bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of leakage on the low-frequency calibration of supraaural headphones
Authors: Dillon H.
Published: October 2005

The general validity of calibration of supra-aural headphones by the method of an inserted probe tube is examined. In particular, the possibility of the probe tube affecting the seal between the headphone and the ear is considered. Experimental proof that this can occur is obtained by the use of a small microphone located within the ear canal. Furthermore, attention is drawn to the fact that single cavity couplers such as the NBS9A make no attempt to simulate the ear’s impedance and so a discrepancy between probe and coupler responses can be expected. In the light of these factors, some recommendations about the design of artificial ears are made.
Identification and discrimination of the relative onset time of two component tones: Implications for voicing perception in stops
Authors: Pisoni David B.
Published: October 2005

Experiments on the voiced–voiceless distinction in stop consonants have shown sharp and consistent labeling functions and categorical-like discrimination functions for synthetically produced speech stimuli differing in voice-onset time (VOT). Other research has found somewhat comparable results for young infants and chinchillas as well as cross-language differences in the perception of these same synthetic stimuli. In the present paper, four experiments were carried out to investigate a possible underlying basis of these seemingly diverse results. All of the experiments employed a set of nonspeech tonal stimuli that differed in the relative onset time of their components. In the first experiment identification and discrimination functions were obtained with these signals which showed strong evidence for categorical perception: the labeling functions were sharp and consistent, the discrimination functions showed peaks and troughs which were correlated with the labeling probabilities. Other experiments provided evidence foir the presence of three distinct categories along this nonspeech stimulus continuum which were separated by narrow regions of high discriminability. Based on these findings a general account of voicing perception for stops in initial position is proposed in terms of the discriminability of differences in the temporal order of the component events at onset.
Chart for estimating the efficiency of the broadband sound-power radiation by randomly vibrating pipe walls
Authors: Kennedy Warren C. , Young Frederick J.
Published: October 2005

A general curve is derived for the broadband radiation efficiency of a pipe where walls undergo random vibration. Once the mean amplitude of vibration of the pipe wall is known one can use this curve to predict the broadband sound power level radiated by the pipe.
Deep-ocean hydrophone array
Authors: Behrens John A. , Stokes Robert H.
Published: October 2005

A curved face hydrophone array has been designed, constructed, and tested for 20 000-ft-depth operations. A basic description of the hydrophone design, in which the hydrophone consists of a beamforming array of staves mounted on the circumference of a 20-in-diam. cylindrical housing, is presented. Since conventional pressure-release materials cannot be used in the construction, solutions to problems encountered, such as improper backing impedances for the individual elements and flexural waves genernated in the housing wall, will be briefly discussed. A presentation of the hydrophone frequency response and beam patterns shows that the transducer properties are insensitive to hydrostatic pressures as great as 1000 psi.
Analysis of source-motion effects on sound transmission in the deep ocean
Authors: Jacyna G. M. , Jacobson M. J.
Published: October 2005

Analytical methods are employed to obtain general results for the effect of cw source motion on the total acoustic field at a fixed receiver in the deep ocean. A bilinear sound-speed profile is used, a long range is assumed, and SOFAR rays are considered. Equations are developed which give amplitude and phase as functions of receiver time. Then, an investigation is made of stability regions, defined as range intervals for which all rays for given numbers of SOFAR-axis crossings arrive at the receiver. Three types of such regions are identified and examined. Amplitude and phase are linearized for a short source run, and novel numerical results for these quantities are presented. Approximate formulas for cumulative phase and Doppler-shift frequency are derived and discussed. Finally, an analytical description is presented for two mechanisms responsible for amplitude fades.
Simulation of acoustic phase modulation by a first-mode directional internal wave
Authors: Jobst W. , Zabalgogeazcoa X. , Weinberg N. L.
Published: October 2005

Acoustic propagation is simulated in the presence of a first-mode internal wave with a 90-km wavelength. For a shallow source, deep receiver, and a 450-km source-receiver separation, phase modulation of the multipath sum increased linearly with increasing acoustic frequency and with increasing internal-wave amplitude. Modulation was highly dependent upon internal-wave direction with the greatest modulation occurring when the internal-wave propagation direction was perpendicular to the acoustic path.
Vibrations of cross-supported viscoelastic plates
Authors: Nagaya Kosuke
Published: October 2005

This paper discusses a free- and a forced-vibration problem of elastically cross-supported rectangular viscoelastic plate with various edge conditions. A three-elements viscoelastic model is adopted in the analysis. The result for the viscoelastic plate is obtained from the correspondence principle by applying the Laplace transform to the constitutive equation for the viscoelastic materials and to the equation of motion in terms of unknown forces which are equivalent to reaction forces and resisting moments of the supports. Some numerical results are shown for steady-state and transient response problems.
Viscously damped dynamic absorbers of conventional and novel design
Authors: Nobile M. A. , Snowdon J. C.
Published: October 2005

