bluuebunny/crossref_metadata_2025 huggingface dataset:
ON INTERFERENCE ELIMINATION WITH THE WARBLE TONE
Authors: Barrow W. L.
Published: September 2005

The effect of a frequency modulated tone, also called warble tone, in eliminating the disturbing space and time interference phenomena which accompany the use of a single tone in objective acoustical measurements is discussed. A criterion for determining the minimum allowable frequency variation is set up, this being that the frequency change should be just large enough to shift the relative phase of direct and reflected sound waves through 180°.Based on this criterion the relative change of frequency is derived in terms of the original frequency and the path difference L, where L denotes the difference in distances from source to transmitter travelled by the direct and reflected sound waves. The warble tone may be represented by: f(t) =  ∑ n=−∞∞Jn(Afα) sin 2π(f0+nα)t. It is then shown that the effectiveness of the warble tone depends upon the path difference L and upon the middle frequency f0. A desirable value for L is found to be L≧3λ0, where λ0=v/f0 (v = velocity of sound in air) is the wave length corresponding to f0. While Δf/α alone is the controlling factor for the frequency spectrum of the warble tone, its suitableness for acoustic purposes is governed instead by Δf/f0. It is demonstrated that a very slow frequency variation through a given band may be replaced by several simultaneous equal amplitude components arranged symmetrically with that band, provided the band width and location are given the proper value corresponding to the particular value of L. The standing waves (R.M.S. value) produced by a warble tone are calculated and illustrated on an example, from which the above consequences are made more obvious. The standing waves of simultaneous equal amplitude tones are also shown. The factors governing the elimination of transient interference with the warble tone are found to be the same as those valid for the elimination of standing waves.
A MINIATURE CONDENSER TRANSMITTER FOR SOUND-FIELD MEASUREMENTS
Authors: Hall William M.
Published: September 2005

The problem of sound-field measurements is analyzed with a view to indicating the requirements of measuring devices for use in such fields. A condenser transmitter is then described which is an approach towards the ideal set forth in the analysis.
A Method of Measuring Acoustic Impedance
Authors: Flanders P. B.
Published: September 2005

An apparatus s described whereby acoustic impedances may be measured in terms of a known acoustic impedance and the complex ratios of two electrical potentiometer readings to a third. As a known impedance, there is chosen the reactance of a closed tube of uniform bore which is an eighth wave-length long. The electrical readings are obtained by balancing the amplified output of a condenser transmitter against the electrical input of the source of sound. The condenser transmitter picks up the acoustic pressure at the junction of the sound-source and the attached impedance. A balance is made for each of three successively attached impedances: (1) a closed tube an eighth wave-length long, (2) a rigid closure of the sound-source, and (3) the impedance to be measured. The unknown acoustic impedance Z is then calculated in terms of the known acoustic impedance Z0 by means of the equation Z = 'Z0 z1 − z2z3 − z2, where z1, z2 and z3 are, respectively, the three electrical impedance settings of the potentiometer. As indicated by this equation, the constants of the electrical circuit are involved only as ratios, so that the response characteristics of the source of the sound, condenser transmitter and amplifiers (provided they are invariable) do not affect the measurement.

Illustrations are given of impedance measurements on a closed tube of uniform bore, a conical horn, an exponential horn, an “ infinite ” tube, and a hole in an “ infinite ” wall.
QUASI-STANDING WAVES IN A DISPERSIVE GAS
Authors: Bourgin D. G.
Published: September 2005

For application to standing wave experiments an explicit formula is derived for the influence of absorption on the node position for quasi-standing waves. The effect is of the “second order” in the coefficient of absorption and is inversely proportional to the frequency.
THE THEORY OF ACOUSTIC FILTRATION IN SOLID RODS
Authors: Lindsay R. B. , White F. E.
Published: September 2005

The transmission of longitudinal waves through an infinitely long solid rod loaded at equal intervals with equal heavy masses is treated by a method analogous to the so-called “branch transmission” theory of acoustic filtration in air. The masses are assumed to be so concentrated that they move as a whole and longitudinal motions alone are considered. Transmission bands are found for frequencies satisfying the inequality relation − 1 ≦ cos 2kl − ωm/2ρ0cS ⋅ sin 2kl ≦ + 1, where k = ω/c = 2πν/c ν being the frequency and c the velocity of sound in the rod, m the mass of the concentrated load, S the cross-sectional area of the rod, ρ0 the density of the rod material and 2l the distance between consecutive loads. The loaded rod is thus found to act like a low-pass filter with the cut-off frequency given by the first root of the transcendental equation ωm/2ρ0cS = cot kl. As the frequency increases there are alternate transmission and attenuation bands. Comparison is made between the theory and the experimental results of H. F. Olson (1925) and rather good agreement is found. The case of the transverse waves in a stretched string loaded at equal intervals with mass particles is also treated by the same method and the filter characteristics of this structure very simply obtained in agreement with the previous results of Crandall and others using different methods. Investigation is made of the propagation of longitudinal waves through a solid rod to which are attached at equal intervals strings loaded with masses at their free ends. It is shown that in general such a structure acts like a low-pass filter but that in the limiting case where the loaded ends are fastened to a completely rigid, motionless support the structure has the characteristics of a high-pass filter. Unfortunately the transmission and attenuation bands are of such a nature as to render such an arrangement of doubtful practical value.
SOME IMPROVEMENTS ON THE OPERATION OF THE BELLS OF A CARILLON
Authors: Giannini G. M.
Published: September 2005

