bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaural alternation, information load, and speech intelligibility
Authors: Wingfield Arthur , Wheale John L.
Published: October 2005

Speaks and Trooien [J. Acoust. Soc. Am. 56, 640–644 (1974)] report a failure to replicate selective intelligibility loss typically associated with rapid alternation of speech between the two ears. Results from several studies show the effect to be real, but that listeners must be under some load for the loss to appear. This can be accomplished by requiring ’’shadowing’’ as a response measure, using linguistically complex messages, or increasing input rate of the speech signal.

Subject Classification: 70.30, 70.35.
Cetacean echolocation signals and a new model for the human glottal pulse
Authors: Altes R. A. , Evans W. E. , Johnson C. S.
Published: October 2005

A theoretical explanation for cetacean sonar systems can also be applied to human speech. The theory leads to a mathematical model of the human glottal pulse that is considerably different from those employed in the past.

Subject Classification: 80.50; 70.20.
Ultrasonic heating of V
i
c
i
a f
a
b
a roots
Authors: Eames F. A. , Carstensen E. L. , Miller M. W. , Li May
Published: October 2005

Irradiation of Vicia faba root tips with 2.3-Mhz ultrasound at 10 W/cm2 causes a small but measurable heating of the tips and an immediate reduction in root growth rate. Roots exposed to comparable temperature increments without ultrasound show no reduction in growth, thus leading to the conclusion that the mechanism responsible for the biological effects of ultrasound on roots is nonthermal. From the time course of ultrasonic heating of the roots it appears that the thermal conductivity of the root material is comparable to that of water, and the acoustic absorption coefficient of the root tissue is higher than that of mammalian tissues.

Subject Classification: 80.40; 35.75.
Sound-velocity perturbations due to low-frequency motions in the ocean
Authors: Mooers Christopher N. K.
Published: October 2005

The properties of low- and intermediate-frequency external and internal waves in the open ocean, and the nature of the acoustic velocity perturbations they produce, are examined. The basic principles are illustrated with theoretical calculations based on representative oceanic cases. Such calculations provide a rational estimate for the vertical and horizontal dependence of the perturbation of the acoustic velocity field due to external and internal waves. External waves can cause travel-time fluctuations by their horizontal velocity fluctuations (or fluctuations in the total sound velocity). Internal waves can cause acoustic travel-time fluctuations both by their vertical displacement of isotherms (or isolines of sound speed) and by their velocity fluctuations (or fluctuations in total sound velocity). Both external and internal waves can have horizontal wavelengths ranging from a fraction of a kilometer to hundreds of kilometers. The longer waves can be effective in producing travel-time fluctuations over long propagation paths; the shorter waves are probably most influential in the scattering of acoustic energy.

Subject Classification: 30.20.
Vibration of generally orthotropic skew plates
Authors: Srinivasan R. S. , Ramachandran S. V.
Published: October 2005

This paper presents a numerical method for finding the natural frequencies and mode shapes of generally orthotropic clamped skew plates subjected to in-plane forces. As illustrations, two aspects are considered. First, the natural frequencies and mode shapes of a rhombic plate (without any in-plane forces) are determined for different orientations of the axes of orthotropy. Marked changes in the mode shapes, which are not easily predictable, are found to take place. Secondly, the influence of in-plane forces (both unidirectional tension/compression and uniform shear) on the natural frequencies is studied. The results indicate that in all cases but one the relationship between the square of the frequency and the in-plane force is nonlinear. The numerical method employed makes use of integral equations of beams with appropriate boundary conditions, along the skew coordinates, for transforming the governing differential equation into a set of algebraic equations. These equations are then solved to find the eigenvalues and eigenvectors.

Subject Classification: 40.24.
N-parameter ducts
Authors: Molloy Chuck
Published: October 2005

The exact solution to Webster’s differential equation for sound in an initial variable area duct is used to generate new families of duct shapes with their exact solutions. In most cases the shapes and their solutions may be expressed in terms of nth-order determinants (Wronskians, in fact) whose elements are solutions to the initial duct and derivatives of these solutions. The nth-order determinant contains 2n+1 arbitrary parameters which are available for the design of ducts. The initial duct may be any duct for which the solution to Webster’s equation is known. The method is applied to a uniform duct to derive new families of ducts where both the duct shape and its solution are expressed in closed form in terms of elementary functions. Special cases include filters, constrictions, and new horn shapes in addition to the well-known conical horn, Bessel horns, the exponential horn, the Salmon horn, and the sinusoidal duct.

