bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of Transmission Loss through Partition Walls
Authors: Bedell E. H. , Swartzel K. D. 
Published: September 2005

This paper reviews the theory and describes the method used at Bell Telephone Laboratories of measuring the transmission loss through partition walls.
The partition to be tested is built into an opening between two adjacent but structurally isolated rooms. A loudspeaker acts as a source of sound in one room and a portion of the sound energy is transmitted into the second room through the test partition. The transmission loss is taken as TL = L1 − L2 − 10 log10 (a2/A) where L1 and L2 are the intensity levels in the source and test room respectively, expressed in db, a2 is the absorption in the test room and A is the area of the partition. The levels L1 and L2 are measured and plotted with a moving coil microphone and an automatic level recorder, and a beat frequency oscillator is used as a source of tone so that the frequency may be varied continuously. Measurements with a continuous variation in frequency enable resonances in the partition to be much more easily and quickly detected than is possible when measurements are made at discrete frequency intervals. Both pure and frequency modulated tones have been used for the measurements. Results of measurements on a few partitions are given.
Velocity and Absorption Measurements at Supersonic Frequencies
Authors: Pielemeier W. H. 
Published: September 2005

Importance of Supersonics. This field is related in varying degrees to gas theory, thermodynamics, chemistry, physical chemistry, mechanics, heat, radio engineering, navigation and biology.
The author's work in this field began in 1919 and has been confined to a search for a suitable high-frequency source and to the measurement of velocity and absorption in air, in oxygen and in carbon dioxide. Quartz slabs, properly cut from the original crystal and sputtered on both faces with metal were found far superior to the other tested sources for measurements requiring constant frequency and intensity. With such crystals, there were obtained frequencies ranging from 300 to 2000 k.c.
The velocity in air was found to be approximately 331.6 m/sec. in this range. At the lower frequencies the absorption appeared to exceed that predicted by the earlier theory. No serious deviation from expected values were found in oxygen. With carbon dioxide the velocity was found to increase about 3 percent from 300 to 2000 k.c. The absorption greatly exceeds the values predicted by the earlier theory. Both velocity and absorption values are in good agreement with those obtained theoretically by Kneser.
Violin Intonation
Authors: Greene Paul C. 
Published: September 2005

The purpose of the study was to determine whether violinists, in unaccompanied performance, typically play in either the natural or the equally tempered musical scale, and if not, whether they tend systematically to expand or contract musical intervals as compared with their theoretical magnitudes. Six professional violinists participated in the investigation. Unaccompanied performances of three standard violin selections were recorded by an oscillographic technique. The average fundamental frequency of the main body of each of the tones was measured, and interval extents then were computed. The major part of the study was limited to an analysis of five intervals—major and minor seconds, major and minor thirds and perfect fourths. Tests of reliability of measurement showed that the largest expected error of measurement (±3 SDs) for any given frequency was approximately 0.03 tone, but in at least 78 percent of the cases, measurements were statistically significant to 0.01 tone.
The major findings were: (1) The six violinists typically performed in neither the natural nor the equally tempered scale. (2) As compared with both natural and equally tempered intonation, major seconds and major thirds tended to be expanded, minor seconds and minor thirds on the average were contracted, and perfect fourths tended to approximate the theoretical scale values for that interval. (3) The average extent of each of the five intervals approximated its theoretical magnitude in Pythagorean intonation.
The Nature and Origin of Aural Harmonics
Authors: Newman E. B. , Stevens S. S. 
Published: September 2005

Problems as to the nature and origin of the aural (subjective) harmonics, tones which are heard, but which are not present in the sound wave outside of the ear, have concerned musicians and scientists for many years. It is customary to assume that these harmonics arise because of non-linearity in the functioning of the middle ear. Their magnitudes have been measured by indirect means, such as the method of best beats, but there has been no adequate direct study.
We have used several means to attack this problem. (1) The minimum amount of distortion (2nd harmonic) which the ear can detect in a tone was studied by determining the thresholds for the second harmonic when it is added, outside the ear, to a pure fundamental in various phase relations. (2) Since it is possible to pick up from the cochlea an electrical potential which gives a good indication of the functioning of the auditory mechanism, we made an analysis and measurement of the harmonic components present in the cochlear response of animals under normal and certain abnormal conditions. (3) The phase relations of the harmonics in the cochlear response were determined with the aid of a cathode-ray oscillograph. (4) Externally generated harmonics were added to the fundamental in various phase relations both for human and animal subjects.
The results show that, for purposes of analysis, we can distinguish two sources of aural harmonics. The odd harmonics arise, from non-linearity, when the amplitude of vibration approaches the elastic limit of the ear. The even harmonics are due to an asymmetry produced by tension of the muscles of the middle ear, and consequently, their magnitudes can be experimentally controlled.
Professor Hallowell Davis aided in the work on animals.
A Scale for the Measurement of the Psychological Magnitude Pitch
Authors: Volkmann J. , Stevens S. S. , Newman E. B. 
Published: September 2005

