bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of Impact Sound Transmission Through Floors
Authors: Lindahl Robert , Sabine Hale J. 
Published: September 2005

Existing methods of measuring the transmission of impact noise through floors and of stating the results are inadequate in two respects: (1) Published data give the difference in intensity of impact noise measured above and below a given floor construction, but do not permit an accurate comparison of the noise transmitted by different constructions. (2) No attempts have been made to determine the comparative transmission-frequency characteristics of different constructions.
A new method of measurement is described. The impact noise is generated by a mechanical tapper, and the sound transmitted is measured with a sound level meter. By means of band pass filters the sound level in each of six octave-wide frequency bands is determined. The sound transmitted by a bare concrete slab is arbitrarily assigned a level of zero decibels for each frequency band, and the levels measured for other constructions are stated as decibel reductions at each frequency referred to the zero levels for the concrete. The over-all rating for each construction is taken as the average of these decibel reductions for the six frequencies 128 to 4096 cycles. Comparative ratings arrived at in this way agree satisfactorily with subjective estimates of the comparative “noisiness” of the transmitted sound.
Studies of the Vocal Cords in Relation to the Quality of Certain Speech Sounds
Authors: Cowan Milton 
Published: September 2005

Recent experimental investigations by W. Trendelenburg, H. Wullstein, W. Hartmann and F. Trendelenburg are reviewed. Three experiments on fresh calf and human larynx preparations and one on human subjects are described.
W. Trendelenburg and Wullstein made simultaneous recordings of glottal lip movement, shadowgraphs of the glottal chink, and oscillograms of air vibration at various points above and below the glottis. The vocal cords constituted the moving plate of a condenser microphone for registration of the lip movements. An optical system sent a beam of light from the trachea through the glottal chink and this photographed shadowgraphs above when the cords were brought into vibration by means of a controlled current of air up through the trachea. A condenser microphone was used to record air vibrations. Plastellin forms approximating the shapes of the supralaryngeal cavities for the vowels “a” and “o” were placed above the larynx. The recordings showed that, with or without the resonators, the lip movements were essentially sinusoidal, that there was no back-coupling between cavities and cords, that the glottis was open for a relatively short portion of the cycle, that the formant frequencies were especially noticeable immediately following the glottal opening and closure and were highly dampened during the closure phase of the glottal cycle.
Hartmann bored through the side of the larynx at the level of the cords and obtained simultaneous shadowgraphs of the lateral and vertical movements of the cords. The maximum glottal opening coincided with the highest point reached in the vertical movement. After closure the downward movement of the cords continued to a minimum at about the middle of the glottal closure phase. Averages: total vertical movement = 1.25 mm; glottal opening = 1.43 mm; ratio = 1:1.15.
Hartmann and Wullstein recorded glottal shadowgraphs and light density variations simultaneously. Maximum density coincided with maximum glottal opening. On the human preparation, light density decreased after the glottal closure, indicating a pressing together of the cords. When the cords were made opaque by staining, light density variations coincided with the area of the aperture.
Following up the observation that formant frequencies were especially prominent immediately following the glottal opening and closure, W. Trendelenburg found subjects who were able to intone vowels so that the first cycle was essentially the same as the succeeding ones in frequency, intensity and overtone structure. The typical energy maximum coinciding with the opening phase of the glottis was again apparent in the first cycle and was named the “initial group.” Further work with F. Trendelenburg utilizing octave filters showed that it is possible to determine the time of glottal closure in any cycle of a vowel. The records from the octave filters will show two vibration groups or vibration maxima which can be related to the opening and closure of the glottis.
Analyses of Tones of Wind Instruments and of Resonating Strings
Authors: Saunders F. A. 
Published: September 2005

