bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Study of Journal Bearing Lubrication Effected by Journal Misalignment as a Result of Shaft Deformation Under Load
Authors: Sun Jun , Gui Changlin , Li Zhiyuan
Published: September 2005

Journal bearing friction pair system is one of the most general and essential parts used in various mechanical devices. A special test bench is developed for the study on lubrication performance of cylindrical journal bearings. The effect of journal misalignment as a result of shaft bending under load is studied. The results show obvious changes at distribution and value of oil film pressure, oil film thickness and oil temperature of journal bearing due to journal misalignment. The higher the load on the shaft, the larger the journal misalignment resulted from shaft deformation, the more obvious effect on lubrication performance of journal bearing.
Numerical Analysis of a Journal Bearing With a Heterogeneous Slip/No-Slip Surface
Authors: Fortier Alicia E. , Salant Richard F.
Published: September 2005

The no-slip boundary condition is part of the foundation of the traditional lubrication theory. It states that fluid adjacent to a solid boundary has zero velocity relative to the solid surface. For most practical applications, the no-slip boundary condition is a good model for predicting fluid behavior. However, recent experimental research has found that for certain engineered surfaces the no-slip boundary condition is not valid. Measured velocity profiles show that slip occurs at the interface. In the present study, the effect of an engineered slip/no-slip surface on journal bearing performance is examined. A heterogeneous pattern, in which slip occurs in certain regions and is absent in others, is applied to the bearing surface. Fluid slip is assumed to occur according to the Navier relation. Analysis is performed numerically using a mass conserving algorithm for the solution of the Reynolds equation. Load carrying capacity, side leakage rate, and friction force are evaluated. In addition, results are presented in the form of Raimondi and Boyd graphs. It is found that the judicious application of slip to a journal bearing’s surface can lead to improved bearing performance.
Elastic-Plastic Finite Element Analysis of Nonsteady State Partial Slip Wheel-Rail Rolling Contact
Authors: Wen Zefeng , Jin Xuesong , Jiang Yanyao
Published: September 2005

A finite element analysis with the implementation of an advanced cyclic plasticity theory was conducted to study the elastic-plastic deformation under the nonsteady state rolling contact between a wheel and a rail. The consideration of nonsteady state rolling contact was restricted to a harmonic variation of the wheel-rail normal contact force. The normal contact pressure was idealized as the Hertzian distribution, and the tangential force presented by Carter was used. Detailed rolling contact stresses and strains were obtained for repeated rolling contact. The harmonic variation of the normal (vertical) contact force results in a wavy rolling contact surface profile. The results can help understand the influence of plastic deformation on the rail corrugation initiation and growth. The creepage or stick-slip condition greatly influences the residual stresses and strains. While the residual strains and surface displacements increased at a reduced rate with increasing rolling passes, the residual stresses stabilize after a limited number of rolling passes. The residual stresses and strains near the wave trough of the residual wavy deformation are higher than those near the wave crest.
Vibration Monitoring and Damage Quantification of Faulty Ball Bearings
Authors: Choy F. K. , Zhou J. , Braun M. J. , Wang L.
Published: September 2005

More often than not, the rolling element bearings in rotating machinery are the mechanical components that are first prone to premature failure. Early warning of an impending bearing failure is vital to the safety and reliability of high-speed turbomachinery. Presently, vibration monitoring is one of the most applied procedures in on-line damage and failure monitoring of rolling element bearings. This paper presents results from an experimental rotor-bearing test rig with quantified damage induced in the supporting rolling element bearings. Both good and damaged radial and tapered ball bearings are used in this study. The vibration signatures due to damage at the ball elements and the inner race of the bearing are also examined. Vibration signature analyzing schemes such as frequency domain analysis, and chaotic vibration analysis (modified Poincare diagrams) are applied and their effectiveness in pinpoint damage are compared in this study. The size/level of the damage is corroborated with the vibration amplitudes to provide quantification criteria for bearing progressive failure prediction. Based on the results from this study, it is shown that the use of the modified Poincare map, based on the relative carrier speed, can provide an effective way for identification and quantification of bearing damage in rolling element bearings.
Frost-Air Interface Characterization Under Natural Convection
Authors: Hao Y. L. , Iragorry J. , Tao Y.-X.
Published: September 2005

Surface frosting from atmospheric humidity under natural convection is encountered in conventional refrigeration systems, cryogenic surgery, and cryogenic stress relief of die casting metal forming applications. To advance the predictability of frost initiation and formation processes, this study reports a microscopic analysis of frost growth on a flat surface during the onset period of freezing when subcooled droplets are formed and changed to the ice phase. The onset of freezing is quantified by the mean droplet size and ice particle fractions at a critical time (when water droplet freezing point is reached) with the aid of a video microscope. An early-stage frost formation model with effective parameters is demonstrated to provide the important information for the transition to the steady-growth model. The model results are compared with the measured air-frost surface temperatures at different cooling and ambient boundary conditions, using holographic interferometry. The comparison between the model prediction and experimental results demonstrates the sensitivity of effective parameters in simulating the frost thickness and air-frost interface temperature.
Natural Convection Patterns in Right-Angled Triangular Cavities with Heated Vertical Sides and Cooled Hypotenuses
Authors: Ridouane El Hassan , Campo Antonio , Chang Jane Y.
Published: September 2005

