bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear scattering of crossed ultrasonic beams in the presence of turbulence-Intensity measurements versus turbulent reach number
Authors: Korman Murray S.
Published: October 2005

An experimental scattering arrangement involving the nonlinear interaction of two mutually perpendicular intersecting beams (frequencies f1 = 2.1 MHz and f2 = 1.9 MHz), overlapping in a region of turbulence is investigated. In the absence of turbulence no radiated scattering intensity I+ is observed at the combination frequency, f+ = 4 MHz. However, in the presence of turbulence scattering is observed at f+. This radiated component shows considerable amplitude modulation and exhibits spectral broadening. The experiment is performed in a 12 ft deep × 20 ft × 20 ft section of the U.S. Naval Academy Hydrodynamics Tow Tank facility. Two 2.54 cm-diam transducer units are pulsed at f1 and f2, respectively. They are both located 1 m from the interaction region X and form a plane with a 4 MHz receiving unit located (in cylindrical coordinates) 3 m from X at the angular position of 45° from the axis of both sending beams. A 4.81-cm-diam submerged nozzle is aimed perpendicular to the crossed beam plane and located 20 nozzle diameters above it. Measurements of the 32 scattered intensity I+ versus nozzle exit velocity U0, show that I+ ∞ U3.20 over the range 27–62 ft/s. U0 can be related to turbulent fluctuations in the interaction volume. Theory and experiment, for I+, lead to predictions of an average turbulent length scale dependence on Reynolds number. The sensitivity of detecting turbulence with this apparatus is discussed and measurements of spectral broadening versus U0 will be presented. [Work supported by the Naval Academy Research Council.]
Measurements of random structure in the ocean and the earth by use of acoustic fluctuations
Authors: Flatté Stanley M.
Published: October 2005

High-frequency (≳ 1 cpd) variations in travel time of acoustic transmissions over ocean mesoscale distances are known to be dominated by the effects of internal wave displacements of the sound speed stratification (Flatté, 1983). A typical application involves 10-ms-wide pulses travelling over 300 km. It has been demonstrated that this type of data can be inverted for internal-wave strengths. Information can be obtained about range-averaged mean energy level and about energy distribution in the vertical. Data from the 1983 Tomography Experiment (Worcester, Spindel, and Howe, 1985), consisting of 41 days of transmissions between two moorings 300 km apart, have been used to observe the statistical field strength of internal waves (Flatté and Stoughton, 1986; Stoughton, Flatté, and Howe, 1986). It is shown that the accuracy of measurement of these variances is not strongly affected by the partially saturated nature of the sound propagation. Application of the path-integral method of wave propagation through random media to the analysis of seismic-wave propagation through the Earth's mantle is underway. Seismic waves with periods of 1 to 10 Hz received at 100-km-square arrays on the surface of the earth exhibit paradoxical wave-front properties involving small phase (or travel time) fluctuations combined with large amplitude fluctuations. A description of these observations will be given.
Two-scale solutions of the coherence equations in inhomogeneous random media
Authors: Beran Mark J.
Published: October 2005

The two-scale method of solution of the coherence equations in inhomogeneous random media and present typical solutions that have been obtained will be reviewed. The method was first used to study caustic corrections and the effect of a random medium on these corrections. Subsequently it was applied to the solution of the fourth-order coherence function which yields the scintillation index and correlation of intensities as special cases. Recently the sixth-order coherence function was treated in order to determine the next highest moment of the probability distribution of the intensity fluctuations. Although most of the two-scale solutions for the scintillation index have been for plane wave and point-source initial conditions in a random medium without a background sound-speed profile, a solution for the scintillation index in a quadratic channel will also be presented.
Scale model investigation of propeller induced pressures on a fuselage
Authors: Richarz Werner G.
Published: October 2005

In order to optimize sound transmission loss into the interior of an aircraft cabin, the incident pressure field must be known. Heretofore, only rms pressures were considered. It is well known that coupling with flexural waves can occur under certain conditions; thus the phase velocity of the sound field is required. For typical propeller installations, the sound field on an aircraft fuselage is governed by the nearfield of the propeller and the diffracted field. Before the sound reaches the fuselage, it must also propagate through a refracting boundary layer. In order to obtain some insight into this complex problem, a series of scale model tests have been conducted with a 7-inch propeller placed near a circular fuselage of comparable diameter. The fuselage was instrumented with ten flush-mounted microphones and could be rotated about its axis of symmetry. The rms pressures and phase velocities are measured at several blade passage frequencies and under simulated flight conditions typical of takeoff, climb, and cruise. The resultant pressure and phase contours are compared with relevant analytical models. [Work supported by the Natural Sciences and Engineering Research Council of Canada.]
Efficient monitoring of aircraft noise near a military operating area
Authors: Young Robert W. , Awbrey Frank T.
Published: October 2005

