bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear Flexural Vibrations of Sandwich Plates
Authors: Yu Yi-Yuan
Published: September 2005

A set of nonlinear equations describing the vibrations of sandwich plates is derived. These equations are then applied to a plate vibrating in plane strain and to a rectangular plate; with the boundary edges assumed to be hinged in both cases. It is shown that the nonlinear frequencies increase with the amplitude of vibration. It is shown also that transverse shear deformations play an important role; however the effect produced by these deformations decreases with increasing amplitudes of vibration.
High-Frequency Extensional Vibrations of Sandwich Plates
Authors: Chu Hugh N.
Published: September 2005

In this paper there is derived a set of approximate equations governing the extensional motion of a sandwich plate, together with the associated initial and boundary conditions. Both the sandwich core and the facings are assumed homogeneous and isotropic, and the facings are assumed thin and identical to each other. The coupling effect of the thickness deformation of the core is considered in the derivation.

Frequency-wavelength curves are then obtained from these equations for an infinite plate in plane strain. The corresponding curves for the same plate according to the three-dimensional exact theory of elasticity are also obtained. These two sets of curves are then used as a basis for discussion of the accuracy of the approximate equations.

The curves indicate that for commonly used core materials and for wavelengths about three times the plate thickness and longer, the approximate equations are reasonably good up to frequencies somewhat higher than the fundamental thickness-stretch frequency of the plate.
High-Fidelity Philosophy from a European Standpoint
Authors: Rodrigues de Miranda J.
Published: September 2005

Questions: What is High Fidelity? What are the weak spots in the complete transmission chain? High-Fidelity in radio sets: It has become more difficult in the last decade to honor a radio set with the epithet Hi-Fi because of FM broadcast and longplaying records, but it might well be worthwhile to aim at Hi-Fi in a radio set. Hi-Fi in radio must be cheap. The amplifier part: The output transformer is the main quality limiting factor. First line of attack: applying the two channel system. Split the functions of the output stage, one for bass, one for treble. High output, small intermodulation. Second line of attack: do away with the output transformer. Made possible by single-ended push-pull amplifier and high-impedance (800-ohm) loudspeaker. Third line of attack: combining the two-channel system with transformerless output stages. Fourth line of attack: improving distortion and intermodulation figures by ingenious circuitry. Loudspeakers: The cabinet limits the lowest bass. Use good speakers. For the higher frequencies speakers with constant impedance and with good directional characteristics should be employed. Cabinets: Several factors influencing reproduction. High-fidelity amplifier systems with separate loudspeaker enclosures. Much higher limits for price, but no use in overdoing. Same principles. Good enclosures expensive. Advantage of indirect radiation for higher frequencies. Problem of presence. Importance of place of loudspeakers. Demonstrations, if possible.
Effect of a Negative Impedance Source on Loudspeaker Performance
Authors: Werner Richard E.
Published: September 2005

A direct radiator moving coil loudspeaker driven by an amplifier whose output impedance approaches the negative of the blocked voice-coil impedance can be made to exhibit extended low-frequency response with reduced distortion. The effect of the system is in some ways analogous to a many-fold increase in loudspeaker efficiency. In a typical case, neutralization of 75% of the blocked voice-coil impedance completely damps the cone resonance, as well as substantially reducing the nonlinear distortion below resonance. When the amplifier is compensated for the falling radiation resistance at low frequencies, uniform output can be obtained to any arbitrary low frequency, limited only by the ultimate power handling capability of the amplifier and speaker. In this system, no additional amplifier power is required at frequencies down to the speaker resonance; additional power is required below that point.
Auditory Acuity and the Perception of Speech
Authors: Kryter Karl D. , Williams Carl , Green David M.
Published: September 2005

The results of audiometric and various speech tests of persons with normal and different degrees of nerve-type hearing impairment are reported. Correlation regression coefficients (“beta” weights) were found between the hearing loss measured at a number of pure-tone frequencies and the speech test results. These beta weights indicate that taking the average of the decibel hearing loss at either 2000, 3000, and 4000 cps or at 1000, 2000, and 3000 cps provides a reasonably adequate rank-order indicator of the ability to understand speech. The relation between our results and other studies are discussed; it is suggested that some speech tests and methods of scoring that have been used in experiments of this type in the past introduce a bias that leads to an underestimation of the importance of auditory acuity at frequencies above 2000 cps.
Learning, a Major Factor Influencing Preferences for High-Fidelity Reproducing Systems
Authors: Kirk Roger E.
Published: September 2005