The present investigation deals with the numerical computation of laminar natural convection in a gamma of right-angled triangular cavities filled with air. The vertical walls are heated and the inclined walls are cooled while the upper connecting walls are insulated from the ambient air. The defining apex angle α is located at the lower vertex formed between the vertical and inclined walls. This unique kind of cavity may find application in the miniaturization of electronic packaging severely constrained by space and/or weight. The finite volume method is used to perform the computational analysis encompassing a collection of apex angles α compressed in the interval that extends from 5° to 63°. The height-based Rayleigh number, being unaffected by the apex angle α, ranges from a low 103 to a high 106. Numerical results are reported for the velocity field, the temperature field and the mean convective coefficient along the heated vertical wall. Overall, the matching between the numerically predicted temperatures and the experimental measurements of air at different elevations inside a slim cavity is of ordinary quality. For purposes of engineering design, a Nu¯H correlation equation was constructed and also a figure-of-merit ratio between the Nu¯H and the cross sectional area A of the cavity was proposed.
An Experimental Investigation of the Influence of Gas and Solid
Particle Interaction on the Heat Transfer Effectiveness of a Falling-Bed Heat
Exchanger
Authors: Frain Matthew J. , Schmidt David P. , Fiveland Woodrow A.
Published: September 2005

The objective of this investigation is to quantify and understand the performance of falling-bed heat exchangers. Experimental steady-state heat transfer data, whose quality is demonstrated with an accurate energy balance between the gas and particle streams, are presented. Measured temperatures, pressures, and overall heat transfer rates are compared to predicted values from a one-dimensional analytical model, and the capabilities and deficiencies of the model are discussed. In addition, the effect of a particle distributor on the performance of the falling-bed heat exchanger is measured. While the model is shown to be unable to provide a quantitatively accurate prediction of the performance of the heat exchanger, it does provide an estimate of the maximum possible effectiveness of the heat exchanger. A simple particle distributor is shown to provide relatively poor effectiveness, while the use of a more complex distributor causes the effectiveness of the heat exchanger to approach the upper bound. The combination of experimental data and model results offers useful insight for developing falling-bed heat exchangers and provides a useful test case for future modeling efforts.
A Theory of Film Condensation in Horizontal Noncircular Section Microchannels
Authors: Wang Hua Sheng , Rose John W.
Published: September 2005

The paper presents a theoretical model to predict film condensation heat transfer from a vapor flowing in horizontal square and equilateral triangular section minichannels or microchannels. The model is based on fundamental analysis which assumes laminar condensate flow on the channel walls and takes account of surface tension, interfacial shear stress, and gravity. Results are given for channel sizes (side of square or triangle) in the range of 0.5–5 mm and for refrigerants R134a, R22, and R410A. The cases considered here are where the channel wall temperature is uniform and the vapor is saturated at the inlet. The general behavior of the condensate flow pattern (spanwise and streamwise profiles of the condensate film), as well as streamwise variation of local mean (over section perimeter) heat-transfer coefficient and vapor mass quality, are qualitatively in accord with expectations on physical grounds. The magnitudes of the calculated heat-transfer coefficients are in general agreement with experimental data for similar, but nonidentical, channel geometry and flow parameters.
Enhancement of Heat Transfer by an Electric Field for a Drop Translating at Intermediate Reynolds Number
Authors: Subramanian Rajkumar , Jog M. A.
Published: September 2005

The enhancement of heat transfer by an electric field to a spherical droplet translating at intermediate Reynolds number is numerically investigated using a finite volume method. Two heat transfer limits are considered. The first limit is the external problem where the bulk of the resistance is assumed to be in the continuous phase. Results show that the external Nusselt number significantly increases with electric field strength at all Reynolds numbers. Also, the drag coefficient increases with electric field strength. The enhancement in heat transfer is higher with lower ratio of viscosity of the dispersed phase to the viscosity of the continuous phase. The second heat transfer limit is the internal problem where the bulk of the resistance is assumed to be in the dispersed phase. Results show that the steady state Nusselt number for a combined electrically induced and translational flow is substantially greater than that for purely translational flow. Furthermore, for a drop moving at intermediate Reynolds number, the maximum steady state Nusselt number for a combined electrically induced and translational flow is slightly greater than that for a purely electric field driven motion in a suspended drop.
Radiative Heat Transfer Using Isotropic Scaling Approximation: Application to Fibrous Medium
Authors: Tagne Hervé Thierry Kamdem , Baillis Dominique Doermann
Published: September 2005

