bluuebunny/crossref_metadata_2025 huggingface dataset:
Auditory Testing of a Simplified Description of Vowel Articulation
Authors: House A. S. , Stevens K. N.
Published: September 2005

An auditory test to establish the adequacy of an idealized specification of vowel articulation is described. Articulatory configurations of the vocal tract are specified by means of three numbers: the position of the point of greatest constriction, the degree of constriction at that point, and the size of the mouth opening. The stimuli in the recorded test are the outputs of 279 such configurations of an electrical vocal-tract analog. All sound samples are highly similar in duration, intensity, start-stop characteristics, and fundamental frequency and inflection. The instructions to subjects are standardized, and are of two types: one restricts responses to one of nine vowel categories while the other permits a nonvowel response as well. Subjects were experienced in phonetic transcription.

The ranges of articulatory configurations identified as given vowels by the subjects are plotted as contours, and these data are compared to results of other investigators. Certain disagreements are pointed out and discussed. The results, in general, show good agreement with previous data, and demonstrate, therefore, the adequacy of the three-number articulatory description.
Measurements of the Sound Absorption Coefficient and the Sound Transmission Loss at the Kobayasi Institute of Physical Research
Authors: Sato Kozi , Koyasu Masaru
Published: September 2005

During the past three years, five reverberation chambers were constructed in our institute. These chambers are now used for the measurements of the sound absorption coefficient and the transmission loss. Chamber No. 1 has a volume of 513 m3 surrounded by nonparallel walls, and the reverberation time of this chamber is greater than 20 sec at 500 cps. In this chamber, the position of the microphone and test specimens does not affect the absorption coefficient. Chambers No. 3 and No. 4, which are used for transmission loss measurements, have a volume of 164 m3, respectively. The shape of these chambers is similar to chamber No. 1. The opening between these two chambers is 3.3 m by 3.3 m. Under chamber No. 4, there is chamber No. 5, which is used for the receiving room for impact sound transmission loss measurements.
Determination of Absolute-Intensity Thresholds and Frequency-Difference Thresholds in Cats
Authors: Elliott Donald N. , Stein Leon , Harrison Mary Jane
Published: September 2005

While the cat's basilar membrane is only two-thirds the length of the human, its auditory-frequency range is at least three times as great. Behaviorally defined absolute-intensity and differential-frequency thresholds have been determined for the cat and are compared with those of humans. The cat's absolute thresholds lie well below those of humans over nearly all of the frequencies the two species respond to in common. The cat's differential thresholds, however, are larger at all frequencies. But because of the cat's larger frequency range, the total number of discriminable steps appear to be about equal. Counts of ganglion cells and hair cells for the cat are reported and compared with counts for humans. The greater density of the cat's ganglion cells may explain its lower absolute thresholds, but there appears to be no direct relation between ganglion-cell density and frequency discrimination. The lower density of hair cells for the cat, coupled with its shorter basilar membrane, may account for its poor frequency discrimination.
Ultrasonic Shutter
Authors: Darner Charles L. , Bobber Robert J.
Published: September 2005

The ultrasonic shutter is a thickness-expander plate of barium titanate which, when placed in a beam of ultra-sound, will control the transmission of sound through it over a 40 db range near the frequency of half-wave resonance. Control is exerted by means of a passive electrical network connected directly to the plate electrodes.

Theory of the “shutter effect” and supporting experimental data are presented.
Stereophonic and Quasi-Stereophonic Reproduction
Authors: Lochner J. P. A. , de V. Keet W.
Published: September 2005

In stereophonic reproduction there are two distinct qualities which distinguish it from single-channel reproduction. The first of these is a directional separation of sound sources and the second, and probably the most important characteristic of stereophonic reproduction, is the sensation of “depth” and “presence” that it creates.

It is well known that the relative amplitudes and times of arrival at an observer's ears of first sounds received from the loudspeakers determine the apparent direction of the sound sources in a stereophonic system, and it is often assumed that this is also responsible for the perception of “depth” and “presence” normally linked with this system. It appears, however, that only the former quality, directional separation, is based on the relative amplitudes and times of arrival of first sounds and that the latter quality, which we call “ambience,” is entirely on account of delayed reflections or echoes recorded and reproduced through the separate channels of the stereophonic system.

