bluuebunny/crossref_metadata_2025 huggingface dataset:
Pre- and Post-Equalization of Compandor Systems
Authors: Steinberg J. C.
Published: September 2005

In order best to fit the volume range of the program material into the volume range available in sound film, it is generally advantageous to pre-equalize the program material before recording, and to compensate for the equalization by means of a complementary post-equalizer on reproduction. The type and amount of pre-equalization depend upon the properties of hearing and on the characteristics of the program material and the film noise. This paper discusses the relations between these quantities for systems using compandors, where the film noise varies up and down in level as the compandor gains vary. Ideally, different types of pre-equalization are needed for different types of program material, and a compromise must be made if a single type is to be used. The considerations leading to the choice of the pre-equalization used in the stereophonic recording and reproducing system are discussed.
Electrical Equipment for the Stereophonic Sound-Film System
Authors: Snow W. B. , Soffel A. R.
Published: September 2005

An electrical system is described which permits the use of sound film, with its limited signal-to-noise ratio, as a recording medium for wide-range stereophonic reproduction of symphonic music. Noise reduction is accomplished both by pre-equalization, rising to 18 db above 8000 cycles, and by automatic signal compression and expansion of 30 db. To secure maximum suppression of noise and freedom from distortion, a pilot-operated, fiat-top compandor system was selected. In each channel low level signals are recorded on a separate track with constant gain 30 db above normal, which places them above the film noise. Higher-level signals cause automatic gain reductions and are recorded at substantially full modulation. These signals vary the intensity of a pilot tone, which in turn controls the compressor gain. There is a pilot frequency for each of the three channels, and the three are combined and recorded together on the fourth film track. During reproduction they are separated by filters, and operate expandors which restore the signals to their original forms but reduce the noise to inaudible levels. The compressor and expandor gains are made proportional to pilot level in db, and the expandor range over which this relation holds is 45 db. Therefore a 15-db variation in average pilot level during reproduction causes a corresponding average level change but no distortion. This is used to allow expansion of the original signal intensity range during recording or re-recording by simple gain controls in the pilot circuits. The paper describes the apparatus and circuits developed to accomplish these results, and discusses the frequency, load, distortion, noise, and dynamic characteristics of both constant and variable gain elements. Also included are considerations of microphone and loudspeaker arrangement and equalization to secure high fidelity of reproduction.
A Light Valve for the Stereophonic Sound-Film System
Authors: Wente E. C. , Biddulph R.
Published: September 2005

This paper describes a light valve incorporating large electro-magnetic damping and operating directly through the ribbon resonance region. Resonance response is only 5 db above low frequency response and so permits easy equalization. A suitable equalizer provides uniform string displacement per unit driving voltage over the band 30–14,000 cycles with very nearly constant phase shift per cycle. Problems of structure and size have furnished a mechanical design having several interesting features, among which are mechanical robustness, protection against dirt and moisture, built-in ribbon and optical adjustments, and an optical system integral with the valve structure thus permitting rapid replacement of valves in the recording machine. This unit has proved a rugged, stable, light modulator especially free from intermodulation products.
Internally Damped Rollers
Authors: Wente E. C. , Müller A. H.
Published: September 2005

Special damping rollers, capable of damping oscillations of rotating shafts without adding a steady load, were first devised by Prof. H. A. Rowland. These rollers had either an annular channel along the periphery filled with a liquid, or a wheel mounted loosely on a shaft coaxially fixed in an outer shell, the interspace being filled with a liquid. The theory of the action of such rollers in reducing fluctuations in the speed of rotation caused by disturbances from either the load or the driving side is developed and the results are illustrated by graphs. A new form of roller is described in which liquid filling an annular channel within the shell of the roller is coupled to the shell by a mechanical resistance.
A Problem in Acoustically Treated Enclosures
Authors: Bonvallet G. L.
Published: September 2005

The low frequency energy prevalent in sound treated rooms becomes perceptible and even objectionable as the size of the room decreases. The door-less acoustically treated telephone booth is subject to this difficulty in a few installations of prevailing high intensity low frequency energy. Increasing the mass or stiffness of the components of the structure decreases the resonant frequency. These solutions, however, lead to a product of prohibitive cost. Mismatching and damping of the panels lead to another solution. Efforts have been made along these lines to produce a marketable structure. Experimental models have been made which are a step in the right direction, but the “natural” has not yet been found. These models have by no means exhausted the ingenuity of combining materials to obtain the desired effect.
A Phonograph Pick-Up of the Moving Coil Type
Authors: Lindenberg Theodore
Published: September 2005

