bluuebunny/crossref_metadata_2025 huggingface dataset:
Intensity fluctuations. Part I: Theory
Authors: Uscinski B. J. , Macaskill C. , Ewart T. E.
Published: October 2005

This paper deals with the problem of the intensity fluctuations arising in a wave when it propagates through a medium that is randomly inhomogeneous in space and time. It is assumed that multiple scattering can occur and that the intensity fluctuations can become large. The parabolic moment equation for the fourth moment of the wave field is solved for a monochromatic point source immersed in the medium. Approximate expressions are obtained for the space–time spectrum of intensity fluctuations at any distance in the medium. The solution of the fourth moment equation is compared with results of the Rytov method of smooth perturbations, and the limitations of the latter are discussed.
Distant storm noise versus local wind noise at 165 Hz in the northeastern Pacific Ocean
Authors: Wilson James H.
Published: October 2005

An example of distant storm noise is presented at 165 Hz at a measurement site located away from normal Pacific storm paths of major east–west Pacific shipping lanes. The local wind speed and local shipping density are low enough at this site to allow distant storm noise to be dominant during the passage of very large Pacific storms. Sites with these characteristics have potential significance because very low noise periods occur between winter storms. A simplified storm noise model is developed that allows a separate estimate of distant storm noise and local wind noise through the use of a simple hand calculator. For typical calm and stormy weather conditions, the model estimates of ambient noise agree very well with nominal ambient noise measurements during calm and stormy weather conditions at this site at 165 Hz. The model results imply that distant storm noise is dominant over local wind noise at this site and frequency during storm periods, and this result is supported by ambient noise measurements taken during two storm periods. Since ambient noise is highly site- and frequency-dependent, no generalizations can be made to other sites or frequencies. However, the model can easily be applied to other sites and frequencies and it is reasonably easy to estimate the relative importance of distant storm noise, local wind noise, and shipping noise.
Line-of-sight propagation through atmospheric turbulence near the ground
Authors: Daigle G. A. , Piercy J. E. , Embleton T. F. W.
Published: October 2005

Line-of-sight measurements of the log-amplitude and phase fluctuations of pure tones between 250 and 4000 Hz propagated over distances between 2 and 300 m in the turbulent atmosphere close to the ground are compared quantitatively with simple theory using simultaneously measured meteorological variables. The theory is based on the assumption of homogeneous and isotropic turbulence and approximates the availability of eddy sizes in the source region of turbulence by a Gaussian spectrum. In particular the transverse or mutual coherence function (the coherence in a plane perpendicular to the direction of propagation) and the coherence in the direction of propagation which we call the longitudinal coherence, are also calculated and compared with the measurements. When the measured mean square phase fluctuations are compared with the theory using the meteorological measurements, good agreement is obtained. However the measured mean square log-amplitude fluctuations are in general substantially smaller than predicted and, in addition, show clear evidence of saturation. The distance to saturation is shown to correspond to the longitudinal coherence length. Because of this behavior of the amplitude fluctuations both the transverse and longitudinal coherences are essentially a function of the phase variance only.
PEST reduces bias in forced choice psychophysics
Authors: Taylor M. M. , Forbes S. M. , Creelman C. Douglas
Published: October 2005

Observers performed several different detection tasks using both the PEST adaptive psychophysical procedure and a fixed-level (method of constant stimuli) psychophysical procedure. In two experiments, PEST runs targeted at P(C)=0.80 were immediately followed by fixed-level detection runs presented at the difficulty level resulting from the PEST run. The fixed-level runs yielded P(C) about 0.75. During the fixed-level runs, the probability of a correct response was greater when the preceding response was correct than when it was wrong. Observers, even highly trained ones, perform in a nonstationary manner. The sequential dependency data can be used to determine a lower bound for the observer’s ‘‘true’’ capability when performing optimally; this lower bound is close to the PEST target, and well above the forced choice P(C). The observer’s ‘‘true’’ capability is the measure used by most theories of detection performance. A further experiment compared psychometric functions obtained from a set of PEST runs using different targets with those obtained from blocks of fixed-level trials at different levels. PEST results were more stable across observers, performance at all but the highest signal levels was better with PEST, and the PEST psychometric functions had shallower slopes. We hypothesize that PEST permits the observer to keep track of what he is trying to detect, whereas in the fixed-level method performance is disrupted by memory failure. Some recently suggested ‘‘more virulent’’ versions of PEST may be subject to biases similar to those of the fixed-level procedures. Experimenters are advised to use the original version of PEST rather than fixed-level psychophysics or ‘‘improved’’ versions of PEST when accuracy as well as speed of psychophysical measurement is important.
Localization of sound in rooms
Authors: Hartmann W. M.
Published: October 2005

