bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring attitudes toward co-workers affected by hearing loss in noisy industry
Authors: Hétu R. , Getty L. , Philibert L. , Beaudry J.
Published: October 2005

Previous studies have shown that the attitudes of hearing workers toward their hearing-impaired colleagues strongly contribute to the handicap associated with occupational hearing loss (OHL). In order to characterize such attitudes, a questionnaire has been designed. In phase I, a preliminary version of 45 items was equally divided into measures of beliefs, attitudes and reported behaviors toward co-workers affected by OHL. Answers from 176 workers from a metal products plant allowed to identify discriminative items that belonged to an appropriate factorial structure. In phase II, answers from 125 miners to a second version of the questionnaire, comprising 32 items, permitted further refinements. The final version was tested with 283 workers from three metal products plants, with a response rate of 86%. Answers on the scale measuring beliefs showed that noise-exposed workers did not know many of the consequences of OHL. Attitudes toward hearing impaired co-workers were generally favorable, but this finding appeared to reflect a strong social desirability bias. Reported behaviors indicated that a majority of workers are not inclined to adopt conducts that favor communication with victims of OHL. These findings offer useful clues for developing an awareness raising program on the consequences of OHL. [Work supported by IRSST.]
Effects of high-intensity impulse noise on the hearing of humans wearing hearing protection
Authors: Patterson James H. , Johnson Daniel L.
Published: October 2005

Current exposure limits for high-intensity impulse noise are based on very limited amounts of data. This study was undertaken to provide new data on the effects of a variety of impulse noises on humans exposed while wearing hearing protection. The impulses used in this study were produced by detonation of explosive material. Two types of impulses were used. One had an A duration of approximately 3.0 ms, while the other had an A duration of approximately 0.8 ms. Exposures were presented at one impulse per minute. The results of the long duration impulse have been presented previously. This presentation focuses on the short duration impulse. Sixty-five volunteers were exposed on successive days to six impulses with intensities ranging from 178 to 196 dB SPL for the shorter impulse. The number of impulses then was increased from 6 to 100 at the tolerable level. The results indicate that minimal hearing protection is adequate for 6 of the 0.8 impulses up to 196 dB SPL. It was inadequate for 12 or more impulses at 193 or for 50 or more impulses at 190 dB SPL. Protection is adequate for 50 impulses at 187. Hearing protectors which provide more attenuation were adequate for all conditions used in this study.
Micrometeorological effects on line-of-sight acoustic propagation
Authors: Maniet Edward R.
Published: October 2005

Experimental studies investigated the effects of atmospheric surface-layer convective turbulence on the amplitude fluctuations of line-of-sight sound propagation. Several pure tones between 25 and 125 Hz were continuously monitored at a distance of 758 m for periods of 4 to 6 days by two microphones at heights varying between 0 and 8 m. Simultaneous surface-layer micrometeorological measurements were made at the same site. Statistics of the acoustic transmission loss (TL) were analyzed along with the sensible heat flux (Q), a measure of the strength of convectively driven turbulence. It was observed that only the lowest studied frequency, 27.6 Hz, showed any dependence on the value of the sensible heat flux. The average standard deviation of the TL for the 27.6 Hz tone was twice as great under strongly convective conditions than under conditions with weak or no convection. It is suggested that turbulent static pressure fluctuations associated with surface-layer thermal plumes were responsible for the increased TL variability at 27.6 Hz.
Prediction of the sound-speed profiles and the index of turbulence associated with various meteorological conditions
Authors: L’Espérance A. , Gabillet Y.
Published: October 2005

Sound propagation over the ground is greatly influenced by the sound-speed profiles and the atmospheric turbulence, and there exist a number of models taking these effects into account. However, for practical outdoor sound propagation studies, it appears to be unrealistic to measure the effective sound-speed profiles (SSP) and turbulence index 〈μ2〉 to obtain acoustical predictions. For a complete prediction model, these parameters should therefore be estimated from general atmospheric conditions. To fulfill the needs of acoustical prediction models, a meteorological model was developed to estimate SSP and 〈μ2〉. This model is based on estimations of the roughness length and the Monin–Obukhov length, which define the shape of the wind-speed profiles, temperature profiles, and the index of turbulence [Panofski and Dutton, AtmosphericTurbulence (Wiley, New York, 1984)]. The roughness length is estimated according to the surface of the site, and the Monin–Obukhov length using an empirical relation proposed by Golder [Bound. Layer. Meteorol. 3, 47–58 (1972)]. To verify the precision and the limitation of this model, the theoretical SSP and 〈μ2〉 were compared to experimental results for various meteorological conditions. These comparisons show the capability and the limitation of this meteorological model, which may limit the accuracy of a complete acoustical prediction scheme.
A numerical study of sound propagation through a turbulent atmosphere
Authors: Juve Daniel , Blanc-Benon Philippe , Chevret Patrick
Published: October 2005