The frequency-range preferences of 210 college students for reproduced music and speech was determined by an A B A preference test. A high-quality electroacoustic reproducing system with high- and low-pass filters was used to present the stimuli. The stimuli consisted of five high-fidelity phonograph records. Two experimental groups were matched on the basis of the above test with two control groups. One experimental group listened to music reproduced under a 30- to 15 000-cps frequency range, while the other experimental group listened to music under a 180- to 3000-cps frequency range. The two control groups received no organized music listening program. After the experimental groups had listened to music, two hours a week for six and one-half weeks, a frequency range post-test was given to both experimental and control groups. The results indicate that continued contact with music and speech reproduced over a particular frequency range produces significant shifts in preference for this frequency range. The magnitude of the observed preference shift for a particular type of music is a function of the amount of similar music which was played during the listening sessions. Work done while at The Ohio State University, Columbus, Ohio.
The E. M. I. Stereo Recording and Reproducing Systems
Authors: Dutton G. F.
Published: September 2005

The development of this system was originated by Blumlein in 1931 and the basic principles were published in the British Patent Specification 394,325. This system attempts to reproduce at the listener's ears the same relative sound pressures and time phases as the listener would have experienced in the original sound field. This is accomplished, to a very good approximation, by using only two recording channels and two loudspeakers. It is recognized that it is not possible to produce the required phase differences at the ears by controlling the phase differences at the loudspeakers. If, however, the loudspeakers are supplied with signals in phase, the required phase differences at the ears can be effected by a control of the intensity differences at the loudspeakers, and if these are properly related to the direction of the sound arriving at the transmitting end of the system, localization of sounds over the whole frequency range can be effected by the listener. The two channels are interconnected in such a way that the final pair of outputs control the necessary magnitude differences at both low and high frequencies to drive the loudspeakers. An important feature of the arrangement is that, although two microphone channels are employed, these are used at such close spacing that the microphone system is to all intents and purposes a single transducer. One method of operating the system is to use two directional microphones in juxtaposition and inclined at equal angles to the central direction. The two microphone outputs may be taken direct to their respective loudspeakers or they may be modified by taking the sum and difference of the two microphone outputs and adjusting, if necessary, the gain of the difference channel relative to the sum channel and recombining to form two loudspeaker outputs. In 1934, this system was applied to a single-track disk recording, one channel being recorded “hill and dale,” and the other lateral cut. At that date the frequency range was limited to below 5 kc/sec. The advent of twin channel domestic tape records allowed this stereosystem to be operated on a commercial scale and this was launched on the market in August, 1955.
Acoustics of Circumaural Earphones
Authors: Shaw E. A. G. , Thiessen G. J.
Published: September 2005

When an electro-acoustic transducer is added to a circumaural ear defender the requirements of minimum sound transmission and maximum earphone sensitivity are partially incompatible. The transmission and response of simple (single cavity) and compound (two cavity) systems have been determined by an analog method. The preferred system is a rigid structure with resistive coupling between the two cavities. This system has maximum effective coupling volume at low frequencies thus providing maximum noise attenuation and a smaller effective volume at high frequencies affording increased earphone response. When the cavities contain suitable porous materials and are coupled by an annular slit, the two cavity system becomes a lossy waveguide. Analysis of hemispherical and plane wave acoustical models indicates an effective volume which is constant up to a transition frequency and decreases steadily with further increase in frequency. The theory is supported by measurements on an experimental earphone having complementary transducer and cavity characteristics leading to constant response over a wide-frequency range. Probe microphone data show that above 1 kc the real ear response of circumaural earphones is generally greater than the flat-plate coupler response.
Generalized Theory of Acoustic Propagation in Porous Dissipative Media
Authors: Biot M. A.
Published: September 2005

The theory of acoustic propagation in porous media is extended to include anisotropy, viscoelasticity, and solid dissipation. A more refined analysis of the relative motion of the fluid in the pores is also developed by introducing the concept of viscodynamic operational tensor. The nature of this operator is analyzed by applying variational and Lagrangian methods. Viscoelasticity and solid dissipation are introduced by applying the correspondence principle as derived from thermodynamics in earlier work by the author. Various dissipative models are discussed and the corresponding operators and relaxation spectra are derived. The physical chemistry of the multiphase porous medium including surface effects lies within the scope of the thermodynamic theory. The nature of thermoelastic dissipation and electrokinetic effects in relation to the thermodynamic theory is also brought out.
On the Transition to the Geometrical Approximation in the Theory of Elasticity
Authors: Levin M. L. , Rytov S. M.
Published: September 2005

As it was shown previously by one of the authors (S.M.R.), the transition to the approximation of geometrical optics not from scalar wave equation but from Maxwell's equations permits to obtain a new complementary result, viz. the law, accordingly the polarization alters along the ray: dφ/ds=1/T. (1) Here φ, denotes the angle between the electric field strength and the principal normal of the ray, ds and T denote an element of the length of the ray and its radius of torsion, respectively. In the present paper it is shown that the same law (1) follows in geometrical approximation from the equations of the linear theory of elasticity for inhomogeneous media. Thus, only for such an inhomogeneity of a medium, for which the rays appear to be the plane curves, the unit vector of the transversal displacement u is immovable relative to the natural trihedr (the angle φ between the principal normal n and u is not changed). The rotation of u obeys the law duds=−tcos φR, (2) where t and R denote the unit tangent of the ray and its radius of curvature, respectively. According to Eq. (2), the rotation of u with respect to the independent fixed coordinates stops at those points of the ray, where u is colinear to the binormal (φ = ± π/2), and at the points of the zero curvature. These results might find their application in the problems concerning the propagation of seismic waves.
Theoretical and Experimental Investigation of a Pseudo-Rayleigh Wave
Authors: Strick E. , Roever W. L. , Vining T. F.
Published: September 2005