The behavior of dynamic vibration absorbers of conventional and novel design has been investigated experimentally and found to compare closely with prediction. The dynamic absorbers were employed to suppress the transmissibility at resonance across a 1-df primary system. Initially considered was a dynamic absorber with a conventional mass-spring-dashpot configuration; the primary system was undamped. Subsequently considered were (1) so-called dual dynamic absorbers, and (2) a single, nominally undamped absorber, or two such absorbers, attached to the primary system after it had been damped heavily. The dual absorbers—a conventional viscously damped absorber used in parallel with a less massive undamped absorber—introduced a pronounced transmissibility trough without the appearance of unwanted ’’compensating’’ peaks at lower and higher frequencies. The attachment of a nominally undamped absorber to the heavily damped primary system also introduced a pronounced trough without giving rise to compensating peaks. Further, the attachment of two such absorbers introduced pronounced troughs at two frequencies that could be varied independently of one another. Thus, the novel absorber systems considered here behaved as mechanical ’’notch’’ filters, providing at specific ’’low’’ frequencies a high degree of isolation that other passive systems cannot duplicate without exhibiting a marked loss in isolation at neighboring frequencies.
Doppler effects for randomly moving scatterers and platforms
Authors: Middleton David
Published: October 2005

Previous studies of scattering from randomly moving media, interfaces (and platforms) generally do not provide an adequate or correct treatment of the ensuing Doppler effects. This has occured chiefly because of the failure to apply a suitably explicit Doppler analysis, which recognizes that the scattering elements act like randomly moving sources of (re-)radiation, with path delays which are critical functions of the dynamic geometry between the moving source (T), scattering element (S), and receiver (R), and which accordingly require appropriately modified Langevin equations (ensembles of propagation equations). The principal random Doppler (i.e., motional) effects are O (c−1) and appear as (space–time) random displacements about the equilibrium positions of the scatterers, thus producing phase modulations (or equivalent frequency modulations, proportional to velocity), with, however, the proper time delays of T,S,vis-à-visR. Not only have incorrect path delays been employed in most previous studies, but also an explicit Doppler analysis has been lacking, which further makes it impossible to include the effects of platform motion adequately. The present analysis remedies these defects and, in addition, provides many new results of interest for problems in underwater acoustics specifically here (under conditions of zero velocity gradients, ∇c=0). These include platform and scatterer Doppler effects, for the practical cases of small Dopplers and farfield operation; iteration procedures for these relations and high-order corrections, and conditions for their validity; finite aperture solutions; mono- and bistatic operation; deterministic velocity components, which generate scanning effects, attributable to this type of platform motion. Results for the approximate first- and second-order statistics of these Doppler phenomena needed in scattering analysis are also presented, for both cases of broadband- and narrow-band-injected signals. Particular attention is given to Doppler phenomena from moving wave surfaces. The treatment is generally canonical, however, in that all modes (surface, volume, and bottom) are included in the formal analysis, both from the viewpoint of a fixed reference system (in the motionless medium) and from the viewpoint of the observer on a moving platform.
Effects of temporal distribution of sound energy on temporary threshold shift produced by intermittent and varying noise exposures
Authors: Hétu Raymond , Trémoliéres Claude
Published: October 2005

Adequacy of industrial noise dosimetry based on the equal-energy assumption has been tested by measuring temporary threshold shifts (TTS) following nine temporal patterns of exposure to a broadband noise of identical cumulated sound energy: one steady-state conditions at 96 dBA and eight conditions with noise levels alternating periodically either between 99 and 45 dBA under intermittent exposures or between 98 and 93 dBA under varying noise exposures. Under these eight conditions, the noise levels were presented at their low and high levels every 0.5, 4, 16, or 32 min, depending upon the condition. Total exposure time was 128 min in all nine conditions. A group of nine subjects were exposed to intermittent and steady-state conditions; another group of ten subjects was submitted to varying noise and steady-state conditions. It was found that (a) amounts of TTS following steady-state noise were larger than those from any intermittent exposure, even after 125 min of recovery; (b) among the intermittent conditions, amounts of final TTS2 were a logarithmic function of the intermittency period; (c) equal amounts of TTS were obtained following the steady-state and the four varying noise exposures. These results imply that the equal-energy rule may provide an adequate index for the assessment of hazards to hearing from steady-state and varying noises but not from intermittent exposures. The protection afforded by the reference noise dose of 90 dBA for 8-h daily exposure and by the 5-dB time-intensity trading relationship are also discussed. It is concluded that current principles of noise dosimetry ignore the parameters of intermittent exposures that determine their potential danger to hearing.
Rotating tones and binaural beats
Authors: Perrott David R. , Musicant Alan D.
Published: October 2005

