bluuebunny/crossref_metadata_2025 huggingface dataset:
New Developments in Underwater Acoustics for Marine Applications
Authors: Blumberg Randolph
Published: October 2005

Underwater acoustics provides one of the most economical and dependable methods of underwater communication available to ocean industries. Rapid expansion of offshore activity should quadruple the number of underwater acoustic devices in service within the next decade. This paper discusses the importance of an accurate understanding of the effects of the ocean environment on the fidelity of acoustic transducers. Improvements in pulse-code modulation and other signal-identification techniques to prevent unwanted triggering of valves and releases by improperly coded signals are discussed. A forecast of trends in ocean engineering application of underwater acoustics is made, highlighting current research in underwater acoustic techniques.
Cinefluoroscopic Observations of Abdominal Muscular Functions in their Relation to the Support-Vibrato Syndrome in Singing
Authors: Appelman D. Ralph
Published: October 2005

Cinefluoroscopic techniques were used to observe the variations in the movement of the diaphragm during the alteration of the vibrato rate in singing. Four singers were selected for their ability to control the vibrato rate by means of abdominal pressure. All movement of the diaphragm was measured by caliper from its position at maximum inspiration before the onset of phonation. The vocal tasks were (1) nine pulsated tones sung legato on 234 Hz (male) and 468 Hz (female), (2) the same frequencies sung with normal vibrato rate, and (3) the vibrato controlled (slow, fast, slow). Observation shows the diaphragm dislodgement to vary with each subject. The average dislodgment was 4–6 mm in vocal task 1, 2–4 mm in vocal task 2, and 0–8 mm in task 3. Results suggest that the vocal vibrato is directly related to the senation of support—that it is produced by minute alterations of body pressures which are reflected in the undulation of the breath column. This variation in subglottal air pressure causes the pitch to vary as singer keeps the mass length tension and elasticity of the vocal folds constant through laryngeal controls.
Measurements of the Vertical Directivity of Ambient Sea Noise in the Deep Ocean
Authors: Wing T. E.
Published: October 2005

Measurements of the vertical directivity of ambient sea noise in the deep ocean are presented. The measurements were made with a vertical array located near the bottom of the sound channel. The measurements were made with 10% filters at the frequencies of 35, 50, 100, 141, 200, 400, and 750 Hz. The ambient noise was found to be made up of two components. One component is nearly omnidirectional and is generated by the local wind; the second component is anisotropic with the maximum near the horizontal, presumably generated by sources at long range. A seasonal dependence was found in the shape of the anisotropic component. In the winter, when the vertical array was below the bottom of the sound channel, the maximum in the anisotropic component was in the horizontal direction, while in the summer, when the array was within the sound channel, the maximum in this component was approximately 9° above the horizontal. [This work was supported by the U. S. Navy Electronic Systems Command.]
Analog Computer Simulation of an Acoustic Homing System
Authors: Horwath T. G.
Published: October 2005

An acoustic homing system consists of several interdependent subsystem functions, related to the areas of acoustic sensing, signal processing, guidance control, and aerodynamics. These subsystem functions have to be studied in conjunction with each other in an attempt to define the behavior of the over-all homing system. A suitable method utilized for this purpose is described. The main element is an analog computer model of the flight dynamics and guidance functions, which is interconnected with real signal-processor electronics. Reproduced acoustic target signals are received by a four-element microphone array in an anechoic chamber. The electrical output signals of these microphones together with the electrical output signals of four individual noise generators, representing the flow noise, are applied to the signal processor. The method yields directly the trajectory of the acoustic homing system in three space dimensions. The simulation arrangement which operates in real time is of stochastic nature and hence approximates the real-world conditions to a high degree. Typical results obtained with the simulation arrangement are presented. [This work was conducted at the Systems Development Office of the U. S. Army MERDC, Fort Belvoir, Virginia 22060.]
Significance of Attenuation and Loss Mechanisms
Authors: White J. E.
Published: October 2005

Seismic waves fall within the general category of acoustical phenomena, and there is some logic to considering “underground sound” as an extension of underwater sound. Just add shear waves and proceed as in case one. Attenuation in earth materials disturbs the parallel and prevents the adoption of underwater sound techniques for underground applications. As examples in the petroleum industry, the Borehole Televiewer scans only the surface of the borehole wall; attempts to telemeter information along a drill string or a pipeline are foiled by the surrounding Iossy solid; and resolution of seismic prospecting is controlled by attenuation. Measurements of attenuation in earth materials describe a situation which has not been explained to this writer's satisfaction. Data strongly indicate an attenuation constant directly proportional to frequency and a velocity virtually independent of frequency. On the face of it, these two results contradict causality, which of course is not acceptable. The loss mechanism yielding these results is almost certainly nonlinear. The writer has shown that propagation in a lumped-element model of a solid yields the above results, if the springs in the model exhibit hysteresis. It would be more satisfying to have a nonlinear wave equation which similarly yielded attenuation proportional to frequency and negligible dispersion over the frequency range for which data have been gathered on earth materials.
Wave Propagation in Fluid-Filled Boreholes
Authors: Rosenbaum J. H.
Published: October 2005

