bluuebunny/crossref_metadata_2025_split huggingface dataset:
Holographic interferometry applied to the investigation of tympanic-membrane displacements in guinea pig ears subjected to acoustic impulses
Authors: Dancer A. L. , Franke R. B. , Smigielski P. , Albe F. , Fagot H. 
Published: October 2005

The displacements of the tympanum of guinea pigs undergoing the action of acoustic impulses were investigated using holographic interferometry. The motion of the umbilicus is approximately 7.5 times smaller than that of the maximum elongation point of the tympanic membrane located between the umbilicus and the annulus fibrocartilagineus in the prolongation of the manubrium mallei. The results attempt to explain why tympanic lesions originated under the action of acoustic impulses frequently appear in the lower area of the pars tensa in the case of guinea pigs. The holographic visualization of tympanic-membrane displacements appears to offer a number of practical applications allowing to throw light into the transmission of acoustic energy at the level of the tympanic membrane.
Subject Classification: 65.24; 35.65; 80.50.
Internal-combustion engine intake and exhaust system noise
Authors: Bender Erich K. , Brammer Anthony J. 
Published: October 2005

In this paper the state of the art of characterizing and controlling intake and exhaust system noise of internal-combustion engines is reviewed. Various types of internal-combustion engines are discussed as sources of noise and in terms of their interaction with intake and exhaust systems. A review of muffler technology shows that linear resistive and reactive effects are well understood, as are certain nonlinear effects. However, effects of high sound pressure levels, flow, duct perforations, and temperature gradients all acting together require study. The paper also shows that mufflers providing 30–35 dBA of insertion loss are practical and that insertion loss can be predicted, but only roughly.
Subject Classification: 10.60; 50.30, 50.50.
Second-order gradient unidirectional microphones utilizing an electret transducer
Authors: Sessler G. M. , West J. E. 
Published: October 2005

A class of second-order gradient microphones with unidirectional directivity characteristics is analyzed. These microphones consist of four in-line sensors whose outputs are added with proper delays. The directivity characteristics of such microphones are rotationally symmetric and given by (α+cosϑ)(β+cosϑ), where α and β are constants and ϑ is the angle of incidence relative to the rotational axis. The calculated maximum directivity factor is 9. Experimental systems consist of an electret transducer enclosed in a cylindrical cavity and four tubes, paired in length, extending from the cavity to sample the sound field. Measurements on a transducer with α=1 and ‖β‖ ≪ 1 yield a sensitivity of about −80 dBV/μbar in the direction of mzximum pickup (ϑ=0) with variations of less than ±3 dB in the frequency range from 0.2 to 4 kHz. The measured sensitivity is about 20 dB lower for ϑ=90, 180 and 270°. Because of their large directivity factors, such microphones are of interest in environments with high noise levels or in situations where reverberation or acoustic feedback have to be suppressed.
Subject Classification: 85.62, 85.44, 85.40.
Frequency dependence of threshold ultrasonic dosages for irreversible structural changes in mammalian brain
Authors: Dunn F. , Lohnes J. E. , Fry F. J. 
Published: October 2005

Threshold ultrasonic single-pulse exposures for irreversible structural changes in the mammalian brain have been extended to include the frequencies 1, 3, 4, 4.5, and 9 MHz. The acoustic intensities of the delivered doses range from approximately 102 W/cm2 to 2×104 W/cm2 with the corresponding exposure durations ranging from 2.5 sec to 5×10−4 sec, respectively. The threshold dosage curves can be described by the relation It1/2=c (f,T), where I is the acoustic intensity delivered to the site of the irreversible change, t is the time duration of the single acoustic exposure, and c is a weak function of frequency and possibly also of base temperature of the specimen.
Subject Classification; 80.40.
Masked hearing thresholds of ringed seals
Authors: Terhune J. M. , Ronald K. 
Published: October 2005

