bluuebunny/crossref_metadata_2025 huggingface dataset:
Representative 24-h Leqs arising from a combination of occupational and nonoccupational noise exposures
Authors: Berger Elliott H. , Kieper W.
Published: October 2005

The noise exposure of occupational populations and their resultant noise-induced hearing losses have been well studied in the literature. However, the same cannot be said for those exposed off-the-job and/or recreationally. To better understand the ‘‘normal’’ development of hearing loss with age (presbycusis plus sociocusis) data on societal noise exposure is required. This was recently high-lighted by Berger etal. [CombattingNoiseinthe ’90s: ANationalStrategyfortheU.S. (ASHA, Rockville, MD, 1991)]. As a result of his participation in this conference, the first author became interested in this problem and began an informal study to collect 24-h noise exposure data on primarily nonoccupationally noise-exposed friends and co-workers living in Indianapolis, IN. Data from the subjects who were asked to ‘‘wear’’ dosimeters 24 h/day for week-long periods, will be presented and anecdotal findings will be reviewed. Thus far, the average 24-h Leq across the available sample of 14 people, is 77 dBA with the lowest observed 24-h Leq equal to 56 dBA and the highest value found to be 90 dBA.
Nonoccupational noise exposures and their estimated daily L (eqs.) for general commercial air travel and local bars, restaurants, discos, and socialization establishments
Authors: Royster Larry H. , Royster Julia D.
Published: October 2005

Over a period of several years the authors have collected noise exposure data (N≳150 samples) during normal commercial air travel. The data were collected utilizing noise dosimeters, and an octave-band analyzer. The resulting noise exposures for air passengers will be presented, including the distribution of the measured A-weighted sound pressure levels. In addition, as part of regular class assignments, the students of the first author’s Effects Of Noise And Vibration graduate class have collected sound exposure data over several years at popular bars, restaurants, discos, and socialization establishments in the Raleigh, NC area. The noise exposures and sound level distributions from these surveys will also be presented.
Initial results of study of aircraft noise effects on residential sleep disturbance
Authors: Fidell S. , Pearsons K. , Howe R. , Tabachnick B. , Silvati L. , Barber D.
Published: October 2005

More than 1800 subject-nights of observations have been completed in a large-scale, in-home study of awakenings associated with nighttime aircraft noise exposure in the vicinity of an Air Force base, a major civil airport, and several sites in urban neighborhoods with negligible nighttime aircraft noise exposure. A statistically reliable relationship was found between behaviorally confirmed awakenings and indoor sound exposure of individual noise events. This relationship is similar to one reported in another recent large-scale field study, and also with a relationship summarizing the findings of several earlier field studies of noise-induced sleep disturbance. The findings do not, however, agree well with those typically found in laboratory studies of sleep disturbance, nor with an interim dosage-response relationship adopted by the Federal Interagency Committee on Noise. [Research sponsored by U.S. Air Force Armstrong Laboratory, Wright-Patterson Air Force Base, OH.]
Auto traffic noise, air traffic noise, and the environmental quality of city streets: Test of a model
Authors: Meyers William R. , Meyer Mary , Weiler Ernest M. , DeRonde Laura , Sparnall Jo Ann , Stroop Matthew
Published: October 2005

In Jan. 1991 the Greater Cincinati Airport opened a new runway whose traffic flies directly over heavily populated residential areas which had little prior exposure to aircraft noise. Our evaluative study design replicated with modifications the classic and influential Appleyard and Lintell [(1969); Appleyard, LivableStreets (1981)] studies of the effects of auto traffic on residential life. As did Appleyard and Lintell, three streets were chosen called High, Medium, and Low, based on observed noise levels (and dBA measures of flights; many were found to be in the 90 to 100 dBA range), and conducted, using their questionnaire, 36 structured in-depth interviews with 12 randomly sampled households on each street, concerning five components of ‘‘perceived livability’’: traffic hazard; psychological stress, social interaction with neighbors; privacy and home territory; and environmental awareness. Residents gave numerical ratings of these components, as well as giving detailed verbal descriptions. Using ANOVAS and Tukey tests of the ratings, and structured analyses of the verbal descriptions, we found perceived livability was lowest on the High noise street and highest on the Low noise street, implying that the Appleyard and Lintell model for assessing residential livability effects of auto traffic noise is also useful for air traffic noise.
The acoustic environment at Ridgetop elementary school ,Students in the Fall, 1993 Noise Control Class and
Authors: Busch-Vishniac Ilene J.
Published: October 2005

During the Fall, 1993 semester, students in a combined undergraduate and graduate noise control class examined the acoustical environment at Ridgetop elementary school in Austin, Texas. This school is directly under the flight path for Austin’s Mueller Airport, and was recently soundproofed to prevent aircraft noise from interfering with instruction. The purpose of the project was to introduce students to the types of acoustic measurements typically made by noise control engineers, and the conclusions that can be drawn from them. Measurements included background noise levels, transmission loss from one room to its neighbors and through windows, reverberation time for a typical classroom, and barrier excess attenuation (using the school as the barrier). The results show that outdoor sound levels at Ridgetop elementary school peak at quite high values when aircraft are landing at Mueller airport. However, indoor sound-pressure levels are such that aircraft noise is generally inaudible, and certainly not disruptive. Further, the rooms are well designed for speech communication. Student assessments of the project experience will be presented.
Measuring regular whale call intervals with the summed autocorrelation
Authors: Mellinger David K. , Weisburn Beth A. , Mitchell Stephen G. , Clark Christopher W.
Published: October 2005

