bluuebunny/crossref_metadata_2025 huggingface dataset:
Sound pressure in air from a source in water and vice versa
Authors: Bordelon Derrill J.
Published: October 2005

Young's approximation for the sound field in air due to a point source in water is questioned regarding its presumed quadripole character. A new approximation, of dipole character, based on Young's approximation for the sound field in water due to a source in air, is derived and for a scattering of source and field points is shown to be in good agreement with Waters expression, which neglects the lateral wave and surface roughness. It is shown that Horton's graphs can be scaled to produce satisfactory estimates of Waters values. Finally, on examination, Horton's isobaric contours are found to be satisfactory.
Subharmonic response of bubbles to underwater sound
Authors: Eller Anthony I.
Published: October 2005

Past experiments have indicated that underwater bubbles in a sound field can help to generate acoustic signals at subharmonics of the driving frequency. Furthermore, theoretical evidence indicates that a likely mechanism for subharmonic generation is the nonlinear pulsation of the driven bubbles. This letter describes results of a computer study of subharmonics that occur in nonlinear bubble pulsations. The results show that the subharmonic of order one-half can be excited over a broad frequency range, and not just for a driving frequency of twice the bubble resonance frequency. The results also reveal jump and hysteresis effects in the subharmonic response as the driving acoustic pressure and frequency are varied.
Large-amplitude vibrations of elastically restrained circular plates
Authors: Ramachandran J.
Published: October 2005

Using Berger's version of the simplified dynamic Von Karman's equations for large-amplitude vibrations of circular plates, solutions are obtained for elastically restrained edges. The period of vibration is plotted versus amplitude for various values of transverse and rotational spring constants.
Effect of sound on the germination rate of turnip seeds
Authors: Hageseth Gaylord T.
Published: October 2005

The number of seeds that germinate as a function of time has been examined keeping all environmental parameters constant with the exception of the sound pressure level and frequency These data were very reproducible. At 100 dB all the single-frequency sound data have essentially the same characteristic curve. Broad-band noise data indicate that the initial germination is delayed about two hours longer than the single-frequency sound and quiet data. The data obtained when 1000-Hz 100-dB sound is turned off 16 h after wetting indicate that the germination process slown down almost to zero soon after the sound is turned off. Frequencies of 100, 1000, 2000, 4000, and 9000 Hz as well as broad-band noise all at 100 dB were used in the experiment.
Measurement of meter ballistics
Authors: Corliss Edith L. R.
Published: October 2005

Measurements of transient phenomena such as impact sounds are influenced by the characteristics of the metering system used. This note describes a method for obtaining the undamped natural frequency and the relative damping of a meter. From this information and the measured electrical impedance of the meter circuit the ballistic behavior of the meter can be predicted.
Application of the response probability density function technique to predicting the probability of sonic-boom glass breakage
Authors: Hershey Robert L. , Higgins Thomas H. , Magrab Edward B.
Published: October 2005

The response probability density function (pdf) technique developed here utilizes the pdf's of the excitation and sensitivity to obtain the pdf of the response. This technique was used in a statistical model for estimating the probability of glass breakage from sonic booms, as a function of nominal overpressure, window size, aircraft vector, boom duration, and whether the glass was in good condition or cracked. A model window population was devised from available data which includes the pdf's of the dynamic amplification factors and breaking pressures for seven window types. From the histograms of the test data, the distribution of both sonic-boom stresses and glass strengths were found to be lognormal, which reduced the statistical model to a particularly simple form. It was estimated that there would be 1.1 breaks per million panes in good condition boomed at a nominal overpressure of 1 psf. This agrees well with sonic boom claims data of 0.6 breaks per million panes boomed.
Pitch, consonance, and harmony
Authors: Terhardt Ernst
Published: October 2005

Comparison of recent psychoacoustic data on consonance with those on roughness reveals that “psychoacoustic consonance” merely corresponds to the absence of roughness and is only slightly and indirectly correlated with musical intervals. Thus, psychoacoustic consonance cannot be considered as the basis of the sense of musical intervals. The basis of that sense seems to be provided by the concept of virtual pitch. This concept is introduced with a model. The concept accounts for many psychoacoustic and musical phenomena as, e.g., the ambiguity of pitch of complex tones, the “residue,” the pitch of inharmonic signals, the dominance of certain harmonics, pitch shifts, the sense for musical intervals, octave periodicity, octave enlargement, “stretching” of musical scales, and the “tonal meaning” of chords in music.
High-performance magnetostrictive tranducers
Authors: Edson A. P. , Huston E. L.
Published: October 2005

This paper is directed to the use of magnetostrictive materials for the generation of high-intensity mechanical-vibration, sound, and ultrasound. It will present a mathematical analysis of a novel method of polarization and excitation which affords previously unattainable combinations of peak-to-peak magnetostrictive strain energy, electromechanical efficiency, and linearity. To achieve these results, magnetic excitation is applied at a large angle relative to the axes of static magnetic polarization and mechanical output. Because this is usually most conventiently achieved by application of magnetic vectors at right angles to one another, the method has been termed “orthogonal excitation.”
Comment on “Characteristics of line and disk underwater sound transducers in the near- to farfield transition region” [C. M. McKinney, K. W. Harvel, and G. E. Ellis, J. Acoust. Soc. Am. 51, 1076–1082 (1972)]
Authors: Freedman Albert
Published: October 2005

