bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of optically and piezoelectrically sensed acoustic emission signals
Authors: Kline Ronald A. , Green Robert E. , Harvey Palmer C.
Published: October 2005

The usual sensor for acoustic emission is the piezoelectric transducer. Although this transducer is readily available, reasonably inexpensive, and very sensitive to ultrasonic transients, it has several serious drawbacks as a transducer: It distorts the signals being measured, it exhibits resonances, it has limited bandwidth, it responds differently to surface acoustic waves and bulk waves (because of its large sensitive area), and its calibration is a matter of considerable uncertainty. Essentially, it is a qualitative transducer. Furthermore, it cannot measure local effects within a millimeter of an emission source, where the mechanisms causing the ultrasonic transient are presumably most clearly distinguishable. Optical transducers, on the other hand, have the great advantage of providing accurate, quantitative, highly localized information; they do not disturb the waves being measured and are not limited by frequency response.
The electroacoustic sensitivity of radially polarized ceramic cylinders as a function of frequency
Authors: Burt J. A.
Published: October 2005

The voltage response is derived for radially polarized piezoceramic cylinders when pressure is applied on the cylinder inside surface. Both static and oscillating pressures are considered. A 2.54 cm diameter cylinder of PZT-4 (Vernitron) material is used as a model in the frequency response which is calculated up to 10 MHz.
The application of broadband ultrasonic spectroscopy to the study of layered media
Authors: Haines N. F. , Bell J. C. , McIntyre P. J.
Published: October 2005

An investigation has been made of the frequency dependence of amplitude and phase information when broadband ultrasonic pulses, in the region 1–30 MHz, are reflected from layered targets. An on line computer performing Fourier analysis of sampled ultrasonic pulses allowed both amplitude and phase information to be studied. Layers of various acoustic impedances, velocities, and attenuation have been investigated, and in particular, layers of magnetite grown on mild steel. In all cases excellent agreement between experiment and theory has been achieved. The possible use of the techniques of deconvolution has also been considered for the measurement of the thickness of layers. The methods developed have found application in the problem of determining the thickness of a corrosion layer on the inside surface of a component where access can only be gained through the outer surface.
Natural frequencies of curved elastic arcs
Authors: Kudva N. J. , Nayfeh A. H. , Kamat M. P.
Published: October 2005

A perturbation analysis is presented for calculating the inextensional natural frequencies of curved elastic arcs. Variation of the radius of curvature along the arc length is accounted for by considering the curvature to be a perturbation from a constant curvature, and utilizing the method of strained parameters. Frequencies thus derived for hinged parabolic arcs demonstrate good agreement with finite element solutions. The analysis could easily be extended to determine the natural frequencies of noncircular curved plates and shells.
Edgetones versus pipetones
Authors: Elder S. A.
Published: October 2005

It is here argued that the commonly held view of organ pipe oscillation as pipe-controlled ’’edgetone’’ oscillation is misleading. Edge-related effects, being of higher multipole order than the pipe-related air motion, are inherently less efficient, and may be ignored in the presence of strong resonator coupling. It is proposed that the term edgetone or ’’jet-edge oscillation’’ be applied to a free jet-edge (or weakly coupled pipe) situation, while a normal resonant organ pipe oscillation should be referred to as ’’pipetone.’’
Sexual characteristics of preadolescent childrens’ voices
Authors: Bennett Suzanne , Weinberg Bernd
Published: October 2005

This investigation was undertaken to enlarge current understanding of the acoustic properties which influence the perception of maleness and femaleness in the voices of prepubertal children. Perceptual judgments of sexual identity were obtained in response to tape recordings of whispered and normally phonated vowels, normally spoken sentences, and sentences spoken in a monotonous fashion. Seventy-three children provided recordings. The four utterance types were chosen to experimentally manipulate selected physical properties of speech thought to exert an influence on listener judgments of sexual identity. The results of this work suggest that cues stemming from differences in vocal tract dimensions and/or articulatory behaviors provided the primary cues about the sexual identity of these preadolescent children. Although laryngeal source cues could have provided relevant information about the sex of a few children, this variable was felt to play a relatively minor role in the sex recognition process. New information was uncovered about the role certain suprasegmental factors play in the identification of child sex.
Complex wattmeter measurements in a reactive acoustic field
Authors: Stanton T. K. , Beyer R. T.
Published: October 2005

A wattmeter is described which is capable of measuring separately the real and imaginary parts of the complex acoustic intensity in water. A general expression for the complex intensity is derived and used to provide a basis for the experimental measurements. The instrument was tested for the case of a point source. The results show the real part of the intensity to decrease as 1/r2 from the source and the imaginary to decrease as 1/r3 as predicted by the theory.
The effect of bone conduction on the intensity independence of dichotic chords
Authors: Yund E. W. , Efron R. , Divenyi P. L.
Published: October 2005

