani
Published: October 2005

The objective is to identify musical instruments using a computer. The characteristics of a musical instrument can be determined by the frequency spectrum of a specific note. The spectrum will vary for different instruments. This variation identifies the instrument. The waveforms of musical instruments (simulated by an electronic keyboard) are stored in the computer. Experimental data were collected for clarinet, trumpet, flute, accordion, violin, and piano. A computer program is developed to characterize the various spectra. The frequency of maximum power is determined first. Then the ratios of the power levels corresponding to the first five harmonics are calculated. For each instrument, the above ratios are determined from several trials. It is found that a characteristic feature of a musical instrument corresponds to specific values of these ratios. A computer program compares the ratios obtained from playing an instrument in real time with the stored ratios of various instruments to identify and display the instrument played. The identification method agrees very well with psychoacoustic data obtained from human beings [Saldanha and Corso, J. Acoust. Soc. Am. 36, 2021–2026 (1964)].
Specifying noise control for offshore platforms
Authors: Keith Reginald H.
Published: October 2005

With the greater importance of off-shore exploration and production, the number and scale of off-shore platforms has increased dramatically. The cost of building, locating, and maintaining off-shore facilities has resulted in special acoustical requirements that are not found in similar on-shore facilities. This has resulted in the need to re-evaluate the manner and methodologies used in evaluating and specifying noise control treatments on off-shore platforms. This paper reviews the traditional methods of evaluating and specifying noise control treatments and how these methods can be modified to ensure proper evaluation of noise control treatments.
Noise control procedures to meet platform safety standards
Authors: Austnes Jan Arne
Published: October 2005

Noise abatement requirements are an inevitable content of the statutory safety standards for offshore production/exploration platforms. The Norwegian authorities are strictly following up all acoustical aspects of concern to a safe operation of the facility. Project planning has a key role in the implementation of a successful platform noise control. Its specific scope of work shall be covered by an accurate set of cost time resource (CTR) plans. To maintain engineering feasibility at its maximum, all phases of the project design have to be monitored by an acoustic specialist engineer. He shall be permanently present as a part of the project design team. The IDC routing of documentation and purchase specifications is his main ‘‘trains’’ of giving inputs to the acoustic performance. The agreed noise control technologies are implemented by the system disciplines/manufacturers. The acoustic engineer does the verification calculations through noise prediction reporting by three to five revisions throughout the project. During commissioning, phase measurements are performed to state the ‘‘as-built’’ performance. These headlines of the paper roughly describe the quality assurance procedures normally followed during a topside design/construction/commissioning project. The lecture is illustrated by case histories from 15 years of design/construction/retrofit experience.
Noise control evaluation for control rooms and crew quarters on off-shore platforms
Authors: Pelton Howard K.
Published: October 2005

Noise sources on off-shore drilling and production platforms are similar to those found on-shore; i.e., engines, turbines, generators, gear boxes, pumps, compressors, etc. The major difference is they are located on a steel structure that transmits noise and vibration energy very efficiently. For those that live aboard, for a crew shift of as much as 3 weeks, their exposure time may not be limited to the 12-h daily work shift. Thus areas like control rooms, laboratories, bunk houses, dining, and recreation rooms should have lower noise levels, be located away from noise sources, and/or isolated from structureborne and airborne noise. This requires a different criteria and design approach. The criteria for this type of noise control problem is related to the speech interference and sleep interruption. Two case histories will be discussed that illustrate the scope of the problem, practical noise control solutions, and results. These include: (1) a semisubmersible combination drilling and production platform located in the Gulf of Mexico; and (2) smaller fixed leg flow station platforms off Indonesia.
Elimination of the influence of wearer’s voice by a two-dosimeter system
Authors: Giua P. E. , Messino C. D. , Johnson D. L.
Published: October 2005

Results are reported on a two-dosimeter system for the measurement of the daily personal exposure to noise. This system is supposed to estimate the true noise dose without the influence of the voice of the wearer. Two identical dosimeters were used with their microphones located on a helmet, in the front and back positions, respectively. The dosimeters simultaneously measured the Leq and the n-percentile-exceeded levels. These data were then used to eliminate the voice contribution to the noise dose. Provided certain constraints are fulfilled, preliminary results obtained in various environmental conditions have shown good performance of this system, especially at low noise levels. Main constraints are: (1) the daily measurement should be divided in homogeneous periods with respect to noise, and (2) if the wearer speaks for a certain period fraction, his or her voice level should be consistent with the Lombard effect. Examples are given.
Low field ultrasonic studies on melt-textured YBa2Cu3O7−δ
Authors: Sarma Bimal K.
Published: October 2005