Efficient monitoring of aircraft noise near a military operating area requires: (a) adoption of A-weighted sound exposure level as the physical measure first to be applied to any noise event; (b) instrument design goals aimed exactly at the primary physical measure; (c) detailed knowledge of extreme time patterns such as sonic booms (frequency characteristics); (d) performance specifications for monitoring instruments, including tests for compliance, to ensure measurement within appropriate limits of A-weighted sound exposure level of aircraft noise characterized by extreme time patterns; (e) the procedure to apply to a succession of sound exposure levels to form 1-h average (A-weighted) sound level as the short-term summary, and to form yearly average day-night average sound level, for example, as a long-term summary; (f) tests to determine the psychoacoustic validity of time-average sound levels, both short term and long term. As an example of detailed knowledge about an extreme time pattern, this paper reports sound exposure spectrum level from 0.5 to 2000 Hz for a 100-ms sonic boom caused by fighter aircraft on Luke Air Force Range in Arizona. The C-weighted and A-weighted sound exposure levels of this and four other sonic booms measured in the same hour are utilized for illustrative calculation of A-weighted and C-weighted day-night average sound levels near a military operating area.
Aircraft noise impact considerations at Orange County (JWA) Airport
Authors: Lane Samuel R.
Published: October 2005

JWA has not been in compliance with the California Airport Noise Standard for many years. A variance process allows California airports to operate out-of-compliance and the state does not consistently or vigorously enforce the process or the regulations. A great many single-family residences are located within the excessive noise zone near the airport. The principal method used by the county to “reduce” the noise is to condemn the properties. Restrictions on commercial jet aircraft operations are also imposed that are supposed to prevent any increase in the size of the excessive noise zone. However this is a flawed process based on inconsistent reasoning that leaves an excessive noise impact unmitigated. This is because the allowable noise limit is too high, the noise zone area is inherently inaccurate, and the noise monitoring and impact rating procedures ignore significant considerations. For example, even if all commercial jet operations were terminated, the noise impact would still be excessive due to commuter and private aircraft operations.
The new ANSI standard for bandpass filters
Authors: Sepmeyer Ludwig W. , Marsh Alan H.
Published: October 2005

The initial American standard for bandpass filters for analysis of sound or vibration was prepared by a Working Group of the Acoustical Society of America's Standards Committee S1 on Acoustics and was approved in 1966 as American National Standard ANSI S1.11-1966. The 1966 standard was re-affirmed in 1976 without technical changes. With advances in microelectronics and digital data-processing techniques available in the 1980s, it was decided in 1981 that a thorough revision of the 1966 Standard was needed. In 1986, the new ANSI Standard was published as ANSI S1.11-1986 with specifications for both analog and digital implementations of octave-band and fractional-octave-band filters including devices that utilize discrete-Fourier-transform techniques to synthesize fractional-octave-band filters. This paper describes the principal technical features of the new standard including the specification of filter design Order Number, Type Number based on error in the analysis of a white noise signal, and a Subtype designation based on error in the analysis of signals having specified positive and negative slopes. Errors are determined relative to the equivalent power that would have been transmitted by an ideal filter having infinite rejection at frequencies outside the range of specified passband-limiting frequencies. Examples are shown to demonstrate how various filter designs would conform to the specifications of the new Standard.
Investigation of the dependence of excess attenuation of aircraft noise on distance
Authors: Wolf Richard K. , Raspet Richard
Published: October 2005

In previous studies of sound propagation using the Fast Field Program, one aspect of our investigation has been of the excess attenuation versus a logarithmic sound velocity gradient parameter for fixed ranges [Proc. INTER-NOISE 86 Conf., 419–424 (1986)]. However, the dependence of excess attenuation upon distance is of greater interest for purposes of environmental assessment. This paper describes the decay of sound levels with distance for ground-to-ground propagation, under both upward and downward refraction conditions, and suggests how an average curve for acoustically hard and soft surfaces can be developed from this information. [Work jointly supported by the FAA and the U.S. Army Construction Engineering Research Laboratory.]
Universal power spectra for acoustic turbulence: Applications to wind waves, 1/f noise, and classical second sound
Authors: Putterman Seth , Larraza A. , Roberts P. H.
Published: October 2005

A continuum pumped full of wave energy at an amplitude sufficiently large so that reversible nonlinearities dominate irreversible linear response becomes wave turbulent. In the limit of high nonlinearity acoustic turbulence and wind wave turbulence accumulate at 1/f and 1/f5 power spectra, respectively. A wave turbulent system can support new propagating energy modes analogous to second sound in superfluid He4. This hyperbolic (nondiffusive) transport could account for the anomalous diffusivity observed in plasma devices and for the difficulties faced in achieving confinement. The key to the understanding of these phenomena is the nonlinearity in the continuum mechanics which leads to three basic effects: (1) scattering of sound by sound to produce waves with sum and difference frequencies; (2) refraction of waves by a slowly varying (inhomogeneous) background; (3) reaction of the background due to changes in the distribution of sound waves. Details of these processes are presented in the framework of the Euler equations.
Prediction of the surface impedance of depth-varying ground surfaces
Authors: Berry A. , Nicolas J.
Published: October 2005

