bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation and scattering from large axisymmetric structures in an infinite or semiinfinite fluid medium
Authors: Patel J. S.
Published: October 2005

A complex axisymmetric structure immersed in an infinite or semiinfinite fluid medium, excited by a plane acoustic wave or by a spherical or cylindrical acoustic wave emanating from a source in the vicinity of the structure or by a mechanical force acting on the structure, scatters and/or radiates the acoustic waves in the fluid medium. At a lower frequency range of excitation, vibrations of the structure and the radiating acoustic pressure strongly couples, whereas at higher frequency of excitation the structure can be regarded as rigid. A program called FIST (Fluid Interacting with STructures) is developed to analyze these problems. Using the Helmholtz integral, one can write a linear relation between the particle velocity normal to a cavity surface and the corresponding acoustic pressure. For efficiency and economy of calculations and for the consistency of velocity distribution between the structural elements and the corresponding fluid elements in contact, the distribution of pressure and velocity on the cavity surface is described by a cubic polynominal. These fluid equations couple with the equations of motion of the structure. Combining the fluid and structural equations we get Mẍ + Cẋ + Kx = Finc + Fmech. (1) Since this is a steady-state excitation problem, differential equation (1) reduces to a set of algebraic equations (− Mω2 + iωC + K)x = Finc + Fmech (2) Here matrix C is full and complex, K is real and banded, and M is real and diagonal. Further, the elements of K are several orders of magnitude larger than those of C. This ill conditioning causes a severe degradation in computational accuracy when one attempts to decompose the dynamic matrix. Two alternatives are available. (a) Iterate Eqs. (2) using the initial vector given by the solution of the in vacuo response of the structure. (b) Transform Eqs. (2) using in vacuo modes of the structure. We opted for the second approach and using that we have calculated the signature of a full scale marine structure. Construction of fluid and the modal matrices are computationally quite intensive. An original attempt to use a UNIVAC 1108 was dropped because it would have taken approximately 250 h of CPU time to calculate one bistatic plot. A UNIVAC 1110, although faster, took 50 h of CPU time to calculate one bistatic plot. Using a CRAY computer with its large core and speed of computations, it took only 20 min of CPU time to calculate a complete monostatic plot.
A numerically efficient global matrix approach to the solution of the wave equation in stratified environments
Authors: Schmidt Henrik
Published: October 2005

Solution of wave propagation problems in horizontally stratified environments arises in many fields, including underwater acoustics, seismology, and ultrasonics. When the environment is considered range-independent the wave equation can be separated in depth and range by standard integral transform techniques. The depth-dependent solution is then found by matching boundary conditions at horizontal interfaces, and the field as a function of range is found by evaluating the inverse integral transforms. Several numerical methods have been developed for this purpose, in underwater acoustics known as the fast-field technique and in seismology as full wave field and reflectivity methods. These methods have generally been based on propagator matrix solutions for the multilayer Green's function. In contrast to these techniques, the use of a global matrix approach to solve the depth-separated wave equation automatically yields the possibility of treating problems with several sources and receivers without requiring separate Green's function calculations. Unconditionally stable solutions are obtained in a computationally efficient fashion, leading to a code that is an order of magnitude faster than existing models. The generality and efficiency of this global matrix method makes it well suited to a wide class of propagation problems, as demonstrated by selected examples from underwater acoustics. Total wave fields in depth and range are calculated for both cw and pulsed sources.
Reflection and transmission of narrow beams at a water/bottom interface
Authors: Schmidt Henrik , Jensen Finn B.
Published: October 2005

The reflection and transmission of narrow sound beams at the interface between two fluid media was studied experimentally by Muir et al. Sound Vib. 64, 539–551 (1979)] who found that narrow beams impinging on a sedimentary bottom at grazing angles below the critical angle will not be totally reflected as predicted by Snell's law. Here a numerical model yielding an exact solution to the wave equation in horizontally stratified environments is used to analyze the observed phenomenon. A beam of any realistic width is generated by introducing a vertical source array and properly phasing the single sources. It is shown that the deviation from Snell's law is due to the finite width of the angular spectrum of narrow beams, and the results given are in good qualitative agreement with the experimental results.
Numerical implementation of intrinsic mode Green's functions for oceans with weakly sloping penetrable bottom
Authors: Topuz E. , Felsen L. B. , Yaniv J.
Published: October 2005