If a fluid-solid interface be excited by a transient point or line source in the fluid, then, as was previously discussed [W. L. Roever and T. F. Vining, Bull. Am. Phys. Soc. Ser. II, 1, 98 (1956); E. Strick, ibid.], there will be a buildup in the pressure response that begins well before the time of arrival for critically refracted transverse waves. As the ratio of transverse wave velocity in the solid to longitudinal wave velocity in the fluid is increased, this buildup before the direct wave is followed by a decrease in pressure and for still higher ratios passes through zero. When this zero occurs, the point of zero pressure amplitude travels along the interface with the Rayleigh velocity of the free boundary elastic solid. Even larger contrast allows for a separation of the refracted transverse and pseudo-Rayleigh [L. Cagniard, Réflexion et Réfraction des Ondes Séismiques Progressives (Gauthlers-Villars, Paris, France, 1939), pp. 233–237; J. G. Scholte, Koninkl. Ned. Akad. Wetenschap., Proc. 52, 2, 652–653 (1949)] waves from the Stoneley waves. The pressure amplitude of the pseudo-Rayleigh wave is then roughly fifty times that of the critically refracted arrivals. However, this pressure wave cannot be a true Rayleigh wave because it is radiating into the fluid. Particle velocities have been calculated and show wave forms and retrograde motion almost identical with those obtained by Lamb [H. Lamb, Phil. Trans. Roy. Soc. A203, 1–42 (1904)] for a vertical impulse on a free boundary semi-infinite elastic solid.
Corrected Analysis of Plane Finite Waves
Authors: Fay R. D.
Published: September 2005

When the errors in a previous paper are corrected and the method of attack is somewhat modified, a remarkably straightforward analysis yields an expression for the attenuation of repeated saw-tooth waves. The expression is in substantial agreement with those obtained by other methods.
Elastic Waves in Corrugated Plates
Authors: Junger Miguel C. , Smith P. W.
Published: September 2005

The dynamic characteristics of thin corrugated plates with cylindrical corrugations subtending an arbitrary angle are studied. It is found that a sizable number of types of elastic waves exist. Their phase velocities are a function of frequency and of the direction of propagation with reference to the corrugation orientation. Attention is centered on types of waves determining the sound insulating properties of corrugated plates; i.e., essentially transverse waves with wavelengths large in terms of corrugations. [Work was initiated with Office of Naval Research support while authors were with the Acoustics Research Laboratory, Harvard University, Cambridge, Massachusetts.]
Nonspecular Reflection of Sound by Finite Plates and Shells in Liquids
Authors: Ljamshev Leonid M.
Published: September 2005

Results are given of a detailed theoretical and experimental investigation of the nonspecular reflection (N.R.) of sound by thin plates resulting from flexural waves, as well as of a new type of N.R., resulting from longitudinal waves in a thin plate, and the phenomenon of N.R. in cylindrical shells and thick plates found by the author. It is shown that during N.R. an effect of coincidence resonance takes place. The fine structure of N.R. due to coincidence resonance has been experimentally observed and investigated. It is shown that N.R. takes place also in case of scattering of sound by finite thin cylindrical shells and thick plates. The peculiarities of N.R. in the above-mentioned cases are stated. It is shown that if the radius of the cylindrical shell is substantially greater than the wavelength of sound in liquid, the direction of N.R. from a shell coincides with the direction of N.R. from a plate of the same thickness and material. It is shown further that in case of a thick plate the number of maximums of N.R. at great thicknesses and high frequencies of vibrations is very high and decreases with the decrease of frequence. In limiting cases only two N.R. (thin plate) are observed. The N.R. in thick plates is shown to be due to the propagation of the so-called normal waves in the plate considered as an elastic layer of finite thickness.
Ratio Relationships in Melody
Authors: Boomsliter Paul C. , Creel Warren
Published: September 2005

Forced choice between the tempered scale and one of the just scales in an atypical melody does not provide an adequate test of tuning preferences. Experiments by other methods indicate that small whole number ratios do operate in melody.
Ultrasonic Phase Microscopy
Authors: Suckling E. E. , Ben-Zvi S.
Published: September 2005

An ultrasonic microscope operating at 9 Mc and using phase contrast has been described which can detect a polyethylene strip 112 thousandths of an inch thick and 40 thousandths of an inch wide.
Disk-Loaded Torsional Wave Delay Line. II. (Theoretical Interpretation of Results and Design Information)
Authors: Thurston Robert N.
Published: September 2005

