bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimum array detection in fluctuating ambient noise fields
Authors: Adams S. L. , Nolte L. W. 
Published: October 2005

In practical underwater signal detection problems using an array, the statistics of the ambient noise field vary spatially and temporally. This paper considers the problem of detecting a farfield signal source of known location and waveform which generates a known signal field at an array aperture. The power of the ambient noise field is considered to be a random function of space and time and the Bayes approach is used to derive optimum receiver structures and their performance. For all cases considered, the optimum array processor either requires spatial filtering which is not accomplished by a beam former or requires spatial processing in addition to that provided by a beam former. The loss of detection performance due to uncertainty in the parameters of the ambient noise field is determined for several specific cases.
Subject Classification: 60.20; 25.35.
Influence of rotary inertia and shear deformation on acoustic transmission through a plate
Authors: Stepanishen Peter R. 
Published: October 2005

The reflection and transmission of a harmonic acoustic plane wave from a fluid-loaded plate is investigated using the Timoshenko–Mindlin plate equation. In contrast to the classical plate theory, the effects of rotary inertia and shear deformation are included in the Timoshenko–Mindlin theory. The usual acoustic coincidence frequency and angle based on the classical theory are shown to depart from the present results based on the Timoshenko–Mindlin theory as the frequency–plate thickness product increases. Furthermore, an additional acoustic coincidence frequency and angle are also noted in the present analysis for large frequency-plate thickness products. Several numerical results are presented to illustrate the effects of the incident angle, frequency, plate thickness, and damping on the transmission of an incident acoustic plane wave through a steel plate in water.
Subject Classification: 20.60; 40.24; 20.30.
Excitation of a Helmholtz resonator by a turbulent boundary layer
Authors: Panton Ronald L. , Miller John M. 
Published: October 2005

A turbulent boundary layer on the fuselage of a glider was used to excite a Helmholtz resonator. The resonator orifice was flush with the surface and smaller than the boundary-layer thickness. Resonator frequencies were chosen so they would tune with different portions of the boundary-layer wall pressure spectrum. The resonators were excited at both the Helmholtz frequency and a standing wave frequency. The results show a shift in the Helmholtz frequency when the boundary layer is present. This shift indicates the degree to which the turbulence interacts with the acoustic motion in the orifice and modifies the end correction. Four of the nine resonators tested were ’’strongly’’ excited and radiated considerable acoustic sound. This phenomenon occurs when turbulent eddies about the size of the orifice are convected past the orifice with the proper velocity to impose a frequency that matches a resonant frequency of the resonator. Turbulent eddies which are either smaller or larger than the orifice will not produce strong excitation.
Subject Classification; 28.65, 28.60; 85.32; 20.40.
Energy evaluation of wide-band SOFAR transmission
Authors: Porter Robert P. , Leslie H. D. 
Published: October 2005

Transmitted energy levels for wide-band SOFAR transmission are calculated for arbitrary sound-speed profiles using ray-mode analysis [R. P. Porter, J. Acoust. Soc. Am. 54, 1081–1091 (1973)]. The analysis of the received field has been generalized to include arbitrary normal modes and range-varying, sound-speed profiles. It is shown that computations of wide-band propagation based on ray-mode analysis require an order of magnitude fewer calculations than do calculations by harmonic analysis. A computer code has been developed and used to estimate the wide-band loss for profiles from the Mediterranean and the North Atlantic. Comparisons with continuous tone, normal-mode calculations yield agreement to within 3 dB.
Subject Classification: 30.20, 30.25; 20.20, 20.40.
Sampling statistics for cylindrical modes of higher order
Authors: Jones Kenneth E. , Waterhouse Richard 
Published: October 2005

