bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-frequency ocean ambient noise variability: Measurements
Authors: Browning David G. , Carey William M. , Von Winkle William A.
Published: October 2005

The interaction of the wind with the ocean surface is recognized as a major source of ambient noise, however, at low frequencies (<200 Hz) it is often difficult to isolate wind-generated noise from shipping noise. This is further complicated by a relatively low transmission loss at these frequencies which allows possible noise contributions from long distances and various propagation paths. An analysis is made of historic ambient noise data based on recent developments in noise generation and sound propagation theory to sort out the ship-generated noise component. The results appear to support two distinct wind-generated noise mechanisms which may be delineated, as suggested by Kerman, by a critical surface velocity.
Measurements of ambient noise “hot spots” along the ice edge in the Greenland Sea Marginal Ice Zone
Authors: Biggs Kristian P. , Gruber Patricia L. , Bourke Robert H.
Published: October 2005

During July 1987, an experiment was conducted to measure ambient noise along the ice edge in the Greenland Sea. Ambient noise “hot spots,” concentrated areas of relatively high noise levels, were located along the ice edge using a towed array. Ambient noise levels were then recorded using sonobuoys deployed from P3 aircraft. The sonobuoy data were averaged in time to obtain the noise spectra below 2 kHz. The temperature structure of the area was determined by XBT and AXBT buoys and the ice edge location was determined from coincident satellite photos, 90-Ghz microwave imagery, and P3 radar ice edge maps. The relationship between the environmental and acoustic data suggests the existence of hot spots which are (1) primarily related to wind and sea state and (2) primarily related to ice edge compaction by eddy flow.
Demonstrations of underwater noise generation by bubbles
Authors: Crum Lawrence A. , Pumphrey Hugh C.
Published: October 2005

In 1933, Minnaert demonstrated that the sound of a babbling brook was due to the oscillations of gas bubbles entrained in the water [M. Minnaert, Philos. Mag. 16, 235 (1933)]. In 1959, Franz discovered that rain drops could produce relatively large amounts of underwater noise through the entrainment of gas bubbles during drop impact [G. J. Franz, J. Acoust. Soc. Am. 31, 1080 (1959)]. In 1988, Prosperetti suggested that a major contribution to ocean ambient noise was due to bubbles [A. Prosperetti, J. Acoust. Soc. Am. 84, 1042 (1988)]. A series of demonstration experiments will be presented that are not difficult to assemble and that will show that gas bubbles are a major source of underwater noise for a variety of hydrodynamic situations. [The research leading to the understanding of these effects has been supported by the ONR.]
Development of a “dry” system for the measurement of porosity
Authors: Champoux Yvan , Stinson Michael R. , Daigle Gilles A.
Published: October 2005

In this paper, an experimental system that permits rapid and convenient measurement of the porosity of materials is described. The use of liquid, either directly in the technique or for temperature stabilization, is avoided. In this sense, it is truly a dry porosity measurement technique. Porosity is one of several physical parameters required for various theoretical models, to characterize a porous material. The proposed technique is based on the approach suggested by Beranek [J. Acoust. Soc. Am. 13, 248 (1942)]. The pressure change in a closed volume (with and without a sample) is monitored for a given change in volume. To simplify the manipulation and to improve the precision, the liquid is replaced by a calibrated plunger and an electronic pressure transducer. The volume displacement being kept small, the temperature rise is minimal and the isothermal condition is obtained without the need to use any liquid-filled bath to stabilize the temperature. A calibration procedure is required though, to account for possible movement of the transducer diaphragm. Preliminary experimental results and error analysis suggest that porosity can be measured with this approach with 1%–2% accuracy.
Forward projection of a transient tomographically reconstructed pressure field. II
Authors: Forbes Michael J. , Letcher Stephen V. , Stepanishen Peter R.
Published: October 2005

The forward projection of transient pressure fields from ultrasonic transducers has been investigated both experimentally and theoretically. The transient pressure field of a plane in front of a transducer is projected to another plane further from the transducer using wave-vector and time-domain methods that are implemented using FFT's. We have previously shown that this projection algorithm gives good results when applied to the field of a piston that is calculated using impulse-response methods. In the current work, experimentally determined transient pressure fields in a plane in front of typical medical or NDE transducers have been obtained using optical tomographic methods to measure a two-dimensional slice of the field as a function of time. The forward projection of the space- and time-dependent field via our projection algorithm yields results that are in good agreement with the optically measured field at the new plane. A comparison of analytical and experimental results will be discussed along with potential applications of the method for transducer calibration and characterization.
Unidirectional magnetostrictive/piezoelectric hybrid transducer
Authors: Butler John L. , Butler Stephen C. , Clark Arthur E.
Published: October 2005

