bluuebunny/crossref_metadata_2025 huggingface dataset:
Serpentine array processing
Authors: Fricke J. Robert
Published: October 2005

Often one must determine the wave-number spectra of complicated spatial wave fields, which contain significant energy propagating in a broad range of directions. In this case a single linear array must be steered to endfire to compute some of the wave numbers of interest. To alleviate this need a multilinear array, e.g., a Mill’s Cross, is often used. This paper discusses a broadband wave-number spectral estimation methodology wherein the array elements may be placed in an arbitrary serpentine pattern. The array processing technique is a modified radon transform for serpentine arrays, which may be interpreted as a plane wave decomposition. The elements of the serpentine array are projected onto virtual linear arrays steered in the intended direction for plane-wave estimation. A weighting function is computed to compensate for multiple serpentine array segments being projected onto a single virtual array segment. The compensation varies with each steering angle. The length of the virtual linear array at each steering angle determines the resolution of the serpentine array. [Work supported by ONR.]
Digital acoustic video image transmission system for deep-sea research submergence vehicle ‘‘SHINKAI 6500.’’
Authors: Tsuchiya Toshio , Amitani Yasutaka , Ochi Hiroshi , Suzuki Michiya
Published: October 2005

High-speed video image transmission from a research submersible to the mother ship is desirable to facilitate effective deep-sea research by a submersible. Therefore, a digital acoustic image transmission system was developed, and was installed in the manned deep-sea research submergence vehicle ‘‘SHINKAI 6500’’ of the Japan Marine Science and Technology Center. This system which adopts 4-DPSK modulation with a carrier frequency of 20 kHz, has a communication capability of 16 kbit/s and is able to transmit a color-still image of 256×240 pixels in 8 s. Its communication range is more than 6800 m. In order to transfer a high-quality color image in a short time, (a) a wide band transducer, that doubles the transmission band, (b) a DCT- (discrete cosine transform) based image coding technique that reduces transmission data volume, and (c) an adaptive equalizer and phase controller, that improve communication quality and Doppler compensation, are employed. Results of a performance test (various video images) were successfully received from the ‘‘SHINKAI 6500’’ from a depth of 6500 m to the surface vessel. After a successful performance test, this system will probably be installed in the ‘‘SHINKAI 6500,’’ and new biological or geological experiments will be carried out by the system in the deep sea of the western Pacific Ocean.
Time compression processing of M sequences from the Heard Island Feasibility Trial
Authors: Heard Garry J. , Schumacher Ian
Published: October 2005

Canada was one of nine participating countries in the Heard Island Feasibility Test (HIFT) and had two towed-array receivers operating, one in the Pacific and one in the Atlantic. Due to the extremely long propagation paths the Canadian data were found to have relatively low signal-to-noise ratios that complicated the M-sequence time-compression correlation processing. An analysis was carried out to determine if time-compression processing of the data was possible with the low signal-to-noise ratio data available. A means of removing Doppler variations from the data based on phase tracking the heterodyned baseband signal was developed and applied to several of the stronger HIFT receptions. Useful correlation results were obtained using this technique. Initial estimates of the travel time differences for the dominant acoustic arrivals were obtained from the correlations.
Noise cancellation, environmental focusing, and source localization
Authors: Collins Michael D.
Published: October 2005

The ability to localize an acoustic source in the ocean is often limited by ambient noise and other types of noise. If the nature of the noise is at least partially understood, this limitation can be reduced significantly by including the noise parameters in the space of search parameters. The performance of this approach has been tested in simulations involving a source buried in ambient noise and interference noise due to a source at a known location. Uncertainty in the ocean environment is another limiting factor that can be reduced by expanding the space of search parameters [Collins and Kuperman, J. Acoust. Soc. Am. 90, 1410–1422 (1991)]. By including the source, noise, and environmental parameters in the search space, it is possible to localize an acoustic source buried in noise in an uncertain environment. Special cases of this optimization problem include source localization, tomography, geoacoustic inversion, focalization, and imaging with acoustic daylight [Buckingham etal., J. Acoust. Soc. Am. 91, 2318(A) (1992)].
Theoretical signal-to-noise gain formulas for energy signal bicorrelation and tricorrelation detection
Authors: Pflug Lisa A. , Ioup George E. , Field Robert L. , Ioup Juliette W.
Published: October 2005

In the past the authors have examined energy signal detection and time delay estimation performance of ordinary and higher-order correlations using Monte Carlo simulations and hypothesis testing [for example, Pflug etal., J. Acoust. Soc. Am. 91, 2763 (1992)]. For some circumstances higher-order detector performance and SNR gains can be predicted theoretically based on third- and fourth-order moments. SNR gain formulas for higher-order detectors have been derived for a probability of detection of 0.5 and are discussed in this paper. Comparisons of these theoretical results are made to simulations with a model signal whose moments can be varied. Validity of the theoretical results is confirmed with eight diverse test signals which have been used in previous simulation studies. The formulas make possible the calculation of minimum third, and fourth-order moment values needed for the bicorrelation and tricorrelation detectors, respectively, to outperform the cross-correlation detector. [Research supported by Office of Naval Research, Program Element 61153N, with technical management provided by NRLSSC.]
Minimum entropy deconvolution of underwater acoustic transients
Authors: Broadhead Michael K.
Published: October 2005