The distribution functions are considered for the random sampling in space of a three-dimensional acoustic mode. Expressions are obtained for the probability density and cumulative functions for a single mode excited in an ideal elastic fluid contained in a right-circular cylindrical enclosure. In earlier work, axisymmetric modes of lower order were treated; here the work is extended to some modes of higher order, and in addition the rms values of the modal function are sampled, as well as the mean-square vales. The rms modal function ‖J0(⋅) ‖ contains cusps on the abscissa, and these cause the distribution functions to differ from those pertaining to the square of the modal function. In both cases, however, the density functions have a number of poles which increases with the order of the mode. Computed values of the functions are presented, together with values of the variances of the distributions.
Subject Classifications: 45.30; 55.20.
Automatic segmentation of speech into syllabic units
Authors: Mermelstein Paul 
Published: October 2005

As a first step toward automatic phonetic analysis of speech, one desires to segment the signal into syllable-sized units. Experiments were conducted in automatic segmentation techniques for continuous, reading-rate speech to derive such units. A new segmentation algorithm is described that allows assessment of the significance of a loudness minimum to be a potential syllabic boundary from the difference between the convex hull of the loudness function and the loudness function itself. Tested on roughly 400 syllables of continuous text, the algorithm results in 6.9% syllables missed and 2.6% extra syllables relative to a nominal, slow-speech syllable count. It is suggested that inclusion of alternative fluent-form syllabifications for multisyllabic words and the use of phonological rules for predicting syllabic contractions can further improve agreement between predicted and experimental syllable counts.
Subject Classification: 70.40, 70.60.
Effect of delayed channel on the perception of dichotically presented speech and nonspeech sound
Authors: Porter Robert J. 
Published: October 2005

Subjects were asked to identify dichotically competing pairs of CV syllables and two types of acoustically comparable nonspeech sounds. Dichotic signals were presented with onset asynchronies ranging from 0 to 150 msec. Subjects identified lagging signals more accurately and reported them as clearer than the leading signals at asynchronies between 30 and 75 msec. This advantage for the lagging signal was larger, more reliable, and had a different form for the speech sounds than for the nonspeech sounds. Similarities in the pattern of results for speech and nonspeech were interpreted in terms of the forward-, backward-, and simultaneous-masking effects occurring early in the central processing of auditory events. The differences in speech and nonspeech results, on the other hand, were seen as reflecting the particular sensitivity of later stages of speech processing to the masking effects. This sensitivity may be related to the way in which the phonetic message is encoded in the sound stream and the special speech processing occasioned by this encoding.
Subject Classification: 70.30; 65.58; 65.75.
Interaural–intensive differences and dichotic listening
Authors: Speaks Charles , Bissonette Linda J. 
Published: October 2005

Interaural-intensive differences were introduced in a dichotic-listening experiment with CV syllables. Six listeners with a right-ear advantage (REA) in syllable-identification scores were tested. In one condition, speech level in the right ear was attenuated in 8-dB steps from each of four reference intensities for the left ear: 80, 70, 60, and 50 dB SPL. In a second condition, speech level in the left ear was amplified in 8-dB steps from the same four reference intensities for the right ear. The right-ear advantage was canceled by attenuation of signal level in the right ear, but the amount of attenuation required to cancel the REA varied with reference intensity. For the three higher reference intensities, amplification of speech level in the left ear did not overcome the REA. The REA was canceled with amplification of the left-ear signal only for the 50-dB reference.
Subject Classification: 70.30.
Computer-based sound spectrograph system
Authors: Strong William J. , Palmer E. Paul 
Published: October 2005

Sound spectrographs based on digital computers are of interest because of the versatility they offer in generating and displaying sound spectrograms. A particular computer-based sound spectrograph is described in which digitized time waveforms stored on disk memory are spectrally analyzed and the resulting data stored back on disk for later display. Analyses are also performed to obtain the voicing fundamental frequency and the overall-intensity level of the signal which are displayed time registered with the spectrogram. While viewing the spectrographic display, the user is able to tailor the display before making hardcopy. This permits the user to specify a spectral threshold level, the dynamic range represented in the display, spectral contrast, and spectral emphasis.
Subject Classification: 70.62, 70.40; 85.32.
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Authors: Kelly Joseph C. , Nelson Donald R. 
Published: October 2005