This paper is concerned with the localization of sources of sounds by human listeners in rooms. It presents the results of source-identification experiments designed to determine whether the ability to localize sound in a room depends upon the room acoustics, and how it depends upon the nature of the source signal. The experiments indicate that the localization of impulsive sounds, with strong attack transients, is independent of the room reverberation time, though it may depend upon the room geometry. For sounds without attack transients, localization improves monotonically with the spectral density of the source. Localization of continuous broadband noise does depend upon room reverberation time, and we propose the concept of direct signal to reverberant noise ratio to study that effect. Source identification experiments reveal certain localization biases, invisible to minimum-audible-angle experiments, and of uncertain origin. Appendices to this paper develop the statistics of the source-identification paradigm and show how they relate to the minimum audible angle.
Characters of the air flow inferred from detailed spectral analysis of acoustic sounder echoes
Authors: Fiocco Giorgio , Mastrantonio Giangiuseppe
Published: October 2005

Detailed spectral analysis of sodar echoes can be utilized to yield information on the structure and vorticity of the wind field within the scattering volume. The analysis is applied to a case of unusually intense turbulence and wind shear recorded at the Capanna Margherita, Monte Rosa, Italy (4559 m.a.s.l.).
Transient waves in an elastic plate: Theory and experiment compared
Authors: Proctor T. M. , Breckenridge F. R. , Pao Y. H.
Published: October 2005

Waveforms calculated by generalized ray theory for a thick plate driven by a step-function point force are compared with experimental waveforms obtained on a glass plate using an improved piezoelectric displacement-sensing transducer.
Frequency information in the auditory brainstem response evoked by tonal transients
Authors: Helfer Thomas M. , Gerken George M.
Published: October 2005

The auditory brainstem response (ABR) is a composite of potentials generated by neural activity stemming from several regions of the cochlea. A derivation technique is described for reducing the contributions to the ABR that arise from frequencies outside of the frequency band of interest. The technique treats averaged waveforms in an algebraic manner and uses a method of successive substitutions to obtain a derived waveform. The recorded and derived ABR waveforms were analyzed with respect to changes of latency and morphology. The behavior of the waveform components of the derived regional responses was in accord with the data of other studies in which narrow-band responses were derived from waveforms produced by high-pass masking of click stimuli. Frequency information was thus extracted from the ABR without the simultaneous presence of other stimuli as in masking-based derivations. The method of successive substitutions used with brief transient stimuli of different frequencies appears to yield derived ABRs that reflect activity from different cochlear regions.
A stochastic analysis for cross-spectral density method of measuring acoustic intensity
Authors: Mathur Gopal P.
Published: October 2005

A stochastic analysis for the cross-spectral density method of measuring acoustic intensity is presented. The analysis is based on the theory of linear mean-square estimation as applied to stochastic processes and its generality is preserved through the use of some concepts from the theory of multidimensional stochastic processes. A general theoretical expression, in terms of spatial-correlation and cross-spectral density functions between two closely spaced microphones, is obtained for estimating acoustic intensity. The stochastic analysis presented in this paper highlights the effects of incorporating finite difference approximations. It is also shown that how the present cross-spectral density formula can be reduced to an exact expression for the specific case of plane-wave sound field.
Normal mode filtering in shallow water
Authors: Lo En-Cen , Zhou Ji-Xun , Shang Er-Chang
Published: October 2005

In the shallow water of the Yellow Sea, filtering of mode 1 and mode 2, by employing a vertical array of nine hydrophones, has been realized in the frequency range of 250–800 Hz with a near isovelocity condition. Eigenfunctions of the mode were calculated by two parameters (P, Q) to describe the characteristics of bottom reflection approximately at small grazing angles. The advantage of treating the bottom in terms of P and Q rather than using the familiar sound speed, density, and attenuation coefficient is that the bottom reflection loss due to the effect of bottom roughness can be incorporated. Results of mode filtering were quite favorable. Group delay measurement of mode 1 and mode 2 agrees well with theoretical values calculated by a fitting value of the bottom reflection phase shift parameter P. The parameter Q of the bottom reflection loss can be extracted from the amplitude ratio of mode 1 and mode 2. The extracted values of Q were near those of Q obtained by other approaches.
Rapid solutions to the transient response of piezoelectric elements by z-transform techniques
Authors: Challis Richard E. , Harrison John A.
Published: October 2005

Calculation of the transient response of piezoelectric elements by analytical means is only possible for a small range of exciting functions for which simple Laplace transforms exist. Calculation tends to be tedious due to the large number of terms which must be evaluated. A method is presented by which the Laplace transformed three-port model of a piezoelectric element is approximated by a discrete time system by application of the z-transform. A recurrent time domain solution is developed and this is applied in the manner of a digital filter to a variety of exciting functions. The method has the advantage that the response to any real input can be evaluated and it is thus of considerable use in the testing of piezoelectric elements or the measurement of their physical properties in transient tests. Experimental results are presented which show that the technique is reliable and accurate.
Integration of spectral and temporal cues in discrimination of nonspeech sounds: A psychoacoustic analysis
Authors: Espinoza-Varas Blas
Published: October 2005

