bluuebunny/crossref_metadata_2025 huggingface dataset:
Relation of the loudness function to the intensity characteristic of the ear
Authors: Hellman W. S. , Hellman Rhona P.
Published: October 2005

A representation of the pure−tone loudness function given by Ψ = xϑF (x), where x is the ratio of stimulus to threshold intensity, is discussed. The form of F (x) is obtained from the empirical loudness curves at 1000 and 250 Hz. The structure of F (x) is shown to be in quantitative agreement with known steady−state driven firing rate activity of eighth−nerve units. We suggest that F (x) is proportional to the driven firing rate function RD(x) of the auditory sensory receptor. A specific choice is made for the algebraic form of RD(x) by identifying it with the driven rate function in a sensory receptor model proposed recently by Zwislocki. Within the model, a three−parameter fit to the loudness function is obtained. It is shown that similar results can be obtained for vibrotaction.

Subject Classification: 65.35, 65.50.
Systematic error in some methods of reverse correlation
Authors: Wilson J. P. , Evans E. F.
Published: October 2005

Two methods of triggered correlation using an averager were tested on several types of filter network. Under certain conditions systematic differences were found between the reverse correlograms and the directly measured impulse responses of the filters. The basis of this error would appear to be that threshold events are not always sampled randomly in these methods.

Subject Classification: 65.20, 65.35.
Forced vibration of the damped bilinear hysteretic oscillator
Authors: Masri S. F.
Published: October 2005

An exact solution is presented for the steady−state motion of a sinusoidally excited single−degree−of−freedom system exhibiting bilinear hysteresis and subjected to viscous damping that may be different in the ’’elastic’’ region from the ’’yielded’’ region.

Subject Classification: 40.20.
Elastic waves in free plates
Authors: Vrba J. , Haering R. R.
Published: October 2005

We have investigated the dispersion curves of free waves in free plates. We have shown that for certain conditions a simple exact solution is possible, since incident shear (SV) waves are decoupled from the transmitted longitudinal (P) wave (and vice versa). The concept of phase decoupling yields a useful description for the construction of approximate dispersion curves in terms of certain decoupled modes M1−M4. The validity of various approximations based on these modes is discussed. The fomulation may be readily extended to anisotropic and to active plates.

Subject Classification: 40.24.
Directivity of truck noise in the normal plane
Authors: Commins Daniel E.
Published: October 2005

Measurements have been performed of the sound pressure levels of highway noise sources, including trucks, with an array of microphones in the plane perpendicular to the direction of motion. The results show that highway sources exhibit quasi−omnidirectionality, when described in terms of A−weighted levels, at angles up to 45° above the horizontal independently of the type of vehicle or of the type of exhaust. For trucks there is limited evidence of a weak distortion of the directivity pattern of the radiated noise which increases with the number of wheels at high speed. One−third−octave−band spectral analysis at angles between 6° and 45° from the horizontal do not reveal a significant variation in the spectrum from one angle to another. For the purpose of highway noise prediction, it appears reasonable to assume that the noise radiated from conventional vehicles, including trucks, is omnidirectional.

Subject Classification: 50.50, 50.25.
Prediction of transmission loss in mufflers by the finite−element method
Authors: Young Cheng−I James , Crocker Malcolm J.
Published: October 2005

A numerical technique based on the finite−element method has been developed for analyzing the performance of systems of acoustic elements including expansion chambers in mufflers. The theories developed are, firstly, the variational formulation of the acoustic field existing in the system and, secondly, the finite−element approximate solutions of the variational problems. The predictions of transmission loss are then made by forming the equivalent acoustic four−terminal transmission network in which the acoustic four−pole constants are calculated from the finite−element method. As used, the finite−element approach is perfectly general and may be applied to any system component with arbitrary boundary geometry provided this may be realized by an assembly of rectangular elements. The method is applied to simple expansion chamber models because the results are tractable and theoretical results from acoustic filter theory are available for comparison purposes. The comparison brings out an important fact: the accuracy of the prediction of transmission loss implies that the variational formulation and finite−element approximations are adequately applicable to a number of practical applications.

Subject Classification: 50.40; 20.40.
Nonlinear internal waves in the atmosphere
Authors: Cho H. R. , Liu C. H. , Yeh K. C.
Published: October 2005

Nonlinear dispersive effects on the propagation of atmospheric internal waves are investigated. The finite amplitude buoyancy oscillation is analyzed to obtain an amplitude−dependent oscillation frequency. A nonlinear dispersion relation for finite−amplitude internal waves is derived. Its relation to the nonlinear buoyancy oscillation is discussed. The nonlinesr dispersion relation is then used to study the stability of finite−amplitude modulated internal wave trains. It is found that, for certain modulations, wave trains propagating in certain directions may become unstable.