Single recording-channel quasi-stereophonic systems, in which these echoes were brought out as in the stereophonic system, but which could not give separation of sources, were subjectively compared with true stereophonic systems and the results are presented in this paper.
On the Lowest Flexural Resonant Frequency of a Circular Disk of Linearly Varying Thickness Driven at Its Center
Authors: Thurston E. G. , Tsui Y. T.
Published: September 2005

A solution for the lowest, flexural, resonant frequency of a center-driven, circular disk of linearly varying thickness is obtained by application of the Rayleigh-Ritz method. Experimental results obtained with a series of aluminum disks are given and compared with those predicted by the analysis.
Protective Effect of the Acoustic Reflex for Impulsive Noises
Authors: Fletcher John L. , Riopelle Arthur J.
Published: September 2005

Twenty-four male subjects were trained in the use of the Békésy audiometer. Then they were exposed to 100 rounds of machine-gun fire, both with and without a pre-exposure to a 1000-cps tone for activating the acoustic reflex. Pre- and post-firing audiograms, taken under both conditions, were compared to determine temporary threshold shifts. Shifts obtained with the reflex-activating tone were found to be significantly smaller than those obtained in its absence.
Extension of the Myklestad Matrix Method to Include Rotary Inertia and Shear Deformation
Authors: Saunders Herbert
Published: September 2005

An extension to the matrix procedure of Thomson's adaptation to Myklestad's method is formulated to include both rotary inertia and shear deformation. These additions modify the frequency determination especially for the higher modes.
Continuous Tone Underwater Reverberation
Authors: Conley Patrick
Published: September 2005

Continuous tone underwater reverberation is the signal observed when the transmitting and receiving transducers are in linear motion, the transmitter is operating at a single frequency, and no major reflecting bodies are in the beam paths. This reverberation has been measured as a function of frequency for ocean depths of 9.5 to 85.7 meters, at transducer speeds up to 7.5 meters per second, and for various sea states. The techniques for measurements are described, and some typical reverberation spectra are shown. The spectra are shown having maxima at approximately the frequency corresponding to the Doppler shift caused by the transducer motion. The spectra are asymmetrical about the maximum, with the general reverberation level decreasing with increasing depth and decreasing sea state.
New Instruments and Methods for Speech Analysis
Authors: Sakai Toshiyuki , Inoue Sei-ichi
Published: September 2005

Some important features involved in the zero-crossing waves of the signal generated by the human voice are described. The method of analyzing the vocal sound by a Sonagraph using the natural wave forms is compared with our new method using the zero-crossing waves. Next, three kinds of devices are described which have been developed by the authors to analyze speech sounds. These include devices to analyze automatically the zero-crossing intervals, to display the zero-crossing waves in three-dimensional form, and to make a visible pattern of the zero-crossing waves. In this paper, as examples of an important application of these devices, the following are described: the results of analysis of vowels in the Japanese language, some characteristics of a number of groups of consonants (after the separation of the consonant and the vowel parts), and the discrimination of the nasal consonants, [m] and [n].
New Method of Recording the Sound Transmission Loss of Walls as a Continuous Function of Frequency
Authors: Waterhouse Richard V. , Cook Richard K.
Published: September 2005

An apparatus has been developed which records as a continuous function of frequency the difference in decibels between the sound levels in two rooms separated by the partition under test. The quantity recorded differs from the transmission loss only by a small correction for the Quiet-room absorption and partition area. Experimental results are presented.

An electronic potentiometer recorder is used as a self-balancing device. The voltages produced by microphones in the Loud and Quiet rooms are applied to the recorder, which drives a logarithmic attenuator and continuously reduces the Loud voltage to the same value as the Quiet voltage. The voltages are balanced at an attenuator setting which is determined by the sound transmission loss and this is plotted linearly in db on an 11 inch scale, which may be chosen as 0–60 db or less.
Use of Flat Splitter Construction in Aviation Test Cell Silencing
Authors: Hirschorn Martin
Published: September 2005

A scale model of a 16 ft × 16 ft vertical test cell was constructed for the purpose of testing acoustic attenuation characteristics of various splitter configurations. The result was a system with a reverse stagger pattern and expansion chambers having high acoustic attenuation characteristics. The scale model results were verified by full scale tests with a jet engine as a noise source.
Dimensional Analysis of Cochlear Models
Authors: Tonndorf Juergen
Published: September 2005

It is generally known that events occurring in different systems which, although differing in size, are physically similar can be quantitatively related to each other by Dimensional Analysis. The significance for Auditory Theory of various phenomena observed previously in cochlear models would be considerably increased if a dimensional analysis were performed of these models.

This paper represents an attempt at such an analysis. In the amplitude domain, its results suggest a close relation between the levels at which Bekesy's eddies first become visible in the model and at which harmonic distortion first becomes audible in the human ear. In a previous paper on cochlear models, evidence had been given that the appearance of Bekesy's eddies represents the onset of harmonic distortion in the model. The present analysis has strengthened the validity of this concept.
Reflection and Transmission of Sound by a Moving Medium
Authors: Keller Joseph B.
Published: September 2005

The reflection and transmission of sound by a moving medium are investigated theoretically and the reflection and transmission coefficients are determined. These coefficients are found to depend only upon that component of the velocity of the medium which lies in the plane of incidence. The reflection coefficient increases with the velocity of the moving medium until a velocity is reached at which total reflection occurs. Total reflection persists until a still higher velocity is reached above which the reflection coefficient decreases as the velocity increases.
Calibration for Carrier Operated Microphones and Other Reversible Transducers
Authors: Burkhard M. D. , Corliss E. L. R. , Koidan W. , Biagi F.
Published: September 2005

An insert technique described in this paper makes it possible to carry out sound pressure measurements using a microphone operated in a carrier circuit with almost the same accuracy as can be achieved with more conventional preamplifiers. The carrier system is modified to include a microphone polarizing voltage if the transducer is not self-polarized. Then a calibrating audio-frequency voltage is used to drive the transducer diaphragm to the same displacement amplitude as that generated by the sound pressure. Instead of matching the open-circuit voltage of the microphone, diaphragm motion is matched. A displacement response constant, independent of frequency, is used to determine sound pressure, in contrast to the usual open-circuit response, which depends on frequency.