The relative salience of the pitch components of a two-tone dichotic chord is invariant with respect to the relative intensity of the two tones over a wide range of interaural intensity differences [R. Efron and E. W. Yund, J. Acoust. Soc. Am. 889–898 (1976)]. According to a recently developed model, the range of intensity independence is limited by the bone-conducted energy from the more intense tone [E. W. Yund and R. Efron, J. Acoust. Soc. Am. 62, 607–617 (1977)]. The model predicts that a decrease in bone conduction such as the one achieved by using insertion earphones, must increase the range of intensity independence. This prediction is confirmed.
Array gain of a broadside vertical line array in shallow water
Authors: Buckingham M. J.
Published: October 2005

An analysis is presented of the signal gain and the noise gain of a broadside vertical line array operating in a shallow-water channel with one lossy boundary. The signal gain is derived by representing the signal field as a sum of normal modes, and is shown to lie between N and 2N provided the number of modes in the field is less than (h/2L); and a simple criterion is derived for the maximum useful aperture of the array, beyond which no significant improvement in signal gain can be achieved. The derivation of the noise gain is based on the assumption that, over the aperture of the array, the noise field can be represented as a linear superposition of plane waves. On introducing the high-N approximation it is shown that, for arbitrary anisotropy, the noise gain is the reciprocal of a series of Bernoulli polynomials, the coefficient of each being determined by the directional density function of the noise. A discussion of the noise gain in isotropic noise and in three different anisotropic noise fields illustrates the utility of the approximate method for determining the noise gain.
Acoustic shadow zones in the horizontal plane
Authors: Harrison C. H.
Published: October 2005

Horizontal bending of long range underwater sound rays can be caused by repeated reflection from a sloping sea bed, and in a previous paper the author used ray invariants to calculate the horizontal projection of ray paths analytically. At low frequencies ray-mode equivalence imposes restrictions on the initial ray elevation angles, which in turn cause shadowing in the horizontal plane. Analytical ray paths and shadow zone boundaries are derived here in a simple way for some bottom topographies of interest including a wedge, a ridge, and a seamount. Horizontal shadow zones have important implications for hydrophones near the edge of the continental shelf because the shadows are well developed in shallow water and may easily extend into deep water.
Measurements of the temporal, spatial, and frequency stability of an underwater acoustic channel
Authors: Jobst W. , Dominijanni L.
Published: October 2005

Measurements of the stability of an underwater acoustic channel were made at long range (500 km) and relatively low acoustic frequency (206 Hz). The source depth and depth of the two receiving hydrophones were carefully chosen to limit the number of totally refracted acoustic paths. In addition, a discrete spectrum coded waveform was transmitted to allow time domain resolution of refracted and reflected arrivals. The results show considerably less channel time spreading than is predicted by recent theoretical models, and indicate that coherence bandwidths of 100 Hz are obtainable with proper source and receiver geometry. Received pulses wander systematically with changes in acoustic path length strongly influenced by energy at the frequency of the semidiurnal tide. The spatial coherence of signals propagated to two receivers separated by 250 m indicates that acoustic paths are similarly modulated by ocean processes with frequencies below the Brunt–Väisälä internal wave cut-off. Above the Brunt–Väisälä frequency, coherence is small indicating that processes with space scales much less than 250 m are responsible for path length fluctuations.
Super-resolution imaging system using waves with a limited frequency bandwidth
Authors: Ikeda Osamu , Sato Takuso , Suzuki Katsumichi
Published: October 2005

A super-resolution imaging method in connection with spectral synthesis is presented. The basic idea is to apply the sampling theorem to the heterodyned signal in the frequency domain and to estimate the data obtainable within a wide frequency range through matrix calculation, using the data obtained within a narrow bandwidth. The principle and some practical problems in the use of this method, such as the required number of the raw data and the effect of additive noise in the received signal, are described theoretically, and the effectiveness of super-resolution in range is demonstrated by using the results of computer simulation and laboratory experiment.
On the dynamic behavior of poroelastic materials
Authors: Wijesinghe A. M. , Kingsbury H. B.
Published: October 2005

Poroelastic materials are two phase material systems consisting of a porous linear elastic solid phase filled with a Newtonian viscous fluid. Analytical investigations have demonstrated that poroelastic structures can, depending on loading and geometry, exhibit elastic response or the creep and relaxation response associated with various models of linear viscoelastic materials. This paper examines the dynamic response to harmonic loading of a disk or slab of poroelastic material. Biot’s dynamic theory for deformable poroelastic media is applied to derive expressions for a complex modulus of the material in terms of poroelastic material coefficients. Both a quasistatic analysis, accounting for dissipation but neglecting inertia, and a dynamic analysis, which neglects dissipation, are presented. For a choice of poroelastic coefficients roughly appropriate to water filled sandstone or compact bone, the poroelastic layer is shown to exhibit rubber-to-glass transition in a low-frequency range. Resonance effects arising due to inertia are shown to take place at much higher frequencies than those at which changes due to dissipation take place.
Effects of early multiple reflections on subjective preference judgments of music sound fields
Authors: Ando Y. , Gottlob D.
Published: October 2005