This study investigated rotating tones and binaural beats as a function of the frequency of the standard signal (f0) and the interaural frequency ratio (f1/f0). Both beats and rotating tones ’’disappear’’ as the frequency of the standard signal is increased. Using a 2AFC procedure, the upper limits for rotating tones and binaural beats were estimated to be 1170 and 1255 Hz, respectively. Rotating tones were observed with large interaural-frequency ratios and were observed almost exclusively with the perception of a single fused image. Binaural beats were obtained with smaller interaural-frequency ratios and nonfused images (a separate tone was heard at each ear). The present results suggest that binaural beats and binaural rotating tones may be mutually exclusive phenomenon, with the latter being dependent upon both the binaural capacity to fuse disparate signals and the peripheral auditory system’s capacity to code the temporal information in the signal’s microstructure.
Syntactic blocking of phonological rules in speech production
Authors: Cooper William E. , Lapointe Steven G. , Paccia Jeanne M.
Published: October 2005

The duration of a stressed syllable is shortened when it is immediately followed by an unstressed syllable. Previous work showed that this effect operates across word boundaries but may be blocked by the presence of an intervening syntactic boundary. It may be assumed that certain syntactic boundaries act as junctures in processing which prohibit look ahead for phonological rules normally operating across word boundaries. In three experiments, the blocking phenomenon has been tested for a variety of syntactic boundaries in phonetically matched sentences. The results for 11 speakers show that the shortening effect is blocked in the presence of a number of boundaries. No blocking effect was observed for two other weak boundaries. The difference between the strong and weak boundaries has been accounted for in terms of the structural property of branching depth. An alternative to the blocking notion, involving possible differences in phrase-final lengthening, is also considered.
Context-sensitive perception of naturally produced stop and fricative consonants by infants
Authors: Eilers Rebecca E.
Published: October 2005

In six separate experiments using controlled natural stimuli and a modification of the high-amplitude sucking paradigm, infants’ ability to perceive voicing differences in stop and fricative consonants in both prevocalic and postvocalic position was assessed. An attempt was also made to investigate the role of vowel duration as a supplemental cue to the difference between postvocalic voiced and voiceless consonants for infants. Results of a previous experiment by Trehub and Rabinovitch [Dev. Psycho. 6, 74–77 (1972)] indicate that infants have little difficulty perceiving the difference between the stop consonants [d] and [t] in prevocalic position. Present results indicate that infants discriminate postvocalic [d] and [t], even when vowel-duration cues are minimized in the vowel–consonant (VC) syllables. However, no evidence of discrimination was observed when durational differences were presented in the absence of voicing differences in consonants. In contrast, perception of the difference between the fricative consonants [s] and [z] could not be demonstrated either in consonant–vowel (CV) syllables or in VC syllables with vowel-duration cues minimized. Evidence of discrimination was obtained in VC syllables when the [s] and [z] stimuli differed in vowel duration, frication duration, formant-transition information, and voicing.
Real-ear threshold level comparisons between the Telephonics TDH-39 earphone with a metal outer shell and the TDH-39, TDH-49, and TDH-50 earphones with plastic outer shells
Authors: Michael Paul L. , Bienvenue Gordon R.
Published: October 2005

There has been a recent expression of concern that the metal shells of most audiometric earphones could consitute a safety hazard because they can conduct electricity and are often used near electrical-power supplies. In response to this potential safety hazard, Telephonics has constructed new TDH-49, and TDH-50 earphones with nonconducting outer shells. Real-ear threshold comparisons were used to determine if the samples of plastic-cased earphones could be substituted directly for the standard, metal-cased earphones. The ten, trained-listener subjects showed normal audiometric thresholds with good reliability. The real-ear performance of the plastic-cased earphones did not differ significantly from the of the metal-cased earphones and it was concluded that these earphones could be used interchangeably in audiometric testing.
Comparison of two normal-mode solutions based on different branch cuts
Authors: Bartberger C. L.
Published: October 2005

In obtaining normal-mode solutions of the wave equation in a horizontally stratified ocean, a choice may be made between two different branch cuts in the complex plane. The solution based on the Ewing–Jardetsky–Press cut consists of two terms, (1) the sum of a finite number of ’’proper’’ modes and (2) a branch line-integral contribution. The solution based on the Pekeris cut consists of three terms, (1) the ’’proper’’ mode sum, (2) the sum of an infinite number of ’’improper’’ modes, and (3) a branch line-integral contribution. It is found in two examples that a solution based on the Pekeris cut leads to the same results as Stickler’s solution based on the Ewing–Jardetsky–Press cut.
Relative sound velocities of sea salts at 25°C
Authors: Millero Frank J. , Ward Gary K. , Chetirkin Peter V.
Published: October 2005

