bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation of vibration reduction design for underground sources
Authors: Kostarev Stanislav A. , Rybak Samuil A. , Makhortykh Sergey A.
Published: October 2013

The problems of ecology situation control near intensive underground acoustical sources is considered. Studied vibration absorbers are modeled by multi-component system of connected oscillators with damping. Obtained oscillatory equation system was investigated numerically. Frequency dependencies of absorbers efficiency have been calculated. An influence of the physical-mechanical parameters of the surrounding ground on the value of vibration reduction has been determined. Some variants of principal realization of vibration absorbers for the case of underground railway are discussed. [Work supported by Russian Foundation for Basic Researches Grants Nos. 01-02-16127, 02-02-17143.]
Stimulus-based similarity and the recognition of spoken words
Authors: Auer Edward T.
Published: October 2013

Spoken word recognition has been hypothesized to be achieved via a competitive process amongst perceptually similar lexical candidates in the mental lexicon. In this process, lexical candidates are activated as a function of their perceived similarity to the spoken stimulus. The evidence supporting this hypothesis has largely come from studies of auditory word recognition. In this talk, evidence from our studies of visual spoken word recognition will be reviewed. Visual speech provides the opportunity to highlight the importance of stimulus-driven perceptual similarity because it presents a different pattern of segmental similarity than is afforded by auditory speech degraded by noise. Our results are consistent with stimulus-driven activation followed by competition as general spoken word recognition mechanism. In addition, results will be presented from recent investigations of the direct prediction of perceptual similarity from measurements of spoken stimuli. High levels of correlation have been observed between the predicted and perceptually obtained distances for a large set of spoken consonants. These results support the hypothesis that the perceptual structure of English consonants and vowels is predicted by stimulus structure without the need for an intervening level of abstract linguistic representation. [Research supported by NSF IIS 9996088 and NIH DC04856.]
Effects of blocking and presentation on the recognition of word and nonsense syllables in noise
Authors: Benkí José R.
Published: October 2013

Listener expectations may have significant effects on spoken word recognition, modulating word similarity effects from the lexicon. This study investigates the effect of blocking by lexical status on the recognition of word and nonsense syllables in noise. 240 phonemically matched word and nonsense CVC syllables [Boothroyd and Nittrouer, J. Acoust. Soc. Am. 84, 101–108 (1988)] were presented to listeners at different S/N ratios for identification. In the mixed condition, listeners were presented with blocks containing both words and nonwords, while listeners in the blocked condition were presented with the trials in blocks containing either words or nonwords. The targets were presented in isolation with 50 ms of preceding and following noise. Preliminary results indicate no effect of blocking on accuracy for either word or nonsense syllables; results from neighborhood density analyses will be presented. Consistent with previous studies, a j-factor analysis indicates that words are perceived as containing at least 0.5 fewer independent units than nonwords in both conditions. Relative to previous work on syllables presented in a frame sentence [Benkí, J. Acoust. Soc. Am. 113, 1689–1705 (2003)], initial consonants were perceived significantly less accurately, while vowels and final consonants were perceived at comparable rates.
Simple algorithm for classification of target in shallow water
Authors: Sarkissian Angie
Published: October 2013

When applying classification algorithms to the scattering response of a target in shallow water, algorithms that attempt to deconvolve the free field target response from the environment, such as modal decomposition or time reversal, typically require multiple receivers. A simple algorithm is applied here that requires a single source and a single receiver. The impulse response of the target is Fourier transformed to the frequency domain; the magnitude of the frequency domain response is transformed back to the time domain; the resultant time domain response is truncated. The algorithm is applied to a hemispherically end-capped cylindrical shell under various shallow water conditions. The response obtained for the target in shallow water is correlated against the target free field response. [Work supported by ONR.]
Separation of signals from near field noise via pressure and velocity field measurements
Authors: Stepanishen Peter R.
Published: October 2013

The separation of acoustic plane wave signals from near field noise sources is addressed using both pressure and velocity measurements at the same location in the fluid. A compact broadband noise source at a known location is first assumed to generate the noise field. Using a time domain approach a simple signal processor is presented to separate the unknown signal from the noise. Effects of sensor and quantization noise are included in the analysis. A frequency domain analysis of the noise separation approach is presented along with numerical results to illustrate the sensitivity of the method to field point location, noise spectrum, and sensor and quantization noise. The separation of plane wave signals from spatially distributed near field noise sources is then addressed. A signal processor using both pressure and velocity measurements at a single point is developed to separate a plane wave signal from a spectrally pure evanescent noise field generated at a planar interface close to the sensors. Numerical results are presented for several examples to illustrate the noise separation process for a wide range of signals. In particular, the case of overlapping signal and noise spectrums is addressed.
Covariance of the forward propagated field through a waveguide containing random inhomogeneities
Authors: Ratilal Purnima , Makris Nicholas C.
Published: October 2013

