bluuebunny/crossref_metadata_2025 huggingface dataset:
The Intervalgram as a Visual Representation of Speech Sounds
Authors: Chang S. H. , Pihl G. E. , Wiren J.
Published: September 2005

The points of zero crossing and the points of zero slope of the oscillograms of speech sounds are considered to contain the essential information for intelligibility. The intervals between zero crossings θ0, and the intervals between zero slopes θm, are plotted as points in rectangular coordinates. The ordinate of the dot is a function of θ (θ0 or θm), and the abscissa is a function of the time of occurrence t of the particular θ. The resulting intervalgram gives a half-tone picture (consisting of dots) of speech sounds. The patterns may be proportioned to show either a detailed or general representation of the variation of the interval distribution. One type of pattern portrayed at the speech rate on a cathode-ray oscilloscope with a screen of long persistence has been found quite similar in certain respects to the patterns obtained using the sound spectrograph as described in the book Visible Speech by Potter, Kopp, and Green. The equipment involved in obtaining the intervalgram, however, is much simpler.
Tentative Recommended Practice for Laboratory Measurement of Airborne-Sound Transmission Loss of Building Floors and Walls
Authors: London A.
Published: September 2005

The American Society for Testing Materials recently promulgated the tentative recommended practice which is reproduced below with the permission of that Society. As far as is known this is the first successful tentative standard which has been adopted in the field of architectural acoustics in this country, even though standardization efforts along these lines go back to the late 1930's. This specification was prepared by Subcommittee VII on Sound Transmission of ASTM Committee E-6 on Building Constructions. The chairman of the Subcommittee is Richard K. Cook, while members of the writing group were Albert London and William A. Jack.

Copies of the specification may be obtained from the ASTM at a cost of 25 cents each. The complete unabridged tentative is as follows (the “Society” referred to in the tentative is of course the American Society for Testing Materials).
On the Relation between the Sound Fields Radiated and Diffracted by Plane Obstacles
Authors: Wiener Francis M.
Published: September 2005

In the past, acoustic diffraction and radiation problems have often been treated separately, although their intimate connection is clear from theory. In the case of plane piston radiators and plane rigid scatterers exposed to a perpendicularly incident plane wave, this connection becomes particularly simple and useful. It is easy to show that the radiated sound field is everywhere the same as the field scattered (diffracted) in the diffraction case, except for a factor of proportionality. It is also shown that the reaction of the medium on the radiator, as expressed by the mechanical radiation impedance, is equal to the force per unit incident pressure exerted on the same obstacle, held rigid as a scatterer, except for a factor of proportionality. By way of illustration, the foregoing principles are applied to the important case of the circular disk.
The Scattering of Sound from a Prolate Spheroid
Authors: Spence R. D. , Granger Sara
Published: September 2005

This paper presents the results of calculations of the scattering of a plane sound wave from a prolate spheroid. Scattering patterns are given for the major axis equal to λ/π, 2λ/π, 3λ/π, for the ratio of axes equal to 0.10, 0.20, 0.29, 0.37, and for the angle of incidence measured from the major axis equal to 0°, 30°, 60°, 90°.
A Time Constant Meter for Tuning Forks and Other High Q Devices
Authors: Morrow Charles T.
Published: September 2005

The time constant meter described operates on the principle that differentiation of an exponentially decaying rectified envelope decreases it in inverse proportion to the time constant and reverses its sign. Hence, it is possible to obtain a null by balancing the differentiated signal against a portion of the original. The circuit is simple, requiring only one amplifier tube and a tuning eye.
Wave Effects in Isolation Mounts
Authors: Harrison Mark , Sykes Alan O. , Martin M.
Published: September 2005

Both theoretical and experimental studies of wave effects in isolation mounts have been made. From the standpoint of vibration isolation, wave effects are important in the sense that the vibration isolating properties of a mount are changed by their presence. The well-known “lumped parameter” theory of vibration mounts predicts that the vibration isolation of a mount increases at 12 db per octave for frequencies well above the resonant frequency of the spring-mass system. This theory holds true only when the wavelength of the elastic wave in the mount is large compared to the dimensions of the mount. Standing waves occur, as would be expected, which in certain frequency ranges decrease the vibration isolation properties of the mount by as much as 20 db. For practical mounts, wave effects are most detrimental in the most audible frequency range (500 to 1000 cps). The theoretical and experimental treatments are in good agreement, and indicate various methods for improving the vibration isolation properties of the mount. Experimental data concerning isolation mounts fabricated of various materials are presented.
DC Resting Potentials Inside the Cochlear Partition
Authors: v. Békésy Georg
Published: September 2005

Inside the cochlear partition there is without any acoustical stimulus a dc potential difference between the organ of Corti and the endolymph of the order of 100 millivolts. The possible significance of this potential difference has been pointed out. The magnitude of the potential difference seems to indicate that the cochlear partition represents a pool of energy.
A Precise Recording Ultrasonic Interferometer and Its Application to Dispersion Tests in Liquids
Authors: Barthel Romard , Nolle A. W.
Published: September 2005

A precise recording ultrasonic interferometer is presented which is particularly well suited for measuring dispersion in liquids. The device is an interferometer of the two-crystal type in which the separation of the crystals is continuously varied. The recording process is equivalent to placing a mark on a rotating recording drum whenever the receiving crystal has moved a distance of one wavelength of sound in the liquid. Thus the wavelength of sound may be derived from the known mechanical constants of the system. The precision of the dispersion measurement is about 0.8 part in 10,000; the precision of the absolute determination of sound velocity is 0.2 m/sec. The instrument has been applied also to sound velocity measurements in solids under restricted conditions.