The minimum entropy deconvolution (MED) method [R. Wiggins, Geoexploration 16, 21–35 (1978)], is used to produce source signature estimates from underwater acoustic transients, which has application in the passive sonar classification problem. The Green’s function, representing environmental distortion effects, is treated as a non-Gaussian random process. The MED method implemented in this paper leads to a one-parameter model that doesn’t require accurate knowledge of the source location and environmental parameters, or the computation of Green’s functions. Results from applying the MED method to single-sensor, broadband ocean acoustic measurements are shown, where source signature estimate correlation coefficients range between 0.87 to 0.91. The method is also applied to realistic simulations, produced with a parabolic equation (PE) model, using a source pulse that was longer and more complex than the measured source. Source signature estimate correlation coefficients ranged between 0.95 and 0.99. The technique assumes that the input random process is non-Gaussian, which is justified by high kurtosis values of the computed (PE) Green’s functions associated with this data set. [Work supported by Office of Naval Research, with technical management provided by the Naval Research Laboratory.]
The effects of a bottom-limited ocean on signal kurtosis—Applications to tricorrelation detection and minimum entropy deconvolution of broadband signals
Authors: Field R. L. , Leclere J. H.
Published: October 2005

As signals propagate in the ocean their temporal and spectral features vary as a function of space and time. This is especially true in bottom-limited environments where the signal may encounter numerous boundary interactions with significant loss due to absorption. This environmental distortion can have a significant effect on the ability to detect and classify broadband signals. A broadband parabolic equation model is used to predict signal distortion over a 25–150-Hz bandwidth in both range-independent and downslope, bottom-limited environments. Signal kurtosis is used to characterize signal distortion in range and depth. Comparisons are made between the kurtosis predicted by the model and that estimated from experimental data. It is shown that the model, together with good environmental information, can accurately predict signal kurtosis as a function of range and depth in the ocean. The significance of the variation of signal kurtosis is discussed in terms of the tricorrelation detector and minimum entropy deconvolution of broadband signals. [Work supported by Office of Naval Research, Program Element 61153N, with technical management provided by the Naval Research Laboratory.]
Results on the identification of acoustic objects in motion from the fourth-order cumulant spectrum
Authors: Dwyer Roger F.
Published: October 2005

It was reported [J. Acoust. Soc. Am. 93, 1460–1465 (1993)] that the Doppler component and both the magnitude and phase of an object’s transfer function could be extracted from the fourth-order cumulant spectrum. Results for three elastic spherical objects in motion will be discussed. Specifically, performance results for the extraction of the Doppler component, phase, and magnitude of the object’s transfer function from the fourth-order cumulant spectrum will be compared with classical first- and second-order methods.
Shallow water reverberation, signal motion loss, and acoustic navigation: A preliminary study for autonomous underwater vehicle target detection
Authors: Steward W. Kenneth , Tang Xiaoou , Chu Dezhang
Published: October 2005

It is usually difficult to use autonomous underwater vehicles (AUV) for locating targets in shallow-water ocean environments due to the strong wave surge and multipath acoustic reverberations. A preliminary study of some environmental effects unique for a shallow-water sound channel helps place bounds on possible solutions and reduce program uncertainty. Accordingly, three interrelated issues are addressed in this paper: Signal masking by shallow-water reverberation, signal loss caused by extreme platform motions, and shallow-water acoustic navigation. A model estimating the signal motion loss and the average reverberation intensity in the shallow-water environment is developed. The computer simulation of multisensor navigation serves not only as a precise vehicle-positioning device but also as the platform motion data input for the model. As a result of the shallow-water experiments and acoustic modeling, conclusions of this preliminary study are (1) SML is not the dominant factor for sonars in the frequency range of interest (≳200 kHz) with respect to target detectability, (2) beam patterns can be manipulated to effectively reject most interferences caused by surface reverberation and noise, and (3) a multisensor navigation filter is practical even with limited sensor data quality.
Dialect differences in vowel perception
Authors: Faber Alice , Best Catherine T. , Di Paolo Marianna
Published: October 2005