The unsatisfactory performance of the bells of a carillon from a musical standpoint is discussed and an improvement is suggested. This is the use of a damping device to permit greater musical possibilities in the playing of carillons. The operation of the electrical apparatus which performs the damping is described.
A NEW ANALOGY BETWEEN MECHANICAL AND ELECTRICAL SYSTEMS
Authors: Firestone F. A.
Published: September 2005

By considering each mass in a linear mechanical system as having two terminals, one fixed in the mass and one fixed to the frame of reference, every linear mechanical system is reduced to a multiplicity of closed mechanical circuits to which force and velocity relations similar to Kirchhoff's laws, may be applied. The conventional mechanical-electrical analogy is derived from the similarity of the equations v = f/z and I = E/Z. It is incomplete the following respects which lead to difficulty in its application.

I. There is a lack of analogy in the use of the words “through” and “across” which indicates a fundamental difference in the nature of the analogous quantities, for instance, force through and e.m.f. across.

II. Mechanical elements in series must be represented by electrical elements in parallel, and vice versa.

III. Mechanical impedances in series must be combined as the reciprocal of the sum of the reciprocals while electrical impedances in series are additive.

IV. There is an incompleteness the mechanical analogues of Kirchhoff's laws.

The new analogy is derived from the similarity of the following equations: v = fz̄ and E = IZ where z̄ is the reciprocal of the mechanical impedance as usually defined. This new analogy is complete in all of the above-mentioned respects in which the old analogy failed. It leads to analogous relations of a simple sort and permits an equivalent electrical circuit to be drawn in an easy intuitive manner.
SOUND ABSORPTION IN NON-REACTIVE GAS MIXTURES
Authors: Lawlor Reed
Published: September 2005

Abello's results for binary gas mixtures may be derived simply if it is assumed that the gases mixed are non-reactive. It is found that if any number of non-reactive gases are mixed, the attenuation constant of the mixture is a linear homogeneous function of the volume percentages of the components. Values of the absorption coefficients of CO2, N2O, H2, He, A, and N2 at 612 kc are calculated.
COMPONENT TONES FROM A BELL
Authors: Jones Arthur Taber , Alderman George W.
Published: September 2005

The gravest sixteen partials of three bells (weights 900 kg, 675 kg, 464 kg) have been examined by the method described by Tyzzer. The numbers of nodal meridians and nodal circles found for the partials of these bells agree with those found on three smaller bells by Tyzzer, except that some additional circles are now found in the upper parts of the bells. The levels at which nodal circles are found are given. The relative frequencies of certain modes of vibration of the bells now studied are compared with those for the corresponding modes of a thin ring. Various reasons are adduced for believing that the vibrations of bells have a considerably larger compressional component than has usually been supposed. Oscillograms have been obtained from which the amplitudes of the partials have been calculated. When a bell is struck in the usual manner the most prominent partial at first is the fifth. In less than half a second—on the bells investigated—the fifth has yielded to the third, which is the most prominent until about four seconds after the stroke. After that the first partial is the most prominent. An appendix gives an approximate method of correcting for the beats with which some partials are affected.
A Study of the Velocity of Sound in Air
Authors: Grabau Martin
Published: September 2005

This study of the velocity of sound in air involves the use of the magnetostriction oscillator in an experiment similar to those of G. W. Pierce and others, who used piezoelectric crystals as sources of sound. The wave system generated by the source is investigated by observing the reactions of the source when the sound waves are reflected back upon it from a moveable reflector. The range of frequencies used extends from 20,000 to 70,000. The irregularities of the wave system near the source are studied in some detail. It is found that these irregularities vary with the frequency, as well as with the diameters of both the source and the reflector, and that they vanish at relatively large distances from the source. The values of the velocityof sound then obtained show no variations with respect to the frequency.
A New Analyzer for the Audible Frequency Range
Authors: Hall H. H. , Clifford D. G.
Published: September 2005