Since the earliest acoustic phonographs passed into history and vacuum tube amplification became a practical reality, an ideal pick-up design has been the goal of recording engineers. This development has followed three basic types; magnetic, crystal and moving coil, and a new design of the latter forms the subject of this paper. Considering the physical mass of the moving elements of the three above-mentioned types and their mechanical construction, the writer's design provides a considerable reduction of moving mass together with durable mechanical design. This reduction in mass, higher stylus compliance, lower stylus pressures, together with a unique “floating head” arm design, provide a frequency range and freedom from harmonic distortion which have been heretofore unattainable save with very fragile laboratory models. Inasmuch as the unit is a true generator, this paper also covers the design of a rather simple capacitance, resistance, equalizer to match output to the various recording characteristics in general use today.
Properties of the Dulled Lacquer Cutting Stylus
Authors: LeBel C. J.
Published: September 2005

The recent improvement in disk recording standards is emphasized. The combined cutting and burnishing action of a standard lacquer cutting stylus is explained. It is emphasized that cutting and burnishing take place simultaneously (in terms of wave-length) at low frequencies; but that at higher frequencies the two operations are separated by a discrete wave-length fraction; phase shift and attenuation result. These depend upon circumferential velocity, hence are worst at low rotational speed and small distance from the center of the record. The experimental study, therefore, is confined to 3313 r.p.m. recordings at various diameters, and the recorded velocity as a function of frequency and diameter is determined for needles with different lengths of dulling. The effect of amount of dulling on surface noise is determined, and a technique for comparing the perfection of action of cutting and burnishing is given. It is emphasized that for modern quality standards the length of dulling must be restricted and that the resulting increase in surface noise is not of great importance.
The Influence of Elastic Properties of Disk Material upon the “Pinch-Effect” in Lateral Recording
Authors: Begun S. J. , Lynch T. E.
Published: September 2005

It has been held that the properly designed lateral phonograph pick-up should have incorporated between the stylus tip and the generating unit, an element which is flexible to vertical motion and does not generate voltages due to vertical excitation. This flexibility is supposed to reduce the mass forces generated by the “pinch-effect” vertical accelerations to a minimum, and thus reduce groove and stylus wear and also harmonic distortions. It is shown, however, that the elastic properties of all common disk materials is such that the stylus rides in pockets in the groove walls, and these displacements or pockets have a value given by the stylus forces generated by the groove geometry. It is further shown that the “pinch-effect” forces can be absorbed by the elastic properties of the record material without destructive forces. From this it appears that there is no practical necessity for providing the aforementioned coupling member between stylus tip and generating element in the lateral pick-up.
High Fidelity from the Musician's Viewpoint
Authors: Bartholomew Wilmer T.
Published: September 2005

Many musicians are typically suspicious or condescending toward reproduced sound. Some of their common criticisms are discussed in this paper, together with their psychological implications.
High Fidelity from the Musician's Viewpoint
Authors: La Prade Ernest
Published: September 2005

In recent years high fidelity sound reproduction has been widely publicized, but whether the public really wants it is an open question. Observers have long noted a tendency among untrained music lovers to favor low-frequency tone. They seem to prefer the contralto voice to the soprano, the 'cello to the violin, etc., and this tendency is confirmed by a survey made in 1940 by Samuel E. Gill which showed that owners of radio receivers equipped with tone control mechanism seldom used that device to obtain the maximum available frequency range. Such preference for low pitches suggests that the desire for increased frequency range is something less than universal. However, fidelity is not solely a question of frequency. Faithful reproduction of music involves other factors, such as dynamic range, studio acoustics, balance and perspective. Higher fidelity in these respects might prove more valuable and more acceptable to the public than increased frequency range.
City Noise
Authors: Wynne Shirley W.
Published: September 2005

While noise was recognized as a nuisance prior to 1928 there was no authoritative evidence that it was a health hazard. Consequently Health Departments experienced difficulty in suppressing loud noises except during the hours between 11 P.M. and 7 A.M., and then only on the basis that loud noises disturbed sleep. Since that time scientifically conducted experiments have demonstrated definitely that loud noise does affect health, not only by disturbing our sleep at night but by causing us to react at all times. It has likewise been demonstrated that noise lessens the efficiency of children at school and workers in the office and factory. As soon as the general public realizes that noise is injurious, engineers will find means of lessening it. The public has failed to make use of this knowledge as it has failed to make use of much of the knowledge of preventive medicine which we have acquired within recent years.
Report of Activities of the National Noise Abatement Council
Authors: Little George P. , McGee F. Edgar
Published: September 2005