Finback whales (Balaenopteraphysalus) emit pulses of approximately 20 Hz at 10 to 20-s intervals. A method is presented here for measuring the pulse rate of whales; the method may potentially be useful for tracking individual whales over time, for characterizing sounds of finback herds, or for behavioral study. The method uses the finite-time-support summed autocorrelation, which is computed by taking a finite time window of a signal, autocorrelating and squaring, and then summing the autocorrelation over multiples of possible finback pulse periods. Repeating this operation over time gives a map of extant pulse periods over time, in which peaks are then tracked. The method is tested on several hour-long and longer recordings of finback calls obtained from U.S. Navy SOSUS arrays. Call SNR’s vary from 30 dB to below 0 dB. The method is found to be effective even at very low SNR. In addition, it is capable of measuring and distinguishing pulse periods of several simultaneously calling finbacks, a critical property for studying this type of whale. The method also is compared to other techniques for measuring periodicity, including Fourier analysis and autocorrelation, and found to work better on the test signals studied. [Work supported by ONR.]
Acoustic backscatter from a dolphin
Authors: Au Whitlow W. L.
Published: October 2005

Backscatter measurements of an Atlantic bottlenosed dolphin under controlled conditions were made. The target strength for a broadside aspect was measured as a function of frequency from 23 to 80 kHz. The relative target strength as a function of the polar angle about the animal was also measured using a transientlike click signal with a peak frequency of 67 kHz. Finally, the relative reflective strength of different portions of the animal’s body was determined. The mean target strength at the broadside aspect decreased from −11 to −24 dB as the frequency increased from 23 to 45 kHz. As the frequency increased from 45 kHz, the target strength rose to a local maximum of −18 dB at 66 kHz and then decreased to −23 dB at 79 kHz. Maximum target strength was measured at the broadside aspect and minimum at the tail aspect where the target strength was 21 dB below the broadside value. The target strength at the head aspect was 5 dB below that of the broadside aspect. Most acoustic energy was reflected from the area between the dorsal fin and the pectoral fins, corresponding to the location of the dolphin’s lungs.
The perception of relative pitch in the bat M. lyra.
Authors: Preisler Annemarie , Schmidt Sabine
Published: October 2005

As opposed to humans, animals perceive pitch predominantly in terms of absolute categories. In order to establish relative pitch formation in bats, three animals were trained to discriminate falling from rising two-tone sequences in a two-alternative, forced choice behavioral test. Stimuli were six pairs of complex tones, consisting of the first three harmonics. In the first experiment, the spectra of high and low tones fell into different frequency regions (first harmonic of low tone: 9–10.4 kHz; high tone: 34–39.3 kHz). After 2 months, two animals were able to perform the task with an error rate of less than 5%. In the second experiment, 12 tone pairs with overlapping harmonics were presented. The frequency ratio between the two fundamentals of a pair was 2:3, with the fundamental of the lower tone between 13.2 and 18.1 kHz. Only one animal was able to perform this task after 2 weeks of training. Control tasks revealed that the bat utilized absolute pitch clues only to a minor extent. Nevertheless, later experiments showed that the animal was not able to transpose relative pitch categories to frequency ranges beyond the original stimuli. [Work supported by Humboldt Foundation and SFB 204 ‘‘Gehör,’’ München.]
Target surface texture discrimination by the echolocating bat, Eptesicus
fuscus.
Authors: Zagaeski Mark , Moss Cynthia F.
Published: October 2005

Echolocating bats perceive the details of their surroundings through an active bisonar system having an acuity which rivals vision in other mammals [AnimalSonar, ProcessesandPerformance, edited by P. F. Nachtigall and P. W. B. Moore (Plenum, NY, 1988)]. To explore one facet of their acoustic imaging, big brown bats (Eptesicusfuscus) were trained to discriminate between targets based upon their surface roughness. Pairs of cylinders (7.6 cm diam by 20 cm) were covered with different grades of gravel or sandpaper. Individual bats were able to discriminate targets having a difference in mean grain size of about 0.5 mm, in general agreement with earlier results from a different bat species (Megadermalyra). Big brown bats actively control the parameters of their short (1–5 ms) broadband (100–20 kHz) echolocation sounds to shape the acoustic information available to their bisonar systems. To monitor the bat’s vocal control of echoes, vocalizations were recorded and compared to the sounds used by the same animals in a simple detection task. Echoes from the targets using synthesized bat sounds were also recorded and analyzed to explore the acoustic cues which the bats may use to perform texture discrimination. [Work supported by the Whitehall Foundation and NSF.]
Detecting pink bollworm in cotton bolls using a multiple acoustic sensor system
Authors: Hickling Robert , Lee Peter , Wei Wei , Walters Geyer Michelle , Pierce David , Staten Robert , Henneberry Thomas
Published: October 2005