The relative sound velocities (u−u0) of aqueous HCL, LiCL, NaF, NaCL, NaBr, NaI, NaNO3, NaOH, NaHCO3, Na2SO4, KF, KCL, KBr, KI, KNO3, K2CO3, K2SO4, RbCl, CsCl, NH4Cl, NH4Br, MgCl2, CaCl2, SrCl2, BaCl2 and MgSO4 solutions were measured from 0.01 to 1.0 at 25°C. The sound velocities were fitted to a function of molality (maximum standard deviation 0.05 m sec−1) u=u0+Am+Bm(3/2)+Cm2, where u0 is the sound velocity in pure water, and A, B, and C are temperature dependent parameters. The adiabatic compressibilities βS were determined from the sound velocities and were used to calculate the adiabatic apparent molal compressibilities φK(S) of the salts. The φK and βS of seawater were estimated by using Young’s rule. The calculated values of φK and βS agree with those determined from the measurements on seawater solution to ±0.18×10−4cm3mol−1bar−1 and ±0.004×10−6bar−1. The sound speeds of seawater calculated from the values of βS estimated from Young’s rule agree on the average to ±0.02m sec−1 (maximum standard deviations 0.07 m sec−1) with the direct measurements of Millero and Kubinski.
Relationship between plate and surface modes of a tube
Authors: Rosenberg R. L. , Thurston R. N.
Published: October 2005

A circular tube will support axially sysmetric surface acoustic waves at both surfaces, and also a pair of axially symmetric platelike modes. The two pairs of modes are analogous to similar mode pairs on a flat plate. The relationships between surface and plate modes are well known for the flat-plate geometry. It is shown here that for the tube geometry, the mode relationships are of a different kind. Whereas the high-frequency surface modes on a flat plate are superpositions of the two lowest Lamb modes, the high-frequency surface modes on a tube are in general not superpositions at all. On a tube, each surface mode is the high-frequency representative of a single platelike tube mode.
Impulsive sound-level response statistics in a reverberant enclosure
Authors: Dunens E. K. , Lambert R. F.
Published: October 2005

Some response measures of a reverberant enclosure excited by an impulsive noise source are considered from both experimental and analytical viewpoints. The response measures of interest are the rms sound pressure and the sound-pressure-level exceedance probability distribution. A variety of experimental situations are examined for infrequently occurring source impulses — a situation for which an analytical approach can be readily developed. The model involves the use of an energy-partition method in order to estimate the rms sound pressure and the use of an equivalent linear single-degree-of-freedom system in order to calculate the normalized exceedance probability distribution. The calculated response statistics agree quite well with measured data. Results of these studies have applications in predicting total noise exposure, for example, when dealing with impulse noise-control problems.
Review of noise propagation in the atmosphere
Authors: Piercy J. E. , Embleton T. F. W. , Sutherland L. C.
Published: October 2005

A general review is presented of most areas of sound-propagation outdoors that are of interest for the control of community noise. These areas are geometrical spreading, atmospheric absorption, ground effect, (near horizontal propagation in a homogenous atmosphere close to flat ground), refraction, the effect of atmospheric turbulence, and the effect of topography (elevation, hillsides, foilage, etc.) The current state of knowledge in each area is presented and suggestions made concerning research activities, applications of existing research, and practical problems which arise in the prediction of noise levels.
Superdirective spherical radiator
Authors: Butler John L. , Ehrlich Stanley L.
Published: October 2005

The condition for the maximum directivity from a spherical radiator is presented and it is shown that this directivity index is 20 log N, where N is the number of consecutive modes excited. For superdirectivity, the relationship among the expansion coefficients is particularly simple and a closed-form expression for the beam-pattern function results. Using this method, a high directivity may be obtained no matter how small the sphere is, provided that the prescribed velocity distribution is maintained. Examples of the resulting beam patterns are given.
Diffraction of plane elastic waves by ellipsoidal inclusions
Authors: Datta S. K.
Published: October 2005

The method of matched asymptotic expansions has been used to obtain a low-frequency solution for the diffraction of a plane compressional or shear wave by an elastic ellipsoidal inclusion. Attention has been focused on the scattered farfield, angular dependences of which are illustrated graphically for ellipsoidal cavities of different axes ratios.
Wide-band projecting transducer
Authors: Batey R. L. , Wallace R. H.
Published: October 2005

A technique for obtaining a significant increase, compared to more conventional means, in percentage bandwidth for a projecting transducer has been developed. Multiple sets of elements with each set tuned to a slightly different frequency are used to obtain the increase in bandwidth. Phase problems at midfrequencies normally associated with multifrequency operation are solved to a satisfactory degree. An analytical study concerned with bandwidth, beam pattern, and relative per-element sensitivity is presented. Experimental data are shown to support the analytical study.
Vibration response of fluid-loaded structures to low-speed flow noise
Authors: Chandiramani K. L.
Published: October 2005

Consider a spatially homogeneous and temporally stationary random pressure field exciting a spatially homogeneous structure. It is well known that when the power exchange between the pressure field and the structure results from a ’’surface interaction’’ rather than from a scattering-induced ’’edge interaction,’’ it is immaterial whether a finite or infinitely extended model of the structure is used to calculate this power exchange. This equivalence is discussed and used to estimate vibration response of fluid-loaded structures when excited by a low-speed turbulent boundary-layer flow. Connections, established previously for structures in vacuo, between group velocity, modal density, and point and line conductances, are also generalized to apply to fluid-loaded structures. Finally, an approximate but simple method is suggested for estimating vibration characteristics of spatially nonhomogeneous structures excited by surface interactions.
General formulation of the source extraction problem
Authors: Vasholz David P.
Published: October 2005