Sound velocity in distilled water at 25°C as measured with this instrument is 1496.2±0.2 m/sec, a value somewhat lower than that obtained by earlier investigators.

Dispersion in the frequency range 5–25 Mc is shown to be no greater than 0.8 part in 10,000, the limit of experimental error, for all the liquids studied: water, geraniol, xylene, isobutyl alcohol, and solutions of sucrose, NaCl, MgSO4, NaHCO3, CdCl2, CdSO4, Na3PO4, Pb(NO3)2, ZnSO4, and K3Fe(CN)6.
Acoustical Determinants of Audiogenic Seizures in Laboratory Mice
Authors: Frings Hubert , Frings Mable
Published: September 2005

Albino mice were tested for susceptibility to audiogenic seizures in sound fields of various frequencies and intensities. An attempt to fix the ears of the mice with respect to the sound source by suspending the mice with a large spring clip which grasped the dorsal skin-fold proved fruitless, for too few seizures were induced at any intensity. The mice were therefore tested in a small wire mesh cage suspended in front of the sound-transducer, and the positions of their ears during the treatment were recorded. At 10 kc, at least 92 db was needed to induce seizures in mice which had no previous seizures, while only 83 db were needed for animals which had previous seizures. The most effective frequencies for the induction of seizures were between 12 and 25 kc. Below 10 kc, the effectiveness dropped off sharply and was very low at 5 kc. Studies were not made above 25 kc. The peak of the mouse's audiogram is probably near the frequencies which are most effective for induction of seizures and is thus a little lower than that of the rat and about 1.5 octaves above that of man. The ability of mice to hear at frequencies which are ultrasonic for the human ear is probably the reason for the intense reactions of mice to complex sounds which seem of moderate intensity to man.
The Noise Field of a Turbo-Jet Engine
Authors: von Gierke H. E. , Parrack H. O. , Gannon W. J. , Hansen R. G.
Published: September 2005

The noise fields generated by a standard turbo-jet aircraft engine have been measured for three different power settings. Measurements were made at points on circles around the engine having radii of 25 and 50 feet. For the 50-feet distance the directional characteristic presented for the over-all sound pressure and for the noise in the different octave bands starting at 37.5 cps. From these measurements the total acoustic power radiated from the engine is calculated to be approximately 69 kw at full engine power. The distribution of this power over the different frequency bands and space angles is shown. The highest total energy per cycle and the highest sound levels are found at frequencies near 100 cps for the higher power settings of the engine. Above that frequency range the total energy per cycle drops approximately as the reciprocal of the square of the frequency. The data should help us understand qualitatively the jet engine as a sound source and are therefore discussed in that respect. On the other hand, the data have practical significance with respect to the design of test facilities for adequate protection of personnel. They are equally important with respect to problems of noise control on an airport.
Experimental Investigations on the Origin of the Anomalous Absorption of Ultrasonic Waves in Liquids
Authors: Wada Yasaku , Shimbo Sotoshi
Published: September 2005

There are two classes of liquids which show anomalous absorption of ultrasonic waves, class A1 (nonassociated liquids) and A2 (associated liquids). In mixtures of two liquids of class A1, both density and sound velocity vary almost linearly with concentration, in spite of the anomalous variation of sound absorption. The smaller the ultrasonic absorption of a liquid of class A1, the greater is the decrease of absorption per unit concentration in a dilute benzene solution of the liquid. This does not hold in liquids of class A2, such as alcohols. The inverse correlation between the absorption of ultrasonic waves and infrared radiations was found in the case of liquids of class A1. It was concluded from the above facts that the absorption of ultrasonic waves in nonassociated liquids should be a result of the so-called “molecular absorption,” in the same way as in gases. In the case of associated liquids some part of the absorption is probably ascribed to the molecular absorption, but the remaining part may be caused by another relaxation mechanism, a slow change in local order of molecules. The contribution of the molecular absorption to that, in highly viscous liquids. is also estimated.
Spherical Wave Propagation in Solid Media
Authors: Blake F. G.
Published: September 2005

Divergent compressional waves in solids differ from similar waves in fluids, even though the particle displacement is parallel to the direction of propagation in both media. The wave propagating from a radially oscillating spherical cavity in an infinite solid medium sees an acoustic radiation impedance which is a function of the Poisson's ratio of the medium as well as of the usual parameters. The radiation resistance has the same form as in a fluid medium, but the reactance is a negative or stiffness reactance, except at high frequencies in media of low rigidity. When an impulsive pressure is generated in the cavity, as by an explosion, the form of the radiated pulse is a damped oscillating wave train which does not closely reproduce the original pressure pulse.
Radiation Loading of a Piston Source in a Finite Circular Baffle
Authors: Watson Robert B.
Published: September 2005

