bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of spectral errors with quantization of frequencies and bandwidths of LPC poles
Authors: Atal Bishnu S.
Published: October 2005

In low bit rate speech coding systems, the LPC spectral information is often coded in terms of quantized partial correlations or line-spectral pairs. The distribution of spectral errors with such quantization has been studied in the past. However, not much is known about the distribution of spectral errors when the frequencies and bandwidths of LPC poles are quantized. The quantization of frequencies and bandwidths has important advantages because the perceptual sensitivity to quantization of these parameters can be estimated from data on just-noticeable differences. In this paper, results will be presented on the spectral error introduced by the quantization of frequencies and bandwidths of LPC poles as a function of the different number of predictor coefficients and the different number of bits used to represent the spectrum. The distribution of spectral errors using frequency-bandwidth quantization will be compared with other procedures based on quantization of partial correlations and line-spectral pairs, and relative strengths and weaknesses of these quantization schemes will be discussed.
Singing synthesis with models of phonatory and articulatory kinematics
Authors: Titze Ingo R.
Published: October 2005

Singing synthesis to date has been attempted primarily in the acoustic domain. In an effort to learn more about the interactions between the source and subglottal and supraglottal resonators, a simulation strategy is employed that computes pressures and flows on the basis of vocal fold and articulatory movement. Some aspects of the perception of vocal registers are shown to be related to subglottal resonances. In particular, the first subglottal formant (ca. 500 Hz) helps to trigger the involuntary chest-falsetto transition in untrained voices. Roundness in the medial surface contour of the vocal folds also helps to distinguish chest-falsetto and male-female differences. Vocal tract constrictions in the vicinity of the glottis are shown to affect vocal quality, in particular, the perception of vocal ring. Frication in the glottis and the vocal tract is computed on the basis of critical Reynolds numbers and is an automatic consequence of changes in subglottal pressure and airway constriction. Some examples of simulated sound will be given. [Work supported by NIH, Grant No. NS 16320-08.]
Analysis and synthesis of the singing voice and mnsical applications
Authors: Rodet Xavier
Published: October 2005

IRCAM (Institut de Recherche et de Coordination Acoustique/Musique) has been involved in sound analysis and synthesis for contemporary music creation for many years. Accurate analysis and high-quality sound synthesis are thus extensively studied. Some of the methods that have been developed are described with particular attention to the singing voice and speech. A power spectral density estimate has been developed of the speech signal, which is simultaneously very precise and computed on very short segments of the signal in order to follow rapid transitions such as those found in plosives. Spectral envelopes are represented in a flexible way: They are coded in terms of frequency, amplitude, and bandwidth of pairs of conjugate poles (formants). An algorithm has been developed giving an harmonic/noisy decision in narrow frequency bands covering the entire spectrum. This technique has greatly improved the sound quality. Several synthesis methods have been developed and compared, including formant waveform synthesis (analogous to parallel formant synthesis), additive synthesis, and serial filter synthesis. Two types of synthesis rules have been studied. On the one hand, rules concerning phoneme coarticulation using formant coded diphones, sophisticated algorithm smoothing formant trajectories by taking into account three successive phonemes, durations of phonemes, speed of singing, speed of transitions, and relative timing of formant trajectories. On the other hand, a set of rules has been built with musical performance. Those rules calculate such features as vibrato excursion and rate, vocal effort, and formant locations according to fundamental frequency. Examples of synthesis by rule are given showing different types of voices and styles plus excerpts from concert pieces.
Synthesizing singing
Authors: Sundberg Johan
Published: October 2005

An attempt to synthesize singing is presented in which a synthesizer containing five cascaded formants is complemented by two noise generators and fixed filters. The performance is controlled by computers reading the input notation and processing it with pronunciation and musical performance rules. Both solo and choral singing are synthesized. Various effects will be demonstrated, such as timing of pitch changes and consonants, coloratura, markato, timbre, legato, and multiple pitch singing. Also, some effects concerning musical expression will be presented.
Analysis, resynthesis, and modification of sound signals with the help of wavelet transforms (i.e., time-and-scale representations)
Authors: Kronland-Martinet R. , Grossmann A.
Published: October 2005

An attempt will be made to present an up-to-date survey of results on wavelet transforms of signals, with particular emphasis on examples involving sound. The main feature of a wavelet transform is that it associates to a signal s(t) an appropriate function S(b,a) of two parameters: a time b and a scale parameter a. If it is required that the correspondence s → S be linear, the definition of a transform involves an “analyzing wavelet” g, which has to satisfy some conditions, and, given by S(b,a) = Ka−1/2 × ∫ s(t)g−[(t − b)/a]dt, g− is the complex conjugate of g. This correspondence has a stable inverse. A transform S(b,a) is fully determined by its values on a suitable discrete grid of the (b,a) open half-plane. Wavelet transforms are close relatives of time-frequency representations, the frequency being replaced by a scale parameter. The aim will be to describe some of the mathematical background, to give a description of some existing implementations, and to display an appropriate set of examples, involving acoustical signatures in the field of speech and music. There will be auditive examples showing the possibilities of intimate modifications of sound by these methods.
Airport noise compatibility planning perspectives
Authors: Starley Steven
Published: October 2005