Subject Classification: 28.20.
Effect of voiced speech parameters on the intelligibility of PB words
Authors: Agrawal Arun , Lin Wen C.
Published: October 2005

The voiced/unvoiced regions of PB words are segmented on the basis of the energy in time segments. It is shown that the energy parameter works quite well and better than zero crossings rate (ZCR) for this segmentation. The real poles and formants of the voiced speech production model are obtained by solving a polynomial whose coefficients are determined by Prony’s or covariance formulation of linear prediction. The effect of these poles and formants on the intelligibility is investigated by using zero filters to suppress them adaptively. With this approach, one or more formants or real poles are removed from the natural speech without affecting anything else. The processed words were presented to listeners using an on−line speech intelligibility measurement system. The results indicated that the suppression of real poles and third and fourth formants did not degrade intelligibility, while the suppression of first and second formants lowered the average intelligibility scores by 7.6% and 27.6%, respectively.

Subject Classification: 70.30.
Measurement of the glottal waveform
Authors: Sondhi Man Mohan
Published: October 2005

The glottal volume flow is usually estimated by inverse−filtering the speech wave, by taking a motion picture of the vocal−cord vibration, or by a variety of other methods that estimate the size of the glottal opening. We present a much simpler alternative based on the following idea: The effect of the vocal−tract resonances on the glottal pulse is considerably reduced by speaking into a reflectionless uniform tube. If, in addition, the tract is held in a neutral position, the effect is almost entirely eliminated and the glottal waveform may be recorded by a microphone in the uniform tube. Some examples are presented of glottal pulses recorded in this manner. The new method is compared to the ones available heretofore, and some potential uses of the method are suggested.

Subject Classification: 70.60.
Mach bands in auditory masking revisited
Authors: Small Arnold M.
Published: October 2005

Further data are provided in an attempt to replicate the Carterette, Friedman, and Lovell [J. Acoust. Soc. Am. 45, 986−998 (1969)] report of lateral inhibitions in the auditory system. These data show no evidence of this effect.

Subject Classification: 65.58. 65.75.
Quadrature sampling error formula
Authors: Persons C. E.
Published: October 2005

It is known that the Grace−Pitt interpolation formula [O. D. Grace and S. P. tt, ’’Quadrature Sampling of High Frequency Waveforms,’’ J. Acoust. Soc. Am. 44, 1453−1454 (L) (1968)] allows an exact reconstruction of a high−frequency bandlimited waveform when the sampling rate is an integer submultiple of the center frequency. The problem addressed here is the determination of the ratio of the power in the error bands to the power in the signal band when the formula is used for any sampling frequency.

Subject Classification: 60.XX.
Mechanism for aural pulse compression in mammals
Authors: Altes R. A.
Published: October 2005

The pulse compression phenomenon is examined in terms of nonlinear phase functions in the frequency domain. The concepts of neural inhibition and critical bandwidth filtering are then employed to show that a logarithmic spectral phase function can be easily synthesized in the mammalian auditory system. Pulse compression of linear period−modulated signals, such as those used by some bats, can therefore be simply implemented at a peripheral level of the aural processor.

Subject Classification: 65.35, 65.42.
Binaural pinna disparity: another auditory localization cue
Authors: Searle C. L. , Braida L. D. , Cuddy D. R. , Davis M. F.
Published: October 2005

Physical measurements of the transfer function from a free−field sound source to a microphone in the subject’s ear canal indicate that there are two independent localization cues generated by the pinna. For sound sources in the vertical median plane, there is a systematic change in the frequency response as a function of elevation angle, and a disparity between the left−ear and right−ear responses which also changes systematically with elevation angle. Independent psychophysical measurements indicate that these pinna cues are detectable by subjects, and both are used by subjects in vertical localization tasks.

Subject Classification: 65.62, 65.75.
Excitation of surface elastic waves in a piezoelectric layered structure
Authors: Ponamgi S. R. , Tuan Hang−Sheng
Published: October 2005

The excitation of Rayleigh surface waves by an interdigital transducer (IDT) on a piezoelectric layered structure has been studied in this paper. The surface wave velocity, optimum finger width, and number of fingers for maximum bandwidth for the IDT have been calculated for several values of the product (ks) of wavenumber and layer thickness. The frequency response and equivalent circuit of the IDT have been determined. Numerical examples are also presented and discussed.

Subject Classification: 20.15.
Vibration and wave propagation in ribbed plates
Authors: Rumerman M. L.
Published: October 2005

A formalism for handling problems of wave propagation and forced vibration in ribbed plates is presented. A general solution is obtained for the forced vibration of an infinite thin plate, periodically stiffened by identical, uniform ribs. The ribs are idealized as parallel line attachments capable of exerting line forces and line moments upon the plate, and the magnitudes of these forces and moments are related to the motion of the plate through the impedances of the ribs and plate. The assumption of an externally applied pressure excitation, which varies harmonically in time and in the plane of the plate, permits an explicit solution, and the principle of superposition is then used to construct the solution to an arbitrary excitation. By setting the amplitude of the harmonic excitation equal to zero, an equation for the free modes of the ribbed plate is derived.