This instrument was designed for comparatively rapid analysis of sound spectra produced by musical instruments. It is a heterodyne analyzer using an intermediate frequency of 20 kilocycles per second. The filter is a magnetostrictive resonator of very low decrement capable of distinguishing between two frequency components only forty cycles per second apart while differing by some fifty decibels in amplitude. The amplitudes are measured by a logarithmic voltmeter controlling a cathode-ray oscillograph which records their relative magnitude, calibrated directly in decibels, on a strip of photographic paper. The recording camera is geared to the oscillator which furnishes the heterodyne frequency in such a way that the audible range up to 10,000 cycles per second may be swept out in a comparatively short time. Every effort has been made to reduce the duration of transients in the system. Preliminary tests indicate that a complete analysis may be made in about twenty seconds.
An Experimental Study of the Rôle of the Tympanic Membrane and the Ossicles in the Hearing of Certain Subjective Phenomena
Authors: Lewis Don , Reger Scott
Published: September 2005

It is usually contended that so-called subjective tones are due to vibrations introduced either by asymmetrical action of the tympanic membrane or by nonlinear functioning of the ossicles. The experiments here reported were designed to determine whether the tympanic membrane and the ossicles play any part in the generation of these phenomena. Individuals who had neither tympanic membranes nor ossicles served as observers. The harmonic constitution of each of the complex tones used as stimuli was such as to make the fundamental tone audible to the normal ear, when it was absent and only two or more overtones were present. It was easy to discover whether or not an observer heard this fundamental tone by having him match the pitch of the complex tone with a pure tone produced by a beat-frequency oscillator. The harmonics present in each of the complex tones was determined by means of harmonic analysis. The results of the investigation indicate that the tympanic membrane and the ossicles are probably not involved in the hearing of subjective tones.
The Ventricular Bands and the Physiology of the Voice
Authors: Josephson E. M. , Simmions Louis
Published: September 2005

Recent studies in the anatomy of the ventricular bands and of the thyro-arytenoid muscles, and physiologic researches in the mechanics of the larynx have compelled changes in concept of voice formation.

These studies have revealed the presence of structures which have been overlooked which impart to the false vocal cords an independent motility and an action antagonistic to that of the thyro-arytenoid muscles; and which actively alter the conformation of the Sinus Morgagni. These studies stress the hitherto unemphasized importance of the function of the suspensory mechanism of the larynx, and the interrelation of the motor mechanisms of respiration and voice formation.

Clinical studies prove that ventricles of the larynx play an important rôle in the formation of the human voice. Filling of the ventricles by disease processes which do not in any wise impair the motility of the true vocal cords or their freedom to vibrate, nevertheless results in complete or high-grade aphonia and dysphonia. Similar disorders are associated with disease of the ventricular bands. These studies indicate the need of extensive researches in the mechanism of the voice; for they contradict much that has been written and dogmatically taught on the subject of the voice.
Some Notes on the Character of Bell Tones
Authors: Curtiss A. N. , Giannini G. M.
Published: September 2005

This paper presents some new data on the frequency and position of the partials of a bell. The decrement curve of the sound and the fine structure of the component tones are discussed and the description of the apparatus used in the experiments follows. Modifications in the design of bells are proposed in order to lessen the criticisms on present types of carillons.
On Frequency Modulated Signals in Reverberation Measurements
Authors: Hunt F. V.
Published: September 2005

A point-by-point curve tracer, similar to that described by Norris and Andree [J.A.S. 1, 366 (1930)] but permitting a longer period of decay to be traced, is employed to study the reverberant decay of pure tones and tones having various degrees of frequency modulation (so called “warble” tones). Straight lines (db vs. time) are fitted to the decay curves by the assumption that the slope determined by every pair of points should be weighted in the average according to the decay time included between the two points. This leads to a simple numerical procedure when the points are equally spaced on the time axis.

The deviations of individual points from the best straight line are computed and found to fall into regular and consistent time patterns, from which large group deviations can be seen to gradually disappear as the degree of warble is increased. These time patterns differ from point to point in the sound chamber but the magnitude of the deviations and the slope of the decay curves (within a limit of accuracy consistent with the deviations) is practically independent of position.

Conclusions are drawn regarding the accuracy with which decay rates can be determined using pure and warble tones.
Experimental Evidence of Nonlogarithmic Sound Decay
Authors: Chrisler V. L. , Miller Catherine
Published: September 2005

In this paper experimental data are presented showing that in a room containing the average acoustical installation the distribution of sound energy does not remain uniform as the sound decays. In consequence the decay of the sound energy is not logarithmic. As one of the fundamental assumptions in all reverberation theories is that the sound energy does decay logarithmically and that it remains uniformly distributed during the decay, it is evident that the reverberation formulae as now given do not apply in most cases. The error introduced in computing the reverberation time where there is a ceiling treatment only may be as much as 30 percent.