Pink bollworm [Pectinophoragossypiella (Saunders)] infestation is a chronic problem for cotton growers in the Southwestern United States. The information needed to control such infestation is based on cutting and examining cotton bolls gathered from the fields, for larvae presence and numbers of pink bollworm. This procedure is laborious and error prone, representing a potential weak link in the information gathering process. A new procedure based on acoustic detection of larvae found within the boll is presented. Larvae eat and move almost continuously, generating sounds that can be detected by a sensitive acoustic sensor. At the USDA, APHIS, PPQ Methods Development Center in Phoenix, boll cutting was compared with acoustic detection, in tests using a multiple acoustic sensor system developed by the National Center for Physical Acoustics at the University of Mississippi. The system consists of 48 sensing units in parallel, each listening to a different boll. Each unit consists of an electret microphone within a stethoscope head and an electronic circuit for signal processing. The units are contained within a sound-proof box that is closed during the tests. It is shown that this acoustic system compares favorably with the cutting process, providing fast, accurate, labor-reducing, insect detection.
Monostatic seismoacoustic scattering from 45° oblique cylindrical hole in thick floating ice plate
Authors: Chamuel Jacques R.
Published: October 2005

Laboratory ultrasonic modeling results are presented characterizing monostatic scattering of broadband pulsed seismoacoustic waves (2<ka<8) from a 45° oblique cylindrical hole in a thick floating ice plate. A vertical compressional disk transducer placed on the free surface of a floating plate is used to generate and detect diagonally propagating shear waves created by the vertical displacement of the disk [G. F. Miller and H. Pursey, Proc. R. Soc. London Ser. A 233, 55–69 (1955)]. Compressional, shear, and Rayleigh wave velocities are simultaneously obtained from the oblique hole reflections. Backscattering results from oblique empty and water filled holes in Plexiglas and ice models are compared. Data from a layered plate model shows the effect of velocity variation with depth on ray bending and monostatic scattering. In other experiments, the compressional transducer is located in the water below the floating plate. The described oblique hole monostatic reflection seismology method may be used to determine sea ice shear velocity using a compressional transducer on the free surface of the ice and a 45° hole made by a coring machine such as the PICO 45° ice coring rig currently used in sea ice electromagnetic and optical oceanography. One-sided accurate velocity measurements may be achieved because the wave propagation distance between transducer and reflection point deep inside the ice can be determined from the surface. The findings are applicable to NDE and geophysics. [Work supported by ONR.]
On the interpretation of observed anomalous high acoustic backscatter from Arctic Basin using 2-D horizontal hydrophone array
Authors: Chamuel Jacques R.
Published: October 2005

A two-dimensional horizontal hydrophone array when used to receive acoustic waves backscattered from an entire ocean basin and its margin can identify individual features in azimuth and in range. Localized anomalous strong low-frequency acoustic backscatter from the Canada Basin near 73.2 °N, 139 °W was observed by Dyer etal. [J. Geophys. Res. 87, C12, 9477–9488 (1982)] using a long-range 2-D hydrophone array, however, recent bathymetric charts do not reveal the existence of large bathymetric highs nearby [A. Grantz etal., J. Geophys. Res. 89, C2, 2105–2108 (1984) and I. Dyer, J. Geophys. Res. 89, C2, 2109 (1984)]. The author hypothesizes that the anomalous observed backscatter is likely caused by the limitation of a 2-D acoustic array in presence of focused multiple scattering. When direct scattering is assumed, range is calculated based on total travel time, however, when multiple scattering is ignored, range tends to be overestimated. Scaled 3-D laboratory ultrasonic modeling results are presented demonstrating that long near-elliptical segments of the Beaufort slope focus the acoustic waves onto raised bottom features (water depth about 3500 m) near (a) 73.5N, 140.4W (b) 72.9N, 147.4W, and (c) 73.1N, 144.3W oriented to reflect the waves back toward the source. The range of these features can be overestimated by 45%–65% when focused multiple scattering is ignored. Future bathymetric measurements need to be conducted at the corresponding range predicted when multiple scattering is included. [Work supported by ONR.]
Small scale flow inversion by diffraction tomography
Authors: Rouseff Daniel , Winters Kraig B.
Published: October 2005

The reconstruction of a moving fluid from acoustic transmission experiments is considered. To fully characterize the fluid, inversion for both the scalar index of refraction and the vector velocity fields describing the flow is desired. A standard approach is to use rays as a forward model for the acoustics. At sufficiently short ranges, refraction can be neglected and a straight-ray transmission assumed. By measuring the time-of-flight through the flow from many directions, the index of refraction can be recovered. The full vector velocity field, however, cannot be recovered; the inversion is underdetermined within the assumed forward model. In this talk, a linearized time-harmonic wave equation is used to model the acoustics. It is shown that within this model a unique inversion for the vector flow velocity is possible. The result is a distinctly finite wavelength result indicating why ray-based methods fail to produce a full reconstruction. [Work supported by ONR.]
Realistic modeling of resonant scattering from fish swimbladders
Authors: Feuillade C. , Love R. H. , Werby M. F.
Published: October 2005