Attention is called to Stenzel's important paper on the nearfield of a rectangular piston.
Acoustic effect caused by a deep thermohaline stepped structure in the Mediterranean Sea
Authors: Mellberg Leonard E. , Johannessen Ola M. , Lee Owen S.
Published: October 2005

Recent oceanographic observations in the Tyrrhenian Sea and Sardinian Channel show a well-defined stepped thermohaline structure below the core of the Levantine water (∼500 m). Such a stepped structure has also been found under the Mediterranean outflow west of Gibraltar. The effects of the Tyrrhenian Sea stepped structure on sound propagation are examined qualitatively using ray tracing techniques. The predominant effect occurs for energy that has travelled along rays that have vertexed in the steps. Shadow zones, regions of high propagation loss, and caustics are then generated.
Psychoacoustic calibration of the Telex 1470 earphone
Authors: Causey G. Donald , Beck Lucille B.
Published: October 2005

Reference-threshold levels for the new Telex 1470 audiometric earphone were determined at ten frequencies. The psychophysical method of adjustment was employed, utilizing a transfer standard technique. Based on the judgments of 12 subjects, mean reference-threshold sound-pressure levels in the NBS 9-A type coupler were found for the Telex 1470 earphone.
Source level and bistatic target strength of the sperm whale (Physeter catodon) measured from an oceanographic aircraft
Authors: Levenson Coleman
Published: October 2005

Sounds produced and reflected by sperm whales (Physeter catodon) have been recorded by a sonobuoy array deployed from an oceanographic aircraft and analyzed for source level and target strength. Mean octave-band source levels ranged from 139.3 dB re 1 μPa in the 250–500 Hz band to 162.3 dB in the 4000–8000 Hz band. Mean octave-band target strengths ranged from −2.5 to 10.8 dB in the octave-bands centered at 375 and 12 000 Hz, respectively.
Propagation of waves along an impedance boundary
Authors: Wenzel Alan R.
Published: October 2005

A theoretical analysis of the scalar wave field due to a point source above a plane impedance boundary is presented. A surface wave is found to be an essential component of the total wave field. It is shown that, as a result of ducting of energy by the surface wave, the amplitude of the total wave near the boundary can be greater than it would be if the boundary were perfectly reflecting. Asymptotic results, valid near the boundary, are obtained both for the case of finite impedance (the soft-boundary case) and for the limiting case in which the impedance becomes infinite (the hard-boundary case). In the latter, the wave amplitude in the farfield decreases essentially as r−1, where r is the horizontal propagation distance; whereas in the former (if the surface-wave term is neglected) it decreases as r−2. The results obtained here are compared with results of experimental studies of sound propagation along boundaries, and it is suggested that some apparently anomalous experimental findings might be explained in terms of the present theory.
Vibration of generally orthotropic skew plates
Authors: Nair P. S. , Durvasula S.
Published: October 2005

Vibration problem of generally orthotropic plates with particular attention to plates of skew geometry is studied. The formulation is based on orthotropic plate theory with arbitrary orientation of the principal axes of orthotropy. The boundary conditions considered are combinations of simply supported, clamped, and free-edge conditions. Approximate solution for frequencies and modes is obtained by the Ritz method using products of appropriate beam characteristic functions as admissible functions. The variation of frequencies and modes with orientation of the axes of orthotropy is examined for different skew angles and boundary conditions. Features such as “crossings” and “quasi-degeneracies” of the frequency curves are found to occur with variation of the orientation of the axes of orthotropy for a given geometry of the skew plate. It is also found that for each combination of skew angle and side ratio, a particular orientation of the axes gives the highest value for the fundamental frequency of the plate.
Acoustic reflection from elastic spheres and rigid spheres and spheroids. II. Transient analysis
Authors: Dragonette Louis R. , Vogt Richard H. , Flax Lawrence , Neubauer Werner G.
Published: October 2005

Curves relating the reflected acoustic pressures to frequency for a rigid sphere and spheroid and for elastic spheres of aluminum, brass, and tungsten carbide in water are obtained. Experimental measurements using single short acoustic pulseforms are compared with theory. Excellent agreement is obtained for the limited ranges of ka over which the experiments were done. Only the case of monostatic reflection is considered.
Acoustic waves from an impulsive source in a fluid-filled borehole
Authors: Roever W. L. , Rosenbaum J. H. , Vining T. F.
Published: October 2005

