bluuebunny/crossref_metadata_2025 huggingface dataset:
Signal coherence and energy effects of propagating internal solitary wave packets
Authors: Duda Timothy F. , Preisig James C.
Published: July 2002

Order-400 Hz sound propagated through continental-shelf internal solitary wave packets is shown by simulation to fluctuate strongly via mode coupling. The coupling is controlled by the modal input conditions, wave and packet dimensions, and the ambient sound-speed profile. In the case of a moving packet, relative modal phase changes dominate over the others, changing the coupling and controlling signal fluctuations. The phasing within the packet varies over minutes in a moving packet, causing fluctuations with comparable time scales. The directionality of energy flux between high-order acoustic modes and (less attenuated) low-order modes determines a gain factor for distantly detected signals. A significant finding is that a packet near a source will amplify low-order modes if the source favors high-order modes, giving amplification at distant ranges. Conversely, a packet far from a source can energize otherwise quiet higher modes. Intermittency in the coupling means that signal energy fluctuations and modal diversity fluctuations at a distant receiver are complementary, with energy fluctuations suggesting a source-region packet and mode fluctuations suggesting a receiver-region packet. In addition to the monochromatic results described above, the effects on pulses (broadband signals) will be compared with experimental observations. [Work supported by ONR Ocean Acoustics.]
The two domains in envelope spectrum of ocean ambient noise
Authors: Furduev A. V.
Published: July 2002

Analyzing level fluctuations of the natural ambient underwater noise shows that the spectrum of the envelope usually consists of two frequency domains of different physical nature. The low-frequency domain is governed by variations in wind speed, that is, variations in surface density of the source power. The high-frequency domain is related to rough-surface sound scattering. The boundary between the domains correspond to frequencies of 0.05–0.1 Hz. Experiments have shown that both cross-frequency noise correlation and correlation between the noise and wind speed fluctuations are high if only frequencies lower than 0.1 Hz are retained in the spectrum, these correlations being low for unfiltered noise. Thus, if there is no ship-traffic noise, the frequency correlation coefficient remains to be 0.6–0.8 within 0.1–10 kHz if the high-frequency domain is cut off and it is close to zero in disjoint filtering bands for unfiltered noise. The experimental data are discussed and interpreted with the use of the noise model allowing for space–time parameters of the wind speed.
Wave propagation in the ocean with fine structure stratification
Authors: Shvachko Remir F.
Published: July 2002

The highly anisotropic fine-structure inhomogeneities may be interpreted as being irregular (stochastic) in depth and regular (deterministic) in horizontal coordinate. These properties lead to the Bragg sound scattering, and hence to sound penetration into the shadow zones, prereverberation, and stochastic channeling. In other words, due to various effects of sound reradiation by the inhomogeneities, the sound penetrates into (spatial, temporal, angular) domains that are forbidden by the geometrical acoustics. Sound fields in the shadow zones carry information on the ocean fine structure stratification and thereby may be used in tomography experiments. The phenomenon of insonifying the shadow zone over a 10-m-thick microchannel was confirmed experimentally at a frequency of several kHz, up to distances of about 25 km. Because any convergence zone gives rise to volume-scattered signals that penetrate into the next shadow zone, the second-zone signal may have the same order of magnitude as the multiply bottom-reflected ones, the volume-scattered signals predominating within the third zone. The developed models for the leakages caused by the subsurface and fine-structure channels and by fine-structure scattering agree well with the experimental data obtained in different ocean regions.
An energy-conserving one-way coupled mode propagation model
Authors: Abawi Ahmad T.
Published: July 2002

The equations of motion are used to derive a coupled mode model for wave propagation in a range-dependent waveguide. Traditionally in ocean acoustics the wave equation has been used to derive these equations. The use of the equations of motion has three major advantages over the use of the wave equation: (1) It results in coupled mode equations that are first order, (2) the resulting coupling coefficients are anti-Hermitian, which guarantees energy conservation, and (3) simple expressions can be derived for the coupling coefficients in terms of local modes and their vertical derivatives. In contrast, the coupled mode equations derived from the wave equation are second order. Also, simple expressions for the coupling coefficients are hard to obtain because they involve second derivatives of the modes with respect to range. This model is applied to the ASA benchmark problem [J. Acoust. Soc. Am. 87, 1499–1510 (1990)]. The results show excellent agreement with those obtained from other well-known range-dependent models.
On the adiabatic normal modes in the 3-D inhomogeneous waveguide
Authors: Godin Oleg A.
Published: July 2002