A numerical simulation of the effect of turbulent conditions on the propagation of acoustic waves in the atmosphere has been developed. The turbulence is represented as a set of realizations of a random field generated by a limited number of random Fourier modes [Karweit etal., J. Acoust. Soc. Am. 89, 52–62 (1991)]. Through each individual realization, the acoustic pressure field is computed in the parabolic approximation. Ensemble averaging is thus performed to obtain the statistical properties of the field: mean level, standard deviation of the fluctuations, probability density functions, etc. Results will be given in particular for upward refracting conditions, when turbulence diffracts sound into the deterministic shadow zone.
On the aging of sonic booms
Authors: Plotkin Kenneth J.
Published: October 2005

Sonic boom minimization exploits the shaping of nonasymptotic ‘‘mid-field’’ signatures of large aircraft [F. E. McLean, NASA TN D-2877 (1965)]. This is assisted by the ‘‘freezing’’ effect of downward propagation in the real atmosphere [W. D. Hayes and H. L. Runyan, Jr., J. Acoust. Soc. Am. 51, 695–701 (1971)]. Cleveland and Blackstock [J. Acoust. Soc. Am. 92, 2331 (A) (1992)] have recently shown that true freezing occurs for flight altitudes in excess of 80 000 ft. Recent studies of boom minimization, however, show greater success at much lower altitudes, and that shaping is increasingly more difficult at higher flight altitudes. Parametric analysis of the age parameter with regard to altitude and distance shows that successful minimized booms are not close to asymptotic freezing, and that ‘‘freezing’’ is not necessarily the best perspective. There is concern that increasing flight altitude as fuel load decreases might put a low-boom aircraft design into an off-design condition of higher boom. It is shown that, for realistic flight profiles, the increased age parameter is more than offset by reduced weight, so that sonic boom loudness will decrease throughout supersonic cruise.
Acoustic impedance of porous pavements: Comparison between a microstructural and a phenomenological model
Authors: Bérengier Michel C. , Hamet Jean-François , Daigle Gilles A. , Stinson Michael R.
Published: October 2005

For the last 6 years, new porous road structures (drainage asphalt or pervious macadam) have been studied in several countries, particularly in Europe. In addition to their drainage qualities (i.e., elimination of splash and spray), these porous structures lead to reduced noise levels from traffic. To study further their acoustical performance, measurements of propagation over real road surfaces have been made, for grazing and oblique incidence conditions. The experimental results are compared to theoretical predictions based on two different models for the surface impedance: One model is a microstructural model that requires airflow resistivity, porosity, tortuosity, and shape factor; the other is a phenomenological approach that has been extended to include energy dissipation through thermal conductivity effects. Additionally, these impedance models are compared to direct measurements of the acoustical properties, e.g., absorption coefficient and impedance.
A stochastic, relaxation model for sound propagation in porous media
Authors: Wilson D. Keith
Published: October 2005

By assuming that the averaged acoustic fluid velocity and temperature fields satisfy simple relaxational diffusion equations, a new model for sound propagation in porous media has been developed. The resulting model agrees quite well with the exact solutions for uniform circular or triangular pores, despite not being based upon any specific assumptions regarding the pore geometry. Other benefits of the new model include simpler equations (no Bessel or Kelvin functions are used) and the need for fewer parameters. Extension of the model to fractal pore surfaces will also be discussed.
Perception of the pitch of speech and of the pitch of music by children
Authors: Castro-Sierra Eduardo
Published: October 2005

The perception of fundamental changes within word (Mandarin and Cantonese) and phrase (English) samples was compared to the perception of fundamental frequency changes between the members of pairs of steady complex tones or of tonal intervals between the members of pairs of small tunes composed of similar tones in 5- to 12-year-old monolingual speakers of these languages. Some of these children had had training in Western instruments for from 1 to 5 years. A certain correlation was found between the perception of tonal intervals of major and minor second magnitude between notes in the pairs of tunes and the perception of similar intervals within the English phrase samples among native speakers of this language. This correlation was increased in subjects with a musical background. In contrast, there was a lack of correlation between the perception of frequency changes between isolated tones and the perception either of frequency changes within Mandarin or Cantonese word samples or of frequency changes at the end of English phrase samples.
Reaction times to phonemic restoration
Authors: Amano Shigeaki
Published: October 2005

To investigate how acoustic information is integrated into phonemic restoration, reaction times to noise-replaced plosives in a vowel-consonant-vowel (VCV) sequence were measured. There were (a) a naturally spoken VCV, (b) a VCV made by concatenating the independently spoken V and CV, and (c) a VCV made by cross splicing the initial V and the following CV. In a naturally spoken VCV, the consonant information at the end of the initial V matches that at the beginning of the following CV. In an independently spoken VCV, however, there is no relationship between the consonant information at these locations, and in a cross-spliced VCV, they conflict. When the noise-replaced plosive was perceptually restored to the original plosive, reaction times to the plosive in the naturally spoken VCV was shortest. The next shortest reaction times were to the plosive in the independently spoken stimuli, and the longest times were to that in the cross-spliced VCV. This order was reversed, however, when the noise-replaced plosive was perceptually restored to the nonoriginal plosive. These results show that the integration of acoustic information at the end of the initial V is primary and faster than the integration of information at the beginning of the following CV.
Update on modern noise dosimeters
Authors: Krug Robert
Published: October 2005