It should be possible by further study of this problem to introduce some form of a correction factor in the present formulae so as to take care of most cases encountered in practice.
A High Speed Level Recorder and Some of Its Uses in Acoustical Measurements
Authors: Wente E. C. , Bedell E. H. , Swartzel K. D.
Published: September 2005

A device has been developed which will record the intensity of audiofrequency currents directly on a moving strip of paper by means of a stylus. A wide range of intensities may be covered and the deflection of the stylus is proportional to the logarithm of the input current; the recorder thus has a uniform scale in decibel units. It is capable of following fluctuations in the input current up to 150 per second, and will follow changes in intensity at a rate up to 240 db per second. When used in conjunction with a microphone the recorder lends itself to many types of acoustical measurements. It has been extensively used for reverberation time measurements for which it is particularly well adapted because it will plot the intensity of the reverberant sound on a logarithmic scale during the decay period, a complete decay curve being obtained each time the test tone is interrupted. When used with a beat frequency oscillator curves of intensity vs. frequency may be obtained. This type of curve is useful for loudspeaker and microphone calibrations for determining the distribution of sound in rooms and for intensity measurements for obtaining the sound transmission through partitions. Examples of the above types of curves and others obtained with speech and music are given.
Loudness of a Complex Tone, Its Definition, Measurement and Calculation
Authors: Fletcher H. , Munson W. A.
Published: September 2005

At the meeting of the Society held one year ago Fletcher presented a paper by this title in which was discussed the formulation of a promising method for computing the loudness of a non-fluctuating complex tone from the measured values of the intensity levels and frequencies of the components. Also at that time Munson presented a paper on the loudness of pure tones. The present paper combines the material of these two previous papers with the results of subsequent experimental work, describes some further modifications in the formulae of this method of computing loudness and illustrates the application of the formulae to some examples. In view of the complex nature of this problem, this computation method is not considered to be fully developed and further work is required to define its scope. In addition, it is necessary to determine experimentally to what extent the proposed computation method may be applicable to the types of fluctuating complex tones encountered in speech, music and noise.
On Frequency Modulated Signals in Reverberation Measurements
Authors: Hunt Frederick V.
Published: September 2005

A point-by-point curve tracer, similar to that described by Norris and Andree but modified to permit variations in sound intensity to be measured by a substitution method, is employed to study the reverberant decay of pure tones and tones having various degrees of frequency modulation (so-called “warble” tones). Straight lines (db vs. time) are fitted to the decay curves by an analytic process which is described. The deviations of individual points from the best straight line are computed and found to fall into systematic time patterns which are critically dependent upon frequency and upon the position of either microphone or loudspeaker in the sound chamber. Major characteristics of the time-deviation pattern usually persist as the frequency modulation of the source is increased but the magnitude of the deviations may be reduced considerably. An approximate relation between the average deviation and the fractional frequency modulation (Δf/f) is given. In view of the frequency selectivity of absorption, twenty percent is recommended as a satisfactory, degree of warble for all frequencies. It is pointed out that large errors in the measured decay rate may arise from an ordered arrangement of the time-deviation pattern. An evaluation of these errors in terms of the average deviation of the experimental points from linearity is given which is believed to be applicable generally to any sound decay measurements. It is concluded that the warble tone is distinctly useful for securing decay curves that are more nearly linear but that space effects may still exist which are capable of introducing serious errors.
A Uni-Directional Ribbon Microphone
Authors: Weinberger Julius , Olson Harry F. , Massa Frank
Published: September 2005

Directivity has been found to be desirable in sound collecting systems to improve the ratio of direct to generally reflected sounds and to otherwise discriminate against undesirable sounds. The bi-directional ribbon microphone is a pressure gradient instrument in which the response corresponds to the velocity component in a sound wave. By using a mass controlled element the velocity of the ribbon is in phase with the velocity in a sound wave. By a suitable combination of this microphone with a pressure-operated nondirectional ribbon microphone, a uni-directional ribbon microphone is obtained. The pressure ribbon microphone is resistive controlled and the response is a measure of the pressure component in a sound wave. The velocity of the ribbon in this type of pressure microphone is in phase with the pressure. Combination of the outputs of the pressure and velocity ribbon microphones produces a uni-directional characteristic. The response as a function of the angle θ between the normal to the ribbon and the direction of propagation of the incident sound is expressed by R = R0(1 + cos θ), where R0 is the sensitivity of either the pressure or velocity microphone for θ = 0. Results with an experimental microphone utilizing these principles verify the theory with respect to the phase relations and the directional characteristics. This microphone has been found to be useful in sound motion picture recording, radio broadcasting and sound reinforcing systems where the direct sounds originate in front and undesired sounds to the rear of the microphone.
Acoustic Filtration in Non-Homogeneous Media
Authors: Lindsay R. B. , Lewis C. R. , Albright R. D.
Published: September 2005