Acoustic waves generated by an impulsive source in a fluid-filled borehole have been experimentally measured and theoretically analyzed by means of modal and ray-type expansions. Outstanding features of the response are obtained in closed-form expressions, which are leading terms of asymptotic series. For source and detector near the borehole axis, the first refracted P-arrival decays approximately as 1/(z log2 z), where z is the nondimensional axial source-to-detector distance. The first refracted S-arrival is much larger for moderate z, but decays as 1/z2. The relation between the S-arrival and “pseudo-Rayleigh” wave is discussed on the basis of modal theory; a simple description of the “tube wave” in terms of integrals of Airy functions is presented. In the radial-ray picture, the borehole axis is a caustic, where rays are subjected to a 90° phase shift; for the pulse problem, the waveform is replaced by its Hibert transform. The simple theoretical expressions agree with the results of model studies. For source and detector located off the borehole axis, the observed signal is more complicated. This can be ascribed to the fact that a number of circumferential modes can enter into the description of the response.
Nonlinear acoustic propagation in two-dimensional ducts
Authors: Nayfeh Ali Hasan , Tsai Ming-Shing
Published: October 2005

The method of multiple scales is used to obtain a second-order uniformly valid expansion for the nonlinear acoustic wave propagation in a two-dimensional duct whose walls are treated with a nonlinear acoustic material. The wave propagation in the duct is characterized by the unsteady nonlinear Euler equations. The results show that nonlinear effects tend to flatten and broaden the absorption versus frequency curve, in qualitative agreement with the experimental observations. Moreover, the effect of the gas nonlinearity increases with increasing sound frequency, whereas the effect of the material nonlinearity decreases with increasing sound frequency.
Analysis of the effect of a Rossby wave on sound speed in the ocean
Authors: Baer R. N. , Jacobson M. J.
Published: October 2005

The effects of an assumed Rossby wave on density, pressure, current, and sound speed are examined and analyzed. It is shown that the zeroth-mode wave solution has only slight effect on sound speed, while the first-mode solution is significant. A dispersion relation is developed, having as one solution an east-west wavelength of 210 nautical miles and a period of 114 days, for parameters consistent with the Sargasso Sea area. This first-mode solution predicts the gross behavior of observed sound speed versus depth variations, and provides striking agreement with measured curves of constant sound speed. The addition of a second-mode solution to the first leads to a crossover of sound-speed profiles in qualitative agreement with observations.
Averaged sound transmission in range-dependent channels
Authors: Smith P. W.
Published: October 2005

We derive an integral formula as an estimate of the averaged, steady-state transmission ratio for two points in a channel whose environmental parameters vary slowly with range. We base the derivation on the theory of ray acoustics with lossy specular reflection from the boundaries. The averaging eliminates all but gradual changes with range of the transmission loss (TL); dependence on the depth of each point is retained. Detailed tracing of ray paths over many cycles is not required. Numerical results for an isogradient channel with constant bottom slope are exhibited, and an appendix contains modal interpretation of the general formulation.
Direct measurement of surface-scatter channel coherence by impulse probing
Authors: Zornig J. G. , McDonald J. F.
Published: October 2005

A method of studying the statistical properties of the random time-varying surface-scatter channel using ultrasonic scale modelling and using a novel digital-probing system is discussed. Measurements of the coherent transfer function of such channels are presented and are shown to be in minor disagreement with existing theoretical predictions. Various mechanisms to explain this disagreement are explored leading to the tentative conclusion that a violation of the Kirchhoff condition is probably responsible for the effect observed.
Axisymmetric vibrations of laminated composite cylindrical shells
Authors: Sun Chang-Tsan , Whitney J. M.
Published: October 2005

A refined theory of vibration of laminated composite thick shells is developed. The present theory includes the effects of transverse shear deformation, transverse normal stress and strain, rotary inertia, and higher-order stiffness terms. Numerical results of natural frequencies under axisymmetric vibrations for graphite-epoxy composites are evaluated and compared to results obtained from Flugge's theory. A significant difference between these two results is observed for shells having relatively large thickness-to-length ratio.
Cochlear partition stiffness—a composite beam model
Authors: Allaire P. , Raynor S. , Billone M.
Published: October 2005

A mathematical model of the human cochlear partition is developed to investigate the partition's stiffness. To date, no experiment has been performed on the partition to determine the difference between the dynamic and the statically measured stiffness. Nonlinearities observed in the partition's dynamic motions and dynamic stiffness measurements on bone and muscle tissue indicate that previous investigations of the cochlear partitions's stiffness may not be adequate. In this study the cochlear partition is modeled by a series of composite beams whose stiffness is due to linear bending rigidity at normal amplitudes of motion. At larger amplitudes (in the nonlinear range near the threshold of pain), the model's stiffness is increased, owing to the nonlinear stretching of the basilar membrane. The model also includes the increase in stiffness, above the static stiffness, due to dynamic loading, as observed in the studies of bone and muscle tissue. The dynamic cochlear partition stiffness predicted by this model increases approximately by a factor of 100 from apex to base. Except near the stapes, the model's stiffness in the linear range at 100 Hz is approximately the same as measured statically. At 10 000 Hz the model's stiffness in the linear range is nearly twice as large as the statically measured value.
Lateralization and the binaural masking-level difference
Authors: Henning G. Bruce
Published: October 2005

