bluuebunny/crossref_metadata_2025 huggingface dataset:
Problems in the prediction of speech recognition among normal-hearing and hearing-impaired listeners
Authors: Dirks Donald D. , Dubno Judy R. , Bell Theodore S.
Published: October 2005

The overall goal of our research program is to determine the accuracy of the articulation index (AI) for predicting speech recognition among hearing-impaired listeners. Speech recognition performance is determined, in part, by the stimulus presentation level, the listeners' auditory thresholds, and the relative contribution of each frequency region within the speech spectrum to intelligibility (i.e., the information function). For hearing-impaired listeners whose auditory thresholds are usually not elevated equally across frequency, calculation of the sensation level of the speech presents special problems because of the complex interaction among speech level, auditory threshold, and the information function, each of which varies differently across frequency. In addition, the relative contribution of each frequency region to the intelligibility may be influenced by the phonetic composition and redundancy of the particular speech materials. This paper will describe the importance functions and transfer functions that relate the AI to speech recognition scores, for several speech materials. In addition, comparisons of AI predictions for hearing-impaired subjects will be made utilizing importance and transfer functions determined directly from these speech materials, rather than by assuming more general functions recommended in Standards or obtained from the literature. Use of functions appropriate for specific speech materials may result in more precise predictions of speech recognition, especially when used for certain applications, such as exploring the communication abilities of listeners with hearing impairment. [Work supported by grants from the National Institute on Deafness and Other Communication Disorders.]
Validity of intelligibility measures for adaptive beamforming hearing aids
Authors: Jayaraman Sriram , Soli Sigfrid D. , Hoffman Michael W. , Buckley Kevin M.
Published: October 2005

Intelligibility-weighted, averaged gain [P. M. Peterson, “Adaptive array processing for multiple microphone hearing aids,” MIT (1989)], GI, has been used as a figure of merit to evaluate adaptive spatial filtering algorithms for noise cancellation hearing aids. GI is computed from the input and output signal and noise power spectra. An estimate of GI, GI(w), can also be computed from the instantaneous directional frequency response of the adaptive spatial filter. GI(w) and GI are equivalent when the input signal and noise spectra are identical and the sound-field nonreverberant; however, their relationship for other signal and noise spectra is unknown. Since GI(w) is computed by the filter coefficients, it can potentially be used as a criterion for design of spatial filtering algorithms that maximize intelligibility rather than signal/noise ratio. Studies were conducted to evaluate GI(w) as a predictor of intelligibility by comparing GI(w) with GI(w), AI, and actual measured intelligibility and sound quality. The two-sensor Griffiths-Jim beamformer with speech and noise inputs processed by a reverberant room simulation to produce the evaluation materials is used. The results of these evaluations will be presented, and the validity of these measures for use in the design of noise cancellation hearing aids will be discussed.
Systematic relationship between variance and mean intelligibility found in Diagnostic Rhyme Test (DRT) scores
Authors: Smith Caldwell P.
Published: October 2005

The mean intelligibility score obtained with the Diagnostic Rhyme Test (ANSI S3.2-1989) is the average of an ensemble of scores for phonetic features. From analyzing diagnostic scores from multispeaker tests evaluated with eight listeners, it was found that a systematic relationship exists between the mean scores and the variance of the ensemble of feature scores. The data set studied included 64 multispeaker tests (44 tests with equal numbers of male and female talker subjects, and 20 with three male talkers; the tests with male and female talkers included ten 18-speaker tests and thirty-four 6-speaker tests). Twenty-four diagnostic scores were obtained for each speaker in each test. A least-squares fit to this data resulted in the linear regression equation: variance (of feature scores) = 2399 − 24.46×mean DRT score, with r2 = 0.96. This corpus of data conformed with the cited equation with a mean-square error of 0.97 in estimating standard deviation in relation to a test's mean DRT score. From the trend in the relationship between mean score and variance, coupled with the previously reported finding that ensembles of diagnostic scores, converted to frequency counts of numbers of listener errors, conform with the negative binomial probability distribution, it was possible to calculate a nomograph of contours of percentiles of diagnostic scores in relation to mean score, i.e., the values that will be exceeded by 50%, by 90% and by 95% of the ensemble of feature scores, in relation to mean intelligibility score.
A practical sensor for acoustic detection of larvae and insects in harvested commodities
Authors: Hickling R. , Chang S. T. , Webb J. C.
Published: October 2005