This study presents a psychoacoustic analysis of the integration of spectral and temporal cues in the discrimination of simple nonspeech sounds. The experimental task was a same–different discrimination between a standard and a comparison pair of tones. Each pair consists of two 80-ms, 1500-Hz tone bursts separated by a 60-ms interval. The just-discriminable (d′=2.0) increment in duration Δt, of one of the bursts was measured as a function of increments in the frequency Δf, of the other burst. A trade off between the values of Δt and Δf required to perform at d′=2.0 was observed, which suggests that listeners integrate the evidence from the two dimensions. Integration occurred with both sub- and supra-threshold values of Δt or Δf, regardless of the order in which the cues were presented. The performance associated to the integration of cues was found to be determined by the discriminability of Δt plus that of Δf, and thus, it is within the psychophysical limits of auditory processing. To a first approximation the results agreed with the prediction of orthogonal vector summation of evidence stemming from signal detection theory. It is proposed that the ability to integrate spectral and temporal cues is in the repertoire of auditory processing capabilities. This integration does not appear to depend on perceiving sounds as members of phonetic classes.
Geometrical theory of diffraction by an open rectangular box
Authors: Saha Pranab , Pierce Allan D.
Published: October 2005

Predictions based on the geometrical theory of diffraction for sound radiation from a source within an open rigid rectangular box are compared with a set of experimental and numerical results obtained by Furue, Terai, and Matsu’ura (9th International Congress of Acoustics, Madrid, Spain, July 1977). The comparison with the experimental results shows a substantial verification of the theory.
The acoustic radiation force on a heated (or cooled) rigid sphere—Theory
Authors: Lee Chun P. , Wang Taylor G.
Published: October 2005

A finite amplitude sound wave can exert a radiation force on an object due to second-order effect of the wave field [L. V. King, Proc. R. Soc. London, Ser. A 147, 212–240 (1934)]. In this work we study the radiation force on a rigid small sphere (i.e., in the long wavelength limit), which has a temperature different from that of the environment. This investigation assumes no thermally induced convection and is relevant to material processing in the absence of gravity. Both isotropic and nonisotropic temperature profiles are considered. In this calculation the acoustic effect and heat transfer process are essentially decoupled because of the long wavelength limit. The heat transfer information required for determining the force is contained in the parameters which are integrals over the temperature distribution.
Fundamental frequency as an acoustic correlate of stop consonant voicing
Authors: Ohde Ralph N.
Published: October 2005

Fundamental frequency (F0) and voice onset time (VOT) were measured in utterances containing voiceless aspirated /ph,th,kh/, voiceless unaspirated /sp,st,sk/, and voiced /b,d,g/ stop consonants. Although VOT was very similar for voiceless unaspirated and voiced stops, F0 contours were nearly identical for voiceless unaspirated and voiceless aspirated stops, and both types of voiceless stops were associated with significantly higher F0 values than were voiced stops. The F0 contours in all contexts were generally falling; the data do not support a simple rise–fall dichotomy in F0 at voicing onset as an invariant acoustic correlate of the voicing feature. The variations in F0 as a function of voicing appear to be best accounted for by vocal cord tension rather than aerodynamic influences. Moreover, the results are consistent with physiological data showing that the position of the hyoid bone and the height of the larynx influence the absolute value of F0.
Matrix viscosity and cavity-size distribution effects on the dynamic effective properties of perforated elastomers
Authors: Gaunaurd G. C. , Barlow J.
Published: October 2005

The study presented here introduces a novel methodology to predict the (frequency-dependent) effective material parameters characterizing the dynamic behavior of viscoelastic substances containing many randomly located air-filled perforations. These composite materials have uses as underwater sound absorbers. The methodology described here is an extension of our earlier work which pertains to the case of gas-filled perforations in nonabsorbing matrices. [G. Gaunaurd and H. Überall, J. Acoust. Soc. Am. 71, 282–295 (1982)]. That prior work was extended here to the case of absorbing matrices containing ensembles of cavities of various sizes following several arbitrary size-distribution functions. The method accounts for the effect of resonances, for arbitrary levels of viscosity, for arbitrary cavity-size distributions, and it is fundamental insofar as it generates direct predictions accounting for all these effects starting straight from the basic principles of Continuum Mechanics. Computer codes to implement the model predictions were generated, and a large number of pertinent plots of the frequency dependence (at fixed concentrations) or of the concentration dependence (at fixed frequencies) of the various effective moduli and other material descriptors have been computed and displayed in many graphs. Under various conditions the present results reduce to many of the earlier results available in the literature which serve as checkpoints. The various plots generated here pertain to various chosen cavity-size distribution functions and to various selected levels of (dilatational and shear) absorption in the matrix. The generation and display of graphs such as these permit the present analysis of these matrix-viscosity and size-distribution effects mentioned in the title.
Sound-speed profile sensitivity of deep-ocean multipath receptions
Authors: Bilazarian P. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