Observers can readily detect interaural delays in certain complex waveforms even when the energy in the waveform is confined to high-frequency regions. However, the detectability of such complex waveforms is not measurably dependent on interaural phase—that is, there is no masking-level difference with high-frequency signals in spite of the fact that interaural phase effects are readily observed as changes in the apparent location of the source of the signal.
Binaural interaction in cat and man. I. Signal detection and noise cross correlation
Authors: Hoppe Susan A. , Langford Ted L.
Published: October 2005

Detection of diotic 500-Hz tones partially masked by diotic and dichotic noise was studied in the cat and compared with similar detection data for man. The interaural correlation of the masker was varied by delaying the channel to one ear from 0 to 5 msec in steps of 1 msec. An avoidance response was used to measure detectability. The absolute sensitivity of the cat was less than that of man and smaller MLDs were found for the cat at each delay. The temporal interval over which the binaural system of the cat is able to effect a correlation between events occurring at the two ears was estimated to be smaller, while the critical band appears to be wider than in man.
Detection of interaural onset and offset disparities
Authors: Perrott David R. , Baars Bernard J.
Published: October 2005

Interaural time difference thresholds for transient differences in signal onset and offset were examined. Lateralization of the acoustic image to either onset or offset transients was observed with signal pulses 1 and 10 msec in duration but not with longer pulses. Interaural difference thresholds for signal onset were observed with smaller time disparities than those obtained with signal offset transients. Both onset and offset transient thresholds were inversely related to signal duration and directly related to signal correlation.
Doppler structure in echoes from schools of pelagic fish
Authors: Holliday D. V.
Published: October 2005

The frequency distribution of energy in direct path echoes from three schools of pelagic fish is presented. One-half-second 30-kHz CW pulses were used to study motions internal to the fish schools from distances up to 1200 m. The measured Doppler spread of echo energy ranged from 30 Hz to 70 Hz. The Doppler spread-at-side aspect is related to swimming motions by a simple algebraic model based on Bainbridge's equation relating fish swimming speed, length, tail-beat amplitude, and tail-beat frequency. The mathematical model was used to estimate the length of the fish in two of the schools. These length estimates agree with average fish lengths derived from school cruising speeds. Near head or tail aspect, the observed Doppler structure appears to be related to behavioral swimming characteristics.
Upper limit on the use of weak-shock theory
Authors: Pestorius F. M. , Williams Solon B.
Published: October 2005

The use of weak-shock theory fails to describe adequately the behavior of very intense finite-amplitude waves. In this letter, we report the development of an improved version of the weak-shock result that is used to predict the propagation of sawtooth waves. This new result is then used to investigate the upper limit on the strength of waves that may be accurately modeled by the use of ordinary weak shock theory.
Reply to “Comments on ‘Rytov's method and large fluctuations’” [D. A. de Wolf, J. Acoust. Soc. Am. 54, 1109–1110 (1973)]
Authors: Brownlee L. R.
Published: October 2005

De Wolf comments that the results of exhaustive research into Rytov's method indicate that it has a larger domain of applicability than the Born approximation and implies that the author has been misled by comparing terms in a differential equation. This letter shows Rytov's method to have no more applicability by yet another method, not by using the “cone approximation” as before, but by showing the assumption that ψ′ is not small to be untenable using Rytov's method.
Measurement of the absorption spectrum using correlation/spectral density techniques
Authors: Barry Timothy M.
Published: October 2005

The correlation peak-height ratio method for the determination of acoustic absorption coefficients is reviewed. In addition, a method utilizing a truncated cross-correlation function and spectral density ratios is presented; it enables the calculation of an absorbing material's absorption spectrum.
Automatic urban noise monitoring and analysis system
Authors: Foreman J.E.K. , Dickinson S. M.
Published: October 2005

This letter describes an automatic, continuous-duty, sound-detection monitor together with the associated data-retrieval and processing system which were designed, built, and used for a recent urban noise study of the cities of London and Woodstock, Ontario, Canada.
Algebraically growing waves in ducts with sheared mean flow
Authors: Nayfeh Ali Hasan , Telionis Demetri P.
Published: October 2005

Standing or traveling waves which vary algebraically with the axial distance in uniform ducts with sheared mean velocity profiles are investigated. The results show that such waves are not possible for ducts with uniform cross sections and fully developed mean flows.
Exhaust noise field generated in the JT8D core engine—noise floor presented by the internal noise sources
Authors: Grande Edvard
Published: October 2005

An experimental study has been conducted to determine the strength of the acoustic radiation generated in the combustion and turbine stages of a JT8D core engine and transmitted out through the primary jet exhaust duct. The acoustic field within the tail pipe duct extension was measured by an array of microphones flush mounted on the extension wall. The interpretation of the cross-power spectral densities of the microphone signals by means of a theoretical model of the sound propagation within the duct permitted the acoustic energy transmission out of the nozzle exit to be determined. The results show that the internally generated noise is a dominant noise component from the core engine at larger angles from the jet axis for the case of low engine power settings. Although the internally generated core engine noise component lies well below the JT8D engine jet noise and fan noise components at the higher engine power settings, it represents an additional noise parameter that must be considered in the application of fan noise and jet noise suppression techniques.
On the performance of a dual frequency parametric source via matched asymptotic solutions of Burgers' equation
Authors: Fenlon Francis Hugh
Published: October 2005