Analytic expressions are derived for the spatial covariance of the field from a point source after forward propagation though a waveguide containing random surface and volume inhomogeneities. It is shown that the depth-averaged second moment and expected power of the forward propagated field can be obtained analytically. The mean forward propagated field has also been obtained analytically in terms of modal attenuation and dispersion coefficients in a waveguide [P. Ratilal and N. C. Makris 112, 2403 (2002)]. The covariance between two receiver depths of the forward propagated field through the entire random medium can then be determined by invoking the equi-partition of modal energy after significant multiple scattering. It is expressible as a sum of modal covariance terms. Each term depends on (1) the modal extinction cross-section [P. Ratilal and N. C. Makris, 110, 2924–2945 (2001)] of an expected elemental inhomogeneity of the medium, and (2) the scatter function variance of an elemental inhomogeneity which couples each mode to all the other modes.
Energy-conserving and single-scattering parabolic equation solutions for elastic media
Authors: Kusel Elizabeth T. , Siegmann William L. , Collins Michael D. , Lingevitch Joseph F.
Published: October 2013

Parabolic equation techniques are efficient for solving nonseparable wave propagation problems. When the properties of the medium vary gradually in range, parabolic equation solutions are also very accurate for many problems. The key to achieving accuracy and efficiency simultaneously is to apply energy-conservation or single-scattering corrections to account properly for range dependence. This approach has proven to be very effective for acoustic media. Some progress has been made on the elastic case [J. Acoust. Soc. Am. 94, 975–982 (1993); 94, 1815–1825 (1993)], but this problem has not been fully resolved. In this paper we will discuss some recent progress in the formulation of the elastic parabolic equation [W. Jerzak, J. Acoust. Soc. Am. (submitted)], a single-scattering approach for a vector wave problem [J. Acoust. Soc. Am. 104, 783–790 (1998)], and how they are being used to improve the accuracy of parabolic equation solutions for problems involving elastic sediments. [Work supported by ONR.]
The coupling of elastic, surface-wave modes by a slow, interfacial inclusion
Authors: Harris John G. , Block Gareth
Published: October 2013

The coupling of in-plane, elastic, surface waves guided by a homogeneous layer on a similar substrate, but perturbed by the presence of a second, long, slow, interfacial layer, of slowly varying thickness, is studied. By projecting the elastic-wave equations onto a basis of local eigenmodes, an infinite system of coupled-mode equations describing the evolution of the amplitudes of each mode is obtained. Within the equations, the coupling is manifested by the presence of coupling coefficients that depend critically on the difference between the wavenumbers of adjacent modes. This system is truncated and solved by noting under what conditions the modes can be satisfactorily described by a WKBJ approximation (propagating without coupling) and under what conditions they are coupled by adjacent wavenumbers being brought into proximity by the slowly changing propagation environment. The criteria for coupling is that the difference in neighboring wavenumbers be of the same order as the slope of the inclusion. The case of the first three modes is worked out in detail: it is shown how initially modes one and two couple followed by the coupling of modes two and three.
Optimal temperature sampling with SPOTS to improve acoustic predictions
Authors: Rike Erik R. , DelBalzo Donald R. , Samuels Brian C.
Published: October 2013

The Modular Ocean Data Assimilation System (MODAS) uses optimal interpolation to assimilate data (e.g., XBTs), and to create temperature nowcasts and associated uncertainties. When XBTs are dropped in a uniform grid (during surveys) or in random patterns and spaced according to resources available their assimilation can lead to nowcast errors in complex, littoral regions, especially when only a few measurements are available. To mitigate, Sensor Placement for Optimal Temperature Sampling (SPOTS) [Rike and DelBalzo, Proc. IEEE Oceans (2003)] was developed to rapidly optimize placement of a few XBTs and to maximize MODAS accuracy. This work involves high-density, in situ data assimilation into MODAS to create a ground-truth temperature field from which a ground-truth transmission loss field was computed. Optimal XBT location sets were chosen by SPOTS, based on original MODAS uncertainties, and additional sets were chosen, based on subjective choices by an oceanographer. For each XBT set, a MODAS temperature nowcast and associated transmission losses were computed. This work discusses the relationship between temperature uncertainty, temperature error, and acoustic error for the objective SPOTS approach and the subjective oceanographer approach. The SPOTS approach allowed significantly more accurate acoustic calculations, especially when few XBTS were used. [Work sponsored by NAVAIR.]
Acoustical and electronic media design aspects of the Texas Capitol restoration
Authors: Dickensheets Kenneth
Published: October 2013

A presentation of the studies involved in preparation for the restoration of the Texas State Capitol building and the implementation of acoustical, noise and vibration control and electro-acoustical recommendations to ensure that legislative bodies’ and committees’ deliberations would be heard while allowing for faithful historical restoration of the facility. Specific attention to and examples in the Senate Chamber will be presented. Solutions to difficult noise and acoustical issues in the context of historical preservation will be discussed. Historical and present photos will be shown.
A new seamless, smooth, interior, absorptive finishing system
Authors: D’Antonio Peter
Published: October 2013