A subjective scale for the measurement of pitch was constructed from determinations of the half-value of pitches at various frequencies. This scale differs from both the musical scale and the frequency scale, neither of which is subjective. Five observers fractionated tones of 10 different frequencies at a loudness level of 60 db. From these fractionations a numerical scale was constructed which is proportional to the perceived magnitude of subjective pitch. In numbering the scale the 1000-cycle tone was assigned the pitch of 1000 subjective units (mels).
The close agreement of the pitch scale with an integration of the differential thresholds (DL's) shows that, unlike the DL's for loudness, all DL's for pitch are of uniform subjective magnitude. The agreement further implies that pitch and differential sensitivity to pitch are both rectilinear functions of extent on the basilar membrane.
The correspondence of the pitch scale and the experimentally determined location of the resonant areas of the basilar membrane suggests that, in cutting a pitch in half, the observer adjusts the tone until it stimulates a position halfway from the original locus to the apical end of the membrane.
Measurement of the subjective size of musical intervals (such as octaves) in terms of the pitch scale shows that the intervals become larger as the frequency of the mid-point of the interval increases (except in the two highest audible octaves). This result confirms earlier judgments as to the relative size of octaves in different parts of the frequency range.
Reverberation and Absorption
Authors: Meyer Erwin 
Published: September 2005

We distinguish between geometrical and dynamical acoustics of rooms, which both have to be considered to obtain good quality of speech and music. Using a simple automatic method of recording the sound decay on an instrument with a logarithmic scale, concert and auditory rooms with and without audience are acoustically investigated.
Generally the sound absorption materials are tested in reverberation chambers. The results of different laboratories are not in agreement, the reasons being probably, that the rooms are small and that geometrical instead of diffuse sound reflection occurs. Comparison tests therefore have been made in the reverberation chamber of the Institute and in the intake chamber (Wasserschloss) of a big hydroelectric power station: this chamber had a size of 13,000 m3 and an average reverberation time (60 db) of 40 sec. The results are discussed. It is interesting to make similar experiments in optics with “Ulbricht” balls. These experiments show that it is only possible to measure absorption coefficients of light in boxes with scattering walls. Therefore a model reverberation chamber was built with interchangeable walls reflecting either geometrically or diffusely. Under “diffuse” conditions the results were more in agreement with theory. For practical measurements it seems best to standardize the measuring device.
Finally special kinds of nonporous flexible sound absorbing materials are discussed. It is shown, that these materials in connection with an air space very strongly absorb the low and middle-pitched tones.
Theory of the Haskell Organ Pipe
Authors: Jones Arthur Taber 
Published: September 2005

Some twenty-five years ago William E. Haskell patented an organ pipe which has the characteristics of an open pipe of the usual form but is considerably shorter. The pipe is similar to an ordinary open pipe with a smaller tube, closed at the top, mounted inside of it. The pipe gives the same overtones that are obtained from an ordinary open pipe of length equal to the sum of the lengths of the main pipe and the inserted tube. No theory of the Haskell pipe appears ever to have been published.
The pipe is here regarded as made up of three parts: (1) The main pipe up to the bottom of the inserted tube, (2) the inserted tube, (3) the part of the main pipe that surrounds the inserted tube. Suitable boundary conditions are introduced, and a general equation for the frequencies of the normal modes of vibration is obtained. If the inserted tube ends at the top of the main pipe, and if the cross-sectional area of the inserted tube is half that of the main pipe, the equation reduces to that for an open pipe of the length stated above.
Spherical Torsion Pendulum as Supersonic Radiation Pressure Meter in Liquids
Authors: Klein Elias 
Published: September 2005