Subject Classification: 20.15.
Time and frequency analyses of auditory signal detection
Authors: Ahumada Al , Marken Richard , Sandusky Arthur
Published: October 2005

Observers rated 500−msec bursts of wide−band Gaussian noise for presence or absence of a 100−msec, 500−Hz signal tone. The tone was present on half of the 400 trials and was centered in the noise bursts. Bandwidth and integration time estimates were found for each observer by correlating the observer ratings with the output of energy detectors of various bandwidths (20, 40, 100, 250 Hz) and integration times (50, 100, 300, 500 msec) to find the best correlating energy detector. The results, computed separately for signal (SN) and no signal (N) trials, indicate a bandwidth of 40 Hz and an integration time of 100 or 300 msec fit best on both SN and N trials. Energy variations in 25 50−Hz by 100−msec segments of the noise were correlated with the observer ratings and showed negative correlations in frequency and time intervals immediately surrounding the signal region on SN trials, but not on N trials. The results suggest observer monitor detectors sensitive to temporal and spectral changes in the energy of the noise bursts, not just the absolute level of the output of a simple filter−integrator energy detector. The N trial results are accounted for by assuming that the observer is looking for the same pattern of temporal and spectral changes as on SN trials, but is uncertain as to the exact location of the signal tone.

Subject Classification: 65.58, 65.35.
Influence of middle−ear muscle contraction on pure−tone suprathreshold loudness judgments
Authors: Morgan Donald E. , Dirks Donald D.
Published: October 2005

Some effects of middle−ear muscle (MEM) contraction on TTS and suprathreshold loudness judgments have been assessed in three experiments. Experiment I was designed to demonstrate the effect of MEM contraction on TTS while in Experiments II and III the influence of MEM contraction on the loudness of suprathreshold pure−tone stimuli was measured. In Experiment I, MEM contraction decreased the effective level of a high−intensity TTS−inducing stimulus reaching the cochlea. In Experiments II and III signal paradigms were chosen to reduce or eliminate the effects of binaural loudness summation, and contralateral remote and backward masking effects, and to maximize the influence of MEM contraction. Results of the loudness judgments indicated no effect of binaural interaction, whereas the MEM contraction affected the loudness of pure tones only when the stimuli were low frequencye (250, 500 Hz) and high intensity (≳100 dB SPL). The results further imply that at high intensity levels there was an interaction between the effects of the intensity of the loudness−judgment stimulus and the intensity of the reflex−inducing stimulus. That is, when the reflex was induced the effect on loudness increased as the intensity of the loudness−judgment stimulus was raised; likewise, when the loudness−judgment stimulus was maintained at a constant sound−pressure level but the intensity of the reflex−inducing stimulus was increased, the effect on loudness increased.

Subject Classification: 65.50, 65.22, 65.24.
Reaction time procedure for measurement of hearing. II. Threshold functions
Authors: Pfingst Bryan E. , Hienz Robert , Miller Josef
Published: October 2005

The reaction−time (RT) procedure applied to the measurement of suprathreshold functions in the preceding paper may also be used to measure threshold. This paper examines threshold contours measured by the RT procedure in human and monkey subjects with normal and impaired hearing. In the human subjects, thresholds obtained using the RT procedure closely paralleled those obtained in the clinic but were an average of 2.7 dB lower; RT thresholds were an average of 5 dB above thresholds obtained in a forced−choice procedure. Thresholds obtained from monkey subjects paralleled the normal human contours within the human frequency range of hearing, but were slightly higher at frequencies below 4 kHz and lower at frequencies above 4 kHz. The monkeys’ hearing extended approximately 11/4 octave above the humans’. Thresholds measured using the RT procedure in human and monkey subjects agreed well with thresholds previously reported in the literature. The effects of sound presentation and calibration procedures on the shape and position of the threshold contours are examined in an appendix.

Subject Classification: 65.50, 65.64, 65.75; 85.24.
Audotory intensity discrimination with bursts of reproducible noise
Authors: Raab David H. , Goldberg Israel A.
Published: October 2005

Auditory−intensity discrimination was investigated using gated bursts of reproducible noise. Weber fractions were determined at a number of energy levels with stimuli that differed in intensity, duration, and bandwidth. Weber’s law was approximated in all cases. In addition, discriminability was found to be somewhat dependent on burst duration and relatively independent of noise bandwidth; threshold signal−to−noise ratios improved when duration was increased from 10 to 100 msec, but not when bandwidth was increased from 500 to 5000 Hz. The data were compared with the results of a second experiment in which the stimuli were random—rather than pseudorandom—noises. Finally, the results of both experiments were compared with predictions about intensity discrimination derived from two theoretical models: (1) a Poisson−counting mechanism and (2) an energy detector incorporating additive internal noise.

Subject Classification: 65.35, 65.58.
Control of pharyngeal cavity size for English voiced and voiceless stops
Authors: Bell−Berti Fredericka
Published: October 2005

This study reports on pharyngeal cavity size change mechanisms associated with voiced−voiceless stop contrast in English. Electromyographic recordings were obtained from pharyngeal and infrahyoid muscles of three speakers, using bipolar, hooked−wire electrodes. The EMG potentials were sampled and averaged under computer control. The utterances sampled were 27 pairs of nonsense disyllables that contrasted only in the voicing of one stop consonant. All the English stop cognate pairs were included. Two modes of expanding the pharynx for voiced stops are proposed, each applying to a different group of muscles; an ’’active’’ mode, requiring increased muscle activity to expand the pharynx; and a ’’passive’’ mode, requiring suppression of muscle activity to expand the pharynx. The data reveal different patterns of use of the two expansion modes for the three subjects. The results are discussed in terms of current phonological theory.