The critical ratios of two ringed seals were estimated by determining pure-tone thresholds (yes–no, forced choice) in the presence of various noise bands. Data obtaind from both seals were pooled. The critical ratios (using spectrum noise levels of −30 and −40 dB re 1 μbar) were 30±5.4, 32±3.8, 34±2.8, and 35±4.5 dB at 4, 8, 16, and 32 kHz, repectively. These values are consistent with findings of other mammalian species. In the open ocean, meteorological and man-made noises below 100 kHz may mask the underwater hearing of marine mammals. As there is less than 10-dB variation in the noise (spectrum level) above 100 kHz, an echolocation system operating in this range would be less subject to varying amounts of masking.
Subject Classification: 80.50; 65.22, 65.58.
Resonant transmission-line configurations for optimum FM detection of vibration using capacitance transducers
Authors: Paré V. K. 
Published: October 2005

Resonant transmission-line configurations are described which give maximum frequency modulation amplitude when modulated by a small terminating capacitance. If the termination is a capacitive vibration transducer, there results a wide-band, absolutely calibrated system which can detect small vibration amplitudes in a severe environment.
Subject Classificairon: 85.44; 40.75; 85.22.
Active electrical load for simulating a transducer in an array
Authors: Truchard James J. , Nowlin William C. 
Published: October 2005

This paper describes the design, fabrication, and use of both passive and active electrical dummy loads which simulate the electrical impedance of an individual transducer element in a large array over a wide range of frequencies. These impedance characteristics allow the use of this dummy load for the testing of a prototype amplifier at both its operating frequencies and frequencies where the stability and noise performance of the amplifier may be affected by the impedance characteristics of the load. Since an active port is included in this dummy load, the impedance characteristics of a transducer element at various positions in the array could readily be simulated. An example of the use of this dummy load for the testing of a 1-kW switching type prototype amplifier is given.
Subject Classification: 30.85; 85.40, 85.64.
Acoustic phase fluctuations resulting from axis meander and transport variation of a geostrophic ocean current
Authors: Widtfeldt J. A. , Jacobson M. J. 
Published: October 2005

A treatment is presented of total-field phase fluctuations of a cw signal, transmitted across a slowly varying northward geostrophic flow. Only refracted/bottom-reflected rays are considered, and the ocean bottom is horizontal. Unlike earlier investigations, the flow is of finite width and transport-axis location, as well as volume transport, may be varied. We begin with a rather general current model having factorable dependence on depth and distance across the flow. The current is taken to decrease linearly with depth, and the surface current is specialized to a cubic polynomial. Sound speed is calculated from the density and pressure solutions. It is then approximated by a linear least-squares fit, so that the acoustics problem is equivalent to that in a convergent channel with linear sound speed versus depth. In an application, the total-field phase is shown to be highly sensitive to transport-axis meander as well as to changes in volume transport.
Subject Classification: 30.20, 30.25.
Scattering of spherical pressure pulses by a hard cylinder
Authors: Huang H. 
Published: October 2005

The transient scattering of spherical pressure pulses by an infinitely long acoustically hard circular cylinder is analyzed. The pressure in the neighborhood of the reflected wavefront is calculated by the method of series expansion in conjunction with the transport equations. From the wave equation, a simple integral formula is derived by means of which the solution to the present three-dimensional problem can be effectively constructed from the two-dimensional line source solution. Thus, the pressure in the neighborhood of the diffracted wavefront is computed based upon Friedlander’s diffraction formulas pertaining to the scatttering of a cylindrical pulse by a hard cylinder. Outside the neighborhood of the scattered wavefronts, the solution is obtained by the Fourier series and integral transform techniques and is accurately computed by this formula. By combining the various solutions, the true time histories of the scattered pressure are inferred for various locations on the cylinder. Some features of the three-dimensional resultant pressure field are also discussed.
Subject Classification: 20.30.
Comparison of sonar system performance achievable using synthetic-aperture techniques with the performance achievable by more conventional means
Authors: Cutrona Louis J. 
Published: October 2005