Several distinct formulations of the adiabatic approximation have been proposed in the literature on modal propagation in the 3-D, range-dependent waveguide. These formulations predict the same phase but differ in the adiabatic mode amplitude and, hence, in their reciprocity and energy-conserving properties. These formulations, including those due to L. M. Brekhovskikh and O. A. Godin [Acoustics of Layered Media. 2. Point Sources and Bounded Beams (Springer-Verlag, Berlin, 1992), p. 253] and M. B. Porter [J. Acoust. Soc. Am. 96, 1918–1921 (1994)], are compared with respect to their accuracy and domain of validity assuming small and smooth variation of mode propagation constants characteristic of underwater acoustic waveguides. Perturbation theory for horizontal (modal) rays and dynamic ray tracing are used in the analysis. A new approximate expression for the adiabatic mode amplitude in 3-D problems is derived that requires environmental information only along source–receiver radial and possess higher accuracy than previous formulations. The domain of validity of the result is determined in terms of horizontal gradients of environmental parameters. Mode phase corrections due to horizontal ray curvature are evaluated. Implications on applicability of the uncoupled azimuth approximation for sound propagation modeling in a horizontally inhomogeneous ocean are discussed. [Work supported by NSERC.]
Channel characterization using FSK wave forms
Authors: McDonald Vincent K. , Rice Joseph , Green Dale
Published: July 2002

Automatic characterization of underwater acoustic communication channels can support connectivity over a wide range of operational ocean environments. With quantitative measures of the prevailing channel, adaptive modems may optimize the modulation and initialize the demodulation equalizer. A novel channel-estimation technique involving noncoherent processing of received FSK wave forms has been described recently by Green and Rice (Proc. IEEE Oceans’98) and Rice and Green (Proc. MTS Ocean Community Conference, 1998). This technique uses received handshake signals to measure temporal and spectral spreading and signal excess directly, and to estimate coherence parameters. This effort will focus on applying this channel-estimation technique to received and autonomously recorded 8–13 kHz MFSK signals using shallow horizontal channels. [Work supported by ONR 32 and SPAWARSYSCEN.]
Colored-noise performance of the order-truncate-average-ratio (OTAR) filter
Authors: Shapiro Jeffrey H. , Green Thomas J.
Published: July 2002

Spectrogram background normalization for narrow-band passive acoustic detection systems has a long history. This presentation addresses a more complicated scenario in which broadband background whitening is still desired, with simultaneous preservation of intermediate-bandwidth spectral features and suppression of narrow-band interference. Toward this end, a nonlinear processor—the order-truncate-average-ratio (OTAR) spectral filter—is presented and analyzed. While much is known about order statistics, closed-form expressions for the mean and covariance of the output of this filter appear to be unattainable. However, for white Gaussian noise-input time-series with no spectral averaging (conditionally exponential spectral statistics), approximate expressions for the output mean and covariance have been derived. Moreover, for scenarios employing spectral averaging on colored Gaussian noise-input time-series, expressions for the output mean have been derived. All of these analytical results agree well with simulation of the OTAR filter. The analysis has been applied to evaluate an appropriate transfer function for the filter and to illustrate a number of other interesting properties. [Work supported by SPAWAR, under Air Force Contract F19628-95-C-0002.]
Psychoacoustic measurement of roughness of vehicle interior noise
Authors: Pflueger Martin , Hoeldrich Robert , Brandl Franz , Biermayer Werner
Published: July 2002

In analyzing vehicle interior noise there exists hardly any correlation between the subjective impressions of test persons and available roughness parameters. It has become necessary to develop a new roughness model for these sounds and to set up a subjective database as a basis for the analytical description of interior noise quality. This paper focuses on psychoacoustical experiments for the assessment of roughness by using different methods and different kinds of vehicle interior sounds. The analysis of the results shows that small experimental manipulations lead to a large variety of different results. The different meanings of the word roughness have to be taken into account. Each person has his or her own interpretation of roughness differing between the phenomena of roughness, r-roughness, rumble, fluctuation strength, etc. Another important point is the reduction of accidental influences of psychoacoustical parameters, like, for example, the influence of loudness on the perception of roughness. By using a special headphone–subwoofer playback system in the laboratory, it is possible to achieve ratings comparable with field experiments. As reported in a companion paper, a new generalized psycho- acoustical model of modulation parameters was successfully tested with the obtained roughness rankings.
Sound power measurements at low frequencies
Authors: Schaffner Albert
Published: July 2002

The sound power level of a sound source is usually determined by sound intensity or sound-pressure measurements either in a free-field environment or in enclosures. Although these measurements provide good comparable results for the middle- and high-frequency range, there are large discrepancies at low frequencies. Using the sound intensity method as reference, it can be shown that these discrepancies are systematic. In the case of measuring sound pressure in a free field, they are due to the near-field error depending on the distance of the measurement surface to the source. Measuring sound pressure in enclosures—especially in rooms with hard walls—interference effects cause a change in the sound power output of the source, depending on the distance of the source to the room boundaries. The effects described above have been investigated theoretically and the results have been confirmed by accurate measurements.
Perception and meaning of warning signals in urban contexts
Authors: Vogel Corsin , Polack Jean-Dominique , Castellengo Michele , Dubois Daniele
Published: July 2002