Government architecture typically employs classic forms of vaults, domes and other focusing or reflective shapes, usually created with hard materials like concrete and plaster. The use of conventional porous absorption is typically rejected as an acoustical surface material for aesthetic reasons. Hence, many of these new and existing facilities have compromised speech intelligibility and music quality. Acousticians have sought a field-applied, absorptive finishing system that resembles a smooth plaster or painted drywall surface, since the dawn of architectural acoustics. Some success has been achieved using sprayed cellulose or cementitious materials, but surface smoothness has been a challenge. A new approach utilizing a thin microporous layer of mineral particles applied over a mineral wool panel will be described. This material can be applied to almost any shape surface, internally pigmented to match almost any color and renovated. Because of these unique characteristics the new seamless, absorptive, finishing system is being specified for many new and renovated spaces. Application examples will be presented.
Multipurpose council chambers ‘‘in the round’’ poses acoustical challenges
Authors: Logsdon Edward L.
Published: October 2013

The City of Aurora Council Chambers is used for both municipal and public meetings. The room is configured to provide close-in seating with good sightlines from each of the 300 stadium-style seats. Presentations can be made from the central podium location to either the audience or council dais requiring multiple loudspeaker zoning and control. The cylindrical ceiling, shaped to accommodate video projection and lighting equipment, is acoustically treated to eliminate late reflections. The City Council meetings are broadcast to public TV on a regular basis from this room requiring good room acoustics and sound isolation to reduce echo and achieve acceptably low background noise levels while satisfying the aesthetic palette of the interior designers. A case history will be presented along with photographs showing how specialty wood materials, both absorptive and diffusive, were incorporated along with absorptive plaster and cloth-covered fiberglass panels into the design of the building.
Detection and classification of right whales in the Bay of Fundy using independent component analysis
Authors: Linford Michael , La Cour Brian
Published: October 2013

A novel method of the detection and classification for marine mammals is presented which uses techniques from independent component analysis to solve the blind source separation problem for right whales in the Bay of Fundy. Using the fundamentally non-Gaussian nature of marine mammal vocalizations and data collected on multiple hydrophones, we are able to separate right whale source spectra, up to an unknown scale, from ambient noise. This technique assumes that the array data is a linear combination of the source signals but does not require specific knowledge of the array geometry. A detector/classifier algorithm is demonstrated which compares the estimated source spectra against known right whale vocalizations.
Dolphin echolocation strategies studied with the Biosonar Measurement Tool
Authors: Houser Dorian S. , Martin Steve W. , Phillips Michael , Bauer Eric , Moore Patrick W.
Published: October 2013

Two free-swimming dolphins (Tt722 and Tt673) were trained to carry the Biosonar Measurement Tool (BMT) during open water, proud target searches in order to explore echolocation behavior without the constraints of traditional experimental designs. The BMT recorded the angular motion, depth, and velocity of the dolphin as well as echolocation clicks and echoes returning from insonified targets. Mean search time for Tt722 was 24.6±7.3 s and 6.5±3.0 s for Tt673 on target present trials, the former strategy resulting in the lower false alarm rate. The majority of clicks exceeded 195 dB re: 1 μPa throughout all trials for both animals but each demonstrated preferences for particular frequency bands of echolocation. Considering all trials, only 3.6% of all clicks produced by Tt722 contained peak frequencies greater than 60 kHz whereas Tt673 produced clicks with peak frequencies above 60 kHz 20.4% of the time. Distinctive frequency bands in the distribution of clicks were notable: bands for Tt673 occurred at 38, 54, and 69 kHz with less defined higher order bands; bands for Tt722 occurred at 25, 35, and 40 kHz. Distinctive frequency bands suggest a preferential use or mechanical constraint on harmonically related click frequencies.
Frameless processing of bird songs using set membership identification
Authors: Mohammad Rafi , Wilde Mark M. , Joachim Dale
Published: October 2013

This paper describes a novel approach to feature extraction from bird songs using a set-membership identification (SMI) algorithm. The low computational complexity of the SMI algorithm allows frameless pointwise feature estimation and real-time processing. Both energy-based end-point detection and set-to-point classification methods are incorporated in this SMI processing for enhanced labeling performance. The described algorithm serves as a front end to a fully automated bird identification system in which training data collection is automated by scheduled computer generated phone calls to a cellular monitoring station. RASTA processing of feature vectors compensates for the telephone channel effects.
Identification and assessment of constrictions in a branched tube system
Authors: Du Youhua , Al-Jumaily Ahmed M.
Published: October 2013