In a manner analogous to the determination of open-circuit pressure response by the reciprocity technique, the acoustic admittance of the microphone may be evaluated from a series of three voltage ratio measurements and the calculated acoustical transfer admittance of a calibrating coupler. This result can be combined with the open-circuit pressure response determined by the reciprocity technique to give an explicit evaluation of the electromechanical coupling constant.
Entropic Equations of State and Their Application to Shock Wave Phenomena in Solids
Authors: Duvall George E. , Zwolinski Bruno J.
Published: September 2005

The front of a shock wave in an ideal fluid is characterized by a discontinuous transition from the undisturbed state to a highly compressed state in which the entropy of the fluid has increased. The relations between pressure, density, propagation velocity, and particle velocity behind the shock front are represented by the equations for conservation of mass, momentum, and energy and by the equation of state of the fluid. The entropy change produced by the transition is third order in the compression for weak shocks. The propagation of shock waves through metals can be described by a hydrodynamic theory which assumes that the metal is an ideal fluid behind the shock front, and that the hydrostatic equation of state is applicable there. Three hydrostatic equations of state for Al, Cu, Fe, and Pb are compared with experimental data at low pressures and quantum mechanical calculations pressures up to several hundred megabars. With these equations of state the hydrodynamic theory is used to calculate explicitly the entropy increase across the shock front, the amount by which the pressure exceeds the adiabatic pressure for a given compression, and the temperature rise after the shock pressure has been relieved for the metals mentioned above.
Vibration of Simply Supported Isosceles Trapezoidal Flat Plates
Authors: Klein Bertram
Published: September 2005

Solutions are given for the lowest natural frequency of flexural vibration of isosceles trapezoidal flat plates which have simply supported edges. The results of the calculations are presented graphically so that one may determine rapidly a desired fundamental frequency. The range of the values of the geometric parameters defining the plate is large enough to cover most practical cases.
Propagation of Sound in Thin Elastic Shells
Authors: Young James E.
Published: September 2005

A wave theoretical analysis of symmetric mode propagation in a medium confined by a cylindrical elastic shell is carried out. An expression is obtained for the axial propagation constant, specialized to that case of a thin steel shell surrounding a column of air. This is further restricted to the description of the lowest symmetric mode.

The dispersion predicted by the analysis is in order of magnitude agreement with that obtained on a transmission line picture.
Measurement of Correlation Coefficients in Reverberant Sound Fields
Authors: Cook Richard K. , Waterhouse R. V. , Berendt R. D. , Edelman Seymour , Thompson M. C.
Published: September 2005

Reverberation chambers used for acoustical measurements should have completely random sound fields. We denote by R the cross-correlation coefficient for the sound pressures at two points a distance r apart. R = 〈p1p2〉Av/(〈p12〉Av〈p22〉Av)12, where p1 is the sound pressure at one point, p2 that at the other, and the angular brackets denote long time averages. In a random sound field, R = (sinkr)/kr, where k = 2π/(the wavelength of the sound). An instrument for measuring and recording R as a function of time is described. A feature of this instrument is the use of a recorder's servomechanism to measure the ratio of two dc voltages. The results of correlation measurements in reverberant sound fields are given.
Study of Acoustical, Requirements for Teaching Studios and Practice Rooms in Music School Buildings
Authors: Lane R. N. , Mikeska E. E.
Published: September 2005

Acoustical measurements are presented on teaching studios and practice rooms of several music buildings located at four southwestern universities. Data were taken on a wide range of wall construction and recommendations on room response and acoustical isolation between rooms are presented.
Fluctuations in Intensity of Short Pulses of 14.5-kc Sound Received from a Source in the Sea
Authors: Sagar F. H.
Published: September 2005