A general formulation of the problem of extracting information about random wave sources is presented. The formulation places no restrictions upon the complexity of the propagation and applies to any situation where the propagation may be adequately described by a deterministic Green’s function. It is shown that the general problem may be cast into the form of an integral equation, the kernel of which contains the physics of the propagation and the solution of which describes the location and spectral content of all sources. The special case of a homogeneous medium is examined in detail, and it is shown that conventional processing techniques may be viewed as attempts to solve an approximate version of the integral equation. An exact formal solution for the case of an arbitrary medium is derived. This formal solution, although it may not be implemented per se, is nonetheless expressed in such a form that a useful procedure for generating approximate solutions is suggested. This procedure, which is a generalized version of beamforming, may then be used to investigate limitations on the performance of hypothetical systems imposed by only approximate knowledge of the propagation and by observation of the transmitted wave field over only a limited spatial domain.
Low-frequency technique for the underwater calibration of individual elements of a line hydrophone array
Authors: Zalesak Joseph F. , Trott W. James
Published: October 2005

A calibrator for use with long line hydrophones (seismic streamers) has been designed, constructed, and tested. Comparison calibrations may be obtained for individual elements or small groups of interconnected elements of a line hydrophone array in the frequency range of 20 to 3000 Hz. Absolute calibrations may be obtained in the frequency range of 20 to 100 Hz. The calibrator may be operated in either of two configurations. The first configuration has the calibrator submerged in a water trough. In the second configuration the calibrator, with the hydrophone inserted, forms a closed chamber through which water is continuously circulated during operation. A comparison between results obtained by using the calibrator, and independent measurements is presented. The theory of operation of the device, and of the sonic resistors used to reduce standing waves within the calibrator, is presented in the appendixes.
Estimation of background ambient noise levels from the spectral analysis of time series with application to cw propagation-loss measurements
Authors: Shooter Jack A. , Watkins Steven L.
Published: October 2005

An application of percentile measurements is presented as a method for estimating background ambient noise levels from spectral density functions. The advantage of a percentile method over an average method is that it allows an accurate measure of background noise containing a sine wave, that is essentially independent of the sine-wave amplitude. This feature makes the percentile method very useful in the measurement of cw propagation loss, where it is frequently necessary to subtract an estimate of the background noise from a signal-plus-noise measurement, including the case when the noise contains sine waves close in frequency to the cw signal. A percentile-level estimate may be easily used to calculate an average level estimate for chi-square data and it is found that a percentile estimator is just as accurate and essentially just as stable as an average estimator. Theory based on chi-square statistics and experimental data from the ambient sound field in the deep ocean are shown to be in good agreement.
Effects of noise on sleep of babies
Authors: Ando Y. , Hattori H.
Published: October 2005

The reactions of babies to aircraft noise were studied by means of electroplethysmography (PLG) and electroencephalography (EEG). It was found that the babies whose mothers had moved to the area around the Osaka International Airport before conception (group I) or during the first five months of pregnancy (group II) showed little or no reaction on PLG and on EEG to aircraft noise. In contrast, babies whose mothers had moved closed to the airport during the second half of the pregnancy or after birth (group III or IV) and the babies whose mothers lived in a quiet living area (group V) reacted to the same auditory stimuli. The babies in groups I and II showed differential responses depending on whether the auditory stimuli were aircraft noise or music. Abnormal PLG and EEG were observed in the majority of babies living in an area where noise levels were over 95 dBA. This suggests that the deep sleep of the babies living in such an area was disturbed.
Waves in thin-walled, nonuniform, perfectly elastic tubes containing incompressible inviscid fluid
Authors: Barclay D. W. , Moodie T. Bryant , Haddow J. B.
Published: October 2005

Wave propagation in a semi-infinite, nonuniform, elastic thin-walled tube filled with incompressible, inviscid fluid is considered. A one-dimensional problem, with the tube and fluid initially at rest and a pressure disturbance applied at the end, is solved for different axial variations of the tube properties. Formal asymptotic techniques are applied to the linearized partial differential equation governing the pressure and simple progressing wave and high-frequency solutions are obtained for Heaviside and oscillatory-pressure boundary conditions, respectively. These asymptotic series solutions terminate for certain parameter variations to give exact solutions for the pressure. Numerical results are presented and some interesting observations concerning the accuracy of the formal results are made.
Model-scaling laws for sound-absorptive boundaries
Authors: Junger M. C.
Published: October 2005