Acoustical scattering from fish is an important issue for biologists, aquaculturalists, and the military community. Their physical characteristics, behavior, and abundance can be determined by coupling acoustical measurements with accurate mathematical formulations of the scattering problem. Generally, scattering from fish is enhanced at resonance frequencies. The resonances are due to excitation of vibrational motion of the fish bladders in much the same way that bubbles resonate. Scattering from fish bladders is the central issue in determining fish resonance properties. The aim of this work is to present a mathematical/physical formulation which couples acoustical signals with realistic biophysical properties to correctly describe the acoustical scattering from fishes. Fish bladders are usually elongated and contain viscous properties in the medium surrounding the bladder. Elongation increases the resonance frequency while viscosity decreases resonance effects. A complete formulation of the problem is given by combining descriptions of scattering from deformed bubbles with spherical swimbladder models. [Work supported by ONR Technology Directorate (Element 602435N) and by the Naval Research Laboratory 6.1 Program (Element 601153N). Technical management provided by NRL-SSC.]
Standard definitions for sound source levels in the ocean
Authors: Carey William M.
Published: October 2005

Recently, increased attention has focused on the use of sound in long-term ocean-acoustic experiments. The question being the determination of begin levels or the quantification of acceptable levels. This is an important consideration due to the increased use of higher power sound sources and our increased awareness of the effects of sound on mammals. Recent discussions and papers at the 126th Meeting of the Acoustical Society illustrate the confusion which exist with respect to characterization of acoustic source levels and has resulted in erroneous and misleading reports (i.e., see information from John R. Potter reported by Malcolm B. Browne, ‘‘Science Times,’’ New York Times, 19 Oct. 1993). This paper presents some standard definitions for the comparison of decibel levels with references of peak pressure, energy, or power. Frequency-dependent characteristics of oceanic noise sources shall be discussed and the relative importance of sound levels from air guns, surface ships, marine mammals, and other sources shall be placed in perspective. Finally these sources of sound will be further examined in light of the propagation effects found in both shallow waters and the deep ocean.
Improvement in the shallow water prediction of sonobuoy detection ranges for ASW aircraft using on-site acoustic measurements
Authors: Wiseman Charles
Published: October 2005

Sonobuoy detection ranges predicted at shore stations for use by ASW (antisubmarine warfare) aircraft are based on historical data and on XBT (expendable bathythermograph) data that is typically at least 6 to 12 h old. The accuracy of such predictions is questionable as shown by measurements and analysis. Prediction accuracy needs to be improved to increase the effectiveness and lower the costs of antisubmarine search and barriers using sonobuoys dropped from ASW aircraft. These predictions can be improved during the mission by measuring the on-site sound propagation loss between a specially modified air-dropped electronic sound source, similar in concept to a long-lived MK 84 SUS sound projector, and the acoustic receivers in the air-dropped sonobuoys. The derived propagation loss, used in conjunction with the XBT-based predictions, can be used to more effectively select sonobuoy depths and patterns. The existing Mk 84 SUS projector could be modified to be neutrally buoyant and provide 140 ping seconds of preprogrammed transmissions over a 6-h life. The transmissions can be shaped for low probability of intercept or mimicry. Similar applications to improve sonar range prediction for surface ships are also addressed.
Ocean circumstance effects on the sound scattering of thermocline
Authors: Lin Junxuan , Bao Qinghua
Published: October 2005

R. Kind’s method of calculation was adopted in dealing with the reflected coefficient spectrum from layers of nonuniform plane waves. With measurements of temperature, salinity, and depth at the Southern Yellow Sea in China, data of simulated scattering signals were obtained. Compared with what the scattering signals were measured, it was proven that the mechanism of sound scattering was mainly dependent on the nonuniformity of temperature in the shallow sea. According to the magnitude of sea waves and the parameter of plankton distribution, it is possible to expound the fluctuation of sound scattering signals affecting by the ocean circumstance. The influence of the distribution of plankton density was merged as a background noise in it. The results showed that the primary factors of interference were the wind waves and swells. Under a second degree ocean condition, the variance of the arrived times of scattering signals is about 0.2 ms. In the case of a third ocean condition, the variance of the arrived times of scattering signals is 3.5 ms due to the wind wave and 1.5 ms due to the swell.
Sound scattering by rough interfaces and volume inhomogeneities of a layered seabed
Authors: Ivakin A. N.
Published: October 2005