In order to account for the magnitude of the delays reported in Part I, the effects of distributed mass and elasticity in the disks must be included in the analysis. Formulas for the torsional impedance at the inner circle of a thin annular elastic disk with a free outer boundary were first derived by H. T. O'Neil as part of a mechanical filter research program directed by W. P. Mason. One finds from these formulas that the structure can properly be represented by lumped electrical elements over a relatively wide frequency range. This electrical analog is a tandem arrangement of identical low-pass filter sections for which formulas are conveniently available. Complicated elastic effects near the sudden change of diameter are not included in the theory, and these effects may account for the small discrepancy between theory and experiment. Relatively simple empirical corrections should be possible after a sufficient number of tests. The design of disk-loaded delay lines is discussed in the light of the above-mentioned analysis and the available experimental results.
Interactions of Nonuniform Shock Waves
Authors: Drummond W. E.
Published: September 2005

The interactions of shock waves with boundaries and with each other have been considered rather fully in the literature for the case of uniform shock waves. The purpose of this paper is to present an approximate method for analyzing the interactions of “weak” nonuniform shock waves. The method is to map the entire problem—differential equations, boundary conditions, shock equations—into the hodograph plane. Because of the approximation used, this mapping is particularly simple and leads directly to the numerical solution of the problem. The approximation (that used by Chandrasekhar and Friedrichs in connection with the formation and decay of nonuniform shock waves) is to neglect third-order terms in the shock strength; i.e., (ρ−ρ0/ρ0)3, (u−u0/c0)3, and (c−c0/c0)3. The virtue of this approximation is twofold: First, since the entropy change across a shock front is a third-order effect, entropy change may be neglected everywhere. Secondly, in this approximation the locus of states which can be connected by a shock (called a “shock polar”) is identical with the locus of states which can be connected by an adiabatic compression. Thus, in the hodograph plane the shock polars and Γ characteristics coincide, and the mapping can be effected in a simple way. In metals, treated hydrodynamically, the very small compresibility allows the approximation to yield accurate answers for shocks as strong as 500 000 atmos. Numerical results will be presented.
Bone Conduction: A Review of the Present Position with Especial Reference to the Contributions of Dr. Georg von Békésy
Authors: Hood J. D.
Published: September 2005

The very great advances in our knowledge of bone conduction that have been made by Békésy's fundamental investigations are outlined and considered in relationship to the influence they have brought to bear upon the investigations of later workers in this field. The topics considered include the mode of vibration of the skull, the theoretical mechanisms of bone conduction, the so-called occlusion effect, bone conduction in a free sound field, and the interaural attenuation across the head.
Acoustic Streaming in the Vicinity of a Sphere
Authors: Thrasher Robert W. , Westervelt Peter J.
Published: September 2005

The evaluation of the stream function describing the acoustic streaming in the vicinity of a sphere has been completed. This stream function was described at the last meeting [R. W. Thrasher and P. J. Westervelt, J. Acoust. Soc. Am. 28, 155 (1956)], and it contained two definite integrals of the exponential type. These integrals have been evaluated on the Brown University I.B.M. C.P.C. computer with an accuracy adequate to enable a comparison of our results with those worked out for the cylinder [S. Skavlem and S. Tjötta, J. Acoust. Soc. Am. 27, 27 (1955)]. Steady flow velocity profiles and boundary layer thickness curves will be presented. The application of this work in connection with determining the interaction force between two spherical particles in a sound field will be discussed. Heretofore the influence of streaming on the two-body interaction force in viscous fluids has been ignored. [This work has been supported by the U. S. Air Force, Wright Air Development Center, and the National Science Foundation.]
Approximate Calculation of the Dimensions of Traveling-Wave Envelopes in Four Species
Authors: Greenwood D. D.
Published: September 2005

Calculations were made of the dimensions of traveling-wave envelopes in four species. The calculations were based on Békésy's measurements of the tuning curves of single points on the basilar membrane of each species, and on four empirical functions, one per species, relating frequency to position of maximum amplitude on the basilar membrane. The functions were in approximate agreement with other observations by Békésy. It was found that the distances over which a traveling wave damps from maximum amplitude to fractions of maximum amplitude—i.e., to one-half maximum, to two-tenths maximum, or to “zero” amplitude, respectively—appear to be approximately constant, independent of the position of maximum amplitude on the membrane. In comparing the traveling wave envelopes of the four species, elephant, man, guinea pig, and chicken, it was found that (1) the shape of a traveling-wave envelope is quite similar among the four species, (2) the distance over which a traveling wave damps from maximum to “zero” amplitude is the greater the longer the basilar membrane, (3) this distance, in the species compared, seems to be an approximately constant fraction of the length of the basilar membrane, independent of the length of the membrane.
Computational Model for Basilar-Membrane Displacement
Authors: Flanagan James L.
Published: September 2005