It is important to prevent the spread of infestations of quarantine insect pests such as those of the Caribbean and Mediterranean fruit fly. It is important also to prevent insect infestations of stored grain. Rigorous visual inspection procedures are used by the USDA and other agencies to detect larvae in fruit for both the import and export markets and to detect adult insects in grain. Such procedures, however, are not completely reliable and involve destruction of fruit. It has been known for some time that it is possible acoustically to detect larvae and insects in fruit and grain [J. C. Webb and P. J. Landolt, J. Environ. Sci. Health A 19, 367–375 (1984)]. Recently practical, inexpensive sensors have been developed that make it possible to apply this technology in the field. Results are presented that demonstrate the effectiveness of these sensors for detecting larvae of the Caribbean fruit fly, Anastraepha suspensa (Loew), in a number of different types of fruit at different stages in the development of the larvae. Results are also presented that demonstrate the effectiveness of the sensors for detecting adults and larvae of the lesser grain borer, Phyzopertha dominica (F.), in grain. [Work supported by the USDA.]
Self-protection in the anuran auditory system
Authors: Narins Peter M.
Published: October 2005

Sound-pressure levels at a distance of 50 cm from a calling frog have been measured as high as 90-110 dB SPL, depending on the species. Two puzzling aspects of this observation are if and how a vocalizing frog protects himself from acoustic overstimulation during his own calling. In this study, it was asked, what is the velocity or displacement of the eardrum during the frog's own vocalization? A calling male tree frog, E. coqui, was located on a tree trunk or other solid substrate in his natural habitat. A He-Ne laser Doppler vibrometer was located 18.2 cm from the animal and aimed at the tympanum. It is demonstrated that both call notes “appear” on the frog's eardrums when he vocalizes. However, the mean vibration amplitude in response to a male's call is not significantly different than that caused by a free-field stimulus presented at moderate levels for the “Co” note (1 kHz), and lower than that caused by a free-field stimulus presented at moderate levels for the “Qui” note (2 kHz). [Work supported by NIH and UCLA.]
Active control of sound and vibration
Authors: Fuller C. R.
Published: October 2005

Due to recent advances in DSP technology, active control now shows much promise for reducing sound and vibration in a number of difficult applications. In this tutorial the concepts behind the active control approach will be introduced with some historical perspective. The basics of feedforward control will then be reviewed and related to the more traditional state feedback methods. Application of the technique to fundamental problems in the control of sound and vibration will be given with some consideration of the design and choice of the appropriate control transducers and cost functions. Useful analytical methods and mechanisms of control will be considered. Recent successful applications of the technique to realistic systems will be reviewed and future promising research directions discussed.
Internal wave contributions to ocean remote sensing by acoustic scintillation analysis
Authors: Lataitis Richard J.
Published: October 2005

Previous theories describing the use of acoustic scintillation analysis for the measurement of transverse currents and microscale variability along horizontal acoustic paths were limited to turbulent flows. These theories are extended to include internal wave contributions to the scintillation signal. It was found that the measurement of currents using the delay to the peak in the intensity cross covariance between two spaced receivers is relatively unaffected by internal waves because the phase speeds of those waves that are most effective in producing scintillation are often small compared to current speeds of interest. In addition, it was found that spatial-filter systems comprising linear arrays of transducers potentially allow the turbulence and internal wave signatures to be unambiguously identified. Ideally the spatial-filter temporal spectrum contains information about the flow speed, the micro- and finescale variability, the degree of internal wave anisotropy, and the power law behavior of the internal wave spectrum. The feasibility of retrieving and profiling these parameters along the propagation path and the limitations of this technique in terms of the attainable spatial and spectral resolution will be discussed.
“Zoeppritz” rationalized, and generalized to anisotropic media
Authors: Schoenberg Michael , Protazio Joao
Published: October 2005

This paper is meant to be a guide through a labyrinth of reflectivity and transmissivity at interfaces between anisotropic elastic media. The Zoeppritz equations for isotropic plane-wave reflection and transmission coefficients are cast in a form from which explicit elementary expressions for the reflectivity and transmissivity matrices are derived in terms of four submatrices of the Zoeppritz coefficient matrix, two submatrices associated with each of the two media. The two submatrices associated with a medium are also the building blocks for a simple construction of the propagator matrix for a layer of that medium. All expressions are applicable to anisotropic media, subject to the requirement that the media involved must be at least monoclinic with a mirror plane of symmetry parallel to the reflecting plane. The submatrices associated with a medium depend only on the elastic properties of that medium and are functions of the eigenvalues and eigenvectors of the Christoffel equations governing plane-wave propagation in the medium. The advantages of this approach to reflectivity are (a) heuristic and (b) it allows a programmer to further modularize computer codes needed for computation of reflection coefficients and propagator matrices in anisotropic elastic layered media programs. Some curious results concerning reflectivity between isotropic and orthorhombic media are presented.
Experiments of elastic wave propagation through stacks of thin plates
Authors: Hsu Chaur-Jian , Schoenberg Michael
Published: October 2005