Some 4000 measurements of acoustic pressure obtained from experiments (using 1.3-millisecond pulses), in which resolution was achieved between direct and echo pulses, are reported. Of the usual causes producing fluctuation, many were either eliminated or corrected for. Transducer oscillations of the linear and rotational types remained, together with attenuation changes due to temperature-microstructure effects. Two ships were employed, both multianchored to ensure range constancy, work being restricted to conditions of low sea state and to ranges of from 70 to 500 yards. The depths of the projector and the hydrophones were respectively 60 and 45 ft. The area selected was about 50 miles from the mainland of the North Island of New Zealand and here only small streams drain from the coast into the sea. Work was performed in a 130-foot patch of secluded water between a few steep rocks and islands, the drainage from the latter also being negligible. Fluctuation from signal to signal was small, the largest value of the ratio “maximum pressure to minimum pressure” for the longest experiment (85 minutes) being 1.94 while the variation coefficients for 48 separate pulse sequences relating to a variety of conditions fell in the range 5.0% to 12.4%. No clear correlation was found to exist between fluctuation and range, transducer depth or tidal current, but some correlation existed with sea state. Percentage deviations from the average pressure-signal value per hydrophone, gave histograms, for any one experiment, which are approximately Gaussian in shape, the largest value of deviation encountered being plus 40%. Histograms constructed from data from selected hydrophones possessing identical spatial irregularities have a modified shape consistent with the conclusion that fluctuation is here entirely due to continuous transducer rotations about the suspension cables.
Fixed Path, Variable Frequency Acoustic Interferometer
Authors: Leon Herman I.
Published: September 2005

A fixed path, variable frequency acoustic interferometer is described that is particularly suited for measuring ultrasonic velocities in liquids as a continuous function of temperature and pressure of the medium. The interferometer contains two clamped crystals: one, a low intensity ultrasonic source; and the other, a fixed, parallel reflector. The frequency of excitation, supplied from a frequency generator, is varied, and cyclic changes in input impedance are detected in an impedance bridge circuit. Crystal resonance is avoided. The interferometer, addition to the usual advantages of a fixed path system over a variable path one, operates at very low power levels; hence, it avoids problems occasioned by high intensity pressure waves. Frequency, the measured variable, is one that can be precisely measured with comparative ease.

The complete equivalent network for either the fixed or variable path interferometer is presented, from which the operation of the fixed path, variable frequency system is derived. The effect of crystal backing impedance is discussed, and the characteristics of the interferometer are shown to be those of a double crystal interferometer having infinite backing impedance.

The velocity of sound in water is measured between 25 and 53°C in the frequency range of 600 to 800 kc. At 25.0°C the measured velocity is 1496.8±0.3 meters/second, and the temperature coefficient is +2.7 meters/second °C.
Design and Performance of a High-Frequency Electrostatic Speaker
Authors: Bobb Lloyd , Goldman R. B. , Roop R. W.
Published: September 2005

An electrostatic speaker has been developed which provides a high quality of high-frequency reproduction not available with electromagnetic tweeters. The diaphragm consists of a thin plastic film bearing an evaporated metallic layer. The membrane is stretched around a semicylindrical perforated electrode on which ridges are embossed to provide clearance. The response varies less than ±2 db in the frequency range between 8 and 16 kc. The azimuthal distribution pattern is excellent, owing to the cylindrical geometry, and is essentially independent of frequency in the same range. The second harmonic distortion inherent in this type of speaker is maintained at a low value. An indication of the quality of high-frequency reproduction is provided by oscillograms of the response to tone burst signals. The speaker is in quantity production and has been incorporated in several models of home reproduction instruments.
Speech Bandwidth Compression through Spectrum Selection
Authors: Kryter Karl D.
Published: September 2005

PB word and sentence intelligibility tests were conducted with unfiltered speech and with speech filtered (1) by a 100–7000 cps bandpass filter, (2) by a 100–1600 cps bandpass filter, (3) by a 500 2000 cps bandpass filter, (4) by a 1000–2500 cps bandpass filter, and (5) by various configurations of one, two, or three bandpass filters, each 500 cps wide. The positions of the center frequencies of the bandpass filters 500 cps wide were systematically varied during the tests. If we use constant speech intelligibility as our criterion, the results indicate that the total “effective” bandwidth required for the best multiple pass band system is less than that required for the best contiguous pass band systems by a factor of 2. Also, a feature of the signal resulting from this multiple sampling in the frequency domain is that it sounds “natural” and the identity of a talker's voice appears to be maintained.
Mechanical Impedance of the Forehead and Mastoid
Authors: Corliss Edith L. R. , Koidan Walter
Published: September 2005

A method has been developed for determining the resistive and reactive components of the impedance of the human head and mastoid, or of other high mechanical impedances, using a special direct-recording measuring system that records both force and motion. Impedances presented to driving tips of 12.5 and 20 mm diameter have been measured over the audio-frequency range from 40 to 10 000 cps. The effects of static force coupling the head to the driver have been compared for 500- and 1000-g coupling forces. Over a large part of the audio-frequency range, the predominant characteristic of both head and mastoid impedance is a stiffness reactance, with some damping. In the high-frequency range, a small mass reactance parameter appears. The mass load due to the whole head influences the impedance only at the low-frequency extreme of the measurement range.