Noise dosimeters have been undergoing a quiet revolution in recent years. They have progressed from the simple single reading dosimeter, into a multifunction general purpose noise measuring terminal. Dosimeters are available that can measure noise dose with two or three separate criterion levels as well as separate channels for peak, A-, and C-weighting. Time histories are stored and retrieved with durations as short as every 1/16 s for several hours. Exceedance levels are available along with time-weighted average, equivalent sound level per day, and many additional features. Readout is possible with front panel displays, printer interfaces, and computer storage. While functions have increased greatly, size and weight have been reduced. Electromagnetic susceptibility problems still exist but are being addressed in the current generation of dosimeters.
Simulation of the transmitted pressure field inside a water-saturated porous (sand) sediment
Authors: Kibblewhite A. C. , Wu C. Y.
Published: October 2005

As part of a study of the effects of porosity on reflectivity the influence of an underlying solid basement on the reflection from the interface between the water and a porous sedimentary structure has been examined analytically and numerical calculations made for various versions of this model. This paper presents the results of two applications of the codes developed. In the first the transmitted pressure field inside a sand sediment, resulting from a source above the water–sediment interface, is calculated and compared with that measured in a recent experiment which appears to demonstrate the Biot slow wave [Boyle and Chotiros, J. Acoust. Soc. Am. 91, 2615–2619 (1992)]. The simulation appears to confirm the demonstration of the slow wave in the tank experiment but suggests it is identified with a different feature in the experimental contour plot. In the second example signatures of the vertical component of the seabed displacement are calculated at various ranges from a very low pressure source, in a simulation of the potential use of both the shear and slow wave in the study of the geoacoustic properties of near-bottom sediments. [Work supplied by ONR.]
Solution of wave scatter problems in poroelastic media using exact analytical and boundary integral equation methods
Authors: Zimmerman Chris , Stern M.
Published: October 2005

Methods are developed for obtaining solutions to the harmonic form of the equations governing wave propagation and wave scatter in a poroelastic medium. An analytical solution in the form of an infinite series is obtained for the problem of scatter of an incident plane compression wave by a sphere. The incident wave may be composed of any linear combination of Biot ‘‘fast’’ and ‘‘slow’’ waves, and the sphere may be fixed and rigid, may be composed of elastic solid, or it may be a fluid-filled cavity. A desingularized set of boundary integral equations is developed for the harmonic problem, and these are incorporated into a three-dimensional boundary element computer program. Results obtained from this boundary element program are compared to results obtained using the series solution discussed above. The forbidden frequency problem is shown to be inherently absent from the poroelastic problem.
An empirical model for acoustic backscatter from trapped gas bubbles in sediment
Authors: Boyle Frank A. , Chotiros Nicholas P.
Published: October 2005

Recent experimental backscatter data suggest a volume scattering mechanism involving resonant trapped gas bubbles [N. P. Chotiros and F. A. Boyle, J. Acoust. Soc. Am. 89, 1852(A) (1991)]. A preliminary model for shallow grazing angle high-frequency acoustic backscatter from sediment is developed. The model begins with an estimation of grain and pore size distributions based on analyses of existing measurements taken at sea. The bubble size distribution is assumed to follow the pore size distribution. This bubble size distribution is then combined with an existing model for resonant backscatter from bubbles [Clay and Medwin, AcousticalOceanography: PrinciplesandApplications] to arrive at a model for backscatter from sediments. The model is then compared with existing experimental data.
Reflection and propagation loss over porous sediments
Authors: Chotiros Nicholas P. , Stern M.
Published: October 2005

A full wave acoustic propagation model in a stratified viscoelastic medium [H. Schmidt and F. B. Jensen, J. Acoust. Soc. Am. 77, 813–825 (1985)] was combined with Biot’s theory for propagation and reflection in a porous medium [Stern etal., J. Acoust. Soc. Am. 77, 1781–1788 (1985)] to produce a model of acoustic propagation in a stratified porous medium. Sample results were compared with a normal mode model [T. Yamamoto, J. Acoust. Soc. Am. 73, 1587–1596 (1983)]. The model was extended to account for the effect of gas bubbles in the pore fluid [J. A. Hawkins and A. Bedford, J. Acoust. Soc. Am. Suppl. 1 88, S131 (1990)]. Significant differences between viscoelastic, poroelastic, and gassy poroelastic models were investigated. [Work supported by ONR.]
A review of initial matched-field inversion experiments
Authors: Diachok Orest
Published: October 2005