Subjective preference tests were performed in synthetic sound fields with multiple early reflections. The results show that sound fields with a smaller degree of the interaural cross-correlation are always preferred. The most appropriate time delay of the strongest reflection depends on the autocorrelation function of the music signal and the total amplitude of the reflections. The optimal values may be taken into account for the design of concert halls.
Passive ranging errors due to receiving hydrophone position uncertainty
Authors: Carter G. Clifford
Published: October 2005

A mathematical comparison of wavefront-curvature and triangulation methods for passive ranging is presented. The similarities of the two methods, coupled with an extension of previous triangulation results, are used to predict ranging errors due to any positional uncertainty in the receiving hydrophones. These results are compared with other theoretical results and shown to agree well. For a triple-aperture array, the relative range error is well approximated by twice the product of two terms. The first term is the ratio of the range of the source to the effective interarray separation. The second term is the ratio of the standard deviation of the midarray perturbation to the interarray separation.
Lateralization of tonal signals which have neither onsets nor offsets
Authors: Hafter E. R. , Dye R. H. , Gilkey R. H.
Published: October 2005

In order to ascertain the special importance of binaural cues conveyed in the transient portions of dichotic signals, thresholds for interaural differences of time (Δt) and intensity (ΔI) were studied using stimuli whose onsets and offsets were masked. Intense noise was used to mask all portions of each experimental trial except for the two intervals of a two-interval, forced-choice detection task. During those intervals, the noise was turned off with decay–rise times of 10 ms. What remained were tones whose interaural phase or intensity was different for intervals one and two. Performance was compared to control conditions which used unmasked gated sinusoids. For longer durations, detection without onsets and offsets was about as good as that with no masker. For the shorter signals, detection without transients was poorer than with standard lateralization, but this is attributed to forward and backward masking which reduced the effective durations of those stimuli. The ability to detect interaural differences of time with the onsets and offsets masked was extended to conditions in which the decay times of the noise were 100 ms. Performance here was slightly worse, but not by so much as to change the basic result. This is interpreted as showing that performance with the faster decay–rise times was not a product of momentary undershoots in neural following, but depended, rather, upon a true encoding of the interaural information in the stimulus fine-structure.
A stereo-fiberscope with a magnetic interlens bridge for laryngeal observation
Authors: Fujimura O. , Baer T. , Niimi S.
Published: October 2005

A stereoscopic method of observation of the larynx and the pharynx during speech utterances has been devised, making use of fiber-optic cables and a magnetic bridge. The cables are inserted via the subject’s nostrils. The bridge makes the two objective lenses at the tips of the cables abut within the pharynx near the uvula, and the two images viewed through the separate lenses at the prescribed mutual distance are recorded on each frame of a 16-mm film side by side for computer processing of the three-dimensional data.
Strain gauge transduction of lip and jaw motion in the midsagittal plane: Refinement of a prototype system
Authors: Muller Eric M. , Abbs James H.
Published: October 2005

This paper describes the design refinements made in an earlier prototype system for transducing lip and jaw movements in the midsagittal plane. Major improvements over the prototype system included: reduced transducer loading, improved two-dimensional separation and resolution, elimination of possible artifacts due to lateral-medial or rotational movement, electrical isolation of the subject from the transducer, increased capability to transduce movements of children as well as adults, and an accessory instrument for orienting the transducers with reference to defined anatomical planes.
Acoustical analysis of the Boehm flute
Authors: Coltman John W.
Published: October 2005

Experimental determinations were made of the acoustic reactance of finger holes and keys typical of the modern C flute, and of the column-lengthening properties of the cavities formed by the closed keys. Formulas are given by which these parameters can be used to predict the effect of variations in finger holes. Calculations of resonance frequencies are made for a flute, and compared with the intonation as played. The transmission line analogy is used to calculate standing-wave distributions, wall losses and radiation losses for some notes in the third register.
Direct ultrasonic velocity measurements of mammalian collagen threads
Authors: Goss S. A. , O’Brien W. D.
Published: October 2005

Direct ultrasonic velocity measurements have been made in fresh collagen threads from mammalian tendon at a frequency of 100 MHz using the scanning laser acoustic microscope. Tendon is of interest since it contains an unusually large amount of collagen, a structural protein thought to be important to the echographic visualizability of normal and pathologic tissues in medical ultrasound. Results indicate that ultrasonic velocity is appreciably higher than in soft tissues, lending support to the view that tendon, as well as collagen, is markedly distinguished ultrasonically from other biological tissues.
On the aerodynamic noise source in circular saws
Authors: Cho H. S. , Mote C. D.
Published: October 2005

