bluuebunny/crossref_metadata_2025 huggingface dataset:
Word juncture perception as a function of word-initial phonemes
Authors: Dukes Kathleen D. , Nakatani Lloyd H.
Published: October 2005

A previous study showed that allophonic variations in word-initial phonemes were the primary cues for word juncture perception. This study examined juncture perception as a function of the word-initial phonemes occurring singly and in clusters. Pairs of two-word phrases contrasting in juncture location (e.g., “he praises” and “heap raises”) and representing a wide variety of word-initial vowels, consonants and consonant clusters were recorded in sentence contexts by four talkers. The phrases were excised from the sentences and played to listeners who indicated which phrase they heard. Juncture perception was good for word-initial voiceless stops, vowels, affricates, and nasals, and fair for fricatives and voiced stops. Juncture perception was poor for liquids and semivowels, but good when they occurred in a consonant cluster. Juncture perception for clusters beginning with /s/ was better than for /s/ alone. Juncture perception was poor when the same consonant occurred before and after the juncture (e.g., “heap praises”); this suggests that segmental duration is not an important cue for juncture perception.
Spectrum analysis—a diagnostic tool for high speed rotating machinery
Authors: Boyce Meherwan P.
Published: October 2005

The role of the spectrum analyzer as a too] in the location of problem areas is finding greater acceptance in the field of high-speed rotating machinery. Its use as a diagnostic instrument has been limited due to an inadequate understanding of the various signals. To achieve a better understanding of the signed analysis of the various types of transducers and their effect on signature analysis is discussed. The development of data banks to enhance the understanding of various types of signals is described. This data bank is developed by isolating individual problems and recording their signature patterns. These signature patterns can be used both visually or programed for computer matching. In this manner the spectrum analyzer can be used as on line diagnostic system. Test patterns and actual field tests are described to show the impact that such a system would have when combined with performance data as a diagnostic tool.
Analytical studies of sodar observations at Delhi
Authors: Singal S. P. , Datta N. N. , Gera B. S. , Aggarwal S. K.
Published: October 2005

A monostatic sodar system has been operating at the National Physical Laboratory, New Delhi (28.6°N, 77.2°E) since December 1974. Echograms obtained up to May 1976 (operational period of approximately 1500 h) have been qualitatively analyzed with respect to their structural details. Layers are a general feature of the sodar echograms with their thickness lying mostly within 20 m. Their percentage occurrence reaches a maximum of 95% between 1600–2000 h and a minima of 40% between 1200–1400 h. The height of the layers has a primary maximum (average height 220 m and maximum height 350 m) between 0200–0400 h, a minimum (average height 175 m) between 0800–1000 h and a secondary maximum (average height 190 m) between 1100–1400 h. Turbulence is a very characteristic observation under stable conditions and is present for about 13% of the time. The turbulent as also the layer structures have been classified into various categories according to their typical features. Discernible thermal plume structures have been rarely seen over Delhi. The structure is mostly affected by the prevalent ambient wind. The convective activity is maximum around 1200–1400 h.
Vibrational energy transition rates from recent sound absorption measurements in moist air and in moist nitrogen
Authors: Bass H. E. , Shields F. D.
Published: October 2005

Recent measurements of sound absorption in moist air at temperatures between 0°F and 100°F have been analyzed to extract that part of the absorption due to the vibrational relaxation of oxygen. The measurements extend to higher water-vapor concentrations than most previous measurements and show the shift in frequency of maximum relaxation absorption per wavelength with percent water vapor to be less than that extrapolated from previous measurements. The fmax versus percent-H2O curve has been analyzed in conjunction with previous measurements in binary mixtures of H2O and O2 to give more accurate values for the rate of v-v exchange between H2O and O2 and for the v-R, t rate in H2O-H2O collisions. Measurements have also been made of the vibrational relaxation absorption in moist nitrogen at 100, 200, and 300°F. In these measurements fmax was found to increase linearly with H2O concentration and a more accurate value for the v-R, t (or v) rate for H2O deexciting N2 vibration has been determined at each temperature. [Work supported NASA—Langley Research Center and NASA—Lewis Research Center.]
Applications of digital color display techniques for sodar
Authors: Thomson D. W. , Sheib J. P.
Published: October 2005

The monostatic—bistatic Doppler Sodar at Penn State University has been equipped with a digital color display unit for presenting signal amplitude and Doppler information. Effective system performance for measurements of planetary boundary layer structure and dynamics has been markedly improved. The color technique greatly enhances effective grey-scale resolution in vertical-time section displays of received signal amplitude. Color presentation of signal Doppler information facilitates analysis of wave phenomena and thermal convection in the planetary boundary layer. The system is in use for a variety of field measurements. In some, a research aircraft is radio directed into the region of meteorological interest. Other experiments involve the development of user-oriented color display techniques for ready interpretation of air pollution related parameters. [Research supported by EPA Grant R800397.]
Calculations of the slant visual range (SVR) based on acoustic radar records
Authors: Werner Ch.
Published: October 2005