Experimental data are exhibited for the radiation loading of a piston source enclosed in a circular finite baffle of dimensions of the order of the wavelength. A partial explanation of the data is given in terms of the direct radiated wave from the piston source, the diffracted wave arising at the edge of the baffle, and the wave arising from vibration of the baffle. The effect of flexural vibration of the piston source is shown to increase the radiation loading appreciably. Examination of the theoretical attempts to evaluate the radiation loading shows the lack of suitable expressions for calculation.
Inharmonicity of Plain Wire Piano Strings
Authors: Young Robert W.
Published: September 2005

The inharmonicity of plain wire strings in situ has been measured in six pianos of various styles and makes. By inharmonicity is meant the departure in frequency from the harmonic modes of vibration expected of an ideal flexible string. It is shown from the theory of stiff strings that the basic inharmonicity cents (hundredths of a semitone) is given by 3.4×1013n2d2/v02l4, where n is the mode number, d is the diameter of the wire in cm, l is the vibrating length in cm, and v0 is the fundamental frequency. A value of Q/ρ = 25.5 × 1010 (cm/sec)2 was assumed for the steel wire, where Q is Young's modulus and ρ is the density. The observations are entirely compatible with the relationship given. In general terms the inharmonicity of the plain steel strings is about the same in all the pianos tested, being about 1.2 cents for the second mode of vibration of the middle C string. Above this point every eight semitones it is doubled. Below middle C the inharmonicity is consistently less in large pianos than in small ones.
The Reflection of a Pulse by a Spherical Surface
Authors: Anderson D. V. , Northwood T. D. , Barnes C.
Published: September 2005

The Kirchhoff integral is applied to obtain an approximate solution for the pulse reflected from the surface of a sphere to a receiver near the source. The solution shows that for a reflection path of minimum time (in the sense of Fermat's principle) the reflected pulse should develop a “coda” and that for a path of maximum time, a “prelude.” The approximations are such that the coda and prelude should have an amplitude greater than that predicted by the integral. It was found experimentally that a prelude did result from a reflection over a path of maximum time. The information from reflections over paths of minimum time was less definite, but it can be safely inferred that a coda developed as well. In addition, the pulse diffracted from the edge of an open reflector was examined and found to have the sign predicted by the integral. It can be concluded that the Kirchhoff integral can be used to give a good description of pulse reflection.
A Theoretical Model for Sound Scattering by Marine Crustaceans
Authors: Machlup Stefan
Published: September 2005

With an eye to application in the investigation of sound scattering by marine life, the reflectivity of a spherical elastic shell containing a fluid is studied. It is found that for incident wavelengths of the order of magnitude of the sphere, the behavior for thin shells is similar to that of the fluid sphere alone. For longer wavelengths a correction is computed, good to terms in the first power of the thickness: diameter ratio of the shell.
The Use of Perforated Facings in Designing Low Frequency Resonant Absorbers
Authors: Callaway D. B. , Ramer L. G.
Published: September 2005

The effect of perforated facings of a small percent open area on the specific acoustic resistance of backing materials of appreciable thickness was investigated for several backing materials. The resistance was found to increase by factors of 2 to 7 depending on the percent open area of the facing and the resistance of the backing material. The increase was considerably less in all cases than 1/p, where p is the open area ratio of the facing. It was found that the specific acoustic resistance of a resonant absorber can be varied considerably above and below the resistance of the uncovered backing by means of an air space between the facing and the porous backing.
The Anomalous Behavior of the Threshold of Hearing in Relation to the Equal Loudness Contours
Authors: Guelke R. , Helm H.
Published: September 2005

It is shown that for a 100-cycle note the well-known compression of the loudness contours at low frequencies is no longer valid near threshold. Measurements are carried out on 38 subjects in a free field test, and on 10 subjects in a monaural test to show that the intensity jump from threshold to 10 phons is greater at 100 cycles per sec than at 1000 cycles per sec. This is contrary to experience at higher intensities where the intensity jump is smaller at 100 cycles than at 1000 cycles. A possible explanation for the effect is put forward involving the middle ear muscles.
A More Rapidly-Convergent Expansion for the Velocity Potential of a Piston Source
Authors: Elrod Harold
Published: September 2005

The purpose of this note is to present a more rapidly convergent variation of the Carter and Williams' expansion for the velocity potential of a piston source in an infinite, rigid wall. This new variation is expecially useful for calculations in the paraxial regions, where it shows the terms neglected by earlier approximate formulas.
The Reciprocity Calibration of Piezoelectric Accelerometers
Authors: Harrison Mark , Sykes A. O. , Marcotte Paul G.
Published: September 2005