Air transportation is mass transportation and its continuing growth has spawned a complex set of interrelated noise and capacity problems. Airport proprietors, who are responsible for noise damages, are turning to the use of restrictions to limit noise in adjacent communities. Use restrictions at one airport affect system capacity and operations at other airports. When capacity limitations affect interstate commerce, airports are caught between their adjacent communities and the Federal government that cannot allow an undue burden on interstate commerce. Airport noise abatement planning, which is effective for airport specific problems, may be a factor in the growth of national problems. Thus a national perspective must be applied to the solution of local problems. This paper traces the development of airport noise abatement planning, discusses some newly emerging areas of interest at both the local and national level, and presents a glimpse of some alternative futures.
The cooperative approach to noise compatibility planning at Portland International Airport
Authors: Newell John P.
Published: October 2005

The Port of Portland's cooperative approach to airport noise compatibility planning has produced a plan that seeks to balance the concerns of the community with the needs of the airport and its users. This plan has reduced the number of residents within the Ldn 55 contour by 85%, without employing costly operating restrictions. The success achieved is directly attributable to the cooperative process that involves the utilization of an advisory committee to help identify and resolve airport noise issues. This committee, consisting of all parties having an interest in the airport noise issue, has worked together since 1982 in structuring and implementing the noise abatement plan. This plan is made up of three interrelated programs: an operational program, a land use program, and a review and monitoring program. The operational program includes specific flight track assignments, while the land use program requires sound insulation of some residential dwellings, and adoption of city and county noise overlay zones. The review and monitoring program is the part of the plan that insures the ongoing cooperative process, and maintains compatibility with the community.
The use of local opportunities in aircraft noise abatement planning
Authors: Woodward Jon M.
Published: October 2005

Aircraft noise abatement planning often overlooks low-cost, easy to implement solutions that take advantage of unique local conditions. The focus is too often on generic “cookbook” solutions that are applied to every airport in the same way, e.g., curfews, aircraft type restrictions, or noise budgets. For every airport, careful analysis will reveal unique conditions that provide opportunities to abate noise. These include airport operating schemes such as preferential runway use programs, rerouting of traffic along corridors of compatible land uses, and the use of comparative aircraft versus background noise levels to direct traffic flows. Preferred aircraft operating procedures are selected based upon local underlying surface conditions of land use or terrain. Limitations on aircraft operation through imposition of local legislation can result in noise reduction in specialized cases. Construction of new facilities most often is driven by capacity needs as well as noise abatement. Examples of the effects of using local opportunities for noise abatement are presented for each type of measure from airport noise compatibility planning projects at Portland, Seattle, Phoenix, Anchorage, Indianapolis, Baton Rouge, New Orleans, Chicago, Omaha, Little Rock, and Reno.
Use of seasonal Ldn for airport noise compatibility planning
Authors: Harris Andrew S.
Published: October 2005

The differences between Ldn from yearly average operations and Ldn from busy day or seasonal operations are examined. Civil and military airports are considered. For civil airports, the issue of seasonality is addressed as it relates to the Federal Aviation Administration's requirements under FAR Part 150. For both civil and military airports, current examples are discussed. The environments of civil and military airports are also examined in the context of EPA Task Group 3's recommendations about seasonality [“Impact Characterization of Noise Including Implications of Identifying and Achieving Levels of Cumulative Noise Exposure,” for Environmental Protection Agency Aircraft/Airport Noise Report Study, Task Group 3, Henning von Gierke, Chairman, Washington, 1 June 1973.] Methods for developing seasonal noise exposure are examined.
Combined masking under conditions of high uncertainty
Authors: Neff Donna L. , Jesteadt Walt , Callaghan Brian P.
Published: October 2005

Simultaneous maskers composed of a few sinusoids scattered over a wide frequency range produce large amounts of masking if the frequency composition of the maskers is changed with each stimulus presentation. This masking appears to be produced primarily by more central processes driven by stimulus uncertainty. In this study, the masking produced by combining these maskers with broadband noise is examined. Growth of masking functions for broadband noise and for multicomponent maskers with 2, 6, 10, 50, and 100 components were used to select levels for individual maskers that produced 10, 20, 30, or 40 dB of masking. Multicomponent and noise maskers were then presented in equated and unequated combinations. The average amount of additional masking beyond a power summation measured for equated conditions decreased from around 12 to 2 dB as the number of components in the multicomponent masker increased from 2 to 100. The data are well fitted by Lutfi's model for combined simultaneous maskers, with exponents that approach 1.0 as the number of components increases to more closely approximate broadband noise. [Work supported by NIH and AFOSR.]
Changes in the masked thresholds of brief tones produced by preceding bursts of bandpass and notched noise
Authors: Carlyon Robert P.
Published: October 2005