The dimensionless ratios governing sound propagation in acoustic boundary layers and capillaries, indicate that the specific acoustic impedance of Rayleigh solids can be made invariant under scaling, as required for model experiments involving sound reflection by, or diffraction over, absorptive boundaries. Specifically, if macroscopic dimensions L, such as the acoustic wavelength or the thickness of the porous layer are scaled down to L/s in the model experiment, the capillary diameter and spacing must be scaled down by a factor of only s1/2. More generally, a correct model of fibrous layers requires that intersticial dimensions be scaled as s1/2, the layer thickness as s, and that the porosity remain unchanged, i.e., that the number of interstices per unit area be scaled up by a factor s.
Space variance for rectangular modes
Authors: Waterhouse R. V. , Palthe D. W. van Wulfften
Published: October 2005

In a recent paper, the free-wave and eigenmode models of the sound field in a reverberation chamber were compared, and evidence was presented to support the thesis that the two models were consistent. Here a further piece of this evidence is given. We consider the spatial variance of the mean-square pressure in a reverberant sound field of one frequency which has a mean value of unity. This variance, when calculated from the free-wave model is known to have the value of unity. It is also know that, for one oblique rectangular mode, the corresponding value of the variance is 2.375. It is shown here that for N such modes, whose frequencies coincide but whose phases are uniformly distributed, the variance approaches 1 as N approaches ∞.
Ultrasonic spectrum analysis for nondestructive testing of layered composite materials
Authors: Scott W. R. , Gordon P. F.
Published: October 2005

In this paper, a simple model is presented which predicts the ultrasonic frequency spectra for a broad class of layered composite materials having a finite number of laminas. This model predicts spectra for arrays of glass plates in water and these spectra are experimentally verified. Precisely regular spectra are predicted for single plates, while irregular spectra are predicted for all of the arrays studied. Results relating to nondestructive testing which have emerged from this investigation include methods for predicting spectra for layered composite materials and techniques for mapping small changes in the modulus and thickness of composite materials. Also discussed is the existence of forbidden frequency bands for which ultrasound transmission is strongly attenuated in thick layered composites.
Nonlinear mode coupling of elastic waves
Authors: Sugimoto Nobumasa , Hirao Masahiko
Published: October 2005

The theory of nonlinear elasticity is applied to a study of mode coupling of elastic waves at a particular frequency, called the critical frequency, in a long circular wire. It is assumed that the wire is of homogeneous isotropic elastic material and that the nonlinearity of medium (the effects of higher-order elasticity) is primary rather than that involved in the Lagrangian stress and strain tensors. The latter is suggested from the fact that the third-order elastic constants are of larger order of magnitude than the Lamé constants. The method of multiple scales is employed to obtain a system of equations which describes the behavior of the amplitudes involved in the mode coupling. The analysis of the equations shows that nonlinear mode coupling can occur at the critical frequency and that, except at this frequency, the wave undergoes only a phase shift. Further, progressive wave solutions show that the two wave amplitudes can be expressed in terms of Jacobian elliptic functions, and energy exchange between two modes takes place. Under special conditions, these periodic solutions degenerate to the solitary or shocklike solutions.
Combined influence of spatially uniform currents and tidally varying sound speed on acoustic propogation in the deep ocean
Authors: Hamilton K. G. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

The effects of a combination of sound-speed and current fluctuations on propagation of a cw signal in a deep-ocean model are analyzed. The mean sound-speed structure is assumed bilinear, and the channel boundaries are horizontal. The horizontally independent sound speed oscillates with a 12-h period, while the spatially uniform currents consist of quasisteady and diurnally varying components. The total acoustic field for surface-reflected–bottom-reflected rays is investigated for dependence on time, source-receiver separation, and environmental parameters. Multipath propagation is demonstrated for larger propagation ranges, for which case the number, depths, and occurrence times of amplitude fades are shown to be very sensitive to parameter changes. Where the total field is dominated by one ray, contributions from combined sound-speed and current fluctuations to phase are investigated. In both cases, phase generally can be influenced by both sound-speed and current fluctuations, but the former more effectively influence amplitude.
Statistical analysis of ambient noise
Authors: Jobst W. J. , Adams S. L.
Published: October 2005

This paper presents an approach to the characterization of the low-frequency ambient-noise continuum. A tutorial presentation of several statistical tests is given, followed by the application of these tests to the characterization of narrow-band low-frequency ambient noise as a function of space, time, and frequency. Measurements of temporal stationarity, spatial homogeneity, and frequency homogeneity are presented.
Peruvian whistling bottles
Authors: Garrett Steven , Stat Daniel K.
Published: October 2005

Measurements were made of the frequency and sound pressure level from 73 ceramic whistling bottles blown by compressed air. The bottles represent nine pre-Columbian civilizations which inhabited the north and central coasts and highlands of Peru during a 2000-year time span from 500 B.C. to A. D. 1550. We have found that Peruvian whistling bottles group acoustically by culture. The bottles are generally regarded by anthropologists as utilitarian liquid containers with the whistle providing an amusing method of venting. We are suggesting an alternative interpretation of the bottles as having been specifically produced as whistles. We base this interpretation on the clustering of frequencies by individual culture, the fact that the frequencies fall in the region of the ear’s greatest sensitivity, and the high sound pressure levels produced by the bottles when blown orally.
Digital computer simulation of a piezoelectric thickness vibrator
Authors: Schwarz R.
Published: October 2005