The first successful demonstration of the feasibility of localizing a source in the ocean with matched-field processing was in the Arctic Ocean (Fizell and Wales). This environment/site was chosen because of the essential range independence of its sound-speed structure and minimal bottom reflectivity. Replica fields were generated with Kutschale’s well-tested, precise but computationally exhaustive FFP code. Soon thereafter Porter demonstrated that the precision of his much faster normal mode code equaled FFP, permitting computations of large numbers of replica fields and rapid ‘‘testing’’ of numerous environmental hypotheses,’’ i.e., matched-field inversion. The first inversions were of under-ice reflectivity and phase versus grazing angle (Livingston and Diachok). Other inversions through matched-field processing soon followed: ocean sound-speed profile (Kerengeleu and Diachok; and Goncharov and Voronovich), and bottom geoacoustic parameters (Fizell and Diachok; Chapman and McKirdy; and Collins, Kristensen etal.).
The evaluation of acoustic parameters in shallow-water matched-field processing
Authors: Feuillade C.
Published: October 2005

The principal application of matched-field processing (MFP) over the last several years has been the determination of acoustic source information, primarily location parameters. In shallow water, where the channel characteristically promotes strong boundary interactions, the successful implementation of MFP methods requires accurate environmental information to accurately model the acoustic field. When the environmental data used to calculate the replica field are incomplete or inaccurate (leading to data ‘‘mismatch’’) MFP performance can be seriously impaired. While it is clear that errors in all of the contingent acoustic parameters will affect MFP, much work has been devoted to establishing a scale of relative importance for these quantities, so that appropriate effort can be expended to obtain reliable values for the most important ones and to determine the effects that inaccuracies in them will have. In this paper, a review is presented of some of the numerical and experimental studies that have been performed to understand the data mismatch issue; and also a discussion of how this has motivated and directed the search for ‘‘robust’’ MFP methods that provide stable performance even when the environment is not known well will be presented. One particular class of estimators, involving ‘‘dimensionality reduction’’ eigenvector techniques, attempt to overcome this problem by isolating the effects of mismatch in the vector space outside of that which is processed. This talk describes how this approach may be adapted to do the inverse problem: to use MFP to provide data about the acoustic environment. [This work was supported by the Naval Research Laboratory.]
Estimation of seismoacoustic properties of the ocean bottom by matched-field inversion
Authors: Chapman N. Ross , McKirdy M. L.
Published: October 2005

Matched-field processing of acoustic field data provides a straightforward but powerful method for estimating the elastic properties of the ocean bottom. The success of the inversion depends in part on having an efficient algorithm for searching the multidimensional parameter space of ocean bottom models. This paper considers the use of simulated annealing as a search algorithm for matched-field inversion (MFI), and presents results of inversions for data obtained from the PACIFIC ECHO experiments. A method is described for adaptively guiding the annealing process by adding a feedback loop that assesses the significance of the matched-field correlations for each parameter. The search is guided to regions of the parameter space associated with above-average correlations. Simulations for a vertical line array (VLA) are presented to demonstrate the limits on performance of MFI with respect to uncertainties in experimental geometry, and low signal-to-noise ratio. The method is applied to VLA data from thin-sediment PACIFIC ECHO environments where the age of the upper oceanic crust varied from 0.1 to 66 million years. The MFI results indicate an age dependence of the compressional and shear wave speeds of the basalt, and the values are significantly lower than those obtained for thickly sedimented crust.
Parameter estimation bounds on estimating geophysical parameters using matched-field tomography
Authors: Baggeroer Arthur B. , Schmidt Henrik
Published: October 2005

Matched-field tomography uses full wave modeling to infer geophysical parameters of the propagation medium. As such, it is fundamentally a problem in estimation theory. The signal processing literature has long used bounding methods to establish performance limitations and identify coupling among estimates of a set of parameters. The most extensive of these is the Cramer–Rao bound, which has been applied to the source localization problem for matched-field processing. The Cramer–Rao, as well as other bounds for analyzing the sidelobe, or ambiguity, problem can be applied to matched-field tomography. These will be derived and applied to problems in identifying the sound-speed profile and elastic properties of the seafloor.
Using circulation models to improve ocean imaging (and vice versa)
Authors: Kuperman W. A. , Shen C. , Porter M. B.
Published: October 2005

Circulation models predict the ocean weather (temperature), which in turn determines the manner in which sound propagates. The ocean models, like their atmospheric counterparts, tend to drift away from reality as they are marched forward in time. In order to prevent this, tomographically constructed images of the ocean are assimilated into the circulation model. Furthermore, flow constraints provided by the ocean circulation model are used to exclude unrealistic structures and thereby enhance the quality of the tomographic imaging. The algorithmic issues of linking acoustic and ocean circulation models in this fashion, and the benefits of doing so, are discussed.
Demonstration of the large and small sector limits for large vertical array sector focused matched-field processing in a deep water environment
Authors: Smith George B. , Morris Dane
Published: October 2005