A careful measurement of slant visibility becomes every day more important for safe and regular aircraft landing operations. The use of an optical, single-ended radar (lidar) is restricted by safety rules and increasing costs. Monostatic acoustic radars are used by air pollution engineers for control and forecasting. Under the assumption that the interested visibility conditions are given by the temperature and humidity structure of the lowest few hundred meters of the troposphere, the acoustic radar in combination with ground-based visibility meters can be used as a practicable compromise to detect SVR. The monostatic acoustic radar gives information about the inversion layer and the top of low clouds. Calculations based on the measured visibility near the ground and the measured vertical-temperature structure by sodar in addition with the known behavior of the aerosol particles with the relative humidity show that in most cases it would be possible to detect SVR. Some examples of a field experiment are given.
Analysis of shallow water sound propagation by normal mode theory
Authors: White D. , Gordon D. F.
Published: October 2005

Normal-mode computations agree well with experimental sound propagation data observed in shallow water in the South China Sea. The sound-speed profile has negative gradients in the water over a structured silt bottom. Determining a sufficient set of modes can be aided by the relationships between certain fundamental parameters of ray and mode theory. Interference distance between adjacent modes and ray theory loop length can be equated through their phase velocity. The ray theory accuracy can be improved by a frequency correction [E. L. Murphy and J. A. Davis, J. Acoust. Soc. Am. 56, 1747–1760 (1974)], Mode attenuation loss over one loop length can be attributed to the loss at one bottom reflection. A bottom reflected phase shift can also be derived from mode theory. Optimum propagation occurs at the lowest frequency that permits a mode to attain maximum loop length.
Low-frequency shallow water propagation in Barrow Strait, N.W.T., Canada
Authors: MacKinnon R. F. , Ozard J. M.
Published: October 2005

A study is made of wave dispersion from explosive charges over ranges of 7–15 km in water of 150-m depth at a location in the Canadian Arctic archipelago. At frequencies below 40 Hz, speeds are found to be as high as 7.4 km/sec and lower than 0.8 km/sec with a particularly large arrival occurring at a speed of 1.2 km/sec. At higher frequencies most energy travels at speeds near the speed of sound in water. Independent seismic surveys have shown the area of interest to be characterized by nearly horizontal strata in the bottom consisting of an extremely thin cover of unconsolidated sediment over layers of Paleozoic carbonates. General features of the observed wave trains are discussed on the basis of a theoretical three-layer model with a bottom consisting of two elastic layers. Attenuation is observed to be severe generally and as a function of frequency possesses a maximum near 30 Hz.
Overview of recent research—summary of the 1976 International Symposium on Shipboard Acoustics
Authors: Junger Miguel C.
Published: October 2005

Recent Legislation in Europe on permissible noise levels in commercial shipping has heightened concern and increased research efforts to solve noise-control problems. Technisch Physische Dienst TNO-TH, Delft, Netherlands, has organized an international symposium of invited speakers on this topic in order to encourage dissemnation of new research results. In this summary of the conference by this participant, some of the more significant research results will be discussed. Results will be selected with regard to their expected significance for influencing the design of new commercial ships or modifications of existing ships.
Noise-control design problems of air cushion vehicles (ACV) and surface effect ships (SES)
Authors: Dvornak M. E.
Published: October 2005

A description of SES and ACV design features which make these craft/ships unique from conventional displacement type ships are presented. The uniqueness of the SES/ACV designs are shown to present new problems relative to ship acoustical design. The impact of the SES/ACV design features on the source-receiver acoustic environment are defined as well as the airborne and structure-borne noise paths between the noise sources and receivers. Examples of test measurements made on SES/ACV type craft are presented to show the contribution of the various noise sources to the total noise at a particular location. The primary noise problem on SES/ACV type craft are shown to be predominately in the low-frequency region. The noise criteria utilized in the design of SES/ACV's are also examined. Noise-control design approaches which address the various noise sources on SES/ACV's are presented relative to meeting the established noise criteria. Lastly, SES/ACV noise-control design approaches are compared to those utilized for land-based applications.
Echolocation ontogeny in the pallid bat (Antrozous pallidus)
Authors: Brown Patricia E.
Published: October 2005

The ability to heat and emit the ultrasounds necessary for echolocation is not present at birth in the pallid bat and does not appear until at least a week postnatally. Dramatic changes occur both in pulse structure and auditory tuning as the bat matures. Pallid bats begin to fly at four weeks of age, but continue to nurse until seven weeks old. This allows them time to coordinate the flight and echolocation skills necessary for survival. Bats learn to correlate outgoing pulse with returning echoes. Naive bats approaching an obstacle do not exhibit the expected increase in pulse repetition rate, which occurs after some experience. The normal development of echolocation skills as judged by obstacle avoidance can be correlated with sound emission. Deficits occur in bats raised in environments in which their echoes are distorted or attenuated.
Subdivision of the beat: Estimation and production of time ratio by skilled musicians
Authors: Knoll Ronald L. , Sternberg Saul , Zukofsky Paul
Published: October 2005