Subject Classification: 70.20.
Considerations for the detection of acoustic emission waves in thin plates
Authors: Egle D. M. , Brown A. E.
Published: October 2005

A series of simulated acoustic emission experiments in thin plates and bars conducted to assess the effects of structural geometry on the detection of emission is described. It is shown that the structure introduces peaks in the received signal spectra corresponding to thickness resonances that may be estimated from Lamb wave theory. Spectra of acoustic emission signals from a thin−walled pressure vessel show a peak at the frequency corresponding to the lowest symmetric plate mode. It is concluded that a significant portion of the energy detected by a surface contact transducer on a thin−walled structure is concentrated at these resonances and should be accounted for in choosing a detection system.

Subject Classification: 35.10, 35.80.
Model for ultrasonic field analysis in solids
Authors: Rose Joseph L. , Meyer Paul A.
Published: October 2005

In this paper a theoretical model is presented that can be used to evaluate analytically ultrasonic transducer longitudinal wave−generation characteristics in homogeneous isotropic solids. Comparisons with fluid−type solutions are also outlined. A continuous wave solution is determined first, from which particle displacement, particle velocity, and stress solutions for arbitrary pulse shapes are obtained. The ultrasonic field distributions resulting from several basic pulse shapes are presented along with the results of an experimentally obtained distribution. Nearfield and beam angle of divergence for pulse output transducers are also discussed. In addition to developing data for ultrasonic field analysis in solids, the equations developed can be used for obtaining solutions to many other ultrasonics problems. For example, it now becomes possible to develop equations that can analyze the resulting stress and particle velocity distribution in a multilayer structure for materials subjected to either normal beam incidence or angle beam incidence. The work may also be extended to include many aspects of ultrasonic field measurement analysis for flaw characterization work.

Subject Classification: 35.65; 20.50.
Transfer matrix approach to elastodynamics of layered media
Authors: Bahar Leon Y.
Published: October 2005

A transfer matrix approach is developed to determine the dynamic response of a layered elastic medium, loaded by arbitrary time−dependent tractions on the boundaries of the finite medium.

Subject Classification: 40.20; 20.15, 40.24.
Acoustic emission: some applications of Lamb’s problem
Authors: Breckenridge Franklin R. , Tschiegg Carl E. , Greenspan Martin
Published: October 2005

A method for obtaining the signatures (waveforms) of certain acoustic emission events has been developed. The waveform is that at the source, free of contamination by ringing of the specimen, apparatus, and transducer. The technique is based on the comparison of two signals at the transducer, one from the event in question and one from an artificial event of known waveform. The apparatus is also adapted to the calibration of transducers in a certain sense. The configurations of source (real or simulated acoustic−emission event) and receiving transducer correspond to those of some special cases of Lamb’s problem. As a byproduct, the results may be of some interest to seismologists.

Subject Classification: 40.42; 35.54, 35.80, 35.68; 40.50; 85.44.
Wave propagation in two−layered piezoelectric plates
Authors: Cheng N. C. , Sun C. T.
Published: October 2005

Wave propagation and thickness vibrations in two−layered piezoelectric plates are investigated by the three−dimensional theory of piezoelectricity and approximate theories. Piezoelectric materials of hexagonal symmetry are considered. The sixfold axes of the materials are assumed to be parallel or perpendicular to the plate. Dispersion curves and frequencies for thickness vibrations are presented. The electromechanical coupling effect is examined and
Parametric array in air
Authors: Bennett Mary Beth , Blackstock David T.
Published: October 2005

An experimental investigation of the parametric array in air was conducted using a circular piston transducer which produced spherically spreading, collinear, primary beams at frequencies of 18.6 and 23.6 kHz. Since source levels were not strong (about 110 dB re 0.0002 μbar at 1 ft), the 5−kHz difference frequency signal generated by the parametric array was relatively weak. Because of space limitations, all measurements were made in the nearfield of the array. Spurious difference frequency signals resulting from intermodulation distortion in the receiving system were suppressed by judicious choice of electronic components and by the addition of an acoustical filter in front of the microphone. The classic properties of the parametric array were observed. The 5−kHz beam was narrow, and no minor lobes were evident. The propagation curve first increased with increasing range, reached a broad maximum, and then gradually decreased. Theoretical predictions were based on a perturbation solution of Burgers’ equation and on the integral solution of the inhomogeneous wave equation. Comparison of measured results with these predictions conclusively demonstrated the existence of the parametric array in air. Beam patterns and propagation data obtained for the second−harmonic and sum−frequency signals also confirmed theoretical predictions.

Subject Classification: 25.35.
Measurement of the sound speed in bottom layers
Authors: Stickler D. C.
Published: October 2005

In many applications of underwater acoustics, the ocean bottom is adequately characterized by a critical angle and a density. An estimate of the sound speed in the bottom is obtained by seismic refraction measurements (i.e., measurements of arrival time) or bottom−reflection measurements. In this paper, the theoretical basis is presented for an alternate technique that, it is hoped, will simplify the determination of the critical angle(s) associated with high−speed bottom layers. The technique requires the measurement of the normal component of the specific acoustic impedance at the ocean−bottom interface. As a function of incidence angle, this impedance function displays a strong peak near the critical angle. The precise location depends in a predictable manner on the location of the source, the source frequency, and the sound speed in the bottom. This technique exploits this dependence to obtain an estimate of the sound speed in the bottom.