Ultrasonic experiments were performed to investigate the elastic behavior of systems of closely spaced (relative to wavelength) parallel linear interfaces [M. Schoenberg, J. Acoust. Soc. Am. 68, 1516–1521 (1980)], which have been used to model fractured media. The sample was composed of lucite plates with roughened surfaces and pressed together with controlled stress normal to the plates. Wavelengths were of the order of ten plate thicknesses. Compressional and shear velocities were measured normal and parallel to the plates. Quasicompressional and quasishear velocities were measured at a variety of oblique angles. The higher the confining stress, the less compliant the interfaces were, and the closer the medium behavior was to isotropic. According to the long wavelength linear slip model [M. Schoenberg and J. Douma, Geophys. Prosp. 36, 571–590 (1988)], the medium is transversely isotropic with certain constraints on the moduli and is characterized with four independent parameters: the Lamé constants of the background as well as two interface compliances. Data obtained at a variety of confining stresses agree very well with this model. Experiments were also conducted with some of the interfaces saturated with honey; the overall compliances measured were consistent with the mixing law derived from the linear slip model.
Multidimensional elastic scattering for inclusions buried in inhomogeneous media. Part I: The forward problem
Authors: Aymé-Bellegarda Eveline J. , Habashy Tarek M. , Chang Hung-Wen
Published: October 2005

The purpose of this work is to study, both analytically and numerically, the field scattered by a finite-size inclusion buried in a multilayered, elastic background medium, and to correlate this information to the geometrical and elastic properties of the inclusion. In this first part, the goal is to compute the scattered field generated by a known object. The framework developed is based on an integral equation formalism for elastic scattering. Unlike some past studies, restrictive assumptions on the background medium properties are avoided. For example, both longitudinal and shear waves are allowed to propagate inside the layers, and abrupt changes in the elastic properties of the background medium are permissible. Also, cross polarization at the boundaries and multiple reflections within the layers are taken into account to compute the scattered field everywhere in space. To illustrate this new algorithm, a selected set of numerical simulations is presented, relevant to the case of an inclusion of variable size and contrast buried in a four-layered background structure illuminated by an ultrasonic point force. The results are shown to compare favorably with those obtained independently using a finite-difference technique.
The pitch of odd-harmonic tones: Evidence of temporal analysis in the dominance region
Authors: Bashford James A. , Warren Richard M.
Published: October 2005

Previous studies have shown that tones consisting solely of odd harmonics can produce two types of low pitch, one matching the fundamental frequency and another approximately 1 octave higher. The present study examined the bases of these pitches. Musicians provided matches for odd-harmonic triads (3rd, 5th, and 7th; 5th, 7th, and 9th;…; 17th, 19th, and 21st) having a common, missing fundamental ranging from 100 to 200 Hz. Low-order triads were matched to the fundamental, whereas high-order triads produced pitches approximately 1 octave higher, but deviating from exact doubling of the fundamental by an amount consistent with the waveform pseudoperiodicities. Interestingly, the change from fundamental to pseudoperiod matching occurred with triads centered at about the 9th or 11th harmonic, which have frequency separations approximating those of the dominant partials in an “all-harmonic” signal. These results, together with neurophysiological evidence in the literature, indicate that harmonics within the dominant region interact sufficiently to provide a temporal basis for pitch. It appears that the dominant region is a transition zone where two modes of pitch analysis overlap. [Work supported by AFOSR and NIH.]
Discrimination of FM glide direction and slope
Authors: Feth Lawrence L. , Neill Mary E. , Hsu Chien Yeh
Published: October 2005

Transitions of the second formant in speech sounds have been called the single most important carrier of linguistic information in the speech signal [Liberman et al., Psychol. Rev. 74, 431–461 (1967)]. Both the direction and the slope of the formant transition may be essential in cuing place of articulation, for example. Attempts to study listener performance in laboratory tasks that use frequency-modulated tones to “simulate” such formant transitions are often confounded by pitch differences between the signals to be discriminated. A procedure analogous to the “roving level” procedure used in profile analysis and intensity perception studies to counter the influence of this pitch artifact has been devised. In a two-cue, two-alternative forced-choice (2Q, 2AFC) paradigm, listeners are asked to determine which FM glide differed either in direction or in rate of transition (slope). For each listening interval, the starting frequency of the glide is randomly chosen from a uniform rectangular distribution centered on fc. Because each glide in the trial begins on a random frequency, the listener cannot use pitch differences to determine glide direction or slope. The current version of the program operates three simultaneous adaptive-tracking rules, with signals generated in real time using an Ariel DSP-16 board. Preliminary results for fc from 250 through 4000 Hz, and glide durations from 25 through 100 ms, will be presented. [Work supported by a grant from AFOSR.]
Components of a hypothetical odontocete biosonar signal generator
Authors: Cranford T. W.
Published: October 2005