The sensitivity of oceanic sound transmissions to the choice of a sound-speed profile is analyzed using ray theory. The profile may be any one from a collection of depth-dependent, single-minimum profiles which can be used to model a deep-ocean sound channel. Several configurations are considered with fixed source and receiver, separated by less than about 50 km, so that different types of ray propagation can occur. Given a specified profile, procedures are prescribed for constructing a simpler profile, for which all important acoustic quantities are either identical or negligibly different. The construction methods have physical interpretations and identify the critical aspects of profile data which influence transmissions. The ray geometries associated with the two profiles are shown to be very close. Useful formulas are presented which demonstrate that per-ray phases and amplitudes corresponding to the simpler profile approximate accurately those of the specified profile. The total-field phase and amplitude differences associated with the two profiles are discussed briefly. Thus, when our procedure is applied, propagation results are not sensitive to the type of profile selected.
Acoustic studies of broadband scattering from a model rough surface
Authors: Thorne Peter D. , Pace Nicholas G.
Published: October 2005

Experimental measurements of the normal incidence underwater acoustic backscatter from a model rough surface having Gaussian statistics with a rms height 0.22 cm and a correlation length 1.9 cm are presented. Scattering measurements were obtained over the frequency range 20–1200 kHz for a variety of transmitter and receiver distances from the model surface. A novel feature of the experiment was the use of a parametric array as the wideband, highly directional acoustic source. An important aspect of the study is the use of a Fresnel phase approximation in the development of the theoretical expressions; this approach allows an understanding of the range dependence of the scattering coefficients. Theoretical and experimental values of the normal incidence scattering coefficients show good agreement over the range of frequencies and transmitter/receiver distances employed.
Arctic Ocean background noise caused by ridging of sea ice
Authors: Pritchard Robert S.
Published: October 2005

A new method is presented to explain how noise is generated under pack ice by ridging of the pack ice. The energy dissipated during the ridging process is assumed to be the proper measure of the noise source level. Noise source levels generated by ridging are simulated. Noise intensity at a specific site is calculated by summing signals from all these sources after accounting for propagation losses. Calculations are made to compare this simulated noise with observations for an experiment conducted during the winter of 1975–76 in the Beaufort Sea. During a 120-day period, 46% of the intensity of the noise signal is explained using this process, and over several 20-day periods, in excess of 64% is explained. In addition to explaining a significant amount of energy and ambient noise, the model is attractive on physical grounds and properly explains lack of noise when winds are high but ice is strong enough to resist ridging.
The vibrational response of the rectangular parallelepiped with completely stress-free boundaries
Authors: Hill Eric v. K.
Published: October 2005

Presented here are exact normal mode solutions for the free and forced vibration of the rectangular parallelepiped (block) with completely stress-free boundaries. Such solutions are meaningful in the field of quantitative nondestructive evaluation where the object is to deduce flaw growth mechanisms from perceived transducer outputs. In order to do this, it is necessary to know the frequency response of the specimen, the transducer, and the specimen–transducer interface, since each of these elements distorts the flaw growth signal. This presentation quantitatively describes the specimen response for the stress-free rectangular parallelepiped with both impulsive and step function inputs, two common forcing functions used to model acoustic emission source mechanisms.
Elements of a geoacoustic model of the upper crust
Authors: Diachok Orest I. , Dicus Ronald L. , Wales Stephen C.
Published: October 2005

Elements of a geoacoustic model of the geologically young (< 10 million years) upper crust, the top few hundred meters of the basalt subbottom, are described. The model is based on analysis of low-frequency reflectivity versus angle data at a 1 million-year-old sediment-free site, as well as limited Deep Sea Drilling Project downhole logging results, and extrapolated seismic refraction measurements. The upper crust at this site, which is in close proximity to the crest of the East Pacific Rise, may be characterized by low interfacial velocities (Vp∼2800 m/s and Vs∼800 m/s), large gradients (3–5 s−1), and substantial rms roughness (∼5 m). The low-inferred shear speed implies no shear critical angle. Hence, low-frequency energy incident on the bottom at small grazing angles is in large part transmitted into the rock, refracted by the gradient, and reradiated into the water. Scattering loss occurs at both the initial incidence and the interaction of the refracted energy at the boundary. Low interfacial shear speeds lead to large grazing angles at the boundary for the transmitted shear waves, large wavenumbers and, hence, large boundary-scattering losses; small changes in interfacial shear speed produce large changes in subsurface boundary-scattering loss, and hence in the reflection coefficient. A summary of logging and extrapolated seismic refraction measurements in the young crust, below 10 million years, suggests that the range of interfacial shear speeds is between about 800 and 2400 m/s. In older crust, the range of shear speeds is projected to be significantly different. Ramifications of the site dependence of upper crustal properties, particularly shear speed, on sound propagation are discussed.
Reflection of impulses as a method of determining acoustic impedance
Authors: Cramond A. J. , Don C. G.
Published: October 2005