This paper focuses on developing an analytical methodology, based on the frequency spectrum of the input acoustic impedance, to identify and assess the location and severity of constrictions in a branched-treelike tube system. The method is applied to two models, one is for the trachea with the first-generation asymmetric bronchi and the other is for the trachea with two-generation bronchi. To develop the methodology, a different size constriction is introduced at various locations along the branches and resonant frequencies are analyzed. Correlation is performed between the resonant frequencies and the location and size of these constrictions. For the two models, charts are generated which can be used to determine the location and size of a constriction just by observing the trend of various resonances. For the first model it is shown that in the frequency range of 1–4000 Hz the third and sixth resonances reflect constriction occurrence in the larger branch and the fourth and seventh reflect constriction in the smaller branch. However, for the second model it is indicated that constriction is reflected: in first branch by the sixth resonance, in the second branch by the seventh resonance, and in the third branch by the ninth resonance.
Numerical modeling of Harmonic Imaging and Pulse Inversion fields
Authors: Humphrey Victor F. , Duncan Tracy M. , Duck Francis
Published: October 2013

Tissue Harmonic Imaging (THI) and Pulse Inversion (PI) Harmonic Imaging exploit the harmonics generated as a result of nonlinear propagation through tissue to improve the performance of imaging systems. A 3D finite difference model, that solves the KZK equation in the frequency domain, is used to investigate the finite amplitude fields produced by rectangular transducers driven with short pulses and their inverses, in water and homogeneous tissue. This enables the characteristic of the fields and the effective PI field to be calculated. The suppression of the fundamental field in PI is monitored, and the suppression of side lobes and a reduction in the effective beamwidth for each field are calculated. In addition, the differences between the pulse and inverse pulse spectra resulting from the use of very short pulses are noted, and the differences in the location of the fundamental and second harmonic spectral peaks observed.
On the temporal window of auditory-brain system in connection with subjective responses
Authors: Mouri Kiminori
Published: October 2013

The human auditory-brain system processes information extracted from autocorrelation function (ACF) of the source signal and interaural cross correlation function (IACF) of binaural sound signals which are associated with the left and right cerebral hemispheres, respectively. The purpose of this dissertation is to determine the desirable temporal window (2T: integration interval) for ACF and IACF mechanisms. For the ACF mechanism, the visual change of Φ(0), i.e., the power of ACF, was associated with the change of loudness, and it is shown that the recommended temporal window is given as about 30(τe)min [s]. The value of (τe)min is the minimum value of effective duration of the running ACF of the source signal. It is worth noticing from the experiment of EEG that the most preferred delay time of the first reflection sound is determined by the piece indicating (τe)min in the source signal. For the IACF mechanism, the temporal window is determined as below: The measured range of τIACC corresponding to subjective angle for the moving image sound depends on the temporal window. Here, the moving image was simulated by the use of two loudspeakers located at ±20° in the horizontal plane, reproducing amplitude modulated band-limited noise alternatively. It is found that the temporal window has a wide range of values from 0.03 to 1 [s] for the modulation frequency below 0.2 Hz.

Thesis advisor: Yoichi Ando

Copies of this thesis written in English can be obtained from Kiminori Mouri, 5-3-3-1110 Harayama-dai, Sakai city, Osaka 590-0132, Japan. E-mail address: km529756@aol.com
Three-dimensional acoustic backscatter measurements in the water column with hull-mounted and towed multibeam echo-sounders
Authors: de Moustier Christian , Gallaudet Timothy C. , Brogan Daniel S.
Published: October 2013

Multibeam echo-sounders have been used very effectively to map the seafloor for nearly 30 years but their use in water column measurements has received little attention. This is partly due to the usually narrow-band, single-frequency operation of bottom mapping sonars which is not well suited to water column applications, and to the 40–60 dB higher receiver sensitivity and gain needed for acoustic backscatter measurements in the water column, leading to echo saturation in seafloor mapping applications [de Moustier and Alexandrou, J. Acoust. Soc. Am. Suppl. 1 83, S48 (1988)]. Recent work with towed toroidal multibeam sonars [Gallaudet and de Moustier, J. Acoust. Soc. Am. 112, 489–503 (2002)] has shown the potential benefits of 3-D water column acoustic backscatter measurements obtained with such sonars. However care must be taken to avoid multipath boundary interferences received through the sidelobes of beams pointed in the ocean volume that can significantly bias the measurements. Ocean volume reverberation measurements recorded with the original 12-kHz SeaBeam hull-mounted swath bathymetry sonar, with towed multibeam volume search sonars, are used to illustrate the spatial and temporal resolution capabilities and limitations of such measurements. [Work supported by NRL/ONR.]
Analytic expressions for time-domain forward propagation through a waveguide with random inhomogeneities including causality and dispersion relations
Authors: Chen Tianrun , Ratilal Purnima , Makris Nicholas C.
Published: October 2013