Horn sharks were conditioned to pure-tone audio signals in two different laboratory test situations. In the first experiment, conducted in a small, air-speaker-driven enclosure, four sharks were conditioned to cross a barrier to avoid electrical shock. The sharks responded from 25 to 160 Hz, with the lowest pressure threshold at 40 Hz. The second experiment, conducted in a large tank with an underwater speaker, used four different sharks and employed a heart-rate technique in which shock and sound were paired to elicit conditioned bradycardia. These sharks responded over a similar frequency range of 20 to 160 Hz. When tested at two subject-to-transducer distances, their acoustic pressure thresholds increased with distance while their acoustic particle-motion thresholds remained the same. The lowest pressure threshold was at 40 Hz (12 dBμb), and the lowest particle-motion threshold was at 80 Hz, with a displacement of 1.4×10−6 cm and a velocity of 7×10−4 cm/sec (104 μvar).
Subject Classification: 80.50, 80.60; 65.50.
STL–Ionophone: Transducer properties and construction
Authors: Fransson Frans J. , Jansson Erik V. 
Published: October 2005

The STL–Ionophone is a simple electroacoustical transducer well suited to many applications in an acoustic laboratory, even one with modest equipment. Its transducer element consists of a glow discharge in the atmospheric air, which is initiated and maintained by a highly stable dc power supply and a large current-limiting resistor. The discharge emits sound when an ac current is superimposed on the dc current. The STL–Ionophone is a sound emitter of small dimensions, of high acoustical impedance, and has constant source strength (volume velocity) from infra- to ultrasonic frequencies. It can also register sound down to zero frequency as voltage variations. In this report, we describe how the correct discharge is obtained, present basic transducer properties of the discharge, and give practical construction hints together with applications in which the STL–Ionophone has been used. The information presented is sufficient for design and use of the STL–Ionophone.
Subject Classification: 85.40, 85.60, 85.62.
Coarticulatory effects of voiced stops on the reduction of acoustic vowel targets
Authors: Ohde Ralph N. , Sharf Donald J. 
Published: October 2005

Five male subjects recorded three samples of the American English vowels /i/ and /u/ and two lists of CVCV utterances, one in which the vowels /i, u/ and consonants /b, d, g/ were used symmetrically and one in which the vowels /i, u/ were used symmetrically but the consonants /b, d, g/ were used asymmetrically with /h/ always in the other consonant position. In addition, one of the subjects recorded a list of hVC utterances using the same vowels and consonants. Vowel targets were established for each subject on the basis of spectrographic measurements of F2 from the isolated vowels. Vowel reduction was determined by comparing these target values with spectrographic measurements made from steady-state portions of vowels in context. Right-to-left (R to L) effects were determined from utterances in which /b, d, g/ were the second consonants and left-to-right (L to R) effects were determined from utterances in which /b, d, g/ were the initial consonants. The results were as follows: (1) L to R effects of consonants on vowel reduction were considerably greater than R to L effects; (2) R to L effects on vowel reduction in hVC utterances were no greater than those in hVCV utterances; (3) vowel reduction for combined hVCV and CVhV utterances was somewhat greater than for symmetrical CVCV utterances, and (4) all utterances reflected greater influence of /d/ on vowel reduction than other consonants and greater reduction of /u/ than of /i/. The results are discussed in terms of models of speech production and the apparent paradox in the relationship between the greater L to R acoustic effects and the assumed primacy of R to L perception.
Subject Classification: 70.20, 70.30, 70.70.
Sound radiation from a simple source in circular and helical motion
Authors: Chandrashekhara N. 
Published: October 2005

The analysis of sound radiation from a time-varying simple source in uniform circular and helical motion is made. The expressions for the mean-square farfield sound pressure and the overall sound-power output are derived. The retarded time approach is used and illustrates the relative significance of the time rate of pulsations and the acceleration due to rotation of the source.
Subject Classification; 20.15, 20.55; 30.50.
Improved efficiency in the parametric transmitting array
Authors: Merklinger Harold M. 
Published: October 2005