Two piezoelectric accelerometers have been calibrated by an absolute reciprocity technique in the frequency range from 100 cps to 10 kc. A theoretical and experimental evaluation of the technique is given.
Acoustic Radiation Pressure of Plane-Compressional Waves at Oblique Incidence
Authors: Borgnis F. E.
Published: September 2005

The forces due to acoustic radiation in a beam of finite cross section in a nonviscous medium striking a plane reflector at oblique incidence are derived from simple mechanical considerations. The formulas are applied to a wedge-shaped vane. For a vane, the wings of which include an angle of 90°, the force turns out to be quite independent of the coefficient of reflection at the boundary between vane and medium.
A New Method for the Visualization and Measurement of Ultrasonic Fields
Authors: Bennett G. S.
Published: September 2005

A new method for the observation of ultrasonic field distributions described, utilizing a starch plate in a dilute solution of iodine in a manner analogous to the use of photographic emulsions. Near-field diffraction patterns are shown as illustrative of results, which appear to be superior to those of other methods, and the advantages of the new method over previous techniques are described.
Ultrasonic Velocity, Dispersion, and Absorption in Dry, CO2-Free Air
Authors: Ener C. , Gabrysh A. F. , Hubbard J. C.
Published: September 2005

The velocity, dispersion, and absorption of ultrasonic waves in dry, CO2-free air have been measured at 32°C, and at two and three Mc/sec, and at pressures ranging from 0.020 to one atmos. Dispersion of the velocity has been found beginning at 30 Mc/atmos, increasing by five percent at 100 Mc/atmos, accompanied by a large increase in absorption such that at the higher limits of f/p, reached measurements became nearly impossible with the equipment used. The ratio αexp/αclass decreased from about 2.4 to 1.3 and Cv/R from 2.5 to nearly 1.5 as f/p increased. The changes in velocity, absorption, and internal specific heat are interpreted as the result of the slowing of energy exchange between translational and rotational states. Assuming that relations for relaxation of translational-vibrationai exchange also hold for this case, the relaxation time for translational-rotational exchange as derived from the dispersion measurements has been found to be 2.29×10−9 sec. This corresponds to a frequency of the midpoint of the dispersion curve of 116 Mc/atmos, and to 16 as the number per molecule of collisions required for an energy exchange between translational and rotational states. Absorption results were more difficult to secure; using low frequency values a relaxation time of about 3×10−9 sec is indicated, giving 87 Mc/atmos as the f/p value of the midpoint of the dispersion curve, and 21 as the number of collisions required for the energy exchange.
The Perception of Speech Sounds by Deafened Persons
Authors: Fletcher Harvey
Published: September 2005

In a previous paper by Fletcher and Galt [J. Acoust. Soc. Am. 22, 89 (1950)] a method was described for measuring experimentally and also for calculating the interpretation aspect of the perception of speech. The listeners were considered to have normal hearing. In the present paper the same principles are applied to persons having abnormal hearing.
Dimensions of the Cochlea (Guinea Pig)
Authors: Fernández César
Published: September 2005

Measurements have been made under the microscope of many structures in the cochlea of the guinea pig and the results plotted graphically as a function of position along the cochlea. The structures measured are the spiral lamina, Rosenthal's canal, the basilar membrane (length, width and thickness), the channels and windows of the cochlea (cross-section area) and the hair cells (angles of orientation).
On the Effect of Frequency and Amplitude Distortion on the Intelligibility of Speech in Noise
Authors: Pollack Irwin
Published: September 2005

The effect upon the intelligibility of speech in noise of the interaction of sharp frequency limiting and severe peak clipping was studied. The results are compared with previously reported results of similar tests with frequency-limited speech signals that were not subjected to amplitude distortion. The intelligibility of unclipped speech, relative to that of the peak-clipped signal under corresponding experimental conditions, is a function of the signal-to-noise (S/N) ratio under test and is, to a rough approximation, independent of the frequency range of the speech signal passed. At high S/N ratios, the intelligibility of the unclipped speech signal is higher than that of the severely peak-clipped signal. Under low S/N ratios, however, the intelligibility of the latter is considerably higher than that of the unclipped signal.
Some Experiments on the Perception of Synthetic Speech Sounds
Authors: Cooper Franklin S. , Delattre Pierre C. , Liberman Alvin M. , Borst John M. , Gerstman Louis J.
Published: September 2005

Synthetic methods applied to isolated syllables have permitted a systematic exploration of the acoustic cues to the perception of some of the consonant sounds. Methods, results, and working hypotheses are discussed.
Dependence of Pfeifenton (Pipe Tone) Frequency on Pipe Length, Orifice Diameter, and Gas Discharge Pressure
Authors: Anderson A. B. C.
Published: September 2005

Measured dependences of the Pfeifenton frequency on static flow pressure, orifice diameter, and pipe length are presented, based upon studies of air flowing through pipes terminated various orifices. Frequency measurements were made of the vibrations inside the pipe. The Pfeifentöne are not a series of discrete single valued harmonics. Each covers a range of frequencies, any specific value of which is determined by the discharge flow-velocity or pressure. When the orifice diameter approaches zero the behavior of the primary Pfeifenton frequencies is as if they were produced by an open-closed organ pipe; when the orifice diameter approaches that of the pipe, the behavior is as if they were produced by an open-open organ pipe. A mechanism for the excitation of the Pfeifentöne is proposed.
Attenuation of Sound Resulting from Ionic Relaxation
Authors: Hall L. H.
Published: September 2005