This paper considers theoretically the propagation of compressional waves in a structure consisting of an infinite series of alternating layers of two different media which may be either fluid or solid. It is shown that such a structure acts as a low-pass acoustic filter. A number of special cases are computed and it is found that the cut-off frequency depends essentially on the section length and the relative acoustic impedance of the media. The problem is shown to be mathematically quite analogous to that of the propagation of acoustic waves in air through an infinite tube containing alternate constrictions and expansions. Moreover the loaded solid filter considered in a previous paper by Lindsay and White proves to be a limiting case of the non-homogeneous medium filter of the present article.
A Selective Microphone for Use in Acoustic Altimeters
Authors: Delsasso L. P.
Published: September 2005

A modification of Bragg's amplitude meter is applied to a resonant diaphragm, associated with a parabolic horn, to provide a highly selective microphone. When used with an impulsive source of sound it makes possible the measurement of distances as low as 10 ft. while in the presence of sounds comparable to those in aircraft.
Reverberation Measurements of Sound Absorption Coefficients
Authors: Sabine Paul E.
Published: September 2005

A comparison is made of the results of the measurement of the absorption coefficients of twenty-five commercial materials by the organ pipe and ear method with the results obtained by measuring the rates of decay by electrical means. A consistent variation in these results is shown, which can be explained by assuming a slight departure from linearity in the time versus logarithmic intensity relation.
The Place of the Acoustical Materials Industry in the Acoustical Society of America
Authors: Waterfall Wallace
Published: September 2005

Brief history of the connection between the acoustical materials industry and the formation of the Acoustical Society of America and a statement of the purposes for which the Acoustical Materials Association has recently been formed.
Architectural Appraisal of Sound Absorbents
Authors: Smith M. A.
Published: September 2005

This paper considers the various physical and architectural properties, other than that of mere sound absorbing efficiency, that affect the value of commercial absorbents, and attempts to present a rational basis for the appraisal of such materials by the architect.
Reverberation Measurements in Auditoriums
Authors: Stanton G. T. , Schmid F. C. , Brown W. J.
Published: September 2005

The purpose of this paper is to present some of the results obtained in the measurement of reverberation in auditoriums. The methods used are described and certain limitations pointed out. Examples of decay curves obtained with a high speed level recorder under differing conditions are shown, and their relationship to reverberation time discussed. The results and their discussion are supplementary to other work in this field, and are offered at this time as an indication of present day opportunities for study of sound decay conditions.
Phonetic Frequency Distribution in Formal American Pronunciation
Authors: Voelker Chas. H.
Published: September 2005

The speech of radio announcers was chosen as approaching the norm for a formal type of general American Speech. 5946 radio announcements were studied. The announcer was identified through the mail after his program had been phonographically recorded through a vertical cut electrical recording head directly from the radio onto a wax record. These records were played and replayed until certainty as to just which sounds occurred could be ascertained. These records totalling 665,094 were recorded in phonetic notations (I.P.A.). The occurrence of each sound was counted and the data tabulated into frequency tables. The relative percentages of occurrence of each sound were determined and compared.
The Consonant—An X-Ray Analysis of Its Vocal Organ Modifications by Other Sounds
Authors: Russell G. Oscar
Published: September 2005

Since, as the Abbé Rousselot, Scripture, Panconcelli-Calzia, Crandall and a large number of others have pointed out, consonant sounds are of very short duration, analysis of their physiological characteristics by means of the x-ray demands an automatic and very rapid technique. This is especially true of the unvoiced occlusives. Particularly in English. Notably in intervocalic positions. Likewise in certain combinations where laws of assimilation operate. But some unvoiced fricatives are also of very short duration. Crandall gives the mean for “p,” “t,” “k” and the unvoiced “th” as 0.05 sec. But the actual consonant contact or characteristic entity is obviously less than half that length. That demands an x-ray time of at least no more than 1/120th of a second. Also an absolutely automatic opening of the exposure taking place with contact or rather a fractional few thousandths of a second after this central phase position has been assumed. That we have been able to accomplish in this study. Consequently the resonance cavity dimensions throughout the whole length in median plane can now be ascertained, even for these very fleeting sounds, and one must no longer be required to fake their position entity by an artificial prolongation, as has of necessity been done in all the casual studies heretofore undertaken. One of the moot questions which can also now be studied is that about which Crandall and Paget disagreed. That involves consonants which can even be prolonged such as “l.” The question was whether these might normally show varying positions, and consequently resonant cavities “depending on the associated vowel.” But it is even more important to know that fact concerning the above-mentioned fleeting consonants. For the whole question as to the actual importance of resonance cavity effects in creating the characteristic entity of each consonant is obviously involved.
A Physical Definition of “Good Voice-Quality” in the Male Voice
Authors: Bartholomew Wilmer T.
Published: September 2005