A model for an ultrasonic transducer is described which allows direct evaluation of the time response by means of digital computing techniques. In analogy to the equivalent circuit of a transmission line, the proposed model represents the piezoelectric thickness vibrator by lumped elements, i.e., capacitor, inductor, and current-controlled current source. Simulation of the model is easily available by applying standard electrical network analysis techniques. The time behavior of an ultrasonic transducer, transmitting or receiving planar longitudinal sound waves, is calculated.
Effective acoustic center redefined
Authors: Trott W. James
Published: October 2005

A redefinition of the effective acoustic center is proposed.
Comment on ’’Sonoluminscence from water containing dissolved gases’’ [J. Acoust. Soc. Am 60, 100–103 (1976)]
Authors: Plesset Milton S.
Published: October 2005

In connection with a recent paper in this Journal by F. R. Young under this title, attention is called to a previous analysis by R. Hickling which appeared in this Journal in 1963 [J. Acoust. Soc. Am. 35, 967–974 (1963)].
Poisson transduction of noise stimuli: Some results of a computer simulation
Authors: Schacknow Paul N. , Raab David H.
Published: October 2005

A Monte-Carlo procedure was used to simulate noise-intensity discrimination. Poisson transduction (with compression) was modeled in both ’’energy-summation’’ and ’’neural-summation’’ versions. Penner’s analysis [J. Math. Psychol. 9, 286–293 (1972)] of these two mechanisms was confirmed. When noise energies are analyzed into one-third octave bands before being mapped onto counts, Weber functions and bandwidth reciprocities depart slightly from those given by an energy detector.
New method for fast continuous measurement of the lip-opening area
Authors: Kretschmar Jürgen
Published: October 2005

An electronic device for measuring the articulatory parameter ’’lip-opening area’’ is presented. The measurement rate is 50 values per second. Utilizing the video signal of a TV camera, the device produces a voltage proportional to the dark area of the mouth opening surrounded by a bright boundary (lips painted white). High contrast is achieved by using fluorescent paint and ultraviolet illumination. As an example, a measured lip-opening area is shown as a function of time.
Physiologic adjustments for frequency change in trained and untrained voices
Authors: Shipp Thomas , Morrissey Philip
Published: October 2005

Data from two research laboratories appear to be discrepant in reporting on the mechanism for voice-frequency change. An attempt is made to explain the reported physiological differences on the basis of the population studied (singers versus nonsingers), the vocal registers described (falsetto versus light) and the muscles sampled (vocalis versus thyroarytenoid).
Mode conversion in shallow-water sound propagation
Authors: McDaniel Suzanne T.
Published: October 2005

Coupled equations for modal power transfer are applied to calculate the energy transferred between normal modes as a result of scattering from the ocean floor. Numerical estimates are presented for mode conversion in a typical shallow-water environment. The results show that mode coupling can have a significant effect on propagation loss. Mode-coupling predictions obtained for farfield transmission loss are found to display both frequency- and range-dependent features in qualitative agreement with observed shallow-water transmission loss. Excellent agreement is obtained between mode-coupling predictions and experimentally measured mode attenuation.
Geometric properties for reflected fields from a general surface using finite differences
Authors: VanLennep Alfred G. R.
Published: October 2005

It is well known that geometrical acoustics (GA) approximations to reflected fields depend on the surface shape incident to the field in a neighborhood. However, because of the general complexity of these solutions certain canonical problems pertaining to regular shapes, such as cones and spheres, have been solved, but little attention has been given to the problem of approximating the essential geometric properties for a general surface in a neighborhood. Approximations to the reflected field (ka≫1) usually assume (although this is not a limitation of GA as pointed out by Fock [Electro Magnetic Diffraction and Propagation Problem (Perganom, New York, 1965), 1st ed. ] that the surface is a well known geometric shape, i.e., ellipse, cone, etc. This is done to make calculations of curvature and other geometric properties straightforward. This paper will discuss the problem of obtaining the needed geometric properties for more general geometric shapes. It will consider only a small neighborhood of the surface. Using differential geometry and finite differences, it will then show that all geometric properties in a neighborhood may be approximated by a small number of points from that neighborhood. This technique can with a few practical limitations geometrically describe any neighborhood on a surface. These neighborhoods form ’’areas’’ called patches. When the entire surface meets certain conditions, these patches when ’’tied’’ together actually describe the entire surface and all its geometric properties.
Relation between the solutions of the Helmhotz and parabolic equations for sound propagation
Authors: DeSanto John A.
Published: October 2005