Professional musicians served as subjects in experiments on time estimation and production. In one procedure, equally spaced high-frequency clicks defined rhythmic beats. Intervening lower-frequency marker clicks indicated a fraction of the interval between beats. Subjects estimated the fraction. In a second procedure, equally spaced clicks were presented without the intervening marker clicks. Subjects attempted to produce a specified fraction of the interval between beats by responding with a finger tap after each click. If produced fractions are adjusted by estimating the time between click occurrence and response feedback, then any biases in the two tasks should be equal in magnitude and opposite in direction. For large fractions, estimated and produced fractions were unbiased. However, for small fractions, both estimated and produced fractions were too large. With respect to a feedback theory of production, the common direction of the two biases is paradoxical. [Work partially supported by IRCAM and Rockefeller Foundation.]
Recognition of musical triad quality
Authors: Killam Rosemary N. , Lotton Paul V. , Schubert Earl D.
Published: October 2005

Certain patterns of pitch, such as chords and scales, are central to the organization of traditional music. These patterns are identified by standardized nomenclature, and form a basis for analytical listening to music. The auditory processes involved in recognition may be revealed by comparing the ability of trained subjects to categorize these standard patterns. Perceptual confusion among standard, three-tone stimuli was studied in 19 musically trained subjects. A solid-state organ, interfaced to a digital computer, was used to present the stimuli; a terminal connected to the same computer was used to collect the responses. All subjects received the same stimuli, randomly accessed by the computer program. The subject indicated whether the signal presented was major, minor, augmented, or diminished. The three-note signals were presented in three manners: simultaneously, ascending (in pitch), and descending. All stimuli were presented at both O.2- and 0.1-sec note duration. Accuracy wan least for shorter duration and for simultaneous presentation. Different triad qualitites maintained essentially the same performance rank through the different modes of presentation. Patterns of confusion and response bias suggest the subjects' use of pre-existent auditory images.
Speech development in infants—vowel production
Authors: Lieberman P. , Buhr R. , Keating P. , Hamby S. V. , Landahl K. H.
Published: October 2005

Five infants ranging in age from 12 to 66 weeks at the start of the project have been recorded at biweekly intervals during half-hour play sessions with their mothers. Fundamental and formant frequencies were derived from sound spectrograms, Fourier and Linear Predictive analysis. The data reveal differences in the infants' phonetic development as they gradually acquire the vowels of English. Their formant frequency patterns are outside the range reported by Peterson and Barney (1952) for older children but are consistent with the shorter supralaryngeal vocal tracts of these infants. The formant patterns that specify particular vowels change as the infants mature. F1 of/ae/, for example, changes from 1.0 to 0.7 kHz for one infant between 37 and 56 weeks. The infants' vowel production and their mothers' responses are consistent with the presence of an innate vocal tract length normalization perceptual mechanism that enters into the development of speech production.
Korean spiral stop production: a VOT analysis
Authors: Moslin Barbara J. , Knapp John S.
Published: October 2005

An investigation was made of the role of voice onset time (VOT) in distinguishing among Korean apical stop consonants. Measurements were made of VOT values for word-initial apical stops in the speech of four native Korean speakers. Words in citation form, in test sentences, in conversations among Korean adults, and in mothers' speech to children were used. Our results are not in accord with other experimenters who found complete separation of the aspirated from the strong and weak categories of Korean stops. VOT values for word-initial apical stops in the speech of all four speakers showed considerable overlap of the weak and aspirated categories. The strong and weak categories were also found to overlap, but the overlap in the weak and aspirated categories was greater. Our data suggest that although VOT is sufficient to distinguish the strong from the aspirated stops, it cannot effectively distinguish either of these from the weak stops. Our findings support Kim (1965), who proposes a feature of “tensity,” independent of VOT, to distinguish weak stops from the strong and aspirated stops of Korean.
Selective attentional cueing in auditory pattern discrimination
Authors: Watson C. S. , Spiegel M. F.
Published: October 2005

We previously reported that listeners can learn to “hear out” single 40-msec components of 10-tone sequences, when they are trained under minimal-uncertainty conditions. Once the highly accurate frequency discrimination suggestive of selective listening has been achieved, it could be maintained even when the test component was 40 dB below the level of the pattern [Watson and Spiegel, J. Acoust. Soc. Am. 58, S84 (1975)]. Only a single component was tested in each pattern (e.g., the second component was always tested in the eighth pattern). Thus, each pattern could potentially serve as a cue to the position of its test component. Extensions of these experiments, with same-different and with single-stimulus (remembered-standard) methods, support the following conclusions: (1) Once selective listening has been achieved for a specific pattern, it is maintained even when the pattern is presented at random with others. (2) The process of recognizing, a particular pattern and then selectively listening to the appropriate component within that pattern is very rapid. Since listeners can selectively attend to even the earliest components in patterns presented in the single-stimulus procedure, the mechanisms of identification at least operate simultaneously with, and may precede, those of discrimination. [Supported by Grant ♯GMO-1900 from NIGMS to W.U. and Grant ♯NS-03856 from NINCDS to C.I.D.]
Contralateral cueing effects on backward masking
Authors: Puleo J. S. , Pastore R. E.
Published: October 2005

