bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Weighting of Sound Insulation Data Against Frequency
Authors: Ross Ira G. 
Published: September 2005

Any specification of the sound insulating efficiency of a partition or other building unit must express, in terms of normally generated sounds and human hearing, its insulating value over the whole range of normal sound. Attention is called to the fact that, in making such an evaluation of the insulating efficiency, the Reduction Factors over the normal frequency range should be weighted to take account of the manner of distribution through the frequency spectrum of the peak loudnesses of normal sounds, the acuity of hearing and the normally maintained level of incidental noise. Curves of uniform insulation efficiency in terms of Reduction Factor at each frequency are derived from the data on peak loudnesses, acuity of hearing and incidental noise.
It is frequently desirable to reduce the overall insulation value of a partition to expression in a single figure. This has been done in the use of “Average Reduction Factor.” It is suggested, in view of the considerations above, that a more representative expression might be made in terms of minimum insulation value referred to the uniform insulation levels as derived.
Approximations in Determining the Total Absorption of a Room
Authors: Andree C. A. 
Published: September 2005

In the formulae for the decay of sound in a room the total absorption is customarily taken equal to ΣiαiSi, where αi is the absorption coefficient for any uniform area Si. It is shown that this method of determining the total absorption is an approximation requiring the assumption “that sound which is reflected from material having a given reflection coefficient has a probability of encountering, on its next reflection, material with a like coefficient which probability is equal to the ratio of the area of that material to the total area present.” This assumption requires in many instances an amount of “mixing” of the sound in excess of what may normally be expected from dispersion phenomena. The author suggests a method of attack which permits one to account for varying degrees of dispersion and applies this method of attack to the simple case of a cubical room. Numerical values of, ᾱ, the average absorption coefficient are determined which shows the effect of assuming different degrees of dispersion, and the effect of altering the distribution of the absorbing material in the room.
The theory indicates that an error is introduced in determining the sound absorption coefficient of materials due to the uneven distribution of the materials in the average sound chamber.
The Noise Survey of the Rapid Transit Lines of New York City
Authors: Stanton G. T. , Tweeddale J. E. 
Published: September 2005

The extension and increased operation of rapid transit facilities in the larger cities to keep pace with their growth creates a noise problem of the first magnitude. The reduction of existing noise conditions due to elevated and subway lines and the planning of future transportation facilities having a minimum of disturbance can only be effected after a complete and thorough investigation of all contributory noise sources and the various controlling factors.
In view of these considerations, this survey was initiated to study the noise conditions created by the operation of the rapid transit lines of New York City to provide information to guide in the planning of future extensions into outlying undeveloped areas, as well as to determine the effectiveness of proposed noise reduction measures on existing lines. The extensive nature of this survey involved a comprehensive study of all types of elevated and subway constructions—of the various types of cars and auxiliary equipment, roadbed, and the effect of the immediate surroundings, such as buildings and the contour of the land. Comparative data on the noise created for any given combination of conditions was obtained so that representative average results can be predicted showing the effect of the variable factors influencing the creation of noise. From the careful analysis of these results, very important conclusions, which in many cases were contrary to those generally held, were drawn which are of infinite aid in studying the economic feasibility of a constructive program of noise reduction.
General conclusions regarding elevated construction indicated that improvement of the elevated structure and roadbed as well as improved car construction and maintenance will effect a material reduction in noise. In addition, the combination of rapid transit and vehicular facilities in a comprehensive system of regional planning will aid materially in reducing the economic loss caused by these noise sources.
A Reed Organ to Demonstrate the Just Scale
Authors: Jones A. T. 
Published: September 2005

This is a “baby organ” which has been in use in the Department of Physics at Smith College for about a dozen years. There are two stops—one tuned to the equal temperament, and the other tuned in such a way that it is possible to play just scales in the four keys of c major, f major, g major, and a minor. On the special stop the white digitals give the key of c major, while the c♯, d♯,f♯, g♯, and a♯ digitals give respectively the d for the keys of f major and a minor, the g♯ for the key of a minor, the f♯ for the key of g major, the a for the key of g major;and the b♭ for the key of f major.
Since the d in the keys of f major and a minor is a comma flatter than the d in the key of c major, and the a in the key of g major is a comma sharper than the a in the key of c major, it is possible to give certain demonstrations of beats as well as to show the effects of certain chords and successions of chords.
Short Time Variations in the Sensitivity of Condenser Transmitters
Authors: Abbott E. J. 
Published: September 2005