Analysis based on phonemes assumes that ‘‘u,’’ for example, in whatever context is phonologically the same, and that deviations—sometimes extreme—imposed by following approximants do not affect the category membership of the vowel. Informed by Best’s perceptual assimilation model, which predicts perception of non-native speech contrasts from their relationship to native segment inventories, this study investigates the contrasting possibility that American English contrasts like pool-pull and heel-hill are perceived independently of the contrasts between /u/–/inverted closed omega/ and /i/–/i/ in other contexts. Connecticut and Utah listeners heard productions of both contrasts by speakers from both states; the contrasts are acoustically less different for Utah than for CT speakers. Listener groups completed Keyword identification, forced-choice labeling, and AXB discrimination tasks. There were systematic listener dialect differences on the keyword and AXB tasks, and both groups did better on the CT than on the UT contrasts. Heel and hill were identified with the vowels in HID and/or HEED; however pool and Npull were identified with AWED or HOED more than with FOOD or HOOD. Even when pool and pull were identified with the same keyword, one class often contained better exemplars of the keyword than the other, and discrimination was still above chance. These results suggest that pool and pull, and heel and hill, minimally distinct in Utah, may differ primarily in their distance from /open oh/–/o/ and /i/, respectively. [Work supported by NIH Grant Nos. HD-01994 and DC-00403.]
Production and perception of work-initial stops by Korean adults
Authors: Kim Mi-Ran , Read Charles , Kluender Keith , Lotto Andrew
Published: October 2005

In Korean there are three classes of stops: Voiceless unaspirated [t], voiceless slightly aspirated [tb], and voiceless heavily aspirated [thh]. For these classes of stops produced by male and female Seoul and Pusan speakers, voice-onset time (VOT), amplitude of aspiration, and f0 of the first five glottal pulses were measured. VOT was longer for slightly aspirated than for unaspirated stops, and longer still for heavily aspirated stops. Unaspirated and heavily aspirated stops were both produced with significantly higher f0 (more than 30%) than slightly aspirated stops. Gender and dialect (Seoul versus Pusan) differences in these variables were also noted. Then, six 12-step series of syllables differing in VOT (5–82 ms), fundamental frequency (100, 125, 150 Hz), and amplitude of aspiration noise (−33, −21 dB re: vocalic energy) were synthesized. These stops, varying perceptually from [ta] to [tba] to [thha], were presented to 12 native-Korean listeners. Results indicate that all three stimulus variables were perceptually significant for the Korean listeners. [Work supported by NIDCD Grant No. DC-00719 and NSF Grant No. DBS-9258482.]
Traveling wave decomposition of surface displacements on a cylindrical shell: Numerical evaluation displaying guided wave properties
Authors: Kaduchak Gregory , Matula Thomas J. , Marston Philip L.
Published: October 2005

Internal displacements of spherical shells subjected to steady sound waves in water have previously been computed by other researchers [R. Hickling etal., J. Acoust. Soc. Am. 92, 499 (1992)]. Such displacements can be difficult to interpret with a guided wave representation because of the superposition of counterpropagating Lamb waves and the local response to the incident wave. In this research the surface displacements of a cylinder were evaluated since they can be mathematically decomposed into counterpropagating circumferential traveling waves. (Unlike an analogous decomposition for spheres, the amplitudes in the cylinder case are regular at 0 and 180 deg.) By limiting attention to the radial displacements of the outer surface, it was also possible to display the response to short-tone bursts and thereby distinguish between the local response to the incident acoustic wave and Lamb waves launched on the shell. Both the steady-state and burst response situations clearly manifest waves launched on the shell. These can be easily seen for ka as low as 8 for a thin shell. [Work supported by ONR.]
Coupling and launching of supersonic waves in elastic shells
Authors: Norris Andrew , Rebinsky Douglas
Published: October 2005

The interaction of an acoustic wave with a smooth thin shell in a fluid is considered. The coupling mechanism between the acoustic field and the supersonic membrane waves, both longitudinal and shear, is discussed in detail. The coupling is mediated by the shell curvature, and vanishes when the curvature vanishes. Ray methods are used to express the membrane waves by curved wave fronts with amplitudes subject to a transport equation over the curved shell surface. The coupling, and decoupling or launching, then reduces to solving an ordinary differential equation for the unknown ray amplitude. In essence, the transport equation is forced, or ‘‘beaten’’ by the locally phase-matched background field. Explicit expressions are obtained for the coupling and detachment coefficients on arbitrarily curved regions. These are combined, using ray theory for the propagation over the shell, to give the scattered field due to rays traveling over the shell. The general results are explicitly tested on the cylinder and sphere, for which the ensemble of surface rays can be summed into a resonance form, and numerical comparisons are made with the exact results for these canonical geometries. [Work supported by ONR.]
On the acoustic advantages of a helical-ring stiffener in a thin cylindrical shell
Authors: Hwang Y. F.
Published: October 2005