The object of the hybrid transducer is to produce enhanced motion at one end and canceled motion at the other end. In the simplest form the transducer consists of a quarter wavelength section of piezoelectric material joined to a quarter wavelength section of Terfenol-D rare-earth magnetostrictive material. A 3-kHz experimental hybrid transducer with a total length of 18 in. was constructed with a small central mass and two small equal end piston masses. Measurements on this device showed an average front-to-back ratio of approximately 17 dB. The operating theory, equivalent circuit analysis, and measured results will be presented. The results confirm the original 1984 theoretical prediction [U.S. Patent 4,443,731]. [Modeling effort supported by SBIR.]
Power output and efficiency of sound production by crickets
Authors: Forrest T. O.
Published: October 2005

Male crickets produce calling songs that function to attract mates. Sound is produced when membranes of the wings are caused to vibrate during stridulation. Sound fields were measured for three species of crickets. Two species of mole crickets, Scapteriscus acletus and s. vicinus, call from within burrows constructed in the soil. Sound fields of the mole crickets were hemispherical and the power output averaged 4 μW (N = 22, range 2–22 μW). Power output was dependent upon male size and moisture content of soil surrounding the burrow. Efficiency of sound production was estimated to be less than 0.2%. Sound fields of a species of tree crickets, Oecanthus quadripunctatus, approximated that of a doublet source. Power output ranged from 2–17 μW (N = 6) and efficiency was estimated at about 1%.
Detecting FM of coherently and incoherently modulated components of complex sounds
Authors: Carlyon Robert P.
Published: October 2005

Thresholds were measured for the detection of FM of four-component carriers, where each carrier component was modulated by the same percentage of its starting frequency (“F0 modulation”). The frequency spacing between components was such that they were resolvable by the peripheral auditory system. Each component was modulated by a single cycle of a 12.5-Hz sinusoid, whose phase was either the same for all components (“coherent modulation”), or differed between components (“incoherent modulation”). Preliminary experiments revealed little or no effect of modulator coherence on thresholds, for stimuli presented either in quiet or in bursts of pink noise. This noise will be compared to the outcome of further experiments, in which the coherent and incoherent signals were presented with competing frequency-modulated sounds. The results of all the reported experiments will be discussed in relation to the mechanisms by which listeners separate out concurrent complex sounds.
Prosodic information in telephone digit strings
Authors: Basson Sara H. , Spitz Judith , Jankowski Charles R.
Published: October 2005

Intonation of naturally produced telephone digit strings appears to conform to particular patterns. Concatenating strings of digits produced with “default” intonation highlights the importance of maintaining appropriate intonation patterns for intelligible, natural-sounding speech. The purpose of this experiment was to quantify the acoustic events resulting in natural-sounding telephone number digit strings. Acoustic features of approximately 1000 digits produced in the context of telephone digit strings were measured. The data were gathered at MIT by presenting volunteer speakers with lists of seven-digit numbers to read. Shifts in fundamental frequency of the vowel, changes in overall energy, and digit duration as a function of position in the digit string were calculated. These results can prove useful for speech recognition and generation. For automatic speech recognition of digit strings, prosodic contours provide cues about word boundary locations and serve as a source of information for error detection and correction. When concatenating stored speech to produce natural sounding digit strings, these findings provide guidance as to how many templates need to be created. Finally, for text-to-speech synthesis, these results suggest the number of rules necessary to model natural-sounding digit strings.
Perceptual normalization of talker differences
Authors: Nusbaum Howard C. , Morin Todd M.
Published: October 2005

Different talkers may produce the same phoneme with different acoustic patterns and different phonemes with similar acoustic patterns. In order to recognize speech correctly, a listener must use information about the talker's vocal characteristics. A speeded target-monitoring task was used to investigate whether each token of speech contains sufficient information for normalization or whether a sample of a talker's speech must be heard to normalize subsequent segments. Subjects listened to a sequence of syllables for a particular target. In one type of trial, targets and distractors were produced by a single talker; in other trials, targets and distractors were produced by a mix of talkers. If each token of speech is self-normalizing, there should be no difference between conditions. Otherwise, performance should be worse in mixed-talker trials. In another experiment, the available cognitive capacity for recognizing speech was manipulated and recognition of speech produced by a single talker compared to a mix of talkers was examined. The results of these experiments have implications for the type of mechanisms used in normalization and for the attentional limitations they impose on listeners. [Work supported by AFOSR and BRSG.]
Some perceptual correlates of phase in RELP coded speech
Authors: Peet Margot , Evans Ward R. , Creekmore Joseph
Published: October 2005

A series of experiments tested the contribution of phase information to the naturalness of residual excited linear prediction (RELP) coded speech, that is, how close a speaker's voice sounds under RELP coding to its unprocessed analog. Listeners were presented with a corpus of sentences uttered by eight speakers (four male and four female). Three classes of approximations of the residual phase spectra were employed on these sentences: quantized approximations for decreasing bit rates, noise-corrupted approximations for increasing noise levels, and combinations of these over varying window sizes. Listeners classified these utterances on the basis of their proximity to unprocessed speech. Results indicate that residual phase spectrum provides information about voice timbre and quality and acts as a cue to speaker identity in coded speech.
Underwater noise generated by Columbia River hydroelectric dams
Authors: Miyamoto Robert T. , McConnell Steven O. , Anderson James J. , Feist Blake E.
Published: October 2005