Two recently developed related spectral theories [A. Kamel and L. B. Felsen, J. Acoust. Soc. Am. 73, 1120–1130 (1983); J. M. Arnold and L. B. Felsen, J. Acoust. Soc. Am. 73, 1105–1119 (1983)] have provided potentially new options for calculating source-excited sound fields in a weakly range-dependent ocean environment. These theories have so far been applied to a homogeneous two-dimensional ocean and bottom separated by a plane sloping interface. It has been recognized that their common building blocks are what have been referred to as “intrinsic modes” [J. M. Arnold and L. B. Felsen, J. Acoust. Soc. Am. (to appear)]. Intrinsic modes have spectral integral representations that reduce in a lowest order approximation to adiabatic modes, where these can be defined, but which remain uniformly valid in their integral form through the cutoff transition in upslope propagation. An efficient numerical algorithm has been developed for calculating the intrinsic mode Green's function in the ocean and in the bottom. In a sense, this algorithm may be regarded as a range-dependent generalization of the range-independent Fast Field Program (FFP), but with the important difference that angular wave spectra replace the conventional rectilinear spectral decomposition. Numerical results are compared with those from the parabolic equation [F. B. Jensen and W. Kuperman, J. Acoust. Soc. Am. 67, 1564–1566 (1980)] and the augmented adiabatic mode theory [A. Pierce, 3. Acoust. Soc. Am. 74, 1837–1847 (1983)]. Also discussed and compared are asymptotic approximations of the spectral integral, which do not require the patching of the augmented adiabatic model. [Work supported by ONR Ocean Acoustics.]
Finite difference seismograms for laterally varying marine models
Authors: Stephen R. A.
Published: October 2005

The method of finite differences is applied to the elastic wave equation to generate synthetic seismograms for laterally varying seafloor structures. The results are compared with borehole seismic data from the Gulf of California (Deep Sea Drilling Project Site 485) in which lines were shot over flat and rough topography. The significant new phenomenon observed in both the synthetic seismograms and the field data is the generation of a “double head wave” due to the interaction of the incident wavefront with the side of a hill and the flat sea floor adjacent to the hill. In these models the hills are on the order of a seismic wavelength in height and steep velocity gradients occur over distances comparable to wavelengths. Ray theoretical methods would not be suitable for studying such structures. True amplitude record sections are obtained by the finite difference method, which show for these models that the head wave generated at the flat sea floor adjacent to the hill is lower in amplitude than if the hill were not present and is lower in amplitude than the head wave generated at the hill. A second feature which is important for borehole receivers is the existence of the “direct wave root” in the upper basement. This energy occurs below the sharp interface when the direct wave impinges on the interface from above. There is no corresponding Snell's law ray path for this energy and the energy is evanescent with depth in the lower medium. The properties of both the double head wave and the direct wave root are clearly demonstrated in the finite difference “snapshot” displays.
Shear high angle PE (shape): A PE-type wave equation for seismic wave propagation
Authors: Greene Robert R.
Published: October 2005

A model of acoustic propagation in solid media has been derived. It is a one-way wave equation based on a high-order Padé approximation to the square root function. The physical properties of the environment are modeled as thin stratified layers. A generalization of the equations to range-dependent environments is easily implemented by allowing the material properties of the layers to vary in range. Furthermore, reflecting interfaces of variable depth can be approximated by using an equivalent reflector, consisting of two thin layers whose material properties vary in range.
Sound intensity processing under continuous adaptation
Authors: Fay Richard , Coombs Sheryl
Published: October 2005

Using classical respiratory conditioning, the smallest detectable changes in the intensity of a continuous sound were measured in the goldfish as functions of signal duration and overall level. Gap detection thresholds for noise were also obtained. Neural correlates were studied in single auditory (saccular) nerve units. Noise increment detection shows perfect temporal summation (10–160 ms) in that equivalent signal levels for in-phase addition fall by 3 dB per doubling of duration. Thresholds are independent of overall level, in accordance with Weber's law. Noise decrement thresholds grow more rapidly toward a minimum gap of 35 ms. Tone increment and decrement thresholds are identical (0.1–0.2 dB), and show no duration effect. Increment thresholds decline significantly with overall level between 15 and 40 dB SL (Weber's law does not hold). Auditory nerve units vary widely in adaptation patterns and in sensitivity to intensity changes. Recovery from adaptation (a burst of spikes evoked as the sound intensity returns to the adapting level following a decrement) has a different time course for tones and noise and may account for gap detection thresholds. These results are discussed in the context of current theories on hair cell-nerve fiber synaptic mechanisms. [Supported by the NSF and the NIH (NINCDS).]
Intensity discrimination of frozen and random noise bands
Authors: Buus Søren
Published: October 2005

This experiment examines how stimulus bandwidth and variability affect the difference limen, DL ( = 10*log[(I + ΔI)/I]), for a change in intensity. DLs were measured at 30, 60, and 90 dB SPL for a 3-kHz tone and for nine noise bands with bandwidths ranging from 50 Hz to 12 kHz, using an adaptive two-interval forced-choice procedure. Results for three normal listeners show that the DLs are the same for frozen and random noise, except for the narrowest noise bands with steep skirts. For 50-Hz bands, DLs for frozen noise decrease from about 3.5 to 1.2 dB as level increases from 30 to 90 dB, similar to DLs for the tone, but for random noise they are roughly constant, between 3 and 4 dB. Bandwidth has essentially no effect on the DLs at 90 dB, but at the lower levels the DLs decrease as bandwidth increases. An anomalous result is that the DLs are larger at 60 dB than at 30 dB for all bandwidths tested. The interaction of bandwidth and level is consistent with the excitation pattern model, but the effect of level between 30 and 60 dB suggests modifications. [Supported by NIH.]
Discrimination of permuted orders of tones having the same pitch but different qualities
Authors: Gardner Daniel A. , Brubaker Brad S. , Warren Richard M.
Published: October 2005