Many ground surfaces have acoustical characteristics (density, porosity, flow resistivity) which vary with depth. Prediction of the surface impedance can be done by solving the wave equation in the nonhomogeneous medium. An exponential variation with depth of the parameters is usually assumed [R. J. Donato, “Impedance models for grass covered grounds,” J. Acoust. Soc. Am. 61, 1449–1452 (1977); K. Attenborough, “Acoustical impedance models for outdoor ground surfaces,” J. Sound Vib. 99, 521–544 (1984)]. In this paper a new approach is presented. The surface impedance is calculated by discretizing the ground into a suitably large but finite number of homogeneous layers of known characteristics (multilayer approach). This method allows prediction for any depth variation of the ground parameters, and includes the simple hard-backing effect. The analytical results in terms of the impedance gradient, obtained by this multilayer approach are confirmed by theoretical manipulation of the fundamental equations describing the acoustic field in nonhomogeneous media. The numerical results show the typical tendancies caused by the ground inhomogeneity.
Detection of specific periods in a random sequence
Authors: Hafter Ervin R. , Plamondon Lyne
Published: October 2005

Consider a hypothetical neural dimension in which is coded the period between peaks of an acoustic envelope. In hopes of better understanding the organization of this dimension, a kind of “period noise” is used to mask a “period signal.” The masker is a sequence of high-frequency clicks spaced with periods chosen at random from the range 2–10 ms. The signal is a specific period added to the mask, replacing noise periods at randomly chosen locations in the sequence. Using a two-interval, forced choice, thresholds are defined as the proportion of “signals” in the sequence necessary for 71% correct detections. Signals tested ranged from 2–10 ms. In order to prevent spurious cues, the number of clicks in each interval is chosen to make the duration equal, and the levels are varied at random from interval to interval. Extensive data from two subjects show very different pictures of the relation between sensitivity and period. From one, thresholds increase (8%–29%) with signal period, as might be expected from studies of frequency discrimination; from the other, thresholds are reasonably constant (about 7%), regardless of the period tested. [Work supported by NINCDS.]
Detection of partially filled gaps
Authors: Green David M. , Forrest Timothy G.
Published: October 2005

Decrements in broadband noise stimuli were produced by changing the intensity of the noise for a brief interval. As the duration of the interval increases, less change in level is needed to detect the alteration. One can interpret these experiments as probing the impulse response of the auditory temporal mechanism in the manner suggested by Buunen and van Valkenburg [Jr. Acoust. Soc. Am. 65, 534–537 (1979)]. Unlike their results, our measurements are well fit by an exponential function with a short (8–10 ms) time constant. Our results are consistent with the model proposed by Viemeister [Jr. Acoust. Soc. Am. 66, 1364–1380 (1979)] to explain his results obtained with the modulation transfer function (MTF). Direct measurement of the modulation transfer function for these same listeners indicates good agreement between the time constant measured in the gap experiment and the low-pass break point measured in the MTF. We also explored increments in the noise stimuli instead of decrements. The data show symmetry when the increase or decrease in the noise rms is used to express the change in the stimulus. [Work supported by a grant from the National Science Foundation.]
Auditory temporal summation in humans
Authors: Gerken George M. , Bhat Vishwa K. H. , Hutchison-Clutter Margaret , Donnelly Karen L.
Published: October 2005

Monaural sets of thresholds were obtained for 11 human subjects with normal hearing using 24 digitally generated stimuli with cosine onsets and offsets. The purpose of the work was to evaluate modeling of temporal summation data, particularly with respect to the duration assigned to rise-fall time. Assuming similar central mechanisms, it should be possible to combine the temporal summation functions for single- and multiple-burst stimuli by selection of the duration assigned to rise-fall time. This duration was determined by regression analysis and was found to be, on the average, 39% of the equivalent duration calculated on the basis of stimulus power [P. J. Dallos and W. O. Olsen, J. Acoust. Soc. Am. 36, 743–751 (1964)]. A combined summation function was obtained for each subject, and the average slope was 0.593. In no subject did the regression line account for less than 96.5% of the data variance. From these and other results in this experiment, it is concluded that the auditory system does not operate as a simple power integrator. [Work supported by NIH.]
Vibration power measurements using a damped plate as a reverberant structure
Authors: Wallace C. E. , Irvine Thomas
Published: October 2005

A thin damped plate is used, in much the same way as a reverberant sound chamber, to measure the vibration power introduced by a shaker at a point on the plate surface. The power dissipated by the reverberant field is computed from the reverberant field acceleration measurements and compared with the power computed from impedance head measurements. These results are presented in a 500-Hz bandwidth for frequencies up to 4500 Hz. With the exception of the first 500-Hz band, the agreement is within 0.8 dB when the plate damping is determined for individual modes by the exponential method. When the damping is found from the decay of the reverberant field, the agreement is very poor. [Work supported by Garrett Fluid Systems.]
Application of finite element methods to the prediction of power limitation in high-frequency transducers
Authors: Vanderborck Gerard , Steichen William , Lagier Yves
Published: October 2005