The applicability of the isotropic scaling approximation to heat transfer analysis in fibrous medium is discussed. The isotropic scaling model allows the transformation of an anisotropic scattering problem to an isotropic one. The scaled parameters are derived for general anisotropic scattering and for radiative properties dependent of the incidence radiation. Three different isotropic scaling approaches are considered: Directional isotropic scaling, mean isotropic scaling, and P1 isotropic scaling; corresponding to isotropic scaling parameters function of incident radiation, arithmetic mean over all incident direction of radiative properties, and mean on weighted radiative properties, respectively. The discrete ordinate method is used to solve the radiative transfer equation through fibrous medium. The fibers in the medium are randomly oriented either in space or parallel to the boundaries. Numerical results presented for a pure radiation problem show good accuracy on radiative heat flux between the exact solution and solution obtained with both P1 and directional isotropic scaling while using mean isotropic scaling is unsuitable. Using isotropic scaling approximation to model radiative heat transfer is faster than the exact solution and required few quadratures to converge.
Monte Carlo Simulation of Silicon Nanowire Thermal Conductivity
Authors: Chen Yunfei , Li Deyu , Lukes Jennifer R. , Majumdar Arun
Published: September 2005

Monte Carlo simulation is applied to investigate phonon transport in single crystalline Si nanowires. Phonon-phonon normal (N) and Umklapp (U) scattering processes are modeled with a genetic algorithm to satisfy energy and momentum conservation. The scattering rates of N and U scattering processes are found from first-order perturbation theory. The thermal conductivity of Si nanowires is simulated and good agreement is achieved with recent experimental data. In order to study the confinement effects on phonon transport in nanowires, two different phonon dispersions, one from experimental measurements on bulk Si and the other solved from elastic wave theory, are adopted in the simulation. The discrepancy between simulations using different phonon dispersions increases as the nanowire diameter decreases, which suggests that the confinement effect is significant when the nanowire diameter approaches tens of nanometers. It is found that the U scattering probability in Si nanowires is higher than that in bulk Si due to the decrease of the frequency gap between different modes and the reduced phonon group velocity. Simulation results suggest that the dispersion relation for nanowires obtained from elasticity theory should be used to evaluate nanowire thermal conductivity as the nanowire diameter is reduced to the sub-100 nm scale.
The Measurement of Sound Absorption Coefficients by the Reverberation Method
Authors: Sabine Paul E.
Published: September 2005

The paper reports the results of an experimental study of the Reverberation Method. The assumptions made in the Reverberation Theory are critically examined. The fundamental equation at1 = 9.2Vv log10 4Eaı̣v affords two independent means of measuring the change produced in the quantity a for a given room, using a source whose acoustic power may be varied in known ratios. Outstanding differences in the experimental results of the two methods, are reported and possible explanations therefor are discussed. Effects of size and shape of test sample, and quality of test tones on measured values of the absorption coefficients are reported.

For detailed account of some of the matter reported reference may be made to Journal of the Franklin Institute for March 1929. Later work included experimental verification of a linear relation between the amplitude of vibration of the electrically driven piston source and the magnitude of the driving current.
The Tube Method of Measuring Sound Absorption Coefficients
Authors: Wente E. C.
Published: September 2005

The general principles underlying the tube method of measuring sound absorption can be derived conveniently from the analogous equations for the electrical transmission line. These equations show that the actual method of measurement is capable of many modifications, some of which have already been adopted by various experimenters. However, if reliable results are to be obtained, it is important that the apparatus be so designed that the propagation along the tube be rectilinear and the attenuation small, and that the tone be kept free from harmonics.

In the tube method the absorption is measured at perpendicular incidence, whereas in the reverberation method it is measured at random incidence. A theoretical study of the absorption of sound by porous materials as a function of the angle of incidence shows that in some cases there may be a considerable discrepancy between the values obtained by the two methods. The tube method may also give impracticable results for materials which are to be used in the form of large panels and absorb sound largely by virtue of inelastic bending rather than because of their porosity.
Description and Demonstration of an Artificial Larynx
Authors: Riesz R. R.
Published: September 2005

A description is given of the normal vocal tract and the action of the vocal cords in generating sound waves from the steady flow of air from the lungs. For persons whose larynx has been removed the flow of air from the lungs is changed into sound by a device external to the body and this sound is converted into speech by introducing it into the mouth and carrying on the ordinary speech-producing motions with the lips, tongue, teeth, etc. A description is given of a recently developed vibrating reed type of artificial larynx for accomplishing the above. While using this instrument for producing a sustained vowel the rate of expulsion of air is about 125 cc per second and the excess pressure in the lungs is about .005 atmospheres, giving the rate at which the lungs do work as .06 watts. Using Saccia's measurements of the rate of radiation of acoustic energy from the lips of a speaker it is calculated that of the energy used by the lungs in forcing air through the glottis only about 0.17% is converted into useful acoustic energy.
Variation of Sound Absorption Test Data
Authors: Waterfall Wallace
Published: September 2005

In the acoustical treatment of rooms, an accurate knowledge of sound absorption coefficients is necessary. Test data on Type B Acousti-Celotex from seven different laboratories is presented showing a variation from .40 to .47 in values obtained by the reverberation method and from .23 to .40 by the “tube” method. The values .23, .40 and .47 were all obtained on the same samples shipped to the different laboratories. The desirability of standardizing test methods is apparent.