Subject Classification: 20.45; 85.60.
Some relations between energy yield of atmospheric nuclear tests and generated infrasonic waves
Authors: Flores José S. , Vega Angel J.
Published: October 2005

The relation between energy yield in megatons (MT) of atmospheric tests during 1968–1971 at French Polynesia and infrasonic waves recorded at Peñas in Bolivia (a distance of approximately 7300 km) is studied. Yields were estimated from period and amplitude of the early portion of the waveforms using the theoretical relation of Pierce and Posey [Geophys. J. R. Astron. Soc. 26, 341–368 (1971)]. In the present paper, the relation of this derived yield to the Power spectrum of major portions of the waveforms is investigated. The magnitude of the square root of this spectrum that can be considered proportional to the Fourier Integral for a Yield Sample Time (i.e., spectral amplitude) typically has two characteristic peaks, the first of which appears to nearly directly proportional to yield, the proportionality constant being 300 μbar sec1/2/MT. Another waveform feature exhibiting strong correlation with yield is the time duration of the gravity wave train which precedes the acoustic mode waves. For smaller yields, this also appears to vary nearly linear with yield, the proportionally constant being 1000 sec/MT up to about 1 MT. The application of these conclusions to other source–receiver geometries and to other meteorological conditions remains a topic for future study.

Subject Classification: 28.20, 28.30.
Relations among temporal resolution, forward masking, and simultaneous masking
Authors: Smiarowski Richard A. , Carhart Raymond
Published: October 2005

The data from this investigation suggest that both temporal resolution and forward masking are the products of a single underlying mechanism of auditory persistence. Persistence of auditory activity from a burst of noise not only limits the listener’s ability to perceive a trailing noise burst as temporally separate (temporal resolution), but also interferes with his detection of a click that follows the burst of noise (forward masking). After a relatively stable initial period of about 2.5 msec, the magnitude of this persisting residual activity decays linearly over log time, as evidenced by the progressive reduction in the level of both the trailing noise burst in temporal resolution and the click threshold in forward masking. The data also indicate that forward masking of the click bears the same relationship to masker level as does simultaneous masking of the click. The mechanisms of forward masking may be essentially the same as those for simultaneous masking, except that for the former the masking process is a residue that persists from prior stimulation.

Subject Classification: 65.58, 65.75.
Factors in the discrimination of tonal patterns. I. Component frequency, temporal position, and silent intervals
Authors: Watson Charles S. , Wroton Henry W. , Kelly William J. , Benbassat Carole A.
Published: October 2005

Factors which determine the discriminability of tonal sequences, or patterns, were investigated in five experiments. The patterns were generally sequences of ten 40-msec tonal components, which ranged in frequency from 256 to 900 Hz, or from 500 to 1500 Hz, in equi-log intervals. Highly trained (15 to 60 h of training prior to collecting experimental data) listeners’ abilities to detect changes in the frequency of single tonal components in these patterns were measured using a same–different psychophysical method. The just-detectable values of Δf (d′=1.0) were only slightly larger than for single 40-msec tones presented in isolation for tonal components at the end of the temporal sequences (a ’’recency’’ effect). Performance was systematically worse for earlier components, the just-detectable Δf increasing by four to five times from the end of the pattern to the beginning (no ’’primacy’’ effect). The ’’recency’’ effect was interpreted as a matter of later arriving components interfering with frequency resolution for earlier ones, since a brief silent period (80 to 120 msec) following an early component led to as precise discrimination for that early component as for the last one in the sequence. The higher-frequency components in a given pattern were resolved much more accurately than the lower-frequency components for patterns with overall bandwidths of 250 to 900 Hz and also when the bandwidths were raised from 500 to 1500 Hz.

Subject Classification: 65.22, 65.75, 65.64.
New formula for calculating acoustic propagation loss in a surface duct in the sea
Authors: Baker William F.
Published: October 2005

The new formula described has been derived as an empirical fit to experimental data, and gives improved accuracy compared with an earlier formula. Mean errors of typically ± 2 dB, with a standard deviation of 7 dB, have been obtained. The variation of propagation loss with depth has not been investigated.

Subject Classification: 30.20.
Comparison of an acousto-optic and a radiation force method of measuring ultrasonic power
Authors: Haran Michael E. , Cook Bill D. , Stewart Harold F.
Published: October 2005

During the interim period while nationally acceptable methods of measurement of referential standards for ultrasonic power are being developed, comparisons are needed among measurment techniques currently used. This is particularly necessary for determining the acoustic power from ultrasonic medical devices. Such a comparison was made between an optical and a radiation force technique to measure the ultrasonic power output of a 1-MHz 1-in.-diameter PZT crystal from 70 mW to 2.3 W total acoustic power. The optical technique follows the theory of Raman and Nath, assaying the diffraction of monochromatic light by ultrasound. In addition, a correction factor is introduced into the calculation of the phase retardation parameter and eliminates the need to determine the pathlength of the light through the sound. The radiation force technique relates the change of position of an air-backed, self-centering, reflecting float to the ultrasonic power. A linear regression analysis between the square of the voltage applied to the crystal and the measured power of each method was used. For a 99% confidence level, there is no statistical difference between the measurements over the range of power investigated, although the variance of the optical measurements was significantly lower than that of the radiation force.

