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Journal of the Acoustical Society of America

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Jul 1931

Volume 3, Issue 1A, pp. 3-178

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The Muscial Scale and Its Tuning (A)

William Braid White

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 3-3 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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The accepted system of tuning divides the octave into a succession of twelve tones, of which the frequency relations are such that if n be any tone
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from which also it follows that
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This system, however, is purely artificial and was adopted in the eighteenth century in order to effect a practical compromise between the growing demand for freedom of tonal combination, and the limitations of a keyboard which had fastened itself upon practical musical performance. The paper discusses the nature of the musical scale and the anomalies which arise when an attempt is made to evoke intervals and chords in accurate relations of frequency with only twelve separate tones available in each octave. Some of the acoustical defects of equal temperament are pointed out especially in relation to music as heard. A thorough reconsideration of the subject is suggested for the general benefit of the reproducing arts and of the future of Music as a living form of expression.
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Physical Aspects of Piano Tone (A)

Otto Ortmann

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 3-4 (1931); (2 pages)

Online Publication Date: 13 Jun 2005

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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.
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The Woodwind Musical Instruments (A)

Dayton C. Miller

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 4-4 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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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.
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Characteristic Sound Producers of the Organ (A)

Leslie N. Leet

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 4-4 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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Description and demonstration of the factors that influence the tone quality of organ with a brief outline of the general structure of the organ. Illustrated by actual pipe examples played on a miniature laboratory organ.
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Standardization in Teaching the Control of the Human Voice in Speech and in Song (A)

Louis Simmions

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 4-5 (1931); (2 pages)

Online Publication Date: 13 Jun 2005

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The voice teachers of the past and the present have been trying and are tying to standardize their work in teaching the control of the human voice. Without a standard of measurement this was not possible. The acoustical scientists have evolved a standard of measurement in the art of the reproduction of the human voice. The speaker through practical demonstration believes he can prove that the same standard of measurement can be applied to the training of the human voice in speech and in song. With this end in view the speaker has evolved and applied in his teaching an acoustic measuring apparatus with which the student of voice can hear his own voice amplified and measure the right pressure of the vowel continuant through the deflection of a sensitive meter.
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Minimizing Discrepancies of Intonation in Valve Instruments (A)

John Redfield

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 5-5 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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If the crooks for the first, second, and third valves of a brass instrument are made of the proper lengths to produce respectively a tempered whole tone, a tempered half tone, and a tempered tone and a half, then the notes produced by the simultaneous use of any two or more valves are sharper than the corresponding tempered intervals. The problem of tempering the scale of a valve instrument thus becomes a matter of making each valve crook too long for tempered intervals when the valves are used singly, so that the sharpness of notes produced by the combined use of valves shall be reduced as much as possible. The precise lengths of the several valve crooks for minimizing discrepancies of intonation in a valve instrument appear to be unknown both to writers on acoustics and to makers of valve instruments. The paper presents the method of minimizing such discrepancies.
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Open Pipes, Stopped Pipes and Double Stopped Pipes (A)

John Bellamy Taylor

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 5-5 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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Air columns in rigid tubes reflect pulses (sound waves) at the ends. The classical sounding or vibrating air column is the organ pipe, broadly classed as either “open” or “stopped” and giving tones of different quality because lack of symmetry in stopped organ pipes suppresses the evenly numbered harmonic overtones. Pipes of both classes are usually considered to be so rigid that all of the “output” to free air occurs at two ends of open pipe or at single opening (mouth) of the stopped pipes. This rigidity assumption may not be justified.
If a pipe is stopped at both ends, symmetry is restored with opportunity for vibrations in the complete harmonic series. But with no free vent to outer air the double stopped pipes obviously may not be energized by the usual form of air stream; also confined vibrations will not be heard outside. These seemingly unworkable conditions are met by supplying energy and also withdrawing sound output at nodal points, rather than at loops (ventral segments). Such abstraction of energy at node of vibrating air column is useful in cases where the tone or vibration is to be transferred to a denser medium, e.g., to a liquid or to a solid such as a sounding board.
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Further Studies on the Strike Note of Bells (A)

Arthur Taber Jones and George W. Alderman

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 5-6 (1931); (2 pages)

Online Publication Date: 13 Jun 2005

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(1) Difference Tones.—The pitches of the first order difference tones from the fifth and seventh partials have been obtained for 24 bells, and from the seventh and tenth partials for 13 bells. These difference tones are probably not important in the production of the strike note.
(2) Relative Intensities of the Partial Tones.—Curves from bells have been obtained with a condenser transmitter, amplifiers, and an oscillograph. Analysis of the curves from four bells do not indicate the presence of the strike note. They do show that when a bell is first struck the fifth partial is the most prominent, and that this fifth partial is rapidly damped. The relative intensities of the partials fit well with the qualitative results which had already been obtained.
(3) Duration of Contact of Clapper.—296 records of the strokes of the clappers on four bells show that the duration of the contact increases with decreasing strength of blow, and that with increasing strength of blow the duration appears to approach a definite limit. This limiting duration of contact is about half the period of one vibration of the fifth partial, a fact which doubtless explains the early prominence of the fifth partial.
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The Vibrations of a Metallic Plate (A)