Analytic expressions in the time domain are derived for the mean forward field propagated through a waveguide containing random volume and surface inhomogeneities. The results are expressed in terms of the modal attenuation and dispersion coefficients in a waveguide [P. Ratilal and N. C. Makris, 112, 2403 (2002)]. Simulations in a shallow-water waveguide containing bubbles for a finite-time duration pulse show that the scattering leads to additional time delay and distortion of the signal waveform. Stationary phase approximations are also applied to represent the time-domain field in terms of the modal group velocities that are smaller than those in a waveguide without inhomogeneities. We show that the dispersion and attentuation effects cannot be explained by heuristic results based on an effective medium sound speed computed using bulk moduli and volume fractions since it does not account for scattering from inhomogeneities in the medium. The time-domain expressions for the forward propagated field obey causality and are consistent with Kramer–Kronig relations when used in their range of validity.
Kirchhoff approximation for backscattering by partially illuminated circular cylinders: Two-dimensional case
Authors: Marston Philip L.
Published: October 2013

The Kirchhoff approximation is widely used for estimating reflection contributions to the backscattering by rigid surfaces [W. G. Neubauer, J. Acoust. Soc. Am. 35, 279–285 (1963)]. Backscattering of a plane wave by a right-circular cylinder has been approximated this way using Struve and Bessel functions [G. C. Gaunaurd, IEEE J. Ocean Eng. 10, 213–230 (1985)]. For various situations of interest, the cylinder may be partially illuminated such that the illumination is abruptly truncated along lines parallel to the cylinder’s axis. This configuration does not appear to have been analyzed previously. This two-dimensional scattering problem is re-formulated by an application of the plane-wave expansion theorem to a phase factor. The scattering is expressed in terms of an infinite series of terms containing Bessel functions and elementary trigonometric integrals. An evaluation of the integrals and numerical evaluation of the series for the fully illuminated case reduces to the aforementioned Struve and Bessel function result. The partial-illumination case exhibits Fresnel zone behavior and illustrates the limitations of quadratic phase approximations. [Work supported by ONR.]
Statistical characterization of active sonar reverberation using extreme value theory
Authors: La Cour Brian
Published: October 2013

The statistics of reverberation in active sonar are characterized by non-Rayleigh amplitudes in the normalized matched filter output. Unaccounted for, this property can lead to high false alarm rates in fixed-threshold detectors. A new approach to modeling threshold-crossing statistics based on extreme value theory is proposed which uses the generalized Pareto distribution as the unique, asymptotic model of the tail distribution, valid at large thresholds. Methods of parameter estimation are discussed and applied to active sonar reverberation collected on a hull-mounted sonar system. The statistics of reverberation in active sonar are found to generally have a power-law behavior in the tails with a shape parameter that is persistent in time and bandwidth dependent. The threshold needed for accurate parameter estimation is generally found to be well below that of typical fixed-threshold detectors.
Pseudo-hybrid PDF estimators for active sonar classification
Authors: Gelb James M. , Donnell Mark A. , La Cour Brian R.
Published: October 2013

A class of multivariate PDF estimators for use in feature-based target classification in active sonar is presented. The goal is to develop a method that (1) preserves feature identity, (2) captures complex data structures and tails using non-parametric estimates, (3) utilizes parametric models for higher-order inter-feature dependencies, and (4) provides a systematic enhancement to classifier performance given limited target data. The estimators are labeled pseudo-hybrid because (1) they are not true PDFs but they have sensible limiting behavior and (2) they combine non-parametric and parametric models. The simplest form is: PPH(f)=∏i=1Npi(fi)×MN(f)/∏ i=1NMi(fi), where f is the feature set of N features, p’s are the marginal distributions, and MN is a parametric model with marginals Mi. The denominator was chosen so that the overall expression reduces to the correct PDF in the limits that the p’s are independent or MN happens to be the correct model. The efficacy of this PDF estimator to mimic the sampled, test distributions will be demonstrated. Other pseudo-hybrid PDF estimators will also be discussed.
Classroom acoustic evaluation and field study
Authors: Roy Kenneth P. , Campos Micaelina
Published: October 2013

The Saguaros Corazones de Alameda school in Santiago, Chile had a problem—bad acoustics. Both the background noise levels and reverberation time were much too high. The children had a difficult time understanding the teacher such that their attention was less than exemplary. Teachers had a significant absentee rate due to vocal strain issues. A sound reinforcement system was being considered—but architectural acoustic treatments were substituted with very good results. See the video and hear the results that good architectural design can make.
Auralization studies on talker comfort
Authors: Shearer Jessica , Torres Rendell R.
Published: October 2013