Thresholds were measured for 5-ms 1-kHz tones masked by synchronous bursts of noise containing a spectral notch centered on the signal frequency. These thresholds were reduced by prior exposure to a 200-ms burst of a “priming stimulus,” which had the same spectral shape as the masker. This masking release was greatest for notch widths extending between 20%–30% on either side of the signal frequency, and was absent when the masker and primer contained no notch. A smaller masking release could be obtained with primers consisting of only the lower band of a notched noise masker, and, to a lesser extent, of the higher band alone. A primer consisting of a narrow band of noise centered on the signal frequency produced an increase in masking, which could not be attributed to forward masking of the tone. The effects of all of these primers were independent of the 30-dB range of primer levels studied, ruling out an explanation in terms of peripheral adaptation. The results are consistent with the presence of an active neural mechanism that enhances the internal representation of newly arriving energy in a previously unstimulated frequency region. Temporal parameters of the masking release were also studied.
Comodulation masking release (CMR) as a function of masker bandwidth, signal duration, and modulator bandwidth
Authors: Schooneveldt Gregory A. , Moore Brian C. J.
Published: October 2005

Thresholds were measured for a 2000-Hz signal masked by continuous noise varying in bandwidth from 50 to 3200 Hz in 1-oct steps. For random noise maskers, thresholds increased with increasing bandwidth up to 400 Hz and then remained approximately constant. When the masker was amplitude modulated by a low-pass noise, so as to produce coherent envelope fluctuations across frequency, thresholds decreased as the masker bandwidth was increased beyond 200 Hz, giving a CMR. For a 400-ms signal duration, the CMR for masker bandwidths greater than 400 Hz increased from 2.4 to 12.3 dB as the modulator bandwidth was decreased from 400 to 12.5 Hz in 1-oct steps. For modulator bandwidths of 50 Hz or less, a release from masking of 3.5 to 7.3 dB occurred even for maskers with bandwidths of 50 and 100 Hz, less than the critical bandwidth at 2000 Hz. For a modulator bandwidth of 12.5 Hz, the CMR decreased from 12.3 to 5.3 dB as the signal duration was decreased from 400 to 25 ms in 1-oct steps. When the signal duration was less than 100 ms, there was no release from masking for masker bandwidths less than 400 Hz. The results suggest that, for maskers with fluctuating envelopes, across-channel comparisons can reduce signal thresholds even for short signals, but an extra within-channel process can produce a release from masking for long signals. This second process may reflect the ability of subjects to detect a change in the statistical properties of the envelope of the stimulus when the signal is added to the masker.
Signal threshold as a function of the relative modulation depth between on-frequency and flanking masker components
Authors: Grose John H. , Hall Joseph W.
Published: October 2005

It is apparent that the mechanism underlying comodulation masking release (CMR) relies on the existence of temporal fluctuations in the masker envelope. This raises the question of how much fluctuation is necessary to facilitate CMR. The present experiment addresses this question by measuring psychometric functions relating signal threshold to depth of flanker band modulation using sinusoidally amplitude-modulated pure tones as masker components. In the first set of conditions, the on-frequency component had a constant modulation depth of 100%, while the depth of the flanking components was varied between 100% and 0%. As expected, signal threshold improved monotonically as depth of flanker band modulation increased. In the second set of conditions, the on-frequency component had a constant modulation depth of 63%, while the depth of the flanking components was either 100%, 63%, or 0%. Results to date suggest that signal threshold is lowest when the flanking components have the same depth of modulation as the on-frequency component. [Research supported by AFOSR.]
Cross-channel effects in amplitude-modulation detection
Authors: Sheft Stanley , Yost William A.
Published: October 2005

Sensitivity to low-frequency sinusoidal amplitude modulation (AM) at a single-component frequency of an equal-amplitude tonal complex was investigated. All masker components of the complex were modulated with a fixed depth at the same frequency as the probe. The phase between probe and masker envelopes was varied across conditions. For a two-component complex, the change in performance as a function of frequency separation (Δf) depended on the envelope phase relationship. With a 2-kHz probe carrier, the slopes of the AM threshold versus Δf functions are more gradual than would be predicted by envelope interaction in a single-frequency channel. Consistent with AM detection models incorporating broad predetection filtering, performance may be affected by detection of changes in the overall modulation pattern. When the probe and masker envelopes differ, adding masker components at the fringes of the two-component complex can lead to an improvement in probe AM detection. This result suggests that the detection of the modulation pattern of an individual component in a tonal complex may be aided by enhancing cross-channel differences in modulation.
Complex sound discrimination: Predictions of the EWAIF model
Authors: Feth L. L. , Stover L. J. , Gerren R. A.
Published: October 2005