It is shown that the efficiency of the parametric transmitting array may be improved over that obtained where two equal amplitude-frequency components are employed in the primary wave. Through suitable periodic shaping of the envelope of the primary wave, available improvements in the output at the ’’difference’’ frequency of between 2.1 and 6.0 dB are possible in principle. The degree of available improvement depends upon whether the transmitter is peak power or average power limited and whether finite-amplitude attenuation of the primary wave is significant. It is proposed that the on–off modulation of a single-frequency carrier provides a simple, practical method through which near optimum efficiencies may be obtained under most circumstances. A bandwidth greater than the ’’difference’’ frequency is required at the transducer in order to achieve this improvement.
Subject Classification: 25.35; 30.75.
Effect of flow on the acoustic resonances of an open-ended duct
Authors: Ingard Uno , Singhal Vijay K. 
Published: October 2005

The effect of flow on the acoustic resonances of an open-ended, hard-walled duct is analyzed. The flow produces acoustic losses both in the interior of the duct and at the ends. Unless the duct is very long, typically 100 times the diameter, the losses at the ends dominate. At flow Mach numbers in excess of 0.4 the losses are so large that axial duct resonances are almost completely suppressed. The plane-wave Green’s function for the duct with flow is expressed in terms of the (experimentally determined) pressure reflection coefficients at the ends of the duct, and the flow dependence of the complex eigenfrequencies of the duct is obtained. Some observations concerning the noise produced by the flow in the duct are also reported.
Subject Classification: 28.60.
Study of the measurement of transducer directivity with a planar measurement array
Authors: Baker D. D. , Smith D. A. 
Published: October 2005

An experimental study was conducted to investigate directivity measurements made in the farfield of a conventional sonar transducer with a planar array of probe transducers. The principal questions investigated were (1) how closely must measurement probes be spaced for directivity measurements to be of useful accuracy and (2) how does one process and display the data in a useful format. Full-scale experiments were conducted with a probe transducer positionable over a grid of measurement points to simulate a multiprobe array. Measurements were made at probe spacings varying from 0.1 to 0.4 times ψHP, the half-power beamwidth of the sonar transducer. The data were processed by computer and displayed with contour plots, which proved quite easy to use and easy to interpret. The data obtained from the experimental measurements were compared with conventional beam patterns of the transducer; results were encouraging and, in fact, somewhat better than expected, generally. Discrete data taken at 0.1 and 0.2 times ψHP defined all features of the directivity function to within the measurement accuracy of conventional directivity measurements. Data obtained at the spacing equal to 0.4 times ψHP resolved major characteristics of the pattern to within ±2 dB and ±2°. It is believed that the use of more sophisticated interpolation techniques in processing the data prior to contour plotting would improve the accuracy.
Subject Classification: 30.85, 30.82; 85.40.
Wave propagation in a viscoelastic rod with temperature-dependent properties
Authors: Ting Edward C. 
Published: October 2005

In this paper the unidirectional wave propagation in a rod made of viscoelastic material of the Maxwell type is considered. The rod is subjected to nonuniform temperature gradients and its mechanical properties are assumed to be temperature-dependent. A perturbation technique incorporated with the usual Laplace transform method is employed to obtain the analytical solution in series form. The strong temperature-history effect on the attenuation of the wavefront is demonstrated in simple examples for the case where a stress discontinuity due to constant velocity impact propagates along the rod.
Subject Classification: 40.22; 35.50.
Backward recognition masking
Authors: Massaro Dominic W. 
Published: October 2005