Subject Classification: 35.65, 35.80; 85.24.
Ultrasonic attenuation and velocity in two-phase microstructures
Authors: Latiff R. H. , Fiore N. F.
Published: October 2005

The scattering attenuation and velocity of elastic waves propagating in two-phase microstructures are computed by an extension of multiple scattering analysis. The computation is based on a model of an array of isotropic spherical scatterers embedded in an isotropic matrix. Attenuation α is predicted to increase with volume fraction and number density of scatterers and to approach a plateau with frequency. Group velocity vg is predicted to decrease with volume fraction and frequency. Ultrasonic measurements of α and vg are made on model microstructures consisting of Cu spheres embedded in a polymethylmethacrylate matrix. The measured values agree qualitatively with the predicted ones, and physical reasons are proposed to account for the agreement. The inability of the theory to provide accurate quantitative predictions of these quantities is discussed.

Subject Classification: 35.26; 20.30, 20.35.
Damping measurements of a controlled composite material
Authors: Jones E. R. , Sierakowski R. L. , Ross C. A.
Published: October 2005

Increased use of filamentary materials as reinforcements in structural components has necessitated obtaining information on the response of such material systems to a wide variety of loading conditions. One such technically important problem area is that associated with the dynamic response of composite materials to impact-type loading situations. In order to understand the phenomenon of wave travel in material systems, specific knowledge of the damping coefficient and phase velocity as a function of circular frequency is necessary. In the present paper, tests are reported for beam-type specimens of a steel–epoxy composite having controlled volume fractions and varying wire sizes. Measurements are reported on the damping coefficient as a function of circular frequency a (ω) and the real part of the complex modulus E1. The latter parameter has been further used to calculate the phase velocity, and data are presented on phase velocity c (ω) as a function of frequency. Detailed tabular and graphical data are presented for the various specimens tested.

Subject Classification: 40.20, 40.22.
Acoustic pulse techniques for the nondestructive determination of material parameters
Authors: Mattei Michael D. , Shapton William R.
Published: October 2005

The natural frequencies and damping properties of physical systems have provided investigators with valuable information for solving various problems associated with vibrating structures. This paper uses the information associated with natural frequencies and damping in order to determine two physical parameters of a material. Using pulse excitation and noncontacting instrumentation, acoustic methods are presented for nondestructively determining Young’s modulus and martensite start transformation temperature. The material used for this investigation was a nickel titanium alloy referred to as Nitinol. There is no reason, however, that the procedures and techniques described in this paper cannot be used for a variety of other materials.

Subject Classification: 40.60; 40.20.
Contribution of the external auditory meatus to auditory sensitivity underwater
Authors: Hollien Harry , Feinstein Stephen
Published: October 2005

Support for, and a refinement of, the hypothesis that divers hear primarily by bone conduction was provided by Hollien and Brandt [J. Acoust. Soc. Am. 46, 384–387 ( 1969)]. To further test this hypothesis, the thresholds of seven submerged listeners were obtained (at frequencies of 0.25, 0.50, 1.0, 4.0, and 8.0 kHz) under three different conditions; (1) while they wore a full 3/16-in. wet suit with no hood, (2) while wearing a full 3/16-in. wet suit with a 3/16-in. hood, and (3) while wearing a full 3/16-in. wet suit and hood with 1/4-in. rubber tubes passing through the hood to the external auditory meatuses. There were no significant differences between the conditions involving the use of a hood but thresholds were significantly lower in the middle and high frequencies for the no-hood condition. These findings provide further support for the hypothesis that underwater sound energy is transduced predominantly by bone conduction rather than by the normal middle ear linkage.

Subject Classification: 65.50; 30.10; 65.22.
Discriminability of time-reversed click pairs: intensity effects
Authors: Resnick Steffi B. , Feth Lawrence L.
Published: October 2005

The present investigation examined the effects of the interclick intensity ratio (ΔI) and signal level (I0) on discriminability of time-reversed click pairs. Discriminability was assessed for five normal-hearing listeners using a 2IFC procedure. The level of the more intense click (I0) was fixed at 75 or 45 dB SL. Four values of ΔI were employed such that within a click pair the more intense click exceeded the less intense click by 3, 6, 12, or 24 dB. Discriminability of the click pairs was evaluated at eight interclick intervals between 0.5 and 10.0 msec. Discriminability was altered systematically by changes in both I0 and ΔI. The interclick interval required for 75% correct discrimination ranged from less than 0.5 to 1.8 msec. The observed intensity effects suggest that discriminability of the time-reversed click pairs is predictable from temporal masking data.

Subject Classification: 65.75, 65.58, 65.50.
Tongue-pellet tracking by a computer-controlled x-ray microbeam system
Authors: Kiritani S. , Itoh K. , Fujimura O.
Published: October 2005

A high-voltage flying-spot-type x-ray microbeam generator for computer-controlled radiography has been constructed, and a preliminary experiment on automatic tracking of pellets placed on the tongue has been conducted. Main operational features of the x-ray system are described, and some early data on the tongue movements of a Japanese subject uttering syllable sequences are shown.

Subject Classification: 70.20, 70.60.
Patterns in the sounds produced by P
a
r
a
v
e
s
p
u
l
a g
e
r
m
a
n
i
c
a wasps
Authors: Ishay Jacob , Brown Morton B.
Published: October 2005

In the nest of the social wasp P. germanica (Hymenoptera: Vespinae), the workers produce solid-borne tapping sounds by knocking with their bellies on the walls of the comb cells. Analysis of these recorded sounds reveals that they produce series of 20–60 beats, each containing 15–30 subbeats. The patterns of beats and subbeats are shown to be arranged in series of typical duration and spacing. Frequency analysis of the sounds reveals a peak at about 500 Hz and a range of 50–3150 Hz. The possible communicative value of these sounds is discussed.