The envelope-weighted average of instantaneous frequency (EWAIF) model of auditory perception has been successfully applied to simple, two-component signals, simultaneously amplitude- and frequency-modulated tones, and even to the complex signals used in the early “profile analysis” work. The EWAIF model predicts performance from a calculation of the envelope-weighted average of the instantaneous frequency fluctuations inherent in almost every complex periodic sound. When the model is in error, it generally predicts better performance than our listeners achieve. A revised version of the EWAIF model incorporates a temporal processing window. The revised model was tested by comparing its predictions with listeners' performance in a frequency-change discrimination task. The experiment requires the listener to distinguish a smooth frequency glide from a discrete, multistep transition over the same trajectory. The listeners' ability to distinguish the glide from the multistep transition, in a 2IFC task, decreased to chance as the number of steps increased. The EWAIF model performance follows that of the listeners, given the appropriate choice of temporal window parameters. [Work supported by AFOSR and NIH.]
Chaos in underwater acoustics
Authors: Tappert F. D. , Brown M. G. , Palmer D. R. , Bezdek H.
Published: October 2005

The problem of predicting sound propagation in range-dependent ocean environments has been investigated, in which it is supposed that the environment (volume and/or boundary) varies smoothly in range and is exactly known with arbitrary precision. Although this problem as stated is deterministic and not intrinsically stochastic, it has been discovered from numerical and analytical studies of physically realistic examples drawn from deep ocean propagation, shallow-water propagation, and surface duct propagation, that ray path solutions exhibit “classical chaos,” namely, unpredictable and stochastic behavior. Ray paths are found to have a continuous spectrum characteristic of noisy stochastic processes, and ray paths are found to have an exponentially sensitive dependence on initial conditions and environmental parameters characteristic of chaotic processes. This phenomenon of chaos in underwater acoustics is caused by the exponential proliferation of catastrophes (caustics) due to the loss of control implied by the nonseparability of variables in the eikonal equation. As a consequence, even when the ocean environment is known exactly, there exists a “predictability horizon” that limits the range to which acoustic fields can be predicted.
The limits of source localization due to stochastic ocean processes
Authors: Ewart Terry E. , Porter Robert P. , Dworski Juraj , Reynolds Stephen A.
Published: October 2005

The location of a source from acoustic measurements may be estimated in several ways. A known source/receiver geometry is used to study the limits of geometrical techniques. Pulses (2, 4, 8, and 16 kHz) traveling a 6-km path from source to receiver in the Beaufort Sea were received at a 150-m vertical array during the AIWEX acoustic transmission experiment, AATE. Pulse travel times estimated using the Bell-Ewart multipath separation algorithm provide single-path travel time accuracies of a few μ seconds. Treating the source location as unknown allows for the study of the precision of various methods. Ray trace methods were implemented to backpropagate the travel time estimates to a source location using the mean sound-speed profile. A simple source location estimator based on least-squares fitting of the measured to the predicted travel times provides a classical example of a global versus local optimization problem when the array angle is included in the minimization. Methods have been developed to circumvent the optimization problem and range errors of a few centimeters and depth errors of a few meters result. The methods, results showing the effects of the medium, and a discussion of further refinements are presented. [Work supported by ONR.]
Chaos in shallow-water propagation
Authors: Tappert F. D. , Brown M. G.
Published: October 2005

Sound propagation in downward refracting shallow-water environments is considered, in which it is supposed that the water depth varies smoothly in range and is exactly known with arbitrary precision, and the bottom is perfectly reflecting at shallow angles. After a few additional assumptions are used to simplify the physics, it was found that the equations for ray paths (RBR) undergoing multiple bottom reflections reduce to the “standard map” of chaos theory, where the “stochasticity parameter” K is four times the ratio of boundary curvature to ray curvature. Typical values of K greatly exceed the critical value, Kc ≈0.97, above which “global chaos” is known to prevail. Thus ray paths in these deterministic environments typically exhibit chaotic behavior, namely, ray paths have an exponentially sensitive dependence on initial conditions.
Numerical modeling of the scattered acoustic field from elastic ice
Authors: Fricke J. Robert , Stephen Ralph A. , Baggeroer Arthur B.
Published: October 2005

A two-dimensional elastic finite difference modeling program written for marine geophysical applications [M. E. Dougherty and R. A. Stephen, J. Acoust. Soc. Am. 82, 238–256 (1987)] has been modified to study the ice scattering problem. The modified code was checked by comparing modeled plane-wave reflection coefficients at various angles of incidence with the analytical solutions provided by Zoeppritz equations. These tests were calibrated for a flat interface with homogeneous half-spaces of water and ice and resulted in favorable comparisons. Subsequently, various ice models were run to observe the scattered acoustic field. These models include flat ice, flat ice with a single keel, and ice with randomly rough surfaces (top and bottom) derived from different process models (e.g., Gaussian and Poisson). With this program, controlled numerical experiments can be performed for single realizations of ice roughness including full elastic behavior of the ice which is usually neglected in scattering theory. Such a capability can be used as an analysis tool for evaluating scattering approximations (say, the Kirchhoff approximation). In addition, this modeling capability can be used as the synthesis step of a scattering inversion program where ice roughness parameters are to be estimated from a measurement of the scattered field. [Work supported by ONR Arctic Acoustics program.]
Images of waves through random media by numerical simulation
Authors: Flatté Stanley M. , Martin Jan
Published: October 2005