The problem of the timbre of the speaking voice has been studied by various investigators. However, little extended work has been done with the singing voice, which it appears is considerably different from the normal speaking voice. The key to a much-needed revision and “codification” of many methods of teaching voice lies in a precise knowledge of what physiologic and acoustic phenomena are taking place in “good” and in “poor” tone-production. This paper summarizes the results of a three year investigation to determine the ideal frequency characteristics of good voices, as a first step in laying the foundation for a scientific pedagogy of voice. Nearly a thousand oscillograms have been taken, each long enough to include at least one complete cycle of the voice-vibrato. They comprise various qualities from best to poorest from over 40 male and female voices of all degrees of training, at frequent points throughout the pitch series, on various vowels, and at various intensities. A study of these records, including harmonic analysis to 30 components of a selected group of 46 wave forms, brings to light four definite characteristics of good voice-quality, which are discussed together with their physiologic implications.
The Loudness Level of Random Noise
Authors: MacNair Walter A.
Published: September 2005

A calculation according to the method of Fletcher and Munson is made of the loudness level of noise of the random type such as “thermal agitation” noise. The comparison is made that noise of this type changes in loudness level 5 decibels for every 3 decibels change in intensity level if this level is between 0 and 40 decibels above threshold, the range in which noise is frequently heard; whereas the loudness level of speech changes about 3 decibels for every 3 decibels change in intensity level if this level is greater than 60 decibels above threshold, the range in which speech is usually heard.
Application of Sound Measuring Instruments to the Study of Phonetic Problems
Authors: Steinberg John C.
Published: September 2005

This paper gives the results of a period by period analysis of the vowel sound waves occurring when the sentence “Joe took father's shoe bench out” was spoken. Such an analysis gives an approximate picture of the time variations in r.m.s. amplitude of the wave, frequency of voice fundamental, and frequency regions of overtone reenforcement. Although the study is confined to a few sounds and one speaker's voice, it illustrates a method of approach to studies of speech production and measurement.
Certain Anomalies in the Theory of Air Column Behavior in Orchestral Wind Instruments
Authors: Redfield John
Published: September 2005

Assuming the clarinet to be closed at its mouthpiece end, theory requires that only odd partials enter the composite tone produced, while analysis of the tone produced shows traces of all even partials, and Miller finds the twelfth partial the most intense of all. On the other hand, to explain the complete series of partials produced by the oboe, bassoon, saxophone, and brass instruments, it is assumed that these instruments are open at their mouthpieces, although these mouthpieces differ in no qualitative respect from the clarinet mouthpiece which is assumed to be closed.

These contradictions disappear, and the observed facts are explained, by recognizing the fact that no orchestral wind instrument is closed at its mouthpiece end, a closed end being necessarily defined as one which prevents the escape of air. All orchestral wind instruments are thus doubly open tubes producing the full series of partials, the relative intensities of the several partials being determined by the contour of the air-column walls in the several instruments. Thus the lower even partials are relatively weaker than the higher in the clarinet, while the lower and higher even partials of the French horn do not vary materially in intensity.
Design Considerations for a Simple and Versatile Electronic Musical Instrument
Authors: Miessner B. F.
Published: September 2005

Instrumentalities for making music depend for their appeal mainly on the range of pitch, timbre, power, and complexity they provide. Musically the most desirable single instrument is one which gives the most versatile performance, without undue complication of playing technique.

A consideration ,of existing instruments leads to the conclusion that the application of modern electro-acoustic, instead of the old mechanico-acoustic operating principles, permits not only of a great extension of these musically desirable characteristics, but also a far greater flexibility in design, and a lowering of bulk, weight, and cost.

The many principles available for electro-acoustic design are discussed and lead to the struck string as the best compromise as a source of vibratory energy.

Methods for providing a wide range of tonal character and performance are described, and an instrument embodying these methods will be demonstrated, both for separate effects, and in a recital of musical compositions.
Normal Variations in Auditory Acuity
Authors: Josephson E. M. , Harelick Samuel
Published: September 2005

Normal variations in auditory acuity are an important factor in all studies of sound and hearing. In the presence of a normal sound-conductive mechanism, these variations originate either in the cerebral processes involved in hearing, or in the end-organ of hearing, the cochlear mechanism.

Variations in auditory acuity of central origin, such as variations due to the state of attention of variations in the sleeping state, have not been thoroughly studied. They primarily involve the perception of sound. Disease of the perceptive mechanism of hearing, as in the presence of brain tumor or meningitis, gives rise to “central” deafness. Though little attention has been directed by modern otology to the differentiation of “central” deafness and deafness due to disease changes in the inner ear, there are a number of signs available for this differentiation.

Variations in auditory acuity of peripheral origin may be caused by many factors, such as barometric pressure, general bodily and circulatory tone and others; but the most interesting is the variation due to continued stimulation of the ear with sound. Whereas the mental processes involved in hearing perception show fatigue, as manifested by the determination by many observers of an increased differential of intensity, the end-organs of the normal ear do not fatigue on prolonged stimulation with moderate intensities of a frequency. On the contrary, prolonged stimulation of the ear with a moderate intensity of a frequency increases auditory acuity for that frequency, as is manifested by a drop in the threshold of intensity for that frequency by as much as 10 to 20 dbs.