The site and physiologic mechanism(s) responsible for the generation of odontocete sonar signals have eluded investigators for decades. Examination of postmortem odontocete heads with medical imaging devices (x-ray CT and MRI) across diverse taxa has identified a complex of structures that may function as the essential components of a biosonar signal generator. Each monkey lips/dorsal bursae complex (MLDB) is associated with one (right and left) air passage. Each complex is composed of at least two fatty bursae that are embedded in the monkey lips along the airway, a cartilagenous “stiffening” rod, and a stout ligament. The size of the fatty bursae varies with the species but tends to suggest a relationship with wavelengths for peak frequencies of published signals. In addition, the location of these bursae makes them excellent candidates for sonar signal transducers. The details of this complex and its morphologic surroundings will be shown in examples from six extant odontocete families. Preliminary results from an endoscopic investigation of an echolocating dolphin support the hypothesis that this anatomic complex is the site of sonar signal generation.
Reliability of pure-tone detection thresholds for clinical and 2IFC procedures in quiet and in a noise background
Authors: Marshall Lynne , Hanna Thomas E. , Wilson Richard H.
Published: October 2005

Standard deviations reported for clinical (CLIN) procedures generally are higher than those reported for adaptive 2IFC procedures although the two have not previously been directly compared for the same conditions and subjects. One of the differences between the two procedures is size, with the clinical procedure using a 5-dB step size and the 2IFC procedure using a 2-dB step size. This experiment measured CLIN and 2IFC thresholds with 2- and 5-dB step sizes in quiet and in a background of 4-kHz low-pass filtered noise (spectrum level of 20 dB re:. 20μPA) for nine normal-hearing listeners. Each condition had ten replications. The results showed that step size had no effect on the standard deviation across replications. The CLIN standard deviations were about 40% higher than the 2IFC standard deviations. Also, the quiet background resulted in standard deviations about 25% higher than those in noise. CLIN procedures are more efficient (in terms of sweat factors) than 2IFC procedures, albeit subject to criterion bias. The measured reliability of these procedures is affected both by limitations inherent in the psychophysical procedures and variation of thresholds across blocks. The data are consistent with larger threshold variation across blocks in quiet than in noise.
Radiation from an elastic slab under line and point excitation
Authors: Leehey Patrick , Gut Yuksel
Published: October 2005

Solutions are obtained for acoustic radiation into a dense fluid on one side of an infinite elastic slab of thickness h for pure-tone line and point excitations on the other side (where a vacuum is assumed). These results are compared with the corresponding solutions obtained using the Euler thin plate assumption. Comparisons show that significant excess radiation is predicted under the thin plate assumption even for frequencies sufficiently low that the plate free-bending wavelength is appreciably greater than h. These results suggest that the spatial extent of the excitation must also be of order h or greater for the plate approximation to be valid. Implications for the excitation of a structure by a turbulent boundary layer and for radiation associated with structural discontinuities are discussed. [Work supported by ONR.]
Intensity vector and power flow in an infinite cylindrical shell excited by a point force
Authors: Borgiotti Giorgio V. , Rosen Eric
Published: October 2005

The time harmonic forced vibration of a finite cylinder excited by a point force of arbitrary orientation is analyzed by using wave techniques. The vibrational response is constructed as superposition of propagating and attenuating characteristic waves of the structure (“waveguide modes”). The propagating modes are associated with the flow of mechanical power, whereas the attenuating modes are associated with reactive energy stored in the neighborhood of the excitation. Under the assumption of a linear dependence upon the radial coordinate within the shell thickness, the elastodynamic field is completely identified by 15 quantities, 10 of them being forces and moments resultant per unit length—either circumferential or longitudinal—and the other 5 being linear or angular velocities. The 2-D shell intensity vector has a simple expression in terms of these quantities. Numerical calculations of the intensity vector field for point forces of different orientations are presented. [Work supported by the Naval Research Laboratory.]
Effects of rib stiffeners on the wave-number sensitivity of a cylindrical shell to flow excitation
Authors: Hwang Y. F. , Shang P. C.
Published: October 2005

The wave-number sensitivity (square of the absolute of a normalized spatial Fourier transform of a mode function) of a structural mode determines the degree of the coupling between a structure and the flow-induced pressure field. It is of engineering interest to evaluate relative contributions to the coupling in the two regions of the wave-number domain: the high-wave-number region, at and near the hydrodynamic coincidence, and the low-wave-number region, at and near the modal wave number. Modes in a cylindrical shell can be classified as primarily radial (or flexural), longitudinal (or membrane), or circumferential (or torsional); only the radial modal components are responsible for the coupling with the pressure field. For some unstiffened cylindrical shells (an infinite shell or finite shells with radial constraint at the boundary), these modes are elastically uncoupled. This paper compares the wave-number sensitivity of an unstiffened shell and that of a rib-stiffened shell that is calculated from the finite-element model of the structure. It is found that a circular rib stiffener may cause an elastic coupling between the flexural and membrane modes. This elastic coupling tends to increase the low-wave-number sensitivities of the modes that are predominantly flexural and the high-wave-number sensitivities of the modes that are predominantly membrane. [Work supported by ONR.]
Vowel-to-vowel coarticulation in Slavic languages
Authors: Choi John-Dongwok , Keating Patricia A.
Published: October 2005