In the course of studies of violins, it became of interest to find out how much their tone analyses differed from those of certain wind instruments. Analyses were made of flute, clarinet, oboe, English horn, and French horn, rather softly blown, over their whole range. The results show no such violent variations in volume of tone as in violins, though a weak spot appears in the oboe and the clarinet. For low tones in oboe, English horn, and French horn the upper partials are strongest. These die off progressively on the way up the scale until at the top the order of prominence is the order of the partials, as in high violin tones. The order of appearance of the even-numbered partials in the clarinet is interesting; 6, 4, and 2 are absent in the lowest tones, and they appear progressively, in that order. The second passes the third one octave below the top; the fundamental is nearly always loudest.
The violin family includes the viola d'amore, in which seven or more extra wires which are not fingered are added for resonance. Some writers and many musicians believe that the extra wires increase the loudness, though wires were once supposed to kill the sound in an auditorium. To test the matter, analyses were made of A-440 tones from each of two violins played on the D string, with or without allowing the open A string to resonate. The results show no effect unless the tuning is exact, but clearly show that the resonating string weakens the output of the fundamental without appreciably affecting the upper partials. If the energy supply given to the bowed string is constant, it is clear that the roundabout process of producing sound from the violin box by way of the resonating string must involve a loss of energy. The peculiar quality of the viola d'amore, if it exists, must be due to some cause other than the presence of the extra wires.
Ultrasonic Solid Delay Lines
Authors: Arenberg David L. 
Published: September 2005

The development of an ultrasonic delay line for the storage of pulses 1 microsecond long for periods up to 2000 microseconds is discussed. Theoretical considerations of the piezoelectric transducer involving the quartz crystals and acoustical constants of the medium developed by Emslie, Huntington, and Benfield, are applied to determine the band width and power loss of the delay line. Problems, peculiar to the use of solids because of the presence of more than one mode of propagation and the distribution of energy between the different modes on reflection from an air surface, are evaluated for a wide range of Poisson ratios. Measurements of velocity and attenuation in some polycrystalline metals, single crystals, and glasses are given. Fused quartz was found to be the most promising material.
Delay lines constructed using a light source and photo-elastic pick-up were not completely developed, but several types using crystal pick-up as well as transmitter were satisfactory. For delay times longer than 300 microseconds, multiple reflection paths in two and three dimensions were used and their preparation from fused quartz discussed.
Monaural and Binaural Threshold Sensitivity for Tones and for White Noise
Authors: Pollack Irwin 
Published: September 2005

Monaural and binaural thresholds of ten listeners were determined for a 1000-cycle tone and for a white noise. For each of the observers, the binaural threshold was found to be significantly lower than the monaural threshold when the two ears were “equated” in sensitivity, i.e. when the difference in sensitivity between the ears of a given observer was effectively canceled by experimental procedures. Furthermore, the difference between the monaural and binaural thresholds was found to be significantly greater for the pure tone than the corresponding difference for the noise.
Monaural and binaural thresholds were also determined with the two ears “equated” in sensitivity and with the two ears “mismatched” in sensitivity by fixed ratios. It was found that the difference between the binaural threshold and the threshold of the better ear decreased as the difference in the effective stimulation at the two ears was increased. The difference between the binaural threshold and the threshold of the better ear was found to be not statistically significant when the two ears were stimulated at sensation levels more than 6 db apart.
The results of the present study fail to confirm the hypothesis that the auditory threshold is constant and equal to the sum of the effective acoustic powers at the two ears. For most of the observers, the difference between the monaural and binaural thresholds was found to be significantly less than would be predicted by this hypothesis.
Construction Material of the Sound Conduction System of the Human Ear
Authors: Kobrak H. G. 
Published: September 2005

The behavior of the living elastic bodies in the ear must be studied for a full understanding of the ear as sound conductor. Two elementary structural elements possessing restoring forces are the collagen fiber and the elastic fiber. These two tissue elements form membranes, ligaments, tendons, and articulations in the ear.
The physical behavior of these two fiber systems is described. Three areas in the ear are distinguished according to their construction material. Methods of measuring the physical characteristics of the ear structures are described. The linear displacement of the center of the ear drum as a function of static pressure changes in the outer ear canal is given. Static movements of the stapes footplate due to reflectoric muscle contractions were used to calculate the elongation of the stapes ringband in vivo.
The Directional Characteristics of a Clamped-Edge Disk
Authors: Merrill Lynn L. , Slaymaker Frank H. 
Published: September 2005