This subject is of special importance in the description of the acoustic-logging process. Acoustic logging can be modeled on a high-speed computer; it can also be investigated in the laboratory with the aid of physical models. The signals of interest are pulses and wavetrains, whose characteristics depend upon the properties of the surrounding formations. Simple descriptions of the salient features of the signals can be derived from theoretical analysis in terms of radial and circumferential modes or the corresponding rays. Results of the experimental, numerical, and theoretical approaches will be compared.
Sonic Boom Propagation in a Steady Atmosphere
Authors: Hayes W. D. , Runyan H. L.
Published: October 2005

The physical features in the evolution of the sonic boom signature due to a supersonic aircraft are presented and incorporated in a general prediction method. The method includes the effects of a variable stratified atmosphere, allows for maneuvers, and is based on geometrical acoustics. A weak nonlinear shock is treated, and it is shown that the signature will become “frozen” after a certain “aging” period. Agreement with experiment has been shown to be excellent.
Sonic Boom Simulation Technology
Authors: Edge Philip M.
Published: October 2005

Research on aircraft-generated sonic booms has led to the development of special techniques to generate controlled sonic-boom-type disturbances without the complications and expense of supersonic flight operations. This paper contains brief descriptions of several of these techniques along with the significant hardware items involved and indicates the advantages and disadvantages of each in research applications. Included are wind tunnels, ballistic ranges, spark discharges, piston phones, shock tubes, high-speed valve systems, and shaped explosive charges. Specialized applications include sonic boom generation and propagation studies and the responses of structures, terrain, people, and animals. Situations for which simulators are applicable are shown to include both small-scale and large-scale laboratory tests and full-scale field tests. Although no one approach to simulation is ideal, the various techniques available generally complement each other to provide desired capability for a broad range of sonic boom studies.
Behavior of Liquid Sodium in a Sinusoidal Pressure Field
Authors: Hammitt Frederick G.
Published: October 2005

By utilizing an ultrasonic vibratory cavitation facility, the onset of cavitation was observed in liquid sodium for different sodium temperatures and imposed sinusoidal pressure frequencies. This work has been reported (R. E. Nystrom, PhD thesis). It was observed that the pressure oscillation to initiate cavitation decreased strongly as sodium temperature was increased from 500° to 1500°F. Also, threshold pressure amplitude increased substantially with frequency above ∼20 kHz. These tests were primarily motivated by interest in the effects of highly transient temperature pulses on boiling initiation in molten sodium as in nuclear fast breeder reactors. Thus, the pressure threshold data was converted into temperature data, assuming thermodynamic equilibrium. Aside from this technological application, such sodium tests offer interesting scientific possibilities. For the 500°–1500°F temperature range, the solubility of inert gases in sodium is minute; hence, rectified diffusion, important in water tests, cannot appreciably influence results. [See discussion by M. S. Plesset and authors' closure (Nystrom, thesis).] Since gas “nuclei,” entrained or resident in crevices of wetter material, must be the predominant factor for bubble nucleation (which is a measurement of the gas nucleation), a measurement of the gas nuclei spectrum would characterize such a sodium experiment. For water, the transfer by rectified diffusion and other solubility effects of important quantities of gas between the dissolved and entrained state must also be considered.
The Time-Dependent Force and Radiation Impedance on a Piston in a Rigid Infinite Planar Baffle
Authors: Stepanishen P. R.
Published: October 2005

An approach is presented to compute the time-dependent force acting on a piston in a rigid infinite planar baffle as a result of the specified velocity of the piston. The approach, which is based on a Green's function solution to the time-dependent boundary-value problem, utilizes a transformation of coordinates to simplify the evaluation of the resultant surface integrals. An impulse response function is defined as a function of a single surface integral. The time-dependent force can then be obtained by differentiating the convolution of the impulse-response and piston-velocity time functions. The approach to compute the force is applicable for both sinusoidal and nonsinusoidal velocity pulses and is valid for all piston shapes. Numerical results for the impulse response and forces on square pistons resulting from sinusoidal piston velocities are then presented and discussed. Finally, an approach is presented to compute the radiation impedance as a function of normalized frequency from the impulse response data. The approach, which is based on sampling theory, is used to obtain the normalized radiation resistance and reactance for square pistons. The results are then compared to those of earlier investigators.
Seismic and Underwater Responses to Sonic Boom
Authors: Cook J. C. , Goforth T. T. , Cook R. K.
Published: October 2005