Two yes-no detection experiments were used to investigate the effects of a contralateral cue on the detection of a brief 20-msec, 500-Hz signal followed by a monotic masking noise. The masking stimulus, a 20 dB increment in an otherwise continuous (41.5 dBA) broadband noise, was presented at various specified time delays (1 ⩽ Δt ⩽ 320 msec) following the observation interval. The signal and cue were narrow bandpass filtered noise bursts in one experiment, and sinusoids in the other. Both signal (p = 0.5) and cue (p = 0.1) were presented during the same observation interval under three different phase conditions: 0°, 180°, and random phase. Relative to the no cue condition, the amount of backward masking found in both experiments under all cue conditions was significantly reduced (∼3–5 dB) at short delays (Δt < 20 msec), and only slightly reduced at longer delays. Under all cue conditions, the reduction in the amount of simultaneous masking and the reduction in backward masking at long delays was approximately equivalent. [This research was supported by a grant from NINDS.]
Characteristics of phasic “on” neurons in the inferior colliculus of unanesthetized bats with observations relating to mechanisms for echo ranging
Authors: Pollak G. D. , Marsh D. S. , Bodenhamer R. , Souther A.
Published: October 2005

Single units with phasic “on” firing patterns were recorded from the colliculus of unanesthetized bats (Tadarida brasiliensis mexicana). Our intention was to identify a population of neurons whose response characteristics are suitable for measuring the time interval between an emitted pulse and echo and, therefore, would be of value for echo ranging. Three catagories of units are distinguished on the basis of the consistency of the initial spike latent periods elicited by repetitive signals. Most important are the “phasic constant latency responders” (PCLR) in which the dispersions of initial spike latencies were at most ± 250 μsec at any intensity and where the mean latency charged by at most 1.7 msec when the signal level was increased from 3–6 dB to 30–40 dB above threshold. The initial spike latencies in most PCLR's were erratic with tone bursts but became highly synchronous with frequency-modulated (FM) signals resembling the natural chirps of this species. Each PCLR had a “hair trigger” threshold to FM signals where the firing probability rose from near 0.0 to 0.8–1.0 as the signal level was increased from threshold to 2–6 dB above threshold. In addition, each of these units exhibited an “independent recovery” pattern where the presentation of an initially loud pulse did not effect the response to a simulated echo following shortly thereafter. The response and recovery characteristics of the PCLR's were correlated with behavioral data reported in previous studies and it is shown that the PCLR's have the capability for measuring the time interval between a pulse and the returning echo. Moreover, by assuming that the bat can correct for inherent “errors” resulting from dissimilar pulse-echo intensities the population of PCLR's can provide a measurement of target distance that becomes progressively more accurate as the bat homes in on its target. [Supported by NSF Grant P401855-000.]
Measurement of the average noise level for impulsive noise sources
Authors: Sutherland L. C. , Burke R. E. , Lee M. C.
Published: October 2005

A wide range of artificial impulsive-type signals was measured with an impulse sound level meter to determine the relationship between the known (energy) average signal level and the observed meter reading for various settings of the meter time constant and frequency weighting network. The artificial signal consisted of tone bursts superimposed on continuous background noise. The tone bursts lasted from 1 to 100 msec, were repeated in intervals from 2 to 2000 msec and had an rms level 10–50 dB above that of the random background noise. The latter was either pink noise or was shaped to resemble typical community noise. For impulse repetition rates greater than 1 pulse/sec, the impulse sound level meter reading on the average within ±1.3 dB of the energy average signal level, provided the meter was set on A-weighting “slow,” the upper or maximum meter deflection was used, and this meter reading fell on the lower parts of the meter scale. Errors for lower pulse rates are also discussed in this paper. [This work was supported by the U. S. Environment Protection Agency.]
Computer predictions of refinery noise levels
Authors: Judd S. H. , Walker G. M.
Published: October 2005

The predictions of a computer model [S. H. Judd, S. L. Dryden, and L. Tornheim, “Development of a community noise prediction model” and S. H. Judd and S. L. Dryden, “Application of a computer model for predicting remote noise levels”, J. Acoust. Soc. Am. 58, S16(A)(1975)] agree closely with the measured noise levels around a major refinery. This is illustrated by octave band and A-weighted results. The construction of major new facilities which partially shield the existing plants has provided attenuation consistent with the algorithm used in the model as shown by before and after data. The model is being used to verify design predictions of source sound power levels and to assist in the selection of noise control measures.
Generalized theory of the photoacoustic effect
Authors: McDonald F. A. , Wetsel G. C.
Published: October 2005