Sector focused matched-field processing is a technique that has been developed to stabilize high-resolution estimators against random phase errors and environmental mismatch. This technique produces satisfactory high-resolution matched-field localization over a wider latitude of environments than does conventional high-resolution techniques. Its implementation requires the selection of several parameters such as sector size, shape and dimensionality. In this work, general guidance is given for the use of this technique by establishing the properties of the small and large sector limits. Specifically, it is demonstrated that in the small sector limit, sector focusing behaves like replica correlator processing (robust and low resolution). Whereas, in the large sector limit, sector focusing behaves like reduced maximum-likelihood processing (high resolution, but not as robust). The demonstration is accomplished by plotting signal gain degradation versus three sediment sound-speed parameters. These plots show a small hot spot at the correct environment immersed in very cool surroundings for the conventional high-resolution estimator (mvdr). Whereas, for sector focusing, the plots show a rather wide swath of acceptable environments. In most cases, the technique peaks on the correct environment. [This work was supported by the Office of Naval Research, with technical management provided by the Naval Research Laboratory, Stennis Space Center, MS.]
Application of neural and statistical classifiers to the problem of seafloor characterization
Authors: Michalopoulou Zoi-Heleni , Alexandrou Dimitri
Published: October 2005

Simulated seafloor backscatter is obtained by employing the Kirchhoff approximation and the statistical properties of bottom reverberation. Such data are presented to multilayer perceptrons for training and testing, aiming at the development of a neural processor that discriminates among signal returns coming from seafloors with different roughness parameters. Experiments on the same data sets are performed with optimum Bayesian classifiers as well; a comparison of the results indicates suboptimum performance for the perceptrons. The same procedure is followed with real data collected by the bathymetric system Sea Beam over Horizon Guyot and Magellan Rise. In this case, the perceptron performance is comparable to that of the Bayesian classifier, which is no longer optimum, since no prior knowledge of the probability distribution parameters is available. In addition, self-organizing maps have been applied to both synthetic and real data sets and resulted in a successful separation of the output space into distinct regions corresponding to the existing classes. [Work supported by the Office of Naval Research, Code 1125GG, through Contract No. N00014-93-I-0049.]
The influence of bottom geoacoustics on the dispersive behavior of Scholte interface waves
Authors: Ali Hassan B. , Bibee L. Dale
Published: October 2005

Scholte seismic interface waves can be an important component of very-low-frequency (VLF) acoustic propagation, particularly in shallow-water environments. The propagation characteristics of these seismic waves, including their presence in the water column, are dependent on bottom geoacoustics (particularly shear speeds) and the types of layers overlying the basement level. This work examines the results of recent NRL/Stennis Space Center measurements and compares them with numerical predictions based on the SAFARI model. Scholte waves measured off the Oregon Margin (1991) are shown to have strikingly different characteristics from those obtained off the San Diego coast (1992). In particular, those obtained off the San Diego coast are characterized by strongly dispersed Scholte waves in the 1- to 5-Hz band, whereas those measured off the Oregon Margin contain mostly lower frequencies (1–2 Hz) and display less clearly defined dispersive behavior. The differences in the two data sets are attributed to the significantly diverse bottom/subbottom geoacoustics at the two test sites. [Work supported by The Office of Naval Research under the NRL/SSC Interface Waves Project.]
A parallel learning model of musical pitch perception
Authors: Laden Bernice
Published: October 2005

Musical pitch perception involves the ability to extract and internalize a template that represents harmonic information. Template extraction is important to other perceptual processes such as melody recognition and chord classification, although these involve extraction of intervallic information. In order to explore how templates might be learned, a parallel learning algorithm was developed. This algorithm is based on the notion that a stimulus does not need to be physically present for a response to be learned. An artificial neural network was trained with this algorithm to identify the pitch of a tone complex. The network had 116 input units (log frequency) and 88 output units (pitch). After training, it correctly identified the pitch of 88 tone complex prototypes. It was tested with a variety of incomplete patterns as well as dyads and triads. All test patterns were correctly identified, although output strength dropped when simultaneous tone complexes were presented. The results indicate the parallel learning algorithm may be superior to other learning algorithms in terms of both accuracy and speed.
Multidimensional scaling of synthetic musical timbre: Perception of spectral and temporal characteristics
Authors: Samson Séverine , Zatorre Robert J. , Ramsay James O.
Published: October 2005

