bluuebunny/crossref_metadata_2025 huggingface dataset:
Impulse noise and startle
Authors: Flindell Ian H.
Published: July 2002

It is well known that impulsive noise caused by gunfire, explosive devices, and high speed overflight by aircraft at low altitudes can cause an acoustic startle effect (ASE). The ASE is one of many possible startle effects which are normally associated with unexpected stimuli. The ASE always consists of a sequence of largely defensive reflex actions with physical, physiological, and psychological components. It is generally accepted that the ASE can be a direct contributor to accidents in inherently risky situations, but what is more controversial is the possibility of some, presently undefined, linkage to longer term health effects. Based on a critical review of the literature, this paper reports some general findings on the possible theoretical bases for any such linkage and makes a number of suggestions for future research. The available evidence suggests that if there is such a linkage, it must be mediated either through individual differences in reactivity and habituation, or through the less well-specified ‘‘general stress hypothesis.’’ The fact that many of the direct physiological responses observed in the ASE are not generally considered harmful in other contexts, such as exercise, is likely to be an important consideration.
Comparison of procedures for the quantification of the impulsivity of environmental sounds
Authors: Brambilla Giovanni
Published: July 2002

Any procedure for the quantification of the impulsivity of environmental sounds should meet the following requirements: (i) sufficiently adequate in describing the human perception of impulsivity; (ii) easy to perform in the field by means of basic instrumentation or in the laboratory without requiring expensive apparatus and too much time. Among the several procedures proposed in the last decade, those more frequently used or promising have been considered in this paper and compared to one another. For this purpose data collected in earlier European studies have been reanalyzed. The data considered refer to 26 environmental sound stimuli heard in laboratory at 55 LAeq level for 20 s by a number of people varying between 48 and 112 subjects. The subjective data on clear perception of impulsivity have been related to the selected descriptors, such as LAI-LAS, increment, etc. The potential of these objective parameters in describing the perception of impulsivity, as well as the determination of the threshold value for the onset of impulsivity, has been investigated by means of their correlation with the subjective data and determination of sensitivity and peculiarity of each descriptor.
Acoustic measurements in an airport environment and the identification of the sound radiated by aircraft wake vortices
Authors: Fine Neal , Rees Frank , Von Winkle William
Published: July 2002

Results are presented of an effort to measure the sound generated by aircraft wake vortices. The objective of the research is to estimate the spectral shape and source levels characteristic of the sound generated by aircraft wakes during approach and landing. Measurements were made at JFK airport in August 1997, for various aircraft, using three Bruel & Kjaer outdoor microphones. The data were recorded to tape, and spectrum analysis was performed using a B&K portable spectrum analyzer. The three microphones were placed near the beginning of runways 13L and 22L, arrayed in several configurations parallel to and perpendicular to the runway centerline. Initial spectrum analysis of the data revealed a prominant broadband ‘‘hump’’ in the one-third octave sound-pressure level spectra, centered at approximately 50–60 Hz for a B-747 landing (with a bandwidth of roughly 20–30 Hz). The timing of the hump is consistent with that expected for wake vortex sound and it is hypothesized to be generated by the wake vortices. Cross correlations between microphones arrayed parallel to the runway will test this hypothesis. Additional data, which are to be recorded in January 1998, will also aid in identifying the wake vortex sound characteristics.
Scattering by partially buried shells
Authors: Lim Raymond
Published: July 2002

An extension of a previously derived transition-matrix solution for acoustic scattering by a three-dimensional elastic obstacle partially buried at a water/sediment interface [Lim, J. Acoust. Soc. Am. 99, 2498 (1996)] was carried out and numerically executed to allow for the obstacle to be layered. The formulation adapts an approach previously used to improve convergence for high-aspect-ratio obstacles in a homogeneous fluid host, where spherical harmonics were employed to expand the exterior surface fields of the object [A. Boström, J. Acoust. Soc. Am. 76, 588–593 (1984)]. Although the analytical solution is expected to be exact, numerical stability is best if the obstacle layering is smooth and obeys certain convergence restrictions. In particular, for surface fields expanded in basis functions of spherical geometry, the origin-centered sphere that circumscribes the inner boundary of each homogeneous obstacle layer should never overlap the origin-centered sphere that inscribes its outer boundary. While this restriction becomes a problem for elongated shells, the acoustic response of spherical shells or shells with near-spherical cores can be calculated. Results are presented to examine the dynamics of partially buried shelled obstacles.
Eigenvalues gap optimization with sensitivity criteria in coupled acoustic-structural systems
Authors: Casas Walter P. , Pavanello Renato
Published: July 2002