In 1940 Mr. J. H. Rand wrote the heads of several prominent business concerns reminding them of the various sporadic attempts toward noise abatement throughout the country, and suggested that since these companies manufactured products that minimized noise, it might be in order for them to meet and discuss the possibility of cooperatively assuming this job on a national scale. Out of this meeting grew the National Noise Abatement Council. The enthusiastic participation of local committees and organizations in the National Council's program, which centered around Noise Abatement Week as a practical beginning, indicates that this movement has definitely established itself in the national scene. Local committees in most of the principal cities participated in this activity in 1941. The Council has again uncovered a tremendous national interest in noise abatement, and has apparently found a practical way to deal with the problem through a nation-wide effort, as recommended by the Noise Committee of the Acoustical Society several years ago. It is hoped that a means of cooperation between the Council and the Acoustical Society can be originated during this noise abatement session.
The Acoustical Society and Noise Abatement
Authors: Sabine Paul E.
Published: September 2005

This paper considers the possible fields of cooperation between the Acoustical Society and its membership with groups interested in noise abatement on a nation-wide scale. It emphasizes the fact that the ultimate objectives of acoustical research and technology lie in their application to humanitarian ends rather than in the advancement of pure science. Hence, there arises an obligation on the part of the Society to promote actively a movement directed toward the alleviation of noise in the working and living conditions of the community as a whole. Various ways and means of participation in a long range program for noise abatement are suggested.
The Effect of High Intensity Noise Levels on Surrounding Areas
Authors: Parkinson J. S.
Published: September 2005

The noise generated by airplane motors under test is of such high intensity that it may be annoying for distances of one-half mile or more and may be audible for distances up to twenty miles. Normal atmospheric radiation losses were investigated over a wide range of frequency bands. These losses approximated the inverse square relationship except at high frequencies. The effect of obstructions such as buildings is noted. The observations permit general conclusions as to what levels will be tolerated during the day and at night by residents of surrounding areas.
Apparatus for the Direct Measurement of Force-Displacement Characteristics of Mechanical Systems at Audiofrequencies
Authors: Haynes J. R.
Published: September 2005

Dynamic characteristics of displacement as a function of driving force applied to mechanical systems are obtained by using a piezoelectric crystal to measure the dynamic force and a parallel plate condenser to measure the resulting displacement. The voltages developed across the crystal and condenser are amplified and impressed on the vertical and horizontal plates of a cathode-ray oscilloscope. In this way a trace of displacement as a function of the driving force for the mechanism attached to the crystal is obtained. The area of this force-displacement characteristic is the energy dissipated by the mechanism per cycle. Viscous dissipation may be easily separated from hysteretic. The reactance and mechanical resistance may be derived from the shape of the oscillograph trace. The apparatus has been used to study the dynamic characteristics of carbon transmitters, the inherent amplification and distortion of microphonic contacts, and the sliding of metal contacts.
Directivity and the Acoustic Spectra of Brass Wind Instruments
Authors: Martin Daniel W.
Published: September 2005

A single-point harmonic analysis of the pressure wave radiating from a brass instrument is inadequate as a physical expression of the instrument's acoustic output. This is partly due to the dependence of the analysis upon the relative position of the receiver. A complete statement would require a rather laborious expression of the analysis as a function of position. Probably an analysis of the total power output is the simplest single expression which is an improvement over the point analysis. Measurements of the directional radiation characteristics of several instruments in an outdoor location were obtained by driving the horn electroacoustically and plotting the sound pressure field. By integration of the intensity over a sphere, a ratio is obtained between the total power of a cornet and the power of a non-directional source having the same pressure amplitude as on the cornet's axis. A curve of this ratio is used to convert from an axial pressure wave analysis to the total power analysis which is a more representative property. Also when experimental changes are made in any part of the instrument except the bell, such a conversion curve expedites a study of the effect of the change on the power output analysis.
Performance of Broadcast Studios Designed with Convex Surfaces of Plywood
Authors: Boner C. P.
Published: September 2005

This paper is a preliminary report on the performance of a number of broadcast studios designed with convex plywood surfaces. Reverberation-frequency characteristics, obtained by high speed level recorder, are presented as a basis for preliminary estimates of the absorption coefficient of the plywood cylinders. The effect of painting is estimated from studies on studios in various stages of finishing. Insofar as they are available, experiences of studio personnel in using these studios will be given in the paper.
Contemporary Problems in Television Sound
Authors: Townsend C. L.
Published: September 2005

The present rapid development of television is introducing new problems in sound pick-up and operation. As the art progresses, engineering tools and methods must not only keep pace with, but generally anticipate, the needs of the program-producing staff in the production of more and more intricate material. The nature of the acoustic problems so raised, and their solutions, are treated in this paper. New tools necessary to proper operation and the methods of their employment are discussed. For a better understanding of television requirements, the methods normally employed in motion pictures and standard radiobroadcasting are compared with those in use in the present television studio. Some indications as to what may be required in the near future are discussed and possible developments suitable for such use are described.
An Analyzer for Sub-Audible Frequencies
Authors: Scott H. H.
Published: September 2005