Using the SDSC/CRAY, an extended random medium has been modeled by a set of two-dimensional thin phase-changing screens with phase power spectral densities having various power-law indices and inner and outer scales. The strength of the index of refraction in the medium has been varied. At small strength, the propagation is unsaturated, and the random intensity patterns at the final screen are dominated by the effects of the small-scale parts of the medium. As the strength of the medium fluctuations is raised, the images of intensity at the final screen show striking patterns, with caustics forming and interference fringes near the caustics being visible. For even larger medium strength, regions of high intensity associated with many caustics clump into large-scale patterns that are related to the large-scale structure of the medium. Intensity spatial spectra and variance will be given, but it should be emphasized that the observed patterns are not well characterized by a simple, random-phase. realization of a power spectrum. Some comparisons with experiments in laser-beam propagation through the atmosphere will be given.
Martin Greenspan's work in acoustical physics
Authors: Cook Richard K.
Published: October 2005

Martin (Moe) Greenspan's long career at the National Bureau of Standards began in 1936 in the general area of the strength of engineering materials and structures. His theory of stress distribution in perforated plates was an important contribution to modern linear elastic fracture mechanics. In 1947 he began to work in physical acoustics and continued in this until 1987. His landmark accomplishments include the theoretical analysis and measurement of sound propagation in rarefied gases, development of an instrument for measurement of sound velocity in sea water, and determination of the important physical influences leading to cavitation in liquids by ultrasound. In recent years, he worked on methods for measuring accurately the acoustical emissions (stress waves) generated by physically stressed materials of engineering. The influences of his work on sound in rarefied gases persist today; the database he obtained in the late 1940s–1950s was far in advance of the analytical capabilities for sound propagation in rarefied gases at that time. The data are still used for evaluation of new theoretical developments. Moe's work has always been characterized by an excellent coordination between theoretical-mathematical development and laboratory experiment.
Acoustic goofs or irreproducible effects in acoustics
Authors: Cook I. Rudnick
Published: October 2005

Our respected and beloved friend, Moe, had a genius for being able to put his finger on mistakes that made their way into experiments and theories. He was a bubble buster. Listed below are some acoustic goofs. Moe contributed his skill in correcting some of them. There will be brief discussions of some of the topics as time allows: (1) Fitzgerald's folly; (2) The universal sequence in subharmonic generation or when is a decibel not a decibel?; (3) What is zero sound in liquid helium 4?; (4) Isothermal and adiabatic propagation in metals; (5) Shearing in longitudinal wave propagation; (6) Weber's folly. Webster's dictionary: goof—to make a mistake or blunder.
Adiabatic invariance, the cornerstone of modern physics
Authors: Putterman Seth J.
Published: October 2005

The article by M. Greenspan on the Boltzmann-Ehrenfest adiabatic principle [J. Acoust. Soc. Am. 27, 34 (1955)] is used as the starting point for discussing the role of adiabatic invariance (or integrability) in modern physics. These conserved properties of open systems constitute the key concept upon which all advances in modern physics have been focused. These include the origin of thermodynamic irreversibility for Hamiltonian systems and the quantization of motion. Delauney (1860) was first to employ adiabatic invariants as dynamical variables with an aim toward determining the stability of the solar system. This issue eventually culminated in the work by Kolmogorov, Arnold, and Moser on the stability of nearly integrable systems. The solution to the problem of soliton motion by the inverse scattering transformation is in fact a transformation to the adiabatic invariant as the canonical momentum. Recent acoustical applications of adiabatic invariance include a determination of the potential in an acoustic levitator and a prediction of second sound in acoustic turbulence.
Gas-filled spherical resonators: The current state of experiment and theory
Authors: Mehl James B. , Moldover Michael R.
Published: October 2005

In the past decade, spherical acoustic resonators have proved to be useful tools for high-accuracy measurements of the speed of sound in gases. Applications include thermophysical property determinations, acoustic thermometry, and the recent redetermination of the gas constant. The complex resonance frequencies of the resonator are described by a theoretical model that includes the effects of the viscous and thermal boundary layers, shell motion, imperfect spherical geometry, and other, less important, effects. The theoretical model is tested by comparing the consistency of speed-of-sound determinations using different modes, and by comparing the resonance half-widths with the theoretical predictions. The current level of agreement of experiment and theory will be reviewed.
Cavitation nuclei and cavitation noise
Authors: Strasberg M.
Published: October 2005