A conventional circular-ring stiffener in a thin cylindrical shell may cause undesirable sound radiation due to the scattering of subsonic flexural waves. Vibration in each of a set of disjointed circular rings may stay within the ring, which results in a resonant buildup that acts as a localized excitation of the shell. Furthermore, elastic waves in a cylindrical shell tend to propagate, having a plate-wave front, along the axis of the cylinder. A circular ring is oriented in the plane normal to the direction of wave propagation and therefore it sees the elastic wave as a normal incident wave. These rings are separated at a certain distance in tandem. An incident wave in the shell may be reflected back and forth between a pair of adjacent rings. Therefore, a circular ring may not only be an efficient scattered, it could also scatter the same wave several times causing a reverberant buildup in the shell between rings, and, consequently, enhance acoustic radiation from the shell. This paper discussed the technical rationale to alleviate these shortcomings by using a continuous helical-ring stiffener in a thin cylindrical shell.
Echoes from a submerged spherical elastic shell coupled to an internal mechanical system
Authors: Huang H. , Gaunaurd G.
Published: October 2005

The scattering of sound waves by a submerged spherical elastic shell coupled to an internal two-degrees-of-freedom mechanical system is studied. The problem is solved using the classical separation-of-variable technique taking into account the effects of the trilateral interaction between the incident wave, the elastic shell, and its internal mechanical system. Numerical results show that echoes from the shell varies significantly with the mechanical properties of the internal system. Particularly, the analytical solution indicates that at the ‘‘fixed base’’ resonance frequencies of the internal system, the shell motion stops at the point where the internal system is attached. The scattered acoustic pressure fields at these frequencies are analyzed in detail. [Work supported by NSWC.]
The interaction of pitch, harmonics, and the equal loudness curves in timbre analysis of musical tones
Authors: Pyne James M.
Published: October 2005

Highly skilled musicians encounter great difficulty when attempting to communicate information concerning the timbre of musical tones. This can be a barrier to effective teaching in that musicians tend to think of individual sounds as unified single events rather than complex compounds that establish timbre characterizations. When taken into the realm of visual representation, understanding can be more easily achieved. The utilization of a Spectral Dynamics real-time analyzer has allowed coached student performers to react to a spectral display and has proven useful in tone quality development. Of special concern has been the reduction of excessive harshness when producing loud tones, and clarity when producing soft tones, both common problems in performance. Further definition concerning the interaction of pitch, harmonic content, and the equal loudness curves has been useful in a better mutual understanding of this process and it may also be pertinent for traditional music theorists as well.
A regional difference within the United States in perception of the tritone paradox
Authors: Ragozzine Frank , Deutsch Diana
Published: October 2005

A previous study [Deutsch, J. Acoust. Soc. Am. 88, S1 (1990)] reported a striking difference in perception of the tritone paradox between subjects who had grown up in California and those who had grown in the South of England: When the Californians tended to hear the pattern as ascending the English group tended to hear it as descending, and vice versa. One of us (FR), who had grown up in Mahoning and Trumbull Counties in Ohio hears the pattern in a fashion typical of the southern English rather than the Californians. A study was therefore undertaken to examine perception of this pattern in subjects from this region. A statistically significant difference was found between those subject whose parents had also grown up in this region and those whose parents had not. The former group formed a bimodal distribution, and approximately half the subjects producing a histogram similar to that obtained from Californians and the others producing one similar to that obtained from the southern English. In contrast, those in the latter group produced a histogram uniformly similar to that obtained from Californians. This demonstrates regional differences in perception of this pattern, and also an effect of familial background.
Undergraduate experiments for duct acoustics and wind instruments
Authors: Hoekje Peter L.
Published: October 2005

The acoustics of ducts presents a rich spectrum of practical student laboratory activities, from exposition of basic wave physics to exploration of important characteristics of musical wind instruments. A variety of duct experiments will be described, extracted from a musical acoustics course for music majors and a junior level vibrations course for physics majors at the University of Northern Iowa, as well as from an advanced acoustics seminar at Northern Illinois University. Basic physical phenomena explored include resonance, wave speed, and wavelength. These can be extended to open-end corrections, pressure, and velocity in a standing wave, acoustic impedance, and the dependence of sound speed on temperature, pressure, and gas composition. Wind instrument frequency responses can be easily observed. Small bore perturbations shift normal mode frequencies, demonstrating that resonance frequencies are affected by bore shape. Many of the experiments described use an inexpensive impedance head built by students from a piezoelectric driver and an electret microphone. This device can be customized for specific apparatus, and stimulates discussion of transducer design and use. Overall, students use simple apparatus to build a foundation of conceptual understanding which can be extended to fruitful research.
A simple water-filled compliant-tube calibrator
Authors: Gardner David L. , Gabrielson Thomas B.
Published: October 2005

Several geometries for low-frequency underwater calibrations are in common use, but often require either anechoic walls, rigid walls, or tanks (or lakes) of large dimensions with respect to a wavelength. Such facilities are frequently not practical for use in teaching laboratories either because of inaccessibility or because the facility must be shared with active researchers. The compliant, water-filled cylindrical tube described in this paper permits low-frequency calibrations in a laboratory environment, with modest cost and size. The sound speed inside one such device is approximately 300 m/s, which allows 100-Hz measurements in tubes 1 m long. The limitations of the compliant tube calibrator and examples of measurements made using the calibrator will be discussed.
A one-year acoustics laboratory course at UCSD
Authors: McGehee Duncan , Hildebrand John A. , Anderson Victor C.
Published: October 2005