The low frequency degenerative analyzer is the latest development in a line of measuring equipment designed particularly for industrial noise and vibration applications. Based upon the principle of selectivity through inverse feedback, which was first described four years ago and which is particularly adapted to low frequency applications, the new Type 762-A vibration analyzer extends the range of accurate measurements down to 212 cycles per second. The instrument is intended primarily to supplement the Type 761-A vibration meter, but is also useful in other applications where a low frequency analyzer, tuned amplifier, or filter is required. Design details and applications of the instrument will be described.
The Stapedius Muscle in Relation to the Conduction of Sound to the Inner Ear
Authors: Wever Ernest Glen , Bray Charles W.
Published: September 2005

The action of the stapedius muscle was simulated by applying tension to a thread attached to the stapedius tendon. The experiments were performed on cats under Dial anesthesia and curare, and the electrical responses of the cochlea were used to measure the effects. The application of tension to the stapedius tendon causes, in general, a reduction of transmission. The change is greatest for low tones, and grows less as the frequency is raised. Exceptional effects are shown for a limited range of tones in the region of 2000∼; for these tones slight tension may cause an increase in response. However, this increase is limited, and as the tension is further raised the response passes through a maximum and rapidly falls. For all tones, therefore, transmission is reduced by large tensions. The results thus show that the function of the stapedius muscle is fundamentally that of protecting the ear against over-stimulation. Observations were made also on the effects of tension upon the patterns of distortion in the ear. These results will be discussed in relation to the general problem of auditory distortion.
Temporary Deafness in Birds
Authors: Bray Charles W. , Thurlow W. R.
Published: September 2005

It has been reported by hunters that certain birds become temporarily deaf. Ewald suggested that the deafness is caused by a change of intralabyrinthine pressure resulting indirectly from opening the mouth. In order to test Ewald's hypothesis, the electrical responses of the cochlea to sound stimulation were observed in the pigeon with mouth open and with mouth closed. The results show that the cochlear responses are reduced when the mouth is opened. Even slight movements of the lower jaw, such as those sometimes associated with breathing, produce a noticeable effect. The maximum effect, occurring when the mouth is wide open, varies from 8 to more than 10 db. The effect occurs for all frequencies used, from 100 to 10,000 cycles. It is suggested that the primary source of the effect is tension on the ear drum rather than a change in intralabyrinthine pressure. It may be concluded that movements of the mouth of the pigeon, even such movements as those of eating, drinking and singing, impair the hearing of the bird to a considerable extent.
An Appeal to Science for Specialized Hearing Aids of True Selective Amplification
Authors: Winston Matie E.
Published: September 2005

Research engineers during recent years have added much to the development of the present-day hearing aids. However, I cannot accept the school of thought determining that a limit of the development has been reached. Somehow, a greater offering must yet be possible for the aid of the hard-of-hearing baby. I am deeply concerned that greater progress be speedily made in the development of the means to reach the residuum of hearing possessed by the very young deaf—literally thousands of babies—coming on to school age. I am keenly aware that we should be able to offer this ever-increasing number of our population a better chance in the effort to take a rightful normal place in the family circle and in business life, which means a better use of the residual hearing by reaching it with all we have to give for all it can take.
A Method for Measuring the Percentage of Capacity for Hearing Speech
Authors: Fowler Edmund Prince
Published: September 2005

Actual speech cannot be used for measuring the capacity to hear. Speech is made up of many frequencies and intensities and depends for its understanding so much upon background, practice, environment, inherited and acquired reactions in mental, neural and muscular coordinations and in attention. The most dependable method for testing is with a pure tone audiometer, but the threshold curve of hearing (the audiogram) alone does not show how much a person can hear unless it is used in conjunction with the relative importance of the different frequencies for hearing speech and the hearing for sounds well over threshold. The total capacity of the human being to hear speech depends upon the use of his two ears and the percentage of loss of capacity varies in proportion to the decibel losses in different frequency regions and the different degrees of “recruitment” of loudness due to nerve deafness. A simple method for coordinating the physical measurements and clinical data observed in both nerve and obstruction deafness is set forth and a table is constructed for estimating the percentage of loss of capacity to hear speech. By changing the weighting, the method may be used in other categories of hearing function.
A Basis for the Prediction of Performance of Deaf Aids
Authors: Balbi Charles M. R.
Published: September 2005