Present understanding of the influence of nuclei on the onset of cavitation and the generation of radiated cavitation noise is reviewed. It is now generally accepted that the formation of cavities in a liquid at only moderate negative pressures requires the presence of nuclei in the liquid; the experiments of Greenspan and Tschiegg, among others, leave no doubt about this. However, there is still no agreement concerning the form of these nuclei or the mechanism causing them to persist under conditions that should ordinarily make them disappear. Various possible stabilizing mechanisms are discussed. It is shown that although nuclei determine whether cavitation occurs at all, once it occurs, their presence has little effect on the characteristics of the radiated noise generated by the cavitation. The factors that do influence the spectrum and the magnitude of the noise will be discussed, mainly in terms of hydraulically induced cavitation.
Theory of radiatian induced cavitation
Authors: Apfel Robert E. , Lo Y.-C.
Published: October 2005

Data from two different experiments fall on the same general nondimensional curve: The first set of data is that of Greenspan and Tschiegg on neutron-induced acoustic cavitation [J. Acoust. Soc. Am. 72, 1327 (1982)]; the second is that of Apfel et al. on neutron-induced (nonacoustic) cavitation of superheated drops [Phys. Rev. A 31, 3194 (1985)]. The physics is the same. The theory begins with the neutron-nucleus interaction, continues as the recoil ion deposits its energy as heat along a line, and ends with the formation of a bubble that must exceed a critical size if a macroscopic bubble is to be produced. The theory will be reviewed and its predictions compared with both sets of experimental results. [Work supported by D. O. E. grant DEFG02-87ER6050.]
Adjusting syllable durations in a demisyllable speech synthesis system
Authors: Urbanczyk Suzanne C. , Eady Stephen J. , Dickson B. Craig
Published: October 2005

This paper describes the durational aspects of a speech synthesis system designed to generate words and sentences of English based on smaller synthetic speech units known as demisyllables [O. Fujimura, J. Acoust. Soc. Am. Suppl. 1 59, S55 (1976)]. Each syllable of a word is composed of an initial and a final demisyllable. The demisyllable inventory (totaling less than 900 units) is prerecorded and stored in LPC format. Demisyllables are linked to form syllables, which are then joined into words. Syllable duration is one of the more complicated features of word formation using this technique. Our strategy for producing syllables of appropriate length is to record the demisyllable units with relatively long durations and then to reduce the duration of the demisyllable components when they are joined together. Durational adjustment is accomplished using a spectral distance metric, which identifies regions of the syllable where the spectral components are least dynamic. The less dynamic regions can then be deleted to shorten a syllable, while maintaining perceptually relevant acoustic characteristics. This method is used to adjust syllable durations at both the word and sentence levels. [Work supported by Science Council of British Columbia.]
A semiempirical model for the wave vector-frequency spectrum of turbulent wall pressure on a smooth planar boundary
Authors: Chase D. M.
Published: October 2005

The analytical framework and construction of a model of turbulent boundary-layer pressure on a planar wall by its relation to velocity-product fluctuations regarded as its sources are reviewed. Expansion for low (subconvective) wavenumbers and low Mach numbers provides a basis for such a trial model of the wall-pressure spectrum that is potentially satisfactory at all wavenumbers from the acoustic domain to the convective. The proposed form for source cross spectra incorporates the principle of wall similarity, a kinematic assumption about space-time correlation, possible wall-normal profiles of vorticity cross spectra, and assumed non-negativity. The wall-pressure model is obtained by analytical integration over the source-spectral profiles in limiting domains followed by convenient rough interpolation. The experimental basis for determination of parameter values of the model is considered by reference to classical wind-tunnel measurements dominated by the convective wavenumber domain and to more ambiguous ones directed to the subconvective but superacoustic domain. The inadequate state of validation and determination of parameters characterizing the acoustic domain and the domain of pertinence of the Kraichnan-Phillips theorem is confronted. Likewise, the open but experimentally resolvable question of the joint dependence on wave vector components in the convective domain is recalled.
The influence of surface roughness on wall-pressure fluctuations and the radiated sound from a turbulent boundary layer
Authors: Howe M. S.
Published: October 2005

The noise and vibration produced during turbulent boundary-layer flow over a nominally plane flexible surface are governed by the low wavenumber and acoustic regions of the wall-pressure wavenumber-frequency spectrum. In the case of a rough surface, the spectrum differs from that on a smooth wall on two counts: (i) the strengths of the turbulent Reynold stress fluctuations, which are ultimately responsible for the pressure field, are increased by the action of surface roughness; (ii) the pressure field produced by those enhanced pressure sources is redistributed in the wavenumber plane by diffraction by the roughness elements. The wall-pressure spectrum can be expressed in the form P(k,ω) = P0(k,ω) + PR(k,ω), where P0 denotes the spectrum that would be associated with the roughness-enhanced Reynolds stresses if the wall were assumed to be perfectly flat, and PR is the additional component due to the diffraction mechanism (ii). It will be shown that PR is expected to dominate the behavior of the wall pressure in the low-wavenumber and acoustic regions over a wide range of frequencies. Certain problems associated with experimental studies of rough wall boundary-layer noise will also be discussed.
Comparison between design and installed acoustic characteristics of the NASA Lewis 9- × 15-ft low-speed wind-tunnel acoustic treatment
Authors: Dahl Milo D. , Woodward Richard P.
Published: October 2005