The design optimization can be made following a hard repetitive time consuming process, through the analysis of the design with a few modifications in its parameters, until the required system is encountered. To solve this problem, it is better to use the sensitivity analysis, letting one evaluate the model performance without realizing new analysis. The purpose of this work is to optimize the gap between two eigenvalues in coupled acoustic-structure systems in order to avoid the resonance phenomena in a certain frequency interval, taking the thickness of the structural elements as control variables subject to one constant structural volume. The finite element method is used for discretization of the system, and one nonsymmetrical formulation up with Hermissian matrices in displacement of the structure and fluid pressure describes the system, being necessary to use the left and right eigenvectors concept. For simplicity the nonzero and nonrepeated eigenvalue case is considered. The sequential quadratic programming algorithm is used for the constrained nonlinear optimization, and in the optimization process is considered the modal sensitivity analysis to choose the more sensible parameters. The validity of the study is verified by applying it to a coupled bidimensional system. a)Currently at UNICAMP-FEM-DMC.
Finite-difference studies of structural–acoustic interaction
Authors: Kristiansen Ulf
Published: July 2002

The behavior of an acoustic fluid coupled to an elastic structure has been investigated by a numerical technique, i.e., the finite-difference method. The technique is simple to apply and convert the governing differential equations to a system of simultaneous algebraic equations in mesh-point unknowns. The chosen example is a 2D cavity enclosed by three hard walls and a flexible beam. The coupled modes are calculated. To incorporate an external field, the beam is assumed to be situated in an infinite baffle. Coupling to the external field is done either by extending the finite-difference model to this region, or by a boundary element method. Different examples of forcing functions will be discussed: mechanical, acoustical, and turbulent flow. The presentation will also discuss how the errors inherent in this type of numerical approximation might be reduced. Higher-order finite-difference operators and Richardson extrapolation are two such techniques.
Factors influencing the detection and intelligibility of speech in competing message environments
Authors: Ericson Mark A. , Bolia Robert S. , Nelson W. Todd
Published: July 2002

While monitoring multiple conversations, a listener often needs to know not only what was said but who said what to whom. An exploratory investigation into these questions involved eight talkers saying similar, simultaneous messages. Four male and four female talkers speaking call sign phrases and logical phrases were digitally recorded. All phrases were adjusted in overall gain to have the same average power and onset time. Between one and seven competing messages were played back over loudspeakers in an anechoic chamber. Thereby, angular separation between the speech signal and speech babble was also a controlled factor. Physical attributes of the eight talkers’ speech were analyzed using the Multi-Dimensional Voice Program from Kay Elemetrics. Nineteen acoustic attributes of the talkers’ voice samples were quantified. Voice samples were analyzed during sustained phonation and continuous speech conditions. A correlational analysis was used to investigate which aspects of the talkers’ speech facilitate detection and intelligibility against a cacophony of competing voices. The salient features of the eight talkers’ voice samples will be discussed.
The enhancing effect of subsequent context in the perception of the sentence-initial word
Authors: Kawashima Takayuki , Kashino Makio , Sato Takao
Published: July 2002

The authors examined whether the perception of the initial word in a Japanese sentence is enhanced by semantically related subsequent context. Phonemic restoration effects under periodic noise replacement were compared for two types of sentences. In the first condition, the initial word of a sentence was semantically predictable from the subsequent context (high-predictability condition). In the second condition, the initial word was not directly predictable from the subsequent context (low-predictability condition). The intelligibility of the sentence-initial words was higher in the high-predictability condition than in the low-predictability condition (58% vs 10%). On the other hand, the intelligibility of the subsequent portions was not significantly different between the two conditions (71.1% vs 66.3%). These results show that word perception can be enhanced by subsequent semantic context in Japanese.
An inexpensive light-weight ocean acoustic research array
Authors: Heard Garry J.
Published: July 2002

Current and past research arrays built at the Defence Research Establishment Atlantic (DREA) have been intended for indefinite and repeated use. Building, maintaining, and using these arrays has been expensive in terms of both money and labor due to the rugged construction practices, complicated electronics, and materials. With the reduced resources available in most laboratories today, there is considerable need for cheaper research array systems that are easily maintained and deployable from a variety of platforms: from Zodiacs to full-sized AGOR vessels. This paper describes the initial development of a light-weight research array that is expected to meet the requirements of the Ocean Acoustics Group at DREA. The array uses epoxy resins for most of the structural components, has a serial-digital bus, has low-power requirements, is easily reconfigured, and is essentially disposable, although the intention is to reuse the array in whole or in part as long as it remains serviceable. The prototype array, which is scheduled for sea testing in July 1998, will be a bottom-deployed 500-m aperture horizontal line array with 16 channels sampled at 2048 Hz.
Detection and tracking of a moving source with application to real data (SWELLEX)
Authors: Tantum Stacy L. , Nolte Loren W.
Published: July 2002