The photoacoustic effect is the production of an acoustic signal when a sample in an enclosed cell is illuminated with chopped light. The absorbed light produces a periodic heat flow from the sample to the surrounding gas and backing material, causing pressure variations in the gas which are detected by a sensitive microphone. A theoretical treatment will be presented which involves simultaneous solution of thermal-diffusion equations for the sample and backing material and fluid-dynamic equations for the gas. The resulting acoustic signal depends on the chopping frequency, the optical absorption coefficient and thermal properties of the sample, and on other material and system parameters. The conditions under which the approximate treatment of Rosencwaig and Gersho [J. Appl. Phys. 47, 64–69 (1976)] is valid will be discussed. Application of the theory to solid and liquid samples will be considered.
Wave interactions at plane and grating interfaces
Authors: Breazeale M. A.
Published: October 2005

Schlieren photography is used to show how an ultrasonic beam incident onto a liquid-solid interface couples in a resonant manner to a wave propagating laterally along the interface. At plane interfaces the lateral wave is a surface wave which produces a positive displacement of the reflected beam. At grating interfaces the lateral wave can result from a tangential diffraction order which can have a negative propagation vector. This leads to a negative displacement. The velocity of the lateral wave in this case is very nearly equal to the velocity of a compressional wave in the liquid. A motion picture shows the behavior of both types of interaction as the angle of incidence is changed. [Research supported by the U. S. Office of Naval Research.]
Microparticle detection with focused ultrasound
Authors: Abts L. R. , Beyer R. T. , Richardson P. D. , Galletti P. M. , Karlson K. E.
Published: October 2005

A 5-MHz ultrasonic sensing device which detects and monitors microparticles in a moving fluid stream has been described, constructed, and calibrated, The ultrasonic transducer is so placed that a thin section of plexiglas exists between the transducer and the fluid stream. This section is of piano-concave shape and acts as a converging lens to focus the transducer at approximately 1.36 cm from the surface of the lens. The pulsed ultrasonic signal is transmitted into the fluid which flows through a calibrated and mapped sound radiation field. The calibration of the field for particle size was done through the use of carbonized microspheres, glass beads and air bubbles of known sizes. The device is calibrated to detect and monitor microparticles in the range of 7–400 μm in diameter. A formula was derived from these calibration studies which relates reflected amplitude to particle size. The radiation field was mapped using a target ball of 0.635 cm in diameter. The apparatus has been used successfully during in vivo extra-corporeal studies done on sheep, and has recorded microparticles during these procedures. [Work supported by Rhode Island Heart Association.]
Reflection from absorbing cylinders
Authors: Schuetz L. S. , Neubauer W. G.
Published: October 2005

The theoretical solution for reflection of an acoustic plane wave by an elastic cylinder of infinite length, which may absorb energy, is formulated. The sensitivity of computations to the variation of physical parameters is discussed. Reflections as a function of frequency and angle, are compared with experimental data taken using finite cylinders immersed in water.
Effect of variations in properties of silicon rubbers on the scattering of sound
Authors: Flax L. , Davis C. M.
Published: October 2005

The scattering of plane waves by absorbing silicon rubber spheres and cylinders is investigated theoretically. The bodies are immersed in water. The effect of inclusion and exclusion of shear losses are examined. The scattering solution is calculated for a range of densities, velocities, and absorptions characteristic of many silicon rubbers.
Sound-scattering properties of curved surfaces with complex impedance
Authors: George Jacob , Überall H.
Published: October 2005

Specular reflection which accounts for most of the reflected signal at farfield depend on both the curvature of the scatterer and its acoustic impedance. As specific cases, we calculate the backscattering cross section for plane waves reflected from circular cylinders and spheres. Results using both the Kirchhoff approximation and the Luneburg-Kline (LK) method [J. B. Keller et al., Commun. Pure Appl. Math 9, 207–265 (1956)] are presented and compared. The LK expression for cross section contains up to (ka)−2 terms for the cylinder and up to (ka)−1 terms for the sphere. The cross sections for the limiting cases of rigid and soft spheres are compared with those obtained by retaining up to (ka)−1 terms in an asymptotic expansion. It is found that the LK method gives better results in the presence of a complex impedance. Dependence of the cross section on relative magnitudes of real and imaginary parts of the impedance are studied. Variation of the LK cross section with the angle of reflection is discussed. [Supported in part by ONR.]
Theory of scattering by rigid bodies with thin liquid coatings
Authors: Eisler T. J.
Published: October 2005

We consider a plane-wave incident on a rigid body which is partially or totally surrounded by a thin liquid coating whose (possibly variable) density and sound velocity differ from those of the ambient medium. The wavelength is assumed to be small compared with the dimensions of the body but large compared with the thickness of the coating, The scattered wave is expressed in terms of integrals similar to the Kirchhoff integral. These are derived by iteration from an integral formulation. The first iteration produces corrections to the uncoated solution which are linear in kδ, where k is the wave number of the incident wave and δ the thickness of the coating. We restrict our attention to these linear terms. The scattering cross section may be evaluated in terms of contributions from the specular point and from points on the edge of the coating at which the incident rays are perpendicular to the edge. In the absence of absorption it is found that the edge contributions Dominate Technology Program, ONR.]
Measurement of the acoustic field scattered at the liquid-solid interface of an echelette grating
Authors: Numrich S. K.
Published: October 2005