In the field of high-frequency acoustic arrays for high-resolution sonars, some transducers are driven with very high-power density and long pulse length. This produces a temperature rise in the transducer, leading to the variation of the materials characteristics. This phenomenon may reach the mechanical breaking point. To study this problem, we have developed a tridimensional piezoelectric finite element computer program which takes into account radiation (Helmholtz integral equation) and losses (mechanical, dielectric, piezoelectric). After an acoustic computation, using modal analysis, heat sources due to losses are determined in all the volume of the transducer. A finite element program computes the transient evolution of the temperature. According to the obtained temperatures, materials coefficients are updated and a new acoustic calculation is performed. The process is repeated until maximum dynamic stresses or maximum temperature is reached. Several examples are discussed including transducers with and without matching layer. [Work supported by DRET, France.]
The influence of phonetic context on the acoustical properties of stops
Authors: Randolph Mark A. , Zue Victor W.
Published: October 2005

In American English, stop consonants may be released, unreleased, or deleted (e.g., the phoneme /t/ in “tea,” “basketball,” and “softly,” respectively). The particular acoustical realization is almost obligatory in some environments and highly variable in others. The purpose of our study was to quantify the influence of context, including syllable structure, on the acoustical properties of stop consonants. Or database consisted of some 5200 stops collected from 1000 sentences. Phonemic transcriptions, including lexical stress and syllable markers, were provided and aligned with the speech waveforms. The stops were grouped into categories corresponding to their position within syllables (e.g., syllable-initial-singleton, syllable-final-affix, etc.) and marked according to their local phonemic context. Segment durations were measured and the stops were classified as released, unreleased, or deleted on the basis of their duration and voice onset time (VOT). In the analysis of these data, including the examination of VOT and other durational measurements, we found substantial effects of both syllable structure and phonemic context. For example, over 98% of the stops in syllable-initial position are released, regardless of the preceding phoneme. Syllable-final singleton stops are released 65% of the time when followed by a vowel (as in “oak is”), and unreleased 73% of the time when followed by a consonant (as in “sickness”). A stop is most likely to be deleted (over 40% of the time) when it is the last member of a syllable-final cluster containing an obstruent and followed by a syllable-initial consonant (as in “mostly”). An /s/ preceding a stop consonant or a semivowel following, has a stronger influence on its VOT if it appears within the same syllable. Similarly, a singleton stop's voicing characteristic affects the duration of a preceding vowel differently, depending on whether the two segments are in the same syllable. Detailed results will be presented at the meeting. [Work supported by an AT&T Bell Laboratories Cooperative Research Fellowship and by DARPA.]
Acoustic and articulatory evidence for consonant-vowel interactions
Authors: Fowler Carol , Munhall Kevin , Saltzman Elliot , Hawkins Sarah
Published: October 2005

Previous acoustical research [e.g., C. Fowler, Phonetica 38, 35–50 (1981)] has suggested that consonants and vowels are not produced strictly sequentially but rather overlap in time. By this account, the degree of co-production of underlying segments affects the pattern of the resulting acoustical durations. In the present experiment, two subjects produced utterances of the form CVC(C), where the vowels were either /ε/ or /æ/ and the following consonants were /p/, /k/, /s/, /ps/, /ks/, /sp/, or /sk/, Movements of the lips and jaw were monitored with a Selspot system. Laryngeal movements were measured by means of transillumination, and the accompanying acoustic signal was recorded. Analysis of the acoustic durations revealed that vowel duration was shorter when followed by a cluster than by a singleton in both vowel contexts. However, the following consonant durations were longer for the vowel /ε/ than for /æ/. Analyses of the lip and jaw kinematics suggested that the vowel shortening in the cluster contexts was produced in part by greater temporal overlap of the underlying segments. The influence of the intrinsic vowel duration on the following consonants may reflect a syllabic constraint on articulatory timing. The results will be discussed in terms of the articulatory structure of phonetic segments and the sequential coordination of consonant and vowel gestures. [Work supported by NINCDS.]
Spanish as a “syllable-timed” language
Authors: Amador-Hernandez Mariscela
Published: October 2005

Spanish has been characterized as “syllable-timed” as opposed to English and German, which have been called “stress-timed” languages. This report describes a search for phonetic correlates of the term “syllable-timed.” Measurements were made of the relative durations of the stressed and unstressed vowels in polysyllabic words spoken by four speakers of Mexican Spanish. A perceptual experiment was then conducted using the method of self-adjustment, where subjects could independently control the duration of each vowel in a synthesized polysyllabic word in order to produce stress on a certain specified syllable. Vowel durations were slightly different for the same test word in production and perception studies, with the unstressed vowels of the latter being more uniform. Although absolute equality of vowel (or syllable) duration was not found (since stressed vowels are always longer than unstressed), unstressed vowels generally had uniform durations. This uniform duration phenomenon appears to be what underlies the perception of “syllable-timed” in Spanish.
Detailed spectral analysis of a female voice
Authors: Klatt Dennis H.
Published: October 2005

