bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Mean Pressure and Velocity in a Plane Acoustic Wave in a Gas
Authors: Westervelt Peter J. 
Published: September 2005

The one-dimensional wave equation is discussed to the second order of approximation by means of a transformation that carries the equation from the Eulerian to the Lagrangean form. Airy's solution to this equation in Lagrangean form has been shown by Fubini to be an excellent approximation to an exact solution of Earnshaw's equation of motion; therefore, Airy's solution is chosen as the basis for much of this discussion. An expression for the local mean hydrostatic pressure in a plane progressive wave is obtained by transforming Airy's solution from particle to local coordinates. In a similar way, the particle velocity in fixed coordinates is shown to possess a time-independent component proportional to, and in a direction opposite to, the intensity vector This d.c. counter-velocity is predicted without recourse to viscous forces and is compatible with zero average mass velocity. For a sound pressure level of 151 decibels in air there should exist a steady particle velocity of 1 cm/sec. Small particles suspended in the field can, under certain circumstances, acquire this velocity. An approximate treatment is suggested for handling second-effects arising from stationary field configurations. The influence of viscosity is discussed qualitatively.
One purpose of this paper is to correlate work in the field which has not so far been published in this country.
The Acoustic Pathways to the Cochlea
Authors: Wever Ernest Glen , Lawrence Merle 
Published: September 2005

Measurements are made of the relative effectiveness of the round window as a route of entrance of sounds to the cochlea. When the ear is normal this route is of no importance, but when the middle ear apparatus is absent and its advantage is lost to the oval window route a sound will have nearly equal access by both windows. When the inner ear is reached by both pathways at once the cochlear potentials represent the vector sum of what would result from the two separate waves. As phase and intensity relations between the two pathways are altered the potentials pass through maximum and minimum values, which for equal intensities of the two waves vary from a 6 db gain to a complete loss.
Evidence is produced to show that each pathway of stimulation excites the same sensory cells and in the same intensity pattern.
Over the major portion of the frequency range a minimum of response results when the waves are in phase as they enter the oval and round windows. Departures from this relation, which are most prominent at the highest frequencies, are explained as the result of reactance differences between the two windows.
These results apply to the explanation of forms of deafness caused by interruption of the ossicular chain, and also to the explanation of the treatment of otosclerosis by means of the fenestration operation.
Resonance Characteristics of a Finite Catenoidal Horn
Authors: Thiessen G. J. 
Published: September 2005

Expressions for the impedance components of a finite catenoidal horn are derived and a comparison with similar exponential and conical horns made. The impedance of a section of a catenoidal horn is also calculated and it is shown how, for the finite as well as the infinite horn, this approaches that of the exponential as more length is trimmed from the throat end.
The assumption that the resonance characteristics of a horn are the same as that of a uniform tube, provided the higher velocity of sound for the horn is used, seems to be borne out for the catenoidal horn but for the exponential horn the agreement is not very good except at higher frequencies.
Physical Factors Involved in Ultrasonically Induced Changes in Living Systems: I. Identification of Non-Temperature Effects
Authors: Fry W. J. , Wulff V. J. , Tucker D. , Fry F. J. 
Published: September 2005

The results of the first step in a systematic investigation of the mechanism of the action of ultrasound on tissue are reported. The temperature changes resulting from absorption of acoustic energy were determined while irradiation was in progress.
Experimental evidence is presented which demonstrates the existence of non-temperature effects in various nerve tissue preparations.
Microphonics Produced by Touching the Cochlear Partition with a Vibrating Electrode
Authors: v. Békésy Georg 
Published: September 2005