A relation can be established whereby the performance of a deaf aid can be rated in a manner comparable with other scientific apparatus. By using normal hearing observers determinations were made for representative types and makes of hearing aids, of the relative distances compared with a laboratory reference system for equal intelligibility. Test equipment consisting of a microphone amplifier was devised for determining a patient's intelligibility loss in decibels. From the data obtained with the normal hearing observers, taking into account the inverse square variation of intensity with distance and from the patient's intelligibility loss, it was possible to formulate a chart from which to assess the benefit to be derived by the employment of any particular deaf aid for any person suffering with a deafness up to 70 db. Data are given on the number of deaf aids in use in the United Kingdom since 1918.
Tinnitus and Other Subjective Phenomena—and the Hearing Process
Authors: Josephson Emmanuel M.
Published: September 2005

Disease, intoxications and injuries cause subjective phenomena of hearing that shed much light on the mechanism of hearing, and on the causes of deafness. Paralysis of the tensor tympani muscle arising from injury to the fifth cranial nerve causes dysakusia for low frequencies—a condition in which high intensities produce discomfort or actual pain. Hyperacousis, or increased acuteness of hearing, in which the loudness of sound is accentuated, follows injuries to the facial nerve paralyzing the stapedius muscle. Affections of these middle ear muscles by myasthenia gravis, or other diseases which give rise to muscular fibrillations, cause roaring, “boiler factory” tinnitus. In the absence of the ear drum, high intensities of low frequencies cause vertigo and falling. These phenomena parallel in many respects animal experimental findings such as those reported by Drs. Wever and Bray; and indicate that the middle ear mechanism serves primarily as a sound impedance that protects the inner ear, rather than as a specialized sound conductor. Tinnitus of inner ear origin may be caused either by anemia, congestion, allergy or spasm of blood vessels. Intoxication by quinine, aspirin and other salicylates, and ergot are among the most frequent causes of these types of tinnitus and deafness. They act by causing spasm of the blood vessels. The incidence of progressive deafness could be considerably reduced by restriction of these drugs. Increased pressure of the perilymph on the inner ear gives rise to tinnitus which is readily cleared up by spinal tap and by medical therapy designed to keep the pressure down. Hallucinations of hearing often characterize disease of the brain involving the central nervous mechanism of hearing.
Observations on the Acoustic Vibrations of the Ossicles
Authors: Kobrak H. G.
Published: September 2005

This paper is a continuation of a presentation given a year ago before this Society. At that time the acoustic vibrations of various parts of the cadaver ear were demonstrated in a moving picture film. Curves are shown in which the amplitudes of the ossicles are given as a function of tone intensity. For overthreshold intensities the movements are astonishingly large and can be observed with low magnification. The effect of the middle ear muscles on sound conduction is shown. Resonance phenomena of the system are demonstrated. Under stroboscopic illumination the movements of the ossicles can be readily seen in temporal bones and on living animals in which the middle ear has been exposed. In addition it has been possible for the first time to observe and photograph the acoustic vibrations of the ear drum on ear normal persons and on patients suffering from deafness.
Edge Tones with Turbulent Air Sheets
Authors: Jones A. T.
Published: September 2005

When the wind from the slit comes fast enough, and the opposing wedge is not too close to the slit, the edge-tone frequency changes continuously with changing slit-wedge distance or changing pressure, instead of exhibiting “jumps” in pitch. The pitch may change continuously through several octaves, and throughout this range the frequency N and slit-wedge distance h satisfy approximately the relation Nh1.45=const. The velocity of the air is so high as to make it likely that the motion is turbulent, and that the frequency is not related to any discrete vortices. The tone is probably maintained by the injecting of masses of air, first on one side of the wedge and then on the other. The resulting compressions cause an alternating flow that carries the air sheet from one side of the wedge to the other. This alternating flow passes through the constriction between slit and wedge, and by making use of the Bernoulli change in velocity in this constricted region it is possible to account for the various phenomena observed.
Acoustic Properties of Small Cavities
Authors: Sabine Paul E.
Published: September 2005

This paper presents the results of an experimental study of sound pressures in apertured hard wall cavities, 2.5 cm in diameter and depths varying from 0.3 to 1.5 cm, as a function of cavity dimension, length and diameter of aperture and frequency of the sound. The results are given in decibels increase of sound pressure level over the pressure at the face of an imperforate baffle. Curves showing resonance frequencies as functions of aperture and cavity dimensions are shown. No theoretical explanation is offered.
Notes on Acoustic Impedance Measurement
Authors: Sabine Hale J.
Published: September 2005

Considerable interest has been shown recently in tube methods for measurement of acoustic impedance and sound absorption coefficients. Construction details of a tube of the “fixed length, movable pickup” type are described, and direct reading charts for the determination of impedance and normal-incidence absorption coefficient are presented. A discussion is given of the factors affecting the accuracy of this method of measurement.
Supersonic Transmission at Oblique Incidence through a Solid Plate in Water
Authors: Smyth J. B. , Lindsay R. B.
Published: September 2005