It is well known that to obtain very small side lobe radiation the amplitude distribution across a radiating surface should be such that the maximum amplitude is at the center and the minimum at the edges. The Gaussian distribution gives no side lobes, but requires an infinitely large radiator. This paper gives the analysis of the clamped-edge disk, vibrating in its first normal mode. It shows that the dynamic curve approximates the Gaussian form and that the sound pressure distribution has very small side lobes, the amplitude of the first side lobe being 33 decibels below that of the axial lobe.
For a disk of a given diameter the width eft the axial lobe may be decreased by raising the frequency of the first normal mode, which requires a corresponding increase in the disk thickness. At very high frequencies the disk thickness may become prohibitive. In such cases a thin disk can be forced to vibrate in the shape of the first normal mode by a proper radial distribution of the driving force.
Calculation of the Directivity Index for Various Types of Radiators
Authors: Molloy C. T. 
Published: September 2005

This paper gives the derivations of the “directivity index” formulas for several types of sound radiators. The “directivity index” is defined as “the ratio of the total acoustic power output of the radiator to the acoustic power output of a point source producing the same pressure at the same point on the axis.” The utility of the directivity index concept is that it permits power calculations to be made for all radiators in the same manner as for point sources. Directivity index formulas, together with graphs covering practical cases, are given for the following types of radiators:
1. General plane piston in infinite baffle,
2. Circular plane pistion in infinite baffle,
3. Rectangular plane piston in infinite baffle,
4. Sectoral horn,
5. Multicellular horn,
6. Piston set in sphere.
Thickness-Shear Vibrations of Thin Anisotropic Plates
Authors: Hok Gunnar 
Published: September 2005

The vibrational boundary conditions of a free, thin, rectangular, plane-parallel plate can be satisfied by the sum of an infinite series of plane wave components. When the ratios of the thickness to the length and width of the plate are small, this series converges rapidly enough to give a fair approximation with a reasonable number of terms.
Frequency spectra as well as standing-wave configurations are calculated approximately for AT and BT cut quartz plates. Some observed data are given for comparison.
The Time Integral Basic to Optimum Reverberation Time
Authors: Maxfield J. P. 
Published: September 2005

Equations showing the relation between the volume, V, of an auditorium and its optimum reverberation time, T0, were published independently by MacNair and Lifschitz. MacNair's equation was derived from the following basic assumptions: ∫ 0T1 (logρ)dt = a const., E = const., where ρ=instantaneous value of the energy density of sound during decay,T1=time of decay to minimum audibility,E=rate of supply of energy during the steady state condition.
This paper shows that an equation, relating T0 and V, can be deduced which more nearly fits all the empirical facts by basing the derivation on the following assumptions: ∫ 0T1 ρ ⋅ dt = a const., E = GVn, where G=a constant,n=a constant which should be less than unity.
The resulting equation for n = 23 is T0 = 0.212 V1/6. This is in agreement with the empirical data and with the equation derived by Maxfield and Albersheim from acoustic “liveness” considerations.
The psychologists and physiologists studying the mechanism of hearing should be interested in these results, as they have a bearing on the manner in which the ear integrates the sound being perceived.
Reflection of Sound From Submerged Plates
Authors: Finney W. J. 
Published: September 2005