Low-frequency (10–1000 Hz) underwater noise measurements have been made in water within and upstream from four Columbia River hydroelectric dams. The motivation for these measurements was to map out the sound field within and upstream from the power dams as a first step in understanding the effect of this field on the behavior of migrating salmonids that must choose between the bypass system or intakes to the turbines. Eventually sound may be used to guide the juvenile fish safely past the turbine intakes and into the bypass system. Thus far, single hydrophone measurements have been made in the bypass slots within the dam and at a number of locations upstream from the dam. The noise level varies with location, decreasing as the hydrophone is moved upsteam from the dam and as the hydrophone is moved closer to the water surface immediately upstream of the dam as well as in the bypass slot. The noise spectra below 200 Hz are highly modulated, displaying one or more sharp peaks, which indicates resonances in the structural generating mechanism or propagation path. The spectrum level and modulation vary significantly from one dam to another and sometimes from one configuration to another (e.g., when one of the turbines is on or off). A final set of measurements will be made at the Bonneville Dam using several hydrophones placed at a number of locations in the vicinity of the intake channel, and these may help identify sources and propagation paths to the hydrophone. [Work sponsored by U. S. Army Corps of Engineers.]
VLF acoustic ambient ocean noise measurements using Swallow floats
Authors: D'Spain G. L. , Hodgkiss W. S. , Culver R. L. , Edmonds G. L.
Published: October 2005

A set of independent, freely drifting, neutrally buoyant, VLF (1–20 Hz) acoustic sensors have been under development at the Marine Physical Laboratory. These Swallow floats each contain a three-component geophone for measuring VLF particle velocity, a magnetic compass, an 8-kHz acoustic localization system, and hardware to record 24 h of digitized data. By modeling the ambient noise field as a sum of independent, randomly distributed plane waves, the particle velocity power spectra estimated from geophone data can be converted into equivalent pressure power spectra. Derived pressure power spectra from four deep water (water depth > 3.5 km) deployments are compared to pressure spectra recorded by concurrently deployed sonobuoys and bottom-mounted hydrophones and to previously reported pressure spectral levels. In a recent deployment, four floats were equipped with VLF hydrophones as well as geophones. Comparisons are made between the power spectra estimated from geophone and hydrophone data collected at the same time and place by these floats. [Work supported by ONR.]
Relevant factors in modeling laryngeally controlled vocal vibrato
Authors: Shipp Thomas , Doherty E. Thomas
Published: October 2005

Rhythmic frequency oscillations that characterize vocal vibrato are produced by either of two mechanisms. One involves driving the system with respiratory pulses and the other by intrinsic laryngeal muscle activity. In this latter mode, vibrato is most readily produced when several laryngeal aspects are in order: (1) the singer's neuromuscular system has matured beyond a childhood level; (2) a critical balance of adductory-to-abductory force is applied to the vocal fold margins; and (3) the larynx is positioned vertically in the airway so that excessive vertical stiffening of the mucosal lining is avoided. When these conditions are met, the intrinsic laryngeal muscle activity to produce a given pitch changes from a relatively stable interference pattern to quasiperiodic modulated muscle activity oscillating at about 5.5 to 6.0 Hz. The average value of the modulated EMG pattern equals the steady-state EMG signal used to produce that frequency without vocal vibrato. Whether only the cricothyroid muscle or other intrinsic and/or extrinsic muscle are involved in this type of vibrato production is unknown at this time.
Acoustic studies of the voice source in male singers
Authors: Sundberg Johan
Published: October 2005

This paper reviews various recent investigations with various co-workers of male singers' vocal fold function mainly studied by inverse filtering for deriving the waveform of the transglottal airflow during phonation. Theoretical and experimental studies confirmed the dominating acoustic importance of (1) the peak airflow Ûg for the amplitude of the voice source fundamental, and (2) the negative peak amplitude of the differentiated waveform dU/dt for the SPL of the radiated sound. Unlike nonsingers, some professional baritone and bass singers have been found to retain a high Ûg during loud tones at high pitches. Different strategies are possible for increasing dUg/dt for loudness variation: increasing Ug, increasing the duration of the closed phase, and skewing the pulse shape. Different singers use different combinations of these alternatives depending on pitch, loudness range, and voice type. Some of the physiological correlates of these strategies can be postulated. Here, Ûg seems highly dependent on the degree of glottal adduction and dUg/dt on subglottal pressure. However, influence of the breathing strategy has also been quantitatively demonstrated.
Vedic chanting and vowel intrinsic pitch: Evidence from an ancient source
Authors: Ananthapadmanabha T. V. , Silverman Kim , Prasad M. G.
Published: October 2005