Sonic booms produced by aircraft moving at supersonic speeds apply moving loads to the earth. The deformation of a layered half-space depends on the seismic surface-wave modes. Those modes are selected which have phase velocities equal to the load speed. Dunkin and Corbin (1970) have shown theoretically that, in addition, the deformation contains terms that reduce to the static deformation as the load speed tends toward zero. Espinosa, Sierra, and Micky (1968) were able to relate experimentally observed low-frequency seismic wavetrains to some of the trapped (normal) seismic modes. McDonald and Goforth (1969), using seismograph systems with broader frequency response in 178 NASA tests, were able to identify the two dominant high-frequency peaks of the sonic boom seismic signature as the deformation resulting from the two rapid pressure changes associated with the N wave, to identify a fundamental air-coupled Rayleigh wavetrain, to show that peak ground motion is proportional to sonic boom overpressure, and that typical ground motion is less than 1% of structural damage thresholds. R. K. Cook (1970) and others have calculated that sonic booms moving over water at speeds below hydroacoustic velocity generate prolonged, weak precursor, and tail wavetrains, and that acoustic energy diminishes with depth in the water, over half being confined to within one N-wavelength of the surface. Recent efforts to determine other sonic boom effects are briefly summarized.
Recent Sonic Bang Studies in the United Kingdom
Authors: Warren C. H. E.
Published: October 2005

The paper summarizes the sonic bang studies that have been made in the United Kingdom since 1965, which embrace flight trials, field experiments, and laboratory studies. The main flight trial concerns the measurement of the sonic bang from the Concorde. It is shown that, when flying at 45 000 ft, the Concorde waveform at the ground has attained its fairfield N-waveshape, although this is not quite so when it is flying at 37 000 ft. The measured characteristic overpressures for these two altitudes and a Mach number of 1.3 are 110 N/m2 (2.3 lb/ft2) and 120 N/m2 (2.5 lb/ft2), respectively. The effects of sonic bangs on cathedrals is discussed, and the vibrational responses likely to be induced by the sonic bang are compared with those already arising from other environmental causes. Finally, the results of a study of the effects of simulated sonic bangs on some greenhouses are discussed, which seem to indicate that most damage can be ascribed to a triggering effect.
Masking Produced by Sinusoids of Changing Frequency
Authors: Ronken Don A.
Published: October 2005

A masking stimulus was produced by modulating the frequency of a sinusoid with a low-frequency tooth waveform. The signal to be detected was a 20-msec tone added to the masker at some delay relative to the sawtooth. or equivalently, at a time when the masker was at some particular instantaneous frequency. Maskers that swept through a range of 75, 250, and 750 Hz in the vicinity of 1000 Hz were used. For a sawtooth period of 25 or 50 msec, the masking was well-described by the power spectrum of the masker. When the sawtooth period was 150 msec, frequency contours of the masking were narrower than the long-term power spectrum of the masker and were centered near the instantaneous frequency of the masker. This suggests a short-term analysis by the auditory system, and the shape of the frequency contours may be used to provide a rough estimate for the time constant. The direction of frequency sweep, up or down, appears to have little effect on the masking.
On the Magnitude of Critical Ratios
Authors: Reed C. M. , Bilger R. C.
Published: October 2005

Critical ratios were found at nine frequencies between 250 and 8000 Hz for a wideband masker. Three different noise levels, spaced 10 dB apart, were used. The lowest noise level for each frequency was intense enough to provide 30 dB of masking. Five listeners, with normal hearing, served as subjects. Quiet and masked thresholds were obtained by means of an adaptive procedure based on 4IFC. The critical ratios found here were considerably smaller than those traditionally reported, but they did show the expected dependence on frequency. Critical ratios for frequencies at 1000 Hz or higher, however, were found to vary systematically with spectrum level of the masker. This noise level effect, 1.4 dB change in critical ratio for 20 dB change in masker level, was statistically significant at the 0.01 level.
Masking at Two Nonintegral Multiples of a 1000-Hz Tone
Authors: Clack T. D. , Erdreich J. , Knighton R. W.
Published: October 2005

The threshold of a harmonically related pure-tone maskee (Me) varies sinusoidally as its phase is shifted relative to a sufficiently intense masker (Mr) when both are simultaneously presented to one ear. This phenomenon can be explained by either of two approaches. One involves the assumptions that (a) there is a summation between waveforms within the cochlea and (b) the threshold measurements are consequences of peak detection. To test this interpretation, six normal listeners traced their thresholds at 1500, 2000, and 2500 Hz in the presence of a 1000-Hz Mr at each of five intensities, 50–90 dB (SPL) at 10-dB intervals. Within each session, the phase was shifted in randomly ordered 60° steps through one complete period (of the Me). When confusions due to a 500-Hz difference tone are avoided by using a narrow-band (270–540 Hz) masking noise, no phase effects at 1500 and 2500 Hz are evident. The thresholds for the 2000-Hz Me, however, show the usual phase dependencies at equal Mr levels. These findings are inconsistent with the two-tone interaction explanation and thus support the interpretation that emphasizes a nonlinear response of the auditory system and direct interference between aural and acoustic harmonics.
An INDSCAL Analysis of the Miller-Nicely Consonant Confusion Data
Authors: Wish M.
Published: October 2005