Untrained subjects judged whether two sequences of tones were different or the same. Each sequence consisted of three tonal items (A = filtered pulse train, B = sinusoidal tone, C = filtered square wave) which were arranged either in the form [ABCABC⋯A] followed by [ACBACB⋯A] (different) or [ABCABC⋯A] followed by [ABCABC⋯A] (same). Each tonal item had the same waveform repetition frequency (800 Hz) and pitch, but possessed a distinctive quality. Duration of items was the same within sequence pairs, and was varied systematically from item durations of several seconds (permitting easy verbal labeling of components in the proper order) down to 10 ms (components could not be recognized). Accuracy of judgments was well above chance at each item duration. It is suggested that discrimination of differences in the order of items was accomplished through a naming of individual components in order of occurrence for longer item durations, and through recognition of qualitative differences between sequences for brief item durations. Implications for perception of sequences of sounds in speech and music will be discussed. [Work supported by NIH and NSF.]
A superposition model for coarticulation in certain CVC utterances
Authors: Broad David J. , Clermont Frantz
Published: October 2005

Formant trajectories throughout the vowels of American English C, VC2 syllables are modeled for C1, C2 = /b,d,g/ as linear combinations f(t) + T + g(t), where T is a vowel target, and f and g are time-dependent functions for the C1V and VC2 transitions. The T's, f's, and g's are obtained directly from formant contours measured from three readings of 10 vowels uttered by a single speaker in VC2 and C1V/d/contexts. The rms errors (44, 101, and 126 Hz) in predicting the F1, F2, and F3 contours of an independent test script are near the minimum theoretical values (38, 99, and 120 Hz) based on inter-repetition variation and its contribution to uncertainty in the model elements. The f's and g's can, except for F2 of /i/ and F3 of /i/ and /ɜ/, be represented by the phonetically motivated form c(T − L)G(t), where c is a scale factor, L is a consonant locus, and G is a data-derived contour shape. The G's can further be fit by exponentials, to within about 11, 3, and 6 percent of their total range for F1, F2, and F3.
Acoustic characteristics of nasal consonants in American English
Authors: Glass James R. , Zue Victor W.
Published: October 2005

Although in the last decade much research has been directed towards the study of acoustic characteristics of speech sounds in continuous speech, there is still a need for the quantification of many of these properties. As a step in this direction, this work attempts to quantify the temporal and spectral characteristics of the nasal consonants in American English. A corpus consisting of over 200 words with the nasal consonant appearing in various positions, both as a single consonant and as part of a cluster, was designed. Care was taken to include words that form minimal pairs such as ben, bent, bend, bet, and bed, as well as words with acoustic characteristics that are similar to nasals such as need, deed, and lead. Six speakers, three males and three females, read the words embedded in a carrier phrase, resulting in a database of over 1200 utterances. All the recorded words were digitized and their phonetic transcriptions were aligned with the waveform. The analysis focuses on the static characteristics of the nasal murmur, the effect of nasalization on the spectral shape of vowels, and the properties of the transitional region between the nasal consonant and the adjacent vowel. Preliminary results suggested that: (1) the duration of the nasal murmur is strongly influenced by the environment in which it appears, (2) for a given speaker, the spectral shape of the nasal murmur is relatively unaffected by the phonetic enviroment, and (3) for a given speaker, the spectral shapes of the nasal murmur are very similar for all nasal consonants. [Work supported by the Natural Sciences and Engineering Research Council of Canada and by the Office of Naval Research under contract N00014-82-K-0727.]
An acoustic analysis of connected Japanese digits
Authors: Kawasaki Haruko
Published: October 2005

This study investigated the acoustic characteristics of coarticulatory phenomena in connected Japanese digits. Its aim was to discover acoustic phonetic regularities that could be used in a knowledge-based continuous speech recognition system. The data consisted of 840 six-digit strings spoken by seven males and three female native speakers of Japanese. A variety of intra- and inter-digit coarticulatory phenonema were examined using synchronized displays of digitized waveforms, wideband spectrograms, total energy, low-frequency energy, and zero crossings rate. Among the questions assessed were: whether allophonic processes often cited in the phonological literature are readily observable in the acoustic signal, whether they are consistently observed across tokens and speakers, and whether seemingly free variants occur truly randomly or are conditioned by such factors as phrasal structure, accentual pattern, and speaking rate. The allophonic processes examined included: devoicing/shortening of high vowels, gemination of voiceless stops, deletion/lenition of word-medial sonorants, glottalization, lenition of [h], vowel nasalization, frication/nasalization of [g], affrication of [z], etc. Current affiliation: Voice Processing Corporation, 1 Broadway, Cambridge, MA 02142.
Age-related changes in the syntactic interpretation of prosodic cues
Authors: Cowin Elizabeth , Mann Virginia , Schoenheimer Joyce , Berman Judith
Published: October 2005