The character of the dominant aerodynamic noise source for rotating rigid circular saws is concluded to be represented by a point dipole model. The source strength is directly dependent upon Reynold’s number and saw design. A theoretical model is presented for prediction of the farfield noise. Experimental measurement of the fluctuating lift force on particular tooth models was used to identify the dipole source and a hot wire anemometer, rotating with the saw, measured the tooth wake. The theoretical predictions of dipole noise dependence upon parameter variation are generally consistent with literature noise data.
The existence of Stoneley waves as a loss mechanism in plane wave reflection problems
Authors: Hawker Kenneth E.
Published: October 2005

In a previous paper [’’Influence of Stoneley waves on plane-wave reflection coefficients: Characteristics of bottom reflection loss,’’ K. E. Hawker, J. Acoust. Soc. Am. 64, 548 (1978)] it was shown that for certain configurations of layered fluids overlying a rigid (solid) substrate, the reflection loss would display narrow peaks of significant amplitude. It was suggested in that paper that these peaks were due to excitation of Stoneley waves at the fluid–solid interface. In the present paper this association is made more precise and definite. Through an extension of the classical theory of Stoneley waves to the case of inhomogeneous media, it is shown that the angles at which the reflection-loss peaks occur are precisely those angles for which the horizontal component of phase velocity in the fluid equals the Stoneley wave phase velocity. In addition, the near independence of the reflection loss peaks on frequency is explained quantitatively.
The response of a cavity backed panel to external airborne excitation: A general analysis
Authors: Guy R. W.
Published: October 2005

A multimodal analysis is made of the response of a cavity-backed panel to an arbitrarily defined external forcing function. A general solution is developed which details the systems ’’characteristic functions.’’ These functions are examined and their properties detailed, in particular, the evaluation of poles and their representation in partial fraction form is achieved. Any external forcing function, provided that it is susceptible to finite Fourier cosine transformation with respect to spatial dependence and Laplace transformation with respect to temporal history, may be applied to the ’’characteristic functions’’ to determine the panel response. The general analysis is applied to the specific case of constant external pressure loading and the derived expressions are favorably compared with, and represent a further development of an accepted contemporary work.
Psychophysical tuning curves: Restricting the listening band to the signal region
Authors: Johnson-Davies David , Patterson Roy D.
Published: October 2005

Psychophysical tuning curves were generated for three listeners by determining threshold for a 2.0-kHz sinusoid fixed at 20 dB SPL as a function of the level and frequency of a narrow-band noise masker. Then the listening band available to the listeners was restricted by inserting a low-level (?18 dB SPL) stationary masker at 1.8 kHz. The stationary masker alone did not mask the signal but it depressed the upper branch of the tuning curve by as much as 20 dB. The lower branch of the curve was essentially unaffected. When the low-level stationary masker was repositioned to 2.2 kHz the effect was reversed; the lower branch of the tuning curve was depressed but the upper branch was little changed. The combined results show that the thresholds on the two branches of the tuning curve are based on information in different frequency regions and indicate that even at reasonably low signal levels the traditional psychophysical tuning curve overestimates the frequency selectivity of the ear.
Hybrid ray-mode formulation of ducted propagation
Authors: Felsen L. B. , Ishihara T.
Published: October 2005

High-frequency propagation in waveguides or ducts can be formulated in terms of a guided mode or a ray expansion. When the duct is very wide, the excessively large number of modes or rays often necessitates the truncation of the resulting mode or ray series. This paper examines the truncation problem and shows that a hybrid formulation, in terms of a properly chosen number of rays and guided modes, can account for the remainder field in either case. The hybrid field representation has appealing physical content in that a few of the lowest modes account for the collective behavior of rays with many reflections, while a few of the lower-order rays account for the collective behavior of the higher-order guided modes. Other field representations involving rays, modes, a canonical integral, a continuous spectrum, and nearfield perturbation are also examined. Numerical comparisons for a specific example show the utility and range of validity of these alternative representations.
Stop consonant discrimination based on human audition
Authors: Searle C. L. , Jacobson J. Zachary , Rayment S. G.
Published: October 2005

A system for discrimination of stop consonants has been designed on the basis of studies of auditory physiology and psychophysics. The system consists of a one-third octave filter bank as an approximation to auditory tuning curves, a bank of high speed, wide dynamic range envelope detectors, a logarithmic amplifier, and a digital computer for analysis and display. Features, chosen on the basis of psychophysical experiments, are then abstracted, and fed to a discriminant analysis program which decides on the most probable phoneme. Discrimination accuracy of about 77% for stop consonants in initial position has been achieved, with a 15-speaker data set.
Numerical method for calculating input impedances of the oboe
Authors: Plitnik George R. , Strong William J.
Published: October 2005