A computational model is described for estimating basilar membrane displacement in the human ear when the sound pressure at the eardrum is known. The model embodies rational-function approximations of middle ear transmission and of stapes to-membrane transmission. The physiological data upon which it is based stem primarily from the researches of Békésy. Besides computational convenience, the rational-function format has the additional advantage that the model can, if desired, be realized in terms of lumped-constant electrical circuits. The model has been found to be a useful analytical tool for relating subjective auditory behavior and the acoustomechanical operation of the ear.
Functional Implications of the Nature and Submicroscopic Structure of the Tectorial and Basilar Membranes
Authors: Iurato Salvatore
Published: September 2005

The nature and the submicroscopic structure of the tectorial and basilar membranes have been studied with phase-contrast, polarized-light, and electron microscopy; x-ray diffraction; and analytical chemistry. It is shown that the protein found in these membranes has nothing to do with collagen and elastic substance. Perhaps it may be classed in the same group as keratin, epidermin, myosin, and fibrinogen. The tectorial membrane consists of submicroscopic filaments which have a diameter of 96±4 Å, arranged fairly compactly, to form numerous transverse and a few longitudinal fibrous bundles. The basilar membrane consists of a supporting layer which is covered on the tympanic face by the basilar-membrane cells. The supporting layer is made of filaments with a diameter of 85±105 Å, strictly, arranged in a transverse direction. In the pars recta, they lie side by side, whereas, in the pars pectinata, they are grouped in variously sized fibers, separated by a cottony ground substance. These results are compared with those of Békésy's experiments, in order to find a relationship between structure and mechanical properties. The mechanical anisotropy observed in the tectorial membrane by Békésy finds a perfect agreement with the results of the submicroscopic investigations. The mechanical isotropy shown by Békésy in the basilar membrane apparently contrasts with the evident structural anisotropy. It could be explained by the lack of independence in the oriented structures and by the presence of the cottony ground substance which forms a system binding the filaments and the fibers. The transverse orientation of filaments and fibers is not the effect of mechanical forces alone, but could also be connected to other factors, such as those of morphogenesis and growth.
Neural Mechanism of the Peripheral and Central Auditory System in Monkeys
Authors: Katsuki Y. , Suga N. , Kanno Y.
Published: September 2005

The cochlear nerve of the monkey is composed only of the axons of the primary neurons. In Part I of this article, the properties of the primary auditory neuron—i.e., tonotopic organization, response pattern, and response area—have been studied. Two groups of neurons could be stochastically separated in terms of threshold in the low- and middle-frequency range and not in the high-frequency range. The rate of increase of impulse frequency with the change of sound intensity was examined at the characteristic frequency (CF) of a neuron after the measurement of its response area. The rate of increase and the threshold of a neuron were found to be well-correlated. This result seems to show the validity of Békésy's hypothesis on the pitch-intensity coordinate system of the inner and outer hair cells.

Part II is concerned with the responses of the cortical neurons of unanesthetized monkeys. Two types of response areas, wide as well as narrow, were obtained with single-tone bursts. By the simultaneous delivery of two sounds, these areas were found to be altered in different ways, even though they were originally similar. The response patterns for beat sounds also were different from neuron to neuron. The cortical neurons are characterized by the phasic on, off, and on-off response patterns. Intracellular recording of the membrane potentials of neurons revealed that a brief depolarization was often found before or after a long hyperpolarization by a sound stimulation. Owing to such types of responses, very many cortical neurons may be able to discriminate such complex sounds as musical sounds or voices which are always changing. The spatial and temporal funneling action in the neural mechanism of hearing is discussed.
Cavitation and Chemical Effects in Ultrasonic Stationary Fields
Authors: Gabrielli Italo , Iernetti Glauco
Published: September 2005

An experimental setup, based on a properly designed torsion balance has been built, which allows to produce ultrasonic standing waves and to control, through the radiation pressure, the energy density of the field during the time of its application. The control of the energy density is usually difficult, when employing transducers rigidly connected with reflectors, in particular at high energies and when cavitation occurs. The standing waves produced by this device have been used to investigate the darkening of photographic plates in water and the coloration of starch plates in dilute iodine solutions. These processes have been studied with reference to their dependence on the energy density, frequency, time, cavitation, and hydrodynamic flow within the liquid. A comparison is made between the experimental results obtained with standing waves and with progressive waves at the same frequency and energy.
Pitch of the Residue
Authors: Schouten J. F. , Ritsma R. J. , Cardozo B. Lopes
Published: September 2005

The residue is defined as the joint perception of a number of Fourier components. Depending on circumstances outside the scope of this paper, it has a pronounced pitch. The consequences of this phenomenon for the theory of hearing are briefly reviewed in the light of past experiments. Special attention is then called to what are termed the first and second effects of pitch shift. The first effect is found when equidistantly shifting the entire Fourier spectrum. The second effect shows itself primarily in a slight drop in pitch when increasing the frequency spacing of the Fourier components. Presented are rather extensive measurements of these effects for a spectrum consisting of three components. Their inherent connection is shown along with their mathematical relationship. As an important experimental finding, the ambiguity of pitch is presented, measured in two more-or-less independent ways. All these phenomena strongly point towards a pitch-extracting mechanism different from and subsequent to the basilar membrane and operating in the time domain.
Variation on a Theme of Békésy: A Model of Binaural Interaction
Authors: van Bergeijk Willem A.
Published: September 2005