The purpose of this paper is to shed further light on the aetiology and speech specific nature of vowel intrinsic fundamental frequency (IF0), by investigating its presence in vedic chanting. This is one of the earliest forms of chanting (circa 5000 years old) which is still prevalent today, predating much of Indian classical music. It is interesting to study vedic chanting as it represents the borderline between speech and singing. There are three distinct tone levels in this chanting referred to as: (a) udatta high, (b) anudatta low, and (c) svarita, in-between. Sanskrit grammarians classify vowels according to the position of the tongue body and use the same labels as above for marking the tones. The interaction of vowel height and tone level in this vocal mode is investigated. Several vedic passages from three chanters with different vowels occurring with the same tone level and different tone levels for the same vowel have been recorded. Initial measurements of F0 suggest that chanters can override the effect of IF0 to achieve the same relative pitch values. This implies that the effect of IF0 depends on vocal mode and an active control of IF0 is possible.
Evolving ideas of cochlear sound analysis and stimulus representation in hearing
Authors: Goldstein Julius L.
Published: October 2005

Classical principles of cochlear operation and function in hearing are undergoing major revision because of recent biophysical discoveries that normal cochlear sound analysis is largely determined by centrally controlled nonlinear motor responses from the outer hair cells and that neural temporal entrainment can represent monaural stimulus information. Helmholtz's psychophysically and anatomically based hypothesis of tonotopic cochlear analysis is fully supported, but revision is required of the classical model he inspired, of that analysis as a tonotopic array of linear filters passively monitored by short-memory energy detectors. Challenges to the classical model have been presented throughout the history of auditory science from psychophysical studies of combination tones, idiotones, masking, and periodicity pitch. Hence, it is proposed that psychophysics can now be exploited systematically and interactively with biophysical knowledge to contribute to developing the required revised cochlear principles. To get beyond the establishment of correlations between psychophysical and biophysical data for specific phenomena, models of some generality are needed for cochlear nonclassical responses and for psychophysical measurement. It is proposed that ideal observer theory provides a general working hypothesis that has been successful in filling the second need. A new signal processing model for nonlinear and active cochlear frequency analysis was formulated to fill the first need. Two modeling studies of the relationship between psychophysics and physiology will be described in detail for periodicity pitch and nonlinear masking.
Vibration transmission in and sound radiation from a scaled model of a ship's engine room
Authors: Levi Alfred , Lyon Richard H.
Published: October 2005

The vibration transmitted from a power plant foundation through supporting structure and fluid containing tanks into the hull structure, and then into the surrounding fluid has been studied for a scale model of a frigate ship. The scale model is approximately 1:6 and the scale frequency range is from 315–10 000 Hz. Transfer functions relating structural vibration and radiated sound power to input force (or injected mechanical power) have been measured. These experimental results have also been compared with SEA calculations of vibration transmission and sound radiation. Of special interest is the role of in-plane vibrations on the energy transmission within the structure, and into the sound field.
Acoustic attenuation in syntactic foam and heavy silicone rubber composites
Authors: Lim Raymond , Hackman Roger H.
Published: October 2005

Recently, a particularly effective underwater sound attenuator has been described experimentally by workers at the Naval Surface Weapons Center using an impedance tube to measure echo returns [W. M. Madigosky et al., Multiple Scattering of Waves in Random Media and Random Rough Surfaces, edited by V. V. Varadan and V. K. Varadan (Pennsylvania State University, 1985), p. 615]. The attenuator studied was composed of a rigid syntactic foam matrix loaded to 40% by volume with many large viscoelastic rubber inclusions. The present paper uncovers the fundamental attenuation mechanisms operating in this composite by analyzing the scattering behavior of a single spherical scatterer embedded in an elastic matrix. Effects due to resonant scattering by elastic and viscoelastic spheres are studied via the T-matrix formalism. The dynamics of the scattered field at the water-syntactic foam interface are also analyzed via classical elastic theory at a plane interface. The results of these analyses point to resonant compressional to shear mode conversion at the inclusion sites as ultimately responsible for the attenuations observed by Madigosky et al. Consequences of the mode conversion leading to attenuation include the trapping of backscattered shear waves and the enhancement of dissipation mechanisms within the inclusion.
Boundary element analysis of viscoelastic structures involving fractional operators
Authors: Xie Ke-jun , Ciskowski Robert D. , Royster Larry H.
Published: October 2005

The boundary element method (BEM) is applied to solve viscoelastic structural problems. The viscoelastic characteristic of the structure is represented using the fractional integrodifferential operators. The fractional operator representation of viscoelasticity provides a means to more accurately describe the mechanical behavior of viscoelastic materials. In this paper, a direct BEM formulation for the transient dynamic analysis of three-dimensional viscoelastic structures modeled by the fractional operator constitutive equations is presented. The BEM formulation is developed in the Laplace transformed domain. The transient problem is first solved in the Laplace transformed domain and the time domain solutions are obtained by using an FFT based numerical inversion procedure. Example problems are solved using this BEM formulation and the results are compared.
Inverse filtering for the analysis of vocal function
Authors: Rothenberg Martin
Published: October 2005