Subject Classification: 80.50, 80.60.
Velocity of ultrasound in binary solutions of pyridine with heavy water
Authors: Stumpf F. B. , Gupta P. K.
Published: October 2005

The velocity of sound at a frequency of 19.5 MHz was measured as a function of concentration in binary solutions of pyridine with heavy water. The velocity versus concentration studies were made at 15 °C, 25 °C, and 35 °C.

Subject Classification: 35.24.
Is it VOT or a first-formant transition detector?
Authors: Lisker Leigh
Published: October 2005

Discussion of voicing as a distinctive property of English stop consonants in initial position has centered on the measure of ’’VOT,’’ the time of onset of laryngeal signal relative to the noise pulse generated by the stop release, but it has been shown that listeners’ selection of ‖b,d,g‖ vs ‖p,t,k‖ responses to synthetic stop+vowel stimuli is not determined entirely by VOT. Significant effects have been reported to depend on the behavior of the first formant (F1) frequency immediately following voice onset, and on this basis it has been suggested that a ’’feature detector’’ responsive to a rapidly shifting F1 better explains the infant’s discrimination of the two stop categories than some mechanism which measures VOT directly. The relative importance of VOT as against the presence versus absence of F1 frequency shift after voice onset is assayed in several synthesis experiments in which VOT and F1 configurations are systematically varied. Labeling data obtained indicate that varying VOT regularly effects a significant change in listeners’ judgments, and that varying F1 has some effect too, but this latter variation is neither necessary nor sufficient generally to shift judgments decisively from one stop category to the other. The data further suggest that the presence of an F1 rising transition after voice onset serves as a voiced-stop cue not so much because of its dynamic aspect, but simply because its onset frequency is low, i.e., at a value appropriate to a closed or almost closed state of the oral cavity.

Subject Classification: 70.30, 70.20, 70.70.
Seeding the field of acoustical signal processing
Authors: Anderson Victor C.
Published: October 2005

This is a historical look at the contributions to the field of acoustical signal processing which originated under the nurture of F. V. Hunt at the Harvard Acoustics Research Laboratory. The early research is highlighted by the work of Faran and Hills on the use of correlators for space–time processing. This early work was followed by research in the use of multiple element arrays and by the development of real-time processors for correlation and beamforming applications. The impact of these contributions can be seen in the expanding field of signal-processing research today. Upon retirement, Hunt transferred the pursuit of his last research interest, ’’Sir Transit Sonitus’’—a ship transit detector, to the Marine Physical Laboratory, where a real-ocean investigation of the technique is currently underway.

Subject Classification: 10.60; 60.10.
Behavior of sound in a bounded space
Authors: Berman J. M.
Published: October 2005

Theoretical predictions and reported experimental evidence of sound behavior in an enclosure are discussed and are shown in certain cases (e.g., normal-mode theory) to be inconsistent. A concrete model of a rectangular room was constructed so that the number of boundaries could be varied. Steady-state and transient responses are presented tor two-, three-, and four-boundary configurations, and these are compared with digital computations from a time-domain image simulation. The experimental results were found to be consistent with those of other researchers and the computer model was able to account for all the principal phenomena, including those at wavelengths comparable with the boundary dimensions where normal-mode concepts are usually substantiated. It was found that tone-burst responses in a bounded configuration whose reflection density increases with time can exhibit amplitude, phase, and ’’frequency’’ modulation throughout the frequency range. In reconciling these results with the normal-mode theory, the normal mode must be regarded as a mathematical function valid only in the context of an infinite series or integral in which, if principal features of the behavior are to be reproduced, the exact phase relationships are of vital importance. Finally, the tone-burst results are discussed in the light of recent work on the hearing mechanism.

Subject Classification: 55.20, 55.55, 55.40.
New methods in architectural investigations to evaluate the acoustic qualities of concert halls
Authors: Plenge G. , Lehmann P. , Wettschureck R. , Wilkens H.
Published: October 2005

A series of experiments were conducted at a number of concert halls in order to evaluate their acoustic ’’quanlity.’’ The quality was determined from a comparison of subjective assessments of a hall with a set of specified parameters describing physical characteristics of the sound field. Notable differences in the sound field in the hall and detected by artificial heads were correlated to position, reverberation time, brilliance, and so on. Using a factor analysis a finite number of independent factors emerged. It is concluded that the quality of a hall is better described by a set of such factors rather than by a single ’’reduced’’ number, as was done in the past.