The contrast between “He showed her the bird seed,” and “He showed her bird the seed,” can be marked by an article and prosody, or by prosody alone. Aural comprehension of such sentences develops between ages 5 and 13, and comprehension of sentences marked by prosody alone is last to emerge [R. J. Scholes, D.C. Tanis, and A. Turner, Lang. Speech 19, 212–223 (1976)]. We have replicated this finding among a population of 8- and 10-year-old children, and, in three subsequent experiments, have explored the basis of age-related changes in use of prosody. The first experiment reveals that age-related differences in use of prosodic cues extend to another syntactic structure. The second shows that young children's perception of the relevant prosodic cues is superior to their syntactic interpretation of them. The third shows that while emphasis of prosodic cues does not improve comprehension, disruption of either work stress or juncture pause can penalize children's performance, more so for older children than younger ones. Thus it may not be the perception of word stress or juncture pause so much as the syntactic interpretation of them that increases between ages 8 and 10. A further finding is that interpretation of prosodic cues is related to reading ability. Relative to the good readers at each age, the poorer readers possessed equivalent perceptual skills, but their sentence comprehension skills were less mature. [Work supported by Bryn Mawr College, NICHD, and BRS.]
Structure of movement trajectories as a function of rate
Authors: Gentil Michèle , Harris Katherine S. , Horiguchi Satoshi , Honda Kiyoshi
Published: October 2005

In a previous paper [Gentil et al., J. Acoust Soc. Am. Suppl. 1 75, S23 (1984)], we reported invariance in interarticulator timing over rate changes in production of some simple disyllables, as indicated by muscle activity onsets, for a speaker of French. The present study extends the previous one, in that it examines the relative timing of articulator movements. Infrared LEDs attached to lip and jaw were monitored using an optical tracking system, to determine onsets of consonant and vowel related lip and jaw movement. Ratios were computed between consonant-to-vowel and vowel-to-vowel intervals, in French disyllables of /pVCap/ type, where V = /i, ɑ, u/ and C = /p, t, s/ at two speaking rates. Our findings confirm and extend for a speaker of a different language (French rather than English) the results of a previous kinematic study [Tuller and Kelso, J. Acoust. Soc. Am. (in press).]
Effects of speaking mode and sentence focus on fundamental frequency patterns
Authors: Cooper William E. , Eady Stephen J. , Mueller Pamela R.
Published: October 2005

Global characteristics of fundamental frequency (F0) contours in English were examined in three task environments, including (a) spontaneous speaking about an academic topic, compared with subsequent oral reading of a transcript thereof, (b) oral description of pictures, and (c) oral reading of isolated sentences whose focus was determined by variations in preceding questions. The results of the first two studies showed in general absence of F0 declination in spontaneous speech, in agreement with other recent work. The results of the third study indicated that F0 declination occurs throughout the oral reading of isolated sentences, even when sentence focus is located near the end of the sentence, in disagreement with preliminary data for Swedish [G. Bruce, Lund Univ. Working Papers 22, 51–116 (1982)]. These and additional results are discussed in terms of a model of F0 patterns that sharply distinguishes global and local attributes. [Work supported by NIH.]
Motor vehicle noise measurements and standards—The U.S. industry viewpoint
Authors: Pataky Paul P.
Published: October 2005

When motor vehicle regulatory noise standards are established, they are typically based on the use of specific compliance test procedures. Currently, there are a number of basic exterior noise test procedures in use, each designed to measure the maximum noise generated by the vehicle during specific modes of operation. However, because of new developments in automotive technology, such as computer-programmed automatic transmissions and infinitely variable (gearless) transmissions, and the desire of regulatory officials to significantly lower vehicle noise standards, questions are being raised with respect to the adequacy and relevance of these test procedures. To answer these questions, the U.S. industry recommends a comprehensive assessment of the validity of the existing compliance test procedures in relation to community noise levels, applicability to future high-technology vehicles, and the possible development of more relevant, harmonized compliance test procedures and appropriate noise level standards.
In-fluid wave fields of discretely stiffened cylindrical shells
Authors: Sandman B. E. , Harari A.
Published: October 2005

An in-fluid shell design application in an environment of dynamic loading necessitates a characterization of the complex frequency response of the structure with the induced acoustics of the surrounding medium. Structurally efficient cylindrical shells frequently utilize ring stiffeners to maintain general and local stability under external loads. Depending upon the frequency range of interest, the detail of the shell/ring stiffener geometry can be a primary influence in controlling the nature of the shell response and the accompanying acoustic pressure field. In this presentation the authors provide a summary of analytical approaches and relevant results in their effort to capture the physics of fluid-structure interaction of discretely stiffened cylindrical shells. A stiffened, finite length, in-fluid cylindrical shell is defined in terms of a generalized mathematical model which includes a complete set of boundary conditions and arbitrary variations of wall thickness, stiffener size, and spacing. The nature of the response is captured in terms of the in-vacuo and in-fluid displacement fields under various spatial descriptions of time-harmonic excitation. For the case of in-fluid response the nearfield acoustic pressures in the immediate neighborhood of the cylindrical surface are calculated. The issues of stiffener flexibility and size as they relate to shell discontinuity impedance, shell wave propagation, nearfield acoustics, and radiation efficiency are addressed.
Some results of speech analysis by parallel processor
Authors: Hemdal John F.
Published: October 2005