The model of binaural interaction proposed by Békésy in 1930 which has received very little attention in modern theories is re-examined the light of recent anatomical and physiological findings. A modified model is proposed in which time and intensity are mapped independent of each other in the accessory nuclei of the superior olive; excitatory and inhibitory neural signals interact at the accessory nucleus neurons, giving rise to time-intensity trade. The behavior of the model is in qualitative accord with psychophysical and physiological observations.
Cochlear Responses to Acoustic Transients: An Interpretation of Whole-Nerve Action Potentials
Authors: Teas Donald C. , Eldredge Donald H. , Davis Hallowell
Published: September 2005

Intracochlear electrodes in the guinea pig are used to measure the relations among cochlear potentials in response to slow acoustic transients. The traveling wave of Békésy is described in terms of cochlear-microphonic (CM) voltage as functions of time and place along the cochlear partition. The results are consistent with previous observations in the ear and on models of the basilar membrane. Interpolations of wave velocity and wave amplitudes between places used for the measurements allow continuous representations of the traveling-wave pattern of CM in either space or time. From these representations, it is clear that the duration of the stimulating phase of CM along the cochlear partition significantly exceeds the apparent duration of the whole-nerve action-potential (AP) response to these transients.

Selective changes in the waveforms of the AP responses, as opposed to simple reductions in amplitude, are observed when the transients are accompanied by bands of noise and after local chemical or mechanical injury to the organ of Corti. The selective changes in waveform allow consideration of the waveform removed from the normal AP response by the noise as well as the response remaining during noise. The responses removed by each of successive increases the bandwidth of the noise reveal the presence of AP responses at times not apparent in the normal whole-nerve AP waveform. These observations are most easily explained by assuming that the basic neural response is diphasic as conventionally recorded. When neurons become active in an orderly sequence, the positive phases of the earlier individual responses coincide with and may conceal the negative phases of later responses. The whole-nerve AP waveform is thus considered as the convolution (complex product) of two functions in time, the diphasic unit of response and the numerical sequence of newly active neurons. An empirical model for the diphasic unit of response “divided” into the AP waveform reveals patterns of neural activity that are compatible with the traveling wave of CM. The same model satisfactorily explains several details of the whole-nerve AP waveform recorded during stimulation with a burst of high-frequency tone.
On the Discontinuity of Sound Velocity in Elements and Compounds near the Boiling and Fusion Points
Authors: Schaaffs Werner
Published: September 2005

From the increase of entropy at the boiling point, to which Trouton's rule applies, it can be concluded that the ratio of the sound velocities in the liquid state and in the gaseous state is to a first approximation a constant. It will be shown that this constant has a value in the vicinity of 5 for organic compounds without strong association. In the case of a few elements which liquify only at very low temperatures (helium and hydrogen, for example), and also in the case of mercury, the ratio of Trouton's coefficient to the discontinuity of the sound velocity has the almost constant value of 3.46 cal per grad mole. Analogous regularities can be found for the fusion point. It is shown from data available for 11 metallic elements that fuse at low temperatures that the ratios of the sound velocities for longitudinal waves of the solid and of the liquid phases lie about an average value of 1.26, and that the velocity ratio of the extensional waves of the solid phase and the longitudinal waves of the liquid phase lie about unity. It would be desirable if these results were investigated for metals that fuse at higher temperatures.
Additive Relationships between Molecular Quantities and Sound Velocity in Liquids
Authors: Schaaffs Werner
Published: September 2005

For the investigation of interrelations between molecular quantities and sound velocities, organic compounds are particularly appropriate, since they are constructed of only few elements iu numerous variations, and since they are either liquids or can be easily liquified. The author has shown in a number of publications, that the sound velocities are functious of molecular quantities for which it is possible to state additive relationships. His investigations can be summarized in the statement that the sound velocities are a measure of the degree to which the molecules fill the space and of their collision properties. From these results it is possible to derive and to interpret the formula of Rao which has become well known through the investigations of Lagemann, Weissler, Wada, and their collaborators. Its independence of temperature is due to the fact that the temperature coefficient of the mole volume and that of the molecular volume of organic compounds have opposite signs (plus or minus). The additive properties of Rao's expression can be derived from the same molecular quantities that also determine the degree to which the molecules fill the space as well as their collision properties.
Experiments with Soap Films
Authors: Bergmann Ludwig
Published: September 2005

The eigen oscillations of membranes can be studied by reflection of light from acoustically excited soap film. In order to obtain a uniform soap film, it proves advantageous to rotate the film so that a uniform thickness is obtained. The oscillations may be obtained even when the films have been made extremely thin due to long rotation. In addition, one finds at certain eigen oscillations strange streaming phenomena which are shown in several pictures.
Changes in the Cochlear Microphonic of the Guinea Pig Produced by Mechanical Factors in the Inner Ear
Authors: Legouix J.-P.
Published: September 2005