An impulse technique has been developed which allows investigation of the reflection of acoustic transients at different angles from an impedance boundary. From measurements of the direct and reflected impulses, the complex surface impedance has been calculated from the ratio of the corresponding Fourier components. The surfaces were modeled as a locally reacting boundary between homogeneous media; this representation was found to be adequate for grassland and a carpet layer but unsatisfactory for a thick fiberglass layer. There was no need to include a ground wave term when reconstituting pulse shapes at different angles over grass or carpet for the range of frequencies and angles investigated in this paper.
A search for central lateral inhibition
Authors: Hartmann W. M.
Published: October 2005

A central spectrum explanation of the existence of the binaural edge pitch [Klein and Hartmann, J. Acoust. Soc. Am. 70, 51–61 (1981)] appears to require central lateral inhibition in the human auditory system. We have looked for this effect in central masking experiments. Using the binaural-edge noise, which creates the binaural edge pitch, as a masker (in standard notation: No below and Nπ above a phase boundary frequency), we measured pulsation thresholds for sine tones in two frequency ranges where the binaural edge pitch exists. We also obtained reference data, using the same pulsation threshold technique, for standard binaural conditions NoSo, NoSπ, NπSo, and NπSπ. These data revealed masking level differences. Theoretically the difference between the binaural-edge thresholds and the reference data should show the peak and valley signature of lateral inhibition. No such structure was found. We suggest that this negative result does not exclude the possibility of central lateral inhibition, but that the time course of central lateral inhibition makes the pulsation threshold technique an inappropriate means for observing the effect.
Absolute pitch and pure tone identification
Authors: Balzano Gerald J.
Published: October 2005

In a partial replication of an experiment reported in this Journal [Lockhead and Byrd, J. Acoust. Soc. Am. 70, 387–389 (1981)] possessors of absolute pitch were tested for pitch identification of sine tone stimuli. Performance was far from pefect, but considerably better than the results previously reported. Deviations from perfect identification were both systematic and more frequency-specific than the original study. Some suggested reasons for the discrepant findings and some general remarks about absolute pitch are offered.
Labial coordination in children: Preliminary considerations
Authors: Watkin Kenneth L. , Fromm Davida
Published: October 2005

The development of the coordination of the upper lip and lower lip was investigated in children ages four, seven, and ten. Strain gauge transduction techniques were employed to monitor lip movement during the production of selected disyllables. Significant changes in lip coordination were observed between the ages of seven and ten. Results are discussed in light of current understanding of neuromuscular maturation.
Low-frequency sound propagation in the South Fiji Basin
Authors: Denham R. N. , Bannister R. W. , Guthrie K. M. , Browning D. G.
Published: October 2005

In March 1976, a joint experiment of the Naval Underwater Systems Center, New London, and the New Zealand Defence Scientific Establishment was carried out to investigate the characteristics of low-frequency (10–400 Hz) underwater sound propagation in the South Fiji Basin north of New Zealand using explosive sound sources. The source depth was 18 m and as a result propagation nearly everywhere within the basin was dominated by bottom-reflected modes. There were 5-dB level enhancements associated with the bathymetric features forming the southern, western, and eastern boundaries of the basin and 15–20-dB enhancements associated with the slope up to the Fiji Plateau to the north. The propagation loss across the abyssal plains is predicted well, while the level enhancements associated with all the features bounding the basin and the typically 15-dB shadowing losses associated with the ridges east and west of the basin can be approximately predicted with a model (ASTRAL) which allows for horizontal changes in the environment. However, it appears that more sophisticated models may be required to accurately predict the enhancement and shadowing.
Sensorineural hearing loss and the discrimination of vowel-like stimuli
Authors: Turner Christopher W. , Van Tasell Dianne J.
Published: October 2005

It has been hypothesized that the wider-than-normal auditory bandwidths attributed to sensorineural hearing loss lead to a reduced ability to discriminate spectral characteristics in speech signals. In order to investigate this possibility, the minimum detectable depth of a spectral ‘‘notch’’ between the second (F2) and third (F3) formants of a synthetic vowel-like stimulus was determined for normal and hearing-impaired subjects. The minimum detectable notch for all subjects was surprisingly small; values obtained were much smaller than those found in actual vowels. An analysis of the stimuli based upon intensity discrimination within a single critical band predicted only small differences in performance on this task for rather large differences in the size of the auditory bandwidth. These results suggest that impairments of auditory frequency resolution in sensorineural hearing loss may not be critical in the perception of steady-state vowels.
Parameterization of the glottal area, glottal flow, and vocal fold contact area
Authors: Titze Ingo R.
Published: October 2005

A new set of parameters is described for analysis and synthesis of glottal area, vocal fold contact area, and glottal volume flow. Parameters are all nondimensionalized and consist of an abduction quotient, a shape quotient, a phase quotient, and a load quotient in addition to fundamental frequency and vibrational amplitude. The parameters show promise in interpretation of electroglottographic, photoglottographic, and inverse filtered volume velocity waveforms in terms of the glottal configuration. Some comparisons between modeled and measured glottographic waveforms are made.
On duration and smoothing rules in a demisyllable-based isolated-word recognition system
Authors: Kahn Daniel , Rabiner L. R. , Rosenberg A. E.
Published: October 2005