The driving system consisted of a tubular section of polarized barium titanate, rigidly clamped at one end to a massive wall. Force and motion were measured close to the point of contact with the lead, to minimize errors arising from flexure in the driver or between the sensing elements. The system was calibrated by loading the driving tip with known masses.
Dynamic Mechanical Properties of Polyethylene from 25° to 150°C
Authors: Fitzgerald Edwin R. , Watson M. T.
Published: September 2005

Measurements of the complex shear compliance (J* = J′ − iJ″) have been carried out for three polyethylene samples of increasing weight average to number average molecular weight ratios (M̄w/M̄n) of 19, 70, and 110. The measurements extended to temperatures well above the crystalline melting points of the polyethylenes and over a frequency range from 25 to 2500 cps. A sudden increase in compliance occurred at all frequencies at the melting points of each type of polyethylene; there were no marked differences in dynamic mechanical behavior below the melting points. Above the melting points values of storage compliance (J′) were very nearly the same for all the polyethylenes but differences in the loss compliance (J″) were found. In particular at higher frequencies (1300 cps) values of J″ diverged with temperature in ascending order as M̄w/Mn increased. Values of mechanical loss tangent (J″/J′) showed sudden jumps at the melting points but them was no evidence of maxima or peaks at these temperatures. Attempts to superpose the data in the melt were unsuccessful as values of J″ at various temperatures could not be shifted into coincidence even though values of J′ superposed fairly well. The superposition anomalies are tentatively ascribed to the presence of a secondary maximum in the loss compliance vs frequency characteristics of the materials while the secondary maximum, in turn, is attributed to either (1) a split molecular weight distribution with two separate maxima, or (2) a β mechanism involving the motion of very long branches.
Auditory-Threshold Recovery after Exposures to Pure Tones
Authors: Hirsh I. J. , Bilger R. C.
Published: September 2005

A modified Békésy-type audiometer was used to obtain a continuous recording of the auditory threshold before and after monaural exposures to different durations and intensities of pure tones. Preliminary studies confirmed the observations of Reger that the amount of temporary hearing loss at 1 kc following a 1-min exposure to a 1-kc tone is greater when the stimulating tone is 20 db above threshold than when it is 80 db above threshold. Temporary hearing loss at higher frequencies, however, increases with exposure level. These preliminary results led to an investigation of the dependence of temporary hearing loss on the duration and the intensity of exposure tones.

Recovery curves for the threshold at 1 kc following exposure by 1 kc indicate that exposure tones at or above 60 db sensation level yield a rapid recovery followed by either a slowing down of the recovery process or a second rise in the threshold. Following exposure to a 20-db tone, however, this rapid recovery is not so apparent, and therefore, when the temporary threshold shift is measured soon after exposure, the apparent loss after 20 db is greater than after higher intensities. The hearing loss two minutes after exposure does not change with increasing exposure level until the sensation level exceeds 80 db. Also, temporary hearing loss does not change significantly with exposure durations from 15 sec to 1 min but increases as the durations increase to 2 and 4 min.

These findings do not hold when the threshold for 1400 cps is measured following exposure to 1 kc. Here, temporary hearing loss increases directly with duration for sensation levels at 80 db or above, and it increases directly with level for sensation levels greater than 60 db. Although these results are somewhat obscured by differences among individuals, the recovery curves, and their dependence on intensity and duration of exposure, point to more than one underlying recovery process.
Method for Measurement of |E′/I′| in the Reciprocity Calibration of Condenser Microphones
Authors: Koidan Walter
Published: September 2005

A simple method is described for accurately measuring the ratio of the driving current through a capacitor-type sound source to the open-circuit voltage of a microphone used as the sound receptor. Determination of this ratio in a reciprocity calibration procedure eliminates the need for measurement of the capacitance of the reversible microphone.
Simultaneous and Alternate Listening and Speaking
Authors: Poulton E. C.
Published: September 2005

Listening and speaking simultaneously was compared with listening and speaking alternately. The presented message was masked by the subject's voice to approximately the same extent in the two cases. Results: the simultaneous condition gave more errors than the alternate condition.

In learning to repeat back what they heard in the simultaneous condition, all subjects initially tried to repeat what they heard as they heard it. They thus made meaningless sounds, without being aware that they were doing so.
Simple Way to Observe Optical Diffraction Patterns Produced by Shear Waves
Authors: Breazeale M. A. , Hiedemann E. A.
Published: September 2005

The diffraction pattern due to shear waves in glass can be observed in the absence of compressional waves by submersing the glass in a liquid and exciting the shear waves by means of ultrasonic waves in the liquid impinging on the glass at an angle larger than the critical angle for longitudinal waves.
Propagation of Low-Frequency cw Sound Signals in the Deep Ocean
Authors: Guthrie Albert N. , Tolstoy Ivan , Shaffer John
Published: September 2005

The acoustic field of a 10-cps cw source, towed at slow speeds at a depth of 24 m was measured by a stationary hydrophone out to ranges of about 70 km. The depth of the hydrophone was approximately 450 m. The records obtained are compared with theoretical calculations of the wave field, using a method developed by one of the authors. The degree of agreement is fair enough for one to feel that further work along these lines should lead to a quantitative understanding of long range sound propagation in the oceans.
A Numerical Solution for the Problem of Long-Range Sound Propagation in Continuously Stratified Media, with Applications to the Deep Ocean
Authors: Tolstoy I. , May J.
Published: September 2005