A comparison is made of the signal-to-noise characteristics of synthetic-aperture sonar and conventional sonar. For the synthetic-aperture sonar case a design procedure is described which makes possible the choice of essentially any unambiguous range and any resolution. Often multiple beam receivers are required. It is shown for the synthetic-aperture sonar case that the horizontal aperture is the major factor affecting area coverage rate. The comparisons are made with as many parameter values as spossible identical for both the synthetic-aperture cases and the nonsynthetic-aperture cases. If identical physical aperture dimensions are used and other parameters held to identical values, the synthetic-aperture sonar gives higher signal-to-ratio than does the nonsynthetic-aperture sonar primarily because the latter must operate at higher acoustic frequencies for which signal attenuation becomes extremely large. If the sonar systems are operated at the same frequency, then the nonsynthetic aperture sonar can give a higher signal-to-noise ratio only when its physical aperture is larger than that used in the synthetic-aperture case.
Subject Classification: 30.82; 60.20.
Scattering of sound from a point source by a rough surface progressing over an isovelocity ocean
Authors: Harper E. Y. , Labianca F. M. 
Published: October 2005

A perturbation procedure is applied, through the second order of approximation, to the three-dimensional problem of scattering of sound from a point source by a rough surface progressing in the wind direction over an isovelocity ocean. The results satisfy conservation of energy, in a ray-theoretic sense, and are uniformly valid throughout the field. At points in the region of surface-image interference (Lloyd’s-mirror region), the signal is shown to be strongly modulated. Results are presented which depict the power in the carrier and signal sidebands. The latter are not, in general, symmetric in amplitude about the carrier. However, it is demonstrated analytically that, on two specific planes in the field, the signal power spectrum is symmetric about the carrier.
Subject Classification: 30.40, 30.20, 30.25.
Coherent component of specular reflection and transmission at a randomly rough two-fluid interface
Authors: Kuperman William A. 
Published: October 2005

The specular reflection and transmission of an acoustic plane wave at a randomly rough two-fluid interface is studied. The perturbation method of Bass is used to derive a new set of boundary conditions to replace the unperturbed boundary conditions. The new conditions are valid for surfaces characterized by arbitrary anisotropic correlation functions. Using these new boundary conditions, reflection and transmission coefficients are derived. It is shown that in the Kirchhoff approximation, the reflection and transmission coefficients reduce to those obtained earlier by Eckhart, Clay, Medwin, and Hagy. In the limit of the density of one of the fluids going to zero, the reflection coefficient for a rough pressure release surface is obtained. Results are presented using ocean surface models in terms of wind speed and direction.
Subject Classification: 30.40, 30.30, 30.25,30.20.
Low-noise chambers for auditory research
Authors: Vér István L. , Brown Robert M. , Kiang Nelson Y. S. 
Published: October 2005

The experimental work of the Eaton–Peabody Laboratory of Auditory Physiology requires chambers unusually free of ambient acoustic, vibratory, and electric noise, so that small mechanical or electric signals in response to low-level sounds can be measured. This paper deals with the problems that arose in setting of criteria, the design, and the construction of such chambers, and reports on the evaluation of their performance. The ambient acoustic noise is well below the human threshold of hearing even with the ventilation system operating. The noise reduction between the control rooms and the chambers is almost 80 dB at 250 Hz and more than 90 dB above 500 Hz. The octave-band ambient vibration acceleration level at the experimental tables in the chambers is below −120 dB re lg.
Subject Classification: 55.40; 65.10.
The five distractors experiment: exploring the critical band with contaminated white noise
Authors: Kaplan Howard L. 
Published: October 2005