Perception of warning signals in urban context points out the question of their efficiency with regard to the citizens. Efficiency of warning signals can be described in terms of their meaning for persons who are concerned with. Indeed, subjects can adequately react to the signals only if these latter are identified, that is, only if the signals make sense to the subjects. Therefore, information about mental representations of citizens exposed to warning signals is necessary. An experiment was realized involving 15 signals mixed with two different urban contexts: steady traffic noise and public park ambience. Results show that the two contextual constraints influence the perceptual thresholds of the warning signals as well as their identification. Warning signals can be classified with respect to their different meanings in different urban contexts. Especially, it appeared that signals having an identical semantic description nevertheless may present very different acoustical properties. The classes of signals obtained with the psychological description are a way to determine new acoustical features related to the meaning of warning signals, and so to their efficiency.
Measurements of the acoustic absorption coefficient of double-layer asphalts: Analysis of variability
Authors: Casini David , Fagotti Cesare , Poggi Andrea , Secchi Simone
Published: July 2002

The measurements of the acoustic absorption coefficient were carried out on two kinds of double-layer asphalt located in an urban environment. Three different methods of analysis were used: pseudorandom MLS signal, intensimetry, and Kundt’s tube. The measurements with MLS signal were done with a loudspeaker 3-m high and a 1/2-in. microphone 1.5 m above the asphalt. The absorption coefficient has been obtained by the deconvolution of the MLS signal. In the analysis with the Kundt’s tube, the transfer function method was used on an asphalt core sample (10-cm diameter) extracted ‘‘in situ.’’ Two layers, respectively, 2.5 and 5 cm thick, with different granulometry, composed the first asphalt analyzed. In the second asphalt, the superior layer has a larger granulometry. All the results obtained with the different measurement techniques point out a major absorption peak around 630 Hz and a secondary peak around 2000 Hz, for the first asphalt, and 500 and 4000 Hz for the second asphalt. The measurements point out a large variability of the results obtained in different sections of the road. Variation with asphalt’s composition and measurement uncertainty is analyzed.
A progress report on E. C. proposed noise mapping
Authors: Hinton John
Published: July 2002

As an integral part of the development of a framework directive for the assessment and reduction of environmental noise, the European Commission has set up five working groups on the perception of noise. Working Group 4 (W.G.4) is investigating noise mapping techniques and is required to produce a position paper for the E. C. giving guidelines for effective noise mapping. It is now widely accepted that the provisions of mapping information is essential to a process designed to reduce exposure of citizens throughout Europe to unacceptable levels of environmental noise. This will be achieved by providing the public and politicians with information on the scale of the problems that are faced and by providing decision makers at local, regional, national, and European level with the information they require to develop action plans for noise reduction. Mapping will also provide a means of monitoring the implementation and effectiveness of such plans. W.G.4 held its first meeting just prior to the Invitational Conference on the European Unions Future Noise Policy held in Copenhagen in early September 1998. The paper will provide a progress report of W.G.4.
Acoustic investigation of a vorticity filament using time-reversal mirrors
Authors: Manneville Sébastien , Maurel Agnès , Fink Mathias , Bottausci Frédéric , Petitjeans Philippe , Weisfred Eduardo
Published: July 2002

A new experiment of a filamentary vortex in water characterized by ultrasound is presented. The flow is generated by two corotating discs in an infinite medium, and suction can be applied at the center of the discs. Acoustic time reversal mirrors [see Roux et al., ASA Proc. 1433 (1998)] provide dynamical, nonintrusive, and global measurements of the vortex characteristics. Three different regimes are observed depending on the control parameters (distance between the discs, rotation frequency of the discs, and suction flow rate): (1) a regime of stable, stationary vortex where the velocity profile is compared to the Burgers model and scaling laws are investigated when varying the control parameters, (2) a regime of intermittency with cycles of vortex breakdowns, and (3) a domain where the vortex never shows up.
Production of free radicals in ultrasound fields
Authors: Price Gareth J.
Published: July 2002

It is well known that a major consequence of cavitational collapse in liquids is the production of highly reactive chemical species such as free radicals. These can be used to perform useful chemistry, although in some cases they can be undesirable byproducts of a reaction. A series of trapping techniques to study radical formation in organic and aqueous systems has been developed. These include the use of UV/visible, fluorescence, and electron spin resonance spectroscopies. The paper will describe the methods and give some results to demonstrate the effects of varying the experimental conditions on radical formation. Examples will be taken from synthetic chemistry, from polymerization reactions, and from aqueous solutions (including biomedical ultrasound sources) to illustrate the factors of importance and the implications of the results for these processes.
Kinetics of halogenated organic compounds degradation by ultrasound
Authors: Hung Hui-Ming , Colussi A. J. , Hoffmann M. R.
Published: July 2002