Following King's theoretical work, a series of measurements has been carried out with bronze spheres varying in diameter from 14 to 112 inches. In plane stationary waves in water at frequencies between 100 and 200 kc. King's predicted dependence of radiation pressure on the location of the spheres relative to the position of nodes and loops is verified. Neglecting the viscosity of the medium and the compressibility of the spheres, it was found that the radiation pressure approximates inverse variation with the radius a of the sphere when the latter's size is such as to make 2πa/λ greater than unity and less than four.
Considering the spherical torsion balance a likely laboratory acoustic standard in liquids, it is possible to calibrate as secondary standards any pressure microphone for subaqueous use in the supersonic range. Such calibration was effected upon tourmaline crystal microphones by the usual resonance tube method. The piston source was telescopically fitted into the end of a horizontal rigid cylinder about 6 in. in diameter and 15 in. long. The other end was machined and covered either by a blank quarter wave plate which acted as a perfect reflector or a quarter wave plate in the reflecting face of which the tourmaline crystal was inserted. The spherical torsion balance was suspended over the center of the cylinder so as always to maintain the sphere on the axis of the cylinder. The whole suspended system was provided with horizontal motion by means of a micrometer screw of 4 in. travel.
The results obtained by this calibration compare favorably with other methods and check roughly with the pressures calculated from the static piezoelectric constant of the tourmaline crystals.
On Sound Localization
Authors: Wallach Hans 
Published: September 2005

The binaural cues for sound localization are effective only in determining the angle between a given direction of sound and the axis of the ears (lateral angle). Since there is localization in the median plane, a second factor should be found which determines the direction of sound in this dimension.
Head movement during sound localization might yield such a factor. With head movement the lateral angle of the sound changes giving a sequence of lateral angles characterizing the direction of sound geometrically in both dimensions.
That sound localization actually works on this principle is proved by experiments in which directions of sound are synthetically produced. The sequence of lateral angles which a certain elevated direction of sound would yield with a certain head movement was determined. While the observer performed this head movement a sound was shifted in the horizontal plane in a way to present the same sequence of lateral angles. The observer perceived the sound in the direction from which the presented sequence of lateral angles was derived instead of in the actually given shifting position.
The Mobility Method of Computing the Vibration of Linear Mechanical and Acoustical Systems
Authors: Firestone F. A. 
Published: September 2005

It is shown that the conventional mechanical-electrical analogy (velocity across→current through; force through→voltage across) has grave defects which have hindered its general adoption as a method of solving vibration problems. The new analogy however (velocity across→voltage across; force through→current through) can be safely applied in such a natural intuitive manner that it becomes unnecessary to distinguish between the mechanical system and the analogous electrical circuit. The problem solving techniques of electricity are taken over bodily into mechanics with the aid of the following devices: The mechanical systems are diagrammed with the aid of a set of conventionalized two-terminal symbols which picture the springs, mechanical resistors, and masses comprising the system. The letter symbols for velocity, force and mass are changed from the usual v, f and m to e, i, and c, respectively. A complex constant called the “mobility” (ease of motion) is defined as z = e/i = velocity/force and it is found that the mobility of the mechanical elements is of a familiar form (ze = jωl, zr = r, zc = −j/ωc) while series and parallel combinations of z's are made by the familiar rules. The solution of the mechanical problem is thus reduced to a determination of the mobilities at different points in the system and the application of the equation e = iz. The problem remains a problem in mechanics and there is no reference to electricity.
Not only can forced vibration be computed in this manner, but the normal frequencies and normal modes of free vibration of resistanceless systems can be found. The concept of “acoustical mobility,” Z = E/I = volume velocity/sound pressure, permits the calculation of mechanical-acoustical systems.
The Journal of the Acoustical Society
Authors: Watson F. R. 
Published: September 2005

The Acoustical Journal is the official publication of the Acoustical Society. It includes scientific papers describing important developments in acoustics, also various miscellaneous items of interest. It reaches a wide circle of readers at home and abroad, thus satisfying the demand for authoritative information about acoustics.
The Journal is managed by an Editorial Board that determines the policy of the magazine, reviews all the material intended for publication and has general charge of the Journal activities. The final editing of papers is delegated to the capable supervision of the Editorial office of the American Institute of Physics, which also makes arrangements for the printing.
The papers published cover a wide variety of subjects—the fundamental characteristics of sound, the phenomena of hearing, supersonics, the control of sound in buildings, the characteristics of musical sounds with reference to speech, music and musical instruments, etc.—all of which indicate the active interests in acoustics in the United States.
The Journal is an integral unit in the Acoustical Society, setting forth in a permanent record the progress and accomplishments of this young and vigorous organization.
Speech Production as Revealed by Vocal Cord Photography and Sound Wave Analysis
Authors: Steinberg John C. 
Published: September 2005