Although much research has focused on determining optimal acoustical environments for students in classrooms, relatively little has addressed the classroom as an acoustical workspace for teachers, who may suffer from stress and vocal strain due in part to poor acoustical environments. Although the primary problem is typically the background noise level (whether due to ventilation or students), it is also interesting to study systematically how controlling early reflections may improve the audible ‘‘room response’’ at the teacher’s speaking location without inordinately increasing the reverberant level of the background noise. Moreover, the room response at the talker’s position may help reduce the perceived need to strain the voice, as long as the reflections are not so delayed as to be disturbing. In this study approximately ten configurations of absorptive and reflective surfaces in a ‘‘typical-sized’’ classroom are auralized in real time. For each room condition, subjects rate the ‘‘talker comfort’’ in terms of perceived loudness of their speech, possible disturbance from echoes or increased background noise, and other factors. The primary descriptive physical parameter is essentially the relative amplitude and delay of clusters of early reflections, which are not always well characterized by the classical room-acoustics descriptors. Initial results of the modeling and subject testing will be presented.
Instrumentation for measuring speech privacy in rooms
Authors: Horrall Thomas , Pirn Rein , Markham Ben
Published: October 2013

Federal legislation pertaining to oral privacy in healthcare and financial services industries has increased the need for a convenient and economical way to document speech privacy conditions in offices, medical examination rooms, and certain other workspaces. This legislation is embodied in the Health Insurance Portability and Accountability Act (HIPAA) and Gramm-Leach-Bliley Act (GLBA). Both laws require that reasonable measures be put in place to safeguard the oral privacy of patients and clients. While techniques for privacy documentation are known within the acoustical consulting community, it is unlikely that community alone has the capacity to provide the surveys needed to evaluate acoustical conditions and demonstrate compliance with the legislation. A portable computer with integrated soundboard and a suitable amplified loudspeaker and test microphone are all that are needed to perform in situ measurements of articulation index or other accepted indices of speech privacy. Along with modest training, such instrumentation allows technicians to survey a large number of sites economically. Cost-effective components are shown that can meet the requirements for testing in most common environments where oral privacy is likely to be required. Example cases are presented to demonstrate the feasibility of such instrumentation.
Protocols for calibrating multibeam sonar
Authors: Foote Kenneth G. , Chu Dezhang , Baldwin Kenneth C. , Mayer Larry A. , McLeod Andrew , Hufnagle Lawrence C. , Jech J. Michael , Michaels William
Published: October 2013

The use of multibeam sonar for quantifying scatterers in the water column requires calibration. Principal elements of this include measurement of the directional characteristics of the transducer array or arrays, the determination of dynamic range, the definition of the system sensitivity, and the verification of linearity and time-varied-gain functions. Protocols developed or proposed in the course of a three-year project are reviewed. [Work supported by NSF Grant No. OCE-0002664.]
Calibration trials with multibeam sonars
Authors: Chu Dezhang , Foote Kenneth G. , Baldwin Kenneth C. , Mayer Larry A. , McLeod Andrew , Hufnagle Lawrence C. , Jech J. Michael , Michaels William
Published: October 2013

A series of calibration trials have been performed with several multibeam sonars by means of the standard-target method. These have included multiple units of the Simrad SM2000 Multibeam Echo Sounder operating at 90 or 200 kHz, with external transmitter in each case. The principal measurements have been of the full two-dimensional directivity characteristics of the main lobes. Issues of sensitivity, linearity, dynamic range, and near-field effects have also been studied. [Work supported by NSF Grant No. OCE-0002664.]
A new multibeam echo sounder/sonar for fishery research applications
Authors: Andersen Lars Nonboe , Berg Sverre , Stenersen Erik , Gammelsaeter Ole Bernt , Lunde Even Borte
Published: October 2013

Fisheries scientists have for many years been requesting a calibrated multibeam echo sounder/sonar specially designed for fishery research applications. Simrad AS has, in cooperation with IFREMER, France, agreed on specifications for a multibeam echo sounder and with IMR, Norway for a multibeam sonar, and contracts were signed for development of such systems in January 2003. The systems have 800 transmitting and receiving channels with similar hardware, but different software, and are characterized by narrow beams, low-sidelobe levels, and operate in the frequency range 70–120 kHz. The echo sounder is designed for high operating flexibility, with 1 to 47 beams of approximately 2°, covering a maximum sector of 60°. In addition, normal split beam mode on 70 and 120 kHz with 7° beams for comparison with standard system is available. The sonar will be mounted on a drop keel, looking horizontally, covering a horizontal sector of ±30°, and a vertical sector of 45°. Total number of beams is 500, 25 beams horizontally with a resolution of ∼3°, and 20 beams vertically with a resolution of ∼4°. Both systems are designed for accurate fish-stock assessment and fish-behavior studies.
Midwater acoustic modeling for multibeam sonar simulation
Authors: Buelens Bart , Williams Ray , Sale Arthur , Pauly Tim
Published: October 2013