In this paper, following a brief review of previous contributions to the field of Parametric Acoustics, plane and spherical wave solutions of Burgers' equation are derived by the method of successive approximations for the difference-frequency signal which results from nonlinear interaction in the medium of two different-frequency primary waves radiated simultaneously by a finite-amplitude source. These solutions are then matched asymptotically obtain a farfield solution which includes the influence of nonlinear interaction within the Fresnel and Fraunhofer zones of the primary waves, from which an expression for the “equivalent difference-frequency source level” is derived. The analysis assumes that the primary-wave amplitudes, which induce the nonlinear interaction are below their respective shock thresholds as defined by a criterion which relates the steepest slope of the waveform to a predetermined upper bound approximation of an ideal discontinuity. In order to determine the predictive reliability of the solutions, a parameter which characterizes the “equivalent difference-frequency source level” is compared with empirical results obtained over a wide range of experimental conditions. Finally, a quasiplane three-dimensional equation (which in one dimension assumes the form of Burgers' equation) is also analyzed in order to obtain a second-order farfield directivity function for the difference-frequency signal.
Influence of the subsurface sound channel on long-range propagation paths and travel times
Authors: Fitzgerald R. M. , Guthrie A. N. , Nutile D. A. , Shaffer J. D.
Published: October 2005

Explosive sound sources were detonated at shallow depths in two long-range deep ocean experiments. Signals were recorded from a shallow hydrophone in the first experiment (May 1967) and from a SOFAR channel hydrophone in the second (May 1969). The propagation was strongly influenced by subsurface sound channels. The shot arrival patterns were analyzed by a graphical method to determine the convergence zone locations and the average sound speed in the subsurface channel. In the first experiment the bottom was flat and the medium could be characterized by a single velocity profile having a weak subsurface channel. Numerous bottom reflections were observed. In the second experiment the bottom was rough. Two profiles were required to characterize the medium, one of which exhibited a strong subsurface channel. Bottom reflections were not in evidence. Energy was detected which traveled more than 800 km entirely within the subsurface channel.
Mathematical methods for the study of nonlinear vibration problems
Authors: Sethna P. R.
Published: October 2005

A symptotically valid mathematical results, based on the “Method of Averaging,” are given for nonlinear dynamical systems dependent on a parameter. Procedures are given for the study of transient and steady-state motions and for obtaining nonlocal domains of attraction of steady state motions of high-order nonlinear systems. The analysis is extended for the study of systems dependent on a “fast” and “slow” time, and connections of these systems to singularly perturbed systems are discussed.
Nonlinearities in structural dynamics
Authors: Crandall S. H.
Published: October 2005

Causes and effects of nonlinearity in structures are surveyed and illustrated by means of examples. Geometrical and material nonlinearities, and nonlinearities due to bearings, friction, clearance, stops, etc., are described. Nonlinearity in stiffness is contrasted with nonlinearity in damping. Dynamic effects of nonlinearity, including jump phenomena, subharmonic resonance, and nonlinear coupling between modes, are illustrated. A discussion of criteria for smallness of motion to justify linearized treatment of nonlinear systems is given. Illustrative examples including vibration of flat plates, vibration of antenna mounts, and earthquake response of multi-story buildings are described. A structural earthquake isolation system utilizing friction-controlled foundation pads is presented. Analytical and numerical techniques for predicting the statistical response of the system are demonstrated. [Supported by NSF Grant GI-34945. ]
Nonlinear effects in shock and vibration
Authors: Curreri J. R.
Published: October 2005

Results of analytical and test investigations of two-degree-of-freedom nonlinear systems, history of prior work, computer solutions for shock inputs, and the Ritz averaging method for steady-state vibrations are discussed. Nonlinear effects due to nonlinearities in either or both elastic members are also considered. The nonlinearities may be either hardening or softening. Viscous damping is introduced into both systems. For a single nonlinear spring, either hardening or softening, one mode response is much more nonlinearly affected than the other. Changing mass ratio does not change this result. Analytical study regarding stability in two-degree-of-freedom systems is discussed. Steady-state stability analysis by Floquet type theory is used to obtain a characteristic determinant. This approach has been used for the study of linear equations with periodic coefficients. For nonlinear vibrations, off-diagonal elements must be used in the characteristic determinant. Stability results show that some mathematically stable roots are close to instability over a wide range of system parameters.
Effects of shocks with similar shock spectra on multi-degree-of-freedom systems
Authors: Butzel L. M. , Merchant H. C.
Published: October 2005

The responses of a large collection of mechanical structures to shocks satisfying the same shock spectrum specification are examined. Maximum responses of 4224 four-degree-of-freedom systems are determined for each of two different shocks: a drop-type half-sine shock pulse, and a complex electromagnetic exciter-type pulse (superposition of decaying sinusoids) having similar shock spectra over a range of damping factors and frequencies. The results indicate that the different shocks cause significantly different maximum response behavior in the 4224 systems. Some implications of shock spectrum equivalence of shocks suggested by this analysis are discussed.
Vibration analysis of thin rectangular orthotropic plate
Authors: Elishakoff I.
Published: October 2005