These variations in auditory acuity are of high significance in the differentiation between deafness of peripheral and central deafness, which is thus for the first time made possible. For in the presence of peripheral deafness of the progressive type, the hearing shows marked fatigue on prolonged stimulation and a rise in threshold, as contrasted with the drop in threshold in the normal ear. In cases afflicted with central deafness there is found frequently a normal response of the ear to prolonged stimulation, pointing to normality of the ear and the end-organ and the central nervous nature of the disease process. The experience of one of us (Dr. Josephson) stresses the importance of this differentiation in cases of deafness; for he has found about 20 per cent of the cases referred to him with diagnosis by competent otologists of progressive deafness to be deafness symptomatic of tumor or disease of the brain.
Loudness and Pitch of Musical Tones and Their Relation to this Intensity and Frequency
Authors: Fletcher H.
Published: September 2005

Loudness and pitch are psychological terms which are used to describe sensations produced when certain types of waves operate upon the hearing mechanism. Intensity and frequency are the corresponding terms to describe the physical quantities power transferred per unit area and vibrations per second executed by the sound wave. The relation between these psychological and physical aspects of a musical tone has been investigated using a group of typical listeners.

Precise scales were invented and used for representing the sensations of loudness and pitch. In comparing loudness a pure tone having a frequency of 1000 cycles per second and with intensity variable throughout the audible range is used as a reference tone. In comparing pitch, a pure tone having a constant loudness and with frequency variable throughout the audible range is used as a reference tone.

The intensity of a complex tone with ten components all equal in intensity but different in frequency is ten times that of each component, as is well known. On the other hand, the loudness of one such complex tone with frequencies which are harmonics of 500 cycles per second was found to be equal to that of the 1000 cycle component raised one thousand times rather than ten times in intensity.

An observer's location of the pitch was found to depend upon the intensity as well as the frequency. For example, the pitch of a 200 cycle tone was located at a position which was as much as one-quarter of an octave lower at the very high intensities than at the low intensities. For pure tones having frequencies near 2000 or 3000 cycles per second, no difference of pitch was observed as the intensity was changed.

Similar small pitch changes were observed with complex tones. Some very large changes were observed with particular changes in the components. For example, the pitch of a complex tone having four components of equal intensity, but with frequencies of 400, 600, 800, and 1000 cycles per second, was perceived as that corresponding to a 200 cycle tone. If to this complex tone, three additional components having frequencies of 500, 700 and 900 cycles per second, are added, then the pitch will be perceived as an octave lower or that corresponding to a 100 cycle tone.

An experimental demonstration will be given.
Extraneous Frequencies Generated in Air Carrying Intense Sound Waves
Authors: Thuras A. L. , Jenkins R. T. , O'Neil H. T.
Published: September 2005

In high quality reproduction of sound the trend toward large power output necessitates a consideration of the more exact equations of wave propagation in air. If the displacement amplitude of a plane sound wave is not small the equation representing the propagation is not linear, and consequently harmonics and combination tones are generated. The pressure of these extraneous frequencies in terms of the fundamental pressure, frequency, and distance from the source has been mathematically determined by Earnshaw, Rayleigh and others. Rocard has recently applied the equation to exponential horns.

Measurements of the second harmonic and combination tones have been made at various points within a long tube, and in front of an exponential horn. Measurements, in general, agree with theory, but the absolute values are 3 to 4 db lower than the calculated values. An experimental demonstration will be given.
Some Applications of Modern Acoustic Apparatus
Authors: Wolf S. K. , Sette W. J.
Published: September 2005

Applications of the high speed level recorder, the crystal harmonic analyzer, and the Reed frequency analyzer, all recently developed at the Bell Telephone Laboratories, are described. These include reverberation measurements, loudspeaker response measurements, noise analyses, piano tone analyses, and studies on the singing voice. Examples of the data obtained in each instance are given and discussed.
Aural Rectification
Authors: Stowell E. Z. , Deming A. F.
Published: September 2005

Rectification in the ear is of some importance in the study of propeller noise. Data on this phenomenon have been obtained by using modulated signals. Twenty out of twenty-one observers were able to hear the modulating frequency as a result of rectification. Quantitative estimates of the magnitude of this subjective tone have been obtained. Measurements have been made of the increase in loudness level due to rectification. Results indicate that rectification may be a property of the basilar membrane rather than of the ear drum or the ossicles of the middle ear, as previously supposed.
A Precision Study of Piano Touch and Tone
Authors: Hart Harry C. , Fuller Melville W. , Lusby Walter S.
Published: September 2005