In a recently proposed approach to isolated-word recognition, word reference templates are constructed from a universal set of demisyllable units by concatenating the appropriate demisyllables for each vocabulary item. A dynamic time warping (DTW) algorithm is used to align test and reference patterns optimally. Nevertheless some sort of syllable duration preadjustment is necessary because of the large potential difference in duration between isolated and in-context syllables. We have found that a simple rule that reduces the length of rhyme (final) demisyllables in nonword-final stressed syllables to approximately half their isolated-syllable duration provides recognition accuracy as high as that attained through use of complex, highly context-sensitive rules. In addition to its practical application, this result can be regarded as a further demonstration of the power of DTW. We have also investigated the requirements for parameter smoothing at demisyllable boundaries. We find that an optimal window duration for smoothing is about 60–90 ms, but that failure to smooth reduces recognition accuracy only about 2% in an 1109 word test set; that linear and parabolic smoothing are equally effective; and that it does not appear that recognition accuracy can be improved by smoothing in certain phonetic contexts only. Taken together, these results can be viewed as confirming the suitability of the demisyllable as the basic unit in recognition systems.
Ultrasonic absorption by solvent–solute interactions and proton transfer in aqueous solutions of peptides and small proteins
Authors: Strom-Jensen Philip R. , Dunn Floyd
Published: October 2005

Ultrasonic absorption values in aqueous solutions of myoglobin, apomyoglobin, α-lactalbumin, bacitracin, and the C- and N-terminal CNBr cleavage fragments of myoglobin were determined by the cylindrical resonator technique at temperatures of 4 °C and 20 °C in the frequency range 0.5–7 MHz. A proposed mechanism of absorption in solutions of proteins and peptides is perturbation by the ultrasound of the equilibrium between protein bound and free water, producing a distribution of relaxation processes occurring within the frequency range of the investigation. The hypothesis is supported by the dependence of the ultrasonic absorption on solute surface area and molecular weight. Another mechanism of absorption is that due to proton transfer which occurs noticeably in the presence of phosphate ions. Those proteins (myoglobin and α-lactalbumin) with significant globular structure appear to undergo additional relaxation processes at frequencies above 7 MHz.
Response of an edge-supported circular membrane electret earphone. Part II—Experimental results
Authors: Busch-Vishniac Ilene J.
Published: October 2005

This paper presents experimental measurements of the static and dynamic behavior of an edge-supported circular membrane electret earphone. It is shown that the measured value of static capacitance and sound pressure level generated in a cavity agree well with theoretical predictions. The experimental results dramatize the nonlinear dependence of the earphone sensitivity on many of the transducer parameters. The effects of fluid loading of the foil electret and damping are considered. It is shown that the air surrounding the foil electret can significantly increase its apparent mass, and that damping effects may be ignored below the system fundamental resonance.
Nearfield diffraction patterns at a sphere or cylinder
Authors: Waterhouse R. V.
Published: October 2005

A steady train of plane waves impinges normally on a right circular cylinder of infinite extent. The nearfield diffraction patterns for the normalized rms pressure were computed for values of ka from 1.5 to 6, where k is the wavenumber and a is the radius of the cylinder. Charts are given, showing the contours of rms pressure for ka=1.5, 2, 3, 4, 5, and 6, for each of two boundary conditions, pressure reflecting and pressure release. Each chart shows the contour pattern out to a distance of ten radii. The computed expressions are infinite series containing Bessel functions and their gradients. In some cases 75 terms in the series must be evaluated to get convergence to within 1%. The charts show that there are substantial areas where the pressure differs from the undisturbed value by 6 dB or more. Similar charts are given for the diffraction patterns at a sphere.
On the acoustics of a coupled space
Authors: Thompson Charles
Published: October 2005

An examination of acoustic wave propagation in a coupled space is presented. The analysis presented is limited to the first two longitudinal modes of the cavity. It is shown that the spacial behavior of the modes of vibration in the cavity is affected by the coupling discontinuity. The degree with which the discontinuity influences the pressure variation is parametrized by a single small parameter ε, where ε is the ratio of the typical cavity height, H0 to the cavity length L0. An approximate solution for the pressure in the space is obtained using the method of matched asymptotic expansions. Experimental results are also presented as verification of the theoretical results.
Point-source representation for laser-generated ultrasound
Authors: Rose L. R. F.
Published: October 2005