A new approximate method is proposed for the vibration analysis of a rectangular orthotropic plate under arbitrary conditions (but same along any given edge). The plate is treated as if it were supported along apposing edges (Lévy problem) with the analogs of the wavenumbers in the coordinate directions as unknowns in a pair of simultaneous transcental equations, derived in turn from the solution of two auxiliary (one-dimensional) eigenvalue problems. It is shown that the proposed method reduces to Bolotin's “dynamic edge effect” method for large wavenumbers. Numerical values of the fundamental frequency parameter are given for all possible combinations of edge conditions.
Experimental analysis of the motion of a vibrating surface by speckle interferometry and optical spatial filtering
Authors: Mehta A. V.
Published: October 2005

Optical spatial filtering [J. A. Clark and A.V. Mehta, J. Acoust. Soc. Amer. 54, 291 (1973)] and speckle interferometric techniques are employed to analyze the motion of vibrating surfaces for many cases (e.g., rectangular bar, circular disk, etc. ). Data, which is displayed in real time as contours of equal displacements over the image of vibrating surface, are recorded by time average, real time, and stroboscopic photographic methods using ordinary camera equipment. Calibration procedures are also described along with advantages and limitations of the method. The analysis compares well with the theoretical solutions.
Spectrum of rotor noise caused by atmospheric turbulence
Authors: Hanson D. B.
Published: October 2005

The spectrum of blade leading and the associated noise caused by interference of a propeller, helicopter rotor, or fan rotor with inlet turbulence are studied experimentally and theoretically. One test with hot-wire anemometers in a static inlet and another test with pressure transducers on the blades of a fan rotor reveal inlet turbulence to be highly anisotropic. The intensity of the transverse velocity component was found to be 2.5% of the mean flow and the streamwise component was 0.9%, with ambient winds of about 2 mph. The transverse integral scale of the turbulence is a fraction of an inlet diameter, while the streamwise integral scale is over 100 diameters. Evidence indicates the source of these disturbances is atmospheric turbulence. The associated noise is partially coherent with spectrum peaks which are so narrow as to be difficult to distinguish from true harmonics. A novel blade loading model is developed using concepts from random pulse modulation theory. Theoretical spectrum predictions indicate for the test fan that the peak at blade passing frequency and the high-frequency broad-band noise are due to inflow turbulence. It appears that this narrow-band random mechanism explains spectrum peaks which have previously been described as harmonic noise due to fixed inflow distortion.
Inlet turbulence—rotor noise
Authors: Mani R.
Published: October 2005

The present contribution is concerned with aerodynamic noise from isolated, subsonic tip rotors. With large axial spacing between blade rows and elimination of inlet guide vanes, at least the forward radiated noise from modern single-stage acre-engine fans is dominated by isolated rotor noise. In an early study, Sharland described three agencies by which such a rotor would produce noise, namely, vortex shedding, turbulent boundary layer noise, and noise due to inflow distortion or inlet turbulence. The present study develops means of computing inlet and discharge PWL spectra due to impingement of inlet distortion or inlet turbulence on an isolated rotor. Both dipole and quadrupole mechanisms are analyzed as only the latter afford a good explanation of why fan noise is pressure ratio dependent at constant wheel rpm. The input parameters needed are a description of the inlet distortion far upstream of the rotor and of the inlet turbulence and steady-state design parameters of the isolated rotor. Preliminary ideas of the author have been expanded in several directions by the author's colleagues at GE, especially in the direction of experimental verification of the analysis. This study will emphasize such comparisons.
Quiet airplane paradox and its theoretical explanation
Authors: Griffith E. D. , Revell J. D.
Published: October 2005

Farfield noise radiated from low-tip-speed propellers on the YO-3A quiet observation aircraft and measured in flyover tests exhibited unexpected levels and trends that have been called the “quiet airplane paradox.” Levels of rotational propeller noise were found to be higher than predicted by conventional axisymmetric theory, and as propeller tip speed was decreased below a given value, at constant thrust, both harmonic and broad-band noise levels actually increased. Thus a “bucket” was formed in the SPL vs tip speed curve. In addition, the harmonic character of the flyover propeller noise was markedly different than that observed in static propeller tests. These data were declassified in 1973, and a program was conducted to investigate the paradoxical experimeutal results and to develop a theoretical explanation. The theoretical study considered propeller blade aerodynamics, nonuniform inflow through the propeller, chordwise blade loading, and, finally, propeller blade wake/wing interaction. It was concluded that the principal explanation of the paradox lies with the non-uniformity of inflow through the propeller disk causing circumferential variations of blade loads. The blade wake/wing interaction rated second in important. [Original experiments with the YO-3A aircraft were supported by the Army and this research program was supported by the Air Force.]
Microstructure in mammalian kidney tissue as seen with the acoustic microscope
Authors: Fields S. I. , Kessler L. W. , Dunn F.
Published: October 2005