The University of California, San Diego offers a one-year acoustics laboratory course to both undergraduate and graduate students. The lab is structured to parallel a graduate level theoretical acoustics class taught jointly by the electrical and computer engineering department, and the Scripps Institution of Oceanography. The acoustics laboratory course examines fundamental principles of acoustics with emphasis on oceanographic applications. Also stressed are methods for handling random data and the professional reporting of results. A GPIB bus computer is used to control laboratory instrumentation, and students develop application programs for each experiment. The course is divided into 17 separate experiments. The first quarter is devoted to the measurement of mechanical impedance and resonance in a spring-mass system, velocity and dispersion in strings and bars, and normal modes in a bar. The second quarter examines the calibration of transducers, including self-reciprocity and beam-pattern measurements, reflection and transmission in multiple media, sound-speed dependence on salinity, and normal modes in a channel. The third quarter emphasizes the treatment of random data including: Power measurements of band-limited white noise, scattering of sound from surfaces of varying roughness, and detection threshold experiments.
Sensitivity of axial vibration reactions to design asymmetries in a Stirling cycle cryocooler dual-opposed compressor assembly
Authors: Hausle Fred W.
Published: October 2005

Stringent constraints are placed upon allowable vibration reactions from cryocoolers used for space-borne optical sensors. Stirling cycle cryocoolers typically use dual-opposed compressors to virtually cancel the net axial reaction produced by the steady-state driven oscillations of paired pistons by virtue of symmetry. Under steady-state operation, harmonics of the drive frequency occur due to the nonlinear characteristics of both the working gas and the mechanical piston support spring stiffnesses. Asymmetries in the system design due to fabrication tolerances may result in intolerable net reactions primarily at the harmonics of the drive frequency. The axial dynamics of a simple two-degree-of-freedom compressor model are examined using a finite-difference time-step Runga–Kutta algorithm. The sensitivity of the axial reaction harmonics to asymmetric characteristics between the paired compressors such as gas volume, support spring stiffness and piston mass is examined. A Fourier decomposition of the limit cycle is conducted to observe the frequency content of the vibration reactions. Comparison is made with results of an application of perturbation methods. Cryocooler design parameter asymmetry tolerances based upon specified limits on peak vibration reaction responses are obtained.
A simple apparatus for measurement of the acoustical impedance of membranes, plates, and the bulk properties of porous materials
Authors: McIntosh Jason
Published: October 2005

An apparatus has been built that can measure the acoustical impedance (Z) of a variety of acoustical objects including membranes, plates, and porous materials. It is also possible to use the technique to measure the complex bulk modulus (B) of air within a porous material. When B is combined with Z, a complete linear description of the bulk properties of porous material is obtained. The apparatus is very simple, consisting of two volumes, one of which is driven by a loud speaker at frequencies low enough so that the two volumes can be accurately modeled as lumped elements. It is shown that Z and B primarily depend upon on the pressure transfer function between the two volumes, which can be measured very quickly and accurately with modern analyzers. Due to the simplicity of the apparatus, it is felt that this technique is superior to methods previously used [J. D. McIntosh etal., J. Acoust. Soc. Am. 88, 1929–1938 (1990)], however it is limited to lower frequencies (<500 Hz with the current apparatus). Measured impedance data of membranes, plates, ports, perforated plates, and porous material is presented as well as bulk properties of open cell foam.
Characterizing scatterer size via measurements of multiple acoustic parameters
Authors: Jiang Peng , Apfel Robert E.
Published: October 2005

A multiple parameter approach for characterizing mixtures has been investigated. It is found that one can characterize scatterers (droplets) in immiscible mixtures of water, fat (oil), and protein, in term of volume fraction and size, from measurements of the mixture’s effective acoustic parameters (density, sound speed, the acoustic nonlinear parameter, and attenuation). Mixture laws [P. Jiang etal., Ultrasound Med. Biol. 17(8), 829–838 (1991)] were used to determine the composition of a mixture. A procedure for choosing a reliable composition predictor was proposed. Good agreement between the predicted compositions and the known values has been demonstrated. After the volume fraction of the scattering droplet was found, an effective radius of the droplets was obtained by using an appropriate attenuation law with the measured frequency-dependent attenuation. The deduced radius is close to that of the majority of droplets observed under an optical microscope. A discussion is given on how to apply the technique to characterize the size distribution of scatterers. [Work supported by NIH through grant R01-GM30419.]
Relation invariance of expressive microstructure in music performance across moderate changes in tempo
Authors: Repp Bruno H.
Published: October 2005