The purpose of this study was to investigate a numerical method for obtaining input impedances of double-reed instruments—the oboe in particular. To this end, the physical dimensions of an oboe were used to compute its input impedance as a function of frequency for several different fingerings. The numerically computed input impendances of the oboe were compared to experimentally measured curves with good agreement resulting in most cases. The reasons for the observed discrepancies are discussed and suggestions for improving the ageement between the predicted and experimental frequencies are given.
Mechanical properties of single motor units in speech musculature
Authors: MacNeilage Peter F. , Sussman Harvey M. , Westbury John R. , Powers Randall K.
Published: October 2005

Electromyograms were recorded from three subjects during steady, low-rate discharge of single motor units of anterior belly of digastric, accompanying maintenance of isometric tension. The overall tension developed in muscles subserving mandibular depression was recorded from a force tansducer situated inferior to the mandibular symphysis. The force transducer output from the 90 ms period immediately following each of the several hundred discharges of a motor unit was averaged to obtain a characteristic tension curve for the contractile response (twitch) of that unit. Peak twitch tensions and time taken to develop peak tension (contraction time) were recorded for 27 motor units. The obtained median twitch tension of 0.26 g and contraction time of 29 ms were compared with values obtained for units in other human muscles and in animal muscles. As expected from the size principle, later recruited units possessed higher twitch tensions. Contrary to some statements of the size principle, contraction times were not shorter in later recruited units. Data on muscles elevating the mandible were also evaluated.
Amplitude density of a finite amplitude wave
Authors: Webster Don A. , Blackstock David T.
Published: October 2005

A theoretical analysis of the effect of nonlinear propagation distortion on the amplitude density of a sample noise signal in a lossless medium is given. It is found that under certain general conditions the amplitude density prior to shock formation is unaffected by the distortion. However, it is demonstrated qualitatively that the amplitude density changes after shock formation.
Larger ear replica for KEMAR manikin
Authors: Maxwell R. J. , Burkhard M. D.
Published: October 2005

A larger external ear replica for use on a KEMAR manikin has been developed to meet the needs of hearing aid designers and other manikin users. The ear was selected from the 24 subject sample used by Burkhard and Sachs (1975) as the basis for the original ear development. Ear dimensions were chosen to be two standard deviations larger than the existing ear. A mirroring technique was used to give right and left ears with nearly identical properties. Responses of the manikin with the new ears are given and compared with responses with the original ears.
Propagation in a liquid layer lying over a liquid half-space (Pekeris cut)
Authors: Bucker Homer P.
Published: October 2005

Sound propagation in a uniform duct can be represented as a sum of normal modes plus a branch line integral(s) contribution. In the case of a homogeneous liquid layer lying over a homogeneous liquid half-space the complex modes exhibit a complicated migration as frequency is changed. In the case of a Pekeris branch cut this can result in the mode changing from a proper to an improper Riemann sheet or vice versa. This is accompanied by a discontinuous change in the branch line integral. This paper examines the migration of a typical mode and discusses a simple algorithm for calculating the Pekeris branch line integral.
Response of plate to nonstationary random load
Authors: Ahmadi G. , Satter M. A.
Published: October 2005

The response of a rectangular plate subjected to nonstationary random load is studied. The general expressions for the autocorrelation and the mean square displacement are derived and discussed. Similar study was carried out for the stress components. The random excitation is then assumed to be a modulated white noise or narrow-band process. It is shown that when the damping coefficient is small, simple approximate expressions can be obtained for the variances of the lateral displacement as well as the stress components. Several examples using a simply supported plate are presented.
A method to simulate noises from a machine system under the progress of abnormality
Authors: Sato Takuso , Sasaki Kimio , Toyoda Naokuni
Published: October 2005

To simulate the noises from machine systems under the progress of abnormality, a simple stochastic model is proposed. It consists of two complementary variable gain amplifiers, which are excited by the actual noises under a normal state and a fairly deep abnormal state, respectively, and an adder for them to get the final output. As an example to show very faint changes of state, the noise from a gear train is simulated. The measured power spectral and bispectral characteristics indicate the similarity of the generated signal to the actual noise and show the effectiveness of the method.
Response to ’’Theory of optimal plane diffusors’’ [J. Acoust. Soc. Am. 65, 1334 (1979)]
Authors: Schroeder M. R. , Gerlach R. E. , Steingrube A. , Strube H. W.
Published: October 2005

Sound-diffusing wall and ceiling structures based on quadratic-residue sequences have wide angular reflection patterns with equal amplitudes—if calculated according to the well-known ’’Kirchhoff approximation’’ in diffraction theory. A ’’local impedance’’ treatment of the diffraction problem (Berkhout et al.) gives uneven reflection amplitudes. However, the standard deviation of the energy fluxes in different directions is usually quite small (typically a few decibels). An even more accurate ’’mode-matching’’ theory yields substantially similar results, in good agreement with measurements on actual sound-diffusing surfaces.
The augmented passive radiator: A workable speaker system
Authors: Clarke Thomas L.
Published: October 2005