Experimental measurements have been made of the acoustic field produced by sound scattered at the brass-water interface of an echelette grating. Theoretical calculation of the reflection coefficients for the various orders of scattered waves have been completed by J. DeSanto. Schlieren photographs are used to indicate the angular dependence of the scattered field and hydrophone measurements of the acoustic field are compared with the theoretical model.
Influence of surface waves on plane wave bottom reflection loss for realistic ocean sediments
Authors: Hawker Kenneth E.
Published: October 2005

Plane-wave reflection coefficients have been computed for several cases of fluid sediments, containing a constant sound-speed gradient, overlying a homogeneous solid substrate. It is shown that for realistic sediment descriptions, a pronounced maximum in bottom loss can occur at low grazing angles (well below the shear-wave critical angle). This maxima is well defined in angle and can occur only for special combinations of sound-speed gradient, frequency, and sediment thickness. It is shown that this phenomena is due to Stoneley waves propagating in the neighborhood of the sediment-substrate interface. These surface waves can become excited only when their phase velocity equals the parallel component of the phase velocity equals the parallel component of the phase velocity of the incident plane waves. Calculations are presented showing excellent agreement between the location of the bottom loss maxima and the predictions of a simplied theory based upon the excitation of Stoneley waves. The frequency, layer thickness, and sound speed gradient dependence are all adequately accounted for.
Variable and adaptive masking sound systems
Authors: Chanaud Robert C.
Published: October 2005

Increased usage of masking sound systems in open plan offices has shown that certain additional features are both useful and desirable and these will be described. One such feature is the automatic control of both level and spectrum throughout the day, including automatic, but slow, shutoff to conserve energy. Another feature is multiple use of the loudspeakers. Both paging and music have been superimposed on the masking sound already. In addition it is possible to have the masking sound controller respond to alarm signals, such as a smoke detector, activate a prerecorded taped message, and give emergency instructions over the sound system. Other uses, such as nighttime security monitoring, will be described. A number of masking sound spectra have been used in open offices but we have found that a modified PNC-40 contour yields minimum Articulation Index for a given A-weighted sound level.
Doppler velocity extraction from atmospheric acoustic echoes using a level crossing technique
Authors: Melling H. , List R.
Published: October 2005

The scattering of a narrow-band acoustic signal from atmospheric turbulence generates an echo of rapidly varying amplitude and frequency. The mean frequency of the echo power spectrum is related by a Doppler shift to the mean motion of the scatterers. In the level crossing technique this shift is deduced from measurements of the “instantaneous” envelope amplitude and rate of zero crossing of one component of the complex echo waveform. Data interpretation is based on an analysis of the statistics of instantaneous echo frequency and power which shows the probability density function of frequency to depend only on the first two moments of the power spectrum [R.C. Srivastava and R. E. Carbone, Radio Sci. 4, 381–393 (1969)]. These moments may be determined from averages in the time domain without the need for Fourier transformation. The technique has been tested on an electronically simulated echo signal and found to yield statistics in good agreement with the theoretical predictions. Similar tests on atmospheric echoes show good agreement for the frequency statistics but not for those of power.
Binaural integration of tonal patterns
Authors: Deutsch Diana
Published: October 2005

It has been argued that a limitation exists in the rate at which we can switch attention between ears in monitoring auditory information. Listeners identified melodic configurations formed by rapid sequences of tones. When these sequences were presented diotically, near perfect performance was obtained. Yet when they were presented with the tones switching between ears, performance was close to chance. However when these same dichotic sequences were accompanied by a drone that always occurred in the ear opposite to the ear receiving a component of the melody, performance rose dramatically, approaching that in the diotic condition. This improvement in performance could not have been due to processing the harmonic relationships between melody and drone, since when instead the drone occurred in the same ear as the component of the melody, performance was at chance. It is concluded that difficulties in binaural integration observed under some conditions are due, not to a processing limitation, but to a strategy that is invoked under certain conditions to prevent confusion in monitoring individual sound sources.
The epiglottis as an articulator
Authors: Laufer Asher , Condax I. D.
Published: October 2005

We find that the epiglottis functions as an articulator in the production of (1) pharyngeals, (2) the vowel [a], (3) whisper. In pharyngeals we find the epiglottis articulates against the posterior pharyngeal wall: The constriction varies from a full closure (pharyngeal stop) in the extreme case of [ʕ] in slow careful speech, through narrow opening (fricative [ħ,ʕ] in connected speech to fairly open glide [ʕ]. The epiglottis folds toward the pharyngeal wall independently of the tongue root in these consonants. In the vowel [a] the opening is of the same shape as for the pharyngeal consonants, but the opening is substantially larger. The opening allowing the escape of air is between the epiglottis and the pharynx (never between the tongue and the pharynx lateral to the epiglottis). The independence of the epiglottis from the tongue is seen in some cases and not in others for [a]. In whisper the epiglottis is in general more retracted than during normal speech. These observations are based on approximately 100 minutes of videotape made using a fiberscope positioned in the upper pharynx, spectrograms, and dissection of cadaver materials. [This work was supported in part by the UCLA Phonetics Laboratory, NIH grant NS9780, and by Faculty of Humanities of Hebrew University of Jerusalem.]
Acoustic modeling of an oceanographic swirl
Authors: Browning D. G. , Gallagher J. J. , Eubanks G. E. , Schneider H. G.
Published: October 2005