Commercially available parallel processors with special cellular computer architecture are able to perform certain nonlinear transformations, viz., the covering transformations much more efficiently than Von Neumann type machines. Additionally, these computers' interactive image processing capabilities often result in discovering insightful ways of approaching old problems. It is natural to inquire whether the inherent advantages of cellular processors would be of benefit in speech analysis. This paper discusses the early results obtained by treating the speech spectrogram as an “image” and analyzing this “image” on a Cytocomputer™. Results include the characterization of the distinctive features of speech in mathematical morphological terms. Examples of morphological transformations of speech spectrograms will be presented which suggest applications in speech analysis, automatic speech recognition, speech synthesis, bandwidth compression, and speech enhancement.
Estimating the frequency response of a structure from static loading
Authors: Cuschieri J. M.
Published: October 2005

The noise radiated from a structure is directly related to the level of surface vibration or the structural response at the excitation point. That is an estimate of the response of the structure is an important parameter for the prediction of the radiated noise energy, or surface vibration level. The response of a structure can be divided into two sections: the low-frequency regime and the high-frequency regime. The low-frequency regime is that below the first natural frequency of the structure. In this regime the response is directly related to the static stiffness. Above the first resonant frequency the structure goes through a series of resonances and antiresonances. At high frequencies, the bandwidth separating successive modes becomes less than the bandwidth associated with each mode, for typical machine structures, with a high level of structural damping. The frequency at which this occurs is sometimes less than 1 kHz and the response approaches a mean level. A direct relation exists between the high-frequency mean level and the response level in the low-frequency regime. This relationship is also dependent on the value of the structural damping. Thus, the mean structural response level can be estimated from knowledge of the static response or static stiffness.
An analysis of wave propagation around a railroad wheel rim using the discrete collocation method (DCM)
Authors: Fahmy M.N. , Finch R.D. , VanArsdale W. E.
Published: October 2005

The DCM is used to determine igenfrequencies for a harmonic wave propagation around a railroad wheel rim. The free boundary is discretized into N equally spaced points. The discrete Fourier transformation (DFT) of normal and tangential stress components is performed on the boundary by using the FFT algorithm. If L terms are retained in the DFT, then the truncated series has 3L arbitrary coefficients. If the boundary is stress free, then there will be 3L homogeneous linear equations for 3L unknown coefficients. This set of equations has a nontrivial solution if its determinant is equal to zero. The position vector, displacement, and stress components are periodic with every cycle around the closed boundary and have a nonbandlimited Fourier series. Thus aliasing error in their DFT cannot be absolutely prevented but it can be minimized by choosing the right values of N and L. By using the DCM the computation time is reduced since the FFT is used in calculating the frequency determinant elements and the size of this determinant is reduced from 3N × 3N to 3L × 3L (where L < N). The calculated and the measured frequency values of a 33-in. railroad wheel are compared. [Work supported by the Association of American Railroads.]
Using the eigenvalue expansion to solve for crack diffraction in an elastic waveguide with a numerical example of a surface crack on a railroad wheel rim
Authors: Fahmy M. N. , Finch R. D. , VanArsdale W. E.
Published: October 2005

Surface waves are produced by hammer impact on the rim of a railroad wheel. They travel around the wheel tread. If a crack is present in the rim surface, there will be an extra impulse in the first arrival [M. N. Fahmy and R. D. Finch, J. Acoust. Soc. Am. 75, 1283–1290 (1984)]. The transient response of a railroad wheel to an impact force is obtained using the eigenvalue expansion method on the principal modes of the surface wave. The eigenfrequencies and corresponding displacement field for these modes are calculated by using the discrete collocation method. The crack echo diffraction is modeled using a planar cut in the back rim face. This type of crack occurs in 60% of the wheels withdrawn from service. Reflection off the crack face modifies results for the good wheel. The calculated and the measured frequency response of a 33-in. railroad wheel with and without a 3/4-in. surface crack are compared in the frequency range 0–15 kHz. [Work supported by the Association of American Railroads.]
“Air pistons,” bells, and tone holes as barriers to wave propagation in a tube
Authors: Strong William J. , Dudley J. Duane
Published: October 2005

Wave disturbances in wind instruments are coupled to the outside air via an unbaffled “air piston” in the case of a woodwind with no open tone holes, a bell in the case of a brass instrument, or an open tone hole lattice in the case of a woodwind. The coupling mechanism also forms a barrier to wave propagation from the tube which results in reflected waves that are important in establishing the standing waves that help to drive the reed. The input impedance of a wind instrument—which should have large amplitude and harmonically related maxima for mechanical reed woodwinds and brasses—is strongly influenced by the barrier at the output end of the instrument. Four “instrument” configurations are considered to illustrate the effects of different barriers. The four configurations consist of a cylindrical tube open at its output end, with a conical bell attached, with a brass bell attached, and with an open tone hole lattice attached. The power reflection coefficient at the output end of the cylindrical tube, the input impedance of the cylindrical tube, a standing wave below the barrier cutoff frequency, and a standing wave above the cutoff frequency are calculated for each of the four configurations to demonstrate the effects of the different barriers.
Clarinet mode-alignment measurement under playing conditions
Authors: Benade A. H.
Published: October 2005