Slowness in the rearrangement of ion configuration under acoustic perturbation should cause sound absorption in ionic solutions. This mechanism investigated from the standpoint of the Debye-Ḧckel theory of strong electrolytes. The electrostatic part of the free energy of the solution is formulated in terms of temperature, volume, and an ion configuration function. The partial derivative of this expression with respect to volume gives the electrostatic component of pressure. A rate equation for change of ion concentration at a point enables us to find the variation in the ion configuration function with a small harmonic fluctuation in volume. Since the pressure is expressed in terms of the configuration function, this leads readily to the relaxational bulk modulus connected with rearrangement. The rate equation involves a parameter which in interionic theory has been identified as the relaxation time of the ionic atmospheres and can be evaluated from conductivity data. A calculation made for MgSO4 solutions sets the relaxation frequencies for 0.001 and 0.01 molal concentrations at 21 and 143 mc, respectively, and shows the maxima in the wavelength absorption coefficients to be 20 and 660× 10−9 respectively. The recently reported much higher excess absorptions for MgSO4 at lower frequencies are thus due to processes other than ionic relaxation.
Acoustic Relaxation in a van der Waals Gas
Authors: Beyer Robert T.
Published: September 2005

Expressions are given for the sound velocity and the absorption coefficient per unit wavelength for a van der Waals gas. Numerical calculations have been carried out for several triatomic gases. In general, the velocity corrections, under standard conditions, average about 0.5 percent, while the absorption corrections are two or three times larger.
Acoustical Interference Filters
Authors: Curtis K. K. , Hadley L. N.
Published: September 2005

An analysis of the problem of a longitudinal wave normally incident upon the first of the four parallel boundaries separating five distinct media is presented. The filtering action which is characteristic of this physical situation is discussed, and it is found that this arrangement acts as a band pass filter with very narrow pass bands whose centers are separated by a frequency difference primarily dependent upon the thickness of the third medium. On the basis of this analysis, filters have been built which behave experimentally much as they are predicted to behave throughout the frequency region investigated (5000–20,000 cycles per second).
Atmospheric Winds and Temperatures to 50-Kilometers Altitude as Determined by Acoustical Propagation Studies
Authors: Richardson John M. , Kennedy William B.
Published: September 2005

An average of three measurements per month of upper atmosphere winds and temperatures was made during the period July 21, 1950 through May 31, 1951 by means of acoustical propagation studies. Field operations were centered in Wray, Colorado (40° N. lat, 102° W. long) and extended radially 200 km. A variation in azimuth and distance from sound source to recorder positions permitted the separation of wind and temperature components of the observed upper atmosphere sonic velocity gradients. It was found that upper winds were generally westerly and of large magnitude during the winter (autumnal to vernal equinox) and easterly and of small magnitude during the summer, with wide fluctuations during the equinoctial periods. Short-term fluctuations in the wind vector were observed to be of the same order of magnitude as the vector itself. The short-term fluctuation is now well established. A doubly-periodic annual variation in temperature was observed above 25-km altitude, with mean value in agreement with accepted NACA values.
A Reverberation Chamber with Polycylindrical Walls
Authors: Botsford J. H. , Lane R. N. , Watson R. B.
Published: September 2005

A reinforced concrete reverberation chamber has been constructed with diffusing cylinders of random size cast in the ceiling and walls. Energy loss in the empty chamber is low because the rigid, heavily enameled walls have a low absorption coefficient and the attenuation loss in the air is moderate for such a small volume. Materials are tested in the frequency range from 250 cps to 12 kc using half-octave noise bands.
Acoustical Properties of Trumpets
Authors: Igarashi Juichi , Koyasu Masaru
Published: September 2005

Acoustical properties of the B♭ trumpet were investigated. By comparing two trumpets judged to have good and poor musical quality, respectively, it was found that the air leakage at the pistons reduced the Q value of the resonance. An irregular frequency distribution of the higher normal modes of the trumpet was also studied. The effect of the connecting condition of the tube and horn of the trumpet on the harmonic relation of the normal modes of the air column was studied. The measured resonance frequencies were found to agree well with the maximum driving point radiation resistance computed for various combinations of tube and horn.
The Calibration and Use of Probe-Tube Microphones
Authors: Benson Robert W.
Published: September 2005

A study was undertaken to obtain the free-field and the coupler calibrations of several probe-tube microphones with tubes of different sizes and to determine those characteristics of a probe tube which are necessary for accurate measurements in both a free field and in closed couplers. For accurate measurements with a probe-tube microphone, precautionary measures must be taken. The probe tube must be sealed to the frame of the microphone in order to prevent an acoustic leak. Such a leak causes reduction in the output of the probe-tube microphone at the lower frequencies. A probe tube with a high input impedance should be used for making measurements in a closed coupler. A high input impedance is necessary if the pressure in the coupler is to remain the same as before the insertion of the probe tube. If measurements are to be made with the accuracy of measurements made with a standard laboratory microphone, there is a significant difference between the pressure and the free-field calibrations of probe-tube microphones.
Temperatures Produced in Tissues by Ultrasound: Experimental Study Using Various Technics
Authors: Herrick J. F.
Published: September 2005