The stress-free thermal strain corresponding to the temperature rise induced in a target by an incident laser pulse constitutes a volume source of ultrasound. In the present work, the appropriate point-source representation is derived by starting from a general representation theorem for volume sources. A formal solution for the double (Hankel–Laplace) transform of the displacement potentials is obtained for axially symmetric configurations, with the point-source lying within or on the surface of a half-space or a plate. The Cagniard-de Hoop technique is used to invert these double transforms. For the source on the surface of a half-space, detailed results are presented for the wave-front expansions, the displacement along the axis of symmetry and on the surface, the directivity pattern, and the partition of energy between longitudinal, transverse, and surface waves. For the source within or on the surface of a plate, only the epicentral displacement is considered in detail.
Wave-front dislocations in the soundfield of a pulsed circular piston radiator
Authors: Wright Francis J. , Berry Michael V.
Published: October 2005

Wave-front dislocations are lines in space along which wave fronts end, named by analogy with dislocations in imperfect crystals. Continuous waves and quasimonochromatic pulses (of continuous waves with slowly varying envelopes) are conveniently represented by complex-valued wavefunctions, the zeros of which correspond to wave-front dislocations. Pulse dislocations move through the wavefield, and may interact, as the pulse propagates. As examples of realistic model wavefields, the soundfields of a rigid circular piston radiator vibrating in a fixed rigid baffle plane, driven both by a sinusoidal source producing continuous waves and by this source modulated by a Gaussian envelope, are computed exactly and displayed. The birth of dislocations in the nearfield and their propagation with the pulse into the farfield are observed and discussed, and birth and death events in the nearfield are displayed in detail. The behavior of quasimonochromatic pulses and their dislocations may be understood in terms of the carrier wavefield, both qualitatively and, via a perturbation theory, quantitatively.
Using eigenvalue analysis to identify interference in ambient sea noise vertical directionality measurements
Authors: Kewley D. J.
Published: October 2005

Ambient noise vertical directionality measurements at low frequencies have shown that noise arrives from long distances at near horizontal angles, from moderate distances at larger angles, and from local sources at high angles. Therefore levels of noise from different sources can be measured by examining vertical linear array beam powers at the appropriate angles. However, when measurements are made, it is important to be able to distinguish between acoustic signals, ambient noise, and data contamination. Some experimental results are examined, using conventional and adaptive beamforming and eigenvalue–eigenvector decomposition, and used to establish criteria useful in deciding whether the measurements are ambient noise or otherwise.
Wave propagation in an infinite long bar of arbitrary cross section and with a circular cylindrical cavity
Authors: Nagaya Kosuke , Watanabe Tatsuya
Published: October 2005

This paper presents a method for solving wave propagation problems of an infinite bar of arbitrary cross section with a circular cylindrical cavity. In the analysis the exact solution of the wave equations based on the three-dimensional theory of elasticity which satisfies the boundary conditions of the inner circular cylindrical cavity has been utilized. The boundary conditions of the outer arbitrarily shaped surface of the bar are satisfied by use of the Fourier expansion collocation method. The analysis derives the frequency equation for determining the phase velocities of the bar of arbitrary cross section with the cavity. As an example numerical calculations have been carried out for an elliptical cross-section bar with a circular cylindrical cavity.
A different look at the anechoic wedge
Authors: Warnaka Glenn E.
Published: October 2005

Anechoic wedges are conventionally installed with the tapered point of the wedge pointing toward the test space and with the flat base of the wedge either against a rigid wall or separated from the wall by an air gap. A comparative investigation has been carried out in which the wedges were first conventionally oriented and then turned 180° so that the points of the wedges faced the wall. These comparative tests were performed in reverberation rooms both here and in Europe and also in two different impedance tubes. The results are extremely interesting. They tend to indicate that a ‘‘reversed’’ anechoic wedge can give a lower cutoff frequency than when conventionally oriented. Some possible explanations are offered for the measured performance.
Under ice measurements of the noise produced by a helicopter and a tracked vehicle
Authors: de Heering Philippe , White Bryan F.
Published: October 2005

Brief samples of the noise generated by the Bombardier SV-301-D tracked vehicle and a Bell 206 helicopter standing on 2-m-thick first-year ice were measured in water, 22 m below the vehicles. Results are presented in the form of third-octave levels, in the range 250 Hz–40 kHz.
Sound levels as a function of speed for Spanish trains
Authors: Manglano de Más J. L. , Estellés Belenguer H. , Belmar Ibañez F.
Published: October 2005

In this paper we have obtained, experimentally, similar results for five train types which normally move along the Spanish railway lines, and specifically in the city of Valencia.
Use of the articulation index for assessing residual auditory function in listeners with sensorineural hearing impairment
Authors: Pavlovic Chaslav V.
Published: October 2005