Three observers tried to detect a 500-Hz target in white noise in one of two temporal intervals. A distractor tone was added to the target interval on half of the trials and to the nontarget interval on the remainder. When the distractor was within about 40 Hz of 500 Hz, the 80% correct threshold for the target was elevated or depressed depending on whether the distractor was added to the nontarget or target interval. Thus, the critical band around 500 Hz is estimated to be about 80 Hz wide. It is possible to compare the relative sizes of the two threshold shifts against the predictions of two models of detection: the classical, integrated-energy model, and a model emphasizing contrast among the energy of the components within the band. To make these predictions, simulated observers were run under the identical procedure. Within the limits of experimental error, the simulation matched the data well only under the integrated-energy model. Under that model, the observers are performing about 2. to 3 dB worse than what the simulation predicts, which provides an estimate of the internal noise as nearly equal to the external noise.
Subject Classification: 65.58, 65.75; 50.70.
Spiral membrane speaker enclosure
Authors: Kaiser Jr. Julius A. 
Published: October 2005

Acoustical transmission lines formed into a spiral configuration possess the latent property of having different lengths along adjacent lines when traversing along a radius: for an acoustical spiral, sound waves in adjacent transmission lines will progress from an antiphase relation at the center of the spiral to an in-phase relation at some radius r (λ) from the center. This is a transformation dependent only upon wavelength. When those transmission - line walls that are facing the environment are covered with a low-mass, tightly stretched membrane, radiation from this secondary surface will occur at the appropriate time. Radiation of a transverse wave rotating about the spiral axis occurs when sound waves in adjacent transmission lines are in phase. In this paper, several radiation modes and phasing properties are discussed. Owing to automatic adjustment of aperture size with change in frequency, the spiral membrane enclosure has a broad and constant beamwidth. An acoustical source, such as a loudspeaker cone each side of which is contiguous to the end of an acoustical transmission line, generates within those transmission lines longitudinal waves that are antiphase relative to each other. Constant loading of the source occurs over a wide range of frequencies, providing uniform electrical/acoustical performance. An experrimental model is described.
Subject Classification: 85.60; 20.40.
An accurate method for the experimental evaluation of the acoustical impedance of a black box
Authors: Kathuriya M. L. , Munjal M. L. 
Published: October 2005

Among different methods, the transmission-line or the impedance tube method has been most popular for the experimental evaluation of the acoustical impedance of any termination. The current state of method involves extrapolation of the measured data to the reflecting surface or exact locations of the pressure maxima, both of which are known to be rather tricky. The present paper discusses a method which makes use of the positions of the pressure minima and the values of the standing-wave ratio at these points. Lippert’s concept of enveloping curves has been extended. The use of Smith or Beranek charts, with their inherent inaccuracy, has been altogether avoided. The existing formulas for the impedance have been corrected. Incidentally, certain other errors in the current literature have also been brought to light.
Subject Classification: 85.20.
Real-time ultrasonic imaging methodology in nondestructive testing
Authors: Knollman G. C. , Weaver J. L. , Hartog J. J. , Bellin J. L. 
Published: October 2005

Acoustic imaging techniques are described for real-time nondestructive testing of highly attenuative material having irregular shape. Specific application is made to rapid, on-line inspection of tapered cylindrical billets for display of interior spherical voids as small as 2.5 mm. Basic parameters for sonovision operation and function are presented first, including unfocused and focused shadow imaging of a void versus backscatter imaging. A fixed-focus acoustic lens of appropriate focal depth and image resolution is advanced for shadow imaging of minimum-size or larger voids. A focused insonification system is described, and both single-element and linear-array solid-state acoustic receivers are presented as imaging devices. Methods for mechanical scan of object and/or ultrasonic transducers are outlined together with the accompanying real-time cathode ray tube display. Aqueous glycerol solution constitutes an immersion fluid for enhancement of acoustic imaging in the nondestructive test of many solid materials. Two sonovision systems for on-line nonintrusive inspection are presented based on helical scan. Special features of the ultrasonic imaging arrangements include pulse operation, receiver gating, acoustic shielding, and automatic contrast control.
Subject Classification: 85.10; 35.65, 35.26.
Ray-theoretic analysis of a mathematical model for SOFAR propagation
Authors: Goda M. A. A. , Rao C. R. A. 
Published: October 2005