Two pianists played Shumann’s ‘‘Träumerei’’ three times conespressione at each of three musically acceptable tempi, and the performances were recorded in MIDI format. A perceptual test showed that artificial modification of the tempi of these performances within the same moderate range does not lead to a noticeable deterioration of performance quality. Subsequent analyses confirmed that the expressive timing patterns very nearly maintained relational invariance across tempo changes. Other temporal details, however, did not expand or contract in this fashion but were unaffected by tempo; they included chord asynchronies, tone overlaps, and possibly pedal timing. This indicates distinct levels of cognitive and technical control in music performance. Dynamic patterns were essentially unaffected by tempo changes, though a slight increase in overall dynamic level with tempo was noted. The generality of these findings needs to be tested with other types of music.
Sonic boom wave propagation from air into water: Implications for marine mammals
Authors: Sparrow Victor W.
Published: October 2005

At the 1993 NASA High Speed Research Program Sonic Boom Workshop, hosted by NASA Ames Research Center, it ws noted that the development of a high speed civil transport in the next several years will focus only on overwater travel. At that meeting it was also made clear that some have raised concerns about the effects of sonic booms on the activities of marine mammals. Once a fleet of supersonic passenger aircraft are in service, there could be hundreds of flights per day, and, therefore, the effects of sonic booms on marine mammals should be well understood. The purpose of the present paper is to briefly describe the acoustic pressure and intensity variations that one can predict underwater due to a sonic boom impinging on an air–water interface. Arbitrary angles of incidence are investigated, and the proportion of energy incident and reflected from the interface are given for typical sonic boom wave forms.
Using sound and vibration to diagnose machinery faults
Authors: Lyon Richard H.
Published: October 2005

The relation between the dynamical forces and structural elements of a machine and the vibratory or acoustical signals produced as it operates is far from straightforward. Nevertheless, a number of developments in measurement technology, system modeling, and signal processing have made it more possible in the last few years to extract information about both mechanism performance and structural integrity from vibration or acoustical measurements. Measurement advances include smaller and more sensitive transducers. System modeling advances include hybrid FEA and dynamic simulation methods. And signal processing includes a number of methods for amplitude and frequency demodulation and deconvolution procedures. The paper will outline a number of these advances, illustrated by some of the author’s experiences.
Acousto-ultrasonic nondestructive evaluation of materials and structures
Authors: Reis Henrique
Published: October 2005

A review of the nature and the underlying rationale of the acousto-ultrasonic methodology is presented. The term acousto-ultrasonics denotes a nondestructive evaluation technique that combines some aspects of acoustic emission methodology with ultrasonic simulation of stress waves. Unlike most nondestructive evaluation techniques, acousto-ultrasonics is less concerned with flaw detection than with the assessment of the collective effects of the various flaws and materials anomalies. Acousto-ultrasonics is primarily concerned with material properties variations, such as the significant reduction in strength and toughness caused by combinations of minor flaws and diffuse flaws populations. Porosity content, and fatigue and impact damage are typical examples of factors that affect material properties variations. Applications of the acousto-ultrasonic approach to the nondestructive evaluation of wire rope, porosity in laminated composites, fatigue damage in ceramic matrix composites, and adhesive bond strength in finger joint connections of structural lumber and in other structural systems are presented and discussed.
The three-dimensional laser vibrometer
Authors: Vignola Joseph , Houston Brian H.
Published: October 2005

In the field of structural acoustics, two of the central tools necessary for studying the physics of interactions and vibration transmission paths are a measure of structural intensity and the generation of k-ω dispersion relationships. It is particularly important in the study of fluid-loaded structures to be able to characterize both the in-plane and out-of-plane motions in order to identify mechanism conversions at apertures and discontinuities. A noncontact underwater probe for measuring simultaneously the three components of vibration induced displacement on the surface of submerged structures has been constructed. Optical fiber is used so that a compact optical probe with no electronics is the only device in the water. The probe is used to measure the three components of motion of a point on the surface of a target from a distance of approximately 2 ft. Data for acoustic studies are obtained by collecting data at a series of points on a target surface. Experimental results will be presented. An analysis of the sensitivity, frequency response, and detection threshold of the system will also be included.
Music as noise: Sound transmission and unbiased annoyance
Authors: Nelson David A.
Published: October 2005

Music is often perceived as noise pollution, especially when it invades one’s solitude or one’s own music making. This is generally a major issue in multiunit residential buildings and in music facilities for rehearsal, broadcast, and recording. However, current noise control methods of design and classification do not address the ongoing trend in popular music toward strong bass content. Analysis of broadcast music signals using unbiased annoyance [E. Zwicker, ‘‘On the dependence of unbiased annoyance on loudness,’’ Proc. Internoise 89, pp. 809–814] indicates that (i) contemporary music can be adequately modelled as pink noise from 50 to 4000 Hz, (ii) after passing through a partition the 63-Hz octave band dominates loudness and unbiased annoyance, (iii) existing single-number ratings (such as STC) cannot identify structures with critical low-frequency resonances, thus potentially overestimating performance against this type of noise. Ramifications for noise control practice and effective single-number ratings are explored.
Variability in behavioral reaction thresholds of bowhead whales to man-made underwater sounds
Authors: Richardson W. John , Greene Charles R.
Published: October 2005