The waveform of the volume velocity of the airflow through the larynx, as obtained by inverse filtering the volume velocity of the airflow exiting the mouth and nose, is a potential convenient noninvasive measure of the vibratory pattern of the vocal folds during voiced speech. Of special interest is a measure that is sufficiently robust for clinical use in the detection, monitoring, and treatment of voice disorders. The problems in this application are of three types: (1) The parameters of the inverse filter must be set to match the acoustic transfer function of the vocal tract; (2) glottal airflow is, in some way, not an accurate indicator of vocal fold motion; and (3) the analysis must be accurate under a wide range of normal and disordered voice qualities and possible nasal coupling. Because of these problems, it has been difficult to find a robust and accurate automatic procedure, even if the analysis is restricted to only the simplest case of open vowels. However, there appears to be a rather straightforward, although unconventional, solution to this inverse-filtering problem if (1) the vocal fold vibratory parameters of most interest are properly defined, (2) physiological restrictions on the possible vibratory patterns are taken into account, and (3) the nonlinear interaction between the glottal source and the vocal tract acoustics is used in the analysis procedure.
Inverse problems in nondestructive evaluation
Authors: Thompson R. B.
Published: October 2005

The goal of nondestructive evaluation is to obtain information about the state of a structural or electronic component that will allow a quantitative assessment of its future serviceability. Because of the ability to penetrate opaque media, ultrasound is one of the most widely used forms of interrogating energy. This paper will consider several current problem areas, ranging from the measurement of material properties such as porosity or grain structure through the characterization of the nature of discrete flaws and the determination of their size and shape. In each case, an interpretation of the measurement in terms of elastic wave scattering theory will be followed by a discussion of the inverse theories used to interpret the data, with emphasis on assumptions required to obtain unique solutions. The presentation will conclude with a discussion of future directions of needed research.
Multiparameter inversion for acoustic and elastic media
Authors: Burridge Robert , Beylkin Gregory
Published: October 2005

Inversion and imaging of an acoustic two-parameter medium and for a three-parameter isotropic elastic medium from seismic data are discussed. The inverse problem is linearized by considering the actual medium as a perturbation from a known background model. By using the single-scattering approximation, integral equations relating the singly scattered field linearly to the unknown parameters are obtained. Asymptotic solutions of the linearized inverse problem are derived using the generalized Radon transform. This method is closely related to methods of seismic migration. Spatially varying background parameters and an almost arbitrary source-receiver configuration are allowed. The computation is performed in the time domain. All available data are used even if redundant. Combinations of the parameters which can be reconstructed best and worst are identified. The data may be read just once and in an arbitrary order.
Exact analytic reconstruction in multidimensional inverse problems
Authors: Nachman Adrian I.
Published: October 2005

This presentation will review some recent mathematical breakthroughs in inverse scattering theory. Consider the pressure wave p(r,s,ω) generated by a point source s oscillating harmonically with frequency ω ∇r⋅{[1/ρ(r)]∇rp(r,s,ω)} + ω2K(r)p(r,s,ω) = −δ(r−s). The problem of determining the density ρ(r) and the compressibility K(r) from knowledge of p(r,s,ω) for sources s and receivers r located on a given surface S has been considered notoriously difficult. Traditional approaches rely on Born or Rytov approximations. A new constructive method for recovering ρ and K from measurements on a surface S with arbitrary geometry, at two frequencies ω1, ω2, will be presented. The procedure involves the solution of certain integral equations on S. No simplifying approximations are made, and the reconstruction is, in principle, exact.
Phase space and path integral methods in direct and inverse scattering
Authors: Fishman Louis
Published: October 2005

Direct and inverse wave propagation models in ocean seismoacoustics are often complicated by the extended, variable, three-dimensional channeling environments encountered. Even for the zeroth-order picture of a transversely inhomogeneous environment, the domain of interest is entirely within the scattering regime, with the subsequent absence of an “asympotically free,” or homogeneous, region. While there are numerous methods for attacking the one-way direct calculation, most approaches to the corresponding inverse (tomographic) problems essentially rely on a linearization about a well-chosen, zeroth-order model. Phase space and path integral techniques, which extend homogeneous Fourier methods to inhomogeneous environments, lead to comprehensive mathematical and computational direct models, in addition to providing the framework for the exact solution of the transversely inhomogeneous refractive index profile reconstruction problem. These pseudodifferential and Fourier integral operator methods are largely based upon the properties and interrelationships of the corresponding operator symbols. This talk will present the most recent developments and applications of the phase space and path integral methods, as applied to the scalar Helmholtz equations, for one-way direct and inverse modeling. [Work supported by NSF, AFOSR, ONR.]
Inverse problem for an immersed solid/liquid/solid plane structure
Authors: Izbicki J. L. , Lenoir O. , Rembert P. , Maze G. , Ripoche J.
Published: October 2005