Data from the Miller-Nicely study [J. Acoust. Soc. Amer. 27, 338–352 (1955)] of perceptual confusions among acoustically degraded consonants were reanalyzed by Carroll and Chang's INDSCAL procedure [Psychometrika (1970) (to be published)]. While the input to ordinary multidimensional scaling is a single matrix of interstimulus similarities, the input to INDSCAL consists of several such matrices, one for each subject or other data source. The output shows the coordinates of the stimuli on the dimensions of a “group stimulus space” and also indicates the importance, or weight, of each dimension to every source. The similarities for a particular source are simply related to interpoint distances in a “private space” obtained by applying that source's weights to the respective dimensions of the “group stimulus space”. In this application the matrices arising from confusions among 16 consonants under each of 17 degradation conditions (the data sources) served as input. Six dimensions, interpreted as “Voicing,” “Nasality,” “Voiceless Stops versus Voiceless Fricatives,” “Second Formant Transition,” “Sibilance,” and “Sibilant Discrimination” arose from the analysis. The relative importance of these dimensions was systematically related to the kind and degree of degradation the consonants had undergone. Implications of the results for perception of consonants are discussed.
Phonemic Restoration in Speech Perception
Authors: Warren Richard M.
Published: October 2005

When acoustical information concerning the identity of one or more speech sounds in a sentence is replaced completely by an extraneous sound (such as a cough, buzz, or tone), the listener believes that he hears the missing speech sounds, and he displaces the extraneous sound to some other position in the sentence. However, if a silent gap replaces the same phonemes, the interruption is more readily localized in its true position, and phonemic restorations (PhR's) occur less frequently. PhR's are not diminished either by knowledge that speech sounds are stimuli, but the apparent location of the extraneous sound is shifted to a later position following familiarization with the sentence. If prior content does not indicate unequivocally the identity of the missing speech sounds, the appropriate illusory PhR can be determined by the context following several words after the ambiguous fragment, allowing a measure of the temporal limits of the corresponding short-term storage, and the relative effectiveness of grammatical and semantic constraints. PhR's appear related to other auditory illusions and temporal confusions reported in literature, and also to mechanisms employed normally for verbal organization.
Just-Noticeable Differences for Selected Aspects of Synthetic Fundamental-Frequency Contours
Authors: Klatt D. H. , Zue V. W.
Published: October 2005

An A-B-X paradigm has been used to find the just-noticeable difference (jnd) for selected aspects of voice fundamental frequency (F0) contours by varying the F0 control parameter of a digitally simulated terminal analog speech synthesizer. Data have been obtained from three subjects for a number of 250-msec segments of the synthetic vowel /ɛ/ differing only in fundamental frequency. Results indicate that subjects are an order of magnitude less sensitive to changes in average F0 when the F0 contour shape is a linear descending ramp (jnd = 2.4 Hz) as opposed to a constant F0 contour (jnd = 0.3 Hz). Sensitivity to rate of change of F0 in linear ramps is surprisingly good; greatest sensitivity occurs when one ramp increases and the other decreases (jnd = 12 Hz/sec). High-pass filtering of the stimuli improves performance slightly, suggesting that the fundamental component is not involved in the detection of changes in F0. Substitution of the synthetic stimulus /ya/ with its nonconstant formant contours in place of /ɛ/ degrades performance only very slightly. [Work supported in part by an NIH grant.]
Ultrasonic Method for Equation-of-State Measurements in Polymers
Authors: Jarzynski J. , Hartman Bruce
Published: October 2005

A new method for measuring the equation of state of polymers is described. The polymer is immersed in a suitable liquid (mercury was used), and the combined volume of the polymer and the liquid is determined at each temperature and pressure by measuring the time of flight of an ultrasonic pulse reflected from the free surface of the liquid. The volume of the polymer is then calculated from these data and the equation of state of the liquid used. Results are presented of measurements on polyethylene oxide at temperatures from room temperature to above its melting point (68°C) and at pressures up to 1000 atm.
High-Transmission-Loss Wall Panels
Authors: Sharp B. H. , Eldred K. M. , Swing J. W.
Published: October 2005

Under a program sponsored by the Department of Housing and Urban Development, several unique wall designs have been developed and tested. These designs incorporate several features that enable high values of transmission loss to be obtained, values much higher than those presently available from common walls presently in use. In addition, it has been found that simple modifications to common constructions can result in a substantial increase in acoustic performance with little increase in the over-all cost. This paper will review some of the construction details and the preliminary laboratory test results obtained during the program, and will present details of a series of tests designed to investigate the acoustic behavior of double-panel constructions.
The Use of Stationary Near-Field Diffusers for Improving Low-Frequency Measurements in a Reverberant Room
Authors: Ingalls Douglas J.
Published: October 2005

For a monopole source, the interior reverberant mean-squared pressure is within ±1 dB of the asymptotic value if the source distance is greater than 0.5λ from a wall. For a spherical random dipole source, such as the Ilg reference sound source (RSS) used in the substitution technique of measuring sound power, this distance increases to about 1.0λ. Since most reverberant room dimensions are of the order of 2λ in the lowest 13-oct band of interest, some care must be exercised in low-frequency measurements. The mean-squared pressure was experimentally measured as a function of the location of the RSS in a 300-m3 a reverberant room. The results suggest that the first reflection from the walls dominates the pattern It is experimentally shown that stationary nearfield diffusers placed at the walls can be used to decrease the variance of the sound power output arising from the location of the RSS. The use of tilted walls in the design of a reverberant room should have the same effect.
Piezoelectric Effect in Polyvinylchloride and Polyvinylfluoride
Authors: Cohen J. , Edelman S.
Published: October 2005