Subject Classification: 55.45.
Wide-band directivity of receiving arrays
Authors: Faran James J. , Hills Robert
Published: October 2005

The method of maximizing the directional gain of a receiving array (heretofore useful only at a single frequency) is extended to the case of operation at a finite bandwidth. It is also shown how to design for maximum effective gain in the presence of noise which might arise within the individual transducers or their preamplifiers. Some necessary noise-field correlations are computed, and numerical examples are included to show the effects of bandwidth and self noise on the overall gain for reception which can be achieved. The directional gain of a broadside linear array for operation at a finite bandwidth is always less than that for operation at a single frequency, but is always greater, and often considerably greater, than the gain realized by use of the single-frequency design at the finite bandwidth. Unlike the single-frequency design, whose directional gain falls very rapidly as the operating bandwidth is increased from zero, the wide-band designs operate with good gain over a wide range of bandwidths.

Subject Classification: 30.82; 85.40; 60.30.
Radiation and scattering by submerged elastic structures
Authors: Junger M. C.
Published: October 2005

Analysis of submerged vibrating structures and of the associated sound fields requires the simultaneous solution of the vibrational and acoustical problems, because surface pressures exerted by a dense medium are typically comparable to inertia and damping forces in metal structures. The scattered field generated by a submerged structure may be similarly altered by the elastic response to the incident wave. This feedback phenomenon, whereby forces exciting the structure must be combined with radiation loading dependent on the structural response, is unimportant in the atmosphere. Consequently, as underwater sound approached airborne sound in practical importance during World War I, acousticians were forced to develop new analytical and experimental techniques for studying structure–water interactions. The development of this hybrid branch of acoustics and structural mechanics is reviewed with regard to radiation and scattering. Hunt, even though never personally active in this field, was interested in its applications. He performed his characteristic function of an unselfish teacher by encouraging doctoral candidates and postdoctoral fellows in the Harvard Acoustics Research Laboratory to venture into this novel area of acoustics.

Subject Classification: 30.30, 30.40, 30.50; 10.85.
F. V. Hunt and the disc recording arts
Authors: Bauer Benjamin B.
Published: October 2005

If necessity is the mother of invention, F. V. Hunt surely was its father. Confronted with the need to play some delicate recordings of the Harvard Tercentenary in 1936, Ted invented the first phonograph pickup capable of operation with 5-g bearing forces—a 10:1 advance in the state of the art—thereby ushering in the era of high-fidelity sound reproduction. This was followed in rapid succession by a definitive study of tracing distortion with Pierce and Lewis, including an uncanny prediction of the feasible parameters of a long-playing record. In 1941 and 1945 he received patents on inventions related to pickup and stylus structures, and in 1962 he again reduced the pickup bearing weights by an order of magnitude, producing successful 1/10th-g models which are yet to be commercialized. But Ted’s favorite saying was that he would receive most accolades for the work done through and by his students. Two among them, Frank G. Miller (1950) and James V. White (1970), made significant contributions to the understanding of a stylus–groove contact, thus laying a new theoretical basis for continued leadership of the disc record as a means of high-fidelity sound reproduction in the home.

Subject Classification: 10.60; 85.66, 85.68.
Bjerknes forces on bubbles in a stationary sound field
Authors: Crum Lawrence A.
Published: October 2005

This paper concerns the translational forces exerted on pulsating air bubbles in a stationary sound field. These forces, normally called Bjerknes forces, are derived by simple arguments and classified as to their origin. Measurements have been made of the relative velocity of appoach of two bubbles undergoing a mutual Bjerknes force. The measurements were made in a rigid glass container oscillated in a vertical direction at 60 Hz by a shaker table. The ambient pressure above the liquid was reduced in order to obtain large pulsations, and the attracting bubbles were photographed with a movie camera. Oberved and calculated values for the velocity of approach are in agreement provided a drag law assuming interfacial slippage is used.

Subject Classification: 25.60.
Frederick Vinton Hunt ⋅ 1905–1972
Authors: Bouyoucos John V.
Published: October 2005

Fredrick V. Hunt’s accomplishments in promoting and developing contemporary acoustics research, as well as his contributions to the field of underwater sound, studies of phonograph-record reproduction, and acoustic signal processing, are outlined.

Subject Classification: 10.60; 05.60.
Student’s viewpoint of F. V. Hunt
Authors: Blake F. Gilman
Published: October 2005

The author pays a personal tribute to Ted Hunt as a friend and as a stimulating, thought-provoking, and effective teacher.

Subject Classification: 05.60; 10.85, 10.60.
Colleague’s viewpoint of F. V. Hunt
Authors: Brooks Harvey
Published: October 2005

The influence of Ted Hunt on the career and interests of this author, while both were working at the Harvard Underwater Sound Laboratory, is detailed. Outlined are the research projects and breakthroughs which, through Ted’s inspiration and his ever-present guidance while director of the laboratory, set the pattern for most of the antisubmarine research to date.

Subject Classification: 05.60; 10.85, 10.60.
Sponsor’s viewpoint of F. V. Hunt
Authors: Pryce Aubrey W.
Published: October 2005

Hunt’s relationship with the Office of Naval Research and his performance as an acoustics researcher on other Navy-related activities are discussed. Particular attention is given to ’’Task Order X,’’ a series of projects carried on under Navy sponsorship over a 24-year period.