The kinetics of degradation of CH2Cl2, CHCl3, CCl4, C2Cl4, C2Cl6, CH3CCl3, and CHCl2CH2Cl as induced by ultrasonic irradiation in Ar-saturated solution at frequencies of 205, 358, 618, and 1078 kHz were investigated. Optimal degradation rates were obtained at 618 kHz. At the same frequency, the degradation rate constants for the chlorinated hydrocarbons increases with their Henry’s law constants due to the enhanced rectified diffusion. A quantitative analysis of rectified diffusion from Eller–Flynn’s model within the framework of recently developed sonochemical observations is able to account for the experimental results [T. G. Leighton, The Acoustic Bubble (Academic, New York, 1994), pp. 379–438]. The model predicts a sonochemical reaction efficiency of about 20% for these halogenated hydrocarbons. [Work supported by ONR and Argonne National Laboratory.]
Determination of porous material data via two-port measurements
Authors: Abom Mats
Published: July 2002

The classical model used to describe porous materials of fibrous type is the so-called equivalent fluid model. For typical fibrous materials this model is valid except for low frequencies where solid frame vibrations become important. Since porous materials are widely used in dissipative silencers, the trend for better and better modeling requires a good knowledge of acoustic data for such materials. This means that a complete characterization is necessary to provide input data for, e.g., FEM or BEM codes. As known from theory, this is possible by specifying the complex wave number (Ka) and complex characteristic impedance (Za) for a propagating plane wave. Of course, for a nonisotropic material, these data must be measured in more than one direction. The standard technique to determine Ka and Za is to use a standing wave tube and measure the complex impedance for two samples of different thickness. In this paper an alternative approach is suggested based on the measurement of the acoustic two-port for a single sample mounted in a duct with plane wave propagation. The paper describes the development of such a two-port test rig and discusses the advantages compared to earlier used techniques.
Atmospheric sound propagation: Application to the case of aircraft landing and take off
Authors: Cremezi Cora , Legros Claude P.
Published: July 2002

Atmospheric sound propagation has been studied for a long time in the case of source and receiver close to the ground. In the case of an elevated source, studies are scarce and influence of the different propagation effects has not been studied in detail. As transport noises become more and more of a great concern, and among other, aircraft noise around airports, it is necessary to study what phenomena really happen. In aeronautics, this knowledge could initiate new thoughts about noise indices. This study is characterized by a great number of parameters (meteorology, source characteristics, atmosphere) and the main difficulties lie in difficult meteorological condition knowledge and aircraft flight condition uncertainties. A simple ray tracing has shown creation of shadow areas, caustics, and source height influence on propagation, according to meteorological profiles. Then, a more complete propagation model based on a parabolic equation method has been developed. It takes into account aircraft movements, considering an infinite number of fixed sources to represent the flyover. The model and some preliminary results are presented while an experimentation is going on to validate it better. Once validated, it should allow the estimation of noise level probabilities according to meteorological probabilities.
Calculation of sound reduction by a thick noise barrier in downwind conditions
Authors: Forssén Jens
Published: July 2002

The downwind propagating sound field from a monopole source is solved by applying a Hankel transform in a stratified medium, according to the method by Rasmussen. The influence of the noise barrier is calculated using the equivalent source method with ring sources of zero order placed inside the fictious surface of the barrier. At the surface the boundary condition is fulfilled by choosing the correct amplitudes of the equivalent sources. The total field is then calculated as the sum of contributions propagated downwind from both the original source and the equivalent sources.
Infrasound detector design for recording sonic booms and events of CTBT interest
Authors: Haak Hein , Evers Läslo
Published: July 2002

The Royal Netherlands Meteorological Institute (KNMI) is involved in a project concerning the detection of nuclear explosions and sonic booms. The main area of research and development is concerned with the infrasonic instruments. This includes the pressure sensor, electronics, and the noise-reducers. An optimal array-layout is necessary, next to a suitable instrument, to succesfully record infrasonic events. Therefore, the theoretical design of the array and practical implementation at Deelen are of main concern for the acquisitional part of the project. Once data are recorded, the data processing and interpretation has to be done. An on-line data analyses tool was developed to distinguish an infrasonic event from noise and other useless signals. The instruments are based on the Validyne Differential Pressure devices. To create an instrument sensitive in the 0.01–100 Hz frequency range, several constructional efforts were made p.e. acoustic capillary, backing volume, and signal inlet volume. The signal inlet volume is coupled to a noise-reducer, porous hoses or pipes. The symmetrical layout of the hoses/pipes guarantees an improvement in signal-to-noise ratio through spatial integration. The array of 16 microbarographs has an apeture of 2 km. Array techniques, i.e., slowness analyses, were applied to determine the most optimal layout.
Effects of instantaneous phase shifts and gap duration on pitch of unresolved complex tones
Authors: White Louise J. , Plack Christopher J.
Published: July 2002