Since the formal solution for guided waves excited by a point source in an arbitrarily stratified medium is well known, in the sense that it can be written down in terms of (unexplicited) eigenfunctions and their derivatives, it follows that evaluation of the long-range sound field becomes a purely computational problem once these eigenfunctions can be calculated. One of a number of possible methods is presented here. It consists of two steps. First, the continuous sound velocity, α(z), is approximated by a succession of layers such that α has the form (pz+q)−12 in each: the exact wave functions for a layer are then known (combinations of Bessel functions of order ±13). The second step, which puts this scheme within easy reach of moderately fast computers such as the IBM 650, consists in representing these wave functions by polynomials (argument of Bessel function ⩽ 2.5π) or by the first few terms of their asymptotic expansions (with better than six-figure accuracy in both cases). Accurate solutions are obtained in this manner without difficulty, for both strong or weak velocity gradients. Some typical results for a deep ocean are displayed. It is also shown that near field problems can be solved in the case of a source and receiver in, or near, a local velocity minimum or duct.
Absorption Characteristics of Upholstered Theater Chairs and Carpet as Measured in Two Auditoriums
Authors: Lane R. N.
Published: September 2005

Data on the absorption of upholstered theater chairs as measured during the construction of a 496-seat auditorium and a 738-seat auditorium are presented. These data obtained on the seats after placement in each auditorium indicate a much lower absorption per seat over the entire audio-frequency band than has previously been reported. Before the seats were installed in the 496-seat auditorium, 1080 ft2 of Axminster carpet were laid on the floor of this room, and the absorption characteristics of this full scale sample were determined. These data are also reported in this paper.
Sensitivity to Changes in the Interruption Rate of White Noise
Authors: Mowbray G. H. , Gebhard J. W. , Byham C. L.
Published: September 2005

Difference-limens for the discrimination of intermittence were obtained at ten interruption rates of random noise between 1 and 320 cps. The duty cycle of the intermittent noise was 0.5 and the sound pressure level was 75 db. Data from four listeners give average deviations from the standard frequency (ΔF) of 0.02 to 9.74 cps. The graph relating ΔF and F from 1 to 320 cps shows ΔF to be a monotonically increasing function of F. When the data are plotted with logarithmic coordinates, two functions are revealed, suggesting a change in the method of frequency discrimination at about 5 cps. This change appears due to the listener's ability to count the noise bursts from 1 to 5 cps, but not above about 5 cps. The relationship between 5 and 320 cps may be described by a parabolic function of the form y = axb. Below 5 cps, the form of the relationship cannot be determined from the data available. The relative difference-limen, ΔF/F, lies between 0.008 and 0.03, and graphic integration of 1/ΔF yields 560 just noticeable differences in the range studied. These data show difference-limens for flutter that are smaller than those previously reported.
Light Diffraction by Two Distorted Ultrasonic Waves
Authors: Mayer Walter G. , Hiedemann E. A.
Published: September 2005

Light intensities in the orders of diffraction patterns produced by two distorted ultrasonic waves 180° out of phase are investigated. In the case where the two waves have the same intensity, the first diffraction orders vanish. The simultaneous increase in light intensity in the second orders is a measure of the second harmonic present in the waves, given for varying distances from the transducers. The change in light intensities in the zero and second orders is given for varying pressure ratios of the two waves.
Automatic Extraction of Formant Frequencies from Continuous Speech
Authors: Flanagan James L.
Published: September 2005

Two electronic devices for automatically extracting the first three formant frequencies from continuous speech are described. Both devices are designed to yield three continuous dc output voltages whose magnitudes, as functions of time, represent the formant frequencies of the input speech. The principles of operation and the design features of both devices are discussed, and typical examples of the operation of each are presented.
On the Calculation of the Axisymmetric Modes and Frequencies of Conical Shells
Authors: Goldberg John E. , Bogdanoff John L. , Marcus Lee
Published: September 2005

A numerical method is presented for determining the axisymmetric modes of vibration and natural frequencies of thin conical shells such as loudspeaker cones. Assuming the applicability of the classical theory of thin shells, the pertinent differential equations are presented in a form which is well-suited to numerical integration on an electronic digital computer. The method may be used also to determine the impedance of the cone at other than the natural frequencies, and to calculate the mechanical impedance of the assembly comprising the cone and the voice coil. Results are shown, by a numerical example, to compare favorably with a previously available method based upon the use of power series.
Vibrations of Rods at Frequencies below Their Radial Resonance
Authors: Biesterfeldt H. J. , Lange J. N. , Skudrzyk E. J.
Published: September 2005