Subject Classification: 30.25, 30.20.
Vibration of simply supported rectangular and square plates to which lumped masses and dynamic vibration absorbers are attached
Authors: Snowdon J. C.
Published: October 2005

The forced vibration of internally damped rectangular and square plates with simply supported boundaries is described theoretically. Calculations that illustrate the frequency dependence of the force transmissibility and driving−point impedance of the plates are presented. Both central and noncentral driving forces are considered, and the reduction in plate vibration that results from the attachment of central loading masses and dynamic vibration absorbers is demonstrated. The way in which the natural frequencies of the plates are moved to progressively lower frequencies as the loading mass is increased is explained and illustrated. Conditions of optimum tuning and damping for the dynamic absorbers are described and design data are tabulated. The resilient mounting of massive vibrating items on the plates is also considered. The vibrating items are supported via four damped springs that are symmetrically, but otherwise arbitrarily, located with respect to the plate centers. Advantageous reductions in force transmissibility are shown to result from judicious choice of spring locations that enable the excitation of several modes of plate vibration to be avoided.

Subject Classification: 40.24, 40.70.
Flexural and extensional vibrations of simply supported laminated rectangular plates
Authors: Thomas Charles R.
Published: October 2005

The author has previously derived an effective stiffness, velocity−corrected theory of laminated composite plates based upon a microstructure plate theory developed by C. T. Sun. This theory is now used to study the flexural and extensional vibrations of simply supported rectangular plates; comparisons will be made to similar results obtained from a reduced effective modulus or transversely isotropic plate theory. Free vibration frequency equations for simply supported edges are developed by passing solutions harmonic in both length and width through the differential equations while at the same time automatically satisfying the boundary conditions for simple supports. The variation of dimensionless frequency for such dimensionless variables is discussed and comparisons of the effective stiffness and effective modulus frequency results are made.

Subject Classification: 40.24.
Analysis of intermodulation in thickness−shear and trapped energy resonators
Authors: Tiersten H. F.
Published: October 2005

Electroelastic equations containing terms up to cubic in the small mechanical displacement field, but no higher than linear in the electric variables, are applied in the analysis of intermodulation in rotated Y−cut quartz oscillators. Both pure thickness−shear vibrators and essentially thickness−shear trapped energy resonators are treated. In the linear part of the analysis of the trapped energy resonator, a closed−form asymptotic expression for the frequency wavenumber dispersion relation for the fundamental and odd overtone thickness−shear branches near cutoff is obtained from the three−dimensional linear equations. Lumped parameter representations of the solutions, which are valid in the vicinity of a resonance, are presented for the linear and nonlinear portions of both the pure thickness−shear and trapped energy thickness−shear problems. The influence of the driving and detecting circuitry is included and, in particular, in each case the relation between the intermodulation and driving voltage is obtained. Application of this relation to a number of AT−cut quartz fundamental and third overtone trapped energy resonators yields good agreement with experiment and an estimate of the fourth−order elastic constant cE46666 for the AT−cut.

Subject Classification: 40.24, 40.20, 40.65; 85.32.
One− and two−frequency stimulation of tactile receptors: test of a model
Authors: Lopater Sanford , Hahn J. F.
Published: October 2005

Sinusoidal mechanical stimulation of Type I or Type II tactile single units in cat with single frequencies or with two mixed frequencies typically yields rate−intensity functions that include irregularities called ’’plateaus’’ and ’’dips.’’ These functions are predicted by a simple model of exponential sensitivity recovery after the occurrence of each impulse. This requires determination of only a resting threshold and a time constant for the unit.

Subject Classification: 65.70, 65.28.
Nonlinear distortion of ultrasonic waves in solids: approach of a stable backward sawtooth
Authors: Bains James A. , Breazeale M. A.
Published: October 2005

A large−amplitude pulsed ultrasonic wave at 30 MHz in fused silica is shown to generate second harmonics out of phase with those generated by the same ultrasonic wave in copper. This phase difference, interpreted as evidence of the approach of a backward sawtooth in fused silica, results from the fact that C111 is positive. In copper C111 is negative.

Subject Classification: 25.15, 25.20; 35.26.
Preliminary experiment to measure periodicities of large-scale ocean movements with acoustical signals
Authors: LaCasce E. O. , Beckerle J. C.
Published: October 2005

The acoustic signals received from explosive charges, fired at 1200-m depth and range of about 370 km from a hydrophone at 1200 m along three bearings only 10 ° apart, showed measurable differences for each bearing, although the thermocline sound-speed conditions were only slightly different. Since large-scale (300–500 km) internal baroclinic waves that propagate slowly westward in the ocean (period 50–200 days) perturb the thermocline to a much greater extent, a proposal to monitor with acoustic signals the period of thermocline oscillations caused by these waves is feasible.