Two experiments were performed to explore the feasibility of deriving an articulation index (AI) based scheme for quantifying residual auditory function in listeners with sensorineural hearing impairment. In the first experiment the AI procedure was applied to audiograms of normal and sensorineural hearing-impaired individuals in order to predict speech discrimination under various conditions. Good predictions were found for the normal and the less impaired subjects, but not for those with greater impairments. These subjects exhibited a disproportionate loss in speech discrimination compared to that predicted on the basis of the AI procedure. In the second experiment it was investigated whether the AI predictions for presbycusic individuals could be improved by making use of the proficiency factor that is not a function of frequency. The results indicate that the deficit in suprathreshold speech processing is frequency-specific and that, therefore, the proficiency factor is not independent of frequency. It assumes the value of 1 at those frequencies where hearing sensitivity is normal and is substantially reduced for frequencies where hearing threshold is elevated.
Spectral analysis of sung vowels. I. Variation due to differences between vowels, singers, and modes of singing
Authors: Bloothooft Gerrit , Plomp Reinier
Published: October 2005

Average 1/3-oct filter spectra of vowels, sung by seven professional male and seven professional female singers, were measured. The material consisted of nine different vowels, sung at six fundamental frequencies (F0, ranging from 98 up to 880 Hz). For each vowel the singers were requested to sing in the following nine modes: neutral, light, dark, pressed, free, loud, soft, straight, and extra vibrato. To study origins of spectral variation, the quantity of spectral variance, based on band filter sound levels, was used. For each fundamental frequency and separately for males and females, portions of total spectral variance associated with the main effects and the interactions of the factors ‘‘vowels,’’ ‘‘singers,’’ and ‘‘modes of singing’’, were computed. A considerable decrease in total spectral variance was found when F0 rose from 98 to 880 Hz, mostly due to the reduced spectral variance between vowels. Above about F0=660 Hz spectral variation was dominated by differences related to singers and modes of singing. Additional analyses revealed that for all F0 values (1) vowel spectra of the tenor and the soprano singers varied more than those of the bass and the alto singers, (2) there was only a slight dependence of spectral differences between vowels on the mode of singing, and (3) the amount of spectral variation in a vowel, sung by different singers with different modes of singing, was vowel dependent.
Sampling in digital holographic reconstruction
Authors: Lee Hua , Wade Glen
Published: October 2005

The Nyquist rate is well known as the lower limit for signal sampling which avoids aliasing. A bandlimited analog signal can be completely represented by an infinite number of data samples with the sampling frequency equal to or higher than the Nyquist rate. However, to perform image reconstruction in digital holography, only a finite number of samples are taken at the receiving aperture. As a result, aliasing is unavoidable. We introduce here an alternative sampling method formulated in such a way that correlation among the components used in forming the image is minimized and the signal-to-noise ratio of the resulting image is maximized.
Development and application of multiple-input models for structural noise source identification of forge hammers. Part II: Application
Authors: Trethewey Martin W. , Evensen Harold A.
Published: October 2005

The application of multiple-input models to analyze structurally generated noise from a forge hammer is discussed. Part I of this article presented the rationale for developing and interpreting multiple-input models for structural noise source identification. An investigation of the transducer requirements for characterizing the sound radiation from a monolithic element showed that a single, well-placed accelerometer may be sufficient for each element. Part II of this article analyzes the application of the multiple-input modeling technique to the structural noise source identification of a Chambersburg ♯8 die forger. A comparison of three-, five-, and seven-input models applied to the forge hammer under production conditions indicates that as few as five transducers would suffice to characterize the sound contributions of the five structural elements. Analysis of these models indicates that the ram is the dominant source of sound energy, the columns are secondary sources, and the yoke and anvil are minor sources when detected through a microphone at the operator’s position. The analysis also shows that the coupling between the hammer structural elements is sufficient to render conventional wrapping identification methods unreliable for analyzing hammer noise.
Free vibration of a point-supported circular cylindrical shell
Authors: Irie Toshihiro , Yamada Gen , Kudoh Yasunori
Published: October 2005

An analysis is presented for the free vibration of an elastically or rigidly point-supported circular cylindrical shell. For this purpose, the deflection displacements of the shell are written in a series of the deflection functions of beam. The dynamical energies of the shell are evaluated, and the frequency equation is derived by the Ritz method. For a rigidly point-supported shell, the Lagrangian multiplier method is conveniently employed. The method is applied to a cylindrical shell supported at symmetrically located four points; the natural frequencies and the mode shapes are calculated numerically, and the effects of the point supports on the vibration are studied.
State prediction for environmental noise system by a generalized adaptive function model
Authors: Ohta Mitsuo , Uchino Eiji , Hatakeyama Kazutatsu
Published: October 2005

This paper describes a new attempt at predicting the fluctuations of an environmental noise system by use of adaptive functions. Principally, some kinds of correlations (in some cases, in the form of simple inertia) can be actually found between the recorded past data and the future values. In this paper, the basic correlative relationship of this kind is expressed universally with the use of newly introduced adaptive functions of both the linear, and nonlinear types. In prediction algorithms, discrete or continuous adaptive functions of orthogonal and/or nonorthogonal types are employed to meet the actual observation mechanism and to get the effective data processing. Finally, the effectiveness of the proposed method has been confirmed by computer simulation and application to actually obtained road traffic noise data.