Several thousand DFT magnitude spectra have been produced for a selected sample of speech from a single female speaker having a pleasant voice quality. The speaker sustained a number of different vowels while undertaking different laryngeal gestures including (1) slow 1-oct pitch glides up or down and (2) reiterant imitations of different sentences, using either [?V] of [hV] replacements for the pattern of stressed and unstressed syllables in each sentence, where [V] is one of six English vowels. An attempt has been made to quantify the effects on the harmonic spectrum of changes to fundamental frequency, syllable stress, and position of the syllable in the utterance. Also of interest is the detailed way that voicing is initiated and terminated in laryngealized versus breathy onsets and offsets. Previous analyses that used inverse filtering to study the glottal waveform seem to have missed several important aspects of the source spectrum and its change over time. Our analysis reveals the presence of considerable random breathiness noise at frequencies above 2 kHz over portions of many utterances. The strength of the fundamental component and of the various formant peaks relative to overall rms energy in the signal under all of the conditions outlined above have been quantified. There is variation in both the general tilt of the harmonic spectrum and the strength of the fundamental component depending largely on the (presumed) degree to which the larynx is spread/constricted. Locations of spectral zeros have been studied and related to the duration of the open part of glottal period. Synthesis has also been attempted using a modified version of the Klattalk synthesizer, which provides direct control over voicing source open period, source spectral tilt, breathiness noise, and degree of instability in the fundamental frequency contour (the latter parameter being particularly important for natural synthesis of a vowel sustained at constant pitch). Sentences spoken by replacing all of the syllables by [?V] were somewhat easier to synthesize—than sentences spoken by replacing all of the syllables by [hV]. The reason appears to be that in the latter materials, additional spectral peaks—presumably related to tracheal resonances—were sometimes observed in the vowel spectra. Except for this possibly important aspect of voice quality, the synthesis results are very encouraging; source control parameters and formant parameters are monotonic slowly varying continuous functions, suggesting that rules for the synthesis of more natural female voices might be formulated as a next step. [Work supported in part by NIH.]
Aeroacoustic considerations for phonation
Authors: McGowan R. S.
Published: October 2005

The source of sound called “voice” should be characterized from a fluid mechanical point of view. The aeroacoustic theories developed for engineering noise problems can provide the connection between the fluid mechanics and the acoustics of the voice source. The high-impedance characteristics of the piston, which is usually pictured as the source, appears correct. However, the piston velocity should not be equated to the fluid particle velocity at the glottis, since the fluid particle velocity at the glottis is not the acoustic particle velocity. Rather, the oscillating jet at the glottis serves to create pressure fluctuations necessary for acoustic propagation. As a result, only a fraction of the fluid energy is converted into acoustic energy at the glottis. A few basics for this point of view will be presented, while a detailed model awaits development. [Work supported by NINCDS.]
A dynamic analysis of reiterant speech production in three languages
Authors: Vatikiotis-Bateson Eric , Kelso J. A. S.
Published: October 2005

Previously, supralaryngeal articulatory motion in reiterant speech produced by speakers of English and Japanese in terms of an underlying dynamical model [Kelso et al., 1. Acoust. Soc. Am. 77, 266–280 (1985); Vatikiotis-Bateson and Kelso, J. Acoust. Soc. Am. Suppl. 1 78, S38 (1985)] has been analyzed. Here, the analysis is extended to French, a language whose temporal structure is believed to be different from that of English or Japanese, and a preliminary comparison of movements of the lower-lip/jaw complex for speakers of the three languages is presented. The cross-language comparison is based on articulatory movement data from 13 speakers (five English, five Japanese, and three French). Analysis of reiterant /ba/ and /ma/ productions reveals that French speakers make language-specific linguistic (e.g., stress) and performance (e.g., speaking rate) distinctions that are qualitatively similar in terms of kinematic relations to those observed for Japanese and English. Quantitative differences due to the intrinsic temporal properties of each language are also evident (e.g., in the slope of the peak velocity-displacement relation). It is suggested that the same abstract dynamical model, appropriately parameterized for each language, can characterize the observed articulatory behavior. [Work supported by NINCDS and ONR.]
The effect of thermohaline steps on range-dependent acoustic propagation near the northeast coast of South America using high resolution data
Authors: Ching-Bing Stanley A. , King David B. , Boyd Janice D.
Published: October 2005