Current techniques in acoustic microscopy have been employed to examine the structure of tissue on a microscopic basis. Acoustic micrographs of unstained specimens of mouse kidney tissue were produced at frequencies of 100 and 220 MHz, with resolutions of 20 and 9 μm, respectively. The acoustically revealed structures were studied with reference to the established microanatomy. Preliminary results show high-contrast details corresponding to the boundaries of connective tissue supporting elements of the nephron. Various regions of the kidney, specifically, the cortex and the three medullary layers, can be differentiated acoustically. The acoustic visualization of structures at these frequencies is considered to result from scattering at connective tissue interfaces, i.e., acoustic impedance discontinuities, rather than from intrinsic absorption in the microstructures of the tissue.
Ultrasonically induced tissue damage under elevated ambient pressure
Authors: Veranth J. A. , Csuri J. O. , Lele P. P.
Published: October 2005

Knowledge of the mechanism of tissue damage by ultrasound of low-megahertz frequency is essential for the prediction of safe dosage levels for diagnostic and theraputic use. Both ultrasonically induced heating and cavitation can cause or contribute to damage in organized tissues. Separating the effects of the two mechanisms is difficult, since temperature rise and cavitation are concurrent; also, synergism between thermal and mechanical effects has been proposed. A series of experiments was conducted under sufficiently high ambient pressures to suppress cavitation. Since all absorbed energy is dissipated as heat, elevated ambient pressure would not affect a thermal mechanism. Cat brain was irradiated with focused ultrasound at ambient pressures up to 40 atm and the acoustic emission was measured to assess the presence and magnitude of cavitation. The relation between ultrasonic dosage and the extent of damage in the cat brain under elevated ambient pressures was observed. The results are discussed in terms of the proposed mechanisms. [This work was supported in part by USPHS Grant No. NIH-5-P01-HL14322.]
Threshold dips and cubic difference tone perception
Authors: Sachs R. M. , Wightman F. L.
Published: October 2005

Recently, Smoorenburg [J. Acoust. Soc. Am. 52, 615–632 (1972)] measured the audibility of the cubic difference tone (CDT), 2f1 − ;f2, in one listener who had a 40-dB dip in his audiogram at 2.5 kHz. Smoorenburg reported that with the primary tones (f1,f2) in the dip region, the CDT could not be heard unless the primaries were at a high enough level to be audible. He also observed that, in most cases, when the primary tone frequencies were adjusted to produce a CDT in the dip region, the CDT could not be heard. The purpose of the present study was to reexamine CDT perception in several listeners exhibiting threshold dips in the more typical 4-kHz region. The best beats and cancellation methods as well as Houtgast's pulsation threshold technique were used to measure the strength of the CDT in two frequency regions: (A) f2 at the notch frequency, f1 and CDT in a lower-frequency region, and (B) CDT at the notch frequency, f1 and f2 in a higher-frequency region. In region A, no subject could hear the CDT unless both primary tones were above threshold. In region B, results were more variable. Data are presented which show how the strength of the CDT varies as a function of primary tone levels in both frequency regions. Results are in agreement with Smoorenburg's, and suggest that the defect causing the dip precedes the nonlinearity causing the CDT.
Nonmonotonic behavior of distortion product 2f1 − f2 in a nonlinear model of the basilar membrane
Authors: Hall J. L.
Published: October 2005

It has previously been reported [Smoorenburg, J. Acoust. Soc. Am. 52, 615 (1972)] that for some stimulus conditions the psychophysically observed distortion product 2f1 − f2 behaves nonmonotonically. As either the frequency or the intensity of the primary tones is changed, the amplitude of the distortion product goes through an abrupt null and the phase goes through a sudden shift. We have observed a similar effect in a non-linear model of the basilar membrane. The basilar membrane is modeled as a 175-section transmission line, and nonlinearities are introduced into the viscous damping term of each section [Hall, J. Acoust. Soc. Am. 53, 324 (1973); Kim, J. Acoust. Soc. Am. 53, 324 (1973)]. In the model, the nulls are caused by standing waves at frequency 2f1 − f2 produced by reflections from the basal end of the membrane. Primary-tone frequencies for which the nulls occur can be determined analytically [Schroeder, J. Acoust. Soc. Am. 53, 429 (1973)]. If the same mechanism is operative in humans, then psychophysical investigation of these nulls should provide information about mechanical properties of the basilar membrane.
Auditory nonlinearity: prediction and estimation of inaudible aural combination tones
Authors: Erdreich J. , Clack T. D.
Published: October 2005