A vibrating electrode has been developed, with which the microphonics produced at a single point on the cochlear partition can be measured. With this electrode, which can be made to vibrate in any of three orthogonal directions, different places on the cochlear partition were investigated. The basilar membrane is more sensitive to displacement in the radial direction than in the direction perpendicular to its plane. The important question is whether microphonics are produced by a constant stationary displacement or whether they are produced only during the movement of the cochlear partition. With the aid of trapezoidal waves it was possible to show that in a fresh cochlear preparation only the static displacement produces the microphonic voltage. A single displacement of the basilar membrane produces astatic voltage lasting for several seconds. This fact has an important bearing on the energetics of the microphonics.
Preliminary experiments suggest that the same technique may be used to investigate the inner parts of the cochlear partition.
Measurements of Ultrasonic Absorption in Various Mixtures of Nitrobenzene
Authors: Sette Daniele 
Published: September 2005

To obtain information the characteristics of relaxation phenomena in liquids, measurements of ultrasonic absorption were performed in seven binary mixtures having nitrobenzene as one component.
The absorption coefficients in some systems (benzene, chloroform) confirm the results obtained previously in mixtures formed by an unassociated, very absorbing liquid and another component with much smaller absorption coefficient. In this case, the absorption coefficient decreases quickly when small quantities of the second liquid are added to the first one. The explanation of this behavior seems to be found in the fact that an increase of the efficiency of collisions between the molecules occurs. When different molecules are added to the high absorbing liquid, they decrease the time necessary to establish equilibrium among the internal degrees of freedom of the high absorbing molecules.
In other mixtures the two components have similar absorption coefficients. These systems are of great interest, because the characteristic behavior of the ultrasonic absorption in the mixture then depends on the nature of both pure liquids. If the two liquids are unassociated and their molecules do not interact strongly between themselves, the curve of the absorption coefficient versus concentration presents a very clear minimum. If, instead, there are strong interactions, the shape of the curve is altered. This would indicate the presence of an additional type of energy loss.
In the systems of nitrobenzene and an alcohol, the absorption coefficient, as a function of the mole fraction, has a maximum at an intermediate concentration, just as happens in some mixtures of water and alcohols.
Acoustic Wave Propagation Along a Constant Normal Impedance Boundary
Authors: Lawhead R. B. , Rudnick I. 
Published: September 2005

An expression is obtained for the amplitude and phase of an acoustic wave above a boundary due to a point source on or near a boundary which exhibits a constant normal specific acoustic impedance. This is shown to be a special case of the solution for an isotropic medium with constant characteristic acoustic impedance; specifically, the case is one in which the ratio of the propagation constant in the upper medium to that in the lower approaches 0.
A material which obeyed a constant normal impedance boundary condition was constructed from ordinary drinking straws. Measurements of amplitude and phase as a function of receiver position along and above the boundary showed good agreement with theory.
The nature of the approximations involved in the solution are discussed and it is shown to be an adequate representation of the sound field for distances greater than one wavelength from the source.
Recovery of the Auditory Threshold after Strong Acoustic Stimulation
Authors: Hirsh I. J. , Ward W. D. 
Published: September 2005

After an ear is exposed to an intense sound, the absolute threshold for many sounds is raised, usually temporarily. The manner in which the absolute threshold recovers to its normal value after such stimulation is the subject of these experiments. It is found that recovery from such auditory fatigue is not a simple monotonic process. Rather these experiments show that under certain conditions the threshold first recovers to an approximately normal value about 1 minute after the cessation of the exposure but then rises again to a higher value that reaches a maximum at about 2 minutes after the exposure. This diphasic recovery curve, with its characteristic “bounce,” is found when the exposure involves sound pressure levels between 100 and 120 db and durations of the order of several minutes.
Recovery curves are shown for the auditory thresholds of clicks, bands of noise, and pure tones. Fatiguing stimuli include bands of noise and pure tones.
Two subsidiary observations are also reported. First, in many recovery curves there is evidence for a second “bounce” or rise in the threshold after stimulation. Second, after stimulation by moderate intensities the initial recovery (about 1 minute after stimulation) may demonstrate facilitation, i.e., a temporary reduction in the absolute threshold below the normal value. Qualitative observations concerning the pitch and timbre of the test stimuli and of tinnitus following stimulation are related to some of the data.
Gross Localization of the Place of Origin of the Cochlear Microphonics
Authors: v. Békésy G. 
Published: September 2005