Vowel-to-vowel coarticulation is the interaction of vowels across an intervening consonant. In general, consonants differ in how strong an interaction they permit; in particular, the presence of a secondary articulation on a consonant has been hypothesized to block vowel-to-vowel coarticulation. This hypothesis is tested by comparing coarticulation in three Slavic languages (Russian, Polish, Bulgarian) whose phonetic secondary articulations differ in their phonemic status and in their distribution. The three languages are also compared with English. Data consists of F2 measurements at the offset of the first vowel and at the onset of the second vowel in V-stop-V sequences, where the vowels are /i/ and /a/. Analysis of variance shows almost a full range of coarticulatory effects in English and none in Bulgarian, as expected. Against expectations, however, Polish and Russian are intermediate cases, showing coarticulation for some but not all segment sequences. These will be examined to see how the coordination of oral articulations influences measured vowel-to-vowel coarticulation.
Effect of vowel on preceding click in Xhosa
Authors: Sands Bonny
Published: October 2005

Previous work [Sands, J. Acoust. Soc. Am. Suppl. 1 86, S123 (1989)] reported that the acoustic properties of the primary release in clicks was not affected by the height or backness of the following vowel, due to the requirements on the tongue body during the production of the click. This paper will show that the velar or secondary closure also exhibits no such coarticulatory effects, unlike pulmonic velar consonants. Words containing dental, lateral, and alveolopalatal voiceless unaspirated clicks before the vowels /i, e, a, o, u/ from seven Xhosa speakers were digitized at 20 kHz. The noise of the primary click release was removed in order to isolate the release of the secondary closure. The edited tokens were presented in a fixed choice task to six trained phoneticians who evaluated the place of articulation of the prevocalic segment. The main vowel effect seen is that front vowels tend to favor a uvular interpretation. It will be argued that this is not a coarticulatory effect, but rather that listeners expect velar fronting and hear nonfronted velars as uvular. Formant transitions for voiceless unaspirated clicks and velar consonants before /i, a, u/ were compared to support this interpretation.
Identification of natural and synthetic silent-center syllables
Authors: Miranda Salvatore , Strange Winifred
Published: October 2005

Identification of natural and synthetic /dVd/ syllables in two conditions, full and silent center, was compared to investigate the role of dynamic spectral information in the specification of coarticulated American English vowels. Synthetic tokens were generated on a serial formant synthesizer using parameters obtained through a linear predictive coding analysis of the natural tokens. Silent center stimuli were then prepared in the same manner for both natural and synthetic syllables: that portion of the syllable excluding the initial consonant burst and first 40 ms and the last 40 ms before the final consonant closure was attenuated to silence. The original temporal relationship between the 40-ms parts was not modified. Results of perceptual tests showed that both the natural and synthetic full syllables were well identified with error rates of 2% each. Error rates on the silent-center tokens, however, were 16% for the natural syllables and 60% for the synthetic, suggesting that synthetic syllables failed to capture important dynamic spectral information available in the syllable onsets and offsets. [Work supported by NIDCD-00323 and NICHHD-HD-01994.]
X-ray microbeam speech production database
Authors: Westbury John , Milenkovic Paul , Weismer Gary , Kent Raymond
Published: October 2005

A broad review of literature describing lingual function during speech shows that speaker samples per study are typically small (N<3 in more than 80% of all cases), and that speech samples, and representational and analysis conventions are highly variable. Similar conclusions can be drawn for other articulators. Thus it is fair to argue that there is still not available any valid, statistically-defensible sense of normal speech motor behavior, against which disordered articulatory behavior can be compared. Accordingly, a large-sample, 50-speaker x-ray microbeam speech database will be developed at the University of Wisconsin, incorporating point-parametrized representations of lingual, labial, mandibular, and velar movements in association with the resulting acoustic sound pressure wave, for a rich set of utterances and oral motor tasks, and lengthy recording interval (circa 18 min/speaker). The database is intended to be uniform across speakers in task inventory and descriptive kinematic framework; sufficiently accurate and deep to withstand scrutiny of variance, within and across speakers, and perhaps most importantly, an open source available for unlimited inspection and use by other speech scientists. Descriptions of the proposed speech inventory, experimental protocol, speaker sample, and timetable for database development will be provided. [Work supported by NIH DC00820.]
Expansion technique for the solution of a normal mode propagation model
Authors: Werby M. F. , Soileau Joe
Published: October 2005