Robert Cameron Colwell

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 6-6 (1931); (1 page) | Cited 1 time

Online Publication Date: 13 Jun 2005

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Hitherto a Chladni plate has been set in vibration by means of a violin bow. This procedure made it necessary to clamp the plate at some point. It has been found, however, that with a mechanical vibrator, a square (or round) metallic plate may be set in vibration while resting freely upon a rubber mat. In this way many new sand figures may be formed. The vibrations of such a plate is closely analogous to that of a membrane; so that some of the simpler figures permit a mathematical treatment. A brief mathematical theory will be given for several of these.
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Measurement and Frequency Analysis of Sound from Large Reduction Gear Units (A)

E. J. Abbott

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 6-6 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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In order to determine noise specifications in absolute units for a certain type of large reduction gear measurements were made of the sounds produced by ten machines in operation at a large central generating station. An average weighted total intensity, and a frequency analysis were made of the noise of each machine. It appears that these data are suitable and sufficient for absolute noise specifications on this type of machine.
It was found that 1 db. represents an important difference in loudness in these machines which places quite rigorous requirements on the apparatus and the methods of measurement in order to eliminate errors due to wave patterns, location, load, speed, etc. Data on these points are given.
A very close check was obtained between the observed frequencies of the various notes, and the movements of certain parts of the machine. By a comparison of the frequency analyses of the different machines it was possible to locate which part of the machine was responsible for the noise, and something of the nature of the defect producing the noise.
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A Planetary Reduction Gear System for Turntables (A)

A. V. Bedford

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 6-7 (1931); (2 pages)

Online Publication Date: 13 Jun 2005

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In the common synchronous gear drives for phonograph or talking picture turntables there is at least one driven gear which makes the same average revolutions as the turntable and which is driven by a higher speed gear (or worm). Commercial gears have slight but appreciable errors in both tooth spacing and shape, which necessitates a variation in the relative angular speeds of the two gears. These irregularities may introduce disturbances of frequencies corresponding to the frequency of revolution and its multiples.
The effect of the higher harmonics can be easily reduced by filtering, but to filter the lower frequencies the turntable must be prohibitively massive or the couplings must be so flexible as to put the table speed at the mercy of the irregularities of its bearings and endanger the synchronism of sound and picture.
The planetary gear system, to be described, increases the speed of the lowest‐speed gear with respect to the gear meshing it, thereby increasing the frequency of the disturbance and greatly facilitating mechanical filtering.
The main turntable bearings are also run at higher speed with similar effect upon disturbances arising from frictional irregularities. Damping is also provided to dissipate transient disturbances of speed.
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Experimental Judgments of Relative Loudness by a Number of Observers as Related to the Decibel Scale (A)

John S. Parkinson

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 7-7 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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A large number of experiments were made, both on trained and untrained observers, to determine the factors which influenced individual judgments of the relative loudness of tones. These experiments included a considerable range of levels and a number of different frequencies. The results show a marked uniformity but do not appear to be related directly either to the intensity or the loudness levels as measured in decibels.
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Differential Pitch Sensitivity of the Ear (A)

E. G. Shower and R. Biddulph

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 7-7 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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Differential pitch sensitivity is defined as the minimum percentage change in frequency which can be detected by the ear. The value of this ratio was measured over a frequency range from 32 cycles to 11,600 cycles and from the thershold of audibility to a sensation level of 90 db. in the case of ten normal ears. A number of subsequent observations were made using binaural and bone conductions timuli. In a region above 1,000 cycles and above a 20 db. sensation level the minimum detectable variation Δ/f is approximately constant at a value of .003. Below 1,000 cycles the function Δf is approximately constant for any one sensation level. Binaural and bone conduction stimuli tend to increase the sensitivity of the ear to pitch changes in the general region below 500 cycles but above this region there is very little effect. The errors encountered in this type of measurement are discussed, together with the design and technique necessary to minimize such effects. A series of observations taken with modified apparatus show the effect of several such factors upon the results.
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Acoustic Insulation and Cancellation Effects at the Basilar Membrane (A)