According to Helmholtz's classic description, aural harmonics and combination tones arise from the same nonlinear process (i.e., x = a0 + a1p + a2p2 + ⋯ + anpn). This polynomial nonlinearity hypothesis predicts identical growth rates for difference tones and aural harmonics of equal order as well as independence from any frequency effects. To further evaluate its validity, estimates of second and third aural harmonics of 1000 Hz (f1) have been obtained from six normal-hearing listeners. Coefficients of the power series were computed and used to predict amplitudes of certain combination tones. Experimentally obtained estimates of the quadratic sum (fh + f1;fh/f1 = 1.2), the cubic sum (2f1 + fh;fh/f1 = 1.2 and 2fh + f1;fh/f1 = 1.6), and cubic difference tones (2fh − f1;fh/f1 = 1.6) compared well with predicted values. The exception is 2fh − f1, an inaudible cubic difference tone which was consistently about 25 dB above the other comparative distortion products. Growth rates of all distortion products including 2fh − f1 were consistent with the hypothesis. Frequency effects such as reliable amplitude differences for 2f1 + fh as fh changed from 1200 Hz to 1600 Hz were not found. Agreement between aural harmonic and combination tone amplitudes, accelerated growth rates of higher-order subjective tones, and lack of frequency dependence support the classic hypothesis of subjective tone generation. The discrepancy in the absolute amplitude of 2fn − f1 remains to be explained.
Auditory recognition of intonation patterns
Authors: Takefuta Yukio
Published: October 2005

Intonation is considered to be represented by a pitch pattern. This pattern, however, is not obtainable in a traditional psychophysical experiment. It can be obtained only in an acoustico-linguistic experiment, since physical parameters of speech signals are perceived in a special manner. Two methods can be considered for detecting the features used in the auditory recognition of intonation patterns: one is to collect all minimal contrasts in the language and find the smallest number of patterns necessary to distinguish all the contrasts; the other is to systematically transform the experimentally obtained patterns until a sufficiently large number of contrastive (not necessarily minimal) intonations are all distinguished. In such signals as intonation, which are extremely difficult to classify into minimal contrasts, the second method seems to be the only alternative. In this report, such a method of determining the auditorily perceived pattern of intonation is described. This study was conducted by simulating the auditory recognition of intonational signals by a computer. The simulated analysis included the extraction, normalization, and segmentation of the physical parameter, F0, and transformation and classification of processed F0 into intonation patterns.
Pitch and attention
Authors: Tumolo Richard S. , Thomas Ian B.
Published: October 2005

We have been investigating the ability of listeners to detect Morse-Code-like messages solely on the basis of pitch from a mixture of three such messages heard binaurally through headphones, Each message consists of tone bursts of a particular frequency having two “longs” (tone bursts of duration 400 msec) and two “shorts” (tone bursts of duration 200 msec) in various combinations. Silent intervals between bursts for a particular message invariably have durations of 100 msec. Tones are adjusted beforehand to have equal loudness if each were “on” solely and continuously. All messages have the same duration, Two basic variants of the experiment have been investigated so far. In the first, listerners receive no pitch cue and are asked to find the “middle” (or “low” or “high”) pitch message. In the second, listeners hear a pure tone of frequency equal to the desired message (pitch cue) prior to hearing the message mixture and are asked to determine the message of that pitch. Cues and/or messages can be heard as often as the subject desires. If all three messages have frequencies below roughly 1500 Hz but are well separated with respect to the critical band, then “getting the message” is easy, pitch cue or not, unless two of the frequencies are an octave apart. In that case, the pitch cue is essential for high recognition rates. If at least two of the constituent frequencies are above 1500 Hz, then “getting the message” is highly dependent on the pitch cue. [Work supported by NIH.]
Sensory and verbal coding strategies in subjects with absolute pitch
Authors: Siegel Jane A.
Published: October 2005

The performance of six absolute-pitch and six control subjects was examined in three studies involving recognition memory for tone frequency. When the standard and comparison were 1/10 semitone apart, absolute-pitch subjects reported using a sensory coding strategy and did not differ from the controls in overall performance or rate of forgetting. When the stimulus difference was 3/4 semitone, absolute-pitch subjects shifted to a verbal coding strategy, and their memory for pitch was significantly better than the controls. With a one-semitone difference, the absolute-pitch group showed no significant forgetting over a 15-sec retention interval filled with interference tones. These findings support the hypothesis that possessors of absolute pitch show superior pitch memory only when they can differentially label the stimuli with musical-note names.
Tone and pitch perception in Yoruba
Authors: Curtiss Susan , Lord Carol
Published: October 2005

One dichotic listening experiment studying hemispheric specialization for pitch in a linguistic context (Thai) (Van Lancker and Fromkin, 1973) found a right-ear advantage for words that are differentiated by tone only; in another study (Cantonese) (Benson, Smith, and Arreaga, 1973) no ear advantage was found for perception of tone in words. Both studies included contour tones, i.e., stimuli which involve pitch changes in time; however, it has been established that the left hemisphere is involved in temporal-order processing of auditory and visual stimuli (Cartoon and Nachson, 1971), and that subjects with left-hemisphere brain damage show impairment in processing temporally ordered auditory stimuli (Efron, 1963). Since the left hemisphere's sequence-processing role may be a factor in the processing of contour tones, a question remains regarding ear advantage in perception of purely level (i.e., noncontour) tones. Our study tests ear advantage in perception of level tones by speakers of Yoruba. Three sets of monosyllabic word pairs are presented dichotically: (1) pairs differing in tone only, (2) pairs differing in initial consonant only, and (3) a monosyllable presented on different musical pitches. Relative degree of hemispheric specialization is compared for each set.