The optimum uncertain field tracking algorithm (OUFTA) incorporates knowledge of source motion as well as uncertainty in the propagation environment [S. L. Tantum and L. W. Nolte, ‘‘Tracking and localizing a moving source in an uncertain shallow-water environment,’’ J. Acoust. Soc. Am. 103, 362–373 (1998)]. It is shown how detection, tracking, and adaptivity to an uncertain environment can be formulated within a unifying and optimal framework. Performance results and trade-offs are presented for simulated data. Results are also presented using this approach with low signal-to-noise ratios and real data (SWELLEX). [Research supported by ONR.]
Time-reversal mirror with variable depth focusing
Authors: Song Hee Chun , Kuperman William A. , Hodgkiss William S. , Akal T. , Ferla C. , Jackson Darrell R.
Published: July 2002

Recent time-reversal mirror (TRM) experiments conducted in the Mediterranean Sea demonstrated variable range focusing using the frequency-range invariant property in a shallow-water waveguide [Song et al., J. Acoust. Soc. Am. 102, 3171(A) (1997)]. The technique involves retransmitting the data at a shifted frequency according to the desired change in focal range in almost real-time fashion. As opposed to the variable range focusing, there does not appear to be an environmentally independent elegant solution for variable depth focusing. However, a method based on knowledge of the environment, which translates to being able to compute the acoustic modal structure, permits a focal depth shift. The method involves projecting out the important modes received at the vertical source–receive array (SRA) and appropriately altering their excitation to focus at another depth. In the May 1997 experiment, some limited results demonstrated that this method is feasible. Comparison of data with simulations and theoretical analysis will be presented and discussed. [Work supported by ONR.]
A parabolic equation-based backpropagation algorithm for matched-field processing
Authors: Thomson David J. , Ebbeson Gordon R. , Maranda Brian H.
Published: July 2002

In applications of matched-field processing (MFP) to passive sonar, signals measured on a hydrophone array due to a source at some unknown position xs=(rs,zs) are correlated with signals predicted by a propagation model (replicas) due to a source at a given position x=(r,z). This matching is carried out for many assumed x’s within a search region (range, r and depth, z) to form a (normalized) ambiguity surface whose peak value provides an estimate of xs. For an N-element array, reciprocity is invoked to reduce the computational effort to computing N replica fields at each point on the search grid. In this paper, a matched-field processor proposed by Tappert et al. [J. Acoust. Soc. Am. 78, S85 (1985)] is revisited that combines measured data with PE starting fields to effectively backpropagate an (unnormalized) ambiguity surface outwards from the receiving array. This unnormalized processor generates the ambiguity surface N times faster than the normalized one. The effectiveness of the backpropagation algorithm is examined by applying it to some multi-tonal data obtained during the Hudson Canyon experiment. Issues relating to normalization and incoherent/coherent frequency averaging are discussed.
A study of improvements to acoustical conditions for singers
Authors: Noson Dennis
Published: July 2002

While numerous recent studies have been reported on improving stage acoustics for orchestral performers, the preferred acoustical conditions on performing stages for singers has received limited attention in the past 30 years, with pioneering studies by Nakamura and Marshall. A series of acoustical modifications has been proposed for a Seattle church to improve the acoustics for both the listeners and the performing choir. An investigation was made, within the constraints of the existing acoustical environment of the church, to determine what direction the acoustical modifications should take to improve conditions of ensemble and balance among the singers while simultaneously improving the sound field for the audience. Acoustical conditions were modified both by adding temporary reflecting panels and introducing simulated reflections with strategically located loudspeakers. The results indicate a potential for noticeable improvement in the existing chancel acoustics, with most of the benefit applying to the singers rather than the listeners. Comparison will be made between the measured changes to the sound field and the predicted response of the singers using Ando’s theory of subjective preference.
Bubbles and surf zone oceanography
Authors: Terrill Eric J. , Melville W. Kendall
Published: July 2002

Breaking waves in the surf zone entrain high-density clouds of bubbles which are subsequently transported offshore via rip currents and turbulent diffusion. The presence of the bubbles presents a complex problem for acousticians interested in the propagation of natural and man-made sound in this shallow water regime. To investigate the acoustical properties of this area, a multi-investigator experiment was performed near the Scripps Pier in March 1997. A broadband acoustic technique, developed at the Marine Physical Laboratory, was deployed in a four-channel configuration in water of 6-m depth. Each channel of the system allows the determination of the bubble size distributions at a discrete depth via inversion of the measured sound speed and attenuation. Analysis of the data shows high concentrations of bubbles advecting offshore via rip currents, resulting in acoustic attenuations ranging from O(1)–O(100) dB/m. Vertical gradients were observed in the bubble concentrations. Simultaneous measurements of the wind, waves, and currents provide a synoptic view of the overlying oceanography during the course of the experiment. Results of the experiment will be discussed in the context of the transport of surf-generated bubbles through the measurement site.
Effects of bubbles on high-frequency sound propagation in very shallow water
Authors: Elmore Paul A. , Caruthers Jerald W. , Stanic Stephen J. , Goodman Ralph R.
Published: July 2002