Substantial piezoelectric activity has been obtained in roll-elongated films of polyvinylchloride and polyvinylfluoride. The piezoelectric modulus g31 was determined to be 0.2 to 0.7 Vm−1/Nm−2 in the former and 0.1 to 1 Vm−1/Nm−2 in the latter. These values compare quite favorably to those of conventional piezoelectric materials. The effect was produced by applying tensile stress to a clamped specimen at a fixed frequency of 20 Hz, and is believed to be due to mechanical distortion of dipoles oriented in the direction of rolling.
Lateralization in Squirrel Monkeys Using Time and Intensity Cues
Authors: Don Manuel , Starr Arnold
Published: October 2005

Four squirrel monkeys were trained to make right or left lever responses to trains of clicks presented binaurally with varying differences in the interaural time, interaural intensity, and the over-all click level. Time and intensity differences and over-all level were varied in 20 μsec, 2 dB, and 10 dB steps, respectively. For any given daily session, either the time or the intensity parameter alone was varied at only one of three over-all click levels. A modified Block up-down procedure was used. Percent-correct lateral judgments were plotted as a function of interaural time and intensity differences for three click levels. Criterion performance of 85% correct lateral judgments was achieved at time differences ranging from 60 to 120 μsec and at intensity differences ranging from 6 to 10 dB that varied both with the individual monkey and the over-all click intensity. End point for lateralization was also examined for time differences. Performance fell below the criterion level between 2.0 and 3.5 msec depending upon the intensity level used. [Supported by NINDS grant.]
Discrimination Learning of Selected CVC Syllables by 5-Yr-Old Children
Authors: Gilbert John H.
Published: October 2005

In the present investigation, a discrimination-learning paradigm was used to examine processes of phoneme learning in situations where distinctive and articulatory features were major variables. Children of 5 yrs chronological age were given the general task of identifying four syllabic stimuli that constituted an ensemble. The characteristics of the stimuli were manipulated in CVC syllables using the consonants /p/, /b/, /t/, /d/, /f/, /r/, /s/, /z/ and the vowel /a/. These stimuli were actual utterances of a trained talker. The CVC items were used in ensembles in which six distinctive features and seven articulatory features were contrasted, in specific combinations. Because of the “neutral” quality of the vowel used, all syllables were of the nonsense variety. The results of the experiment indicate a significant difference between the learning of plosives versus fricatives. That is, discrimination learning by 5-yr-old children within the limitations of the experimental design is dependent on manner of articulation and relatively unrelated to place of articulation or the voice-voiceless dichotomy. A comparison was made between the results of this study and distinctive features as proposed by Jakobson, Fant, and Halle. Distinctive-feature interpretation was not successful in describing the features that emerged in this study. The results would seem to indicate that discrimination learning of the selected CVC syllables used could best be described in terms of traditional properties of the vocal tract, particularly manner of articulation.
A Consideration of Stimulus Length in Developmental Studies of Delayed Auditory Feedback
Authors: Buxton Lawrence F.
Published: October 2005

One of the methodological problems encountered in developmental studies of delayed auditory feedback (DAF) is that speakers of different ages have different rates of speech under normal auditory feedback conditions, which affect speech under DAF. That is, if a speaker can speak fast enough under certain conditions of DAF, he can complete the stimulus phrase before the DAF has returned to his ears (or substantially affected his speech). These differences in speech rate would seem to favor age groups whose speakers have faster rates of speech (older speakers) rather than age groups whose speakers have slower rates of speech (younger speakers). Consequently, fixed-length stimulus phrases read under DAF present varying degrees of difficulty depending on how rapidly the speaker can complete the stimulus. The present paper evaluates the use of the differential-length appending clause as a technique to equalize these differences in speech rates of various age groups, originally used by MacKay [D. G. MacKay, J. Acoust. Soc. Amer. 43, 811–821 (1968)], and suggests the design for a study that would help determine the effects of the differential-length appending clause upon speech under DAF.
Perception of Dichotically Presented Vowels
Authors: Weiss M. S. , House A. S.
Published: October 2005