It is sometimes desirable to obtain a normal mode solution of a waveguide problem in a closed mathematical form. In particular, here, the vertical part of the solution in terms of a sine series for a variable velocity profile where the sine functions are eigenvalues for a suitable isovelocity case is desired. This problem has been done within the context of conventional perturbation theory and was found to be too limiting, particularly for the lower-order modes. It is possible, however, to exploit Sturm-Liouville theory and closure to obtain a coupled system of equations that leads to an adequate sine expansion as well as the appropriate eigenvalues. A new perturbation method is also derived from the results that is less limiting than the conventional perturbation approach and should be of general value to other classes of problems. Calculations are performed and compared with other numerical techniques.
A two-dimensional downslope propagation model based on coupled wedge modes
Authors: Primack Harel , Gilbert Kenneth E.
Published: October 2005

A “wedge-mode” representation of the acoustic field [M. J. Buckingham, J. Acoust. Soc. Am. 82, 198–210 (1987)] has been implemented in a 2-D propagation model that can treat realistic sound-speed profiles. Wedge-mode calculations are compared to parabolic equation (PE) calculations for an isospeed profile and profiles typical of the Mediterranean sea in summer and winter. For an isospeed profile over a penetrable bottom, the wedge modes are almost uncoupled. For a realistic depth-dependent profile, however, the modes are significantly coupled. Moreover, at the beginning of the downslope region, mode-continuum-mode coupling (tunneling) occurs. When only the wedge-mode coupling is accounted for, fair agreement is obtained with the parabolic equation results. When, in addition, the tunneling effect is accounted for with a hybrid mode-PE model, excellent agreement is obtained with the full parabolic equation calculation.
Higher-order methods for an elliptic model of wave propagation
Authors: Knightly G. H. , St. Mary D. F.
Published: October 2005

Elliptic models of wave propagation valid in the far field are often factored to derive one-way wave equations. For certain parameter ranges, the elliptic models generate stable marching methods directly even though the underlying initial value problem is ill posed. The introduction of Padé approximations to operators in the cross range variables leads to higher-order methods for an elliptic model. The stability of the method is analyzed and calculations are presented showing good agreement with exact solutions for some test problems. [Work supported in part by ONR.]
Sonar system for obstacle localization with insights from the echolocating bat
Authors: Barshan Billur , Kuc Roman
Published: October 2005

An active wide-beam sonar system for obstacle localization in 2 D is described. Efficient localization is achieved by mimicking the multiple sensor configuration of bats and employing an improved method for time-of-flight (TOF) estimation. Three transducers are employed, with a transmitter in the middle (the mouth) flanked by two receivers (the ears). After the transmitted pulse encounters an obstacle, the TOF information is extracted from the noisy echoes detected by each receiver, to estimate the range r and azimuth θ of an obstacle located within the active region of the sonar system. Simple thresholding does not produce accurate results due to the inevitable bias error in the TOF measurement. An unbiased estimate of TOF is developed by modeling the leading edge of the echo waveform by a parabola, whose vertex corresponds to the actual TOF. Based on this TOF information, unbiased range and azimuth estimates are derived for an isolated obstacle. Experimental results show that the estimates are most reliable if the obstacle is located along the system line-of-sight and that they improve with decreasing range, providing a novel interpretation for bat foraging. Experimental results indicate only a slight degradation compared to the Cramér-Rao lower bounds for estimator variances. [Work supported by NSF:ECS-8802627.]
Ray tracing errors caused by approximating sound-speed profiles using cubic splines
Authors: Bold Gary E. J. , Morris Michele Y. , Tan Sze M.
Published: October 2005

If a smoothly varying, range-independent sound-speed profile and its first derivative are known everywhere, in principle it is possible to trace classical rays through it with arbitrary accuracy. In practice, sound-speed profiles are often delivered to modelers as a set of discrete speed/depth pairs, and only the values at sampled depths are known a priori. Some form of interpolation must be used to estimate the profile at depths between the sampled points, and cubic splines were proposed nearly 30 years ago as a convenient (though not the only) and computationally simple way of doing this. However, when spline fitting is used, errors in the ray paths arise due to the splining errors. Using a simple (Munk) sound-speed profile, the magnitude, behavior, and causes of such ray-path errors are investigated.
Extraction of geometrical information from the solution for acoustic wave propagation in the ocean as obtained from chaos theory
Authors: Akers Geoffrey R.
Published: October 2005

One obtains the time evolution geometrical information in the form of a “strange attractor” for the propagation in the ocean as a nonlinear medium. This represents the asymptotic behavior of the propagation in the chaotic ocean environment. The trajectory of the points (u, u̇) as two phase variables is obtained and presented as an addition to the previous work, which describes their evolution in time in the ocean.
Intelligibility in classrooms
Authors: Brüel Per V.
Published: October 2005