Ultrasonic attenuation and velocity measurements have proved to be a useful probe for the study of conventional superconductors, where the electron–phonon coupling is the dominant pairing mechanism. Since the discovery of high Tc superconductors, ultrasonic measurements have been performed on these systems with moderate success. In the absence of large single crystals, measurements have been performed on isotropic sintered pellets and partially oriented sintered pellets of these high Tc compounds. Low field ultrasonic measurements in the melt textured YBa2Cu3O7 have proved to be interesting. With shear waves one can see a coupling of the sound waves to the flux lattice. As the field is increased, there is an abrupt jump in both the sound velocity (ΔV) and the attenuation (Δα) at a field Hc1’, which is close to Hc1. The temperature dependence of Hc1’ is the same as that of Hc1. ΔV is found to be proportional to the square root of Hcl’, that is inversely to the average distance between the flux lines. Δα goes to zero at Tc and at T=0, going through a maximum at ∼55 K. Measurements have been done for various orientations of the magnetic field. As no anisotropy is seen in the value of Hc1’, it is surmised that Hc1’ is the lower critical field for the intergranular matrix. [Work supported by ONR.]
Application of wavelet transforms to ultrasonic medical imaging
Authors: Gan Woon S.
Published: October 2005

In this paper, wavelet transform is applied to study ultrasonic medical imaging. Nondiffracting source ultrasonic computed tomography and diffraction ultrasonic tomography are considered. The multiresolution property of wavelet transform is used. Wavelet transform is also applied to study nonstationary ultrasonic medical images such as blood flow in heart which windowed Fourier transform (short-time Fourier transform or Gabor transforms) is not convenient to use. For the nondiffracting (straight ray) sources, the Fourier slice theorem and parallel and fanbeam reconstruction algorithm are modified for wavelet transforms. For diffracting sources, and Fourier diffraction theorem is modified for wavelet transforms. The wavelet approach to multiresolution decomposition is studied. The multiresolution wavelet model is reviewed which shows that the difference of information between two successive resolutions can be computed by decomposing the signal in a wavelet orthonormal basis. This is an improved multiresolution pyramid algorithm. The equivalence between multiresolution approximations and wavelet basis is used to derive wavelet bases. The concept of multiresolution which gives different information of an image at two different resolutions is particularly useful to texture discrimination in medical imaging. A preliminary simulation result is given.
Effects of ocean turbulence on multipath beamforming
Authors: Tarng J. H. , Chen K. S.
Published: October 2005

In this report, effects of ocean environments on a sonar array pattern is evaluated by a theoretical approach, the path integral technique, and a numerical simulation method, the split-step method. The contributions of turbulence and deterministic sound-speed distribution in the ocean are considered. The former contribution broadens the synthesized beamwidth and the latter one interferes with the array pattern through the existence of multipath. It is found that turbulence can also smooth the pattern interference. Both the cases of temperature fine structures and a Gaussian spectrum are used to model the fluctuation of the sound-speed distribution. The result shows that the former model has stronger smoothing effect when they have the same fluctuation strength. In the numerical simulation, the average array pattern is shown to be similar to the theoretical one. It is illustrated that both the normalized beamwidth and its variance of the array pattern are increased as sound-speed fluctuation strength increases or the scale length of turbulence decreases.
Enhancing a model of auditory information processing to exhibit accommodation
Authors: Ellis Daniel P. W.
Published: October 2005