It has recently been found that eddy-like oceanographic features can persist at certain locations due to bathymetric considerations. These features have been called swirls due to the nature of their circulation pattern. Various fixed and variable profile sound propagation prediction models were used to predict the effect of these swirls on sound propagation at frequencies between 50–15000 Hz. A typical case was 100 km in diameter and was fed by cold water current at the edge which spirals clockwise inward gradually heating to form a warm core. It was found that the most significant features were the temperature of the central core which depressed the depth of the main sound channel axis and the rate of cold water flow at the edge which determined the vertical width of a secondary sound channel which gradually diminished toward the center of the swirl. [Sponsored by Naval Underwater Systems Center.]
Acoustic propagation characteristics of the South Fiji Basin
Authors: Denham R. N. , Guthrie K. M. , Bannister R. W. , Browning D. G.
Published: October 2005

The South Fiji Basin, situated to the north of New Zealand, is a large flat basin with a water depth of 4000 m surrounded almost entirely by ridge systems. A thermal front crosses the northern part of the area. Four propagation loss sections which traversed the basin and margins were made in 1976 using 18-m-depth explosive sources. The data were received on a hydrophone at a depth of 400 m near the center of the basin. Signal enhancement was found near the basin margins, followed by a typically 15 dB signal loss for sources outside the basin. In the vicinity of the thermal front similar signal losses were evident over a range of 50 km. [Work supported by NUSC and DSE.]
Sound absorption in sea water
Authors: Fisher F. H. , Simmons V. P.
Published: October 2005

An equation for sound absorption in Lyman and Fleming sea water (S= 35‰, pH=8) is presented as a function of frequency. temperature, and pressure. It represents the contributions to absorption due to boric acid, magnesium sulfate, and water. The pressure effect on sound absorption by magnesium sulfate is treated in more detail than Schulkia and March did. The equation is based on the laboratory work at atmospheric pressure by Simmons for MgSo4 and boric acid, on the pressure work by Fisher in 0.5m MgSO4 solutions, and on pressure work by Litovitz and Carnevale in pure water. For frequencies from 10 to 400 kHz up to pressures of 500 atm the absorption is substantially lower than that calculated from the Schulkin and Marsh equation. The pressure results are in good agreement with field data obtained by Bezdek. [Work supported by Office of Naval Research.]
Effect of a ground surface on acoustic propagation
Authors: Van Moorhem W. K. , Lanter S. K.
Published: October 2005

An investigation has been carried out in which ground impedance measurements and propagation data were obtained at the same site to assess the existing theoretical results. The ground impedance was determined by an oblique reflection method. The values of the impedance obtained for a grass-covered earth surface are in general agreement with the results of previous investigator in the frequency range of 400–1000 Hz, but a large phase shift in the impedance occurred below 400 Hz. Impedance measurements were also attempted on a snow-covered surface. Generally good agreement was found between the propagation data and theoretical results using the measured impedance data and both exact and approximate analytical expressions. [Work supported by NSF.]
Some effects of environmental stress on the electret condenser microphone
Authors: Djuric S. V.
Published: October 2005

Over the past several years improvements have been made in the basic design of electret condenser microphones. A thinner ,and tougher diaphragm and a new design of the diaphragm support have produced an exceptional resistance to mechanical and thermal shocks, During a mechanical shock test five microphones were let fall from a height of 2 m (6 ft, 7 in.) onto a hard floor (concrete covered with thin plastic tile). The sensitivities of these microphones changed between +0.1 and +1.4 dB. Two microphones were exposed to thermal shock by suddenly changing the ambient temperature from −40 to +25°C. Their sensitivity shifted +0.7 and +1.2 dB, respectively, and they were immediately covered by frost. Within 30 min they recovered to within 0.3 dB of initial sensitivity. These microphones have a temperature coefficient of sensitivity typically less than +0.01 dB/°C at frequencies below 2 kHz, and it remains less than +0.015 dB/°C through the frequency range up to 20 kHz. The inherent immunity to high humidity of electret microphones is further improved by using a better insulator material.
Diffraction fields of echosonde antennas
Authors: Adekola S. Adeniyi
Published: October 2005