Reactions of bowhead whales, Balaenamysticetus, to actual and simulated oil industry activities were studied in the Beaufort Sea during spring, summer, or autumn from 1980 to 1991. Received levels of oil industry noise that elicited behavioral reactions varied widely, depending partly on the source and characteristics of noise, the activity of whales when exposed, and the physical situation (all levels in dB re: 1 μPa, 20–1000-Hz band). Reactions to increasing noise levels from approaching boats occurred at received levels as low as 90 dB. In summer, roughly half the bowheads showed avoidance when the received level of steady drillship or dredge noise was about 115 or 20-dB above ambient. Results in spring were similar, but some bowheads tolerated received levels of drilling sound up to 135+ dB if the only available migration route through ice required close approach to a sound projector. In contrast, repetitive pulses from airgun arrays elicited avoidance only at received levels exceeding 150–180 dB (although weaker pulses may elicit subtle behavioral changes). Besides the variability among sound types and situations, there is much whale-to-whale variation in any one situation. No single received level criterion is appropriate to all situations. [Work supported by Minerals Management Service.]
Responses of wintering humpback whales to vessel traffic
Authors: Bauer Gordon B. , Mobley Joseph R. , Herman Louis M.
Published: October 2005

Responses of humpback whales to vessel traffic were monitored over two winter seasons during 1983–1984 in Maui, Hawaii. A variety of vessel characteristics including vessel numbers, speed, and proximity were associated with changes in whale behaviors, including swimming speed, respiration, and social behaviors. Smaller pods and pods with a calf were more affected than larger pods. A case study indicated that a calf could be sensitized by the passby of a large vessel, so that it subsequently breached in response to noise from a smaller boat engine which had not previously elicited any behavior change. These findings in conjunction with similar results from summering humpbacks in Alaska indicated disturbance of humpback whales at both ends of their range. Although substantial short-term effects were noted, long-term negative consequences are not apparent. Recent aerial surveys of the Hawaiian Islands indicate substantial increases in the number of humpback whales.
Responses of humpback whales to sonar sounds
Authors: Maybaum Hilary L.
Published: October 2005

Controlled sound playback experiments were used to assess effects of a low-frequency sonar system on humpback whales, Megapteranovaeangliae, in Hawaiian waters. Focal pods were presented with sounds of a 3.3-kHz sonar pulse, a sonar frequency sweep from 3.1 to 3.6 kHz, or a control (blank) tape. Behavior, movement, and underwater vocalizations were monitored and compared with baseline periods. While the two types of sonar signals differed in their effects on the whales, both elicited avoidance behaviors. Humpbacks responded to the pulse by increasing their distance from the sound source. The strength of this effect varied directly with time. Responses to the frequency sweep primarily consisted of increased swimming speeds and track linearity. The latter was a direct function of increasing sound intensity. Overall, the sounds did not strongly or consistently affect the whales’ dive cycles or vocalizations. Observed avoidance reactions may have resulted from possible resemblance between the sonar signals and natural sounds in humpbacks’ environment that are associated with biological threats or warnings.
New directions for research on the perceptual evaluation of synthetic speech
Authors: Pisoni David B.
Published: October 2005

A review of previous research on the perceptual evaluation of synthetic speech produced by rule reveals that most studies have focused on behavioral measures of segmental intelligibility of isolated words. For the most part, except for a few isolated studies, research on sentence processing and comprehension of long passages of fluent speech has received very little attention. This is not surprising because these are areas of research in spoken language processing that are difficult to study without the investment of time and energy in developing new methodologies that go well beyond phoneme perception and isolated word recognition. Studies of prosody and the role of naturalness in intelligibility and comprehension are needed at this time to quantify the contribution of these sources of knowledge to spoken language processing. In this presentation, some of the recent studies from this laboratory that have attempted to measure these more complex processes will be reviewed. Studies using a sentence verification task and several on-line measures of comprehension will be described. Other methods need to be developed in the future to study intelligibility, comprehension, and retention of synthetic speech. [Work supported by NIH Research Grant No. DC00111-17.]
Sector-focused matched-field inversion for enhanced environmental parameter estimation with reduced sensitivity to measurement errors
Authors: Chandler Howard A. , Feuillade C. , Smith G. B.
Published: October 2005