A speculative model of the ‘‘internal representation’’ of a sound in the auditory system stores only the peak energy trajectories from a cochlear filterbank [P. W. Ellis and B. L. Vercoe, J. Acoust. Soc. Am. 91, 2334(A) (1992)]. This representation appears to code relevant features, as verified by resynthesis, and can be used for signal separation. One marked shortcoming is the absence of accommodation: a loud but steady stimulus has equal prominence throughout its duration; the subjective experience is that such sounds are rapidly relegated to ‘‘background.’’ A related problem with the model is that high-energy components distort and mask nearby low-energy features, even when the former are static and the latter varying; on listening to such a sound, the quieter details are far better resolved by our ears than is apparent in the representation. A simple subtractive feedback scheme can remove the influence of stable components, regardless of energy. Differentiation in time achieves this, but more interesting results are obtained by feeding back a higher-level analysis. Examples of sonic details separated by such methods will be shown and played.
Three-dimensional global acoustic PE model
Authors: Tappert Frederick
Published: October 2005

A fully three-dimensional PE/SSF global ocean acoustic model with 360-deg azimuthal coverage has been developed that predicts sound-pressure levels at all points in the world’s oceans from a source that is omnidirectional in azimuth. Full coupling in both horizontal and vertical planes is included for the outgoing waves. A high angle propagator is used, that allows deflections up to nearly 90 deg in both vertical angle and azimuthal angle, giving a forward bistatic reverberation capability. Backward monostatic reverberation is provided by means of the multiple forward scatter single backscatter approximation, which weakly couples outgoing and incoming waves. Standard deterministic geophysical databases are used, and are supplemented by stochastic descriptions of surface, bottom, and sub-bottom interface roughness. [Work supported by ONR, Code 11250A.]
Approximations for the 2-D Green’s function of a fluid-loaded plate
Authors: Photiadis Douglas M.
Published: October 2005

Simple analytical formulas to predict the acoustic component of the 2-D Green’s function of a fluid-loaded plate are presented. The formulas do not require any side computations such as numerical zero finding or numerical integrations. The simplest result obtained provides a good estimate of the Green’s function for a very broad range of frequencies, being degraded only near the coincidence frequency. A somewhat more complicated formula, almost uniformly valid in frequency, and yielding reasonable accuracy even at coincidence, is also presented. Numerical results comparing the asymptotic approximations to the ‘‘exact’’ Green’s function are presented, and show significant improvement over a basic steepest descents-based approximation. For large values of x, very high accuracy can be achieved with relative errors of less than 0.1%. For other less stringent applications, the approximations are accurate to within 10% at fairly small distances from the source, requiring only kfx≥1 and k0x≥0.5.
Acoustic sensitivity to structural modification
Authors: Hahn Steven R. , Ferri Aldo
Published: October 2005

It is currently possible to analyze the acoustic radiation and scattering from submerged elastic structures in the low to moderate ka range. However, in the mid- to high-frequency range, tradition techniques, such as finite element/boundary element (FE/BE) methods, have failed to yield reliable results. One reason for the poor performance of such computational techniques, in the mid- to high-frequency range, is sensitivity to structural detail. Here, a method is presented that calculates sensitivities to structural changes. The technique uses perturbations to pre-existing structural-acoustic models. The sensitivity data can be used to indicate areas where attention to detail should and should not be placed, leading to a more efficient mesh refinement process. It can also be useful for more efficient reanalysis and optimization. The analysis presented is based on, but not limited to, FE/BE models. Several numerical examples are presented that illustrate the calculation of the sensitivities and how they can be used for design optimization and model refinement.
An experiment in spoken language acquisition
Authors: Gorin A. L. , Levinson S. E.
Published: October 2005

At present, automatic speech recognition technology is based upon constructing models of the various levels of linguistic structure assumed to compose spoken language. These models are either constructed manually or automatically trained by example. A major impediment is the cost or even the feasibility of producing models of sufficient fidelity to enable the desired level of performance. The proposed alternative is to build a device capable of acquiring the necessary linguistic skills duringthecourseofperformingitstask. The mechanisms underlying this research program comprise an information-theoreticconnectionistnetwork embedded in a feedbackcontrolsystem, and involve both spoken and typed language. Recent experiments in spoken language acquisition will be described, within the application scenario of an Inward Call Manager. This speech understanding system is unique in that its vocabulary and grammar are unconstrained, being acquired during the course of performing its task. It is also unique in that no text is involved in the training of this system. Previously, results have been reported for this system with text input, and some preliminary experiments in speech involving a small (100 utterance) database. These current experiments are more detailed, and involve a larger database of 1105 utterances.
Finite-amplitude propagation of sound beams, improvements of the Bergen code
Authors: Fro/ysa Kjell-Eivind
Published: October 2005