Simulation and modeling software has been developed to generate synthetic midwater multibeam data. Essentially, the simulator can be considered as a virtual test tank. In order to develop multibeam data analysis methods for fisheries research, it is essential to have a variety of test data sets available, which are ground truthed, georeferenced and corrected for vessel motion. Since equipment and ship time are expensive and data quality not always guaranteed, the simulator provides an effective alternative. The seabed and any objects in the water column such as fish and fish schools can be defined in a 3-dimensional space. A specification for a generic linear array multibeam sonar and its position in space and time can be chosen. The acoustic model implements the technique of acoustic ray-tracing to obtain the pressure at the transducer face, which is converted to individual samples by modeling the working of a digital multibeam system. Beamforming is performed on the fly, and both raw and beamformed complex data sets are generated. Current research on model validation, calibration and analysis techniques will be presented along with an outline of planned future research.
Software tools for developing an acoustics multimedia CD-ROM
Authors: Bigelow Todd W. , Wheeler Paul A.
Published: October 2013

A multimedia CD-ROM was developed to accompany the textbook, Science of Sound, by Tom Rossing. This paper discusses the multimedia elements included in the CD-ROM and the various software packages used to create them. PowerPoint presentations with an audio-track background were converted to web pages using Impatica. Animations of acoustic examples and quizzes were developed using Flash by Macromedia. Vegas Video and Sound Forge by Sonic Foundry were used for editing video and audio clips while Cleaner by Discreet was used to compress the clips for use over the internet. Math tutorials were presented as whiteboard presentations using Hitachis Starboard to create the graphics and TechSmiths Camtasia Studio to record the presentations. The CD-ROM is in a web-page format created with Macromedias Dreamweaver. All of these elements are integrated into a single course supplement that can be viewed by any computer with a web browser.
Numerical modeling of the acoustic guitar
Authors: Chaigne Antoine , Derveaux Grégoire , Joly Patrick , Bécache Eliane
Published: October 2013

An interactive DVD has been created, based on a numerical model of the acoustic guitar. In a first chapter, the retained physical model is described and illustrated, from the pluck to the 3D radiation field. The second chapter is devoted to the presentation of the numerical tools used for solving the equations of the model. Numerical simulations of plate vibrations and radiated sound pressure are shown in the third chapter. A number of simulated sounds are presented and analyzed in the fourth chapter. In addition, the DVD includes a discussion between a guitar maker, an acoustician, a guitar player and a mathematician. This discussion is entitled ‘‘towards a common language.’’ Its aim is to show the interest of simulations with respect to complementary professional approaches of the instrument. This DVD received the Henri Poincaré Prize from the 8th Research Film Festival of Nancy (June 2003), sponsored by the CNRS, in the category ‘‘Documents for the scientific community and illustrations of the research for teaching purpose.’’
Modeling of shallow water reverberation data
Authors: Yudichak T. W. , Knobles D. P. , Cable P. G.
Published: October 2013

A broadband model of seabed reverberation in a shallow water waveguide is used to analyze data measured in the Area Characterization Test I (ACT I). Given a source spectrum, a mean geoacoustic profile for the waveguide, and statistics characterizing the scattering sources (including fluctuations in seabed sound speed and density as well as seabed interface roughness) the model simulates time series measured in a monostatic geometry. It accomplishes this by solving the integral form of the Helmholtz equation in a random medium in the Born (or single scattering) approximation using the ORCA normal mode model to compute the unperturbed Green’s functions. Statistics of the scattering sources are inferred from comparisons between modeled time series and experimental data. Also, the effects of uncertainties in the source spectrum are considered, and the validity of the Born approximation in this context is discussed. [Work supported by ONR.]
Comparison of modeled and measured sonar returns from calibrated targets in the Main Acoustic Clutter Experiment 2003
Authors: Lai Yi-san , Lee Sunwoong , Ratilal Purnima , Makris Nicholas C.
Published: October 2013

In a shallow-water environment the sound field scattered by a target can be complicated by waveguide effects such as multimodal propagation and dispersion. It has been shown that relying on the sonar equation in a shallow-water waveguide can lead to errors in estimating a target’s scattering properties [Ratilal, Lai, and Makris, J. Acoust. Soc. Am. 112, 1797–1816 (2002)]. Furthermore, applying conventional beamforming and matched filtering for target localization can yield errors in range and bearing estimation. To quantify these errors, an analytic expression for active sonar returns after beamforming and matched filtering is derived from waveguide scattering theory. This expression is used to model the beamformer and matched filter output from calibrated targets deployed in the Main Acoustic Clutter Experiment 2003. Modeled and measured sonar returns are compared from several calibrated targets, and the errors in target localization and scattering amplitude estimation are quantified in a realistic active sonar scenario. Accurate locations of the source, targets, and receiver array were measured by GPS during the experiment.
Bistatic scattering from flush and partially buried targets in shallow water
Authors: Veljkovic Irena , Schmidt Henrik , Tesei Alessandra
Published: October 2013