Subject Classification: 30.20.
Author’s reply to ’’Comments on ’Analysis of class IV flextensional transducer by use of wave mechanics’ ’’ [Alan H. Lubell, J. Acoust. Soc. Am. 57, 968 (1975)]
Authors: Brigham Gerald A.
Published: October 2005

Subject Classification: 30.85.
Comments on ’’Eigenfrequencies of thin plates and layer potentials’’ [J. Vivoli and P. Filippi, J. Acoust. Soc. Am. 55, 562–567 (1974)]
Authors: Laura P. A. A.
Published: October 2005

It is suggested that, to a certain extent, the difference between theoretical and experimental values of the eigenfrequencies may be due to in-plane compressive stresses induced by the clamping device.

Subject Classification: 40.24.
Comments on (1) ’’Negative resistance mode of forced oscillations of a string,’’ [G. V. Anand, J. Acoust. Soc. Am. 54, 692–698 (1973)], (2) ’’Nonlinear resonance in stretched strings with viscous damping,’’ [G. V. Anand, J. Acoust. Soc. Am. 40, 1517–1528 (1966)]
Authors: Niranjan Parvathy
Published: October 2005

This letter points out certain errors in the mathematical formulations and physical interpretations in the above two articles.

Subject Classification: 40.22, 40.30.
Spherical averaging in a diffuse sound field
Authors: Chien Chi-Shing , Waterhouse Richard , Lubman David
Published: October 2005

In earlier work [Lubman et al., J. Acoust. Soc. Am. 53 650–659 (1973)], the effectiveness of continuous averaging over a surface in a diffuse sound field was compared with that of averaging the field values at discrete points. Here the comparison is extended to the case of continuous averaging over the surface and volume of a sphere. Formulas for the variance are obtained which show that the oversampling of correlated values increases the variance and yields a poorer average.

Subject Classification: 45.30; 50.25; 55.65; 60.20.
On the phase sensitivity of neurons of the cat’s auditory system
Authors: Kotelenko L. M. , Radionova E. A.
Published: October 2005

It is established that neurons from the cochlear nucleus and inferior colliculus in a great majority of cases show a pronounced reaction to the phase shift of one of the components in a two-tone complex signal. Diminution or augmentation of both the phasic and tonic discharge patterns may take place with the phase shift. The interrelation between frequencies and intensities of the components forming the complex signal are of importance for phase effects. There is a certain connection between the phase sensitivity of a neuron and inhibitory phenomena in its activity. The response area, on the contrary, seems to show no correlation with the neuron phase sensitivity.

Subject Classification: 65.44, 65.60.
Wave mechanics of boundary layer turbulence and noise
Authors: Landahl Marten T.
Published: October 2005

Recent advances in the understanding of the structure of boundary layer turbulence form the basis of a new conceptual model for the fluctuating velocity field. In this, an ’’active’’ mode of small-scale motion is coupled to a large-scale ’’passive’’ mode by aid of wave mechanical considerations. The small-scale motion originates during the intermittent ’’bursting’’ in the wall layer, leading to excitation of large-scale, damped, traveling shear waves. It is argued that the passive-wave-like mode gives the major contribution to the pseudosound, whereas the active bursting mode serves as the predominant source for the radiative noise. It is shown that the bursting mode gives rise to compact noise sources of both dipole and quadrupole type whose strengths are related to the turbulent shear stress production.

Subject Classification: 28.65; 50.55.
Study of acoustical fluctuations and ocean movements over one deep-ocean skip distance
Authors: Beckerle John C. , Broek Howard W. , LaCasce E. O.
Published: October 2005

This experiment studies the relationship between ocean movements and acoustical fluctuations southwest of Bermuda. Sound transmission over a single skip distance RSR path was maintained for a 33-h period. During the same time interval, ocean changes were monitored both at the source and near the second turning point of the sound-ray path. Some correlations were observed among some of these observations.

Subject Classification: 30.20; 28.60.
Helmholtz equation as an initial value problem with application to acoustic propagation
Authors: Fitzgerald R. M.
Published: October 2005

The parabolic equation method for the solution of the elliptic Helmholtz equation in a waveguide is analyzed in terms of normal modes and is found to involve two approximations. The approximate treatment of mode coupling becomes exact in the limit of negligible scattering into the backward hemisphere. The approximate treatment of mode propagation becomes exact in the limit of uncoupled, single-mode propagation. An estimate of the maximum range over which multimode propagation is accurately predicted is derived and a procedure is indicated whereby this maximum range can be increased. The result is a method, based on the parabolic equation approximation, whereby the Helmholtz equation can be solved as an initial value problem. The solution obtained approaches the exact solution in the limit of negligible backscatter. Application is considered to the problem of acoustic propagation in an ocean medium having range- and depth-dependent properties.