The test section of the NASA Lewis 9- × 15-ft low-speed wind tunnel was acoustically treated to allow the measurement of sound under simulated free-field conditions. The treatment was designed for high sound absorption at frequencies above 250 Hz and to withstand the environmental conditions that exist in the test section. To achieve the design requirements, a fibrous bulk absorbing material was packed into removable panel sections. Each section was divided into two equal-depth layers that were packed with material to different bulk densities. The lower density was next to the face of the treatment. The facing consisted of a perforated plate and screening material layered together. Sample tests for normal incidence acoustic absorption were conducted in a small rectangular duct. Tests with no air flow involving the measurement of the absorptive properties of the installed treatment combined the use of time delay spectrometry with a previously established free field measurement method. These measurements were compared to the design model and sample tests of the treatment.
Rayleigh's influence on engineering vibration theory
Authors: Crandall Stephen H.
Published: October 2005

The first ten chapters of The Theory of Sound constitute an unprecedented exposition of vibration theory. This tour de force set the mold for the teaching of vibration for more than a century. The central core is linear modal analysis applied to lumped parameter systems and to strings, bars, beams, membranes, plates, and shells. In addition, there are preliminary investigations of nonlinear vibrations, parametrically excited vibrations, and random vibrations. Most of the textbooks on vibrations for engineers that have appeared in the past 50 years may be viewed as attempts to explain Rayleigh's idea to university students. Rayleigh's paradigm has served us well for a century but it appears that we are now on the threshold of major changes in the way vibration theory is taught. These changes are being driven by the tremendous advances in instrumentation and data processing facilities. The second coming of modal analysis (modal testing, really) is largely based on the concept of transfer functions. Although Rayleigh occasionally used the complex exponential and even computed a few transfer functions in passing, he did not attach any special significance thereto. It is interesting to speculate what Rayleigh would have done had he envisioned today's multichannel spectral analyzers. Other advances, unavailable to Rayleigh, which are currently entering vibration courses, are discussed.
Lord Rayleigh's contributions to nonlinear acoustics
Authors: Beyer Robert T.
Published: October 2005

While the overwhelming majority of Rayleigh's contributions to acoustics have been in the linear domain, there are many nonlinear topics on which he made early progress and set the stage for further progress in the future. His work on radiation pressure, cavitation, shock waves, and flow-induced sound will be discussed and the developments that followed from them will be described.
Rayleigh's observations of wave interference, evanescent fields, and sound cancellation
Authors: Swanson David C.
Published: October 2005

In Chap. 23 of The Theory of Sound, Rayleigh made some outstanding observations of wave interference in an experiment designed to show that the source of “grave notes” in pipe organs was due to difference tones rather than a nonlinearity in the ear as proposed by Helmholtz [J. W. S. Rayleigh, The Theory of Sound (Dover, New York, 1945), pp. 461–462]. When the organ keys for d′″ (1174 Hz) and e′″ (1318 Hz) are played simultaneously, a grave note of 144 Hz (between a C♯ and D) is also heard, giving a displeasing sound. Rayleigh carefully tuned the pipes so that the grave note gave the slowest possible beat with a tuning fork of 128 Hz. Rayleigh noted that if the grave note was due to the ear, the sound of the tuning fork would not cause the slow cycles of sound cancellation. He also noted that the sound field from the fork-pipe combination (during constructive interference) fell off more rapidly with distance than the sound field from the fork alone, which is characteristic of an evanescentor nearfield. These observations provide an interesting lesson for all experimentalists on basic scientific reasoning and the importance of reporting all relevant observations revealed by experiment.
Speech recognition using time-delay neural networks
Authors: Waibel A. , Hanazawa T. , Shikano K. , Hinton G. , Lang K.
Published: October 2005

A time-delay neural network (TDNN) approach is presented to speech recognition that is characterized by two important properties: (1) Using multilayer arrangements of simple computing units, a TDNN can represent arbitrary nonlinear classification decision surfaces that are learned automatically using error back propagation. (2) The time-delay arrangement enables the network to discover acoustic-phonetic features and the temporal relationships between them independent of position in time and, hence, not blurred by temporal shifts in the input. The TDNNs are compared with the currently most popular technique in speech recognition, hidden Markov models (HMM). Extensive performance evaluation shows that the TDNN recognizes voiced stops extracted from varying phonetic contexts at an error rate four times lower (1.5% vs 6.3%) than the best of our HMMs. To perform this task, the TDNN “invented” well-known acoustic-phonetic features (e.g., F2 rise, F2 fall, vowel onset) as useful abstractions. It also developed alternate internal representations to link different acoustic realizations to the same concept. The TDNNs trained for other phonetic classes achieve similar high levels of performance. The integration of such smaller networks into large phonetic nets and propose strategies for the design of neural network based large vocabulary speech recognition systems is discussed.
Speech recognition with layered networks
Authors: Burr D. J.
Published: October 2005