An apparatus was developed that made it possible to push an electrode automatically with an absolutely even and smooth velocity through the cochlear partition of an anesthetized guinea pig. The ac and dc potentials of this perforating electrode were recorded during the perforation when sound was applied to the eardrum, or when an electrical generator was connected to the vestibular and tympanic channels of the cochlea. These measurements enable us to show that the endolymph is surrounded by an electrically insulating layer, and that the inner part of the organ of Corti is protected from external electrical potential fields. Further, it was shown that the microphonics produced by a vibration of the eardrum have larger values inside the endolymph than in the perilymph or near the round window. The microphonics seem to reach a maximum near the organ of Corti.
The perforation measurements also made it possible to discriminate three types of tissues in the cochlea: (1) highly sensitive cells with large microphonics and dc potentials; (2) cells that do not produce large microphonics but still have in them large dc potentials; and (3) tissues that are electrically indifferent and can be represented by an electrical resistance. These distinctions and the measurement of the electrical conductivity of the endolymph permit a coarse description of the electro-anatomy of the cochlear partition.
The Thermal-Noise Limit in the Detection of Underwater Acoustic Signals
Authors: Mellen Robert H. 
Published: September 2005

The criteria for an “optimum” hydrophone receiving system for underwater acoustic signals are considered, and the equilibrium thermal-noise pressure spectrum expression is shown.
Experimental ambient sea-noise spectrum levels are in excess of the thermal noise at all frequencies below 25 kc. Extrapolation of experimental curves (−5 db/octave) shows intersection with thermal-noise spectrum (+6 db/octave) between 50 and 200 kc, depending on sea state. (For a definition of “sea state,” see Instructions to Marine Meteorological Observers (U. S. Department of Commerce Weather Bureau, U. S. Government Printing Office, Washington, D. C., June, 1941), seventh edition, circular M.) The ambient-noise level is expressed as a function of the equivalent temperature.
Formulas are then derived for the required plane-wave signal level for which electrical signal-to-noise ratio is unity. The operating noise factor is defined in terms of the electroacoustical efficiency of the linear reversible hydrophone, the amplifier noise figure, and the equivalent ambient-noise temperature for the sea condition and frequency under consideration.
The Space-Time Pattern of the Cochlear Microphonics (Guinea Pig), as Recorded by Differential Electrodes
Authors: Tasaki I. , Davis H. , Legouix J.-P. 
Published: September 2005

Pairs of very small electrodes were placed in two or more turns of the cochlea of the guinea pig. The cochlear microphonic from a short segment (about 1 mm) of the cochlear partition can thus be recorded, and without contamination by action potentials. The outputs of the second, third, and fourth turns were compared with that of the first turn with respect to both amplitude and phase as a function of frequency. The space-time pattern thus revealed is a traveling wave which passes up the cochlea to a distance that depends on the frequency. The pattern agrees well with that of mechanical movement (Békésy) except that the cochlear microphonic shows relatively greater amplitude (voltage) in the basal turn. Low frequencies travel farther up the cochlea than do high. The velocity (for a 750 cps tone) is about 100 m/sec in the basal turn and about 2 m/sec in the fourth turn. Phase differences of as much as 5π were observed, by means of Lissajous patterns, between the responses of the first and the third turn. Certain discontinuities in the input-output relationships and in phase relationships were found to be a function of frequency and of position along the cochlear partition. These discontinuities occurred at or near the frequencies that showed a phase difference of 2π from the basal end of the cochlea. The relation of these critical frequencies to position along the cochlea constitutes a new “frequency-map” of the cochlea.
The space-time pattern of the cochlear microphonic proved to be very little affected by removal of portions of the bony wall of the cochlea or delivering acoustic energy through a hole near the apex. It is concluded that, in addition to “direct driving” of the cochlear partition by pressure differences between the two scalae and to “surface waves” arising from such drying, the transmission of transverse waves along the solid structures of the cochlear partition must also be included for a satisfactory interpretation of all of the available data.
Brownian Motion and the Transmission of Energy in the Cochlea
Authors: de Vries H. L. 
Published: September 2005