The results of an experiment performed off the research pier at the Scripps Institute of Oceanography that measured the acoustic effects of small bubbles in very shallow water (6 m) are discussed. The results presented are in coordination with researchers who conducted other measurements simultaneously. During the experiment, rip currents passed through a field of measurement instruments 300 m offshore. These rip currents were laden with bubbles created in the surf between the instruments and the shore. Pulse signals, between 39 and 244 kHz, were propagated to 10 m through the bubble clouds. The effects of these rip currents on the spatial distributions of the resulting acoustic attenuation are discussed. From the attenuation data, bubble populations are calculated by an iterative procedure based on the well-known resonant bubble approximation. [Work supported by the Office of Naval Research.]
Biological effects of ultrasound
Authors: Nyborg Wesley L.
Published: July 2002

Ultrasound has considerable potential as an agent for modifying cells and tissues. This comes partly from its capability to produce temperature elevation in desired spatial and temporal patterns. It also comes partly from its capability to produce cavitation in one or more of its diverse forms and, in addition, partly from the action of radiation forces, radiation torques, and acoustic streaming. In some situations, several mechanisms are involved and may interact with each other; for example, cavitation can produce heat in a medium, and the resulting temperature rise will affect the cavitation activity. Understanding these and other mechanisms has been, and promises to be, helpful in developing applications of ultrasound to therapy, surgery, and biotechnology, as well as in formulation of criteria for safety in medical procedures involving ultrasound. In this review, examples will be given to which the mechanisms are relevant, and recent developments will be discussed.
Acoustic field of a device for noninvasive pressure wave therapy in orthopedy
Authors: Steiger Eckard , Dreyer Thomas , Mayer Juergen
Published: July 2002

The Storz Minilith SL1 is a device specially designed for the treatment of orthopedical indications as tendinosis calcarea, tennis or golf elbow, heel spurs, or supra spinatus syndrome. A cylindrical electromagnetical source generates an intense ultrasonic pulse, which is focused by means of a parabolical reflector. Measurements in the focal region are performed in degassed water using a fiber-optic probe hydrophone. The whole process of pulse radiation from the source over nonlinear propagation including reflection to the focusing is simulated too. The underlying full wave model is based on a specially developed finite difference in time domain method. Excellent agreements of measured and computed pressure wave profiles in the focal region validate the model. The generation of shock waves in dependence on the energy setting of the therapy device is studied. Further investigations are made to consider the interaction of the SL1-pulse with human tissue structures as they occur in medical applications.
Tempo perception: The multiple-look strategy is limited by a short temporal window
Authors: Panissal-Vieu Nathalie , Drake Carolyn
Published: July 2002

Previous studies [Drake and Botte (1993)] indicated that sensitivity to tempo changes in isochronous sequences improves as the number of intervals in the sequence increases. Further studies suggested that this multiple-look process only works within a limited temporal window of 0.5 or 2 s depending on the tempo of the sequence [Panissal-Vieu et al. (1995)]. This temporal window represents the time required to extract all the necessary temporal information (mean interval duration and dispersion). Two experiments investigated how this mental representation is used to make temporal judgements. In a 2 AFC paradigm, trained listeners identified the slower of two isochronous sequences. The number of intervals was varied in either the first or second sequence, with the temporal window saturated in the other sequence. The number of intervals required to saturate the temporal window of the first sequence varied with tempo, as predicted. However, only three intervals were required in the second sequence. These results suggest a buildup of a stable and accurate memory trace during the first sequence which is subsequently compared with the first two intervals of the second sequence. There is no need to recalculate the memory trace for the second sequence.
Investigations and analysis of assessment word for sound quality attaching importance to high-order sensation
Authors: Ishikawa Tomoharu , Fuyuki Shingo , Miyahara Makoto
Published: July 2002

The standpoint of our research is to evaluate subjectively the sound quality of sound-reproducing systems by evaluating deep emotions which are brought by the sounds of music and speech. In evaluating sound qualities, assessment words that express the emotive meanings which have arisen in an evaluator’s mind are used. The importance of sound reproduction is the transmission of ‘‘mind’’ that a musician wants to send. Therefore the assessment words which can represent the high-order sensations of the sender need to be obtained. Not only conventional assessment words but also assessment words which represent high-order sensation have been investigated and then analyzed. The method is as follows, (1) 35 representative assessment words by the KJ method from 1322 assessment words which were obtained by surveying audio publications over the past three years were obtained. (2) Psychological distances among 35 representative assessment words have been analyzed by the MDS method, and four clusters by hierarchical clustering have been obtained. (3) Independent to (2) above, representative assessment words by the public attention evaluation method have been scored and ranked. (4) The important assessment words which are strongly correlated with the overall sound quality have been selected.
Product design and structural acoustics
Authors: Lyon Richard H.
Published: July 2002