The asymptotic vibration laws that describe the high-frequency behavior of complex systems—on the basis of mode masses and the frequency difference between successive resonances and their damping—also give a significant description of the low-frequency behavior of vibrators from their first resonance onwards. Thus, where problems of noise and vibration insulation are concerned, there seems to be no need for more accurate calculation. This paper derives the necessary theoretical background and substantiates the theory by means of a study of vibrating rods.
Vibrations of Conical Shells
Authors: Saunders Herbert , Wisniewski E. J. , Paslay Paul R.
Published: September 2005

A Rayleigh-Ritz procedure is used to determine the natural frequencies for a certain class of mode shapes of a thin conical shell built in on the edge with the smaller radius and either simply supported free on the other edge. Both bending and extensional energies are included in the analysis. The results show that, for a sufficiently large number of circumferential nodes, the natural frequency predicted by these analyses is very close to the inextensional natural frequency for the same number of circumferential nodes and simply supported at the edge with the smaller radius. The comparison with the inextensional theory predictions is consistent with what has already been found experimentally; i.e., boundary conditions for this type of shell are not as influential on the higher natural frequencies as the lower ones.
Gas Bubbles as Sources of Sound in Liquids
Authors: Strasberg M.
Published: September 2005

Gas bubbles, when entrained in water or other liquid, can generate high sound pressures in the liquid. Significant sound pressures are associated only with volume pulsations of the bubble, whereas oscillations in the shape of the bubble do not result in appreciable sound. Calculations have been made of the sound pressures resulting from excitation of volume pulsations by the following mechanisms: by bubble formation, coalescence, or division; by the motion of a free stream of liquid containing entrained bubbles past an obstacle; and by the flow of liquid containing entrained bubbles through a pipe past a constriction. The calculation of the sound pressure generated by bubble formation has been verified by measurements with bubbles formed at a nozzle.
Investigation of Stationary Ultrasonic Waves by Light Refraction
Authors: Loeber A. P. , Hiedemann E. A.
Published: September 2005

An optical method for the quantitative study of ultrasonic wave fields at frequencies below 1 Mc/sec has been developed and applied to stationary waves. The method is based on the effect of mirage. A detailed theoretical analysis shows the possibility of determining wave forms and sound pressure amplitudes. Some experimental results of sound velocity and pressure amplitude determinations are given. The records of wave forms in several liquids indicate the distortion of waves during propagation.
Radial Vibrations in Short, Hollow Cylinders of Barium Titanate
Authors: Stephenson C. V.
Published: September 2005

The theory of radial vibrations in short, hollow cylinders of barium titanate has been developed. This development results in an expression which relates the radial coupling coefficient to the measurement of the resonant and antiresonant frequencies of the first harmonic of the radial mode of vibration. The important parameter in this development was found to be the ratio of outside diameter to inside diameter, and once this ratio was given, the expression relating coupling coefficient to resonance measurement took a particularly simple form. An interesting result of theory was that for any value of the ratio of diameters, many of the higher harmonics are forbidden in this mode of vibration.

Experiments were devised to test some of the theoretical conclusions and were found to be in excellent agreement with the theory.
Sound Propagation in a Fluid-Filled Tube with Massive Wall Reactance
Authors: Junger Miguel C.
Published: September 2005

The results of an experimental study of a relatively unfamiliar mode of propagation are presented: the zero-order mode in a tube with massive wall reactance. The observed and theoretical disperison curves, which show good agreement, display a high-pass cut-off frequency. There is a dead zone between this frequency and the ring resonant frequency of the tube.

The phase velocities c2 are measured indirectly from the directivity patterns of a receiver in the form of a long rubber hose coupled to a microphone; these patterns are characterized by two symmetrical lobes whose angular separation is 2 cos−1c/c2, c being the sound velocity.
Group Theory of Vibrations of Symmetric Molecules, Membranes, and Plates
Authors: Melvin M. A. , Edwards S.
Published: September 2005

It is shown that the detailed group-theoretical analysis of molecular vibrations can be extended to continuous bodies of various shapes by regarding them as the limits of discrete systems with the number of particles becoming indefinitely large. In this paper an elementary review of the method is given and its application is illustrated with 2-dimensional systems and thin systems having pyramidal symmetry (i.e., tents and shells). Both stationary and rotating systems containing any number of particles arranged with the symmetry of a regular polygon or polygonal pyramid are considered. For macroscopic systems, unlike molecules, different possible constraints must be taken into account in enumerating the genuine vibrations of various types. Otherwise, one proceeds as in the molecular case. By going to the limit of large numbers of particles, one obtains the fractional occurrence numbers of vibrations of various symmetry types for stationary or spinning membranes, plates, tents, or shells of all regular polygonal shapes.
Diffraction of Elastic Waves
Authors: Knopoff L.
Published: September 2005

An integral solution to the differential equations of elastodynamics is given. The solution for the displacement at any point in an isotropic homogeneous, elastic medium is obtained in terms of the initial distribution of body forces within a given volume and the initial distribution of displacements and stresses over the bounding surface of the volume. These quantities appear in the solutions as retarded displacements, stresses, and body forces, with two types of retardation depending upon the velocities of longitudinal and transverse waves.