Experiments have been carried out to investigate ultrasound as a possible therapeutic agent. These show that selective heating occurs in nerves and bones treated in situ. Effects of direct heat on nerves are strikingly similar to the effects of ultrasound. Blocking of nerves by sound or heat with present techniques seems impractical because the margin of safety is too narrow.
A Vibrating-Plate Viscometer
Authors: Woodward J. G.
Published: September 2005

When a thin, flat plate executing linear oscillations in its own plane is immersed in a liquid, shear waves are set up in the liquid, and the liquid exerts a retarding force on the plate. This force, which can be measured by means of an electromechanical transducer to which the vibrating plate is coupled, is a function of the product ηρ of the coefficient of viscosity and the density of the liquid. Electrical measurements thus permit a computation of the value of ηρ. A viscometer which operates on this principle and is simple in both construction and use is described. This instrument gives instantaneous indications of ηρ over a wide range and also permits continuous indications of ηρ as a function of time to be made. A theory based on the impedance offered to an infinite vibrating plate by a liquid in which it is immersed is shown experimentally to give a valid, approximate description of the performance of the vibrating-plate viscometer in its practical form.
Some Acoustical Properties of Lead and Other Substances at Liquid Nitrogen Temperature
Authors: Ernst Paul J. , Zayon Phyllis
Published: September 2005

Simple experiments are described by which some acoustical and elastic properties of lead, copper, and aluminum at liquid nitrogen temperature are partly substantiated, partly disproved. Further investigations by ultrasonical methods are in progress to find a theoretical explanation for the remarkable behavior of these metals.
The Biophysical Mode of Action of Biologic and Therapeutic Ultrasonic Reactions
Authors: Lehmann Justus F.
Published: September 2005

A review is presented of numerous biophysical studies concerning the action of ultrasound on living matter, with particular reference to therapeutic applications. On the basis of the experiments described. involving various physical, physiochemical, and chemical effects, it is concluded that selective heating caused by the radiation plays the major role quantitatively under therapeutic conditions. However, ultrasound also produces a mechanical effect. The diffusion layer at an interface is decreased by stirring, and thus exchange of metabolites is augmented.
The Effects of Viscous Dissipation in the Spherical Acoustic Resonator
Authors: Ferris Horace G.
Published: September 2005

The problem of the spherical acoustic resonator containing a slightly viscous medium is considered. Derivation of the equations of sound waves in a viscous medium is carried out, and it is shown that separation of the particle velocity into a divergenceless vector and a curl-less vector gives rise to both a vector Helmholtz equation and a scalar Helmholtz equation. By using known solutions to these equations in spherical coordinates and imposing suitable boundary conditions, the frequencies of the free vibrations are calculated as well as the attenuation constants associated with each frequency. The effect of viscosity is, thus, seen to decrease slightly the natural frequencies and to cause a time rate of decay of the free vibrations. The attenuation constant for the purely radial modes of vibration is much smaller than that for modes having tangential velocity components.
Radiation Pressure and Dispersion
Authors: Post E. J.
Published: September 2005

The present paper starts with a brief discussion of the two components of acoustical radiation pressure in contrast with the single component obtained for electromagnetic radiation in vacuum. The two components of acoustical radiation pressure are correlated in a simple manner with the two distinct interaction possibilities of the obstacle and the medium, i.e., interaction with the wave motion only or interaction with the wave motion as well as with the medium itself. This picture appears to be consistent with the earlier conclusions of Brillouin and Richter.

Afterwards the result is generalized for dispersive media. It is shown that the component which is usually stated to be independent of the equation of state in the existing nondispersive theories should contain the time parameters of the equation of state in the form of a multiplying factor group, velocity over phase velocity.

The present paper stresses the basic concepts rather than mathematical detail and concludes with an extensive bibliography and commentary.
Precision Measurement of the Velocity of Sound in Air
Authors: Smith P. W.
Published: September 2005

A method for the precise measurement of the velocity of sound is described in which the driving-point impedance of a loudspeaker connected to a closed tube of variable length is the frequency-controlling element of a bridge-stabilized oscillator. The operation of the system and the accuracy of measurement are analyzed. Results of measurements in air at 1 kc/sec, room temperature, and atmospheric pressure yield, when corrected to standard conditions, a velocity of 331.45±0.05 m/sec.
The Accuracy of Reverberation Time Measurements with Warble Tones and White Noise
Authors: Furrer W. , Lauber A.
Published: September 2005

It is shown that in reverberation time measurements warble tones give greater accuracy at the lower frequencies, and white noise at the middle and higher frequencies, this behavior being within a wide range independent of room volume.
An Eleven Megacycle Interferometer for Low Pressure Gases
Authors: Greenspan Martin , Thompson Moody C.
Published: September 2005