If, by structural acoustics the analysis and understanding of noise and related problems through an understanding of mechanical vibration is meant, then structural acoustics has a very long history in product design through the application of isolators and structural damping to products. But the greatest amount of research and methods development has been focused on fairly large commercial and military structures like submarines, aircraft, and spacecraft. The resources for, attention to, and methods for structural acoustics that has been available in these and the automotive industries has not been present for the industries that make most of the products each of us deals with daily. Structural acoustics as applied to hairdryers, vacuum cleaners, and lawnmowers presents challenges in both understanding and cost that the technical community can respond to. For example, designers would like to predict sound from CAD drawings. Such a need can be an inspiration to some of us. This presentation will provide examples of the need and some possible responses.
Acoustic scattering by a three-cylinder scatterer: Theoretical and experimental study of resonances
Authors: Gabrielli Paul , Decanini Yves , Folacci Antoine , Fournier Elisabeth
Published: July 2002

Acoustic scattering by a system of three identical parallel cylinders, located at the vertices of an equilateral triangle, is theoretically, numerically, and experimentally studied by emphasizing the role of the symmetries of the scatterer. Incident and scattered fields are expanded over the different irreducible representations of C3v, the symmetry group of the scatterer. From the boundary conditions, an infinite set of four linear complex algebraic equations is obtained, where the unknown coefficients of the scattered fields are uncoupled. As a consequence, the form function is calculated for various incidence and observation angles, and the positions of the scatterer resonances are numerically determined in the complex plane of the reduced frequency. New types of resonances appear. A physical interpretation of these resonances by the phase-matching of geometrical and surface waves along closed paths is given by using the geometrical theory of diffraction. These resonances are experimentally observed for elastic cylinders immersed in water. The work is a step toward a complete study of chaos (associated with the system of rays) in the context of multiple scattering.
Bandpass filters for the evaluation of short reverberation times
Authors: Kob Malte
Published: July 2002

In building acoustics, evaluating the sound insulation of building elements suffers from rather bad reproducibility. The reason is the energy flow between the building element and the surrounding structure of the test laboratory. To get more reproducible measurements, it is desirable to measure the loss factor of the element, e.g., by evaluation of the reverberation time of the structure. Unfortunately, the evaluation of decreasing reverberation times T60 of building elements, for instance in one third octave bands is distorted by a growing influence of the applied bandpass filter. In literature a minimum permissible product of the bandwidth and the reverberation time of the filter B⋅T=16 can be found but no error in the estimation of T60 beyond this limit is given. A maximum admittable error depending on the B⋅T product is derived for several filters used in real time analyzers. An optimized filter according to the IEC 1260 standard is developed and results of simulated and measured short reverberation time evaluations are presented. Other possibilities of the investigation of the loss factors and their practical use are discussed.
A two-way parabolic equation for a fluid/elastic waveguide
Authors: Lingevitch Joseph F. , Collins Michael D.
Published: July 2002

The parabolic equation (PE) method is applied to acoustic propagation in a fluid above an elastic layer. Two-way PEs have previously been developed for purely fluid or elastic waveguides [M. D. Collins, J. Acoust. Soc. Am. 93, 1815–1825 (1993)]. These methods divide a range-dependent environment into a sequence of range-independent regions and apply the single scattering method to obtain the transmitted and reflected fields at each interface. Recently, these ideas have been extended to mixed media such as fluid/poro-acoustic waveguides. Improved Padé approximations for the interface conditions are useful in stabilizing the iteration formula for the transmitted and reflected fields [F. A. Milinazzo et al., J. Acoust. Soc. Am. 101, 760–766 (1997)]. In this paper, a fluid/elastic waveguide is examined and examples of the coupling between the fluid compressional wave and elastic waves at vertical interfaces are presented. [Work supported by ONR.]
Spatial coherence in range-dependent shallow water environments
Authors: Rozenfeld Ilya , Carey William M. , Lynch James F. , Cable Peter , Siegmann William L.
Published: July 2002

In this presentation, effects of small random fluctuations on the spatial coherence of the sound field in shallow water with multilayered sediments will be examined. These fluctuations occur within the water volume and the sediment layers as well as at the layer interfaces. Most previous work has dealt with either range-independent or weakly range-dependent environments with random variabilities. However, strong range dependence often occurs in sound-speed profiles and at layer interfaces. For example, the region of the ACT III experimental series in the Straits of Korea shows range variability arising from sloping bathymetry and a coastal front. Consequently, spatial coherence for range-dependent waveguides with small random fluctuations will be treated. Numerical simulations of the coherence function will be presented. Results will be compared with coherence lengths of the field extracted from ACT III data.
Thin-sediment shear-induced effects on low-frequency broadband acoustic propagation in a shallow continental sea
Authors: Tollefsen Dag
Published: July 2002