Introducing a phase change between two short bursts of a sinusoid can produce a pitch shift which corresponds to a shift in the peak of the long-term spectrum [I. V. Nabalek, Acustica 82, 531–539 (1996)]. The present experiment examined this effect with a complex tone consisting of unresolved harmonics where the phase change was applied to the envelope of the complex. The hypothesis that a long-term pitch mechanism sensitive to envelope phase is reset in response to a discontinuity in the stimulus was tested: The stimulus was an unresolved complex tone consisting of the harmonics of a 250-Hz F0 filtered between 5500 and 7500 Hz. Two 20-ms bursts separated by short gaps were presented; the starting phase of the first burst, the phase between the bursts, and the duration of the gap were varied. A pitch-matching paradigm was used. If the gap between the bursts causes the mechanism to reset, the resetting hypothesis predicts that a phase manipulation of the second burst will not alter the pitch of the complex. Pitch shifts were obtained which do not support a resetting hypothesis, but rather a mechanism in which the mean pulse rate is used to determine pitch.
Acoustic pressure radiated by a vibrating body in the high-frequency domain
Authors: Landel Eric , Blanc Patrick , Loyau Thierry
Published: July 2002

To develop methods of predicting radiated noise that can be used in design offices, it is essential to formulate hypotheses to simplify the general problem. The expression of the acoustic presssure autospectrum for quasiplane surfaces in far field is used, obtained from the Green’s function, which depends on: the Green’s function, the cross-spectral density function of the normal acceleration on the body. The spatial distribution of the vibrational field on the vibrating body is, in an industrial context, very difficult to obtain, as it would require too many measurement points. It is therefore necessary to approximate it, and to this end it is assumed that: the vibrating body can be approximated by a combination of elementary surfaces; these surfaces are thin plates; the energy of each mode is uniformly distributed in a given frequency band. Once the vibrational field has been characterized in this way, it is possible to deduce the acoustic radiated pressure. A number of validation tests were carried out, which demonstrated close agreement between the computed and experimental data in the two following cases: a baffle plate and a box.
Finite panel sound radiation through an absorbent layer
Authors: Sarradj Ennes
Published: July 2002

It is often required to predict the sound radiated from a vibration through an absorbent layer (trim). Statistical energy analysis may be applied in such a case. The required radiation coupling loss factor is estimated from the radiation efficiency. To get the radiation efficiency for the trimmed panel, that of the panel (into air, without trim) is combined with the transmission loss of the absorbent layer to give a corrected radiation efficiency. Although this procedure is quite straightforward, it may produce poor results. An alternative and more accurate procedure for the estimation of the radiation efficiency is presented. The absorbent layer is fully considered in the calculation, which is done using a wave number integration technique. The results from both methods show remarkable differences.
Low-frequency (ka<10) monostatic scattering and elastic wave generation produced by end insonification of homogeneous, finite rods (l/a=8)
Authors: Yoder Timothy J. , Bucaro Joseph A. , Houston Brian H.
Published: July 2002

A parametric study of the low-frequency (ka<10) monostatic scattering and elastic wave generation produced by end insonification of homogeneous, finite rods (l/a=8) as a function of their material parameters (density, Young’s modulus, and Poisson’s raito) is presented. The monostatic scattering and surface displacement are calculated via finite/boundary elements (verified through experiments performed by Laboratory for Structural Acoustics at NRL) as a function of the rod’s material parameters. These parameters are slowly varied to show the acoustic transitions that occur between rods composed of different materials. One backscattering feature is of particular interest because its amplitude is large and it only occurs for certain materials. The appearance (and disappearance) of this highlight can be used for material identification and is explained by the behavior of the fluid-loaded longitudinal wave dispersion characteristics of the rod. The dispersion characteristics are calculated [P. B. Nagy, J. Acoust. Soc. Am. 98, 454–457 (1995)] and compared to the dispersion found by transforming the surface displacement calculated via finite/boundary elements. This comparison identifies the elastic waves generated on the fluid-loaded rod and is ultimately used to identify the cause of the large backscattering feature.
Measurements of the condition of compliant coatings for prediction of acoustic performance
Authors: Doane John W. , Jarzynski Jacek
Published: July 2002

The goal of this work was to develop a system and analysis procedure for measuring the material properties of a viscoelastic polymer slab. This is accomplished by exciting a transient acoustic wave in the slab which has been bonded to a steel plate and observing the wave’s propagation along the surface of the slab. This propagation is modeled numerically and an iterative analysis process yields the properties of interest. The system is a scanning laser Doppler vibrometer which is capable of measuring the particle velocity on the surface of a reflective target. The scanning feature allows for data to be taken rapidly at a number of locations via a computer-driven algorithm which also digitizes and stores the data for post-processing analysis. There are two numerical models developed for this problem, one based on geometrical ray acoustics and the other based on inverse Fourier and Hankel transform methods. The ray model is developed to give a quicker and relatively simpler way of investigating the physics of the problem whilst the inverse transform method gives a more robust and detailed method for analyzing the peculiarities of the problem.
Acoustic emission model for a thin circular plate with large deflections
Authors: Enescu Nicolae , Bugaru Mihai , Predoi Mihai V.
Published: July 2002