An algorithm for numerical solution of the KZK nonlinear, parabolic equation is developed. It is a new and faster version of the Bergen code algorithms starting with Aanonsen etal. [J. Acoust. Soc. Am. 75, 749–768 (1984)]. The computational time on the nonlinear term is reduced, and the possible numerical instabilities when studying pulsed sound propagation are avoided. The algorithm is used for the study of pulsed finite amplitude sound propagation, and comparisons have also been made with experimental results. [Work supported by the Norwegian Research Council for Science and Humanities.]
On the fundamental physical mechanisms leading to electrical breakdown in spark transducers
Authors: Sutton Stephen P. , Olson Allen H.
Published: October 2005

It is widely assumed that a liquid state leader mechanism leads to arc formation in spark discharge sources, although this hypothesis has failed to yield models sufficient for transducer design. Experimental results are presented that support a new model. Electrical breakdown between spherical electrodes immersed in seawater is shown to be highly correlated with dissipation of a threshold amount of energy to joule heating in the fluid. Acoustic measurements demonstrate that this threshold corresponds to the energy required to initiate vaporization. It is further shown that breakdown times are linearly correlated to the time at which the vaporization threshold is reached. These results are interpreted as strongly supportive of a new model based on vapor formation and subsequent ionization leading to arc formation.
Experimental investigation of highly intense sound beams from two focusing circular transducers
Authors: Nachef Sylvain , Cathignol Dominique , Chapelon Jean-Yves
Published: October 2005

The purpose of this communication is to investigate the pressure fields, for a large range of cw excitation levels, of two different focusing transducers such as those used for the medical applications. The first one (45-mm diameter, 200-mm focal distance, and 6.15 linear gain) works at 1.16 MHz, and the second one (70-mm diameter, 90-mm focal distance, and 63.85 linear gain) works at 2.24 MHz. The pressure signal measured along and across the acoustic axis is transmitted to a computer where its maximum and minimum are recorded, analyzed, and displayed. For the low gain and small aperture source and at low excitation levels, the highest pressure of the field does not occur at the geometrical focus but before it. For the high gain and large aperture source, the highest pressure is measured around the geometrical focus, whatever the excitation level used. Special attention is devoted to the saturation phenomenon.
Temporally smeared speech: Its intelligibility and its relationship to temporal resolution
Authors: Hou Zezhang , Pavlovic Chaslav V.
Published: October 2005

In the past, the effects of deteriorated temporal resolution of the auditory system on speech intelligibility have been studied by measuring the correlation between temporal resolution and speech perception using hearing impaired listeners. These studies have not given consistent results. In the ongoing study, an alternative approach was explored. Essentially, envelopes of speech were temporally smeared in 23 parallel frequency channels. The smeared speech was presented to normal-hearing listeners, and the effects of different smearing magnitudes on speech intelligibility were measured by obtaining direct speech recognition scores. The auditory representations of the smeared stimuli have reduced temporal resolution but nearly normal frequency resolution. The principle of the smearing processing will be discussed. Data on temporal resolution and frequency selectivity obtained using smeared stimuli and normal subjects will be presented. Speech intelligibility of smeared nonsense syllables was also tested.
Variability of heat content in the Northcentral Pacific in summer 1987 determined from long-range acoustic transmissions
Authors: Dushaw Brian D. , Worcester Peter F. , Cornuelle Bruce D.
Published: October 2005

The evolution of the depth integrated heat content in the Northeast Pacific during summer 1987 has been measured using long-range acoustic transmissions between transceivers deployed in a triangle approximately 1000 km on a side. Transmissions at 4-day intervals gave travel times that were inverted to obtain estimates of the range-average sound-speed fields along the sides of the triangle. The estimated sound-speed fields are converted to temperature fields and integrated to obtain depth and range averaged heat content. The acoustically determined sound-speed and temperature fields agree with conventional CTD and XBT data. The accuracy of acoustical measurements of heat content are comparable to estimates from CTD and XBT data and can be made much more frequently. The acoustically measured variability of heat content at short-time time scales limits the accuracy of studies using infrequent XBT sections. Ocean/atmosphere heat exchange from bulk formulas cannot fully explain the observed heat content change; the excess heat change is calculated to be of order 50–150 W m−2. [Work supported by NSF and ONR.]
Seasonal variability of the acoustic energy distribution along a propagation path across the eastern United States continental shelf
Authors: Podeszwa Eugene M. , Botseas George , Browning David G.
Published: October 2005