A geoacoustic model of sound scattering by the sea floor is developed, in which the floor is considered to be an irregular layered medium with random scatterers of two types: The roughness of seabed interfaces and the volume inhomogeneities (spatial fluctuations of the acoustical parameters). Appropriate software has been developed to calculate frequency-angular dependencies of scattering coefficient on the frequency and directions of incident and scattered waves for the bottom model consisting of an arbitrary number of irregular layers. It is shown that characteristic scales of displayed interference patterns essentially depend on parameters of layers, roughness of interfaces, and volume inhomogeneities. An example of remote acoustic characterization of seabed media and estimation of their irregularities from acoustic sensing data is presented using analysis of interference pattern of the frequency-angular dependencies of backscattering coefficient of a bottom consisting of a silty layer overlaying a sandy half-space.‖
Acoustic silicon sensors
Authors: Sessler Gerhard M.
Published: October 2005

Future work in transducer engineering will be directed toward the use of silicon technologies for the fabrication of tiny acoustic sensors. For such devices, a number of transduction methods are suitable, for example the condenser, piezoelectric, and piezoresistive principles. Feasible also are microphones based on sound-wave-induced modulation of the drain current in a field-effect transistor, or acoustic sensors depending on the modulation of light propagation in a micromachined waveguide. Experimental silicon sensors according to all these principles have already been built, but their properties are often not yet satisfactory. Most advanced are two-chip condenser microphones with external biasing; electret biasing, and one-chip designs made with sacrificial-layer techniques are also under study. Future work will concern the improvement of the characteristics of all silicon microphones and the integration of amplifiers or signal-processing electronics on the microphone chip. Optical silicon microphones, as described above, will be particularly interesting in the future because of the rapid development of optical communications. Advantages of silicon microphones are small size (membrane areas∼1 mm2), low vibration sensitivity due to small diaphragm thickness (<1 μm), the possibility of integration of sensor and amplifier on a single chip, and potentially low cost due to batch processing.
Identification of sound radiation from a discontinuity
Authors: Driesch Patricia L.
Published: October 2005

The identification the of far-field sound radiation from a discontinuity on a beam is accomplished using a time-domain-based method that identifies the variations in wave propagation caused by the discontinuity. This identification of the far-field sound radiation includes determining the significance that each local variance in the metal has on the far-field sound radiation. The local variances are the material variances, geometric variances, and the applied stresses. To isolate the effects of the local variances on the far-field sound radiation, comparisons of many cases were made. The cases included aluminum versus steel, no discontinuity versus both a bolted and welded rib attachment, and a welded rib attachment versus the same geometry machined from one-piece of metal. Comparisons of these cases displayed a significant amount of far-field sound radiation around the rib attachment. These cases also displayed reflections of the structural waves at the rib attachment location. There were differences between the aluminum and steel cases, indicating a dependency upon the material. [Sponsored by ONR, Grant No. N00014-93-1-0493.]
Phonetic structures of an endangered language: Khonoma Angami
Authors: Blankenship Barbara
Published: October 2005

Angami is a Tibeto–Burman language spoken in the Naga Hills in the northeastern part of India. This study describes the phonetic inventory of one of the smaller Angami dialects, Khonoma, which is spoken by no more than 5000 people in the extreme west of the Angami region. Data for the study include recordings of two female and four male adult native speakers, along with palatographic samples and aerodynamic data for selected phonemes. Khonoma Angami has 45 consonants, 6 vowels, and 4 level tones. The plosives have a three-way contrast in voice onset time; nearly all other consonants have a two-way contrast, including the nasals and approximants. Angami voiceless nasals are different from the common type exemplified in, for example, Burmese. Aerodynamic measurements show that glottal opening during Angami voiceless nasals lasts until after the supralaryngeal articulatory closure is released, whereas in Burmese the glottis closes well before closure release. Thus Angami voiceless nasals could be described as ‘‘aspirated.’’ The inaudibility of formant transitions between the nasal and the following vowel leads to interesting questions of how place of articulation is perceived in initial voiceless nasals. [Work supported by NSF.]
Temporal masking in automatic speech recognition
Authors: Pavel M. , Hermansky Hynek
Published: October 2005

It is reasonable to expect that relevant features for speech recognition should be the features that are well heard. Therefore the successful extraction of such relevant acoustic features must respect properties of the auditory periphery. To examine its temporal properties full masking (detection) and partial masking (loudness matching) experimental paradigms are used. The results of these masking experiments suggested a model consisting of a combination of linear and nonlinear components. Hence a recently introduced RelAtive SpecTrAl (RASTA) engineering technique for speech feature extraction [Hermansky etal., Proc. Int. Conf. Acoustic, Speech, and Signal Process. (1993)] has been introduced, which employs linear temporal filtering of critical-band spectral energies done between two static nonlinearities and which has been successful as a feature extraction technique in automatic speech recognition. A correspondence between the results of the experiments and the behavior of the RASTA model has been found. Possible modifications of the RASTA technique to incorporate additional details of the experimental results will be discussed.
Statistical trajectory models for phonetic classification
Authors: Goldenthal William , Glass James
Published: October 2005