An automatic recording double crystal interferometer is described which measures the speed and attenuation of sound at about 11 Mc/sec in gases at pressures of a fraction of a mm Hg.
Finite Amplitude Sound Waves
Authors: Keller Joseph B.
Published: September 2005

Exact solutions of the one-dimensional gas dynamic equations, representing periodic sound waves of finite amplitude, are obtained for a particular medium. The progressive wave from a vibrating piston and the standing wave in a closed tube are examined in detail. Limits on the amplitude of the sound wave are found in order to avoid shocks or cavitation.
The Acoustic Wave Guide. I. An Apparatus for the Measurement of Acoustic Impedance Using Plane Waves and Higher Order Mode Waves in Tubes
Authors: Shaw E. A. G.
Published: September 2005

The (1 0) and (2 0) modes of acoustic waves in rectangular wave guides have been excited to the virtual exclusion of plane waves. The experimental techniques depend on the use of acoustic sources equivalent to two or more pistons with appropriate relative phases and amplitudes, precise adjustment of which is accomplished with the aid of an accurately located probe microphone. The standing wave pattern which arises when the wave guide is terminated by a partially absorbing surface may be used to determine the specific normal impedance of the surface, the value of which is characteristic of waves having a particular oblique angle of incidence and may be compared with normal incidence values obtained from plane wave measurements in the same wave guide and at the same frequency; the angle of oblique incidence may be varied by changing the frequency. The apparatus described operates in the 1–3 kc/sec frequency region and the accuracy of impedance measurement with (1 0) and (2 0) waves is comparable with that attainable with the usual plane wave tube techniques. Equivalent angles of incidence at the absorbing surface up to 84° have been used. The principles underlying the design of the apparatus and some of the distinctive problems which arise with higher order mode waves are discussed.
The Acoustic Wave Guide. II. Some Specific Normal Acoustic Impedance Measurements of Typical Porous Surfaces with Respect to Normally and Obliquely Incident Waves
Authors: Shaw E. A. G.
Published: September 2005

The experimental techniques described in Part I have been applied to the measurement of some acoustic properties of specimens of rockwool, hairfelt and acoustic tile, backed by a rigid wall. The more porous surfaces show substantial increases resistance at oblique angles of incidence, an increase of nearly 100 percent at 80° a incidence being observed in one case; smaller changes in reactance also occur. The absorption coefficients corresponding to impedance measurements at oblique incidence are compared with those “predicted” from normal incidence impedance measurements and significant differences are found. The measurement of surfaces having structure of finite dimensions is discussed with particular reference to an acoustic tile specimen, the impedance of which varies only slightly with angle of incidence. In some cases slight scattering of acoustic energy from one mode to another provides evidence of lack of uniformity of impedance over the surface of the specimen.
The Use of High Intensity Ultrasound in Experimental Neurology
Authors: Wall P. D. , Tucker D. , Fry F. J. , Mosberg W. H.
Published: September 2005

The results of a histological study of the changes produced by high intensity ultrasound on tissue of the central nervous system are presented. The study was restricted to the nontemperature effects of the sound since these are of particular significance for neurology. The results obtained show that nerve cell bodies are particularly sensitive to the action of the ultrasound, while blood vessels and nerve fibers are much more resistant.

The use of a focused beam of ultrasound to produce discrete lesions deep in the brain without disturbance of the vascular system or through-going nerve tracts in the region of the lesion is demonstrated by a study on the bulboreticular inhibitor formation of the cat medulla.

Physical factors which require consideration are discussed in terms of the histological work.
Noise of Ventilating Fans
Authors: Peistrup Clifford F. , Wesler John E.
Published: September 2005

Using the apparatus described by Beranek, Reynolds, and Wilson, measurements were made of the acoustic power in watts in twenty-four bands each one-third octave wide for three vaneaxial-type and two centrifugal-type fans of graded sizes. Formulas were derived empirically, enabling the computation of the over-all acoustic power of the noise for the exhaust end of a fan where the input power, the number of blades, blade-tip speed, and other design characteristics are known. The directivity pattern and acoustic power generated for each of the twenty-four bands was also measured at the inlet with the fan mounted in one end of a long duct outdoors. The effects of back pressure were also determined. As a second stage of this investigation, the acoustical characteristics of unlined ducts were studied. The attenuation effects of one and two, 90° unlined bends placed in the ten-inch by twelve-inch duct system were determined. The greatest amount of attenuation was found in those frequency bands that contained the frequencies for which the width of the duct, in the direction of the bend, was 0.5 wavelength and 1.5 wavelength.
Dispersion of Ultrasonic Waves in Esters
Authors: Parthasarathy S. , Chhapgar A. F. , Singh Harkrishan
Published: September 2005

The light diffraction method is used in the endeavor to detect ultrasonic dispersion of a group of esters in the frequency range from 4.3 to 15.9 mc/sec. No measurable dispersion was detected.
Attenuation of Sound in a Tube
Authors: Angona F. A.
Published: September 2005