The effects of large thermohaline steps on acoustic transmission loss (TL) for a range-independent sound velocity profile (SVP) near the northeast coast of South America were reported [Chin-Bing and King, J. Acoust. Soc. Am. Suppl. 1 76, S84 (1984)] using a high resolution SVP (in depth), a discrete standard depth SVP, and a depth thinned SVP. The thermohaline step structure created adjacent regions of near isovelocity connected by a high gradient small transition region; this “step” structured SVP affected the TL even at low frequencies. The study is now extended to include recent experimental high resolution range-dependent thermohaline data. Range-dependent TL comparisons are made using SVPs obtained from (1) the high resolution data, (2) an oceanographic forecast model, (3) discrete standard depths, and (4) a depth thinned profile. This range-dependent study supports the basic finding from the range-independent study—TL structure can be adversely affected by failing to include the detailed SVP step structure. Furthermore, oceanographic forecasts models that provide SVPs need a high degree of accuracy in regions where these vertical anomalies exist.
Waveform inversion to extract permeability and porosity of marine sediments
Authors: Turgut Altan , Yamamoto Tokuo
Published: October 2005

Propagation of acoustic pulse through marine sediments is modeled by the Biot theory. It is shown that the dispersion and attenuation of acoustic waves through a marine sediment are unique functions of porosity and permeability. A waveform inversion scheme has been developed to extract permeability and porosity from pulse deformation measurements. Uniqueness and consistency of the inversion have been examined using synthetic data. It is concluded that the proposed inverse method is useful for remote sensing of permeability and porosity of marine sediments. [Work supported by ONR.]
Low-frequency underwater acoustic waves from an ice plate-edge leaky Rayleigh wave
Authors: Chamuel Jacques R.
Published: October 2005

Leaky Rayleigh waves propagating along the bottom side of floating sea-ice plates experience cylindrical geometrical spreading and have their low-frequency limit determined by the ice plate thickness that corresponds to about 560 Hz. A second type of leaky Rayleigh wave can exist along ice plate edges propagating with no geometrical spreading and has its low-frequency limit determined by the large plate horizontal dimensions. Laboratory ultrasonic modeling results are presented demonstrating the detection of low-frequency Rayleigh waves radiated from ice plate edges. In one experiment, the plate-edge leaky Rayleigh wave wavelength was greater than 12 times the ice plate thickness. The results suggest that a 3-m-thick ice plate in the Arctic may easily radiate 10- to 100-Hz components from its edges. The ice plate edge acting nearly as a finite length line source produces high directionality of the radiated leaky Rayleigh wave into the water. The low-frequency plate-edge leaky Rayleigh waves may be detected in the water at significant distances from the ice edge. Additional physical insights into the controversial leaky Rayleigh wave are provided by comparing water/ice and Freon-113/ice interface conditions where a high-density low-velocity liquid is used. [Work supported by ONR.]
A shallow-water range-dependent acoustic propagation problem with a stepwise coupled mode solution
Authors: Evans Richard B. , Syck James M.
Published: October 2005

A particular shallow-water range-dependent environment was chosen and the stepwise coupled mode model COUPLE was applied. The problem consisted of a refracting water layer overlying an isospeed liquid sediment. The water depth varied between 120 and 210 m over a range of 50 km. The calculations were done at 50 and 300 Hz. The main range-dependent effect considered was the redistribution of energy due to forward and backscatter caused by both large and small scale bathymetic changes. The large scale changes, that evolve slowly with range, produced a smooth transition of energy between different sized sets of locally propagating modes. The more rapid, small scale, changes caused a pronounced energy loss due to forward scattering into highly attenuated high-angle modes. The effects of backscatter were negligible. The results are compared in this paper to IFD/PE and, in a subsequent paper, with other parabolic equation models.
Measurement of speech privacy in open plan offices
Authors: Moreland J. B.
Published: October 2005

The proper design of an open plan office for speech privacy and for overall acoustical comfort considers many variables, all of which interact to produce the final acoustical environment. Using a loudspeaker to represent the talker, the sound spectrum that would be heard by a listener in an adjacent workstation is measured. From these measurements, the articulation index (AI) between adjacent workstations is calculated. Adjacent workstations are focused upon because it is generally more difficult to obtain good speech privacy for the occupants of these workstations than it is for workstations that are farther apart. Also, a PNC35 spectrum is used as the baseline masking spectrum. The PNC35 has an overall level of 43 dBA, and is representative of low-to-moderate levels of sound masking. A few trends emerge from this study. The sitting of workstations near hard room boundaries can be expected to have poorer speech privacy than corresponding workstations away from such room boundaries. Second, the acoustically hard screens whose NRC is 0.1 or less will have poorer speech privacy than will acoustically soft screens whose NRC is 0.5 or more.
Study of acoustic response of anisotropic steel structures
Authors: Cordonnier P. , Biron D. , Pauzin S.
Published: October 2005