This talk presents phonetic models that capture both the dynamic characteristics and the statistical dependencies of acoustic attributes in a segment-based framework. The approach is based on the creation of a track, Tα, for each phonetic unit α. The track serves as a model of the dynamic trajectories of the acoustic attributes over the segment. The statistical framework for scoring incorporates the auto- and cross-correlation properties of the track error over time, within a segment. On a vowel classification task [W. Goldenthal and J. Glass, ‘‘Modeling Spectra Dynamics for Vowel Classification,’’ Proc. Eurospeech 93, pp. 289–292, Berlin, Germany (1993)], this methodology achieved classification performance of 68.9%. This result compares favorably with other studies using the timit corpus. This talk extends this result by presenting context-independent and context-dependent experiments for all the phones. Context-independent classification performance of 76.8% is demonstrated. The key to implementing the context-dependent classifier consists of merging tracks trained separately on left and right contexts to synthesize any desired context during classification. This method allows one to synthesize a track for triphone contexts not seen in the training set. Using a total of 4167 gender-dependent biphone tracks, 58 phonetic statistical models, and no phone grammar, a context-dependent classification performance of 80.5% was achieved. This result increases to 85.8% when a trigram phone grammar is added.
Phonetic structures of endangered languages: Investigative techniques
Authors: Ladefoged Peter , Maddieson Ian
Published: October 2005

The survival of many languages is endangered as the speakers die out or are absorbed into larger communities. Probably over half the 8000 languages in the world will not be spoken by the end of the next century. Their disappearance will result in a permanent loss of data for future phonetic investigations. Given the magnitude of the loss, there is a research problem in deciding which languages should be documented phonetically, and what is the best way of describing their phonetic structures. It was decided to investigate endangered languages that (1) are still actively spoke by a sizable community; (2) are sufficiently well studied so that their phonological structure is known; (3) have features that are of phonetic interest. At least five speakers were recorded saying sets of words and phrases that illustrate the phonological constrasts. Then standardized descriptions were made in quantified form using a set of basic phonetic measures, designed to characterize both specific and universal phonetic features. The data include aerodynamic records that reveal airstream mechanisms and the timing of articulatory gestures, video of lip movements, and palatographic records showing articulatory contacts. Full acoustic analyses are made in the UCLA Phonetics Laboratory. [Work supported by NSF.]
Phonetic transition modeling for continuous speech recognition
Authors: Phillips Michael , Glass James
Published: October 2005

Currently, most speech recognition architectures model the speech signal as a nonoverlapping sequence of phonetic segments. A set of phonetic models is created that attempt to capture the acoustic-phonetic properties of individual phones, but do not explicitly model the transition between phones. It is readily apparent, however, that these transitions contain important information about the identity of neighboring phones. While context-dependent phonetic modeling may capture some of this information, it is likely that more explicit models of phonetic transitions could offer performance improvements. In this talk, the use of phonetic transition models will be discussed within the context of summit, a segment-based continuous speech recognition system [Zue etal., ‘‘Acoustic Segmentation and Phonetic Classification in the summit Speech Recognition System,’’ Proc. ICASSP 89, pp. 389–392, Glasgow, Scotland (1989)]. The transition models use a feature vector based on Mel-frequency spectral coefficients (MFSC’s). The vector is created by concatenating multiple spectral averages on both sides of a transition. For example, in one configuration a total of eight averages were used which spanned a total time interval of 150 ms. In order to reduce the number of dimensions, a principal component analysis was performed. A set of diagonal Gaussian models is used to model the transitions. The models were tested by applying them to the N-Best sentence hypotheses from the recognition system. Each of the N-Best hypotheses is rescored using a linear combination (optimized on training data) of the segment and transition scores. Initial experiments have resulted in 10%–20% reductions in word error rates.
Issues in feature-based recognition of speech mixed with impulsive sounds
Authors: Bitar Nabil N. , Mani Ramamurthy , Espy-Wilson Carol Y. , Nawab S. Hamid
Published: October 2005

In this study, the feasibility of a knowledge-based approach to speaker-independent speech recognition in the presence of impulsive environmental sounds such as knocks, clinks, and claps is examined. Statistical approaches to speech recognition have had some success in dealing with steady background, probably because they have concentrated on routinely encountered steady background sounds, most of which can be modeled as white or colored noise. However, current statistical approaches are less suited to dealing with environments containing sporadic occurrences of various discrete-event sounds because of (1) the enormous variety of discrete-event sounds and (2) discrete-event sounds can be mixed with the speech signal with different loudness and temporal alignments. In this study, experiments are being performed on feature-based speech recognition using speech sounds (from a database of spoken telephone numbers) mixed with impulsive sounds (from a database of everyday environmental impulsive sounds). An important objective of this research is to determine how different acoustic cues (formants, pitch, frication noise, stop bursts, etc.) are influenced by the presence of different impulsive sounds. [This research was supported by NSF Research Grant No. IRI-9300194.]
A feature-based broad speech classifier
Authors: Bitar Nabil N.
Published: October 2005