It has been found that an appreciable reflection occurs in the direction of the incident wave when high frequency underwater sound strikes a submerged steel plate at an oblique angle of incidence. The magnitude of this “non-specular” reflection, together with the associated transverse vibrations in the plate, has been studied experimentally as a function of frequency, plate dimensions and angle of incidence. Significant non-specular reflection occurs from bounded plates between about one-quarter inch and two inches thick, when the product of thickness in inches and frequency in kilocycles per second lies between about 20 and 60 in.-kc. Within this range, the angle of incidence for maximum non-specular reflection, η is described by the empirical relation: sinη = 2.16/(bf)13. This relation has been found to apply also to 0.002 inch plates at 15 megacycles.
The results of the present study are in agreement with a theoretical analysis by Fay, and with the experimental results obtained by Sanders at frequencies of several megacycles.
The Coupling of a Cylindrical Tube to a Half-Infinite Space
Authors: Miles John W. 
Published: September 2005

The radiation admittance of a semi-infinite space, as seen by a cylindrical tube through an aperture in an infinite plane, is computed. The pressure fields in the tube and half space are developed in terms of the axial velocity in the aperture, and an integral equation for this velocity is determined. It is shown that the velocity function which satisfies this integral equation makes the real and imaginary parts of the radiation admittance absolute minima. An asymptotic expression for the field at a distance from the aperture is developed, and reflection and transmission coefficients are determined in terms of the radiation admittance.
The general theory is applied to a circular tube and an infinite slot. Numerical results are given in the form of curves, and the results for the circular tube are compared with those obtained by Rayleigh.
Radiation from a Diaphragm Struck Periodically by a Light Mass
Authors: Strasberg Murray 
Published: September 2005

Expressions are obtained for the energy radiated by a clamped circular diaphragm excited by periodic impacts. The radiation consists of a line spectrum with intensity maxima in the neighborhood of the resonant frequencies of the various vibrational modes of the diaphragm. The energy in the spectrum lies almost entirely below a frequency equal to twice the reciprocal of the time of contact of the hammer with the diaphragm at each impact.
Expressions for the efficiency of the system as a converter of mechanicai energy into acoustical energy are derived, and the conditions resulting in maximum efficiency are determined. Curves are presented to assist the calculation for the case of a steel diaphragm in water.
Vibration of the Head in a Sound Field and Its Role in Hearing by Bone Conduction
Authors: v. Békésy Georg 
Published: September 2005

In a sound field the head is set into forced vibrations, and the vibrations are sometimes heard by bone conduction. For clinical purposes it is important to know the magnitude of these vibrations of the head so that, in cases of partial deafness, the roles of air conduction and bone conduction can be understood.
The pattern of the head vibrations and the velocity of the deformation waves traveling along the bony wall of the skull were measured. For the velocity we found c = 570 m/sec. In the course of the experiments, a new method of calibrating a vibration pick-up with a sound level meter was developed.
It was found possible to construct an earphone that reduces the amount of “cross-hearing” to a very low value. With this earphone, hearing thresholds can be measured in many cases without using noise to mask the ear with the better hearing, even though the difference between the sensitivities of the two ears is greater than 40 db.
It is shown that the maximal sound insulation that can be obtained with an ear plug is determined by the elastic forces acting between the skin of the ear canal and the bony wall of the ear canal.
The Propagation of Sound in Composite Media
Authors: Urick R. J. , Ament W. S. 
Published: September 2005

A theory is outlined for the propagation constant in media containing numerous small spherical particles. Using expressions derived by Lamb for the zero and first-order scattering coefficients of a particle free to move in a sound field, an expression for the complex propagation constant is derived whose real part yields a velocity which reduces to the homogeneous case for extremely small particles, and whose imaginary part yields an absorption coefficient identical with that derivable from the viscous-drag theory outlined in a previous paper.
Using both an interferometer and a pulse-reflection method, measurements of sound velocity and absorption at megacycle frequencies have been made on mercury-in-water and bromo-form-in-water emulsions of non-uniform particle size, up to a volume concentration of about 50 percent of emulsified liquid. These materials, though showing considerable deviation from a homogeneous behavior, are found to have a velocity and absorption in good agreement with the theory up to concentration of about 25 percent by volume.
Propagation of Sound Waves along Liquid Cylinders
Authors: Jacobi William J. 
Published: September 2005