The perceptual correlates of the acoustic parameters involved in musical timbre have not yet been clearly established. To investigate this issue, perception of single tones and melodies were examined using nine hybrid synthetic sounds, derived from crossing three levels of spectral and temporal changes (number of harmonics and rise time, respectively). Multidimensional scaling analysis was carried out on the pairwise dissimilarity judgments of 15 subjects, using an 8-point rating scale. The configuration resulting from the analysis was best fit by a three-dimensional model, but the first two were most important, and accounted for 44% and 38% of the variance, respectively. The perceptual space derived from the analysis indicates that these two orthogonal dimensions corresponded closely to the spectral and temporal differences inherent to the stimuli. Similar results were obtained with melodies as with single tones. Thus, it appears that even musically unselected subjects are sensitive to spectral and temporal information in a tone, and are able to use them independently in making perceptual judgments of musical timbre.
Individual variability in the use of acoustic cues to place and voicing contrasts
Authors: Hazan Valerie L. , Bo Shi
Published: October 2005

At the 123rd Meeting of the Society, initial results were reported of a study on individual variability in the perception of word and sentence material in synthetic and degraded natural speech conditions. The same group of 50 listeners, homogeneous in terms of a set of basic listener characteristics, were also tested on a series of identification tests. These included a /g/–/d/ place contrast and /g/–/k/ voicing contrast presented in three vocalic contexts (/i/, /ei/, /æ/). Each contrast was presented in various full- and reduced-cue conditions, in order to evaluate the relative weighting given by listeners to different acoustic cues. For the place contrast, perceptual weighting given to the burst and formant transition cues varied widely according to individual listeners and vocalic context. However, for the voicing contrast, much more homogeneous results were obtained. No strong relation was found between listeners’ performance on reduced-cue identification tests for place and voicing contrasts and intelligibility scores for VCV utterances and sentence material. [Work supported by SERC.]
The perception of speech gestures
Authors: Surprenant Aimée M. , Goldstein Louis , Neath Ian
Published: October 2005

An experiment was conducted to evaluate the hypothesis that speakers perceive the intended gestures of the talker, not merely the sound that is carried to their ears. This is a central assumption of the revised motor theory of speech perception [Liberman and Mattingly, Cognition 21, 1–36 (1985)]. Of relevance to this hypothesis is how listeners perceive instances of consonant gestures that show extreme overlap in casual speech and that may, therefore, lack the expected correlates in the acoustic signal (so-called ‘‘hidden’’ gestures). To test this, utterances that showed varying degrees of actual gestural overlap were selected from an x-ray microbeam study investigating the production of consonant sequences. These were presented to listeners in a phoneme monitoring task. Results show that as the temporal distance between centers of overlapping gestures decreases, detection also decreases. That is, as the target gesture becomes more and more hidden by the subsequent gesture, subjects report hearing it less and less. This result is qualified by the finding that the magnitude of the gesture also decreases when a gesture is hidden. This research is a first step towards using natural utterances with known articulatory properties to investigate theories of speech perception.
The vanished Lombard effect
Authors: Weiss William
Published: October 2005

It is well known that the presence of noise produces an increase in vocal levels [E. Lombard, Ann. Maladies Oreille Larynx 37, 101–119 (1911); H. Lane and B. Tranel, J. Speech Hear. Res. 14, 677–709 (1971)]. Pick etal. [J. Acoust. Soc. Am. 85, 894–900 (1989)] suggested that through training the effect could either be enhanced or reduced but not completely eliminated. It is possible, nevertheless, that people with voice training react differently to that effect [W. D. Ward and E. M. Burns, J. Res. Singing 1 (2), 24–44 (1978)]. Two groups, one with voice training (n=23) and one without voice training (n=23) were recorded with and without masking noise. It was found that 39% of the masked speech samples of the trained group failed to produce the Lombard sign whereas only 9% of the untrained (n=23) did not increase vocal levels under masking noise. Voice training was significantly related to cases where the Lombard effect was absent. This contradicts Pick etal.’s conclusion that the Lombard sign is always present in masking noise.
On the correlation among neighboring energy pixels in the speech spectrogram
Authors: Houtgast T.
Published: October 2005

The energy at any location fiti in the speech spectrogram can be derived by convolution of the speech signal with appropriate Gaussian-shaped cosine and sine waves. This leads to the so-called pixel energy, with an integration window centered at fiti and Gaussian-shaped in both frequency and time. Analysis of the correlation for pairs of pixels at a given mutual distance in the spectrogram provides a parametric representation of speech, which shows interesting characteristics. One such representation is the spectral correlation matrix: the correlation for pairs of energy pixels drawn at the same instance at two different frequencies fi and fj, with fi and fj chosen from a range of values at appropriate intervals along the frequency scale. It is found that, for a given talker, this spectral correlation matrix stabilizes after analyzing a speech token of about 10 to 15 s: Its features are then typical of speech as such, and do not depend on the actual content of the speech token. Details of such spectral correlation matrices appear to be characteristic of the talker.
Low-frequency bottom scattering strengths for a shallow water site in the Gulf of Mexico
Authors: Cable Peter G. , Kooij Theo , Steele Mike
Published: October 2005