In this paper we establish an integral transform relation between the solutions of the Helmholtz and parabolic equations for sound propagation in an arbitrary two-dimensional waveguide. The sound speed is a function of both depth and range. For range-independent sound speeds, the integral transform is proved to be exact by using a normal-mode expansion. For range-dependent sound speeds the stationary phase approximation of the transform is, in lowest order, equivalent to the usual parabolic approximation. Corrections to the parabolic approximation are also calculated using the stationary phase method.
Ultrasonic studies of relaxation in dichloromethane and dibromomethane with high-resolution Bragg reflection method
Authors: Takagi Kenshiro , Choi Pak-Kon , Negishi Katsuo
Published: October 2005

A method of high-resolution Bragg reflection was utilized to measure ultrasonic velocity and absorption in liquid dichloromethane and dibromomethane near the room temperature, over the frequency range from 60 to 700 MHz. In both liquids, considerable velocity dispersion and decrease in α/f2 were observed and described with single relaxation frequencies, 192 MHz for dichloromethane and 393 MHz for dibromoethane at 20° C. The observed relaxation strengths were roughly consistent with the theoretical values calculated from the hypothesis of the vibrational relaxation associated with all but the lowest mode. The hypersonic velocities were measured in dichloromethane with the technique of Brillouin scattering. No dispersion was observed between 700-MHz and gigahertz region. The second relaxation involved with the lowest mode was expected to be in the range higher than 10 GHz, and the volume viscosity was estimated to be ηv?3ηs, the shear viscosity.
Experiments in ultrasonic imaging for weld inspection
Authors: Turner William R.
Published: October 2005

Defects in butt welds were visualized against a dark field by obliquely insonifying the weldment and focusing the scattered ultrasonic energy onto an electronic sensor for conversion into a nonholographic visual display. Also shown are comparative images obtained by radiographic and ultrasonic Delta techniques. The artifacts encountered as a result of source side lobes, cylindrical collimation, multipath distortion, and wave interference are described together with the techniques for analyzing and suppressing them. The system appears adaptable to automatic object movement and computerized interpretation of data at rates approaching 10 000 resolvable image points per second.
Bispectral holography
Authors: Sato Takuso , Sasaki Kimio
Published: October 2005

In conventional holography, information at a hologram plane is obtained by taking the cross correlation between the signals at the points on the plane and a reference signal. In this paper we show that this information can also be obtained by using bispectral analyses of random signals detected at two points on the hologram plane, that is, the signal detected at a fixed point and the signal detected at scanning points on the same plane. The method, which uses this hologram and a conventional reconstrucion process and is named bispectral holography, has two special features: (i) it is completely free from additive Gaussian noises of any power spectra, and (ii) random signals, which have non-Gaussian properties, can be used as the object illuminating signals. These properties may extend the application of holographic techniques. The theoretical aspects and some discussion of the method are presented.
Comments on ’’Influence of range-dependent environments on low-frequency volume attenuation measurements in the sea’’ [J. Acoust. Soc. Am. 61, 369–374 (1977)]
Authors: Browning D. G. , DiNapoli F. R. , Mellen R. H. , Schneider H. G.
Published: October 2005

Despite the claim of ’’substantial evidence,’’ the Hanna–Rost article does not provide any meaningful results in support of its premise. The article presents distortions of the Naval Underwater Systems Center (NUSC) work which are pointed out in this reply.
Attack and release times of automatic-gain-control hearing aids
Authors: Burnett Edwin D. , Schweitzer H. C.
Published: October 2005

The attack and release times were measured on each of three samples of 27 different models of compression-type hearing aids using the test conditions specified in ANSI Standard S3-22 (1976). The results indicate that almost all of the hearing aids tested have attack times less than or equal to 10 ms. A little more than half of the hearing aids had release times of 50 ms or less. The range of the attack times varied from 1 to 23 ms and the release times from 5–600 ms.
Ultrasonic absorption in liquid selenium
Authors: Ring E. M. , Beyer R. T.
Published: October 2005

The temperature and frequency dependence of the ultrasonic absorption coefficient in molten selenium have been studied in the range from 200° to 400° C and from 30 to 70 MHz. The data are consistent with the values in the literature for the high-temperature range but supersede the previous results below 300° C. A theoretical model is prepared in which the monomer (rings) of the selenium represent a nonrelaxing component with the polymer chains forming a relaxing component.
Model for the relative salience of the pitch of pure tones presented dichotically
Authors: Yund E. William , Efron R.
Published: October 2005

The perception of dichotic chords is characterized by two unique properties—invariance of the relative salience of the two pitch components with respect to large interaural intensity differences (’’intensity independence’’) and a tendency for the tone delivered to one ear to be relatively more salient (’’ear dominance’’) [Efron and Yund, J. Acoust. Soc. Am. 59, 889–898 (1976)]. A simple model is described which can account for these effects and the changes in the magnitude of these effects as a function of stimulus parameters. The model assumes (1) the existence of tuned frequency specific monaural filters, (2) a compressive intensity-response function, and (3) a central combination of corresponding monaural channel responses. The model’s performance is not only consistent with all previously published experimental data but also anticipates experimental results described in the two companion papers.