As part of a feature-based speech recognition system, a broad classifier that automatically labels the speech signal in terms of one of the six categories silence, stop, fricative, vowel, semivowel, and nasal was developed. The classifier is based on the detection of acoustic correlates for the linguistic features consonantal, continuant, nonsyllabic, and sonorant. Acoustic properties for the features are detected on the basis of events such as minima, maxima, or changes from a low to high value (or vice versa) in some defined signal parameters (e.g., low-frequency energy). These landmarks may point up particular instants in time, or they may define regions within the waveform. Fuzzy logic is used to represent the fact that features are manifest in the signal with varying degrees of strength. Preliminary results with the TIMIT database are promising and our analysis shows that phenomena such as coarticulation and phonetic lenition are better handled if all of the acoustic properties are extracted in parallel so that a decision about a speech category is not made until all information is available. [This research was supported by NSF Research Grant No. BNS-8920470.]
An investigation of continuous speech recognition performance from unconstrained speech utterances
Authors: Rose R. C. , Juang B. H. , Lee C. H. , Lee L.
Published: October 2005

This paper is concerned with small vocabulary speech recognition from conversational utterances over the telephone network. Modeling techniques are investigated for dealing with large numbers of nonvocabulary words and artifacts that arise in these utterances. A hidden Markov model (HMM)-based continuous speech recognition system using a frame synchronous Viterbi beam search decoder is used for recognition. Keyword models compete in the finite state network with ‘‘filler’’ models of nonkeyword speech. Several issues were investigated relating to the quality of acoustic representations and language representations for this task. The first issue that was investigated was the definition of acoustic subword units using allophone clustering procedures. The second issue was the size of the vocabulary used for modeling non-keyword utterances. Finally, the last issue was the use of language models in unconstrained speech tasks. Experimental results will be presented for a 20-keyword recognition task where performance was evaluated on continuous utterances from 22 speakers. The results showed that all of the procedures including decision tree based allophone clustering, better out-of-vocabulary speech representations, and language models contributed to overall recognition performance. The best performing system provided 76% average probability of keyword detection at 5.8 false alarms per keyword per hour.
The two-scale model from the point of view of a small slope approximation
Authors: Voronovich A. G.
Published: October 2005

The two-scale model (TSM) is widely used for interpretation of data concerning wave scattering at rough surfaces. On the other hand, a small slope approximation theory (SSA) is able to consider the same situation without introducing somewhat arbitrary scale-dividing parameter. It is shown that under appropriate conditions the SSA reproduces the results of TSM. Dividing of spectrum of roughness into two components can be considered in this case as a numerical mode for calculating the corresponding integrals arising in SSA. Moreover, statistical dependence of the small-scale component of roughness upon shape of large-scale undulating surface is taken into account. Thus the statistics of small-scale component of roughness is not assumed to be space homogeneous. As a result the small-scale component of spectrum in the final expression for scattering cross section is modified. The forms of correlation functions of roughness which should be substituted to the presented theory are specified. Corresponding results can be of interest for scattering of high-frequency waves from surfaces possessing wide spectrum of roughness (as wavy sea surface). [This work is partly supported by NRC.]
Can strong mode coupling be exploited?
Authors: McDonald B. Edward , Kuperman W. A.
Published: October 2005

The Heard Island Feasibility Test brought to light higher levels of acoustic mode coupling than some researchers had expected. Mode coupling appears to complicate the interpretation of propagation experiments. Investigation is beginning into whether complexity in modal energy distribution has positive rather than negative implications for the ATOC program (acoustic thermometry of ocean climate). Mode coupling matrix elements consist of vertical integrals involving the local acoustic eigenmodes and horizontal gradients of environmental variables. The coupling matrix separates into a component due to bathymetric interaction and a component due to volumetric inhomogeneities. The different symmetries of these two components may help to identify their separate contributions to mode coupling along a specific propagation path. For strong mode coupling, the eigenstates of the coupling matrix and examined. Such eigenvalues consist of vertical mode populations (which are called ‘‘supermodes’’) in which energy circulates among the acoustic modes in fixed patterns along the propagation path. The question of what the supermodes look like, and whether they can be identified in propagation experiments will be addressed. [Work supported by NRL and ARPA.]
Acoustic thermometry in the Northeast Pacific: 1983–1989
Authors: Spiesberger John L. , Merdes Daniel
Published: October 2005

Between 1983 and 1989, acoustic thermometers were used to measure basin-wide temperatures in the Northeast Pacific. One set of experiments was conducted between the Kaneohe source (133 Hz, 60-ms resolution) and about ten U. S. Navy SOSUS stations. The other set of experiments was conducted between three moored sources (250 Hz, 16-ms resolution) and the same SOSUS stations. Over 14 of the 16 sections, the multipaths can be understood using ray theory. Even though sound from the Kaneohe source interacts with the bottom many times, ray theory succeeds in interpreting the multipath pattern. In the summer of 1987, the Northeast Pacific is colder than climatology based on Levitus’ atlas. [Work supported by Advanced Research Projects Agency and Office of Naval Research.]
Internal-wave effects on multi-megameter oceanic acoustic tomography
Authors: Flatté Stanley M. , Bracher Charles , Colosi John A. , Rovner Galina
Published: October 2005