Acoustic transmission and reverberation measurements from 25 Hz to 1 kHz were made in 100 fathom water on the West Florida Shelf during Area Characterization Test I (ACT I) in September 1992. Explosive charges were detonated at 90-m depth and reverberation data were received on collocated vertical and horizontal hydrophone line arrays, each array having 25 hydrophones in nested sub-apertures designed for 100, 200, and 400 Hz. Near-monostatic source-to-receiver separation (2 km) and bistatic separations of 10 to 40 km in 10-km increments were employed in the test. From the reverberation data and the transmission loss measurements total monostatic and bistatic bottom scattering strengths have be determined and compared. Also, from the vertical array data monostatic scattering strengths versus scattering angle have been determined. The scattering strengths from ACT I have been compared with determinations from other shallow water measurements having similar bottoms. In addition, these results have been compared with angle and frequency dependencies for different scattering models. [Work supported by the DARPA Adverse Environments Program.]
The effect of frequency-dependent bottom reflectivity on transmission loss in shallow water over a sandy bottom
Authors: Tattersall J. Matthew , Chizhik Dmitry , Cole Bernard F. , DiNapoli F. R.
Published: October 2005

The effect of frequency dependence of bottom reflectivity on acoustic transmission in shallow water over a sandy bottom is investigated using transmission loss data from measurements conducted at a wide range of frequencies. Biot’s theory of acoustic wave propagation in fluid-saturated porous media is applied to prediction of bottom reflectivity for a sea bottom consisting of medium grain size sand. For a homogeneous half-space the theory predicts a frequency-dependent bottom reflectivity in contrast to the fluid or solid bottom models. Transmission loss predicted using the Biot model of the sediment shows agreement with measurements at all frequencies considered, which ranged from 100 to 8000 Hz. The fluid model, which assumed a dispersionless velocity and an attenuation that is proportional to frequency, has performed poorly at the low frequency of 100 Hz. [Work supported by Naval Sea Systems Command 06UR1.]
A simple ray model of plane-wave reflection from a thin sediment layer
Authors: Chapman David M. F. , Chapman N. Ross
Published: October 2005

Plane-wave reflection from a thin, elastic solid sediment layer over a hard basement is modeled by a simple ray model that includes only two ray families: a family of compressional waves that transit the sediment layer any number of times before returning to the water; and a similar family that includes doubly converted compressional waves. (The latter are compressional waves that are converted to shear waves at the basement, make one or more round-trip transits of the sediment layer, and are converted back into compressional waves at the basement.) The theory is applied to homogenous sediment layers with low shear speeds, and it provides valuable insight into the physical processes governing reflection from several seabed environments of interest. The coherent sum of all the rays belonging to these families leads to a closed-form expression for the overall reflection coefficient that includes several characteristic features also simulated by full wave-theoretical numerical models, such as bottom-loss resonances related to sediment shear waves and large losses associated with the excitation of interface waves at the sediment/basement boundary. Calculated examples are provided.
Vowel continuity and perception of /ba–wa/
Authors: Lotto Andrew J. , Green Kerry , Kluender Keith R.
Published: October 2005

When CV syllables have longer vowels following a stop /b/ or glide /w/, the duration of transition necessary to perceive a stimulus as /w/ is longer as well. Perceived continuity/duration of following vowels was manipulated by exploiting the phenomenon of auditory induction. All syllables were 315 ms in duration, and transition duration was varied from 15–65 ms for four series of syllables. After the first 100 ms of each syllable (transition + vowel), broadband noise either replaced or was added to the second 100 ms of syllable. Noise was either the same intensity as or 12 dB greater than the intensity of the vowel. Results from a signal detection task indicated that listeners could reliably report when the signal was deleted and replaced by the less intense noise; however, they could not reliably report whether the vowel was deleted when the noise was more intense (+12 dB). Listeners were asked to label these four series of stimuli as beginning with /b/ or /w/, and there was no effect of either the presence or absence of the vowel or of noise intensity. Even when subjects’s phenomenal experience was one of intact continuous syllables (+12-dB noise with vowel present or absent, or equal intensity noise with vowel present), subjects’ labeling boundaries were virtually identical to those for syllables perceived as interrupted (equal intensity noise with vowel absent) or for syllables of only 100-ms total duration. Theoretical implications and results from follow-up experiments will be reported. [Work supported by NIDCD Grant No. DC-00719 and NSF Grant No. DBS-9258482.]
Training native English speakers to identify Hindi dental and retroflex consonants
Authors: Pruitt John S.
Published: October 2005