A number of experimental studies have shown that, under conditions of dichotic stimulation, consonants are perceived better in the right ear while vowels are perceived equally well in both ears, suggesting that consonants and vowels may not be processed in the same cerebral hemisphere. The present study attempts to demonstrate that in the dichotic listening mode the identification of vowels is more accurate in the right ear. The stimuli were the spoken word and nonsense materials in which 10 common vowels of American English were the significant variables. Digital methods were used to match the competitive pairs of signals for level, duration, and time of onset. White noise was mixed with the speech materials to produce two listening conditions, 0 dB and −10 dB S/N, for presentation under high-quality earphones to a listening crew of 13 young adults. An analysis of individual ear responses revealed that, on the average, right-ear scores were 6% higher than left-ear scores at −10 S/N; no significant difference between ears was found at the more favorable S/N ratio. The way in which listener response characteristics affect estimates of “ear preference” and the role of independent psychoacoustic factors of the dichotic listening situation will be discussed.
Sound Transmission in Isogradient Shallow Water over a Plane Sloping Bottom
Authors: Smith P. W.
Published: October 2005

Analytical estimates for sound transmission loss in propagation between two points in the environment described in the title have been formulated by an averaging method akin to Brekhovskikh's [Soviet Phys. Acoust. 11, 126 (1965)]. The basic postulates are those of ray acoustics with lossy specular reflection at boundaries. Curvature of ray projections on a horizontal plane is neglected. The contribution of each ray bundle is weighted by the probability of irradiating points at receiver depth in the course of a complete ray cycle (surface-bottom-surface). For transmission downslope, calculations show a surface duct at long range which is deeper than the minimum water depth (typically by a factor 2), within which the transmission loss is less than for a flat bottom. Thus the bottom acts as a “lossy megaphone,” launching much energy into the duct after a few bounces. This effect is also important in transmission over an obstacle. Dimensionless estimates for transmission loss and duct depth show the influences of boundary lossiness, slope, depth, and speed gradient. [Study supported by Office of Naval Research.]
Volume Backscattering in the Coral Sea
Authors: Hall Marshall
Published: October 2005

Volume backscattering strengths for three depth intervals at the frequencies 2.5–12.5 kHz in 13-oct steps were measured at a number of deep water stations in the Coral Sea in May 1968. At daytime stations the scattering did not vary systematically with depth at the lower frequencies; but at the higher frequencies, the scattering was strongest in the 450- to 750-m depth interval. At evening stations, 1 h before sunset, the scattering was generally a maximum in the interval 0–750 m. At 1 h after sunset, however, the scattering was a maximum in the interval 0–450 m at all frequencies. Over sunset, the average volume scattering strengths at 5, 6, and 8 kHz at a range of 740 m were usually 5 dB greater than the corresponding results at a range of 1500 m. This suggests that the backscattering may have been a function of the horizontal range between the acoustic transducer and the scattering region.
From Acoustics to Exploration Seismology
Authors: Sherwood J. W. C.
Published: October 2005

From 1953 to 1956, this author had the privilege of performing postgraduate research work in the Acoustics Group at Imperial College. Under the enlightened guidance of Dr. R. W. B. Stephens, this group worked on a wide range of topics, and it was therefore not to surprising to find oneself conducting a scaled-down model experiment in basic seismology. This fortunate circumstance led to a stimulating career in seismic exploration for oil, the development of which is naturally dependent on basic acoustic-wave propagation concepts. This paper will be concerned with some of these simple concepts which are particularly significant to exploration and will indicate the degree of sophistication to which they have been developed with the recent aid of large-scale digital computers.
Absorption Coefficients of Surfaces Calculated from Decaying Sound Fields
Authors: Embleton T. F. W.
Published: October 2005

A modified form of the Eyring equation is derived which explicitly takes account of the anisotropy of a sound field due due to the deviation of the energy reflection (absorption coefficient) of individual surfaces from the mean value for all surfaces. When all surfaces have the same energy absorption coefficient, the equation simplifies to that of Eyring; when in addition these absorption coefficients are small, the usual simplification to the Sabine equation is valid. Using a simplified version of this modified Eyring equation, one can show that the effective absorption coefficient of a single absorptive surface in a hypothetical reverberation room is a complicated function of the location and total area of randomly oriented scattering panels. Apart from any correction for diffraction, the effective absorption coefficient is also a function of the area of the absorptive surface. In typical situations, this theory predicts that the effective coefficient will be greater (0% to 40%) than the energy-absorption coefficient. In general terms, this agrees with measured values. In extreme situations not usually found in reverberation rooms, effective absorption coefficients are predicted to vary more widely and be either greater or less than the energy-absorption coefficient.
Social and Legal Implications of Noise Performance Regulations
Authors: Goodfriend L. S. , Senko A. , Wielette R. E.
Published: October 2005

The noise performance regulations written into the Chicago zoning ordinance in 1955 set the stage for the widespread noise limits in performance zoning regulations in the United States. Such performance regulations are widely used at every level of government to provide some measure of noise control in industrial and industrial park zones. However, actual sound levels specified within these regulations are often selected without regard to the existing ambient conditions or to features of the master plan of the area. Even when statistical pictures of the ambient are available, selection of sound levels for the performance regulation and the point at which these levels must be measured are extremely difficult to select. The need has become apparent for guidelines for the selection of appropriate performance limits and the possible recasting of the regulations in any particular municipality in order to achieve the desired social result. The present procedures appear to create legal liabilities rather than to provide protection to the members of the community.
Steady Rotation of Particles in a Sound Field
Authors: Nyborg Wesley L.
Published: October 2005