Due to hygiene requirements in modern school buildings, the materials used in classrooms and auditoriums have to be durable and hard. The materials must also be very strong to withstand the abuse from the young pupils, resulting in a very poor acoustical environment with low intelligibility and stressful working conditions for both teachers and pupils. Through the RASTI method, it is possible to measure the intelligibility in the room taking both reverberation, early decay, and noise into account. This paper shows a practical use of the RASTI method suggesting how to develop a modern classroom that meets all hygiene requirements and at the same time provides good acoustical performance and excellent intelligibility for communication. The principle is to apply sound-absorbing material, out of reach of the pupils, to surfaces where no reflection is needed, while reflection from the middle part of the ceiling and back walls is utilized. After treatment, the RASTI figure is over 0, 70, which is in the upper end of good.
Interferometric optical fiber dynamic mechanical sensors
Authors: Bucaro J. A.
Published: October 2005

The use of fiber optic interferometers for detecting dynamic mechanical parameters has matured significantly since the first reports on them appeared just about a decade ago. This paper will discuss the current state-of-the-art in this technology with particular emphasis on devices for measuring acoustic waves and dynamic structural strains. Contrasts will be discussed between two-fiber single mode sensors and the more recently developed single-fiber dual mode systems.
Fiber optic sensing of magnetic fields
Authors: Bucholtz F.
Published: October 2005

Interferometric fiber sensors using highly magnetostrictive amorphous metals have demonstrated the capability to detect magnetic fields with high resolution. These sensors have potential applications in the areas of geophysics, medical technology, and a variety of commercial and military fields. This paper discusses the magnetoelastic properties of amorphous metal transducers in terms of the coherent rotation model for a magnetic domain. The general operating principles of fiber optic magnetic sensors, including single and multiple axis devices, are developed and theoretical limitations arising from phase noise, shot noise, and thermal noise are discussed. Finally, the results of a number of experiments with fiber magnetometers for both low-(⩽ 100 Hz) and high-frequency (> 100 Hz) magnetic field measurements are presented. These include high-resolution measurements on laboratory devices, testing of a compact three-axis magnetic heading sensor, and a demonstration of fiber optic detection of the mixing of spin wave modes in a metallic glass sample.
Hybrid fiber optic sensors
Authors: Lenz James , Bjork Paul
Published: October 2005

For more than 10 years, fiber optic sensors have been projected as a dominant sensor technology for the future. This projection has yet to be realized. There continues to be a substantial level of research and development in various fiber sensors concepts, yet only a few products are available commercially. The major factors limiting the success of the fiber sensors in the marketplace will be identified. An alternate approach to fiber sensors is described which takes a systems approach to producing fiber sensors. It combines the advantages of optical fibers with the low-power electronic sensor technology currently available. A single multimode fiber connected between the readout is converted to electricity at the transducer. Optical energy transmitted from the readout is converted to electricity at the transducer. Digital data from the transducer are synchronously transmitted over the fiber to the readout. Magnetic (i.e., current), temperature, position, and proximity sensors have been built and will be described. A discussion comparing optical and electrical sensors is also included.
Hot topics in bioresponse to vibration
Authors: Brammer Anthony J. , Nyborg Wesley L.
Published: October 2005

At very low frequencies, vibration or intense infrasound may excite body organs, with the (lumped) responses involving smaller physiological structures, and ultimately the skin, as frequency increases. At high frequencies, tissue response forms the basis for medical applications. Of particular interest at this time are acoustic lithotripsy and acoustic hyperthermia. Investigating the biophysical mechanisms of tissue response aids in establishing safety limits for diagnostic applications of ultrasound, which remain a major concern. At low frequencies, exposure limits for vibration transmitted to the hands from power tools are the subject of active debate, as well as the reversibility of symptoms after reduction or cessation of exposure, owing to the implications for compensation. Vibrotactile assessment of sensory thresholds is emerging as a valuable tool for monitoring peripheral sensorineural loss, with the presentation of results in the form of “tactograms” providing the tactile equivalent of an audiogram. Portable devices will require the development of appropriate skin stimulators, which are also crucial for the widespread application of tactile communication devices among the hearing and visually impaired.
Recent advances in musical acoustics
Authors: Rossing Thomas D.
Published: October 2005

Musical acoustics includes the production of musical sound, its transmission to the listener (in the concert hall or through recordings), and its perception by the listener. Exciting developments in all three areas have been closely linked to advances in computers and digital signal processing. Computer music has come of age, digital music synthesizers are within the reach of every composer, and researchers of acoustical instruments have acquired new understanding through computer modeling and computer-aided measurements in the laboratory. In the area of recorded music, compact discs have all but replaced phonograph records, and digital audio tape has appeared on the consumer market. Finally, digital signal generation and signal processing have enabled researchers to carry out sophisticated experiments on music perception that have led to an enhanced understanding of human auditory and neurological processing systems. This report will highlight mainly the production of musical sound by electronic and acoustical instruments.
Effects of aircraft noise on humans: Overview of NSBIT research program
Authors: Finegold Lawrence S. , Fidell Sanford A.
Published: October 2005