A. G. Pohlman

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 7-7 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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The perceptive mechanism presents an apparatus of phenomenal sensitivity and of equally phenomenal capacity to withstand acoustic insult. The physiological requirement calls for a place of reasonable quiet in which the end organ may analyze the vibrations conducted to it. This is fulfilled by immersion of the end organ in the liquid of the internal ear, and the insulation (a factor of 40 db.) is overcome by the sound transmission apparatus which is about equally efficient throughout the audiorange. The auditory cells act as selective transformers and rest on the basilar membrane which is flanked by the two scalae. Vibrations pass into the internal ear through both windows and the basilar membrane is placed nearly edge‐on to the advancing wave front. This would result in a cancellation effect at the basilar membrane and would present a shock absorber which is instantaneously operative at all frequencies. The interpretation is opposed to the generally accepted ideas both on transmission of vibrations to the internal ear and to the function of pitch analysis as dependent on mechanical factors which lie extrinsic to the auditory cells themselves. This is supported by both morphological and experimental evidence.
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The Salient Features of the Functioning of the Cochlea, with Demonstration of a Transparent Hydraulic Model (A)

Max F. Meyer

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 7-8 (1931); (2 pages)

Online Publication Date: 13 Jun 2005

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In constructing a model for demonstration of the function of the cochlea two assumptions are what we ought to keep clearly out of our mind: (1) that the living cochlea might contain dead building material of such physical properties as vulcanized rubber or tensile metal, (2) that the cochlea might contain contractile tissue, muscle tissue, that is, building material, which, in itself or in the supports in which it is inserted, could, from time to time at least, actively produce any stresses.
A mechanical theory must recognize four salient features: (1) that any sound pervades the cochlea no matter whether the window flexibility is considered in theorizing or put down as negligible in theorizing or is actually (pathologically) impaired—just as any sound pervades any building with all its rooms and partititions, and that such a primitive function is almost certain to have at least a weak and otherwise limited stimulating effect; (2) that the main and more adequate (but not exclusive) stimulating effect in mammalian animals (having an elongated cochlea tube) is likely to result from displacements of the phragma due to pressure differences between the windows, which are unsymmetrical to the meatus; (3) that the bulge formed by the displaced phragma can not travel, but can only lengthen itself, as is demonstrated by inspection of the hydraulic model; (4) that the formation of a bulge on either side of the average location of the phragma is succeeded by the development of stress in the phragma, as is demonstrated by inspection of the hydraulic model.
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The History of the Microphone—Its Development and Use (A)

H. A. Frederick

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 8-8 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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Most of the many possible types of microphones as they are now known to exist were tried during the few years immediately following Bell's original invention. The more important types are described, dated, and identified as to their inventor. During the last 15 years, the theoretical and experimental technique for the test, analysis and development of the microphone has advanced greatly with the result that many of the early types have again become of interest. The development of the vacuum tube amplifier during this period, moreover, has removed the old requirement of large electric output from the microphone and greatly altered the practical aspects of the situation. The refinement of the microphone during these 15 years is sketched and the characteristics of some of the more important recent instruments are given.
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The Technique of Microphone Calibration (A)

Stuart Ballantine

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 8-8 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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The distinction between pressure and free wave calibration of the microphone will be brought out and two or three methods using electrostatic actuator, thermo-phone and piston-phone will be described. Experimental precautions required in use of each of these will also be given.
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An Improved Form of Moving Coil Microphone (A)

E. C. Wente and A. L. Thura

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 8-9 (1931); (2 pages)

Online Publication Date: 13 Jun 2005

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Microphones of the moving coil type have been previously used but difficulties have been encountered in attempts to cover a wide frequency range with uniform sensitivity. The paper describes an electrodynamic microphone of moderate size having incorporated in its design an acoustical network by means of which a uniform sensitivity is obtained from forty-five to ten thousand cycles per second. It is shown how by changes in dimensions the instrument may be given other forms of response curves. The sensitivity is such that ten millivolts per bar of sound pressure are impressed through a transformer on the grid of a vacuum tube.
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Mass Controlled Electrodynamic Microphones: The Ribbon Microphone (A)

Harry F. Olson

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 9-9 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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One of the requirements of a high quality microphone is uniform response over a wide frequency range. To attain this objective in an electro-dynamic microphone the ratio of the velocity of the mechanical system to the pressure or velocity in the acoustic system must be independent of the frequency. To maintain constant velocity in a mass controlled microphone the driving force actuating the mechanical system must be proportional to the frequency. This may be accomplished by the designing of the mechanical system so that the actuating force is derived from the pressure gradient of the sound wave. Provided the system is small compared to the wave-length of the incident sound wave the resultant pressure available for actuating the system is proportional to the frequency.
One example of this type is the ribbon microphone which consists of a light ribbon suspended in a magnetic field. The ribbon is driven from its position of equilibrium by the difference in pressure due to the difference in phase existing between the two sides. The acoustic impedance of the ribbon and air load is proportional to the frequency. The velocity of the ribbon (or the generated e.m.f.) is determined by the ratio of the resultant pressure and the acoustic impedance. In the case of the ribbon microphone this quantity is independent of the frequency.
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Plane Sound Waves of Finite Amplitude (A)