To determine which absorption values should be used in engineering work, a study was made of a large number of completed installations. A small 512 cycle organ pipe was calibrated for acoustic output both at the University of Illinois and at the Bureau of Standards. The 3A Audiometer was used to determine the amount of noise, if any, in the rooms and it was found possible to correct the measurements for the threshold shift caused by the noise. From the data, 45 installations are selected as typical. Using .47 as the coefficient, the total absorption in each room was calculated. In 24 of the rooms the test absorption was greater than the calculated absorption by an average of 9.7%. In 21 of the rooms the test absorption was less than the calculated absorption by an average of 12.1%.
An Instrumental Measurement of Reverberation
Authors: Ross Ira G.
Published: September 2005

In measuring the time of reverberation in a room instrumentally, the usual practice of timing the decay of intensity from the maximum produceable by a given source to the threshold of audibility, possesses the disadvantage of requiring very sensitive sound detectors even when the “threshold” value is fixed at a relatively high level. It is proposed to measure, rather, the time of building-up of sound in the room from quiet conditions to some fixed fraction of the maximum intensity. This method presents the advantage of definitely fixing the low-intensity end of the time interval as the instant of starting emission at the sound source, while the end point lies in the region of high intensity and may be more readily determined instrumentally.

The sound intensity increase is followed by a condenser microphone, amplifier and valve voltmeter, a short-period galvanometer relay in the plate circuit of the latter being actuated when the sound intensity reaches a predetermined level. The time of building-up, between the starting of the sound source and the closing of the relay, is equally as useful as the time of reverberation and from it the latter may readily be computed if desired.
An Instrumental Method of Reverberation Measurement
Authors: Norris R. F. , Andree C. A.
Published: September 2005

The usual method of measuring the period of reverberation with organ pipe and stop watch is uncertain, due to extraneous noises, variation in sensitivity of the ear, and other difficulties. Attempts to determine the period through measurements of the sound intensity level established by a calibrated source were unsuccessful.

A new method is here described in which a regular succession of equally timed and constant strength sounds are emitted. At desired instants in the intervals between the emission of sound the intensity is measured. From this data the period of reverberation is determined as tp = 6t′/log10 (Eave/E′ave), where t′ is the time in which the intensity decays from Eave to E′ave, these three quantities being directly observable.

Chief of the advantages listed is the elimination of errors due to variations in the observer's acuity of hearing. The method is also applicable to the measurement of the sound-absorption coefficients of materials.
Mechanism of Speech
Authors: Russell G. Oscar
Published: September 2005

Past experiments have been confined mostly to an examination of the recorded speech curves or of speech phenomena after the sound emits from the vocal passages. And the physiological cause was imagined. Various conflicting vowel theories have resulted.

A new method of attack has been carried out in the present investigation. Wheatstone harmonic or Willis cavity tone (erroneously called Helmholtz) theories are checked upon by direct physiological processes. Not only the forms but the exact dimensions of the speech cavities have been ascertained by means of X-rays, palatograms and larnygoperiskopik measurements, made simultaneously and instantaneously so that exact measurements of the vocal tract resonators are had in three planes making it possible to reconstruct these cavities with a high degree of accuracy. By attaching an artificial glottis to the model it should be theoretically possible to reproduce the vowel if the total air volume functioning as a resonator were responsible for vowel quality. I am sorry to have to admit however that although 116 different types of reeds and other sound stimuli were used for such a purpose, the results were negative. All vowel cavities gave sounds which were much alike and but poor imitations of the original, just as are all other mechanical imitations of human speech which we have heard.
Theory of Vibration of the Larynx
Authors: Wegel R. L.
Published: September 2005

A theoretical derivation of the equations of motions of the larynx is given and the analogy with the simple vacuum tube oscillator pointed out. This simple circuit consists of two meshes, the grid and plate circuits which are coupled by a unilateral mutual impedance, the amplifier constant, and a bilateral “feed back.” Sustained oscillation takes place when these constants, which may have a variety of forms, have certain relative values. The vocal cords of the larynx are analogous to the grid, the glottis (the space between the vocal cords) to the plate circuit. A charge on the grid alters the resistance of the plate circuit and the displacement of the vocal cords alters the resistance of the glottis. The “B” battery corresponds to the lung pressure and the plate current to the air stream. The “feed back” of the larynx is the impedance of the lungs and that of the upper air chambers added to a “gyrostatic” coupling due to modulation of the mass of air in the glottis. The latter is most important and has no analog in electrical circuits.