The selective transmission of oblique supersonic waves through a solid plate immersed in water is studied theoretically and experimentally over a frequency range from 0.7 to 3 megacycles. Three cases are considered: (1) transmission for angles of incidence less than the critical angles for both dilatational and shear waves; (2) transmission for angles of incidence between the two critical angles; (3) transmission for angles greater than both critical angles. In the frequency region studied good agreement is found between the measured transmission, using the torsion disk method, and the theoretical values. Particular interest attaches to case (3). A method is devised for using the experimental results to determine the elastic constants of the solid plate.
A Method for Changing the Frequency of a Complex Wave
Authors: Kent E. L.
Published: September 2005

This method makes it possible to change the fundamental frequency of a complex wave and retain essentially the same wave shape. For example, suppose it is desired to analyze the harmonic content of a wave whose fundamental frequency is, say, 25,000 c.p.s. With this frequency changer it is possible to divide all frequencies in that wave by the same number and keep the relative amplitudes and phase relations between the partials the same, This being true, a conventional wave analyzer having a range from 20 to 16,000 c.p.s. may be used to analyze a super audio-wave. It might be useful also in studying musical tones for it is possible to change the pitch of a tone without altering its wave form. The method may be performed by simple circuits using conventional radio tubes and components or it can be done with greater precision with a special, but simple, cathode-ray tube. This method is limited to applications where it is desired to reduce the frequency of a wave and the highest significant partial in the reduced wave must be lower than the fundamental frequency of the original wave.
An Automatic Direct Inking Audiofrequency Response Recorder
Authors: Olney Benjamin
Published: September 2005

This recorder and oscillator assembly draws curves in ink on standard semi-logarithmic graph paper. The frequency range is from 30 to 10,000 cycles per second and the ordinate scale covers 40 db in 1-db steps. Internal calibrating means are provided for establishing reference levels of pressure and voltage. The graph sheet is carried on a flat platen and is entirely visible at any stage of the recording. The recording pen is driven by a vibrating type of motor which has particular advantages for this application. Convenient adjustments are provided to permit recording the average value of a fluctuating quantity such as the output of a rotating microphone.
Transmission of Sound Signals in Congested City Areas
Authors: Kelly Joseph B.
Published: September 2005

To study the transmission of sound signals in congested city areas, primarily for determining the number and size of sirens required to give adequate signal coverage in areas vulnerable to air raids, tests were made in several cities with the high power siren described by R. Clark Jones. The results of tests conducted in New York City are reported. Measurements were made on the roofs of tall buildings in line of vision with the sound source and in the streets. Some effects of the wind on the transmission of the sound are also discussed.
Sound Power Density Fields
Authors: Enns J. H. , Firestone F. A.
Published: September 2005

A theoretical study of the sound power density field radiated from a simple source, a doublet source, a single point source before a totally reflecting plane (free as well as rigid), and a piston vibrating in an infinite fixed wall have been investigated. Formulae are worked out to allow the computation of percent of total radiation flowing through a given area. By interpolation of the graphs plotted from these equations, the streaming or flow of energy for the above radiation fields is shown. In connection with this work the numerical integration of the definite integral ∫z′Pm(z)Pn(z)dz, in which the P's are the Legendre polynomials, was carried out for all the even values of m and n from 0 to 20, and for the argument z taking thirteen different values in the interval 0⩽z⩽1. In case these computations are not published, they are available from the authors upon request.
Observations on the Vibrations of Piano Strings
Authors: Schuck O. H. , Young R. W.
Published: September 2005

The behavior of single struck strings in their normal positions was investigated through measurement of the frequencies and amplitudes of their partials as functions of time after striking. Three-dimensional figures showing partial amplitudes versus time are presented. The frequencies of the partials of the tone were found to be essentially independent of striking force and time after striking, and directly identifiable with the modal frequencies of the string. The higher modal frequencies are progressively sharp with respect to true harmonics of the fundamental; for a particular string the sharpening follows approximately a square law with respect to modal number. The resulting inharmonicity in the tone is least in the two octaves below middle C, rises sharply at the high end and more or less sharply at the low end, depending upon the type of piano. A correlation between inharmonicity and subjective tone quality rating is suggested, and the effect of inharmonicity upon piano tuning is discussed.
Inhibition of Auditory Nerve Activity by Acoustic Stimulation
Authors: Galambos Robert , Davis Hallowell
Published: September 2005