In this paper a theoretical and experimental treatment is given of guided sound wave transmission along circular cylinders of ideal liquid with various non-dissipative boundary conditions. The field patterns, phase velocities, and cut-off frequencies are calculated for the natural modes of propagation in the following cases: (1) liquid cylinder with rigid walls; (2) liquid cylinder with pressure-release walls; (3) liquid cylinder embedded in infinite liquid; (4) liquid cylinder with liquid walls; (5) liquid cylinder with thin solid walls. The problem of determining the field produced by an arbitrary excitation in terms of the natural modes is also discussed.
Experimental results are presented for cases (2) and (5) above. It is shown that the measured values of phase velocity are in agreement with those predicted by the theory.
The Acoustic Reactance of Small Circular Orifices
Authors: Bolt R. H. , Labate S. , Ingård U. 
Published: September 2005

A precise experimental study of the reactive component of the complex impedance of small circular orifices has been made for a number of orifices varying in diameter from 2 cm down to 0.357 cm, with diameter/thickness ratios from 4 to 40, over the frequency range from 200 to 1000 c.p.s. The measurement of the impedance is performed with a precision impedance tube.
A theoretical correction for the influence of the tube walls is applied by considering the orifice to act as a plane piston and taking into account the influence of all possible higher order modes of the tube in the neighborhood of the orifice. Comparison between calculated and measured values of reactance shows that, as far as this quantity is concerned, the assumption that the orifice acts like a plane piston appears valid for radii equal to or greater than 1 cm for “thin” orifices within the range of variables specified above. For orifices of radii less than 1 cm, however, a modification of the radius is necessary to make the classical theoretical equation for orifice reactance fit the measured data. The observations and analyses reported here are restricted to wave-lengths much greater than the hole diameter and to the low velocity region where reactance is independent of particle velocity.
Wave Propagation in Piezoelectric Crystals
Authors: Kyame Joseph John 
Published: September 2005

The propagation of plane waves in a piezoelectric medium has been studied. A simultaneous solution of Maxwell's field equations and Newton's law of force gives the necessary conditions for wave propagation in the infinite medium. By piezoelectric coupling, every electromagnetic wave has associated with it an elastic wave. Nonpiezoelectric crystals are, at best, birefringent electromagnetically and trirefringent acoustically. In piezoelectric media, the electromagnetic and elastic modes are coupled, thus giving five phase velocities for both the electromagnetic and acoustic waves. These media are therefore electromagnetically and acoustically pentrefringent. The slower electromagnetic waves are the field variations accompanying the elastic waves, while the fast elastic waves are the mechanical deformations accompanying the electromagnetic wave.
The displacement in the elastic wave will differ in phase by ninety degrees from the electromagnetic wave, its amplitude being proportional to the electric field strength and inversely proportional to the frequency of vibration. The flux of energy will, in general, be in directions different from that of phase propagation. The generalized Poynting vector will be the sum of two vectors representing separately the flux of electromagnetic energy and the flux of elastic energy.
Analysis was made of propagation in a particular direction in sphalerite. The orientation of the vectors involved has been calculated for the fast and slow modes of vibration.
A study of specific boundary value problems gives interesting results. The piezoelectric effect gives a contribution to the reflection of electromagnetic waves at an interface. This results in a small correction to be applied to the familiar expressions for the reflection coefficients. This correction might be used to determine piezoelectric constants, providing it is possible to measure accurately the reflection coefficients and other constants involved.
Slabs of piezoelectric media may be set into vibration by an incident electromagnetic wave. At particular frequencies the crystal may be set into resonance. At resonance for the elastic wave there is almost perfect reflection of the incident electromagnetic wave. It should be possible to detect these resonances by absorption measurements.
The piezoelectric slab, if set into resonance by an acoustic wave, emits a weak electromagnetic signal.