The scalar diffraction integral is used in the present paper to obtain transforms of aperture field-distributions of an echosonde (acoustic echo-sounding) antenna. A highly convergent Lommel series of the form Ω0m(ν, η), is used to obtain the antenna Fresnel-zone field near the boresight of the antenna, The zero-order Hankel transforms of the real aperture-field distributions, which can also be used to synthesize the antenna-pattern, are obtained for circularly symmetric aperture-fields. The zero-order Lommel transforms are applied in the case of complex aperture-fields using the type of radial phase-changes (across the aperture) previously discussed [Adekola et al., Radio Sci. 12, 11–22 (1977)], The zero-order Lommel transforms arising from uniform excitations are expressed in closed forms using the Anger—Weber functions. Echosonde antennas are useful for investigating the thermal-structures and dynamics of the lower atmosphere [S. A. Adekola, J. Acoust. Soc. Am. 60, 230–239 (1976)]. Halfpower beamwidth-variations between 13.45° and 3.16° are obtained within 1–5 kHz. Sidelobe attenuations are between 50 and 60 dB. The theory is in good accordance with available experimental data. Atmospheric turbulence-components producing the strongest scatter range from 0.165 m at 1 kHz through 0.035 m at 5 kHz. The antenna-aperture is of several wavelengths from 3.7λ at 1 kHz through 25.7λ at 5 kHz. [Work supported by NRC.]
Sounds of superfluid helium
Authors: Putterman S.
Published: October 2005

A review of the hydrodynamic interpretation of the various sound or collective modes which propagate in superfluid helium will be presented. These will be separated into two categories: (a) bulk geometries, (b) helium confined between walls as narrow as 10 Å. As regards the bulk, the thermal propagating waves (second sound) as well as ordinary density waves will be discussed. For the confined geometries third sound (analogous to long gravity waves with the restoring force replaced by the van der Waals attraction to the substrate) and fourth sound (another pressure wave propagated through a modified compressibility) will be discussed. Use of the propagation and attenuation of sound to measure various thermodynamic properties will be explored.
Some applications of second sound to the study of superfluid helium
Authors: Ahlers G.
Published: October 2005

The generation and detection of second sound in superfluid helium will be described. Measurements of the second-sound velocity and attenuation can be applied to obtain important information about many aspects of the physics of superfluid helium. A few selected examples of these applications will be discussed.
Application of fourth sound to study the superfluid helium-4 and the recently discovered superfluid helium-3
Authors: Kojima H.
Published: October 2005

Fourth sound is propagated in a superfluid placed in the tiny pores of tightly packed fine powder. Since it is a type of usual sound (pressure-density) propagation, fourth sound may be excited and detected by condenser transducers. In superfluid helium-4 fourth sound has been used (1) to determine the superfluid component density by measuring the sound velocity, and (2) to study the nature of persistent currents using Doppler-shifted fourth sound. In superfluid helium-3 propagation of fourth sound provided conclusive evidence of superfluidity of liquid helium below 2.6 mK. Superfluid component density and some anisotropic properties of superfluid helium-3 have been investigated using fourth sound.
Innovation and experimentation in percussion instruments
Authors: Bowers Stacey , Kvistad Garry , Otte Allen
Published: October 2005

Percussion instruments, man's oldest musical instruments (with the exception of the human voice), have recently experienced a new surge of interest and popularity. Many novel percussion instruments instruments have been built, and novel ways to perform on existing ones developed. A number of innovations will be described and demonstrated.
Gas transport effects on cavitation noise in turbulent shear flows
Authors: Arndt R. E. A.
Published: October 2005

The effects of turbulence, nuclei, and gas transport on cavitation inception and noise are briefly reviewed. Cavitation inception occurs as a result of pressure peaks that have a magnitude as high as ten times the rms value. The resulting noise is governed by the number of nuclei in the flow and the transport of initially dissolved gas across the bubble wall during the growth phase. A study of these effects was made during an investigation of cavitation noise from a sharp-edged disk. The research program was carried out in both a water tunnel and a unique depressurized towing tank. The results show conclusively that both free and dissolved gas can significantly affect the spectrum of the noise signal. Coherent structure in the wake is apparently an overiding factor in the inception of cavitation, the intensity of the pressure fluctuations inducing cavitation being related to the characteristics of the boundary layer on the face of the disk. [Work supported by Netherlands Ship Model Basin.]
Aural representation of the Doppler-shifted—CF-processing area in the primary auditory cortex of the mustache bat
Authors: Manabe T. , Suga N. , Ostwald J.
Published: October 2005

To study how cortical neurons express directional information about a stationary echo source, responses of single neurons were recorded from the Doppler-shifted—CF-processing area of the mustache bat (Pteronotus parnellii rubiginosus). All cortical neurons studied were excited by contralateral stimuli and were either excited or inhibited by ipsilateral stimuli. They are called E-E and I-E neurons, respectively. Each penetration orthogonal to the cortex was characterized by either E-E neurons. I-E neurons, or neurons exhibiting binaural interaction, which varied with depth. Thus the cortex consists of three types of binaural columns. E-E neurons were poorly directional and showed maximum responses to tone bursts directed at the front of the head. I-E neurons were sharply directional. E-E neurons (or columns) were mainly located ventrally in the Doppler-shifted—CF-processing area, while I-E neurons were mainly distributed dorsally. E-E neurons, which were more sensitive to weaker echoes, are suited for integrating signals from both ears for echo-detection. I-E neurons, which were more sensitive to stronger echoes, are best suited for processing echo direction. [Work supported by NSE.]