GOATS’98 experiment had as one of its objectives to explore the possibility of vastly increasing the coverage rate of shallow water mine countermeasures (MCM), especially for buried targets using subcritical seabed penetration. The evanescent incident field combined with 3D bistatic configuration brought about a rich and intricate set of physical phenomena occurring in the target scattering and radiation process. Resonance of manmade elastic targets is a pivotal concept distinguishing targets from rocks or other clutter. Nevertheless, burial in sediment results in a variety of modifications to the scattered response caused by different physical mechanisms, geometric constraints, and intrinsic sediment properties. It is the goal of this work to identify, analyze, and explain the fundamental effects of the outer sediment and the proximity of the seabed interface on the scattering from elastic shells insonified at subcritical incident angles in a bistatic configuration. Using time-frequency and spectral analysis, a new, more comprehensive, understanding of GOATS’98 experimental data was obtained distinguishing the effects of the acoustics environment from the resonant signature of buried elastic targets. To achieve this, and to further investigate the details of the scattering process a new target scattering module of OASES-3D modeling framework was used. [Work supported by ONR.]
Hybrid volume scattering model: Application of the Biot theory to the fluid-bottom model
Authors: Ohkawa Keiichi , Yamamoto Tokuo
Published: October 2013

The volume backscattering model, which was derived by Yamamoto (1996) applying the Born approximation to the Helmholtz equation, is improved by replacing transmission coefficients at the fluid–fluid interface to those at the fluid–porous seabed interface. The spectra of velocity and density fluctuations in sediments are assumed to be the same. The sea bottom is hereby treated as an isotropic porous medium, in which sound speeds have frequency dependence. Frequency dependent reflection and transmission coefficients at the fluid–porous seabed interface for a compressional wave incident from fluid upon porous media and vice versa are easily calculated applying the mode’s decoupling method to Biot’s body waves without considering behaviors of inhomogeneous waves in porous media. In this problem the reflection and transmission coefficients in terms of displacement potentials are computed. The hybrid model is applied to medium to high frequency bottom backscattering from the sandy bottom. In soft sediments, however, the difference between the hybrid and the fluid–fluid bottom models is small. It is concluded that the hybrid model can be applied to volume backscattering from any kind of unconsolidated sediments throughout the frequency range. [Work supported by ONR Code 321OA.]
Low frequency evaluation and treatment of small rooms
Authors: D’Antonio Peter
Published: October 2013

At low frequencies, the acoustical coupling of the listener and loudspeakers with reflections from the room’s boundary surfaces and its modal pressure distribution can cause significant acoustical distortion. For rectangular room’s, software programs exist to predict the magnitude of these effects. However, there is no substitute for experimental measurements. When evaluating small rooms, it is often desirable to isolate the modal effects from the speaker-boundary effects, so that appropriate corrective measures can be applied. A MLS measurement procedure will be presented. After the room dimensions and listener/loudspeaker positions are optimized, one can apply dedicated low frequency absorbers to further control low frequency problems. The characterization of low frequency absorbers will be described, using a 7-ton, 22 long impedance tube.
Improvement of low frequency sound variability in a small enclosure by use of a source with frequency-independent radiated power
Authors: Loubeau Alexandra , Tichy Jiri
Published: October 2013

The irregularity in the low frequency response encountered in small rooms adversely affects the transmission of sound from a source to a receiver. Variations in the frequency response, which are dependent on source position, receiver position, and room absorption, result in perceived inconsistencies in sound quality throughout the room. This computational study examines the effect of constant sound power radiation on the sound field variability with frequency in a small enclosure. Effects of the parameters listed above are investigated. Frequencies of interest are 20–80 Hz. Source positions include the room corner, typical subwoofer locations, and typical full-range loudspeaker locations. Grids of receiver positions are selected around the center of the room, forward of center, back of center, and to the side of center. Room absorption values explored correspond to reverberation times of 0.5 s, 1 s, and 2 s. The benefit of constant sound power radiation is shown using the metric of standard deviation. Depending on the location of the source and receiver, the standard deviation of the frequency response decreases by approximately 2–3 dB with constant sound power radiation. [Research supported by Penn State ARL.]
The nature and location of gassy sediment sections in the continental shelf and slope in the northwestern Gulf of Mexico
Authors: Bryant William
Published: October 2013

In the northwestern Gulf of Mexico continental shelf and upper slope gassy sediments are a pervasive phenomena and an important consideration relative to engineering and acoustic activities on the sea floor. An examination of seismic data from over a thousand M.M.S. geohazard reports and core logs of 1,670 foundation boreholes drilled to an average subbottom depth of 125 m on the continental shelf and upper slope in the northwestern Gulf, has revealed that gassy sediment sections are most abundant near the Mississippi River Delta, in the sediment fill of buried stream channels that were eroded during the early and late Wisconsinan, and in Miocene and Plio–Pleistocene depocenters on the continental shelf and upper slope. Out of the 1,670 bore holes examined 1,158 (68%) contained indications of gassy sediments most of which is of biogenic origin. Large patches of gassy sediments exist, some exceeding 10 km in size but most are less than 500 m. The examination of 500 piston cores, up to 40 meters in length, taken on the mid and lower continental slope areas were almost void of gassy sediments as the result of the halokeiesis of allocthonous salt.