For more than a century, wide differences of opinion have been held as to the function of the vocal cords in speech production. In the present paper, this problem is approached by utilizing high speed motion picture photography to determine the vibrations of the cords during phonation and a method of Fourier analysis to determine the characteristics of the sound waves.
By taking pictures at a rate of 4000 per second and projecting them at the normal viewing rate of 16 per second, the motion is slowed down by a factor of 250 to 1. Thus, if the cords execute 250 vibrations in one second, they appear to make one vibration per second and the details of their movements may be seen. Pictures suitable for monocular viewing, and also stereoscopic pictures showing the movements of the cords in full relief, have been obtained.
For the lower pitches, the cords appear to be completely relaxed, and there appears to be a phase difference between the movements of the lower and upper surfaces. They do not move as units, but more as folds or lips, the motion of the upper surfaces lagging behind that of the underneath surfaces. The tension increases as the pitch is raised, the cords elongate and tend to move more nearly as units with somewhat smaller amplitudes than for low pitches. The movements appear to begin toward the front end of the cords and to extend progressively toward the back, so that the motion has a horizontal as well as vertical phase difference.
The analysis of the vocal cord vibrations indicates a vibration form composed of a fundamental having a frequency equal to the vibration rate of the cords and overtones, which diminish in amplitude with increasing order or number of the overtone. Such vibration forms do not possess the distinguishing characteristics of the different speech sounds. The latter characteristics are produced by the passage of the sound waves through the throat, nose and mouth cavities.
The paper will be illustrated by motion pictures showing the movements of the cords in ultra-slow motion, and by variable area recordings of the sound waves and their corresponding analyses. Stereoscopic motion pictures will be available for limited viewing so that the cord movements may be seen in relief.
Statistical Measurements on Conversational Speech
Authors: Dunn H. K. , White S. D. 
Published: September 2005

Several types of measurement are reported. R.m.s. pressures in one-eighth-second intervals, from the speech of a single voice, are compared with similar measurements in one-fourth-second intervals. The values obtained in the first case are only slightly more widely distributed than in the second, and the difference is least when attention is confined to high frequencies.
To earlier r.m.s. measurements, on the voices of six men and five women, is applied the relation found more recently between pressure at a point and total voice power. The resulting curves represent average spectra of voice power for the men and women.
Measurements of the distribution of instantaneous pressures in speech are also given.
Practical Application of Acoustical Correction in University Buildings
Authors: Horner George L. 
Published: September 2005

The University of Iowa has for many years recognized the value of sound control and has at different times dealt with all its various divisions. It is not often though that all the various divisions of sound control are embodied in one problem. Such was the problem in designing the University Theater.
The first division was the audition qualities of the auditorium, and after consulting acoustical experts, a design was worked out whereby it was thought all acoustical treatment might be omitted. The design proved successful and no sound absorbing materials were required in the auditorium.
The second division, reducing the noise level, was also considered in connection with rehearsal rooms; however, insufficient funds have prevented the carrying out of this correction 100 percent.
The third division, sound isolation, the most difficult in many ways to correct, was corrected by the use of sound barriers. Most of these barriers are of structural materials, brick and tile. In ventilating ducts, duct lining was used and all air is handled at low velocities to reduce air noises.
The fourth division, the control of noise generated by machinery, was probably our most serious problem. Great care was used in mechanical design and all motors were specified “special quiet”. All machinery was mounted on rubber isolators. Most equipment was designed to meet a 30-decibel reading in the auditorium.
The theater as used by the Dramatics Department requires a very low sound level and through the use of care in design and the corrections as outlined, this result was obtained.
The Music Building, various classrooms, lecture rooms and laboratories have been treated acoustically—the majority for better audition qualities although some, the Music Building, have been treated for sound isolation and reducing the noise level.
It is quite obvious that a University is a fertile field for acoustics, particularly its application, in fact too fertile. Too many classrooms and laboratories need sound control of some kind and insufficient funds usually hamper the completion of projected plans.
Planning Functionally for Good Acoustics
Authors: Maxfield J. P. , Potwin C. C. 
Published: September 2005

The science of architectural acoustics has now taken its position as one of the bases of creative design. Planning of the interior shape of the auditorium to fulfill both the acoustic and the functional requirements is but two phases of a single problem.
This paper will present an empirical study of the control of auditorium acoustics by the correlation of the internal geometry with the amount and placement of absorbing materials. A brief discussion will be given of some of the subjective experiences which led to the development of the empirical design technique.
Correlations Between Air and Bone Conduction Acuity Measurements in Different Types of Deafness
Authors: Reger Scott N. 
Published: September 2005

Several audiograms of various types of deafness, indicating both air and bone conduction threshold measurements, will be shown and discussed from the standpoint of the value of the correlations between the air and bone conduction determinations. A method of ascertaining the functional efficiency of the ear drum and ossicles on the basis of bone conduction acuity measurements with the ear canal open and then occluded also will be described. The necessity of masking while making bone conduction measurements will be considered briefly.
Some of the deficiencies of tuning forks and various types of bone conduction receivers or vibrators supplied with audiometers will be discussed and constructive criticism offered from the clinical point of view.