The musical advantage of aligned first- and second-mode air column resonance frequencies for all clarinet low-register fingerings has been clear for 15 years. Practical exploitation requires efficient measurement of the f2/f1 modal frequency ratio and systematic air column correction methods. The alignment error ε = 1719(f2/3f1 − 1) cents. Clarinetists must sometimes tolerate 40 > |ε| > 30¢. They accept |ε| in the range 30– 15¢ and consider |ε| < 10¢ excellent. (ε is not the tuning error of normally played twelfths.) Techniques to find frequencies having Im Zin = 0 have long been available, giving ε with accuracies of ± 3¢, but these ignore player, reed, humidity, and temperature effects. Before elucidation of reed-resonance phenomena, existing “players' experiments” for ε were difficult to teach. Adjustment of embouchure tension can align the reed-resonance frequency .f1 relative to the air column mode-2 frequency f2 such that f1/f2 ≃integer. Only then is a second-register note playable sans register key, thereby precisely defining the air column's upper-end active boundary condition at a playing frequency P2. Momentary interruption of the oscillation by tonguing causes a transition to the more favored low-register note playing at P1. The P2/P1 ratio is insensitive to reed structure and ambient temperature, giving ε under playing conditions within ± 5¢ from day to day, player to player. The method is readily taught and cross checks are available. [Work supported by NSF.]
Violin bridge tuning—A discussion
Authors: Hutchins Carleen M.
Published: October 2005

Some master violin makers are expert at “tuning” a bridge to a particular instrument. Others tend to cut bridges to a given set of dimensions. A demonstration discussion will be presented using a violin with several differently cut bridges, based on hologram studies of Reinicke, to show the effect on violin tone of changing bending stiffnesses at various points.
Piano string-hammer interaction
Authors: Hall Donald E.
Published: October 2005

Only in textbooks does a hammer deliver a delta-function impulse to a string. A real hammer generally remains in contact with the string until one or more reflections from the string ends return to kick it free. The spectrum of the string vibration that finally results depends on the relative mass of hammer and string as well as on the striking point. Some results for the idealized case of a point mass hammer will be presented. The problem of generalizing the theory to lossy, compliant hammers will be discussed.
An analytic description of the interaction between two acoustic transducers that are specified by their Green's functions
Authors: Rudgers Anthony J.
Published: October 2005

Expressions for the self and mutual radiation impedances of two interacting transducers are analytically constructed in terms of the Green's functions of the individual transducers. One applies a symbolic iterative procedure to the expression for the pressure field of the transducers. This is best implemented by the successive application of a particular linear operator to quantities involving the Green's functions and the surface velocities on the active parts of the transducers. The radiation impedances are expressed in the form of symbolic power series in this linear operator. Individual terms of these series have simple physical interpretations. The power (i.e., index) of the operator defines the kind of interaction occurring. Thus, a term with index zero expresses the interaction of a transducer with its own field, as if the other transducer were absent; one with index unity expresses the interaction of a transducer with the field directly radiated to it by the other transducer; one with index two expresses the interaction of a transducer with its own field after this has been diffracted once by the other transducer, and so on. The iterative analytic technique can also be applied to more than two interacting transducers and in problems involving free-space Green's functions.
Radiation from an acoustic array moving at transonic velocities
Authors: Berthelot Yves H. , Busch-Vishniac Ilene J.
Published: October 2005

According to classical acoustic theory, the Doppler shift associated with an acoustic source moving at constant velocity induces the following straining of the time coordinate: t′ = t|1-M cos α|. Here t′ denotes the time coordinate in the fixed frame of reference (receiver), M is the Mach number of the source, and α is the angle between the direction of motion and the direction of observation. At transonic velocities t′ can assume a value of 0, in which case all the acoustic energy is received in an infinitesimal increment of time. This implies a transfer of infinite power so it is not physically realizable. We have used the method of characteristics to find the exact Doppler shift to a transonic source and the corresponding maximum amplitude observable at the receiver. Two cases are considered: a point source and a line source, both moving rectilinearly above a point receiver. [Work supported by the Office of Naval Research ONR.]
Transduction efficiency for sound waves systematically pumped by controlled motion of laser beams across water surfaces
Authors: Hsieh Hsiao-an , Pierce Allan D.
Published: October 2005