Although one decibel ordinarily represents a very minor change in loudness, it is often desirable to obtain an accuracy of measurement of a few tenths decibel. For example, in machine noise reduction it is often necessary to study the effect of a proposed change in the presence of several similar sounds. Hence the overall effect of a single change may be considerably less than a decibel, but if taken together with other similar changes the combined effect may be large.
Since the microphone represents the only part of the usual type of sound meter which cannot be calibrated fairly readily, it is usually depended upon to maintain its calibration over considerable periods of time. It appears that a microphone may maintain an average calibration, and still be subject to short time fluctuations in sensitivity which are liable to be serious in certain sound meter applications.
The literature on microphone calibration deals chiefly with the theory of various methods, and the effects of certain corrections. Little has been published concerning how well one might hope to determine the sensitivity of a particular microphone on the basis of an accepted method with accepted values for some of the uncertain constants. This paper presents data obtained in an attempt to obtain a reference standard for microphone calibration at our laboratory, and illustrates certain variations which are attributed largely to changes in microphone sensitivity. Although these variations are doubtless familiar to those who have worked with absolute microphone calibration, it is hoped that the material will be of interest to many others who use sound meters.
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 = fz I = EZ wherein velocity v is analogous to current I. It is incomplete in the following respects which lead to difficulty in its application.
The new analogy is derived from the similarity of the following equations: v = fz̄ E = IZ wherein force f is analogous to current I and 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.
Effect of Rotating Vanes in a Reverberation Room
Authors: Chrisler V. L. , Miller Catherine E. 
Published: September 2005

Rotating vanes have been installed in the reverberation room at the Bureau of Standards with the result that the rate of decay of sound is logarithmic even when a highly absorbent sample is in the room.
Since the vanes have been installed the change in the apparent coefficient with the size and shape of the sample is much smaller than has been previously measured. It is believed that this is due to the fact that the sound is kept more uniformly distributed by the rotating vanes.
The Supersonic Interferometer and Absorption Measurements
Authors: Hershberger W. D. 
Published: September 2005

The previously developed theory of the supersonic interferometer is extended with the particular view of utilizing it for absorption measurements in gases. It is shown that the mechanical impedance of the interferometer is Z = Z0 + Z(l) where Z0 = j(mω − s/ω) + r Z(l) = Acρtanh 2αl + Acρsinh 2αlejθ θ = −arctan sin 2Kl sinh 2αlcos 2Kl cosh 2αl − 1.
That is, if reactance is plotted against resistance we obtain an impedance spiral with center (Acρ/tanh 2αl, 0) and radius Acρ/sinh 2αl. The action of the interferometer is studied in terms of the properties of the spiral.
Absorption measurements are effected by compensating for the changes in the equivalent series electrical resistance due to changes in 1 by adjusting a shunt resistance in the circuit so the e.m.f. across the crystal is held constant, irrespective of 1. Absorption in the medium is calculated from the values of shunt resistance for the path lengths of interest. Measurements were taken at five frequencies in the range 298.6 k.c. to 2514 k.c. The quantity 2αλ2 a as measured by the interferometric method is not constant but shows a systematic change with frequency. The possible significance of that change is pointed out.
The Resonant Characteristics of Soft-Walled Cavities
Authors: Cotton J. C. 
Published: September 2005

Resonance is undoubtedly of great importance in voice production, but little attention has been given to the resonant characteristics of such cavities as are found in the human vocal mechanism. A soft-walled cavity obviously must react quite differently to a complex tone than does the ordinary hard-walled resonator. X-ray photographs showing the human vocal cavities and motion pictures of the vocal cords indicate that more than simple resonant reenforcement must be responsible in creating voice differences. Without question, absorption plays an important part.
It is now possible to determine quantitatively the effect of soft-walled cavities on complex tones by means of an electro-acoustical set-up developed in the Phonetics Laboratories at Columbus. A beat-note oscillator, a sound source of the loudspeaker type, and a potentiometer arrangement serve to produce tones of constant intensity from 75 to 10,000 cycles. A condenser microphone, a resistance coupled amplifier, and a copper oxide voltmeter indicate the sound intensity.
The cavity under investigation is coupled to the sound source and the frequency slowly varied over any portion of the afore-mentioned frequency range. Deviations of the frequency-response curve from a straight line indicate directly the frequency characteristics of the cavity.
Vocal Chords Control Pitch Only and Not Vocal or Vowel Quality Demonstration
Authors: Taylor John Bellamy 
Published: September 2005