This paper presents a model for the acoustic emission of a circular plate, in the domain of large deflections. The thin circular plate is considered homogeneous, isotropic, and fixed on the boundaries. In the hypothesis of large displacements, the nonlinear von-Karman dynamic model was adopted. The external action is periodic and axisymmetric. An approximate analytical method was developed, based on the Kantorovich method and the asymptotic method, to compute the dynamic response of the plate. Starting from the characteristic parameters of the nonlinear vibrations of the plate, a model of acoustic emitter based on the Rayleigh formulation was developed, to obtain the acoustical pressure and the spatial directivity characteristic. Experimental tests were developed in an anechoic chamber, in order to confirm the model. The physical model of the plate consists of a circular frame having a high rigidity and a brass plate of 0.2-mm width. In the transverse direction, passing through the mass center of the plate, it acts as an excitatory device and the acoustic emission of the plate is analyzed. In this way, the natural frequencies of the plate and the spatial directivity characteristic have been determined and a satisfactory agreement with the theoretical results has been found.
The acoustic power radiated by a circular plate hanged articulately
Authors: Rdzanek W. J.
Published: July 2002

Radiation of the acoustic wave by vibrating planar circular plate, hanged articulately into a planar rigid infinite baffle is considered. Axially symmetric, harmonic in time vibrations are investigated. Frequency characteristics of radiated real power are determined. There is achieved the comparative analysis of the real power in the case of articulated hanging of the plate and radiated power by a plate with a rigidly fixed edge.
Voiced–unvoiced classification for recognition of stop consonants
Authors: Krishnamoorthy Mahesh , Yuk DongSuk , Dayanidhi Krishna , Chennoukh Samir , Sinder Daniel , Flanagan James
Published: July 2002

Significant error in stop consonant recognition is caused by the confusion between voiced stop consonants and their unvoiced counterparts. The recognition is based on HMM’s which use 12 MFCC’s and energy with their time derivatives. The voicing state is the distinctive feature of homorganic stop consonants. According to recognition error-rate analysis, it seems that the cepstral feature does not accurately represent the voicing state of the modeled phone. For this purpose, a voiced–unvoiced classifier in conjunction with HMM’s is proposed to improve the recognition of stop consonants. The recognition is done in two passes. In the first pass, a phone recognizer uses well-trained HMM’s to identify a stop consonant. This pass provides the recognized stop consonant in addition to the log probability. In the second pass, the voiced–unvoiced classifier checks if the voicing state of the phone segment matches with its phonetic description. In the case of mismatch and low probability of recognition, the voiced (unvoiced) consonant is swapped with its corresponding unvoiced (voiced) counterpart. Recognition results are presented in terms of error rate, using different techniques of voiced–unvoiced classification. This method reduces the recognition error rate of stop consonants. [Research supported by DARPA Contract Nos. DABT63-93-C-0037, N66001-96-C-8510, and NSF Contract No. IRI-9618854.]
Speech segmentation and the use of sequential phonological constraints
Authors: Olivier Crouzet , Nicole Bacri
Published: July 2002

Previous experiments [Crouzet (1997); Vroomen and De Gelder (forthcoming)] led to the claim that constraints on legal and illegal consonant clusters may help to segment the speech signal. Two paradigms (word spotting and phoneme monitoring in nonwords) are contrasted in order to get a better understanding of (1) whether the previous results were actually linked to early phonological processes, to lexical competitions, or to distributional constraints and (2) whether the legality status of consonant clusters should be understood as the application of an abstract phonological knowledge on an already deciphered phonemic string or as a disruption of a speech rhythm that would increase the perceptual prominence of sound sequences and that could consequently take place before phonemic coding has been accomplished. The results of the word spotting experiment allows the argument that the effect should be interpreted in terms of phonological constraints. However, in the phoneme monitoring experiment, the reversed effect was observed. This fact could lead to the rejection of the speech rhythm disruption hypothesis. The phoneme monitoring task could not be relevant yet to investigate this issue and the use of another paradigm (speech perception in noise) that would be more appropriate is proposed.
The acoustic front-end of the FUL speech recognition system
Authors: Reetz Henning , Lahiri Aditi
Published: July 2002

The featurally underspecified lexicon (FUL) speech recognition system converts the incoming speech signal into hierarchically organized monovalent phonological features in an early processing stage without identifying segments. After this conversion, only the presence of these features is used to access items from a 100000 word dictionary which contains featural, segmental, morphological, and semantic information. The extraction of these features from the acoustic signal is based on standard LPC analysis for vowels, semi-vowels, and liquids, and from spectral shapes of DFT spectra for other sounds. Acoustic criteria for these features are only broadly specified to allow a wide range of speaker and dialectal variation. Most features are generated online from the signal without any further delay other than the width of the spectral windows. Only the feature [abrupt] uses some contextual temporal information.
Use of temporal envelope cues for the recognition of words and phonologically significant contrasts
Authors: Kishon-Rabin Liat , Nir-Dankner Michal
Published: July 2002