From the integral solution the diffraction of elastic waves through large apertures bounded by opaque walls in solid materials is formulated. The incident wave motions may be either of longitudinal or transverse polarizations. The expected shear-compression interaction is obtained in the course of the computation. By analogy with optical procedure, Fraunhofer diffraction of elastic waves may be investigated as a special case.

In the example of diffraction by a slit, an incident compression wave is diffracted into (1) a compression wave with the “ordinary” spatial distribution similar to that obtained in the corresponding optical problem and (2) a weaker shear wave with an “extraordinary” distribution. In the case of incident shear waves, there is obtained a diffracted shear wave with an ordinary distribution, and a possible weak compression wave with the extraordinary distribution. The presence of the diffracted compression wave depends upon the polarization of the incident shear wave.

Opacity in the Kirchhoff sense is a property of materials which are perfectly rigid.
Survey of Organ-Pipe Oscillations in Combustion Systems
Authors: Putnam Abbott A. , Dennis William R.
Published: September 2005

Fifty-three references from the open literature dealing with organ-pipe combustion oscillations are reviewed; these oscillations were generated in various types of combustion systems by the flame, or the combustion process. The many systems discussed range from simple singing-flame burners to industrial furnaces and high-duty rockets. The combustion systems are classified, for purposes of discussion, according to the basic arrangement of the components of the unit. These classes are burners with singing diffusion flames, flash tubes, gauze-tone burners, rocket-shaped burners, burners utilizing secondary air, and ram-jet type burners. The acoustical behavior of each system is described, and possible driving mechanisms for producing the observed oscillations are indicated. Some general remarks are made, based on the survey, concerning the mathematical formulation of mechanisms to explain the oscillations in particular cases.
Rotational Relaxation in Hydrogen Chloride
Authors: Breazeale M. A. , Kneser H. O.
Published: September 2005

The absorption and velocity of sound in hydrogen chloride have been measured by use of the pulse technique. Between f/p = 0.5 and f/p = 16 Mc/atm, the measured absorption is 1.47 times the classical absorption. The number of collisions during one relaxation time Zrot = 7. The low value of Zrot is attributed to the fact that HCl has a strong dipole moment.
Organ-Pipe Oscillations in a Burner with Deep Ports
Authors: Putnam Abbott A. , Dennis William R.
Published: September 2005

Data are presented on acoustic oscillations produced by a burner using a hexagonal bank of hypodermic tubes as deep ports. Most of the tests were made with ethane as the fuel, but some tests were run with methane and propane, for comparison. Both the diameter and length of the combustion chamber were varied.

It was found that the combustion chamber could be considered as a driver which forced the slugs of gas in the ports to oscillate. Burning of the incremental pulses of combustible mixture periodically issuing from the ports furnished energy to drive the oscillations when the pulses burned in phase with the oscillating component of the pressure in the chamber. The phasing depended on a time-lag factor which was a function of the velocity of the gases through a space, similar to dark space, between the burner ports and the mean burning points, and the width of the space itself.

The oscillations not only ceased when there was a failure to satisfy the timing criterion, but also ceased upon approach to either rich or lean blowoff limits of the conventional type. This premature cessation apparently results from the flame burning from fewer ports as the limits are approached, less driving energy being available.
Experimental Characteristics of Continuously Variable Resonant Frequency Crystal Systems
Authors: Dunn Floyd , Fry Frank J. , Fry William J.
Published: September 2005

The experimentally determined characteristics of a continuously variable resonant frequency crystal transducer are presented for the system operating under radiating conditions. These characteristics are presented for a high-power variable resonant frequency transducer of large radiating area, which utilizes the second harmonic and operates over the 2:1 frequency range from 22 kc to 44 kc with no more than a 2:1 variation in the pressure amplitude at a fixed point on the axis of the beam. Curves of pressure amplitude, input conductance, band width, half-power beam width, and efficiency, all as a function of the resonant frequency, are shown. The measured characteristics are compared with calculations based on a one-dimensional theory.
Dynamic Magnetostrictive Properties of Alfenol
Authors: Davis C. M. , Ferebee S. F.
Published: September 2005

The magnetostrictive properties of Alfenol, a cold-rolled Al-Fe alloy, were investigated to determine its suitability for use in electromechanical transducers. The effects of various processing techniques are included. The material, in the form of laminated toroids, was evaluated by the motional impedance method. Measured values of the electromechanical coupling coefficient, the mechanical Q in air, the reversible permeability, the dynamic magnetostrictive constant, and other parameters are given. The measurements indicate that the performance of 12- or 13-Alfenol is comparable to that of nickel, at least for low-power applications. The electromechanical coupling coefficient (approximately 0.29) is comparable to that of nickel; the electrical resistivity is at least ten times greater than that of nickel.