Low-frequency acoustic broadband propagation loss data collected in areas of a shallow continental sea where the seabed is composed of hard substrates covered by thin deposits of sediment is presented. Data are shown to exhibit several characteristics consistent with loss due to coupling to interface waves at the sediment–substrate interface; in instances of a physically thin sediment cover, loss is attributed to guided elastic waves in the sediment [S. J. Hughes et al., J. Acoust. Soc. Am. 88, 283–297 (1990)]. The interpretations are supported by numerical modeling of propagation loss using a recently developed wave number intergation code for horizontally layered fluid–solid media, and geoacoustic models consistent with geophysical data from the sites of acoustic experiments.
FFT beamforming with cylindrical arrays: Application to the Toroidal Volume Search Sonar
Authors: deMoustier Christian P. , Gallaudet Timothy C.
Published: July 2002

FFT beamforming is typically applied to arrays of coplanar and equally spaced elements. For curved arrays, conventional delay and sum beamforming should be the norm because the elements are not coplanar and the projection of their position on a tangent plane yields unevenly spaced elements. However, with appropriate phase correction coefficients, FFT beamforming can be applied to the elements contained in a 90° sector of a cylindrical array if beams formed within ±35° about broadside are kept. Within this sector results are essentially identical to those obtained via conventional beamforming but the FFT technique is more efficient computationally and better suited to real-time applications. The error bounds associated with FFT beamforming on cylindrical arrays are discussed and we present applications of the technique to data collected with the Toroidal Volume Search Sonar by the Coastal System Station, Panama City, FL. [Work sponsored by ONR-NRL (Contract No. N00014-96-1-G913).]
Range spread measurement of underwater scatterers and channels using active sonar probing signals and a cross-correlation process
Authors: Kisenwether James J. , Ricker Dennis W.
Published: July 2002

A method for measuring range spread of underwater scatterers and channels based on the cross-correlation processing of the tones of a multicomponent waveform has been developed. The correlation terms which comprise the measure are samples of the time-frequency correlation functions (TFCF) of scatterers and channels. The measure has been used to characterize the time-frequency spread and represents the signal coherence. This paper will provide a review of two frequency correlation function representations and their characterization using the aggregate coherence measure, termed correlation mass. The sensitivity of this measure as a function of waveform parameters, scatterer structure, and measurement platform motion will be defined and its robustness on a multiping basis assessed. It will be shown that this measure can be decomposed into correlated components resulting from interaction with a scatterer and a channel. Essentially the composite correlation is obtained by sampling the product of the scatterer and channel TFCF’s. Data from in-water experiments and digital sonar simulations will be presented which validates the linear systems model of the composite scattering process. [Work supported by ONR.]
Measurement at low ultrasonic frequencies of absorption due to suspended particulate matter
Authors: Brown Niven R. , Leighton Timothy G. , Richards Simon D. , Heathershaw Tony D.
Published: July 2002

The visco-thermal absorption of sound by suspended particulate matter can be reliably measured using a reverberation technique. This absorption may have an adverse effect on the performance of sonars operating at low ultrasonic frequencies in coastal waters where suspensions are often present in significant concentrations. A series of experiments has been performed to study the viscous absorption by suspensions in the frequency range of 50–150 kHz by taking the difference in reverberation times of a volume of water with and without particles. Measured attenuation agrees reasonably well with that predicted by theory for concentrations above 0.5 g/l. A number of interesting phenomena have also been observed which are related to the measurement system and the turbulent flow required to keep the particulate suspended. For accurate measurement, losses at the container walls must be minimized. Although there are small losses at the surface by transmission, along with losses due to absorption in the acoustic boundary layer, the presence of bubbles and dissolved gas, and turbulence, the relative measurement gives a good assessment of the absorption by the particles. These effects are discussed and results for particulate absorption are presented.
Scholte wave dispersion by rippled liquid/solid interface topography
Authors: Chamuel Jacques R.
Published: July 2002

The effect of sand ripples on seismoacoustic waves is not yet understood. Quantitative results are presented characterizing the dispersion of Scholte waves propagating along a rippled surface of an immersed ‘‘soft’’ solid half-space. One model has a sinusoidal profile with a ratio of corrugation amplitude to wavelength of 0.25. The observed Bragg frequency components of broadband transient received waveforms are shifted by 180° as the receiver is displaced one cycle along the corrugation, however, the other frequency components are delayed by a smaller amount following the dispersion characteristics. Scholte and Rayleigh wave experimental dispersion graphs obtained from ‘‘soft’’ solid models are compared with replotted scaled numerical results on Rayleigh wave dispersion along a ‘‘hard’’ corrugated solid half-space [Glass et al., ‘‘Propagation of Rayleigh surface waves across a large-amplitude grating,’’ Phys. Rev. B 24, 6843–6861 (1981)]. The findings reveal that a rippled ‘‘soft’’ liquid/solid interface can decrease the velocity by more than 70% of high-frequency Scholte wave components propagating normal to the ripples. The accuracy of acoustic inversion and detection of buried objects depends on predicting the effect of seafloor topography. [Work supported by ONR.]
Structure-borne transmission in lightweight buildings
Authors: Craik Robert J. M.
Published: July 2002