R. D. Fay

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 9-9 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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The principal object of the analysis is to find the change in type of periodic plane waves of sound of finite amplitude propagated in free air.
A solution of the exact equation of motion is obtained as a Fourier series. Due to the nonlinear relation between pressure and specific volume there is found to be a gradual transfer of energy from components of lower frequency to those of higher frequency. Since the effect of viscosity is to attenuate the higher frequency components more than the lower, there is always a wave form having the harmonic components in a stable relation such that the decrease in relative magnitude of any component due to viscosity is compensated by the relative increase due to non-linearity. The conditions for stability vary with intensity. There is therefore no permanent wave form, but the stable wave will change its form more gradually than any other wave of the same intensity and wave length. The change in type of any wave is toward this stable form. There is a marked departure from the sinusoidal in the stable type even for waves of very moderate amplitude.
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Some Uses of Pressure Gradient Microphones for Acoustic Measurements (A)

Irving Wolff and Frank Massa

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 9-10 (1931); (2 pages)

Online Publication Date: 13 Jun 2005

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The difference between microphones whose action depends on the pressure and those whose action depends on the pressure gradient in the sound wave is pointed out, and illustrations are given of each type. The characteristics of the pressure gradient in a complex sound field is discussed. It is shown that under certain conditions the pressure gradient gives a measure of the particle velocity in the sound wave. Illustrations and experiments are described which show how the vector characteristics of the pressure gradient may be used to advantage in making acoustic measurements.
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Some Physical Factors Affecting the Illusion in Talking Motion Pictures (A)

J. P. Maxfield

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 10-10 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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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.
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Audible Frequency Ranges of Music, Speech and Noise (A)

W. B. Snow

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 10-10 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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This paper describes the use of an electro-acoustic system, transmitting the audible frequency range almost uniformly, in determining by ear the frequency ranges required for faithful reproduction of music, speech, and certain noises.
Sounds were reproduced alternately with and without filters limiting the frequency range transmitted by the electrical circuit. The filter cut-offs producing just noticeable changes in the reproduction were deduced from judgments of listeners as to the presence or absence of filters. It was found that for absolute fidelity all musical instruments except the piano require reproduction of the lowest fundamentals. The frequencies above 5,000 cycles were shown to be important, some instruments and particularly noises requiring reproduction to the upper audible limits.
Tests were made in which experienced listeners judged the degradation of “quality” produced by a series of filters. The judgments showed definitely that the quality continues to improve as the frequency range is extended down to 80 or up to 8,000 cycles. Although somewhat indefinite on cut-offs outside these limits, they indicated that reproduction of the full audible range was considered most perfect.
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Means for Radiating Large Amounts of Low Frequency Sound (A)

E. W. Kellogg

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 10-10 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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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.
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Reduction of Noise in Subways (A)

F. R. Watson

J. Acoust. Soc. Am. Volume 3, Issue 1A, pp. 11-11 (1931); (1 page)

Online Publication Date: 13 Jun 2005

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A new consideration in the reduction of the disturbances of noisy machines recently occurred to the author. The matter arose in connection with a study of subway noises, in which it appears that the sources of disturbance are traceable to the following sources—the impact between car wheels and the rails that causes both of these elements to vibrate; the grinding of the gears that communicate the power from the motor to the car axles, together with the vibration of the gear wheels; and finally the vibration and rattle of the loose parts of the car.
A simple experiment showed that the rail vibrations could be deadened effectively by clamping pads of felt on the web of the rail. In actual use, however, the use of such deadened rails produced no noticeable effect—an apparent paradox. Consideration of the action of the ear gives a simple explanation of the paradox. Suppose that each of the five sources of noise mentioned has approximately one billion units of threshold intensity, the total intensity thus being 5,000,000,000 threshold units, with a loudness of 97 decibels. If now the rail noise is completely eliminated, the intensity is reduced to 4,000,000,000 threshold units, but the loudness is reduced only one unit to 96 decibels, and therefore would not be detected by the ear. By the same reasoning it is apparent that to reduce the noise appreciably, say to 50 decibels it is necessary to reduce all the disturbing elements to at least 100,000 threshold units. If only one remains with an intensity of 1,000,000,000 threshold units, the loudness still has the high value of 90 decibels. In other words, it is waste of effort to quiet any one element of a noisey machine; it is necessary to reduce the vibrations of all the disturbing elements, assuming them to be of about the same intensity.
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