Seasonal oceanographic changes can have a strong impact on shallow-water sound transmission loss. Additionally, in any one season, several distinct oceanographic regions may be encountered along a shallow-water propagation path. Using the range-dependent IFD propagation model, propagation loss contours are presented for a 300-km propagation path across the continental shelf starting near Charleston, SC. The relative impact of horizontal and vertical seasonal oceanographic changes are determined in terms of propagation loss and shifts in the acoustic energy distribution throughout the water column.
Parametric models for acoustic convergence zone variations
Authors: Bongiovanni K. P. , Siegmann W. L. , Ko D. S.
Published: October 2005

A model that is designed to provide feedback for assessment and improvement of ocean prediction models is presented. Typical prediction model temperature field output is assumed to be modeled statistically and parametrically. An objective is to relate resulting ocean environmental parameters to some natural acoustic metrics corresponding to measurable features of the received field. The approach uses a canonical sound-speed profile [J. C. Miller, J. Acoust. Soc. Am. 71, 859–862 (1982)] which has closed-form ray solutions in a range-independent medium. By incorporating the environmental parameters into the sound-speed profile and employing the ray geometry for a shallow acoustic source, expressions for convergence zone widths and ranges are developed. A sensitivity examination shows that thermocline scale is the dominant factor for convergence zone variabilities. Implications of the relationships for model assessment will be discussed. [Work supported by INO.]
Weather observations using autonomous acoustic drifters
Authors: Nystuen Jeffrey A.
Published: October 2005

Wave breaking and precipitation produce unique sound underwater. This sound can be used as a signal to measure wind speed and rainfall rate in oceanic regions where other insitu technologies perform poorly. A new technology using expendable autonomous acoustic drifters is described to provide these needed measurements. Nine months of data collected from three prototype acoustic drifters will be presented and compared to simultaneous estimates from a passive microwave satellite sensor (the SSM/I). Wind-speed estimates from the two technologies are well correlated, but appear to depend on water mass type. In the Pacific Ocean, the slope of the empirical relationship relating the acoustical and satellite wind-speed estimates changes significantly as the drifters move from California coastal waters to mid-Pacific tropical waters at approximately 31.5°N. This change was seasonally independent. An adjustment for local refractive conditions was applied to the acoustical data. Examples of the acoustical detection of drizzle and acoustical measurement of heavy rainfall will be presented and compared to satellite data. [Work supported by the Tactical Oceanogr. Warfare Support Prog. Office, Naval Res. Lab. Detachment, Stennis Space Center, MS.]
A silicon micromachined condenser microphone/hydrophone
Authors: Bernstein Jonathan J.
Published: October 2005

A micromachined monolithic condenser hydrophone less than 1 mm in diameter has been designed, fabricated, and tested on a silicon chip. This device is a small variable capacitor with spring-supported silicon electrode and a fixed, perforated counter electrode. In use as a hydrophone, the device is filled with a dielectric fluid and sealed in a package that contains an acoustic cavity and an acoustic inlet port. Sensitivity with these devices has been measured at −223 dB re: 1 V/μPa. Tests of the sensor chips in air show they have potential as wideband microphones. Sensitivity was measured from 300 Hz to 100 kHz, with peak sensitivity measured at −60 dB re: 1 V/Pa. The chips were fabricated by standard micromachining technology. High-concentration boron diffusions are used to create silicon electrode and springs that remain after selective etching. Electroforming is used to create a closely spaced counter electrode with fine perforations. A wide variety of fill fluids have been investigated for use in filling these hydrophones, including silicone oils, halogenated hydrocarbons, esters, and liquid crystals. Device and fluid characterization by current-voltage and capacitance-voltage measurements allows the device capacitance and spring constant to be extracted. Details of these calculations will be given.
New inorganic electret materials for miniaturized microphones
Authors: Guenther Peter
Published: October 2005