For each single auditory-nerve fiber (cat) there is a “response area” clearly defined in terms of the frequency and intensity of the tones which excite activity. For most fibers the discharge of nerve impulses aroused by such adequate tones (T1) can be reduced or abolished by other tones (T2) or by noises (hiss or rattle) presented concurrently. Not all tones inhibit the response to T1. Those which do inhibit fall into one or more well-defined “inhibitory areas” which are different for different fibers and for different T1's presented to a given fiber. The inhibitory areas are adjacent to the response areas and often include some tones which lie within the response area. For a few fibers no single pure tone (T2) inhibits the response to T1, but in such cases the activity can usually still be abolished by noises. Inhibition of auditory-nerve activity by acoustic stimulation might result from mechanical interference in the auditory receptor or from neural interaction. Control experiments seem to exclude mechanical interference at the middle ear or basilar membrane level as an explanation. The possibility that neural interaction is involved and its implications for the interpretation of masking will be discussed.
Acoustical Characteristics Apparent in a New Anatomy of the Human Voice
Authors: Benedict Claire
Published: September 2005

This paper will set forth anatomical and acoustical confirmation of findings in the related fields of music and speech, by way of basic principles in sound causation and control as embodied in their common instrument. Analogies apparent in the vox humana of the pipe organ to structural and acoustical characteristics inherent in the vocal pipe will be shown: specifically, those which account for the sound effects used in or for speech. Further analogies in the facial structure to a three-dimensional amplifier will be supported by oscillograms in which a contact microphone was used. Final confirmation of these findings comes only from the field of application: from the response of the natural mechanics of the voice to a new technique: combining the voicing of this type of pipe with the blowing and fingering required in wind instruments of smaller scale; making it possible to bring the voice up to a recognized standard in speaking—and in all languages—as an essential preliminary to singing; and then to develop an even scale throughout the full range of the voice as used in music.
Introduction to Music in Industry
Authors: Burris-Meyer Harold
Published: September 2005

Historical résumé of music in industry: Definition of objectives. Efforts to determine the degree to which the music does its share of the work. Conflicting theories concerning the relative importance of the objectives and means for achieving them. Present state of the art.
Industrial Music and Morale
Authors: Halpin Dan D.
Published: September 2005

Internal relations can be improved by the use of the new technique of industrial broadcasting as used by numerous industrial organizations. Forty-four suggested uses are highlighted with human interest applications of these ideas. The presumptive functions of industrial broadcasting as a technique for maintaining understanding between employer and employee, mutually represented on “Production drive committees to maintain production,” will be discussed.
The Growing Appreciation of Music and Its Effect upon the Choice of Music in Industry
Authors: Pepinsky Abe
Published: September 2005

The attempt at the reduction of boredom and fatigue among industrial workers by the use of music introduces the necessity of consideration of the individual's reaction to musical sounds. Furthermore, it should be noted that consistent exposure to musical literature tends to develop an ever-increasing appreciation of better music; better in the sense of its lasting qualities. Such a discriminatory process implies an appreciation of music supplemented, as it usually is, by the radio and phonograph in the home, together with explanatory and programmatic comment. This condition will, of necessity, demand a keen understanding of the individual's possible satisfaction or annoyance when subjected to a bath of musical sound. If such a situation is not given due consideration, we may well experience what was evidenced by a prominent restaurant in a cosmopolitan mid-western city which advertised “No Orchestral Din!”
Programming Music for Industry
Authors: Selvin Ben
Published: September 2005

Outline of a typical day's program, suitable for industry. Discussion of types of orchestras, instrumentation and musical arrangements. Comparisons between the techniques used in the making of a phonograph record and a transcription designed for industry. Hazards of too much music. Music for luncheon periods. Discussion of the effect on industrial music of the current recording situation. The effect of employee's preferences on production.
The Statistical Method in Determining the Effects of Music in Industry
Authors: Cardinell R. L.
Published: September 2005

The diversity of opinion with respect to music in industry necessitates objective methods of determining the results. The primary purpose of a musical program in a plant is threefold: the relief of boredom, the relief of fatigue, and the creation of pleasanter atmosphere in which to work. Other results are secondary in nature but are, of course, of primary interest to plant management and personnel. Among these corollary results are increased production, improved attendance, reduced accident rate, fewer rejections, and better quality in the product. Plant records are not usually in convenient form to show changes brought about by music. It becomes necessary to take original data and to compute plant records to a common base. Discussion of specific examples. Particular consideration must be given to other elements which may possibly affect production. Statistical analyses are of primary importance in planning a musical program. Production rise achieved as a result of this practice far outweighs the costs involved.
Filtered Thermal Noise—Fluctuation of Energy as a Function of Interval Length
Authors: Rice S. O.
Published: September 2005