Subject Classification: 30.20.
Perturbation method for determining acoustic rays in a two-dimensional sound-speed medium
Authors: Jacobson M. J. , Siegmann W. L. , Weinberg N. L. , Clark J. G.
Published: October 2005

Sound speed is assumed to be a function of one horizontal coordinate and depth, and the medium is taken to be time independent during a sound transmission. Rays are assumed to lie in a vertical plane and a differential equation is given for their solution. A perturbation technique is presented for determining the rays, and is applied when the horizontal sound-speed variation is slow and much less than the vertical variation. Under appropriate assumptions, ray arcs above the SOFAR axis are found to be approximately elliptical, and a modified Snell’s law is given. The sound speed is taken to be bilinear with depth, with the upper portion pivoting with range, thereby approximating the effect of a single-frequency internal wave. Numerical examples of SOFAR ray geometry are presented and interpreted for various internal-wave phase angles and wavelengths. The sound speed near the source has a major effect on geometry, even at long range. However, variations in geometry along the ray suggest the importance of horizontal sound-speed changes over the entire propagation range.

Subject Classification: 30.20; 20.25.
Investigation of noise due to structural vibrations using a cross-correlation technique
Authors: Kumar Sudhir , Srivastava Narayan S.
Published: October 2005

In this paper are presented certain basic considerations of the dependence of noise on vibrations of surfaces. It deals with the problem of cross-correlating vibration and noise for a given system in a semireverberant environment, taking into account the effects of multiple sources of similar character, surface-area contributions, and reflections from the boundaries. Limitations of this approach and the standard error involved are given. Also indicated are expressions for the percentage contribution from the vibration of an individual component to the total noise pressure. The applicability of this method has been demonstrated in an investigation of structural vibration-generated noise of a high-powered diesel engine. It is concluded that the method can be applied successfully to investigate quantitatively the vibration-related noise of a complex machine or structural system, even in a semireverberant acoustic field and in the presence of multiple noise sources of similar character.

Subject Classification: 20.60; 40.20; 45.40.
Scattering by periodic surfaces
Authors: Waterman P. C.
Published: October 2005

Reflection behavior is examined for an interface having periodic height variation. Upon employing the Bloch theorem, in conjunction with the extended boundary condition, exact matrix equations are obtained for surface fields, as well as transmitted and reflected wave amplitudes. Tunneling considerations then lead to new energy constraints for problems of this type, in which propagating waves are coupled with evanescent modes. In the limit of surface corrugations shallow compared with impinging wavelength, analytic results are obtained confirming both the energy constraints and early computations by Rayleigh. Numerical results demonstrate the efficiency of the method.

Subject Classification: 20.30.
Normal-mode program with both the discrete and branch line contributions
Authors: Stickler D. C.
Published: October 2005

In a stratified ocean model, in which the sound speed and density become constant as the depth coordinate becomes infinite, the pressure field can be represented as a finite sum of modes plus an integral superposition of modes. This later contribution is given by an integration around a branch cut. In this analysis the sound-speed and density profiles are partitioned in layers such that in each layer the square of the index of refraction can be approximated by a straight line and the density by a constant. The profile is terminated in a high-speed isovelocity half space. Using this profile, it is possible to express the depth-dependent portion of the pressure field in terms of Airy functions. Evaluation of the modal and branch line contributions shows that the branch integral can contribute significantly to the pressure field over a range equal to at least one water depth and in some cases to many water depths.

Subject Classification: 30.20, 30.25.
Tone-burst rod apparatus and experiments
Authors: Hillery H. V.
Published: October 2005

A tone-burst rod analogous to a fluid-filled pulse tube has been developed for studying audible sound propagation in small solid objects. The apparatus consists of a long aluminum rod driven at one end with longitudinal tone bursts by a small loudspeaker. Instrumentation is provided for measuring the input force, the particle displacement at points along the rod, and the force propagated to the remote end. The interval between the arrival at a displacement probe of outgoing and echo tone bursts is used to determine the impedance of objects attached to the rod. Experiments show that the quality of the mechanical tone bursts is good, the longitudinal wave sound speed in aluminum is largely independent of static tension and frequency, and the acoustical energy propagated along a statically stressed rod departs from the stressed path onto unstressed branch rods.

Subject Classification: 40.85, 40.60.
Resonant vibrations of free cylinders and disks
Authors: Rasband S. N.
Published: October 2005

A complete solution is obtained for nonaxisymmetric resonant vibrations of a free cylinder or disk involving infinite sums. For axisymmetric longitudinal vibrations an alternative to previous solutions is included. In principle, the solutions satisfy exactly the stress-free boundary conditions , in contrast to the approximate bending-mode solutions due to Pickett or approximate solutions based on a small diameter/length ratio and small shearing stresses at the ends.

Subject Classification: 40.26, 40.24; 20.40.
Reverberation performance of phase-correlating sonars
Authors: Miller Norman B.
Published: October 2005

Processing gains against reverberation of phase-correlating sonar processors are compared with linear processors. Formulas are derived which predict reverberation test results obtained at low and moderately high sea states. The signals tested have time–bandwidth (TW) products in the range from 2 to 70, representing a variety of spectral shapes. Reverberation statistics data illustrate the variances of phase-correlator outputs as a function of Doppler. The phase correlator is a constant false-alarm device with maximum variance at zero Doppler of approximately (4 TWe)−1. A definition of the equivalent bandwidth We is derived for general signal spectral shapes and Doppler distributions in the medium. Phase-correlator response to reverberation depends upon signal bandwidth, integration time (pulse-length), and scatterer agitation. The measured Doppler spreading of reverberation is consistent with a normal distribution of scatterer velocities.