Electret microphones made with the methods of silicon technology require electret materials other than the conventional polymers. Up to now, amorphous SiO2 has proven its good electret characteristics, and SiO2-electret microphones have already been developed as prototypes. In this paper, new manufacturing methods for SiO2, namely cold plasma deposition and the sol–gel process, are presented. The charge storage behavior, which could be improved by heat treatment or chemical surface modification, was investigated by isothermal and thermally stimulated discharge measurements and the results were compared to the discharge characteristic of thermally wet grown SiO2 electrets. In addition, the chemical composition of the electret surface was investigated by the ESCA method, which revealed the stoichiometry of the differently manufactured and treated SiO2.
Computer modeling and auralization in room acoustics: An overview on computer models for room acoustics
Authors: Klasco Michael
Published: October 2005

The first personal computer modeling software for sound system design began to appear about 10 years ago. These early programs primarily were intended as aids for optimizing the aiming of loudspeaker horns. Very little attention was given to the acoustical characteristics of the room, except for plugging-in the midband reverberation time. As the speed and power of personal computers grew, the sound system engineering programs became more ambitious and began to address acoustical characteristics. Room models, which initially were only floor plans, now had walls, ceilings, and surface finishes. Ray tracing and image modeling capabilities were included and simulations of STI intelligibility measures using the room model are offered by a number of programs. The use of image modeling can derive an approximation of the impulse response of the room. This impulse can be exported and convoluted with external signal processing programs and computer-based DSP hardware to allow auralizing. An overview and history of each of the major programs, along with key strengths and weakness, will be provided.
Characteristics of near-surface, low-frequency sound speeds
Authors: Cartmill John , Su Ming-Yang
Published: October 2005

The bubble size density for radius of 34 to 1200 μm in near-surface ocean from depths of 0.25 m down to 7.00 m were measured by an acoustic resonator array during a 1992 field experiment in the Northeast Pacific. The void fractions were computed by integrating those bubble densities. The low-frequency (less than 1 kHz) sound speed, averaged over 3.5 s, is then estimated from the void fraction based on a theoretical computation. A set of more than 50 time series of the low-frequency sound speed, each of about 12 min in length, were then subjected to several statistical analyses. The statistical characteristics include (a) the probability density which provides, in turn, the mean and standard deviation, skewness and kurtosis, (b) Gaussian distribution fit, and (c) autocorrelation coefficient. The mean sound-speed deficit from the nominal sound speed of 1500 m/s and the corresponding standard deviation (in the order of 100 m/s) are at least 10 times larger than expected earlier. Large zero-crossing times of the autocorrelation on the order of 100 s for depth <1 m are also found for wind speed between 10 and 15 m/s. The autocorrelation analysis further indicates the evidence of coupling between the fluctuation in the bubble density and the prevailing dominant wave train. [Work supported by ONR Acoustical Reverberation SRP.]
Delayed microbubble radiation due to aerosols from large raindrop splash; dependence on surface wave slope
Authors: Miller Glenn , Medwin Herman , Nystuen Jeffrey A.
Published: October 2005

Previously, this group has demonstrated that the underwater sound due to 1-mm-diam (‘‘small’’) water drops is a function of surface slope [Medwin etal., J. Acoust. Soc. Am. 88, 413 (1990)]. It has also been shown that ‘‘large’’ raindrops of diameter ≳2.2 mm cause a splash that creates strong microbubble radiation of frequency 2–10 kHz [H. Medwin etal., J. Acoust. Soc. Am. 92, 1613–1623 (1992)]. The most recent experiments with terminal speed large drops reveal that the microbubble phenomena are affected by the local angle of incidence of the large water drop and that, in addition to the splash microjet creation of bubbles, the small aerosols from the splash also generate microbubbles. The new observations add distinctive characteristics to the spectrum of rain noise that will be useful in solving the inverse problem of determining rainfall from underwater sound. [Work supported by the Office of Naval Research.] a)Lt., US Navy. b)Oceanogr. Dept.
Modifications to stutterers’ respiratory, laryngeal, and supralaryngeal kinematics that occur with fluency improvement
Authors: Alfonso Peter J. , Kalinowski Joseph S.
Published: October 2005