It has been observed that ultrasonic irradiation of biological cells often results in rotation of intracellular or intranuclear bodies and structures. This rotation may sometimes be significant in affecting fundamental biological processes. A theoretical approach will be discussed for explaining and predicting such motions. This approach is based on the theory for acoustic streaming and is carried out rather simply for cylindrical objects. It is found that a cylinder immersed in liquid and subjected to a sound field with special characteristics is subjected to steady torque. The characteristic required is that the first-order motion should be elliptical in nature. This is true, for example, in a region traversed by crossed plane waves of suitable relative phase, or at the edge of a diffraction lobe.
The Effects of Ultrasonically Induced Stress on Cells in Suspension
Authors: Connolly C. C.
Published: October 2005

The mechanism of interaction of ultrasonic energy with biological material is still in doubt. Mechanical and thermal interactions have been postulated as the prime cause of biological damage. This paper shows that mechanically induced unidirectional stresses are of prime importance for cells in suspension. Heating is implicated as a factor of major importance in decreasing the mechanical resistance of the membrane to stress. Experiments have been performed on human erythrocytes at frequencies between 1 and 10 MHz at intensities up to 330 W/cm in the plane wave. Pulsing conditions in the ultrasonic beam have been found to be of considerable importance in causing damage and are a reflection of the viscoelasticity of the cell surface. A new method of measuring the viscoelastic constants of the cell surface has been found.
Ray Tracing with Non-Linear Sound Velocity Profiles
Authors: Weinberg N. L.
Published: October 2005

Sound-velocity profiles were used to derive underwater acoustic-ray-path equations resulting in functions such as the parabola, ellipse, hyperbola, cycloid, catenary, and sinusoid. Of these, the most useful are the ellipse and hyperbola, for which detailed expressions were developed from actual sound-velocity profiles. A typical profile from the Straits of Florida was selected and curve-fitted by equations which yield a hyperbolic ray path at depths from 440 to 180 m and an elliptical path above this. The techniques for calculating these rays are illustrated, including the method for determining range and maximum ray height above the bottom for RBR rays. As a means of comparison, the linear gradient of the same profile based on a least-squares fit was obtained, and, in addition, the profile was approximated by three linear segments and the circular rays calculated. The differences between these three cases were striking, with the segmented curves more closely approximating the hyperbolic-elliptic case. Expressions for travel time were also derived, and the results for the three cases again showed considerable variations. The nonlinear gradient method is simple and straightforward, and yields a more exact solution.
Multipath Interference of Broad-Band Signals in RBR Propagation
Authors: DeFerrari H. A. , Nguyen Ba Hien
Published: October 2005

Propagation experiments with fixed source and receivers in the Florida Straits have been characterized by large temporal fluctuations in transmission loss for both CW and sequences of pulsed sinusoidal signals. Multipath interference can result in fading of received signals of as much as 50 dB for CW propagation at 420 Hz and as much as 20 dB for pulses of 8 cycles in duration. These deep fading events occur at random intervals when the slowly varying sound-velocity structure is such that signals arriving from various paths interfere destructively, a condition that may persist for several minutes. For the types of signals used (BW = 100 Hz at 420 Hz) interference effects are responsible for the largest fluctuations in transmission loss. A model of refracted bottom reflected (RBR) propagation in an ideal ocean having horizontal bottom and two layers of negative constant-velocity gradient is used to examine multipath interference. The conditions for occurrence of fades are determined by varying model parameters. For pulse signals, the magnitude of transmission loss for a particular fade depends upon average characteristics of the sound-velocity structure, while the condition for occurrence of a fade is sensitive to small variations about these averages. Results from the model are used to interpret recent experimental results from project MIMI.
Noise Control in Buildings
Authors: Goodfriend Lewis S.
Published: October 2005

In this session, some of the fundamental aspects of noise generation, radiation, and propagation in buildings were illustrated. One novel demonstration was a miniature ripple tank effectively lighted and projected by a standard overhead projector (Baade). The point was emphasized that there is no single current text suitable for use in teaching acoustics to architects (Kingsbury). Illustrations of practical aspects of noise-control engineering were presented in three papers. One discussed the multiplicity of noise control problems in a typical modern architectural project (Kleinschmidt). Another showed that analytical methods may be helpful in practical vibration isolation problems (Champ). A third paper demonstrated that innovative solutions to floor and ceiling isolation problems need not be costly or complex to be effective (Ostergaard). ISO activities related to vibration and building noise control were summarized (Muster). In the area of field testing of floors and partitions, the differences between laboratory and field installations were outlined (Oliphant). It was shown that, by using ASTM E90 in the laboratory and ASTM E336 in field tests, results were essentially the same. In the closing paper, Kodaras stressed the type and nature of training necessary for municipal officials and inspectors to enforce a modern building code.
Control of Noise Generated by Aircraft at Subsonic Speeds
Authors: Eldred K. M.
Published: October 2005