Subject Classification: 60.XX.
Gold and Pumphrey revisited, again
Authors: Green David M. , Wier Craig C. , Wightman Frederic L.
Published: October 2005

We investigated two periodic sequences: (1) identical sinusoidal pulses repeated regularly in time and (2) a sequence in which alternate pulses were inverted. These are the same stimuli used by Gold and Pumphrey. An analysis of the spectra of these two pulse trains suggested that the critical cue for the discrimination between them is a pitch difference. This pitch difference is the result of a difference in the ripple in the power spectra of the stimuli. This analysis provides an explanation of Gold and Pumphrey’s results that does not require the assumption of extemely narrow tuning, as made in their analysis.

Subject Classification: 65.35, 65.60, 65.75.
Ultrasonic absorption in aqueous solutions of chondroitin sulfate
Authors: O’Brien W. D.
Published: October 2005

Ultrasonic absorption and velocity were determined in aqueous solutions of chondroitin sulfate, the major sulfated mucopolysaccharide which is distributed throughout mammalian connective tissue, as a function of ultrasonic frequency (2.39–62.4 MHz), temperature (10 °–37 °C), and pH (0.85–13.3). A broad distribution of relaxation frequencies is required to describe the absorption spectra. The apparent activation energy is 3.7 kcal/mole at a concentration of 0.054 gm/cc and at neutral pH over the frequency range 8.87–50.5 MHz. It is suggested that the same absorption mechanism(s) may be responsible in aqueous solutions of chondroitin sulfate and dextran at neutral pH. The absorption peaks near pH 2.5 and 11.5 are typical of those observed for the proton-transfer mechanism.

Subject Classification: 80.20; 35.24.
Low-frequency sound attenuation in Baffin Bay
Authors: Mellen Robert H. , Browning David G. , Ross John M. , Merklinger Harold M.
Published: October 2005

At low frequences, the attenuation in underwater sound channels appears frequently to be dominated by forward scatter from large-scale inhomogeneities. Propagation-loss measurements were made in Baffin Bay in September 1972, when there was a relatively strong sound channel with the axis depth near 100 m. The attenuation above 200 Hz shows a frequency-independent scatter loss of 0.02 dB/kyd. Below 200 Hz, the loss falls off as f4, and thus suggests Rayleigh scatter from inhomogeneities with a scale size near 3 m.

Subject Classification: 30.20.
Cochlear neurons: frequency selectivity altered by conductance change in scala tympani
Authors: Johnstone J. R. , Johnstone B. M. , Yates G. K.
Published: October 2005

It has recently been reported that when perilymph is removed from scala tympani of guinea pig cochlea, the tuning curves of auditory nerve ganglion cells are seriously affected. This suggests that measurements of basilar membrane vibration under similar conditions may also be affected and not representative of the normal cochlea. Hence the discrepancy known to exist between neural tuning curves and basilar membrane tuning curves could be explained. We have confirmed the existence of this effect on neurons, but we present two kinds of evidence that it is not due to a basilar membrane change. First, the amount of perilymph which must be removed is greater than that routinely removed for mechanical measurements. Second, filling the scala with isotonic sucrose produces the same change. We conclude that removal of perilymph affects auditory neurons by changing the electrical properties of the cochlea and that the difference between tuning curves of the basilar membrane and ganglion cells is due not to a basilar membrane mechanical filter but to a second filter which acts at a later stage.

Subject Classification: 65.26, 65.28.
Effect of training on human underwater sound-localization ability
Authors: Stouffer James L. , Doherty E. Thomas , Hollien Harry
Published: October 2005

Experimental evidence has suggested that humans have a moderately functional sound-localization capability underwater; it appeared appropriate to determine if this ability could be improved by training. Signals of 1000 Hz and 25 pps were presented to the subjects at five angles (to the head). Four sets of stimuli were employed: the first and last sets constituted the pre- and post-tests, respectively, and the middle sets were a training procedure where subjects were informed of the actual source location after each presentation. The obtained scores demonstrated a significant increase in correct responses for the 1000-Hz signal; improvement for 25 pps was not as great and did not show statistical significance.

Subject Classification: 65.62; 30.85.
Comments on ’’Lateralization and the binaural masking-level difference’’ [G. B. Henning, J. Acoust. Soc. Am. 55, 1259–1263, (1974)]
Authors: Yost William A.
Published: October 2005

Henning [J. Acoust. Soc. Am. 55, 1259–1263 (1974)] showed that certain complex waveforms can be lateralized on the basis of interaural temporal differences when the energy in the waveforms is confined to high-frequency regions. However, when the high-frequency waveforms are presented in a background of noise, Henning showed that their detection is not dependent on interaural temporal differences. In the present demonstration experiment these high-frequency waveforms were not as easily lateralized with a noise background as were low-frequency stimuli. This result is consistent with an assumption that lateralization and binaural detection of complex waveforms are not essentially different.

Subject Classification: 65.62, 65.60, 65.58.