Theory is given showing effects of relative values of the evaluated constants on sustained oscillation as in singing, and on subsidence or accretion of vibration as in speaking.
Speech Power and Its Measurement
Authors: Sivian L. J.
Published: September 2005

The paper is chiefly concerned with the important speech power quantities—frequency spectra, distributions of instantaneous, average, syllabic and peak amplitudes, etc.—as they obtain in actual speech for a large range of voices, talking levels, and subject matters. The analysis is not nearly so complete nor so fine-grained as that which, in principle, can be derived from oscillographic records of individual speech sounds. Its advantage is in the speed with which data can be secured, under widely varying conditions and on a scale which warrants statistical conclusions. Some of the methods in use for measurements of this type are described. These include forms of apparatus developed prmarily for use in telephone plant work, as well as those developed for detailed laboratory investigations. The data discussed are mainly those obtained in the laboratory with an integrator and with a peak meter. The former gives the average value of the instantaneous sound amplitudes; the latter gives the magnitude and frequency of occurrence of the peak values. The distribution of average and peak amplitudes in the frequency spectrum is obtained in addition to their values in the entire sound wave. Illustrative results are given for samples of speech, music and noise.
Frequency of Occurrence of Speech Sounds in Written English
Authors: Dewey Godfrey
Published: September 2005

There has been much qualitative research by fonetists and acoustic engineers dealing with the speech sounds of English, but until lately very little quantitative analysis, which is equally important in determining the relative importance of the various speech elements—words, syllables, and sounds—as measured by their relative frequency of occurrence.

The author's recent study entitled “Relative Frequency of English Speech Sounds” (Harv. Univ. Press) gives a classified quantitative analysis of the commoner words and syllables and all the sounds of 100,000 words of representative written English.

The word count data show that 10 words—the of and to a in that it is I—make up over 25% of all writing; that 100 words, including of course these 10, make up over 50%; and justify the conclusion that the 1,000 commonest words of English will make up about 75% of all ordinary non-technical writing.

The data on syllables and sounds, impossible to summarize briefly, are of far more important practical significance to the acoustic engineer than the word count data, and, unlike the latter, are at present the only authentic and comprehensive data in that field.
A Spark Chronograph Developed for Measuring Loudness of Piano Tones
Authors: Hickman C. N.
Published: September 2005

This chronograph was developed for use in recording the loudness of blows from piano hammers as an artist is making an Ampico record. It records accurately the velocity of each hammer at the moment it strikes the strings.

The chronograph, which is of the spark type, records on either stationary or slowly moving paper. A cylindrical drum with a spiral conductor distributes the time interval sparks at right angles to the motion of the paper.

A new method of making visible the spot, where the secondary spark punctures the paper, is described. This method permits the use of a very feeble current. A secondary spark energy sufficient to puncture the paper is all that is needed. The punctured spot may be made visible regardless of its size.

A simplified electrical circuit for producing the secondary spark is described.

Curves and data are given showing the relationship between the velocity of the hammer and the loudness of the piano tone in sesation units.

The chronograph with its auxiliary system of recording feeble sparks is applicable to many fields of scientific investigation.
Scientific Measurements of Piano Playing as Used in Making Ampico Records
Authors: Stoddard Charles Fuller
Published: September 2005

This paper, illustrated by 30 lantern slides, was in the nature of a demonstration of the making of an Ampico record showing the various processes through which a record passes in its development between the time of playing to the finished reproduction.

The complete recording apparatus from the Ampico Laboratories was moved to the hall, and at the beginning of the reading of the paper, a record was taken of an artist's actual playing in person of Chaminade's Air de Ballet. Mr. Leslie Loth of New York was the artist. The paper explained in detail how every characteristic of the pianist's playing including quality of tone, feeling of “touch,” exact loudness of every individual note, etc. was translated into note sheet performations which give a facsimile perfect enough to reproduce the emotional characteristics of the artist's performance.

After the reading of the paper, the Ampico reproduced Mr. Loth's playing of the Air de Ballet from a record which had been taken in the Ampico Laboratories three weeks previously and produced by the method explained in the paper.
Human Factor in Piano Tone Production
Authors: White William Braid
Published: September 2005

A special form of portable Westinghouse oscillograph, using a Western Electric double-carbon-button 387-W microphone, and one stage of radio amplification, was used to obtain a large number of sound-wave photographs representing the sounds produced at the piano by various eminent artists, particularly Rudolf Ganz, John Powell, Ernest Schelling, and Olga Samaroff. The object was to discover how variations in attack upon the piano keys, transmitted to the strings through the hammers, affect (a) the intensity, (b) the quality of the sounds produced. The following conclusions were arrived at as a result of many experiments.