Eight papers were given in the session on aircraft noise. These included a summary of the status of noise control for gas turbine engines and several detailed presentations on specific technical subjects. The summary included a discussion of the proven technology for reducing noise from various types of aircraft propulsion systems (Hubbard), a survey of trends in aircraft-engine noise control (Marsh), a detailed example of the application of the gain in noise-reduction technology of the 1960s to flight hardware of the future (Eldred), and an outline of the problems encountered in measuring aircraft noise (Zwieback). This summary was followed by a plea for greater noise reduction so that the ariport-community noise problem can have a national solution, and a projection of the effect of FAA noise certification and new technology on aircraft in the future (Odell). Specific technical subjects included the effect of segmented blades on fan noise (Embleton and Thiessen), the understanding of nearfield noise for high-speed subsonic jets (Maestrello and McDaid), and the response of panels to supersonic turbulence (Maestrello).
An Overview of Interface Wave Properties
Authors: Farnell G. W.
Published: October 2005

A review is presented of the dispersion properties of elastic waves propagating in thin layers on thick substrates, including the effects of crystal symmetry and piezoelectricity on mode coupling. The relation of these layer modes to plate, Rayleigh, and Stoneley modes and the displacement distributions for various asymptotic conditions is considered for both isotropic and anisotropic examples. [This work is supported by the National Research Council and the Defence Research Board of Canada.]
An Overview of Creeping Wave Formulation and Its Relationship to Surface Waves
Authors: Überall H.
Published: October 2005

Interface phenomena in the propagation of plane or spherical acoustic waves over plane interfaces between two media are well known; the corresponding “lateral” and “Schmidt head waves” were studied theoretically and experimentally. Less well understood are the analogous effects at curved surfaces, although considerable progress was made here in the last few years. For impenetrable obstacles of simple shape (cylinders, spheres), Franz's theory of circumferential waves, based on the Watson transformation, can be directly taken over from the electromagnetic to the acoustic case (Überall, Nussenzveig); the corresponding “creeping waves” can be shown to emerge from the conventional normal-mode solution (Rudgers), and their existence was demonstrated experimentally (Harbold and Steinberg; Neubauer; Wright). For general smooth convex surfaces, Levy's and Keller's theory leads to similar “diffracted surface rays.” This may be generalized to penetrable elastic media (Keller and Karal; Chen; Rulf), and made quantitative for simple shapes (Beckmann and Franz; Mishra; Streifer and Kodis; Doolittle, Überall, and Uginčius; Nussenzveig; Ludwig). Transmitted waves (Brill and Überall) complicate the experimental search for surface waves (Bunney, Goodman, and Marshall; Neubauer and Dragonette). The characteristics of surface waves may be studied independently of their mode of excitation (Viktorov; Wait; Norwood and Miklowitz; Brekhovskikh; Lapin; Junger and Feit).
Nonlinear Interactions on Interface Waves
Authors: Lean E. G.
Published: October 2005

Pronounced nonlinear effects require high-power density. Surface acoustic waves and guided optical waves, which increase the power densities two to three orders of magnitude in comparison with the similar bulk wave cases due to the interface wave properties, are ideal for nonlinear interactions. Such nonlinear interactions as harmonic generation and parametric mixing of surface acoustic waves, and the diffraction of guided optical waves by surface acoustic waves, have been reported. In this study, the basic interaction mechanisms are reviewed. The current experiment results on the harmonic generation and parametric interaction of surface acoustic waves in lithium niobate substrates with a small artificial dispersion, and the interaction of guided optical waves by surface acoustic waves are presented together with theoretical calculations. Device applications of such nonlinear interactions are included. [This work is partially supported by the Office of Naval Research.]
Determination of the Shape of a Lossy Vocal Tract
Authors: Sondhi M. M. , Gopinath B.
Published: October 2005

It is known that the area function of a lossless vocal tract can be determined from the input impedance at the lips. It is also known that no input measurement can provide information about the losses. However, the possibility exists of obtaining improved area estimates if the losses are known a priori. This last possibility is discussed in this paper, including some examples of loss distribution for which the exact area can be reconstructed from input measurements.
Periodicity Pitch for the Random Component of a Pulse-Width Modulated Waveform
Authors: Leshowitz Barry
Published: October 2005

Consider a pulse-width modulated waveform that is of unit amplitude for 0<t<ki and zero for ki<t<T, where ki are intervals uniformly distributed between zero and T/2. This waveform can be subdivided into a periodic component and a random component. The random component is of interest for two reasons. First, since its derivative is always positive at nT, where n is an integer, it has the appearance of a periodic waveform. Second, if the random component were to be full-wave rectified, then it would be periodic. In an effort to determine whether rectification occurs in the auditory system, the pitch of the rectified and unrectified random component was measured. In a second study, pitch matches were obtained for interrupted white noise. For the rectified waveform, accurate frequency matches between the stimulus and a pure tone were obtained over a wide range of frequencies. For the unrectified random component and the interrupted noise, discrimination was significantly less accurate. In each case, discrimination became progressively poorer above 500 Hz.