The move away from mass as a means of reducing sound transmission in buildings has led to the development of lightweight buildings. High levels of sound insulation are achieved by introducing discontinuities while retaining structural integrity. This paper will examine structure-borne sound transmission in lightweight framed buildings. For sound transmission through a wall or floor it is the coupling between the frame and the lightweight panels which must be considered. The coupling can be classified as either a line connection or a point connection. Each of these cases will be examined and the theories for sound transmission compared with experimental results. Flanking transmission must also be considered and models for the coupling between the structural elements will also be examined. These models are different from traditional buildings as many of the elements behave as beams rather than as plates. The structure is therefore a collection of beams and plates rather than just plates. Some of the transmission paths for transmission between adjacent rooms will be examined both for the case where all walls and floors are lightweight constructions and for the case where there is a mixed construction with traditional walls but lightweight floors.
Identification of dolphin schools by bioacoustical unique features
Authors: Kebkal Konstantin , Bannasch Rudolf , Kulagin Valeriy
Published: July 2002

Long-term acoustical observations conducted on bottle-nosed dolphins (Tursiups truncatus ponticus) in the State Oceanarium of Ukraine as well as in the open sea revealed the existence of school specific acoustic features. It was found that each dolphin school uses a unique set of whistle contours in conjunction with a preferable frequency band and certain time characteristics. If the latter two characteristics somewhat vary according to particular surrounding and behavioral situations, the composition of normalized whistle contours stays stable. Each single whistle can be described by a set of polynomial coefficients characterizing its shape. Referring to the whole set of whistles emitted, a diagram of signal preferences can be built. Several samples will be presented to demonstrate that such diagrams represent acoustical portraits unique for every dolphin school. Based on those analyses, the development of a system for passive automatic monitoring of dolphin abundance and migration activity is in progress. The system should consist of radio-acoustical buoys placed in the sea to record signals and to transmit them to a coastal station and an automatic signal analyzer in conjunction with an expert-system capable of determining whether the respective signals belong to a school registered earlier, or a new one.
Observations of the movements of humpback whales about an operating seismic survey vessel near Exmouth, Western Australia
Authors: McCauley Robert D. , Jenner Micheline-Nicole , Jenner Curt , Cato Douglas H.
Published: July 2002

As part of a project investigating the interaction of air-gun noise and marine animals, monitoring of migrating humpback whales traversing the track of a seismic vessel was conducted in October 1996. Four separate pods traveling SW in 100–120 m of water were followed as they approached a seismic vessel traveling on an east/west heading and operating a 2678 cui air-gun array every 8 s. The response of pods was to change course at 3–6 km from the vessel so as to pass in front of or behind it. In one instance a single animal was observed moving slowly at 4.2 km NNW of the vessel, then to suddenly accelerate to 10–12 kn on a SW course across the vessel’s bow at a closest range of 1.5 km. It then swam S at 5–10 kn until it was 4 km from the vessel. During the period of rapid swimming the animal stayed close to the surface with the tail flukes often breaking the water, maintaining a 40-s blow interval. The animal then swam steadily SW, eventually stopping and commencing singing on encountering a pod of two animals at 15 km from the still operating seismic vessel. [Work supported by the Energy Research and Development Corporation, Australian Petroleum Production and Exploration Association, and WMC Petroleum.]
Ultrasound-induced transcutaneous transport for drug delivery and diagnostics
Authors: Kost Joseph , Mitragotri Samir , Langer Robert
Published: July 2002

In spite of major research and development efforts in transdermal systems and the many advantages of the transdermal route, impermeability of the human skin is still a major problem that limits the usefulness of the transdermal drug delivery approach. Application of ultrasound induces temporary structural changes in the skin resulting in enhanced transdermal transport of molecules (sonophoresis). Experimental findings suggest that among all the ultrasound-related phenomena evaluated, cavitation plays the dominant role in sonophoresis, suggesting that application of low-frequency ultrasound should enhance transdermal transport more effectively. It was found that at the low ultrasound frequencies high molecular weight molecules including insulin, interferon, and erythropoietin can be transported through the skin. Recently it was shown that the enhanced skin permeability during sonophoresis also facilitates outward diffusion of glucose present in the interstitial fluids beneath the skin. The in vitro as well as in vivo experiments show that the amounts of glucose extracted by sonophoresis are proportional to the blood glucose concentrations. Furthermore, the amount of glucose extracted by ultrasound can be measured and used to predict temporal changes in the blood glucose levels. These results demonstrate the feasibility of developing a noninvasive method of drug delivery and diagnostics using ultrasound.
Ultrasound for the mediation of a therapeutic agent through the blood–brain barrier
Authors: Bond Leonard J. , Ng Lawrence
Published: July 2002