The goals of this study were: (1) measure the recognition of words and speech pattern contrasts using temporal cues only, and (2) to evaluate the effect of training on the ability to perceive segmental, suprasegmental, and phoneme information from the speech waveform only. Fifteen subjects, 20–40 years of age, with normal hearing, were tested before and after extensive training. Test stimuli consisted of: (a) eight segmental and two suprasegmental contrasts of the SPAC test using a binary forced-choice paradigm, and (b) monosyllabic words from the isophonemic AB word lists presented in open set. Spectral information was eliminated by multiplying the speech waveform with white noise using commercially available array processing software. Testing and training were under computer control. Preliminary results suggest that: (1) intonation and stress are perceived well using temporal information only, (2) manner is perceived better than either place or voicing contrasts, (3) training improves the perception of speech using temporal cues only, and (4) there is a strong correlation between speech pattern contrasts as measured in open and closed set paradigms. The findings will be discussed in relation to the relative importance of the stimuli’s spectral and temporal cues and their relevance to clinical data of individuals with profound hearing loss.
Do harmonic consonant clusters in Georgian have only one release?
Authors: McCoy Priscilla C.
Published: July 2002

It has been claimed that in Georgian, a language in the Kartvelian or South Caucasian family of languages, harmonic consonant clusters have a single release. To examine this claim, different constituencies and orderings of harmonic consonant clusters and nonharmonic consonant clusters were recorded and analyzed in order to (1) assess the phonetic reality of the initial claim; and (2) compare durations of cluster releases and whole cluster segments in nonharmonic environments to those, if any, exhibited in harmonic environments. Preliminary results of the relative distribution of release durations across these two groups illustrate an interesting division of release and cluster duration figures and (2) show a possible positive correlation of a sonority hierarchy [G. N. Clements, ‘‘The role of the sonority cycle in core syllabification,’’ in Between the Grammar and Physics of Speech, edited by J. Kingston and M. E. Beckman, Papers in Laboratory Phonology 1 (Cambridge U.P., Cambridge, 1990)]. This also builds on previous work on Georgian consonants and their relationship to a sonority hierarchy by McCoy [1995]. The implications for consonant clusters and Georgian phonology are investigated, which in turn suggests some phonological priorities in Georgian.
The relevance of F4 in distinguishing between different articulatory configurations of American English /r/
Authors: Espy-Wilson Carol Y. , Boyce Suzanne
Published: July 2002

American English /r/ is often cited as a segment exemplifying a many-to-one articulatory to acoustic relationship. Articulatory data show a continuum of vocal tract configurations for /r/, ranging from ‘‘retroflexed’’ to ‘‘bunched,’’ all involving three constrictions: (1) in the pharynx, (2) along the palate, and (3) at the lips. Researchers have noted, however, that all of these configurations result in similar acoustic profiles, at least for F1, F2, and F3. In this study, acoustic and articulatory data were used to investigate the mechanisms which determine the shape of the F4 trajectory for /r/. Articulatory positioning data and simultaneous acoustic data were collected from five subjects who said the phrase ‘‘Say warav for me.’’ The Electromagnetic Midsagittal Articulometer (EMMA) system was used to record the positions of three points on the tongue. Preliminary analysis based on the y position of the front, mid, and back transducers suggests that the behavior of F4 changes with different /r/ configurations and that the frequency of F4 is based on the length of the cavity between the palatal and pharyngeal constrictions.
Perceptual vowel spaces derived by computer game
Authors: Miller James D. , Heidbreder Arnold F. , Wyzinski Nicole N.
Published: July 2002

A same–different task embedded in a computer game is used to obtain latencies of responses to vowel pairs. The ‘‘player’’ responds as fast as possible when the sounds in a pair are different and is not to respond when they are the same. The game concept and computer program were originally developed by K. Manabe and R. Dooling of the University of Maryland. Vowel sounds /i,ae,a,u/ were synthesized with interformant valley depths of 9, 18, 36, and 99 dB. All vowels were equalized in loudness based on balances made by four normally hearing listeners. Five listeners, two with normal hearing, two hearing-aid users, and one cochlear-implant user were tested four times, once at each valley depth. The logarithmic mean latencies for each different pair were taken as similarity measures for multidimensional scaling (mds). Average latencies decreased with increasing valley depths. For the two normally hearing listeners and one of the hearing-aid users, the perceptual vowel spaces derived by mds looked like the vowel equilateral, and the intervowel distances correlated highly with distances in Millers Auditory Perceptual Space. For one hearing-aid and the cochlear-implant user the vowel spaces were abnormal in appearance. Individual results will be presented.
Perceptual consequences of unintended epenthetic stops
Authors: Warner Natasha , Weber Andrea
Published: July 2002