An experimental method of measuring the attenuation of sound in a circular tube for gases at reduced pressures has been developed. Since the tube effect is inversely proportional to the square root of the pressure, a reduction in pressure increases the attenuation and thus increases the experimental accuracy. The tube attenuation was measured for the frequency over pressure ratio of 8 to 2000 kc/atm. The measured attenuation was found to be 4.5 percent greater than that predicted by the Kirchhoff formula.
Direct Viewing of an Ultrasonic Beam in a Transparent Solid
Authors: McNamara F. L. , Rogers T. F.
Published: September 2005

Temporary birefringence, induced by ultrasonic stress, causes a depolarization in a plane polarized light beam traversing a transparent quartz plate. Detection of this depolarization allows the complete sound field to be made visible. Photographs taken by this technique are shown.
The Aircraft Noise Problem
Authors: Bolt Richard H.
Published: September 2005

Aircraft noise presents a system problem which to date has been attacked mainly at the level of individual components. The system includes: (a) aircraft as noise sources; (b) atmosphere and terrain as influences on sound propagation; (c) people, under several classes and conditions, as responders to noise; (d) physical components for controlling noise; (e) operating procedures for reducing noise exposure in communities; (f) public relations; (g) aviation planning policies and economics; and (h) many organizations concerned with characteristics and consequences of aircraft noise. The nature of these components is reviewed in a general way, with emphasis on their inherent interrelations. This discussion provides a framework for unifying the several subjects included in the present Aircraft Noise Symposium.
Noise Characteristics of Pulse-Jet Engines
Authors: Veneklasen Paul S.
Published: September 2005

Data obtained as part of a noise control program are presented to show the magnitude, spectral characteristics, directional properties, and variation with operating conditions of the noise produced by two sizes of pulse-jet engines.
Experimental Studies of Jet Noise
Authors: Hubbard H. H. , Lassiter L. W.
Published: September 2005

The mixing region of a jet is observed to be a complex noise generator. The noise produced is highly directional and is affected by various geometric and flow parameters as well as by conditions in the settling chamber upstream of the nozzle. Noise measurements for a family of circular model air jets ranging in diameter from 34 to 12 inches are consistent with available data for a turbojet engine. The intensity of the fluctuating pressure field near the jet is greatest at an axial distance of approximately two diameters downstream from the nozzle exit and decrease generally with increasing distance. The frequency spectrums recorded near the jet boundary are usually peaked, the peak frequencies being higher near the jet exit than at points farther downstream. These noise frequencies generally increase with increasing jet fluid velocity and decrease with increasing jet size. Hot wire surveys of turbulence (axial velocity fluctuation) in the jet stream indicated spectrums which were very similar in quality to the noise spectrums recorded just outside the jet boundary and at the same axial stations.
Aircraft Engine Noise Control as Viewed by the Engine Manufacturer
Authors: Hazard Donald M.
Published: September 2005

The aircraft engine manufacturer has been continually confronted with the factor of noise control in conjunction with the development and production testing of engines. The scope of this control activity has increased many fold during recent years as the result of the rapid growth in types and size of military power plants. Presented in this paper is a review of the over-all control procedure including typical noise sources, control objectives, recent techniques used in the control and attenuation of aircraft powerplant noise, problems associated with the design of noise control provisions, and limitations in the existing methods. This review includes data on reciprocating, turbojet, turboprop, and ram jet powerplants along with a description of installations used for controlling the noise both in ducted exhaust systems and in propeller-type test cells. This discussion cites cost, space, and high tolerance in design factors as being the major design problems. Areas of continued endeavor are outlined for the engine manufacturer, acoustical consultant, and the noise control equipment manufacturer.
The Compressibility of Solutions. II. An Ultrasonic Study of Aqueous Solutions of Some Simple Amino Acids and Their Uncharged Isomers at 25°C
Authors: Gucker Frank T. , Haag Robert M.
Published: September 2005

Some time ago, the first author showed that the apparent molal compressibility of the solute in a dilute aqueous solution is a linear function of the square root of the concentration for electrolytes, and of the first power of the concentration for nonelectrolytes. Both of these linear relationships may hold up to fairly concentrated solutions and afford convenient interpolation formulas for the compressibility as a function of concentration. The conclusion about electrolytes has been confirmed by several others, but little has been done with nonelectrolytes.

This article describes a 4-Mc interferometer used to determine adiabatic compressibilities of solutions to about ±0.01 percent. Studies of several amino acids and their uncharged isomers, including glycine and glycolamide; α- and β-alanine and lactamide, from about 0.05 M to near saturation, show linearity with concentration in dilute solutions and a general increase in the limiting slope and decrease in the limiting value of the apparent molal compressibility with increasing dipole moment of the solute molecules. These results are interpreted qualitatively by the theories of dipolar interaction developed by Fuoss and Kirkwood, and of dipolar charging energy developed by Kirkwood, but systematic deviations are observed for the apparent molal compressibilities and the volumes and heat capacities studied previously.