Suppose that a source of thermal noise is connected to the input of a band pass filter. Let the output current flow through a resistance of one ohm and observe the energy dissipated in each of a number of intervals. If the intervals are of the same length T, and are taken at random, the energies have a distribution whose average and standard deviation depend upon T. This dependence is studied. Since the results are derived for thermal noise, the question of when noise may be regarded as thermal noise is also considered.
Recent Developments in Record Reproducing Systems
Authors: Beers G. L. , Sinnett C. M.
Published: September 2005

Some of the more important factors in obtaining satisfactory reproduction of sound from lateral-cut phonograph records are considered. Particular reference is made to such items as vertical force of the stylus on the record, mechanical impedance of the pick-up, mechanical resonances of the pick-up and tone arm, and the over-all frequency response obtained. An experimental record reproducing system employing the principle of frequency modulation, as applied to the pick-up and its associated circuits, is described and data are supplied on the measured and calculated performance characteristics of the system. Curves are also included showing the vertical force required for satisfactory tracking with the experimental frequency modulation pick-up as compared to that required for other pick-ups of conventional design. In conclusion it is pointed out that while all the data shown apply to 78 r.p.m. records, the same performance advantages can be retained in a system designed for 3313 r.p.m. transcription records.
Steady State of Sound in a Room
Authors: Knauss H. P. , Woodward J. G.
Published: September 2005

A relationship based on Sabine's reverberation formula and the assumption that sound from a steady source in a room reaches a uniform steady state intensity is T = KE0V/Is where T is the reverberation time of the room, E0 is the steady state intensity, V is the volume, Is is the intensity within an absorbing chamber coupled to the steady source, and K is a constant. The constancy of K was tested in twelve rooms using warble tones centered at 256 and 512 c.p.s. The mean deviation of K was 33 percent at 256 and 25 percent at 512, but the value at the higher frequency was more than twice as great as that at the lower frequency. The procedure used does not yield useful values of T.
Demountable Soundproof Rooms
Authors: Gorton W. S.
Published: September 2005

Soundproof rooms of plaster on hollow tile are effective acoustically, but have pronounced disadvantages pertaining to their construction and demolition, and have practically no salvage value. This paper describes soundproof rooms composed of panels consisting of two sheets of steel cemented to two sheets of composition board with a rockwool blanket between. The panels are of a few standard sizes, the combination of which enables rooms of almost any size to be constructed. The rooms are supported on industrial type rubber mountings for the reduction of building vibration. For the most effective attenuation of sound a second room is constructed which completely encloses the first room except that the floor of the second room consists of the floor of the building. The construction and the demounting of the rooms involve little dirt and noise, and there is practically complete salvage value. Eighteen such rooms, comprising both kinds, have been constructed in the new building of Bell Telephone Laboratories at Murray Hill, New Jersey. Single-frequency attenuation measurements have not been made owing to the pressure of war work, but noise meter measurements show an attenuation of 43 db for the single rooms and more than 57 db for the double rooms.
The Supersonic Reflectoscope; an Instrument for Inspecting the Interior of Metal Parts by Means of Sound Waves
Authors: Firestone F. A. , Frederick J. R.
Published: September 2005

The supersonic reflectoscope sends into the metal part to be inspected a short wave train of supersonic waves. Any reflections received back at the sending point, before the reflection from the opposite side of the part, are an indication of internal flaws.
Anelasticity of Metals
Authors: Zener Clarence
Published: September 2005

The term anelasticity is used to denote that property of metals in virtue of which strain is not a unique function of stress even at such low stress levels that no permanent set is observed. A review is given of the formal relations between the various anelastic effects, including those which may be measured by acoustical methods. A survey is made of the physical origin of anelasticity. One origin lies in the coupling of the elastic system with the various thermodynamic potentials of the system. A second basis lies in the presence of localized non-crystalline regions or interfaces. Emphasis is put upon the urgent need of a thorough study of the mechanical properties of these localized regions through acoustical studies.
A Fixed Path Supersonic Interferometer for Liquids
Authors: Ballou J. W. , Hubbard J. C.
Published: September 2005

The use of the fixed path supersonic interferometer has been extended to liquids, with a view to its possible application to the measurement of sound velocities in small amounts of liquid. The present study has been confined to small cylindrical cells of fixed length, containing 5 or 6 cc of liquid, bounded at one end by a quartz vibrator having a natural frequency around 3.5 megacycles per second, and at the other by a plane reflector. Successive cell resonances were obtained by varying the frequency, and detected optically by observing the increase in diffracted light intensity which occurs when standing waves are formed. In interpreting the results, account must be taken of the departure from unity of the reflection coefficient γ, which occurs at liquid-solid boundaries. This introduces a phase change which effectively lengthens the cell path. A description of the interferometer, its theory, and the results obtained with water, dextrose solution, and ethyl alcohol are given.