(1) The number of possible variations in key speed and in the control thereof is indefinitely great, much greater than is commonly appreciated by ordinary hearers, or by ordinary players, of the piano.

(2) An indefinitely great number of variations in the velocity of the hammer during its travel to the string is likewise possible.

(3) Every velocity value of the hammer, in a manner dependent among other things upon the physical make-up of hammer and string, produces a corresponding intensity value, and a parallel color value, in the sound.

(4) Faint sounds on the piano tend to converge in color value until at the minimum of intensity all sounds from bass to treble have the same sine wave form, that is, are perfectly simple sounds. Contrariwise, as intensity increases, the number of audible harmonics increases accordingly.

(5) It may therefore be concluded that every change in loudness involves a change in color, and every change in color requires a change in loudness; that is to say, tone color control on the piano is dependent upon control of intensity, that is, upon control of hammer velocity, and that again, on control of the speed and acceleration of the key.

The paper is illustrated with numerous sound-wave photographs, the evidence of which confirms the conclusions arrived at. The interpretation of these photographs is guided by the general rule that amplitude measures loudness, and shape of vibration-pattern measures quantity.
Methods and Apparatus for Measuring the Noise Audiogram
Authors: Galt Rogers H.
Published: September 2005

The audiogram of a noise is the plot of the deafening effect of the noise versus the frequency of the sound which it is desired to hear. A portable apparatus has been developed for analyzing and measuring the deafening due to either acoustical or electrical noise by threshold observations upon a series of complex testing waves generated by a phonograph. Examples of noise measurements are given, and comparison is made between the fields of usefulness of the apparatus and of other noise measuring devices involving threshold observations.
Reverberation Time in “Dead” Rooms
Authors: Eyring Carl F.
Published: September 2005

An analysis based on the assumption that image sources may replace the walls of a room in calculating the rate of decay of sound intensity after the sound source is cut off gives the more general reverberation time equation T = .05V−S loga(1−aa), where T is reverberation time, V the volume of the room, S the surface of the room, and aa the average coefficient of absorption of the wall surface. In the past Sabine's formula, T = .05VSaa, has been used to calculate reverberation time, but for rather large values of aa, that is, for “dead” rooms this equation gives too long a time of reverberation, or in some cases, if the time is measured, it gives a value of aa greater than unity. This we found to be the case in the Sound Stage, Sound Picture Laboratory, Bell Telephone Laboratories, Inc. Reverberation time measurements made in this room support the new formula, however. Sabine's formula turns out to be the special case of the more general equation and is to be used when aa is small, that is, for “live” rooms, but not for “dead” rooms.

The new formula is of importance in the talking picture industry for it indicates that a “dead” room may be obtained by the use of less absorbing material than that calculated by the old formula.
The Effects of Noises—An Abstract of Experimental Findings from Various Sources
Authors: Laird Donald A.
Published: September 2005

A survey of experimentation dealing with effects of various acoustic stimuli on motor functions, simple cerebral functions, complex cerebral functions, respiratory functions, cardiovascular functions, feeling-tone and emotional functions, and on the organism at work. Some thirty experiments cited show that acoustic stimuli have a wide variety of effects on mental and physiological functions and help explain general reactions of people to noise. Way for future development of more relevant studies shown.
The “Strike Notes” from Bells
Authors: Jones Arthur Taber
Published: September 2005

The “strike note” of a bell does not appear to be produced by vibration of the bell in any of its normal modes. The strike note is not far from an octave below the fifth partial tone of the bell, and the suggestion has been made that this fifth partial may come out with especial promptness and strength, and the attention of the ear be afterward quickly caught by lower tones, so that the tone from the fifth partial is judged to be an octave lower than it really is.

Several tests of this hypothesis have been attempted. (1) A number of musicians have given their judgment as to the pitches of the strike notes on three bells. The average is almost exactly an octave below the fifth partial. (2) The sounds from six bells have been picked up from a distance of about 300 meters. When the bells were struck so gently as to be almost inaudible at this distance, beats from suitably tuned forks showed that the fifth partial is at least as prominent as any other. (3) On the same six bells the first order difference tone from the fifth and seventh partials is close to the strike note. (4) The time during which the clapper is in contact with the bell has been found rather roughly for one bell. This time is not far from half the period of the fifth partial.