Sector-focused matched-field localization has been shown to effectively enhance range-depth resolution while remaining insensitive to environmental parameter mismatch. This becomes evident in parameter space ambiguity functions where the response is broad and therefore insensitive to mismatch. For source localization, this is a desirable result. However, for environmental inversion, greater resolution may be desired in parameter space while remaining insensitive to other measurement errors. This may be accomplished by including, in the search sector, replicas derived from a set of ‘‘neighboring’’ environmental parameters. The purpose of this study is to investigate the use of sector focusing to increase resolution in environmental parameter space while mitigating against measurement uncertainty. Results will be presented using the KRAKEN normal mode model to simulate a canonical shallow water environment. [Work sponsored by the Office of Naval Research, Program Element 61153N, with technical management provided by NRL-SSC.]
Trends in signal loss due to reflecting irregular bathymetry in matched-field processing
Authors: Smith James F.
Published: October 2005

Simulations of the potential of matched-field tomography for inverting ocean sound-speed structure (Tolstoy and Diachok, 1991) have to date neglected effects of bottom interacting modes. A study to determine the effect of bathymetry in the thinly sedimented Pacific on matched-field processing has been conducted. A range- and depth-dependent sound-speed field was used. The acoustic field used as synthetic data ‘‘measured’’ at the array was calculated by the parabolic equation program FEPE (Collins, 1991). The program was shown to be highly accurate in matched-field studies against ‘‘exact’’ results produced by the normal modes program KRAKEN (Porter, 1991). The effects of irregular bathymetry and shifts in bottom sound speeds were studied through simulations conducted over extensive range and frequency intervals. The results showed an increase in signal array degradation with increasing range and frequency and reduced source localization. Effects of interaction with far and near sides of seamounts (relative to array position), and the overall trend of signal loss with range due to multiple interactions with the bottom will be discussed.
Oceanic tomography using model-based matched-filter processing of wideband acoustic signals
Authors: Hermand J.-P. , Roderick W. I.
Published: October 2005

As originally conceived, ocean acoustic tomography relies on determining the travel times of pulses that propagate along identifiable multipaths between pairs of transducers. In principle, other properties of acoustic propagation such as amplitude and phase over a broad frequency band can be used to infer environmental parameters. These parameters include range-dependent sound-speed profiles and geoacoustic parameters of the sea bottom. Recent experimental work has demonstrated that the distortion of time-dispersed wideband signals can be compensated effectively by using a model-based matched filter (MBMF). A multi-channel MBMF receiver that incorporates the modeled Green’s function of the medium, determined the correct range and depth of the source and receiver. In this paper, the possibility of applying model-based matched-filter processing to the tomographic inversion problem was investigated. The acoustic data are low-frequency, large time-bandwidth product, linear-frequency-modulated signals transmitted through a range-independent waveguide at a deep water site west of Sardinia. Compared to time-of-flight tomography, the amplitude and phase distortion undergone by the propagated waveforms were fully exploited to reconstruct, in part, the range-averaged sound-speed profile between source and receiver. This was achieved by searching for the set of sound-speed profile parameters that maximized the gain at the output of a multi-channel MBMF receiver.
Extraction of both bottom backscattering strength and reflection loss by inversion of reverberation measurements
Authors: Kamminga Sicco D. , Ellis Dale D. , Gerstoft Peter
Published: October 2005

A method is described to simultaneously extract the bottom backscattering strength and bottom reflection loss as a function of grazing angle from measurements of monostatic reverberation. The least-squares difference between a parametrized model and data is minimized with respect to the parameters using generic algorithms or simulated annealing. The reverberation data are from broadband sources and omnidirectional receivers deployed at a flat-bottomed deep-water area in the Mediterranean. The reverberation model is simple: the propagation is described by straight-line ray paths (although the effective angles are corrected for the sound-speed profile); and parametrized functions are used for the bottom scattering strength and reflection loss. The parameters can also include the water depth, sound speed and gradient, source level, and pulse length. Where they can be compared, the parameters resulting from the inversion show good agreement with the measured ones, leading confidence to the procedure. As well, when the resulting parameters and actual sound-speed profile are input to the generic sonar model, the calculated and measured reverberations are in good agreement. a)Currently at Rijkswaterstaat, P.O. Box 3006, 2280MH Rijswijk, The Netherlands.
Acoustic signatures of imploding underwater light bulbs
Authors: Marshall William J.
Published: October 2005

Imploding light bulbs are sometimes used as underwater sound sources because they produce impulsive signals similar to small explosions, yet are cheaper and more convenient to procure, store, and use. On a recent sea trial, light bulb sources were used to measure the straightness of a bottom-mounted hydrophone array. For this purpose the sharp leading edge was the most important characteristic of the acoustic signature, however the test provided a good opportunity to record and study other signature features as well. Results for a moderate number of common household light bulbs are given. Data include statistics on crush depths, measured acoustic waveforms, and energy spectral levels, and correspondence between these observations and a simple theory of sound generation by imploding gas bubbles. This information should be useful to others planning acoustical tests using such sources. [Work sponsored by the Advanced Research Projects Agency.]