Vibrating columns of air associated with wind instruments are seldom simple or even single. In a typical instrument, especially of the “reed” or “brass” classification, besides the air column that is usually considered, there is a second column or cavity on the air supply side of the “check-valve” or member which by opening and closing, releases air intermittently from bellows or lungs. This check-valve may be recognized as reed, tongue, lips, membranes or vocal cords. This air-column or cavity back of the check-valve has some control over the time of vibration, as was demonstrated by the author at Cleveland meeting of the Society, December 1st, 1931.
Usually the vibrations of the supply-side air column are heard not at all or but faintly, because of restricted opportunity for sound emission. But special devices may be employed (the stethoscope is an example) to hear sound in supply side air column and reduce or effectively suppress sound from external air column (the only one ordinarily considered).
With a microphone in close contact with an individual's chest, an amplifier and loudspeaker will make audible the sounds picked up from internal air column, and with sufficient amplification, the normal sounds of speech and singing are faint in comparison with the other. This set-up demonstrates that while the individual has pitch control on vibrations of the internal air column, he does not and cannot change the character or quality of the supply-side tone by any of the vocal speech or musical efforts.
This result is taken to indicate that the vocal cords have but one mode of opening and dosing (at a given pitch) and play no part in determining the character or quality of vowels and other “vocalized” sounds.
A New Portable Meter for Noise Measurement and Analysis
Authors: Osbon W. O. , Oplinger K. A. 
Published: September 2005

This article describes a new noise meter whose development is based upon several years experience in the field of industrial noise measurements. Care has been taken to make the instrument simple to operate and rugged enough for portable use.
The characteristics of noise and hearing which have been used as a basis for designing the meter are discussed. A superheterodyne analyzer attachment is described which permits analysis of noises with a high degree of selectivity.
The noise meter may also be used for vibration measurements with a moving coil type pick-up which is described.
Sound Measurements on Experimental Airplane Mufflers
Authors: Snyder W. F. 
Published: September 2005

For the past few years the Sound Section of the Bureau of Standards has been cooperating with the Aeronautics Branch of the Department of Commerce in the development of practical methods of reducing the noise in airplanes. A part of this work has been the measurement in absolute intensities of the noise emitted by an airplane engine fitted with various types of experimental mufflers.
The propeller noise was eliminated by connecting the engine to a hydraulic dynamometer instead of the propeller. The dynamometer also served for the measurement of the horsepower. A muffler made of steel barrels placed in the ground allowed measurements to be made in the absence of exhaust noises.
The sound measuring equipment consisted of a calibrated condenser microphone, a sound meter and a set of band-pass filters. Measurements were made with no filter in the circuit and at the frequency bands 0–250, 250–500, 500–1500, 1500–3000 and 3000-etc. The microphone was placed at six different stations ranging in distances from 2 feet to 80 feet from the engine.
It is possible to reduce the exhaust noises by 15 or 20 decibels below that of the unsilenced engine without adding too much bulk or weight to the aircraft. The propeller noise, however, must be below that of the muffled engine for the muffler to become effective.
Transmission of Sound and Vibrations in Buildings
Authors: Meyer Erwin 
Published: September 2005

Three problems are discussed: The insulation from air-borne sound by multiple walls. Structure-borne sound transmission. Measurements of vibrations by electrical apparatus.
It is known that a single wall vibrates almost as a mass, provided its lowest natural period is much lower than the sound frequencies. Therefore a series of single walls with air-spaces between them act as a mechanical low pass filter, with a cut-off frequency and sound dispersion. But these properties are only present, if the component vibrations in the air-space, parallel to the wall are damped. A multiple wall of this kind with a low cut-off frequency has a very large transmission loss.
Building materials propagate sound very well. Their small transmission losses (hysteresis) are investigated by a resonance method. To obtain a loss of 1 db material lengths from 10–100 m or more are required. Materials such as rubber or cork are used to avoid the sound propagation in buildings. Their dynamical properties (elasticity modulus and loss factor) are tested by a special electrodynamical vibrometer.
With a mechanical apparatus the displacement or the acceleration of the ground is determined. The method, which measures the velocity amplitude (obtained from a low resonance-frequency electrodynamical apparatus) is to be preferred. An easily portable apparatus of this kind has been constructed. The average value of the vibrations of buildings due to traffic is 3.10−3 cm/sec. The average vibration frequencies can also be determined. In the horizontal direction buildings oscillate mainly in two ways, as a whole or with one node.
Sound Analysis
Authors: Hall Harry H. 
Published: September 2005