The cochlear microphonics of the guinea pig have been recorded by means of differential intracochlear electrodes located in various turns of the cochlea. Since it has been shown by Békésy that the cochlear-microphonic voltage is proportional to the displacement of the basilar membrane, it is, thus, possible to study the changes in the mechanical movements of the cochlear partition. Mechanical alterations were produced by increase of the fluid pressure inside the cochlea and by local pressure on the basilar membrane. Increased intracochlear pressure produces a selective decrease in the microphonics recorded from the apical part of the cochlea, and when this decrease becomes very large a phase shift is also observed. Touching the basilar membrane with a guinea-pig hair in the basal turn modifies the potential recorded in the same region, but leaves unchanged the microphonics recorded in the upper parts. Pressing on the basilar membrane in the second turn modifies the microphonics recorded in the apical part, but not the microphonics of the basal turn. Rather large destructions of the apical parts of the cochlea modify only slightly, or not at all, the microphonics from the basal part of the cochlea. These various effects are discussed in the light of the mechanisms and the models described by Békésy.
Acoustic Reflex in Man
Authors: Møller Aage R.
Published: September 2005

The intra-aural muscle reflex in man is examined through the change in the acoustic impedance as measured in the auricular canal. The reflex is elicited either by a monaural or binaural sound stimulus, and the acoustic impedance change is measured on both ears simultaneously. When only one ear is stimulated, the sensitivity of the muscle reflex is found to be greater for ipsilateral stimulation than for contralateral stimulation. When both ears are stimulated, the sensitivity of the reflex is greater than for ipsilateral stimulation. Complex sounds with low-peak factor, such as bandpass-filtered noise, are more efficient than sinusoids in eliciting the muscle reflex. Reflex sensitivity was measured in terms of the rms stimulus level required for a constant impedance change. The muscle reflex is approximated to a mechanism consisting of a linear envelope detector followed by an integrator. The frequency-domain transfer function of this mechanism is found to be a convenient description from which response to various stimulus envelopes can be calculated. This general description is also useful in the study of the amplitude regulation of the muscle reflex.
An “Infinite Line” Microphone Probe for Studying Combustor Resonance
Authors: Blackshear Perry L. , Rayle Warren D.
Published: September 2005

An understanding of combustion resonance phenomena requires information as to the nature of the acoustic field within the combusion zone. This paper describes a probe capable of surveying such a field and tells how it can be used in the study of high amplitude sounds. The design employs a microphone which measures the sound level near one end of a very long small bore tube in which reflections may be neglected. The bulk of the work involves the measurement of the damping coefficient of high-amplitude sounds in tubes. A convenient way to calculate the damping coefficient α was examined. This involved dividing α into two parts. Thus, α=αK+αp, where αK is Kirchoff damping coefficient due to viscous effects and αp is damping coefficient of unconfined sawtooth waves. Good agreement between calculated and measured values of α was obtained. A sample survey of pressure amplitude distribution across the flame zone of a screeching combustor is given.
Spherical Waves Coupled to a One-Dimensional Wave Guide
Authors: White James E.
Published: September 2005

Expressions are derived for the disturbance in a one-dimensional wave guide resulting from an expanding spherical wave which is loosely coupled to the wave guide at all points along its length. The example treated is a slender solid rod immersed in a fluid, and curves are presented showing axial stress, strain, and particle velocity due to an expanding step function rise in pressure. When rod velocity is higher than fluid velocity the first signal observed follows the refraction path, and the onset of a secondary signal coincides with the passage of the pressure front in the fluid. When the two velocities are equal, only one signal is observed, and its amplitude increases with distance from the source. When rod velocity is smaller, the first signal coincides with the passage of the pressure front, and a weak secondary signal appears to travel from the point nearest the source at rod velocity. These results are an extension of the approximate theory presented by White [J. Acoust. Soc. Am. 25, 906 (1953)].
Research on the Acoustic Air-Jet Generator
Authors: Brun E. , Boucher R. M. G.
Published: September 2005