Previous analyses of laser-generated sound predict efficiencies of the order of (β/cp)2(ωch/Lch)P/ρ, where ωch each is characteristic frequency of laser intensity modulation, Lch is characteristic length scale of energy deposition region, and P is power output of the laser. Because such efficiencies are typically extremely low, the authors have been considering [J. Acoust. Soc. Am. Suppl. 1 75, S16 (1984)] the possibility of externally controlling the temporal and spatial pattern of heat addition by moving the laser beam such as to systematically pump energy into a traveling acoustic wave. The present paper's analysis demonstrates that doing so can yield efficiencies of the order of (β/cp)2(c2/λch3) E/ρ where λch is a characteristic wavelength of the generated sound and E is the total energy deposited in the water by the laser. The principal distinction from the previous expression is the dependence on laser energy rather than laser power; a lower power laser that operates continuously can be just as efficient a source of underwater sound as a high-power laser. Examples that illustrate this premise include those when the laser is used to generate a periodic array (repetition distance λ) of moving (with sound speed c) slabs of heat desposition. [Work supported by ONR, Code 425 UA.]
The nearfield directivity pattern of a thermoacoustic array
Authors: Berthelot Yves H. , Busch-Vishniac Ilene J.
Published: October 2005

A thermoacoustic array can be generated by modulating the intensity of a laser beam illuminating a liquid. The nearfield directivity pattern of a thermoacoustic array is found by taking the Fourier transform of the impulse response of the opto-acoustic system. A simple expression in integral form has been derived for the directivity of a thermoacoustic array on a pressure release boundary such as an air/water interface. The integral is easily evaluated numerically and it clearly show the presence of side lobes in the nearfield directivity. In the limiting case of farfield radiation the directivity computed numerically reduces to the farfield directivity derived analytically. [Work supported by the Office of Naval Research ONR.]
Model study of the diffraction on an explosive transient by plane barriers
Authors: Raspet Richard , Ezell Jean , Coggeshall Steve
Published: October 2005

The results of a model study of the diffraction of transients from blasting caps over barriers are reported. A prediction technique based on Oberhettinger time domain notation was developed [J. Res. Natl. Bur. Stand. 61, 5 (1957)]. The results of this calculation are compared to the data. Finite wave effects were incorporated into the prediction and were shown to be small for the geometries and charge size employed in the model study. The finite wave effects on diffraction of transient may be important for shorter duration pulses such as N wave from sparks.
Source range information loss in waveguides
Authors: Shang E. C. , Lawson L. M. , Palmer D. R.
Published: October 2005

In a previous paper [E. C. Shang et al., J. Acoust. Soc. Am. Suppl. 1 74, S78 (1983)], the theoretical framework of the passive harmonic source ranging in waveguides based on the mode filtering technique has been proposed. The main purpose of the present paper is to study the range information loss due to the effects of (1) phase fluctuation and (2) the inaccurate description of the environment (waveguide mismatching) by numerical modeling. The phase fluctuation effect is investigated through a two-dimensional Gaussian distribution function. The mismatching effect is investigated by using a numerical normal mode Code INRL, 1980). Source range information loss caused by incorrect description of the sediment type of the bottom and the sound velocity profile in the water column are calculated. Examples for a 100-m water depth shallow water in frequency range of 100–500 Hz are presented. [Work supported by NRC.]
Sensitivity of two high resolution beamforming techniques to the number of line array elements and signal-to-noise ratio
Authors: Meredith Roger W. , Ramsdale Dan J.
Published: October 2005

Two high resolution beamformers, maximum entropy method (MEM) and Wagstaff-Berrou broadband (WB2) [R. A. Wagstaff and J. Berrou, J. Acoust. Soc. Am. 75, 1133–1141 (1984)], were compared with each other and the standard FFT beamformer to determine performance degradation when the number of line array elements and the signal-to-noise ratio (SNR) were decreased. Experimental data from a multi-tonal CW source recorded on an equally spaced horizontal line array were used to investigate the main beam broadening resulting from decreased SNR for SNR values ranging from 30 dB to near zero dB. Additional CW data from an equally spaced vertical line array were used to investigate the main beam broadening which resulted when the number of array elements was decreased successively from 31 to 16, 8, 4, and finally 2. Preliminary results indicate that the main beam broadening due to the decrease in array elements for both MEM and WB2 are similar and that both of these methods offer an order of magnitude decrease in the −3 dB beamwidth with respect to the standard FTT beamformer. [Work supported by Naval Electronic Systems Command, Code 612.]
Directional wind-generated noise and its impact on sensor performance
Authors: Robinson E. R. , Browning D. G.
Published: October 2005

It is well known that characterizing the noise field as isotropic may be an unrealistic assumption, particularly when estimating the performance of narrow beam arrays. In this paper, we investigate the effect of an anisotropic noise field on signal-to-noise ratio (SNR) as a function of range. A theoretical model that simulates the vertical directionality of wind-generated ambient noise in the ocean has been developed and is demonstrated for frequencies between 1 and 24 kHz. Noise received by a Chebyshevweighted planar array is evaluated and displayed for a variety of measurement systems and environmental parameters, including beam elevation angle, array depth, water depth, bottom porosity, sound speed profile, and frequency. Additionally, the model demonstrates the sensitivity of the received noise to multipath energy. Using the noise model results, we then predict SNR versus range for both isotropic and anisotropic noise fields, with higher levels consistently seen in the anisotropic field. A comparison of the noise model predictions at selected frequencies with known data bases shows close agreement.
The effect of improper normalization on the performance of an energy detector
Authors: Struzinski William A. , Lowe Edward D.
Published: October 2005