It is shown that Brownian motion at the eardrum is only partly due to noise of the air. (This part has been calculated by Sivian and White.) The main part is due to Brownian motion of the eardrum itself. The apparent flow of energy is close to the absolute threshold of the ear; it is reduced to one half when the ear is provided with an exponential horn.
The discussion of the Brownian noise in the inner ear reveals a serious discrepancy; considering one individual cell it proves to be very difficult to reconcile the low threshold with the thermal agitation. A mechanism is suggested for the excitation of the sense cells by which the disturbances by Brownian motion are appreciably suppressed; in this model the microphonic activity plays an important part. The model is based on some recent measurements of the microphonic activity of the lateral line organs of fishes, which are shortly summarized. It follows from these measurements that the microphonic potentials are related with the tension of the hairs on the sense cells.
Electromechanical Properties of BaTiO3 Compositions Showing Substantial Shifts in Phase Transition Points
Authors: Berlincourt Don A. , Kulcsar Frank 
Published: September 2005

Incorporation of CaTiO3 or Y2O3 into BaTiO3 ceramics causes a downward shift of the second transition point, resulting substantial improvement of temperature stability in the normal operating range.
Dielectric and electromechanical properties of BaTiO3 ceramics containing CaTiO3, Y2O3, and PbTiO3 are shown from −40° to +120°C. The composition containing 5 weight percent CaTiO3 combines high piezoelectric response with low temperature dependence of operating characteristics.
The Effects of Biological Tissues on 15-mc Pulsed Ultrasound
Authors: Wild J. J. , Reid John M. 
Published: September 2005

The subject of this paper, which is mainly descriptive, grew out of the desire of a biologist to measure the thickness of the human bowel wall in the living intact subject. [J. J. Wild, Surgery 27, 183 (1950)]. The object was to justify certain methods of treatment for the suspected underlying mechanisms at work, the results of which are lumped together by surgeons under the title of bowel distension.
The approach to the subject has been almost entirely biological, not ignoring, however, the theory of sound where applicable. It will be seen that biological methods of control are used as a first approximation in order to justify more detailed examination of the system. Some of the difficulties of the exact approach from theory will be discussed after presentation of the experimental facts. It may be of interest to the more exact-thinking members of the audience to note that a system having a nightmare of complexity to the physicist may be considered simple by the biologist in his blissful ignorance. This situation is perhaps fortunate because otherwise the biologist might be tempted to give up too easily. It is the duty of the biologist to try to simplify complex phenomena so that his more able colleagues in more exact branches of science will be stimulated to “pitch in” and help. We hope that today we shall be able to bring about this desirable end and succeed in stimulating more workers to investigate this field. It should, however, be realized at the outset that the increasing exploitation of the observed phenomena does not necessarily need to wait upon whatever fundamental explanations may be forthcoming. The experimental results will not necessarily be presented in chronological sequence but an attempt will be made to present some of our collected experimental data in as logical a manner as possible.
Graphical Aids in Interpreting the Performance of Crystal Transducers
Authors: Cady Walter G. 
Published: September 2005