Subject Classification: 05.60; 10.60, 10.30.
Acoustically induced explosions of superheated droplets
Authors: Apfel Robert E. , Harbison James P.
Published: October 2005

A novel technique for measuring the tensile strength of liquids was recently reported [R. E. Apfel, J. Acoust. Soc. Am. 49, 145 (1971); Nature (Phys. Sci.) 233, 119 (11 Oct. 1971)]. In this technique, a droplet of the sample rises slowly in a column of another liquid, the ’’host,’’ in which it is nearly insoluble. When the droplet reaches a certain position in the host, an acoustic standing-wave field at about 50 kHz is established in the column, serving two purposes: (1) to balance the buoyancy force on the droplet and thus levitate it and (2) to rend the sample apart by raising the acoustic pressure to a great enough amplitude. If the droplet is simultaneously superheated, the cavitation event takes the form of an irreversible explosion of the sample into its vapor. Taking advantage of the levitation scheme, we have filmed this explosion with both diffuse and shadow lighting at about 3500 frames/sec; this shows resonant oscillations and what appears to be jet formation during the collapse of the vapor bubble.

Subject Classification: 35.68; 25.60.
Lagrange equations applied to flexural mode transducers
Authors: Rosato Frank J.
Published: October 2005

This paper deals with the flexural vibrations of composite piezoelectric transducers excited by electrode pairs configured to produce electric fields in phase opposition. Lagrange equations are used to analyze the electrodynamic characteristics of the transducers. These equations are essentially equations of dynamic equilibrium constructed in terms of derivatives of the kinetic and potential functions of the electromechanical system, themselves expressed in terms of generalized coordinates. For this class of transducers, the strains and electric field are chosen as the independent variables and the electric enthalpy function is the proper thermodynamic potential for use in the Lagrange equations. The present analysis takes account of the strain-induced electric fields in the composite transducer which arises when the strain and electric field have a common direction. The generalized electromechanical equations thus derived are suitably represented by an electric network based on the classical system of analogies. A set of generalized mode impedances is defined for each vibratory mode and is shown to play a significant role in the analog network. By applying known formulas to such a network, the electrodynamic characteristics of the transducer are readily obtained.

Subject Classification: 85.52; 40.22.
Scattering of acoustic point-source fields by random surfaces
Authors: Davies Huw G.
Published: October 2005

Estimates are obtained for the pressure field reflected from random rough surfaces when the surfaces are insonified by a high-frequency, omnidirectional point source. A geometric acoustics or ray-tracing approach is taken together with the assumptions that there is no shadowing of the surface and that each ray undergoes a single reflection. A stationary phase approximation of the Helmholtz integral is used to estimate the field associated with each ray. The emphasis of the paper is on accounting for the phase differences, that is, the interference effects, between the possibly very many geometric rays from source to surface to receiver.

Subject Classification: 20.30.
Application of ray theory to acoustic propagation in horizontally stratified oceans
Authors: Weinberg Henry
Published: October 2005

The acoustic pressure due to a point harmonic source in a horizontally stratified ocean is represented as a multipath expansion of the integral representation. Generalized Wentzel–Kramers–Brillouin–Jeffreys solutions are used to solve the depth-dependent wave equation. By applying numerical integration in conjunction with stationary phase, the problem of caustics is eliminated. Computed predictions are compared with theoretical results and another computer model.

Subject Classification: 30.20; 20.20; 85.84.
Generalized expansions of ray theory in terms of phase velocity. I.
Authors: Pedersen Melvin A. , White DeWayne , Johnson David W.
Published: October 2005

This is the first of a sequence of papers, which develop ray-theory expressions for velocity profiles with depth dependence only where the velocity is expressed as a generalized power series in depth. The method treats nonanalytic as well as all analytic (i.e., expandable in a Taylor series in depth) profiles. This first paper is limited to profile expansions about a velocity minimum and to the case of rays which turn around in a layer. Here the ray-theory results may be expressed as generalized power series in the phase velocity. Ray-theory range, travel time, range derivatives, phase integral function, and group velocity are treated. The method treats certain profiles, which were heretofore regarded as insolvable in closed form. Even when alternative approaches are tractable, the method has certain advantages. These include simpler and more accurate computing techniques, ease of range derivative evaluation, and improved understanding of theoretical results. Complete derivations are presented and results are verified by comparing the new method solutions with classical results for the linear, hyperbolic cosine, and exponential profiles.

Subject Classification: 30.20, 30.25; 20.20.
Validity of aircraft noise data
Authors: Sekyra C. A. , Storey W. C. , Yates R.
Published: October 2005

An analysis of noise measurements taken at various distances from a number of aircraft during noise flight testing is presented. Data scatter is shown to increase with distance and with decreasing aircraft/observer angle. Data normalization techniques, utilizing current standards, are inadequate at large distances and low airplane/observer angles. Aircraft noise measurements taken under uncontrolled situations are of doubtful value in predicting community noise. Noise measurements obtained directly beneath the airplane flightpath, under carefully controlled conditions, are highly repeatable and adjustable for moderate distances (within 1 to 2 EPNdB); however, when adjusted to sideline distances, these data can lead to variations on the order of 5 EPNdB. The accuracy of these sideline noise estimates is of prime concern since they are used to determine aircraft noise ’’footprints’’ in noise-exposure studies. Because a 3-EPNdB change in EPNL can lead to area halving or doubling, it is concluded, based on current technology, that the use of footprints in community noise-impact studies can be extremely misleading.