Backward recognition masking refers to the interference of a second sound on recognition of another sound presented earlier in time. Previous experiments have demonstrated backward recognition masking in an absolute judgment task. In those experiments, all of the experimental conditions were varied randomly within a test session. In the first experiment reported here, backward-masking functions generated between blocks of trials were compared to those determined within an experimental session. The results showed backward masking using both experimental procedures. The next two experiments evaluate backward-masking effects in a two-interval forced-choice task and a successive-comparison task. Backward masking was observed in both experiments. The final experiment showed that selectively attending to the ear of the test tone presentation does not attenuate the backward-masking effects of a second tone presented to the opposite ear.
Subject Classification: 65.22, 65.58, 65.75.
Acoustic impedance of an annular capillary
Authors: Backus John 
Published: October 2005

The behavior of an acoustic impedance formed by a capillary of annular cross section was investigated. The configuration used in previous work consisted of a cylindrical rod spaced concentrically within a cylindrical tube. Experimentally, this configuration was found to have an impedance magnitude which remained reasonably constant with frequency up to values for which the length of the capillary was comparable to the wavelength. This was checked numerically; computer calculations based on the relevant equations showed that for certain ranges of lengths and annulus thicknesses, the impedance magnitudes are reasonably constant over a useful frequency range. Graphs of impedance magnitudes and phases are displayed for representative values in these ranges.
Subject Classification: 75.40; 85.20; 75.35.
Improved efficiency of an acoustic parametric source
Authors: Eller Anthony I. 
Published: October 2005

The efficiency of a parametric source can be increased through use of a multicomponent primary signal in place of the customary two-component primary. The results indicated in this letter form a special case of a general analysis by Merklinger [J. Acoust. Soc. Am. 58, 784–787 (1975)] and offer independent confirmation of part of his paper.
Subject Classification: 25.35; 60.20.
Wave propagation at unbonded interface between two elastic half-spaces
Authors: Murty G. S. 
Published: October 2005

The question whether a Stoneley mode can exist at an unbonded interface between two elastic half-spaces is examined theoretically. Explicit conditions for its existence are derived when the two half-spaces are incompressible or Poisson solids whose elastic constants and material densities are approximately equal.
Subject Classification: 35.26; 20.15.
Vocal frequency and vertical larynx positioning by singers and nonsingers
Authors: Shipp Thomas , Izdebski Krzysztof 
Published: October 2005

Measurements were taken from lateral still photographs of the vertical larynx position of four professional singers and four nonsingers. Subjects sustained phonation at seven discrete intervals between 90 and 350 Hz. Nonsingers generally positioned their larynx upward with increased voice frequency and tended to maintain a level at or above the larynx physiologic rest position throughout their vocal range. Singers usually maintained a laryngeal position below the physiologic rest level throughout their vocal frequency range.
Subject Classification: 70.20; 75.70.
Difference frequency pressure within the interaction region of a parametric array
Authors: Rolleigh Richard L. 
Published: October 2005

A theoretical model that predicts difference frequency pressure within the interaction region of a parametric array is presented. Linear and nonlinear attenuation are neglected, and it is assumed that the primary signals are spherically spreading throughout the interaction region. It is shown that with these assumptions the three-dimensional scattering integral can be reduced to a single integral if the primary pressure fields are axially symmetric. Analyses of the error introduced by assuming the primary fields are spherically spreading and by neglecting linear attenuation are presented. Theoretical results compare favorably to p’revious experimental results. The results indicate that diffraction effects are more important than attenuation when the observation point is within the interaction region and when primary signal level reduction is due more to spherical spreading than attenuation.
Subject Classification: 25.35; 20.30, 20.15.
Sound attenuation by commonly available membranes used for moisture protection of microphones
Authors: Kaye David H. 
Published: October 2005

Rubber condoms have been used to protect microphones used outdoors, but the technical literature includes no evaluation of the effects of this application. We have measured attenuation versus frequency for combinations of foam windscreen and condom and find that the attenuation can be both significant and unpredictable, variable between brands and between methods of application. Because a microphone cannot be acoustically calibrated with currently available portable calibrators after it has been sheathed, we believe that using a condom-protected microphone is likely to result in erroneous data. Another commonly available membrane, the plastic sandwich bag, produces similar erratic results.
Subject Classification; 50.85; 85.24, 85.62.