Within-subject pre- and post-therapy kinematic comparisons of two groups of stutterers who successfully completed one of two intensive therapy programs revealed that certain aberrant kinematic profiles can be modified as a result of therapy, that post-therapy improvement in fluency co-occurred with spatial and temporal adjustments in each of the three systems, that some of the post-therapy kinematic modifications were in the direction of normal speech kinematics observed in the control subjects, and that certain modifications occurred across both groups of stutterrers although the clinical instructions differed. While some of the kinematic modifications appear related to specific clinical strategies associated with each therapy program, those that occurred across both groups of stutterers do not and may be related to normal motor control strategies that underline the production of rapid, perceptually fluent speech. [Work supported by NIH DC 00121 awarded to Haskins Laboratories.]
Nasality in modal speech and twang qualities: Physiologic, acoustic, and perceptual differences
Authors: Steinhauer Kimberly M. , Rekart Deborah M. , Keaten James
Published: October 2005

The habitually confused voice quality terms, nasality and twang, were clarified in two experiments examining physiologic, acoustic, and perceptual distinctions between voice quality combinations of nasality in modal speech and twang. In experiment 1, physiologic and acoustic differences between oral speech, nasal speech, oral twang, and nasal twang were investigated. The results showed that instrumentally validated productions of each voice quality originated at the velopharyngeal port, whereas twang originated at the aryepiglottic sphincter. These physiologic manipulations generated characteristic acoustic differences in format frequency and amplitude shifts. The most significant shifts occurred for frequency at F1 and for amplitude below 1000 Hz (p<0.05). In experiment 2, perceptual distinctions among the voice qualities were identified by naive listeners, music majors, and speech pathology majors. Results of this experiment showed that the listeners perceived four distinct voice qualities by identifying them significantly above the level of chance (p<0.05).
Reflection of axial surface waves from the end of a fluid-loaded cylindrical shell: A Wiener–Hopf analysis
Authors: Means Steven L. , Pierce Allan D.
Published: October 2005

At frequencies somewhat below the ring frequency, a fluid-loaded cylindrical shell supports a surface wave, the energy of which is predominantly in the surrounding fluid. The possible propagation directions are limited to those close to the axial direction. For such waves the inertia of the elastic material is unimportant and the shell behaves nearly as a Winkler foundation, such that the ratio of the external acoustic pressure to the inward displacement is Eh/R2. The present paper seeks to quantify the physical phenomena associated with reflection of such a wave from a free end of a shell, but to make the analysis tractable, the shell is regarded as a semi-infinite locally reacting cylinder extending from −∞ to 0, followed by a rigid cylindrical baffle, also of radius R, extending from 0 to ∞ along the x axis. A known surface wave is incident from x=−∞ and one seeks the amplitude and phase shift of the reflected surface wave along with any acoustic field radiating into the fluid that originates in the vicinity of the shell end at x=0. An exact solution involving contour integrals is derived using the Wiener–Hopf technique and applicable asymptotic results are extracted.
Timing and magnitudes of oral and nasal flow in cochlear implant patients and normals
Authors: Wozniak Jane F. , Matthies Melanie L. , Perkell Joseph S. , Lane Harlan L.
Published: October 2005

Vowel nasalization was assessed in cochlear implant patients pre- and post-implant, and in normal-hearing speakers, using measures of oral, nasal, and total airflow. Speech materials consisted of the utterance /taC/, (where C=/n/, /m/, or /d/, embedded in a carrier phrase. Airflow was transduced with a two-chamber Rothenberg mask. Measures included the relative timing of the onsets of nasal and oral airflow, and the ratios of peak oral and nasal flow to total flow following the /t/ release. Pre- to post-implant differences may reflect an adjustment of the control of the velum, possibly in response to a perceived difference in nasalization and/or as a consequence of concomitant changes in other speech parameters. Preliminary ratio data from one cochlear implant patient indicate a possible enhancement of the nasal/non-nasal contrast post-implant. Further, in the /tad/ utterance, the oral flow pulse at consonant release was accompanied by a small pulse of nasal flow: velar closure during the consonant may have been assisted by the oral pressure increase, thus the pressure drop at consonant release would result in a small passive velar opening movement. These observations and additional measures are being explored further. [Work supported by NIH.]