When the mechanical damping of a transducer is large, as by acoustic radiation from one or both faces into a liquid or solid, the circular diagram that represents its characteristics requires special treatment. As a background for this treatment, the uses and limitations of the conventional circle for a resonator with small losses is first reviewed. The problem of the transducer with large losses is then considered with special reference to the equations and graphs for a thickness-type transducer with unsymmetrical loading. For plane-wave transducers the expressions are exact for all loads and at all frequencies, including harmonics. Either the voltage or the current may be constant. From the admittance or impedance diagrams the magnitude and phase of current, voltage, particle velocity, and vibrational amplitude at any frequency can be obtained immediately. Similar results would be found with plates in lengthwise vibration. A new type of diagram is developed for representing vibrational amplitudes. As an illustration, the case of a quartz plate radiating into three liquids of widely different acoustic properties is treated.
When the load is unsymmetrical, there is no true node anywhere in the crystal except when the load is zero or infinity. There is, however, a plane of minimal vibration, the amplitude and location of which are derived. The equations indicate certain peculiar effects when the specific acoustic resistance of the medium is just twice that of the crystal.
Loudness Relations in Two-Component Tones
Authors: Small Arnold M. , Thurlow Willard R. 
Published: September 2005

A two-component tone was presented under a number of frequency and intensity conditions. The loudness of each component and the total loudness of the combination were traced as the intensity of the higher frequency and were brought from masked threshold to well above masked threshold. Loudnesses were determined by equating the tone or tones under consideration to a comparison tone.
When the higher frequency of the pair was at or below 1000 cps, it showed a loudness loss, relative to its loudness when presented alone, at medium intensities above its masked threshold; but as its intensity was increased, it tended to regain its normal loudness. When the higher frequency of a pair was above 1000 cps, it exhibited a greater than normal loudness at medium intensities above its masked threshold which again approached normal with increased intensity. The lower frequency of a pair seemed to be little affected by increases the intensity of the higher frequency within the limits of intensity used. Total loudness tended to be the algebraic sum of the components' loudnesses. The results indicate that the effect of a tone upon the loudness of another is not so simple a phenomenon as a tone's effect upon the threshold of another.
Ultrasonic Relaxation and Its Relation to Structure in Viscous Liquids
Authors: Litovitz T. A. , Lyon T. , Peselnick L. 
Published: September 2005

Measurements of ultrasonic propagation of longitudinal waves in pentachlorobiphenyl were made over a large range of viscosity at frequencies in the range 7.5 to 52.5 Mc. The data at low viscosities demonstrated the presence of both shear and compressional viscous processes. Measurements in the relaxation region indicated that a single relaxation time theory could not explain the results. Several possible explanations are discussed. The data at very high viscosities showed a frequency independent absorption loss per wavelength, which indicated the possible presence of a nonrelaxational type of hysteresis.
The thermal coefficient of the high-frequency velocity was measured and found to be about twice the coefficient of the low-frequency velocity. The thermal coefficients of the instantaneous elastic moduli are compared to the low-frequency elastic moduli. It was concluded that the differences in the temperature dependence of these moduli could be related to the changing degree of order in the liquid.
Hearing Losses of Aircraft Repair Shop Personnel
Authors: Webster J. C. 
Published: September 2005

The Navy Electronics Laboratory's warble-tone audiometer test was administered from magnetic tape to 1133 overhaul and repair shop personnel. They were tested in groups of 18. The results were analyzed (1) by percentiles within each ten year age grouping, and (2) by classifying each audiogram into one of four deafness categories: normal, conductive, nerve, and mixed. In both analyses the results were compared to similar analyses on a large reference non-noise-exposed population.
The results show that roughly half the population is not adversely affected by noise. The worst hearing quarter of the noise-exposed population show considerable hearing losses especially at the higher frequencies when compared to the worst hearing quarter of the nonexposed population. The number of audiograms classified as “normal” drops from 78 percent to 66 percent, and the number classified as nerve deafness increases from 10 percent to 22 percent when the noise-exposed population is compared to the nonexposed population.
A set of masking contours is included on a sound-level chart so that knowing the noise level in a prospective test room, the minimum level of hearing loss that can be measured in that room can be readily determined.