The scattering from an immersed plane multilayer is studied in order to determine the physical parameters of the multilayer. It is composed by two solids that are coupled by a film of water about 0.3 mm thick. The insonification is performed by short pulses. The frequency range is about from 0.5 to 3 MHz. The longitudinal phase velocities of the two solids are obtained through an angular study. The FFT processing of parts of the signal is performed at normal incidence. The thicknesses of the two solids are thus derived. Absolute measurements of the specular echo give the density of the first solid. The density of the second solid is obtained from an absolute measurement of the reflection coefficient of the whole structure. At oblique incidence, at resonances, guided waves are generated. Their spectral analysis allows the shear phase velocity of the two solids to be determined. All parameters are determined wihin an error of 10%. [Work supported by DRET DGA Contract 87-261.]
Phone restoration
Authors: Repp Bruno H.
Published: October 2005

When a speech segment is replaced by an extraneous sound of not too dissimilar spectral structure, the speech often seems intact (the “phoneme restoration” effect). Does this occur because the missing phonological segment is filled in at the level of lexical access, or because the missing phonetic information is filled in at a prelexical stage? This issue was investigated by probing subjects' perception of the extraneous noise burst that replaced the frication of an [s] inside a short sentence. The results showed that the noise was perceived as lower in “pitch” than an identical noise presented before or after the sentence, or inserted into the silent closure of a [th] in a similar sentence. This suggests that the [s] was restored phonetically by auditory subtraction from the noise occurring in its place, which left a perceived extraneous residue that was depleted of high frequency energy. Additional experiments investigated whether this “phone restoration” was induced by phonetic cues to the missing segment in adjacent signal portions, or whether lexical access played a role. [Work supported by NICHD.]
Identification of place of articulation in nasal phonemes using a time-frequency approach
Authors: Velez Edgar F. , Absher Richard G. , Lubker James F.
Published: October 2005

Acoustic cues to place of articulation are present in the highly nonstationary region between nasal consonants and vowels. A need for a speech processing tool capable of accurately representing these transient events led to consideration of the Wignet-Ville distribution (WVD). Previous use in speech analysis was limited due to the presence of multiple interference terms (crossterms), which hindered its direct interpretation. These crossterms can be attenuated by time-frequency smoothing (SWVD). Time and frequency resolution may be chosen independently, thus avoiding the trade-off existing in wide- and narrow-band spectrograms. Despite its apparent complexity, the SWVD can be computed about four times faster than a spectrogram. SWVD analysis of nasal-vowel transitions accurately shows fine spectrotemporal details in the murmur release, initial slope of the formant transitions, and abrupt energy changes. Identification of place of articulation experiments performed on labial and alveolar nasal consonants in various vocalic contexts in continuous speech, using the SWVD of 20- to 60-ms segments around the transition, shows good correlation with previous perceptual experiments.
Larynx frequency information for lipreading speech in Mandarin Chinese
Authors: Ching Yuk Ching
Published: October 2005

Prosodic contrasts are important sources of information in a tone language like Chinese. Each syllable is characterized by a tonal contour that determines the lexical meaning of the word in isolation. In continuous speech, the overall stress and intonation patterns contribute significantly to understanding speech. These contrastive speech patterns are directly related to the fundamental frequency of the speaker's voice, which is relatively invisible. When speech communication is dependent on lipreading, auditory voice pitch information can thus be the most effective aid. That this is so in an English-speaking context has been shown in numerous studies. The present work evaluates the contribution of larynx frequency information to lipreading connected discourse, and specifically to resolving ambiguities that are primarily signaled by contrastive stress patterns and tone patterns in Mandarin Chinese. The results have important implications for the design of speech processing aids and the development of speech perceptual assessments in a tone language community.
Interpreting visual speech signals using neural networks
Authors: Yuhas Ben P.
Published: October 2005

When the acoustic speech signal is degraded by noise, compensatory information can often be obtained by watching the speaker's mouth [W. H. Sumby and I. Pollack, J. Acoust. Soc. Am. 26, 212–215 (1954)]. The aim of the work to be presented is to explore the structure of this compensatory information, as it might be used to assist automatic speech recognition. Starting with visual images taken from laser disc recordings of speaker's faces [Bernstein et al., J. Acoust. Soc. Am. Suppl. 1 82, S22 (1987)], a small box centered at the mouth is identified and extracted. A variety of neural networks are then taught to process these images based upon two interpretation schemes. The first approach is to classify the visual images as belonging to a particular class. The second approach is to extract acoustic constraints directly from the image. Toward this end, neural networks are trained to estimate the short-term power spectral envelope of the acoustic signal given the corresponding visual image as input. Performance is evaluated on nine vowels obtained from two speakers. These results will be reported and compared with results from more traditional classification and estimation techniques. [Work supported by AFOSR Contract No. 86-0246.]
Refraction and reflection of an obliquely incident finite amplitude plane P wave at a plane solid—solid interface
Authors: Shu Kun-Tien , Ginsberg Jerry H.
Published: October 2005