The results of other tests are not yet sufficiently definite to be of significance. The work is to be continued next summer.
The Influence of Phase on Tone Quality
Authors: Beasley W. C.
Published: September 2005

A special generator was built to permit alteration of phase between two fundamentals to a known degree, with an output of separate currents permitting inspection of the frequency ratios 15:16, 9:10, 2:3, 5:8, 3:5, 9:16, 5:9, 1:2, 1:3, 5:16. A useful formula is developed to predict the amount of phase retardation in the component of higher frequency necessary to effect a maximum change in compound wave form due to phase retardation, maintaining amplitude and frequency in the components constant. A differential gear driving mechanism is constructed to effect the critical amount of phase change during the same period of time for all frequency ratios. The results are contrary to those found by any former investigations. The conclusion is established that with change of phase, the relative loudness of the partial tones varies in opposite directions at the same time, the amount of change in relative loudness being roughly inversely proportional to the magnitude of the ratio terms of the fundamentals when these ratio terms are reduced to unity difference; further, the amount of change in relative loudness is a function of auditory sensitivity at various frequency levels. Tests were made over the frequency band 450 to 2400 cycles, at various sensation levels.
The Use of Sound in Navigation
Authors: Lamson Horatio W.
Published: September 2005

Modern methods for employing under-water sound as an aid to navigation are based upon the binaural sense.

The earliest devices, exemplified by the “C” tube, etc., mechanically placed the ears of the observer on the extremities of a beam to be rotated in a horizontal plane beneath the sea. Such cumbersome equipment was improved by employing fixed under-water receivers in conjunction with an adjustable compensator for obtaining a binaural balance.

Electrical lag lines have replaced acoustical tubes for obtaining the necessary time lag to affect compensation. The effectiveness of such a two-spot system is hampered whenever more than one sound source is present. This difficulty was subsequently overcome by obtaining a directional sensitivity by means of a multi-spot system which compensates simultaneously for a binaural and maximum focus.

Observations upon the compensators may likewise be made upon sounds traveling in a vertical plane. This enables continuous depth soundings to be taken with the vessel under way at full speed, a valuable feature.

Apparatus has also been perfected for acoustic depth soundings by timing the echo of sound reflected from the sea bottom. The use of super-audible sound waves, which can be projected in a slightly diverging beam, offer great possibilities for the location of icebergs, etc.
Absolute Amplitudes and Spectra of Certain Musical Instruments
Authors: Sivian L. J. , Dunn H. K. , White S. D.
Published: September 2005

Systems for the reproduction of music are limited in the frequency range and in the amplitude of the sounds which they can reproduce without distortion. In order to determine what requirements such a system should meet for faithful reproduction of common forms of music, those instruments which were believed to contribute largely to low or high frequencies, or to have large amplitudes at any frequency, have been investigated. Those examined were: bass drums of three sizes, snare drum, cymbals, triangle, bass viol, bass saxophone, bass tuba, trombone, trumpet, French horn, clarinet, flute, piccolo, piano, and organ. Several measurements have also been made upon complete orchestras.

The measurements included average and peak sound pressures corresponding to the whole spectrum, and also the same quantities in thirteen bands of frequencies which together covered the complete spectrum. Several hundred peak measurements were taken in each band, each measurement representing the highest peak in one-eighth second of music. They were taken in such a way that the frequency of occurrence of the peaks in ten amplitude zones, each zone covering six decibels, was obtained. The musician in each case played a representative selection for his instrument, lasting two or more minutes.

With the complete orchestra, the highest peaks were found to lie in the region between 2,000 and 4,000 c.p.s. The greatest peaks below 64 c.p.s. were obtained when the bass drum was prominent, while the greatest peaks above 8,000 c.p.s. were very plainly due to the cymbals.
The Approximate Networks of Acoustic Filters
Authors: Mason W. P.
Published: September 2005

The original theory of acoustic filters, given by Stewart, is based on the representation of such filters by means of lumped constants in the form of a T-network. More recently, the writer has presented a theory of acoustic filters, showing that they are equivalent to a combination of electric lines. Stewart and Lindsay have pointed out that the first theory is a first approximation of the second theory—obtained by taking the first terms of the trigonometrical expansion occurring in the latter theory.

This approximation holds well for low pass filters, at low frequencies, but does not represent very adequately the band pass filter. Accordingly a second approximation is developed in this paper. Methods are given for determining the transmission characteristics of any types of acoustic filters. These methods have been applied to analyzing all of the single band pass filters possible with one main branch and any side branch combination. There are five of these filters, and design formulae for them have been worked out. It is possible, from these formulae, to determine the dimensions of a filter necessary to have a given attenuation and impedance characteristic.
An Error in the Derivation of the Reverberation Formula
Authors: Germond Hallet H.
Published: September 2005

Sabine's formula T = 55.3V/avs yields finite values for the period of reverberation even when the coefficient of absorption is unity. This formula is a first approximation to that developed by Norris T = −24V/vs Log10 (1−a); the latter yields T=0 for a=1. An error in the interpretation of the fundamental differential equation in the derivation of Sabine's formula is demonstrated.