Parabolic-equation numerical simulations which utilize environmental data and which take into account sound-speed perturbations obeying the Garrett–Munk spectral model for internal waves have been carried out. Several effects of these simulated internal waves have been compared with path-integral calculations: of the internal-wave bias, the wander of the wave front assuming a fixed ray trajectory, and the fluctuation of arrival time due to other effects such as the spread of the arrived pulse. The range dependence of these effects were determined. The effects of internal tides on measurements of mesoscale structure will be discussed. Also discussed are the speed and coupling of the amplitudes of vertical acoustic modes as a function of frequency, range, and mode number. The implications of these findings for ocean acoustic tomography of mesoscale structure and of climate will also be discussed. [Work supported by ONR Ocean Acoustics.]
A global survey of the impact on acoustic propagation of deep water warm core ocean eddies
Authors: Browning David G. , Christian Raymond J. , Petitpas Linda S.
Published: October 2005

Warm core eddies have been reported throughout the oceans of the world, usually associated with warm boundary currents such as the Gulf Stream. The physical characteristics and impact on acoustic propagation conditions were compared for various eddies at locations ranging from the East Greenland Current to the Tasman Sea. The eddies were found to have some common features such as a conical shape and increased sound speed. On the other hand, the acoustic impact was significantly determined by the sound-speed profile in the adjacent water to the eddy and this was found to vary greatly from site to site. In addition, seasonal secondary sound channels were formed across the eddies at some locations. In general, the greatest acoustic impact of a warm core eddy was for a shallow source and receiver configuration.
The frontal effect in ATOC
Authors: Shang E. C. , Wang Y. Y.
Published: October 2005

Acoustic propagation along the Hawaii–Aleutain path of ATOC has been investigated based upon two ocean models: (1) Levitus annual mean data on a 1-deg grid and (2) Semtner–Charvin’s model of one realization (Feb.) with 1/2-deg resolution. The adiabaticity has been evaluated by using four indicators: (a) adiabatic travel time discrepancy, (b) modal repopulation, (c) modal dispersion, and (d) mode-coupling matrix. It is found that significant mode coupling takes place at the sub-Arctic front area (N-44.8°) in Semtner–Charvin’s model but not in Levitus model because Semtner–Charvin’s model gives a much stronger double channel at that area than Levitus data. [Work supported by ARPA and NOAA.]
Global acoustic propagation modeling using MaCh1
Authors: Brown Michael G.
Published: October 2005

MaCh1 is a broadband, range-dependent acoustic propagation model based on the one-way form of the Maslov integral representation of the wave field. The one-way propagation assumption may—but need not—be combined with a parabolic approximation. MaCh1 model predictions along multi-megameter great circle propagation paths using climatological sound-speed structure and coarse resolution bathymetry will be shown. Model predictions will be compared to preliminary ATOC (acoustic thermometry of ocean climate) program measurements if the latter are available.
Exploring the Japanese McGurk effect using various S/N ratios and speakers
Authors: Sekiyama Kaoru , Nishino Keiko
Published: October 2005

The McGurk effect demonstrates that perceivers integrate auditory and lip-read speech even when two sources of information conflict. Whereas this effect is robust in English, it was found [K. Sekiyama and Y. Tohkura, J. Phon. 21, 427–444 (1993)] that it is much weaker among Japanese perceivers. This was further examined. In experiment 1, Japanese subjects were tested under various S/N conditions produced by combining four speech (65, 58, 51, and 44 dB) and four white noise (56, 48, 40, and 32 dB) levels. The audio-visual speech stimuli were those used in the earlier study and were created from a Japanese speaker’s utterances of ten monosyllables (/ba,ma,pa,wa,da,na,ta,ga,ra,ka/). Subjects were asked to report what they heard. When the noise level was lower than the speech level, the McGurk effect was not as strong as the one reported for English. In experiment 2, Japanese subjects were tested with a new stimulus set created from four Japanese speaker’s utterances of eight monosyllables. The stimuli (58 dB) were presented without adding noise. The weak McGurk effect was replicated. From these results, it is generalized that the Japanese tend to be less subject to the McGurk effect.
Talker variability and the identification of American English /r/ and /l/ by Japanese subjects
Authors: Magnuson James S. , Yamada Reiko A.
Published: October 2005

Experiments are described that designed to investigate how Japanese subjects develop criteria for ‘‘R’’–‘‘L’’ decisions. Subjects were asked to identify English words beginning with /r/ and /l/ in two conditions: blocked (all words produced by one talker) and mixed (words produced by several talkers). Subjects performed more accurately in the blocked condition than in the mixed condition. This indicates that, as is generally true for native-language perception, stable talker characteristics facilitate non-native speech perception. Subjects also exhibited preferences for ‘‘R’’ or ‘‘L’’ responses for some talkers in one condition, but the opposite or no preference in the other. Together, these results indicate that in the blocked condition, subjects adopted talker-specific criteria. However, when the talker changed randomly in the mixed condition, subjects were not able to adjust their criteria for each talker, but apparently based their criteria upon the range of all /r/s and /l/s they heard. Thus subjects made more responses based on the ‘‘R’’ category for some talkers, and more based on ‘‘L’’ for others. The implications for theories of perceptual normalization and non-native speech perception will be discussed.