There is a critical need to develop safe, noninvasive, nonchemical methods to enhance the delivery of nonlipophilic neuropharmaceuticals to the brain. A novel method for mediating nonlipophilic drug transport across the blood–brain barrier (BBB) will be presented. Preliminary data were obtained using a unit operating at 1.6 MHz with ultrasound coupled through water and an attenuating layer onto an in vitro cell-culture model of the BBB. The effects of different intensities on permeation rate and cell integrity were investigated. Various microscopic techniques were used to determine cell condition and viability. At low intensities no effects were seen. At intermediate intensities enhanced permeation up to levels of a factor of 3 increase were measured. At the highest intensity substantial cell disruption was observed. Preliminary observations regarding the mechanism for the interaction of ultrasound with the BBB will be presented. Work is in progress to determine the conditions for effective trans-cranial delivery of ultrasound using phantoms constructed to model in vivo brain. By promoting transport of nonlipophilic drugs across the BBB, this approach has the potential to safely and effectively treat a wide range of brain and central nervous system disorders.
The effects of age on annoyance caused by low-frequency noise
Authors: Adams Rukhsana , Shield Bridget M.
Published: July 2002

A laboratory study into the response of subjects to noises of varying intensity and frequency content has been carried out. Eighty subjects ranging in age from approximately 20 to 70 yr were asked to rate sounds according to annoyance. The hearing levels of the subjects were tested using pure-tone audiometry. The annoyance ratings have been analyzed to investigate relationships between annoyance and spectral shape, and also to determine whether the annoyance responses are related to age or hearing acuity. Preliminary results suggest that there is a strong relationship between age and response to low-frequency sound, subjects over the age of 45 finding sounds with high levels of noise below 200 Hz significantly more annoying than younger subjects. However, the annoyance ratings of the older subjects do not appear to be related to hearing levels, suggesting that the response may be due to some other factor such as the association of the noise.
The investigation of a towed trailer test for passenger tire coast-by noise measurement
Authors: Thompson James K. , Williams Thomas A.
Published: July 2002

It is difficult to quantify the portion of coasting vehicle noise that is due to tire-pavement interaction alone. There are often contributions from aerodynamic noise of the vehicle, transmission whine, noise from suspension components, and other miscellaneous sources. The towed-trailer method used in the revised SAE J-57 standard has been shown to be an effective means of isolating tire-pavement noise for truck tires. This paper reports the results of a test program conducted by SAE Tire Noise Standards Committee to evaluate the feasibility of towed-trailer coast-by testing of passenger and light truck tires. The results of tests conducted in April 1996 at the Ohio Transportation Research Center are described and they indicate that accurate measurements are possible for towed-trailer testing of passenger tires. It is shown that a key aspect of performing such a test is reducing the noise of the tow vehicle and that sufficient reduction is possible even for quiet test tires. During the period of this work, the ISO/TC 31/WG 3 working group developed a draft trailer test method for evaluating tire noise. This test procedure was also evaluated. The results show the proposed test method to be highly accurate for tire noise evaluation.
Noise from sandblasting
Authors: Ognedal Tonnes , Harbak Rune
Published: July 2002

With respect to the increased focus on the working environment, a project has been carried out in order to investigate the noise exposure for personnel working with sandblasting and UHP-water blasting. For sandblasting, three different aspects that influence the noise exposure have been evaluated: (a) Noise from the nozzle and the blasting object, (b) noise generated by the air supply in the masks/helmets, and (c) sound attenuation of the masks and helmets. Normal A-weighted noise levels outside the protective gear are between 110 and 120 dB while sandblasting. The noise level inside the mask and the inner hood will vary from 95–105 dB from the sandblasting. The noise generated by the air supply can be as high 90–100 dB inside the inner hood. Thus the total average noise exposure for the personnel (without earplugs) is 97–107 dB with today’s most common equipment in Norway. Noise from UHP-water blasting can also reach levels up to 110–120 dB, depending on the blasting object and the acoustic environment. Normal working gear gives less protection to the ear than the sandblasting gear. Both the sandblasting and the UHP water blasting may create loss of hearing to the workers.
Sonochemical preparation of protein microspheres
Authors: Suslick Kenneth S. , Kolbeck Kenneth J. , Kufner Gregory S. , Szewczyk Gregory W.
Published: July 2002

Aqueous suspensions of protein microspheres with Gaussian-like size distributions in the micron size range can be produced with high-intensity ultrasound by the sonochemical oxidation of cysteines to form interprotein disulfide cross links. The microspheres can be synthesized containing a core of aqueous or organic liquids (i.e., microcapsules) or air (i.e., microbubbles such as Albunex). The micron sized spheres are contained by a 60-nm layer of protein (approximately ten protein molecules.) The small diameter (less than 5 μm) of the microspheres permits the microspheres to circulate through the bloodstream, while sonochemically linking native protein to form microspheres prevents the expected l immune response. To date, we have synthesized microspheres that can be monitored with in vivo imaging techniques (MRI and x-ray) as well as microscopy. The distribution and circulation lifetime in the bloodstream has been altered by modifying the properties of the microsphere. These microspheres have many potential biomedical applications such as drug delivery vehicles, blood substitutes, and radiological imaging agents.