Another mode of attack permits a more correct analysis of a room under certain specified distributions of absorbing material.
Some Physical Factors Affecting the Illusion in Talking Motion Pictures
Authors: Maxfield J. P.
Published: September 2005

The advent of talking pictures has brought the physicist and engineer face to face with problems which lie not only in the field of material things but also in the field of art. This implies that many of the criteria for the judgment of excellence may be of a psychological rather than a physical nature.

The paper describes results of an empirical study of methods for controlling some of the factors available to the engineer in the field of sound recording and photography in such a manner that a pleasing illusion of reality is created in the theater. Empirical quantitative curves are given.
Means for Radiating Large Amounts of Low Frequency Sound
Authors: Kellogg E. W.
Published: September 2005

Present electrical sound equipment has little output below about 100 cycles. An electrical device of large output in the range 30 to 200 cycles would afford new musical effects not hitherto possible.

From a review of existing literature it is concluded that an acoustic output of at least one watt should be provided. Ten watts would be desirable. The result can be attained in several ways and the amount of equipment required with various arrangements is calculated. The results should serve as a guide in the design of installations.
The Effect of Humidity Upon the Absorption of Sound in a Room
Authors: Knudsen V. O.
Published: September 2005

P. Sabine and E. Meyer have noted that for frequencies above 2,000 d.v. the rate of absorption of sound in a room increases as the relative humidity decreases. The writer has investigated and confirmed this effect during the past year and has obtained some quantitative data which have a bearing upon problems in architectural acoustics and sound signaling. Assuming that the intensity of a plane wave in air diminishes in accordance with e—mct where c is the velocity t the time and m the absorption coefficient in the air the reverberation formula becomes (in British units) t = .049V−S loge (1 − a) + 4mV.

By making reverberation measurements, under different conditions of humidity, in two rooms having the same boundary material (painted concrete) but different mean free paths, it is possible to determine both m and a as functions of the frequency and humidity of the air. For frequencies below 512 d.v., m is negligible. It increases approximately with the square of the frequency. At 4,096 d.v., m increases from about .0015 at 70 per cent relative humdidity (21°C) to .0033 at 20 per cent relative humidity. At frequencies above 6,000 d.v., the absorption in the air in a room may be greater than the absorption by the boundaries. The absorptivity of painted concrete remains nearly constant above 512 d.v., and has a value of about .016.
Measurements with a Reverberation Meter
Authors: Chrisler V. L. , Snyder W. F. , Miller C. E.
Published: September 2005

A description is given of apparatus with which the rate of decay of sound energy in a room may be measured. A loud speaker is used as a source of sound. When the sound has reached a steady state the loud speaker circuit is opened and at the same time a timer is started. When the sound energy has decayed to some definite value the timer is automatically stopped.

If made in a portable form this equipment may be used to study the acoustical properties of auditoriums.

Attention is called to the errors which may occur in these measurements.

Measurements are given showing absorption due to diaphragm action of materials.
Physical Aspects of Piano Tone
Authors: Ortmann Otto
Published: September 2005

A brief exposition of the principles of tone-production on stringed keyboard instruments, represented by the modern piano-forte, including descriptions of the nature of piano tone and possibilities of its variation; of the relations of pitch, intensity, and duration to the quality of the tone; of the effect of the noise elements upon the sound complex; and of percussiveness as the primary element of the characteristic piano tone-quality. So far as possible, these topics will be illustrated with oscillograms, showing the effect of variations in instrumental structure and key manipulation upon the tone.
The Woodwind Musical Instruments
Authors: Miller Dayton C.
Published: September 2005

The wood-wind group of musical instruments includes four distinct types, commonly known as flutes, oboes, clarinets, and saxophones. According to peculiarities of size or method of construction these instruments have a variety of names among which are: recorder, galoubet, piccolo, flageolet, English horn, bassoon, bag-pipe, doodlesack, etc. Originally these instruments were made of wood, now many are made of metal.

A discussion is given of the tone production and of the relations of the nodes and loops of the vibrating air-column to the mouth-piece and the tone-holes in the several types of instruments. The varying qualities of tone are due to the prominence of certain overtones which are characteristic of each instrument; the general nature of these peculiarities have been determined by analysis of photographic records of the tones.

The positions of tone-holes were primitively determined by the number and length of fingers conveniently available in playing and varies according to custom. Our musical scale of the octave has been by the peculiarities of the hand! Very little of the scientific method is applicable to the design of musical instruments. Theobald Boehm, of Munich, just one hundred years ago, first made use of the principles of acoustics in the making of an orchestral instrument; this consisted simply in placing the tone-holes according to the intervals of the equally tempered scale. He followed this with a study of tone-quality which resulted, in 1847, in the present-day Boehm Flute. These studies influenced the design of all the other wood-wind instruments. A discussion is given of possible further improvements through laboratory research.

Exhibition and demonstration of primitive and modern instruments will be made with various specimens selected from the writer's historical collection of flutes, now the largest in the world.