Instruments for sound analysis may be grouped into five classes—graphic, resonance, heterodyne, stroboscopic, and diffraction analyzers. The operation of each type of instrument is briefly described and examples of analyses performed by the various methods are presented.
From the point of view of analysis sounds may be classified roughly into four groups:
(1) Steady state sounds or sounds which may be maintained at constant fundamental frequency, constant intensity and unvarying quality for long enough to carry out the analysis.
(2) Sounds which are essentially transient in nature.
(3) Sounds which may be maintained constant on the average but whose frequency, intensity and wave form are modulated at a constant frequency.
(4) Noise, or sounds which are entirely random in form but which are continuously maintained.
The sound spectra corresponding to each group are described and the application of the various types of instruments to the analysis of these spectra is discussed.
The Dependence of Hearing Impairment on Sound Intensity
Authors: Steinberg John C. , Gardner M. B. 
Published: September 2005

Although hearing impairment is ordinarily measured for tones of threshold intensity, attention has recently been turned to the measurement of impairment for tone levels above threshold. It has been found that some people may have an appreciable hearing impairment for threshold sounds yet hear normally for loud tones. Others show the same hearing impairment at all levels of sound intensity.
Loudness studies indicate that the variable or recovery type impairment should occur if the impairment is due to an atrophy of nerve fibers, and hearing losses calculated on this assumption are quite similar to observed losses. From this viewpoint the hearing loss caused by the presence of a masking noise should be of the variable type which was found to be the case.
Thus the often made statement that deafened people hear better in noisy places turns out to be true when the deafness is of the variable or recovery type. The implication of the statement that the noise as such improves the hearing however, is wrong.
An Investigation of Subjective Tones by Means of the Steady Tone Phase Effect
Authors: Trimmer J. D. , Firestone F. A. 
Published: September 2005

An observer listens with one ear to a combination of two pure tones. One is a loud 100-cycle tone, the other is a weaker 200-cycle tone. A phase relation between the two tones can be found such that the loudness of the two tones together is about one decibel less than the loudness of the fundamental alone. This is an example of the steady tone phase effect, in which a fundamental and one of its harmonics are heard together, the phase relation between the tones, as well as the pressure level of the harmonic, being subject to arbitrary control by the observer.
This effect was studied with a fundamental of 100 cycles kept at a sound pressure level of 104 db above 0.0002 dyne/cm2. Harmonics up to the fifth were used, with particular emphasis on the second and third. Measurements of the phase of the harmonic sound pressure giving minimum loudness averaged approximately 180° for the second harmonic and 0° for the third (epoch angle of cosine functions relative to fundamental). Loudness measurements at these phase settings showed the loudness of the combined fundamental and harmonic to be about 1 db less than that of the fundamental alone. 180° from the phase of minimum loudness the loudness of the combined tones was about 1 db greater than that of the fundamental alone. The variation of quality with phase relation was also studied.
Interesting variations between observers were investigated and attributed partly to psychological and physiological differences in individuals. But consideration of all the data obtained points to the conclusion, supported by theory, that the phase effect is a more complicated phenomenon than has commonly been assumed. Since this effect has been the basis for many studies of subjective tones, the concept of subjective tones is analyzed and interpreted in a new light.
On Hearing by Electrical Stimulation
Authors: Stevens S. S. 
Published: September 2005

The well-known fact that the ear generates an electric potential in response to stimulation by a sound wave has its counterpart in the fact that, when an alternating current is passed through the head, an auditory sensation results. The observer hears a tone whose pitch is determined by the frequency of the alternating current.
Measurements were made of the power needed to elicit a sensation using currents of various frequencies. The power, rather than the simple voltage or current was measured, because the body presents a complex impedance to the current. The total impedance, when the electrodes are applied in a standard manner, decreases with increasing frequency. The power factor varies slightly with frequency. When the power is increased about 20 db above the threshold value, the threshold of electric shock—a stinging sensation—is reached. This effect severely limits the size of the auditory area under electrical stimulation.
The amount of distortion present makes it difficult to understand speech when the observer is connected directly to the output circuit of a radio set, but music can be readily identified. The rectification producing this distortion appears to be largely electrical.
It is probable that the alternating current sets up vibrations in the inner ear due, perhaps, to a residual charge on the basilar membrane which makes it behave as a condenser microphone.