The augmented passive radiator is a workable speaker system which has a larger efficiency constant than other direct radiator systems.
The response of a fluid-filled piezoceramic cylinder to pressure generated by an axial laser pulse
Authors: Burt J. A.
Published: October 2005

A closed-form, analytic solution is given for the pressure generated at the inside wall of a piezoceramic cylinder by a laser-excited fluid contained in it. The pressure then generates a voltage across the electroded inner and outer surfaces of the radially poled cylinder. The experimental response when a 1 J laser beam traverses the cylinder axis is presented for the case when the cylinder is water filled and when filled with methanol. The analysis reveals that the dominant frequency in the response is not that arising from simple considerations of the cylinder geometry, but depends on a complex of factors including the natural frequencies due to cylinder geometry, the natural frequencies arising from cylinder expansion by the fluid and the natural resonant frequencies of the piezoceramic cylinder. The phenomenon of beats is essential in determining the overall response.
Arrival times of scattered ultrasonic signals from a solid inclusion in an elastic material
Authors: Rhodes Deborah J. , Sachse Wolfgang
Published: October 2005

Measurements are reported of the arrival times of broadband ultrasonic pulses scattered by a circular, cylindrical, solid inclusion imbedded in a matrix whose longitudinal wave speed is lower than that of the scatterer. The wavenumber-inclusion radius product ka, ranges from approximately 1 to 15. The matrix materials are water, polyester, and brass; and the inclusion materials are copper, quartz, stainless steel, and tungsten. A strong, scattered pulse, corresponding to a circumferential wave on the cylinder is observed for cs≳cP, where cs is the shear wave speed of the inclusion material and cP is the longitudinal wave speed of the matrix material. These observations are in agreement with results published by others. The experiments also show that the pulse corresponding to the circumferential wave is not observed for cs<cP. It is shown how the approximate diameter and longitudinal wave speed of the inclusion can be determined from measurement of the arrival times of the scattered pulses.
Finite amplitude two-dimensional waves in a rectangular duct induced by arbitrary periodic excitation
Authors: Ginsberg Jerry H.
Published: October 2005

The nonlinear two-dimensional acoustic waves that occur within a rectangular duct of semi-infinite length as the result of periodic excitation are determined by an asymptotic method. A regular perturbation expansion is employed to obtain the velocity potential as a solution of a nonlinear wave equation. Uniformly valid expressions for the particle velocity components and pressure are then derived with the aid of a coordinate straining transformation that features both spatial coordinates. The response is found to be formed from the linear superposition of nondispersive groups of propagating nonlinear waves, each of which corresponds in linear theory to a fundamental wave and all overtones having the same phase speed, together with exponentially decaying standing waves resulting from excitations below the cutoff frequency. Typical spatial profiles and temporal responses for one nondispersive group are discussed in an example.
A formula for resonance frequencies of a whistler nozzle
Authors: Hasan M. A. Z. , Hussain A. K. M. F.
Published: October 2005

The self-sustained oscillation of a circular jet coupled with a whistler nozzle has been investigated experimentally for a range of the controlling parameters, viz., nozzle length, collar length, step height, and jet speed. It is shown that these parameters are related through an empirical formula which can be used to predict pure-tone frequencies at which a whistler nozzle can induce controlled excitation of a circular jet.
Critical distance measurement of rooms from the sound energy spectral response
Authors: Jetzt J. J.
Published: October 2005

At any point in an ideal room, the standard deviation of the acoustic energy spectral response from its mean is shown to be a function of the direct-to-reverberant acoustic energy ratio at that point. This function yields a method for measuring critical distance, at which these energies are equal, which is more powerful than the traditional total energy response method. The new method relies on measurements made close to the sound source; it does not assume or require that the reverberant energy be uniform in the room. Calculations made for computer-simulated rooms show that the method is valid for rooms having a wide range of average absorption coefficient. In some cases, results can be obtained with the new method where the total energy method fails.
An analysis of triangulation ranging using beta density angular errors
Authors: Hilliard E. J. , Pinkos R. F.
Published: October 2005

Traditional analysis of the triangulation ranging problem utilizes Gaussian distributed angular error models. Since in the true physical phenomena, the angular errors are bounded, the analysis in this paper employs a beta-type density function with finite limits to more realistically model the angular measurement errors. The resultant estimated range density function, the mean range, and standard deviation, together with the associated maximum positive and negative angular error limits over which these statistics are valid, are determined. While the standard deviation for the range error increases approximately four times for a doubling of the exact range, this approximation is shown to be valid for only a finite band of exact range values.
Rhythmic and segmental perception are not independent
Authors: Martin James G.
Published: October 2005