Subject Classification; 50.20, 50.75, 50.80.
Development of noise-reduction concepts for the 707 airplane
Authors: Nelsen M. D. , Callaway V. E.
Published: October 2005

Flyover noise characteristics are presented for the Boeing 707-300B/C equipped with standard production nacelles and with experimental quiet nacelles modified by the addition of sound-absorbing materials. Acoustic-treatment theory and technology required to develop the quiet nacelles are discussed. Results from, and techniques for, noise-certification flight testing to meet FAA regulations are presented. Comparisons of noise levels of a modified 707 aircraft, noise floors, and noise from other operational aircraft are provided.

Subject Classification: 50.40, 50.50, 50.55, 50.75.
Development of noise-reduction concepts for 727 and 737 airplanes
Authors: Arctander C. L. , Hodge C. G. , Tate R. B.
Published: October 2005

A review is given of various noise-reduction concepts pertinent to JT8D-powered 727 and 737 airplanes, with emphasis on acoustic technology. Acoustic treatment for engine fan noise reduction is shown to result in production airplane configurations that comply with existing FAR Part 36 regulations for new airplanes. Two jet noise suppression concepts aimed at further 727 noise reduction are discussed. An ejector/suppressor concept that has been demonstrated in an FAA-sponsored ground and flight test program is shown to achieve 6- to 8-EPNdB suppression of jet noise at takeoff power. Airplane performance penalties, however, have precluded production application of this configuration. The refan concept, currently under development on a NASA contract, involves JT8D engine modifications to incorporate a higher work-extraction fan. This modification realizes lower jet noise that, when coupled with extensive acoustic treatment, results in significant noise reductions with a minimum impact on airplane performance.

Subject Classification: 50.40, 50.50, 50.55, 50.75.
Comparison between the growth of the averaged electroencephalic response and direct loudness estimations
Authors: Botte M. C. , Bujas Z. , Chocholle R.
Published: October 2005

The question of the validity of the auditory-averaged electroencephalic responses (auditory AER) in auditory research and in audiometry is a very important one. In the present experiments, auditory AER and direct estimates of loudness magnitude were conducted concurrently on the same subjects, in the hope of reducing the consequences of the great within-subject and between-subject variability always encountered in such experiments, and of the differences in the degree of alertness. The peak-to-peak amplitude of the N1 − P2 waves and the N1 and P2 latencies were used as characteristics of the auditory AER. Even in these conditions, no clear relations appeared between the AER and the loudness estimations. The discussion shows that they are probably not directly connected.

Subject Classification: 65.59, 65.50.
Anthropometric manikin for acoustic research
Authors: Burkhard M. D. , Sachs R. M.
Published: October 2005

A manikin for hearing aid and related acoustic research was designed with median human adult dimensions. Ear simulation matches the acoustic response with an auricle, an ear canal, and an eardrum that equal the median ear in dimensions, acoustic impedance and modes. Dimensions of torso and head are based on published anthropometric data, but the auricle is based on data obtained for this development. The ear canal and eardrum are adapted from the earlike coupler by Zwislocki. The ear entrance sound pressure was found to be relatively insensitive to surface or skin impedance of the head. Validating measurements show the manikin, designated KEMAR, to be like a median human in acoustic response to free fields.

Subject Classification: 65.22, 65.80, 65.35,65.82.
Holographic interferometry applied to the investigation of tympanic-membrane displacements in guinea pig ears subjected to acoustic impulses
Authors: Dancer A. L. , Franke R. B. , Smigielski P. , Albe F. , Fagot H.
Published: October 2005

The displacements of the tympanum of guinea pigs undergoing the action of acoustic impulses were investigated using holographic interferometry. The motion of the umbilicus is approximately 7.5 times smaller than that of the maximum elongation point of the tympanic membrane located between the umbilicus and the annulus fibrocartilagineus in the prolongation of the manubrium mallei. The results attempt to explain why tympanic lesions originated under the action of acoustic impulses frequently appear in the lower area of the pars tensa in the case of guinea pigs. The holographic visualization of tympanic-membrane displacements appears to offer a number of practical applications allowing to throw light into the transmission of acoustic energy at the level of the tympanic membrane.

Subject Classification: 65.24; 35.65; 80.50.
Internal-combustion engine intake and exhaust system noise
Authors: Bender Erich K. , Brammer Anthony J.
Published: October 2005

In this paper the state of the art of characterizing and controlling intake and exhaust system noise of internal-combustion engines is reviewed. Various types of internal-combustion engines are discussed as sources of noise and in terms of their interaction with intake and exhaust systems. A review of muffler technology shows that linear resistive and reactive effects are well understood, as are certain nonlinear effects. However, effects of high sound pressure levels, flow, duct perforations, and temperature gradients all acting together require study. The paper also shows that mufflers providing 30–35 dBA of insertion loss are practical and that insertion loss can be predicted, but only roughly.