In many languages, historically an epenthetic stop has appeared between a nasal and a fricative or a nasal and another stop, as /p/ in English ‘‘empty’’ (from earlier ‘‘œmtig’’). Ohala [Phonetica 52, 160–170 (1995), and in press] proposes an articulatory explanation for epenthesis involving listener misperceptions. Ohala predicts that epenthetic stops will match the place of articulation of the preceding nasal. The current study investigates listeners’ perception of epenthetic stops. A speaker produced nonsense words ending in nasal stop sequences, such as /flg@mk, tuloLp/ from orthographic representation. Thus the speaker did not intend to produce epenthetic stops [(floKmpk, tuloLkp)]. Listeners monitored for /p/ or /k/. Listeners perceived a /p/ significantly more often after labial nasals (more /p/ responses to /mk/ final words than to /nk/ and /rhookn k/ final words, p<0.0001), and perceived /k/ significantly more often after velar nasals (more /k/ responses to /loLp/ final words than to /mp/ and /np/ final words, p<0.0001). Tokens with epenthetic stop bursts (acoustic analysis) received the most responses. These results provide experimental verification of the proposed articulatory and perceptual origins of epenthetic stops: listeners perceive stops the speaker did not intend, predominantly in environments where the articulatory explanation predicts epenthetic stops to occur.
Active noise control experiences on a GT high-speed car
Authors: Sollo Antonio , Paonessa Antonio , Lecce Leonardo , Viscardi Massimo
Published: July 2002

The presentation will show some results of an extensive experimental work aimed at the reduction of the engine noise inside the binnacle of a GT high-speed car. The car is completely made by carbon fiber and the engine is rigidly attached to the body and for this reason the vibrations of the engine are directly transmitted inside the binnacle, thus producing very high noise levels in all the oeprating conditions. Preliminary laboratory experiments were made by simulating the noise in the cavity by means of different loudspeakers and a first configuration of the ANC system was optimized. This last included some speaking panels driven by several piezoceramic patches elastically suspended from the roof. The laboratory results were encouraging, and the measured noise reductions were sensible even if the simulated primary field was scaled down due to the nonlinear behavior of the speaking panels at high driving voltages. The second step of the work consisted in optimizing a second configuration of the ANC system which was using two control microphones for each seat and two loudspeakers for each seat, located near passenger heads. The control unit was capable of following seven different engine orders and thus following the rapid changes of the noise field. The results were impressive and very good noise reductions have been measured on the road at different operative conditions (both stabilized and in acceleration).
Active noise within the generating/pumping groups of a large hydroelectric plant
Authors: Lecce Leonardo , Viscardi Massimo , Maja Bruno , Limone Vincenzo , D’Ischia Mario , Di Maso Francesco
Published: July 2002

This work is related to a feasibility study for the implementation of an active noise control system to reduce the hydraulic turbomachine’s noise in the Presenzano power plant. Previous studies showed that interested turbines are low frequencies noise sources, generating pure tones at 150 and 200 Hz (third and fourth harmonics of the turbine’s BPF). At these frequencies passive noise control systems are ineffective in front of relevant costs and an active approach was so decided to be tested. In accordance with a classical architecture, the preliminary system was composed of four error microphones, four secondary noise sources, and a digital controller implementing an adaptive digital filter. Main performed activities could be identified through four successive steps: (i) analysis of the turbomachine’s generated primary field levels and space distribution, (ii) secondary sources generated noise field measurement, ten different loudspeakers locations were investigated at this stage; (iii) sensor and actuator locations’ optimization by the use of a genetic algorithm’s procedure, and (iv) active noise control tests. A mean reduction of 15 dB at 150 Hz and 7.5 dB at 200 Hz was measured at the error sensors during these tests, revealing the good opportunities of such an approach but also the opportune improvement to pass at a practical implementation.
Maintenance of adaptive strategies to oral-articulatory perturbations
Authors: Baum Shari R. , McFarland David H.
Published: July 2002

The present investigation examined whether speakers would adapt to a palatal perturbation in [s] production subsequent to focused practice, and whether the compensatory motor programs developed would be immediately available after a short period of rest. The fricative [s] was produced in three vowel contexts [si sa su] with and without a specially designed artificial palate in place at three time intervals: at the onset of the experiment, after a one-hour period of [s]-intensive practice with the palate in place, one hour later after a period of rest without the palate in place. Recordings of [š] under normal speaking conditions were also made at each time interval to examine any potential carryover effects. Preliminary analyses revealed that centroid frequencies of the [s] productions were significantly lower in the perturbed condition relative to normal upon first insertion of the palate. After the practice period, centroids in the two conditions more nearly approximated one another. However, after a rest period, speakers’ fricative productions were again impaired by the presence of the artificial palate. Results are discussed in relation to the development and retention of adaptive articulatory programs in speech motor control. [Work supported by NSERC.]