The 36 basic ’’sentences’’ in the experiment were six-syllable nonsense sequences of the form DAS a LAS a GAS a or a DAS a BAS a LAS. Either (a) one vowel in the sentence was lengthened or shortened by about 50, 90, or 130 ms by computer-editing routines, or (b) the sentence was left intact (as spoken). The resulting perceptual impression after the vowel change was a change of tempo within the sentence. Vowel changes occurred systematically throughout the sentences, in one of syllables one through five. Reaction time (RT) was recorded to assigned target segments /b, d, or g/ in one of syllables one through six, and RT was compared to targets in tempo-changed versus intact sentences (these were acoustically identical except for the distorted vowel). The listeners responded to over 2000 versions of the sentences. The results were: (a) Tempo changes generally increased segment target RT. (b) Tempo-change effects were ubiquitous; for instance, vowel changes in the first syllable increased RT to targets in later syllables, and the reach of effects spanned four syllables. Both vowel shortening and lengthening increased target RT. (c) Effects attributed to processing time decreased, whereas effects attributed to stimulus expectancy increased, with time into the sentence. (d) Tempo-change effects persisted throughout the experiment despite practice and familiarity with stimuli. The conclusions were: (a) The effects of time distortion of the stimulus on target RT were produced mainly by changes in stimulus-induced expectancy, not changes in processing time. (b) The expected input to perception is the acoustically intact utterance in both its rhythmic and segmental aspects; these aspects are not perceived independently.
Detection versus discrimination of brief tones by cats with auditory cortex lesions
Authors: Cranford Jerry L.
Published: October 2005

In recent years, a number of investigators have provided evidence that the auditory cortex has a critical role in both the detection and discrimination of brief sounds. Dogs and humans with lesions of the neocortical auditory centers have been reported to exhibit significantly elevated detection thresholds for signals shorter than 16 ms in duration. In tests of frequency discrimination, the same subjects also exhibited severe deficits whenever tonal signals were less than 20–40 ms in length. In the present report, we present evidence that cats with auditory cortex lesions exhibit a dissociation between their ability to detect versus discriminate brief tones. Operated cats, while exhibiting normal difference limens for 1-kHz tones of 100-ms duration, have significantly elevated limens for discriminating tones of 8- and 2-ms duration. With further testing, the same operated cats can be shown to have normal absolute thresholds for detecting brief tones.
A mechanical analog to parallel flow stability as modeled by the Orr–Sommerfeld equation
Authors: Garrelick Joel M.
Published: October 2005

A mechanical analog to the Orr–Sommerfeld equation is presented in the form of a vibrating elastic plate resting on a locally reacting foundation of specific form. In the analog, Reynolds number becomes the cube of the slenderness ratio of the plate. Some aspects of the solutions to the Orr–Sommerfeld equation, as it is applied to boundary layer transition, are interpreted in terms of the analogous system.
The acoustic background noise of a liquid metal fast breeder reactor
Authors: Carey W. M.
Published: October 2005

Absolute measuements of the background noise in the upper plenum of an operating liquid metal fast breeder reactor (LMFBR), the Experimental Breeder Reactor II (EBR-II), have been performed over a 17-month period. The temporal spectral density characteristics of the data were found to be representative of a weakly stationary random process. Cross-power spectral density analyses established that below 5 kHz the spectral characteristics were dominated by pump-induced structural vibrations and the excitation of acoustic resonances in the upper plenum volume. The spectral characteristic of the data above 5 kHz were found to be consistent with sonic power generation at the reactor subassembly exit nozzles and the statistical response of the cylindrical plenum volume. The production of sound by the exit flow from the subassembly nozzles was found to produce a broadband pressure level of 16l dB re 1 μPa, corresponding to an acoustic efficiency of 6×10−8. This compares favorably with a theoretical (Lighthill) value of 159 dB re 1 μPa and an acoustic efficiency of 9×10−9 for a submerged water jet. These measurements show that the noise field in the plenum of a fast reactor is a weakly stationary random process with identifiable sources of sound.
The use of stratification to improve the design efficiency of community noise surveys
Authors: Glaser E. R. , Silver C. A.
Published: October 2005

A community noise survey was executed in the Philadelphia area. Temporal and spatial stratification was utilized in both the design and analysis of the monitoring. Measurements of the energy equivalent noise level Leq, the Lx values (noise level exceeded x% of the time), the noise pollution level LNP, and traffic noise index (TNI) were obtained. Analysis of variance was applied to the data, revealing large differences between the variances of several noise descriptors at most levels of stratification. Recommendations are advanced for: (a) stratification of noise monitoring; (b) use of a presurvey to guide stratification; (c) analysis of partial results to improve monitoring efficiency; and (d) measurements of background noise level. It is suggested that neighborhood-averaged L99 may be a good predictor for neighborhood-averaged Leq.
The effect of high-pass noise on the scalp-recorded frequency following response (FFR) in humans and cats
Authors: Gardi John , Merzenich Michael
Published: October 2005