Experiments show that perceptrons may be useful for speech recognition. Perceptrons, or layered networks, can recognize spoken digits, polysyllabic words, and alphabetic text with accuracies exceeding 98%. They do so with varied input representations ranging from Fourier through cepstral and linear prediction coefficients. As in conventional classifiers, the greater the number of training tokens per class, the higher is the accuracy. Trained networks may be analyzed to observe any structure in the weight space. One can see evidence in perceptron networks for both voicing and formant onset detection capability. For a given problem, a layered network has a critical number of hidden units that maximizes recognition accuracy at minimum hardware cost. Additional hardware may be saved by eliminating near-zero weights in upper layers as these have minimal effect on recognition accuracy. A tradeoff may exist between number of weights and network complexity. A small layered network with 264 weights and 12 hidden units achieved 99% accuracy on isolated digits. In contrast, a large perceptron with more than 11 000 weights and no hidden units achieved 98.2% accuracy on the difficult E-set alphabet and perfect recognition on twenty polysyllabic words. Apparently, memory (number of weights) can be traded for logic (number of hidden neurons) as in conventional computer programs.
Reflections from a block of sea ice
Authors: Garrison Gerald R. , Francois Robert E.
Published: October 2005

At an Arctic ice camp in the Beaufort Sea, monostatic acoustic reflections near normal incidence were measured from the lower face of an isolated block of natural sea ice. The measurements were repeated with the transition layer sawed off to leave a surface of solid ice. A comparison of the two results showed that the 15-cm-thick skeletal layer and transition zone cause a reduction in reflectivity, beyond that predicted from the impedance mismatch, that increases from 10 db at 20 kHz to 30 dB at 80 kHz. The system was calibrated using the air-water interface formed at the open bottom of a shallow hollow metal cylinder. Air was forced into the cylinder when it was in place to fill it and thus provided a flat pressure-release reflecting surface. As the measuring transducer was moved away from normal incidence, the response pattern was found to agree with the sidelobe pattern predicted for a flat, perfectly reflecting surface. These measurements of the effect of the skeletal layer on ice reflectivity will be helpful in modeling the reflections from ice keels. [Work supported by the Office of Naval Technology with technical management by NORDA.]
Reflectivity of sea ice
Authors: Francois Robert E. , Garrison Gerald R. , Wen Timothy
Published: October 2005

The reflections from the face of a finite block of sea ice are usually predicted as the combination of two phenomena, as allowed under the Kirchhoff approximation. One is the reflection loss due to the change in acoustic impedance at an infinite water-ice boundary. The other is the interference pattern produced by the coherent return from a finite block face. Measurements of the reflections from a block of natural sea ice, described in a companion paper, showed that the reflection is further reduced by the skeletal layer. More information on the acoustic properties of this layer is needed in order to model its effect. Reflection losses are described by an amplitude reflection coefficient which would be 0.34 due to the impedance mismatch at the water-ice boundary. Reflection coefficients measured for 1- to 2-m-thick ice in the Arctic at frequencies 20–80 kHz are compared with measurements by Stanton and Jezek for thin ice. During the Arctic measurements, the return from the back face of the block was also detected, providing information on the absorption of sound in the ice. Field experiments have been designed to separate the absorption in the skeletal and transition layer from the absorption in solid ice. [Work supported by the Office of Navy Technology with technical management by NORDA.]
An application of a full scattering theory to Arctic propagation
Authors: Hanna J. S. , Rubenstein D. M. , Dozier L. B. , Pearson C.
Published: October 2005

The full scattering theory of Burke and Twersky [J. Acoust. Soc. 40, 883–895 (1966)], which includes both the specular and scattered energy for a rough surface consisting of elliptical bosses on a plane surface, is applied to the problem of propagation under the ice surface. This theory has been efficiently parametrized [D. Rubenstein (unpublished manuscript)] for the case of randomly spaced keels with a Rayleigh distribution of depths. The scattering kernel for this treatment has been used in a coupled mode formulation of the ASTRAL propagation model. The modified ASTRAL can compute the propagation associated with both the specular field and the total field which includes the nonspecular component. The redistribution of energy among the modes occurs continuously with range, so the model can display the mode excitation as a function of range. The model is compared to some measured propagation data, paticularly that of Diachok [J. Acoust. Soc. Am. 59, 1110–1120 (1976)], who applied low- and high-frequency asymptotic forms of the Burke-Twersky theory for just the specular field. [Work supported by the ASW Environmental Acoustic Support Program.]