Training listeners to perceive consonantal contrasts that do not occur in their native language has proved to be difficult. Cross-language training studies usually produce about 10% improvement in performance. This improvement has not transferred to related material in different linguistic contexts. The present research had four aims: (1) to investigate the difficulty experienced by American-English listeners in identifying Hindi dental and retroflex stop consonants in different voicing conditions, (2) to test a new, computer-based, interactive training method, (3) to examine transfer of training to new voicing conditions, to a new vowel context, and to the voice of a new speaker, and (4) to test the hypothesis that increasing stimulus variability (in this case, training with one versus two voicing conditions) increases transfer of training. Subjects had differential difficulty identifying dental versus retroflex consonants produced in different voicing conditions. Further, this relative difficulty was affected by which speaker produced the contrasts and, to a lesser extent, by the vowel context. The computer-based training improved subjects’ consonant identification. However, this improvement showed little transfer to new stimuli. Finally, increasing stimulus variability during training did not affect transfer of training. [Work supported by NIDCD.]
Structural acoustic modeling using a new high accuracy acoustic infinite element
Authors: Burnett David S.
Published: October 2005

This new 3-D time-harmonic acoustic infinite element uses a truncated form of the exact asymptotic series solution for general scattered and/or radiated fields, providing an accurateapproximationallthewaytoinfinity. The infinite element and a companion fluid–structure coupling element have symmetric matrices that fit seamlessly into any structural finite element code, providing a structural acoustic capability as versatile and powerful as the structural code itself. Most important, this approach is severalordersofmagnitude faster, for the same accuracy, than the traditional and almost universally used boundary element method (BEM) for the acoustics, i.e., the surface Helmholtz integral equation, which the author also developed and used for several years. The reason is that the bandwidth of the coupled system equations is much smaller for infinite elements (being a domain method) than for the BEM. Experience with both methods has revealed that the severe computational inefficiency of the BEM limits practical problems to low frequencies and simple structures, whereas this infinite element approach can handle the full range of frequencies and structural complexities that are encountered in purely structural analyses, at little additional cost.
Trading relations; discrete versus continuous perception
Authors: Wright Richard
Published: October 2005

The results of experiments on trading relations have been interpreted as evidence for theories that speech perception is discrete, such as the motor theory [e.g., Libermann and Mattingly, 1985]; however, the experimental stimuli have not tested the predictions of theories of continuous perception [e.g., the FLMP, Massaro, 1987]. The present study addressed this issue using a pair of experiments that use a ‘‘slit–split’’ stimulus continuum varying in /p/ burst amplitude, rather than formant transitions, along the spectral dimension and varying in preburst silence duration along the temporal dimension. Experiment 1 was a 2IAX task in which subjects responded ‘‘same’’ or ‘‘different’’ to ten blocks of stimuli that were presented in pairs with a 300 ms ISI and a 1000-ms inter-block interval. Experiment 2 was a forced choice identification task in which subjects responded ‘‘slit’’ or ‘‘split’’ to ten blocks of stimuli that were presented singly with a 1000 ms ISI. A trading relation occurred between the amplitude of the burst and the duration of the silence. This finding is incompatible with a theory in which a burst is absent or present.
Perceptual weight of acoustic cues for voicing in French [t, d]: Population differences
Authors: Sawallis Thomas R.
Published: October 2005

An experiment is presented concerning perception of edited consonant length, voicing amplitude, and burst+aspiration amplitude in a corpus of natural tokens of French intervocalic [t, d]. The editing is designed using the statistical distributions of those cues as previously measured in the selfsame corpus. This design largely preserves the natural variation of the nontarget cues, and is an advantage over the traditional use of synthesis or prototype based series. Then, mathematical tools borrowed from signal detection theory are used on the perceptual test results to derive sensitivity measurements for the cues. Measurements of this type can be compared autonomously, without trading-relationship-style equivalences, across cues, environments, languages, etc., and this property makes them amenable to use not only in speech perception, but also in formal phonology and general linguistics. In this paper, they are used to explore differential use of cues of listener groups based on native language (French versus other native languages) and on linguistic training (‘‘naives’’ versus phoneticians, linguists, language teachers, etc.).
Multidimensional scaling of the native language prototype effect
Authors: Iverson Paul , Kuhl Patricia K.
Published: October 2005

Previous experiments with human adults and infants have demonstrated that variants of the vowel /i/ are more difficult to discriminate from a prototypic /i/ than from a nonprototypic /i/, suggesting that prototypes assimilate neighboring stimuli [P. K. Kuhl, Percept. Psychophys. 50, 93–107 (1991)]. A series of experiments examined this influence of prototypes using multidimensional scaling. Adults discriminated pairs of /i/ tokens and RTs were measured. Multidimensional scaling was used to place the tokens in a Euclidian space where pairs of tokens with long RTs were close in the space and pairs with short RTs were far apart. Tokens were more closely spaced near the prototypic /i/, demonstrating that prototypes assimilate proximate regions of the vowel space. This effect was stronger with long ISIs (2500 ms) than with short ISIs (25 and 250 ms), suggesting that vowel prototypes distort memory for individual tokens. [Work supported by NIH.]