Low-frequency tone-burst stimuli were used to elicit the scalp-recorded frequency following response (FFR) from normal-hearing adult human subjects and anesthetized adult cats. High-pass masking stimuli (with variable low-frequency cutoffs) were presented simultaneously with these tone-burst stimuli. For a small group of human subjects, analogous psychophysical masking curves (threshold shift and binaural loudness balance) were conducted so that physiologically derived curves (masked FFR) could be related to these psychophysically derived curves. Among the results were the following: (1) human and cat FFR masking curves were very similar; (2) at moderate to high probe-tone stimulus levels, the amplitude of the FFR masked with a 2-kHz cutoff was approximately 70% to 75% of the amplitude of the unmasked FFR; (3) at probe-tone stimulus levels near FFR threshold, the amplitude of the FFR masked with cutoffs of 1.5, 1.8, and 2.0 kHz was equivalent to the amplitude of the unmasked FFR; (4) a sizable fraction (10% to 30%) of the masked FFR amplitude remained during masking by stimuli with low cutoffs (about 900 Hz or less); (5) the latency of the FFR recorded from humans and cats (using probe-tone levels of 80-dB peak SPL or greater) increased systematically at lower and lower masker cutoffs; (6) at lower probe-tone levels, FFR latency recorded from cats did not increase using masker cutoffs of 2.0, 1.8, and 1.5 kHz, but with the use of lower-frequency cutoffs, latency values obtained from the cat data showed systematic increases similar to those previously cited for humans; and (7) FFR masking curves did not correspond with psychophysically derived curves except at low probe-tone stimulus intensities. These results suggest that although the area of stimulation (along the basilar membrane) at stimulus frequencies and intensities at which the FFR is commonly generated is broad, the most prominent input arises from the apical half and third of the cochlea (below 2 kHz) for man and cat, respectively. Except for the lower stimulus levels employed in the animal experiments, the responding area was apparently not restricted to a narrow band around the 500-Hz signal. These results are consistent with the interpretation that as the probe-tone level is raised, a greater percentage of FFR amplitude will be accounted for by neurons tuned to high frequencies. Also, as the masking signal level is raised, these results are consistent with the interpretation that complications inherent in simultaneous masking procedures (specifically, masking by low-frequency components in the acoustic stimulus and remote masking by combination components generated by the masker) do not allow masking paradigms to provide a precise definition of the cochlear sites of FFR generation along the basilar membrane.
An indirect estimate of auditory-frequency selectivity from acoustic-reflex measurements
Authors: Stelmachowicz Patricia G. , Lilly David J.
Published: October 2005

Changes in the magnitude of the acoustic reflex were used to estimate frequency resolution of the auditory system for five human subjects. Acoustic-reflex adaptation (decay) was produced by presenting a 2000-Hz sinusoid (adaptor) for 25 s. The spread of this adaptation to adjacent (test) frequencies was determined by evaluating the effect of the adaptor upon the magnitude of the acoustic reflex. The mean data from the experiment suggest that recovery from acoustic-reflex adaptation is more rapid for test frequencies below the adaptor frequency than for test frequencies above the adaptor. When these data are compared to tone-on-tone masking functions, qualitative similarities emerge between frequency selectivity observed psychophysically and those observed during measurement of acoustic-reflex activity.
Detectability of a pulsed tone in the presence of a masker with time-varying interaural correlation
Authors: Grantham D. Wesley , Wightman Frederic L.
Published: October 2005

Detectability of a filtered probe tone (250, 500, or 1000 Hz) was measured in the presence of a narrow-band Gaussian masker centered at the signal frequency. The signal was interaurally phase-reversed (Sπ), and the masker’s interaural correlation varied sinusoidally between +1.00 (N0) and −1.00 (Nπ) at a variable rate (fm=0–4 Hz). The signal was presented at various points on the masker’s modulation cycle. For 0-Hz modulation (fixed interaural correlation) signal threshold decreased monotonically as the masker’s interaural correlation was changed from −1.00 to +1.00 (by a total of about 20, 16, and 8 dB, respectively, for 250-, 500-, and 1000-Hz signals). For fm≳0 the function relating signal threshold to the masker’s interaural correlation at the moment of signal presentation became progressively flatter with increasing fm for all signal frequencies. For fm=4 Hz the function was flat; there was no measurable effect of masker interaural correlation on signal detectability. Estimates of minimum binaural integration time based on these data ranged from 44–243 ms, supporting previous studies which have noted the binaural system’s relative insensitivity to dynamic stimulation. Additionally, the estimated time constants were approximately twice as large at 250 Hz as at 500 Hz, indicating observers could follow binaural fluctuations better at 500 Hz. The time-constant estimates at 1000 Hz were not sufficiently reliable to permit comparisons with the lower-frequency data.
Virtual modes and mode amplitudes near cutoff
Authors: Tindle C. T.
Published: October 2005

For a Pekeris model the contribution of the continuous mode integral is analyzed in terms of virtual modes with particular attention to cases with a discrete mode just below or just above cutoff. There is a steady change of amplitude as a virtual mode changes into a discrete mode. The mode amplitudes decay with range and analytic approximations valid in most practical situations are obtained.