The purpose of our experiment is to learn the influence of stiffening on the acoustic response of steel plates. The investigation is carried out on a rectangular plate that is clamped in an opening (1.20 × 2 m2) between a reverberant room and a test room. The sound transmission loss is determined by using two different methods: a method that is based on the sound pressure measurement and the two-microphone intensity method. The mean radiation efficiency is obtained by measuring the panel vibration velocity with a regular mesh. The measurements are made over a frequency range from 250 to 10 000 Hz for a diffuse field excitation. The following series of samples is tested: a 1.5-mm-thick-steel plate; a plate reinforced with uniformly spaced tubular stiffeners; a plate reinforced with uniformly spaced line stiffeners; and a corrugated panel (the space between the corrugations is the same as the space between the stiffeners). The acoustic effect of variation of bending stiffness is discussed, and all the experimental results provide comparison elements for computed results.
An iterative T matrix for scattering from bounded objects
Authors: Norton Guy , Keiffer Richard , Werby M. F.
Published: October 2005

The extended boundary condition (EBC) method of Waterman has been used extensively over the last few years to describe scattering from bounded objects and usually leads to a mapping (the T matrix) that relates the known incident field with the scattered field. This method arises from an expansion of relevant physical quantities in a partial wave space (i.e., the incident and scattered fields) that upon truncation of the partial wave series leads to a finite matrix problem. The level of truncation relates to convergence and it is not always possible to know at what truncation level one has arrived at convergence. An iterative T matrix approach has been developed at NORDA that starts at some truncation level (N terms in the expansion) and leads via simple vector operations to the N + 1 case. This method can obviate the problem of convergence by interacting upward until enough terms are included to yield a stable solution. In addition to dealing with the convergence problem this method is able to treat the problem of ill-conditioned matrices often encountered in scattering problems more effectively than the direct matrix method. The derivation of this method is presented along with some numerical results.
Evolving theories of vowel perception
Authors: Strange Winifred
Published: October 2005

In the past 15 years, research on the perception of spoken vowels has given rise to new conceptions of vowels as articulatory, acoustic, and perceptual events. This paper traces the evolution of vowel theory starting from “simple” target models in which vowels were characterized articulatorily as static vocal tract shapes and acoustically as points in an F1/F2 vowel space. Within this conceptual framework, two major problems in perception to be accounted for were the Speaker Normalization problem and the Target Undershoot problem. Theoretical developments have taken two directions: (1) “Elaborated” target theories have been hypothesized which account primarily for perceivers' solution of the Speaker Normalization problem; (2) dynamic specification models have been offered (a) to deal with the Target Undershoot problem and (b) to characterize the perceptual significance of vowel diphthongization. Findings of perceptual studies are summarized that motivate these theoretical developments and a characterization is offered of vowels as dynamic gestures giving rise to temporally distributed acoustic information that perceivers utilize in identifying coarticulated vowels. [Research supported by NINCDS.]
Auditory-perceptual interpretation of the vowel
Authors: Miller James D.
Published: October 2005

An account of the simple vowels of American English will be given in terms of the author's auditory-perceptual theory. Data from many sources will be used to illustrate and support this view. In addition to theoretical suggestions concerning an auditory-perceptual transformation and a segmentation rule, the perceptualized spectral patterns associated with the nonretroflex vowels will be shown to fall into regions within a slab in a three-dimensional, auditory-perceptual space. These regions form a “vowel map” that by simple rotations can be related to various “vowel charts” such as those of Jones, Pike, or Fant. While the presentheory is an elaboration of traditional formant-ratio theory, it will be shown that a concept of a perceptual reference is needed not only for talker normalization but also to disambiguate vowels not distinguished by simple formant-ratio theory. Additionally, loci for the retroflex and nasalized vowels illustrate the utility of describing vowel spectra by five numbers combined into three dimensions. Simple F1 by F2 descriptions are not adequate except for enigmatophiles. [Work supported by NINCDS and AFOSR.]
Front vowel perception in fluent speech
Authors: Small Larry H.
Published: October 2005

This study investigated the perceptual effects of misarticulating the English front vowels /i,ɪ,e,ε,æ/ located in two-syllable target words. Subjects were instructed to shadow a taped prose passage containing the misarticulated target words. All misarticulations occurred along the height dimension, in reference to the traditional vowel quadrilateral. Also, all misarticulations involved the stressed vowel of each two-syllable target word. The subjects tended to repeat words containing the vowel misarticulations as heard on the tape, instead of restoring the target words to their original form, indicating that the articulatory changes were noticeable to the subjects. If the changes were not noticeable, a greater number of restoration responses would have occurred. Subjects appeared to rely more on the acoustic-phonetic properties of the misarticulated vowels than on the contextual constraints of the passage. Since vowels are more intense and greater in duration than consonants, it is possible that listeners utilized stressed vowel information as a perceptual anchor during word recognition. That is, stressed vowel information may guide a listener during word recognition. [Work supported by the Axe-Houghton Foundation, New York.]
Perceptual dimensions of alaryngeal vowels
Authors: Trudeau Michael D. , Fox Robert Allen
Published: October 2005