The loudness and tone quality of a piano note are determined by the motion of the hammer at the time of its impact with the string—theoretically, by its velocity, acceleration and higher time derivatives. Practically, due to the great rigidity of the hammer shank, the influence of the acceleration and higher derivatives is negligible. This study presents exact quantitative confirmation of the findings of other investigators that the loudness and tone of a piano note are uniquely determined by the velocity of the hammer at the time of impact with the string.
Static and Dynamic Demonstrations of Harmonic Curves in Two and in Three Dimensions
Authors: Dodd Will C.
Published: September 2005

Motor-driven vibrators combine simple harmonic motions in such a way as to show the complete family of Lissajous' curves on the screen. Addition of a third motion renders three dimensional harmonic figures visible as skew curves in space. These figures exhibit multiple phase changes. Mathematical properties are mentioned. Behavior characteristics of synchronous motors are demonstrated by means of the skew curves. The possibility of a simple, direct laboratory measurement of power factor is indicated.
The Transverse Vibrations of Membranes and Plates
Authors: Colwell R. C.
Published: September 2005

The differential equation for a circular membrane takes the form ∂2z∂t2 = c2(∂2z∂r2 + 1r ∂z∂r + 1r2 ∂2z∂θ2). The solution for the nodal lines is given by the equation z = Jn(kr) cos nθ = 0. This gives a series of circles and diameters. However, when circular membranes are vibrated with a valve oscillator, many other symmetrical figures appear. These must be combinations of nodal lines which are not given by the equation above. Thus the most general solution for a circular membrane is still to be found. Chladni plates are usually about ten inches in diameter and it is rather difficult to vibrate them at high frequencies with a violin bow; but with the valve oscillator they may be vibrated at frequencies up to fifteen kilocycles. It is also possible to vibrate small plates one inch in diameter at fifty kilocycles, which is above the audible range. Photographic reproductions of some nodal figures will be shown.
The Transmission of Sound Through Sea Water
Authors: Dorsey Herbert Grove
Published: September 2005

During the past year experiments have been made by the U. S. Coast and Geodetic Survey to determine the horizontal path of sound through sea water and valuable information has been obtained. Two ships on the Pacific Coast operated in depths of about 1000 fathoms and many oscillograph and chronograph records were made of small bombs fired near the surface and to depths of 600 fathoms, with distances from 16 to 48 km between ships. On the Atlantic Coast two ships experimented first with both in depths of 1450 fathoms, and again with one ship stationed at 793 fathoms while the other steamed towards shore. In each case bombs were fired frequently at first and then less often until about 30 kilometers distant when a depth of 46 fathoms was reached. Time intervals were measured by a chronograph. In general, it seems that up to certain distances the bomb signal may be received by a direct path from the bomb to the hydrophone and by one or more reflections from the bottom and surface. Calculations from records show that in some cases there were as many as 28 reflections from the bottom and 27 from the surface. Refraction of sound is very evident, often causing the direct sound to be bent to the bottom so that no direct sound is received.
Loudness and Intensity Comparisons
Authors: Ham L. B.
Published: September 2005

In a recent paper by Mr. Parkinson and myself (Loudness and Intensity Relations, J.A.S.A. 3, 511–534 (1932)), a series of experiments were described concerning the comparison of the loudness of one tone with a fixed tone of the same frequency characteristics. The present series of experiments are similar except being confined mostly to low tones between 60 and 500 cycles per second. Present experiments carried out with the same frequencies and under similar experimental conditions as the former series yielded similar results. In the very low frequencies, the value of n obtained for the equation used in the former series is larger, which means that the decibel intervals for corresponding loudnesses are smaller. Certain experimental factors, however, have appeared in the present experiments that did not appear in the previously published data due, in part apparently, to differences in experimental technique. We did not find any noticeable effects in the very few experiments tried in the previous series on interchanging the order of the energy decreases. Interchanging the order of energy changes has been tried in the present series.
Fog Signals
Authors: Chrisler V. L.
Published: September 2005

Measurements have recently been made in cooperation with the Lighthouse Service on a number of different types of fog signals at Cape Henry. These measurements indicate that air borne sounds, as now produced, will never give adequate protection to shipping. A large number of observations were made by a number of observers on relative loudness of different types of signals. The relative loudness was also determined by matching with a Western Electric 2 A Audiometer. Making use of the curve worked out by Fletcher relating loudness to loudness level in decibels, the loudness level as determined with the aid of the audiometer has been converted into loudness and compared with the average value obtained by the various observers.
Quantitative Study of the Singing Voice
Authors: Wolf S. K. , Stanley D. , Sette W. J.
Published: September 2005

The field of singing has been handicapped by the lack of suitable quantitative means for simply evaluating the various voice factors. With the aid of recently developed acoustic instruments, the authors have investigated the physical characteristics of vocal tones, including power as a function of pitch, attack, quality, and vibrato. Measurements have been made and repeated on more than fifty singers in various stages of development. On the basis of the results, it is possible to evaluate and criticize a singer's technical equipment, and determine by periodic tests whether the voice is improving or deteriorating.