An earlier paper [K. T. Shu and J. H. Ginsberg, J. Acoust. Soc. Am. Suppl. 1 84, S5 (1988)] proved that the significant finite amplitude aspects of mode conversion of a plane dilatational wave obliquely incident at a plane stress-free boundary may be described in terms of Earnshaw-type solutions for the dilatational and vertically polarized shear waves. In the work described here, the method is extended to an obliquely incident finite amplitude plane dilatational wave at a plane interface between two bounded isotropic solids. It is shown that, not as a consequence of nonlinear interaction effects, but rather as a consequence of nonlinear self-action effects, cumulative growth of higher harmonics occurs in the incident, reflected, and refracted waves. A number of special circumstances of wave reflection-refraction are examined, relative to the incidence angle and the material properties of the two media. Also given are the deformed incident, reflected, and refracted waveforms near one shock formation distance. [Work supported by NSF and ONR.]
Reflection—reduction model for a viscoelastically coated plate
Authors: Strifors H. C. , Gaunaurd G. C.
Published: October 2005

A study is presented of the reflection of a plane cw sound waveform incident on a fluid-loaded elastic plate, quantitatively describing how and how much this reflection is selectively reduced by covering the plate with an ideally bonded viscoelastic layer. The exact equations of acoustics, elastodynamics, and viscoelastodynamics (in the Kelvin-Voigt model) are used to describe the behavior of the external fluid, the elastic plate, and the absorbing coating, respectively. By means of the principle of fading memory and a recently developed formulation [Strifors and Gaunaurd, J. Acoust. Soc. Am. 85, 995–1004 (1989)] with an appropriate number of time constants, the solution is generated in all three media. Once these fields are determined, the reflection (or transmission) coefficient for the coated structure is easily constructed. A number of calculated plots for the echo-reduction levels and their associated phase shifts versus frequency are displayed to illustrate the versatility of this predictive approach in a variety of situations. The approach can be used to evaluate the reflection-reduction capacity of the absorbing layer.
Forced vibration of a submerged spheroidal shell using variational principles
Authors: Chen Pei-Tai , Ginsberg Jerry H.
Published: October 2005

Variational principles are employed to study acoustic radiation from a submerged prolate confocal spheroidal shell. Structural vibration is described by the method of assumed modes, based on Hamilton's principle, in which bending and membrane stresses are included in the strain energy. The surface pressure is described by a variational principle that is derived from the surface Kirchhoff-Helmholtz integral equation. This approach was employed earlier [J. Acoust. Soc. Am. Suppl. 1 84, S6 (1988)] to study a spherical shell under a harmonic, concentrated force. A singularity that occurs in the set of coefficients describing the coupling between surface displacement and pressure was found to require further attention. In the case of a sphere, evaluation of the contribution of this singularity, which arises in an integration over the surface, is expedited by the fact that the singularity is independent of position of the field point relative to the source point. The present paper addresses the evaluation of the coupling coefficients for an arbitrary body of revolution. Convergence is illustrated numerically, and results are compared with those obtained by Yen and Dimaggio from their analytical solution based on membrane theory [J. Acoust. Soc. Am. 41, 618–626 (1967)]. [Work supported by the Office of Naval Research, Code 1132-SM.]
Effects of duration on intensity discrimination: Psychophysical data and predictions from single-cell response
Authors: Fay R. R. , Shofner W. P. , Dye R. H.
Published: October 2005

An ROC analysis was performed on responses of single auditory-nerve fibers (goldfish) and cochlear nucleus cells (gerbil) in order to predict intensity discrimination (in the goldfish and human) as a function of signal duration. To evaluate that the mean and variability of spike counts within single units account for psychophysical performance, spike number distributions were obtained (N = 100) for several durations (20 to 400 ms) and level differences (0.5–4 dB) at a unit's best frequency. The percent correct performance based on spike counts was found by generating ROC curves from empirical distributions and computing the area under the ROC [P(A)]. Theoretical psychometric functions were compared with psychometric functions from human and goldfish listeners obtained using a 21FC paradigm (human) and a rating method in classical respiratory conditioning (goldfish). The forms of the neural and psychophysical duration functions are similar in the mammal and the fish, but the fish shows higher thresholds compared with the human and with the neurophysiological predictions. In general, psychophysical performance is well modeled by the optimum processing of spike counts from individual cells. [Work supported by a Center Grant from NINCDS.]
Low-frequency transmission loss by alternate resonance tuning (ART)
Authors: Bliss Donald B. , Gottwald James A.
Published: October 2005