The present study uses multidimensional scaling to examine the perceptual dimensions underlying the perception of alaryngeal vowels and compares these dimensions with those commonly found in MDS studies utilizing normally voiced vowels. A set of 11 vowels ([iɪεæaΛoᴜᴜuɔɚ] produced by a competent esophageal speaker represented the stimulus vowels. These vowels were compared (pairwise) on a nine-point similarity/dissimilarity scale by 20 listeners and the resulting perceptual distance data were analyzed using INDSCAL. Three perceptual dimensions were obtained (significantly correlated with F2, F1-F0, and F3, respectively), which accounted for 67% of the variance. These dimensions are similar to those obtained in studies using normally voiced vowels and suggest that alaryngeal voice quality does not disrupt the use of these common perceptual dimensions (which depend only upon vocal tract configurations). The nature of these perceptual dimensions will be discussed in terms of both acoustic (i.e., formants) and auditory (i.e., bark-transformed formants) measures.
A comparison of two models of human vowel recognition
Authors: Dutton D. Lauren , Sawusch James R. , Tsoi Kam-Cheong
Published: October 2005

Two models of human vowel recognition were simulated and their performances compared. The first was proposed by Syrdal and Gopal [J. Acoust. Soc. Am. 79, 1086–1100 (1986)] and modified for implementation. Five dimensions composed of critical band differences between spectral peaks (including F0) were computed for each input stimulus. Identification was based on the best match of the input to a set of prototypes. The second was a full octave filtering model simulating central auditory processing. Parallel filters combined all spectral peaks within three critical bands into a single peak. The match between each stimulus and the prototypes was then used as the basis for categorization. The prototypes used in each model were based on Peterson and Barney [J. Acoust. Soc. Am. 24, 175–184 (1952)]. The performance of the two models in identifying vowels will be described. In addition, performance of the models was compared to data of human subjects for tone analogs of vowel and single formant vowels. Relative strengths and weaknesses of the two models will be discussed. [Work supported by NINCDS.]
Ray scattering from a collection of ice keels
Authors: Gordon David F.
Published: October 2005

An ice-keel program that was described at the Spring 1985 meeting [J. Acoust. Soc. Am. Suppl. 1 77, S56 (1985)] is used to investigate the acoustic scattering properties of ice keels at high frequency. Keels are modeled as parabolas. Same sets of keels are generated using published distributions of spacing and sizes [O. I. Diachok, J. Acoust. Soc. Am. 59, 1110–1120 (1976)]. A large number of rays are directed toward the keel set and the emerging rays are collceted into angular bins. Reflections from and refraction through the ice are employed. Specular reflection coefficients computed in this manner are similar to Diachok's published results above 3° grazing angle. No significant specular reflection is found at lower grazing angles. The scattered rays tend to be directed predominantly into angles near the specular angle. [Work supported by NOSC Independent Research.]
Numerical investigations of rough surface scattering
Authors: Berman David H. , Perkins John S.
Published: October 2005

An improved point matching method [H. Ikuno and K. Yasuura, Trans. IEEE Antenna Propagat. AP-21, 657–662 (1973)] is used to calculate surface scattering amplitudes for periodic irregular interfaces. Results of this method can be examined both for energy conservation and least-square satisfaction of boundary conditions. Because of the speed of this algorithm and simplicity of programming, it has been possible to examine fluid-fluid interface scattering in two dimensions, for grazing angles as low as 5 deg, and Dirichlet scattering for simple two-dimensional surfaces. Large-period surfaces with arbitrary structure within a period have been used to mimic random rough interfaces. Reasonable averaged scattering cross sections for the random rough surface problem have been obtained, using ensembles of 10 or 20 surface realizations. When the rough surface is described by a steep power-law spectrum, ensemble averaged cross sections may be dominated by a single ensemble member, in effect giving a false alarm. Doppler effects for moving surfaces have also been calculated.
Resonance frequencies and the phase matching of helicoidal surface waves on impenetrable spheroids
Authors: Merchant Barbara L. , Nagl Anton , Überall Herbert
Published: October 2005

The existence of the (complex) resonance frequencies of acoustic scatterers is explained by the generation of surface waves that match phases after repeated circumnavigations of the objects. The resonance frequencies can be predicted [B. L. Merchant et al., J. Acoust. Soc. Am. 80, 1754 (1986)] for prolate spheroidal objects, in the special case of axial incidence. Here sound-soft, prolate-spheroidal targets subject to obliquely incident signals are considered. The generated surface waves propagate along geodesics of helicoidal type, for which we obtain the condition for closing, and the set of discrete “pitch angles” at which closing takes place. An integral condition is formulated for the phase matching of helicoidal surface waves, using local wavelengths of Franz's surface waves. It is solved numerically for the complex resonance frequencies, found to agree closely with the m > 0 (i.e., containing azimuthal components) resonance frequencies obtained from an independent T-matrix calculation. This agreement confirms the validity of the principle of phase matching for the general case, and the accuracy of the T-matrix results. [Work supported in part by the Office of Naval Research.]