The problem of acoustic wave propagation in an underwater sound channel has been discussed using the ray theory for a model consisting of two semi-infinite liquid media in which the propagation velocity increases exponentially in both directions from the interface. The results predicted by this model are in good agreement with the results of experimental work.
Subject Classification: 30.20; 20.20.
Spectrum of phase fluctuations caused by multipath interference
Authors: DeFerrari Harry , Leung Ricky 
Published: October 2005

Fluctuations of CW phase caused by time-varying multipath interference are simulated with fully coherent ray propagation models. Fixed-system measurements of fluctuations of CW transmission are presented and compared for three ocean ranges. When the sound-speed perturbation used for model inputs are adjusted to give the same statistics of transmission-loss fluctuations (decorrelation time, variance, and mean-square bandwidth) as observed, then the associated fluctuations of CW phase also have the same statistics as the experimental results. Phase fluctuations are shown to be strongly influenced by the nonlinear multipath process. For low-frequency internal waves (less than 1 cycle/h), and especially for internal tides, linear or direct fluctuations influence the phase spectrum, but for higher frequencies it seems likely that nonlinear effects dominate. Therefore, the possibility of a direct linear relationship between the internal-wave spectrum and the spectrum of phase fluctuations is unlikely.
Subject Classification: 30.35, 30.20; 20.20.
Distortion of short-duration stress pulses propagating in solids and liquids
Authors: Felix M. P. 
Published: October 2005

Short-duration, laser-generated, compressive stress pulses were propagated in a variety of solid and liquid materials; and the initially compressive pulses were observed to develop tensile ’’tails’’ for propagation distances of less than 6 cm. This type of pulse distortion cannot be attributed solely to geometric dispersion or material attenuation. It is shown that the observed pulse distortion can be explained using elementary diffraction theory. Since the transition distance from the Fresnel region (nonattenuative) to the Fraunhofer region (1/z attenuation) is dependent upon the wavelength of the acoustical radiation, stress pulses composed of many wavelengths are distorted and not merely attenuated during propagation. Numerical results are presented to substantiate this observed effect and to provide a convenient means of predicting the shape of a stress pulse at any distance in a nondispersive, nonattenuative medium given the shape initially.
Subject Classification: 35.65, 35.24, 35.26; 25.22.
Acoustic radiation force on fused silica spheres, and intensity determination
Authors: Hasegawa Takahi , Yosioka Katuya 
Published: October 2005

The advantages of using fused silica spheres as the target in the radiation force method of acoustic intensity determination are considered. Experimental determination of the radiation force function, for fused silica spheres in water in the range of ka 2–24, was carried out. The experimentally obtained values of the radiation force function agree within 2% of those calculated from the theory of the radiation force on solid elastic spheres. This makes possible determination of ultrasonic intensity and calibration of acoustic probes with uncertainties &lt;2% to values of ka=24, where the accuracy of the radiation force method with stainless steel spheres becomes reduced. The experimental conditions necessary for the realization of this accuracy are discussed.
Subject Classification; 25.45; 30.80; 35.80; 85.22.
Sabine’s reverberation time and ergodic auditoriums
Authors: Joyce W. B. 
Published: October 2005

It is shown in geometrical acoustics that ergodic specular enclosures do exist and that in such auditoriums, but not in general, 4V/S′ is the exact mean directed path length (V is volume and S′ is any part of surface area S). Sabine’s expression is then demonstrated to yield the exact reverberation time, provided the enclosure is mixing and provided the inhomogeneous anisotropic surface absorptivity is sufficiently weak. It is further proven that the functional form of Sabine’s expression cannot be modified so as to become correct for large absorption. In an attempt to reassign credit and to reconcile these results with influential findings to the contrary, a short historical account is added. Conditions imposed upon the surface reflectivity—whether the reflectivity be reversible (specular or other) or irreversible (statistical) —by the second law of thermodynamics and by the principle of detailed balance are evaluated. Extensions (e.g., mean length of curved paths in an ergodic auditorium with a thermal gradient) and other applications (electroluminescent-diode design) are noted.
Subject Classification: 55.20, 55.30, 55.55.