This paper describes the principle design and performance of a new type of static siren operating in both the sonic and ultrasonic ranges. The siren called the “Multiwhistle R. B.” consists essentially of a combination of air-jet whistles operating within an acoustic chamber. With a suitably designed chamber, it is possible to greatly increase the acoustic emission. It is also possible, with a single apparatus, to produce different kinds of acoustic spectrum either simultaneously or successively by exchanging one set of a type of jet whistle for another set or by mixing the various types together. The industrial type of “Multiwhistle R. B.” hereafter described has the advantage of an extremely low maintenance cost and its energy consumption compares favorably with the usual dynamic rotating sirens. For example, a “Multiwhistle R. B.” working in the supersonic range at 33 kc produces an acoustic emission higher than 135 decibels for an air discharge as low as 1.4 g/sec per jet whistle. The “Multiwhistle R. B.” with its exponential horn has an over-all size of 270-mm diameter and is 350 mm high. It can be operated in any position. The emission frequency of this apparatus is quite independent of the power, this last factor being dependent only on the number of whistles in operation. In the investigation of the mechanism of the production of ultrasonic waves it was found possible to produce a high intensity level and a powerful emission whilst operating with low air pressure. The main factors governing the efficiency of this static generator are the characteristics of the jet-whistles and acoustic chamber. Operating with jet-whistle pressures between 1 and 6 kg/cm2 the “Multiwhistle R. B.” produces acoustic waves of frequencies between 3 and 50 kc. In certain cases it is even possible to create maxima complex spectrum both in the sonic and supersonic range, this is of interest for applications such as fog dispersal or industrial aerosol agglomeration.
Note on Powerful Transmitter Research
Authors: Collet M.
Published: September 2005

New technical possibilities continually arise from theoretical studies. However, transposing promising laboratory experiences into industrial applications is only possible with powerful, simple, and good efficiency transmitters. Research is being pursued and has already given interesting results. Among other aims, they specially concern: 1. A friction loudspeaker of long service high acoustical power with high efficiency. 2. A spark generator producing very high peak power pulses for a few microseconds. This device would have to be used for dislocation.
Concerning the Structure of Turbojet Sound Field
Authors: Kobrynski Michel
Published: September 2005

The sound field of several turbojets was studied from recordings of sound levels, before analysis (40–10 000 cps) and by frequency octaves. These recordings obtained in many azimuths and at several distances have been plotted as isobaric curves. These curves show that the spreading of sound source zones is variable according to the considered frequency octave. For a constant gas velocity, the azimuth of the lobes is about 70° from the jet axis for high frequencies, and 20° for low frequencies. For increasing velocities, a rotation of the lobes towards the jet axis is observed. This displacement seems concomitant to the variations of the exponent n, of the velocity V in the expression: where Wa≃ρ2SmVn where Wa is the acoustic power, ρ the gas density, and S the cross-sectional area of the nozzle exit. In this expression, n reaches a maximum value for mean frequencies. Its random value for the whole spectrum is around 5. The value of m is greatest at low frequencies and differs little from 1 for the whole spectrum. The sound source factor η, defined as η = Wa/Wi where Wi is the jet kinetic energy, seems to vary according to 4.5 power of the Mach number for M > 1.
Acoustic Radiation from Pressure-Antisymmetric Modes of a Centrally Vented Cylindrical Cavity
Authors: Hart R. W. , Cantrell R. H.
Published: September 2005

The losses associated with the pressure-antisymmetric modes of centrally vented cylindrical cavities are of special interest because of their relevance to acoustic instability of rocket motors. Because the pressure amplitude of such an unperturbed mode is highly nonuniform over the orifice, the usual lumped circuit calculation is invalid. If it is used in spite of this, one finds no radiation out of the orifice. We have carried out a variational analysis to obtain a quantitative estimate of the loss which should actually occur.
Shift in the Location of Resonant Frequencies Caused by Large Electromechanical Coupling in Thickness-Mode Resonators
Authors: Onoe M. , Tiersten H. F. , Meitzler A. H.
Published: September 2005

The fundamental and overtone resonant frequencies of a thickness-mode, piezoelectric resonator depart from an integral-multiple relationship when the electromechanical coupling of the resonator material becomes large. These frequencies can be calculated from the equation tanX = X/k2, where X is a normalized frequency and k is an electromechanical coupling factor. The ratios of measured resonant frequencies of both thickness-dilatational and thickness-shear mode resonators made from barium titanate, PZT-5, and PZT-7 ceramics were found to show good agreement with the theory. An important practical application of this anharmonicity is in the determination of the coupling factor from the ratios of the measured fundamental and overtone resonant frequencies. For this purpose, roots of the frequency equation are tabulated for values of mode number ranging from 1 to 4 and of coupling coefficient ranging from 0 to 0.99 in intervals of 0.01. These tables can be used in the determination of three different coupling coefficients: kt, k15, and k33. These coupling factors along with the printed tables can be used to determine elastic wave velocities from measured resonant frequencies. An experimental procedure using an admittance bridge is discussed in some detail. An application of the techniques developed in this paper to the study of depoling effects due to thermal and mechanical disturbances of a ceramic material is also discussed.
Transverse Vibration of Free-Free Beams
Authors: Snowdon J. C.
Published: September 2005

Expressions are derived for the input impedance of damped free-free beams vibrating in their transverse modes, and for the transmissibility of one- and two-stage systems comprised of such beams and lumped elements of mass and compliance. The effect upon transmissibility and input impedance of varying the beam damping is considered in detail.
Radiation Efficiency of Panels
Authors: Maidanik Gideon
Published: September 2005

Theoretical predictions are compared with measurements of the radiation efficiencies of gypsum board and concrete panels.