The U.S. Air Force Noise and Sonic Boom Impact Technology (NSBIT) Program is conducting a comprehensive set of research projects on the effects of military aircraft overflight noise on humans. As the requirements for low-level, high-speed military training flights increase and the general public becomes more aware of possible impacts from these flights, it is becoming more important that improved models are developed to predict potential impacts on individual and community annoyance, sleep disturbance, human health, and other potential negative effects of aircraft noise. The problems inherent in using existing models for predicting human impacts are especially difficult when they are applied to military flying training activities because of the sporadic nature of these flights, their rapid onset rates, low altitudes, and high speeds. The NSBIT research program has been ongoing for several years and is yielding new data and improved environmental impact analysis models addressing several human effects issues. The presentation will provide an overview of the NSBIT human effects research program and will focus on the technical approaches being taken in each of the specific topic areas for both current and planned research.
Sonic boom effects on unconventional structures in air combat training areas
Authors: Sutherland Louis C. , Brown Ron , Plotkin Kenneth J.
Published: October 2005

Sonic booms generated by supersonic flight portions, of air combat maneuver (ACM) training for military aircraft are a source of environmental concern to the U.S. Air Force. One of the concerns relates to potential effects on unconventional structures such as historic buildings, early American structures, and avalanche-prone areas. An upgraded statistical model is outlined for the sonic boom environment based on recent measurements and prior studies. The model is applied to the prediction of the probability of damage to unconventional structures using simple shock-response concepts and the relationship between structural velocity and stress [F. V. Hunt, “Stress and strain limits on the attainable velocity in mechanical vibration,” J. Acoust. Soc. Am. 32, 1123–1128 (1960)]. Measured residual shock spectra of a range of ACM sonic booms of widely different wave shapes are shown to be closely predicted by an ideal N-wave spectra. Structural responses to sonic booms measured on two historic buildings in the White Sands Missile Range are shown to be in good agreement with theory. [This work was supported in part by the Dept. of the Air Force, Noise and Sonic Boom Impact Technology Program, code OC-AC HAD/YA-NSBIT, Wright-Patterson AFB, OH 45443-6573.]
On identifying the noise floor of a digital signal analysis system
Authors: Pope J.
Published: October 2005

To assess the validity of a signal analysis, it is imperative that the noise floor of the measurement system be known. It is the experience of the author that many experimenters determine the analysis noise floor intuitively, a typical remark being “I know it when I see it.” This approach, though often acceptable with high-quality analog instruments, can lead to serious errors with modern digital analysis instrumentation. Difficulties arise due to harmonic distortion and spurious components that can be introduced by digitizers and antialiasing filters. Also, the apparent noise may depend upon the initialization state of the digital system. To avoid error, it is essential to consult carefully the system specifications and to perform tests with known signals. Two examples of erroneous intuitive determination of the noise floor leading to incorrect results will be discussed: (1) detection of prominent tones in noise produced by business equipment according to ANSI S12.10; and (2) analysis of an aircraft flyover-noise signal according to FAR, Part 36.
A new approach to the effect of bandpass filters on sound absorption calculations
Authors: Joppa Paul D. , Sutherland Louis C. , Zuckerwar Allan J.
Published: October 2005

Atmospheric absorption losses are usually calculated for single frequencies, but must often be applied to bandpass-filtered data, usually in octave bands or one-third octave bands. The simplest approach, using the absorption value at the bandpass filter center frequency, is inaccurate for broadband sources when the losses are large because the resulting spectrum has a large negative slope with frequency, and thus the band level is dominated by power near the lower band edge. The proposed new approach uses a representative frequency at which absorption is calculated and which depends on the total absorption along the path. An expression for the representative frequency is derived and errors are evaluated for several cases. A practical method, suitable for hand or computer implementation, is proposed.s
Scattering of sound by sound in a waveguide
Authors: VanDoren Thomas W. , Hamilton Mark F.
Published: October 2005

An experiment was performed to investigate the scattering of sound by sound in the plane-wave mode of an air-filled rectangular waveguide. A progressive wave of frequency 2300 Hz propagated through a standing wave of frequency 283 Hz, and the nonlinear wave interaction generated sum and difference frequency sound. The standing wave was formed between the sound source at one end of the waveguide and a Helmholtz resonator tuned to 283 Hz and mounted 4 m downstream to a port in a side wall. The 2300-Hz tone, as well as the sum and difference frequency waves, was relatively unaffected by the resonator. After being amplified within the standing wave field, the sum and difference frequency sound was scattered from the interaction region and propagated freely downstream from the resonator. Predictions based on a quasilinear theory for nonlinear interaction in a rectangular waveguide [Hamilton and TenCate, J. Acoust. Soc. Am. 81, 1703–1712 (1987)] are in good agreement with measurements of the sum and difference frequency sound both inside and outside the nonlinear interaction region. [Work supported by the David and Lucile Packard Foundation and the Texas Advanced Research Program.]