Achieving adequate low-frequency transmission loss through lightweight flexible paneled walls is an important problem, particularly for interior noise reduction of propeller aircraft. Alternate resonance tuning (ART) is a new method of blocking sound transmission through such structures by controlling the dynamics of the wall panels. Adjacent acoustically compact panels are designed to have resonant frequencies alternately above and below the frequency to be canceled. At the design frequency, such panels oscillate with equal amplitude but nearly out of phase. The resulting cancellation from acoustic sources on adjacent panels causes cutoff of the transmitted acoustic modes, which become evanescent and nonpropagating. The concept differs from other noise reduction methods in that it does not rely on reducing the wall motion, but rather alters the wall wavenumber spectrum. There is no serious weight penalty associated with the method, and increasing the structural damping is not advantageous. Experimental and analytical results are presented to demonstrate the effectiveness of the ART concept. Experiments show that very large transmission losses with reasonable bandwidth can be achieved by a simple ART panel barrier in a duct. These findings are corroborated theoretically by an acoustic branch analysis, and results of a parametric study are presented to show the effect of varying system parameters.
Unmasked and partially masked loudness in musical dynamics
Authors: Zwicker Eberhard
Published: October 2005

In music, two varieties of loudness are important. In one case, the loudness of the whole orchestra is being judged. The sensation may be characterized by the expression, “The finale was impressively loud.” In the second case, the loudness of a single voice or instrument that is almost totally masked by other instruments is being judged. Here, the sensation may result in a statement such as, “The voice of the singer was hardly audible.” There are two reasons for such masking, both realized in music: the spectral (simultaneous) partial masking and the temporal (post-stimulus) partial masking. The first is more pronounced in music and influences the transparency of the presentation. The second is related to the reverberation time. Dependencies of partially masked loudnesses are outlined quantitatively using abstract and musical sounds. A videotape presentation will illustrate these effects using the temporal variation of specific loudness-critical band rate distributions outlined on the screen of these loudness meters.
The communication of dynamics between musicians and listeners through musical performance
Authors: Nakamura Toshie
Published: October 2005

Musicians perform music according to their own interpretations. How does a player realize his/her interpretation of a piece of music in the form of tones? How is his/her intention understood by a listener? The relations among the performers' intentions, intensity of tones produced by the performers, and listeners' perception were investigated quantitatively. The noteworthy findings were as follows. (1) Crescendo was easier to recognize than decrescendo. (2) It appeared that rising pitch enhanced an impression of crescendo, and falling pitch enhanced that of decrescendo. (3) The influence of “impression of the end” on crescendo was suggested. These findings were confirmed in the experiments by means of synthesized sound sequences and under well-controlled conditions.
Influence of hammer velocity in piano sound
Authors: Palmer Caroline , Brown Judith
Published: October 2005

Recent models of piano string excitation suggest that string motion is proportional to hammer velocity. Preliminary to measuring dynamics in piano performance, the relationship between radiated piano sound and hammer velocities was studied. A computer-monitored piano allowed reproduction of a range of hammer velocities, and a microphone placed near a pianist's head location recorded radiated sound. The first eperiment indicated that peak amplitude of the waveform was directly proportional to the hammer velocity of individual notes for a wide range of frequencies and hammer velocities. A second experiment investigated the waveforms of notes struck simultaneously and compared these with the waveforms of the individual component notes. The peak amplitude of the dyads was directly proportional (with proportionality close to 1) to the sum of the individual peak amplitudes. A third experiment extended these findings to a wider range of dyadic pitch intervals. These findings suggest linear relationships between hammer velocity, amplitude of string motion, bridge motion, and amplitude of the soundboard vibration for single notes. The additivity of dyads indicates that the principle of superposition is obeyed with a small energy loss. [Work supported by MIT Media Lab, Ohio State University Small Research Grant, and a Wellesley College Brachman Hoffman Fellowship.]
Signal parameters that reduce masking produced by multicomponent simultaneous maskers of uncertain frequency
Authors: Neff Donna L.
Published: October 2005

Large amounts of simultaneous masking can be produced by changing the spectral content of multicomponent maskers with each presentation. This experiment examined whether simple changes in signal properties could reduce this masking. The number of masker components varied from 2 to 100 across conditions. Thresholds for simultaneous masking were measured for four listeners for a 1000-Hz sinusoidal signal equal in duration to the masker (200 ms) and compared to thresholds measured as signal duration was shortened and signal position varied. The largest release from masking occurred for the shortest (10-ms) signal temporally centered in the masker. Dichotic presentation also decreased thresholds relative to diotic or monaural conditions. In contrast, the use of different signal spectra, specifically a narrow-band noise, AM, or QFM signal, all centered at 1000 Hz, did not produce consistent reductions in masking. Overall, the results indicate that changes in the temporal or spatial relation of masker and signal are much more effective in reducing masking than changes in frequency composition under conditions of masker frequency uncertainty. [Work supported by AFOSR.]
In situ acoustic signature of low sea state microbreaking
Authors: Updegraff Garr E. , Anderson Victor O.
Published: October 2005

At sea acoustic and video observations of low sea state microbreaking were carried out with a subsurface instrument in the summer of 1988. Correlation of subsurface video images of riffles and their acoustic signals will be presented. A four-hydrophone array provides spatial localizations of individual bubble signatures. Spectral and intensity distributions of the bubble signatures will be presented.