Subject Classification: 10.60; 50.30, 50.50.
Second-order gradient unidirectional microphones utilizing an electret transducer
Authors: Sessler G. M. , West J. E.
Published: October 2005

A class of second-order gradient microphones with unidirectional directivity characteristics is analyzed. These microphones consist of four in-line sensors whose outputs are added with proper delays. The directivity characteristics of such microphones are rotationally symmetric and given by (α+cosϑ)(β+cosϑ), where α and β are constants and ϑ is the angle of incidence relative to the rotational axis. The calculated maximum directivity factor is 9. Experimental systems consist of an electret transducer enclosed in a cylindrical cavity and four tubes, paired in length, extending from the cavity to sample the sound field. Measurements on a transducer with α=1 and ‖β‖ ≪ 1 yield a sensitivity of about −80 dBV/μbar in the direction of mzximum pickup (ϑ=0) with variations of less than ±3 dB in the frequency range from 0.2 to 4 kHz. The measured sensitivity is about 20 dB lower for ϑ=90, 180 and 270°. Because of their large directivity factors, such microphones are of interest in environments with high noise levels or in situations where reverberation or acoustic feedback have to be suppressed.

Subject Classification: 85.62, 85.44, 85.40.
Frequency dependence of threshold ultrasonic dosages for irreversible structural changes in mammalian brain
Authors: Dunn F. , Lohnes J. E. , Fry F. J.
Published: October 2005

Threshold ultrasonic single-pulse exposures for irreversible structural changes in the mammalian brain have been extended to include the frequencies 1, 3, 4, 4.5, and 9 MHz. The acoustic intensities of the delivered doses range from approximately 102 W/cm2 to 2×104 W/cm2 with the corresponding exposure durations ranging from 2.5 sec to 5×10−4 sec, respectively. The threshold dosage curves can be described by the relation It1/2=c (f,T), where I is the acoustic intensity delivered to the site of the irreversible change, t is the time duration of the single acoustic exposure, and c is a weak function of frequency and possibly also of base temperature of the specimen.

Subject Classification; 80.40.
Masked hearing thresholds of ringed seals
Authors: Terhune J. M. , Ronald K.
Published: October 2005

The critical ratios of two ringed seals were estimated by determining pure-tone thresholds (yes–no, forced choice) in the presence of various noise bands. Data obtaind from both seals were pooled. The critical ratios (using spectrum noise levels of −30 and −40 dB re 1 μbar) were 30±5.4, 32±3.8, 34±2.8, and 35±4.5 dB at 4, 8, 16, and 32 kHz, repectively. These values are consistent with findings of other mammalian species. In the open ocean, meteorological and man-made noises below 100 kHz may mask the underwater hearing of marine mammals. As there is less than 10-dB variation in the noise (spectrum level) above 100 kHz, an echolocation system operating in this range would be less subject to varying amounts of masking.

Subject Classification: 80.50; 65.22, 65.58.
Resonant transmission-line configurations for optimum FM detection of vibration using capacitance transducers
Authors: Paré V. K.
Published: October 2005

Resonant transmission-line configurations are described which give maximum frequency modulation amplitude when modulated by a small terminating capacitance. If the termination is a capacitive vibration transducer, there results a wide-band, absolutely calibrated system which can detect small vibration amplitudes in a severe environment.

Subject Classificairon: 85.44; 40.75; 85.22.
Active electrical load for simulating a transducer in an array
Authors: Truchard James J. , Nowlin William C.
Published: October 2005

This paper describes the design, fabrication, and use of both passive and active electrical dummy loads which simulate the electrical impedance of an individual transducer element in a large array over a wide range of frequencies. These impedance characteristics allow the use of this dummy load for the testing of a prototype amplifier at both its operating frequencies and frequencies where the stability and noise performance of the amplifier may be affected by the impedance characteristics of the load. Since an active port is included in this dummy load, the impedance characteristics of a transducer element at various positions in the array could readily be simulated. An example of the use of this dummy load for the testing of a 1-kW switching type prototype amplifier is given.

Subject Classification: 30.85; 85.40, 85.64.
Acoustic phase fluctuations resulting from axis meander and transport variation of a geostrophic ocean current
Authors: Widtfeldt J. A. , Jacobson M. J.
Published: October 2005

A treatment is presented of total-field phase fluctuations of a cw signal, transmitted across a slowly varying northward geostrophic flow. Only refracted/bottom-reflected rays are considered, and the ocean bottom is horizontal. Unlike earlier investigations, the flow is of finite width and transport-axis location, as well as volume transport, may be varied. We begin with a rather general current model having factorable dependence on depth and distance across the flow. The current is taken to decrease linearly with depth, and the surface current is specialized to a cubic polynomial. Sound speed is calculated from the density and pressure solutions. It is then approximated by a linear least-squares fit, so that the acoustics problem is equivalent to that in a convergent channel with linear sound speed versus depth. In an application, the total-field phase is shown to be highly sensitive to transport-axis meander as well as to changes in volume transport.

Subject Classification: 30.20, 30.25.