In a previous study [W. A. Struzinski, J. Acoust. Soc. Am. Suppl. 1 75, S43 (1984)], an analysis was conducted of four noise background normalization schemes. The four schemes were the two-pass mean, the split three-pass mean, the split average exclude average, and the order truncate average normalizers. In the previous study, each normalizer operated on magnitude data, and a subjective analysis was made of spectrograms. In the subject analysis, the four normalizers operate on magnitude squared data, and the output of each normalizer serve as the input to an automated energy detector. The detection probability and the false alarm probability have been computed for various signal SNR's. It is concluded that the split average exclude average and the order truncate average normalizers are more preferred over the other two normalizers in detection systems. [Work supported by NAVSEA.]
Sensitivity of the reverberation spectrum and medium parameters
Authors: Robinson E. R. , Quazi A. H. , Aidala F. E.
Published: October 2005

The assumption of a Gaussian-like spectrum for received reverberation may no longer yield realistic results as ocean acoustic measurement systems increase in complexity. In this paper, we determine the sensitivity of the reverberation spectrum to both system and medium parameters. Volume, surface, and bottom reverberation received by multibeam sensors on nonstationary platforms are generated by use of a theoretical approach that is now implemented in the Generic Sonar Model. To demonstrate this method, we compute expected reverberation for a variety of parameters, including platform speed, waveform, bearing, and range. Results indicate a high sensitivity of spectral characteristics to these parameters, particularly for the off-broadside beams. Additionally, a comparison is made with measured data to ensure model validation. It is anticipated that this model will have significant implications in underwater acoustic modeling.
Perception of the [m]-[n] distinction: Insights from four converging procedures
Authors: Repp Bruno H.
Published: October 2005

Kurowski and Blumstein [J. Acoust. Soc. Am. 76 (1984), in press] recently investigated the joint contribution of nasal murmur and vocalic formant transitions to perception of the [m]-[n] distinction, applying excerpting techniques to utterances from a single speaker. The present experiment extends their study by using four different converging procedures with CV syllables (C = [m,n], V = [i,a,u]) spoken by three male and three female speakers: (1) Progressive truncation from the beginning. (2) Progressive truncation from the end. (3) Presentation of brief excerpts from the vicinity of the nasal release. (4) Replacement of segments corresponding to these brief excerpts with signal-correlated noise. The results indicate, in agreement with Kurowski and Blumstein, that nasal murmur and vocalic transitions both carry significant perceptual information, and that their relationship is an especially potent cue to the [m]-[n] distinction. This relationship appears to be perceived not only at the point of nasal release, where an abrupt spectral change takes place, but also when the murmur and the vocalic portion are separated by as much as 60 ms of intervening noise. [Work supported by NICHD Grant HD-01994.]
Temporal limits on spectro-temporal fusion in speech perception
Authors: Bentin Shlomo , Repp Bruno H.
Published: October 2005

When the distinctive formant transition of a synthetic syllabic is presented to one ear while the remainder (the “base”) is presented to the opposite ear, listeners report hearing the original syllable in the ear receiving the base. We have found that the mere onset (i.e., the first pitch pulse, 10 ms in duration) of an isolated, contralateral third-formant (F3) transition can be sufficient to cue the /da/-/ga/ distinction. We also varied the relative onset times of isolated F3 and base, compared three types of F3 segments (50-ms time-varying, 50-ms constant, 10-ms onset), and compared dichotic with binaural (electronically mixed) presentation. Subjects' tolerance of temporal asynchrony (roughly + 50 ms) was about the same in dichotic and binaural conditions. Time-varying F3 segments were superior to constant ones, especially when they lagged behind the base. Binaural performance exceeded performance, but only when F3 preceded the base, suggesting that upward spread of masking occurred in binaural presentation when F3 coincided with energy in the lower formants. [Work supported by NICHD grant HD-01994.]
The perception of whispered speech
Authors: Sturm Ruth , Jakimik Jola
Published: October 2005

We examined the perception of voiced and voiceless consonants in whispered speech. The target words were minimal pairs that differed in voicing, either word initially (e.g., bill/pill) or word finally (e.g., mob/mop). Some subjects heard a list of these words, either whispered or spoken normally. Other subjects heard the words at the ends of sentences, which were whispered or spoken normally. The sentences were neutral (e.g., She found the bill/pill) or biased toward one member of the minimal pair (e.g., She paid the bill/pill). In a list and in neutral sentences, identification was worse for whispered speech, especially for voiced word-initial consonants. Appropriate bias improved identification most for voiced word-initial consonants; inappropriate bias changed the pattern of identification. The results show the influence of context on the interpretation of ambiguous speech, using an everyday modification of speech.